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Biomedical subjects

H Köhler

Publications and source records attributed to H Köhler.

At least 37 records · Page 2Linked to original sources
PubMed2003

Effects of the mycotoxin ochratoxin A and some of its metabolites on human kidney cell lines.

The modulations of complement-regulating surface proteins on a human embryonic and a renal carcinoma cell line are described regarding the effects of ochratoxin A and some of its metabolites on the surface markers CD46, CD55 and CD59. Membrane integrity, cell proliferation and metabolic activity were reduced to different extents, depending on the kind of mycotoxin and the dosage, which was ranging from 10 to 1000 ng/ml. The number of cells carrying surface markers was suppressed significantly at 1000 ng/ml, in some cases even at 100 ng/ml, whereas the intensity of receptor expression on the positive cells was found to be stimulated. The fraction RE2 (OTC) isolated from an OTA-containing crude toxin surpassed the effects of all other ochratoxin metabolites. Apart from well-known cytotoxic and genotoxic effects modulation of cell surface marker expression by low concentrations of OTA and OTC deserves more attention with regard to its immuno-pathogenic importance. Furthermore, occurrence and impact of the mycotoxin OTC should be studied more into detail.

Antigens, CD↗
PubMed2003

A human flora-associated rat model of the breast-fed infant gut.

OBJECTIVES: Bacterial colonization of the infant gut may have important influences on the development of gastrointestinal, respiratory, and allergic disease. Early diet is a major determinant of the gut microflora. It is very difficult to carry out studies in human infants that can investigate the interaction of diet, flora, and mucosa. In this study we have developed an infant human flora-associated (IHFA) rat model to allow such investigation. METHODS: Germ-free infant rats were infected with fecal bacteria from exclusively breast-fed infants and were maintained on a modified infant formula for 8 weeks. The fecal and cecal contents were collected and compared with feces of breast-fed infants for bacterial populations, bacterial metabolites, and enzymes and for the ability to inhibit adhesion of pathogenic bacteria to human mucosal cells. RESULTS: The IHFA cecum and feces were dominated by lactic acid bacteria, Bifidobacterium, and lactobacilli, which were representative of the infant feces. The fecal short-chain fatty acid profile was dominated by acetic and lactic acid in a similar manner to human infant feces. Other bacterial metabolites were similar to those of the human infant. Rat intestinal samples were able to inhibit the adhesion of pathogens to mucosal cells, but to a lesser extent than the human samples. CONCLUSIONS: This IHFA infant model of the intestinal flora of the breast-fed infant is considered valid for studying the effect of diet on bacterial colonization and metabolism.

Animals↗
PubMed2002

Dioxin in infants--an environmental hazard?

The concentrations of the most common dioxin and dibenzofuran congeners were measured in different tissues (e.g. liver, kidneys, subcutaneous fatty tissue and spleen) from 27 infants who died suddenly and unexpectedly. The cases could be subdivided into 2 groups consisting of 15 infants who died in 1991/1992 and in 12 infants who died in 1996/1997. The autopsies were carried out using a standardised protocol and additionally the parents were asked to supply details of the nutritional conditions. The age of the mother and the birth order of the infants were also recorded. From the results obtained by correlating these parameters with the dioxin concentrations three main factors could be established: 1) there was a significant decrease in the total dioxin concentration in infant tissues from 1991/1992 to 1996/1997 indicating a decrease in the environmental dioxin levels due to a decrease in dioxin emission, 2) the birth order was inversely and the duration of breast feeding directly proportional to the dioxin concentrations thus showing that the mothers can decontaminate themselves by breast feeding and 3) an accumulation of specific dioxin congeners was observed in the liver tissue but the pathophysiological significance of these observations is not yet fully understood. Because of the well-known beneficial effects of breast feeding and considering the results of the present study, this type of infant nutrition can be recommended without any restrictions.

Adult↗
PubMed2002

Effects of various applications of lipopolysaccharides on blood parameters of pigs.

