ULTRASTRUCTURAL ANALYSES OF STONE HEART SYNDROME AT ONSET AND SIX DAYS LATER FOLLOWING TOTAL SUPPORT OF THE CIRCULATION WITH A PARTIAL ARTIFICIAL HEART OR LEFT VENTRICULAR ASSIST DEVICE (ALVAD)

Ischemic myocardial contracture developed in a 21-year-old man following aortic and mitral valve replacement. The patient's circulation was supported totally for 6 days with an abdominal left ventricular assist device (ALVAD). Cardiac allografting was then undertaken. Samples of myocardium taken at the original operation and 6 days later at transplantation were analyzed ultrastructurally. At the onset of ischemic cortracture, left ventricular abnormalities included hypercontraction of myofibrils, loss of normal A-band and Z-band patterns, mitochondrial swelling with fusion of cristae, interfibrillar edema and glycogen depletion. Capillaries demonstrated swelling of endothelial cells and basement membrane disruption. Six days later, ultrastructural morphology showed further degeneration. The myofibrils remained hypercontracted, but were more fragmented. Degenerative changes in mitochondria were more advanced and calcium deposition in cristae was present. No glycogen was seen. The right ventricular myocardium exhibited significantly fewer ultrastructural abnormalities. The principal right ventricular changes were endothelial swelling and basement membrane disruption. Glycogen granules were present. Ischemic contracture affects the left ventricle more than the right, and the morphology becomes more abnormal with time. To our knowledge, this is the first instance wherein morphologic progressions of the ultrastructural alterations of ischemic contracture have been documented.     

CROSS-RESISTANCE FOLLOWING ARTIFICIAL SELECTION FOR INCREASED DEFENSE AGAINST PARASITOIDS IN DROSOPHILA MELANOGASTER

An increase in resistance to one natural enemy may result in no correlated change, a positive correlated change, or a negative correlated change in the ability of the host or prey to resist other natural enemies. The type of specificity is important in understanding the evolutionary response to natural enemies and was studied here in a Drosophila-paxasitoid system. Drosophila melanogaster lines selected for increased larval resistance to the endoparasitoid wasps Asobara tabida or Leptopilina boulardi were exposed to attack by A. tabida, L. boulardi and Leptopilina heterotoma at 15°C, 20°C, and 25°C. In general, encapsulation ability increased with temperature, with the exception of the lines selected against L. boulardi, which showed the opposite trend. Lines selected against L. boulardi showed large increases in resistance against all three parasitoid species, and showed similar levels of defense against A. tabida to the lines selected against that parasitoid. In contrast, lines selected against A. tabida showed a large increase in resistance to A. tabida and generally to L. heterotoma, but displayed only a small change in their ability to survive attack by L. boulardi. Such asymmetries in correlated responses to selection for increased resistance to natural enemies may influence host-parasitoid community structure.     

INDUCTION OF HEPATOCYTE GROWTH FACTOR IN THE LIVER, KIDNEY AND LUNG FOLLOWING TOTAL BODY IRRADIATION IN RAT

Hepatocyte factor (HGF) has been shown to have a pleiotropic function to act as a potent organotropic factor in the regeneration of injury in various organs, including the liver, kidney and lung. To examine the involvement of HGF in radiation injury, the authors analysed the changes in HGF mRNA and HGF protein levels in the rat organs (liver, lung, kidney) and plasma following 6 Gy of total body irradiation. Expression of HGF mRNA in the liver and kidney increased 6–48 h after total body irradiation and returned to previous values 1 week later. HGF protein levels in lung and liver showed 1.3-2 fold elevations 1–2 weeks after irradiation (P< 0.05). HGF levels in plasma stayed at undetectable levels up to 1 month after total body irradiation. The labelling index determined 2 weeks and 1 month after total body irradiation indicated no enhancement of regeneration. Thus, total body irradiation induced transient HGF elevation in these organs without enhancement of regeneration     

抗心律失常药UK－68798对家兔心脏房室结区不同细胞的电生理作用

在离体家兔ＡＶＮ区标本上,用微电极技术研究了Ⅲ类抗心律失常新药ＵＫ－６８７９８对ＡＮ,Ｎ,ＮＨ,Ｈ４种细胞的电生理效应。浓度５×１０－９至５×１０－６ｍｏｌ／Ｌ的ＵＫ－６８７９８对４种细胞的动作电位幅值（ＡＰＡ）、静息膜电位（ＲＰ）皆无影响。对ＡＶＮ的自搏率有剂量依赖性减慢作用,但不改变Ａ－Ｈ传导时间。在５×１０－８－５×１０－６ｍｏｌ／Ｌ剂量范围,此药使动作电位时程（ＡＰＤ５０）和（ＡＰＤ９０）发生剂量依赖性延长。４种细胞中以Ｎ细胞的ＡＰＤ５０和ＡＰＤ９０延长百分率最高。各种细胞ＡＰＤ９０延长百分率的排列次序为Ｎ＜ＡＮ＜Ｈ＜ＮＨ,当浓度为５×１０－６ｍｏｌ／Ｌ时的延长百分率分别为９５±２６％（Ｎ）,７５±２２％（ＡＮ）,６３±２６％（Ｈ）,４６±２６％（ＮＨ）。在ＵＫ－６８７９８的作用下,４种细胞的有效不应期（ＥＲＰ）也发生剂量依赖性延长,但不存在像ＡＰＤ延长百分率那样的差别。此外,４种细胞ＥＲＰ所相当的复极化膜电位未受药物影响,从而避免了由于兴奋性恢复的不均一性,使ＡＶＮ区成为折返性心律失常的发源地．     

胎脑黑质脑内移植矫正PD鼠纹状体内脑啡肽mRNA过度表达

用６－ＯＨＤＡ损毁大鼠一侧黑质—纹状体通路可引起ＰＤ模型鼠脑纹状体内多巴胺匿乏．同时,亦可导致脑啡肽ｍＲＮＡ过度表达。我们用地高辛标记的ｃＲＮＡ探针对纹状体内脑啡肽ｍＲＮＡ含量进行了斑点杂交定量研究,发现损伤侧脑啡肽ｍＲＮＡ含量较健侧增高８０％,胎中脑移植到失神经支配的纹状体内,脑啡肽ｍＲＮＡ过度表达得以矫正至正常水平,说明胎多巴胺能神经元脑内移植能够调节脑啡肽基因表达,提供了移植物能与宿主发生神经整合、建立突触联系的间接证据。