Genetic variation in the genus Bufo I. An extreme degree of transferrin and albumin polymorphism in a population of the American toad (Bufo americanus)

A population of Bufo americanus from southwestern Ohio exhibited an extreme degree of transferrin and albumin polymorphism. One hundred and eighty-five individuals were collected from this population, and their transferrin and albumin phenotypes were determined by vertical acrylamide gel electrophoresis. Thirteen transferrin alleles were present in 36 phenotypes, and 11 albumin alleles were present in 29 phenotypes. A deficiency of heterozygotes occurred at both protein loci. The possible mechanisms responsible for the polymorphism and deficiency of heterozygotes are discussed.This work was supported by grants from the following agencies to the Senior author: NSF GB23601, Society of the Sigma Xi, and the American Philosophical Society. Miami University contributed the computer and audiovisual services.     

A dihedral angle-vicinal proton coupling constant correlation for the α–β bond of amino acid residues

A coupling constant-dihedral angle correlation for the H? Cα? Cβ? H system of amino acid residues in peptides has been derived from a set of model compounds covering the full range of dihedral angles. The expression obtained, J = 11.0 cos₂ θ ?1.4 cos θ + 1.6 sin₂θ, is close to those already used in pmr studies of peptide conformation, and provides a firmer foundation for them. A factor limiting the precision of this and other “Karplus relations” is illustrated.     

MEIOSIS IN THE OOMYCETES: I. A MICROSPECTROPHOTOMETRIC ANALYSIS OF NUCLEAR DEOXYRIBONUCLEIC ACID IN SAPROLEGNIA TERRESTRIS

A cytological and cytochemical examination of Saprolegnia terrestris Cookson was undertaken to resolve the conflict of opinion regarding the life cycle of fungi in the Saprolegniaceae, i.e., whether meiosis is zygotic or gametic. Microspectrophotometric analysis reveals that pre-divisional oogonial and antheridial nuclei are 4C; a subsequent reduction division in the sex organs produces 1C male and female gametes. These division products coexist in the developing oospore and presumably fuse to produce the diploid zygote. Analysis of the somatic hyphal nuclei shows a 2C DNA content, with the characteristic skew and bimodal character indicative of predominantly G1, and some S-period and G2 types. The evidence is completely consistent with gametic meiosis, i.e., a predominant diploid vegetative phase and short haploid phase, and refutes the notion of zygotic meiosis. Further ramifications of the work are discussed along with preliminary results of related work in progress.     

Characterization of protein–polysaccharides of articular cartilage from mature and immature pigs

Protein-polysaccharides of femoral articular cartilage from pigs of ages 9 months and 5 weeks were compared after extraction at pH6.8 with iso-osmotic sodium acetate followed by 0.63m-calcium acetate. The cartilage from the younger animals had a higher moisture content and contained considerably larger amounts of protein-polysaccharide, but less than half as much collagen/g. dry weight, than cartilage from the older pigs. There was notably less keratan sulphate in the fractions from the less mature animals. After gel filtration on 6% agarose, elution profiles of the calcium acetate extracts were similar to those of the sodium acetate extracts of the same tissue. Chemical analyses, however, showed that in both age-groups the extraction procedure had achieved a sequential solubilization of protein-polysaccharides in that the initial extracts contained a higher proportion of keratan sulphate than those that were extracted subsequently. Both extracts from the older animals contained up to 25% of a relatively small protein-polysaccharide that was retarded on 6% agarose and that had a lower protein content and less keratan sulphate than the larger protein-polysaccharides. In contrast, in extracts from the less mature cartilage only about 5% of the protein-polysaccharides were small enough to be retarded by 6% agarose, suggesting that the small components may not be precursors of the larger. The average length of chondroitin sulphate chains, as calculated from the analytical data, was the same in the smaller protein-polysaccharides as in the larger.     

Microbiological and Pharmacological Behavior of 7-Chlorolincomycin

Replacement of the 7-(R) hydroxyl group of lincomycin by a 7-chloro-substituent produced a compound with greater in vitro activity than the parent. Laboratory studies of this compound showed it to be highly active against all of the following strains of gram-positive organisms examined, including penicillinase- and nonpenicillinase-producing staphylococci, Diplococcus pneumoniae, Streptococcus viridans and Streptococcus pyogenes. The enterococci, as well as all the gram-negative organisms tested, with the exception of some strains of Haemophilus, were uniformly insensitive to this agent. The activity of 7-chlorolincomycin was not affected by serum or inoculum size. Resistance developed in a slow stepwise pattern. Peak levels of approximately 2 mug/ml were achieved in the serum of volunteers after ingestion of 150 mg either in the fasting state or after a meal. No untoward effects were noted. The antibiotic appears to be of potential value in the treatment of infections due to gram-positive organisms, with the exception of enterococcus.     

Synthesis of Desthiobiotin from 7,8-Diaminopel-argonic Acid in Biotin Auxotrophs of Escherichia coli K-12

The synthesis of desthiobiotin from 7,8-diaminopelargonic acid (DAP) was demonstrated in resting cell suspensions of Escherichia coli K-12 bioA mutants under conditions in which the biotin locus was derepressed. The biosynthetically formed desthiobiotin was identified by chromatography, electrophoresis, and by its ability to support the growth of yeast and those E. coli biotin auxotrophs that are blocked earlier in the biotin pathway. Optimal conditions for desthiobiotin synthesis were determined. Desthiobiotin synthetase activity was repressed 67% when partially derepressed resting cells were incubated in the presence of 3 ng of biotin per ml. Serine, bicarbonate, and glucose stimulated desthiobiotin synthesis apparently by acting as sources of CO(2). The results of this study are consistent with an earlier postulated pathway for biotin biosynthesis in E. coli: pimelic acid --> 7-oxo-8-aminopelargonic acid --> DAP --> desthiobiotin --> biotin.     

Time of initiation of the barley endosperm response to gibberellin A3, gibberellin A14 and kaurene

Summary Gibberellin A₁₄ and kaurene, precursors of gibberellin A₃, are active in the barley endosperm reducing-sugar assay, but require longer incubation periods for activity to be observed than does GA₃. This finding shows that the incubation period must be considered when determining whether a compound is active in this assay. The longer incubation periods required by GA₁₄ and kaurene may reflect reduced rates of penetration, or reduced activity within the cell, or the time required for conversion to a physiologically active form.