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Biomedical subjects

H Köhler

Publications and source records attributed to H Köhler.

At least 109 records · Page 6Linked to original sources
PubMed1997

Reconstruction of peritoneal-like structure in three-dimensional collagen gel matrix culture.

The peritoneum is a serous membrane consisting of different kinds of cells and extracellular matrix components (ECM). The aim of the present study was to develop a three-dimensional (3D) in vitro culture system for possible investigation of pathological conditions of the peritoneum. Human omental mesothelial cells (MC) and endothelial cells from the umbilical vein (EC) were cultivated either on (MC) or in (EC) a preformed type I collagen matrix. In 3D culture mesothelial cells showed their phenotypical in vivo characteristics and the synthesis of a new basal membrane (BM). Endothelial cells developed vessel-like structures, produce a BM and express E-selectin after TNF-alpha stimulation. This 3D culture system presents extended possibilities for analyzing mesothelial and endothelial cell behavior as well as the cell-cell and cell-matrix interactions involved in several pathological processes in the peritoneum.

Adipose Tissue↗
PubMed1997

Early changes in the phenotypic composition of lymphocytes in the bronchoalveolar lavage of pigs after aerogenic immunization with Pasteurella multocida aerosols.

The phenotypic composition of bronchoalveolar lymphocytes (BALL) of healthy untreated pigs and of pigs immunized via aerosol with a live Pasteurella multocida mutant was measured cytofluorometrically in comparison to blood lymphocytes (PBL). Cells were analyzed using monoclonal antibodies against porcine IgM, IgA, IgG and SWC3 in single-colour fluorescence and the following antibody combinations for two-colour fluorescence: CD2/SWC1, SWC1/CD25 and CD4/CD8. In nonimmunized pigs, differences between lymphocyte subsets derived from blood and lung were obvious. The numbers of CD2-SWC1+ T-cells, CD25+ activated lymphocytes and IgG+ cells were significantly higher in the bronchoalveolar compartment. Aerosol immunization with P. multocida caused only insignificant changes in the phenotypic composition of PBL whereas the composition of lung-derived lymphocytes changed markedly. The percentage of CD2-SWC1+ lymphocytes and of CD25+ cells coexpressing the SWC1 antigen in BALL increased up to 10 days after aerosol administration, whereas the percentage of all Ig+ cells decreased. These data reflect an early cellular reaction to an aerogenic immunization with a P. multocida aerosol, characterized by an increase in CD2+ T-cells and a T-cell activation.

Aerosols↗
PubMed1997

[Regression of retroperitoneal fibrosis by combination therapy with tamoxifen and steroids].

BACKGROUND: Idiopathic retroperitoneal fibrosis is characterised by proliferation and fibrosis of retroperitoneal tissue. It is complicated by obstruction and encasement of retroperitoneal structures. CASE REPORT: We describe two female patients with idiopathic retroperitoneal fibrosis. Both had to undergo lateralization of the ureter because of ureteral obstruction. Also both patients developed thrombosis of the inferior vena cava resp. the common iliac vein. Because of the eventful course of the disease a combined tamoxifen and steroid therapy was started. Hereafter there was a marked regression of the retroperitoneal fibrotic masses and the previous inflammatory signs disappeared. CONCLUSION: Tamoxifen seems to be effective in the treatment of idiopathic retroperitoneal fibrosis by inducing a regression of the fibrotic masses. Especially in patients with continuous activity of the disease we recommend an additional steroid therapy to prevent a regeneration of the fibrosis.

Aged↗
PubMed1997

[What is reliable in prevention of contrast medium-induced nephropathy?].

Nephropathy is one of the most important side effects of radiocontrast in patients with impaired renal function. Incidence is reported from 20% to 100% depending on underlying disease. For prevention of radiocontrast nephropathy a large number of substances were investigated in experimental and clinical studies. Clinical relevance of this findings will be assessed by this article. In summary of these studies hydration is the most relevant and significant measure for prevention of radiocontrast nephropathy in patients at risk (i.e. serum creatinine > 1.5 mg/dl). 1 ml/kg body weight/h with 0.45% NaCl 12 h before and after administration of radiocontrast should be supplied. Hemodialysis is recommended if impaired renal function (serum creatinine > 3.5 mg/dl) is accompanied by additional risk factors, e.g. diabetes mellitus. The impact of dialysis therapy is not clarified by clinical studies.

