PubMed Health⌕ Search

Biomedical subjects

U Karbach

Publications and source records attributed to U Karbach.

At least 19 recordsLinked to original sources

[A rare cause of hepatic coma].

CASE REPORT: A 65-year-old female patient was admitted to the hospital in somnolent state. During physical examination, she had an increase in blood pressure and a positive bilateral Babinski's sign. Laboratory findings showed elevated liver enzymes, metabolic alkalosis and slightly elevated kidney values. 3 h hours later she lapsed into a hepatic coma (ammonia > 400 micrograms/dl). Subsequently, indirect anamnesis revealed the following affections: ureterosigmoidostomy in 1942, cystectomy in 1943, and right-sided nephrectomy in 1950. DISCUSSION: This case presents with an uncommon origin of the hepatic encephalopathy: in the operated colon, bacterial overgrowth (bacteriogenic ureapoiesis) developed, which led to a hyperammonemia. Furthermore, in mild alcoholic liver disease--as in this case--ammonia cannot be metabolized to urea and leads to hepatic encephalopathy. We considered making this part of the colon poor in bacteria (by consequent administration of antibiotics), thus reducing the formation of ammonia.

Aged↗

Localization of organic cation transporters OCT1 and OCT2 in rat kidney.

Renal excretion and reabsorption of organic cations are mediated by electrogenic and electroneutral organic cation transporters, which belong to a recently discovered family of polyspecific transporters. These transporters are electrogenic and exhibit differences in substrate specificity. In rat, the renal expression of the polyspecific cation transporters rOCT1 and rOCT2 was investigated. By in situ hybridization, significant amounts of both rOCT1 and rOCT2 mRNA were detected in S1, S2, and S3 segments of proximal tubules. By immunohistochemistry, expression of the rOCT1 protein was mainly observed in S1 and S2 segments of proximal tubules, with lower expression levels in the S3 segments. At variance, rOCT2 protein was mainly expressed in the S2 and S3 segments. Both transporters were localized to the basolateral cell membrane. Neither rOCT1 nor rOCT2 was detected in the vasculature, the glomeruli, and nephron segments other than proximal tubules. The data suggest that rOCT1 and rOCT2 are responsible for basolateral cation uptake in the proximal tubule, which represents the first step in cation secretion.

Animals↗

Membrane localization of the electrogenic cation transporter rOCT1 in rat liver.

The polyspecific cation transporter rOCT1 in the rat was the first identified member of a new protein family with 12 presumed membrane-spanning alpha-helices and two large hydrophilic loops. Previous studies showed that rOCT1 is mainly expressed in liver and mediates electrogenic uptake of small organic cations into cells. Antibodies against partial sequences of rOCT1 were raised and their specificity was verified. Immunohistochemistry with rat liver and Western blots with isolated membranes showed that rOCT1 is localized within sinusoidal membranes of hepatocytes. Antibody reactions were also performed with intact and permeabilized human embryonic kidney cells that were stably transfected with rOCT1. They showed that the large hydrophilic loop after the first alpha-helix of rOCT1 is located extracellularly, while the C-terminus is located intracellularly. Translational regulation is suggested since the message of rOCT1 was distributed throughout the liver lobuli, whereas rOCT1 protein was observed only in hepatocytes surrounding the central veins.

Animals↗

Human neurons express the polyspecific cation transporter hOCT2, which translocates monoamine neurotransmitters, amantadine, and memantine.

Recently, we cloned the human cation transporter hOCT2, a member of a new family of polyspecific transporters from kidney, and demonstrated electrogenic uptake of tetraethylammonium, choline, N1-methylnicotinamide, and 1-methyl-4-phenylpyridinium. Using polymerase chain reaction amplification, cDNA sequencing, in situ hybridization, and immunohistochemistry, we now show that hOCT2 message and protein are expressed in neurons of the cerebral cortex and in various subcortical nuclei. In Xenopus laevis oocytes expressing hOCT2, electrogenic transport of norepinephrine, histamine, dopamine, serotonin, and the antiparkinsonian drugs memantine and amantadine was demonstrated by tracer influx, tracer efflux, electrical measurements, or a combination. Apparent Km values of 1.9 +/- 0.6 mM (norepinephrine), 1.3 +/- 0.3 mM (histamine), 0.39 +/- 0.16 mM (dopamine), 80 +/- 20 microM (serotonin), 34 +/- 5 microM (memantine), and 27 +/- 3 microM (amantadine) were estimated. Measurement of trans-effects in depolarized oocytes and human embryonic kidney cells expressing hOCT2 suggests that there were different rates and specificities for cation influx and efflux. The hypothesis is raised that hOCT2 plays a physiological role in the central nervous system by regulating interstitial concentrations of monoamine neurotransmitters that have evaded high affinity uptake mechanisms. We show that amantadine does not interact with the expressed human Na+/Cl- dopamine cotransporter. However, concentrations of amantadine that are effective for the treatment of Parkinson's disease may increase the interstitial concentrations of dopamine and other aminergic neurotransmitters by competitive inhibition of hOCT2.

