Biomedical subjects

W Meier

Publications and source records attributed to W Meier.

At least 91 records · Page 5Linked to original sources

PubMed1993

[Assessment of whole cell deformability of individual erythrocytes with a capillary rigidometer--possibilities for standardization and modification].

Human erythrocyte deformability is determined by cell geometry and volume, membrane elasticity and cytoplasmic viscosity. The deformability of red blood cells and their distribution among the total cell population, can be studied with the Capillary Rigidometer. This device is based on the kinetic measurement of red blood cell deformability, which has been developed, by modifying the micropipette aspiration technique. In order to investigate the validity of the method and the measuring parameters, a number of determining factors (heat treatment, osmolarity-changed cells) influencing the deformability were studied, and the sensitivity of the defined parameters for changes in deformability discussed. The results are examined in connection with different flow rates in the micropipette and show that the parameters are influenced by the flow conditions, so that they have to be related to these conditions. Initial studies using microspheres aimed at standardising the method are described.

Erythrocyte Deformability↗

PubMed1992

Tributyltin-induced effects on early life stages of minnows Phoxinus phoxinus.

Toxicity and histopathological effects of tributyltin chloride (TBT) were studied in early life stages of minnows Phoxinus phoxinus. Eggs and yolk sac fry (newly hatched larvae) were exposed in a static-renewal procedure to aqueous TBT concentrations ranging from 0.82 to 19.51 micrograms/L for 3 to 10 days at 16 degrees C and 21 degrees C, respectively. Aqueous TBT concentrations were determined by capillary GC-FPD and revealed a concentration decrease during the static phase. TBT exposure led to mortality, behavioral, gross morphological and histopathological effects. In larvae, increased mortality, deformation of body axis, paralysis and opaque eyes occurred at 4.26 micrograms/L TBT and higher both in the embryonic-larval and larval exposure. Histological changes were evident at initial TBT concentrations of 0.82 up to 19.51 micrograms/L, and were more pronounced after embryonic-larval exposure than after larval exposure. Degenerative alterations occurred in skin, skeletal muscle, kidney, corneal epithelium, lens, pigment layer of the retina and choroid, retina, and CNS including spinal cord. Hydropic vacuolation of the cytoplasm and, in more pronounced cases, irreversible nuclear alterations such as pycnosis, karyorrhexis and karyolysis were also evident. Exposure to 0.82 micrograms/L TBT resulted in alterations in skin, muscle and kidney, with greater effects occurring at 21 degrees C than at 16 degrees C. Toxicity was significantly reduced in the presence of sediment. The observed histopathological effects suggest that early life stages of fish may be negatively affected in environments that are considerably polluted by TBT.

Abnormalities, Drug-Induced↗

PubMed1992

On-line coupled liquid chromatography-gas chromatography (LC-GC) and LC-LC-GC for detecting irradiation of fat-containing foods.

On-line coupled liquid chromatography-gas chromatography-flame ionisation detection (LC-GC-FID) enables efficient and unambiguous determination of irradiation for some fat-containing foods (e.g. meat). Other products, however, contain interfering components or are contaminated, e.g., with mineral oil. Since more selective detection by mass spectrometry has limited success, the determination was improved by a more selective isolation of some key components among the fat degradation products, e.g. the dienes or trienes, by LC-LC-GC-FID. Applications are shown for soup mixes, some spices, fish, and shrimps.

Alkanes↗

PubMed1992

[Age-related differences and changes in clinical aspects and follow-up of cervix cancer since 1973].

