氯化锂对小鼠生殖和胚泡细胞遗传毒性的研究

目的：观察氯化锂的遗传毒性特征并对其毒作用机制做一切初步探讨。方法：以氯化锂为受试物,昆明种小鼠为受试对象,进行小鼠生殖细胞遗传毒性试验。结果：氯化锂经口灌胃染毒后,小鼠睾丸细胞染色体畸变率增加,着床前胚泡细胞微核率增加,结论：一定剂量的氯化锂对小鼠生殖和胚泡细胞具有遗传性毒性用。     

单宁酸——氯化铁法媒染肝微血管的光镜研究

目的：光镜下观察单宁酸－－氯化铁法媒染的肝内微血管构筑。方法：用单宁酸配制的混合媒染固定液灌流大鼠,取肝脏冰冻切片,入氯化铁溶液中呈色。结果：肝小叶中央静脉、肝血窦以及小叶间动、静脉、小叶下静脉均显示良好,肝小叶周边有很横断面的血窦,肝板较饱满,窦壁上有许多细丝缠绕。结论：单宁酸－－氯化铁法可很好地显示肝内微血管构筑,小叶周边存在与中央静脉平行的血窦。     

单宁酸——氯化铁法媒染心脏微血管的研究

应用单宁酸－氯化铁法媒染大鼠心脏微血管,光镜下观察其形态学特点。结果：左、右心室及空间隔、心房的微血管得到了良好的显示。左、右冠状动脉细小分支在心外膜层、心肌层及心内膜层形成了三层血管网,内、外两层微血管互相吻合成网;心肌层微血管则与心肌纤维平行,很少吻合。各级微血管的形态自然真实,有明显立体感。因此,单宁酸－氯化铁法是显示心脏微血管的理想方法。     

纳络酮用于改善小鼠学习记忆障碍的研究

采用口服氯化铝建立小鼠学习记忆障碍模型,应用跳台法观察了纳络酮对铝(Al)中毒所致小鼠学习记忆障碍的改善作用,用火焰原子吸收分光光度法测定血锌(Zn)、铜(Cu)、锰(Mn)等含量.结果显示,氯化铝可导致小鼠学习记忆障碍,且有降低血Zn、Cu含量的作用(P<0.05);纳络酮治疗有改善Al中毒小鼠学习记忆障碍的作用,同时也增加了血Zn、Cu的含量.     

跨上皮电位差对蛙直肠上皮顶膜氯通道的作用

氯离子跨紧密上皮转运主要采取细胞通路,其转运调控的关键部位是上皮细胞顶膜氯通道。应用上皮电压钳技术、高钾除极化技术和Ｕｓｓｉｎｇ上皮组织灌流系统结合测定氯离子通量,观察跨上皮电位差对氯离子跨蛙直肠上皮转运的影响。实验结果表明跨上皮电位差对氯离子跨蛙直肠上皮吸收是必不可少的。跨上皮电位差作为转运驱动力外,还能激活蛙直肠上皮细胞顶膜的氯通道。     

Compatibility and stability of bryostatin 1 in infusion devices

Bryostatin 1 is currently in phase II clinical trial sponsored by the National Cancer Institute as an anticancer chemotherapeutic agent. Bryostatin 1 for injection was supplied in a dual pack containing a drug vial and a diluent vial and was manufactured by Ben Venue Laboratories, Inc (Bedford, OH). The stability and compatibility of the bryostatin 1-PET formulation, diluted to 1 and 10 ug/mL in saline and benzyl alcohol preserved saline, with polypropylene (PP) and polyvinyl chloride (PVC) bags at room temperature (27°C) were studied. All experiments were conducted in triplicate and analyses were performed using a validated, stability-indicating, high performance liquid chromatography (HPLC) assay.Bryostatin 1 solutions were compatible with PP bags. At both concentrations and with both salines, the bryostatin content remained unchanged during the 28-day storage period, benzyl alcohol concentration in the preserved saline solutions also remained relatively constant. In PVC bags, however, a decrease in bryostatin 1 concentrations without generation of decomposition products was observed at both dilutions and with both salines during the 28-day storage. A decrease in benzyl alcohol concentration in the preserved saline was also observed. While no diethylhexylphthalate (DEHP) leakage into the solution was observed in PP bags, DEHP leakage in PVC infusion bags was observed on day 2 of storage which increased with storage time and leveled off on day 6. The amount of DEHP leached into drug solution is dependent on the drug concentration. This study suggests bryostatin-PET formulation diluted with preserved saline can be used for long-term (4 week) intravenous administration using PP infusion bags, but not with PVC bags.     

