Phylogenetic relationships of chimaeroid fishes are investigated in detail. The six genera studied, Callorhinchus, Rhinochimaera, Harriotta, Neoharriotta, Chimaera and Hydrolagus belong to the subclass Chimaeroidei and are the only living representatives of the class Holocephali. The comparative morphology of the lateral line canals, skeleton, tooth plates, secondary sexual characteristics and musculature of all six living genera of chimaeroid fishes is described. Development of the jaws, hyoid arch and ethmoid canal is briefly described for Callorhinchus milii of the family Callorhynchidae. Using anatomical characters a phylogeny of higher level chimaeroid relationships is hypothesized. The infraorder Neochimaeroidi is erected to include Rhinochimaera, Harriotta, Neoharriotta, Chimaera and Hydrolagus on the basis of eight synapomorphies and a new classification of chimaeroid fishes is proposed.

The onset and termination of female rat sexual receptivity are regulated by the activation of steroid hormone receptors. In addition, the onset and termination of sexual receptivity are influenced by mating stimulation. For example, repeated mating stimulation increases sexual behavior in previously unreceptive estradiol-primed female rats. Apparently, sensory cues from the male rat lead to changes in female sexual behavior. The current studies investigated the exact sensory cues responsible for these changes and the mechanisms by which they influence sexual behavior. Mating-induced increases in sexual behavior appear to result largely from vaginal-cervical stimulation (VCS) received from intromissions and ejaculations. Furthermore, it is likely that the effects of VCS are mediated by ligand-independent activation of progestin receptors. Likewise, odors from male rats are necessary for maximal increases in sexual behavior following repeated mating; however, unlike VCS, odors do not seem to influence sexual behavior via a progestin receptor-dependent mechanism. Mating stimulation also accelerates estrous termination. The mechanisms mediating the acceleration of estrous termination following mating were also investigated. It has been hypothesized that mating-induced estrous abbreviation results from down-regulation of progestin receptors; however, several immunocytochemical studies found no evidence supporting this hypothesis. Instead, it appears that the effects of mating stimulation on estrous termination are more complex than previously appreciated. It appears that, while VCS decreases levels of sexual behavior, other sensory cues (e.g. flank stimulation and odors) maintain high levels of sexual receptivity. Thus, the results suggest that estrous duration is the result of a complex interplay between those factors that promote the expression of sexual receptivity and those that inhibit it.

Breastfeeding women experience changes to their bone mineral density over the course of lactation. The exact nature of the relationship between breastfeeding and lactation-induced change in bone density is not well understood but it is known that bone density decreases during lactational amenorrhea and increases after menses resumes. In studies that have explored the relationship between breastfeeding and bone density, variation in breastfeeding behaviors is considered 'noise' to be eliminated. This study explores this relationship by focusing on the role of breastfeeding variation on the rate of bone density change, both before and after menses resumes. To date, most research on breastfeeding and bone density has been conducted by clinical researchers. This study differs from these studies because of an anthropological approach that puts at the forefront of the analysis behavioral variation. Using a biocultural framework, the study design draws from the methods and theories from both biological and cultural anthropology. The theoretical lens, the methodologies, and the theories combine to reveal the complexities in the topic of breastfeeding and bone density. A total of 35 women participated in a six-month longitudinal assessment of bone density change during breastfeeding. They recorded all breastfeeding activity over a 24-hours period each time that their bone mineral density was measured. Results of the study showed that greater intensity of breastfeeding in the amenorrheic months significantly attenuated bone density loss in this population of U.S. women. Amenorrheic women who breastfed with less intensity showed greater decline in their bone mineral density. Similar benefits to the maternal skeleton were not demonstrated in high intensity breastfeeders after menses resumed. Furthermore, the evaluation of the breastfeeding styles of the women in this population showed them to conform to AAP breastfeeding guidelines despite their own assertions that they do not adhere to such recommendations.

