The properties of batrachotoxin-modified cardiac Na channels, including state-dependent block by tetrodotoxin

Batrachotoxin (BTX) modification and tetrodotoxin (TTX) block of BTX-modified Na channels were studied in single cardiac cells of neonatal rats using the whole-cell patch-clamp recording technique. The properties of BTX-modified Na channels in heart are qualitatively similar to those in nerve. However, quantitative differences do exist between the modified channels of these two tissues. In the heart, the shift of the conductance-voltage curve for the modified channel was less pronounced, the maximal activation rate constant, (tau m)max, of modified channels was considerably slower, and the slow inactivation of the BTX-modified cardiac Na channels was only partially abolished. TTX blocked BTX-modified mammalian cardiac Na channels and the block decreased over the potential range of -80 to -40 mV. The apparent dissociation constant of TTX changed from 0.23 microM at -50 mV to 0.69 microM at 0 mV. No further reduction of block was observed at potentials greater than -40 mV. This is the potential range over which gating from closed to open states occurred. These results were explained by assuming that TTX has a higher affinity for closed BTX-modified channels than for open modified channels. Hence, the TTX-binding rate constants are considered to be state dependent rather than voltage dependent. This differs from the voltage dependence of TTX block reported for BTX-modified Na channels from membrane vesicles incorporated into lipid bilayers and from amphibian node of Ranvier.     

墨红鲜花香气(头香)成分分析

利用 XAD-4憎水性吸附树脂采集墨红头香,以毛细管气相色谱双柱保留指数和 GC/MS/DS 联用方法鉴定头香的化学成份。共分离鉴定或初步鉴定了45种组份,其中含量较大的有乙酸芳樟酯(14.98%),柠檬烯(12.07%),甲基苯甲醚(9.88%),香茅醇(4.82%),乙酸巳酯(3.98%),β-石竹烯(4.55%),芳樟醇(3.18%),正巳醇(3.17%)等.     

Formation of lymphocyte colonies under serum-free culture conditions in normal individuals and patients with chronic lymphocytic leukemia

This paper describes a culture system which supports the formation of B cell and some T cell colonies under serum-free conditions in peripheral blood samples of normal individuals and patients with chronic lymphocytic leukemia (CLL) of B cell type. In this system, serum is replaced by bovine serum albumin, transferrin, cholesterol, insulin and catalase or horseradish peroxidase. In addition, it is necessary to add staphylococcus protein A, mitomycin-treated T cells as feeders and phytohemagglutinin leukocyte-conditioned medium as a source of growth factors. The plating efficiency is greatly enhanced when normal cells are incubated with galactose oxidase prior to plating and when CLL cells are exposed sequentially to neuraminidase and galactose oxidase.     

Isolation of a Cellodextrinase from Bacteroides succinogenes

An enzyme which released the cellobiose group from p-nitrophenyl cellobioside was isolated from the periplasmic space of Bacteroides succinogenes grown on Avicel crystalline cellulose in a continuous cultivation system and separated from endoglucanases by column chromatography. The molecular weight of the enzyme was approximately 40,000, as estimated by gel filtration. The enzyme has an isoelectric point of 4.9. The enzyme exhibited low hydrolytic activity on acid-swollen cellulose and practically no activity on carboxymethyl cellulose, Avicel cellulose, and cellobiose, but it hydrolyzed p-nitrophenyl lactoside and released cellobiose from cellotriose and from higher cello-oligosaccharides. These data demonstrate that the enzyme is a cellodextrinase with an exotype of function.     

Plasmid DNA adsorbed to pH-sensitive liposomes efficiently transforms the target cells

We have previously reported that plasmid DNA entrapped in the pH-sensitive immunoliposomes effectively transforms the target cells (Proc. Natl. Acad. Sci. USA, in press). In the present study, we demonstrate that DNA adsorbed on the same liposome also transforms the target cells. The transformation activity is antibody dependent, as liposomes containing no targeting antibody had reduced activity. The activity could be significantly inhibited by excess non-specific DNA (salmon sperm). Since some DNA are likely adsorbed to the liposomes during the entrapment process, the activity of the entrapped DNA is partially accounted for by the adsorbed DNA. The possibility of developing a simple DNA-mediated transfection protocol using liposome adsorbed DNA is discussed.     

Uniformly oriented gramicidin channels embedded in thick monodomain lecithin multilayers.

Phosphatidylcholine multilayers, containing 20% water by total sample weight and gramicidin/lipid molar ratios up to 1:40 were aligned by low temperature annealing (less than 60 degrees C) and mechanical stressing. We were able to obtain large (greater than 80 micron thick X 40 mm2 area) monodomain defect-free multilayers containing approximately 10(17) uniformly oriented gramicidin channels. The alignment of lipid multilayers was monitored by conoscopy and polarized microscopy. The smectic defects, which appeared during the alignment process, were identified and dissolved. The incorporation of gramicidin into the multilayers in the form of transmembrane channels was indicated by its circular dichroic (CD) spectrum. A well-defined CD spectrum of uniformly oriented gramicidin channels was obtained. The oriented samples will allow spectroscopic studies of the ion channel in its conducting state and diffraction studies of the channel-channel organization in the membrane.     

Alteration of protein phosphorylation patterns in cell lines morphologically transformed by human cytomegalovirus

Human fibroblastic cell lines morphologically transformed by either live virus or DNA fragments of human cytomegalovirus had altered plasma membrane protein composition; quantitative changes, and gains and losses in protein composition in comparison to normal parent cell lines were detected. These transformed cell lines showed altered total cell protein phosphorylation patterns when compared to parent cell lines. A two to four fold increase in in vivo protein phosphorylation at serine and threonine residues was observed; no increase in phosphorylation at total cell tyrosine residues was detected. Analysis of the in vivo phosphorylated protein by two dimensional gel electrophoresis revealed some similarities as well as differences in the types of polypeptides phosphorylated between transformed and control cell lines. Increased (two-to sixfold over parent cell extracts) casein kinase and polyamine dependent casein kinase activities were detected in HCMV transformed cell extracts.     

嘉兰栽培及其秋水仙碱含量测定

嘉兰原属热带性地区的植物,但从云南南部引种到广州地区种植。表现生长发育良好,且其秋水仙碱含量高达0.40—0.45％。是一种有推广种植价植的药用植物。     

中药灵香草及其混淆品种的比较鉴别

本文比较了中药灵香草Lysimachia foenum-graecum Hance及其混淆品种垂花香草Lysimaehia nutantiflora Chen et C.M.Hu的植物形态、药材性状以及茎、叶组织显微特征。指出垂花香草无灵香草特有的芳香。也无药用记载。应仔细区别,不宜混用。