磷脂酶C与生殖

磷脂酶C(PLC)是磷脂酰肌醇信号转导途径中一个关键酶。目前确认的哺乳类PLC共有PLC β、PLC γ、PLC δ、PLC ε和最近新发现的PLC ζ 5种亚型 ,12种同工酶。不同亚型的结构、调控和组织分布各有差异。PLC在调控信号转导通路中的特性使其在顶体反应、卵子激活中发挥了巨大的作用。本文综述了PLC家族 5种亚型的结构、调控机制及PLC在男性生殖领域的相关内容 ,包括PLC引起卵子发生Ca2 + 振荡、激活卵子、促进胚胎发育等 ,并进一步探讨了PLC在临床上可能的应用前景。     

喷雾(冰冻)干燥法制备钠、锂快离子导体

对两种性能较好的快离子导体Na_3Zr_2Si_2P_3O_(12)(Nasicon)和Li_(1.8)Ti_(1.2)·Cr_(0.8)P_3O_(12)用喷雾干燥法和冰冻干燥法制备粉料和陶瓷烧结,并对样品进行了X射线衍射分析,形貌和显微结构观察以及阻抗谱测量等。实验结果表明:两种方法制备的粉料具有颗粒细,均匀性好,合成温度低等优点。在300℃时,两种样品的电阻半分别为10.05 Ω.cm和94.8 Ω.cm。激活能分别为0.25 eV和0.27ev。     

Radiofrequency Catheter Ablation of the Anterosuperior and Posteroinferior Atrial Approaches to the AV Node for Treatment of AV Nodal Reentrant Tachycardia

Catheter Ablation Techniques in AVNRT. Radiofrequency catheter ablation has been established as a first-line curative treatment modality in patients with symptomatic AV nodal reentrant tachycardia (AVNRT). The successful sites of stepwise catheter ablation approaches of the so-called fast and slow pathways strongly suggest that AVNRT involves the atrial approaches to the AV node. The typical fast pathway ablation sites are located anterosuperior toward the apex of the triangle of Koch, which also contains the compact AV node, whereas the usual slow pathway ablation sites are located posteroinferior toward the base of the triangle of Koch at a greater distance to the compact AV node and bundle of His. Accordingly, ablation studies with large patient cohorts have demonstrated that fast pathway ablation carries a higher risk of inadvertent complete AV block. Thus, the slow pathway is clearly the primary target site, and fast pathway ablation is rarely necessary. Different approaches for slow pathway ablation have been elaborated: anatomically oriented stepwise techniques, ablation guided by double potentials recorded within the area of the slow pathway insertion, and combined techniques. The modern concept of AVNRT suggests that this arrhythmia involves the highly complex three-dimensional nonuniform anisotropic AV junctional area. Accordingly, mapping and ablation studies demonstrated that the anterior approach is not identical with fast pathway ablation, and the posterior approach is not identical with slow pathway ablation. Therefore, it is essential for interventional electrophysiologists to familiarize themsdves with the anatomic and electrophysiologic details of this complex and variable specialized AV junctional region. In this review, the anatomic and pathophysiologic aspects of the AV junctional area as they relate to interventional therapy are summarized briefly, and the catheter techniques for ablation of the so-called fast and slow AV nodal pathways for the treatment of AVNRT are described.     

Chemical and enzymatic treatment of endothelin

Endothelin-1 (ET), the most potent vasoconstrictor yet discovered, is a peptide containirig 21 amino acids with two intrachain disulfide bridges. With the aim of obtaining two-chain derivatives, Et was submitted to chemical and enzymatic treatments. Reaction of ET with CNBr in 70% HCOOH gave, in addition to the expected [Hse⁷ lactone]-7,8-seco-ET and unreacted material, a by-product whose molecular weight was 25 m.u. greater than that of ET. When the reaction mixture, after lyophilisation, was immediately quenched with NH3-saturated dry MeOH, two products could be recovered in a 5:1 ratio, both obtained by nucleophilic attack of the homoserine lactone: the expected [Hse⁷-NH₂]-7,8-seco-ET and [Hse⁷]ET, resulting from competitive intramolecular reaction of the deprotonated α-amino group of the Asp⁸ residue. The Lys⁹-Glu¹⁰ bond turned out to be very resistant to enzymatic attack both by Lys-C-endopeptidase and trypsin. The 9,10-seco-ET derivative could be obtained by treatment with Lys-C-endopeptidase only by using a high enzyme/ET ratio and after a prolonged incubation time. Cleavage of the Lys⁹-Glu¹⁰ bond could not be achieved by treatment with trypsin, even with a high enzyme/substrate ratio. The main product was 13, 14-seco-ET, deriving from the action of chymotripsin (present as an impurity in the trypsin preparation) on Tyr¹³. The structure of these peptides was confirmed by amino-acid sequence analysis and fast atom bombardment mass spectrometry (FAB-MS). Nicking of the ET structure at different positions had different impact on the biological properties of the resulting derivatives. © Munksgaard 1995.     

