MAP kinase activator from insulin-stimulated skeletal muscle is a protein threonine/tyrosine kinase.

A 'MAP kinase activator' was purified several thousand-fold from insulin-stimulated rabbit skeletal muscle, which resembled the 'activator' from nerve growth factor-stimulated PC12 cells in that it could be inactivated by incubation with protein phosphatase 2A, but not by protein tyrosine phosphatases and its apparent molecular mass was 45-50 kDa. In the presence of MgATP, 'MAP kinase activator' converted the normal 'wild-type' 42 kDa MAP kinase from an inactive dephosphorylated form to the fully active diphosphorylated species. Phosphorylation occurred on the same threonine and tyrosine residues which are phosphorylated in vivo in response to growth factors or phorbol esters. A mutant MAP kinase produced by changing a lysine at the active centre to arginine was phosphorylated in an identical manner by the 'MAP kinase activator', but no activity was generated. The results demonstrate that 'MAP kinase activator' is a protein kinase (MAP kinase kinase) and not a protein that stimulates the autophosphorylation of MAP kinase. MAP kinase kinase is the first established example of a protein kinase that can phosphorylate an exogenous protein on threonine as well as tyrosine residues.     

Heart sarcolemmal Ca2+ transport in endotoxin shock: I. Impairment of ATP-dependent Ca2+ transport

Effects of endotoxin administration on the ATP-dependent Ca²⁺ transport in canine cardiac sarcolemma were investigated. The results show that the sidedness of the sarcolemmal vesicles was not affected but the ATP-dependent Ca²⁺ transport in cardiac sarcolemma was decreased by 22 to 46% (p < 0.05) at 4 h following endotoxin administration. The kinetic analysis indicates that the V_max for ATP and for Ca²⁺ were decreased by 50% (p < 0.01) and 32% (p < 0.01), respectively, while the Km values for ATP and Ca²⁺ were not significantly affected after endotoxin administration. Magnesium (1–5 mM) stimulated while vanadate (0.25–3.0 M) inhibited the ATP-dependent Ca²⁺ transport, but the Mg²⁺-stimulated and the vanadate-inhibitable activities remained significantly lower in the endotoxin-treated animals. These data demonstrate that endotoxin administration impairs the ATP-dependent Ca²⁺ transport in canine cardiac sarcolemma and that the impairment is associated with a mechanism not affecting the affinity towards ATP and Ca²⁺. Additional experiments show that the Ca²⁺ sensitivity of the Ca²⁺-ATPase activity was indifferent between the control and endotoxic groups suggesting that endotoxic injury impairs Ca²⁺ pumping without affecting Ca²⁺-ATPase activity. Since sarcolemmal ATP-dependent Ca²⁺ transport plays an important role in the regulation of cytosolic Ca²⁺ homeostasis, an impairment in the sarcolemmal ATP-dependent Ca²⁺ transport induced by endotoxin administration may have a pathophysiological significance in contributing to the development of myocardial dysfunction in endotoxin shock.     

Comparative analysis of glycoprotein and glycolipid composition of virulent and avirulent strain membranes ofMycoplasma hyopneumoniae

The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M ofMycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 160, 180, and 181 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 180 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z.     

Localization of the pupil trigger in insect superposition eyes

Summary In the superposition eyes of the sphingid moth Deilephila and the neuropteran Ascalaphus, adjustment to different intensities is subserved by longitudinal migrations of screening pigment in specialized pigment cells. Using ophthalmoscopic techniques we have localized the light-sensitive trigger that controls pigment position.In both species, local illumination of a small spot anywhere within the eye glow of a dark-adapted eye evokes local light adaptation in the ommatidia whose facets receive the light. Details of the response pattern demonstrate that a distal light-sensitive trigger is located axially in the ommatidium, just beneath the crystalline cone, and extends with less sensitivity deep into the clear zone. The distal trigger in Deilephila was shown to be predominantly UV sensitive, and a UV-absorbing structure, presumably the distal trigger, was observed near the proximal tip of the crystalline cone.In Ascalaphus we also found another trigger located more proximally, which causes local pigment reaction in the ommatidia whose rhabdoms are illuminated (the centre of the eye glow). The light-sensitive trigger for this response appears to be the rhabdom itself.     

心房钠尿肽对血管紧张素II促血管平滑肌细胞增殖...

By means of technique of cell culture, 3H-thymidine incorporation and dot blot, it was demonstrated that angiotensin II (AGT II) stimulated proliferation and c-fos oncogene expression in cultured SHR vascular smooth muscle cells (VSMC) in a dose-dependent manner. This effect of AGT II was significantly inhibited by co-incubation with ANP. The results suggest that proliferation of VSMC is regulated by some interaction between AGT II and ANP.     

刺激隐神经中C类纤维诱发的小脑浦肯野细胞简单...

Simple spike of cerebellar Purkinje cells (PC-SS) was recorded with microelectrode. In the NCCVF (normalized cross-covariance function) histogram, spontaneous PC-SS does not show obvious peak. When the saphenous nerve is stimulated at lower intensities, which elicits the A-fiber input only, the discharge response (A-CED) consists of an early component with a latency of 16.7 +/- 0.9 ms and a late component with a latency of 270.8 +/- 12.8 ms. After A-fibers are blocked selectively by polarizing current, the stimulation at a suprathreshold strength for C-fiber evokes a characteristic response (C-CED) with a latency of 142.4 +/- 4.3 ms. However, the C-CED can not be evoked by the inputs of A- and C-fiber simultaneously. In NPSDF histogram, the spontaneous activities of PC-SS can be divided into two groups, the high and the low peak group. The high peak group (n = 15) has a peak energy value of 15.7 +/- 4.7 x 10(-3) and peak frequency of 4.07 +/- 1.69 Hz. A-fiber input causes an increase of the peak value, while C-fiber input causes a decrease. The low peak group (n = 16) has a peak energy value 8.4 +/- 1.4 x 10(-3) and peak frequency of 3.67 +/- 2.90 Hz. Both A-fiber and C-fiber inputs cause an increase of the peak value, but the effect of A-fiber input was more prominent. The results show that the pure C-fiber input can reach the cerebellar PC and elicit characteristic simple spike response.     

小麦体细胞再生株（R1）的染色体变异分析

本文研究了普通小麦(Triticum aestivum)、“宁麦三号”等5个基因型的体细胞再生株(R_1)减数分裂各期的染色体异常行为。结果表明:再生株 R_1代有丝分裂时表现为染色体数量上的变异,最常见的有2n-2类型,其次是2n-1类型,也有少数为2n 1和2n-4等变异类型;再生株 R_1花粉母细胞减数分裂过程中出现单价体、多价体、染色体桥、落后染色体、断片和微核等异常现象,并与各基因型细胞遗传程度上差异有关。     

降香黄檀着叶期和无叶期次生韧皮部筛分子的超微结构

利用透射电镜技术研究了生长在海南岛的热带落叶树降香黄檀(Dalbegia odorifera T.Chen)1—2年生枝条着叶期和无叶期次生韧皮部筛分子的超微结构,并就这两个时期的筛分子进行了比较。着叶期每个成熟筛分子内有一个带尾的纺锤形P-蛋白质体,主体由稠密而散乱的P-蛋白质细纤维组成,尾部呈结晶状;筛分子具有横向端壁和单筛板,在邻近筛板处,细胞壁向筛分子腔内形成明显的突起。无叶期仍然保持着与着叶期大致相同厚度的有功能韧皮部,筛分子具有正常的原生质体,P-蛋白质和筛板孔的结构也与着叶期的相同,但筛分子内有较多的淀粉粒和囊泡。