Volatile anesthetics gate a chloride current in postnatal rat hippocampal neurons.

A volatile anesthetic-gated current was characterized in patch-clamped cultured postnatal rat hippocampal neurons. In this preparation, the major volatile anesthetics, isoflurane, halothane, and enflurane, open an anion-selective conductance. This volatile anesthetic-gated current exhibits anion selectivity with a chloride-to-acetate permeability ratio of 15, shows outward rectification well described by the constant field equation, and is activated in a dose-dependent fashion with half-maximal response to isoflurane at 0.8 mM (0.032 atm). The current persists in the absence of external Ca2+ and is not blocked by strychnine, a glycine antagonist. However, the gamma-aminobutyric acidA (GABAA) antagonists, bicuculline and picrotoxinin, and the nonspecific anion channel blocker, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), completely block the response. These observations suggest that volatile anesthetics, like several other general anesthetics such as barbiturates, steroids, and etomidate, have a GABA-mimetic effect on vertebrate central neurons in culture. It is not clear whether this GABAA-gating property is a prerequisite for all general anesthetics. However, under normal physiological conditions of low intracellular Cl-, it is likely that drugs with both direct GABA agonist and GABA modulatory properties will produce overall depression of the central nervous system by increasing the normal inhibitory synaptic influence and by directly hyperpolarizing neurons.     

Resolution and stability of oxazepam enantiomers

A solvent mixture containing dioxane, acetonitrile, and hexane was found to be suitable as a mobile phase to resolve oxazepam enantiomers by chiral stationary phase high performance liquid chromatography using covalent Pirkle columns. The resolved oxazepam enantiomers in this solvent mixture had a racemization half-life greater than 3 days at 23°C. When desiccated at 0°C as dried residue, OX enantiomers were stable for at least 50 days with less than 2% racemization. The conditions which stabilized OX enantiomers significantly facilitated the determination of racemization half-lives of OX enantiomers in a variety of aqueous and nonaqueous solvents and at different temperatures. © 1992 Wiley-Liss, Inc.     

Metacercarial infections of Paragonimus westermani in freshwater crabs sold in markets in Seoul

Status of metacercarial infections of Paragonimus westermani was observed in freshwater crabs, which were purchased at 3 markets in its peak season of 1990. All of 85 crabs were Eriocheir japonicus. No other species of Eriocheir were found. When crushed muscle and viscera was examined individually, the infection rate was 11.8%; and mean number of metacercariae was 2.1 per infected crab. Unless adequately cooked, freshwater crabs are still potential sources of human paragonimiasis.     

Monoclonal Antibodies against Apple 1-Aminocyclopropane-l-Carboxylate Synthase

1-Aminocyclopropane-l-carboxylate (ACC) synthase from applefruits was purified over 5,000-fold by conventional column chromatography.By immunizing mice with this partially purified enzyme preparation,8 hybridoma lines producing monoclonal antibodies against appleACC synthase were isolated. While all 8 clones immunoprecipitatednative ACC synthase, only two clones recognized the putative(48 kDa) ACC synthase on Western blots. When a partially purifiedACC synthase preparation was incubated with S-adenosyl-L-[carboxyl-¹⁴C]methionine(AdoMet), only one radioactive protein of 48 kDa was detectedon sodium dodecyl sulfate-poly-acrylamide gel electrophoresis.This radioactive protein was specifically immunoprecipitatedby the monoclonal antibodies, indicating that apple ACC synthaseis specifically radiolabeled by its substrate AdoMet, as istomato ACC synthase. Thus, the monoclonal antibodies recognizedboth native and AdoMet-inactivated forms of ACC synthase. Whilethese antibodies failed to im-munoprecipitate ACC synthase isolatedfrom ripe tomato fruits, ripe avocado fruits or auxin-treatedmungbean hypocotyls, they were effective in immunoprecipitatingthe enzyme isolated from ripe pear fruits. (Received August 11, 1990; Accepted October 17, 1990)     

T-URF 13 Protein from Mitochondria of Texas Male-Sterile Maize (Zea mays L.) : Its Purification and Submitochondrial Localization, and Immunogold Labeling in Anther Tapetum during Microsporogenesis

The protein T-URF13 (URF13) is specific to mitochondria of maize (Zea mays L.) with Texas (T) male-sterile cytoplasm and has been implicated in causing male sterility and susceptibility to T-cytoplasm-specific fungal diseases. T-URF13 was purified from isolated mitochondria from maize (line B73) with T cytoplasm by gel filtration and a quasi two-dimensional polyacrylamide gel electrophoresis system. Antibodies to the purified and denatured protein were produced in rabbits. Anti-T-URF13 antiserum was used to show that T-URF13 is in the inner membrane of mitochondria and behaves as an integral membrane protein when mitochondria are fractionated with sodium carbonate or Triton X-114. The antiserum and protein A tagged with 20-nanometer-gold particles were used to localize T-URF13 in T mitochondria by electron microscopy of sections of isolated mitochondria from etiolated shoots and sections of roots and of tapetal cells at pre-and post-degeneration stages of microsporogenesis. The microscopic study confirms that T-URF13 is specifically localized in the mitochondrial membranes of all of the T mitochondria tested, notably those in the tapetum from the meiocyte stage to the late-microspore stage. No change in the amount of labeled T-URF13 protein in the mitochondria of aging tapetal cells was detected.     

