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Biomedical subjects

A Peacock

Publications and source records attributed to A Peacock.

At least 19 recordsLinked to original sources
PubMed2005

Factors affecting a climber's ability to ascend Mont Blanc.

The aim of the study was to determine the factors affecting a climber's ability to ascend Mont Blanc using a number of variables collected at the Gouter Hut (3,817 m) before and after an attempted ascent on the Mont Blanc summit. Subjects (n=285) were tested at 3,817 m prior to their ascent of Mont Blanc. Maximum height ascended in the last 14 days was recorded. End tidal CO2, arterial oxygen saturation (SaO2), heart rate and respiratory rate were measured using a Capnograph (Nellcor Patrick NPB75). Acute mountain sickness (AMS) was assessed using the Lake Louise scoring system. Summit information is available for 216 subjects. None of the subjects who attained 4,000 m in the previous 14 days failed to reach the summit (P=0.04). Previous recent exposure to an altitude of 4,000 m resulted in faster ascent times to the summit than those who had not been above 3,000 m in the previous 14 days (4.02+/-0.6 vs. 4.46+/-0.8 h, P=0.009), higher SaO2 on arrival at the Gouter Hut on day 1 (88.6+/-5 vs. 86.3+/-6%, P=0.004) and lower AMS scores upon arrival at the Gouter Hut after the attempted ascent to the summit 2.5+/-1.8 versus 4.7+/-2.5 U (P=0.001), respectively. It is concluded that recent exposure to 4,000 m confers an advantage to those who wish to ascend a 4,800 m peak.

Adolescent↗
PubMed2004

Performance at altitude and angiotensin I-converting enzyme genotype.

The "insertion" (I) rather than "deletion" (D) variant of the human angiotensin-converting enzyme (ACE) gene is associated with both lower tissue ACE activity and elite performance at high altitude. We examined whether the onset of acute mountain sickness (AMS), and further performance on reaching the summit of Mt. Blanc are influenced by the ACE I/D polymorphism. Two hundred and eighty-four climbers (235 males, [37.0 (11.0 years], (86 DD, 142 ID, 56 II)) had assessment of their AMS status upon arrival to the Gouter hut (3,807 m) on day 1, and again on day 2 after an attempted ascent to the summit of Mt. Blanc (4,807 m). Success in reaching the summit was genotype dependent (87.7% of DD, 94.9% of ID and 100% of II individuals; P=0.048); I allele frequency for those reaching the summit was 0.47 compared to 0.21 for those who did not (P=0.01). The onset of AMS on day 1 appeared to be dependent on genotype (P=0.003), but with those heterozygous being less affected. ACE genotype was not associated either with AMS onset or severity on day 2. Thus, ACE I/D genotype is associated with successful high altitude ascent in this prospective study-an association not explicable by genotype-dependence of AMS onset or severity. Values are given as mean (SD) unless otherwise stated.

Adult↗
PubMed2004

In situ bioreduction of technetium and uranium in a nitrate-contaminated aquifer.

The potential to stimulate an indigenous microbial community to reduce a mixture of U(VI) and Tc(VII) in the presence of high (120 mM) initial NO3- co-contamination was evaluated in a shallow unconfined aquifer using a series of single-well, push-pull tests. In the absence of added electron donor, NO3-, Tc(VII), and U(VI) reduction was not detectable. However, in the presence of added ethanol, glucose, or acetate to serve as electron donor, rapid NO3- utilization was observed. The accumulation of NO2-, the absence of detectable NH4+ accumulation, and the production of N2O during in situ acetylene-block experiments suggest that NO3- was being consumed via denitrification. Tc(VII) reduction occurred concurrently with NO3- reduction, but U(VI) reduction was not observed until two or more donor additions resulted in iron-reducing conditions, as detected by the production of Fe(II). Reoxidation/remobilization of U(IV) was also observed in tests conducted with high (approximately 120 mM) but not low (approximately 1 mM) initial NO3- concentrations and not during acetylene-block experiments conducted with high initial NO3-. These results suggest that NO3(-)-dependent microbial U(IV) oxidation may inhibit or reverse U(VI) reduction and decrease the stability of U(IV) in this environment. Changes in viable biomass, community composition, metabolic status, and respiratory state of organisms harvested from down-well microbial samplers deployed during these tests were consistent with the conclusions that electron donor additions resulted in microbial growth, the creation of anaerobic conditions, and an increase in activity of metal-reducing organisms (e.g., Geobacter). The results demonstrate that it is possible to stimulate the simultaneous bioreduction of U(VI) and Tc(VII) mixtures commonly found with NO3- co-contamination at radioactive waste sites.

