Copolymerization of propene with 1-alkenes using a MgCl2/TiCl4 catalyst

Copolymerization of propylene

1 System name: propene.

and 1-alkenes (1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene) were studied with the catalyst system MgCl₂/TiCl₄-Al(i-Bu)₃. It was found that the polymerization productivity and the consumption rate of propylene are improved significantly in the presence of the comonomer. The total productivity of propylene/1-alkene copolymerizations decreases as follows: 1-octene > 1-decene > 1-dodecene > 1-hexadecene > 1-tetradecene. The reactivity ratios were estimated from the copolymerization results.     

Stereoselective inhibition of neuronal sodium channels by local anesthetics. Evidence for two sites of action?

The objective of this study was to determine if the "tonic," resting inhibition of Na+ channels by local anesthetics results from binding at a site different from that for "phasic," use-dependent inhibition. Stereoselective actions of four local anesthetics were examined in isolated frog peripheral nerve and single Na+ channels. Using the sucrose-gap method on desheathed nerves, four actions of local anesthetics were assayed: 1) tonic depression of compound action potentials at low stimulation frequency (one per minute); 2) phasic depression of the compound action potential during trains of stimulation at 5, 10, and 20 Hz; 3) competitive antagonism of the reversible Na+ channel activator veratridine assayed through the depolarization of the compound resting membrane potential; and 4) depression of the depolarization of the compound resting membrane potential initially induced by the irreversible channel activator batrachotoxin. For assays 1, 2, and 3, all local anesthetics showed a stereoselectivity, where rectus, or (+), enantiomers were more potent than sinister, or (-), enantiomers. In contrast, for the noncompetitive antagonism of veratridine's action and the depression of batrachotoxin-induced depolarization, also a noncompetitive interaction between anesthetic and activator, the (-) enantiomer was more potent than the corresponding (+) enantiomer. Blockade of single Na+ channels activated by batrachotoxin in planar lipid bilayers was also stereoselective for the (-) enantiomer. These findings, along with previously reported voltage-clamp results, can be applied to infer properties of a local anesthetic binding site in activator-free channels. Local anesthetic molecules with more sharply angled shapes have stronger stereoselectivities than less angled, more planar drugs. The inversion of the stereopotency induced by the activators can be explained by either of two mechanisms. There may be two binding sites for local anesthetics, one of high and one of low affinity and of opposite stereoselectivity; activators may change the conformation at the high affinity site, reducing its local anesthetic affinity below that of the usual low affinity site and thereby revealing the pharmacology of the weaker site. Alternatively, only a single binding site may exist and be conformationally altered by activators such that both anesthetic affinity and stereopotency are modified. In activator-free channels, however, a single, high-affinity binding site with a constant stereoselectivity can account for both tonic and phasic inhibition by local anesthetics.     

对肝外胆管梗阻时“软藤征”的再认识

本文回顾性分析了48例“软藤征”的病因,其中恶性疾病28例(占58.3％),良性疾病20例(占41.7％)。据本文资料,作者认为“软藤征”是肝管分叉部及肝外胆管急性完全(或接近完全)性梗阻时肝内胆管扩张的特征性X线表现,并非恶性梗阻特有,良性梗阻亦常见。作者指出,只要肝内胆管无或仅有轻度炎症,胆管具有良好的弹性和扩张性,不论良、恶性病变都可出现“软藤征”。那种认为当梗阻病变未显示时,仅根据“软藤征”即可作出恶性梗阻诊断的观点很值得商榷。作者认为,“软藤征”的定性及病因诊断主要应根据PTC或ERCP,或二者联合显示梗阻局部病变的形态学特征来确定。     

The effect of unilateral internal carotid arterial occlusion upon contralateral duplex study: criteria for accurate interpretation.

To determine the influence of unilateral internal carotid arterial occlusion (ICO) on Doppler frequency spectral analysis (DFSA) of the patent contralateral carotid artery, a retrospective review of 154 patients between July 1987 and December 1991 with angiographically confirmed ICO was performed, correlating duplex and arteriographic findings in a blinded fashion. Biplane arteriograms and bilateral carotid artery duplex studies that used a 5.0 MHz Doppler probe with a 1.5 mm3 sample volume at a 60 degree angle of insonation were performed on all patients. Each carotid artery was categorized by the severity of stenosis as quantified by arteriography: 1% to 15% (n = 41); 16% to 49% (n = 48), 50% to 79% (n = 21), 80% to 99% (n = 34), and bilateral occlusion (n = 10). DFSA peak systolic frequencies were commonly exaggerated in the presence of contralateral ICO and use of standard criteria for DFSA interpretation overestimated bifurcation stenoses in 43 of 89 lesions (48.3%) when determining nonhemodynamically significant lesions (less than 50% diameter reduction) with a sensitivity of only 57.3% and specificity of 96.9%. Conversely, prediction of hemodynamically significant lesions (greater than 50% diameter reduction) with standard criteria had 96.9% sensitivity but only 57.3% specificity. Modification of these criteria to account for the velocity increase or "jet effect" in the ipsilateral carotid artery system increased the sensitivity and specificity to 97.8% in predicting nonhemodynamically and hemodynamically significant stenoses respectively. A Doppler frequency spectrum with a peak systolic frequency (PSF) greater than 4.0 kHz and end-diastolic frequency (EDF) less than 5 kHz with an "open window" distinguished lesions with less than 50% diameter reduction.(ABSTRACT TRUNCATED AT 250 WORDS)     

