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Biomedical subjects

A Dörrenhaus

Publications and source records attributed to A Dörrenhaus.

8 recordsLinked to original sources
PubMed2000

Cultures of exfoliated epithelial cells from different locations of the human urinary tract and the renal tubular system.

Exfoliated human urinary tract epithelial cells and renal tubular cells from urinary sediments of healthy adults, of urological patients and of internal patients were isolated and cultured. Cells started proliferating within 1 week after seeding a sediment. Proliferating cells formed colonies of different morphologies, designated as type-1 or type-2 cell colonies. Type-1 cell colonies showed irregular contours and spindle-like cells within the colonies. Subcultivation of type-1 cells for up to six passages was possible. Type-2 cell colonies showed smooth-edged contours and subcultivation was not possible. The epithelial character of type-1 cells was demonstrated by positive immunohistochemical staining for cytokeratin-7. In contrast to carbonic anhydrase-positive stained Madin Darby canine kidney cells (MDCK), which were used as positive controls for renal tubular cells, type-1 cells were carbonic anhydrase-negative on staining with the cobalt phosphate method. This indicates that type-1 cells were not of renal tubular origin. Type-2 cells were positively stained for carbonic anhydrase, indicating that type-2 cells were renal tubular cells. Type-2 cell colonies could be assigned to two subgroups with different cell forms. Colonies of cobblestone-like cells more often occurred than type-2 cell colonies with spindle-like cells, which are described in this study for the first time. Colonies with cobblestone-like cells formed domes (hemicysts), whereas spindle-like type-2 cell colonies did not. Cultures of urinary sediments from healthy adults, elderly multimorbid patients treated with furosemide, and urological patients with urolithiasis treated with sulfamethoxazole/trimethoprim and/or with a percutaneous nephrostomy catheter were compared. In 52% of all cultured sediments from healthy adults, in 30% of those from multimorbid patients, and in 75-80% of those from urological patients cells proliferated to colonies. The ratios of type-1 to type-2 cell colonies were 3.3:1 (healthy adults), 1.4:1 (urological patients with urolithiasis), and 1.8:1 (urological patients with urolithiasis, urine was directly collected from the renal pelvis with a percutaneous nephrostomy catheter). Successful cultures of the urinary sediments from these three groups revealed means of 3 or 4 colonies, 14 colonies, and 21 colonies, respectively. Differences in the number of colonies in relation to sex were observed only for the group of urological patients. It was shown that type-1 cells were urothelial cells, which did not show morphological differences due to their locations of origin within the urinary tract, whereas type-2 cells were probably renal tubular cells. These findings offer new aspects in the culturing of human urothelial or kidney epithelial cells with a method based on noninvasive collecting of specimens and requiring only minimal culture effort. The cultures obtained by this method can be used for in vitro studies in toxicological and clinical research.

Adolescent↗
PubMed2000

Induction of unscheduled DNA synthesis in primary human urothelial cells by the mycotoxin ochratoxin A.

Ochratoxin A (OTA) is a widespread contaminant in human staple food. Exposure of humans to this mycotoxin is a matter of concern because OTA is a known rodent carcinogen. As the urothelium is one target tissue of this mycotoxin, primary cultured human urothelial cells (HUC) from adults and children were used to analyze the induction of unscheduled DNA synthesis (UDS) by OTA. HUC were isolated from the ureters or renal pelves of two nephrectomized adults and of two children with ureteropelvic junction stenosis and cultured under serum-free conditions. After a confluency of 70-80% was reached, cell proliferation was suppressed by arginine-deficient medium (ADM), and UDS was assessed autoradiographically by 3H-thymidine incorporation upon exposure to OTA (10-2000 nM), ethyl methanesulfonate (EMS, 5 mM, positive control), or dimethyl sulfoxide (DMSO, 0.2%, solvent control). In control cultures the level of UDS was low. Exposure to EMS resulted in an induction of UDS (2-to 5-fold compared to control), thus allowing the sensitive detection of repair resulting from induction of DNA lesions in all four specimens, and demonstrating that repair of EMS-induced DNA lesions can take place under the chosen culture conditions. In two HUC cultures derived from adults, a significant induction of UDS was observed in the concentration range of 50-500 nM OTA. The highest fraction of cells in repair (CIR) was found at 50 nM OTA for the HUC from the older male (50% CIR). The maximum response in the other specimens from the adult female and the 7-year-old boy were seen at OTA concentrations of 500 and 250 nM, respectively. In contrast to all other specimens, no significant induction of UDS by OTA was found in the HUC cultures derived from an infant's urothelium. Signs of cytotoxicity were observed above 500 nM OTA in all cultures. The varying susceptibility toward OTA observed in vitro may hint at varying predispositions of individuals in vivo.

Adult↗
PubMed1997

Determination of degradation rates of transfer and ribosomal ribonucleic acids in cultured rat hepatocytes by measuring N6-threoninocarbonyladenosine, dihydrouridine, and pseudouridine in medium using high-performance liquid chromatography.

