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Biomedical subjects

T Madsen

Publications and source records attributed to T Madsen.

At least 37 records · Page 2Linked to original sources
PubMed1992

Anaerobic transformation and toxicity of trichlorophenols in a stable enrichment culture.

The transformation and toxicity of trichlorophenols (TCPs) were studied with a methanogenic enrichment culture derived from sewage sludge. Transformation of TCPs rapidly resumed after heating of the culture at *) degrees C for 1 h, suggesting that the dechlorinating bacteria are spore-forming anaerobes. 2,4,6-TCP was rapidly dechlorinated via 2,4-dichlorophenol to 4-chlorophenol. During the transformation of 2,4,6-TCP, the most probable number of dechlorinating bacteria increased by 4 orders of magnitude. The most extensive dechlorination was observed in media with complex carbon sources such as yeast extract, peptone, and Casamino Acids, but glucose, galactose, and lactose were also used by the consortium. Experiments using chloramphenicol indicated that the reductive dechlorination of 2,4,6-TCP was regulated by an inducible enzyme system. The highest initial concentration at which dechlorination of 2,4,6-TCP was observed was 400 microM. 2,4,5-TCP and 3,4,5-TCP were dechlorinated to, respectively, 3,4-dichlorophenol and 3-chlorophenol at initial concentrations of less than or equal to 40 microM. Toxicity for the acid-producing and methanogenic bacteria in the consortium was a function of chemical structure, as the inhibition of these activities increased from 2,4,6-TCP, via 2,4,5-TCP, to 3,4,5,-TCP.

Biotransformation↗
PubMed1992

Isolation and characterization of an anaerobic chlorophenol-transforming bacterium.

An obligately anaerobic bacterium which transforms several chlorinated phenols was isolated. Dechlorination of the substituents ortho to the phenolic OH group was preferred, while removal of a meta-substituted chlorine was observed only with 3,5-dichlorophenol. The bacterium was a gram-positive, endospore-forming, motile, slightly curved rod. Sulfate was not reduced. Nitrate was reduced via nitrite to ammonium. The bacterium is related to the genus Clostridium. The highest growth rate was obtained in a medium containing pyruvate and yeast extract. Pyruvate supported growth as the sole source of carbon, and the fermentation of pyruvate produced almost equimolar amounts of acetate.

Bacteria, Anaerobic↗
PubMed1992

Effect of acid-base management with or without carbon dioxide on plasma phosphate concentration during and after hypothermic cardiopulmonary bypass.

Variations of the phosphate concentration in plasma were studied in two groups of 12 patients undergoing cardiac surgery with hypothermic cardiopulmonary bypass (CPB). Management of the acid-base status differed between the groups, according to whether or not carbon dioxide was added to the anesthetic gas mixture during hypothermia ('pH-stat' vs. 'alpha-stat' mode) following correction vs. no correction of pCO2 and pH for body temperature. Phosphate variations throughout the study were mostly within normal limits. From the start to the end of CPB, the mean rise in phosphate levels was 70% in the pH-stat group and 37% in the alpha-stat group (p < 0.001). During 3 hours after CPB, the phosphate values continued to rise by a mean of 25% in the alpha-stat patients, but fell by a mean of 3% in the pH-stat patients (p < 0.001). Such different phosphate patterns during and immediately after CPB may reflect profound metabolic disturbances and may be related to the altering effects of CO2 addition and respiratory acidosis on intracellular metabolic activity and phosphate homeostasis.

Acid-Base Equilibrium↗
PubMed1991

Effects of sulfuroxy anions on degradation of pentachlorophenol by a methanogenic enrichment culture.

