DNA cleavage by hydroxyl radicals generated in a vanadyl ion-hydrogen peroxide system.

Vanadyl ion (+4 oxidation state) has been shown to be an effective agent for chemoprotection of cancers in animals. For understanding the mechanism, distribution of vanadium was studied. More vanadium was found to accumulate in the nuclei of the liver of rats when it was given as vanadyl sulfate than when it was given as sodium vanadate (+5 oxidation state). The reactivity of vanadyl ion with DNA was investigated by the DNA cleavage technique and the reaction mechanism by ESR spectroscopy. Incubation of double-strand DNA with vanadyl ion and hydrogen peroxide resulted in marked concentration- and pH-dependent DNA cleavage. Studies by the ESR spin-trap method demonstrated that hydroxyl radicals are generated during the reactions of vanadyl ion with hydrogen peroxide. Thus the antineoplastic action of vanadyl ion is proposed to be due to DNA cleavage by hydroxyl radicals generated in the cells.     

Food habits of sika deer on the Boso Peninsula,central japan

The rumen contents of sika deer (Cervus nippon Temminck) on the Boso Peninsula, central Japan, were analyzed to identify local, sexual and age-specific differences in food habits. Graminoids and woody plants were the primary foods throughout the year. In winter, the use of evergreen broad leaves increased. The food habits of sika deer on Boso Peninsula were intermediate between those of populations inhabiting northern and southern Japan. Acorns, mainlyLithocarpus edulis Nakai, were consumed in fall and winter with a peak in October. Since the availability of acorns is not influenced by foraging in previous years, it can be regarded as a stable food supply and hence may be important for deer on the Boso Peninsula. The local difference between the Amatsukominato (AT) area, having a large plantation ofLithocarpus producing acrons, and the Kamogawa-Katsuura (KK) area, having a small plantation ofLithocarpus, was recognized; seeds and fruit were consumed more in AT than in KK in fall and winter. Males consumed more seeds and fruit than females at both sites in fall. This can be attributed to sexual differences in nutritional requirement.     

Isolation of a bacterium that causes anaaki disease of the red algae Porphyra yezoensis

Anaaki disease causes severe damage to the red algae Porphyra yezoensis from which the Japanese traditional food 'nori'is produced. The causative agent of anaaki disease was isolated by several repeats of single-colony isolation and infection experiments, and was identified as Flavobacterium sp. LAD-1. The bacterium showed hydrolytic activity toward porphyran but not toward other polysaccharides composing the thallus of Porphyra , such as β-1,3-xylan or β-1,4-mannan. The bacterium also showed β-D-galactosidase activity.     

Evolution of restriction sites of ribosomal DNA in natural populations of the field mouse,Apodemus speciosus

An analysis by restriction endonuclease digestion of ribosomal DNA (rDNA) was carried out in natural populations of Apodemus speciosus, a field mouse that is endemic to Japan. Two restriction sites, the EcoRI (E3) and DraI (D4) sites, in the nontranscribed spacer region downstream from the gene for 28S RNA showed polymorphism within and between individuals in the populations from the Japanese main islands. By contrast, populations from the small adjoining islands which are thought to have separated from the main islands 1–2 × 10⁴ years ago showed relatively low levels of polymorphism within and between individuals, i.e., one of the polymorphic bands in the case of each enzyme was predominant in these populations, irrespective of the variants. These results indicate that the rate of fixation of site variations depends on population size and that the direction of fixation is random. Furthermore, each polymorphic restriction site seems to be fixed independently.Correspondence to: H. Suzuki     

Annual survival rate and age structure of habu,Trimeresurus flavoviridis (Viperidae), on Minna island,Japan: Estimation from removal trapping

A population of a viperid snake,Trimeresurus flavoviridis, was studied over 10 years by removal trapping on a small subtropical island in Japan. The sex ratio of trapped individuals changed seasonally, but was not biased to either sex in the whole sample of 258 individuals. The age of each individual was estimated through the size structure and the age-size relationship. The minimum number of individuals at the beginning of the study was estimated through accumulating older individuals trapped in the subsequent years. By assuming an annual natural survival rate in the course of this accumulation, an age structure was simulated which led to calculate a resulted natural survival rate. The assumed rate of 0.62 fitted best to the resulted one. The annual trapped proportion estimated on the simulated absolute number of individuals was higher in older individuals than in younger ones with the overall mean of 16%.     

