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Biomedical subjects

J S Wood

Publications and source records attributed to J S Wood.

At least 19 recordsLinked to original sources
PubMed1995

Variations in astronaut radiation exposure due to anisotropic shield distribution.

The dose incurred in an environment generated by extraterrestrial space radiations within an anisotropic shield distribution depends on the orientation of the astronaut's body relative to the shield geometry. The fluctuations in exposure of specific organ sites due to astronaut re-orientation are found to be a factor of 2 or more in a typical space habitation module and typical space radiations. An approximation function is found that overestimates astronaut exposure in most cases studied and is recommended as a shield design guide for future deep space missions.

Astronauts↗
PubMed1993

Results using the biofragmentable anastomotic ring for colon anastomosis.

The Biofragmentable Anastomotic Ring (BAR) (Valtrac, Davis & Geck, Inc.) is a newly approved device intended for colonic anastomosis. We have used the device in 47 patients to date. These patients were studied to determine the effectiveness, uses and limitations of this new device. The BAR is similar in concept to the older Murphy "Button" used circa World War I, but it's constructed of polyglycolic acid rather than metal. Anastomosis is effected by placing the two bowel lumens over the device, tying the purse-string sutures snugly, and "clicking" the device closed. The BAR fragments and is passed 2 to 3 weeks postoperatively. The patients ranged from 14 to 82 years of age. Thirty-nine patients were operated on for cancer, four for diverticulitis, and four for colostomy closure. One transverse colectomy (THC), 15 left hemicolectomies (LHC), 23 sigmoid colectomies (SC), two low anterior resections (LAR), four colostomy closures, and two right hemicolectomies were performed. There were no anastomotic leaks and no complications. We found that because of the need to have access distally to "click" the device closed, BAR anastomosis after LAR is rarely feasible. Because of the small lumenal size of the distal ileum, the BAR is seldom usable for ileocolonic anastomosis after right hemicolectomy (RHC). The newly approved 25-mm BAR may change this. We found that the time required to perform an anastomosis with the BAR is equivalent to stapled techniques. At our hospital, the cost of the device is equivalent to one intestinal stapler. Since multiple staplers are used in most colon anastomotic techniques, there is a modest cost advantage for the BAR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Gene disruption of the pcbAB gene encoding ACV synthetase in Cephalosporium acremonium.

Plasmid pPS96 was used to disrupt the genomic region immediately upstream of pcbC in C. acremonium by homologous integration. Approximately 4% of the C. acremonium transformants obtained with pPS96 were unable to produce beta-lactam antibiotics. All transformants obtained with other plasmids and isolates which had not been exposed to transforming DNA retained the ability to produce beta-lactams. Enzyme analysis showed that ACV synthetase activity was missing in the beta-lactam-minus pPS96 transformants. Southern copies of pPS96 in all beta-lactam-minus transformants analyzed. However, predictable alterations of the targeted region were not detected. Transformation of antibiotic-minus transformants with plasmid pZAZ4, carrying a wild-type copy of the region targeted for disruption, resulted in restoration of the ability to produce beta-lactams in greater than 80% of the transformants recovered. Location of the pcbAB gene upstream from pcbC was confirmed by comparing the amino acid sequence of internal peptides from purified ACV synthetase with that deduced from the DNA sequence of the region targeted for disruption. The direction of transcription of the pcbAB gene is opposite that of the pcbC gene. Further analysis of amino acid sequence data from ACV synthetase revealed regions of strong similarity with the peptide synthetases responsible for production of tyrocidine and gramicidin S in Bacillus brevis.

Acremonium↗
PubMed1987

Confirmation of clorsulon residues in cattle kidney by capillary gas chromatography-negative-ion chemical-ionization mass spectrometry.