Amantadine↗

Expression of the Na+-D-glucose cotransporter SGLT1 in neurons.

In brains of the rabbit, pig, and human, expression of the high-affinity Na+-D-glucose cotransporter SGLT1 and of the protein RS1, which alters the activity of SGLT1, was demonstrated. In situ hybridization showed that SGLT1 and RS1 are transcribed in pyramidal cells of brain cortex and hippocampus and in Purkinje cells of cerebellum. In neurons of pig brain SGLT1 protein was demonstrated by western blotting with synaptosomal membranes and by immunohistochemistry, which showed SGLT1 in pyramidal and Purkinje cells. To test whether SGLT1 in neurons may be activated during increased D-glucose consumption, an epileptic seizure was induced in rat brain, and the uptake of specific nonmetabolized substrates of SGLT1 [[14C]methyl-alpha-D-glucopyranoside ([14C]AMG)] and of Na+-independent transporters [2-deoxy-D-[14C] glucose ([14C]2-DG)] was analyzed by autoradiography. During the seizure the uptake of AMG and 2-DG was increased in the focus. Within two hours after the seizure 2-DG uptake in the focus returned to normal. In contrast, the AMG uptake in the focus area was still increased 1 day later. The data show that the high-affinity Na+-D-glucose cotransporter SGLT1 is expressed in neurons and can be up-regulated.

Animals↗

Cloning and characterization of two human polyspecific organic cation transporters.

Previously we cloned a polyspecific transporter from rat (rOCT1) that is expressed in renal proximal tubules and hepatocytes and mediates electrogenic uptake of organic cations with different molecular structures. Recently a homologous transporter from rat kidney (rOCT2) was cloned but not characterized in detail. We report cloning and characterization of two homologous transporters from man (hOCT1 and hOCT2) displaying approximately 80% amino acid identity to rOCT1 and rOCT2, respectively. Northern blots showed that hOCT1 is mainly transcribed in liver, while hOCT2 is found in kidney. Using in situ hybridization and immunohistochemistry, expression of hOCT2 was mainly detected in the distal tubule where the transporter is localized at the luminal membrane. After expression in Xenopus laevis oocytes, hOCT1 and hOCT2 mediate tracer influx of N-1-methylnicotinamide (NMN), tetraethylammonium (TEA), and 1-methyl-4-phenylpyridinium (MPP). For cation transport by hOCT2 apparent K(m) and K(i) values were determined in tracer flux measurements. In addition, electrical measurements were performed with voltage-clamped oocytes. Similar to rOCT1, cation transport by hOCT2 was pH independent, electrogenic, and polyspecific; however, the cation specificity was different. In voltage-clamped hOCT2-expressing oocytes, inward currents were induced by superfusion with MPP, TEA, choline, quinine, d-tubocurarine, pancuronium, and cyanine863. Cation transport in distal tubules is indicated for the first time. Here hOCT2 mediates the first step in cation reabsorption. hOCT1 may participate in hepatic excretion of organic cations.

Amino Acid Sequence↗

Elevated cell-associated levels of interleukin 1beta and interleukin 6 in inflamed mucosa of inflammatory bowel disease.

