Student perceived impact of a physical, kinetic and interactive model.

Current instructional tools for anatomy education are insufficient scaffolds for learning abstract visual concepts such as basic biomechanics. Diagrams, illustrations and even computer-generated models may be adequate for identification purposes, but are typically not effective when it comes to demonstrating dynamic functions. Evidence from educational concepts, such as the active learning principle in constructivism, indicate that current tools are ineffective due to a lack of opportunity for hands-on or interactive, learning. To address this, our interdisciplinary team designed an instructional model of the canine thoracic limb which is physical, kinetic and interactive. We hypothesised that the unique combination of these three crucial elements would enhance the student learning experience. In order to test this hypothesis, we asked 126 undergraduate students in a biomedical anatomy course to interact with the model. Students were then invited to complete a survey evaluating their experience using the thoracic limb model. Results from completed surveys showed that students perceived the model as easy to use and helpful with understanding basic biomechanical concepts. These results indicate that there is potential for the model to positively impact the students' learning. Future studies will include quantitative evaluation of student performance and cognitive impact in the biomedical anatomy course.

Insulin-like growth factor-I activates KiSS-1 gene expression in the brain of the prepubertal female rat.

KiSS-1 gene expression has been shown to increase as puberty approaches, and its peptide products, kisspeptins, are involved in LHRH secretion at puberty. Factors contributing to increased KiSS-1 expression, however, have not been identified; thus, the purpose of this study was to assess whether IGF-I could induce transcription of this gene in prepubertal female rats. IGF-I or saline was centrally administered to immature rats that were killed 2, 4, and 6 h later. Real-time PCR revealed that IGF-I induced (P < 0.01) KiSS-1 gene expression at 6 h in a tissue fragment that contained both the anteroventral periventricular (AVPV) and arcuate (ARC) nuclei. Subsequently, the AVPV and ARC nuclei were separated to assess whether region-specific effects could be identified. IGF-I stimulated (P < 0.01) KiSS-1 gene expression in the AVPV nucleus at 6 h after injection, with no change observed in the ARC nucleus. Serum estradiol (E2) levels were not altered at any time point after IGF-I, demonstrating that the increased KiSS-1 expression observed was not caused by an elevation in E2. Additionally, the IGF-I action to induce KiSS-1 gene expression in the AVPV nucleus was further demonstrated when the IGF-I was administered systemically. E2 appears to play an important permissive role because 1-d ovariectomized rats responded to IGF-I with increased (P < 0.01) KiSS-1 expression, whereas, 20 d after ovariectomy, when the E2 levels had fallen below assay sensitivity, the IGF-I was unable to induce KiSS-1 expression. The IGF-I effect was further demonstrated by showing that the IGF-I receptor antagonist, JB-1, blocked the IGF-I-induced increase in KiSS-1 expression. Collectively, these data indicate that IGF-I is an activator of the KiSS-1 gene in the prepubertal female rat.

The pyrethroid pesticide esfenvalerate suppresses the afternoon rise of luteinizing hormone and delays puberty in female rats.

BACKGROUND: One of the most widely used classes of insecticides is the synthetic pyrethroids. Although pyrethroids are less acutely toxic to humans than to insects, in vitro studies have suggested that pyrethroids may be estrogenic. OBJECTIVES: We assessed pubertal effects by orally administering 0.5, 1.0, and 5.0 mg/kg/day of the type II pyrethroid esfenvalerate (ESF) to female rats beginning on postnatal day (PND) 22 until vaginal opening. ESF administration suppresses serum estradiol and delays pubertal onset. MATERIALS AND METHODS: To assess possible hypothalamic and/or pituitary effects, animals received 0.5 or 1.0 mg/kg ESF or corn oil on PNDs 22-29. On PND30, we drew three blood samples (200 microL) from each rat at 15-min intervals beginning at 1000 hours, and again at 1500 hours. To test hypothalamic responsiveness, after the third afternoon sample, all animals received an intravenous injection of N-methyl-d,l-aspartic acid (NMA; 40 mg/kg), and then we drew two more samples. We performed a second experiment as above except that animals received luteinizing hormone-releasing hormone (LHRH; 25 ng/rat) to test pituitary responsiveness. RESULTS: Basal levels of luteinizing hormone (LH) in the afternoon hours were higher in control animals than in animals treated with 1.0 mg/kg ESF (p < 0.05). Furthermore, NMA- and LHRH-stimulated LH release was similar in control and ESF-treated animals, indicating that both hypothalamic and pituitary responsiveness, respectively, were unaffected. CONCLUSIONS: Although the hypothalamus is able to respond to exogenous stimuli, absence of a normal afternoon rise in LH would indicate a hypothalamic deficit in ESF-treated animals.

Comparison of reactive oxygen scavenging systems between a cetacean (DKN1) and a porcine renal epithelial cell line (LLC-PK1).

A transformed renal epithelial cell line, (DKN(1)), from an Atlantic Bottlenose Dolphin, Tursiops truncatus was established in this laboratory and has been used for in vitro genomic analysis and initial toxicological evaluations of dolphin cells. Studies were initiated to compare maintenance of normal antioxidant mechanisms in DKN(1) with similar mechanisms in cells of a pig kidney line, LLC-PK(1). Levels of catalase, glutathione peroxidase, and of reduced glutathione in these dolphin cells were significantly lower than in the porcine cells. Both cell lines were then challenged with hydrogen peroxide at 0.01, 0.1, and 1.0 mM concentrations. The dolphin cells exhibited increased cytotoxicity with a concurrent increase in apoptosis at lower concentrations (0.1 mM) than those required to initiate cytotoxicity in the porcine cells (1.0 mM). Taken together, these results would indicate that the dolphin cells are more susceptible to the damaging effects of certain reactive oxygen species than their terrestrial counterparts.

