Location of O-acetyl groups in the acidic d-xylan of mimosa scabrella (bracatinga). A study of O-acetyl group migration

Extraction with dimethyl sulfoxide of wood-meal of the stem of bracatinga (Mimosa scabrella), a south Brazilian hardwood, that was defatted and delignified by treatment with aqueous chlorine at 0–5° followed by extraction with cold ethanol, gave a soluble O-acetylated 4-O-methyl-d-glucurono-d-xylan having (1→4)-linked β-d-xylopyranosyl residues that were unsubstituted (65%) and 2-O-(14%), 3-O- (16%), and 2,3-di-O-acetylated (5%), as determined by methylation analysis. Another preparation obtained by use of refluxing ethanol in the delignification process showed neither removal nor migration of acetyl groups. By comparison with synthetic, partly O-acetylated d-xylans of known composition, ¹³C-n.m.r. spectroscopy indicated that O-acetyl group migration does not occur during treatment with cold aqueous chlorine, refluxing ethanol, or water at 70°. Methyl 2-O-acetyl-4-O-methyl-β-d-xylopyranoside (6) was also unaffected by aqueous chlorine. O-Acetyl group migration took place more readily in aqueous and dimethyl sulfoxide solutions of 6 than of O-acetyl-d-xylans. The lowest temperatures at which migration was observed in monosaccharides was at 50 and 70° for solutions in D₂O and (CD₃)₂SO, respectively.     

Analysis of lumped and distributed elements models of cut muscle fibers in vaseline or sucrose gap preparations

A general method of finding the time course and the steady state distribution of potential in Vaseline or sucrose gap preparations is given by making use of the linear cable equation. The general solution has been found analytically in terms of its Laplace transform and then numerically inverted. Two particular experimental situations, namely the single gap and the double gap preparations, have been analyzed. The results have been compared with the solutions of the commonly used lumped elements models. While for the double gap no large errors are introduced by the lumped model, for the single gap there are significant differences. The dependence of the voltage distribution on various electrical and geometrical parameters has been examined. It is suggested that the proposed mathematical treatment might be used by experimenters as a reference to assess the validity of simplified lumped models.     

Antagonism of diazepam-induced feeding in rats by antisera to opioid peptides

Diazepam-induced feeding in rats is antagonized not only by the opiate antagonist naloxone but also intraventricular administration of specific antisera to the endogenous opioid peptides met-enkephalin or beta-endorphin. Pituitary beta-endorphin is probably not implicated in the diazepam effect since blockade with the glucocorticoid dexamethasone of the release of beta-endorphin from the anterior pituitary does not modify the diazepam-induced feeding, which is however prevented by TRH, a suggested physiological antagonist of some of the effects of opioid peptides. The possible central participation of both beta-endorphin and met-enkephalin in the ingestive behavior induced by diazepam gives further support to the postulated physiological role of endogenous opioids in appetite regulation.     

Clastogen-induced chromosomal breakage as a marker for first trimester prenatal diagnosis of Fanconi anemia

Summary Using cultured trophoblast cells obtained by chorionic villus biopsy, we diagnosed Fanconi anemia (FA) in two pregnancies and excluded it in eight pregnancies at risk for the syndrome. Baseline chromosomal breakage and breakage induced by diepoxybutane (DEB) were analyzed. Increased breakage was used as a marker for the syndrome. Our results were unambiguous and provide a reliable method for prenatal detection of FA in the first trimester of pregnancy.     

Cloning and sequencing of mRNAs coding for two adult alpha globin chains of the salamander Pleurodeles waltlii

A cDNA library of erythrocyte mRNAs was established from immature red blood cells of the adult amphibian, Pleurodeles waltlii (urodele; salamander). The cDNA clones corresponding to the four adult globin chains were first identified and characterized by positive selection and the cDNAs derived from the two (major and minor) alpha-globin chains sequenced. The sequences presented contain both the complete 3'-noncoding region and the coding region of both chains, with the exception of the first nine codons of the minor alpha-chain, and a portion of the 5'-noncoding region of the major chain. The amino acid sequences of the encoded alpha-globin polypeptides have been deduced and compared with those of Xenopus laevis and of man. These comparative studies suggest that the alpha-globins of Pleurodeles waltlii and Xenopus laevis may have diverged from a common ancestral gene at the time when mammalian and amphibian lines diverged, and that they then evolved separately. Duplication of the alpha-gene, which is responsible for the polypeptide heterogeneity, appears to have occurred earlier in Pleurodeles waltlii than in Xenopus laevis.     