The aim of this study was to investigate the involvement of the monocyte-derived cytokines interleukin 1beta (IL-1beta), interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) in idiopathic inflammatory bowel disease. Endoscopic biopsies of normal and inflamed intestinal mucosa were obtained from patients with ulcerative colitis (n = 11) and with Crohn's disease (n = 10). Intestinal mucosal cells were isolated by collagenase digestion. Cell viability, morphology and CD14 expression were determined. To measure cell-associated cytokine levels, cells were lysed and analysed for IL-1beta and TNF-alpha in specific radioimmunoassays and for IL-6 using a biological assay. Compared with mucosal cells from control patients without inflammatory bowel disease the inflamed intestine in ulcerative colitis and Crohn's disease displayed markedly enhanced levels of IL-1beta (median 245 pg 10(-6) cells, range 30-1275) and IL-6 (median 22 U 10(-6) cells, range 1-298). Non-inflamed mucosa in patients with ulcerative colitis and Crohn's disease did not show elevated levels of IL-1beta (median 50 pg 10(-6) cells, range 33-90) or IL-6 (mean below detection limit of assay, i.e. 1 U 10(-6) cells). In contrast, no clear cut difference between inflamed and non-inflamed mucosa could be detected for TNF-alpha. High tissue levels of IL-6 were associated with a high endoscopic grade of local inflammation. These results suggest that the monocyte-derived cytokines IL-1beta and IL-6 are mediators of inflammation in inflammatory bowel disease.

Adult↗

[Vaso-occlusive crises in sickle-cell anemia].

HISTORY AND FINDINGS: Severe pain suddenly occurred in the shaft of the right thigh in a 21-year-old patient of Turkish descent with known homozygotic sickle cell anaemia. He also had marked scleral jaundice and anaemia (haemoglobin 9.1 g/dl). An X-ray film of the lower leg pointed to a bone infarct. Type of pain, partial pressure of oxygen in blood (70 mm Hg), concentration of lactate dehydrogenase and the bilirubin level (4,5 mg/dl) as signs of haemolysis, as well as the fall in haemoglobin, indicated a vascular occlusive crisis in sickle cell anaemia. TREATMENT AND COURSE: The symptoms regressed within 8 days of the patient receiving fluids, analgesics and oxygenation by nasal tube. A few weeks later he developed a fever, productive cough and severe pain in joints and abdomen. Blood p02 was 54 mm Hg. Pneumonia in the right lung base was the cause of this renewed life-threatening crisis, which was again associated with haemolysis. Klebsiella having been found in sputum he was treated with cefotaxim (1 g twice daily intravenously) and oxygen insufflation via nasal tube (7 l/min). His condition quickly improved. CONCLUSIONS: In patients with sickle cell anaemia it is important (1) to regard crises as potentially life-threatening conditions, (2) to detect and treat infections as possible causes early and (3) to provide sufficient oxygen insufflation quickly, especially in pulmonary infections.

Acute Disease↗

Calibration of misonidazole labeling by simultaneous measurement of oxygen tension and labeling density in multicellular spheroids.

To correlate misonidazole concentrations and oxygen pressures (Po2) at identical locations within EMT6/Ro multi-cell spheroids (mean diameters +/- SD: 867 +/- 20 microns), Po2 measurements were performed with oxygen-sensitive microelectrodes during incubation of these spheroids with tritiated misonidazole (10 mg/I; 445 microCi/mg). In each individual spheroid, Po2 profiles were correlated with the corresponding spatial distribution of misonidazole as quantified by conventional autoradiography and grain counting. To compare the oxygenation status of spheroids in the measuring chamber with that of spheroids in spinner culture, misonidazole labeling was performed in both environments following the same protocol. All experiments were conducted in 20% oxygen and BME or in 5% oxygen and DMEM to obtain spheroids with different degrees of oxygenation. Labeled misonidazole was fairly evenly distributed in the outer, better oxygenated regions of EMT6 spheroids. In contrast, there was an accumulation of the labeled substance near central necrosis where low oxygen tensions were measured. Grain densities were similar at corresponding oxygen pressures under both environmental conditions. Except for some scatter, grain density as a function of oxygen pressure showed little variation in the Po2 range of 20-60 mm Hg, but exhibited a steep increase below 10 mm Hg. The findings imply that a substantial rise in local misonidazole labeling indicates a metabolically active tissue region at low Po2 that is not necessarily identical with the radiobiologically hypoxic cell fraction. A comparison of the labeling densities of spheroids in spinner flasks and in the Po2 measuring chamber indicates that oxygenation of spheroids is better in rotation culture than during microelectrode measurements.

Animals↗

Measurement of transit disorders in different gastrointestinal segments of patients with diabetes mellitus in relation to duration and severity of the disease by use of the metal-detector test.

