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Biomedical subjects

U Gerlach

Publications and source records attributed to U Gerlach.

At least 19 recordsLinked to original sources
PubMed2001

The role of KCNQ1/KCNE1 K(+) channels in intestine and pancreas: lessons from the KCNE1 knockout mouse.

KCNE1 (IsK, minK) co-assembles with KCNQ1 (KvLQT1) to form voltage-dependent K(+) channels. Both KCNQ1 and KCNE1 are expressed in epithelial cells of gut and exocrine pancreas. We examined the role of KCNQ1/KCNE1 in Cl(-) secretion in small and large intestine and exocrine pancreas using the KCNE1 knockout mouse. Immunofluorescence revealed a similar basolateral localization of KCNQ1 in jejunum and colon of KCNE1 wild-type and knockout mice. Electrogenic Cl(-) secretion in the colon was not affected by gene disruption of KCNE1; in jejunum forskolin-induced short-circuit current was some 40% smaller but without being significantly different. Inhibition of KCNQ1 channels by 293B (IC(50) 1 micromol l(-1)) and by IKS224 (IC(50) 14 nmol l(-1)) strongly diminished intestinal Cl(-) secretion. In exocrine pancreas of wild-type mice, KCNQ1 was predominantly located at the basolateral membrane. In KCNE1 knockout mice, however, the basolateral staining was less pronounced and the distribution of secretory granules was irregular. A slowly activating and 293B-sensitive K(+) current was activated via cholinergic stimulation in pancreatic acinar cells of wild-type mice. In KCNE1 knockout mice this K(+) current was strongly reduced. In conclusion intestinal Cl(-) secretion is independent from KCNE1 but requires KCNQ1. In mouse pancreatic acini KCNQ1 probably co-assembled with KCNE1 leads to a voltage-dependent K(+) current that might be of importance for electrolyte and enzyme secretion.

Animals↗
PubMed2001

Synthesis and activity of novel and selective I(Ks)-channel blockers.

Since the discovery of the I(Ks)-potassium channel as the slowly activating component of the delayed rectifier current (I(k)) in cardiac tissue, the search for blockers of this current has been intense. During the screening of K(ATP)-channel openers of the chromanol type we found that chromanol 293B was able to block I(Ks). Chromanol 293B is a sulfonamide analogue of the K(ATP)-channel openers but had no activity on this target. Experiments were initiated to improve the activity and properties based on this lead compound. As a screening model we used Xenopus oocytes injected with human minK (KCNE1). Variations of the aromatic substituent and the sulfonamide group were prepared, and their activity was evaluated. We found that the greatest influence on activity was found in the aromatic substituents. The most active compounds were alkoxy substituted. We chose HMR1556 ((3R, 4S)-(+)-N-[-3-hydroxy-2,2-dimethyl-6-(4,4,4-trifluorobutoxy)chroman-4-yl]-N-methyl-ethanesulfonamide) 10a for development as an antiarrhythmic drug. The absolute configuration, resulting from an X-ray single-crystal structure analysis, was determined.

Animals↗
PubMed2001

Cardioselective K(ATP) channel blockers derived from a new series of m-anisamidoethylbenzenesulfonylthioureas.

Sulfonylthioureas exhibiting cardioselective blockade of ATP-sensitive potassium channels (K(ATP) channels) were discovered by stepwise structural variations of the antidiabetic sulfonylurea glibenclamide. As screening assays, reversal of rilmakalim-induced shortening of the cardiac action potential in guinea pig papillary muscles was used to probe for activity on cardiac K(ATP) channels as the target, and membrane depolarization in CHO cells stably transfected with hSUR1/hKir6.2 was used to probe for unwanted side effects on pancreatic K(ATP) channels. Changing glibenclamide's para-arrangement of substituents in the central aromatic ring to a meta-pattern associated with size reduction of the substituent at the terminal nitrogen atom of the sulfonylurea moiety was found to achieve cardioselectivity. An additional change from a sulfonylurea moiety to a sulfonylthiourea moiety along with an appropriate substituent in the ortho-position of the central aromatic system was a successful strategy to further improve potency on the cardiac K(ATP) channel. Among this series of sulfonylthioureas HMR1883, 1-[5-[2-(5-chloro-o-anisamido)ethyl]-2-methoxyphenyl]sulfonyl-3-methylthiourea, and its sodium salt HMR1098 were selected for development and represent a completely new therapeutic approach toward the prevention of life-threatening arrhythmias and sudden cardiac death in patients with coronary heart disease.

