ORCID Profile
0000-0002-4554-8366
Current Organisation
University of South Australia
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Publisher: Wiley
Date: 12-02-2014
Abstract: Phosphorylation of eIF4E by human mitogen-activated protein kinase (MAPK)-interacting kinases (Mnks) is crucial for human tumourigenesis and development. Targeting Mnks may provide a novel anticancer therapeutic strategy. However, the lack of selective Mnk inhibitors has so far h ered pharmacological target validation and clinical drug development. Herein, we report, for the first time, the discovery of a series of 5-(2-(phenylamino)pyrimidin-4-yl)thiazole-2(3H)-one derivatives as Mnk inhibitors. Several derivatives demonstrate very potent Mnk2 inhibitory activity. The most active and selective compounds were tested against a panel of cancer cell lines, and the results confirm the cell-type-specific effect of these Mnk inhibitors. Detailed cellular mechanistic studies reveal that Mnk inhibitors are capable of reducing the expression level of anti-apoptotic protein Mcl-1, and of promoting apoptosis in MV4-11 acute myeloid leukaemia cells.
Publisher: American Society for Microbiology
Date: 04-2003
DOI: 10.1128/AAC.47.4.1364-1370.2003
Abstract: The stabilities of colistin and colistin methanesulfonate (CMS) in different aqueous media were studied by specific high-performance liquid chromatography (HPLC) methods. Colistin was stable in water at 4 and 37°C for up to 60 days and 120 h, respectively. However, degradation was observed when colistin was stored in isotonic phosphate buffer (0.067 M, pH 7.4) and human plasma at 37°C. The stability of CMS from three different sources in water was explored by strong-anion-exchange (SAX) HPLC for CMS and by measuring the concentrations of colistin formed from the hydrolysis of CMS. The peaks of CMS in SAX HPLC disappeared almost completely after 12 h at 37°C, but appeared to remain intact for up to 2 days at 4°C. Over the same period, there was no formation of colistin at 4°C. In water, phosphate buffer, and plasma, there was rapid formation of colistin within 24 to 48 h at 37°C from the three sources of CMS. The hydrolysis products were assumed to be a complex mixture of many different sulfomethyl derivatives, including colistin. The stability of a fourth source of CMS in Mueller-Hinton broth examined during 30 min at 37°C revealed no formation of colistin. Along with previous microbiological studies, this suggested that different sulfomethyl CMSs possess intrinsic antibacterial activity. These results will be helpful for understanding the pharmacokinetics and pharmacodynamics of colistin and CMS in humans and animals.
Publisher: Oxford University Press (OUP)
Date: 04-02-2008
DOI: 10.1093/JAC/DKM511
Abstract: The optimal dosing regimen for colistin methanesulphonate (CMS) against Pseudomonas aeruginosa is unknown. CMS is converted in vivo to its active form, colistin. We evaluated three colistin dosage regimens in an in vitro pharmacokinetic harmacodynamic model. Three intermittent dosage regimens involving 8, 12 and 24 h dosage intervals (Cmax of 3.0, 4.5 or 9.0 mg/L, respectively) were employed. Antibacterial activity and emergence of resistance were investigated over 72 h using two strains of P. aeruginosa: ATCC 27853 and 19056. The areas under the killing curves (AUBC(0-72)) and population analysis profiles (AUCPAP) were used to compare regimens. No difference in bacterial killing was observed among different regimens. For ATCC 27853, substantial killing was observed after the first dose with less killing after subsequent doses irrespective of regimen regrowth to between 5.95 and 7.49 log10 cfu/mL occurred by 72 h (growth control 7.46 log10 cfu/mL). AUCPAPs at 72 h for the 12 hourly (4.08 +/- 1.54) and 24 hourly (4.16 +/- 2.48) regimens were substantially higher than that for both the growth control (1.63 +/- 0.08) and 8 hourly regimen (2.30 +/- 0.87). For 19056, bacterial numbers at 72 h with each regimen (1.32-2.75 log10 cfu/mL) were far below that of the growth control (7.79 log10 cfu/mL) AUCPAPs could not be measured effectively due to the substantial killing. No difference in overall bacterial kill was observed when the recommended maximum daily dose was administered at 8, 12 or 24 h intervals. However, the 8 hourly regimen appeared most effective at minimizing emergence of resistance.
Publisher: Elsevier BV
Date: 2005
DOI: 10.1016/J.IJANTIMICAG.2004.10.001
Abstract: Infections caused by multi-resistant Gram-negative bacteria, particularly Pseudomonas aeruginosa, are increasing worldwide. In patients with cystic fibrosis (CF), resistance in P. aeruginosa to numerous anti-pseudomonal agents is becoming common. The absence since 1995, of new substances active against resistant Gram-negative bacteria, has caused increasing concern. Colistin, an old antibiotic also known as polymyxin E, has attracted more interest recently because of its significant activity against multi-resistant P. aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae, and the low resistance rates to it. Because its use as an anti-pseudomonal agent was displaced by the potentially less toxic aminoglycosides in 1970s, our knowledge of this drug is limited. However, there has been a significant recent increase in the data gathered on colistin, focussing on its chemistry, antibacterial activity, mechanism of action and resistance, pharmacokinetics, pharmacodynamics and new clinical application. It is likely that colistin will be an important antimicrobial option against multi-resistant Gram-negative bacteria, for some years to come.
Publisher: Wiley
Date: 2001
DOI: 10.1002/JLCR.450
Publisher: Springer Science and Business Media LLC
Date: 1979
DOI: 10.1007/BF00568203
Publisher: American Society for Microbiology
Date: 08-1985
DOI: 10.1128/AAC.28.2.293
Abstract: Moxalactam kinetics during continuous ambulatory peritoneal dialysis (CAPD) was followed in eight patients after a single intraperitoneal dose of 1 g. Approximately 60% of the dose was absorbed after a dwell time of 4 h. Dialysis solutions were exchanged at 4-h intervals with an overnight dwell of 8 h. The mean (+/- standard deviation) elimination half-life was 13.2 +/- 2.9 h, and the mean apparent volume of distribution was 0.22 +/- 0.08 liters/kg. Mean total clearance was 11.5 +/- 2.4 ml/min, with a mean dialysis clearance of 2.3 +/- 0.5 ml/min. The maximum concentration in plasma ranged from 24.5 to 54.1 micrograms/ml. Moxalactam concentrations in the peritoneal dialysis fluid were above 80 micrograms/ml during the first exchange and above 2 micrograms/ml for a further three exchanges. A suggested intraperitoneal dose regimen for patients undergoing CAPD is 1 g initially, followed by 15 to 25% of the recommended dose for normal patients given at the same time intervals, or 30 to 50% of the recommended dose at twice the usual intervals. Moxalactam is suggested for initial treatment of peritonitis in CAPD patients who do not have ready access to the antibiotic of choice.
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.JCHROMB.2005.12.046
Abstract: Effective use of the antianginal agent perhexiline is difficult because saturable metabolism by the polymorphic cytochrome P450 2D6 (CYP2D6) isoform produces elevated plasma perhexiline concentrations that have been associated with serious hepatic and neurological toxicity. Perhexiline is marketed for therapeutic use as a racemate and there is evidence for differences in the disposition of its enantiomers. The current study describes an enantioselective HPLC-fluorescent method utilising pre-column derivatization with (R)-(-)-1-(1-napthyl)ethyl isocyanate. Following derivatization, the enantiomers are resolved on a C18 column with gradient elution using a mobile phase composed of methanol and water. The method described is suitable for the quantification of (+)- and (-)-perhexiline in human plasma following clinical doses and demonstrates sufficient sensitivity, accuracy and precision between 0.01 and 2.00 mg/l for each enantiomer, with intra-assay coefficients of variation and bias <20% at 0.01 mg/l and <10% at 2.00 mg/l, and inter-assay coefficients of variation and biases <15% at 0.03 mg/l and <10% at 0.40 and 0.75 mg/l. The application of this method to plasma s les collected from a patient treated with perhexiline revealed that (+)-perhexiline concentrations were higher than (-)-perhexiline concentrations, confirming the stereoselective disposition of perhexiline. The current study describes an enantioselective method that utilises pre-column formation of fluorescent diastereomers that are resolved on a C18 HPLC column using a gradient of methanol and water.
