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Biomedical subjects

M Meyer

Publications and source records attributed to M Meyer.

At least 577 records · Page 32Linked to original sources
PubMed1985

[Tangier disease. A rare thesaurismosis].

The authors report the case of a 15-year old boy with Tangier disease characterized clinically by grossly enlarged tonsils, liver and spleen. Blood counts showed signs of hypersplenism, and blood lipid assays disclosed hypercholesterolaemia with moderate hypertriglyceridaemia and very low levels of high density lipoproteins. The diagnosis was confirmed by biopsies of the liver, spleen, rectal mucosa, tonsils and bone marrow, all tissues which contained foamy histiocytic cells staining like adipose cells. Following splenectomy, the child developed an unexplained, persistent (6 months) fever, then died suddenly of digestive haemorrhage. A genetic study showed a high degree of inbreeding, with 2 deaths probably due to Tangier disease. The authors contrast the surprising severity of this case with the apparent benignity of the disease as described in other publications.

Adolescent↗
PubMed1985

Intercellular network in articular cartilage of pigs with experimentally induced arthritis. I. Fact or artifact?

Porcine articular cartilage from cases of experimentally induced Erysipelas arthritis was examined with different histological techniques and by electron microscopy. A small percentage of specimens of osteoarthritic cartilage revealed an interlacunar network in the extracellular matrix. These "matrix-streaks" showed characteristic features of densely packed fibrillar elements and collagenous fibrils, as narrow bands connecting adjacent chondrocytes. In a given cartilage site the network had a constant pattern. It is hypothesized that the network formation is correlated with altered joint metabolism and represents regressive changes in cartilage matrix as a result of external mechanical forces. Using a variety of methods, the possibility of the network being an artifact of histological processing could virtually be ruled out. As there are so far only few and contradictory reports on the interlacunar network of articular cartilage, its precise biological significance remains to be established.

Animals↗
PubMed1985

Tangier disease. A histological and ultrastructural study.

A case of Tangier disease with results of histological and ultrastructural studies is reported. The clinical, biological and histological picture was typical, with enlarged liver and spleen, voluminous tonsils, low blood levels of alpha-lipoproteins and cholesterol and high blood levels of triglycerides. The histological study revealed widespread tissue storage of cholesterol esters in the Mononuclear Phagocyte System. Lipid deposits were located in foamy histiocytes by staining with lipid-specific stains. The ultrastructural study revealed intracytoplasmic vacuoles unbounded by membranes and often confluent. Unlike other previously described cases, this one had a rapid fatal outcome.

Adolescent↗
PubMed1985

Model simulation of single-breath washout of insoluble gases from dog lungs.

Intrapulmonary gas mixing by convection and diffusion is analyzed on the basis of various analog lung models incorporating singly or in combination series inhomogeneity, parallel inhomogeneity, intercompartmental diffusion, sequential inspiration, and sequential expiration. The slope of the alveolar plateau of insoluble gases is used as an indicator for incomplete gas mixing. By use of the models, we have attempted to simulate experimental results obtained in artificially ventilated dog lungs with simultaneous single-breath washout of He and SF6 (Meyer et al., J. Appl. Physiol. 55: 1795-1802, 1983). Sufficient agreement with experimental data is obtained only when diffusion between serial-parallel compartments and sequential expiration are incorporated, the first being mainly responsible for separation of He and SF6, the latter for the slope of the alveolar plateau of these gases. A combined operational model comprising two parallel compartments connected to a mixing compartment, with both convective and diffusive gas transport between the compartments, could account for most of the experimental observations.

Animals↗
PubMed1985

Arterial-alveolar CO2 equilibration in exercising dogs during prolonged rebreathing.

Arterial-alveolar equilibration of CO2 during exercise was studied by normoxic CO2 rebreathing in six dogs prepared with a chronic tracheostomy and exteriorized carotid loop and trained to run on a treadmill. In 153 simultaneous measurements of PCO2 in arterial blood (PaCO2) and end-tidal gas (PE'CO2) obtained in 46 rebreathing periods at three levels of mild-to-moderate steady-state exercise, the mean PCO2 difference (PaCO2-PE'CO2) was -1.0 +/- 1.0 (SD) Torr and was not related to O2 uptake or to the level of PaCO2 (30-68 Torr). The small negative PaCO2-PE'CO2 is attributed to the lung-to-carotid artery transit time delay which must be taken into account when both PaCO2 and PE'CO2 are continuously rising during rebreathing (average rate 0.22 Torr/s). Assuming that blood-gas equilibrium for CO2 was complete, a lung-to-carotid artery circulation time of 4.6 s accounts for the observed uncorrected PaCO2-PE'CO2 of -1.0 Torr. The results are interpreted to indicate that in rebreathing equilibrium PCO2 in arterial blood and alveolar gas are essentially identical. This conclusion is at variance with previous studies in exercising humans during rebreathing but is in full agreement with our recent findings in resting dogs.

