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Biomedical subjects

G A Tomlinson

Publications and source records attributed to G A Tomlinson.

17 recordsLinked to original sources
PubMed2006

A Bayesian meta-analysis of prophylactic granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor in children with cancer.

The purpose of this analysis was to examine the efficacy of prophylactic hematopoietic colony-stimulating factors (CSFs) in pediatric cancer and to describe how a Bayesian meta-analysis can be conducted and then modified to incorporate information not readily included in a frequentist meta-analysis. Three Bayesian models were developed. The simplest model used the same data as a published frequentist meta-analysis. The second model included data that could not easily be incorporated into the frequentist meta-analysis, including data from different courses of chemotherapy and continuous outcomes that did not report variance estimates. The third model examined the effect of CSF type (granulocyte CSF vs. granulocyte-macrophage CSF). Compared with the frequentist model, the Bayesian model with the most data suggested a greater benefit of CSFs, with a 3.2-day reduction in duration of parenteral antibiotics (95% credible interval: -7.1, 0.7) in the expanded Bayesian model compared with a 0.8-day (95% confidence interval: -2.3, 0.7) reduction in the frequentist model. Bayesian meta-analysis also suggested that, compared with granulocyte-macrophage CSF, granulocyte CSF was associated with a 4.8-day decrease in the duration of parenteral antibiotics. Bayesian meta-analysis can readily include information not easily incorporated in a frequentist meta-analysis. Some treatment effect estimates were larger by a clinically important amount when additional data contributed to the pooled estimate.

Bayes Theorem↗
PubMed2004

Medieval trabecular bone architecture: the influence of age, sex, and lifestyle.

Osteoporosis has become a growing health concern in developed countries and an extensive area of research in skeletal biology. Despite numerous paleopathological studies of bone mass, few studies have measured bone quality in past populations. In order to examine age- and sex-related changes in one aspect of bone quality in the past, a study was made of trabecular bone architecture in a British medieval skeletal sample. X-ray images of 5-mm-thick coronal lumbar vertebral bone sections were taken from a total of 54 adult individuals divided into three age categories (18-29, 30-49, and 50+ years), and examined using image analysis to evaluate parameters related to trabecular bone structure and connectivity. Significant age-related changes in trabecular bone structure (trabecular bone volume (BV/TV), trabecular number (Tb.N), trabecular separation (Tb.Sp), and anisotropic ratio (Tb.An)) were observed to occur primarily by middle age with significant differences between the youngest and two older age groups. Neither sex showed continuing change in trabecular structure between the middle and old age groups. Age-related changes in bone connectivity (number of nodes (N.Nd) and node-to-node strut length (Nd.Nd)) similarly indicated a change in bone connectivity only between the youngest and two older age groups. However, females showed no statistical differences among the age groups in bone connectivity. These patterns of trabecular bone loss and fragility contrast with those generally found in modern populations that typically report continuing loss of bone structure and connectivity between middle and old age, and suggest greater loss in females. The patterns of bone loss in the archaeological samples must be interpreted cautiously. We speculate that while nutritional factors may have initiated some bone loss in both sexes, physical activity could have conserved bone architecture in old age in both sexes, and reproductive factors such as high parity and extended periods of lactation could have played a key role in female bone maintenance in this historic population. The study of qualitative elements (such as trabecular architecture) is vital if we are to understand bone maintenance and fragility in the past.

Adolescent↗
PubMed2000

Bone mineral density, osteopenia, and osteoporosis in the rhesus macaques of Cayo Santiago.

This cross-sectional study investigates metabolic bone disease and the relationship between age and bone mineral density (BMD) in males and females of a large, well-documented skeletal population of free-ranging rhesus monkeys (Macaca mulatta), from the Caribbean Primate Research Center Museum collection from Cayo Santiago, Puerto Rico. The sample consists of 254 individuals aged 1.0-20+ years. The data consist of measurements of bone mineral content and bone mineral density, obtained from dual-energy X-ray absorptiometry (DEXA), of the last lumbar vertebra from each monkey. The pattern of BMD differs between male and female rhesus macaques. Females exhibit an initial increase in BMD with age, with peak bone density occurring around age 9.5 years, and remaining constant until 17.2 years, after which there is a steady decline in BMD. Males acquire bone mass at a faster rate, and attain a higher peak BMD at an earlier age than do females, at around 7 years of age, and BMD remains relatively constant between ages 7-18.5 years. After age 7 there is no apparent effect of age on BMD in the males of this sample; males older than 18.5 years were excluded due to the presence of vertebral osteophytosis, which interferes with DEXA. The combined frequency of osteopenia and osteoporosis in this population is 12.4%. BMD values of monkeys with vertebral wedge fractures are generally higher than those of virtually all of the nonfractured osteopenic/osteoporotic individuals, thus supporting the view that BMD as measured by DEXA is a useful but imperfect predictor of fracture risk, and that low BMD may not always precede fractures in vertebral bones. Other factors such as bone quality (i.e., trabecular connectivity) should also be considered. The skeletal integrity of a vertebra may be compromised by the loss of key trabeculae, resulting in structural failure, but the spine may still show a BMD value within normal limits, or within the range of osteopenia.

