Evolution of the National Oceanic and Atmospheric Administration's capabilities for polluted water diving.
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Diving↗
Biomedical subjects
J M Wells
Publications and source records attributed to J M Wells.
An evaluation of waist to hip ratio measurement methods in relation to lipid and carbohydrate metabolism in men.
The purpose of this study was to determine which method of measuring waist to hip ratio (WHR) was the most effective in assessing decrements associated with an abdominal fat distribution in 46 non-obese, middle to older aged men (mean +/- s.e., age 52.8 +/- 0.88 years; body fat 19.7 +/- 0.72 percent). Circumferences were obtained at the following sites and WHR calculated (waist circumference/hip circumference): (1) minimal waist/maximal hip; (2) level of umbilicus/maximal hip; (3) level of umbilicus/level of greater trochanters; (4) level of umbilicus/level of superior iliac spine; and (5) level of 1/3 of the distance between the xiphiod process and umbilicus/level 4 cm below the superior iliac spine. Significant (P less than 0.05) associations were observed for measurement methods 1, 2 and 3 with indices of lipid and carbohydrate metabolism, body composition, and fitness level. Measurement method 5 was not related to any metabolic or physiological variables, while measurement method 4 was intermediate in terms of the strength of the associations. These findings suggest that the predictive strength of WHR can vary depending upon the measurement method used.
Anthropometry↗
Curability of tumors bearing herpes thymidine kinase genes transferred by retroviral vectors.
Retroviral vectors constructed to contain the herpes simplex virus thymidine kinase (HSV-TK) gene were used for transduction of this gene into murine sarcoma and lymphoma cells to yield sublines susceptible in vitro to the cytotoxicity of ganciclovir, a drug specifically activated by HSV-TK. In vivo, ganciclovir induced complete, durable regressions in most mice bearing transplanted HSV-TK-positive sarcomas; its efficacy against lymphomas was only marginal, possibly because of their greater instability of gene expression. The results imply the potential value of an anticancer strategy entailing the prophylactic use of retroviral vectors to create tissue mosaicism for drug sensitivity.
Animals↗
Lymphoma regression induced by ganciclovir in mice bearing a herpes thymidine kinase transgene.
The dose limitations imposed on cancer chemotherapeutic agents by their lack of selectivity can, in theory, be circumvented by a strategy entailing the prophylactic insertion into hosts of drug-sensitivity genes that are acquired or expressed in some but not all cells. This strategy predicts that neoplasms arising from drug-sensitive cells might be safely treatable with tumor-eradicative drug doses because the presence of a modicum of drug-insensitive stem cells will protect vital tissues from lethal depopulation. To test this prediction, lymphomas were induced with Abelson leukemia virus in mice bearing a herpes simplex virus thymidine kinase (HSV-TK) transgene selectively expressed in lymphoid cells. Of 12 transgenic mice treated with the HSV-TK-specific substrate ganciclovir (GCV), 11 exhibited complete tumor regressions; 5 of these mice remained tumor-free over observation periods that exceeded 100 days. Among the lymphomas that recurred, most appeared to represent mutant subpopulations that were GCV-insensitive because they had lost HSV-TK, implying that independent insertion of multiple HSV-TK gene copies might provide a means of preventing recurrences. The results of this study demonstrate that chemosensitivity genes can enhance the efficacy of treatment in hosts who subsequently develop a neoplasm. While the use of a germ-line gene insertion model precludes direct human application, the results also imply the merits of exploring an alternative version of the strategy in which somatic insertion of chemosensitivity genes in mosaic fashion is used prophylactically to enhance the prospect that a subsequent tumor will respond to therapy.
Animals↗
Gene exchange in African trypanosomes: frequency and allelic segregation.
The existence of a system of genetic exchange in Trypanosoma brucei is now established, but the frequency with which mating occurs and the mechanisms by which genes are exchanged are still unknown. This paper presents the results of a study of one pair of trypanosome stocks, which show that mating is a non-obligatory but frequent event in a life-cycle stage within the insect vector. Analysis of ten progeny clones using a total of eleven markers (iso-enzymes and DNA probes detecting restriction fragment length polymorphisms) has indicated that segregation of alleles occurs at five of these loci. The segregation patterns of a polymorphic EcoRI site in the maxi-circle of the kinetoplast DNA (kDNA) show that the progeny inherit one or other of the parental kDNA types. These results demonstrate that segregation of alleles occurs and that new combinations of alleles at different loci are generated in the progeny clones. The implications of these findings for defining the mechanism of gene exchange are discussed in relation to a simple mendelian genetic system involving meiosis and syngamy.
Alleles↗
Genetic evidence that metacyclic forms of Trypanosoma brucei are diploid.
The hypothesis that metacyclic trypanosomes are haploid has been tested genetically. Five cloned stocks of Trypanosoma brucei (each having four known isoenzyme markers and six known restriction fragment length polymorphisms) have been independently transmitted through tsetse flies. Fifteen individual metacyclic organisms were taken from flies with mature cyclical infections and used to establish fresh clones. All the sub-clones from all the flies proved to be identical to the starting (parental) stocks, with respect to all the markers examined, including those markers which were heterozygous in the parental stocks. We conclude that metacyclic trypanosomes are diploid, and are not the product of an obligatory meiosis.