Biodegradation, Environmental↗
PubMed2004

End points in pulmonary arterial hypertension: the way forward.

Pulmonary arterial hypertension is a rare disease of poor prognosis. Despite its rarity >1,000 patients have been randomised in placebo-controlled trials using novel therapies, including prostacyclin analogues, endothelin receptor antagonists and, most recently, phosphodiesterase 5 inhibitors. Nearly all of these trials have used exercise capacity, measured by the unencouraged 6-min walking distance, as the primary end point and a variety of other measurements as secondary end points. This approach has been productive, leading to the licensing of a number of effective treatments. Future clinical trials, however, will probably assess drug combinations, make comparisons between drugs and include less severely ill patients. It is, therefore, timely to examine the end points used. The authors discussed the various end points that have been used in the past and possible end points that might be used in the future. End points considered included measurements of: exercise capacity, haemodynamics, quality of life, imaging of the right heart and circulation, and chemical markers of pulmonary hypertension. Many of these show promise but will have to be used in parallel and compared with conventional end points such as the 6-min walking distance before their value can be demonstrated convincingly to the regulatory authorities.

Antihypertensive Agents↗
PubMed2003

Indigenous and contaminant microbes in ultradeep mines.

Rock, air and service water samples were collected for microbial analyses from 3.2 kilometres depth in a working Au mine in the Witwatersrand basin, South Africa. The approximately metre-wide mined zone was comprised of a carbonaceous, quartz, sulphide, uraninite and Au bearing layer, called the Carbon Leader, sandwiched by quartzite and conglomerate. The microbial community in the service water was dominated by mesophilic aerobic and anaerobic, alpha-, beta- and gamma-Proteobacteria with a total biomass concentration approximately 10(4) cells ml(-1), whereas, that of the mine air was dominated by members of the Chlorobi and Bacteroidetes groups and a fungal component. The microorganisms in the Carbon Leader were predominantly mesophilic, aerobic heterotrophic, nitrate reducing and methylotrophic, beta- and gamma-Proteobacteria that were more closely related to service water microorganisms than to air microbes. Rhodamine WT dye and fluorescent microspheres employed as contaminant tracers, however, indicated that service water contamination of most of the rock samples was < 0.01% during acquisition. The microbial contaminants most likely originated from the service water, infiltrated the low permeability rock through and accumulated within mining-induced fractures where they survived for several days before being mined. Combined PLFA and terminal restriction fragment length profile (T-RFLP) analyses suggest that the maximum concentration of indigenous microorganisms in the Carbon Leader was < 10(2) cells g(-1). PLFA, 35S autoradiography and enrichments suggest that the adjacent quartzite was less contaminated and contained approximately 10(3) cells gram(-1) of thermophilic, sulphate reducing bacteria, SRB, some of which are delta-Proteobacteria. Pore water and rock geochemical analyses suggest that these SRB's may have been sustained by sulphate diffusing from the adjacent U-rich, Carbon Leader where it was formed by radiolysis of sulphide.

Air Microbiology↗
PubMed2002

Sea level and acute responses to hypoxia: do they predict physiological responses and acute mountain sickness at altitude?

OBJECTIVES: To compare a range of physiological responses to acute sea level hypoxia at simulated altitudes with the same physiological responses and acute mountain sickness (AMS) scores measured at altitude (similar to the simulated altitudes) during a 17 day trek in the Himalayas. METHODS: Twenty men and women aged 18-54 years took part in the study. End tidal CO(2) tension (PETCO(2)) and saturated oxygen (SaO(2)) were measured using a capnograph. Observations made at sea level and some simulated altitudes were compared with those in the Himalayas. Pairwise correlations were used to examine the correlation between variables and regression, with 95% prediction intervals providing information on how well one variable could be predicted from another for a given subject. RESULTS: There was only a significant correlation for a few comparisons. The 95% prediction intervals for individual SaO(2) values at a range of simulated altitudes were fairly wide going from +/- 4% to +/- 5%. All of the correlations between laboratory and Himalayan PETCO(2) values were not statistically significant. There was a significant correlation for the relation between SaO(2)and PETCO(2) at sea level for the laboratory data (r=-0.51; p=0.05). For the Himalayan data, there were significant correlations at Namche Bazaar (3450 m; day 3) (r=-0.56; p=0.01) and Dingboche (4300 m; day 6) (r=-0.48; p=0.03). The correlation between SaO(2) and PETCO(2) and AMS was generally poor. CONCLUSIONS: The results indicate that limited information can be gained on a subject's response to altitude by assessing physiological variables at sea level and a range of simulated altitudes before the subject carries out a trek at altitude.

