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Biomedical subjects

H Richter

Publications and source records attributed to H Richter.

At least 73 records · Page 4Linked to original sources
PubMed1997

Advanced glycation endproducts stimulate the MAP-kinase pathway in tubulus cell line LLC-PK1.

Advanced glycation endproducts (AGEs) are suggested to play an important role in diabetic nephropathy. They induce specific cellular responses such as the release of cytokines in different cell lines. The effect of AGEs on signal transduction pathways was investigated in the renal tubulus cell line LLC-PK1. Using a serine-phosphate-specific antibody AGE-induced cellular responses associated with phosphorylation/dephosphorylation events were demonstrated. In particular, the p42MAP kinase and its downstream target, the AP-1 complex, are shown to be activated by AGE-BSA but not by BSA. In contrast, only partial phosphorylation is observed for the p70S6-kinase. Thus, AGEs appear to induce specific signal transduction pathways.

Animals↗
PubMed1997

Developmental changes of inward rectifier currents in neurons of the rat entorhinal cortex.

A slice preparation was used to investigate inward rectifier currents (I(H)) of entorhinal cortex (EC) neurons. Using the whole-cell configuration of the patch-clamp technique, I(H) was studied in pyramidal cells from layer IV of the rat EC and in stellate cells from layer II of the EC. Inward rectifier currents were analyzed in neurons of newborn (P1-3), juvenile (P8-14) and adult (>P28) rats. Pyramidal cells of juvenile rats possessed a significantly larger current density of I(H) than pyramidal cells of newborn rats, whereas no differences in the current density of I(H) were found between pyramidal neurons of juvenile and of adult animals. In contrast, the current density of I(H) of stellate cells was significantly increased in juvenile rats compared with newborn rats as well as in adult rats compared with juvenile rats. Moreover, in adult rats the current density of I(H) was larger in stellate cells than in pyramidal cells, whereas opposite data were obtained in juvenile animals.

Age Factors↗
PubMed1997

Reduced activity in the extrastriate visual cortex of individuals with strabismic amblyopia.

In order to examine the relationship between reduced visual acuity in human strabismic amblyopia and the cortical activation pattern, we studied, by use of positron emission tomography (PET) and the H2(15)O bolus technique, changes in the regional cerebral blood flow (rCBF) induced by monocular visual stimulation of 8 individuals with this disorder. Individual amblyopic thresholds for monocular detection of the checkerboard pattern were employed as stimuli for both eyes during PET scans. Statistical analysis of subtracted images showed significant increases in rCBF (P < 0.05) by the stimulation of the sound eye localized bilaterally to Brodmann's areas (BAs) 17-19. The cortical response evoked by the amblyopic eye was significantly reduced (P < 0.05) in the ipsilateral BAs 18, 19. These results suggest that the reduction in contrast sensitivity (pattern vision) in amblyopia is coupled with deactivation in identifiable regions of occipital visual areas, including ipsilateral BAs 18,19.

Adult↗
PubMed1997

An in vivo study of the biodegradation of the hydrophilic Mitrathane.

The present study analyzes the kinetics of the in vivo degradation of hydrophilic Mitrathane in the peritoneal cavity of mice over a period ranging from 1 to 180 days. The mechanical milling of the polyurethane films produced regularly flattened fragments that in vivo spontaneously oriented into piles. The morphological observations and analysis with the aid of an image analysis system demonstrated that after seven days of swelling the polymer fragments undergo a continuous degradation that leads to an irregular thinning and phagocytosis of the smaller fragments by macrophages with very little chronic inflammation response from surrounding tissues.

Animals↗
PubMed1997

[Reduction of cataract by plasma etching of intraocular lenses. An animal experiment study].

BACKGROUND: We studied if a modification of the silicon intraocular lens (IOL) by plasma etching is able to promote a bonding of the IOL surface and the capsular bag which might inhibit proliferation and migration of lens epithelial cells. METHODS: Silicon-disc lenses (90D, Adatomed), as disposable for regular cataract surgery, were used. Their haptic surface was etched via the use of a SO2 plasma, leaving the optic unmodified. The experiments were done on dwarf rabbits to allow for tight apposition of IOL and bag. Nine rabbits underwent extracapsular lensectomy using propofol anaesthesia and phaco/clear cornea surgical technique. Six eyes each received either no, a regular or a modified IOL. After 11 weeks the eyes were enucleated. Capsular bag and IOL were digitized using a flatbed scanner with transparency adapter. The data obtained were calibrated against a densitometric standard. The densities of the various specimen were analyzed quantitatively using self designed software. RESULTS: In aphacic eyes no significant posterior capsule opacification (PCO) was detectable. In the same time-span the regular IOL had developed a dense, heterogenous PCO. The plasma-treated IOL showed, especially in the central areas, a significant reduction of PCO as compared to untreated IOL. CONCLUSION: The reduction of PCO could not be explained by adhesion of the IOL surface and the capsular bag, which would impair migration of lens epithelial cells and thereby PCO. Likewise, lower PCO may be related to improved hydrophilic properties of the surface-modified IOL.

