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[Electrical conductivity profiles in the wood of central European tree species, determined with the "Vitamat"]
1993
Bucher, H.P. | Kucera, L.J. | Walter, M. | Bonsen, J.M. (Eidg. Forschungsanstalt fuer Wald, Schnee und Landschaft, Birmensdorf (Switzerland))
Optic critical duration and contrast thresholds in the freshwater fish, Lepomis macrochirus, as determined behaviourally
1993
Kawamura, G. (Kagoshima Univ. (Japan). Faculty of Fisheries) | Shimowada, T.
The distribution of Sindbis virus proteins in mosquito cells as determined by immunofluorescence and immunoelectron microscopy
1993
Miller, M.L. | Brown, D.T.
Two Aedes albopictus (mosquito) subclones, C7-10 and C6/36, were examined by immunofluorescence and immunoelectron microscopy for the distribution of Sindbis virus structural and non-structural proteins. Both the viral glycoproteins, E1 and E2, and the non-structural proteins, nsP1 and nsP2, were found within vesicles and electron-dense, amorphous matrices associated with Sindbis virus infection. The labelling patterns indicated that both replication of viral RNA and production of virus particles were localized within the same structures in the infected cell. The data support previous reports that alphavirus infection is contained within specific structures in the cytoplasm and provide additional evidence that the C6/36 and C7-10 subclones may represent different tissue types in the adult insect.
Mostrar más [+] Menos [-]The contributions of bacteria and protozoa to ruminal forage fermentation in vitro, as determined by microbial gas production
1993
Hidayat (Rowett Research Inst., Aberdeen (United Kingdom)) | Hillman, K. | Newbold, C.J. | Stewart, C.S.
Glucose repression of lactose/galactose metabolism in Kluyveromyces lactis is determined by the concentration of the transcriptional activator LA1C9 (K1GAL4)
1993
Zachariae, W. | Kuger, P. | Breunig, K.D.
In the budding yeast Kluyveromyces lactis glucose repression of genes involved in lactose and galactose metabolism is primarily mediated by LAC9 (or K1GAL4) the homologue of the well-known Saccharomyces cerevisiae transcriptional activator GAL4. Phenotypic difference in glucose repression existing between natural strains are due to differences in the LAC9 gene (Breunig, 1989, Mol. Gen. Genet. 261, 422-427). Comparison between the LAC9 alleles of repressible and non-repressible strains revealed that the phenotype is a result of differences in LAC9 gene expression. A two-basepair alteration in the LAC9 promoter region produces a promoter-down effect resulting in slightly reduced LAC9 protein levels under all growth conditions tested. In glucose/galactose medium any change in LAC9 expression drastically affects expression of LAC9 controlled genes e.g. those encoding beta-galactosidase or galactokinase revealing a strong dependence of the kinetics of induction on the LAC9 concentration. We propose that in tightly repressible strains the activator concentration drops below a critical threshold that is required for induction to occur. A model is presented to explain how small differences in activator levels are amplified to produce big changes in expression levels of metabolic genes.
Mostrar más [+] Menos [-]Estimates of linkage disequilibrium and the recombination parameter determined from segregating nucleotide sites in the alcohol dehydrogenase region of Drosophila pseudoobscura
1993
Schaeffer, S.W. | Miller, E.L.