SYMPOSIUM: Experimental Biology 1995 Role of Mesangial Cell Ion Transport in Glomerular Physiology and Disease: ANGIOTENSIN II-INDUCED TYROSINE PHOSPHORYLATION IN MESANGIAL AND VASCULAR SMOOTH MUSCLE CELLS

• 1 Angiotensin II (AngII)-induced, activation of phospholipase C (PLC) and Ca²⁺-dependent Cl^? channels is an important signal transduction pathway for the regulation of vascular smooth muscle cell (VSMC) and glomerular mesangial cell contraction and growth. While AT receptors are traditionally thought to be G-protein coupled to the β isoform of PLC, recent evidence suggests that in some tissues AT receptors may also activate the PLC-γ isoform via tyrosine phosphorylation.
• 2 By western analysis, we identified PLC-γ1 in the above cell types. We found that within 3 min of exposure to 10^?7 mol/L AngII, tyrosine phosphorylation of PLC-γ1 was observed; however, peak response (> 3-fold increase) occurred within 0.5 min. In addition, pre-incubation of these cells with the tyrosine kinase inhibitor genistein blocked the tyrosine phosphorylation of PLC-γ1 by AngII. In contrast, preincubation with the tyrosine phosphatase inhibitor sodium vanadate increased the levels of tyrosine phosphorylation of PLC-γ1. Similar results were found when intracellular levels of 1,4,5-IP₃ were measured after AngII exposure.
• 3 By using patch clamp techniques on cultured rat mesangial cells exposed to AngII, we found that the release of 1,4,5-IP₃-sensitive intracellular Ca²⁺ stores stimulated low conductance Cl^? channels. Preincubation with genistein, abolished the usual 10-fold increase in Cl^? channel activity observed with AngII.
• 4 Therefore, we conclude that in VSMC and glomerular mesangial cells (i) AngII transiently stimulates PLC activity via tyrosine phosphorylation of the γ1 isoenzyme, (ii) tyrosine phosphorylation of PLC-γ1 and production of 1,4,5-IP₃ in response to AngII is dramatically inhibited by tyrosine kinase inhibition and stimulated by tyrosine phosphatase inhibition, (iii) activation of Ca²⁺-dependent Cl^? channels by AngII-induced release of 1,4,5-IP₃-dependent intracellular Ca²⁺ stores is also abolished by tyrosine kinase inhibition. In summary, this AngII-induced signal transduction cascade provides a possible mechanism for both the contractile and growth-stimulating effects of AngII on VSMC and glomerular mesangial cells.

     

α-Smooth-muscle actin expression in normal and fibrotic human livers

To determine the significance of the expression of -smooth-muscle actin in the fibrotic human liver, normal and diseased livers were stained with anti--smooth-muscle-actin antibody by an immunoperoxidase method. Vitamin A-containing lipocytes were also identified by the modified Kupffer's gold chloride method. In the normal human liver, lipocytes as well as vascular smooth muscle cells expressed -smooth-muscle actin. In alcoholic liver disease, there was an increase in the cells positive for -smooth-muscle actin adjacent to the fibrotic areas, but the response of lipocytes to the gold chloride reaction diminished. In chronic hepatitis, the cells positive for -smooth-muscle actin increased around the enlarged portal areas, and the response to the gold chloride reaction did not change appreciably. An increase in the cells positive for -smooth-muscle actin was associated with the progression of hepatic fibrosis in the liver of patients with alcoholic liver disease and chronic hepatitis.     

