Biomedical subjects
Publications and source records attributed to S Baba.
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The hypothalamic content and concentration of thyrotropin-releasing hormone (TRH) were determined by radioimmunoassay in normal, thyroidectomized, hypophysectomized and cold-exposed rats with or without thyroxine. In normal animals, the single administration of thyroxine (1,5 and 20 microgram/100 g B.W.) altered neither the content nor the concentration of TRH in the hypothalamus. However, seven days' administration of this hormone resulted in the dose-dependent increase in the hypothalamic TRH levels. In thyroidectomized rats the hypothalamic TRH levels were slightly reduced in spite of the marked increase of plasma TSH levels and decrease of pituitary TSH levels. In the animals given thyroxine (10 microgram/100 g B.W.) for 7 days in addition to thyroidectomy, however, the TRH levels exceeded that in the animals which underwent throidectomy alone. The hypothalamic TRH levels were markedly reduced in hypophysectomized rats. Conversely, in hypophysectomized rats given 7 days' thyroxine (1 and 5 microgram/100 g B.W.), the levels were increased dose-dependently. In cold-exposed rats, the plasma TSH levels roughly doubled, but the TRH levels remained unchanged. These findings strongly suggest that the feedback site of thyroxine extends not only to the pituitary gland but also to the hypothalamus, and that thyroxine has an increasing effect of the hypothalamic TRH level, though the mechanism(s) remain to be clarified.
A high concentration of gamma-aminobutyric acid (GABA) and a high activity of glutamate decarboxylase (GAD), enzyme for GABA synthesis, were demonstrated in the rat pancreatic islets using a recently developed assay method combining the GABase system with the enzymatic NADP-NADPH cyclin method. Both GABA concentration and GAD activity in the pancreatic islets were comparable to those in the central nervous system (CNS). An insulinoma consisting mainly of B cells possessed a high concentration of GABA and a high activity of GAD. On the other hand, in the pancreatic islets of rats after treatment with streptozotocin, a specific attacker of B cells, GABA was negligible in amount. The occurrence of GABA in the pancreatic islets, at least B cells, apparently supports the view of Fujita that the islet cells are paraneurons. Presence of exogenous GABA does not influence the glucose- and amino acid-induced insulin release. The uptake of 3H-GABA into the pancreatic islet was small in amount as compared with that into the brain tissue such as the substantia nigra. These observations suggest that the different compartmentation of GABA in the islets from that in the CNS.
In order to clarify the physiologic role of somatostatin in insulin release, rat pancreatic islets treated by somatostatin antiserum were incubated in media containing various concentrations of glucose. Insulin release from antiserum-treated islets was significantly elevated above that from nontreated ones at 3.3 and 8.3 mM glucose, while the former was not different from the latter at 16.7 mM glucose. It is suggested that somatostatin plays an important role in the regulation of insulin release in the physiologic range of glucose concentration.
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The patients are 15 year old and 13 year old males who complained of a headache, vomiting and general malaise. The plain skull films showed thinning and bulging of the left temporal squama, forwards enlargement of the middle fossa and the elevation of the lesser wing of the sphenoid. The left carotid arteriography indicated significant elevation of the middle cerebral artery and the opercular portion of the middle cerebral artery was absent. Left frontotemporoparietal craniotomy was performed, and the large cyst as the space taking mass lesion of the middle fossa was noted. The cyst contained xanthochromic fluid and its wall probably consisted of arachnoid membrane. In both cases the cyst occupied anterior 6 cm of the left middle fossa and no brain tissue was noted between the cyst and the anterior part of the middle cranial fossa. Histologically, the membrane of the cyst was arachnoid. Their recognition and management are discussed.
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