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Biomedical subjects

M Brauer

Publications and source records attributed to M Brauer.

At least 37 records · Page 2Linked to original sources
PubMed2000

[First continuous nerve monitoring in thyroid gland surgery].

UNLABELLED: A new "all in one" sensing device was developed for continuous transtracheal intraoperative monitoring and in situ detection of the recurrent laryngeal nerve (RLN) during thyroid surgery. PATIENTS AND METHODS: The new system is based on a double-balloon endotracheal tube with integrated atraumatic stimulating and tracing electrodes. The recurrent laryngeal nerve is stimulated transtracheally and compound action potentials are recorded from the laryngeal muscles. Fifty-five patients were introduced into a phase-one clinical trial. Thirty-five patients with primary thyroid operations, 20 patients with reoperations, 10 of whom had neck dissections. All patients were evaluated laryngoscopically and phoniatrically by an ENT specialist before and after surgery. RESULTS: Compound muscle action potentials were recorded continuously during the whole operation and responded sensitively to tension and pressure to the nerve. There were no accidental permanent RLN palsies. CONCLUSION: The new system offers five advantages: (1) it is atraumatic; (2) it is easy to use; (3) it can monitor continuously with an audio feedback to the surgeon; (4) it works outside the operation field; and (5) it is highly sensitive, even indicating reversible irritation to the nerve.

Adult↗
PubMed2000

Exposure of chronic obstructive pulmonary disease patients to particulate matter: relationships between personal and ambient air concentrations.

Mot time-series studies of particulate air pollution and acute health outcomes assess exposure of the study population using fixed-site outdoor measurements. To address the issue of exposure misclassification, we evaluate the relationship between ambient particle concentrations and personal exposures of a population expected to be at risk of particle health effects. Sampling was conducted within the Vancouver metropolitan area during April-September 1998. Sixteen subjects (non-smoking, ages 54-86) with physician-diagnosed chronic obstructive pulmonary disease (COPD) wore personal PM2.5 monitors for seven 24-hr periods, randomly spaced approximately 1.5 weeks apart. Time-activity logs and dwelling characteristics data were also obtained for each subject. Daily 24-hr ambient PM10 and PM2.5 concentrations were measured at five fixed sites spaced throughout the study region. SO4(2-), which is found almost exclusively in the fine particle fraction and which does not have major indoor sources, was measured in all PM2.5 samples as an indicator of accumulation mode particulate matter of ambient origin. The mean personal and ambient PM2.5 concentrations were 18 micrograms/m3 and 11 micrograms/m3, respectively. In analyses relating personal and ambient measurements, ambient concentrations were expressed either as an average of the values obtained from five ambient monitoring sites for each day of personal sampling, or as the concentration obtained at the ambient site closest to each subject's home. The mean personal to ambient concentration ratio of all samples was 1.75 (range = 0.24 to 10.60) for PM2.5, and 0.75 (range = 0.09 to 1.42) for SO4(2-). Regression analyses were conducted for each subject separately and on pooled data. The median correlation (Pearson's r) between personal and average ambient PM2.5 concentrations was 0.48 (range = -0.68 to 0.83). Using SO4(2-) as the exposure metric, the median r between personal and average ambient concentrations was 0.96 (range = 0.66 to 1.0). Use of the closest ambient site did not improve the median correlation of the group for either PM2.5 or SO4(2-). All pooled analyses resulted in lower correlation coefficients than the median correlation coefficient of individual regressions. Personal SO4(2-) was more highly correlated with all ambient measures than PM2.5. Inclusion of time-activity and dwelling characteristics data did not result in a useful predictive regression model for PM2.5 personal exposure, but improved the model fit from simply regressing against ambient concentration (R2 = 0.27). The model for SO4(2-) was predictive (R2 = 0.82), as personal exposures were largely explained by ambient levels. These results indicate a relatively low correlation between personal exposure and ambient PM2.5 that is not improved by assigning exposure to the closest ambient monitor. The correlation between personal exposure and ambient concentration is high, however, when using SO4(2-), an indicator of accumulation mode particulate matter of ambient origin.