The existence of gastrointestinal transit disorders in other intestinal segments beside the stomach in Type-1 diabetes mellitus (DM) and occurrence in Type-2 DM and in uremia has yet been confirmed only in few studies. Eleven healthy volunteers, 34 patients with Type-1, 32 patients with Type-2 DM in different stages of their disease and 34 non-diabetic patients with endstage-renal disease were investigated by use of the metal detector test. Patients were divided in three subgroups, depending on the duration of their disease: < 1 year: "Short", 1 - 10 years: "Middle", > 10 years: "Long". For comparison with the metal detector test scintigraphic studies of esophageal and gastric transit were performed in 17 patients and small intestinal transit was studied by use of the H2-lactulose breath test in 20 patients with long-standing DM Type-1. In Type-1 DM there is an increase of gastric (135 +/- 18, p < 0.01; 218 +/- 26, p < 0.0001 vs. 73 +/- 7 min.) and large intestinal transit times (79 +/- 18, P < 0.02; 76 +/- 11, p < 0.04 vs. 40 +/- 5 h) in patients with middle or long standing DM. In Type-2 DM similar transit disturbances occur (gastric emptying, long group: 120 +/- 15 min., p < 0.02; colonic transit, long group: 80 +/- 13 h, p < 0.01). In uremia transit disturbances were only found in patients with chronic ambulatory peritoneal dialysis (colonic transit: 71 +/- 9 h, p < 0.05). In 65% gastric scintigraphy and in 55% of cases the H2-lactulose breath test showed a prolongation of gastric emptying or a prolonged mouth-to-cecum transit. Transit disorders can occur in every stage of DM with preferential involvement of the stomach and the colon. These findings are of clinical relevance, since transit disturbances can result in instable metabolic condition.

Adult↗

[Gastrointestinal involvement in progressive systemic scleroderma].

The complained gastrointestinal symptoms in PSS are probably caused by several complex disturbances like intestinal transit disturbances (ITD), bacterial overgrowth of the small intestine caused malabsorption of bile acids and altered kinetics of intestinal hormones. 25 patients with PSS and eleven healthy controls were tested for the existence of ITD by use of the metal-detector test (MDT). Twelve patients were also tested for a malabsorption of primary bile acids by radioimmunological measurement of clolylglycine serum levels before and after a meal. In addition serum concentrations of gastrin (nine patients) and plasma concentrations of cholecystokinin (CCK) (eight patients) and motilin (eleven patients) were measured by radioimmunoassay pre- and postprandial. Interdigestive gastric emptying was accelerated in patients with PSS (53 +/- 3 min. vs. 73 +/- 7 min.; p<0.01). Small intestinal transit times were similar in both groups (115 +/- 17 min. vs. 121 +/- 13 min.). Colonic transit in patients with PSS was significant prolonged (63 +/- 6 h vs. 39 +/- 5 h; p<0.05). There were no significant differences between the two groups concerning the pre- and postprandial levels of cholylglycin. Basic and postprandial levels of gastrin, CCK and motilin were higher in the PSS group. In contrast to scintigraphic studies using semisolid meals gastric emptying of the copper pellet in PSS was accelerated. A general malabsorption of primary bile acids was not found. Prolonged colonic transit times correlate well with frequently complained obstipation. Gastric hypacidity could be the reason of elevated gastrin levels. The high motilin-levels in PSS could be due to a lack of the feed-back inhibition as a result of diminished phase-III activity of the interdigestive migrating motor complex. The elevation of CCK-levels could reflect compensation of neurogenic or myogenic disturbances of gallbladder contraction.

Adult↗

[New findings on the mechanism and regulation of intestinal calcium transport].