In an attempt to clarify, whether the malignant potential of cervical cancer is age-dependent and whether this has changed in the last decade, we analysed the data from 1496 patients suffering from cervical cancer. The patients were treated between 1973 and 1988 at the second Universitäts-Frauenklinik, Lindwurmstrasse and at the Frauenklinik Grosshadern, both of the Ludwig-Maximilians-Universität München. After 1973, the total number of patients with cervical cancer decreased, whilst at the same time, the percentage of young patients increased. In the sub-group of surgically treated patients (n = 555), the percentage of patients with lymph node metastases increased after 1973. The increase in lymph node involvement was most pronounced in young patients with small tumours (stage Ib disease, 35 years of age). In this group, the percentage of lymph node involvement rose from 6.3% in 1973 to 38.6% in 1988. Lower stage disease was significantly more frequent in the young patients. Accordingly, the overall mean survival time was longer in the young patients. In the sub-group of surgically treated patients, however, when comparing equal stages, the survival time was shorter in the young patients. In small tumours (confined to the uterine cervix), pelvic lymph node involvement was more frequently seen in the younger patients. Secondary metastases developed more rapidly and significantly more often in the young patients. Our data supply evidence to indicate an enhanced malignancy of cervical cancer in young patients.

Adult↗

PubMed1992

[Prognostic significance of the CA 125 half-life for the further outcome of ovarian cancer].

Since only approx. 30% of patients with ovarian carcinoma present themselves in the early stages, and as a result of the lack of effective screening methods, primary interest has been applied to the improvement of the treatment quality in the later stages. Improvement of therapeutic strategies implies an adaptation of specific characteristics of the patient and the tumour. For instance, in cases of primary progression during chemotherapy, it is not justified to continue an aggressive treatment, which causes additional serious side effects. Surprisingly, it has not been possible, to utilize established or suspected prognostic factors for treatment strategies in ovarian cancer. This might result, in part, from the uncertainty of criteria such as stage of disease, residual tumour and histological grading. The single most relevant prognostic factor today is the residual tumour mass. In 1988 van der Burg suggested for the first time a potential prognostic relevance of the CA 125 half-life. This study was designed, to investigate the use of CA 125 half-life in therapeutic strategies. From January 1984 to June 1990, 346 patients with primary ovarian cancer were treated at our institution. Preoperative CA 125 levels were determined in 292 patients; in 220 patients the levels were complete for a period of more than 6 months so that the CA 125 half-life could be calculated. Survival times of patients with a half-life of less than 20 days were significantly (p less than 0.0001) different from patients with a half-life of more than 20 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Tumor-Associated, Carbohydrate↗

PubMed1992

Cerebral potentials elicited by mechanical stimuli to the human leg: influence of artifacts.

Mechanical stimulation with a reflex hammer was applied to the quadriceps muscle tendon of healthy volunteers and patients. The time-locked electrical signals were recorded from the scalp. In all cases, reproducible potentials could be recorded, with latencies in a range of 20 ms to 100 ms. The potentials recorded in patients under complete spinal anesthesia were similar to those derived before the anesthesia. In brain dead patients who showed absence of median nerve or posterior tibial nerve SEP, reproducible potentials after mechanical stimuli could be recorded as well. The results suggest that the hammer taps lead to mechanical shock waves which are propagated along the body producing time locked artifacts in the EEG record which are not eliminated by the averaging technique.

Adult↗

PubMed1992

[Fish diseases in Switzerland. A statistical evaluation of the diagnostic material of the Fish Research Institute from 1979-1988. II. Special aspects].

The frequency of fish diseases diagnosed at the Fish Disease Laboratory at the University of Berne from 1979 to 1988 is presented. Parasitic infections have been found to be the most frequent diagnosis. Among noninfectious diseases poisonings were predominant. Six infectious diseases have been considered to be economically relevant. These diseases (according to their frequency: Gyrodactylosis, Costiosis, Ichthyophthiriosis, Viral Hemorrhagic Septicemia (VHS), Saprolegniosis and Furunculosis) were further analysed. Their incidence varies with season, species, origin and length of fish. Possible explanations for these findings are discussed.

Animals↗

PubMed1991

CD4-binding regions of human immunodeficiency virus envelope glycoprotein gp120 defined by proteolytic digestion.

