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Biomedical subjects

M Meyer

Publications and source records attributed to M Meyer.

At least 505 records · Page 28Linked to original sources
PubMed1989

Helium and SF6 washout from dog lungs during high-frequency ventilation.

Simultaneous washout of He and SF6 was studied in anesthetized paralyzed dogs (mean body weight 19 kg) subjected to high-frequency ventilation at varying frequencies (10-40 Hz), stroke volumes (20-40 ml), lung volumes (0.8-1.2 L) and fresh gas flow rates (7-13 L/min). The washout curves could be analyzed into three exponential components for both test gases. The rate constants of the intermediate and slow components were slightly but significantly higher for He than for SF6 while the fast component was the same for the two test gases. The data were analyzed on the basis of a series lung model with a dead space compartment and two serially arranged alveolar compartments. The He/SF6 ratio of the effective conductances for gas transfer between the alveolar compartments averaged 1.15 +/- 0.08 (SD). Since this ratio is much closer to unity, predicted for convective transport, than 6 to 7, predicted for diffusive transport, it is concluded that during high-frequency ventilation gas transport in peripheral airways occurs by both convection and diffusion, convection being quantitatively more important.

Animals↗
PubMed1989

Chlamydia trachomatis infection in a male college student population.

Male university students were studied to evaluate the merit of routine screening for chlamydia urethritis. Two hundred fourteen sexually active male students answered a questionnaire about symptoms of urethritis and exposure to and treatment for sexually transmitted diseases (STDs). All subjects were screened for chlamydia by enzyme immunoassay (Chlamydiazyme, Abbott Laboratories). Overall, Chlamydiazyme was positive in 42 of 214 subjects (19.6%). Eighty-six subjects had no symptoms and no history of untreated exposure to STD; 6 of these had positive Chlamydiazyme assays. Based on our results, we conclude that the proportion of male urethral chlamydia infections that are asymptomatic may be much higher than has previously been believed. We further conclude that asymptomatic sexually active male students on this campus are a high-risk population for whom routine chlamydia screening is appropriate.

Adolescent↗
PubMed1989

Cardiogenic mixing: mechanisms and experimental evidence in dogs.

Cardiogenic mixing was studied in seven anaesthetized closed-chest dogs undergoing mechanical ventilation by comparing single-breath washout of two poorly soluble inert gases of widely differing diffusivities (helium (He) and sulphur hexafluoride (SF6)) in normal conditions with the heart beating (control), and during reversible temporary myocardial arrest (heart arrest). Cardiac arrest of approximately 20 s duration was induced repeatedly (8-15 times) by intracoronary injection of acetylcholine (approximately 35 mg) facilitated by a non-occluding 7-French gauge angiographic catheter maintained in the left coronary artery. After equilibration of lung gas with 1% helium and 1% SF6, single breath, constant flow expirograms were recorded in the tracheal tube by mass spectrometry after inspiration of test gas-free air. Series deadspace (VD) and relative alveolar slope (S) (increment of expired partial pressure, normalized to mixed expired-inspired partial pressure difference per increment of expired volume (S = (delta P/(PE-P1]/delta VE litre-1], were determined as indices for intrapulmonary gas mixing. The effects attributable to the action of the heart were quantified by the heart arrest: control ratio of VD and S, which were not significantly different from unity (P greater than 0.05) (VD: 0.95 (SD 0.05) for helium and 0.94 (0.07) for SF6; S:1.03 (0.10) for helium and 1.05 (0.14) for SF6. The He:SF6 ratios of VD and S (0.90 and 0.64, respectively), indicating diffusion dependent separation of gases, also were unaffected by the mechanical action of the heart. The data indicate that convective mixing by the mechanical action of the heart did not significantly enhance intrapulmonary mixing and transport.

Acetylcholine↗
PubMed1989

Eyelid reconstruction using temporalis fascia.

