The regulation of thyrotrophin secretion by exogenous thyroxine and triiodothyronine

The inhibition of thyrotrophin secretion by oral doses of 3,5,3'-triiodo-thyronine and thyroxine was studied in subjects with suppressed thyroidal secretion to test the hypothesis that thyroxine has intrinsic metabolic activity in the control of TSH secretion.Five previously untreated female patients with hyperthyroid Graves' disease were given 40 mg carbimazole daily throughout the study. After six weeks of treatment, thyroid hormone replacement was started. In phase 1, they received 20 μg triiodothyronine/day for six weeks, which was then increased to 30 μg/ day, 40 μg/day and 50 μg/day at weekly intervals. In phase 2, the patients received 20 μg triiodothyronine/day for five weeks. Thyroxine supplements were then added to the regimen commencing with 50 μg/day for one week, then 100 μg/day followed by 150 μg/day, each for one week. Total and free triiodothyronine and thyroxine, total 3,3',5'-triiodothyronine (reverse triiodothyronine) and basal TSH were measured by radioimmunoassay in serum samples taken before each change in thyroid hormone supplement.In both phases of the study, a stepwise increase in triiodothyronine concentration was associated with a fall in thyrotrophin concentration. The inhibition of thyrotrophin secretion in phase 2 in relation to serum triiodothyronine concentration was parallel to that observed in phase 1 despite a progressive increase in thyroxine to levels in the low normal range. It has not been possible to demonstrate that thyroxine, at the concentration studied, plays a role in the regulation of TSH secretion independently of its conversion to triiodothyronine.     

银杏苦内酯B对重症急性胰腺炎大鼠p38丝裂原活化蛋白激酶活性的影响

目的观察银杏苦内酯B(BN52021)对重症急性胰腺炎(SAP)大鼠胰腺组织p38丝裂原活化蛋白激酶(p38MAPK)活性的影响。方法Wistar雄性大鼠随机分为阴性对照组(NC组)、SAP模型组(SAP组)、BN52021治疗组(BN组),每组按术后不同时相点(1、2、3、6、12、24h)分为6小组,用Western blotting法分别检测胰腺组织p38MAPK表达与激活情况,同时对胰腺组织进行病理学观察和测定血清淀粉酶活性的变化。结果血清淀粉酶和病理学结果显示SAP造模成功,BN52021能降低SAP大鼠的血清淀粉酶活性,病理学评分在3、6、12h较SAP组显著降低(P<0.05);NC组在各时相点均只检测到少量磷酸化的p38MAPK,SAP组和BN组在各时相点均较NC组显著升高(P<0.05),BN组在6、12、24h较SAP组显著降低(P<0.05)。结论BN52021可部分抑制SAP大鼠胰腺组织p38MAPK的活化,从而发挥其治疗作用。     

Post-ischemic RSR13 amplifies the effect of dizocilpine on outcome from transient focal cerebral ischemia in the rat

Nitric oxide (NO) is a major non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmitter in the gastrointestinal tract. NO released from the myenteric plexus enhances colonic transit and facilitates propulsion of the colonic contents by mediating descending relaxation. Although it has been suggested that colonic transit delays with aging, the mechanism of delayed colonic transit in aging remains unclear. We hypothesized that advanced age is associated with decreased expression of neuronal NO synthase (nNOS) and concomitant reduction in synthesis of NO in the rat colon. We studied nNOS mRNA expression, nNOS-immunohistochemistry, nNOS-immunoblotting and NOS catalytic activity in the mid-colon obtained from young (age 4–8 months) and aged (age 22–28 months) Fisher (F344×BN)F1 rats. Western blot analysis of PGP 9.5, a generic neuronal marker, of the colonic tissues were employed to study whether the total number of neurons of the myenteric plexus is reduced with aging. The number of nNOS-immunoreactive cells and nNOS synthesis in the colonic myenteric plexus were significantly reduced in aged rats. In contrast, expression of PGP 9.5 in colonic tissues was not affected in aged rats. Northern blot analysis demonstrated that the expression of neuronal nNOS mRNA was significantly reduced in the colonic tissues in aged rats. Basal and veratridine-induced release of -[³H]citrulline were significantly decreased in colonic tissues from aged rats, compared to young rats. It is suggested that advanced age is associated with diminished gene expression of nNOS, nNOS synthesis and catalytic activity of NOS. This may explain the mechanism of delayed colonic transit observed in advanced age.     

