大鼠脊髓中的α受体在减压反射和失血性休克中的作用

大鼠脊髓蛛网膜下腔注射α激动剂可乐宁1μg,引起血压降低、心率减慢及腹腔神经节后交感神经干放电抑制。应用α阻断剂酚妥拉明阻断脊髓内源性 NE的作用,可部分抑制血压升高时反射性的心率减慢和交感神经放电抑制反应,使压力感受器反射的敏感性降低。在颈动脉放血造成不可逆性失血性休克的动物,脊髓蛛网膜下腔注射酚妥拉明可使动脉血压有一定程度的回升。以上结果表明,由脊髓α受体调制的心血管抑制效应参与减压反射以及失血性休克的发病机制。     

Aspects Affecting Biosynthesis and Biotransformation of Secondary Metabolites in Plant Cell Cultures

Abstract

Biosensors are useful analytical devices that can be integrated with on-line process monitoring schemes. In this article, the principles and applications of these devices for bioprocess monitoring are considered. Several different types of biosensors are described, and the applications and limitations of flow injection analysis (FIA) for these applications are discussed. It is hoped that the background provided here can be useful to researchers in this area.     

下丘脑外侧区注射TRH对大鼠胃酸分泌的影响

本文采用连续收集胃腔灌流法,观察下丘脑外侧区(LHA)注射促甲状腺激素释放激素(TRH)对大鼠胃酸分泌的影响,并分析TRH在LHA促进胃酸分泌的作用机制。结果表明:(1)LHA注射TRH(1μg)明显地刺激胃酸分泌;(2)预先向LHA注射酚妥拉明(10μg)、美多心安(5μg)及胃泌素抗体1μl(1:640)并不影响TRH的泌酸作用,如预先向LHA注射阿托品(5μg)则可消除TRH的泌酸效应;(3)垂体摘除及肾上腺切除均不影响TRH的泌酸作用;(4)隔下迷走神经切断后,LHA注入TRH的泌酸效应仍然出现,但持续时间显著缩短;腹腔交感神经节摘除后,TRH仍能促进胃酸分泌,但分泌量少而平稳。以上结果提示:LHA是TRH中枢泌酸效应的有关结构之一,其中枢机制是通过胆碱能M受体中介的,腹腔交感神经节和膈下迷走神经是TRH泌酸效应的传出途径。前者引起的泌酸反应出现较早且引起泌酸高峰,但持续时间短;后者则引起低平的持续分泌。     

Structure and composition of influenza virus. A small-angle neutron scattering study

A detailed analysis is presented of the small-angle neutron scattering curves of homogeneous solutions of influenza B virus, both intact and after treatment with bromelain, which removes the external glycoprotein spikes. The two sets of data are consistent with the following low-resolution structure: the virus particles are spherical, about 1200 A in diameter and of Mr about 180 X 10(6). The lipid bilayer is centred at a radius of 425 A, is 40 A to 50 A thick and constitutes 25% to 28% of the virus mass. The surface glycoproteins, predominantly haemagglutinin, contribute 40% to 46% of the total mass. Surprisingly little protein is found in the interior of the virus. It is suggested that the reason for this is that many particles do not contain the full complement of ribonucleoprotein complexes. These results are in good agreement with recent scanning transmission electron microscopic measurements of molecular mass and cryo-electron microscopic observations of the same preparations. Appendix 1 describes a new method of deriving spherical shell models from contrast variation neutron scattering data on viruses, in which scattering curves from all measured contrasts are used simultaneously. There is also a discussion of the assumptions and limitations implicit in the structural interpretation of such models, with emphasis on viruses containing lipid bilayers. Appendix 2 examines the effect on the scattering curves of various arrangements of the surface glycoproteins.     

The population dynamics of some freshwater carideans (Crustacea: Decapoda) in Hong Kong,with special reference to Neocaridina serrata (Atyidae)

During a 15-month investigation of the population dynamics of three caridean shrimp species in the Lam Tsuen River, New Territories, Hong Kong, the numbers of the commonest species, Neocaridina serrata (Stimpson)(Atyidae), were reduced as water temperatures fell. By contrast, Caridina lanceifrons Yu became more numerous during the winter. The relatively scarce Macrobrachium hainanense (Parisi)(Palaemonidae) tended to be more abundant during the summer, and the abundance of this species was directly correlated with that of N. serrata. The population size of these two species was positively correlated with water temperatures prevailing one and two months prior to the collection of samples, but there was no significant relationship between C. lanceifrons abundance and water temperature.All species exhibited similar growth patterns with an inflection at the attainment of sexual maturity, occurring after the (presumed) 14th moult for N. serrata and in the (presumed) 13th and 18th stadium for C. lanceifrons and M. hainanensis respectively. Ovigerous shrimps of all species were only recorded when water temperatures exceeded 20 °C and the % incidence of ovigerous N. serrata was positively correlated with prevailing temperatures. It is suggested that restriction of freshwater caridean breeding periods by low temperatures may be common in the subtropics while perennial breeding is more likely to be typical of tropical regions.The mean carapace length of N. serrata populations was negatively correlated with prevailing temperatures, but more strongly correlated with temperatures recorded one and two months prior to sampling when gametogenesis may have taken place. Smallest mean sizes were recorded in late summer upon the cessation of juvenile recruitment. N. serrata has a maximum longevity of approximately 12 months and reproduction occurs in the 7th month of life or later. The hatchlings are well developed and clutch size is not related to the size of the brooding female. An annual life cycle, as seen in N. serrata, may be typical of many small freshwater carideans.Department of Zoology, The University of Hong Kong     