A case is reported of traumatic full-thickness loss of half the upper eyelid. The defect was reconstructed using a pedicled temporalis fascial flap in conjunction with a skin graft. The method is useful when more standard forms of reconstruction are impossible. The advantages of using temporalis fascia and some pitfalls are described.

Adolescent↗
PubMed1989

Pulmonary gas exchange in panting dogs: a model for high frequency ventilation.

Panting in animals can be expected to represent a naturally occurring physiological counterpart to today's techniques of mechanical high-frequency ventilation. To analyze the mechanisms underlying the gas exchange inefficiency during ventilation with high frequencies, steady-state pulmonary gas exchange was studied in seven conscious dogs (32 kg mean body weight) during panting elicited by mild thermal stress. The animals had a chronic tracheostomy and an exteriorized carotid artery loop and were exposed to 27.5 degrees C ambient temperature for 2 h (65% relative humidity). Open-circuit techniques were used and PO2 and PCO2 from the tracheostomy tube were continuously monitored by mass spectrometry using a special sample-hold phase-locked gas sampling technique. PO2 and PCO2 were determined in arterial blood collected from the carotid artery. During the exposure, the following variables of steady-state gas exchange were determined (means +/- SD): breathing frequency 313 +/- 19 min-1; tidal volume, 167 +/- 21 ml; total ventilation, 52 +/- 9 l.min-1; effective alveolar ventilation, 5.5 +/- 1.3 l.min-1; partial pressures (torr; a, arterial; E', end-tidal): PaO2, 106.2 +/- 5.9; PaCO2, 27.2 +/- 3.9; (PE'-Pa)O2, 26.0 +/- 5.3; (Pa-PE')CO2, 14.9 +/- 2.5. According to the conventional lung model, parallel-dead space ventilation (ventilation of unperfused lung regions) would account for about 55% of the alveolar ventilation and for 2/3 of the (PE'-Pa)O2 difference. However, the lack of an 'alveolar plateau' in the CO2 and O2 expirograms suggests that incomplete serial mixing in peripheral airways contributes to the enhanced gas exchange inefficiency during panting as reflected in the increased blood/gas differences for O2 and CO2.

Animals↗
PubMed1989

Pulmonary gas exchange in panting dogs.

Pulmonary gas exchange during panting was studied in seven conscious dogs (32 kg mean body wt) provided with a chronic tracheostomy and an exteriorized carotid artery loop. The animals were acutely exposed to moderately elevated ambient temperature (27.5 degrees C, 65% relative humidity) for 2 h. O2 and CO2 in the tracheostomy tube were continuously monitored by mass spectrometry using a special sample-hold phase-locked sampling technique. PO2 and PCO2 were determined in blood samples obtained from the carotid artery. During the exposure to heat, central body temperature remained unchanged (38.6 +/- 0.6 degrees C) while all animals rapidly switched to steady shallow panting at frequencies close to the resonant frequency of the respiratory system. During panting, the following values were measured (means +/- SD): breathing frequency, 313 +/- 19 breaths/min; tidal volume, 167 +/- 21 ml; total ventilation, 52 +/- 9 l/min; effective alveolar ventilation, 5.5 +/- 1.3 l/min; PaO2, 106.2 +/- 5.9 Torr; PaCO2, 27.2 +/- 3.9 Torr; end-tidal-arterial PO2 difference [(PE' - Pa)O2], 26.0 +/- 5.3 Torr; and arterial-end-tidal PCO2 difference, [(Pa - PE')CO2], 14.9 +/- 2.5 Torr. On the basis of the classical ideal alveolar air approach, parallel dead-space ventilation accounted for 54% of alveolar ventilation and 66% of the (PE' - Pa)O2 difference. But the steepness of the CO2 and O2 expirogram plotted against expired volume suggested a contribution of series in homogeneity due to incomplete gas mixing.

Acepromazine↗
PubMed1989

Elastase and papain inhibition by serum of mammals.