Adolescent↗
PubMed2001

Utility of high performance liquid chromatography/electrospray/mass spectrometry of polar lipids in specifically Per-13C labeled Gram-negative bacteria DA001 as a tracer for acceleration of bioremediation in the subsurface.

Specific fatty acids from phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) recovered from a per 13C-labeled bacteria can be detected in environmental samples and used as measures of bacterial transport in the subsurface. Detection of palmitic acid (16:0) and oleic acid (18:1) at m/z 271 (255+16) and 299 (281+18) as negative ions in PG and PE separated by high performance liquid chromatography (HPLC) and detected after up-front collisionally induced dissociation (CID) utilizing electrospray (ES) mass spectrometry (MS) provided sufficient sensitivity and specificity for detection in the presence of the indigenous microbiota. Application of tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) was use to monitor selected transitions. MRM can increase the sensitivity so that polar lipids recovered from cell densities currently at about 10(4) cells/sample can be detected. This technology provides a non-intrusive mechanism for monitoring the distribution of bacteria added to accelerate in situ bioremediation of subsurface sediments.

Biodegradation, Environmental↗
PubMed2001

Lessons to be learned: a case study approach a case study of the temporal onset of pulmonary hypertension with pre-existent cirrhotic portal hypertension.

We report the occurrence of pulmonary hypertension in a 37-year-old male patient with cirrhosis of the liver, portal hypertension and oesophageal varices. Although this is a rare combination, previous reports have shown that the association of portal and pulmonary hypertension is not coincidental; the temporal onset of primary pulmonary hypertension is hard to predict and our patient was asymptomatic for a number of years. The pathogenesis of portal hypertension leading to pulmonary hypertension is not known. Diagnosis is difficult because the clinico-pathological symptoms in both conditions are similar. Treatment is limited to calcium channel blockers, vasodilators, nitrous oxide and prostacyclin, although most patients will eventually require visceral transplantation.

Adult↗
PubMed2001

Impact of herbicides on the abundance and structure of indigenous beta-subgroup ammonia-oxidizer communities in soil microcosms.

In this study, mixtures of five herbicide-formulated products (atrazine, dicamba, fluometuron, metolachlor, and sulfentrazone) were applied to soil microcosm columns in increasing concentrations. The toxic impact of herbicides on the indigenous beta-subclass Proteobacteria autotrophic ammonia-oxidizer (beta-AAO) community was assessed. The beta-AAO population abundances were estimated by competitive polymerase chain reaction (PCR) targeting the gene amoA, encoding the alpha-subunit of ammonia monooxygenase. Community structure was examined by PCR and denaturing gradient gel electrophoresis targeting 16S rDNA with band excision and sequence analysis, and by analysis of amoA gene fragment clone libraries. The 16S rDNA analyses showed that a single ribotype of Nitrosospira cluster 3 was the dominant beta-AAO in all treatments. At a finer scale, amoA clone library analysis suggested a shift in community structure corresponding to the 100-ppm application. Competitive PCR indicated significant differences between treatments. The control exhibited relatively stable population abundance over the time period examined. The 10-ppm treatment induced a population increase, but a significant decrease was induced by the 100-ppm application. At 1,000 ppm, the ammonia-oxidizer population dropped below the method detection limit by the first sampling point. An impact on ammonia oxidizers resulting from the application of herbicides was observed, both in abundance and community structure.

Ammonia↗
PubMed2000

Physiological Status and Community Composition of Microbial Mats of the Ebro Delta, Spain, by Signature Lipid Biomarkers.

