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Biomedical subjects

B Thomas

Publications and source records attributed to B Thomas.

At least 181 records · Page 10Linked to original sources
PubMed1988

Strain comparison of systemic N-nitrosohexamethyleneimine carcinogenesis in BALB/c, SENCAR and CD-1 mice.

SENCAR mice have been selectively bred for hypersusceptibility to 2-stage chemical skin carcinogenesis. In this study the relative susceptibilities of SENCAR, BALB/c and CD-1 mice to systemic carcinogenesis by N-nitrosohexamethyleneimine (NHEX) were examined. NHEX was administered twice weekly (1 mg/mouse) in corn oil by gavage for 30 weeks. NHEX caused primarily liver and lung tumors in all 3 strains of mice. Hemangiosarcomas (but not other liver tumors) were more common in CD-1 mice than BALB/c or SENCAR mice. Lung tumors (adenomas and adenocarcinomas) and forestomach tumors (squamous carcinomas) were more common in SENCAR mice than BALB/c or CD-1 mice. Survival was better in SENCAR mice dosed with NHEX than in the other 2 strains. These results indicate that SENCAR mice are not unusually sensitive to liver carcinogenesis by NHEX, but are relatively sensitive to tumorigenesis in 2 epithelial tissues, lung and forestomach.

Animals↗
PubMed1988

Plasma growth hormone-releasing hormone levels in type 1 (insulin-dependent) diabetic children following a mixed meal.

Following a mixed meal, plasma hormone responses were measured in four type 1 diabetic children and in eight short normal children. Between 60 and 150 min after ingestion of the mixed meal there was a significant increase in circulating growth hormone-releasing hormone values both in diabetic and in normal children. Mean plasma GHRH peak values were not different between diabetic patients (27.0 +/- 3.9 ng/l) and controls (24.6 +/- 4.9 ng/l). No time relationship to spontaneous growth hormone peaks was observed. Whereas normal children showed a characteristic biphasic plasma somatostatin response, somatostatin plasma levels in diabetic children did not change. In normal children plasma insulin values increased between 30 and 150 min, but remained unchanged in type 1 diabetic patients. Blood glucose response was more pronounced in diabetic children than in short normal children. These results indicate that circulating growth hormone-releasing hormone does not play a dominant role in the regulation of insulin and somatostatin.

Adolescent↗
PubMed1987

Chlamydia trachomatis and reactive arthritis: the missing link.

Reactive inflammatory arthritis is a common sequel to sexually acquired non-gonococcal genital-tract infection. Approximately 50% of cases are associated with Chlamydia trachomatis infection in the genital tract, although conventional cultures of joint material are sterile. Synovium, synovial-fluid cells, or both, from eight patients with sexually acquired reactive arthritis (SARA) and eight with knee effusions associated with other rheumatic diseases were examined by means of a fluorescein-labelled monoclonal antibody to C trachomatis ('Micro Trak'; Syva). Typical chlamydial elementary bodies were seen in joint material from five patients with SARA but in none of the controls. An inclusion-like cluster of elementary bodies was seen in one synovial biopsy sample. All five patients had high titres of serum chlamydial antibody. It is likely that the synovitis of SARA results directly from the presence of chlamydial elementary bodies in the joint.

Adult↗
PubMed1987

Plasma levels of growth hormone-releasing hormone and somatostatin in response to a mixed meal and during sleep in children.

Following a mixed meal, plasma levels of GHRH, GH, SRIH and insulin were measured in 7 prepubertal children with constitutional delay of growth and adolescence (CDGA) and in 3 children with proven GH-deficiency which responded to GHRH-injection. In children with CDGA, plasma levels of GHRH increased between 60 and 120 min (10.1 +/- 1.2 ng/l vs 25.5 +/- 4.4 ng/l; P less than 0.01). Although no GH increase occurred in patients with GH-deficiency, their plasma GHRH increases were comparable to those in CDGA children. No time relationship was present between circulating GHRH and GH, SRIH, or insulin, nor was there any correlation between their integrated hormone response areas. Sleep-induced plasma GHRH, GH and SRIH values were determined in 10 prepubertal children with CDGA. Spontaneous variations of plasma GHRH and GH values occurred with no temporal or quantitative relationship. SRIH values did not change during nocturnal sleep. In one child with GH-deficiency, comparable GHRH plasma fluctuations occurred, although GH values were all below 1 microgram/l. Our results support the concept that circulating GHRH does not only represent hypothalamic GHRH, but derives mainly from extrahypothalamic sources, possibly from the gastrointestinal tract.

Adolescent↗
PubMed1987

Drug reviews.

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Aged↗
PubMed1987

Chromosome protection by WR-2721 and MPG-single and combination treatments.

The radioprotective action of thiol compounds 2-mercaptopropionylglycine (MPG) and S-2(aminopropylamino) ethyl phosphorothioic acid (WR-2721) was evaluated either alone or in combination on the bone marrow chromosomes of Swiss albino mice after 4.5 Gy of 60Co radiation. Single drug administration of WR-2721 at 300 mg/kg body weight resulted in a 50% reduction in the yield of aberrant cells at 24 hours post irradiation, while the other single drug doses were less effective. The combination of the two drugs increased the effect in the sense that 150 mg/kg WR-2721 with 20 mg/kg MPG gave equal protection as 300 mg/kg WR-2721 given alone. Moreover, on day 14, when WR-2721 produced an increase in the precent aberrant cells the above combination brought down the value to normal. It appears that MPG neutralizes to some extent the toxic effect of WR-2721, without impairing the protective efficiency.

