The participation of adenosine receptors in the adenosine 5''-triphosphate-induced relaxation in the isolated rabbit corpus cavernosum penis

AIM: To investigate the participation of adenosine receptors in the adenosine 5'-triphosphate (ATP)-induced relaxation in the corpus cavernosum penis (CCP) of rabbits. METHODS: The ATP-induced relaxation was assessed on the noradrenaline precontracted CCP of rabbits in the presence and absence of 8-(3-chlorostyryl)caffeine (CSC); an adenosine A(2A) receptor antagonist; alloxazine and MRS1754; adenosine A(2B) receptor antagonists; and ARL67156, an inhibitor of ecto-nucleoside triphosphate diphosphohydrolases. RESULTS: Adenosine and ATP relaxed the noradrenaline precontracted CCP of rabbits in a concentration-dependent manner. The adenosine- and ATP-induced relaxations were suppressed by alloxazine and MRS1754, but not by 8-(3-chlorostyryl)caffeine. ARL67156 potentiated the ATP-induced relaxation but not the adenosine-induced one. MRS1754 suppressed the ATP-induced relaxation potentiated by ARL67156. CONCLUSIONS: The above results suggest that, in the CCP of rabbits, the adenosine receptor mediating adenosine-induced relaxation is of the A(2B) receptor and the ATP directly causes relaxation through the A(2B) receptor on the CCP.     

Nonspecific immunity in pregnancy: monocyte surface Fcγ receptor expression and function

The state of pregnancy is an immunological enigma during which the body must prevent rejection of the antigenically foreign fetus while at the same time maintain sufficient maternal host defense mechanisms to combat infection. Although most studies on the immunology of pregnancy focus on immune suppression, several studies have shown an increase in nonspecific host defense, which is postulated to be a compensatory mechanism for decreased specific immunity during pregnancy. Studies in this laboratory have shown that monocyte surface FcγRI (CD64) and FcγRII (CD32) expression progressively increase throughout pregnancy, while surface MHC class II expression remains unchanged. Functional studies revealed that the number of phagocytic monocytes which could be isolated from pregnant women was increased. These cells exhibited an increased capacity to ingest IgG-opsonized human erythrocytes. This study shows for the first time that monocyte surface FcγR expression and FcγR-mediated functions are increased during pregnancy. These results support the hypothesis that nonspecific immunity as represented by FcγR expression and function is increased during pregnancy.     

Nerve growth factor and p75NGFR factor receptor mRNA change in rodent CNS following stress activation of the hypothalamo-pituitary-adrenocortical axis

The synthesis of nerve growth factor (NGF) by the hippocampus raises the possibility that NGF may play a role in the regulation of the hypothalamic-pituitary-adrenal axis (HPAA). Subchronic cold stress has been shown to activate the HPAA in a mild noninvasive manner, to stimulate serum glucocorticoid levels, and to perturb NGF binding in hippocampus and basal forebrain. One or repeated episodes of cold stress increased NGF mRNA levels in the hippocampus and p75^NGFR mRNA levels in the basal forebrain. These changes were not due to elevated serum glucocorticoid levels since treatment with exogenous corticosterone had no effect on NGF and p75^NGFR mRNA levels. Adrenalectomy did not prevent the stress induced increases in NGF and p75^NGFR mRNA. © 1993 Wiley-Liss, Inc.     

重症肌无力中枢神经系统受损模型

目的近年研究结果表明，重症肌无力（ＭＧ）病变部位并不仅仅局限于神经肌接头（ＮＭＪ）处突触后膜烟碱型乙酰胆碱受体（ｎＡＣｈＲ），烟碱型乙酰胆碱受体抗体（ＡＣｈＲ－ａｂ）病理作用可能波及到中枢神经系统（ＣＮＳ）。因此，有必要建立模拟ＭＧ患者ＣＮＳ损害的动物模型，研究ＭＧ患者脑脊液中存在的ＡＣｈＲ－ａｂ引起ＣＮＳ损害的机制。方法从ＭＧ患者血中提取的ＡＣｈＲ－ａｂ经侧脑室穿刺注入到大鼠脑室系统，然后观察其症状和体征，以及用脑干听觉诱发电位仪（ＢＡＥＰ）检测鼠脑干听觉传导中枢功能。用免疫组化法（ＡＢＣ）研究ＡＣｈＲ－ａｂ与ＣＮＳ神经－ｎＡＣｈＲ之间免疫结合反应及其分布。结果大鼠除了出现脑干听觉传导中枢功能障碍外，还出现类似于ＭＧ动物模型表现的症状。免疫组化研究结果显示，神经－ｎＡＣｈＲ样阳性免疫反应广泛分布于ＣＮＳ许多部位。结论脑室内注入的ＡＣｈＲ－ａｂ与神经－ＡＣｈＲ结合引起ＣＮＳ功能障碍和出现ＭＧ动物模型样症状。我们首次建立的中枢受损的ＭＧ模型将有助于阐明ＡＣｈＲ－ａｂ引起中枢受损和ＣＮＳ下位运动神经元引起横纹肌收缩无力的机制。     

Plasminogen activator is involved in the hCG-induced neutrophil extravasation and vasopermeability increase in the rat testis