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.TOXICON.2005.10.018
Abstract: Ant sting allergy in Australia is predominantly due to the Myrmecia pilosula species complex. Gel separation of M. pilosula venom is necessary so that the allergenic importance of each component can be defined by western blotting. However, previous PAGE methods produced suboptimal resolution and the components of each band were not precisely defined. Venom was resolved in both non-reduced and reduced form by one-dimensional acid urea PAGE, SDS-PAGE and two-dimensional acid urea-SDS PAGE. Resolved peptides were extracted and analysed by HPLC-MS. Acid urea PAGE and acid urea-SDS PAGE proved more effective than SDS-PAGE for resolution of peptides smaller than 10 kDa. All of the major peptides previously observed in M. pilosula venom were observed in gel resolved venom. Venom was found to primarily consist of peptides with molecular weight <10 kDa, most of which contain disulfide bridges. SDS-PAGE of non-reduced venom clearly defined six higher molecular weight proteins between 26 and 90 kDa. An 8546 Da dimer named pilosulin 5 was observed, but pilosulin 4, a peptide recently proposed to be present in venom was not. A variant of pilosulin 4 here named pilosulin 4.1a, existing as an 8198 Da dimer, was observed and has been characterised.
Publisher: American Society for Microbiology
Date: 05-2003
DOI: 10.1128/AAC.47.5.1766-1770.2003
Abstract: The pharmacokinetics of colistin was investigated using specific high-performance liquid chromatography (HPLC) to measure the concentrations of colistin and colistin A and B in plasma and urine in five rats after administration of an intravenous bolus of 1 mg of colistin sulfate/kg of body weight. There were differences in the pharmacokinetic behaviors of unbound colistin A and B. This is the first report of the use of HPLC to study the pharmacokinetics of colistin and its two major components.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.EJMECH.2017.08.006
Abstract: The discovery of novel anti-AML therapeutic agents is urgently needed, but the complex heterogeneity of the disease has so far h ered the development of a curative treatment. FLT3 inhibitors have shown therapeutic potential in clinical trials but a monotherapy regimen has been associated with resistance mediated by the activation of parallel signalling circuitry, including MAPK and mTOR. Therefore, inhibiting a nexus of the two signalling pathways along with inhibition of FLT3 might be advantageous. Herein, we propose that a dual inhibition of FLT3 and Mnk would provide a better clinical option for AML patients compared to targeting FLT3 alone. Thus, a series of N-phenyl-4-(thiazol-5-yl)pyrimidin-2-amines and 4-(indol-3-yl)-N-phenylpyrimidin-2-amines were prepared. Potent Mnk2 inhibitors, FLT3 inhibitors, and dual inhibitors of Mnk2 and FLT3 were identified and their anti-proliferative activities assessed against MV4-11 AML cell lines. Dual inhibition of FLT3 and Mnk2 caused the increased apoptotic cell death of MV4-11 cells compared to inhibition of FLT3 or Mnk2 alone.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 02-02-2010
Abstract: Clinical observation of a synergistic effect of ketamine on morphine analgesia remains controversial. Although a pharmacodynamic basis for an interaction has been explored in animal and clinical studies, the possibility of a pharmacokinetic mechanism has not been investigated. Whereas both morphine and morphine-6-glucuronide are effective analgesics, morphine-3-glucuronide (M3G) lacks activity. Thus, changes in the metabolism and disposition of morphine may result in an altered response. First, we investigated the interaction between morphine and ketamine in the isolated perfused rat liver preparation. The clearance of morphine was decreased from 16.8 +/- 4.6 ml/min in the control period to 7.7 +/- 2.8 ml/min in the ketamine-treatment period, with the formation clearance of M3G decreasing from 8.0 +/- 4.1 ml/min to 2.1 +/- 1.1 ml/min. Fractional conversion of morphine to M3G was significantly decreased from 0.46 +/- 0.17 in the control period to 0.28 +/- 0.14 upon the addition of ketamine. The possible mechanism of the interaction was further investigated in vitro with rat liver microsomes as the enzyme source. The formation of M3G followed single-enzyme Michaelis-Menten kinetics, with a mean apparent K(m) of 2.18 +/- 0.45 mM and V(max) of 8.67 +/- 0.59 nmol/min/mg. Ketamine inhibited morphine 3-glucuronidation noncompetitively, with a mean K(i) value of 33.3 +/- 7.9 microM. The results demonstrate that ketamine inhibits the glucuronidation of morphine in a rat model.
Publisher: Elsevier BV
Date: 02-2008
DOI: 10.1016/J.JCHROMB.2007.12.009
Abstract: A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed to quantify colistin in human plasma and urine, and perfusate and urine from the isolated perfused rat kidney (IPK). Solid phase extraction (SPE) preceded chromatography on a Synergi Fusion-RP column with a mobile phase of acetonitrile, water and acetic acid (80/19/1) at 0.2mL/min. Ions were generated using electrospray ionization and detected in the positive-ion mode. Multiple reaction monitoring was performed using precursor-product ion combinations. Calibration curves were linear from 0.028microg/mL (human plasma, IPK perfusate and urine)/0.056microg/mL (human urine) to 1.78microg/mL (all four media) for colistin A sulfate corresponding values for colistin B sulfate were 0.016/0.032 to 1.01microg/mL. Accuracy and precision were within 10%. The LLOQ for colistin A sulfate was 0.028microg/mL in human plasma, IPK perfusate and urine and 0.056microg/mL in human urine corresponding values for colistin B sulfate were 0.016 and 0.032microg/mL. The low s le volume, short analysis time and low LLOQ are ideal for pre-clinical and human pharmacokinetic studies of colistin.
Publisher: American Society for Microbiology
Date: 03-2001
DOI: 10.1128/AAC.45.3.781-785.2001
Abstract: The in vitro pharmacodynamic properties of colistin and colistin methanesulfonate were investigated by studying the MICs, time-kill kinetics, and postantibiotic effect (PAE) against mucoid and nonmucoid strains of Pseudomonas aeruginosa isolated from patients with cystic fibrosis. Twenty-three clinical strains, including multiresistant strains, and one type strain were selected for MIC determination. Eleven strains were resistant MICs for these strains were mg/liter. For the susceptible strains, MICs of colistin ranged from 1 to 4 mg/liter, while the MICs of colistin methanesulfonate were significantly higher and ranged from 4 to 16 mg/liter. The time-kill kinetics were investigated with three strains at drug concentrations ranging from 0.5 to 64 times the MIC. Colistin showed extremely rapid killing, resulting in complete elimination at the highest concentrations within 5 min, while colistin methanesulfonate killed more slowly, requiring a concentration of 16 times the MIC to achieve complete killing within 24 h. Colistin exhibited a significant PAE of 2 to 3 h at 16 times the MIC against the three strains after 15 min of exposure. For colistin methanesulfonate, PAEs were shorter at the concentrations tested. Colistin methanesulfonate had lower overall bactericidal and postantibiotic activities than colistin, even when adjusted for differences in MICs. Our data suggest that doses of colistin methanesulfonate higher than the recommended 2 to 3 mg/kg of body weight every 12 h may be required for the effective treatment of P. aeruginosa infections in cystic fibrosis patients.
