THE PREOPERATIVE AND POSTOPERATIVE CARE OF ACUTE ARTERIAL OBSTRUCTION

Acute arterial obstruction may result not only from arterial injuries but also from thrombosis or embolism. The fate of the extremity is generally decided in the first few hours following the obstruction of the major artery. It is therefore essential that physicians should be able to recognize acute ischemia of the extremities and institute treatment which will prevent permanent damage and facilitate the reestablishment of normal circulation.Direct application of heat should be scrupulously avoided since the reduced blood flow is unable to supply increased metabolic demand. The extremity should be placed at or just below heart level so as to avoid both the ischemia of elevation and the edema of dependency. Pressure in the form of either encircling plaster or even compression bandages should be avoided and the extremity simply immobilized by a posterior splint. General supportive treatment is essential to maintain adequate pressure and composition of the arterial blood. In selected cases, agents to overcome vascular spasm or to prevent extension of intravascular thrombosis are indicated.     

THE EFFECT OF CALCIUM WITHDRAWAL ON THE STRUCTURE AND FUNCTION OF THE TOAD BLADDER

Previous reports have indicated that calcium is necessary to support active sodium transport by the toad bladder, and may be required as well in the action of vasopressin on both toad bladder and frog skin. The structure and function of the toad bladder has been studied in the absence of calcium, and a reinterpretation of the previous findings now appears possible. When calcium is withdrawn from the bathing medium, epithelial cells detach from one another and eventually from their supporting tissue. The short-circuit current (the conventional means of determining active sodium transport) falls to zero, and vasopressin fails to exert its usual effect on short-circuit current and water permeability. However, employing an indirect method for the estimation of sodium transport (oxygen consumption), it is possible to show that vasopressin exerts its usual effect on Q_oo2 when sodium is present in the bathing medium. Hence, it appears that the epithelial cells maintain active sodium transport when calcium is rigorously excluded from the bathing medium, and continue to respond to vasopressin. The failure of conventional techniques to show this can be attributed to the structural alterations in the epithelial layer in the absence of calcium. These findings may provide a model for the physiologic action of calcium in epithelia such as the renal tubule.     

卡氏膜球藻鞭毛伸缩节律的研究

卡氏膜球藻（Ｈｙｍｅｎｏｍｏｎａｓｃａｒｔｅｒａｅ）是一种单细胞海藻,细胞圆球形,表面覆盖一层球形石（Ｃｏｃｃｏｌｉｔｈｓ）。两条鞭毛稍不等长,着生于细胞前端,鞭毛长约为细胞直径的１．５倍。在２５±℃,光照强度２０００ｌｘ,光暗时间比１４：１０小时条件下,用ＭＥＳⅢ培养基培养卡氏膜球藻,发现细胞在光照条件下伸出鞭毛,活跃游动;在黑暗条件下缩回鞭毛,沉于培养瓶底。进一步试验证明：１．光刺激细胞伸出鞭毛,黑暗刺激细胞缩回鞭毛。２．鞭毛的伸缩与培养中的光暗周期变化严格对应,即光周期开始后２０分钟,细胞开始伸出鞭毛;暗周期一开始,鞭毛就向细胞内收缩。３．在连续光照条件下,鞭毛的周期性伸缩现象消失。所以,卡氏膜球藻鞭毛周期性伸缩是一种受光暗周期调节的外源节律。这种鞭毛伸缩的节律现象在藻类是第一次报道。     

心得安对实验性心肌梗塞大鼠心肌膜β受体的影响

本文采用受体放射自显影术,以银粒数的分布与数量变化作为观察指标,对β受体阻滞剂心得安治疗实验性急性心肌梗塞(AMI)大鼠的心肌膜β肾上腺素能受体(β受体)的影响进行研究.左冠状动脉前降支(LAD)结扎后一周引起心肌梗塞区内[3H]DHA结合位点数显著降低,在非梗塞区亦降低.结扎LAD应用心得安(100ug/kg)治疗一周后梗塞区[3H]DHA结合位点数明显回升,而非梗塞区则进一步降低.引人注目的是,心得安治疗后,[3H]DHA结合位点数在梗塞区/非梗塞区的比值由LAD结扎时的0.24上升为0.87,接近于假手术对照组的0.97.结果证明,心得安是直接作用于心脏的β受体,可能还通过调整了梗塞区与非梗塞区β受体的平衡,改善了心室的顺应性和提高了梗塞心脏的收缩协同作用.从而对AMI的心脏起到保护和治疗作用.