Aged↗
PubMed1999

[Hyponatremia and lung edema in endometrium ablation with rollerball ablation].

OBJECTIVE: Absorption of hypotonic irrigating solution with consecutive severe hyponatremia is a potential risk of the endometrial rollerball ablation procedure. MATERIAL AND METHODS: We report the case of a 45-year-old female, who underwent an endometrial rollerball ablation procedure. RESULTS: After irrigating the uterine cavity for 45 min with 10 1 of 2.7% Sorbitol and 0.54% Mannitol she developed clinical signs of pulmonary edema with severe hyponatremia. CONCLUSIONS: A TUR-like syndrome as a potential risk of the rollerball ablation procedure is discussed briefly. Strategies to minimize the risk and to early detect the TUR-like syndrome are suggested.

Dilatation and Curettage↗
PubMed1998

Kiln emissions and potters' exposures.

Some ten thousand British Columbia potters work in small private studios, cooperative facilities, educational institutions, or recreation centers. There has been considerable concern that this diffuse, largely unregulated activity may involve exposures to unacceptable levels of kiln emissions. Pottery kiln emissions were measured at 50 sites--10 from each of 5 categories: professional studios, recreation centers, elementary schools, secondary schools, and colleges. Area monitoring was done 76 cm from firing kilns and 1.6 m above the floor to assess breathing zone concentrations of nitrogen dioxide, carbon monoxide, sulfur dioxide, fluorides, aldehydes, aluminum, antimony, arsenic, barium, beryllium, boron, cadmium, chromium, cobalt, copper, gold, iron, lead, lithium, magnesium, manganese, mercury, nickel, selenium, silver, vanadium, and zinc. Personal exposures to the same metals were measured at 24 sites. Almost all measured values were well below permissible concentrations for British Columbia work sites and American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs) with the following two exceptions. A single firing duration (495 minute) acrolein measurement adjacent to an electric kiln (0.109 ppm) exceeded these guidelines. One 15-minute sulfur dioxide measurement collected adjacent to a gas kiln (5.7 ppm) exceeded the ACGIH short-term exposure limit. The fact that concentrations in small, ventilated kiln rooms ranked among the highest measured gives rise to concern that unacceptable levels of contamination may exist where small kiln rooms remain unventilated. Custom designed exhaust hoods and industrial heating, ventilating, and air-conditioning systems were the most effective ventilation strategies. Passive diffusion and wall/window fans were least effective.

Aerosols↗
PubMed1998

Chronic ethanol administration alters hepatic rates of glycerol phosphorylation and glycerol 3-phosphate oxidation: a dynamic in vivo 31P magnetic resonance spectroscopy study.

We used dynamic in vivo 31P magnetic resonance spectroscopy to noninvasively study the metabolism of glycerol by the liver in living rats, as a means of detecting subtle metabolic changes induced by chronic ethanol consumption. Rats subjected to chronic ethanol consumption and their pair-fed controls were given a metabolic load of glycerol (0.75 or 1.3 mL glycerol x kg body mass(-1), i.p. or i.v) under normoxic or hyperoxic (98% O2) conditions. Changes in the level of glycerol 3-phosphate were followed in situ by monitoring the hepatic 31P phosphomonoester resonance every 7 or 13 min for up to 330 min. When challenged with a large dose of glycerol, chronic ethanol-treated rats exhibited less accumulation of glycerol 3-phosphate than controls, independent of the route of administration of the glycerol or whether the two groups were fasted or fed. For example, 1.3 mL glycerol x kg(-1) i.v. under normoxic conditions resulted in a two-fold increase in phosphomonoester in ethanol-treated rats compared with a five-fold increase in controls. The ethanol-treated rats also showed a slower rate of phosphorylation of glycerol and slower oxidation of glycerol 3-phosphate than controls, indicating decreased activities of the glycerol kinase and glycerol 3-phosphate dehydrogenase steps, and hence slower glycerol utilization. The rate of glycerol utilization was dose and oxygen concentration dependent. Kinetic analysis indicated that the chronic ethanol-induced decrease in the glycerol 3-phosphate dehydrogenase reaction was due to a decreased rate of NADH reoxidation in the liver, likely owing to a decrease in oxygen supply or utilization in the ethanol-treated rats. These observations support the hypothesis of pre-existing hypoxia in rat liver after chronic ethanol administration. This study demonstrates the utility of dynamic in vivo 31P magnetic resonance spectroscopy in following the metabolism of a glycerol load as a sensitive, nonperturbing, and potentially clinically applicable test of liver function.