Effects of alcohol on intraovarian nitric oxide synthase and steroidogenic acute regulatory protein in the prepubertal female rhesus monkey.

OBJECTIVE: In addition to affecting hypothalamic-pituitary function, alcohol is a gonadal toxin capable of inhibiting ovarian function and suppressing circulating levels of estradiol (E2) in female rats, rhesus monkeys, and adolescent girls. Both nitric oxide (NO) and steroidogenic acute regulatory protein (StAR) are intraovarian substances that influence steroidogenesis in opposite directions. This study was undertaken to determine whether alcohol exposure affects prepubertal ovarian steroidogenesis in female rhesus monkeys by altering nitric oxide synthase (NOS), StAR, or both. METHOD: At 20 months of age, monkeys received a single intragastric dose of alcohol (2.4 g/kg) or an equal volume of a saline/sucrose solution daily until they were 36 months old. Blood and ovaries were then collected for assessment of serum hormone levels and tissue gene and protein expression. RESULTS: Alcohol caused depressed levels of serum E2 (p < .05) and luteinizing hormone (p < .05) but not follicle-stimulating hormone. Real-time polymerase chain reaction (RT-PCR) assessment of ovarian mRNA encoding the three isoforms (i.e., neuronal [n] NOS, endothelial [e] NOS, and inducible [i] NOS) of NOS revealed that alcohol exposure did not alter gene expression of nNOS but caused increased basal levels of eNOS (p < .05) and iNOS (p < .01) mRNA expression compared with control ovaries. Alcohol also increased expression of eNOS (p < .01) and iNOS (p < .05) proteins. In contrast, ovaries from monkeys exposed to alcohol showed decreased (p < .05) StAR gene expression compared with controls. CONCLUSIONS: We showed previously that alcohol exposure during adolescence suppressed E2 and delayed development of regular monthly menstruation patterns in rhesus monkeys. The present results suggest that the combined action of alcohol to elevate ovarian NOS and suppress StAR synthesis contributes to these abnormalities.

Manganese stimulates luteinizing hormone releasing hormone secretion in prepubertal female rats: hypothalamic site and mechanism of action.

We have shown recently that Mn2+ stimulates gonadotropin secretion via an action at the hypothalamic level, and a diet supplemented with a low dose of the element is capable of advancing the time of female puberty. In this study, we used an in vitro approach to investigate the mechanism by which Mn2+ induces luteinizing hormone-releasing hormone (LHRH) secretion from prepubertal female rats. The medial basal hypothalamus from 30-day-old rats was incubated in Locke solution for 30 min to assess basal LHRH secretion, then incubated with buffer alone or buffer plus either a nitric oxide synthase (NOS) inhibitor (N-monomethyl-L-arginine (NMMA); 300 or 500 microM) or a soluble guanylyl cyclase (sGC) inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ); 100 or 250 microM) for another 30 min. Finally, the incubation continued for a further 30 min, but in the presence of MnCl2 (50 or 250 microM) to assess the effect of the blockers on stimulated LHRH secretion. Both 50 and 250 microM MnCl2 stimulated LHRH release (P < 0.05 and P < 0.01, respectively). The addition of 300-500 microM NMMA to the medium did not block Mn2+-stimulated release of LHRH, even with the higher dose of MnCl2. Furthermore, while 50, 100 and 250 microM MnCl2 all significantly induced LHRH release, the two lowest doses did not stimulate total nitrite released from the same tissue, an effect only observed with the highest dose. Taken together, these data suggest that Mn2+ is not an effective stimulator of NO. Conversely, inhibiting sGC with ODQ blocked the Mn2+-stimulated secretion of LHRH in a dose-dependent manner, indicating that GC is the site of action of Mn2+. Additionally, we showed that Mn2+ stimulated cGMP and LHRH from the same tissues, and that downstream blocking of protein kinase G formation with KT5823 (10 microM) inhibited Mn2+-induced LHRH release. These data demonstrate that the principal action of Mn2+ within the hypothalamus is to activate sGC directly and/or as a cofactor with available NO, hence generating cGMP and resulting in prepubertal LHRH release.

IGF-1 administration to prepubertal female rats can overcome delayed puberty caused by maternal Pb exposure.

Because prepubertal female rats maternally exposed to lead (Pb) exhibit suppressed serum levels of insulin-like growth factor-1 (IGF-1) and delayed puberty, we investigated the ability of centrally administered IGF-1 to stimulate luteinizing hormone (LH) release in vivo and LH-releasing hormone (LHRH) release in vitro from maternally Pb-exposed prepubertal female rats. Additionally, we assessed whether IGF-1 replacement could affect the timing of female puberty. Results demonstrated that IGF-1 stimulated significantly LH release in both control and Pb-exposed animals. When median eminences from control and Pb-exposed females were incubated with rat IGF-1 in vitro, they responded similarly with significant peptide-induced LHRH release. Lastly, we showed IGF-1 replacement reversed the delay in puberty caused by Pb. These results indicate the central LHRH response to IGF-1 is intact and that Pb-induced delayed puberty is due, at least in part, to suppressed circulating IGF-1 available to the hypothalamus.