Contrast Media↗
PubMed1997

Determination of LSD in blood by capillary electrophoresis with laser-induced fluorescence detection.

Capillary electrophoresis (CE) with HeCd laser-induced fluorescence (LIF) detection and its application in forensic toxicology is demonstrated by the determination of D-lysergic acid diethylamide (LSD) in blood. Following precipitation of proteins, washing of the evaporated supernatant and extraction, the residue was reconstituted in methanol and injected electrokinetically (10 s, 10 kV). The total analysis time for quantification of LSD was 8 min using a citrate-methanol buffer, pH 4.0. With this buffer system it is possible to separate LSD, nor-LSD, iso-LSD and iso-nor-LSD. Using a specific sample preparation, electrokinetic injection, extended light path (bubble cell) capillaries and especially LIF detection (lambda(ex) 325 nm, lambda(em) 435 nm), a limit of detection of 0.1-0.2 ng LSD per ml blood could be obtained. The limit of quantitation was about 0.4-0.5 ng/ml. The quantitative evaluation for LSD was carried out using methylergometrine as internal standard. The precision expressed as coefficient of variation (C.V.) and accuracy of the method were <20% and 86-110%, respectively. The application of the method to human blood samples from two forensic cases and a comparison with radioimmunoassay demonstrated that the results were consistent.

Electrophoresis, Capillary↗
PubMed1997

[Malnutrition in hemodialysis patients. Self-assessment, medical evaluation and "verifiable" parameters].

BACKGROUND: Malnutrition in hemodialysis patient is associated with increased mortality and morbidity. Inventions to treat malnutrition are often ineffective. Underestimation by the patients of the importance of dietary interventions might negatively influence any therapeutic outcome. We examined the correlation between nutritional assessment by the patient himself and clinical assessment by the physician. PATIENTS AND METHODS: Subjective global assessment (SGA) was performed in 68 chronic hemodialysis patients Serum concentrations of albumin, prealbumin, transferrin and cholesterin were measured Protein intake was estimated by protein catabolic rate (nPCR). In form of a questionnaire patients were asked to assess then own nutrition. RESULTS: According to SGA-criteria, moderate to severe malnutrition was found in 34% of our patients. In this unauthorized group serum albumin was < 4.0 g/dl in 45% of patients and correlated best with clinical nutritional assessment. Specificity was lower for prealbumin, transferrin, cholesterin, and nPCR. The questionnaire was completed by 85% of patients. Self-assessment of their own nutrition was discrepant to clinical assessment in 84% of malnourished patients. A similar percentage (79%) of malnourished patients considered their own body weight to be adequate, while only 21% indicated desire to gain weight. CONCLUSIONS: Our data indicate that a significant percentage of malnourished hemodialysis patients shows a tendency to overestimate their own nutrition. This may negatively influence patient compliance and should be considered in dietary counseling of malnourished chronic hemodialysis patients.

Adult↗
PubMed1997

Enantioselective determination of methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in serum, urine and hair by capillary electrophoresis.

A capillary electrophoresis method has been developed for the enantioselective determination of methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in serum and urine. After addition of the internal standard diphenhydramine, the serum and urine samples were extracted at pH 9-10 with n-hexane. Different cyclodextrins were tested for use as chiral selectors. The best results for simultaneous separation of methadone and EDDP were obtained using heptakis-(2,6-di-O-methyl)-beta-cyclodextrin (DIMEB). Data on the accuracy and precision of the method are presented. The method was applied to serum, urine, and hair samples, from individuals undergoing methadone therapy, under consideration of multi-drug abuse.

Electrophoresis, Capillary↗
PubMed1997

[Prospective observational study of surgical therapy of renal hyperparathyroidism].