Animals↗
PubMed1997

[Verotoxin-producing E. coli (VTEC) in feces from cattle slaughtered in Germany].

In man, EHEC infections may result in severe disease. Cattle and foods derived from this animal species are considered as a source of infection. The presence of VTEC being potential EHEC was studied. For analysis, feces samples were examined which had been taken from 204 heads of cattle slaughtered in various regions of Germany. VTEC could be isolated from 97 animals (47.6%). This indicates a presence of VTEC in slaughtered cattle being 5 times higher than known for Germany so far. The aeaA gene could be demonstrated in a mere 23 out of 667 VTEC isolates. The CVD 419 sequence was present in 55.3% of the VTEC isolates. Ehly was found in 61% of them. Consequently, both markers were unsuitable for the detection of VTEC in faeces samples from cattle and in foods with faecal contamination. The VTEC isolates belonged to 54 different serotypes of E. coli, VTEC 0157 have not been found so far. Some of the VTEC serovars found in this study have already been described as associated with human disease following EHEC infection. The presently available laboratory methods do not permit to exclude a risk for humans from bovine VTEC reliably. For this reason, bovine VTEC should be further on considered as potential EHEC and an infection of humans by such agents be avoided.

Abattoirs↗
PubMed1997

[Present problems in detection of sources of infection and chains of infection with enterohemorrhagic E. coli (EHEC)].

In the context of the detection of the haemolyticuraemic syndrome (HUS) and of enterohaemorrhagic E. coli (EHEC) in 13 persons, 372 faeces samples from 13 herds of cattle in northern Bavaria were examined for the presence of EHEC. 128 (34.4%) of the faeces samples were found to be VT-positive. From 78 of these samples (61%), verotoxin-producing E. coli strains (VTEC) could be isolated. During these examinations, E. coli strains with combinations of markers (VT, eae A, EHEC haemolysin) being typical of EHEC were found in 3 samples from animals belonging to the same herd. In 2 cases, these could be assigned to O157:H-, in one, to O118:H16. It has not been possible to detect possible sources of infection and chains of infection assumed to exist in association with the detection of HUS and EHEC infections in humans because most cases had been diagnosed on the basis of verotoxin detection in stool specimens. Moreover, corresponding isolates for a comparative onward differentiation from verotoxin-producing E. coli isolates from animals were not or could not be made available.

Animals↗
PubMed1997

Detection of STEC and epidemiological investigations in surrounding of a HUS patient.

After occurrence of a case of HUS infection in a 2-year-old infant from a dairy farmer's family living near Oldenburg, investigations were performed in the infant's surrounding in order to elucidate the route of infection. Since hospitalization took place at a late stage, it was not possible to isolate EHEC from the patient's stool samples. However, E. coli O157 antibody determinations in serum were positive. Since STEC of serogroup O157 were found in faeces from the 34 dairy cows of the farm, stool samples were taken from 6 members of the child's family and examined. Non-O157 STEC could be isolated from the stools of 2 family members. Determination of other virulence factors and other characteristics such as serotype, biotype and phage type showed identity of the agent for 3 isolates (2 from animals, 1 from humans). By means of pulsed-field gel electrophoresis of the restricted DNA of the isolates and by means of RAPD-PCR it was not possible to establish any differences in the band patterns. It can be assumed, therefore, that the organisms had been transmitted from animals to humans.

Animals↗
PubMed1997

[Detection and occurrence of verotoxin-forming and/or shigatoxin producing Escherichia coli (VTEC and/or STEC) in milk].

Raw milk contaminated with VTEC was described as a source of human EHEC infection. Diagnosis of VTEC from milk is complicated by the low number of VT-positive cells in the total bacterial count, the great variety of serovars with different combinations of virulence markers and the lack of characteristic biochemical properties for the cultural detection of all VTEC. The graduated procedure presented and used for the examination of milk samples is based on VT detection in suitable enrichment cultures and the selective isolation of VTEC by means of VT-specific monoclonal antibodies using the VT-colony immunoblot. This method was used to examine 127 samples of raw milk and 146 samples of certified raw milk (Vorzugsmilch) from 5 different regions in Germany. 3.9% of the raw milk samples and 2.1% of the certified raw milk samples were VTEC-positive. Except for one O157:H- isolate from a raw milk sample, the VTEC found belonged to the group of non-O157 VTEC. They were assigned to 5 different serovars with different combinations of virulence markers. Therefore, raw milk and certified raw milk will continue to present a potential source of EHEC infection. It is recommended to use the procedure presented for the elucidation of the route of infection and for the improvement of detection of VTEC and EHEC-strains in milk in order to obtain comparable data for diagnosis in the official food control laboratories of the federal lands.

Animals↗
PubMed1997

[Optimization of the polymerase chain reaction (PCR) for detection and characterization of shigatoxin producing Escherichia coli (STEC) in food].

The polymerase chain reaction (PCR) was improved to detect shigatoxin producing Escherichia coli (STEC) in milk. Numbers of colony forming units (cfu) in test samples, concentrations and types of primers, amount of MgCl2, types of thermostable DNA-Polymerase, and cycling programs were modified up to obtain the cleanest electrophoretic pattern and the highest sensitivity. Experimental conditions for further characterization of STEC-isolates by means of PCR are given by summarizing data from literature.

