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Biomedical subjects

M Watt

Publications and source records attributed to M Watt.

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↗
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↗
PubMed2000

The effect of amlodipine on respiratory and pulmonary vascular responses to hypoxia in mountaineers.

Calcium antagonists are known to reduce the incidence of high-altitude pulmonary oedema, but the mechanism is unclear. The aim of this study was to examine the effects of the calcium antagonist, amlodipine, on cardiac and respiratory responses in normoxia and hypoxia. Fourteen normal subjects aged 31+/-4 yrs who had climbed to altitudes of 5,000-7,500 m without problems were randomly assigned to a double-blind crossover trial of amlodipine versus placebo, using sea-level inspiratory hypoxia to simulate altitude. Doppler echocardiographic estimates of resting pulmonary haemodynamics and cycle ergometer test results of cardiorespiratory responses to exercise were recorded in normoxia and hypoxia. It was found that, although hypoxic pulmonary vasoconstriction (HPV) was not significantly reduced by amlodipine, the effect of the drug on HPV was inversely related to the serum level of amlodipine. Amlodipine did not alter left ventricular function measured echocardiographically. During exercise, amlodipine increased breathlessness, measured using standard scales, in both normoxia and hypoxia but had no effect on ventilatory variables. It was concluded that amlodipine has the potential to block hypoxic pulmonary vasoconstriction as evidenced by a drug concentration-related decrease in resting tricuspid regurgitation jet velocity without any change in resting myocardial contractility. However, with amlodipine, the subjects felt more breathless during exercise. The reasons for this increase in breathlessness are not clear.

Adult↗
PubMed1999

Use of electroreception during foraging by the Australian lungfish.

A diverse range of animals, including elasmobranchs and nonteleost fish, use passive electroreception to locate hidden prey. The Australian lungfish, Neoceratodus forsteri (Krefft 1870), has ampullary organs analogous in form to the electroreceptors of other nonteleost fish. Afferents from these ampullae project to regions in the brain that are known to process electrosensory information in other species, suggesting that N. forsteri possesses an electric sense that may be used during prey location. To explore this hypothesis directly, we first characterized food-locating behaviour in N. forsteri and then conducted an experiment designed to quantify the effects of manipulating electrical and olfactory stimuli from live prey. A small crayfish, Cherax destructor, was housed in a specially constructed chamber hidden beneath the substrate, which prevented emission of chemical, mechanical and visual cues, but allowed transmission of bioelectric fields. Control treatments included presentation of electrically shielded prey, a dead crayfish and an empty chamber. In some treatments, a competing olfactory signal was presented simultaneously at the other end of the test tank to assess the relative salience of this sensory modality. The lungfish responded to the crayfish in the unshielded chamber with accurate and sustained feeding movements, even with a competing olfactory signal. By contrast, the abolition of electrical cues in the three control treatments reduced the accuracy and frequency of feeding movements in the vicinity of the target chamber. These results show that N. forsteri is capable of perceiving the weak electric fields surrounding living animals, and suggest that it uses this information when foraging to locate prey hidden from view. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Linking development and determinacy with organic acid efflux from proteoid roots of white lupin grown with low phosphorus and ambient or elevated atmospheric CO2 concentration

White lupin (Lupinus albus L.) was grown in hydroponic culture with 1 &mgr;M phosphorus to enable the development of proteoid roots to be observed in conjunction with organic acid exudation. Discrete regions of closely spaced, determinate secondary laterals (proteoid rootlets) emerged in near synchrony on the same plant. One day after reaching their final length (4 mm), citrate exudation occurred over a 3-d pulse. The rate of exudation varied diurnally, with maximal rates during the photoperiod. At the onset of citrate efflux, rootlets had exhausted their apical meristems and had differentiated root hairs and vascular tissues along their lengths. Neither in vitro phosphoenolpyruvate carboxylase nor citrate synthase activity was correlated with the rate of citrate exudation. We suggest that an unidentified transport process, presumably at the plasma membrane, regulates citrate efflux. Growth with elevated (700 &mgr;L L-1) atmospheric [CO2] promoted earlier onset of rootlet determinacy by 1 d, resulting in shorter rootlets and citrate export beginning 1 d earlier as a 2-d diurnal pulse. Citrate was the dominant organic acid exported, and neither the rate of exudation per unit length of root nor the composition of exudate was altered by atmospheric [CO2].

Journal Article↗
PubMed1999

Particulate air pollution and the blood.