The protease-antiprotease imbalance concept has gained wide acceptance in reference to experimental animal models of human pulmonary emphysema. The destructive process may be induced by proteolytic enzymes such as porcine pancreas elastase (E) or papain (P), or by oxidants such as chloramine T (CT) which cause inactivation of alpha-1-antiprotease. The susceptibility to development of severe emphysema has been found to differ among animal species. We investigated the inhibition of elastase and papain by serum of seven species (rat, dog, human, rabbit, sheep, hamster, mini pig) and the effect of CT on serum inhibition. The relative inhibitor concentration of serum was expressed in terms of its inhibitor capacity for elastase and papain (EIC and PIC) defined as number of inhibited units (U) of enzyme catalysed hydrolysis of chromogenic peptide substrate (SAPNA and BAPNA) per unit of serum. The effect of CT on enzyme inhibition was quantified in terms of fractional loss of inhibition relative to control. The serum concentration of inhibitor was highest in the rat (EIC 8642 +/- 989 microU/microliter, PIC 214.2 +/- 110.3 microU/microliter; means +/- SD). Next in order of decreasing EICs were dog, human, rabbit, sheep, hamster, and mini pig exhibiting the lowest EIC (2523 +/- 184 microU/microliter) while sheep had lowest PIC (39.6 +/- 3.5 microU/microliter). The EIC/PIC ratio varied from 20 (mini pig) to about 100. The reduction of elastase inhibition after CT exposure of serum was high (80-100%) in rat, dog, human, and hamster, moderate (40%) in mini pig and rabbit, and low (10%) in sheep. Because papain was directly affected by CT the effect of CT on papain inhibition could not be analysed. The data suggest that the intrinsic antiprotease and antioxidant screen varies among experimental animals. For the purpose of animal models of emphysema, hamster appears to be most susceptible to the progressive destruction of lung parenchyma elicited by experimental burden of proteases or oxidants.

Animals↗
PubMed1989

[Diagnosis of deficiency in cofactor of phenylalanine hydroxylase: a metabolic emergency].

We report on two cases of children suffering from biopterin synthetase deficiency. Both were treated with the same treatment schedule with biopterin and neurotransmitters: 6-hydroxytryptophan and dihydrophenylalanine (DOPA). The only difference between the two cases is the time of diagnosis and therefore of treatment. The child who was treated early has a normal neurologic development. The other one has been treated since he was 7 months old and is mentally deficient (DQ = 0.60). This older child also suffers from dystonia probably secondary to Levodopa treatment. The authors emphasize the uncertainty of these patient's evolution owing to complications of the disease itself or those due to prolonged treatment by neurotransmitters.

5-Hydroxytryptophan↗
PubMed1989

[Possible decontamination of pancreatin with gamma rays and chemical agents].

Certain pre-conditions given, the microbial contamination of pancreatin in powder form can be reduced below international standard values. However, each of the methods whether physical or chemical, causes a variable loss of activity depending on the methods applied and the concentration of the decontaminating agent used. Therefore during preparation of this complex enzymatic compound, highly aseptic conditions must be kept in all stages of the process to avoid an increase of germal contamination. For a final toxicological assessment of the decontaminated products, further tests are required.

Chromatography, High Pressure Liquid↗
PubMed1988

A new genetic fibrinogen variant (fibrinogen Erfurt I). Structurally characterized by an abnormal B beta-chain and present both in plasma and platelets.

An abnormal fibrinogen was discovered in the plasma of a clinically asymptomatic woman. This fibrinogen variant was analyzed by high resolution two-dimensional gel electrophoresis and its molecular abnormality established consisting in a slight decrease in molecular mass of the B beta-chains. Analysis of fibrin revealed that cleavage of fibrinopeptide B by thrombin is normal, the molecular defect being confined to the beta-portion of the B beta-chain. The same fibrinogen variant was detected in the blood platelets of the proposita. This finding supports the assumption of a common origin of plasma and platelet fibrinogen pools. Family studies revealed the presence of the abnormal fibrinogen in a brother of the proposita, thus confirming the genetic nature of the observed variant. The underlying mutant gene occurs in both carriers in heterozygous state.

Adult↗