Noradrenaline transport by rat heart sympathetic nerves: A re-examination of the role of sodium ions

Summary The effect of sodium ion on ³H-(–)-noradrenaline (0.0875 to 0.5 M) transport by rat heart atrial hemi-appendages incubated in vitro has been studied, and the following observations made: a) When sodium was omitted (choline and lithium substitution) there was no evidence for active noradrenaline transport, and only a component that did not show saturation kinetics up to 1 M noradrenaline, remained. b) Omission of sodium or addition of 4×10^–5 M desipramine inhibited noradrenaline transport to exactly the same extent, and their effects were not additive. Alprenolol did not reduce this sodium-independent transport, but tropolone lowered it somewhat. c) No evidence for corticosterone-sensitive noradrenaline transport (uptake-2) was found in this preparation at the low amine concentrations used. d) In control medium, the kinetic parameters of transport were: K _m: 0.59 ± 0.063 M and V _max: 2.44 ± 0.43 (pmoles/mg protein/min). With 26 mM sodium and the rest substituted by choline, K _m:2.26 ± 0.70 M (P0.001) and V _max: 2.74 ± 0.43 (pmoles/mg protein/min) (not significant). Also with 26 mM sodium, but with sucrose substitution, K _m: 0.76 ± 0.13 M (N.S.) and V _max: 1.06 ± 0.13 (pmol/mg/min) (P<0.05). Such results indicate that sodium only modifies the affinity of the transport system for noradrenaline, without changing V _max, and that changes in the latter are only a consequence of a reduction of the ionic strength. e) When noradrenaline transport was studied at different concentrations of external sodium, at constant ionic strength and with precautions to minimize the noradrenaline-releasing effect of low sodium, it was found that the data could be best represented by two hyperbolas placed in series. This suggests that the noradrenaline carrier has two sites for sodium, that do not interact with each other. When the same experiments were repeated in the absence of chloride, it was found that the noradrenaline transport system had lost virtually all its affinity for sodium. f) The effect of prolonged tissue incubation in the absence of sodium was found to produce a relatively small inactivation of noradrenaline transport. Such phenomenon was enhanced by raising the calcium concentration to 2 mM.     

Postsynaptic inhibition of invertebrate neuromuscular transmission by avermectin B1a

The avermectins are a family of novel macrocyclic lactones which paralyze nematodes and insects. One highly potent member of this family, avermectin B1a, has been shown to block neuromuscular transmission in the lobster opener and stretcher muscles. Continuous superfusion of these muscles with the drug (6 microM) resulted in a rapid loss of intracellularly recorded inhibitory postsynaptic potentials. Amplitudes of excitatory potentials and membrane input resistance declined at a slower rate, with a similar time course (25-30 min). These effects were not reversed by prolonged washing. A 3-5 mV hyperpolarization was also observed, which was reversed to depolarization in low chloride lobster saline. Picrotoxin (20 microM) blocked the effects of avermectin B1a on excitatory postsynaptic potentials. Both gamma-aminobutyric acid (GABA) and avermectin B1a decreased the slope of current voltage curves in the stretcher muscle, reflecting an increase in membrane conductance. These changes were greatly reduced by application of bicuculline (50 microM) or picrotoxin (20 microM) Avermectin B1a had no effect on the "fast" axon excitatory electrical responses (glutaminergic) of the cockroach extensor tibiae muscle fibers which lack an inhibitory (GABAergic) input. It is concluded that at the lobster neuromuscular junction, avermectin B1a acts on the GABAergic synapse and lowers input resistance of the muscle membranes by causing an increase in chloride ion permeability.