Infertility is a common sequela to experimentally-induced diabetes mellitus in the male rat as well as to diabetes in the human male. This has been attributed both to alterations in hypothalamo-pituitary and pituitary-testicular activity. In view of the role of serotonin in the hypothalamic regulation of luteinizing hormone secretion, we determined the effects of streptozotocin-induced diabetes on hypothalamic serotonin synthesis relative to circulating levels of luteinizing hormone, folliclestimulating hormone and prolactin in these animals. Half of a group of adult male Sprague-Dawley rats were injected intraperitoneally with 16 mg・kg^-1 of streptozotocin. The other half were injected with vehicle only. The diabetic group was hyperglycemic throughout the study period (488.7±21.2 mg・dl^-1 in diabetic rats vs. 125.1±39.3 mg・dl^-1 in control rats). A third group of rats served as semi-starved controls, weight-matched by total calorie restriction diet to diabetic rats. All of the rats were injected intraperitoneally with 200 mg・kg^-1 of NSD-1015 30 min prior to sacrifice. Accumulation of 5-hydroxytryptophan in various hypothalamic areas was then assayed by liquid chromatography with electrochemical detection as a relative index for the rate of serotonin synthesis. Serum radioimmunoassayable luteinizing hormone, follicle-stimulating hormone and prolactin were also assayed in these animals. Our results show a 50% decrease in serotonin synthesis in the preoptic area-anterior hypothalamus and mediobasal hypothalamus-median eminence 16 weeks after streptozotocin treatment. We also found that serotonin synthesis was inhibited 4 weeks after streptozotocin treatment in the preoptic area-anterior hypothalamus, but not in the mediobasal hypothalamus-median eminence, indicating region-specificity in the early hypothalamic response to streptozotocin-induced diabetes. Serum luteinizing hormone levels were decreased both 4 and 16 weeks after streptozotocin treatment. No changes either in hypothalamic serotonin synthesis or in serum luteinizing hormone levels were observed 1 week after streptozotocin treatment. Serum follicle-stimulating hormone and prolactin levels remained unaffected by streptozotocin treatment throughout the study period. The differential effect of diabetes on the gonadotropins may represent further evidence for the hypothesis of differential regulatory mechanisms governing the secretion of these two hormones and further emphasizes the pathophysiological specificity (i.e., not a generalized metabolic disturbance effect) of diabetes-induced male reproductive neuroendocrinopathy. Our study suggests, at least in part, an explanation for such pathological interaction, namely, diabetic inhibition ofa region-specific neurotransmitter system integral to hypothalamic regulation of luteinizing hormone secretion.

Somatostatin from gastric D-cells exerts inhibitory effects upon acid secretion and gastrin release. From previous morphological investigations, a paracrine mode of action of somatostatin (secretion into the intercellular space) has been postulated. However, the exact route of delivery of gastric somatostatin remains uncertain. To obtain a closer view ofgastric D-cells, their whole shape and their microanatomical relationship were examined in immunostained serial semithin (0.5 μm) sections of the rat pyloric mucous membrane. A minority of D-cells was found to belong to the ‘closed-type’ entero-endocrine cells which showed no contiguity to the luminal surface. The majority of D-cells was of the ‘open-type’. Every D-cell had one (or exceptionally two) basally located and densely immunostained cytoplasmic process which never branched. All these processes regularly extended to capillaries. Only three of fifty D-cells examined were located adjacent to gastrin (G-) cells. Thus, somatostatin may act upon gastric G-cells via a local circulatory system rather than by a paracrine mode of action. Finally, a subpopulation of gastric D-cells was detected which, according to cytological parameters, may also secrete into the gastric lumen. This kind of D-cells seems responsible for the presence of somatostatin in the gastric juice.

Decapsulated ob/ob mouse islets were used to examine the effects of monovalent and divalent cations on ⁴⁵Ca uptake and binding as discriminated by La³⁺-wash technique. At 3 mM glucose (1.28 mM Ca²⁺), intracellular ⁴⁵Ca uptake was increased 1.9-4.5-fold by omission of 125 mM Na⁺, 1.5-fold by omission of 1.2 mM Mg²⁺ and 2.3-fold by reduction of H⁺ (pH 8.5). Omission of 5.9 mM K⁺ was without effect. K⁺ at 30.9 mM increased ⁴⁵Ca uptake 4.7-6.8-fold, whereas addition of H⁺(pH 6.3) or 12 mM Mg²⁺ decreased ⁴⁵Ca uptake by 1.8 and 1.8-2.0-fold, respectively. In control incubations, 20 mM glucose increased intracellular ⁴⁵Ca uptake 5-fold. Stimulation (2.5-3.9-fold) persisted in the presence of 1 mM Ni²⁺ Sr²⁺, Mn²⁺ or Co²⁺ but was abolished by Zn²⁺, Ba²⁺ or Cd²⁺. Of these cations, only Sr²⁺ lacked effects on intracellular ⁴⁵Ca uptake. Basal uptake was decreased 3.8-fold by Mn²⁺ and increased 4.7- and 3.9-fold by Zn²⁺ and Ba²⁺. Mn²⁺ also decreased ⁴⁵Ca uptake 7.2- fold at 20 mM glucose, as did Ni²⁺, Co²⁺, Cd²⁺ (1.4-5.8-fold) but not Zn²⁺ or Ba²⁺. Superficial ⁴⁵Ca binding was increased 7.4- and 10.3-fold by Zn²⁺ and Cd²⁺, respectively. However, binding was not affected by other divalent cations, by 20 mM glucose in their absence or presence, or by the major ionic modifications made with and without osmotic adjustments using choline chloride or sucrose.