Physiological status of microbial mats of the Ebro Delta (Tarragona, Spain) based on the extraction of lipids considered "signature lipid biomarkers" (SLB) from the cell membranes and walls of microorganisms has been analyzed. Data from a day-night cycle show significant differences in viable cells countings (PLFA cells counts) ranging from 1.5 x 10(10) to 5.0 x 10(10) cells g(-1) of sediment. Minimum values were observed at 18:00 and 6:00, when physicochemical conditions change drastically. The diversity of the microbial community was assessed by GC/MS analysis of phospholipid fatty acids (PLFA). The ratio of PLFA, representative of Gram-negative bacteria, comprises 47.8% of the total PLFA of the microbial mat community. The remaining PLFA was representative of Gram-positive (10.0%), anaerobic (5.7%), and eukaryotic microorganisms (5.7%), and other common lipids. Two different approaches were used as a comparative study to assess the physiological status of the microbial mats. Two parameters (cyclopropane fatty acids/omega7c monoenoic fatty acids, and measurement of the trans/cis monoenoic PLFA ratio) showed a minimum at midnight, suggesting the highest microbial activity. Higher values were observed at 18:00 and 6:00, coinciding with lower PLFA cell counts. </hea

Journal Article↗
PubMed2000

Measuring soil microbial community diversity using polar lipid fatty acid and denaturing gradient gel electrophoresis data.

The possibility of calculating useful microbial community diversity indices from environmental polar lipid fatty acid and 16S rDNA PCR-DGGE data was investigated. First, the behavior of the species richness, Shannon's, and Simpson's diversity indices were determined on polar lipid fatty acid profiles of 115 pure cultures, communities constructed from those profiles with different numbers of species, and constructed communities with different distributions of species. Differences in the species richness of these artificial communities was detected by all three diversity indices, but they were insensitive to the evenness of the distribution of species. Second, data from a field experiment with substrate addition to soil was used to compare the methods developed for lipid- and DNA-based diversity indices. Very good agreement was found between indices calculated from environmental polar lipid fatty acid profiles and denaturing gradient gel electrophoresis profiles from matched samples (Pearson's correlation coefficient r=0.95-0.96). A method for data pre-treatment for diversity calculations is described.

Bacteria↗
PubMed2000

Sporadic primary pulmonary hypertension is associated with germline mutations of the gene encoding BMPR-II, a receptor member of the TGF-beta family.

BACKGROUND: Primary pulmonary hypertension (PPH), resulting from occlusion of small pulmonary arteries, is a devastating condition. Mutations of the bone morphogenetic protein receptor type II gene (BMPR2), a component of the transforming growth factor beta (TGF-beta) family which plays a key role in cell growth, have recently been identified as causing familial PPH. We have searched for BMPR2 gene mutations in sporadic PPH patients to determine whether the same genetic defect underlies the more common form of the disorder. METHODS: We investigated 50 unrelated patients, with a clinical diagnosis of PPH and no identifiable family history of pulmonary hypertension, by direct sequencing of the entire coding region and intron/exon boundaries of the BMPR2 gene. DNA from available parent pairs (n=5) was used to assess the occurrence of spontaneous (de novo) mutations contributing to sporadic PPH. RESULTS: We found a total of 11 different heterozygous germline mutations of the BMPR2 gene in 13 of the 50 PPH patients studied, including missense (n=3), nonsense (n=3), and frameshift (n=5) mutations each predicted to alter the cell signalling response to specific ligands. Parental analysis showed three occurrences of paternal transmission and two of de novo mutation of the BMPR2 gene in sporadic PPH. CONCLUSION: The sporadic form of PPH is associated with germline mutations of the gene encoding the receptor protein BMPR-II in at least 26% of cases. A molecular classification of PPH, based upon the presence or absence of BMPR2 mutations, has important implications for patient management and screening of relatives.

Adolescent↗
PubMed1999

Detection of Sphingomonas spp in soil by PCR and sphingolipid biomarker analysis.