Animals↗
Molecular analysis of N6-methyladenine patterns in Tetrahymena thermophila nuclear DNA.
We have cloned two DNA fragments containing 5'-GATC-3' sites at which the adenine is methylated in the macronucleus of the ciliate Tetrahymena thermophila. Using these cloned fragments as molecular probes, we analyzed the maintenance of methylation patterns at two partially and two uniformly methylated sites. Our results suggest that a semiconservative copying model for maintenance of methylation is not sufficient to account for the methylation patterns we found during somatic growth of Tetrahymena. Although we detected hemimethylated molecules in macronuclear DNA, they were present in both replicating and nonreplicating DNA. In addition, we observed that a complex methylation pattern including partially methylated sites was maintained during vegetative growth. This required the activity of a methylase capable of recognizing and modifying sites specified by something other than hemimethylation. We suggest that a eucaryotic maintenance methylase may be capable of discriminating between potential methylation sites to ensure the inheritance of methylation patterns.
Adenine↗
Maintenance of methylation patterns in Tetrahymena thermophila.
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Animals↗
The mitochondrial uncoupling protein gene. Correlation of exon structure to transmembrane domains.
The mitochondrial uncoupling protein, a protein essential for the thermogenic properties of brown fat in mammals, is inserted in the inner mitochondrial membrane by means of six alpha-helical hydrophobic transmembrane domains. We have sequenced a complete cDNA and parts of the gene to determine that the mitochondrial uncoupling protein gene is composed of six exons, each of which encodes a transmembrane domain. We also show that transcription of the uncoupling protein gene is from a single start site; however, the use of alternative poly(A) addition signal sequences results in two mRNAs, the major species of 1221 nucleotides, not including the poly(A) tail, and a minor species of about 1600 nucleotides. The 5'-untranslated region of the mRNA is composed of 231 nucleotides, and the 3'-untranslated region contains 81 nucleotides prior to addition of the poly(A) tail.
Adipose Tissue, Brown↗
Gene exchange in African trypanosomes: characterisation of a new hybrid genotype.
We describe the isolation of a hybrid Trypanosoma brucei clone following the mixed cyclical transmission of two parental clones through tsetse flies. The characterisation of this clone reveals some new facets of the process of genetic exchange in T. brucei. The inheritance of four isoenzyme loci and restriction fragment polymorphisms at two loci was interpretable in 'mendelian' genetic terms, involving meiosis either before or after the genetic exchange event. However, at a further two isoenzyme loci a deviation from mendelian behaviour was observed. Pulse field gel analysis showed that the hybrid clone possessed a new combination of intermediate size chromosomes. Examination of kinetoplast DNA variants showed uniparental kinetoplast inheritance, and with reference to previous work we conclude that the kinetoplast can be inherited from either parent. The nuclear DNA content of the hybrid clone was measured and found to be identical to the parental nuclear DNA contents. This finding, together with the inheritance of isoenzyme and RFLP markers, is discussed with respect to possible models for genetic exchange.
Animals↗
A germ line specific DNA sequence is transcribed in Tetrahymena.
In the ciliated protozoan Tetrahymena 10-20% of the DNA sequences are micronucleus (germ line) specific. Six members of a family of repeated mic-specific DNA sequences are homologous to a 1.5-kb poly(A)+ RNA. The transcript is present in mature cells starved in 10 or 60 mM Tris, in starved immature cells, and in stationary cells. RNA from log-phase and heat-shocked cells does not have detectable levels of the transcript. These data indicate that at least one germ line limited DNA sequence is transcribed in the micronucleus of Tetrahymena.
Animals↗
DNA contents and molecular karyotypes of hybrid Trypanosoma brucei.
We have used restriction fragment length polymorphism markers to characterise parental and hybrid trypanosome stocks. Unexpected differences in the intensities of Southern hybridisation banding patterns led us to suspect that the hybrid organisms contained more DNA than the parental stocks. This has been confirmed using flow cytofluorimetry (FCF). Hybrids contained significantly more DNA than the parents, both as procyclic organisms (1.5 fold) and as bloodstream forms (1.5-1.6 fold). The DNA contents of both forms were stable through prolonged culture (procyclics), or serial passage (bloodstream forms), although limited data indicated that falls in DNA content could occur in bloodstream forms. FCF analysis of purified nuclei revealed that the increased DNA content of hybrids could be wholly ascribed to nuclear DNA. Our methods are able to detect hybrid organisms with elevated DNA contents in uncloned isolates following cyclical mixed transmission. We have used alternating field electrophoresis techniques to investigate whether the inheritance by the hybrids of the smaller chromosomes could account for their elevated DNA contents. Hybrids lacked the single 500 kb chromosome from one of the parents but appeared to have virtually double the amount of minichromosomes. However, this increase could only account for about 20% of the additional DNA. We are unable at present to distinguish between models for hybrid formation based on the fusion of predominantly diploid cells, and models in which the diploid chromosomes participate in conventional meiosis.
