ORCID Profile
0000-0003-2067-3088
Current Organisation
Royal Holloway University of London
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Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-1997
DOI: 10.1097/00007890-199706270-00015
Abstract: Myoblast transplantation (MT) is a potential approach for gene transfer into skeletal muscle, the efficiency of which depends upon the number of copies of donor genome incorporated into the host tissue. We have developed a system for quantitative studies of MT that measures amounts of donor-derived genome in host muscles and estimates the contributions of donor cell survival and proliferation in vivo. [14C]thymidine-labeled, male myoblasts were transplanted into female muscles, providing two donor cell markers, Y chromosome and [14C]. The markers were measured in muscle extracts by slot blotting and scintillation counting, respectively. In each extract, the amount of Y chromosome was used to quantify donor-derived genome, whereas the radiolabel provided an estimate of cell survival. Furthermore, the different modes of inheritance of the markers meant that proliferation of surviving donor cells was detected as a change in marker ratio. This system provides a method for assessing potential improvements of MT.
Publisher: California Digital Library (CDL)
Date: 03-05-2023
DOI: 10.32942/X2FG6R
Abstract: 1. Reproductive performance in birds can be affected by both social environment and small-scale environmental heterogeneity via food abundance, availability of nesting sites, and predation risk. However, to date, the best studies of effects of microhabitat variation on avian populations have been on northern hemisphere passerines using nestboxes, where birds have limited control over nest sites and have a comparatively simple social structure. 2. Here we utilise a multi-decade dataset on the superb fairy-wren, Malurus cyaneus, a southern hemisphere passerine with facultative cooperative breeding. We monitored territory characteristics, nest locations and breeding success, and used GIS to relate these to social organisation and a survey of vegetation characteristics throughout the study area.3. There was a long-term nearly two-fold decline in population density over the study period (1994-2015). This was associated with a corresponding decline in the mean number of helpers per group, and hence in the extent of cooperative breeding: in the first four years of the study (1994-1997), 56% of groups had at least one helper, but in the final four years (2012-2015), this was reduced to 28%. Mean territory size also increased (from 0.74ha in the first four years to 1ha in the final four years) such that on average, years with lower numbers of helpers per territory had larger territory sizes. However, helper number was positively correlated with territory size within years.4. Reproductive performance was related to microhabitat heterogeneity: fledgling production was lower and nest predation higher in territories with dense midstorey vegetation, possibly because avian predators using visual information to detect nests can conceal themselves from nesting birds. Predation during the nesting phase decreased over time, indicating that the population decline was not driven by increased predation.5. The causes of overall population decline remain to be determined, however our analyses have uncovered both microspatial patterns in nesting behaviour of birds, and temporal changes in population density and social group dynamics. From a methodological perspective, the study demonstrates the utility of GIS methods for investigating fine-scale habitat dynamics over time.
Publisher: Rockefeller University Press
Date: 13-05-2002
Abstract: Environmental influences have profound yet reversible effects on the behavior of resident cells. Earlier data have indicated that the amount of muscle formed from implanted myogenic cells is greatly augmented by prior irradiation (18 Gy) of the host mouse muscle. Here we confirm this phenomenon, showing that it varies between host mouse strains. However, it is unclear whether it is due to secretion of proliferative factors or reduction of antiproliferative agents. To investigate this further, we have exploited the observation that the immortal myogenic C2 C12 cell line forms tumors far more rapidly in irradiated than in nonirradiated host muscle. We show that the effect of preirradiation on tumor formation is persistent and dose dependent. However, C2 C12 cells are not irreversibly compelled to form undifferentiated tumor cells by the irradiated muscle environment and are still capable of forming large amounts of muscle when reimplanted into a nonirradiated muscle. In a clonal analysis of this effect, we discovered that C2 C12 cells have a bimodal propensity to form tumors some clones form no tumors even after extensive periods in irradiated graft sites, whereas others rapidly form extensive tumors. This illustrates the subtle interplay between the phenotype of implanted cells and the factors in the muscle environment.
Publisher: Elsevier BV
Date: 04-1994
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Jonathan Beauchamp.