Presynaptic α2 Adrenoceptors Inhibit Glutamate Release from Rat Spinal Cord Synaptosomes

Abstract: The presynaptic regulation of amino acid release from nerve terminals was investigated using synaptosomes prepared from the rat spinal cord. The basal releases of endogenous glutamate (Glu), aspartate (Asp), and γ-amino-butyric acid (GABA) were 34.6, 21.5, and 10.0 pmol/min/mg of protein, respectively. Exposure to a depolarizing concentration of KCl (30 m M ) evoked 2.7-, 1.5-, and 2.9-fold increases in Glu, Asp, and GABA release, respectively. Clonidine reduced the K⁺-evoked overflow of Glu to 56% of the control overflow with a potency (IC₅₀) of 17 n M , but it did not affect K⁺-evoked overflow of Asp, GABA, and their basal releases. Similarly, noradrenaline inhibited the K⁺-evoked overflow of Glu, although phenylephrine and isoproterenol showed no effect. The inhibitory effect of clonidine was counteracted by α₂-adrenoceptor antagonists, rauwolscine, yohimbine, and idazoxan, regardless of the imidazoline structures. Because Glu is considered a neurotransmitter of primary afferents that transmit both nociceptive and nonnociceptive stimuli in the spinal cord, these data suggest that part of Glu release may be regulated by the noradrenergic system through α₂ adrenoceptors localized on the primary afferent terminals.     

Additive Induction of Egr-1 (zif/268) mRNA Expression in Neuroblastoma × Glioma Hybrid NG108-15 Cells via Cholinergic Muscarinic, α2-Adrenergic, and Bradykinin Receptors

Abstract: Administration of carbachol, noradrenaline, and bradykinin induced Egr-1 mRNA expression within 1 h in mouse neuroblastoma × rat gliomahybrid NG108–15 cells. With specific receptor antagonists, the Egr-1 inductions by carbachol and noradrenaline were shown to be mediated via cholinergic muscarinic and α₂-adrenergic receptors, respectively. At their saturation levels for Egr-1 induction, the two agonists had additive effects when added together, but no prolongation of the effect on Egr-1 induction was observed. Addition of carbachol or noradrenaline 6 h after primary stimulation with carbachol or noradrenaline did not result in secondary Egr-1 induction, probably because of receptor desensitization. On the other hand, bradykinin consistently had an additive effect on Egr-1 induction, irrespective of the time of its addition, suggesting that the signal pathways for Egr-1 induction by carbachol or noradrenaline and by bradykinin are different. Treatment of cells with pertussis toxin or cholera toxin strongly inhibited Egr-1 induction by carbachol or noradrenaline but only partially inhibited the induction by bradykinin. Thus, the signals transduced in NG108–15 cells by different neurotransmitter receptors appear to have different effects on Egr-1 induction, depending on the times of stimulation and the combinations of receptors stimulated.     

W-heterochromatin of chicken; its unusual DNA components,late replication,and chromatin structure

About 65% of DNA in the chicken W chromosome has been shown to consist ofXhoI andEcoRI family repetitive sequences. These sequences showed remarkable delay in the electrophoretic mobility at low temperature on a polyacrylamide gel. Three dimensional structures of the 0.7-kbXhoI and the 1.2-kbEcoRI family repeating units were estimated to be irregular solenoids using a computer program based on wedge angles of all the 16 dinucleotide steps. Fluorescencein situ hybridization demonstrated that these two family sequences were localized in a major heterochromatic body in an interphase nucleus. Incorporation of bromodeoxyuridine into the W chromosome in the synchronous culture of MSB-1 cells occurred about 1 h later than the peak of S phase. The chromatin structure formed alongXhoI andEcoRI family sequences was suggested to be different from the total chromatin or chromatin containing the β-actin gene sequence in that the linker DNA lengths of the former were significantly longer. Fractionation of theHaeIII-digested MSB-1 nuclei yielded a chromatin fraction in whichXhoI family sequences were partially enriched. Several DNA-binding proteins showing higher affinity for theXhoI family sequence were present in this fraction.