Absorptiometry, Photon↗
PubMed1994

Mortality among fire fighters in metropolitan Toronto.

Fire fighters are exposed to substances which are recognized or suspected causal agents in cancer or heart disease. The purpose of this study was to determine whether or not fire fighters experience increased risk for any specific cause of death. A retrospective cohort study was conducted, with 5,995 subjects recruited from all six fire departments within Metropolitan Toronto. The mortality experience of the cohort was ascertained through computerized record linkage and compared to that of the male Ontario population specific to cause, age, and calendar period from 1950 through 1989. Average duration of follow-up was 21 years, and there were 777 deaths among the 5,414 males included in the analysis, giving an all-cause standardized mortality ratio of 95 (95% confidence interval: 88-102). Three specific causes of death exhibit statistically significant excesses (brain tumors, "other" malignant neoplasms, and aortic aneurysms). There are also slight increases in risk for some other sites of cancer, and for various diseases of the respiratory, circulatory, and digestive systems. This study is consistent with others in demonstrating that fire fighters experience increased risk of death from cancer of the brain, and in suggesting increased risk for various other causes of death.

Adolescent↗
PubMed1989

Transfer of Halobacterium denitrificans (Tomlinson, Jahnke, and Hochstein) to the genus Haloferax as Haloferax denitrificans comb. nov.

Halobacterium denitrificans (Tomlinson, Jahnke, and Hochstein) was described at a time when the taxonomic subdivision of the family Halobacteriaceae was in a state of flux. On the basis of both biochemical and chemotaxonomic data, this organism exhibits features which indicate that it is more closely related to members of the genus Haloferax. On the basis of such criteria, we propose that Halobacterium denitrificans be reclassified as Haloferax denitrificans comb. nov. The type strain is strain ATCC 35960 (= DSM 4425).

Carbohydrate Metabolism↗
PubMed1987

Polar lipid composition of a new halobacterium.

Investigations of the polar lipid composition of a new aerobic, extremely halophilic aracheabacterium capable of nitrate reduction have shown that this organism contains two previously unknown phospholycolipids derived from diphytanyl glycerol diethers. Comparison of the lipid pattern from this new isolate with other known strains indicate that this organism is novel. On the basis of the unique polar lipid pattern it can be concluded that this organism represents a new taxon, at least at the species level.

Archaea↗
PubMed1986

Halobacterium denitrificans sp. nov., an extremely halophilic denitrifying bacterium.

Halobacterium denitrificans was one of several carbohydrate-utilizing, denitrifying, extremely halophilic bacteria isolated by anaerobic enrichment in the presence of nitrate. Anaerobic growth took place only when nitrate (or nitrite) was present and was accompanied by the production of dinitrogen. In the presence of high concentrations of nitrate (i.e., 0.5%), nitrous oxide and nitrite were also detected. When grown aerobically in a mineral-salts medium containing 0.005% yeast extract, H. denitrificans utilized a variety of carbohydrates as sources of carbon and energy. In every case, carbohydrate utilization was accompanied by acid production. A type culture has been deposited with the American Type Culture Collection, Rockville, Md. (ATCC 35960).

Anaerobiosis↗
PubMed1985

Denitrification by extremely halophilic bacteria.

Extremely halophilic bacteria were isolated from widely separated sites by anaerobic enrichment in the presence of nitrate. The anaerobic growth of several of these isolates was accompanied by the production of nitrate, nitrous oxide, and dinitrogen. These results are a direct confirmation of the existence of extremely halophilic denitrifying bacteria, and suggest that such bacteria may be common inhabitants of hypersaline environments.

