Tadashi Ofuji

Distribution and Characterization of Corticotropin-Releasing Factor and Arginine Vasopressin in Rat Hypothalamic Nuclei

Corticotropin-releasing factor (CFR) was bioassayed and arginine vasopressin (AVP) radioimmunoassayed from punched-out hypothalamic nuclei. The highest concentration of CFR was found in the median eminence (ME), followed by the paraventricular nucleus (PVN), supraoptic nucleus (SON), suprachiasmatic nucleus (SCN), arcuate nucleus (ARC), dorsomedial nucleus (DMN) and ventromedial nucleus (VMN). The AVP concentration was in the order of ME, SON, PVN, SCN, ARC, VMN and DMN. Sephadex G-25 gel filtration of the ME extracts showed one peak for AVP and two peaks for CRF. One CRF peak appeared on the void volume (big CRF) and the other (small CRF) was coeluted with AVP. Gel filtration of the PVN and SON extracts showed one peak for AVP but three or four peaks for CRF. The addition of anti-AVP serum (AVP-AS) to pituitary cell cultures reduced the CRF activities of AVP and ME extracts by approximately 80 and 40%, respectively. When the small CRF fraction of ME extracts was treated with AVP-AS on affinity chromatography, the unbound fraction (AVP-free) still showed significant CRF activity. Re-examination of CRF concentration using AVP-AS showed that it was still highest in ME, but was significantly higher in PVN than in SON, SCN and ARC. These results suggest that the PVN is an important nucleus for producing corticotropin-releasing hormone.

Effects of 2-bromo-α-ergocryptine on β-endorphin-induced growth hormone, prolactin and luteining hormone release in urethane anesthetized rats

Abstract Adult male rats were injected intraperitoneally either with saline or 2-Br- α-ergocryptine(CB-154)(10 ng/0.5 ml/rat) 30 min prior to an intraventricular injection of saline or β-endorphin (1 μg/10 μl or 5 μg/10 μl) and 30 min after β-endorphin, they were sacrificed by decapitation. Intraventricular injection of β-endorphin elicited significant increases in serum GH, prolactin and LH levels in a dose-related manner. Pretreatment with CB-154 inhibited the release of GH, prolactin and LH induced by β-endorphin. These results indicate that the stimulatory effects of β-endorphin on GH, prolactin and LH may be involved in an inhibition of dopaminergic mechanism in the central nervous system.

Vasopressin and CRF-ACTH in Adrenalectomized and Dexamethasone-Treated Rats

Median eminence corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) and pituitary and peripheral plasma adrenocorticotropin (ACTH) and AVP were measured in male Wistar rats 1 and 2 weeks after bilateral adrenalectomy (ADX), sham operation (SHAM) or dexamethasone-treatment (DEX). Median eminence AVP content was unchanged 1 week after ADX but was significantly elevated 2 weeks after ADX, whereas CRF activity was reduced at 1 week after ADX and returned to control range at 2 weeks. Anterior pituitary ACTH content was elevated but posterior pituitary AVP content was reduced at 1 and 2 weeks after ADX. Plasma ACTH was greatly elevated in ADX rats and reduced in DEX rats, whereas plasma AVP did not differ significantly between these two groups or the control group. When ADX and SHAM rats were laparotomized under ether, plasma ACTH increased greatly, but this elevation was prevented by DEX treatment. The plasma AVP level was elevated in all three groups 2.5 min after onset of stress but returned to the basal range at 20 min. Median eminence CRF and AVP and pituitary ACTH and AVP were not significantly changed after onset of stress. These results indicate that the vasopressin and CRF-ACTH responses were not consistent in the median eminence, pituitary and peripheral plasma and suggest that vasopression is not involved in the feedback and acute stress mechanism of CRF-ACTH secretion. However, we have to measure CRF activity and AVP concentration in the hypophysial portal blood to confirm this conclusion.

Effects of bromocriptine on receptor binding of methionine-enkephalin ☆

Bromocriptine inhibited the binding of methionine-enkephalin (ENK) to rat striatal synaptic membranes in a dose-dependent fashion. The bromocriptine IC50 was 16 micrometers. hill coefficients of bromocriptine were 0.7 and 0.3, suggesting that an allosteric effect was involved in bromocriptine inhibition of ENK binding to its receptor. These data suggest that at least a part of the therapeutic antiparkinsonian effect f bromocriptine is its allosteric effects on the ENK receptor, which influences the function of striatal dopamine neurons and/or of striatal cholinergic neurons.

