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Biomedical subjects

M B Baird

Publications and source records attributed to M B Baird.

At least 19 recordsLinked to original sources
PubMed1999

Removal of the laryngeal mask airway: factors affecting the incidence of post-operative adverse respiratory events in 300 patients.

The purpose of this study is to compare the incidence of undesirable respiratory events when the laryngeal mask airway is either removed from patients who are fully awake or from patients who are deeply anaesthetized. Three-hundred patients aged 1.5-81 years were randomly assigned to have their laryngeal mask airway removed either when deeply anaesthetized or after airway reflexes had returned. The occurrence of adverse respiratory events (coughing, oxygen desaturation and airway obstruction) was recorded. Airway obstruction after laryngeal mask airway removal was evident in 20% of patients in the deep anaesthesia group and in 8% of patients in the awake group (P = 0.007). In spite of this finding, oxygen desaturation in children of less than 6 years of age (SaO2 < 96%) occurred most frequently after awake removal (31.3%) compared with deep anaesthesia removal (4.5%) (P = 0.023).

Adolescent↗
PubMed1993

Benzo(a)pyrene enhances atherosclerosis in White Carneau and Show Racer pigeons.

Benzo(a)pyrene (BaP), a major environmental pollutant and component of cigarette smoke, is both carcinogenic and atherogenic in experimental models. We investigated the effect of long-term administration of BaP on atherogenesis in both atherosclerosis-susceptible White Carneau (WC) and atherosclerosis-resistant Show Racer (SR) pigeons. The number and size of arterial lesions in the brachiocephalic arteries in WC and SR females but not males were significantly enhanced after long-term dosing with BaP. Metabolic activation appears to be required for BaP atherogenicity, since benzo(e)pyrene (BeP), a noncarcinogenic analogue of BaP, did not enhance lesion development. Studies with 3H-BaP revealed no significant differences between male and female or between WC and SR pigeons in the arterial distribution of BaP and/or its metabolites. There were no consistent differences in blood pressure or plasma cholesterol levels between breeds or sexes. However, chronic administration of BaP did result in complete infertility in female birds, concomitant with grossly visible changes in ovarian appearance. These results clearly show that long-term dosing with BaP alters ovarian structure and function in treated birds, at the same time aggravating the development of arterial lesions. Thus, BaP-induced atherogenicity in female pigeons may be a consequence of an alteration in estrogen production or of antiestrogenic properties of BaP at the level of the arterial wall and may serve as a highly useful animal model to examine the well-known rapid development of atherosclerosis in postmenopausal women.

Animals↗
PubMed1993

Accumulation of malondialdehyde in mouse heart following acute dosing with adriamycin is strain specific and unaffected by cardiac catalase status.

CDF1 and C57BL/6J male mice were acutely dosed with Adriamycin (ADR), and total cardiac malondialdehyde (MDA) quantitated following isolation by modification of previously developed procedures. Cardiac MDA content in CDF1 mice increased significantly 5 days following ADR dosing as reported by others, but was unchanged in C57BL/6J mice. ADR-induced mortality and a significant loss in cardiac weight 2-3 days after treatment was similar in both strains. Cardiac lipid hydroperoxide (LH) content was also unchanged in C57BL/6J mice dosed acutely with ADR. However, hepatic LH content increased rapidly following treatment with ADR, reaching maximal level 1 day following treatment before returning to below untreated levels 24 hours later. Studies with genetically acatalasemic C57BL/6J mice showed that neither cardiac nor hepatic lipid hydroperoxide content in ADR-dosed animals is affected by tissue catalase levels. These results demonstrate that C57BL/6J mouse heart is refractory to ADR-induced lipid peroxidation (LP) although overall mortality from the drug is unaffected, and do not support the hypothesis that ADR-induced mortality in mice is a consequence of cardiac LP.

Animals↗
PubMed1985

Genetic control of adult lifespan in Drosophila melanogaster.

Two temperature-sensitive X-linked adult lethal mutations were induced by ethyl methane sulfonate in Drosophila melanogaster. These mutations exhibited both a temperature-sensitive and effective lethal phase in adult flies. The existence of this new class of gene mutations provides experimental support for the hypothesis of H.J. Müller (1963, p. 235) that "development is a continuous process of which senility forms the last state." Furthermore, their existence demonstrates that the role of genes in controlling adult lifespan may be dissected by those methods that have been used to successfully probe the genetic control of preadult development.

Animals↗
PubMed1983

A longitudinal study of the relationship between aging and the duration of hexobarbital hypnosis in male CFN rats.