Animals↗
PubMed1996

Induction of dedifferentiated clones of LLC-PK1 cells upon long-term exposure to dichlorovinylcysteine.

Dichlorovinylcysteine (DCVC), the key metabolite of the nephrotoxic and nephrocarcinogenic chemicals, trichloroethylene and dichloroacetylene, exerts potent acute cellular toxicity in LLC-PK1 cells (Vamvakas S., Bittner, D., Dekant, W. and Anders, M.W. (1992). Events that precede and that follow S-(1,2-dichlorovinyl)-L-cysteine-induced release of mitochondrial Ca2+ and their association with cytotoxicity to renal cells. Biochem. Pharmacol. 44, 1131-1138). In the present study we investigated whether long-term exposure of LLC-PK1 cells to low, non-cytotoxic concentrations of DCVC results in stable morphological and biochemical dedifferentiation. After 7 weeks exposure to 1 and 5 microM DCVC, morphologically changed single cells were picked under the microscope and cultured in absence of DCVC for 4-8 weeks. In contrast to the physiological cuboidal shape of untreated LLC-PK1 cells, the clones derived from long-term exposure to DCVC consisted of elongated, spindle-shaped cells tending to form irregular borders. Moreover, glucose uptake, pH-dependent ammonia production and dome formation, important indicators of the renal tubule origin of the LLC-PK1 cells, were severely impaired in the clones. In addition to the loss of membrane polarity, the clones exhibited altered composition of the nuclear matrix and intermediate filament proteins by two-dimensional gel electrophoresis, increased poly(ADP-ribosyl)ation of nuclear proteins and enhanced expression of c-fos. The induction of dedifferentiated LLC-PK1 clones with stable characteristics upon long-term exposure to the nephrocarcinogen DCVC may represent a useful in vitro model to study biochemical alterations involved in chronic renal toxicity and carcinogenicity.

Ammonia↗
PubMed1996

[A method for specific isolation of verotoxin-producing Escherichia coli colonies].

The described colony immunoblot is a special double membrane-agar technology, which permits the specific isolation of VTEC in biological materials decided VT-positive by EIA or PCR. The produced Verotoxin (VT) is detected on the surface of the lower membrane by help of monoclonal antibodies. A direct allocation of the corresponding VT-expressing E. coli-colonies on the upper membrane is possible. So the isolation and further characterisation of potential VTEC is practicable in materials with a high microbial contamination too. This isolation method is available for the examination of VT-positive faeces and foods. In the case of foods it is necessary to work with an enrichment culture.

Bacterial Toxins↗
PubMed1996

[Cyst, pseudocyst or carcinoma? Space-occupying lesions of the pancreas in childhood and adolescence].

A total of 29 children and adolescents underwent surgery for cystic (n = 2) or pseudocystic (n = 23) lesions or papillary-cystic neoplasms (n = 2) of the pancreas. The special conditions of paediatric patients (differential diagnosis, management and prognosis of posttraumatic, postnecrotic, inflammatory and malignant diseases) are discussed in the present literature.

Abdominal Injuries↗
PubMed1995

Glyoxysomal malate dehydrogenase and malate synthase from soybean cotyledons (Glycine max L.): enzyme association, antibody production and cDNA cloning.

In order to investigate a possible association between soybean malate synthase (MS; L-malate glyoxylate-lyase, CoA-acetylating, EC 4.1.3.2) and glyoxysomal malate dehydrogenase (gMDH; (S)-malate: NAD+ oxidoreductase, EC 1.1.1.37), two consecutive enzymes in the glyoxylate cycle, their elution profiles were analyzed on Superdex 200 HR fast protein liquid chromatography columns equilibrated in low- and high-ionic-strength buffers. Starting with soluble proteins extracted from the cotyledons of 5-d-old soybean seedlings and a 45% ammonium sulfate precipitation, MS and gMDH coeluted on Superdex 200 HR (low-ionic-strength buffer) as a complex with an approximate relative molecular mass (Mr) of 670,000. Dissociation was achieved in the presence of 50 mM KCl and 5 mM MgCl2, with the elution of MS as an octamer of M(r) 510,000 and of gMDH as a dimer of M(r) 73,000. Polyclonal antibodies raised to the native copurified enzymes recognized both denatured MS and gMDH on immunoblots, and their native forms after gel filtration. When these antibodies were used to screen a lambda ZAP II expression library containing cDNA from 3-d-old soybean cotyledons, they identified seven clones encoding gMDH, whereas ten clones encoding MS were identified using an antibody to SDS-PAGE-purified MS. Of these cDNA clones a 1.8 kb clone for MS and a 1.3-kb clone for gMDH were fully sequenced. While 88% identity was found between mature soybean gMDH and watermelon gMDH, the N-terminal transit peptides showed only 37% identity. Despite this low identity, the soybean gMDH transit peptide conserves the consensus R(X6)HL motif also found in plant and mammalian thiolases.

Amino Acid Sequence↗