Selective Depletion of Adult GFAP-Expressing Tanycytes Leads to Hypogonadotropic Hypogonadism in Males

In adult mammals, neural stem cells are localized in three neurogenic regions, the subventricular zone of the lateral ventricle (SVZ), the subgranular zone of the dentate gyrus of the hippocampus (SGZ) and the hypothalamus. In the SVZ and the SGZ, neural stem/progenitor cells (NSPCs) express the glial fibrillary acidic protein (GFAP) and selective depletion of these NSPCs drastically decreases cell proliferation in vitro and in vivo. In the hypothalamus, GFAP is expressed by α-tanycytes, which are specialized radial glia-like cells in the wall of the third ventricle also recognized as NSPCs. To explore the role of these hypothalamic GFAP-positive tanycytes, we used transgenic mice expressing herpes simplex virus thymidine kinase (HSV-Tk) under the control of the mouse Gfap promoter and a 4-week intracerebroventricular infusion of the antiviral agent ganciclovir (GCV) which kills dividing cells expressing Tk. While GCV significantly reduced the number and growth of hypothalamus-derived neurospheres from adult transgenic mice in vitro, it causes hypogonadotropic hypogonadism in vivo. The selective death of dividing tanycytes expressing GFAP indeed results in a marked decrease in testosterone levels and testicular weight, as well as vacuolization of the seminiferous tubules and loss of spermatogenesis. Additionally, GCV-treated GFAP-Tk mice show impaired sexual behavior, but no alteration in food intake or body weight. Our results also show that the selective depletion of GFAP-expressing tanycytes leads to a sharp decrease in the number of gonadotropin-releasing hormone (GnRH)-immunoreactive neurons and a blunted LH secretion. Overall, our data show that GFAP-expressing tanycytes play a central role in the regulation of male reproductive function.

Oral perception in tongue thrust and other oral habits

Oral stereognosis is the ability of the mouth to recognize shape and texture. Oral shape recognition is sensitive to repetition and to topical mucosal anesthesia. Age, upper and lower arch perimeter, and labiolingual dysfunction also interact with oral stereognosis. The purpose of this investigation was to define the influence of age, arch size, and oral dysfunction on oral stereognosis when submitted to repeated trials. Fifty subjects were selected before orthodontic treatment. Each subject underwent 4 trials: T1 and T4 without anesthesia and strictly similar, T2 with topical anesthesia of the tongue, and T3 with topical anesthesia of the palate. Five test pieces or stimuli were used. The recognition time (RT) of each stimulus, the perimeter of upper and lower anterior dental arch, and the labiolingual dysfunction index (LLDI) were the main variables statistically evaluated. Subjects with a mild degree of dysfunction needed more time to recognize the stimuli in T3 when compared with T2. The number of RT3 > RT2 was 2.5 +/- 1.12 in the group with a low LLDI (12 +/- 1.5), and 1.57 +/- 0.63 in the group with an LLDI of 16 +/- 2.5 (P >.05). This may be attributed to different manipulation of the test pieces between the 2 groups, which could have been modified through sensory deprivation. Bolus recognition before the swallowing act needs to be paralleled to stereognostic performance.