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Biomedical subjects

W Meier

Publications and source records attributed to W Meier.

At least 127 records · Page 7Linked to original sources
PubMed1987

Fission and refusion of red blood cells using a micropipette technique.

In micropipette experiments with small capillaries and moderate high pressure difference (approximately 1000 Pa) cell fragmentation (fission) of human red blood cells without hemolysis was observed by TV-system for a large number of fresh red blood cells of different donors. After separation, the fragment moves away from the residual cell. In seven cases this process was evaluated quantitatively and was shown that the rate of the fragment was constant in time. Two mechanisms for this phenomenon are discussed. In particular cases a spontaneous re-fusion with the residual cell body in the capillary can be observed. In our opinion probably protein-depleted membrane surfaces arise and membrane fusion is possible simply by mechanical contact without additional electric fields and/or fusion agents.

Cell Separation↗
PubMed1987

The analgesic efficacy of flupirtine in comparison to pentazocine and placebo assessed by EEG and subjective pain ratings.

In a placebo-controlled double-blind study the analgesic efficacy of the non-narcotic analgesic flupirtine (80 mg i.v.) was evaluated in comparison with the opioid pentazocine (30 mg i.v.). The variables investigated were the subjects' pain ratings (E), the somatosensory evoked cerebral potentials (SEP), the auditory evoked potentials (AEP) and the power spectral density of the ongoing EEG (PSD). One stimulus block before (PRE) and one stimulus block after (POST) medication were applied. In one stimulus block 80 intracutaneous electrical stimuli of two- and three-fold pain threshold amperage were given in randomized order of intensity and inter-stimulus intervals. Both treatments reduced the subjects' pain ratings significantly, while the placebo values were constant. These effects on pain ratings were in parallel with the SEP changes. The peak-to-peak amplitudes of the late components were significantly diminished by both drugs. Placebo had no effect on this variable. The AEPs remained considerably constant after all three treatments indicating specific drug effect on the pain-related somatosensory pathways. Flupirtine showed effects similar to those of pentazocine in terms of pain relief. The changes in ongoing EEG activity, however, were of a different kind. Pentazocine changed the EEG in an opiate-like manner, while flupirtine increased relative power in the theta and beta range.

Aminopyridines↗
PubMed1987

Membrane elastic shear modulus of red blood cells with glucose-6-phosphate dehydrogenase and pyruvatekinase enzymopathies.

The membrane elastic shear modulus mu determined by a micropipette technique was found to be elevated by 25% to 200% for red blood cells (RBC) from 7 patients with glucose-6-phosphate dehydrogenase (G-6-PD) and 9 patients with pyruvate-kinase (PK) enzymopathies above the mean value for normal controls. All patients exhibit chronic nonspherocytic hemolytic anemias. A negative linear correlation (r = -0.72) between mu and the number of reticulocytes was obtained in G-6-PD deficiencies. In contrast, a positive correlation (r = 0.88) was found for red blood cells of patients with PK deficiency. A mechanically induced swelling of RBC was observed for some deficient cells. The results are discussed in the framework of structural alterations of the RBC membrane due to the disturbed pentose-phosphate pathway and the diminished ATP supply through glycolysis, respectively.

Elasticity↗
PubMed1986

Biomechanical properties of human intervertebral discs subjected to axial dynamic compression--influence of age and degeneration.

This investigation was performed to study biomechanical properties of human intervertebral discs as a function of age. 178 specimens from 21 spinal sections (Th9-S1, 5-84 yr) were subjected to axial dynamic compression; the load being 950 +/- 540 N. The results revealed three distinct age ranges: From the first to the middle of the third decade: axial deformability decreases within the thoracic region, and remains almost constant within the lumbar spine; creep decreases in both parts. From the middle of the third to the beginning of the sixth decade: the biomechanical behavior scarcely alters. Afterwards: axial deformability remains unchanged; creep, however, again increases within the lumbar spine. The results reveal the discs behave most efficiently within the age range where the incidence of back pain is maximal.

Adolescent↗
PubMed1986

Imipramine reduces experimental pain.