In five experiments, lipopolysaccharides (LPS) of Escherichia coli O26:B6 and O111:B4 were applied intravenously, intramuscularly, subcutaneously or intrabronchially in doses of 5000-15,000 U/kg body mass to a total of 47 weaner pigs and compared with the application of sodium chloride. Different parameters of blood cells were investigated, including cell numbers, in vivo interleukin secretion, radical formation, phagocytosis capacity and IL-6 as well as TNFalpha formation ex vivo. Non-specific effects and dependencies on the type of application and LPS dose are discussed.

Animals↗
PubMed2002

[In vitro studies into the influence of ochratoxin A on the production of tumor necrosis factor alpha by the human monocytic cell line THP-1].

The influence of pure OTA and an Aspergillus-ochraceus crude toxin on the intracellular expression and the secretion of tumor necrosis factor (TNF) alpha by the monocytic cell line THP-1 was studied in vitro. After 4 hours exposure, the secretion of TNF alpha was inhibited to 50% by pure OTA in a concentration of 400 ng/ml and by crude toxin in a concentration of 100 ng/ml. The same concentrations of mycotoxins impaired the mitochondrial activity of THP-1 cells only marginally. The intracellular expression of TNF alpha was not disturbed by pure OTA in the concentrations tested, whereas crude toxin showed an inhibitory effect. The possible reasons for these findings are discussed.

Calcium Channel Blockers↗
PubMed2002

[The importance of allergic skin test with Johnin, antibody ELISA, cultural fecal test as well as vaccination for the sanitation of three chronically paratuberculosis-infected dairy herds in Rhineland-Palatinate].

Three chronically paratuberculosis infected herds were tested for six years twice a year (intradermal Johnin test, antibody ELISA (IDEXX Corp.), microbial culture) according to a sanitary program. Culling of shedding animals and vaccination of calves with NEOPARASEC (Merial Corp.) were part of the program. In course of experiment, 1015 samples of 228 non vaccinated cows and 1502 samples of 293 vaccinated cattle have been tested. 3.8% of the vaccinated animals proved positive in microbial culture. Nearly all vaccinated calves developed granulomas sized from hazelnut to loaf at the injection site. Positive reactions in intradermal test as well as in antibody ELISA were found in very young calves. 24.3%, 33.7%, 25.9%, respectively of the non vaccinated animals were identified as shedders of M. avium subsp. paratuberculosis (MAP) by microbial culture. In the first and in the second herd most shedders of MAP were found in the first herd examination (66.7%, 42.9%, respectively), whereas in the third herd they were detected in the fifth examination (31.0%). At the beginning, 17.9% of non vaccinated animals proved positive in intradermal test, 14.4% in antibody ELISA. Afterwards, the number of positive test results decreased but increased again towards the end of the experiment. 48.5% of the 66 shedders showed positive reactions in intradermal test, 57.6% in antibody ELISA, 77.3% in at least one of these both tests. Antibodies in ELISA were found in rising frequency from two years before the time of shedding. 50.0% of the shedders reacted positive in ELISA at the time of shedding. In selected shedders first positive results were found at the age of about two years. Unfortunately, only incomplete hygienic measures were realized by the farmers. Under field conditions the realisation of attending sanitary programs is difficult. MAP is spread mainly by buying of animals, therefore a certification program for paratuberculosis free herds is urgently necessary as well as an improvement of diagnostic methods.

Animals↗
PubMed2001

Levels of virus-specific CD4 T cells correlate with cytomegalovirus control and predict virus-induced disease after renal transplantation.