We studied the degradation of pentachlorophenol (PCP) under methanogenic and sulfate-reducing conditions with an anaerobic mixed culture derived from sewage sludge. The consortium degraded PCP via 2,3,4,5-tetrachlorophenol, 3,4,5-trichlorophenol, and 3,5-dichlorophenol and eventually accumulated 3-chlorophenol. Dechlorination of PCP and metabolites was inhibited in the presence of sulfate, thiosulfate, and sulfite. A decrease in the rate of PCP transformation was noted when the endogenous dissolved H(2) was depleted below 0.11 muM in sulfate-reducing cultures. The effect on dechlorination observed with sulfate could be relieved by addition of molybdate, a competitive inhibitor of sulfate reduction. Addition of H(2) reduced the inhibition observed with sulfuroxy anions. The inhibitory effect of sulfuroxy anions may be due to a competition for H(2) between sulfate reduction and dechlorination. When cultured under methanogenic conditions, the consortium degraded several chlorinated and brominated phenols.

Journal Article↗
PubMed1991

Ambulatory 23 hour recording of intraoesophageal pressures in normal volunteers: a propagation analysis from one proximal and two distal recording sites.

pH data were obtained from one level and pressure data from three levels in the oesophagus over 23 hours in 24 healthy volunteers, followed by automatic propagation analysis of motility data and analysis of time with pH less than 4. Apart from periods of meal ingestion, isolated pressure complexes were found more frequently in the distal than in the proximal oesophagus. This was especially common in the recumbent position at night. Most contractions of the proximal oesophagus were propagating. In the distal oesophagus were propagating. In the distal oesophagus propagating pressure waves were more frequent during the day than during the night and most frequent during meals. The state of consciousness rather than body position per se is important in determining the frequency of simultaneous contractions in the distal oesophagus.

Adult↗
PubMed1990

Reflux patterns and related oesophageal motor activity in gastro-oesophageal reflux disease.

Simultaneous intraoesophageal pH and pressure monitoring were performed for 12 hours in 20 patients with abnormal acid gastrooesophageal reflux or oesophagitis and in 10 healthy volunteers to determine characteristic reflux patterns with time. Increased acid exposure was not the only factor that characterised patients with oesophagitis. Indeed an overlap existed between patients with and without oesophagitis regarding total acid exposure time. Patients with oesophagitis suffered reflux nearly as much at night and in the morning as during the postprandial period. They also had as much reflux as a result of small and slow changes in pH around the pH limit of 4 as they had due to proper reflux episodes. This did not change over time after the postprandial period. More 12 hour acid exposure was related to more frequent night time reflux. In normal subjects compared with patients reflux triggered increased contractile activity, and contractile activity at a normal pH was greater in patients than in normal subjects.

Adult↗
PubMed1990

Open-heart surgery in Jehovah's Witnesses.

During a 7-year period, 11 adult members of the religious sect Jehovah's Witnesses underwent cardiac surgery with extracorporeal circulation. No homologous blood transfusions were given. Blood-conserving procedures were employed, viz. initial collection of autologous blood, haemofiltration or processing (Cell Saver) of blood collected during extracorporeal circulation and reinfusion of shed mediastinal blood. The total perioperative blood loss averaged 1080 ml (15 ml/kg body weight), equalling 19% of total body blood volume. The mean haemoglobin on discharge from hospital was 11.0 g/100 ml. There was no perioperative mortality. Postoperative pulmonary function was good and there was no serious morbidity. Jehovah's witnesses with serious, surgery-necessitating heart disease can be offered operation comprising recognized blood-conserving procedures.

Blood Loss, Surgical↗
PubMed1989

Effects of erythrocytes, bicarbonate, temperature and albumin on in vitro ionized calcium variations with pH.

