Collagenase of a new streptomycete: Its induction and purification

Rifampin and chloramphenicol inhibited the synthesis of collagenase of Streptomyces sp. A₈, suggesting de novo synthesis. The collagenase was induced by insoluble collagen, its macromolecular fragments, gelatin, peptone, hide powder and yeast extract. Growth as well as collagenase synthesis were dependent on substrate availability. Purification of collagenase by DEAE-cellulose chromatography resulted in approximately 25-fold increase in activity (268.6 μmol glycine equivalents min^?1 mg^?1 protein) relative to the activity of the culture filtrate (10.5 μmol glycine equivalents min^?1 mg^?1 protein).     

Evidence for supercoiled hepatitis B virus DNA in chimpanzee liver and serum Dane particles: possible implications in persistent HBV infection

In chimpanzee hepatitis B virus (HBV) carriers, the mechanism of viral persistence has been examined by analyzing viral DNA molecules in liver and serum. Chimpanzee liver DNA contained two extrachromosomal HBV DNA molecules migrating on hybridization blots at 4.0 kb and 2.3 kb. There was no evidence for integration of HBV DNA into the host genome. The extrachromosomal molecules were distinct from Dane particle DNA and were converted to linear 3.25 kb full-length double-stranded HBV DNA on digestion with Eco RI. Nucleases S1 and Bal 31 converted "2.3 kb" HBV DNA to 3.25 kb via an intermediate of "4.0 kb" apparent length. The HBV DNA molecule that migrated at 2.3 kb represents a supercoiled form I of the HBV genome, and the molecule that migrated at 4.0 kb represents a full-length "nicked," relaxed circular form II. Evidence for supercoiled HBV DNA in serum Dane particles was obtained by production of form II molecules upon digestion with nuclease S1 or Bal 31. It is proposed that most Dane particles represent interfering noninfectious virus containing partially double-stranded DNA circles and that particles containing supercoiled HBV DNA may represent infectious hepatitis B virus.     

Statistical Studies on Protein Polymorphism in Natural Populations. III. Distribution of Allele Frequencies and the Number of Alleles per Locus

With the aim of understanding the mechanism of maintenance of protein polymorphism, we have studied the properties of allele frequency distribution and the number of alleles per locus, using gene-frequency data from a wide range of organisms (mammals, birds, reptiles, amphibians, Drosophila and non-Drosophila invertebrates) in which 20 or more loci with at least 100 genes were sampled. The observed distribution of allele frequencies was U-shaped in all of the 138 populations (mostly species or subspecies) examined and generally agreed with the theoretical distribution expected under the mutation-drift hypothesis, though there was a significant excess of rare alleles (gene frequency, 0 ~ 0.05) in about a quarter of the populations. The agreement between the mutation-drift theory and observed data was quite satisfactory for the numbers of polymorphic (gene frequency, 0.05 ~ 0.95) and monomorphic (0.95 ~ 1.0) alleles.—The observed pattern of allele-frequency distribution was incompatible with the prediction from the overdominance hypothesis. The observed correlations of the numbers of rare alleles, polymorphic alleles and monomorphic alleles with heterozygosity were of the order of magnitude that was expected under the mutation-drift hypothesis. Our results did not support the view that intracistronic recombination is an important source of genetic variation. The total number of alleles per locus was positively correlated with molecular weight in most of the species examined, and the magnitude of the correlation was consistent with the theoretical prediction from mutation-drift hypothesis. The correlation between molecular weight and the number of alleles was generally higher than the correlation between molecular weight and heterozygosity, as expected.     

Oestrous and ovarian activity in a female jaguar (Panthera onca).

The mean +/- s.e.m. duration of oestrus was 12.0 +/- 1.0 days (n = 7) and the oestrous cycle length was 47.2 +/- 5.4 days (n = 6) for a captive jaguar. Ovulation did not occur spontaneously, but was induced by treatment with hCG or LH-RH.     

Fine structural abnormalities in the developing mouse embryo

Initial changes in the fine morphology of apparently normal mouse zygotes and embryos were studied in serial sections of mouse oviducts that had been fixed in situ. These changes included extra sperm in the perivitelline space, nuclear budding, the presence of large nucleoli, perinuclear vesicles, the concentration of cytoplasmic organelles, and the extrusion of cytoplasmic ground substance. Initial changes in the nucleus and cytoplasm were undetectable when the zygotes and embryos were examined with the light microscope. It was concluded that serious abnormalities in zygotes and embryos, which may not be identified at the light microscope level, may be detected if they are examined in the electron microscope. Therefore, zygotes and embryos should be critically evaluated before being rated as normal.     

Estimation of time of divergence from phylogenetic studies.

Recent studies with comparative data on base sequences of homologous DNA's or amino acid sequences of homologous proteins indicate that simultaneous estimation of phylogenetic structure and time of divergence is often cumbersome and time consuming. On the other hand, when the topology of an evolutionary tree is known, it is shown in this paper that the least squares theory may be applied to obtain simple estimates of the relative time lengths for each segment of the tree under the assumption of uniform random substitutions in each segment. The method is illustrated with amino acid sequence data on various globin molecules and cytochrome c. The evolutionary significance of some of the estimates is also discussed.     

Genetic structure of the populations migrating from San Luis Potosi and Zacatecas to Nuevo León in Mexico

The Mexicans residing in the Monterrey metropolitan area in Nuevo León, Mexico, were grouped by generation and birthplace [Monterrey Metropolitan Area (MMA), San Luis Potosi (SLP), and Zacatecas (ZAC)] of the four grandparents to determine the extent of genetic variation within this population and the genetic differences, if any, between the natives living in the MMA and the immigrant populations from SLP and ZAC. Nine genetic marker systems were analyzed. The genetic distance analysis indicates that SLP and ZAC are similar to the MMA, irrespective of birthplace and generation. Gene diversity analysis (GST) suggests that more than 96% of the total gene diversity (HT) can be attributed to individual variation within the population. The genetic admixture analysis suggests that the Mexicans of the MMA, SLP, and ZAC, stratified by birthplace and generation, have received a predominantly Spanish contribution (78.5%), followed by a Mexican Indian contribution (21.5%). Similarly, admixture analysis, conducted on the population of Nuevo León and stratified by generation, indicates a substantial contribution from the MMA (64.6%), followed by ZAC (22.1%) and SLP (13.3%). Finally, we demonstrate that there is no nonrandom association of alleles among the genetic marker systems (i.e., no evidence of gametic disequilibrium) despite the Mestizo origin of this population.     

Effects of plant extract Centella asiatica (Linn.) on cold restraint stress ulcer in rats.

Extract of C. asiatica (Linn.) inhibited significantly gastric ulceration induced by cold and restraint stress (CRS) in Charles-Foster rats, Antiulcer activity of plant extract was compared with famotidine (H2-antagonist) and sodium valproate (anti-epileptic). Plant extract, formotidine and sodium valproate showed a dose dependent reduction of gastric ulceration. Plant extract increased brain GABA level which was also dose dependent. Pretreatment with bicuculline methiodide (specific GABAA-antagonist) at the dose level of 0.5 mg/kg im, reversed the antiulcerogenic activity of both plant extract and sodium valproate. Bicuculline as such did not induce gastric ulceration in normal rat.