Adenosine Triphosphate↗
PubMed1998

Restaurant smoking restrictions and environmental tobacco smoke exposure.

OBJECTIVES: This study evaluated the effectiveness of smoking restrictions. METHODS: We measured particulate concentrations in restaurants with different levels of allowable smoking. RESULTS: Mean particulate concentrations were 70% higher in establishments without smoking restrictions compared with those with partial smoking restrictions. Concentrations in nonsmoking restaurants were reduced by an additional 20% to 30%. Measurements of cadmium, an environmental tobacco smoke (ETS) marker, implicated ETS as the major source of particulate in restaurants that allowed smoking. CONCLUSIONS: Partial smoking restrictions substantially reduce, but do not eliminate, ETS exposure in restaurants. Occupants of nonsmoking restaurants avoid ETS exposure but may experience substantial particulate exposures from cooking emissions.

Air Pollution, Indoor↗
PubMed1998

[Continuous monitoring of the recurrent laryngeal nerve].

A new "all in one" sensing device for tracing and continuous intraoperative monitoring of the recurrent laryngeal nerve during thyroid surgery is described. The system, based on a double ballooned endotracheal tube, is atraumatic, easy to use and sensitive even to imminent trauma to the nerves. The most striking feature of this instrument is that it operates outside the sterile operating field and truly monitors continuously throughout the operation.

Adult↗
PubMed1997

Nitrogen dioxide in indoor ice skating facilities: an international survey.

An international survey of nitrogen dioxide (NO2) levels inside indoor ice skating facilities was conducted. One-week average NO2 concentrations were measured inside and outside of 332 ice rinks located in nine countries. Each rink manager also completed a questionnaire describing the building, the resurfacing machines, and their use patterns. The (arithmetic) mean NO2 level for all rinks in the study was 228 ppb, with a range of 1-2,680 ppb, based on a sample collected at breathing height and adjacent to the ice surface. The mean of the second indoor sample (collected at a spectator's area) was 221 ppb, with a range of 1-3,175 ppb. The ratio of the indoor to outdoor NO2 concentrations was above 1 for 95% of the rinks sampled, indicating the presence of an indoor NO2 source (mean indoor:outdoor ratio = 20). Estimates of short-term NO2 concentrations indicated that as many as 40% of the sampled rinks would have exceeded the World Health Organization 1-hour guideline value of 213 ppb NO2 for indoor air. Statistically significant associations were observed between NO2 levels and the type of fuel used to power the resurfacer, the absence of a catalytic converter on a resurfacer, and the use of an ice edger. There were also indications that decreased use of mechanical ventilation, increased number of resurfacing operations per day, and smaller rink volumes were associated with increased NO2 levels. In rinks where the main resurfacer was powered by propane, the NO2 concentrations were higher than in those with gasoline-powered resurfacers, while the latter had NO2 concentrations higher than in those using diesel. Rinks where the main resurfacer was electric had the lowest indoor NO2 concentrations, similar to the levels measured outdoors.

Air Pollution, Indoor↗
PubMed1997

Analysis of nicotine and cotinine in the hair of hospitality workers exposed to environmental tobacco smoke.