A prospective long-term follow-up study in patients who had had surgical therapy for renal hyperparathyroidism was launched to investigate the results of surgical treatment and to evaluate possible correlations between preoperative laboratory values and the course of symptoms. From August 1987 to December 1995, 79 patients underwent surgery for renal hyperparathyroidism. It was the first neck exploration for 72 patients. Total parathyroidectomy with autotransplantation to a forearm was our preferred procedure (n = 67). The postoperative course of all patients is know. We carried out one to nine reexaminations (median 4) in 74 of 79 patients. The follow-up period ranged from 1 month to 5 years with a median of 18 months. After the operation transient hypocalcaemia occurred in 84.4% of patients. Postoperative hypocalcaemia correlated negatively with the preoperative levels of alkaline phosphatase and intact parathyroid hormone. Within the first month after surgery 60% of the preoperatively affected patients completely recovered from pruritus, whereas the skeletal syndrome took longer to disappear. One year after surgery 75% of the patients with pruritus and 79% of those with skeletal syndrome had became asymptomatic. After total parathyroidectomy with autotransplantation, patients with preoperatively elevated concentrations of alkaline phosphatase (> 200 U/I) experienced faster relief from joint pain than patients with preoperatively normal concentrations (P = 0.0297). To date 4.5% of the patients developed recurrent hyperparathyroidism after total parathyroidectomy with autotransplantation. Morbidity of surgery for renal hyperparathyroidism is influenced by patients' risk factors. Postoperative hypocalcaemia correlates negatively with the grade of renal osteopathy at the time of operation. Preoperative concentrations of alkaline phosphatase influence the rapidity of the relief from joint pain.

Adult↗
PubMed1997

Antibody-mediated clean-up of blood for simultaneous HPLC determination of morphine and morphine glucuronides.

For the interpretation of the concentration of morphine in blood samples of heroin consumers information about the concentration of the analgesic active morphine metabolite morphine-6-glucuronide is very important. Thus a simple but specific clean-up procedure based on immuno-affinity chromatography is presented for the extraction of morphine, morphine-3-glucuronide and morphine-6-glucuronide from whole blood in cases of fatal heroin overdose. The preparation of the immunoabsorber by immobilization of antibodies against morphine-3-BSA and morphine-6-KLH with carbonyldiimidazole-activated trisacrylgel is described. The separation of the extracts is achieved by HPLC using native fluorescence detection. The limits of detection for this method are 10ng for morphine and morphine glucuronides/g blood. The results for the concentration of morphine and morphine glucuronides in blood from seven cases of heroin overdose are presented. By calculating the quotients for the concentrations of morphine-6-glucuronide/morphine the time elapsed since the last intake of heroin is estimated.

Antibodies↗
PubMed1997

Comparison of HPLC and CE for the analysis of dichlorprop in a case of intoxication.

A 49-year-old white male was found lying unconscious at home. He had vomited, his mouth was filled with a white foam and a pungent odour filled the room. After emergency treatment blood, urine and stomach contents were screened for drugs after acid and alkaline extraction with subsequent derivatisation and GC-MS analysis. Large quantites of 2,4-dichlorophenoxypropionic acid (dichlorprop, 2,4-DP) were found in all acid extracts. The man died 3 h later in hospital. Body fluids and tissues obtained at autopsy were analysed for 2,4-DP by high-performance liquid chromatography and capillary electrophoresis. The concentrations of 2,4-DP in cardiac blood, stomach contents, bile, liver, spleen, kidney and brain found by both methods were very similar.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1997

Dynamic blood cell contact with biomaterials: validation of a flow chamber system according to international standards.