Anaerobiosis↗
PubMed1984

The growth of Paracoccus halodenitrificans in a defined medium.

A synthetic medium, consisting of inorganic salts and any of a number of carbon sources, supported the aerobic growth of Paracoccus halodenitrificans when supplemented with thiamine. The same medium plus an appropriate nitrogenous oxide supported anaerobic growth when additionally supplemented with methionine. The observation that vitamin B12 or betaine replaced methionine suggested that P. halodenitrificans had a defect in the cobalamin-dependent pathway for methionine biosynthesis, as well as the inability to synthesize betaine when growing anaerobically.

Ammonium Sulfate↗
PubMed1978

The metabolism of carbohydrates by extremely halophilic bacteria: the identification of lactobionic acid as a product of lactose metabolism by Halobacterium saccharovorum.

Nongrowing cells of Halobacterium saccharovorum oxidized lactose to a product identified as lactobionic acid by thin-layer, paper, and column chromatography, and by identification of the galactose and gluconic acid produced from it after acid hydrolysis. Growing cells oxidized lactose to a product that was identical with lactobionate except that it did not serve as a substrate for galactose oxidase. While the identity of this compound has not been established, it is suggested that the product is lactobionic acid in which the galactose moeity is in the furanose form. Neither lactobionate nor the product produced by growing cells was further metabolized, suggesting that lactose oxidation is not coupled to growth.

Cells, Cultured↗
PubMed1976

Halobacterium saccharovorum sp. nov., a carbohydrate-metabolizing, extremely halophilic bacterium.

The previously described extremely halophilic bacterium, strain M6, metabolizes a variety of carbohydrates with the production of acid. In addition, the organism produces nitrite (but no gas) from nitrate, is motile, and grows most rapidly at about 50 degrees C. These characteristics distinguish it from all previously described halophilic bacteria in the genus Halobacterium. It is suggested that it be designated as a new species, Halobacterium saccharovorum.

California↗
PubMed1966

The formation of bilirubin and p-nitrophenyl glucuronides by rabbit liver.

1. Glucuronide formation of bilirubin and p-nitrophenol in vitro with excess of UDP-glucuronic acid by UDP-glucuronyltransferase from livers of young and adult rabbits was studied. 2. The development of UDP-glucuronyltransferase for the two substrates followed a markedly different pattern during maturation of young rabbits, p-nitrophenol-conjugation ability being much higher at birth than that for bilirubin. 3. Mg(2+) increased bilirubin conjugation, but inhibited p-nitrophenyl glucuronide formation. 4. p-Nitrophenol acted as a potent non-competitive inhibitor for bilirubin conjugation but bilirubin did not affect p-nitrophenyl glucuronidation. 5. The enzyme for bilirubin conjugation was inactivated at pH9 during treatment with snake venom, whereas in the same preparation the activity of the corresponding enzyme for p-nitrophenol was enhanced. In addition, some solubilization of the latter enzyme could be achieved by this method. 6. The possibility of the existence of more than one enzyme system for the formation of O-glucuronides is discussed.

Animals↗
PubMed1965

Cytological Distribution of the Products of Oxidative Assimilation in Pseudomonas aeruginosa.

Tomlinson, Geraldine A. (University of British Columbia, Vancouver, B.C., Canada), and J. J. R. Campbell. Cytological distribution of the products of oxidative assimilation in Pseudomonas aeruginosa. J. Bacteriol. 90:599-603. 1965.-Washed-cell suspensions of Pseudomonas aeruginosa incorporated C(14) largely into the membrane fractions and cytoplasm during oxidative assimilation of uniformly labeled glucose. The ribonucleic acid (RNA) associated with the membranes and the cytoplasm had very high specific activity in contrast to that of the ribosomes. The protein of each fraction comprised the major portion of the radioactivity of that cytological fraction. The proteins of the cytoplasm constituted the predominant product of assimilation. The low level of activity in the ribosomal RNA and protein suggests that oxidative assimilation is not the replenishment of endogenous reserves. The ribosomal fraction, which contained 19.6% of the protein and 65% of the RNA of the extract, incorporated only 2 to 3% of the radioactivity. In contrast, the membrane fraction contained 15.3% of the protein and 6.6% of the RNA, but incorporated 13 to 14% of the radioactivity.

Journal Article↗