Multiplicity of soluble glucan-synthase activity in spinach leaves: Enzyme pattern and intracellular location

Buffer-extractable proteins from leaves of Spinacia oleracea L. were separated by non-denaturing polyacrylamide gel electrophoresis. Gels were stained for adenosine diphosphoglucose (ADPglucose)-dependent glucan-synthase (GS) activity (EC 2.4.1.21). Three major forms of activity were observed. No staining was detectable when ADPglucose was replaced by an equimolar concentration of either uridine, guanosine or cytosine diphosphoglucose. Two of the three GS forms exhibited both primed and citrate-stimulated unprimed activity whereas one enzyme form was strictly dependent upon the presence of an exogenous glucan. For intracellular localization, mesophyll protoplasts and intact chloroplasts were isolated and their enzyme pattern was compared with that of the leaf extract. Intactness and purity of the chloroplast preparations were ascertained by polarographic measurement of the ferricyanide- or CO₂-dependent oxygen evolution, by determination of marker-enzyme activities, and by electrophoretic evaluation of the content of chloroplast- and cytosol-specific glucanphosphorylase forms (EC 2.4.1.1). The three GS forms were present in mesophyll protoplasts. Intact chloroplasts possessed both primer-independent enzyme forms but lacked the primer-dependent one. The latter form was enriched in supernatant fractions of leaf homogenates when the intact chloroplasts had been pelleted by centrifugation. Thus, in spinach-leaf mesophyll cells soluble ADPglucose-dependent GS is located both inside and outside the chloroplast.Abbreviations GS glucan synthase - PAGE polyacrylamide gel electrophoresis This work has been made possible by grants from the Deutsche Forschungsgemeinschaft and from the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen. The authors gratefully acknowledge the generous permission to use the laser densitometer of Professor Dr. W. Barz (Biochemie der Pflanzen, Universität Münster, FRG). They are indebted to Dr. H.-J. Witt (Pflanzenphysiologie, Universität Kassel, FRG) for helpful discussions and to Mr. W. Lamkemeyer for skilfull technical assistance.     

Purification and Characterization of d-Aminoacylase from Alcaligenes faecalis DA1

A d-aminoacylase from Alcaligenes faecalis DA1 has been purified to homogeneity by a simple purification procedure with two columns, Fractogel DEAE-650 and HW-50. The specific activity of the purified enzyme was found to be 580 U/mg of protein with N-acetyl-dl-methionine as the reaction substrate. The apparent molecular weight and isoelectric point of this enzyme were determined to be 55,000 and 5.4, respectively.     

Zinc deficiency and the formation of white structures in immature embryo cultures of wheat (Triticum aestivum L.)

The effect of microelements on the induction of embryogenic callus from epiblast and scutellum of wheat (Triticum aestivum L.) embryos was studied by the sequential omission of each of the microelements from Murashige & Skoog medium. Omission of iron caused a marked decrease in yield and poor shoot formation from embryogenic callus. The yield of embryogenic callus on medium without added manganese was also reduced. Omission of boron, copper-cobalt, iodine, and molybdenum had little effect on the induction of embryogenic epiblast callus. By contrast there was a marked increase in the formation of white structures on the medium without any microelements or, specifically without addition of zinc. Since the formation of typical embryoids of wheat is associated with the formation of white structures, our result highlights the importance of certain microelements on somatic embryogenesis of wheat.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - MS medium Murashige & Skoog medium     

Platinum-supported Bilayer Lipid Membranes modified by ferrocene and its derivatives

The biferrocene-containing Schiff base complexes (1) and (2) were synthesized and characterized by elemental analyses and spectral data. The Pt-supported Bilayer Lipid Membranes (BLMs) modified by ferrocene and its derivatives were studied by cyclic voltametry (CV) and the electrochemical properties of this system are reported. The oxidation mechanism of electrocatalysis of ascorbic acid on the Pt-supported BLMs is discussed.     

Hidden smectic properties of a chiral side-chain co-oligomer

We recently showed that a side-chain industrial co-oligosiloxane presents a quenchable enlarged blue phase behaviour at the cholesteric-isotropic phase transition. In this paper, we present the results of a structural study based on X-ray diffraction, differential scanning calorimetry and optical measurements. In particular, the smectic A organisation is demonstrated in the lower temperature domain, which was hitherto understood as a cholesteric phase. A structural model for this phase is proposed on the basis of the analysis of the anisotropic scattering of stretched fibers. Our results also suggest that the observed glass transition is indeed a rather complex phenomenon, which seems to involve not only the freezing of the main chains, but also smectic correlations at the side-chain level. Moreover, the calorimetric study indicates that, notwithstanding the conservation of the processed film's optical properties, low kinetic reorganisations occur at room temperature.