BACKGROUND: Immunosuppressive treatment in transplant patients frequently causes infectious complications with cytomegalovirus (CMV). The extent of CMV replication can be followed by a number of diagnostic methods. There is, however, no simple diagnostic tool to assess the quality of the cellular antiviral immune response of an individual patient. This would be of particular importance for therapy decisions, as patients with detectable virus load do not necessarily develop CMV-related disease. Using a rapid whole blood assay, the frequencies of CMV-reactive CD4 and CD8 T cells were followed after renal transplantation to characterize their relative contribution in the containment of CMV infection. METHODS: T cells from transplant patients ands healthy control persons were stimulated with CMV antigen in vitro. Based on specific cellular activation and induction of intracellular cytokines, the frequency of CMV-reactive CD4 and CD8 T cells was determined using flow cytometry. Viral load quantified using the "hybrid-capture" assay. RESULTS: The absence of CMV complications in long-term transplant recipients is reflected by stable virus-specific T-cell frequencies, which do not differ from healthy CMV-positive controls. In contrast, during the first months after transplantation, clinical symptoms are preceded by a decrease in CMV-reactive CD4 T-cell frequencies and an increase in CMV load. CONCLUSIONS: The individual immune response and CMV replication are critically balanced and can be characterized by assesing both viral load and antiviral T cells. Our experimental design allows the identification of patients with sufficient, insufficient, or absent T-cell activity and can serve as diagnostic tool to facilitate decisions on antiviral therapy.

Adult↗
PubMed2001

AIDS epidemic at the beginning of the third millennium: time for a new AIDS vaccine strategy.

Current expansion of AIDS pandemic significantly accelerates AIDS vaccine research resulting in development and clinical testing of several AIDS vaccine candidates. At the same time, available experimental and clinical data demonstrate that current AIDS vaccine strategy is unsuccessful resulting in development of inefficient and harmful vaccines. This overview briefly summarizes reported results which point out the requirement for moratorium on the current clinical trials of HIV-1 gp120/160 vaccines and urgent need for development of a new, efficient and safe AIDS vaccine strategy.

AIDS Vaccines↗
PubMed2001

The cloven hoof in legal medicine.

The injury of a horse's leg needed to be investigated to answer the question whether the fracture had been caused by an accident or by intentional manipulation. By toxicology and using scanning electron microscopy with an energy dispersive X-ray spectrometer (SEM-EDX) the suspicion obtained by morphology could be confirmed. Toxicologically a short term anaesthetic was found, and by EDX ferric oxide particles could be detected in the wound indicating that the injury was caused by a sharp pointed metallic instrument and not as stated by the owner by a wooden bar. As the result of the interdisciplinary investigation using modern techniques, there is no doubt that the owner attempted to fraudulently claim on an insurance policy.

Animals↗
PubMed2001

Influence of glutamine and glycyl-glutamine on in vitro lymphocyte proliferation in children with solid tumors.

It is reported that the proliferative response of lymphocytes is lowered in patients with solid tumors. Glutamine is a major nutrient for rapidly proliferating cells. Unlike glutamine itself, the dipeptide glycyl-glutamine as a source for glutamine is stable in aqueous solutions ex vivo. In order to evaluate the possible therapeutic role of glutamine in lymphocyte proliferation, we investigated its influence on lymphocytes of children with solid tumors before and after chemotherapy. Lymphocytes were collected from 21 children and adolescents suffering from solid tumors (before and after chemotherapy) and from healthy controls. Glutamine and glycyl-glutamine, respectively, were added to cell cultures at concentrations between zero and 1.0 mmol/l. ConA or SAC served as T- or B-cell mitogens, respectively. The lymphocyte proliferation in the healthy control group was similar in degree to lymphocyte proliferation seen in the patients with solid tumors, regardless of the mitogen used. No difference in the degree of lymphocyte proliferation before or after chemotherapy was seen with either source of glutamine. Specific subgroups of malignancies showed trends that differed from the overall findings, but these differences were not found to be statistically significant. Routine supplementation with glutamine in children with solid tumors to enhance lymphocyte function is not supported by the data gained from in vitro proliferation tests.

Adolescent↗
PubMed2001

Selective sequestration of cytokine-producing monocytes during hemodialysis treatment.