The gp120 envelope glycoprotein of human immunodeficiency virus type 1 binds the cell surface protein CD4 with high affinity. Here we report the use of proteolysis to define regions of gp120 involved in CD4 binding. Cleavage of gp120 with Staphylococcus aureus V8 protease at residue 269 or with trypsin at residue 432 destroys CD4 binding. These same sites are protected from proteolytic cleavage by bound CD4. Cleavages at 64, 144, 166, 172, and 315 do not affect binding and are not protected by bound CD4, indicating that these regions are not critical for binding CD4. All proteolytic fragments found in coprecipitates with CD4 were covalently associated via disulfides and comprised complete gp120 molecules. Previous conclusions by Nygren et al. [Nygren, A., Bergman, T., Matthews, T., Jornvall, H. & Wigzell, H. (1988) Proc. Natl. Acad. Sci. USA 85, 6543-6546] that both large and small (95-kDa and 25-kDa) V8 proteolytic fragments bind CD4, independently, are not distinguished by their experiments from the result found here that the small fragment immunoprecipitates with CD4 while disulfide-linked to the larger fragment.

Amino Acid Sequence↗

PubMed1991

The increased potency of cross-linked lymphocyte function-associated antigen-3 (LFA-3) multimers is a direct consequence of changes in valency.

We have used chemically cross-linked dimers, trimers, and tetramers of lymphocyte function-associated antigen-3 (LFA-3) to study the role of multivalency in the interaction of the protein with its receptor, CD2. The cross-linked adducts showed enhanced activity in systems where LFA-3 has been shown to (i) block LFA-3/CD2 interactions in a rosetting assay and (ii) provide through the CD2 on peripheral blood lymphocytes a trigger for T-cell proliferation. The level of increase was directly related to the valency state of the multimers. In the rosetting assay, the dimers, trimers, and tetramers, by weight, exhibited 15-, 150-, and 430-fold increases in activity over monomeric LFA-3. In the proliferation assay, the tetramer produced a 6-fold increase in thymidine incorporation at 0.06 micrograms/ml, the trimer was 100 times less active than the tetramer, and the dimer and monomer were inactive. The LFA-3 multimers were generated using a three-step cross-linking chemistry that was targeted at the carbohydrates on LFA-3. With this procedure over 60% of the starting protein was converted into multimers with no effect on function. The cross-linking approach should be applicable to other surface antigens, providing a simple method for analyzing multivalent interactions.

Animals↗

PubMed1991

Time-dependent elastic extensional RBC deformation by micropipette aspiration: redistribution of the spectrin network?

The time dependence of small elastic extensional RBC deformation by micropipette aspiration has been analyzed. This process shows two-phases which are characterized by time constants of the order of some tenths of seconds and about ten seconds, respectively. The equilibrium tongue length is reached after about 30 s. For the first, fast step we assume that the membrane model of immobilized boundaries holds, i.e., the skeleton is tightly associated with the lipid bilayer and no redistribution of the skeleton with respect to the lipid bilayer is allowed. This lipid-spectrin interaction or anchorage is characterized by some association force density. It has been shown that at a given tongue length the force generated owing to the membrane deformation and acting to redistribute the spectrin, overcomes (in some membrane area) the association force density and results in an additional increase of the sucked membrane length. Equations have been derived to describe this process. From the experimental conditions of an RBC aspiration and the determined tongue length corresponding to the second slow aspiration step, the association force density between the lipid bilayer and the spectrin network may be determined. From literature data and our own results a force density of between 40 and 50 Pa has been estimated.

Cytological Techniques↗

PubMed1991

Action of rHuEpo on mechanical membrane properties of red blood cells in children with end-stage renal disease.

By means of a micropipette aspiration technique mechanical membrane properties of RBC in ten uraemic children undergoing haemodialysis were compared to those of nine healthy children. In contrast to the healthy reference group (mu = 4.01 +/- 0.71 microN/m), the mean apparent elastic shear modulus of RBC membrane mu as a parameter of static deformability was significantly increased to 9.05 +/- 1.61 microN/m in children with chronic renal failure measured in the pre-study period. At the 7th week of the correction period of rHuEpo therapy, the haematocrit of treated patients is enhanced to a mean of 0.30 +/- 0.03, whereas mean mu is decreased to 5.41 +/- 0.63 microN/m. Within the maintenance period of rHuEpo treatment (30th week), the parameter mu did not show significant differences to the reference value 3.78 +/- 0.31 microN/m. Additionally, a significant increase in red cell mean corpuscular volume was obtained during rHuEpo therapy. Improved deformability of uraemic RBC induced by the rHuEpo therapy can only be explained by the assumption that in the course of this therapy an increasing number of cells with normalised viscoelastic properties have been formed by stimulated erythropoiesis.