Only in the duodenum and in the colon calcium is absorbed by a cellular 1,25 alpha-Vitamin D3-dependent transport mechanism. Calcium absorption is highest in the proximal large intestine, about ten times higher than in the duodenum or in the descending colon. 1,25 alpha-Vitamin D3 stimulates calcium transport by genomic (slow effect: synthesis of cytosolic calcium binding protein CabP and basolateral Ca-ATPase) and non-genomic action (rapid effect: transcaltachyia, liponomic effect at the brush border membrane). CabP-dependent translocation across the cytosol is thought to be rate limiting step of cellular calcium transport. However, only about 50% of calcium absorption is cellular mediated but the same amount of calcium convectively is absorbed by transepithelial water flow across the paracellular pathway (solvent drag effect). 1,25 alpha-Vitamin D3 not only activates cellular calcium absorption but also increases paracellular permeability for calcium by an unknown mechanism. However, essential steps in the cascade from the interaction of 1,25 alpha-Vitamin D3 with the specific receptor over the regulation of the synthesis of calcium binding and transporting proteins to the induction of cellular calcium transport are not as yet clearly understood. The exact feedback mechanism of synchronized calcium transport across the distinct subcellular compartments seems also to be resolved. Cellular calcium transport is not found in the jejunum or in the ileum, what can be explained by the absence of specific 1,25 alpha-Vitamin D3-dependent carrier systems in these segments. On the other hand calcium is secreted across the jejunum and ileum by an anomalous solvent drag effect. Hence, intestinal calcium metabolism seems to underlie an eneteroenteral circuit: 1,25 alpha-Vitamin D3-controlled cellular calcium absorption across the duodenum is followed by paracellular calcium secretion across the jejunum and ileum. The carrier in the proximal colon which works at the optimal level already under normal nutritional condition could be of physiological importance for the reclamation of unabsorbed dietary calcium and for the reabsorption of calcium that is secreted across the distal small intestine. Under certain pathophysiological conditions, i.e. malabsorption in proximal segments or malnutrition, calcium in addition may be conserved by the 1,25 alpha-Vitamin D3-sensitive carrier in the descending colon.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Plasma kinetics of magnesium and calcium stable isotope tracers in a human subject after simultaneous oral ingestion of 25Mg and 44Ca determined by thermal ionization mass spectrometry.

The plasma concentrations of stable isotope tracers of magnesium (25Mg) and calcium (44Ca) were determined during a 50 h period, after simultaneous oral tracer ingestion in an adult man. The measurements were performed by magnetic sector field mass spectrometry using surface ionization ion sources. The data were used to evaluate the potential of this method in long-term kinetic studies. It is concluded that under the experimental conditions specified, the isotopic tracers will be detectable in blood plasma with sufficient precision and accuracy for approximately 600 h after oral ingestion. The differences in the plasma concentration curves of 25Mg and 44Ca were analysed by means of the convolution integral method. These differences indicate inhomogeneities in the distribution of absorption activity relative to magnesium and calcium within the upper small intestine.

Administration, Oral↗

The cecum is the site with the highest calcium absorption in rat intestine.

In the absence of electrochemical gradients, mucosa-to-serosa Ca transport across the rat cecum is about six times higher than the serosa-to-mucosa flux, resulting in a marked Ca absorption, which is considerably higher when compared with Ca absorption reported for other intestinal segments. The voltage-clamp experiments reveal that 45% of the total mucosa-to-serosa Ca transport measured across the short-circuited tissue is cellular whereas 55% is paracellular. The serosa-to-mucosa Ca flux, however, is purely paracellular. Dexamethasone or 1,25(OH)2D3 has no effect on the Ca transport across the cecum. Diphosphonate, known to inhibit 1,25(OH)2D3 synthesis, abolishes cellular mucosa-to-serosa Ca transport but this effect can be restored by simultaneous exogenous 1,25(OH)2D3 application. It is concluded that the cecum is the site with the highest calcium absorption in the rat intestine. The cellular mucosa-to-serosa Ca transport is dependent on 1,25(OH)2D3 but cannot be increased by exogenous 1,25(OH)2D3 application, suggesting that the Ca carrier in this segment already under normal nutritional conditions works at the maximal level. Ca absorption across the proximal colon therefore seems to be of physiological importance in the regulation of intestinal Ca homeostasis.

Animals↗

Rhabdomyosarcoma spheroids with central proliferation and differentiation.

A novel type of multicellular spheroids was established and characterized with regard to growth behavior, proliferation, and differentiation. The spheroids were grown from clonal rat rhabdomyosarcoma cells using the spinner flask technique. The cell aggregates showed several unique properties that were different from those observed in most of the spheroids investigated to date. These properties include a non-Gompertzian volume growth; the coexistence of undifferentiated mononuclear cells and of differentiated, myotube-like giant cells with numerous nuclei; a relatively homogeneous intraspheroidal distribution of proliferating mononuclear cells with thymidine labeling even in the center of spheroids greater than 1 mm; the absence of necrosis in such large spheroids, and the accumulation of myotube-like cells in the center of these spheroids instead. There was a decrease in the overall proliferative activity of the mononuclear cells with increasing proportion of giant cells in the rhabdomyosarcoma spheroids.

Animals↗