The alcohol dehydrogenase (Adh) region of Drosophila pseudoobscura, which includes the two genes Adh and Adh-Dup, was used to examine the pattern and organization of linkage disequilibrium among pairs of segregating nucleotide sites. A collection of 99 strains from the geographic range of D. pseudoobscura were nucleotide-sequenced with polymerase chain reaction-mediated techniques. All pairs of the 359 polymorphic sites in the 3.5-kb Adh region were tested for significant linkage disequilibrium with Fisher's exact test. Of the 74,278 pairwise comparisons of segregating sites, 127 were in significant linkage disequilibrium at the 5% level. The distribution of five linkage disequilibrium estimators Dij, D(2), rij, r(2) and Dij were compared to theoretical distributions. The observed distributions of Dij, D(2), rij and r(2) were consistent with the theoretical distribution given an infinite sites model. The observed distribution of Dij differed from the theoretical distribution because of an excess of values at -1 and 1. No spatial pattern was observed in the linkage disequilibrium pattern in the Adh region except for two clusters of sites nonrandomly associated in the adult intron and intron 2 of Adh. The magnitude of linkage disequilibrium decreases significantly as nucleotide distance increases, or a distance effect. Adh-Dup had a larger estimate of the recombination parameter, 4Nc, than Adh, where N is the effective population size and c is the recombination rate. A comparison of the mutation and recombination parameters shows that 7-17 recombination events occur for each mutation event. The heterogeneous estimates of the recombination parameter and the inverse relationship between linkage disequilibrium and nucleotide distance are no longer significant when the two clusters of Adh intron sites are excluded from analyses. The most likely explanation for the two clusters of linkage disequilibria is epistatic selection between sites in the cluster to maintain pre-mRNA secondary structure.
Mostrar más [+] Menos [-][Effect of the nitrogenous fertilization in three legume forages on the atmospherical nitrogen fixing (N2) determined by the 15N isotope tracer technique]
1993
Escobedo Monge, F.M.A.
Developmental changes in the composition of proanthocyanidins from leaves of sainfoin (Onobrychis viciifolia Scop.) as determined by HPLC analysis Texto completo
1993
Koupai-Abyazani, M.R. | McCallum, J. | Muir, A.D. | Bohm, B.A. | Towers, G.H.N. | Gruber, M.Y.
Proanthocyanidin (PA) polymers (condensed tannins) were extracted from sainfoin leaves (Onobrychis viciifolia Scop.) at different stages of plant development. Analysis of the phloroglucinol degradation products by high-performance liquid chromatography showed that catechin, epicatechin, gallocatechin, and epigallocatechin were present as terminal units at all stages, while gallocatechin and epigallocatechin were the predominant extension units with lesser amounts of epicatechin incorporated at early stages. Catechin was not incorporated as an extension unit. The number-average molecular weight and degree of polymerization increased with leaf development. There was a very distinct change in the isomerization and degree of hydroxylation of the polymer constituents with development. The composition of cis-isomers decreased from 83 to 48% and the proportion of trihydroxylated B-rings increased from 60 to 90% with increasing leaf maturity.
Mostrar más [+] Menos [-]Efectos de la fertilizacion nitrogenada en tres leguminosas forrajeras sobre la fijacion de nitrogeno atmosferico (N2) determinado mediante la tecnica del isotopo trazador 15N.
1993
Escobedo Monge F.M.A.
Comparison of the protein composition and enzymatic activities during development between effective and plant-determined ineffective nodules in pea
1993
Suganuma, N. | Tamaoki, M. | Takaki, M.
The protein composition and enzymatic activities during development of ineffective nodules, produced by mutant E135 (sym 13) of pea (Pisum sativum L.), were compared with those of the nitrogen-fixing nodules of the normal parent, the Sparkle cultivar. The protein composition of 3- week-old E135 nodules, as determined by SDS-polyacrylamide gel electrophoresis, was quite similar to that of Sparkle nodules. After 4 weeks, however, the intensities of bands of 15-, 38-, and 87-kDa polypeptides were lower in the case of E135 nodules. Western blot analysis using a "nodule-specific" antiserum revealed that most nodulins could be detected in 3-week-old E135 nodules, but a 35.5-kDa nodulin disappeared after 5 weeks and several novel peptides ranging in molecular weight from 26 to 31 kDa appeared after 6 weeks in E135 nodules. The activities of glutamine synthetase, glutamate synthase, alanine-pyruvate aminotransferase, sucrose synthase, and phosphoenolpyruvate carboxylase increased during development of Sparkle nodules, but such increases were not found in E135 nodules after 5 weeks. These results show that the nodules of E135 begin to develop normally but differ from those of Sparkle within 4 weeks, indicating that, during early stages of nodule development, the protein composition and activities of enzymes involved in carbon and nitrogen metabolism are not regulated by the presence or absence of nitrogenase activity.
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