The purpose of this study was to determine if hair nicotine and cotinine levels reflect relative exposure to environmental tobacco smoke (ETS) in subjects who worked in the hospitality industry, where public smoking was permitted. Hair samples from 26 subjects were analyzed by gas chromatograph/mass spectrometry techniques for nicotine and cotinine. An exposure gradient was shown for nicotine but not cotinine. Among nonsmokers, those working in bars where there are no public smoking restrictions had the highest hair nicotine levels, which were close to levels found in smokers. Nicotine measured in hair is useful as a biological marker for exposure to ETS from multiple sources. Bar workers in particular are exposed to high levels of ETS, which may adversely affect the health of nonsmokers.

Adult↗
PubMed1997

Human lung parenchyma retains PM2.5.

There is extensive epidemiologic evidence that increased levels of the inhalable particulate fraction of air pollution (PM10) are associated with increased morbidity and mortality. The mechanisms of these effects are unknown, and the exact types and sizes of particles responsible are a matter of intense dispute. To obtain an idea of the sizes of particles retained in human lung parenchyma, we used analytical electron microscopy to count, size, and identify particles in the upper lobe apical segment parenchyma of autopsy lung tissue from 10 never-smoking long-term residents of Vancouver. The overall geometric mean particle diameter (GSD) was 0.38 microm (2.4); within this broad distribution, silica and silicate particles had a geometric mean diameter of 0.49 microm (2.2), whereas metals had a geometric mean diameter of 0.17 microm (2.0). Ultrafine particles (those with diameter < or = 0.1 microm) constituted less than 5% of the total, and most of these were metals. Translation of these projected area diameters into aerodynamic diameters (d(a)) revealed that 96% of the particles had d(a) less than 2.5. These data indicate that human lung parenchyma effectively retains PM2.5, suggesting that attempts to determine the particles responsible for chronic particulate pollutant effects should concentrate on this size range. These data also suggest that several different type/size classes of particle are present in human parenchyma, but that ultrafine particles make up only a small fraction of the total.

Aged↗
PubMed1997

Endothelin-1 production during the acute chest syndrome in sickle cell disease.

To investigate the role of the endothelial-derived vasoactive mediator endothelin (ET-1) in the acute chest syndrome (ACS), we incubated bovine pulmonary artery endothelial cells (BPAEC) with red blood cells (equivalent to a hematocrit of 20%) and/or autologous plasma (1:10 dilution) from two patients during ACS and during routine clinic visits. Cellular RNA was analyzed for ET-1 transcripts by Northern analysis and ET-1 protein levels in BPAEC supernatants and in plasma measured by radioimmunoassay. ET-1 mRNA expression and protein levels increased in BPAEC exposed to plasma obtained during ACS; in contrast, exposure to plasma obtained during routine clinic visits did not alter BPAEC ET-1 mRNA expression or protein levels. Plasma ET-1 level was elevated during ACS, decreased during resolution, and remained slightly elevated during routine clinic visits. Plasma obtained from one patient 4 d prior to hospitalization for vasoocclusive crisis contained the highest ET-1 level and markedly increased BPAEC ET-1 mRNA expression and protein levels. In both patients, BPAEC ET-1 mRNA and protein expression in vitro and plasma ET-1 levels in vivo correlated with stage of disease and occurred in the absence of direct erythrocyte contact in vitro. These observations suggest that ET-1 production contributes to development of ACS.

Acute Disease↗
PubMed1997

The effects of hypoxia on the bioenergetics of liver in situ in chronic ethanol-treated rats: a noninvasive in vivo 31P magnetic resonance spectroscopy study.

