Phenotypic flexibility of various morphological and physiological characters is widespread in animals. Resident endothermic animals of temperate climates provide a natural experiment in phenotypic flexibility. In this study, we took an integrative approach to assess seasonal and geographic influences on metabolism in Eurasian tree sparrows (Passer montanus). We measured resting metabolic rate (RMR), masses of internal organs, mitochondrial respiration capacities in liver and muscle, cytochrome C oxidase (COX) activities in liver and muscle, and circulating levels of plasma triiodothyronine (T3) and thyroxine (T4) in summer and winter sparrows at two sites from southeastern (Wenzhou) and northeastern (Qiqihar) China that differ in climate. Body masses of tree sparrows were significantly higher in winter than in summer at both sites but did not differ with latitude. RMRs of tree sparrows varied significantly with both latitude and season, with RMRs of Qiqihar birds being higher than those of Wenzhou birds and with RMRs being higher in winter than in summer. Consistently, dry masses of brain, lung, liver, gizzard, small intestine, rectum, and total digestive tract varied significantly with either latitude or season. State 4 respiration and COX activity in liver and muscle were remarkably higher in Qiqihar and increased significantly in winter. Circulating levels of plasma T3 also showed significant seasonal and latitudinal variation and was higher in Qiqihar in winter than in other groups. These data suggest that tree sparrows mainly coped with cold by enhancing thermogenic capacities through heightened activity of respiratory enzymes and higher levels of plasma thyroid hormones (T3). These results are consistent with a pronounced seasonal and latitudinal phenotypic flexibility mediated through physiological and biochemical adjustments in Eurasian tree sparrows.

Expectations of increases in human population growth and accelerated habitat loss, along with the realization that efforts to provide protection for ecosystems that sustain primates have met with limited success, make it critical that conservation plans are grounded firmly in scientific observation. Studies of the diet breadth and feeding behavior of endangered species, therefore, are critical for understanding ecological adaptations and developing a conservation strategy. The diet and feeding ecology of gray snub-nosed monkeys (Rhinopithecus brelichi) were studied in the Fanjingshan National Nature Reserve, Guizhou, China. The monkeys were found to consume 107 different species of trees, shrubs, and ground plants from 58 genera and 28 families. Food items included young leaves, mature leaves, flowers, fruits/seeds, buds, and insects. Among these food items, there were at least 13 evergreen species of tree and liana, 3 species of grasses, and at least 2 kinds of invertebrates collected from decayed wood. Diet varied markedly throughout different seasons. Overall, diet composition (based on feeding records) was 15.3% buds, 25.5% young leaves, 21.8% mature leaves, 9.4% flowers, 21.6% fruits/seeds, and 6.3% other items. The monkeys feed mainly on young leaves and flowers in spring, unripe fruits/seeds and young leaves in summer, ripe fruits/seeds in autumn, and mature leaves and buds in winter. We propose that when inhabiting forests of lower elevation and greater vegetation complexity, R. brelichi is characterized by expanded diet breadth and includes a greater diversity of food types and plant species in its diet. One food type that appears critical to the diet of this species, especially during the winter, are the buds of Magnolia sprengeri. To protect this resource we advocate working with local communities to limit the collection of M. sprengeri, which is used in traditional Chinese medicine and has high economic value for people in the reserve.

The APOBEC3 family of DNA cytosine deaminases functions to block the spread of endogenous retroelements and retroviruses including HIV-1. Potency varies among family members depending on the type of parasitic substrate. APOBEC3A (A3A) is unique among the human enzymes in that it is expressed predominantly in myeloid lineage cell types, it is strongly induced by innate immune agonists such as type 1 interferon, and it has the capacity to accommodate both normal and 5-methyl cytosine nucleobases. Here we apply atomic force microscopy (AFM) to characterize the interaction between A3A and single- and double-stranded DNA using a hybrid DNA approach in which a single-stranded region is flanked by defined length duplexes. AFM image analyses reveal A3A binding to single-stranded DNA, and that this interaction becomes most evident (∼80% complex yield) at high protein-to-DNA ratios (at least 100∶1). A3A is predominantly monomeric when bound to single-stranded DNA, and it is also monomeric in solution at concentrations as high as 50 nM. These properties agree well with recent, biochemical, biophysical, and structural studies. However, these characteristics contrast with those of the related enzyme APOBEC3G, which in similar assays can exist as a monomer but tends to form oligomers in a concentration-dependent manner. These AFM data indicate that A3A has intrinsic biophysical differences that distinguish it from APOBEC3G. The potential relationships between these properties and biological functions in innate immunity are discussed.

No abstract