Chronotoxicity of Sodium Valproate and Its Mechanisms in Mice: Dose-Concentration-Response Relationship

A significant circadian rhythm of acute toxicity was demonstrated in mice with intraperitoneal (i.p.) injection of sodium valproate (VPA). The role of pharmacokinetics on the rhythms of the toxicity and electroshock seizure (ES) threshold was investigated. ICR male mice, housed under a light-dark (12 :12) cycle, were injected intraperitoneally 1200 mg/kg for the acute toxicity study and 300 mg/kg for the anticonvulsant effect study. In the acute toxicity, the highest mortality was found when VPA was injected at 1700 and the lowest at 0900 or 0100. The time course of mean plasma and brain VPA concentrations after an injection of VPA was not different between mice injected at 1700 and mice injected at 0100. In the anticonvulsant effect, no significant circadian rhythm was demonstrated for both the ES threshold and the plasma VPA concentrations after i.p. Injection, although a significant rhythm has been reported for them after oral administration. The results suggest that the circadian rhythm in the mortality after an i.p. Injection of VPA may be due to the rhythm in the sensitivity of the central nervous system to the drug and that the mechanism underlying the rhythm of VPA acute toxicity is different from that of the anticonvulsant action of VPA. The route and the time of drug administration are essentially important to study the anticonvulsant effect and acute toxicity of VPA in mice.     

Toxicity to alveolar macrophages in rats following parenteral injection of mercuric chloride

Alveolar macrophages collected by pulmonary lavage from male Fisher-344 rats at intervals (24–72 h) after HgCl₂ injection (1–5 mg/kg, sc) were analyzed by several techniques. Within 24–72 h, the macrophages showed morphological signs of activation (hypertrophy and ruffled plasma membrane). Lipid peroxidation (increased malondialdehyde concentration) was not detected until 48 h. Dose- and time-related effects of HgCl₂ on malondialdehyde concentration and time-related effects of HgCl₂ on malondialdehyde concentration and mercury content of alveolar macrophages were observed 24–72 h postinjection. Diminished cell viability occurred only at 72 h after the highest dosage of HgCl₂. This study demonstrates that the alveolar macrophage was a cellular target for mercury toxicity following parenteral exposure to HgCl₂.     

Determination of ammonium and L-Glutamine in hybridoma cell cultures by sequential flow injection analysis

A flow injection anlytical system based on a gas diffusion membrane module for ammonia and an ammonium flow-through potentiometric detector has been set up for measurement of L-glutamine and ammonium ions in hybridoma cell cultures. The main feature of the system is that the same basic analytical concept and equipment is used in both measurements, the only difference being for the determination of L-glutamine, in which the sample flows through an immobilized glutaminase cartridge. The conditions to enable the performance of both analysis consecutively, avoiding potential interferences by unwanted deamination of other compounds in the samples, have been determined. Finally, the proposed system has been compared with reference analytical methods for batch hybridoma cell culture experiments.     

Monitoring glutamine in animal cell cultures using a chemiluminescence fiber optic biosensor

Together with flow injection analysis (FIA), a chemiluminescence (CL) fiber optic biosensor system has been developed for determining glutamine in animal cell cultures. Glutaminase (GAH) and glutamate oxidase (GLO) were onto separate porous aminopropyl glass beads via glutaraldehyde activation and packed to form an enzyme column. These two enzymes acted in sequence on glutamine to produce hydrogen peroxide, which was then reacted with luminol in the presence of ferricyanide to produce a light signal. An anion exchanger was introduced on-line to eliminate interfering endogenous glutamate in view of its negative charge at pH above 3.22 (isoelectric pH). Among several resins tested, the acetate form was most effective, and this type of ion exchanger also effectively adsorbed uric acid, acetaminophen, and aspartic acid.There was an excellent linear relationship between the CL response and standard glutamine concentration in the range 1 to 100 muM. A complete analysis could be performed in 2 min, including sampling and washing with a good reproducibility (+/- 4.4%). Both the bi-enzymic and ion exchange columns were useful for at least 500 analyses when the biosensor system was applied for the glutamine determination in murine hybridoma cell cultures and insect cell cultures. The values obtained compared well with those of HPLC, thus validating the applicability of the CL fiber optic system. (c) 1993 John Wiley & Sons, Inc.     

Mycorrhizal associations in Hong Kong Fagaceae

Polyphenols histochemically detected in fresh uninfected roots of Quercus, Castanopsis and Lithocarpus growing in Hong Kong and shown to be condensed tannins were found mainly as intracellular material in the cells of the root cap, the epidermal layer and the endodermis. The cell walls of the outer cortex and the endodermis also contained suberin. Following invasion by compatible ectomycorrhizal symbionts, condensed tannins disappeared from cells of the root cap and the epidermal layer but hyphae were prevented from colonizing the cortex presumably due to suberin barriers. In vitro experiments indicated that a number of broad-host ectomycorrhizal fungi could utilise various polyphenolic compounds, including tannins found in the root exudates of the host trees, with different degrees of efficiency.