Publisher: Oxford University Press (OUP)
Date: 12-2003
Abstract: Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to inhibit the renal tubular secretion of methotrexate. However, the relative contribution of the active S- and inactive R-enantiomers is unknown. This study examined the effect of racemic ketoprofen and its enantiomers on the renal disposition of methotrexate in the isolated perfused rat kidney (IPK). Nineteen kidneys were ided between a control and three treatment groups. Controls were perfused with methotrexate alone (25 μg mL−1, n = 5) over three 30-min periods. Treatment groups were perfused with methotrexate (25 μg mL−1) for the first period, followed by a second period of methotrexate (25 μg mL−1) plus R- (n = 5), S- (n = 5) or RS-ketoprofen (n = 4) at 25 μg mL−1, and a third period of methotrexate (25 μg mL−1) plus R-, S- or RS-ketoprofen (50 μg mL−1). Perfusate and urine were collected over 10-min intervals. Methotrexate was measured by HPLC and its binding in perfusate by ultrafiltration. The clearance ratio (CR) for methotrexate was obtained by iding the renal clearance by the product of its fraction unbound and the glomerular filtration rate. During control experiments, there was no significant change in the CR over 90 min. R-, S- and RS-ketoprofen at 50 μg mL−1 reduced the CR of methotrexate significantly, but there was no difference between the three groups. While the enantiomers of ketoprofen reduced the renal excretion of methotrexate, the interaction was not enantioselective.
Publisher: Oxford University Press (OUP)
Date: 09-01-2006
DOI: 10.1093/NDT/GFK056
Abstract: Trimethylamine (TMA) is a short-chain tertiary aliphatic amine that is derived from the diet either directly from the consumption of foods high in TMA or by the intake of food high in precursors to TMA, such as trimethylamine-N-oxide (TMNO), choline and L-carnitine. The clinical significance of TMA may be related to its potential to contribute to neurological toxicity and 'uraemic breath' in patients with end-stage renal disease (ESRD). Concentrations of TMA and TMNO in plasma from 10 healthy adults (not on haemodialysis) and 10 adults with ESRD undergoing haemodialysis (pre- and post-dialysis) were determined by gas chromatography-mass spectrometry. The concentrations of TMA and TMNO in pre-dialysis plasma (1.39+/-0.483 and 99.9+/-31.9 microM, respectively) were significantly (P<0.05) higher than the corresponding levels in healthy subjects (0.418+/-0.124 and 37.8+/-20.4 microM, respectively). However, there were no significant differences between post-dialysis and healthy subject plasma concentrations. In the ESRD patients, there was a significant (P<0.05) reduction in plasma TMA (from 1.39+/-0.483 to 0.484+/-0.164 microM) and TMNO (from 99.9+/-31.9 to 41.3+/-18.8 microM) during a single haemodialysis session. TMA and TMNO accumulate between haemodialysis sessions in ESRD patients, but are efficiently removed during a single haemodialysis session.
Publisher: Wiley
Date: 04-08-2007
DOI: 10.1111/J.1463-1326.2006.00630.X
Abstract: The aim of this study was to test the effect of isosteviol on blood glucose and insulin levels during the intravenous glucose tolerance test (IVGTT) in Wistar and Zucker diabetic fatty (ZDF) rats. ZDF rats were ided into a control and three isosteviol treatment (1, 5 and 10 mg/kg) groups. Wistar rats were ided into a control group and an isosteviol treatment group (10 mg/kg). The rats were fasted for 12 h prior to infusion of isosteviol and glucose (1.0 g/kg). Blood s les were taken at 0, 5, 15, 30, 60, 90 and 120 min after the injection of glucose. Glucose concentrations were determined by the glucose oxidase method, and plasma insulin was analysed by radioimmunoassay. The area under the curve (AUC) of the net change in plasma glucose concentration was used to compare the isosteviol treatment and control groups. In ZDF rats, isosteviol at 5 and 10 mg/kg caused a significant (p < 0.05) reduction in the AUC of glucose during the IVGTT. However, isosteviol did not increase plasma insulin concentrations in ZDF rats. In Wistar rats, isosteviol did not significantly affect plasma glucose or insulin levels during the IVGTT. Isosteviol exerts an antihyperglycaemic effect during IVGTT in ZDF rats but not in Wistar rats. Isosteviol has no significant effect on plasma insulin concentrations. The glucose-lowering effect of isosteviol may be due to changes in the sensitivity of peripheral tissues to insulin.
Publisher: Elsevier BV
Date: 2008
DOI: 10.1016/J.JPBA.2007.08.028
Abstract: Ant sting allergy is relatively common within south-eastern Australia and is predominantly due to Myrmecia pilosula (Jack Jumper Ant, JJA). Venom immunotherapy has been shown to be effective in preventing anaphylaxis to the sting of the JJA, but analytical techniques to standardise the venom have not been validated. The purpose of this study was to develop assays to analyse JJA venom and apply these to the standardisation of venom prior to new batches being used for the diagnosis and treatment of JJA sting allergy. Venom was analysed by protein content, HPLC-UV, enzyme-linked immunosorbent assay (ELISA) inhibition, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and SDS-PAGE immunoblot. The protein content in JJA venom was adjusted so that all batches were equivalent. A HPLC-UV assay was used to quantify the relative amount of the major allergen Myr p 2 and two minor allergens Myr p 1 and Myr p 3 and allergenic potency was determined by ELISA inhibition. SDS-PAGE and SDS-PAGE immunoblot were used as qualitative tools to determine the protein profile and presence or absence of additional high molecular weight allergens not quantifiable by HPLC-UV. A standardisation procedure has been developed that complies with the requirements described in the European Pharmacopoeia. Techniques used to determine the content of some of the other minor allergens could be developed, which would further improve the standardisation methodology.
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.JPBA.2010.08.024
Abstract: Allergy to Myrmecia pilosula (Jack Jumper Ant) venom is common in Australia, affecting ∼2.7% of some communities. Venom immunotherapy is a highly effective treatment, but for the venom to be widely distributed for clinical use, the stability and shelf-life of formulated Jack Jumper Ant venom must be demonstrated. HPLC-UV, ELISA Inhibition, SDS-PAGE and SDS-PAGE Immunoblot were used to assess venom stability under conditions of varying temperature, pH and in the presence of various stabilising agents. Optimal stability occurred between pH 8 and 10, however the presence of benzyl alcohol within this pH range resulted in a cloudy appearance within 3 days, so a pH of 6 was used. Increasing polysorbate 80 concentrations accelerated the degradation of allergenic peptides in 100 μg/mL venom, but improved stability at concentrations of 1 μg/mL or less. Sucrose reduced degradation of allergens Myr p 1 and Myr p 3, whilst glycerol was destabilizing. In the presence of 22% sucrose, 1.1mg/mL Jack Jumper Ant venom was stable at -18 °C and 4 °C for 12 months following dilution to 100 μg/mL with 0.9% sodium chloride, 10mM phosphate (pH 6), 0.05% polysorbate 80 and 0.9% benzyl alcohol (giving 2% sucrose), venom was stable for 7 days when stored at 4 °C. Concentrated Jack Jumper Ant venom can be stored in 22% sucrose for 12 months, and after dilution to 100 μg/mL for clinical use, it should be discarded after 7 days.
Publisher: Bentham Science Publishers Ltd.
Date: 10-2006
DOI: 10.2174/138920006778520589
Abstract: The vectorial movement of glucuronide conjugates from blood into bile can be an important elimination route for many drug metabolites, however the intrinsic hydrophilicity of those conjugates may conceptually act to reduce the overall efficiency of that process by limiting the flux of such conjugates across the sinusoidal membrane domain of hepatocytes. In this investigation, the hepatic disposition of the diastereomeric glucuronides of (R)- and (S)-2-phenylpropionic acid (a model "profen" compound) have been studied using the isolated perfused rat liver to establish whether a permeability barrier at the sinusoidal membrane domain (demonstrated previously for those conjugates) is of a sufficient magnitude to impact on the overall biliary excretion of these conjugates. Livers were perfused (30 mL/min) with perfusate containing either (R)-PPA, (S)-PPA, (R)-PPA-Glucuronide or (S)-PPA-Glucuronide in order to determine the dispositional profile of each glucuronide administered to the liver as both a preformed and an hepatically-generated metabolite. Once an apparent steady-state condition had been reached, infusion of test compound was ceased in order to establish the kinetics of the hepatic washout. The extent of biliary excretion of each glucuronide was dependent upon whether the glucuronide was presented to the liver as a preformed or hepatically-generated metabolite, and those differences, when analysed using a physiologically-based pharmacokinetic model, were consistent with the sinusoidal membrane acting as a barrier to the cellular entry of the glucuronides. Furthermore, that barrier was more pronounced for (R)-PPAG than it was for (S)-PPAG, suggesting that the hepatocellular uptake of the two diastereomers is stereoselective.