Adolescent↗

PubMed1991

[Fish diseases in Switzerland. A statistical evaluation of the diagnostic materials of the fish research laboratory from 1979-1988. I. General aspects].

The entire diagnostic material of the Fish Disease Laboratory at the University of Berne from 1979 to 1988, a total of more than 3800 cases, is presented. Not included is material of import controls and material from experimental work. The following criteria were evaluated: fish species, origin and length of fish, season, infectious and noninfectious diseases. Furthermore, the results were investigated for changes of the composition of fish species and number of diseases within the ten-year period and for a seasonal influence on the outbreak of diseases. More than 40% of all fish investigated were rainbow trout, followed by brown trout, omamental fish and cyprinids. Over 40% of fish originated from private fishfarms whereas 20% were of governmental origin (governmental fishfarms, rivers, lakes) and 20% from aquaria. Parasites were present in more than 40% of all cases. Bacterial infections were diagnosed in nearly 30%, viral infections in 6% and fungal diseases in 5% of all cases. 20% of all cases concerning noninfectious diseases were caused by unfavourable environmental conditions whereas the incidence of diseases related to nutrition was less than 10%. The occurrence of the different diseases was waxing and waning over the period of ten years but no definite tendencies could be emphasized. However, most of the diseases investigated demonstrated a significant seasonal influence.

Animals↗

PubMed1991

[Fish and their significance from the international and Swiss viewpoints].

In landlocked countries, the role of fish is often poorly known and/or propagated. In many countries fish represent the biggest and qualitatively most valuable protein source (24% of the worldwide available animal protein) for human consumption. At present the economic significance of the production and trade of fish is already very high. However, according to FAO, the future demand of proteins can only be covered by a considerable expansion of the aquaculture production, in particular because of a stagnated fish catch and a continuous reduction of the agricultural production. The ideational value of ornamental fish appears obvious however pet fish keeping represents also a value worth of many millions US dollars worldwide. Finally the importance of fish will not only increase for economic, but certainly also for ecological reasons, because it is well established as an incorruptible bioindicator of our environment.

Agriculture↗

PubMed1991

Elastic properties of passive leukemic white blood cells.

The key role of leukocytes (WBC) in pathologic alterations of microcirculation was repeatedly described in the literature. The aim of this study was to compare the mechanical characteristics of WBC of 4 healthy donors and 6 patients suffering from chronic myeloid leukemia (CML). The elastic properties of individual leukocytes in the passive state were studied by the micropipette technique (aspirating pressure delta P = 100 divided by 250 Pa; internal pipette radius Rp = 1.4 divided by 2.6 microns). The passive elastic rigidity of WBC (PER) from 30 cells/donor was characterized by the amplitude of their steady-state deformation (Dp) normalized for the pipette radius (Rp) against the stress parameter delta P * Rp. The effect of a CML-therapy with cytostatics was monitored by way of differential blood counts. A significantly higher rigidity of healthy lymphocytes (PER = 349.7 +/- 125.9 microN/m; n = 45) than that of polymorphonuclear granulocytes (PER = 226.5 +/- 86.7 microN/m; n = 62) was seen which appears to result from their large, solid nucleus. Control leukocytes have a significantly higher rigidity than leukemic WBC. Leukemic granulocytes (PER = 155.1 +/- 67.7 microN/m; n = 61) and lymphocytes (PER = 134.3 +/- 51.9 microN/m; n = 62) do not differ significantly in their values of rigidity.

Adult↗

PubMed1990

Squamous cell carcinoma antigen and carcinoembryonic antigen levels as prognostic factors for the response of cervical carcinoma to chemotherapy.