Molecular Sieve in Renal Glomerular and Tubular Basement Membranes as Revealed by Electron Microscopy

Bovine glomerular basement membrane (GBM) was isolated and purified according to a modification of Spiros method. Rat and bovine tubular basement membranes (TBM) were isolated and purified by sonic disruption or by the method of Carlson et al. Electron microscopic studies on the ultrastructure of GBM and TBM were performed after negative staining with 1% phosphotungstic acid solution, pH 7.3. When negatively stained, GBM and TBM were seen as fragments varying in size. The surface of the membranes showed a characteristic felt-like or spongy appearance. At higher magnification, GBM and TBM showed a fine meshwork composed of strands and pores which three-dimensionally resembled a crystal lattice. Pores were fairly uniform in size and shape. They were round, oval or polygonal in shape. Some of the pores were elongated to form short straight or bent channels. Strands were also uniform in diameter and surrounded a pore or channel. For an average of 50 pores, the long dimension was 3.1 +/- 0.6 nm and the short dimension 2.5 +/- 0.3 nm in bovine GBM, 3.8 +/- 1.2 and 2.5 +/- 0.7 nm in bovine TBM, and 4.9 +/- 1.5 and 2.8 +/- 0.6 nm in rat TBM, respectively. The strand was 1.8 +/- 0.3 nm in diameter in bovine GBM, 2.5 +/- 0.6 nm in bovine TBM and 3.7 +/- 0.7 nm in rat TBM for an average of 50 strands. The diameters of the pores were less than or close to the short axis of an albumin molecule. It was concluded that renal GBM and TBM were molecular sieves composed of pores and strands.

Effect of metoclopramide on rat prolactin secretion in vivo

Abstract Metoclopramide, a potent antagonist to apomorphine, was used to the rats in vivo to determine its effect on the release of prolactin. A single i.p. injection of metoclopramide at 10 or 100 μg/100 g b.w. under urethane anesthesia increased serum prolactin levels by 1.6 or 7.2 fold, respectively, compared with basa levels. This prolactin increase was completely abolished by 2-bromo-α-ergocryptine (CB-154). These data suggest that metoclopramide stimulates prolactin secretion in rat and this secretion is abolished by dopaminergic stimulant.

Reevaluation of suppressor cell function in systemic lupus erythematosus

Abstract This study was undertaken to reevaluate suppressor cell function in patients with systemic lupus erythematosus (SLE). First, we found that preculture of normal peripheral blood mononuclear cells (PBM) with or without Con A developed suppressor cells that inhibited the capacity of fresh normal PBM to secrete immunoglobulins in response to PWM. The degree of suppression produced by Con A-activated PBM was much greater than that produced by precultured PBM. Then, using this suppressor cell assay, we demonstrated that both precultured and Con A-activated SLE PBM secreted a significant amount of immunoglobulins without any stimulation and, also inhibited the ability of fresh normal PBM to synthesize immunoglobulins in vitro . The suppressive activity of precultured or Con A-activated SLE PBM did not differ from that of normal PBM. Thus, this study demonstrated for the first time that there was no defect in suppressor cell function in SLE in vitro .

Effects of nifedipine on prolactin, growth hormone, and luteinizing hormone release by rat anterior pituitary in vitro.

Summary The release of prolactin, GH, and LH was monitored by radioimmunoas-say in rat anterior pituitary tissue incubated in Krebs-Ringer bicarbonate medium. Nife-dipine, a strong Ca2+ blocker, at 10, 100, and 1000 ng/ml inhibited the release of prolactin in a dose-related manner, but did not inhibit the release of GH and LH. This drug also blocked the TRH-induced GH release and the LH-RH-induced LH release. These results indicate that the release of prolactin may be more closely tied to Ca2+ influx from extracellular fluid and with stimulus-secretion coupling than the release of GH and LH and that Ca2+ may also play a role in the release of anterior pituitary hormones induced by releasing hormones.

Autoimmune hemolytic anemia associated with IgA autoantibody

Abstract A case of warm autoimmune hemolytic anemia associated with IgA antibody is reported. The patients red cells were coated with IgA and C3, and were bound and formed rosettes with monocytes in vitro via C3 receptors. Some evidence suggested that the IgA antibody in the patients serum reacted with red cells and activated complement via the alternative pathway, resulting in C3 coating of the red cells. In vitro phagocytosis of the patients red cells by monocytes occurred when in vivo hemolysis improved after the administration of prednisolone. Although IgG antibody was not detected by direct antiglobulin testing, the presence of a small amount of IgG antibody on the patients red cells could not be disregarded since erythrophagocytosis occurred in a medium lacking divalent cations. We postulate that the destruction of the patients red cells might be mediated mainly through interaction with the C3 receptors on macrophages; however, the cooperative effect of the erythrocyte-macrophage interaction mediated through the Fc receptors for IgA and IgG can not be ruled out.

Mechanism of prolactin release by 5-hydroxytryptophan.

Abstract Male Wistar rats were intraperitoneally administered 300 mg/kg b.w. of α-methyl-p-tyrosine methyl ester(α-MT). These α-MT pretreated rats were anesthetized with urethane and then 5% glucose or dopamine (1 μg/kg b.w./min) was infused for 45 min. At 1 min before or 15 min after dopamine infusion, 10 or 50 mg/kg of 5-hydroxytryptophan (5-HTP) was injected intraperitoneally, and blood samples were taken from the jugular vein for prolactin determination. In rats treated with α-MT, the administration of 5-HTP increases the serum prolactin level in a dose-related manner. Dopamine infusion caused a marked decrease in serum prolactin level. The concomitant administration of dopamine and 5-HTP prevented the dopamine-induced decrease of serum prolactin in α-MT treated rats. These results indicate that the serotonergic stimulus enhanced prolactin release, not by inhibiting the dopaminergic activity, but by stimulating a prolactin-releasing factor or by activating other neurotransmitter systems.