Internal Distribution of Acid Materials within Snow Crystals

We found that river water is acidified not only in the first stage but also in the later stage of the snowmelt season in Japan, which differs from the so called acid shock occurring in the first stage of the snowmelt in the northern Europe. The acid shocks depend on the regional characteristics of the melt-refreeze processes forming the internal distribution of acid materials within snow crystals under the warm metamorphism. In a warm climatic region like the central Japan, there are possibilities to have the complicated distribution structure of acid materials within granular-snow crystals due to the repeated melt-refreeze processes even in midwinter. Consequently, the pH value of meltwater does not always increase as the snowmelt proceeds. Then, we showed the possibility by using the X-ray computed tomography that the domains with the acid materials exist in the inner parts of snow crystals. So, the acidification of the river water may occur even in the later stage of the snowmelt.     

The Physcomitrella genome reveals evolutionary insights into the conquest of land by plants

We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics.     

3,4-dihydroxyproline: a new amino acid in diatom cell walls

An analog of proline, 2, 3-cis-3, 4-trans-3, 4-dihydroxy-L-proline, was found in the cell walls of the eight species of diatoms studied and was isolated from the proteinaceous material of the wall of Navicula pelliculosa. The properties of this substance are described; its structure was confirmed by nuclear magnetic resonance spectros-copy.     

Structural proteins of equine infectious anemia virus and their antigenic activity

Using purified equine infectious anemia (EIA) virus labeled with 3H-glucosamine or 14C-protein hydrolysate, structural proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. As a result, 2 glycoproteins and 10 proteins with molecular weights (mol wt) ranging from 12,000 to 115,000 daltons were demonstrated. Of 12 structural proteins, 3 proteins, namely a glycoprotein with mol wt of 76,000 (gp76) and 2 proteins with mol wt of 25,000 (p25) and 12,000 (p12), respectively, had distinct antigenic activity from one another in immunodiffusion. Development of antibodies against gp76 and p25 was compared in infected horses. The antibody to gp76 appeared earlier and stronger than to p25 in horses infected with the homologous virus strain. The fraction with glycoproteins was found to have hemagglutinating activity which was inhibited by the serum sample from horses infected with equine infectious anemia virus.     

The mechanism of resistance to lindane and hexadeuterated lindane in the Third Yumenoshima strain of house fly

The factors which cause lindane resistance in the Third Yumenoshima strain, a strain of house flies highly resistant to insecticides, were studied using hexadeuterated lindane. Hexadeuterated lindane has the same physicochemical properties as lindane, but the former is much less biodegradable than the latter. The LD₅₀ ratio of lindane to hexadeuterated lindane in this strain, deuterium isotope effect on LD₅₀ values, was larger than that in S_NAIDM, a susceptible (nonresistant) strain. The penetration rates of labeled and nonlabeled lindane through the insect cuticle were about the same for both strains. Thus, penetration rate does not cause resistance. The metabolic degradation of lindane in the resistant strain in vivo occurred much faster than in the susceptible strain. This was also the case for lindane degradation processes in vitro such as microsomal oxidation and glutathione conjugation. In both strains, significant isotope effects were observed in the degradation rates in vitro of labeled and nonlabeled lindane. Therefore, principal biodegradation and detoxication pathways should include reactions which cleave the CH bonds. When the much less biodegradable d₆ counterpart of lindane was applied to both strains, the susceptible strain became much more highly intoxicated than the other within 20 to 30 min. This indicates that a combination of both greater degradability and probably lower sensitivity at the action site are the main factors underlying resistance in the Third Yumenoshima strain.     

Insecticidal activity and microsomal metabolism of biooxidizable lindane analogs

The insecticidal activity of lindane analogs, in which some chlorine atoms were replaced by other groups susceptible to microsomal oxidative metabolism, was determined against mosquitos, house flies, and German cockroaches. When tested with a synergist, piperonyl butoxide, one of the methylthio analogs was as active as lindane, whereas several others were also highly active. By examining the ratio of synergized and unsynergized LD₅₀ values (synergistic ratio value), the highly insecticidal methylthio, methoxy, and methyl analogs appear to undergo metabolic detoxication effectively in house flies. By means of in vitro metabolism experiments using microsomal fraction from house fly abdomen, the methoxy, ethoxy, and methylthio analogs were shown to be metabolized rapidly at similar rates. The synergized insecticidal activities of these compounds against various insect species relate linearly with each other, suggesting that the oxidative degradation is inhibited by the synergist to a similar extent and that the transport process to the site of action is not a limiting factor in determining the relative insecticidal activity.     

Inhibitory effects of pesticides on growth and respiration of cultured cells

Effects of various drugs including pesticides on the growth and respiration of cultured cells were evaluated comparatively using cell lines derived from mosquito ovary and subcutaneous mouse tissues. The concentration producing 50% inhibition of cell growth, I₅₀ (M), was determined for each of 42 drugs. Inhibitors of respiration and nucleic acid and protein biosyntheses such as rotenone, piericidin A₁, actinomycin D, and puromycin had very high pI₅₀ values of approximately 8. Except for the compounds known to be uncouplers of oxidative phosphorylation, the drugs suppressed the respiration rate of the cultured cells to various degrees. The pI₅₀ value (and the pEC₁₅₀, 150% enhancement of the control, value for uncouplers) was determined for each compound. By examining the relation of pI₅₀ (and pEC₁₅₀) values between cell growth and respiration, the compounds could be classified into two groups according to their modes of inhibitory action against the cultured cells. One mode relates to the inhibition of energy synthesis and the other, perhaps, to interference with the biosynthesis of biomacromolecules.     

Macrolides and lincomycin susceptibility of Mycoplasma hyorhinis and variable mutation of domain II and V in 23S ribosomal RNA

A total of 151 strains of Mycoplasma hyorhinis isolated from porcine lung lesions (weaned pigs, n=71, and finishers, n=80) were investigated for their in vitro susceptibility to 10 antimicrobial agents. Thirty-one strains (28 from weaned pigs and 3 from finishers) showed resistance to 16-membered macrolide antibiotics and lincomycin. The prevalence of the 16-membered macrolide-resistant M. hyorhinis strain in weaned pigs from Japanese herds has approximately quadrupled in the past 10 years. Several of the 31 strains were examined for mutations in the 23S ribosomal RNA (rRNA). All field strains tested showed a transition of A to G at position 2059 of 23S rRNA-rendered Escherichia coli. On the other hand, individual tylosin- and lincomycin-resistant mutants of M. hyorhinis were selected in vitro from the susceptible type strain BTS7 by 3 to 9 serial passages in subinhibitory concentrations of each antibiotic. The 23S rRNA sequences of both tylosin and lincomycin-resistant mutants were compared with that of the radical BTS7 strain. The BTS7 mutant strain selected by tylosin showed the same transition as the field-isolated strains of A2059G. However, the transition selected in lincomycin showed mutations in domains II and V of 23S rRNA, G2597U, C2611U in domain V, and the addition of an adenine at the pentameric adenine loop in domain II. The strain selected by lincomycin showed an additional point mutation of A2062G selected by tylosin.