In a homogeneous sample of 20 healthy male students, the analgesic effects of the tricyclic antidepressant imipramine (100 mg) were compared to those of the narcotic meperidine (150 mg) and a further tricyclic compound with assumed analgesic properties (fluradoline, 450 mg). Drugs were orally administered, using a placebo controlled, double-blind repeated measures Latin Square design. Phasic pain was induced by intracutaneous electrical shocks with random intensities and interstimulus intervals. Each stimulus block consisted of 80 stimuli and lasted for 20 min. Pain estimates, somatosensory evoked cerebral potentials (SSEPs) and power spectral density of the electroencephalogram (EEG) were measured under each drug condition. Under placebo, pain ratings and SSEP amplitudes were constant within the entire session lasting for approximately 4 h. Meperidine analgesia was evident within 30 min of drug application, reaching a maximum after about 90 min. Imipramine produced a comparable degree of pain reduction, however, with a delay of 2 h. Under both drugs, the decrease in pain ratings was accompanied by decreased amplitudes of the late components of the SSEP, as well as by a reduction in alpha activity and an enhancement of slow EEG waves. Effects of fluradoline on experimental pain could not be affirmed. These findings are discussed in terms of pain relief and decrease in vigilance.

Adult↗
PubMed1986

Pentazocine and flupirtine effects on spontaneous and evoked EEG activity.

Somatosensory (SEP), auditory evoked potentials (AEP) and power spectral density of ongoing EEG (PSD) were investigated under different drug conditions: the opioid pentazocine (30 mg), the centrally acting non-narcotic analgesic flupirtine (80 mg) and placebo were administered i.v. in a double-blind cross-over study (intersession interval 7 days) with 20 healthy male subjects. Intracutaneous electrical stimuli were applied to the finger tip with randomized intensities of two- and threefold individual pain threshold. One stimulus block consisted of 80 trials. Mean values of two stimulus blocks per session were analyzed: one block before and one block 30 min after treatment. Pentazocine significantly reduced the peak-to peak amplitude of the late SEP components (N150-P240) from pretreatment to posttreatment blocks, and flupirtine diminished this amplitude to nearly the same degree. With placebo no substantial reduction was found. In contrast to these drug-induced changes in SEP, the AEP components showed no significant alterations after any treatment. The PSD under pentazocine showed a reduction of total power. This effect was mainly due to a reduced power in the alpha band. The PSD under flupirtine showed slight increases in power of theta, alpha and beta activity. Again, under placebo no changes from pretreatment to posttreatment conditions occurred. The difference in EEG change might suggest different sites of action of the two analgesics.

Aminopyridines↗
PubMed1986

[Influence of heat-induced changes in the mechanical properties of the membrane on the filterability of human erythrocytes].

The influence of heat induced changes of mechanical membrane properties of human erythrocytes on their filterability was investigated. A 10-minute incubation at 47, 48 and 48.4 degrees C, respectively, leads to an increase of elastic membrane shear modulus (up to 130%, 240%, 260%) and membrane viscosity (up to 220%, 380%, 480%). In comparison to these effects the filterability determined by cellulose filters was diminished relatively slightly (increase of filterability index up to 110%, 130%, 170%), with the mean erythrocyte volume remaining unchanged. Taking into account former investigations it is concluded that the used filtration technique is less sensitive with respect to changes of the elastic and viscous membrane properties compared with changes of cytoplasmic viscosity of the cells.

Blood Viscosity↗
PubMed1986

Biological activity of the C-1, C-3, C-25, beta-D-glucopyranosides of 1,25-dihydroxyvitamin D3.

We have shown previously that the 3-beta-D-glucopyranosides of vitamin D3, 1 alpha-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3 are biologically active in vivo. In order to determine whether the presence of the beta-D-glucopyranoside moiety linked to either the C-3, the C-25 or the C-1 hydroxyl function of the molecule affected the biological activity of the conjugates 1, 2, or 3 derived from 1,25-dihydroxyvitamin D3, we administered increasing amounts of compounds to vitamin D-deficient rats maintained on a low calcium diet. The aglycone, 1,25-dihydroxyvitamin D3 (4), also was administered to another group of such animals. When administered i.v., all three beta-D-glucopyranosides increased intestinal calcium transport in doses as low as 50 pmol/rat. A dose of approximately 500 pmol/rat was required to increase bone calcium mobilization in these same animals. The three glucosides were found to be equally active in both biological responses. A dose of only 5 pmol of 1,25-dihydroxyvitamin D3 (4) increased both intestinal calcium transport and bone calcium mobilization. We also performed similar experiments after the p.o. administration of these compounds to vitamin D-deficient rats maintained on a low calcium diet. The glucopyranosides 1, 2 and 3 were able to increase calcium transport in the intestine, as well as mobilize bone calcium at doses of between 500 and 5000 pmol/rat. Once again, the compounds were equipotent, but were less active than 1,25-dihydroxyvitamin D3 (4). After the i.v. or p.o. doses of the glucosides, plasma concentrations of 1,25-dihydroxyvitamin D3 increased in a dose-dependent manner. We conclude that: The C-3, C-25 and C-1 beta-D-glucopyranosides of 1,25-dihydroxyvitamin D3 are biologically active and equipotent in vivo, most likely as a result of hydrolysis to the free aglycone and they are less active than the aglycone in this respect.