人和兔雪旺氏细胞的体外培养及形态学观察和生物特性研究

雪旺氏细胞(Schwann cell,SC)在神经再生过程中起着重要作用。我们取人胚及兔之坐骨神经,采用“植块多次移出法”培养出纯净度达99％的人和兔的SC。对培养的SC进行了冻存和复苏处理,复苏后的细胞可保持原有的生长特性。     

Studies on the luminescence of channels in rats and its law of changes with "syndromes" and treatment of acupuncture and moxibustion.

We previously reported the discovery of 14 channels in the human body, which possessed the biophysical property of high emission of light. In this study we found the same property on the Ren and Du channels in healthy rats. Additionally, we discovered that the luminance of the related channels in rat models with different "syndromes" varied greatly. For instance, a markedly low luminance appeared on the Du channel in animals with experimental syndrome of Yang deficiency induced by hydrocortisone; while in animals with experimental syndrome of blood deficiency caused by bleeding, an apparently low luminance occurred on the Ren channel. The intensity of the emitted light on Du and Ren channels increased after acupuncture treatment, but not significantly. This phenomenon conforms to the theory in traditional Chinese medicine that the Du channel is the "sea of Yang channels", while the Ren channel is the "sea of Yin channels".     

雷公藤对雄性大鼠脑垂体前叶黄体生成细胞的影响

利用抗β-黄体生成素(β-LH)单克隆抗体,采用免疫组织化学方法,并结合电镜超微结构,观察雷公藤总甙(GTW)和单体T_4对雄性大鼠脑垂体前叶黄体生成细胞(LH细胞)的影响。结果表明,LH细胞出现一些形态改变。随着雷公藤剂量的增加,LH细胞胞浆内免疫酶反应增强,胞浆内出现空泡。超微结构也显示,LH细胞胞核皱缩,胞浆内高尔基复合体和内质网肿胀,在总甙组和T_4大剂量组,LH细胞类似“阉割细胞”样变。提示雷公藤的抗生育作用类似去性腺效应.     

HLA—D抗原的相容性以及封闭因子与习惯性流产的关系的实验研究

运用单向混合淋巴细胞培养的方法分别检测了10例习惯性流产史船娠夫妇间、流产史孕妇和无关第三者(男性)间及9例正常妊娠夫妇间的HLA-D抗原的相容性。结果发现流产史夫妇间的HLA-D抗原相容性大于流产史孕妇和无关第三者(男性)之间及正常夫妇间的HLA-D抗原相容性(P<0.01)。提示夫妇间的HLA-D抗原相容性增大可能是导致习惯性流产的原因之一。同时,在反应体系中分别加入不同孕妇血浆以观察其对单向混合淋巴细胞培养(单向MLC)的影响时发现,流产史孕妇血浆对单向MLC不仅无抑制作用,反而有刺激作用,而正常孕妇血浆对单向MLC有抑制作用。推测正常孕妇血浆中存在特异和/或非特异的封闭因子,而流产史孕妇血浆中缺乏特异和/或非特异的封闭因子。     

Characterization and distribution of [3H]ohmefentanyl binding sites in the human brain

Binding properties and localization of [3H]ohmefentanyl, a new ligand for mu opioid receptors, were investigated on normal human brain sections. Binding assays performed at the level of the basal ganglia revealed: (1) a steady-state binding reached after 60 min incubation at room temperature, (2) the presence, in saturation experiments, of an apparent single class of binding sites with a Kd = 1.68 +/- 0.45 nM and a Bmax = 162 +/- 9 fmol/mg protein, (3) an order of potency to inhibit [3H]ohmefentanyl binding as follows: ohmefentanyl greater than [D-Ala2, MePhe4, Gly-ol5] enkephalin (DAGO) greater than ethylketocyclazocine (EKC) much greater than Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr(OtBu) (BUBU) and U-50,488H. Quantitative autoradiography showed an heterogeneous distribution of [3H]ohmefentanyl binding sites with the highest densities in amygdala, medical geniculate body, thalamus, and caudate nucleus. Binding characteristics and anatomical distribution also show that [3H]ohmefentanyl may bind to a small proportion of additional sites called "DAGO-inaccessible [3H]ohmefentanyl specific binding sites." [3H]Ohmefentanyl binding to these sites can be partly inhibited by sigma ligands such as 1,3-di-o-tolylguanidine (DTG) and haloperidol. However, unlabeled DAGO inhibited more than 80% of [3H]ohmefentanyl specific binding in most of the human brain regions studied, suggesting that the major population of sites labeled by [3H]ohmefentanyl represented mu opioid receptors.