Publisher: American Chemical Society (ACS)
Date: 10-03-2014
DOI: 10.1021/JM4019614
Abstract: ON01910.Na is a highly effective anticancer agent that induces mitotic arrest and apoptosis. Clinical studies with ON01910 in cancer patients have shown efficacy along with an impressive safety profile. While ON01910 is highly active against cancer cells, it has a low oral availability and requires continuous intravenous infusion or multiple gram doses to ensure sufficient drug exposure for biological activity in patients. We have identified two novel series of styrylsulfonyl-methylpyridines. Lead compounds 8, 9a, 18 and 19a are highly potent mitotic inhibitors and selectively cytotoxic to cancer cells. Impressively, these compounds possess excellent pharmaceutical properties and two lead drug candidates 9a and 18 demonstrated antitumor activities in animal models.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 18-10-2006
Abstract: The cytochrome P450 (P450)-mediated 4-monohydroxylations of the in idual enantiomers of the racemic antianginal agent perhexiline (PHX) were investigated in human liver microsomes (HLMs) to identify stereoselective differences in metabolism and to determine the contribution of the polymorphic enzyme CYP2D6 and other P450s to the intrinsic clearance of each enantiomer. The cis-, trans1-, and trans2-4-monohydroxylation rates of (+)- and (-)-PHX by human liver microsomes from three extensive metabolizers (EMs), two intermediate metabolizers (IMs), and two poor metabolizers (PMs) of CYP2D6 were measured with a high-performance liquid chromatography assay. P450 isoform-specific inhibitors, monoclonal antibodies directed against P450 isoforms, and recombinantly expressed human P450 enzymes were used to define the P450 isoform profile of PHX 4-monohydroxylations. The total in vitro intrinsic clearance values (mean +/- S.D.) of (+)- and (-)-PHX were 1376 +/- 330 and 2475 +/- 321, 230 +/- 225 and 482 +/- 437, and 63.4 +/- 1.6 and 54.6 +/- 1.2 microl/min/mg for the EM, IM, and PM HLMs, respectively. CYP2D6 catalyzes the formation of cis-OH-(+)-PHX and trans1-OH-(+)-PHX from (+)-PHX and cis-OH-(-)-PHX from (-)-PHX with high affinity. CYP2B6 and CYP3A4 each catalyze the trans1- and trans2-4-monohydroxylation of both (+)- and (-)-PHX with low affinity. Both enantiomers of PHX are subject to significant polymorphic metabolism by CYP2D6, although this enzyme exhibits distinct stereoselectivity with respect to the conformation of metabolites and the rate at which they are formed. CYP2B6 and CYP3A4 are minor contributors to the intrinsic P450-mediated hepatic clearance of both enantiomers of PHX, except in CYP2D6 PMs.
Publisher: Springer Science and Business Media LLC
Date: 2000
Abstract: To examine the disposition of fexofenadine in the isolated perfused rat liver and the influence of erythromycin and dibromosulphthalein (DBSP) on the hepatic uptake and biliary excretion of fexofenadine. Livers from four groups of rats were perfused in a recirculatory manner with fexofenadine HCl added as a bolus (125, 250, 500, or 1000 microg) to perfusate. Livers from another three groups of rats were perfused with 250 microg of fexofenadine HCl. With one group as control, erythromycin (4.0 microg/ml) or DBSP (136 microg/ml) was added to the perfusate of the other groups. In all experiments, perfusate and bile were collected for 60 min in addition, livers from the second experiment were retained for assay. Fexofenadine was determined in perfusate, bile, and homogenized liver by HPLC. The area under the curve (AUC) of fexofenadine was linearly related to concentration. It was unchanged from control (12,800 +/- 200 ng x h/ml) by erythromycin (14,400 +/- 2000 ng x h/ml), but was increased 95% by DBSP (25,000 +/- 2600 ng x h/ml, P <0.001). The ratios of the concentrations of fexofenadine in liver erfusate were decreased significantly by DBSP those for bile/liver were increased by erythromycin. Erythromycin reduced the canalicular transport of fexofenadine into bile, whereas DBSP reduced uptake across the sinusoidal membrane.
Publisher: Springer Science and Business Media LLC
Date: 08-2010
Publisher: American Society for Microbiology
Date: 10-2002
DOI: 10.1128/AAC.46.10.3304-3307.2002
Abstract: A simple and sensitive high-performance liquid chromatographic method is described for the determination of colistimethate sodium in plasma and urine. The accuracy and reproducibility was within 10.1 and 11.2% with rat plasma and urine, respectively. Several commonly coadministered antibacterial agents do not interfere with the assay.
Publisher: Wiley
Date: 15-09-2007
Publisher: Elsevier BV
Date: 04-2014
DOI: 10.1016/J.CHEMBIOL.2014.01.011
Abstract: Mitogen-activated protein kinase (MAPK)-interacting kinases (Mnks) regulate the initiation of translation through phosphorylation of eukaryotic initiation factor 4E (eIF4E). Mnk-mediated eIF4E activation promotes cancer development and progression. While the phosphorylation of eIF4E is necessary for oncogenic transformation, the kinase activity of Mnks seems dispensable for normal development. For this reason, pharmacological inhibition of Mnks could represent an ideal mechanism-based and nontoxic therapeutic strategy for cancer treatment. In this review, we discuss the current understanding of Mnk biological roles, structures, and functions, as well as clinical implications. Importantly, we propose different strategies for identification of highly selective small molecule inhibitors of Mnks, including exploring a structural feature of their kinase domain, DFD motif, which is unique within the human kinome. We also argue that a combined targeting of Mnks and other pathways should be considered given the complexity of cancer.
Publisher: Elsevier BV
Date: 06-2003
DOI: 10.1093/BJA/AEG131
Abstract: The analgesic effects of morphine are delayed relative to its concentration in blood. The rate of equilibration of morphine between blood and brain may contribute to this delay, but the kinetics of this process have not been modelled. This was determined in conscious instrumented sheep. The lung kinetics of morphine were also determined given their importance in defining systemic kinetics after i.v. bolus administration. Sheep were given short i.v. infusions of morphine (30 mg over 4 min). Cerebral kinetics were inferred from arterio-sagittal sinus concentration gradients and cerebral blood flow, and lung kinetics from the pulmonary artery-aortic gradient and cardiac output. These data were fitted to flow- and membrane-limited models of the kinetics in each organ. Morphine had minimal cardiovascular effects, did not alter cerebral blood flow and caused insignificant respiratory depression. Lung kinetics were best described by a single distribution volume (2036 ml) with a first-order loss (1370 ml min(-1)), which was attributed to deep distribution. The cerebral kinetics of morphine were characterized by a significant permeability barrier. Permeability across the barrier (7.44 ml min(-1)) was estimated with good precision, and was approximately one-fifth of the nominal cerebral blood flow. The distribution volume of morphine in the brain was estimated with less precision, but was described by a brain:blood partition coefficient of approximately 1.4. The time required for 50% equilibration between brain and blood concentrations was approximately 10.3 min. The cerebral equilibration of morphine was relatively slow, and was characterized by significant membrane limitation.
Publisher: Bioscientifica
Date: 12-2016
DOI: 10.1530/ERC-16-0299
Abstract: Cyclin-dependent kinase 9 (CDK9) is a key transcriptional regulator and a lucrative target for cancer treatment. Targeting CDK9 can effectively confine the hyperactivity of androgen receptor and the constitutive expression of anti-apoptotic proteins both being main causes of prostate cancer (PCa) development and progression. In castrate-resistant PCa, traditional therapies that only target androgen receptor (AR) have become obsolete due to reprograming in AR activity to make the cells independent of androgen. CDK9 inhibitors may provide a new and better therapeutic opportunity over traditional treatment options by targeting both androgen receptor activity and anti-apoptotic proteins, improving the chances of positive outcomes, especially in patients with the advanced disease. This review focuses on biological functions of CDK9, its involvement with AR and the potential for therapeutic opportunities in PCa treatment.
