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Biomedical subjects

W Meier

Publications and source records attributed to W Meier.

At least 145 records · Page 8Linked to original sources
PubMed1984

The intracutaneous stimulus: a new pain model for algesimetric studies.

An intracutaneous pain stimulus is described for psychophysiological studies in man, which can easily be applied and which elicits highly reliable pain reactions in sessions repeated on different days, as well as in long-lasting sessions within a single day. The common electrical skin stimulation technique was modified by producing a circumscribed reduction in skin resistance under the stimulating electrode. A standardized procedure is described to reproducibly reduce this resistance by a factor of about 0.1 in a defined skin area of 1 sqmm. After this procedure, a definite and clear pain sensation could be elicited by current pulses which did not cause any sensation when conventionally applied. The reproducibility of pain reactions (pain ratings and late cerebral potentials) was tested in single sessions lasting up to 8 hours, as well as in weekly repeated experiments. First examples for applying these stimuli in algesimetric studies are given by double blind experiments with meperidine.

Adult↗
PubMed1984

[Importance of pH- and osmolarity-dependent changes in deformability- determining factors on the filterability of human erythrocytes].

The deformability of erythrocytes was characterized by measuring their filterability through cellulose filters under low pressure, their cellular geometry and elastic membrane properties. A decreased filterability of suspensions of washed erythrocytes with increasing pH (5.5-7.9) and osmolarity (220-510) was found. The influence of RBC-deformability determining factors on the measured quantity (relative time of filtration) was determined. It is concluded that the viscosity of the cell interior has a predominating influence on the filterability through cellulose filters among all experimentally changed factors determining the deformability. The influence of the cell volume on the filterability is small compared with that of secondary effects of volume changes (dilution or concentration of hemoglobin, changes of cell volume concentration at constant hematocrit). The influence on the erythrocyte volume increases with decreasing pore size.

Erythrocyte Membrane↗
PubMed1983

Antagonism between tilidine and naloxone on cerebral potentials and pain ratings in man.

The effects of the opioid tilidine and the opiate antagonist naloxone on somatosensory evoked potentials (SSEP) and pain ratings (E), elicited by electrical skin stimuli with randomized intensities, were investigated for different, orally administered tilidine and naloxone combinations in a double-blind Latin square design in 15 healthy humans. A high correlation between SSEP amplitudes and E was found for all treatments investigated. Tilidine (100 mg) decreased both SSEP amplitudes and E by about 25% compared to the placebo. No significant differences were found between the analgesic effects of tilidine and TN8 (tilidine 100 mg; naloxone 8 mg). The effects of both treatments were significantly different from those of the naloxone, placebo and TN32 treatments (tilidine 100 mg; naloxone 32 mg), indicating a marked naloxone-induced reversal of tilidine analgesia. Naloxone (32 mg) increased the SSEP amplitudes. No naloxone-induced hyperalgesia was seen in the pain ratings.

Adult↗
PubMed1983

Mechanical membrane properties of human red blood cells and their change due to metabolic disturbance.

Blood of patients suffering from non-spherocytic chronic haemolytic anemia due to individual mutations of glucose-6-phosphate-dehydrogenase (G-6-PD) and pyruvate kinase (PK) was investigated by biochemical and rheological methods. Both enzymopathies are characterized by a strong increase (by the factor 2 to 4) in the overall RBC-rigidity and the elastic membrane shear modulus of the RBC. There was a positive correlation between the changed elastic shear modulus and the clinical picture in the case of PK deficiency and, in contrast, a negative correlation for patients with G-6-PD enzymopathies. The ability of RBC to change their shape or the static deformability is determined by the excess surface regarding to the enclosed volume, by the rheological properties of the hemoglobin content and by the membrane extension and bending moduli. The dynamic deformability is characterized by the time constant for rapid elastic and plastic deformations and becomes important for entrance and discharge processes in the microcirculation. These rheological relevant properties are subjected to metabolic control. Although for both enzymopathies the mechanism of hemolysis is not understood in detail, it has to be assumed that PK deficient RBC are mostly phagocytized and on the other hand G-6-PD deficient cells are destroyed to a higher extent by intravasal hemolysis. The aim of this study was to investigate whether or not expected changes in the RBC membrane structure due to the decreased ATP production by PK enzymopathies and diminished NADPH production by G-6-PD deficiencies result in abnormal mechanical membrane properties. The answer should give a better understanding of the premature RBC destruction.

Anemia, Hemolytic↗
PubMed1982

[Experimental studies on the rheologic behavior of blood in ultraviolet therapy].

The increased apparent blood viscosity proved in peripheral circulatory disease, the frequent failure of therapy by means of vasodilating medicaments and the successful therapy with the help of ultraviolet radiation of blood (UVB) by means of various techniques motivated investigations of the flow properties of blood with UVB. In six patients with angiologically ascertained arterial occlusive disease the flow properties of blood were investigated under standardized conditions by both viscosimetric techniques and independent of it by means of the centrifugation method. Plasma viscosity, apparent blood viscosity, parameters of aggregation and deformation of erythrocytes were determined before and after fictitious UVB on the hand one and before and after real UVB on the other hand. It was shown that within the limit of measurement accuracy there were no significant differences between fictitious and real UVB in plasma viscosities. Both the aggregation parameter of the centrifugation method and the apparent blood viscosity for low shear gradients before the 3rd UVB and all following ones differed significantly from those of the first UVB. No changes were found in the deformation parameters HCC infinity and the apparent viscosity for high shear gradients during UVB therapy. Possible mechanisms leading to the demonstrated improvements of the flow properties of blood by means of UVB are discussed.

Arterial Occlusive Diseases↗
PubMed1981

[Changes in plasma volume during and after middle-ear procedures (author's transl)].

We observed 20 patients undergoing middle-ear surgery under NLA in combination with halothane for controlled hypotension in respect to haematocrit, plasma protein concentration, plasma volume (Evans Blue) and intravascular protein mass during and after anaesthesia and surgery. As surgical bleeding was almost nil and infusion therapy was not necessary, patients behaved as a "closed system". With the start of anaesthesia we found a significant decrease of haematocrit and plasma protein concentration, being complete after 45-60 min, and unchanged thereafter until the end of anaesthesia. Suspicion of an increase in plasma volume could not yet be verified by a measurement of this parameter after 30 min of anaesthesia. Just after termination of anaesthesia we observed a significant increase in haematocrit and plasma protein concentration compared to control values with a downward trend over the next hour. At that point we also measured a decrease in plasma volume by 10% and in plasma protein mass by 6% compared to controls. These findings are interpreted as part of an "arousal reaction" with a temporary disequilibrium between transcapillary filtration rate of water and proteins and back transport of these substances via lymph flow.

Blood Proteins↗
PubMed1981

[Changes in plasma zinc under anesthesia and surgery (author's transl)].

Postoperative hypozincemia is a common finding and may be interpreted as ACTH-induced dissociation of zinc from the albumin fraction in plasma. Due to the high protein-bound fraction of zinc in plasma rapidly developing hypozincemia may be caused by dilution of plasma proteins. This may be roughly checked by dividing plasma zinc concentration by plasma protein concentration. By this means we observed that in middle ear surgery and in laparotomies under NLA during anesthesia and surgery there is no evidence for dissociation of zinc from plasma proteins. This probably stress-induced phenomenon was, however, already seen in the first postoperative hour after laparotomies. During anesthesia and surgery we observed a profound increase in renal zinc excretion, the cause of which in unknown.

Anesthesia↗