The increasing number of patients requiring prosthetic substitution of segments of the vascular system strongly supports the need to optimize a relevant, standardized testing panel for new materials designed for synthetic vascular prostheses. The ISO gives the standard requirements for testing biomaterials provided for implantation. Our primary interest was the establishment of a reliable in vitro panel as a useful and relevant screening system for vascular implant devices to evaluate blood/device interactions under flow conditions. The aim of the present study was to evaluate influences of different flow conditions on blood cell-biomaterial interactions with special emphasis on the interactions of human granulocytes (PMN) and polymeric surfaces. PMN were isolated and vital cells were quantified by flow cytometrical analysis directly before, as well as immediately after the experiments. The viscosity of the final cellular suspension was analysed by using a computerized cone-plate rheometer. As reference materials we used FEP-teflon, PVC-DEHD, PU, PP and PE. Dacron and ePTFE synthetic vascular protheses were tested in a comparative way to those references. The adhesion processes were observed over a period of 40 minutes under arterial (shear stress 0.74 Pa) and venous (shear stress 0.16 Pa) flow conditions in a parallel plate flow chamber system under highly standardized conditions and laminar flow. The cells were observed with the help of inverse light microscopy. Cell behaviour was recorded and analysed in both analogue (video) and digital (imaging system) modes. Samples of the cell suspensions were obtained at regular time intervals and analysed by enzyme linked immuno sorbent assay (ELISA) to quantify LTB4 release. Irrespective of the material, approximately 3 to 4 times more PMN adhered to the biomaterial surfaces under venous flow conditions compared to the arterial. Shear intensity did not influence the running order of biomaterials with respect to cell numbers. This response in descending order at the end of the experiments was as follows: PU, PVC-DEHD, PP, PE and ePTFE. The biochemical analyses indicate that in the system used only a weak effect on LTB4 release induced by the different materials could be determined. A significant effect caused by flow conditions was not observed. Further experiments, both static as well as dynamic, must be performed for multiple, relevant parameters of haemocompatibility, for potential biomaterials as well as those currently in use in vascular prostheses.

Journal Article↗
PubMed1997

From cytotoxicity to biocompatibility testing in vitro: cell adhesion molecule expression defines a new set of parameters.

Determination of potential cytotoxicity is a central issue in current biocompatibility testing standards such as ISO and ASTM. Most of these tests do not assess biocompatibility of a biomaterial with regard to cell function. This study was aimed at screening a number of potential parameters that could be included in assessment of cell functional aspects of biocompatibility. Human umbilical vein endothelial cells (HUVEC) were seeded directly on titanium, NiCr alloy, CoCr alloy, PMMA, PE, PU, PVC, and silicone, or were exposed to the material extracts. Cytotoxicity was assessed for these materials through MTT conversion, crystal violet protein determination and Ki67 expression. In addition, expression of the cell adhesion molecules E-selectin, cadherin-5 and PECAM, as well as of the adhesion-associated proteins fibronectin and vinculin (focal adhesions), was determined by immunocytochemistry and western blotting. Cytotoxicity was not detected with the material extracts. Cells were able to adhere to bare metals, but not polymers. Fibronectin preadsorption resulted in adhesion and spreading also on the polymers. Cells were able to establish cell-cell contacts and focal adhesions. Western blotting, in combination with differential detergent extraction, indicated that linkage of cell-cell adhesion markers to the cytoskeleton may be used as an additional parameter relevant to cell function.

Journal Article↗
PubMed1997

The cell and molecular biological approach to biomaterial research: a perspective.

The past two decades have witnessed a revolution in our understanding of chemical processes in living organisms. This is mainly a result of the massive advances in the fields of cell and molecular biology. These techniques are highly relevant to the biomaterials sector, as they offer the scientist the possibility to better understand the mechanisms involved in the interactions between cells and a material surface-a prerequisite for the rational development of medical devices with optimal biocompatibility. The purpose of the present article is to explain the rationale of the cell and molecular biological approach to biomaterial research and to present typical examples from the authors' laboratory, as well as from the literature, to illustrate its application. Important aspects of interfacial biology, including the underlying biological mechanisms and methodology, are presented. Of the latter the combination of morphological techniques with methods of cell and molecular biology as well as molecular genetics (so-called "combinative techniques") are particularly useful. The applicability of this approach is illustrated from a study on the pathomechanisms of metal ion-induced inflammation. In addition, the approach is essential to the development of targeted intervention strategies, as for example in the luminal surface modification of vascular prostheses to permit endothelial cell seeding.