Publisher: Elsevier BV
Date: 09-2006
Publisher: American Society for Microbiology
Date: 03-2008
DOI: 10.1128/AAC.01101-07
Abstract: The relative nephro- and neurotoxicity of colistin methanesulfonate (CMS) was investigated with rats during 7 days of intravenous administration in regimens mimicking twice- and once-daily dosing of a clinically relevant dose for humans. Histological examination revealed more-severe renal lesions with the regimen corresponding to once-daily dosing, indicating that the potential for renal toxicity may be greater with extended-interval dosing.
Publisher: Elsevier BV
Date: 09-2001
DOI: 10.1016/S0378-4347(01)00326-7
Abstract: A simple, selective and sensitive high-performance liquid chromatographic (HPLC) method is described for the determination of colistin in human plasma. Derivatization with 9-fluorenylmethyl chloroformate was performed in the same solid-phase extraction C18 cartridge used for s le pre-treatment, followed by reversed-phase HPLC with fluorimetric detection. Quantification was achieved using the ratio of the summed peak areas of colistin A and B derivatives to that of the derivative of netilmicin (internal standard). Linear calibration curves were obtained within the concentrations of colistin sulfate from 0.10 to 4.0 mg/l in plasma. Accuracy was within 10% and reproducibility (RSD) was less than 10%.
Publisher: American Chemical Society (ACS)
Date: 16-02-2017
DOI: 10.1021/ACS.JMEDCHEM.6B01670
Abstract: Cyclin D dependent kinases (CDK4 and CDK6) regulate entry into S phase of the cell cycle and are validated targets for anticancer drug discovery. Herein we detail the discovery of a novel series of 4-thiazol-N-(pyridin-2-yl)pyrimidin-2-amine derivatives as highly potent and selective inhibitors of CDK4 and CDK6. Medicinal chemistry optimization resulted in 83, an orally bioavailable inhibitor molecule with remarkable selectivity. Repeated oral administration of 83 caused marked inhibition of tumor growth in MV4-11 acute myeloid leukemia mouse xenografts without having a negative effect on body weight and showing any sign of clinical toxicity. The data merit 83 as a clinical development candidate.
Publisher: Elsevier BV
Date: 11-2004
Publisher: Elsevier BV
Date: 04-1991
DOI: 10.1016/0378-4347(91)80410-E
Abstract: Improvements to previously reported methods for the determination of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) in human plasma are described. The improved methods involve the use of a solid-phase extraction cartridge and a chromatographic system which uses paired-ion reversed-phase high-performance liquid chromatography with a radially compressed column. Only one cartridge is used to prepare each s le for chromatography and each cartridge may be used for at least fourteen 1-ml plasma s les. The recovery is greater than 85%. The improvements to the method of s le pretreatment and in the chromatographic conditions have allowed determination of morphine, M3G and M6G in human plasma down to 13.3 nmol/l (coefficient of variation = 9.3%), 108 nmol/l (6.6%) and 41 nmol/l (6.7%), respectively, using ultraviolet detection alone. It was shown that all three compounds were stable in plasma for up to 101 weeks when stored at -20 degrees C.
Publisher: Oxford University Press (OUP)
Date: 24-03-2004
DOI: 10.1093/JAC/DKH167
Publisher: Springer Science and Business Media LLC
Date: 05-1993
DOI: 10.2165/00003088-199324050-00005
Abstract: The plasma concentrations and renal clearance values of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) were determined in 11 adult cancer patients maintained on a long term oral morphine dosage (10 to 100mg every 4h). Concentrations in plasma and urine were determined by a specific high performance liquid chromatography assay. In this group of patients, whose creatinine clearance values ranged from 52 to 180 ml/min (3.12 to 10.8 L/h), average steady-state plasma concentrations of morphine, M3G and M6G were related (p < 0.01) to the morphine dose per kilogram of bodyweight. The mean total urinary recovery as morphine, M3G and M6G was 74.6 +/- 26.5% of the dose. Renal clearance values for M3G and M6G were closely related (r2 = 0.80 p < 0.0005). It was not possible to detect a relationship between the renal clearance of morphine, M3G and M6G, and that of creatinine. The renal tubular handling of all 3 compounds showed wide interin idual variation, and there was evidence of either net renal tubular secretion or reabsorption. There was no apparent relationship between plasma morphine and M6G concentrations and pain relief.
Publisher: Future Science Ltd
Date: 03-2016
DOI: 10.4155/FMC.15.190
Abstract: The discovery of small molecules that selectively inhibit Mnks is considered of paramount importance towards deciphering the exact role of these proteins in carcinogenesis and to further validate them as anti-cancer drug targets. However, the dearth of structural information of Mnks is a major hurdle. This study unveils the 7H-pyrrolo[2,3-d]pyrimidine derivatives as potent inhibitors of Mnks. ATP and substrate competition assays showed that this scaffold interacts with the ATP binding site, but not with the substrate site. Screened against a panel of cancer cells, Mnk inhibitors were most potent against MV4-11 acute myeloid leukemia cells. The induction of apoptosis was shown to be mediated by downregulation of Mcl-1.
Publisher: Springer Science and Business Media LLC
Date: 02-1990
DOI: 10.2165/00003088-199018020-00004
Abstract: Phorbol myristate acetate (pma) is a potent mitogen for human peripheral blood lymphocytes (PBL) comparable to phytohemagglutinin (PHA) in potency. Inactivation of PHA-responsive lymphocytes by 5'-bromodeoxyuridine and light treatment left the PMA response intact and nice versa. Experiments separating lymphocytes by rosetting with sheep erythrocytes (SRBC) demonstrated that the PMA-responsive lymphocytes segregate with those that have a high affinity for SRBC to a greater than PHA- or concanavalin A (Con A)-responsive cells. These results indicate that a PMA-responsive population in human peripheral blood resides within the T-lymphocyte population and appears to have a high affinity for SRBC and to be distinct from that responding to PHA and Con A. PMA may be useful clinically to assay the size and function of the high affinity or "active" rosette population.
Publisher: Oxford University Press (OUP)
Date: 05-2003
DOI: 10.1211/002235703765344540
Abstract: This study examines the potential for the phytoestrogenic isoflavones, a type of complementary medicine, to be involved in pharmacokinetic interactions in the liver. Rat livers were isolated and perfused to steady state, in single-pass mode, with either 5 μm paracetamol (n=6), or 5 μm paracetamol with a 50:50 molar mixture of genistein and biochanin A or daidzein and formononetin, at a total isoflavone concentration of 1 and 10 μm (n = 6 for each mixture at each concentration). At 1 μm, neither isoflavone mixture had any effect, while at 10 μm both mixtures decreased the clearance of paracetamol and the formation clearance to paracetamol sulfate. Genistein and biochanin A (10 μm) also increased the biliary extraction of hepatically-generated paracetamol sulfate. Additional livers were perfused with an infusion of 5 μm 14C-paracetamol in the absence (n = 4), or presence, of a 10 μm genistein and biochanin A mixture (n = 4). Analysis of washout perfusate and bile s les (up to 30min after stopping the infusion) revealed that the isoflavones reduced the first-order rate constant for paracetamol sulfate transport into perfusate, but not for transport into bile. The results indicate that isoflavones can reduce the formation of paracetamol sulfate and that its enhanced excretion into bile arises from the inhibition of sinusoidal efflux transport.
