Immunohistochemical localization of androgen receptors in female mole rat (Spalax leucodon) tissues

Androgens exert their effects through androgen receptors (AR) in tissues. We investigated the distribution of AR in female mole rat tissues. Tissues were excised, fixed with 10% formalin and embedded in paraffin. Sections were stained after microwave antigen retrieval for immunohistochemistry. Immunostaining of AR immunostaining was detected in the nucleus or cytoplasm of the cells in the cerebral cortex, cerebellum, anterior pituitary, lung, liver, uterus and skin. Granulosa and some thecal cells in the ovary, cardiac muscle cells and adipose cells exhibited a nuclear reaction for AR. In the kidney, labeling of AR was restricted to the cytoplasm of tubule cells. We found that AR could be detected using immunohistochemistry in the nucleus or cytoplasm or both in the presence of androgens.     

Effect of microhabitat on fitness components of larval tiger salamanders,Ambystoma tigrinum nebulosum

Summary Survivorship and growth of larval tiger salamanders, Ambystoma tigrinum nebulosum, in the White Mountains of east-central Arizona were compared in six microhabitats using field enclosures during summers, 1983–85. Microhabitats were vegetated and nonvegetated shallows, surface, middle, and bottom horizontal layers of limnetic areas, and the vertical limnetic water column. Initial enclosure densities (0.025 larvae per 1) were identical among microhabitats. Three enclosures were placed in each microhabitat in two ponds. Larval survivorship and growth were usually greatest in vegetated shallows in lowest in middle and bottom limnetic enclosures, despite several population dieoffs. Lower fitness, as reflected in survivorship and growth, in these latter enclosures was correlated with lower food levels, temperatures, and oxygen concentrations in deeper limnetic areas. Relative fitness varied greatly between years while food levels, temperatures, and oxygen concentrations within microhabitats remained relatively constant indicating additional factors affected fitness. Disparities in fitness between microhabitats apparently affect habitat use patterns of larvae.     

Ontogeny of prey selection inSirthenea carinata: Generalist juveniles become specialist adults

Prey selection bySirthenea carinata (F.) [Hemiptera: Reduviidae] was investigated using both field captured and laboratory-reared nymphs and adults. Small nymphs (instars 1–3) showed no preference for mole crickets [Orthoptera: Gryllotalpidae: Scapteriscus] as prey overGryllus spp. orAnurogryllus muticus (De Geer) [Orthoptera: Gryllidae]. Larger nymphs (4th and 5th instars) and adults showed a significant preference for mole crickets in the same sort of choice experiments, choosing mole crickets 84% of the time. Laboratory hatchedSirthenea nymphs matured faster on a mixed diet ofGryllus spp.,A. muticus, andScapteriscus spp. Than did siblings fed a diet ofGryllus spp. alone, but no differences were found in size or duration of individual stadia between the diet groups.      

非洲蝼蛄(Gryllotalpa africana Palisot de Beauvois)的鸣声结构及声引诱

本工作对北京地区非洲蝼蛄的鸣声结构作了详细分析;明确了在声通讯中起重要作用的参量并以其引诱力最强的召唤信号进行了声引诱实验。在成虫活动高峰期——晚间2小时38分钟内,平均一个声诱捕器捕获蝼蛄556只,最多的一个诱捕922只。     

Habitat use by radio-tagged Namib Desert golden moles (Eremitalpa granti namibensis)

The Namib Desert golden mole (Eremitalpa granti namibensis) is morphologically, physiologically and behaviourally specialized for living in the harsh loose‐sand desert. Ecological studies have relied on visually tracking animals on the surface of sand dunes. A radio tag would allow individuals to be more reliably located, even while under the sand. We developed a radio attachment and gathered preliminary data on winter habitat use by six individuals during 21 days. We compare data from previous studies and suggest that the greater diurnal activity, smaller home ranges, and more restricted movement patterns that we found are related to the unusual thermal and metabolic biology of Eremitalpa.     

Breeding status affects motoneuron number and muscle size in naked mole‐rats: Recruitment of perineal motoneurons?

Naked mole‐rats live in large colonies and exhibit a strict reproductive hierarchy. Each colony has one breeding female and one to three breeding males; all other individuals are nonreproductive subordinates. Subordinates show a remarkable lack of sex differences in behavior and anatomy, but can become reproductive if removed from the colony. We recently reported that the striated perineal muscles and their innervating motoneurons, which are sexually dimorphic in all other mammals examined to date, are not dimorphic in subordinate naked mole‐rats. Here we asked whether sexual differentiation of this neuromuscular system occurs when a subordinate becomes a breeder. The size and number of cells within Onuf's nucleus (homologue of the rat spinal nucleus of the bulbocavernosus) as well as perineal muscle volume were examined in subordinate and breeding naked mole‐rats of both sexes. Sex differences in perineal motoneurons were not observed, regardless of social status. To our surprise, however, counts of motoneurons in Onuf's nucleus were increased ～30% in breeders of both sexes. This was accompanied by a reciprocal decrease in cells in Onuf's nucleus that were characterized by small soma size, and lacked a clear nucleus or nucleolus. Although not exhibiting typical motoneuron morphology, some of these small cells were positive for the motoneuron marker, SMI‐32. The neuronal changes correlate with increased perineal muscle volumes in breeders. We propose that small, relatively undifferentiated cells are recruited to the pool of large Onuf's nucleus motoneurons when subordinate naked mole‐rats become breeders. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006     

Cholesterol-induced protein sorting: an analysis of energetic feasibility

The mechanism(s) underlying the sorting of integral membrane proteins between the Golgi complex and the plasma membrane remain uncertain because no specific Golgi retention signal has been found. Moreover one can alter a protein's eventual localization simply by altering the length of its transmembrane domain (TMD). M. S. Bretscher and S. Munro (SCIENCE: 261:1280-1281, 1993) therefore proposed a physical sorting mechanism based on the hydrophobic match between the proteins' TMD and the bilayer thickness, in which cholesterol would regulate protein sorting by increasing the lipid bilayer thickness. In this model, Golgi proteins with short TMDs would be excluded from cholesterol-enriched domains (lipid rafts) that are incorporated into transport vesicles destined for the plasma membrane. Although attractive, this model remains unproven. We therefore evaluated the energetic feasibility of a cholesterol-dependent sorting process using the theory of elastic liquid crystal deformations. We show that the distribution of proteins between cholesterol-enriched and cholesterol-poor bilayer domains can be regulated by cholesterol-induced changes in the bilayer physical properties. Changes in bilayer thickness per se, however, have only a modest effect on sorting; the major effect arises because cholesterol changes also the bilayer material properties, which augments the energetic penalty for incorporating short TMDs into cholesterol-enriched domains. We conclude that cholesterol-induced changes in the bilayer physical properties allow for effective and accurate sorting which will be important generally for protein partitioning between different membrane domains.