PubMed Health⌕ Search

Biomedical subjects

H O Halvorson

Publications and source records attributed to H O Halvorson.

At least 19 recordsLinked to original sources
PubMed1999

Increasing public involvement in enriching our fish stocks through genetic enhancement.

A total of 70%, of the world's conventional commercial fish species are now fully exploited, overexploited, depleted or recovering from depletion. This dramatic crash in the capture world fisheries production has led to problems in foods distribution, balance of payments, employment, and ecological depletion. Public support for breeding programs with terrestrial farm animals and plants in agriculture have revolutionized this industry over the past few hundred years. However, new genetic rearing technologies to improve marine animal production through aquaculture that utilize modern biology to obtain sustainable aquaculture and preserve biodiversity provide a promise to address these problems. However aquaculture has not been subject to public discussion and approval. Public involvement, not necessarily acquiescence, provide value added in the decision making process. Public understanding and involvement involves three stages. (i) Public concern over the pool of genetic information; (ii) if aquaculture is to respond to the fisheries crises with innovation, the knowledge gap between public understanding and scientific information must be bridged; and (iii) strategies must be developed for achieving this. Release of recombinant DNA to the environment, and handling exotic species, are useful case studies. Illustrations will be given of communication bridges to the public and ways to involve the public in making policy decisions.

Animals↗
PubMed1997

Two generations of spore research: from father to son.

Harlyn O. Halvorson has played an active and defining role in the field of microbiology for more than 40 years. In this article, he reminisces on the major influence that his father, H. Orin Halvorson, had in the direction of his professional life. The two H.O. Halvorson's, often confused in the literature, became one of the only two father and son pairs to head the American Society for Microbiology in 1954 and 1977, respectively. Major scientists of the era, their research and their collaborations, are remembered in relation to their main works. Harlyn O. Halvorson's interest in bacterial and yeast spores, and especially spore germination in bacilli, is the highlight of this memoir. His scientific research thrusts, leadership at Marine Biological laboratories, Woods Hole, NACSEX (North American-Cuban Scientific Exchange) and elsewhere, his dedication to advanced students and numerous other endeavors, both scientific and political, are told here.

Alanine↗
PubMed1994

M13 DNA fingerprinting in differentiation of marine Vibrio species.

The identification and differentiation of bacterial strains and species are frequently carried out by the use of diagnostic biochemical profiles, serology, and the detection of restriction fragment length polymorphisms in genomic DNA. We show here that DNA restriction fragment length polymorphisms detected using a probe derived from bacteriophage M13 can discriminate between several marine Vibrio species. We have also demonstrated that individual isolates of Vibrio species can be differentiated using the M13 probe.

Animals↗
PubMed1991

The possible involvement of trypsin-like enzymes in germination of spores of Bacillus cereus T and Bacillus subtilis 168.

Germination of spores of Bacillus cereus T and Bacillus subtilis 168 was inhibited by the trypsin inhibitors leupeptin and tosyllysine chloromethyl ketone (TLCK) and by the substrates tosylarginine methyl ester (TAME), benzoyl-L-arginine-p-nitroanilide (L-BAPNA) and D-BAPNA. Potencies of these inhibitory compounds were estimated by finding the concentration which inhibited 50% germination (ID50), as measured by events occurring early (loss of heat resistance), at an intermediate stage [dipicolinic acid (DPA) release], and late in germination (decrease in optical density). In B. cereus T, all the compounds inhibited early and late events with the same ID50. In B. subtilis, TAME inhibited early and late events at the same ID50, but all other inhibitors had a lower ID50 for late events than for early events. This suggests that a trypsin-like enzyme activity is involved at two sequential stages in the germination of B. subtilis spores, one occurring at or before the loss of heat resistance and one at or before the decrease in optical density. Different trypsin-like activities were detected in broken dormant spores and germinated spores of B. cereus T and in germinated spores of B. subtilis by means of three chromogenic substrates: benzoyl-L-phenylalanyl-L-valyl-L-arginine-p-nitroanilide (L-PheVA), L-BAPNA and D-BAPNA. Separation of extracts of germinated spores on non-denaturing polyacrylamide gels showed that in both species the substrates were hydrolysed by three distinct enzymes with different electrophoretic mobilities. The three enzymes had different Ki values for the above inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine↗
PubMed1987

Improved resolution of DNA fragments in polysaccharide-supplemented agarose gels.

