Biological Sciences
http://hdl.handle.net/10464/5988
2024-03-28T10:30:18ZBearded dragons (Pogona vitticeps) with reduced scalation lose water faster but do not have substantially different thermal preferences.
http://hdl.handle.net/10464/17145
Bearded dragons (Pogona vitticeps) with reduced scalation lose water faster but do not have substantially different thermal preferences.
Sakich, Nicholas B; Tattersall, Glenn J
Whether scales reduce cutaneous evaporative water loss in lepidosaur reptiles (Superorder Lepidosauria) such as lizards and snakes has been a contentious issue for nearly half a century. Furthermore, while many studies have looked at whether dehydration affects thermal preference in lepidosaurs, far fewer have examined whether normally hydrated lepidosaurs can assess their instantaneous rate of evaporative water loss and adjust their thermal preference to compensate in an adaptive manner. We tested both of these hypotheses using three captive-bred phenotypes of bearded dragon (Pogona vitticeps) sourced from the pet trade: ‘Wild Types’ with normal scalation, ‘Leatherbacks’ exhibiting scales of reduced prominence, and scaleless bearded dragons referred to as ‘Silkbacks’. Silkbacks on average lost water evaporatively at about twice the rate that Wild Types did. Leatherbacks on average were closer in their rates of evaporative water loss to Silkbacks than they were to Wild Types. Additionally, very small (at most ~1°C) differences in thermal preference existed between the three phenotypes that were not statistically significant. This suggests a lack of plasticity in thermal preference in response to an increase in rate of evaporative water loss, and may be reflective of a thermal ‘strategy’ as employed by thermoregulating bearded dragons that prioritises immediate thermal benefits over the threat of future dehydration. The results of this study bolster an often-discounted hypothesis regarding the present adaptive function of scales and have implications for the applied fields of animal welfare and conservation.
2021-06-17T00:00:00ZCulture of Cancer Cells at Physiological Oxygen Levels Affects Gene Expression in a Cell-Type Specific Manner
http://hdl.handle.net/10464/17039
Culture of Cancer Cells at Physiological Oxygen Levels Affects Gene Expression in a Cell-Type Specific Manner
Alva, Ricardo; Moradi, Fereshteh; Liang, Ping; Stuart, Jeffrey A.
Standard cell culture is routinely performed at supraphysiological oxygen levels (~18% O2). Conversely, O2 levels in most mammalian tissues range from 1–6% (physioxia). Such hyperoxic conditions in cell culture can alter reactive oxygen species (ROS) production, metabolism, mitochondrial networks, and response to drugs and hormones. The aim of this study was to investigate the transcriptional response to different O2 levels and determine whether it is similar across cell lines, or cell line-specific. Using RNA-seq, we performed differential gene expression and functional enrichment analyses in four human cancer cell lines, LNCaP, Huh-7, PC-3, and SH-SY5Y cultured at either 5% or 18% O2 for 14 days. We found that O2 levels affected transcript abundance of thousands of genes, with the affected genes having little overlap between cell lines. Functional enrichment analysis also revealed different processes and pathways being affected by O2 in each cell line. Interestingly, most of the top differentially expressed genes are involved in cancer biology, which highlights the importance of O2 levels in cancer cell research. Further, we observed several hypoxia-inducible factor (HIF) targets, HIF-2α targets particularly, upregulated at 5% O2, consistent with a role for HIFs in physioxia. O2 levels also differentially induced the transcription of mitochondria-encoded genes in most cell lines. Finally, by comparing our transcriptomic data from LNCaP and PC-3 with datasets from the Prostate Cancer Transcriptome Atlas, a correlation between genes upregulated at 5% O2 in LNCaP cells and the in vivo prostate cancer transcriptome was found. We conclude that the transcriptional response to O2 over the range from 5–18% is robust and highly cell-type specific. This latter finding indicates that the effects of O2 levels are difficult to predict and thus highlights the importance of regulating O2 in cell culture.
