The chemical characteristics of the neurons of the motion sensitive visual area, area MT, remain to be established. We studied the distribution pattern of two calcium binding proteins, parvalbumin (PV) and calbindin D28K (CB) in this area, using specific monoclonal antibodies and the peroxidase-antiperoxidase (PAP) immunohistochemical technique. Aldehyde fixed 30-micron-thick cryostat sections from area MT of five animals were processed free floating for immunohistochemical staining. Besides studying the morphological characteristics of PV and CB positive neurons, quantitative analysis was carried out to determine their (1) perikaryal area (Pa) and diameter, (2) numerical densities (NV)/mm3 cortical tissue, (3) absolute number (NC) in a column of cortex under 1 mm2 cortical surface along with (4) layerwise absolute number (NL) under 1 mm2 cortical surface and (5) laminar percentage distribution of immunoreactive (IR) neurons. Quantitative analysis was carried out using a Leica QMC 500 image analysis system connected to a DMRE microscope. The results showed that both types of IR neurons were localized to all cortical layers except layer I. The PV +ve neurons were equidistributed between the supra- and infragranular layers, with the highest percentage being present in layer III (45%) followed by layer V (21%). The CB +ve neurons, on the other hand, were predominantly localized in supragranular layers, with the highest percentage being in layer III (54%) and the next highest percentage in layer II (18%). The average Pa and diameter of PV +ve neurons were found to be 96.90 +/- 28.43 micron 2 and 11.01 +/- 1.61 microns respectively. The CB +ve neurons were significantly smaller in size than the PV +ve neurons, with average Pa and diameter of the former being 92.23 +/- 26.18 micron 2 and 10.39 +/- 1.23 microns respectively. The NV for PV and CB +ve neurons showed ranges of 3157-3894 and 2303-2585, with means of 3347 +/- 285 (+/- SD) and 3436 +/- 100 respectively. The values for NC showed ranges of 5230-5444 and 4020-4268 with means of 5378 +/- 85 and 4167 +/- 95 for PV and CB neurons respectively. Variations in size together with the differential distribution of these neurons in the cortical layers may indicate their involvement in different functional circuitaries.

The impact of transient neonatal hypothyroidism on growth and function of puberal testis during different milestones of postnatal testicular development was studied in Wistar rats. Rat pups were made hypothyroid for 10, 15, 30, 40 and 60 days of postnatal age from birth by providing 0.05% (W/V) methimazole (MMI) in the drinking water of the mother, from day 1 postpartum till weaning (25 days postpartum) and thereafter in the drinking water. Control rats were raised without MMI treatment. Sertoli cell number and its function was assessed on day 60 postpartum. Sertoli cell number increased consistently in 10, 15, 30 and 40 days transient hypothyroid rats but decreased in rats subjected to continuous hypothyroidism from birth to 60 days postpartum. Rats subjected to continuous hypothyroidism from birth showed spermatogenic arrest at puberty and had only a single layer of spermatogonia. Transient neonatal hypothyroidism for 10 (or) 15 days from birth increased spermatocytes (pachytene and zygotene), spermatids (elongated and round) whereas, that of 30 and 40 days decreases the number of germ cells. Plasma androgen binding protein (ABP) concentration decreased in puberal rats belonging to all groups, whereas the testicular interstitial fluid (TIF) concentration of ABP increased significantly in 10 and 15 days hypothyroid rats while it decreased in all other groups. These findings indicate that the mitogenic activity of Sertoli cell is increased irrespective of the duration of transient neonatal hypothyroidism. However, the functional activity of Sertoli cells (ABP production) in these puberal rats varies depending upon the postnatal period at which the animals were in hypothyroid state.