A confirmatory assay for residues of the anthelmintic agent clorsulon [4-amino-6-(trichloroethenyl)-1,3-benzenedisulfonamide] in cattle kidney tissue has been developed. The assay involves isolation of a drug-containing fraction by solvent extraction, methylation of the analyte, and fused-silica capillary column gas chromatography-negative-ion chemical-ionization mass spectrometry of the pentamethyl derivative of clorsulon. The intensities of four negative ions [m/z 406 and 408 (trichloro species) and m/z 413 and 415 (dichloro species)] are monitored. Confirmation of the presence of drug in an analyte requires that all four ions appear at the appropriate retention time with their intensity ratios within 10-15% of those arising from analysis of the reference standard, methylated clorsulon; the lower limit of detection is 3 ppb. Quantification of the drug is based on the intensity of the m/z 406 ion. Identification and quantification of residues by the gas chromatographic-mass spectrometric assay gave results in good agreement with those obtained with an electron-capture gas chromatographic assay.

Animals↗
PubMed1986

Isolation of two genes that affect mitotic chromosome transmission in S. cerevisiae.

Two DNA sequences that reduce mitotic fidelity of chromosome transmission have been identified: MIF1 and MIF2. MIF1 is a unique sequence located on the right arm of chromosome XII that stimulates loss and recombination for both chromosomes V and VII when present in a high copy number plasmid. MIF1 is not essential for cell division but is necessary for the normal fidelity of chromosome transmission. MIF2 is a unique sequence located 15 cM distal to HIS6 on chromosome IX that induces a high frequency of chromosome VII loss and a lower frequency of chromosome V loss when present in high copy number; it has no effect on mitotic recombination. Disruption of the genomic MIF2 locus was lethal and cells lacking this function arrested division with a terminal phenotype characteristic of a block in DNA replication or nuclear division.

Aneuploidy↗
PubMed1986

Nursing home care.

The intent of this review is to highlight several difficult questions from a personal perspective while caring for debilitated elderly patients in a nursing home. These problems appear to be encountered less frequently in the acute-care setting. Where possible, supporting literature is cited and legal precedent is indicated. The following topics, among others, are discussed: a framework for physicians' ethical decisions, basic ethical principles, typical problems encountered by the physician, and considerations for withholding treatment.

Aged↗
PubMed1984

Aerobic exercise training and improved neuropsychological function of older individuals.

The effects of a four month aerobic exercise conditioning program on neuropsychological test performance, depression indices, sensory thresholds, and visual acuity of 55-70 year old sedentary individuals were evaluated. Aerobically trained subjects were compared with two age-matched control groups of subjects: those who trained with strength and flexibility exercises and others who were not engaged in a supervised exercise program. The aerobically trained subjects demonstrated significantly greater improvement on the neuropsychological test battery than did either control group. Depression scores, sensory thresholds, and visual acuity were not changed by aerobic exercise. The pattern of results suggests that the effect of aerobic exercise training was on central rather than on peripheral function. We speculate that aerobic exercise promoted increased cerebral metabolic activity with a resultant improvement in neuropsychological test scores.

Aged↗
PubMed1982

A dependent pathway of gene functions leading to chromosome segregation in Saccharomyces cerevisiae.

Methyl-benzimidazole-2-ylcarbamate (MBC) inhibits the mitotic cell cycle of Saccharomyces cerevisiae at a stage subsequent to DNA synthesis and before the completion of nuclear division (Quinlan, R. A., C. I. Pogson, and K, Gull, 1980, J Cell Sci., 46: 341-352). The step in the cell cycle that is sensitive to MBC inhibition was ordered to reciprocal shift experiments with respect to the step catalyzed by cdc gene products. Execution of the CDC7 step is required for the initiation of DNA synthesis and for completion of the MBC-sensitive step. Results obtained with mutants (cdc2, 6, 8, 9, and 21) defective in DNA replication and with an inhibitor of DNA replication (hydroxyurea) suggest that some DNA replication required for execution of the MBC-sensitive step but that the completion of replication is not. Of particular interest were mutants (cdc5, 13, 14, 15, 16, 17, and 23) that arrest cell division after DNA replication but before nuclear division since previous experiments had not been able to resolve the pathway of events in this part of the cell cycle. Execution of the CDC17 step was found to be a prerequisite for execution of the MBC-sensitive step; the CDC13, 16 and 23 steps are executed independently of the MBC-sensitive step; execution of the MBC-sensitive step is prerequisite for execution of the MBC-sensitive step; execution of the MBC-sensitive step is prerequisite for execution of the CDC14 and 23 steps. These results considerably extend the dependent pathway of events that constitute the cell cycle of S. cerevisiae.