Sphingomonas spp possess unique abilities to degrade refractory contaminants and are found ubiquitously in the environment. We developed Sphingomonas genus-specific PCR primers (SPf-190 and SPr1-852) which showed specific amplification of a 627-bp 16S rDNA fragment from Sphingomonas spp. A PCR assay using these Sphingomonas specific primers was developed to detect Sphingomonas aromaticivorans B0695R in three texturally distinct soil types, showing detection limits between 1.3-2.2 x 10(3) CFU g(-1) dry soil. A sphingolipid extraction protocol was also developed to monitor Sphingomonas populations in soil quantitatively. The detection limit of the assay was 20 pmol g(-1) dry soil, equivalent to about 3 x 10(5) cells g(-1) dry soil. Survival of S. aromaticivorans B0695R was monitored in the three different soils by antibiotic selective plate counting, PCR and sphingolipid analysis. All three approaches showed that the B0695R cells persisted in the low biomass Sequatchie sub-soil at about 3-5 x 10(7)cells g(-1) dry soil. In comparison to the plate counting assay, both the PCR and sphingolipid analysis detected a significantly higher level of B0695R cells in the clay soil and Sequatchie top-soil, indicating the possibility of the presence of viable but non-culturable B0695R cells in the soils. The combination of PCR and sphingolipid analysis may provide a more realistic estimation of Sphingomonas population in the environment.

Journal Article↗
PubMed1999

Microbial characterization of a JP-4 fuel-contaminated site using a combined lipid biomarker/polymerase chain reaction--denaturing gradient gel electrophoresis (PCR-DGGE)-based approach.

The impact of pollution on soil microbial communities and subsequent bioremediation can be measured quantitatively in situ using direct, non-culture-dependent techniques. Such techniques have advantages over culture-based methods, which often account for less than 1% of the extant microbial community. In 1988, a JP-4 fuel spill contaminated the glacio-fluvial aquifer at Wurtsmith Air Force Base, Michigan, USA. In this study, lipid biomarker characterization of the bacterial and eukaryotic communities was combined with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of the eubacterial community to evaluate correlation between contaminant (JP-4 fuel) concentration and community structure shifts. Vadose, capillary fringe and saturated zone samples were taken from cores within and up- and down-gradient from the contaminant plume. Lipid biomarker analysis indicated that samples from within the plume contained increased biomass, with large proportions of typically gram-negative bacteria. Outside the plume, lipid profiles indicated low-biomass microbial communities compared with those within the initial spill site. 16S rDNA sequences derived from DGGE profiles from within the initial spill site suggested dominance of the eubacterial community by a limited number of phylogenetically diverse organisms. Used in tandem with pollutant quantification, these molecular techniques should facilitate significant improvements over current assessment procedures for the determination of remediation end-points.

Biodegradation, Environmental↗
PubMed1999

Characterization of metal-resistant soil eubacteria by polymerase chain reaction--denaturing gradient gel electrophoresis with isolation of resistant strains.

Contamination of soils with heavy metal ions is a major problem on industrial and defense-related sites worldwide. The bioavailability and mobility of these contaminants is partially determined by the microbial biomass present at these sites. In this study, we have assessed the effect of the addition of a mixture of toxic metal salts on the prokaryotic community of microcosms consisting of sandy-loam soil using direct molecular analysis of the recoverable eubacterial 16S rDNA molecules by polymerase chain reaction--denaturing gradient gel electrophoresis (PCR-DGGE) and limited phospholipid fatty acid analysis (PLFA). Addition of toxic metals (nonradioactive surrogates of Sr, Co, Cs, Cd) resulted in rapid (ca. 1 week) changes in the DGGE profile of the indigenous eubacterial community when compared with pristine controls. These changes were stable over the course of the experiment (8 weeks). No changes in the eubacterial population of control microcosms were detected. The major changes in community structure in metal-contaminated microcosms consisted of the appearance of four novel bands not detected in controls. Sequence analysis of these bands suggested that two organisms related to the genus Acinetobacter and two related to the genus Burkholderia carried a selective advantage over other indigenous eubacteria under heavy metal induced stress. The Burkholderia spp. were then cultured and further characterized using lipid analysis.

Acinetobacter↗
PubMed1998

An insight into rheumatology resources available on the World Wide Web.

The aim of this study was to gain an overview of rheumatology resources on the World Wide Web (WWW). A list of websites was generated using a commercial search engine and 'rheumatology' as a key word. A total of 154 websites were then evaluated with respect to origin and likely target audience; 43% of this initial group were either not accessible, repeats, or in a language other than English. Of the 87 websites we were able to analyse, we found that 67% originated from medical organizations and 51% were interpreted to be directed specifically at rheumatologists. Only 16% of websites were directed at patients only. The remainder were felt to contain information useful to both groups. Over half the websites felt to be of interest to patients contained advertisements. Although there is a lot of information relating to rheumatology on the WWW, it was invariably time consuming to access and there was little directed solely at patient education.

Advertising↗