The role of proteolytic enzymes in the hCG-induced increase in testicular vasopermeability and neutrophil extravasation was studied using protease inhibitors. An intra-testicular injection of hCG together with incubation medium conditioned by polymorphonuclear leucocytes (PMNs) caused a significant increase in vasopermeability and a coincident extravasation of PMN's from the postcapillary venules in the rat testis. When p-aminobenzamidine, a serine protease inhibitor which inhibits urokinase-type plasminogen activator, was administered together with hCG in the incubation medium, both the permeability increase and PMN extravasation were prevented. Aprotinin, another serine protease inhibitor, and Eglin C, a specific neutrophil elastase and cathepsin G inhibitor were, however, without effect. None of these inhibitors caused any non-specific vascular effects in the testis at the concentrations used. These results support the concept that the hCG-induced increase in vasopermeability in the rat testis is related to extravasation of PMNs and suggest that urokinase-type plasminogen activator is involved in migration of these cells through the postcapillary venular walls.     

Effect produced by acute and chronic administration of the selective 5-HT3 receptor antagonist BRL 46470 on the number of spontaneously active midbrain dopamine cells in the rat

This study examined the effect of acute and chronic administration of the selective 5-HT₃ receptor antagonist BRL 46470A, an analog of granisetron, on the number of spontaneously active dopamine (DA) cells in the substantia nigra pars compacta (A9 or SNC) and the ventral tegmental area (A10 or VTA) in the rat. In the A10 area, the acute administration of BRL 46470A decreased the number of spontaneously active DA cells at a dose of 0.1 mg/kg (0.28 μmol/kg) ip, yet increased the number of spontaneously active DA cells at a dose of 0.3 mg/kg (0.84 μmol/kg). The chronic administration (21 days) of BRL 46470A appeared to produce a multiphasic dose-response curve. Thus, the chronic treatment with BRL 46470A increased the number of spontaneously active A10 DA cells at 0.03 (0.084 μmol) and 0.3 mg/kg, but decreased the number of spontaneously active A10 DA cells at a dose of 0.1 mg/kg. In contrast, BRL 46470A did not decrease the number of spontaneously active A9 DA cells after either acute or chronic administration (0.01-0.3 mg/kg). However, BRL 46470A did increase the number of spontaneously active A9 DA cells at acute and chronic doses similar to those that were effective in A10. The iv administration of (+)-apomorphine (APO) not only failed to reverse the decrease produced by chronic administration of BRL 46470A at 0.1 mg/kg, but further decreased the number of spontaneously active A10 DA cells. Similar to the results obtained with granisetron, the pretreatment of naive rats with either 0.01 or 0.1 mg/kg iv of BRL 46470A significantly potentiated (2-fold) the suppressant action of APO on the basal firing rate of A10, but not A9 DA cells. Overall, our results indicate that similar to granisetron, chronic BRL 46470A at 0.1 mg/kg selectively decreases the number of spontaneously active A10 DA cells, via a mechanism not related to depolarization inactivation. Presently, it is not clear what factors may contribute to the multiphasic dose-response curve of BRL 46470A. © 1994 Wiley-Liss, Inc.     

INTERACTION BETWEEN EPIDERMAL GROWTH FACTOR AND ARGININE VASOPRESSIN IN RENAL MEDULLARY MEMBRANES

1. Epidermal growth factor is a potent mitogen that causes natriuresis, diuresis and inhibition of arginine vasopressin-induced water reabsorption. 2. The aim of this study was to determine any interaction between epidermal growth factor and the V1 (vascular) and/or V2 (antidiuretic) arginine vasopressin receptor subtypes. 3. Radioligand binding displacement assays demonstrated that although arginine vasopressin related peptides displaced both radioligands from renal medullary membranes at low concentrations epidermal growth factor displaced neither. 4. Arginine vasopressin V2 receptor second messenger cyclic adenosine monophosphate (CAMP) production was inhibited by epidermal growth factor (IC₅₀ 2 ± 10^?7 mol/L) as was sodium fluoride cAMP production but only at much higher concentrations. 5. Therefore the diuretic effect of epidermal growth factor is not via direct antagonism of arginine vasopressin receptors but seems mediated via inhibition of the V2 second messenger system.     

Interleukin-2, its soluble receptor,and soluble T8 antigen in acute ischemic stroke

The treatment of neoplasia with interleukin-2 (IL-2) can be complicated by neurological deficits resembling transient Ischemic attack and stroke. We investigated whether interleukin-2 contributes to the natural course of cerebrovascular ischemia and particularly to the pathogenesis of infection-associated stroke. Plasma levels of interleukin-2 were below the level of detectability in almost all measurements. Patients with and without previous infection (n = 11, 805 ±445 U/ml vs n = 19, 824 ± 501 U/ml) did not have significantly higher levels of soluble interleukin-2 receptors than control subjects with (n = 14, 667 ± 229 U/ml) or without vascular risk factors (n = 17, 567 ± 176 U/ml). Receptor levels increased in patients during the first week after stroke (n = 15, 1157 ± 1013, p < 0.02). Levels of soluble T8 antigen (sT8) were higher in patients (n – 26, 320 ± 112 U/ml) than in healthy control subjects (n = 15, 246 ± 92 U/ml; p < 0.05) and sT8 levels increased during the first week after stroke (p < 0.05). These results reflect an immunological response to the cerebral infarct; they do not indicate a general role of the IL-2 system in the pathogenesis of ischemic stroke with or without previous infection.