OBJECTIVE: The effects of hypoxia on bioenergetic parameters of the livers of rats with and without chronic ethanol (CE) treatment has been studied in a totally noninvasive manner, using in vivo 31P magnetic resonance spectroscopy (MRS). METHOD: The effects of hypoxia (10% oxygen for 55 minutes) on the levels of ATP, inorganic phosphate (Pi), phosphomonoesters (PME) and phosphodiesters (PDE) were followed with time. The CE and control rats (four pairs) were starved for 16-20 hours to eliminate the effects of any ethanol still present within the liver. To complement the in vivo studies, perchloric acid extracts from rats (four pairs for each stage) at the three stages, initial (normoxic), hypoxic and recovery, were analyzed using in vitro high resolution 31P MRS. RESULTS: After hypoxic challenge, the hepatic Pi and PME levels increased much more significantly and more quickly for the CE rats compared to those of controls, and ATP levels decreased more dramatically for CE rats. The recoveries of Pi and PME levels after return to normoxic conditions were incomplete for the CE rats in contrast to the controls. The hepatic extract analyses showed that several different PMEs increased during hypoxia, including alpha-glycerophosphate, phosphocholine, AMP, IMP and glycolytic metabolites, and that total hepatic Pi increased during hypoxia in addition to cytoplasmic Pi. CONCLUSIONS: CE-treated rat livers in situ are bioenergetically more sensitive to a hypoxic challenge than are control rat livers, even in the absence of endogenous ethanol. This is consistent with a model of CE-induced liver damage in which CE-treated livers already have centrolobular hypoxia under normoxic conditions and cannot adequately compensate for additional hypoxic stress.

Adenosine Triphosphate↗
PubMed1996

Early detection of cancer cachexia in the rat using 31P magnetic resonance spectroscopy of the liver and a fructose stress test.

The dynamic metabolic effects of a fructose infusion challenge on hepatic intracellular levels of adenosine 5'-triphosphate (ATP), inorganic phosphate (Pi) and phosphomonoesters (PME) were monitored noninvasively by 31P MRS in a remote tumour-bearing rat model. Fisher male rats were inoculated with a methylcholanthrene-induced sarcoma. Seventeen rats were randomized into three groups: control (n = 6), low tumour burden (LTB, n = 6), or moderate tumour burden (MTB, n = 5). The LTB group had tumour burdens of 0.2-2.0% while the MTB group had tumour burdens of 2.6-5.7%. All rats were in the pre-clinical phase of cancer cachexia as determined by food intake and body weight. Rats were infused with 1.2 g/kg of fructose i.v. and the metabolic response of the liver was monitored with time over 1 h via 31P MRS. In all groups an immediate increase in hepatic levels of PME was noted, which returned to baseline values over the course of the experiment, reflecting the phosphorylation of fructose to fructose 1-phosphate. For the MTB rats, the return to baseline levels was more rapid than in the control or LTB group. All groups experienced a 20% decrease in hepatic ATP levels which did not return to baseline over the 1 h observation period. As well, all groups experienced an initial fall in Pi, which recovered to prefructose levels or greater. MTB rats demonstrated a 30-40% increase in Pi concentration and a 60-70% increase in Pi/ATP ratio after infusion with fructose as compared to LTB and control rats (ANOVA;p<0.05). This is consistent with cachexia-induced enhancement of hepatic gluconeogenic activity, and hence more rapid release of Pi from the phosphorylated metabolites in the MTB rats. Thus fructose infusion and hepatic 31P MRS permit pre-clinical detection of cancer cachexia as reflected by increased Pi generation and more rapid removal of PME.

Analysis of Variance↗
PubMed1996

31P magnetic resonance spectroscopy studies in schizophrenia.

Phospholipid metabolism abnormalities have been suggested by a number of postmortem brain and red blood cell studies in schizophrenia. 31P magnetic resonance spectroscopy enables the examination of phospholipid metabolism in living patients. These in vivo studies have demonstrated that schizophrenic patients have lower prefrontal levels of phosphomonoesters and higher levels of phosphodiesters compared to matched controls. Patients with psychotic depression also seem to show lower levels of phosphomonoesters compared to controls. This suggests that membrane phospholipid differences may not be specific to schizophrenia. Preliminary 31P magnetic resonance spectroscopy studies at high field strength on postmortem temporal lobe samples show no differences between treated schizophrenic patients and controls for phosphoethanolamine and phosphocholine which are the main constituents of the phosphomonoester peak. Further studies are underway in the prefrontal region. While 31P magnetic resonance spectroscopy studies have demonstrated membrane phospholipid abnormalities in schizophrenia, it is not clear whether these findings are specific to schizophrenia or part of a generalized membrane phospholipid abnormality.