Using a heart lung machine as an in vitro model, the relation between ionized calcium (cCa2+) and pH has been shown to depend on several variables such as erythrocytes, temperature and albumin as well as the total calcium and bicarbonate concentrations. The respiratory acid-base disturbances were simulated by changing the gas flow between 1.0 and 2.41 min-1 by adding CO2, to the machine at a concentration of 0 to 17%. When pCO2 was used to alter pH, cCa2+ varied from 0.16 mmol l-1 per pH unit to 0.52 mmol l-1. The regression slope of cCa2+ on pH was made steeper by decreasing erythrocyte volume fraction and by increasing temperature and the concentrations of HCO3, calcium or albumin. The metabolic acid-base alterations were produced by HCl or NaHCO3 at a constant gas flow, cCA2+ changes per pH unit were 0.70 mmol l-1 in plasma and 1.04 mmol l-1 in whole blood. The different results found in plasma and in erythrocyte fluids may be explained by their different buffering capacity. Haemoglobin may buffer hydrogen ions, and the formation of HCO3- is catalysed by carbonic anhydrase from the red cells.

Acid-Base Equilibrium↗
PubMed1988

In vivo and in vitro ionized calcium variations induced by acute respiratory acid base disturbances.

The effects of acute respiratory acid base changes on the ionized calcium concentration were studied in mechanically ventilated patients and compared to the results which were found using an in vitro model. In both in vivo and in vitro studies, the ionized calcium changes correlated negatively with the pH variations. The good agreement between the in vivo and in vitro investigations showed a mean ionized calcium change of 0.40 mmol/l per pH unit. At the same time, the ionized calcium changes correlated positively with the changes of plasma bicarbonate. The mean ionized calcium change was 0.01 mmol/l per mmol/l bicarbonate variation. During respiratory acid base disturbances, the ionized calcium variations due to the competitive albumin binding between hydrogen and calcium ions are buffered and blunted by the bicarbonate ions.

Acid-Base Imbalance↗
PubMed1988

Therapeutic consequences of oesophageal function studies in patients with benign oesophageal disease.

Evaluation of oesophageal function was performed in 91 patients referred to a specialized department of cardiothoracic surgery for surgical treatment of benign oesophageal disease. Standard manometry was used in addition to radiology and endoscopy, and in some patients, an acid perfusion test, an acid clearing test, and a prolonged monitoring of pH in the distal oesophagus were additionally performed. The aim of this study was to evaluate whether assessment of oesophageal function is needed in such a patient group, and whether the results of these investigations were taken into account when making the final decision for therapy. Eleven percent of the patients referred with a diagnosis of hiatal hernia or reflux had achalasia or oesophageal spasm. Nine percent of the patients referred for motility disorders had reflux-related disease. The referral diagnosis was changed to a diagnosis with a different therapeutic approach in 16% of the patients. In 33%, a diagnosis of disordered oesophageal function was considered either at referral or during the routine assessment for oesophageal disease. Eighty-one percent of the patients with achalasia were treated in accordance with the manometric results. In all cases where an anatomical diagnosis was replaced by a diagnosis of disordered function, the treatment was in accordance with the findings of the motility studies. None of the patients with oesophageal spasm were suspected of having this disease. It is concluded, that not only anatomical features, but also functional considerations have to be taken into account when selecting treatment for benign oesophageal disease. Treatment failure and unnecessary surgical intervention can thus be avoided.

Adolescent↗
PubMed1988

Calcium, magnesium and phosphate during and after hypothermic cardiopulmonary bypass without temperature correction of acid base status.

The plasma concentration variations of calcium, magnesium and phosphate were studied in ten patients during and after hypothermic cardiopulmonary bypass (CPB) without temperature correction of acid base status. During the study, pH remained stable, but all the other studied components varied significantly (P less than 0.001). At the start of CPB, the mean ionized calcium concentration increased 25%, and magnesium and phosphate decreased 29% and 40%, respectively, from their control values. At the end of blood cooling, ionized calcium was still 11% above its initial value, magnesium 50% above, and phosphate 39% below. Before weaning from CPB, ionized calcium remained 10% above its initial level, magnesium 41% above, and phosphate 26% below. After CPB, the different divalent ions returned to their initial levels within 1 h for ionized calcium, 6 h for phosphate and 9 h for magnesium. One day post-CPB, ionized calcium was at its start level, magnesium 13% lower, and phosphate 36% higher. During cardiac surgery, the acid base regulation without temperature correction (so-called "alpha stat mode") avoided the appearance of carbon dioxide acidosis. There were widespread disturbances of the divalent ions concentrations, due principally to the different fluids used during CPB, pump priming fluids and cardioplegic solution.