Hemodialysis treatment leads to leukocyte activation and cytokine production. Studying this effect has been complicated because cell activation by blood membrane contact also induces adherence factors on leukocytes, leading to margination of cells to the endothelium of the lung. Using single-cell cytokine determination, we studied the relation between cytokine production and cell sequestration during dialysis therapy. Blood was sampled in 11 chronic hemodialysis patients using hemophane dialyzers before hemodialysis and at 20 and 120 minutes of treatment. Lipopolysaccharide (LPS)-induced cytokine production in monocytes was studied by intracellular staining for interleukin-6 (IL-6) and IL-10 and flow cytometry. Results obtained in dialysis patients were compared with samples from an ex vivo dialysis system. Monocyte maturation stage was evaluated by detection of several surface markers through flow cytometry. Within 20 minutes of hemodialysis, the numbers of circulating monocytes decreased to one third of initial values. Before dialysis, 56.7% +/- 15.7% of circulating monocytes responded to LPS by the production of IL-6. This fraction decreased to 21.1% +/- 17.3% (P < 0.001 versus before hemodialysis) at 20 minutes and 32.3% +/- 13.8% (P < 0.001 versus before hemodialysis) at 120 minutes of treatment. A similar decrease occurred for IL-10. Cytokine-positive cells did not decrease during ex vivo dialysis. Surface marker studies showed that mature monocytes expressing HLA-DR or CD86 were predominantly removed. We provide the first evidence for a subtype-specific sequestration of monocytes caused by dialysis treatment. Fully differentiated cells capable of cytokine production and antigen presentation are removed and relatively immature cells remain in circulation.

Aged↗
PubMed2001

Immune reactions in cattle after immunization with a Mycobacterium paratuberculosis vaccine and implications for the diagnosis of M. paratuberculosis and M. bovis infections.

After immunization of four calves with a live modified Mycobacterium paratuberculosis vaccine the course of the humoral and cell mediated immune reactions was studied during a 2-year clinical investigation. Furthermore, the possibility of shedding of the vaccine strain and the influence of the vaccination on the tuberculin skin test was determined. In addition to standard procedures recently developed diagnostic methods (antibody enzyme-linked immunosorbent assay, interferon-gamma test, polymerase chain reaction) were used. A cell-mediated immune reaction, reflected in an increased, specifically induced, interferon-gamma production developed much earlier (1-2 weeks post-immunization) than humoral immunity (8-16 weeks post-gamma immunization). While the increase in antibody titres was transient, declining to extremely low levels 48-60 weeks post-immunization, cell-mediated immunity remained detectable until the end of the investigation. Spread of the vaccine strain into the body and shedding were never detected during the whole course of the study except for one colon site in one calf. As late as 2 years after vaccine application positive or doubtful skin reactions against M. bovis purified protein derivative were measured, reflecting possible interference of the immunization with the diagnosis of bovine tuberculosis. At the end of the investigation, a positive cell-mediated immune reaction was detected the control animal although clinical, pathological and bacteriological examinations gave no indication for a mycobacterial infection.

Animals↗
PubMed2001

The interleukin-10 promoter genotype determines clinical immune function in hemodialysis patients.

BACKGROUND: Immune dysfunction and the impaired hepatitis B vaccination response are complications of chronic renal failure that are tightly associated with inflammation induced by uremia and blood-membrane contacts. Proinflammatory cytokines, such as interleukin (IL)-6, are counter-regulated by IL-10 with a large interindividual variability. Part of the variability of cytokine production is genetically determined since polymorphisms in the cytokine gene promoters lead to high or low production. The aim of this study was to detect the genetic influence of the IL-10 promoter on immune function of chronic hemodialysis patients. METHODS: The IL-10 genotype (polymorphic bases at positions -1082 and -819) was determined in 272 chronic hemodialysis patients using highly specific PCR and related to the patients' response to a triple vaccination against hepatitis B. Secretion of IL-10 and IL-6 by peripheral blood leucocytes in vitro was determined by ELISA. RESULTS: The prevalence of the IL-10 genotypes in dialysis patients with well-preserved immune function (vaccination responders) was similar to the general population. In contrast, prevalence of the -1082G* allele (associated with high production of IL-10) was low in the nonresponders. The relative risk of vaccination nonresponse in patients homozygous for the -1082A* allele was 1.394 (95% CI, 1.091 to 1.781, P < 0.05) compared to those homozygous for -1082G*. There was no relationship between the IL-10 genotype and the type of renal disease. CONCLUSIONS: The IL-10 genotype determines IL-10 production in dialysis patients, which down-regulates uremia- and dialysis-induced chronic inflammation and helps to preserve immune defense functions.