Isolement et sélection de souches d'actinomycètes productrices de substances antifongiques de structure non-polyénique

Résumé Dans le but d'étudier des souches d'actinomycètes productrices de substances antifongiques de structure non-polyénique, 13, échantillons de sol prélevés dans le sud de la France ont été examinés. L'utilisation de milieux sélectifs a permis d'isoler 486 souches d'actinomycètes qui ont été testées vis-à-vis de quatre espèces de champignons et de levures: 18% des souches isolées sont actives sur au moins l'une des espèces utilisées. Parmi celles-ci 14 souches, productrices de substances de structure non-polyénique, ont été sélectionnées après étude des spectres d'absorption en UV des surnageants de culture, des extraits butanoliques de ces surnageants ou des extraits méthanoliques de mycélium. L'utilisation d'un test bactérien de toxicité à court terme (SOS Chromotest) a permis de montrer que 10 souches sur 14 présentent aussi une activité génotoxique.

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Summary In order to study actinomycete strains producing non-polyenic antifungal substances 13 soil samples were collected in S. France. By using selective media 486 strains of actinomycetes were isolated and tested on four species of moulds and yeasts: 18% of the isolated strains were active against one or more of the test organisms. From these isolates 14 producers of non-polyenic antifungal substances were selected by means of u.v. absorption spectra of culture supernatant fractions, butanol extracts of these fractions, or methanol extracts of mycelium. A rapid bacterial toxicity assay (SOS Chromotest) demonstrated that 10 of the 14 selected strains had genotoxic activity.

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Resumen Para el estudio de cepas de actinomicetes productores de sustancias antifúngicas no poliénicas, se recogieron 13 muestras de suelo en el S. de Francia. Utilizando medios selectivos se aislaron 486 cepas de actinomicetes que se ensayaron frente a cuatro especies de mohos y levaduras: 18% de las cepas aisladas mostraron actividad frente a uno o más de los organismos utilizados en el test. De estas cepas se seleccionaron 14 que eran productoras de sustancias antifúngicas no poliénicas mediante el espectro de absorción al U.V. de las fracciones sobrenadantes del cultivo, de extractos butanólicos de dichas fracciones o de extractos metanólicos del micelio. Un ensayo rápido de toxicidad bacteriana (SOS Chromotest) mostró que de las 14 cepas seleccionadas lo tenían actividad genotóxica.

     

Synthesis of hydroxy fatty acids from 4, 7, 10, 13, 16, 19-[1-14C] docosahexaenoic acid by human platelets

Human platelets incubated in the presence of 54 microM [1-14C]22:6 produced hydroxydocosahexaenoic acid (HDHE) at about half the rate with which 12-hydroxy-5,8,10,14-eicosatetraenoic acid is produced from [1-14C]arachidonic acid. More than 90% of the radioactivity in HDHE was distributed among two major isomers, 14-HDHE and 11-HDHE. The production of HDHEs was unaffected by indomethacin but completely inhibited by 5,8,11,14-heneicosatetraynoic acid, which suggests that the hydroxy fatty acids are produced by lipoxygenase. The proportions of HDHE isomers varied with the concentration of 22:6. The ratio 14-HDHE/11-HDHE was higher at 6.8 microM 22:6 than when platelets were incubated with 54 microM 22:6. It is suggested that the amounts of these isomers produced will depend both on the availability of 22:6 as well as by competition of this acid with other acids for lipoxygenase.     

Chromosomal location of the active NORs in theSteropleurus martorelli complex

The chromosomal location of the active NORs has been analyzed by a silver impregnation procedure in theSteropleurus martorelli complex. A primary NOR, which is always present at the first meiotic prophase, has been found in each of the four described races. In addition to this, all races possess one or two secondary NORs which are less active than the former and can be occasionally shown. Usually only one of the two homologous chromosomes has been found to be involved with nucleolus organisation.These results are discussed in relation to hypotheses on the chromosome differentiation of this species complex.