The aim of this dissertation was to explore alterations in human skeletal muscle during a controlled period of immobilization and following spinal cord injury (SCI). Study I examined the effects of an imposed period of immobilization of the adductor pollicis (AP) muscle on muscle function and volume in young (18-25 years) and aged (60-75 years) men. Muscle strength and volume of the AP was assessed before and after immobilization. Results from Study I show that although the older and younger adults had disparate losses in muscle volume they experienced similar losses in muscle strength. These results confirm that even short periods of inactivity promote more rapid losses in muscle volume in older adults, while the ability to generate force is maintained. Study II and Study III of this dissertation explored the molecular alterations in human skeletal muscle in response to immobilization or SCI. Muscle biopsies were analyzed at both the transcriptional (microarray analysis, quantitative Real-Time Polymerase Chain Reaction (qRT-PCR)) and translational (Western blotting, Immunohistochemistry (IHC)) level. In Study II, the knee joint of five young men (aged 18-25 years) was immobilized, and muscle biopsies were performed before and after 48h of leg immobilization. Immobilization resulted in increased expression of genes involved in the ubiquitin proteasome pathway and metallothionein function, but no change in respective protein products. However, results of Study II also showed a decrease in gene expression and protein products for the collagens, which are involved in extracellular matrix (ECM) integrity, indicating that disruption to the ECM is an initial step in the muscle atrophy program following immobilization. In Study III, analysis of muscle biopsies taken two and five days post-SCI, compared to healthy controls, showed increased gene expression for genes that encode components of the ubiquitin proteasome pathway, metallothioneins, and secretory leukocyte protease inhibitors. Western blotting and IHC showed that protein products for components of the proteolytic core and the metallothioneins increased by five days post-SCI, and protein products were localized to the ECM. These results indicate that components of the ECM are initial targets of proteolytic activity within the first days following SCI.

Studies in adults have shown that the role of the postural system during most motor behaviors is more complex than just merely minimizing positional deviations away from a stable equilibrium point. Rather, the postural system appears to be highly coordinated and integrated with other suprapostural behaviors. How the integration and coordination between the postural system and other suprapostural behaviors develops has not been extensively examined. In this project the developmental integration and coordination between posture and manual control was studied in children (7- and 10-years of age) and compared with healthy college aged adults. All subjects were required to fit a block through an opening as precision, postural and visual constraints were manipulated. Trunk and arm kinematics and center of pressure data were obtained. Compared to adults children adopt different postural strategies during the fitting task (Chapter 4), appear less able to modulate postural stability as precision demands increase (Chapter 5), and exhibit less ability to use functionally exploit postural fluctuations (Chapter 6). Taken together, results suggest that even by 10-years of age, the postural system is not integrated with the manual control system at adult like levels.

Mice with a deletion of the hypothalamic basic helix-loop-helix transcription factor Nhlh2 (N2KO) display adult onset obesity, implicating Nhlh2 in the neuronal circuits regulating energy availability. Nhlh2 co-localizes with the hypothalamic thyrotropin-releasing hormone (TRH) neurons in the paraventricular nucleus (PVN) and proopiomelanocortin (POMC) neurons in the arcuate nucleus. N2KO mice become obese due to reduced physical activity in the absence of hyperphagia making them a unique mouse model for the study weight gain, obesity and energy expenditure. Signals that regulate Nhlh2 and the effects of Nhlh2 on peripheral tissues remain largely unknown. The research presented here utilized numerous techniques to investigate the effects of changes in energy availability on Nhlh2 expression. We show that Nhlh2 expression decreases significantly with food deprivation and cold exposure. Nhlh2 expression is stimulated with food return or leptin injection following food deprivation or return to room temperature following cold exposure. These data suggest that Nhlh2 gene expression responds positively to increased energy availability and negatively to reduced energy availability. These findings combined with the phenotype of N2KO mice led us to propose that Nhlh2 integrates energy availability inputs in various hypothalamic nuclei to drive expression of genes required for body weight maintenance. Investigation into peripheral tissues in N2KO mice revealed that responses of genes in the hypothalamus-pituitary-thyroid axis, muscle, and brown and white adipose tissue to changes in energy availability require Nhlh2 expression. The responses of serum total T4 levels and UCP1 mRNA and UCP3 mRNA to energy availability signals are altered in N2KO mice. In addition, N2KO mice maintain body temperature with cold exposure but are unable to maintain body weight. In summary, my work provides new insight into the role of Nhlh2 in coordinating energy availability signals to downstream genes required for body weight maintenance and thermoregulation.

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