Browsing by Author "Yoshimi, Y."

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Gene expression and immunohistochemical localization of megalin in the anterior pituitary gland of helmeted guinea fowl (Numida meleagris)
(Journal of Molecular Histology, 2007) Claudius, L.; Masaru, U.; Horii, Y.; Rudovick, K.; Yoshimi, Y.; Koichi, M.
Megalin/the low density lipoprotein receptor-related protein-2 (LRP-2) is expressed in a variety of epithelia and mediates endocytosis of numerous substances. Megalin is also shown to bind clusterin with high affinity. In the pituitary gland, clusterin is localized in endocrine cells, folliculostellate (FS) cells and colloids. The present study examines the expression pattern of megalin within the gland and assesses its cellular localization to that of clusterin so as to deduce their functional implications in colloidal accumulation as relevant in vivo. Quantity of megalin mRNA expression in pituitary and other endocrine tissues was quantified by real-time PCR using SYBR-green I detective system. High levels were detected in kidneys and pituitary. In situ hybridization showed megalin mRNA in FS cells. Megalin protein detected by immunohistochemistry was also observed in FS cells. Immunoelectron microscopy clearly showed the localization of megalin in peripheral region of colloid-containing follicles and on vesicular structures in FS cells. Immunolabeling was also found to be associated with membranes of vacuoles in apoptotic endocrine cells and cell remnants engulfed by FS cells. Double immunofluorescence labeling was performed to determine whether megalin and clusterin in the anterior pituitary were present within the same cell. Simultaneous localization was detected in almost all FS cells surrounding colloids and in several foci of FS cells surrounding endocrine cells. These findings suggest that megalin may drive ingestion of clusterin complexes with products of digested apoptotic endocrine cells in FS cells, and thereby providing a potential mechanism for a receptor mediated uptake of degenerating endocrine cells and secretion of colloid.
Localization profile of cathepsin L in the brain of African giant rat (Cricestomys gambianus)
(2016) Luziga, C.; Nga, B. T. T.; Kashoma, I.; Katakweba, A.; Yoshimi, Y.
Cathepsins, are members of the papain superfamily of mammalian lysosomal cysteine proteases. Among others there are two prominent members with broad substrate specificity, these are cathepsin B and cathepsin L that are known to be involved in the process of intra- and extra-cellular protein degradation and turnover. However, the in vivo targets of cathepsin L in nervous tissues are yet to be identified. We examined by immunofluorescence studies the distribution pattern of cathepsin L protein and determine the specific cell types synthesizing the enzyme in the brain of African giant rats (Cricetomys gambianus). Results showed that Cathepsin L protein was localized in various brain regions of the giant rats. In the telencephalon, immunoreactivity was identified in cerebral cortex and subcortical structures, hippocampus, amygdala and basal ganglia. Within the diencephalon high density of positive signals was observed in mediodorsal and lateral posterior thalamic nuclei and medial habenular nucleus. In the mesencephalon, cathepsin L was detected in the substantia nigra and cerebral peduncles. Strong labeling in the hypothalamus was present in the anterior commissure and median eminence while in the cerebellum cathepsin L was observed in the deep white matter, granule cell layer, stellate, and basket cells of cerebellar cortex and in the Purkinje neurons. The distribution pattern and functional implications of cathespin L in relation to spatial memory establishment, learning coordination and disease mechanisms is discussed.