Rw Rose

Nonshivering Thermogenesis in a Marsupial (the Tasmanian Bettong Bettongia gaimardi ) Is Not Attributable to Brown Adipose Tissue

The Tasmanian bettong (Bettongia gaimardi, a marsupial) is a rat‐kangaroo that increases nonshivering thermogenesis (NST) in response to norepinephrine (NE). This study attempted to assess whether brown adipose tissue (BAT), a specialized thermogenic effector, is involved in NST in the bettong. Regulatory NST, indicated by resting oxygen consumption (Vo2) of the whole body, was measured under conscious conditions at 20°C with various stimuli: cold (4°–5°C) or warm (25°C) acclimation, NE injection, and the β3‐adrenoceptor agonist (BRL) 37344. In line with the functional studies in vivo, the presence of BAT was evaluated by examining the expression of the uncoupling protein 1 (UCP1) with both rat cDNA and oligonucleotide probes. Both NE and BRL 37344 significantly stimulated NST in the bettong. After cold acclimation of the animals (at 4°–5°C for 2 wk), the resting Vo2 was increased by 15% and the thermogenic effect of NE was enhanced; warm‐acclimated animals showed a slightly depressed response. However, no expression of UCP1 was detected in bettongs either before or after cold exposure (2 wk). These data suggest that the observed NST in the marsupial bettong is not attributable to BAT.

Non-shivering thermogenesis in a carnivorous marsupial, Sarcophilus harrisii, in the absence of UCP1

Abstract The presence of, and the physiological mechanisms behind, non-shivering thermogenesis (NST) were investigated in the Tasmanian Devil (Sarcophilus harrisii, Boitard 1841). This was performed by measuring metabolic rate in response to cold exposure with and without an injection of norepinephrine. We also attempted to identify the presence of uncoupling protein 1 (UCP1) and its involvement (if any) in NST in S. harrisii, prior to and after cold exposure. UCP1 is a specialized protein channel found within the mitochondria of brown adipose tissue that is known to be involved in eutherian NST. Increase in resting oxygen consumption (VO2), were measured under constant conditions at 20°C after various stimuli; long-term cold exposure (14 days at 2–3°C), and with or without subsequent norepinephrine injection was used to indicate the presence of NST. Concurrent with the functional studies, molecular level studies including Western blots and RT-PCR were used to identify the expression of UCP1. We found that injection of norepinephrine significantly increased NST after cold exposure in S. harrisii. The post-acclimation resting (VO2) increased by 11%, whereas the combination of cold exposure and injection of NE elicited an approximately 30% increase in metabolic rate. However, expression of UCP1 in S. harrisii was not identified by the molecular techniques employed, in either the pre- or post-cold-acclimated tissues. These data suggest that S. harrisii shows NST ability and that it is accomplished in the absence of UCP1.

Molecular identification of uncoupling proteins (UCP2 and UCP3) and absence of UCP1 in the marsupial Tasmanian bettong, Bettongia gaimardi.

This study has identified the expression of uncoupling proteins in a marsupial using molecular techniques. The Tasmanian bettong, Bettongia gaimardi, increases non-shivering thermogenesis (NST) in response to cold exposure and norepinephrine, although previous studies have been unable to demonstrate the presence of brown adipose tissue or uncoupling protein 1 (UCP1). This study used molecular techniques to confirm the absence of UCP1 as well as ascertain if this species expresses UCP2 and/or UCP3. Tissue samples from four B. gaimardi were taken prior to and post-cold exposure at 4-5 degrees C for 2 weeks. The tissues were then examined for UCP1, UCP2 and UCP3 expression using Western blotting. UCP2 and UCP3 were amplified through RT-PCR and subsequently sequenced to confirm molecular identity. Our work confirms that B. gaimardi does not express UCP1 and that this species expresses both uncoupling proteins 2 and 3. The sequencing of the amplified B. gaimardi UCP2 and UCP3 cDNAs have revealed a 74% homology with rat UCP2 cDNA, and 65% homology with rat UCP3 cDNA. Although this work has not yet characterised the functional properties of these proteins in the marsupial, it does suggest a possible mechanism to explain the existence of NST in B. gaimardi.

Comparative lactation in two species of rat-kangaroo (Marsupialia)

1. Milk composition and energy content was measured in two related marsupials, Bettongia gaimardi and Potorous tridactylus. 2. Although protein content was consistently higher in bettong milk, lactational trends in both species are similar to those reported for other marsupials. 3. The faster relative growth rate of the bettong may be correlated with the increased protein and a higher milk intake.

Body temperature: Rhythm and regulation in the tasmanian bettong (Bettongia gaimardi) (Marsupialia: Potoroidae)

1. 1. Body temperatures were determined by radio-telemetry in four male Tasmanian bettongs (Bettongia gaimardi) maintained for 72 hr at 20°C followed by 10 days in an outdoor enclosure. 2. 2. In both conditions Tb showed a diurnal rhythm in which Tmax coincided with greatest activity around midnight and tbasal (36.6°C) in laboratory animals) with sleep/rest around mid-day. 3. 3. Tbasal showed little variation between ambient temperatures of 5–30°C but increased at extremes on either side of this range; at 40°C Tbasal remained stable but at − 10°C continuous activity led to variable Tbasal.