The association of endemic elephantiasis of the lower legs in East Africa with soil derived from volcanic rocks

Endemic elephantiasis of the lower legs in Ethiopia, which reaches a maximum of 86·7 per 1,000 adults in affected areas, is related to the distribution of red clay soil derived from volcanic rocks, particularly basalt. Prevalence falls rapidly on leaving these areas.This observation has been tested in regions of non-filarial elephantiasis reported in Kenya and north-western Tanzania and further investigated in volcanic areas of Rwanda where the disease had not previously been reported. The same relationship is found to occur in these areas. The limitation to the lower legs of the bare-footed section of the farming community suggests that the aetiological factor or factors enter by the feet.The occurrence at high altitude (over 1,200 metres) is noted and the predominance of basalt or basalt-like lava in each case is considered significant. The altitude governs rainfall and temperature and thus governs the type of soil produced.The soil produced from these rocks is rich in colloidal iron oxide, alumina and silica, to which a number of metallic ions are adsorbed. This soil is a reddish-brown clay which, when wet, is strongly adherent to the skin. The derived ions are known to be toxic to human tissue and absorption through intact human skin has been shown to occur experimentally. It is suggested that absorption of these irritants through the bare feet is responsible for the irreversible damage to the lymphatic channels.The present studies support the hypothesis that “high-altitude” elephantiasis of the lower legs in East Africa is a geochemical disease.     

The regulation of adenylate cyclase of the adrenal cortex

Since estrogens have been found to exert a marked inhibitory effect on dopaminergic action at the anterior pituitary and striatal levels in the rat, the effect of estrogen treatment has been studied on the binding characteristics of the dopamine (DA) antagonist [³H]spiroperidol and of the new DA agonist [³H]N-n-propyl-N-phenylethyl-β-(3-hydroxyphenylethylamine hydrochloride ([³H]RU24213) in rat striatum, nucleus accumbens + olfactory tubercle, frontal cortex and anterior pituitary gland. Specificity of binding was carefully examined in order to investigate possible changes of the agonist and antagonist states of the DA receptor. Estrogen treatment led to a small increase (approx. 20%) of [³H]spiroperidol and [³H]RU24213 binding in rat striatum, nucleus accumbens + olfactory tubercle and frontal cortex while no significant effect was found in the anterior pituitary gland. That the increased binding is due to a corresponding increased number of binding sites and not to higher affinity is indicated by the absence of effect of estrogen treatment on the IC₅₀ values for displacement of the two labeled ligands by a variety of unlabeled compounds. Specificity of binding of DA agonists and antagonists remained unchanged after estrogen treatment. The present data suggest that the potent desensitizing effect of estrogens on DA action at the striatal and pituitary levels is exerted at a step subsequent to binding of DA to its receptor.     

The Formation Process and Strengthening Mechanism of SiC Nanowires in a Carbon-Coated Porous BN/Si3N4 Ceramic Joint

Porous BN/Si₃N₄ ceramics carbon-coated by carbon coating were joined with SiCo38 (wt. %) filler. The formation process and strengthening mechanism of silicon carbide nanowires to the joint were analyzed in detail. The outcome manifests that there is no distinct phase change in the porous BN/Si₃N₄ ceramic without carbon-coated joint. The highest joint strength was obtained at 1320 °C (~38 MPa). However, a larger number of silicon carbide nanowires were generated in the carbon-coated joints. The highest joint strength of the carbon-coated joint was ~89 MPa at 1340 °C. Specifically, silicon carbide nanowires were formed by the reaction of the carbon coated on the porous BN/Si₃N₄ ceramic with the SiCo38 filler via the Vapor-Liquid-Solid (VLS) method and established a bridge in the joint. It grows on the β-SiC (111) crystal plane and the interplanar spacing is 0.254 nm. It has a bamboo-like shape with a resemblance to alloy balls on the ends, and its surface is coated with SiO₂. The improved carbon-coated porous BN/Si₃N₄ joint strength is possibly ascribed to the bridging of nanowires in the joint.     