Gadolinium-enhanced breath-hold three-dimensional time-of-flight MR angiography of the abdominal and pelvic vessels: The value of ultrafast MP-RAGE sequences

MR angiography (MRA) was performed in 50 consecutive subjects (mean age, 59 years), who had been referred for abdominal MRA, on a 1.5-T superconductive unit that used a body phased-array coil. Three breath-hold three-dimensional sequences were evaluated both in phantom and clinical studies: (a) standard fast three-dimensional gradient-echo sequence (TR = 15, TE = 6; imaging time, 32 seconds), (b) ultrafast three-dimensional gradient-echo sequence (TR = 8.2, TE = 3; imaging time, 18 seconds), and (c) ultrafast magnetization-prepared (MP) rapid acquisition gradient echo (RAGE) (TR = 5.8, TE = 2.9, inversion time [TI] = 20; imaging time, 15 seconds). The initial 30 patients were randomized into three groups by three separate sequences. For the remaining 20 patients, ultrafast-gradient-echo and ultrafast MP-RAGE sequences were performed. Conventional angiography was performed on 36 patients. Signal measurements of the phantom and clinical images of the aorta, visceral branches of the aorta, iliac arteries, inferior vena cavae, and portal veins were performed. The overall image quality and background fatty tissue contrast of the vessels were rated subjectively. Comparison of images between MRA and conventional angiography also was performed. The contrast between the vessels and background fatty tissue was significantly higher in the ultrafast MP-RAGE sequence in both quantitative and qualitative analysis, and image-quality ultrafast MP-RAGE was superior to the other two sequences (P < .01). The aorta and iliac arteries could be visualized in all pulse sequences, and abnormalities of these vessels were diagnosed correctly. The renal artery was visualized more clearly with the two ultrafast sequences.     

健康人视动性眼球震颤的研究

用微处理机(单板计算机)实时分析了视动性眼震,提取了10项参数,其中9项参数得出正常值,可作为评定视动性眼震之参考。各项参数间均有相关,整体评定,可提高诊断水平。将平均慢相速度、快相波辐和累积快相波辐、慢相时间等4项参数分别用计算机处理和人工处理,把两种处理结果进行t检验,无显著差异(P值均>0.05)。将计算机与人工计算的眼震频率进行比较,两者符合率达96.7％以上。采用微处理机可显著提高工效。     

大鼠心内神经节支配肺的研究

15只大鼠分别于左肺门区注入辣根过氧化物酶（HRP，5只）、快蓝（FB，5只），右肺内支气管腔内注入FB（5只），在房壁心内神经节发现示踪剂标记神经细胞。三组标记率分别为1.4％、2.5％及0.9％。标记细胞的出现证实心内神经节部分神经细胞亦是支配呼吸系统肺内、外支气管和肺血管壁、肺泡壁的局部神经细胞；提示心内神经节参与了心肺间功能相互联系及协调的调控。     

导向喷动流化床生物质快速裂解制液体燃料

在冷模试验得到的优化的结构参数基础上，建立了一套生物质最大处理量为5kg／h的导向管喷动流化床生物质裂解反应器。反应在常压和440～520℃进行，以木屑为生物质原料，二氧化碳和氮气为喷动气或流化气，沙子为流化介质。结果表明该喷动流化床反应器可用于生物质的快速裂解。在400～480℃，液体产率随温度增加而上升，高于480℃时，二次反应的加剧又导致液体产品产率下降。固体和气体的产率则随温度的升高而减少。喷动气和流化气流量的增加均强化了反应器内的传热，并使生物质初始裂解产物的停留时间减少，二次反应进行程度减弱。在适当的裂解条件下液体产率可达73．2％，此时气体和焦的产率分别为12．8％和14．0％。所得液体产品为单一相液体，含水约30％，可用于燃烧。与流化床相比，喷动流化床作为生物质快速裂解反应器可明显提高液体产率。     

PARS INTERARTICULARIS STRESS AND DISC DEGENERATION IN CRICKET'S POTENT STRIKE FORCE: THE FAST BOWLER

Cricket fast bowlers are the potent strike force in a multidiscipline team. They subject their spines to repetitive sagittal plane and rotatory movements over many years. The effect of this repetitive stress has not previously been analysed. This study examined 20 former fast bowlers to determine the incidence of spondylolysis, spondylolisthesis and degenerative change. Fast bowlers are noted to have an increased incidence of spondylolysis. A mixed front/side bowling style involving more lumbar hyperextension or rotation has significant association with spondylolysis when compared with side-on bowling styles. There was a high incidence of radiological thoracolumbar degenerative facet joint and disc disease in former fast bowlers.