2022-01-01T00:00:00ZData to accompany manuscript: Thermoconforming rays of the star-nosed mole
http://hdl.handle.net/10464/16980
Data to accompany manuscript: Thermoconforming rays of the star-nosed mole
Tattersall, Glenn; Campbell, Kevin
The star-nosed mole (Condylura cristata) is well known for its unique star-like rostrum (‘star’) which is formed by 22 nasal appendages highly specialised for tactile sensation. As a northerly distributed insectivorous mammal occupying both aquatic and terrestrial habitats, this sensory appendage is regularly exposed to cold water and thermally conductive soil, leading us to ask whether the surface temperature, a proxy for blood flow to the star, conforms to the local ambient temperature to conserve body heat. Alternatively, given the high functioning and sensory nature of the star, we posited it was possible that the rays may be kept continually warm when foraging, with augmented peripheral blood flow serving metabolic needs of this tactile sensory organ. To test these ideas, we remotely monitored the surface temperatures of the star and other uninsulated appendages in response to changes in local water or ground temperature in wild-caught star-nosed moles briefly studied in captive situation. While the tail responded to increasing heat load through vasodilation, the surface temperature of the star consistently thermoconformed, varying passively in surface temperature, suggesting little evidence for thermoregulatory vasomotion. This thermoconforming response may have evolved as a compensatory response related to the high costs of heat dissipation to water or soil in this actively foraging insectivore.
2022-11-18T00:00:00ZDataset to accompany manuscript "Energetic costs of bill heat exchange demonstrate contributions to thermoregulation at high temperatures in toco toucans (Ramphastos toco)"
http://hdl.handle.net/10464/16884
Dataset to accompany manuscript "Energetic costs of bill heat exchange demonstrate contributions to thermoregulation at high temperatures in toco toucans (Ramphastos toco)"
Tattersall, Glenn Jeffery; Chaves, Jussara; Andrade, Denis
Body temperature regulation in the face of changes in ambient temperature and/or in metabolic heat production involves adjustments in heat exchange rates between the animal and the environment. One of those mechanisms include the modulation of the surface temperature of specific areas of the body through vasomotor adjustment and blood flow control, to change the thermal conductance of this region, thereby promoting dissipation or conservation of body heat. In homeotherms, this thermoregulatory adjustment is essential for the maintenance of body temperature over a moderate temperature range, known as the thermal neutral zone (TNZ), without increasing metabolic rate (MR). Thermal windows are poorly insulated body regions and highly vascularized that are particularly efficient for heat dissipation through that mechanism. The bill of the toco toucan (Ramphastos toco) has been described as a highly efficient thermal window and hypothesized to assist in the thermal homeostasis of this bird. Herein, we directly evaluated the contribution of heat exchange through the bill of the toco toucan on thermal homeostasis and metabolic rate and also for the delimitation of the TNZ. To do this, we measured metabolic rate, via oxygen consumption, over a range of ambient temperature from 0 to 35°C (every 5°C). MR measurements were made in birds with the bill intact (control group) and also with the bill artificially insulated (experimental group). The limits of the TNZ, 10.9-25.0°C for the control group and 10.8-24.1°C for the experimental group, did not differ between the treatments. MR differed among treatments only at elevated temperatures (30 and 35°C), reaching values of 0.97 ml O2·g-1·h-1·°C-1 (± 0.06) for the control group and 1.20 ml O2·g-1·h-1·°C-1 (± 0.07) for the experimental group at 35°C. These results indicate that while heat dissipation through the bill does not contribute significantly to widening of the TNZ, it may well be critically important in assisting body temperature regulation at higher temperatures extending above the upper limit of the TNZ. We estimate that the contribution of the bill to total heat exchange approaches 31% of basal metabolic heat production, a not insubstantial amount, providing evidence of the role of peripheral heat exchange and linking the role of appendage size as a key factor in the evolution of thermoregulatory responses in endotherms.
Dataset to accompany manuscript entitled "Energetic costs of bill heat exchange demonstrate contributions to thermoregulation at high temperatures in toco toucans (Ramphastos toco)"
Jussara N. Chaves, Glenn J. Tattersall,, and Denis V. Andrade1
2022-11-03T00:00:00Z