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Biomedical subjects

H Larsen

Publications and source records attributed to H Larsen.

At least 73 records · Page 4Linked to original sources
PubMed1980

Mutagenic action of isocyanates used in the production of polyurethanes.

Isocyanates used in the production of polyurethanes were investigated for mutagenic action in Salmonella typhimurium. These investigations showed that the most commonly used isocyanates, toluene diisocyanate (TDI) and 4,4'-methylene-diphenylisocyanate (MDI), are mutagenic. This effect can be ascribed to the amine analogues formed during the hydrolysis of isocyanates: TDI is mutagenic in TA 1538 and TA 98 after metabolic activation. This finding agrees with the results obtained with the amine analogue 2,4-toluenediamine. MDI, like the amine analogue 4,4'-methylenedianiline, is mutagenic in TA 100 after metabolic activation by rat liver enzymes (S-9 mix). A prepolymerized polyisocyanate of the MDI type is also mutagenic in assays using TA 100 and S-9 mix. It is concluded that isocyanates are potentially mutagenic and carcinogenic to man. In view of their widespread use in the work environment and in light of the high production figures for polyurethanes in industrialized countries, isocyanates must be considered to represent a serious health hazard.

Cyanates↗
PubMed1980

[Cardiorespirographic studies in prematures with apnea and bradycardia during spontaneous breathing and CPAP-therapy (author's transl)].

Cardiorespirographic studies were performed in 11 prematures with episodes of apnea and bradycardia (gestational age: x = 31 weeks, birth weight: x = 1390g). Total registration time was 90 h; 45 h during spontaneous breathing, 45 h during CPAP-treatment. Episodes of bradycardia occured three times more frequently than apnea. The frequency of apnea and bradycardia, the duration of bradycardia and the deceleration area were significantly reduced during CPAP-therapy, whilst the duration of apnea was not influenced. Estimation of deceleration areas as compared to measurements of bradycardia duration offers no further clinical advantage. Respiratory monitoring by impedance has to be supplemental or even replaced by beat-to-beat heart rate monitoring. Cardiorespirography allows assessment of frequency and degree of pathophysiological changes in heart rate and breathing patterns and should be supplemented by transcutaneous oxygen measurements.

Apnea↗
PubMed1979

Trimethylamine oxide: a terminal electron acceptor in anaerobic respiration of bacteria.

Trimethylamine oxide (TMAO) stimulated both the anaerobic growth rate and the growth yield of Proteus NTHC 153. The molar growth yield from glucose and pyruvate in tryptone/yeast extract medium doubled in the presence of TMAO, and the organism grew anaerobically on the non-fermentable substrates L-lactate and formate when TMAO was added to the medium. We conclude that TMAO stimulated growth by serving as a terminal electron acceptor in an oxidative phosphorylation process.

Anaerobiosis↗
PubMed1979

Interrelationships between skeletal muscle adaptations and performance as studied by detraining and retraining.

The effects of 15 days of detraining and 15 days of retraining were studied in 6 well-trained runners. Detraining resulted in significant decreases in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) of 24% and 13% respectively, but no significant increases in these enzymes activities occured with retraining. Maximal oxygen uptake (VO2 max) decreased by 4% with detraining (p less than 0.05), and increased by a similar amount with retraining. Performance time in an intense submaximal run decreased by 25% (p less than 0.05) with inactivity, but still averaged 9% below the initial level after retraining. Maximal heart rate and peak heart rate during the performance run were higher after detraining by 4 and 9 beats per min, respectively (p less than 0.05). With retraining, these heart rate values were decreased by 7 and 9 beats per min (p less than 0.05). Blood lactate concentrations after the VO2 max and performance run were approximately 20% lower after detraining and retraining (p less than 0.05). Muscle fibre areas for three subjects tended to be larger in biopsy samples taken after detraining and retraining. These data suggest that even short periods of detraining result in significant changes in indices of physiological capacity and function in subjects near their upper limit of adaptation, and that a longer period of retraining is necessary for muscle to re-adapt to its original trained state.

Adaptation, Physiological↗
PubMed1979

Evaluation of tcPO2, beat-to-beat heart rate and respiration in neonates with episodes of cyanosis, bradycardia, or apnea.

Episodes of cyanosis, bradycardia, or apnea were studied in 26 newborns and prematures by continuous recording of tcPO2, beat-to-beat heart rate, and impedance pneumography. Hypoxemia related to therapeutic, diagnostic, or care procedures is very common and often is not accompanied by bradycardia or apnea. Idiopathic bradycardia lasting less than 30 seconds will not lead to hypoxemia. However, idiopathic bradycardia of more than 30 seconds' duration can lead to hypoxemia. Beat-to-beat cardiograms and transcutaneous oxygen measurement appear to be the most reliable methods for routine monitoring of these patients.

Apnea↗
PubMed1975

Halobacterium volcanii spec. nov., a Dead Sea halobacterium with a moderate salt requirement.

A halophilic bacterium was isolated from bottom sediment from the Dead Sea. The organism possessed the properties of the halobacteria, but differed from the known species in two important respects, 1) the cells were disc shaped and often cupped when grown under optimum conditions, 2) the optimum requirements for sodium chloride was in the range 1.7--2.5 molar which is about half of that generally reported for the halobacteria. The organism was assigned to the genus Halobacterium and described as Halobacterium volcanni spec. rov. The optimum sodium chloride concentration for growth was close to that found in the Dead Sea. The tolerance for magnesium chloride was very high; the organism grew well in media containing magnesium chloride in the concentrations found in the Dead Sea. Halobacterium volcanii is therefore remarkably well fitted for life in the Dead Sea.

Amino Acids↗
PubMedDate not supplied

Low cost housing.

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Denmark↗