Between January 1986 and December 1988, 36 patients with primary advanced or recurrent cervical carcinoma were treated with cytostatic drugs in our department. Treatment at first was a combination of cisplatin and etoposide. After August 1987, a combination of carboplatin and ifosfamide was used. In all patients showing primary response to therapy, the squamous cell carcinoma antigen (SCC) and carcinoembryonic antigen (CEA) levels fell rapidly to normal after one or two cycles. In contrast, clinical remission was not obtained in those patients with levels which remained high or rose again following an initial decrease. Chemotherapy is often the only available therapy for advanced cervical carcinoma or recurrent disease, although the results of treatment, especially in squamous cell carcinoma, remain poor. The course of the SCC or CEA levels can help to decide whether the patient would profit from a continuation of the therapy. With the tumor markers, treatment can be individualized so that, above all, cases of therapy failure or further tumor progression can be detected early and the patient can be spared the severe side effects of the treatment.

Antigens, Neoplasm↗

PubMed1990

[Late para-aortic recurrence of dysgerminoma].

Most of the recurrences in patients with dysgerminoma occur, in more than 80%, in the first 2 years. Late recurrences are very rare. In this paper we report on a paraaortic recurrence, 12 years after primary therapy. Tumour biology and its influence on indication for surgery are discussed. Therapy of recurrence should be individualized including surgery, chemotherapy and radiotherapy. High remission rates in patients with recurrent dysgerminoma can be expected. In fact, our patient has been tumour-free for more than 5 years.

Adult↗

PubMed1990

[Proliferation kinetics in rat urothelium after unilateral nephrectomy and various doses of dibutylnitrosamine application--an example of the roles of a one kidney state on carcinogenesis].

We investigated the proliferation of urothel of the rat after unilateral nephrectomy and application of DBN with drinking water in various doses. We controlled the measurement of proliferation with 3H-thymidine. The important results of our experiments with DBN-application and unilateral nephrectomy were: 1. the tumour-incidence is higher and 2. the tumour-appear is earlier than in experiments with only DBN.

Animals↗

PubMed1989

Pre-stimulus/post-stimulus relations in EEG spectra and their modulations by an opioid and an antidepressant.

Parametric spectral analysis of late cerebral potential components (later than 80 msec) evoked by painful somatosensory stimuli reveals a stimulus-induced increase of power in the low frequencies, delta and theta. This paper investigates the effect kinetics of the opioid meperidine (150 mg, p.o.) and the antidepressant imipramine (100 mg, p.o.) on spontaneous and evoked EEG activity in a placebo-controlled double-blind cross-over study with 20 healthy male subjects. Brief electrical stimuli (5 msec) were intracutaneously applied on the finger tip with randomized intensities above pain threshold and intervals between 10 and 20 sec. Spectra of short (500 msec) pre- and post-stimulus EEG epochs were evaluated using the maximum entropy method (model order 20). The main findings were: (1) The maximum effects of the 2 drugs upon spontaneous and evoked EEG activity were comparable: in the pre-stimulus (spontaneous) EEG both drugs increased the power in the low frequencies and decreased the power in the alpha range. In the post-stimulus (evoked) EEG the drugs decreased the power in all frequency bands. (2) Since in the low frequency range the drugs exhibited contrary effects upon spontaneous and evoked EEG activity, the pre-/post-stimulus relationship of the delta power was found to be the most sensitive measure for monitoring the cerebral bioavailability of the tested drugs. (3) The time courses of development of the effects of the two drugs were different: maximal effects of meperidine were obtained 85-105 min, and of imipramine 190-210 min after medication. The differences in the effect kinetics agreed with the different pharmacodynamics, with time constants for absorption and elimination of 40 min and 240 min for meperidine, and 240 min and 840 min for imipramine. (4) The most important difference between the 2 drugs was the different effect kinetic. Furthermore, in contrast to meperidine the effects of imipramine upon beta activity could not be separated from placebo, either in the spontaneous or in the evoked EEG activity.

Adult↗