Animals↗
PubMed1985

Blood flow distribution in dog gastrocnemius muscle at rest and during stimulation.

The distribution of blood flow within the isolated perfused dog gastrocnemius muscle (weight 100-240 g) was studied by intra-arterial injection of radioactively labeled microspheres (diameter 15 micron) at rest and during supramaximal stimulation to rhythmic isotonic tetanic contractions of varied frequency against varied loads. After the experiment the muscle was cut into 180-250 pieces of approximately 0.75 g each, and the blood flow to each muscle piece was determined from its radioactivity. The inhomogeneity of blood flow was represented as the frequency distribution of the ratios of regional specific blood flow, i.e., blood flow per unit tissue weight of the piece, QR, to the overall specific blood flow of the muscle, Q. The QR/Q values for the individual pieces of a muscle were found to vary widely both at rest and during stimulation. With rising work load the frequency distribution had a tendency to broaden and flatten, indicating increasing perfusion inhomogeneity. On the average of the experiments, there was no significant difference in specific blood flow between the three anatomic components of the gastrocnemius (lateral and medial heads of gastrocnemius and flexor digitorum superficialis) nor between the superficial and deep portions within these anatomic components, only the distal third of the muscle was relatively less perfused compared with the proximal two-thirds. The considerable inhomogeneity of blood flow as revealed by microsphere embolization and by other methods is expected to exert important limiting effects on local O2 supply, particularly during exercise. Its neglect would lead to serious errors in the analysis of O2 supply to muscle tissue.

Animals↗
PubMed1985

[Lactate concentration in the ventricular fluid and blood plasma following severe craniocerebral trauma].

Cerebral ischemia/hypoxia is of central importance in the sequence of pathogenetic processes after severe head injuries. Investigations in 72 patients showed that after severe head injury the changes of lactate concentration in blood plasma do not allow any statement with respect to cerebral ischaemia/hypoxia. However in ventricular liquor the amount and duration of increase in lactate concentration is significantly different in nonsurvivors in comparison to survivors. In lethal courses after 3rd day after head injury the increase of lactate concentration in ventricular liquor points to secondary cerebral ischemia/hypoxia.

Adult↗
PubMed1984

[Possible regulatory importance of cellular sulfhydryl groups and reduction metabolic pathways for the activation of human blood platelets].

The activation of the blood platelets is the prerequisite for their participation in physiological and pathological intravasal processes. An aimed influence on the distinct functions of the blood platelets presumes an exact knowledge about course and regulation of the activation of the platelets. Investigations on glucose-6-phosphate-dehydrogenase-deficient platelets and on the effect of glutathione-oxidizing substances on normal platelets showed references to a regulatory significance of the cellular thiol/disulphide state in the process of activation. In this case particularly the arachidonic acid balance and the SH/SS-state of platelet proteins seem to be in close connection with reductive ways of metabolism.

Arachidonic Acids↗
PubMed1984

[Malignant neuroleptics syndrome].

The neuroleptic malignant syndrome is clinically characterised by the presence of severe muscular rigidity, altered consciousness, hyperthermia and by signs of autonomic dysfunction. A severe form of the syndrome lasting several weeks was observed in a 20-year-old, mentally retarded female patient while under fluphenazine treatment. Cerebrospinal fluid was examined for monoamine metabolites by high-performance liquid chromatography both during the acute and the convalescent phases of the disease. Since the disease carries a considerable mortality, early diagnosis and rapid withdrawal of all neuroleptic medication is of primary importance.

Adult↗
PubMed1984

Diffusion-perfusion relationships in skeletal muscle: models and experimental evidence from inert gas washout.