Animals↗
Properties of Cytophaga johnsonae strains causing spoilage of fresh produce at food markets.
Two strains of gliding, orange-pigmented bacteria, isolated from fresh bell pepper and watermelon, respectively, showing soft-rot lesions, were identified as Cytophaga johnsonae. They differed from seven type strains of C. johnsonae deposited at the American Type Culture Collection (ATCC) in some properties, such as the ability to utilize glucose, xylose, trehalose, rhamnose, and sucrose. Spherical bodies resembling microcysts of Sporocytophaga sp. in addition to short rods and long filaments were observed in two strains (ATCC 29583 and 29588) throughout the growth cycle and also in aged cultures of other strains. All strains examined were shown to degrade five natural or synthetic polymers (pectin, chitin, starch, protein, and carboxymethyl cellulose). Only six strains (including ATCC 17061, 29587, 29589, and 19366) were able to infect and macerate artificially wounded potato tubers and fruits of pepper, squash, and tomato. The pathogenic strains secreted more pectate lyase in broth medium than the nonpathogenic strains. C. johnsonae, generally known as a soil saprophyte, might occasionally act as an opportunistic pathogen, causing decay of fresh produce in storage or in transit.
Bacterial Proteins↗
Comparison of infection rats and severity of illness for influenza A subtypes H1N1 and H3N2.
In the Houston Family Study, overall rates of infection for the three major outbreaks of influenza A from 1977 to 1981 were higher for subtype H3N2 than for H1N1. Rates in school children were almost identical, but rates of infection with H1N1 were lower in adults and in preschool children, especially those younger than two years of age. However, rates for the two subtypes were similar in young children within families that experienced influenza A infections. In the total population overall illness rates among infected persons were identical, and diagnoses were similar. Among 145 identified primary infections (1977-1982), more H3N2 infections resulted in systemic (febrile) illness or lower-respiratory-tract disease, but a detailed comparison of illness features of 54 primary infections in children aged two to five years showed no significant differences. Epidemiological differences appear to be more important than pathogenic potential in determining the community impact of these two subtypes of type A influenza virus.
Adolescent↗
Nursing administrators' perspective on the U.S.S.R health system.
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Administrative Personnel↗
Individuals infected with two subtypes of influenza A virus in the same season.
Participants in the Houston Family Study were observed during a period of two mixed outbreaks due to two subtypes of influenza A virus: H3N2 and H1N1 (1977-1981). Virus specimens, serum samples, and clinical records were obtained to identify and characterize infections. In 1977-1978, 40% of 238 persons in 59 families were infected by influenza A virus (H3N2), 11% by influenza A virus (H1N1), and 4% by both. In 1980-1981, for 319 persons in 79 families, the corresponding rates were 27%, 20%, and 5%. Interference between subtypes was not detected. Both subtypes were isolated from six children (range of intervals between isolations, six to 55 days), and five of the six were ill with both infections. Nineteen persons had two infections with one or both detected serologically; illnesses were associated with 77% of isolates and up to 56% of seroconversions in these persons. Infection of the same individual with two subtypes in the same season is a newly observed phenomenon that may affect the future epidemiology of influenza A virus as well as preventive measures.
Adolescent↗
Patterns of shedding of myxoviruses and paramyxoviruses in children.
In the Houston Family Study, young children were cultured for virus weekly or biweekly and during acute respiratory illnesses. The interval between the onset of illness and positive culture was examined for 179 infections during 1975-1979. In week 1 after onset, 73%, 73%, and 66% of cultures were positive for influenza A virus, respiratory syncytial virus (RSV), and parainfluenza virus type 3, respectively. Pooled data from influenza B virus infections in 1977 and 1980 showed that 73% of cultures were positive in week 1. Influenza A virus in week 2 or RSV in weeks 2 and 3 was isolated from very few children. However, 37% of cultures were positive for influenza B virus during week 2, and 17% of cultures were still positive for parainfluenza virus type 3 during week 3. Shedding of parainfluenza virus type 3 on days 29-38 was also observed. Parainfluenza virus type 3, RSV, and influenza A virus were isolated up to six days before the onset of illness.
Adolescent↗
Curvularia lunata, a New Source of Cytochalasin B.
A biologically active metabolite was found in crude extracts of Curvularia lunata (Wakker) Boedijn (ATCC 34690) isolated from decayed tissues of litchi fruit (Litchi chinensis Sonn.). The fungus was grown on a shredded wheat-yeast extract-sucrose medium, and cultures were extracted with chloroform after 3 weeks of growth at 21 degrees C. Chloroform extracts were toxic to day-old cockerels and caused abnormal distortion of wheat coleoptile segments. The major toxin had a 50% lethal dose of 700 mg/kg (oral dose) and was a colorless crystalline material with a melting point of 218 degrees C. Elemental and high-resolution mass spectral analyses indicated a formula of C(29)H(37)NO(5) and a molecular weight of 479.62. The crystalline preparation was identified as 97% cytochalasin B and 3% cytochalasin A. The yield of cytochalasin B from C. lunata cultures grown on 4.5 kg of shredded wheat and 9 liters of yeast extract-sucrose medium was 6.24 g of purified material.
Journal Article↗