Flavonoids from Chinese Viscum coloratum produce cytoprotective effects against ischemic myocardial injuries: inhibitory effect of flavonoids on PAF-induced Ca2+ overload

Viscum coloratum has been used in the indigenous system of medicine for the treatment of various diseases such as myocardial ischemia and arrhythmia. Platelet-activating factor (PAF) is an important player in cardiovascular diseases. The aim of this study was to investigate the protective effects of Viscum coloratum flavonoids (VCF) against ischemic myocardial injuries in vivo and to further investigate its regulatory effect on PAF. Studies were performed in a rat model of myocardial infarction and in isolated myocytes. It was found that VCF relieved myocardial injuries during ischemia. PAF (10(-11) m) significantly increased the intracellular free Ca2+ concentration ([Ca2+]i) and VCF inhibited the changes induced by PAF in single cardiac myocytes. The results suggest that VCF can improve cardiac function and that VCF reduces ischemic myocardial injuries via blocking the signaling pathway of PAF. Therefore, PAF blockers may be candidate drugs for preventing cardiac injuries during ischemia/reperfusion, and subsequently improving cardiac function.     

大鼠视网膜细胞间隙连接蛋白Cx43的表达

目的:探讨细胞间隙连接蛋白connexin43(Cx43)在BN大鼠视网膜中的分布特点.方法:以雄性挪威棕色大鼠(Brown Norway)为研究对象,应用免疫组化方法观察Cx43在BN大鼠视网膜中的分布特点.结果:正常视网膜内界膜,视神经纤维层以及神经节细胞层明显表达,神经节细胞表达的主要位置是细胞质和细胞膜,色素上皮细胞全层表达,内外颗粒层及内外层状层无表达.结论:正常视网膜的Cx43主要分布在内界膜,神经纤维层,视网膜节细胞层和视网膜色素上皮层.     

不同品系大鼠对灯盏花素过敏反应差异性研究

目的:比较研究F344、BN、SD、Wistar四种品系大鼠对灯盏花素注射液被动皮肤过敏及其致敏血清中总IgE水平差异性。方法:四种品系大鼠分别随机分为正常对照组、OVA组、灯盏花素组。采用皮下注射给予不同药物致敏,观察各组大鼠被动皮肤过敏反应(PCA)皮肤蓝斑直径大小和阳性率,并检测致敏血清总IgE水平。结果:PCA结果显示,四种品系大鼠的正常组均无蓝斑出现;OVA组,F344、BN、SD、Wistar大鼠蓝斑直径(阳性率)分别为11.67±3.61(6/6)、47.33±5.72(6/6)、5.70±4.81(6/10)、17.90±3.84(10/10),与正常组相比均明显升高且具有显著统计学差异;血清总IgE水平检测结果显示,OVA组血清总IgE含量变化与PCA试验结果一致。对灯盏花素,F344、BN、SD、Wistar大鼠蓝斑直径(阳性率)分别为5.17±2.32(4/6)、2.00±1.79(0/6)、1.67±1.97(0/10)、0.00±0.00(0/10),与正常组相比仅F344大鼠显示出显著性差异;血清总IgE仅F344、BN大鼠血清明显升高,且以F344大鼠变化倍数更高。结论:四种不同品系大鼠对灯盏花素所致被动皮肤过敏反应敏感性及血清总IgE水平均存在一定差异,两者具有一定相关性,其中以F344大鼠最为敏感。