Publisher: Springer Science and Business Media LLC
Date: 1990
DOI: 10.2165/00003088-199018010-00003
Abstract: Phenytoin, which is used primarily as an anticonvulsant agent, has a relatively low therapeutic index, and monitoring of plasma phenytoin concentration is often used to help guide therapy. It has properties which predispose it to an involvement in pharmacokinetic interactions, a large number of which have been reported. These properties include: low aqueous solubility and slow rate of gastrointestinal absorption a relatively high degree of plasma protein binding a clearance that is non-linear due to saturable oxidative biotransformation and the ability to induce hepatic microsomal enzymes. Because of its narrow therapeutic range, drug interactions leading to alterations in plasma phenytoin concentration may be clinically important. Such interactions have often been reported initially as either cases of phenytoin intoxication or of decreased effectiveness. Drugs may modify the pharmacokinetics of phenytoin by altering its absorption, plasma protein binding, or hepatic biotransformation alterations in the absorption and/or biotransformation may lead to changes in both the unbound plasma phenytoin concentration and, as a result, the clinical effect. Preparations which may decrease the gastrointestinal absorption of phenytoin include nutritional formulae and charcoal. There are many reports of drugs which may increase (e.g. folic acid, dexamethasone and rif icin) or decrease (e.g. valproic acid, sulthiame, isoniazid, cimetidine, phenylbutazone, chlor henicol and some sulphonamides) the metabolism of phenytoin. It is important to bear in mind that, as a result of its non-linear clearance, changes in phenytoin absorption and/or biotransformation will lead to more than proportionate changes in plasma drug concentration. Drugs which may displace phenytoin from plasma albumin include valproic acid, salicylic acid, phenylbutazone and some sulphonamides. Although an alteration in the unbound fraction of phenytoin in plasma would not, in itself, be expected to alter the unbound plasma phenytoin concentration, the interpretation of total plasma concentrations for therapeutic drug monitoring may be confounded. Some drugs appear to alter phenytoin pharmacokinetics via dual mechanisms (e.g. valproic acid and phenylbutazone), while for other compounds the mechanism of interaction has not been fully elucidated. Phenytoin has been reported to alter the pharmacokinetics of a large number of drugs. The majority of these interactions arise because phenytoin is a potent inducer of cytochrome P450 microsomal enzymes, and therefore may increase the clearance of drugs which are extensively metabolised drugs affected include carbamazepine, theophylline, methadone, prednisolone, dexamethasone, metyrapone and several cardiac antiarrhythmic agents. With all of these, the resultant decrease in plasma concentrations may be clinically important.(ABSTRACT TRUNCATED AT 400 WORDS)
Publisher: Oxford University Press (OUP)
Date: 10-2003
Abstract: Foods and complementary medicines contain phytoestrogenic isoflavones such as genistein, which undergo hepatic glucuronidation and excretion into bile and can potentially interfere with the hepatic elimination of other compounds. To investigate this potential, livers from Sprague-Dawley rats were perfused in single-pass mode with preformed gemfibrozil 1-O-acyl glucuronide (GG) (1 μM, n = 12) for 60 min followed by a 30-min washout phase, or with gemfibrozil (1 μM n = 10) for 120 min. Half of each group of livers were co-perfused with genistein (10 μM) throughout the experiment. Perfusate and bile were analyzed for GG and gemfibrozil by HPLC. Co-perfusion with genistein significantly (P & 0.05) decreased the biliary extraction ratio of preformed GG from a mean of 0.82 to 0.65 and the first-order rate constant for transport of GG into bile from 0.054 + 0.010 to 0.032 + 0.008 min−1, but increased the first-order rate constant for sinusoidal efflux of GG from 0.128 + 0.023 to 0.227 + 0.078 min−1. Co-perfusion with genistein also significantly decreased the biliary extraction ratio of hepatically generated GG from 0.95 + 0.01 to 0.83 + 0.05. The findings confirm that genistein increases the potential for hepatic and systemic exposure to hepatically generated glucuronides, which may be important for patients on conventional drugs who consume isoflavones.
Publisher: American Society for Microbiology
Date: 07-2009
DOI: 10.1128/AAC.00030-09
Abstract: Nephrotoxicity is an important limitation to the clinical use of colistin against Pseudomonas aeruginosa and other gram-negative pathogens. Previous work reported net tubular reabsorption of colistin by the kidney in vivo, but there is no knowledge of its disposition within the kidney. This study investigated the renal disposition and potential transport mechanisms of colistin in the isolated perfused rat kidney (IPK) model by perfusing with colistin sulfate alone (2 μg/ml) or in the presence of potential inhibitors (tetraethylammonium [TEA], glycine-glycine [Gly-Gly], or hydrochloric acid [HCl]) at three different concentrations. When perfused alone, the renal clearances (CL R ) for colistin A and B (the major components of colistin) in control kidneys were constant and low (mean values 0.05 ml/min throughout the perfusion). The mean clearance ratios [CR, defined as CL R /( f u × GFR), where f u is the fraction of drug unbound in perfusate and GFR is the glomerular filtration rate] were significantly less than 1. It was concluded that there is net tubular reabsorption of colistin, and this exceeded the reabsorption of water. Less than 10% eliminated from perfusate was recovered in urine, suggesting considerable renal accumulation of colistin. The CR values for colistin were significantly increased when perfused with TEA (500 μM), Gly-Gly (833 μM), and HCl (2,500, 5,000, and 10,000 μM). It is proposed that renal reabsorption of colistin may involve organic cation transporters (inhibited by TEA) and peptide transporters (inhibited by Gly-Gly) and that the process is sensitive to the pH of urine.
Publisher: Wiley
Date: 10-2006
Abstract: The pharmacokinetics of L-carnitine and its metabolites were investigated in 7 healthy subjects following the oral administration of 0, 0.5, 1, and 2 g 3 times a day for 7 days. Mean plasma concentrations of L-carnitine across an 8-hour dose interval increased significantly (P < .05) from a baseline of 54.2 +/- 9.3 microM to 80.5 +/- 12.5 microM following the 0.5-g dose there was no further increase at higher doses. There was a significant increase (P < .001) in the renal clearance of L-carnitine indicating saturation of tubular reabsorption. Trimethylamine plasma levels increased proportionately with L-carnitine dose, but there was no change in renal clearance. A significant increase in the plasma concentrations of trimethylamine-N-oxide from baseline was evident only for the 2-g dose of L-carnitine (from 34.5 +/- 2.0 to 149 +/- 145 microM), and its renal clearance decreased with increasing dose (P < .05). There was no evidence for nonlinearity in the metabolism of trimethylamine to trimethylamine-N-oxide. In conclusion, the pharmacokinetics of oral L-carnitine display nonlinearity above a dose of 0.5 g 3 times a day.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2007
Publisher: Elsevier BV
Date: 10-1991
DOI: 10.1093/BJA/67.4.378
Abstract: In a crossover design study we have measured the total body and regional clearances of morphine. Thirteen experiments were performed in four conscious sheep that had been prepared previously with appropriate intravascular cannulae. Morphine (as sulphate pentahydrate) was infused i.v. at 2.5, 5, 10 and 20 mg h-1 to produce constant blood concentrations. Morphine (base) concentrations were measured in blood, urine and tissues with a specific HPLC method. The mean (SEM) total body clearance of morphine was 1.63 (0.21) litre min-1 this comprised 1.01 (0.10) litre min-1 clearance by the liver and 0.55 (0.06) litre min-1 by the kidneys. There was no evidence of dose-dependent clearance or significant extraction of morphine by the lungs, brain, heart, gut or hindquarters at any dose. The kidney clearance of morphine was greater than the 0.21 (0.06) litre min-1 renal clearance determined from the product of the mean total body clearance and the 12.3 (2.4%) of the administered dose recovered as unmetabolized morphine from 48 h urine collection (P less than 0.05). It was concluded that the liver and kidneys account for the majority of morphine clearance, and that the kidneys both excrete and metabolize morphine.