Does the devil sweat

Abstract 1. The cutaneous water loss, respiratory rate and rectal temperature of the Tasmanian devil (Sarcophilus harrisi) was measured before and during heat stress. 2. There was a sevenfold increase in respiratory rate under heat stress indicating panting, whilst cutaneous water loss increased by only 50 per cent and remained below levels considered indicative of thermal sweating. 3. No marsupials are now known to use sweating as a thermoregulatory response when at rest. This response appears to be restricted to the primates and some ungulates.

Molecular Identification of Uncoupling Proteins 2 and 3 in a Carnivorous Marsupial, the Tasmanian Devil ( Sarcophilus harrisii )

This study investigated the expression of uncoupling proteins 2 and 3 (UCP2 and UCP3) in the carnivorous marsupial Sarcophilus harrisii. The current study used molecular techniques to ascertain whether this species expresses UCP2 and/or UCP3. This species increases nonshivering thermogenesis in response to cold exposure and norepinephrine, although our previous study was unable to demonstrate the presence of brown adipose tissue or uncoupling protein 1. Samples of skeletal muscle and white adipose tissues were taken from five S. harrisii pre– and post–cold acclimation (2°–3°C for 2 wk). The tissues were examined for UCP2 and UCP3 expression through Western blots and reverse transcriptase polymerase chain reaction, with subsequent sequencing to ensure identification of the desired gene. These data suggest that S. harrisii expresses UCP2 but not UCP3. The sequencing of the amplified S. harrisii UCP2 cDNA has revealed a 76% homology with human UCP2 cDNA and a 72% homology with rat UCP2 cDNA. The expression of UCP2 but not UCP3 suggests that UCP2 is conserved from a common ancestor to both the Marsupialia and the Eutheria taxa.

Milk composition and growth in the southern brown bandicoot, Isoodon obesulus (Marsupialia:Peramelidae)

Milk and growth data from six litters of southern brown bandicoots (Isoodon obesulus) from south-eastern Tasmania were analysed. Five of these were born in the wild and one was born in captivity. The quantitative changes in milk composition were examined for total protein, carbohydrates (hexose and lactose), lipid, dissolved solids, and estimated energy content. During ‘early-phase’ lactation (before Day 30) protein levels were 10.5 g (100 mL)–1, hexose 0.34 g (100 mL)–1, lipids 10.4 g (100 mL)–1, and solids 27.3 g (100 mL)–1. ‘Mid-phase’ milk (Days 31–45) showed an increase in all constituents: protein 13.8 g (100 mL)–1, hexose 1.66 g (100 mL)–1, lipid 12.2 g (100 mL)–1, and solids 41.4 g (100 mL)–1. Protein and hexose levels decreased in ‘late-phase’ milk (Day 46–60) to 11.3 g (100 mL)–1, and 1.58 g (100 mL)–1, respectively, and the amount of lipids and dissolved solids increased to 26.4 g (100 mL)–1, and 52.3 g (100 mL)–1, respectively. There was no evidence of lactose in milk from the latter half (final 28 days) of lactation. Total milk energy increased from 6.0kJmL–1 in early-phase milk, to 8.9 kJ mL–1 in mid-phase, and 12.0 kJ ml–1 in late-phase. Changes in body mass, head, tail, and pes lengths were examined for 16 pouch young. Instantaneous relative growth rates were calculated for the final 42 days of lactation, revealing a decrease in overall growth rates from 14.0% increase in bodyweight per day in early-phase, to 7.8% daily during mid-phase, and 3.5% daily increase during late-phase lactation. Analysis of the relationship between milk and growth in I. obesulus demonstrates that morphological and developmental changes, especially the development of endothermy and time of first pouch exit, directly correlate with changes in growth rates, milk energy, and milk composition.

The Development of Endothermy during Pouch Life in the Eastern Barred Bandicoot (Perameles gunnii), a Marsupial

Marsupials are born ectothermic and gradually become endothermic during pouch occupancy. In order to study the timing of this transition, we measured the metabolic rates of eight pouch‐young eastern barred bandicoots (Perameles gunnii) at 25°C (the thermoneutral zone of adults), at 35°C (pouch temperature), and after injection with norepinephrine. From 5 to 7 wk of age, oxygen consumption (V̇o2) was higher at 35°C than at 25°C. At 8 wk, V̇o2 was significantly higher at 25°C than at 35°C. Norepinephrine administration at 5 and 6 wk had no effect on metabolic rate, but at 8 wk, near pouch vacation, it resulted in a significant increase in metabolic rate. Our results indicate that signs of thermoregulation for P. gunnii begin at 7 wk, and at 8 wk the species is endothermic, that is, able to increase heat production in response to both cold and norepinephrine. The appearance of fur, first seen at the age of 6 wk and fully developed at 8 wk, coincides with the onset of endothermy.

Precopulatory and mating behaviour in the tasmanian bettongBettongia gaimardi desmarest (Marsupialia: Potoroidae)

Intersexual interactions in Tasmanian bettongs (Bettongia gaimardi) were observed in dyadic combinations. Several behaviours were associated with agonistic confrontations and occurred in predictable response sequences. There was no evidence of a consort period between males and pre-oestrous females. Overt sexual interactions occurred only on the night of oestrus, coincidentally with the maintenance of close spatial proximity. During copulation, multiple intromissions were regularly achieved but the intervals between successive bouts of these acts generally increased. Males were also observed to engage in regular attempts at social (urogenital) investigation and were apparently able to detect the reproductive state of all resident females, presumably utilising olfactory cues. The brevity of sexual interactions occurring between individuals contrasts with the more complex repertoire of the gregarious large macropodoid marsupials.