Acid-Base Equilibrium↗
PubMed1988

The influence of age on esophageal acid defense mechanisms and spontaneous acid gastroesophageal reflux.

Association of age with gastroesophageal pH and motor parameters have been searched for previously, but most studies have been cross-sectional. The aim of the present investigation was to evaluate the influence of age on gastroesophageal sphincter pressure, acid clearing ability, and acid gastroesophageal reflux in the same group of normal subjects. Ten healthy subjects were investigated in the period May 4, 1977, to February 18, 1978, and reinvestigated in the period August 19, 1985, to January 29, 1986. The median interval between the two investigations was 8.0 yr, range 7.7-8.5 yr. There were eight men and two women, with a median age at the second investigation of 36 yr, range 30-53 yr. Measurement of gastroesophageal sphincter pressure (GESP) and an acid perfusion test were performed, and within the same week, an acid-clearing test and a prolonged monitoring of pH in the distal part of the esophagus were carried out (5 cm proximally to the GES). pH monitoring was initiated between 7 and 8 PM and terminated between 7 and 8 AM. There were no changes in GESP between the two investigations. All had a normal acid perfusion test in both investigations. No changes in acid-clearing ability could be demonstrated. Similarly, the number of reflux episodes, as well as the duration of acid reflux, were unchanged. Integration of the pH curve for pH values less than or equal to 4 gave similar results at both occasions. In addition, the relative time with pH values less than or equal to 4 was unchanged. The acidity of the potential reflux material did not change over time, as evaluated by intragastric pH before and after monitoring. In conclusion, this study did not demonstrate any influence of age on esophageal acid defense mechanisms or spontaneous gastroesophageal reflux.

Adult↗
PubMed1987

Natural killer cell activity and lymphocyte function during and after coronary artery bypass grafting in relation to the endocrine stress response.

The effects of elective coronary artery bypass grafting (CABG) and the associated endocrine stress response on natural killer (NK) cell activity in peripheral blood, the distribution of lymphocyte subpopulations, and the phytohemagglutinin (PHA)-induced lymphocyte transformation were studied in 20 patients anesthetized with either etomidate-high dose fentanyl (75-125 micrograms . kg-1) or midazolam-low dose fentanyl (less than 20 micrograms . kg-1). The endocrine response to surgery was measured as changes in serum cortisol, plasma epinephrine, and norepinephrine. Compared with control values, a significant increase of NK cell activity was found in both groups prior to induction of anesthesia, followed by a decrease after induction until initiation of cardiopulmonary bypass (CPB) and a gradual increase to levels exceeding controls during CPB. Postoperatively, NK cell activity and the lymphocyte transformation to PHA stimulation were significantly depressed for at least 1-3 days. These changes were accompanied by severe lymphopenia affecting the T-lymphocytes (T3, T4, and T8) and the NK cells (Leu 11). Apart from a delayed cortisol increase in the etomidate group, the endocrine response showed a similar pattern in the two groups. Compared with control values, a significant decrease in the serum cortisol until CPB could be demonstrated, followed by a significant increase persisting for at least 6 days postoperatively. The plasma catecholamines showed a steep rise and, consequently, a significant increase during CPB, followed by a gradual return to control values in the postoperative period. The results indicate that, in patients undergoing CABG, immune surveillance is impaired prior to CPB and during the early postoperative period.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1987

Relationship between spontaneous non-propagating pressure activity in the oesophagus and acid gastro-oesophageal reflux in pathological and non-pathological refluxers.