In order to study the dependence of blood-tissue gas exchange upon diffusion, the simultaneous washout of two inert gases of differing diffusivity was investigated in isolated-perfused dog gastrocnemius preparations. The muscles were equilibrated with CH4 and SF6 via arterial blood. The washout kinetics were determined from venous blood samples analyzed by gas chromatography. The results revealed the following features: The washout of the test gases was pronouncedly multi-exponential, and could be described by three exponential components when analyzed to 5% of the initial value. The non-exponential washout was attributed to unequal distribution of capillary blood flow to tissue volume. The mean ratio of washout rate constants CH4/SF6 was within 1.10-1.25 and was even smaller than the ratio expected for pure perfusion limitation (1.46). Therefore, no evidence for effective tissue-blood diffusion limitation was obtained. The observed washout rate constant ratio could be explained by a model with veno-arterial back diffusion which more strongly retards washout kinetics of the better diffusible gas (CH4) as compared to the less diffusible gas (SF6).

Animals↗
PubMed1984

Elements for modeling inert gas washout from heterogeneous tissues.

Inert gas washout from tissue may be analyzed using Krogh's cylinder or a simplified model thereof, represented by a series arrangement of compartments. In particular with limited axial diffusion in tissue, washout from this model is multi-exponential, the rate of washout accelerating with time. To explain the experimentally observed multicomponent washout, in which washout retards with time, heterogeneity of flow and/or diffusing capacity to volume is required, either in series or in parallel compartments. While there appears to be a structural basis for both types of heterogeneity, parallel and series, a distinction between both on the basis of washout curves alone is impossible.

Animals↗
PubMed1984

Dual role of diffusion in tissue gas exchange: blood-tissue equilibration and diffusion shunt.

The role of diffusion in inert gas washout from tissue is investigated using simple mathematical models incorporating diffusive blood-tissue equilibration and diffusion shunt due to diffusive gas transfer between precapillary and postcapillary vessels with counter-current blood flow. With increasing diffusivity blood-tissue equilibration is improved, but simultaneously the diffusion shunt by veno-arterial back diffusion is increased. Similarly, with decreasing blood flow, the extent of diffusion limitation in blood-tissue transfer is diminished, but at the same time veno-arterial diffusive shunting is enhanced. Diffusion shunt slows inert gas washout (local tissue clearance) and thus, if not taken into account, leads to an underestimation of capillary blood flow calculated from the washout rate constant. Diffusion shunting of O2 diminishes the efficacy of blood-tissue transfer, but its extent is predicted to be smaller compared to that for inert gases, because the chemical combination of O2 in blood decreases diffusive shunting.

Animals↗
PubMed1984

Normal and myopathic propagation of surface motor unit action potentials.

With the aid of a computer-assisted multichannel EMG system, the propagation of motor unit action potentials is analysed during isometric voluntary muscular contraction under normal and myopathic conditions. A linear array of 30 surface electrodes is fixed above the biceps brachii muscle, parallel to the longitudinal muscle axis and centered over the end-plate zone. The EMG is simultaneously recorded on all channels and displays the propagation of surface potentials on both sides of the innervation band. The mean muscle fibre conduction velocity is computed by a cross-correlation technique. Five adult patients in a late stage of progressive muscular dystrophy show a highly altered propagation behaviour of motor unit action potentials without a time shift between potentials of adjacent electrodes. A mathematical model is described which predicts such a behaviour and suggests that it must be due to a pathological longitudinal spread of end-plates in this patient group. In 5 boys with Duchenne muscular dystrophy and only moderate impairment of the biceps muscle the mean muscle fibre velocity was reduced (2.81 +/- 0.34 m/sec) compared to 17 healthy subjects (4.42 +/- 0.37 m/sec). Each myopathic patient examined could be separated clearly from the group of healthy subjects on the basis of the surface EMG analysis.

Adolescent↗
PubMed1984

Dual role of diffusion in tissue gas exchange: blood-tissue equilibration and diffusion shunt.

The role of diffusion in tissue gas exchange is investigated using a simple mathematical model which incorporates both tissue-blood equilibration and gas transfer between arterial and venous vessels with counter-current flow, leading to 'diffusion shunt'. Both increasing the diffusion coefficient of the gas considered or decreasing the blood flow results in two antagonistic effects: (i) improvement of blood/tissue equilibration, (ii) increase in extent of diffusion shunt. The diffusion shunt retards inert gas wash-out (local tissue clearance) and leads thus, if not taken into account, to an underestimation of capillary blood flow calculated from the wash-out rate constant. For O2 (and CO2) the diffusion shunt reduces the efficacy of blood/tissue transfer, but its extent is expected to be only moderate because of the chemical combination of these gases in blood.

Diffusion↗