ORCID Profile
0000-0002-7209-2915
Current Organisation
University of Adelaide
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: The Company of Biologists
Date: 15-08-2021
DOI: 10.1242/JEB.242597
Abstract: The metabolic rate of vertebrate bone tissue is related to bone growth, repair and homeostasis, which are all dependent on life stage. Bone metabolic rate is difficult to measure directly, but absolute blood flow rate () should reflect local tissue oxygen requirements. A recent ‘foramen technique’ has derived an index of blood flow rate () by measuring nutrient foramen sizes of long bones. is assumed to be proportional to however, the assumption has never been tested. This study used fluorescent microsphere infusion to measure femoral bone in anaesthetized non-laying hens, laying hens and roosters. Mean mass-specific cardiac output was 338±38 ml min−1 kg−1, and the two femora received 0.63±0.10% of this. Laying hens had higher wet bone mass-specific to femora (0.23±0.09 ml min−1 g−1) than the non-laying hens (0.12±0.06 ml min−1 g−1) and roosters (0.14±0.04 ml min−1 g−1), presumably associated with higher bone calcium mobilization during eggshell production. Estimated metabolic rate of femoral bone was 0.019 ml O2 min−1 g−1. Femoral increased significantly with body mass, but was not correlated with nutrient foramen radius (r), probably because of a narrow range in foramen radius. Over all 18 chickens, femoral shaft was 1.07±0.30 ml min−1 mm−1. Mean in chickens was significantly higher than predicted by an allometric relationship for adult cursorial bird species, possibly because the birds were still growing.
Publisher: Wiley
Date: 12-11-2020
DOI: 10.1111/JOA.13106
Publisher: The Royal Society
Date: 13-11-2019
Abstract: Brain metabolic rate (MR) is linked mainly to the cost of synaptic activity, so may be a better correlate of cognitive ability than brain size alone. Among primates, the sizes of arterial foramina in recent and fossil skulls can be used to evaluate brain blood flow rate, which is proportional to brain MR. We use this approach to calculate flow rate in the internal carotid arteries ( Q ˙ ICA ) , which supply most of the primate cerebrum. Q ˙ ICA is up to two times higher in recent gorillas, chimpanzees and orangutans compared with 3-million-year-old australopithecine human relatives, which had equal or larger brains. The scaling relationships between Q ˙ ICA and brain volume ( V br ) show exponents of 1.03 across 44 species of living haplorhine primates and 1.41 across 12 species of fossil hominins. Thus, the evolutionary trajectory for brain perfusion is much steeper among ancestral hominins than would be predicted from living primates. Between 4.4-million-year-old Ardipithecus and Homo sapiens , V br increased 4.7-fold, but Q ˙ ICA increased 9.3-fold, indicating an approximate doubling of metabolic intensity of brain tissue. By contrast, Q ˙ ICA is proportional to V br among haplorhine primates, suggesting a constant volume-specific brain MR.
Publisher: Wiley
Date: 17-08-2022
DOI: 10.1111/JOA.13535
Abstract: If arteries penetrate bones through foramina, regional artery blood flow rates can be estimated from the foramen sizes. Femoral bone blood flow rates estimated from nutrient foramen sizes were previously not absolute, but only a relative blood flow index ( Q i ), because the size relationship between the foramen and the occupying artery was unknown. The current study used vascular contrast and micro‐computerized tomographic scanning to investigate femoral nutrient foramen and nutrient artery sizes in three groups of sub‐adult chickens (non‐laying hens, laying hens, and roosters) of similar ages. The results indicate that the cross‐sectional area of the nutrient artery lumen occupies approximately 20.2 ± 4.1% of the foramen for femora with only one foramen. Artery lumen size is significantly correlated with foramen size. Vascular contrast imaging is capable of estimating blood flow rates through nutrient arteries, as blood flow rates estimated from artery lumen casts are similar to blood flow rates measured by infusion of fluorescent‐labeled microspheres. Laying hens tend to have higher nutrient artery perfusion rates than non‐laying hens, probably due to extra oxygen and calcium requirements for eggshell production, although the calculated blood flow difference was not statistically significant. Histological embedding and sectioning along with vascular contrast imaging reveal variable nutrient foramen morphology and nutrient artery location among femora with more than one nutrient foramen.
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.168625
Abstract: The nutrient artery passes through the nutrient foramen on the shaft of the femur and supplies more than one-half of total blood flow to the bone. Assuming that the size of the nutrient foramen correlates with the size of the nutrient artery, an index of blood flow rate (Qi) can be calculated from nutrient foramen dimensions. Interspecific Qi is proportional to locomotor activity levels in adult mammals, birds and reptiles. However, no studies have yet estimated intraspecific Qi to test for the effects of growth and locomotor development on bone blood flow requirements. This study uses micro-CT and medical CT scanning to measure femoral dimensions and foramen radius to calculate femoral Qi across in-pouch and post-pouch life stages of western grey kangaroos Macropus fuliginosus weighing 5.7 g to 70.5 kg and representing a 12,350-fold range in body mass. A biphasic scaling relationship for Qi on body mass is evident (breakpoint at ca. 1–5 kg body mass right before permanent pouch exit), with a steep exponent of 0.96±0.09 (95% CI) across the in-pouch life stage and an exponent of –0.59±0.90 across the post-pouch life stage. In-pouch joeys show Qi values 50 to 100-times higher than adult diprotodont marsupials of the same body mass, but gradually converge with them as post-pouch adults. Bone modelling during growth appears to be the main determinant for femoral bone blood flow during in-pouch development, whereas bone remodeling for micro-fracture repair due to locomotion gradually becomes the main determinant when kangaroos leave the pouch and become more active.
No related grants have been discovered for Thomas Nelson.