Benzimidazoles↗
PubMed1982

Genetic effects of methyl benzimidazole-2-yl-carbamate on Saccharomyces cerevisiae.

The genetic effects of the mitotic inhibitor methyl benzimidazole-2-yl-carbamate (MBC) have been studied in Saccharomyces cerevisiae. MBC had little or no effect on the frequency of mutation. In some experiments MBC caused an increase in the frequency of mitotic recombination; however, this effect was small and not reproducible. The primary genetic effect of MBC was to induce mitotic chromosome loss at a high frequency. Chromosome loss occurred at equal frequencies for all chromosomes tested (13 of 16). Cells which had lost multiple chromosomes were found more frequently than predicted if individual chromosome loss events were independent. The probability of loss for a particular chromosome increased with length of time cells were incubated with MBC. MBC treatment also increased the frequency at which polyploid cells were found. These results suggested that MBC acted to disrupt the structure or function of the mitotic spindle and cause chromosome nondisjunction.

Alkaloids↗
PubMed1982

Mitotic chromosome loss induced by methyl benzimidazole-2-yl-carbamate as a rapid mapping method in Saccharomyces cerevisiae.

Mitotic chromosome loss induced by methyl benzimidazole-2-yl-carbamate has been utilized as a rapid and simple method for assigning genes to individual chromosomes in Saccharomyces cerevisiae. This technique relied on the segregation of heterozygous markers in a diploid strain after methyl benzimidazole-2-yl-carbamate treatment due to loss of whole chromosomes. Correlations between the expression of an unmapped gene and that of a previously mapped recessive marker indicated chromosomal linkage. Depending on whether the unmapped gene and the marker were located in coupling or in repulsion, either positive or negative correlations were seen. The chromosomal location of several previously mapped genes were confirmed as a test of the method, and one previously unmapped gene, nib1, was mapped.

Benzimidazoles↗
PubMed1982

Immune responses to varicella-zoster in the aged.

Skin test reactivity and in vitro lymphocyte stimulation responses to varicella-zoster (VZ) were examined in a large normal population ranging in age from 6 months to 93 years. Warning of cellular immunity, as examined by skin delayed hypersensitivity, began at age 40 years. Skin test responses to phytohemagglutinin, however, remained positive into the eighth decade of life. In vitro lymphocyte stimulation responses to VZ were usually positive (stimulation index greater than or equal to 2.5) until age 60 years, after which time levels, as observed with nonimmune individuals, were often demonstrated. Antibody levels, as measured by fluorescent antibody to membrane antigen, remained positive into the ninth and tenth decades of life. This was especially so with a history of reactivation (zoster) VZ infections, while skin test and in vitro responses were rarely positive in those individuals. This cellular, as contrasted with humoral, immunity decreases with advancing age, which may account for a propensity to reactivation of VZ virus.

Adolescent↗
PubMed1969

Microsome-associated DNA.

Deoxyribonucleic acid has been isolated from the microsomes of mouse liver homogenates under conditions designed to prevent or greatly reduce mitochondrial and nuclear contamination. The DNA rapidly incorporates tritiated thymidine, and this, together with its reannealing characteristics after thermal denaturation, shows that it is not mitochondrial or typically nuclear DNA.

Animals↗