Estimation of the mean floristic similarity between and within sets of vegetational relevés

Various possibilities of usingSörensen's coefficient of floristic similarity in plant sociology are summarized. A new formula (11), derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés.     

Estimation of the mean floristic similarity between and within sets of vegetational relevés

Various possibilities of usingSörensen’s coefficient of floristic similarity in plant sociology are summarized. A new formula (11). derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés.     

Frequency of resistance to tetracycline and chloramphenicol amongSalmonella strains isolated in the Netherlands in 1962

Out of 12,472 strains ofSalmonella isolated in the Netherlands in 1962, 1365, or 10.94%, were found to be resistant to tetracycline or chloramphenicol or to both. Compared with the findings of the preceding years (1958/59:2.08%, 1960:1.29%, 1961:3.96%) this is a considerable increase. Of these 1365 strains, 1285, or 94.1%, were resistant to tetracycline and 46, or 3.4%, were resistant to chloramphenicol. The remaining 34 strains, or 2.5%, were resistant to both drugs.Among allSalmonella strains isolated in 1962, 5517 belonged to the speciesS. typhi murium. Of these, 1203 or 21.8%, were resistant to tetracycline. The resistance rates of strains originating from human patients, calves, pigs, other animals and other materials were 24.4%, 37.1%, 15.0%, 8.0% and 5.7% respectively.Factors which may possibly have contributed to the greatly increased frequency of drug resistance inS. typhi murium are: (1) the rapid spread of the use of tetracycline for therapeutic, prophylactic and nutritive purposes, and (2) the possibility of an episome-mediated transfer of drug resistance from relatively harmless intestinal bacteria, such asE. coli, toS. typhi murium.     

Informationstheoretisches lernmodell

Summary The formation of the interconnection stimulus-response in a learning system is analysed. The system, a technical or a biological one establishes this correspondence by processing the information fed back from the medium during the learning process. This information has two aspects: a quantitative one related to the probability of the events, and a qualitative one related to the utility of the events in view of a goal. Both aspects are taken into consideration; by successive experiences the system eliminates the double uncertainty concerning the probabilistic dependence: stimulu — sresponse — outcome and its utility. Learning implies then a system for evaluating the utilities of different outcomes in view of a goal, a memory to record them and a decision system for selecting the corresponding responses upon a given criterion.

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Der Beitrag stellt einen Teil der Untersuchungen dar, die zur Ausarbeitung der Doktor-Dissertation am Polytechnischen Institut Gheorghe Gheorghiu-Dej in Bukarest unternommen wurden.     

A Rapid Screening Test for Aflatoxin-synthesizing Aspergilli of the flavus-oryzae Group

A rapid test for the recognition of aflatoxin-synthesizing strains of the Aspergillus flavus–oryzae group is described. For this purpose the strains are cultivated on Czapek–Dox agar enriched with an aqueous extract of groundnuts, and in which sodium nitrate is replaced by ammonium chloride. Toxin production is observed by the production of a bright blue fluorescence in the medium when placed under an ultraviolet lamp.     

Modulation of Histamine Release in the Rat Brain by K-Opioid Receptors

The opioid modulation of histamine release was studied in rat brain slices labeled with L-[3H]histidine. The K(+)-induced [3H]histamine release from cortical slices was progressively inhibited by the preferential kappa-agonists ketocyclazocine, dynorphin A (1-13), Cambridge 20, spiradoline, U50,488H, and U69,593 in increasing concentrations. In contrast, the mu-agonists morphine, morphiceptin, and Tyr-D-Ala-Gly-(NMe)Phe-Gly-ol (DAGO) were ineffective as were the preferential delta-agonists [D-Ala2,D-Leu5]enkephalin (DA-DLE) and [D-Pen2,D-Pen5]enkephalin (DPDPE). Nor-binaltorphimine (nor-BNI) and MR 2266, two preferential kappa-antagonists, reversed the inhibitory effect of the various kappa-agonists more potently than did naloxone, with mean Ki values of 4 nM and 25 nM, respectively. The effects of ketocyclazocine and naloxone also were seen in slices of rat striatum, another brain region known to contain histaminergic nerve endings. We conclude that kappa-opioid receptors, presumably located on histaminergic axons, control histamine release in the brain. However, nor-BNI and naloxone failed, when added alone, to enhance significantly [3H]histamine release from cerebral cortex or striatum, and bestatin, an aminopeptidase inhibitor, failed to decrease K(+)-evoked [3H]histamine release. These two findings suggest that under basal conditions these kappa-opioid receptors are not tonically activated by endogenous dynorphin peptides. The inhibition of cerebral histamine release by kappa-agonists may mediate the sedative actions of these agents in vivo.     

Changes in protein synthesis and phosphorylation patterns during bovine oocyte maturation in vitro

Sequential protein synthesis and protein phosphorylation patterns were generated by radiolabelling bovine cumulus-oocyte complexes after various periods of culture with [35S]methionine and [32P]orthophosphate respectively. The radiolabelled oocytes were assessed for their nuclear status and used individually for gel electrophoresis. Marked changes in the protein synthesis patterns were observed exclusively after germinal vesicle breakdown (GVBD), whereas oocytes which remained in the germinal vesicle stage showed a consistent protein synthesis pattern. The changes were observed after 8 and 16 h or culture, shortly after GVBD and before first polar body extrusion. From 3 h of culture, dominant phosphoprotein bands with apparent molecular weights of 24,000 and two between 50,000 and 60,000 were observed. The latter bands displayed slight molecular weight changes, which were not closely time related. After GVBD, the phosphoprotein band with Mr 19,000 was no longer observed. This study demonstrates that specific changes in protein synthesis and protein phosphorylation are programmed during bovine oocyte maturation.     

Functional vasoactive intestinal polypeptide (VIP) receptors in human neuroblastoma subclones that contain VIP precursor mRNA and release VIP-like substances

Three phenotypically distinct subclones (SH-SY-5Y, SH-EP, SH-IN) of the human neuroblastoma cell line SK-N-SH were found to possess vasoactive intestinal polypeptide (VIP) precursor mRNA, release immunoreactive VIP, and express high-affinity VIP receptors coupled to adenylate cyclase. The apparent molecular mass for the receptor polypeptide, as determined by covalent cross-linking of 125I-VIP, was 49 kDa. After 2 days in culture, a concentration of immunoreactive VIP equivalent to the binding affinity of VIP to its receptor was found in the medium in two of these clones (SH-IN and SH-EP). Conditioned medium from SH-IN cells competitively displaced 125I-VIP binding and increased cAMP levels in SH-EP cells, indicating that all of the necessary components for a potential autocrine action of VIP exist in SK-N-SH cells. After numerous cell passages, the SH-EP subclone converted to a distinct phenotype in which VIP precursor mRNA and VIP immunoreactivity in the cell and medium were no longer detectable. In correlation, the VIP receptor number increased, and the EC50 for VIP stimulation of cAMP production shifted to a lower concentration. This points to the possibility that the continuous presence of endogenous VIP in earlier passage SH-EP cells causes a modification in VIP receptor number and cell responsiveness to VIP.