Humans↗
PubMed1996

Electromyographic facial nerve monitoring during resection for acoustic neurinoma under moderate to profound levels of peripheral neuromuscular blockade.

The facial nerve is monitored intra-operatively using electromyography to identify and prevent damage during the excision of an acoustic neurinoma. In order to determine whether a profound level of peripheral neuromuscular blockade could be achieved without compromising facial electromyographic monitoring, 11 patients undergoing resection of acoustic neurinoma were studied. After induction of anaesthesia, an infusion of atracurium was administered to reduce the integrated electrically evoked muscle potential (EEMP) of the hypothenar eminence by 70-100%. The facial nerve was directly stimulated in the surgical field and the facial evoked muscle potentials (EMPs) were recorded. Even under complete peripheral neuromuscular blockade (i.e. no electrically evoked muscle potential measurable over the hypothenar eminence, no palpable hypothenar muscle response) it was possible to evoke facial muscle electromyographic responses by stimulation of the facial nerve.

Adult↗
PubMed1996

Ozone enhances the uptake of mineral particles by tracheobronchial epithelial cells in organ culture.

We have previously shown that the basal uptake of mineral particles by tracheobronchial epithelial cells in organ culture is mediated in part by active oxygen species (AOS) and can be greatly augmented by exposure to cigarette smoke, a concentrated source of AOS, and other radicals. We hypothesized that ozone, another generator of AOS in tissues, might have the same effect. To test this hypothesis, tracheal explants were exposed to room air (control) or ozone in varying concentrations from 0.01 to 1.0 ppm for 10 min, and subsequently to a suspension of either amosite asbestos or titanium dioxide (rutile) for 1 h. Explants were then transferred to an air/CO2 incubator for 1 wk to allow particle uptake to occur, and uptake was determined by morphometry. We found that ozone exposure increased the uptake of both asbestos and titanium dioxide in a dose-response fashion; this effect appeared at lower exposure levels and was more marked with titanium dioxide than with amosite. The ozone effect could be prevented by addition of catalase but not superoxide dismutase to the particle suspension, or by preincubation of the particles with deferoxamine. These observations indicate that ozone can directly increase uptake of mineral particles by tracheobronchial epithelial cells; this effect occurs with brief exposures at very low ozone levels and appears to be mediated by hydrogen peroxide and possibly by hydroxyl radical. These findings support the general hypothesis that AOS are important mediators of epithelial particle uptake in many different settings. Enhanced uptake may be one of the mechanisms by which ozone impairs particle clearance from the lung and may play a role in the increased morbidity seen in populations with exposure to high levels of both ozone and atmospheric particulates.

Animals↗
PubMed1996

Effect of ambient ozone exposure on lung function in farm workers.

Effects of ozone exposure on outdoor farm workers in the Fraser Valley of British Columbia, Canada, were investigated. Fifty-eight workers underwent spirometry daily before and after each 8- to 14-h workday from June 23 to August 26, 1993. The mean daily maximum (1 h) ambient ozone concentration was 40 ppb (range: 13 to 84 ppb). Concentrations of acid aerosols and fine particulates, potential confounders of ozone effects, were very low. In individual regressions of evening FEV1 and FVC on maximum daily ozone concentration, 47 of 53 workers with valid data (46 of 53 for FVC) had negative slopes. The average slopes (weighted by the inverse SE of the regression coefficients) were -3.3 and -4.7 ml for FEV1 and FVC, respectively, for each ppb increase in ozone (p < 0.001). Following correction for an individual's mean lung function level, date, and temperature, regression of either the afternoon or the daily change (afternoon-morning) corrected for the morning measurement of FEV1 and FVC on ozone showed similar magnitudes of effect. These associations were still apparent on the following morning, suggesting a persistent ozone effect. These results indicate that exposure of a population of outdoor workers to ambient ozone concentrations below 85 ppb is associated with decreased lung function over the day, which persists to the following day.

Adult↗