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Muscle fiber architecture, innervation, and differences in fiber-type composition were examined in the gluteus medius of four horses. In the anatomical part of this study, the gluteus medius of four adult horses were extracted, soaked in a 10% formalin solution, and examined for fiber architecture and innervation patterns. Based on architectural and innervation differences, two distinct anatomical compartments were defined: the dorsal region and the ventral region. The histochemical portion of this study examined the fiber composition of each region by classifying the fiber types on the basis of myosin-ATPase. The dorsal region had a significantly higher percentage of Type I fibers than the ventral region; whereas the ventral region had a significantly higher percentage of Type IIB fibers than the dorsal region. These findings suggest that this subdivided structure may be designed to allow functional independence within the muscle.

Marine oils contain eicosapentaenoic acid, a fatty acid that competes for cyclooxygenase and reduces the synthesis of dienoic prostanoids including prostaglandin E2 (PGE2). Since PGE2 plays an important role in the release of hypothalamic GnRH and the maturation of ovarian follicles and ova release, it was postulated that a diet containing fish oil (FO) would delay first ovulation through inhibitory effects on GnRH release, follicle development and ovulation. Immature female Sprague-Dawley rats were fed a FO diet ad libitum. Controls were pair-fed an identical diet with the substitution of safflower oil. The age of the FO-fed rats was significantly increased at first estrus, and first ovulation was either delayed or inhibited. Preoptic area/hypothalamic and ovarian PGE2 levels were reduced by FO feeding whereas hypothalamic GnRH was significantly increased. A FO-containing diet may delay the onset of puberty through attenuation of preovulatory GnRH release and local impairment of the ovulatory process.

The neurons of the dentate gyrus play a critical role in the hippocampal tri-synaptic pathway. Granule cells located in this cellular layer are responsible for integrating large amounts of information emitted from the entorhinal cortex before propagating signals via the mossy fiber pathway to the CA3 subfield of the hippocampus. This circuitry has been shown to be critical to the formation of episodic and declarative memories. This type of memory is impaired in schizophrenics. Animal models based on the popular glutamate hypothesis have used NMDA antagonist such as PCP and ketamine to mimic the symptoms of schizophrenia to good effect. One such animal model utilizes sub-chronic administration of PCP to non-human primates. Numerous studies have shown that this treatment paradigm reliable produces deficits in prefrontal cortex functioning that mimics the dysfunctions associated with the schizophrenic phenotype. The present study used late adolescent vervet monkeys treated in the sub-chronic paradigm and sought to determine if structural changes occurred in the dentate gyrus. We report that no structural alterations to dentate granular cell morphology were linked to sub-chronic PCP administration. This result may be due to the fact that the late adolescent subjects used had yet to develop fully mature glutatmatergic circuitry and were thus not susceptible to the changes in brain chemistry commonly associated with NMDA antagonist administration / acase@tulane.edu

Pitx1 and Pitx2 define a new family of bicoid related homeobox genes. The respective expression patterns of these two genes suggests their importance during vertebrate embryo development. Of particular interest is the expression and regulation of these genes during murine tooth development. The expression patterns of both Pitx1 and Pitx2 in the tooth forming region as well as the tooth defect found in patients with Rieger syndrome suggest that both Pitx1 and Pitx2 play a role in the early stages of odontogenesis. Studies show that overlapping domains of Fgf8 and Bmp4 signaling regulate the expression of both Pitx1 and Pitx2 in the tooth forming region Since Pitx2 is an early marker for the dental epithelium, the chicken homologue of Pitx2 (cPitx2) was cloned in an effort to search for molecular markers for the presumptive tooth germ in Aves. Interestingly, in addition to the expression of this gene in the chick mandible, cPitx2 was also asymmetrically expressed relative to the left-right axis of the developing embryo. Studies show that regulation of this gene in the left-lateral plate mesoderm is regulated by the well documented shh-nodal pathway. In addition, expression of cPitx2 in the left half of the fused heart tube appears to be regulated by retinoic acid as demonstrated by the reduced expression of cPitx2 in vitamin A-deficient quail embryos. Finally, upon cloning the chicken homologue of Pitx2 , two isoforms of this gene were isolated, isoform A (cPitx2A ) and isoform B (cPitx2B). However, Northern blot analyses indicates that at least 3, possibly more, isoforms are expressed and may correspond to the various expression patterns of cPitx2 throughout embryogenesis. The expression of antisense cPitx2 transcripts was also detected. The presence of antisense cPitx2 transcripts through development in vivo, as confirmed by Northern blot and RNase Protection Assay (RPA) analysis, suggest yet another mechanism for the regulation of cPitx2 activity. The complementary expression pattern of sense and antisense cPitx2 in the endothelial and hematopoietic cells of the embryonic vasculature, respectively, suggest that these two genes may be involved in regulating the differentiation of the endothelial and hematopoietic cell lineages respectively / acase@tulane.edu

This study examined the stimulating factors for prolactin (PRL) and growth hormone (GH). One aim of the study was to establish an anatomical basis for a proposed releasing factor for PRL, vasoactive intestinal peptide (VIP). Ames dwarf mice, which manifest a spontaneous mutation which, when present in homozygous form (df/df), results in absence of PRL and GH, were used in the present study. Immunoreactive VIP and growth hormone releasing hormone (GHRH) were examined and compared between brains of normal and PRL and GH-deficient dwarf mice in order to see whether there is a response of VIP and GHRH neurons to the absence of target hormones, PRL for VIP and GH for GHRH The anatomical source of the hypophysial portal VIP, and the response of the hypothalamic VIP-containing neurons to PRL deficiency was investigated. VIP immunoreactivity was detected in parvocellular paraventricular nucleus neurons. Groups of VIP-containing neurons in the parvocellular paraventricular nucleus project to the median eminence, which contains portal blood vessels that transport hypophysiotropic factors to the pituitary gland. VIP immunoreactivity was also located in axon terminals in both the external and internal zone of the median eminence. Immunoreactive VIP in the cortex, amygdala, bed nucleus of the stria terminalis, and in the suprachiasmatic nucleus were qualitatively comparable between normal and dwarf mice. Qualitative increases in the fiber immunostaining in the external layer of the median eminence and perikaryal immunoreactivity in PVN of the dwarf mouse were detected. The presence of median eminence-afferent VIP neurons in the paraventricular nucleus and fiber immunostaining in the external layer of the median eminence suggest that parvocellular paraventricular neurons may be involved in PRL regulation Studies of the stimulatory factor GHRH in mice have been hampered by the lack of antiserum directed against the mouse-specific peptide. GHRH-containing cell bodies were found to be primarily concentrated in the arcuate nucleus. In addition, new localizations of GHRH-containing cell bodies were demonstrated, such as in the medial preoptic area, anterior hypothalamic area, and in the area lateral to anterior hypothalamic area. It is not known whether these neurons participate in GH regulation. In addition, GHRH-immunoreactive perikarya in the hypothalamic ventromedial nucleus of dwarf mice were noted. Whether these neurons project to median eminence is not known. The number of the GHRH-containing cell bodies in the dwarf arcuate nucleus was increased compared to the number in normals. The increased number of cell bodies was located in the ventral and medial areas of the arcuate nucleus. (Abstract shortened by UMI.) / acase@tulane.edu