To evaluate the oesophageal motor activity preceding episodes of reflux, 10 pathological and 10 non-pathological refluxers and 26 normal subjects were investigated. The pressure events in spontaneous short periods of pressure activity (less than or equal to 60 sec) and in long activity periods were registered. The last contraction before reflux was more frequently found non-propagating than the last contraction of pressure periods not followed by reflux (p less than 0.01). The interval from the last contraction to reflux was shortest, if the contraction terminated in, or confined to the upper part of the oesophagus (p less than 0.001). Increased proportion of reflux episodes were preceded by an upper segmentary contraction (p less than 0.05) and a short activity period (p less than 0.02) in patients with pathological reflux in comparison with non-pathological refluxers. Spontaneously occurring sphincter relaxations might be triggered by preceding non-propagated contractile activity. The relative number of reflux episodes preceded by non-propagated pressure activity seems to be increased in patients with frequent episodes of acid reflux, compared with patients with infrequent episodes, or with normal subjects.

Adult↗
PubMed1987

Effect of cisapride on the gastro-oesophageal function in normal human subjects.

The aim of this study was to investigate oesophageal peristalsis and gastro-oesophageal function in normal subjects after 4 days of cisapride 10 mg p.o. 3 times/day and 10 mg 1.5 h before the investigation. The study was carried out in a double-blind cross-over design with coded cisapride or placebo tablets. Basal sphincter pressure increased after cisapride (p less than 0.002). The peristaltic pressure amplitude in the oesophageal body as well as the duration and velocity of the peristaltic pressure wave were measured after wet swallows. No changes were found. Intragastric pH was unchanged after cisapride. No effect was found on the result of a standard acid clearing test. Plasma concentration of cisapride did not correlate with any of the other variables. Oral cisapride increases fasting gastro-oesophageal sphincter pressure, but does not influence oesophageal peristalsis, acid clearing or intragastric pH in normal subjects.

Adult↗
PubMed1987

Acid gastro-oesophageal reflux and oesophageal pressure activity during postprandial and nocturnal periods. A study in subjects with and without pathologic acid gastro-oesophageal reflux.

The aim of the investigation was to evaluate the relative quantity of acid gastrooesophageal reflux during different time periods in subjects with and without pathologic reflux. Twenty duodenal ulcer patients, 10 with and 10 without pathologic acid gastro-oesophageal reflux, and 26 asymptomatic volunteers were subjected to 12 h of simultaneous monitoring of pH and pressure activity in the oesophagus. The monitoring period was divided into a 3-h postprandial period, a night period of 6 h, and a 3-h period in the morning. The highest reflux frequency and the longest duration of oesophageal acid exposure were found in the postprandial hours (p less than 0.001). Thereafter, all groups had an even reduction in reflux rate. A greater absolute reduction in the duration of oesophageal acid exposure could be measured in patients with pathologic reflux as compared with the other groups (p less than 0.001). In spite of this, both reflux frequency and time with acid in the oesophagus were increased during the night in patients with pathologic reflux (p less than 0.001). Pathologic refluxers had in total 11 times as much reflux as normal subjects, and in addition 37.9% of the reflux took place during the 6 night hours. In contrast, only 5.4% of the reflux recorded in normal subjects occurred during this period. The pressure activity during periods with a normal intraoesophageal pH was reduced in all three groups during the night (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Neutrophil lysosomal enzyme release and complement activation during cardiopulmonary bypass.

Complement activation and neutrophil degranulation were concomitantly studied during uncomplicated cardiopulmonary bypass (CPB). Plasma concentrations of complement factor C4, complement split product C3d, the neutrophil lysosomal enzyme elastase complexed with alpha 1-proteinase inhibitor (PI) and fibronectin were measured in 12 patients, C3d and elastase/PI increased significantly during CPB (volume-corrected results). The C3d rise was almost linear, whereas elastase/PI showed exponential increase. Mean elastase/PI and mean C3d concentrations at different times during CPB covaried closely. The study showed that during CPB neutrophil lysosomal enzyme release is intimately related to complement activation, although activation of the two systems may be caused by a common third activator within the extracorporeal circuit.

Adult↗