Amifostine↗
PubMed1986

Exogenous reinfection with tuberculosis in a shelter for the homeless.

We investigated an outbreak of tuberculosis in a large shelter for the homeless to assess the role of exogenous reinfection as opposed to reactivation of endogenous infection as the cause of secondary tuberculosis in this population. Exogenous reinfection is considered relatively unimportant in the United States and other developed countries. Of 49 shelter-related cases, 22 had cultures resistant to both isoniazid and streptomycin and of the same phage type, indicating recent transmission originating with a single index patient. The probable index patient had a 10-year history of isoniazid and streptomycin resistance--an uncommon pattern at the shelter during the three years preceding the outbreak. In 4 of the 22 cases, the patient had previously had documented tuberculosis infection or disease. These reinfected patients had extensive lung cavitation and numerous acid-fast bacilli on sputum smears--features associated with contagiousness. In contrast, patients with tuberculosis for the first time (primary tuberculosis) are usually less contagious. We conclude that exogenous reinfection may have been an important factor leading to highly contagious secondary cases and an acceleration of the usual pattern of tuberculosis transmission in this highly susceptible population.

Adult↗
PubMed1986

Nursing care of the dying: its relationship to selected nurse characteristics.

This study examined the relationship between the quality of nursing care given to terminally-ill patients and their families, and selected characteristics of 210 nurses caring for terminally-ill patients. Mailed questionnaires received 90% response from nurses in a two-stage, stratified, proportionate, random sampling plan. Independent variables studied were: death anxiety, educational experience, personal experience and professional experience. Dependent variables studied were three measures of the quality of nursing care: communication, continuity of care and family care. Kendall's tau and parametric partial correlation coefficients were used for data analysis. The study results show that 13 of the 18 statistical tests were significant at 0.05.

Adult↗
PubMed1985

Genetical ESS-models. I. Concepts and basic model.

Evolutionarily Stable Strategies (ESS) in phenotypic models are used to explain the evolution of animal interactive behaviour. As the behavioural features under consideration are assumed to be genetically determined, the question arises how underlying a genetical system might affect the results of phenotypic ESS-models. This question can be fully treated in terms of ESS-theory. A method of designing Genetical ESS-Models is proposed, which transfers the question of evolutionary stability to a "lower" level, the genetical basis. Genetical ESS-models - although nonlinear even in the simplest cases - can be analysed in a way that is familiar to ESS-theorists and yield immediate results on gene pool ESSs, which then may or may not maintain ESSs on the phenotypic level. Moreover, general results can be obtained to characterize evolutionarily stable gene pool states and their interrelation with commonsense, phenotypic ESSs. This part of the article presents the basic concepts and an outline of the method of genetical ESS-models. It gives, as a demonstration, a complete analysis for phenotypic two-strategy models (linear or nonlinear) based on a diploid, diallelic single-locus system under random mating. The results in this case suggest that a phenotypic ESS should indeed be expected to evolve but, maybe, only after passing through a succession of temporarily stable states.

Animals↗
PubMed1985

Genetical ESS-models. II. Multi-strategy models and multiple alleles.

The problem of evolutionarily stable strategies (ESS) in sexual populations can be investigated by means of genetical ESS-models which link common sense, phenotypic ESS-models to an underlying genetical system. Thorough results are obtained for multi-strategy models in diploid, panmictic populations on the basis of multi-allelic, one-locus systems. A sexual population will be maintained at a phenotypic ESS if this can possibly be produced by the genotypes currently existing. If there is enough allelic variation, the corresponding gene pool may either be an ESS itself, or belong to an attracting, continuous set of states, which all determine the same evolutionarily stable population. The latter case allows new alleles to enter and spread in the gene pool without disturbing the phenotypic ESS. If a phenotypic ESS cannot be established, ESSs of the genetical model may be found which give rise to stable populations alternatively. Since these depend on the phenotypes determined by the currently existing genotypes, they may be destabilized by the occurrence of new mutations. In this sense, they are less durable than populations maintained at a phenotypic ESS and can be expected to evolve, in the long run, towards a phenotypic ESS.

Alleles↗
PubMed1985

Recombination hot spot in the human beta-globin gene cluster: meiotic recombination of human DNA fragments in Saccharomyces cerevisiae.

We describe a novel system for the analysis of sequence-specific meiotic recombination in Saccharomyces cerevisiae. A comparison of three adjacent restriction fragments from the human beta-globin locus revealed that one of them, previously hypothesized to contain a relative hot spot for genetic recombination, engages in reciprocal exchange during yeast meiosis significantly more frequently than either of the other two fragments. Removal of the longest of four potential Z-DNA-forming regions from this fragment does not affect the high frequency of genetic recombination.

Cloning, Molecular↗
PubMed1985

[Not Available].

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History, Modern 1601-↗