Lack of mutagenicity of irradiated glucose in Salmonella typhimurium using host-mediated assay

Experiments were conducted to study the ability of irradiated glucose to induce reverse mutations in S. typhimurium by host-mediated assay. The results revealed no significant increase in the frequency of reverse mutations compared to controls.     

Marine indoles of novel substitution pattern from the acorn wormGlossobalanus sp.

Summary 4,6-Dibromoindole and 4,6-dibromo-2-methylindole have been isolated from the acorn wormGlossobalanus sp. The biosynthetic implications of this finding are discussed.We wish to thank Prof. Paul J. Scheuer, University of Hawaii for his encouragement and for use of his facilities during spectroscopic work. T.H. gratefully acknowledges the giving of a travel grant by the University of the Ryukyus Foundation for International Exchange.     

Role of active oxygen species in diethyldithiocarbamate-induced gastric ulcer in the rat

Diethyldithiocarbamate, an inhibitor of Cu,Zn-superoxide dismutase, was recently found to be ulcerogenic in the rat stomach, and active oxygen species were found to be responsible for its ulcerogenicity. To clarify which active oxygen species play a role in ulcerogenesis, the effects of various scavengers and iron-chelators were studied. As superoxide dismutase and catalase reduced the ulcerogenesis induced by diethyldithiocarbamate, the superoxide radical and hydrogen peroxide were considered to play a pathogenic role in this ulcer model.     

Inactivation of muscle chloride channel by transposon insertion in myotonic mice.

MYOTONIA (stiffness and impaired relaxation of skeletal muscle) is a symptom of several diseases caused by repetitive firing of action potentials in muscle membranes. Purely myotonic human diseases are dominant myotonia congenita (Thomsen) and recessive generalized myotonia (Becker), whereas myotonic dystrophy is a systemic disease. Muscle hyperexcitability was attributed to defects in sodium channels and/or to a decrease in chloride conductance (in Becker's myotonia and in genetic animal models). Experimental blockage of Cl- conductance (normally 70-85% of resting conductance in muscle) in fact elicits myotonia. ADR mice are a realistic animal model for recessive autosomal myotonia. In addition to Cl- conductance, many other parameters are changed in muscles of homozygous animals. We have now cloned the major mammalian skeletal muscle chloride channel (ClC-1). Here we report that in ADR mice a transposon of the ETn family has inserted into the corresponding gene, destroying its coding potential for several membrane-spanning domains. Together with the lack of recombination between the Clc-1 gene and the adr locus, this strongly suggests a lack of functional chloride channels as the primary cause of mouse myotonia.     

Influence of pinealectomy on corticotropin (ACTH)

Sensory deprivation produced by removing the eyes and olfactory bulbs in male rats allowed pinealectomy to markedly augment the post-adrenalectomy elevation of ACTH levels. Pineal removal or sensory deprivation separately did not have this effect. Thus, intact sensory input and an intact pineal gland are independently capable of restricting the post-adrenalectomy rise in ACTH levels.     

Über optische Untersuchungen an Deckschichten auf Aluminium

Summary The double refraction of oxide films on Al conditioned by an electrolytic treatment of the metal in oxalic acid, sulphuric acid and so on (Eloxal-layers) is due only to the disperse structure of the film (Formdoppel-brechung), since the substances the film consists of are optically isotropic.The optical properties depend, excepting the formation conditions, in a very characteristic manner on the crystallographic orientation of the metallic surface.     

Effect of bleached rhodopsin on signal amplification in rod visual receptors

Bleaching of rhodopsin markedly desensitizes the vertebrate visual system during a subsequent period of dark adaptation. Previous studies have indicated an origin of bleaching desensitization in the visual pigment itself, but have not identified the mechanism of action. A candidate for the site at which densensitization is initially expressed is the activation of transducin (formation of T*) on the rod disk membranes; this reaction directly involves rhodopsin in its photoactivated (R*) form and mediates initial amplification of the visual signal (reviewed in refs 7-9). We have analysed the effect of bleaching on the sensitivity of a flash-induced light-scattering signal known to monitor the disk-based amplifier, and which has been established as specifically monitoring transducin activation. We have recorded this signal from functioning retinal rods in situ ('ATR' signal) and find that bleaches inducing a pronounced, sustained loss in rod electrophysiological sensitivity do not alter the sensitivity of the ATR response after correction for reduced quantum catch. Our results indicate that the biochemical gain of the R*----T* transduction stage remains unchanged in the presence of bleached pigment and implicate a subsequent reaction as the first to show a sustained, bleaching-dependent gain reduction.     

Localization of muscle gene products in nuclear domains

The localization of gene products is central to the development of cell polarity and pattern specification during embryogenesis. To monitor the distribution of gene products encoded by different nuclei in the same cell in tissue culture, we fused cells of different species to form multinucleated non-dividing heterokaryons. In previous fusion studies, cell-surface antigens and organelles contributed by disparate cell types intermixed within minutes. Using heterokaryons produced with differentiated muscle cells, we demonstrate here that a muscle membrane component, the Golgi apparatus mediating its transport, and a sarcomeric myosin heavy chain are localized in the vicinity of the nuclei responsible for their synthesis. These results provide direct evidence that products (organelle, membrane and structural proteins) derived from individual nuclei can remain localized in myotubes, a finding with implications both for neuromuscular synapse formation and for the carrier state of Duchenne muscular dystrophy.     

DNA mutagenesis and recombination

The polymerase chain reaction is used for site-specific mutagenesis and for DNA recombination without any enzymatic reaction in vitro, apart from DNA amplification.