BACKGROUND: Particulate air pollution has been associated with excess deaths from, and increases in hospital admissions for, cardiovascular disease among older people. A study was undertaken to determine whether this may be a consequence of alterations in the blood, secondary to pulmonary inflammation caused by the action of fine particles on alveolar cells, by repeatedly measuring haematological factors in older people and relating them to measurements of exposure to airborne particles. METHODS: One hundred and twelve individuals aged 60+ years in two UK cities provided repeated blood samples over 18 months, 108 providing the maximum of 12 samples. Estimates of individual exposure to particles of less than 10 microm diameter (PM(10)), derived from a mathematical model based on activity diaries and comparative measurements of PM(10) at multiple sites and during a variety of activities, were made for each three day period prior to blood sampling. The relationships between blood values and estimates of both personal exposure and city centre measurements of PM(10) were investigated by analysis of covariance, adjusting for city, season, temperature, and repeated individual measurements. RESULTS: Estimated personal exposure to PM(10) over the previous three days showed negative correlations with haemoglobin concentration, packed cell volume (PCV), and red blood cell count (p<0.001), and with platelets and factor VII levels (p<0.05). The changes in red cell indices persisted after adjustment for plasma albumin in a sample of 60 of the subjects. City centre PM(10) measurements over three days also showed negative correlations with haemoglobin and red cell count (p<0.001) and with PCV and fibrinogen (p<0.05), the relationship with haemoglobin persisting after adjustment for albumin. C reactive protein levels showed a positive association with city centre measurements of PM(10) (p<0.01). Based on a linear relationship, the estimated change in haemoglobin associated with an alteration in particle concentration of 100 microg/m(3) is estimated to have been 0.44 g/dl (95% CI 0.62 to 0.26) for personal PM(10) and 0.73 g/dl (95% CI 1.11 to 0.36) for city centre PM(10) measurements. CONCLUSIONS: This investigation is the first to estimate personal exposures to PM(10) and to demonstrate associations between haematological indices and air pollution. The changes in haemoglobin adjusted for albumin suggest that inhalation of some component of PM(10) may cause sequestration of red cells in the circulation. We propose that an action of such particles either on lung endothelial cells or on erythrocytes themselves may be responsible for changing red cell adhesiveness. Peripheral sequestration of red cells offers an explanation for the observed cardiovascular effects of particulate air pollution.

Aged↗
PubMed1996

Serum neurone-specific enolase as an indicator of stroke volume.

Serum neurone-specific enolase (NSE) and computerized tomography (CT) stroke volume were compared in patients admitted within 24 h of an acute stroke. Serum samples were obtained on admission and daily for the next 4 days. Of 163 patients, CT scans revealed 25 with intracerebral haemorrhages, one haemorrhagic infarct and 83 measurable acute infarcts. The serum NSE levels of those with infarcts was significantly higher than in those with haemorrhages at 48 (P = 0.0003) and 72 h (P = 0.04). The maximum serum NSE value tended to occur later in those with large infarcts (P = 0.0035). There was a significant correlation between infarct volume and serum NSE at 48 h (r = 0.27, P = 0.015) and 96 h (r = 0.27, P = 0.015) and with the maximum serum NSE over the 4 days (r = 0.36, P = 0.001). There was no significant correlation between haemorrhage volume and NSE. In conclusion, serum NSE may be a useful marker of infarct volume in studies of therapy in acute stroke. Sampling for NSE should continue, at least in those with large infarcts, for longer than 4 days. Serum NSE cannot be used to distinguish between haemorrhage and infarction in patients with an acute stroke.

Adult↗
PubMed1995

Violence towards junior doctors in accident and emergency departments.

The experience and training of accident and emergency (A&E) junior doctors with regard to patient aggression was investigated by use of a telephone questionnaire. A total of 114 A&E departments in five different regions in the United Kingdom were telephoned. A total of 100 junior doctors answered the questionnaire. Verbal aggression had been experienced by 96 of them, 50 had received threats and 32 said that patients had tried to assault them. Eighteen doctors had been assaulted by patients on a total of 23 occasions. Thirty-two doctors admitted that they had been upset after a violent incident, so much so that they were preoccupied with it after work. None of those assaulted received any counselling and no police charges resulted from the assaults. Only 11 doctors had received any training on how to manage aggressive patients, although 88 believed that it would be useful. The results of this study indicate that violence towards junior doctors in A&E is a significant problem. Aspects of this problem, including training and support for staff, need to be addressed urgently.

Aggression↗
PubMed1995

Individual exposure to particulate air pollution and its relevance to thresholds for health effects: a study of traffic wardens.

