The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were... more The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were measured daily after each had been initiated by the removal of pouch young. Progesterone levels ranged from 0·6 ng/ml in the early stages of the oestrous cycle to about 2·5 ng/ml at the peak of the luteal phase. There was no significant difference between pregnant and non-pregnant states before the removal of the pouch young nor in the latter half of the cycle. However, the plasma progesterone concentration on days 3–4 after removal of the pouch young was significantly greater in pregnant animals when compared with nonpregnant animals at the same stage and also when compared with the levels before removal of young. This early peak in the concentration of progesterone in peripheral plasma is discussed in relation to the development of the previously dormant blastocyst.
Prolonged drought, necessitating conservation of water, is one of the major environmental challen... more Prolonged drought, necessitating conservation of water, is one of the major environmental challenges faced by many Australian marsupials. Radioactive isotopes of water and sodium were used to assess the ability of two species of marsupial wallabies to maintain water and electrolyte balance during periods of extreme water deprivation in the arid Pilbara region of Western Australia. The spectacled hare-wallaby, Lagorchestes conspicillatus, has the lowest mass-specific rate of water turnover at 27.5 ml.kg(-0.82).day(-1) yet reported for any mammal and was two to three orders of magnitude lower than that of the Rothschild's rock-wallaby, Petrogale rothschildi. Studies of renal function show that the hare-wallaby conserves water by producing a highly concentrated urine under the influence of lysine vasopressin (LVP), the anti-diuretic hormone (ADH) in macropodid marsupials. In contrast, rock-wallabies show unusual renal responses to water deprivation, with no change in LVP levels and a limited response to water deprivation involving a reduction in renal plasma flow and glomerular filtration rate, with no significant change in tubular function. Both species are able to maintain water and electrolyte homeostasis during periods of drought, highlighting the efficacy of their differing adaptive solutions to the problem of water scarcity, although the hare-wallaby is superior to the rock-wallaby in this respect. Rock-wallabies appear to rely primarily on behavioural rather than physiological responses for their survival in the Pilbara and appear to be more vulnerable to extinction in the event of significant habitat modification. The secure nature of their rock habitat, however, means that they have suffered less than hare-wallabies in the recent past.
Journal of Comparative Physiology B Biochemical Systemic and Environmental Physiology, 2009
Rates of protein turnover and synthesis were measured in wild-caught Honey possums (Tarsipes rost... more Rates of protein turnover and synthesis were measured in wild-caught Honey possums (Tarsipes rostratus) in the southwest of Western Australia and compared between males and females with and without pouch young. Possums were injected with 50 μg of 15N-glycine and ammonia collected within 24 h was used as the nitrogen end-product in a single-injection protocol. The overall mean rate of protein synthesis
The first measurements of AVT-sensitive adenylate cyclase activity in specific segments of the ne... more The first measurements of AVT-sensitive adenylate cyclase activity in specific segments of the nephron of the Australian arid-zone agamid lizard,Ctenophorus(=Amphibolurus)ornatus,are reported. All sections of the collecting-duct system of this lizard were found to be sensitive to AVT at a concentration of 1 × 10−6M. In addition, receptors to AVT were located in the thin–intermediate segment linking proximal and distal convoluted tubules. No significant response to AVT was detected in the glomeruli, in either proximal or distal convoluted tubules, or in the ureter. The physiological significance of these particular segments is discussed in terms of the action of AVT in stimulating water and salt reabsorption in the lizard kidney.
The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were... more The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were measured daily after each had been initiated by the removal of pouch young. Progesterone levels ranged from 0·6 ng/ml in the early stages of the oestrous cycle to about 2·5 ng/ml at the peak of the luteal phase. There was no significant difference between pregnant and non-pregnant states before the removal of the pouch young nor in the latter half of the cycle. However, the plasma progesterone concentration on days 3–4 after removal of the pouch young was significantly greater in pregnant animals when compared with nonpregnant animals at the same stage and also when compared with the levels before removal of young. This early peak in the concentration of progesterone in peripheral plasma is discussed in relation to the development of the previously dormant blastocyst.
Prolonged drought, necessitating conservation of water, is one of the major environmental challen... more Prolonged drought, necessitating conservation of water, is one of the major environmental challenges faced by many Australian marsupials. Radioactive isotopes of water and sodium were used to assess the ability of two species of marsupial wallabies to maintain water and electrolyte balance during periods of extreme water deprivation in the arid Pilbara region of Western Australia. The spectacled hare-wallaby, Lagorchestes conspicillatus, has the lowest mass-specific rate of water turnover at 27.5 ml.kg(-0.82).day(-1) yet reported for any mammal and was two to three orders of magnitude lower than that of the Rothschild's rock-wallaby, Petrogale rothschildi. Studies of renal function show that the hare-wallaby conserves water by producing a highly concentrated urine under the influence of lysine vasopressin (LVP), the anti-diuretic hormone (ADH) in macropodid marsupials. In contrast, rock-wallabies show unusual renal responses to water deprivation, with no change in LVP levels and a limited response to water deprivation involving a reduction in renal plasma flow and glomerular filtration rate, with no significant change in tubular function. Both species are able to maintain water and electrolyte homeostasis during periods of drought, highlighting the efficacy of their differing adaptive solutions to the problem of water scarcity, although the hare-wallaby is superior to the rock-wallaby in this respect. Rock-wallabies appear to rely primarily on behavioural rather than physiological responses for their survival in the Pilbara and appear to be more vulnerable to extinction in the event of significant habitat modification. The secure nature of their rock habitat, however, means that they have suffered less than hare-wallabies in the recent past.
Journal of Comparative Physiology B Biochemical Systemic and Environmental Physiology, 2009
Rates of protein turnover and synthesis were measured in wild-caught Honey possums (Tarsipes rost... more Rates of protein turnover and synthesis were measured in wild-caught Honey possums (Tarsipes rostratus) in the southwest of Western Australia and compared between males and females with and without pouch young. Possums were injected with 50 μg of 15N-glycine and ammonia collected within 24 h was used as the nitrogen end-product in a single-injection protocol. The overall mean rate of protein synthesis
The first measurements of AVT-sensitive adenylate cyclase activity in specific segments of the ne... more The first measurements of AVT-sensitive adenylate cyclase activity in specific segments of the nephron of the Australian arid-zone agamid lizard,Ctenophorus(=Amphibolurus)ornatus,are reported. All sections of the collecting-duct system of this lizard were found to be sensitive to AVT at a concentration of 1 × 10−6M. In addition, receptors to AVT were located in the thin–intermediate segment linking proximal and distal convoluted tubules. No significant response to AVT was detected in the glomeruli, in either proximal or distal convoluted tubules, or in the ureter. The physiological significance of these particular segments is discussed in terms of the action of AVT in stimulating water and salt reabsorption in the lizard kidney.
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