Journal Article↗
PubMed1997

Serological evidence for reactivation of EBV infection due to uraemic immunodeficiency.

BACKGROUND: Reactivation of EBV infection is a common finding in immunocompromised individuals. The influence of 'uraemic immunodeficiency' on EBV infection is so far not well defined. METHODS: We determined specific antibodies to EBV nuclear antigens (EBNA) 1 and 2 in sera of 286 patients with immunodeficiency due to progressive chronic renal failure and of 51 healthy controls. We used the baculovirus vector expression system for recombinant production of EBNA1 and EBNA2. RESULTS: Serological evidence of reactivated or chronic persistent EBV infection, i.e. an anti-EBNA1/anti-EBNA2 ratio (E1/E2) < 1, was found in 18% of patients with chronic renal failure not yet receiving renal replacement therapy (CRF), 11% of peritoneal dialysis patients (CAPD), 25% of haemodialysis patients (HD), 24% of renal transplant recipients (TX), and in 6% of healthy controls. Rate of EBV reactivation was significantly increased in HD (P = 0.004) and TX (P = 0.006) patients compared to healthy controls. Moreover, the difference between HD and CAPD patients was statistically significant (P < 0.05). This finding may reflect additional effects modulating the function of the immunosystem, probably through activation of immunologically competent cells by contact with the artificial surfaces of dialysis membranes. Although the rate of EBV reactivations is expected to increase further under conditions of therapeutic immunosuppression, our serological approach did not detect an additional effect of immunosuppressive therapy following renal transplantation. However, this finding may reflect an impaired endogenous synthesis of antibodies caused by immunosuppressive agents. CONCLUSIONS: We conclude that determination of E1/E2 is useful for assessment of EBV infection in patients with chronic renal failure and 'uraemic immunodeficiency'. In patients with immunosuppressive therapy following renal transplantation additional testing including direct estimation of viral load, is necessary to correctly assess the state of EBV infection.

Adult↗
PubMed1997

Insights into potential cellular mechanisms of cisplatin nephrotoxicity and their clinical application.

Cisplatin preferentially accumulates in cells of the S3 segment of the renal proximal tubule and is toxified intracellularly by hydration. The earliest manifestation of toxicity is inhibition of protein synthesis. GSH depletion is another important mechanism causing CP toxicity. Intracellular binding to SH groups leads to GSH depletion, resulting in lipid peroxidation and eventually mitochondrial damage. New measures to prevent GSH depletion and scavenge intracellular free oxygen radicals have been tried in clinical studies. Promising results indicate that cisplatin nephrotoxicity can be further reduced in the future.

Antineoplastic Agents↗
PubMed1997

Physiology and cell biology of the endothelium: a dynamic interface for cell communication.

This manuscript presents a brief overview of the physiology and cell biology of the endothelium, which is the basis for understanding the role of endothelial cells in pathological processes as diverse as atherosclerosis, tumour intravasation and multiple organ failure. Following consideration of general aspects of endothelial function in regulating haemostasis, vascular tone and growth, special emphasis will be placed on endothelial regulation of the inflammatory response, which centres on the microcirculation. A particular role in inflammation is played by cell adhesion molecules (CAM), expressed both on endothelial and blood cells. Cell and molecular biological methods to investigate the expression of CAM in endothelial cells in vitro will be presented, as well as novel data, indicating that cytokine-induced up-regulation of CAM in the endothelium may involve signal transduction pathways other than those culminating in the activation of NF-kappa B. Finally, the phenomenon of angiogenesis will be briefly reviewed as a characteristic of endothelial cell activity of central importance to both physiology and pathology and new experimental data presented from an in vitro model to study the ability of individual endothelial cells to form vessel-like structures. In comparative studies to investigate the roles of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor, the dominant role of VEGF in the formation of capillary networks could be unequivocally demonstrated.

Animals↗