OBJECTIVE: To investigate the differences between measurements of personal exposure to particulate air pollution and static area measurements in a group of people working close to traffic and to determine whether such differences might obscure any threshold for health effects in epidemiological studies. METHODS: Personal air sampling was carried out on two groups of eight traffic wardens for four days on two consecutive weeks in November 1994. These measurements were compared with standard environmental static sampling data that were obtained for the same period. A simulation with log normal distributions of personal exposures was produced, and an arbitrary risk calculated for each exposure, assuming a threshold of 50 micrograms/m3, and an exposure-response curve was calculated. RESULTS: The median concentration for personal samplers in week 1 was 123 micrograms/m3 and 41 micrograms/m3 in week 2. Corresponding area concentrations were 10 micrograms/m3 and 7.5 micrograms/m3. The differences between the personal and area results were significant, as were the differences for personal sampling between weeks 1 and 2. The simulation showed that the variation in individual exposures around an area sampler obscured the threshold. CONCLUSIONS: Area sampling data may be of limited value in the investigation of the biological effects of exposure to pollution and their use may result in real thresholds being obscured. Personal exposure assessment may be crucial in determination of the health effects attributable to different concentrations of air pollutants.

Adult↗
PubMed1994

Management of severe spasticity with intrathecal baclofen delivered by a manually operated pump.

Intrathecal baclofen abolishes spasticity in many patients with neurological diseases but there are few studies on its long-term effectiveness. Since 1986 a manually operated subcutaneous pump has been used to deliver baclofen intrathecally in 21 patients with a follow up of at least one year. Most patients had multiple sclerosis and all were wheelchair-bound. Sixteen patients had a complete and sustained benefit. In four other patients the treatment was effective in the short term but not in the long term. In the remaining patient the pump never worked. Complications included meningitis, pump failure, erosion through the skin, and baclofen overdose. Nevertheless, only three patients have asked to discontinue the treatment. We conclude that intrathecal baclofen, delivered by a manually operated implanted pump, is an effective treatment for severe spasticity in most patients.

Adult↗
PubMed1992

Quality of life in the first 100 days after suspected acute myocardial infarction--a suitable trial endpoint?

STUDY OBJECTIVE: The aim was to determine the loss of quality of life following admission to hospital with suspected myocardial infarction. DESIGN: The study involved a cohort of admissions, with interview and follow up for 100 days. Main outcome measures were the quality of life prior to admission and at each stage of convalescence, estimated using the Rosser-Kind matrix: the calculated number of quality adjusted days during a 100 d follow up period. SETTING: The study took place in a teaching hospital in Scotland. PATIENTS: 206 patients were admitted with suspected acute myocardial infarction. Infarction was confirmed in 160 (Q wave infarcts 100, non-Q-wave infarcts 60), and unconfirmed in 46. MAIN RESULTS: The quality of life scores before the suspected heart attack were similar for patients whose final diagnosis was Q wave infarction, non-Q-wave infarction, or non-infarction. Of the 160 patients with confirmed infarction, only 54 (34%) had regained their previous quality of life scores at the end of 100 days, compared with 26 of 46 (57%) patients with unconfirmed infarction (p < 0.01). The mean numbers of quality adjusted days lost to patients with Q wave infarction, non-Q-wave infarction, and non-infarction were 17.0, 12.4, and 5.9 respectively (infarction v non-infarction, p < 0.0001). Measurements of both quantity and quality of life contributed to these results. CONCLUSIONS: The number of quality adjusted days lost after acute myocardial infarction is a practicable measurement that is relevant to patients' lives. It might be suitable as an outcome measure for clinical trials of thrombolytic therapy.

Adult↗
PubMed1990

A psychotic man.

Explore the source record for details and available documents.

Adult↗
PubMed1985

Mitochondrial granules: are they reliable markers for heavy metal cations?

Mitochondrial granules have been used as markers for heavy metal cations, but since such granules can also be found in tissues in the absence of such cations, an attempt was made to define conditions under which these different granules might be visualised. The tissue used was the smooth muscle of the central ear artery of the rabbit. In all studies, the presence or absence of mitochondrial granules was determined by several observers, using coded specimens so that the previous treatment of the specimens was not at the time known to the observers. Paired tissues were exposed for 30 or 90 minutes at 20, 30 or 39 degrees C to an incubate containing either 10 mmol/l barium or a control barium-free solution. After fixation in osmium tetroxide, there was no difference between the two groups; in both cases granules appeared more frequently the longer the time and the higher the temperature of incubation. In a further series where glutaraldehyde was the fixative, granules were identified in 23 out of 41 tissues incubated with barium, but in only 1 out of 41 control tissues (P less than 0.001). Electron probe microanalysis showed that granules in osmium-fixed tissues contained osmium as the main element, whereas granules in glutaraldehyde-fixed tissues which had been incubated with barium showed barium as the predominant cation. Thus mitochondrial granules can be reliable markers for heavy metal cations, but only under carefully controlled conditions.

Animals↗