The electrophoretic separation of nucleic acids, including small DNA fragments in the range 50-1000 bp, is presently carried out in polyacrylamide gels or in gels containing high concentrations of agarose. We have developed an alternative gel matrix composition which is inexpensive, nontoxic, easy to prepare, and highly transparent to visible and uv light. The composition combines a soluble nonionic polysaccharide such as hydroxyethylcellulose, methylcellulose, or galactomannan with a minimum but sufficient concentration of agarose to form a gel which immobilizes the "liquid phase sieve." These mixtures do not replace polyacrylamide for resolving fragments smaller than approximately 75 nucleotides. However, the new gels show DNA fragment resolution (band separation versus distance traveled) and optical clarity superior to those of conventional agarose.

Carbohydrates↗
PubMed1987

Cloning and expression in Escherichia coli of chromosomal mercury resistance genes from a Bacillus sp.

A 7.9-kilobase (kb) chromosomal fragment was cloned from a mercury-resistant Bacillus sp. In Escherichia coli, in the presence of a second plasmid carrying functional transport genes, resistance to HgCl2 and to phenylmercury acetate (PMA) was expressed. Shortening the cloned fragment to 3.8 kb abolished resistance to PMA but not to HgCl2. In Bacillus subtilis, the 3.8-kb fragment produced mercuric reductase constitutively but did not produce resistance to HgCl2 or to PMA.

Bacillus↗
PubMed1986

The MURFI linker for multiple reading frame insertion of a sense or nonsense codon into DNA.

Blunt-end palindromic DNA linkers with a central restriction site have been designed for the multiple reading frame insertion (abbreviated MURFI) of a sense or nonsense codon into DNA. We have utilized an amber MURFI linker, 5'CTAG TCTAGA CTAG3' to disrupt the lacZ gene, yielding truncated beta-galactosidase proteins. Conditional disruption of the tetr gene in E. coli has also been demonstrated. Nonsense codon MURFI linkers permit conditional fusion of multiple gene products while sense codon linkers can add structural elements (e.g. beta-turn, cationic segment, hydrophobic segment) or a desired amino acid to a protein (e.g. methionine, cysteine). Shotgun or alternatively site-directed insertion of the symmetric linkers is possible. The over-all length of the linker may be adjusted to retain the original reading frame, matching nucleotide additions or subtractions at recipient DNA sites. If a linker restriction site occurs elsewhere in the target DNA, single linker copies may still be inserted using non-phosphorylated linkers.

Base Sequence↗
PubMed1986

Mutations affecting the signal sequence alter synthesis and secretion of yeast invertase.

Insertion mutations previously constructed within the proximal region of the yeast invertase signal sequence did not interfere with secretion or glycosylation of the enzyme. We now describe deletion mutations within the same signal sequence. Large deletions truncating the hydrophobic core of the signal peptide prevented both secretion and glycosylation of the enzyme and increased the intracellular concentration of nonglycosylated invertase. This increase was coupled with the appearance of a new invertase polypeptide, 2 kilodaltons larger than cytoplasmic invertase. The new polypeptide was consistent in size with uncleaved (signal peptide intact) pre-secretory invertase previously identified by using in vitro translation (apparent molecular mass, 62 kilodaltons). The data on enzyme activity indicate that invertase whose secretion is aborted by large deletion mutations augments the normal pool of cytoplasmic invertase found in sucrose-fermenting yeast cells.

Base Sequence↗
PubMed1986

A detailed study of gerJ mutants of Bacillus subtilis.

A total of nine gerJ mutants have now been isolated in Bacillus subtilis. All are defective in their spore germination properties, being blocked at an intermediate (phase grey) stage. The dormant spores are sensitive to heating at 90 degrees C and two of the mutants (generated by transposon insertion) produce spores sensitive at 80 degrees C. The spores of these two more extreme mutants had a visibly defective cortex when studied by electron microscopy, as did some of the other mutants. During sporulation, the acquisition of spore resistance properties and the appearance of the sporulation-specific penicillin-binding protein PBP5* were delayed. A strain probably carrying a lacZ fusion to the gerJ promoter demonstrated increased expression between t2 and t4. We propose that the gerJ locus is involved in the control of one or more sporulation-specific genes.

Bacillus subtilis↗
PubMed1986

Cadmium- and mercury-resistant Bacillus strains from a salt marsh and from Boston Harbor.

Bacteria resistant to cadmium or mercury or both were isolated from the Great Sippewissett Marsh (Cape Cod, Mass.) and from Boston Harbor. Many of these metal-resistant isolates were gram-positive aerobic sporeformers, although not necessarily isolated as spores. Although several of the isolated strains bore plasmids, cadmium and mercury resistances appeared to be, for the most part, chromosomally encoded. DNA sequence homology of the gram-positive cadmium- and mercury-resistant isolates was not demonstrable with metal resistance genes from plasmids of either gram-positive (pI258) or gram-negative (pDB7) origin. Cadmium resistance of all the marsh isolates tested resulted from reduced Cd2+ transport. On the other hand, three cadmium-resistant harbor isolates displayed considerable influx but no efflux of Cd2+. Hg-resistant strains detoxified mercury by transforming Hg2+ to volatile Hg0 via mercuric reductase.

