Comments on the significance of the quasi-valence number for chemical carcinogenesis

Summary A quasi-valence number of less than 3.20 was reported to be significant in correlating carcinogenicity. This criterion has no meaningful relationship since such a large proportion of organic compounds fall in this group, that it provides no selectivity.Acknowledgment. The authors express appreciation to the American Cancer Society (CH-57), the National Institute of Environmental Health Sciences (1-RO1-ES01975-01 PTHB) and the Robert A. Welch Foundation (B-702) for financial assistance of projects related to this paper.     

High-affinity binding ofβ-alanine to cerebral synaptosomes might involve glycine-receptors

Summary High-affinity, Na⁺-independent binding of -alanine to a synaptosomal fraction of rat brain was potently inhibited by glycine and by some other -amino acids, but not by taurine or GABA. This binding mechanism, which was also sensitive to both bicuculline and strychnine, might involve synaptic receptors for both -alanine and glycine.This study was supported in part by Centro Ramón y Cajal and Fundacion Juan March.     

Metabolic studies of Hg-203 onChlamydomonas reinhardi

Summary Sterile cultures ofChlamydomonas reinhardi, WT⁺, were treated with Hg-203 at 25°C to identify probably formed volatile mercury compounds. Experiments were performed with living and dead cells under aerobic or anaerobic conditions, respectively, and the mercury concentration was measured in the system algae/nutrient medium. We found a timerelated decrease of mercury concentration in the cell suspension and the cell-free nutrient medium due to a reduction of Hg⁺⁺ to Hg⁰, probably caused by extracellular enzymes; monomethyl or dimethyl mercury could not be detected.This work was supported by a grant of Österreichisches Bundesministerium für Gesundheit und Umweltschutz.     

Stimulation induced depletion of the synaptic vesicles in excitatory motor nerve terminals of the locust,Locusta migratoria L

Summary Neural stimulation at high frequency induced gross changes in the ultrastructural properties and depleted the synaptic vesicles in fast axon terminals of locust extensor tibiae muscles. After a 1-h-rest the synaptic vesicle populations recovered and the ultrastructural properties of these recovering neuromuscular junctions closely resembled those of the controls.Acknowledgment. The authors wish to thank Mr M. J. Parker for invaluable help with the statistical analyses. R. P. Botham gratefully acknowledges the SRC for financial assistance.     

Successful cryopreservation of auricle fragments from rat hearts at −196°C

Summary The influence of electrolyte composition and glucose concentration of a cryprotective medium on the survival of auricle fragments from adult rat hearts after storage at –196°C was investigated. Using a K⁺-, Mg⁺⁺-, Ca⁺⁺-rich solution with increased glucose concentration, a high rate of surviving fragments was found after cryopreservation.     

Effects of precocene II and juvenile hormone III on the activity of neurosecretory A-cells inOncopeltus fasciatus

Summary Application of precocene II, topically or by contact method, appears to inhibit the synthetic activity of neurosecretory A-cells of the pars intercerebralis ofOncopeltus fasciatus. Treatment of precocene-treated insects with JH III apparently stimulates the secretory activity of these cells.Supported by National Research Council of Canada grant No. A4669.We thank Dr G. B. Staal, Zoecon Corporation, Palo Alto, California, for the gift of precocene II.     

Striated inclusions and defective mitochondria in the restricted form of the ‘amycelial’ mutant ofNeurospora crassa

Summary The cytoplasm of the restrictive form of the amycelial mutant ofNeurospora crassa, growing on sucrosemedium, contains paracrystalline, microfilamentous inclusions and mitochondria with internal membranous whorls lacking in acetate-grown cultures.The support of the Fonds national suisse de la recherche scientifique is gratefully acknowledged.     

GABA-mimetic action of etomidate

Summary A comparison of antagonism by bicuculline or strychnine of the effects of GABA or etomidate on rat isolated superior cervical ganglia, frog isolated hemisected spinal cords and rat central neurones in vivo indicates that etomidate has GABA-mimetic actions.Acknowledgments. This work was supported by the Medical Research Council and etomidate was provided by Janssen Pharmaceutica.     

Naphthoquinone derivatives from the fungusHendersonula toruloidea

Summary 2 yellow naphthoquinone derivatives were isolated from several pathogenic strains ofHendersonula toruloidea Nattrass. They were identified as 2,7-dimethoxy-6-ethyl-5-hydroxy-1,4-naphthoquinone and 2,7-dimethoxy-5-hydroxy-6-(1-acetoxyethyl)-1,4-naphthoquinone by means of physico-chemical methods.Thanks are due to Mr A.J.M. van Beijnen, Laboratory for Organic Chemistry, State University of Utrecht, for optical rotation measurements.The authors are indebted to Mr C. Versluys, Analytical Laboratory, State University of Utrecht, for measuring the mass spectra.We thank Mr J. W. Marsman, Institute for Organic Chemistry TNO, Utrecht, for the PMR-spectra.