In order to evaluate the influence of central neuropeptides on blood pressure regulation, the acute effect of intracerebroventricular administration of several neuropeptides to conscious, normotensive rats was registered. The chronic influence was elucidated by comparing the pressure reaction in normotensive and chronically hypertensive rats. Several of the peptides (bombesin, bradykinin, somatostatin, substance P and vasoactive intestinal polypeptide) induced a rise in blood pressure, which was substantially reduced by α-adrenoceptor blockade. β-Endorphin, which produced a fall in blood pressure, was the only peptide administered that caused a significantly different response in hypertensive as compared to normotensive animals. The underlying mechanism is discussed.

Toxic principles in the venom of the spider, Nephila maculata, were purified with the reverse phase high performance liquid chromatography, and three kinds of the major toxins (NSTX-1, -2 and -3) were isolated. These principles commonly possessed 2,4-dihydroxyphenylacetyl-asparaginyl-cadaveryl moiety in the molecule. The structure of NSTX-3 was concluded to be N-(2,4-dihydroxylphenylacetyl-L-asparaginyl)-N'-(L-arginyl-putreanyl)cadaverine.

Guinea-pig fibroblasts were shown to synthesize mainly small dermatan sulphate proteoglycans. The secreted dermatan sulphate proteoglycans were metabolically labelled with [³⁵S]methionine and/or [³H]glucosamine. The newly synthesized proteoglycans could be recovered as the immune complexes from the culture medium by the addition of polyclonal antibodies against calf skin dermatan sulphate proteoglycans. After digestion with chondroitinase ABC in the presence of proteinase inhibitors, two core proteins (M, 55,000 and 53,000) were detected by SDS-polyacrylamide gel electrophoresis followed by fluorography or autoradiography. Although [³H]glucosamine was incorporated into the core proteins, the small proteoglycans had no ability to interact with concanavalin A Sepharose. Guinea-pig skin fibroblasts also synthesized chondroitin sulphate. However, no labelled chondroitin sulphate-rich large proteoglycans could be detected from the culture medium, suggesting that chondroitin sulphate chains are linked to core proteins different from those of small dermatan sulphate proteoglycans.

Effects of y-aminobutyric acid (GABA) on the inhibitory potentials (i.p.s) in the circular muscle cells of the guinea-pig duodenum were investigated. The amplitude of the i.p.s was increased by atropine and scopolamine while decreased by physostigmine. Guanethidine had no effect on the i.p.s. The amplitude of the nonadrenergic non-cholinergic (NANC) i.p.s was increased by GABA and baclofen, and the excitatory action of GABA was almost disappeared by the treatment with picrotoxin and -aminovaleric acid (AVA). In the presence of atropine, GABA slightly increased the amplitude of i.p.s. In the presence of AVA and atropine, the amplitude of i.p.s was decreased by GABA and baclofen, while it was increased in the presence of picrotoxin and atropine. It is suggested that GABA increases the i.p.s mainly due to inhibition of acetylcholine release via GABA_B-receptors on the cholinergic neuron, and that GABA increases release of the NANC inhibitory neurotransmitter via GABA_B-receptors and decreases it via GABA_A-receptors on the NANC inhibitory neuron, respectively.

Effects of hexamethonium (C₆), capsaicin and substance P desensitization were tested on the cholinergic contraction in response to mesenteric nerve (MN) stimulation in four differently innervated loops of isolated guinea-pig ileum. Effect of oral MN stimulation was more intensive than that of anal MN stimulation in 80% of preparations innervated with both oral and anal mesenteric nerves. The result indicates that the innervation of oral MN is more dominant than that of anal MN. Moreover, overlap of the innervation of oral MN and anal MN was found. Response to oral MN stimulation or anal MN stimulation was unaffected by C₆, but the response to bidirectional and oral-anal MN stimulation was significantly reduced to about 60 and 50% of the control, respectively. Effect of capsaicin or substance P desensitization on the response to each MN stimulation showed no marked differences among the four differently innervated loops.

The role of guanine nucleotide regulatory protein in histamine secretion was investigated using rat mast cells permeabilized with digitonin. The addition of GTP, GTP analogues or NaF increased the sensitivity of secretion in response to Ca at concentrations higher than 0.4 μM, resulting in a shift of the Ca dose-response curve to the left. GDP partially inhibited the stimulatory effect of GTPyS without influencing the sensitivity of secretion to Ca alone. Treatment of cells with pertussis toxin for 2 h did not alter the Ca dose-response curve in the presence or absence of GTP analogues or NaF, though the treatment decreased the response to compound 48/80. These results demonstrate the existence in mast cells of a guanine nucleotide-dependent mechanism that regulates the sensitivity of secretion in response to Ca.

To test the hypothesis that myosin light chain phosphorylation in the rat extensor digitorum longus muscle is under neural control, we studied changes in the extent of phosphorylation of the myosin light chain following sciatic nerve denervation using two-dimensional gel electrophoresis. The phosphorylated form of myosin light chain 2 was rapidly decreased and disappeared 3 days after denervation. No other changes in myosin light chains were observed. The results suggest that phosphorylation of the myosin light chain in fast skeletal muscle is under positive control of fast-type motor-neuron activity.