Telomere dynamics during hibernation in a tropical primate.

Hibernation is a widespread metabolic strategy among mammals for surviving periods of food scarcity. During hibernation, animals naturally alternate between metabolically depressed torpor bouts and energetically expensive arousals without ill effects. As a result, hibernators are promising models for investigating mechanisms that buffer against cellular stress, including telomere protection and restoration. In non-hibernators, telomeres, the protective structural ends of chromosomes, shorten with age and metabolic stress. In temperate hibernators, however, telomere shortening and elongation can occur in response to changing environmental conditions and associated metabolic state. We investigate telomere dynamics in a tropical hibernating primate, the fat-tailed dwarf lemur (Cheirogaleus medius). In captivity, these lemurs can hibernate when maintained under cold temperatures (11-15 °C) with limited food provisioning. We study telomere dynamics in eight fat-tailed dwarf lemurs at the Duke Lemur Center, USA, from samples collected before, during, and after the hibernation season and assayed via qPCR. Contrary to our predictions, we found that telomeres were maintained or even lengthened during hibernation, but shortened immediately thereafter. During hibernation, telomere lengthening was negatively correlated with time in euthermia. Although preliminary in scope, our findings suggest that there may be a preemptive, compensatory mechanism to maintain telomere integrity in dwarf lemurs during hibernation. Nevertheless, telomere shortening immediately afterward may broadly result in similar outcomes across seasons. Future studies could profitably investigate the mechanisms that offset telomere shortening within and outside of the hibernation season and whether those mechanisms are modulated by energy surplus or crises.

Of fruits and fats: high-sugar diets restore fatty acid profiles in the white adipose tissue of captive dwarf lemurs.

Fat-storing hibernators rely on fatty acids from white adipose tissue (WAT) as an energy source to sustain hibernation. Whereas arctic and temperate hibernators preferentially recruit dietary polyunsaturated fatty acids (PUFAs), tropical hibernators can rely on monounsaturated fatty acids that produce fewer lipid peroxides during oxidation. Nevertheless, compositional data on WAT from tropical hibernators are scant and questions remain regarding fat recruitment and metabolism under different environmental conditions. We analyse fatty acid profiles from the WAT of captive dwarf lemurs (Cheirogaleus medius) subjected to high-sugar or high-fat diets during fattening and cold or warm conditions during hibernation. Dwarf lemurs fed high-sugar (compared to high-fat) diets displayed WAT profiles more comparable to wild lemurs that fatten on fruits and better depleted their fat reserves during hibernation. One PUFA, linoleic acid, remained elevated before hibernation, potentially lingering from the diets provisioned prior to fattening. That dwarf lemurs preferentially recruit the PUFA linoleic acid from diets that are naturally low in availability could explain the discrepancy between captive and wild lemurs' WAT. While demonstrating that minor dietary changes can produce major changes in seasonal fat deposition and depletion, our results highlight the complex role for PUFA metabolism in the ecology of tropical hibernators.

Early Cenozoic Decoupling of Climate and Carbonate Compensation Depth Trends.

Our understanding of the long-term evolution of the Earth system is based on the assumption that terrestrial weathering rates should respond to, and hence help regulate, atmospheric CO2 and climate. Increased terrestrial weathering requires increased carbonate accumulation in marine sediments, which in turn is expected to result in a long-term deepening of the carbonate compensation depth (CCD). Here, we critically assess this long-term relationship between climate and carbon cycling. We generate a record of marine deep-sea carbonate abundance from selected late Paleocene through early Eocene time slices to reconstruct the position of the CCD. Although our data set allows for a modest CCD deepening, we find no statistically significant change in the CCD despite >3 °C global warming, highlighting the need for additional deep-sea constraints on carbonate accumulation. Using an Earth system model, we show that the impact of warming and increased weathering on the CCD can be obscured by the opposing influences of ocean circulation patterns and sedimentary respiration of organic matter. From our data synthesis and modeling, we suggest that observations of warming, declining δ13C and a relatively stable CCD can be broadly reproduced by mid-Paleogene increases in volcanic CO2 outgassing and weathering. However, remaining data-model discrepancies hint at missing processes in our model, most likely involving the preservation and burial of organic carbon. Our finding of a decoupling between the CCD and global marine carbonate burial rates means that considerable care is needed in attempting to use the CCD to directly gauge global carbonate burial rates and hence weathering rates.

Amoscanate as a topically applied chemical for prophylaxis against Schistosoma mansoni infections in mice.

Amoscanate (0.1% w/v) in methanol solution applied to skin by tail immersion 1 day prior to cercarial exposure provided mice with better than 90% protection against mature Schistosoma mansoni infections. Cercariae penetrated and schistosomula migrated from treated skins as readily as in control skins. Lung incubation assays, however, indicated that day 7 lung worm burdens were only about half those of control values. By day 20, worm burdens were reduced further to approximately 15% of those for control mice. The delayed prophylactic activity was apparently not due to percutaneously absorbed compound. Wipe application of amoscanate to the skin was nearly as effective as immersion.