Modified ribonucleic acid catabolites excreted into the medium by primary cultures of rat hepatocytes (2.3 +/- 0.42 x 10(6) cells/dish) during a 24-h cultivation period were quantified by reversed-phase high-performance liquid chromatography (fmol/10(3) cells): 613 +/- 81 dihydrouridine, 46 +/- 6 N6-threoninocarbonyladenosine, 1879 +/- 220 pseudouridine. On the basis of these excretion rates and the average frequency of occurrence of these modified ribonucleosides per cytoplasmic transfer ribonucleic acid (residues: 2.6 dihydrouridine, 0.22 N6-threoninocarbonyladenosine, 3 pseudouridine) as well as per cytoplasmic ribosomal ribonucleic acid (residues: 95 pseudouridine), the degradation rates of transfer and ribosomal ribonucleic acids were calculated. The degradation rate of transfer ribonucleic acid (fmol/10(3) cells/24 h) was 236 +/- 31 (via dihydrouridine) and 211 +/- 28 (via N6-threoninocarbonyladenosine) and that of ribosomal ribonucleic acid (fmol/10(3) cells/24 h) was 13.1 +/- 1.7 (via pseudouridine and N6-threoninocarbonyladenosine).

Adenosine↗
PubMed1997

Effects of ochratoxin A on DNA repair in cultures of rat hepatocytes and porcine urinary bladder epithelial cells.

In cultured rat hepatocytes the mycotoxin ochratoxin A (OTA) induced unscheduled DNA synthesis (UDS) only in a narrow concentration range. Using a culture medium supplemented with 1% fetal calf serum, at 750 nM OTA a weak induction and at 1 microM OTA a marked induction of DNA repair was observed (15 +/- 11 and 38 +/- 24% cells in repair, respectively). Concentrations > 1 microM OTA were cytotoxic, and <750 nM no induction occurred. In cultures of cells from the urinary bladder (porcine urinary bladder epithelial cells; PUBEC), a target organ of the mycotoxin, OTA induced UDS in a concentration-dependent manner. To inhibit the proliferation of the cultured epithelial cells, which would counteract the detection of DNA repair, epidermal growth factor was omitted and an arginine-deficient medium (ADM) was used. Under these serum-free culture conditions the amount of cells undergoing DNA repair in PUBEC control cultures was approximately 7 +/- 4%, a value also comparable to those of control cultures of rat hepatocytes. At concentrations between 250 nM and 1 microM OTA a concentration-dependent increase of cells in repair was observed. Above 1 microM OTA was cytotoxic. At this concentration a maximum of approximately 61 +/- 9% of the cells undergo DNA repair. This amount is comparable to control cultures incubated with 5 or 10 mM ethylmethane-sulphonate (EMS) (49 +/- 9 and 69 +/- 10% cells in repair, respectively), used as a positive control. These results show that in cultured rat hepatocytes induction of UDS is relatively weak whereas in urothelial cells this effect was significant. Whether this effect is due to OTA metabolites formed locally in the urothelium cannot be excluded since PUBEC have been shown to be able to metabolize xenobiotics independently from the liver.

Animals↗
PubMed1992

Changes in sensitivity of the dark-adapted eye during concurrent light adaptation of the other eye.

Thresholds for detection of light by a dark-adapted test eye were measured while the other, non-test eye was either similarly dark adapted or while it was exposed to an intense red adapting field. An interocular effect that depends on the retinal location of the test was found: compared to the threshold during binocular dark adaptation, sensitivity decreased during contralateral light adaptation when the test was presented to the foveola and up to 4 deg above it; but sensitivity increased when the test was between 7 and 12 deg, showing a reversal at 5 deg.

Adaptation, Ocular↗
PubMed1975

The aortic arch baroreceptor response to static and dynamic stretches in an isolated aorta-depressor nerve preparation of cats in vitro.

1. The aortic arch baroreceptors of cats were studied in an isolated aortic arch-depressor nerve preparation in vitro to analyse their transmission properties. 2. Sinusoidal length changes of varying amplitudes (0-34-1-2 mm) and frequencies (1-10 Hz) at a given pre-stretch were imposed on the isolated receptor zone to quantitate the velocity sensitivity of these receptors and to test the linearity of the system. 3. The receptor response was evaluated from the spike activity of single fibres of the depressor nerve in number of spikes per stimulus period, average discharge rate, instantaneous frequency, and phase angle between forcing function and instantaneous frequency. 4. The static response is characterized by a threshold, saturation range, and a relatively large linear part between these two non-linearities. 5. The aortic receptors exhibit rate sensitivity. Depending on the stimulus amplitude and frequency the phase angles between the forcing function and the instantaneous frequency ranged from -14 to -68 degrees. 6. The average discharge rate (spikes/sec) is sensitive to stimulus amplitude but not to stimulus frequency at near-threshold operation; in the linear part of the static response curve, the receptor response becomes independent of the stimulus mode. 7. The baroreceptors of the aorta share many properties with other mechanoreceptors of different species and organ systems, particularly with those of the rest of the circulation. They exhibit static and to some degree rate sensitivity and operate physiologically near their thresholds, i.e. the afferent arc of the baroreflexes is highly non-linear.

Action Potentials↗