Publisher: Oxford University Press (OUP)
Date: 12-11-2003
DOI: 10.1093/JAC/DKG468
Publisher: Informa UK Limited
Date: 1996
Publisher: Springer Science and Business Media LLC
Date: 1997
Abstract: Humans and guinea pigs metabolise morphine extensively, forming the isomers morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) in relatively similar ratios. Both metabolites are formed in the liver, and their greater polarity relative to the parent aglycone may limit their permeability across hepatic membranes. This study compared the disposition of hepatically-generated M3G and M6G in perfused livers isolated from guinea pigs. Livers were perfused at 30 ml/min in a non-recirculating manner with Krebs bicarbonate buffer containing morphine (6 to 7 microM). Perfusing medium, venous perfusate and bile were collected at regular intervals and concentrations of morphine, M3G and M6G determined by reversed-phase HPLC. Concentrations of morphine, M3G and M6G in perfusate and the rates of biliary excretion of M3G and M6G were consistent between 20 and 50 min of perfusion. The mean (+/-s.d.) ratio for the rate of formation of M3G relative to M6G was 3.7 +/- 1.5. A mean 33 +/- 3% of morphine extracted by the liver was recovered as summed M3G and M6G. Of the M3G and M6G formed during a single passage, 19 +/- 11% and 9 +/- 9%, respectively, was excreted into bile the values were significantly different (P = 0.002). A greater fraction of hepatically-generated M3G excreted into bile compared to that for M6G reflects differences in their relative transport across sinusoidal and canalicular membranes of hepatocytes, possibly via carrier-mediated systems.
Publisher: Wiley
Date: 12-03-2007
DOI: 10.1111/J.1398-9995.2007.01320.X
Abstract: The 'Jack Jumper Ant' (JJA Myrmecia pilosula species complex) is the major cause of ant sting anaphylaxis in Australia. Our aims were to determine the allergenicity of previously described venom peptides in their native forms, identify additional allergens and if necessary, update nomenclature used to describe the allergens according to International Union of Immunological Societies criteria. Various polyacrylamide gel electrophoresis methods were used to separate JJA venom. Gel resolved venom was Western-blotted and probed with in idual sera taken from patients with a history of JJA sting anaphylaxis and immunoglobulin E radioallergosorbent test (IgE RAST) tracer uptakes of >1% to whole venom. Of 67 available sera, 54 had RAST uptakes >1%. Thirteen IgE binding bands were identified using these sera. Pilosulin 3, [Ile(5)]pilosulin 1, and pilosulin 4.1 were recognized by 42 (78%), 18 (33%) and nine (17%) of the 54 sera that were tested. Immunoglobulin E-binding proteins with estimated molecular masses of 6.6, 22.8, 25.6, 30.4, 32.1, 34.4 and 89.8 kDa were each recognized by three or more in idual sera. Two of these (25.6 and 89.8 kDa) were recognized by 46% and 37% of sera, respectively. Nomenclature used to describe JJA venom allergens has been revised. Pilosulin 3 (Myr p 2) is the only major allergen, whilst [Ile(5)]pilosulin 1 (Myr p 1), and pilosulin 4.1 (Myr p 3) are minor allergens. There are an additional five IgE-binding proteins that require further characterization before they can be named as allergens. These findings provide a framework for standardizing venom extracts for diagnosis and immunotherapy.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 10-02-2017
Abstract: The aim of this study was to determine the effects of garlic and ginkgo herbal extracts on the pharmacokinetics of the P-glycoprotein (P-gp)/organic anion-transporting polypeptides (Oatps) substrate fexofenadine. Male rats were dosed orally with garlic (120 mg/kg), ginkgo (17 mg/kg), St. John's wort (SJW 1000 mg/kg positive control), or Milli-Q water for 14 days. On day 15, rats either were administered fexofenadine (orally or i.v.), had their livers isolated and perfused with fexofenadine, or had their small intestines ided into four segments (SI-SIV) and analyzed for P-gp and Oatp1a5. In vivo, SJW increased the clearance of i.v. administered fexofenadine by 28%. Garlic increased the area under the curve
Publisher: Springer Science and Business Media LLC
Date: 02-2004
DOI: 10.1023/B:JOPA.0000029486.60317.25
Abstract: Numerous studies have previously been conducted with the impulse-response isolated perfused rat liver (IR-IPRL) to establish the role of both physiological and physicochemical factors in determining solutes' pattern of hepatic disposition, however the impact of optical isomerism on hepatic disposition has hardly been studied using this methodology. In this study, the IR-IPRL was used to assess the extent of stereoselectivity exhibited by the kinetic processes involved in the hepatic disposition of the diastereomeric acyl glucuronides of (R)- and (S)-2-phenylpropionic acid (i.e. (R)- and (S)-PPAG). Moment and model-dependent (distributed model and axial dispersion model) analyses were conducted of the hepatic outflow profiles generated upon bolus administration of (R)-(14)C-PPAG or (S)-(14)C-PPAG and 3H-Sucrose (used as a marker of the hepatic vascular space) into the portal inflow of isolated perfused livers of male Sprague-Dawley rats (n = 4). Significant differences between (R)- and (S)-PPAG were apparent in the pharmacokinetic parameters defining the total hepatic disposition of the two diastereomers, the most marked being the hepatic availabilities, where the value for (S)-PPAG (0.721 +/- 0.059) was significantly lower than that of (R)-PPAG (0.909 +/- 0.042). The distributed and axial dispersion model analyses suggested that the more extensive hepatic extraction of (S)-PPAG was (at least in part) due to the higher sinusoidal membrane permeability-surface area product (PS UPT) of the diastereomer, and this has been considered in light of the emerging evidence regarding the role of hepatocellular membrane transport mechanisms. Furthermore, given the potential immunogenicity of acyl glucuronides (through covalent binding to plasma and intracellular proteins), the results of this study suggest that diastereomeric glucuronides may exhibit differing toxicity due to differences in their access to intracellular proteins.
Publisher: Future Science Ltd
Date: 10-2017
Abstract: Selective abrogation of cyclin-dependent kinases (CDK) activity is a highly promising strategy in cancer treatment. The atypical CDK, CDK5 has long been known for its role in neurodegenerative diseases, and is becoming an attractive drug target for cancer therapy. Myriads of recent studies have uncovered that aberrant expression of CDK5 contributes to the oncogenic initiation and progression of multiple solid and hematological malignancies. CDK5 is also implicated in the regulation of cancer stem cell biology. In this review, we present the current state of knowledge of CDK5 as a druggable target for cancer treatment. We also provide a detailed outlook of designing selective and potent inhibitors of this enzyme.
Publisher: Elsevier BV
Date: 02-2004
DOI: 10.1016/S0731-7085(03)00573-9
Abstract: A range of analytical methods exist for the determination of paracetamol in biological fluids. However, to understand the fate of paracetamol and the effect of other drugs on its disposition in vivo, the major metabolites require quantification in urine and plasma. A method to simultaneously quantify paracetamol, paracetamol glucuronide (PG) and paracetamol sulphate (PS) in plasma and urine with superior sensitivity is therefore desired, especially if the volume of plasma available is low. A simple isocratic reverse phase high-performance liquid chromatography (HPLC) assay with spectrophotometric detection has been developed. The method, requiring only 100 microl of plasma and 50 microl of urine, utilizes a reversed-phase C18 column, a wavelength of 254 nm for detection and a mobile phase composed of potassium dihydrogen orthophosphate (0.1 M)-isopropanol-tetrahydrofuran (THF) (100:1.5:0.1, v/v/v) adjusted to pH 3.7 with phosphoric acid. The method is sensitive and linear in plasma within a concentration range from 0.4 to 200 microM for paracetamol, PG and PS. For PG and PS in urine, the method is sensitive and linear within a concentration range from 100 to 20,000 microM. Over these ranges, accuracy and precision were less than 12%. The assay has been used to measure concentrations of paracetamol and the two metabolites in plasma collected by finger-prick s ling and of the metabolites in urine from healthy volunteers administered a single oral dose of 1000 mg of paracetamol.
Publisher: Bentham Science Publishers Ltd.