The duration of hexobarbital hypnosis was determined for individual male CFN rats at three month intervals over their total adult lifespan. The mean duration of hexobarbital hypnosis for the cohort linearly with advancing age. However, the sleeptimes for individual rats fell into one of four categories (gradual increase, terminal step increase, no change, or not possible to assign) when assigned as a function of duration of response to the barbiturate over the lifespan of the animals. These results suggest that the generally well-accepted increase in duration of drug response in aging animals is neither a ubiquitous nor concomitant feature of aging. Furthermore, the varying results obtained for individual animals in this longitudinal study point out the possible error which may be attendant when utilizing pooled tissue extracts to examine hepatic monooxygenase activity in vitro in senescent rodents.

Aging↗
PubMed1979

Senescent changes in rodent hepatic epoxide metabolism.

Age-related alterations in epoxide metabolism were examined in subcellular fractions of liver from 3-, 12- and over 24-month-old male rats and mice. Using styrene oxide as the substrate, glutathione-S-transferase activity remained unchanged while the activity of epoxide hydrase increased with age in both species. The microsomally-mediated binding of benzo[a]pyrene to DNA was also increased in the old animals. Thus, senescent rodents retain or increase their ability to metabolize epoxides. The effect on epoxide metabolism of pretreatment of the senescent rodents with polychlorinated biphenyls was also examined. Glutathione-S-transferase activity was induced only in old animals. However, epoxide hydrase activity, while inducible in all age groups of rats, increased only in young mice. Therefore, there is an age-related difference in response of epoxide metabolizing enzymes to polychlorinated biphenyl treatments between rats and mice.

Aging↗
PubMed1979

Inhibition of 2-fluorenamine-induced mutagenesis in Salmonella typhimurium by vitamin A.

Vitamin A alcohol (retinol) completely inhibited the mutagenicity of the carcinogen 2-fluorenamine (2-FA) in Salmonella typhimurium TA98 when the mutagen was activated by liver microsomes from CFN rats. The mutagenicity of 2-FA activated by 9,000Xg rat liver supernatant S9 was inhibited by retinol to a lesser degree. The decline in the number of his+ revertants was not an artifact due to bacterial killing, inasmuch as retinol was not toxic to the bacteria at levels that totally inhibited mutagenesis by 2-FA. Mutagenesis induced by adriamycin, an antibiotic that does not require metabolic activation for mutagenic potential, was unaffected by vitamin A. These results indicate that retinoids inhibit the metabolic activation of some chemical carcinogens to forms that can interact with DNA. Our findings are consistent with the hypothesis that retinoids may exert anticancer activity by inhibiting carcinogen activation, thereby inhibiting tumor induction. In addition to the more widely accepted role of retinoids in modulating the proliferation of epithelially derived neoplasms.

Animals↗
PubMed1979

Increased production of mutagenic metabolites of carcinogens by tissues from senescent rodents.

Activation of the procarcinogens benzo(a)pyrene and 2-fluorenamine by liver homogenates (S9) prepared from senescent male CFN rats and C57BL/6J mice resulted in an enhanced production of mutagenic metabolites when compared to young rodents, as indicated by an enhancement of the induced reversion frequency in a Salmonella typhimurium bioassay. Similar results were observed when carcinogen activation was mediated by purified hepatic microsomes, indicating that the age-related differences in carcinogen activation did not result from aging changes in carcinogen metabolism involving non-microsomal mechanisms. The metabolites of many procarcinogens are thought to be the ultimate carcinogens in mammals. Therefore, the present findings are consistent with the hypothesis that some fraction of the markedly increased of neoplasia observed in senescent mammals is a result of age-related alterations in the metabolism of chemical carcinogens.

Aging↗
PubMed1978

Increased longevity of Drosophila melanogaster with diiodomethane.

Diiodomethane at a concentration of 10 microgram/ml increased the median life span of the fruit fly, Drosophila melanogaster, by 29.3%. Decreased flight activity was associated with increased longevity when the flies were reared and maintained on diiodomethane. Rearing only on diiodomethane increased life span by 13.6% and eliminated the decreased-flight-activity phenomenon. The effects of iodine, iodoform and hydriodic acid on longevity were also examined.

Animals↗
PubMed1977

Presence of a high-molecular-weight form of catalse in enzyme purified from mouse liver.

Ultracentrifugation studies of purified mouse hepatic catalase revealed that 5-7% of the total material consists of a form with a higher molecular weight than the bulk of the catalase. The two components were separated by sucrose-gradient centrifugation. Polyacrylamide-gel electrophoresis (in borate buffer) demonstrated that high-molecular-weight catalase is enriched in a more slowly migrating component, and sodium dodecyl sulphate/polyacrylamide gel-electrophoresis demonstrated that the molecular weight of the subunits of the high-molecular-weight material is identical with that of the subunits of the major form. These results suggest that high-molecular-weight catalase consists of subunits that are not markedly distinct from those present in the normal catalase tetramer.

Animals↗