Administration, Oral↗
PubMed1985

A comparative analysis of newborn outcome in a hospital-based birthing center.

Medical records of babies born in a hospital-based birthing center were reviewed to determine whether a birthing center alternative to traditional hospital care of the newborn is safe and cost-effective. A cohort of 123 hospital-based birthing center low-risk deliveries was compared to 100 control low-risk deliveries born in the traditional setting at the medical center during the same time period. Morbidity was assessed using the Hollister Classification as reference and was based on treatment need. The analysis of the babies' status at birth, 24 hours, and 72 hours revealed no difference in immediate morbidity. Cost of hospitalization was reduced by $340.00 per cohort baby. These data suggest that this alternative can be safe and cost-effective. This study applies only to hospital-based birthing centers, because the safety of free-standing birthing centers has not been established and because screening for low risk can not eliminate morbidity.

Adult↗
PubMed1985

Biologic activity of 3beta-D-glucopyranosides of vitamin D compounds.

Polar glycosidic conjugates of vitamin D compounds occur in the vegetable and possibly in the animal kingdom. The biologic activity of these conjugates has not been examined systematically. To obtain more information on the biological role of such sterol conjugates, we examined the biological activity of the 3beta-D-glucopyranosyl conjugates of vitamin D3 5, 25-hydroxyvitamin D3 6, 1alpha-hydroxyvitamin D3 7 and 1alpha,25-dihydroxyvitamin D3 8. When these compounds were administered i.v. we found that a dose of between 50 and 500 pmol/rat of the four glucopyranosides tested increased active intestinal calcium transport and increased bone calcium mobilization in vitamin D-deficient rats fed a low calcium diet. Under the same conditions, corresponding doses of the parent vitamin D3 compounds elicited comparable increases in both intestinal calcium transport and bone calcium mobilization. When these compounds were administered p.o. 3beta-D-glucopyranosyl vitamin D3 5 exhibited no biological activity at doses of up to 5000 pmole/rat, whereas the corresponding glycosides of 25-hydroxyvitamin D3 6, 1alpha-hydroxyvitamin D3 7 and 1,25-dihydroxyvitamin D3 8 were active at doses of 500 to 1000 pmol/rat in the intestinal calcium transport system. When the glucopyranosyl conjugates were administered i.v. to vitamin D-deficient rats, 25-hydroxyvitamin D3 and 1alpha,-25-dihydroxyvitamin D3 were detected in the serum at levels less than or equal to those noted in animals dosed with the respective free sterols.

Animals↗
PubMed1985

Biological activity of the three mono-beta-D-glucopyranosides of 1,25-dihydroxycholecalciferol.

The biological activity of the three mono-beta-D-glucopyranosides (mono-glucosides) of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] synthesized chemically has been studied in chicks and Japanese quails. While the 1- and the 3-glucoside showed no or only little effect on serum calcium, bone weight, calcium binding protein (CaBP) or calcium deposition in the egg shell, the 25-glucoside was found to be more than half as active as the aglycone 1,25(OH)2D3. The bioactivity of this glucoside parallels a higher binding constant to the intestinal 1,25(OH)2D3 receptor compared to those of the two other glucosides.

Animals↗
PubMed1984

Biomechanical properties of human intervertebral discs subjected to axial dynamic compression. A comparison of lumbar and thoracic discs.

This investigation revealed biomechanical properties and some morphological parameters of isolated intervertebral discs at various disc levels. One hundred twenty-three specimens were subjected to axial dynamic compressive loads. The duration of testing was 5 minutes, the loads Fd1 = 650 N +/- 400 N (discs from T5-6 to L1-2) and Fd2 = 950 N +/- 540 N (discs from T9-10 to L5-S1). Down the spine, the mean disc heights and cross-sectional areas increased; the water content seemed to be nearly constant. Axial deformation and ventral bulging increased down the spine as well, which is mainly due to the increasing disc height. Creep showed different characteristics. It was smallest within the region T10-11 to L1-2 and increased above and below this level. The increase below L1-2 is mainly due to the increasing disc height; the increase above T10-11 occurs because the thoracic discs behave in a more viscous manner than the lumbar discs.

Adolescent↗