Bacillus↗
PubMed1985

Trypsinlike enzymes from dormant and germinated spores of Bacillus cereus T and their possible involvement in germination.

Trypsin-like enzymes were studied in dormant, activated, and germinated spores of Bacillus cereus T. Dormant spores contained two heat-labile enzyme activities. One was extractable with 2 M KCl and hydrolyzed azo-albumin. The second, a trypsinlike activity, was not extractable with 2 M KCl and hydrolyzed benzoyl-L-arginine-p-nitroanilide. Because of their heat instability, these two enzyme activities are probably not involved in the germination of heat-activated spores. Upon germination of heat-treated spores, a trypsinlike protease which was not detected in intact dormant spores was activated or exposed. This enzyme, when measured in intact germinated spores, hydrolyzed benzoyl-DL-arginine-p-nitroanilide but not azo-albumin and was inhibited in situ by sulfhydryl-blocking reagents such as p-chloromercuribenzoic acid and Hg2+. There was a correlation between the inhibition of germination and enzymatic activity by sulfhydryl-blocking reagents. The enzyme was also inhibited by leupeptin, tosyl-L-lysine chromoethyl ketone, and tosyl-L-arginine methyl ester. Good correlation existed between the inhibition of germination and enzymatic activity by these agents. Electron micrographs showed that in the presence of trypsin inhibitors, the spores did not lose their cortex. The protein extracts of the inhibited spores formed a somewhat different electrophoretic pattern in sodium dodecyl sulfate-polyacrylamide gel electrophoresis than the protein extracts of dormant or germinated spores.

Bacillus cereus↗
PubMed1985

Regulation of repressible acid phosphatase gene transcription in Saccharomyces cerevisiae.

We examined the genetic system responsible for transcriptional regulation of repressible acid phosphatase (APase; orthophosphoric-monoester phosphohydrolase [acid optimum, EC 3.1.3.2]) in Saccharomyces cerevisiae at the molecular level by analysis of previously isolated and genetically well-defined regulatory gene mutants known to affect APase expression. These mutants identify numerous positive- (PHO4, PHO2, PHO81) and negative-acting (PHO80, PHO85) regulatory loci dispersed throughout the yeast genome. We showed that the interplay of these positive and negative regulatory genes occurs before or during APase gene transcription and that their functions are all indispensible for normal regulation of mRNA synthesis. Biochemical evidence suggests that the regulatory gene products they encode are expressed constitutively. More detailed investigation of APase synthesis is a conditional PHO80(Ts) mutant indicated that neither PHO4 nor any other protein factor necessary for APase mRNA synthesis is transcriptionally regulated by PHO80. Moreover, in the absence of PHO80, the corepressor, presumed to be a metabolite of Pi, did not inhibit their function in the transcriptional activation of APase.

Acid Phosphatase↗
PubMed1984

Regulation of galactokinase (GAL1) enzyme accumulation in Saccharomyces cerevisiae.

The regulation of GAL1 RNA and enzyme synthesis has been investigated in Saccharomyces cerevisiae. We have shown that the induction of GAL10 and GAL1 RNAs is coordinate. GAL1 RNA transcripts appear within 4.5 to 6 min and galactokinase synthesis within 6 to 9 min. Steady-state RNA levels were reached within 50 min and the steady-state rate of galactokinase enzyme synthesis within 40-50 min. From these kinetic studies, the initial induction of GAL1 enzyme activity is apparently under transcriptional control. In addition, during early induction, two galactokinase enzyme activities were detected; a major stable form and a minor unstable form.

Enzyme Induction↗
PubMed1984

Conformational alterations in the proximal portion of the yeast invertase signal peptide do not block secretion.

Various amino acid insertions have been introduced into the proximal portion of the signal sequence of secreted yeast invertase. The altered invertase genes have been reintroduced into yeast and monitored for their ability to direct synthesis of secreted invertase in vivo. The insertions should alter the signal polypeptide local secondary structure as predicted by the Chou and Fasman rules (1978). Secretion of these altered invertase polypeptides is not blocked by the amino acid insertions.

Biological Transport↗
PubMed1984

Genetic and physical analysis of the ilvBC-leu region in Bacillus subtilis.

We describe the cloning of a 6.0-kb PstI fragment of the Bacillus subtilis genome which contains much of the ilvBC-leu gene cluster. This plasmid clone and two others that had been previously isolated were characterized physically and genetically to permit the construction of a physical map of this region that is correlated to the genetic map.

Bacillus subtilis↗