Cytokines↗
PubMed2001

Evaluation of renal Kt/V as a marker of renal function in predialysis patients.

BACKGROUND: The use of renal Kt/V (r-Kt/V) as an indicator for the need of dialysis initiation has been recommended in the NKF-DOQI guidelines. In analogy to clinical practice in peritoneal dialysis, a fall of r-Kt/V below a threshold of 2.0 per week may indicate inadequate renal toxin elimination. However, there are no studies linking r-Kt/V with other parameters of glomerular filtration rate (GFR) in predialysis patients, and the validity of r-Kt/V as parameter for timing of dialysis initiation is unknown. METHODS: Renal function was assessed repeatedly in 125 patients (N = 465 measurements). In predialysis patients (r-Kt/V <2.5 per week) r-Kt/V was compared with creatinine [CCr], urea [CUr], averaged creatinine/urea clearance [CCr/Ur], Cockcroft-Gault formula [CCG], and MDRD prediction equation 6 (MDRD6-GFR). The diagnostic performance of r-Kt/V as a parameter for timing the initiation of dialysis was evaluated. RESULTS: Renal Kt/V <2.5 was prevalent in 24.9% of cases (N = 116, mean 1.92 +/- 0.34). In this group mean CCr was 13.8 +/- 4.9, mean CUr 6.7 +/- 1.3, and CCr/Ur 10.2 +/- 2.9 mL/min/1.73 m2. There was no correlation of r-Kt/V with serum creatinine and MDRD6-GFR, but a significantly positive correlation with CCr/Ur (r2 = 0.3382, P < 0.001). Sensitivity of r-Kt/V to detect CCr/Ur < 10.5 mL/min/1.73 m2, defined as the threshold for dialysis initiation, was 73.6% with a specificity of 91.9%. CONCLUSIONS: These results suggest that r-Kt/V is a parameter of acceptable specificity but poor sensitivity for the timing of dialysis initiation. Additional measures of renal function, such as the average of measured creatinine and urea clearance, also should be taken into consideration when deciding on the timing of dialysis initiation prior to the development of clinical signs of uremia and malnutrition.

Adult↗
PubMed2001

Defective expression of B7-2 (CD86) on monocytes of dialysis patients correlates to the uremia-associated immune defect.

BACKGROUND: Specific cellular immune reactions in patients with chronic renal failure (CRF) are impaired by a defect of the antigen-presenting cells. To elucidate the molecular background for this defect, we determined the expression of human lymphocyte antigen (HLA)-DR and costimulatory molecules on monocytes of hemodialysis patients. METHODS: The expression of HLA-DR, B7-1 (CD80), and B7-2 (CD86) molecules was determined on CD14+ monocytes of chronic hemodialysis patients prior to a dialysis session. Mononuclear cells of these patients were cultured, and expression of the respective antigens was determined after in vitro activation by various stimuli. Results were correlated with in vitro proliferation of T cells in a phytohemagglutinin (PHA) assay and the clinical response to a hepatitis B vaccination. All data were compared with healthy controls and patients with CRF who were not on dialysis. RESULTS: Monocytes of chronic hemodialysis patients but not CRF patients expressed low levels of costimulatory B7-2, while HLA-DR expression was normal. B7-1 was only expressed on activated monocytes, and the expression reached normal levels in hemodialysis patients. Baseline expression of B7-2 highly correlated with the results of T-cell proliferation assays in hemodialysis patients and also with the clinical immune response. CONCLUSIONS: Impaired expression and up-regulation of B7-2 is an important feature of the cellular immune defect in chronic hemodialysis patients. It leads to reduced costimulation and effector activation of T cells and contributes to a molecular explanation for the impaired response of hemodialysis patients to the hepatitis B vaccination.

Adult↗