Date: 10-2006
DOI: 10.2174/138920006778520561
Abstract: L-Carnitine has important roles in intermediary metabolism and patients with end-stage renal disease who are undergoing hemodialysis may develop a secondary L-carnitine deficiency. The extent of accumulation of the metabolites trimethylamine and trimethylamine-N-oxide when L-carnitine is administered orally has not been investigated previously in this population. Oral L-carnitine at a dose of 1 g daily was administered for twelve days to six patients with end-stage renal disease undergoing hemodialysis thrice weekly. Pre-dialysis plasma concentrations of L-carnitine (mean +/- SD) increased significantly (P < 0.05) from day 1 (baseline 32.4 +/- 6.1 microM) to day 8 (66.1 +/- 13.8 microM) remaining constant thereafter. Although plasma levels of trimethylamine remained unaltered, the pre-dialysis plasma concentrations of trimethylamine-N-oxide increased significantly (P < 0.05) from day 1 (289.1 +/- 236.1 microM) to day 12 (529.0 +/- 237.9 microM). The hemodialysis clearances for L-carnitine, trimethylamine and trimethylamine-N-oxide were 14.3 +/- 8.2, 14.1 +/- 10.6 and 12.4 +/- 5.4 L/h, respectively, indicating their efficient removal by dialysis. Oral administration of L-carnitine at a dose of 1 g daily increases plasma concentrations of this substance to physiological levels in patients with end-stage renal disease who are undergoing hemodialysis. However, concerns about the possible deleterious consequences of such a dosage regimen still remain given that plasma concentrations of trimethylamine-N-oxide were continually rising and approximately doubled in a two-week period.
Publisher: American Society for Microbiology
Date: 03-2010
DOI: 10.1128/AAC.01114-09
Abstract: Colistin is increasingly used as last-line therapy against Gram-negative pathogens. The pharmacokinetic (PK) harmacodynamic (PD) index that best correlates with the efficacy of colistin remains undefined. The activity of colistin against three strains of Pseudomonas aeruginosa was studied in neutropenic mouse thigh and lung infection models. The PKs of unbound colistin were determined from single-dose PK studies together with extensive plasma protein binding analyses. Dose-fractionation studies were conducted over 24 h with a dose range of 5 to 160 mg/kg of body weight/day. The bacterial burden in the thigh or lung was measured at 24 h after the initiation of treatment. Relationships between antibacterial effect and measures of exposure to unbound ( f ) colistin (area under the concentration-time curve [ f AUC/MIC], maximum concentration of drug in plasma [ fC max ]/MIC, and the time that the concentration in plasma is greater than the MIC [ fT MIC]) were examined by using an inhibitory sigmoid maximum-effect model. Nonlinearity in the PKs of colistin, including its plasma protein binding, was observed. The PK/PD index that correlated best with its efficacy was f AUC/MIC in both the thigh infection model ( R 2 = 87%) and the lung infection model ( R 2 = 89%). The f AUC/MIC targets required to achieve 1-log and 2-log kill against the three strains were 15.6 to 22.8 and 27.6 to 36.1, respectively, in the thigh infection model, while the corresponding values were 12.2 to 16.7 and 36.9 to 45.9 in the lung infection model. The findings of this in vivo study indicate the importance of achieving adequate time-averaged exposure to colistin. The results will facilitate efforts to define the more rational design of dosage regimens for humans.
Publisher: Impact Journals, LLC
Date: 23-07-2016
Publisher: Future Science Ltd
Date: 2015
DOI: 10.4155/FMC.14.145
Abstract: Pim oncogenes are highly expressed in many types of hematological and solid cancers. Pim kinases regulate the network of signaling pathways that are critical for tumorigenesis and development, making Pim kinases the attractive drug targets. Currently, two approaches have been employed in designing Pim kinase inhibitors: ATP-mimetics and non-ATP mimetics but all target the ATP-binding pocket and are ATP-competitive. In this review, we summarize the current progress in understanding the Pim-related structure and biology, and provide insights into the binding modes of some prototypical Pim-1 inhibitors. The challenges as well as opportunities are highlighted for development of Pim kinase inhibitors as potential anticancer agents.
Publisher: Elsevier BV
Date: 07-11-2006
DOI: 10.1016/J.JCHROMB.2006.06.020
Abstract: The use of perhexiline (PHX) is limited by hepatic and neurological toxicity associated with elevated concentrations in plasma that are the result of polymorphism of the cytochrome P450 2D6 isoform (CYP2D6). PHX is cleared by hepatic oxidation that produces three 4-monohydroxy metabolites: cis-OH-PHX, trans1-OH-PHX and trans2-OH-PHX. The current study describes an HPLC-fluorescent method utilising pre-column derivatization with dansyl chloride. Following derivatization, the metabolites were resolved on a C18 column with a gradient elution using a mobile phase composed of methanol and water. The method described is suitable for the quantification of the metabolites in human plasma and urine following clinical doses and for kinetic studies using human liver microsomes. The method demonstrates sufficient sensitivity, accuracy and precision between 5.0 and 0.01, 50.0 and 0.2 and 1.0 and 0.005 mg/l in human plasma, urine and liver microsomes, respectively, with intra-assay coefficients of variation and bias <15%, except at the lowest limit of quantification (<20%). The inter-assay coefficients of variation and bias were <15%. The application of this method to plasma and urine s les of five CYP2D6 extensive metaboliser (EM) patients at steady state with respect to PHX dosing determined that the mean (+/-S.D.) renal clearances of trans1-OH-PHX and cis-OH-PHX were 1.58+/-0.35 and 0.16+/-0.06l/h, respectively. The mean (+/-S.D.) dose recovered in urine as free and glucuronidated 4-monohydroxy PHX metabolites was 20.6+/-11.6%.
Publisher: Oxford University Press (OUP)
Date: 08-2009
Abstract: This study examined the effects of St John's wort (Hypericum perforatum) on the disposition of fexofenadine, a substrate of P-glycoprotein/organic anion transporting polypeptide, in the isolated perfused rat liver. Male Sprague-Dawley rats were given St John's wort, 1000 mg/kg, by intragastric gavage once daily for 14 days. On day 15, livers were isolated surgically and perfused in a recirculating system with fexofenadine (2 microg/ml), either alone or following addition of ciclosporin (0.5 microg/ml) 5 min before the addition of fexofenadine. Perfusate s les and bile were collected for 60 min. Fexofenadine in perfusate, bile and the homogenised livers was measured by HPLC. Administration of St John's wort significantly increased biliary clearance with respect to perfusate and biliary clearance with respect to the concentration in the liver, by 74% and 71%, respectively. This was reversed by ciclosporin. St John's wort enhanced the elimination of fexofenadine into the bile. This could be because it increases the activity of P-glycoprotein on the canalicular membrane of hepatocytes.
Publisher: Informa UK Limited
Date: 22-07-2014
DOI: 10.3109/00498254.2014.942721
Abstract: 1. Perhexiline, a chiral anti-anginal agent, may be useful to develop new cardiovascular therapies, despite its potential hepatotoxicity. 2. This study compared Dark Agouti (DA) and Sprague-Dawley (SD) rats, as models of perhexiline's metabolism and hepatotoxicity in humans. Rats (n = 4/group) received vehicle or 200 mg/kg/d of racemic perhexiline maleate for 8 weeks. Plasma and liver s les were collected to determine concentrations of perhexiline and its metabolites, hepatic function and histology. 3. Median (range) plasma and liver perhexiline concentrations in SD rats were 0.09 (0.04-0.13) mg/L and 5.42 (0.92-8.22) ng/mg, respectively. In comparison, DA rats showed higher (p < 0.05) plasma 0.50 (0.16-1.13) mg/L and liver 24.5 (9.40-54.7) ng/mg perhexiline concentrations, respectively, 2.5- and 3.7-fold higher cis-OH-perhexiline concentrations, respectively (p < 0.05), and lower plasma metabolic ratio (0.89 versus 1.55, p < 0.05). In both strains, the (+):(-) enantiomer ratio was 2:1. Perhexiline increased plasma LDH concentrations in DA rats (p < 0.05), but had no effect on plasma biochemistry in SD rats. Liver histology revealed lower glycogen content in perhexiline-treated SD rats (p < 0.05), but no effects on lipid content in either strain. 4. DA rats appeared more similar to humans with respect to plasma perhexiline concentrations, metabolic ratio, enantioselective disposition and biochemical changes suggestive of perhexiline-induced toxicity.
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