ATP-Binding Cassette Transporters↗
PubMed2001

Properties and function of KCNQ1 K+ channels isolated from the rectal gland of Squalus acanthias.

KCNQ1 (KVLQT1) K+ channels play an important role during electrolyte secretion in airways and colon. KCNQ1 was cloned recently from NaCl-secreting shark rectal glands. Here we study the properties and regulation of the cloned sKVLQT1 expressed in Xenopus oocytes and Chinese hamster ovary (CHO) cells and compare the results with those obtained from in vitro perfused rectal gland tubules (RGT). The expression of sKCNQ1 induced voltage-dependent, delayed activated K+ currents, which were augmented by an increase in intracellular cAMP and Ca2+. The chromanol derivatives 293B and 526B potently inhibited sKCNQ1 expressed in oocytes and CHO cells, but had little effect on RGT electrolyte transport. Short-circuit currents in RGT were activated by alkalinization and were decreased by acidification. In CHO cells an alkaline pH activated and an acidic pH inhibited 293B-sensitive KCNQ1 currents. Noise analysis of the cell-attached basolateral membrane of RGT indicated the presence of low-conductance (<3 pS) K+ channels, in parallel with other K+ channels. sKCNQ1 generated similar small-conductance K+ channels upon expression in CHO cells and Xenopus oocytes. The results suggest the presence of low-conductance KCNQ1 K+ channels in RGT, which are probably regulated by changes in intracellular cAMP, Ca2+ and pH.

Animals↗
PubMed2000

Inhibition of IKs channels by HMR 1556.

Chromanol HMR 1556 [(3R,4S)-(+)-N-[3-hydroxy-2,2-dimethyl-6-(4,4,4-trifluorobutoxy)chroman-4-yl]-N-methylmethanesulfonamide], a novel inhibitor of the slow component of the delayed outward current in heart muscle cells (IKs), has been characterized in several in-vitro systems. mRNA encoding for the human protein minK was injected into Xenopus oocytes, leading to the expression of IKs channels. HMR 1556 inhibited this current half-maximally at a concentration of 120 nmol/l (IC50). Expression of the K+ channels Herg, Kv 1.5, Kv 1.3 and Kir2.1, and also the cationic current HCN2, were blocked little or not at all by 10 micromol/l HMR 1556. In isolated ventricular myocytes from the guinea pig the whole-cell patch-clamp method revealed inhibition of the IKs current with an IC50, of 34 nmol/l. Other current components, like IKr and IK1. were only slightly blocked at an HMR 1556 concentration of 10 micromol/l, whereas 10 micromol/l HMR 1556 inhibited the transient outward current I(to) and the sustained outward current I(sus) in rat ventricular myocytes by 25% and 36%, respectively. The L-type Ca2+ channel in guinea pig cardiomyocytes was blocked by 10 micromol/l HMR 1556 by 31%. Guinea pig right papillary muscles were investigated by the micropuncture technique at various pacing rates. In the frequency range of 0.5-7 Hz HMR 1556 (1 micromol/l) caused a prolongation of the action potential duration at 90% repolarization (APD90) by 19%-27%. In the presence of isoproterenol (10 micromol/l) the prolongation of the APD90 was more pronounced at low pacing rates (47% at 0.5 Hz and 35% at 1 Hz, compared with 25% at 7 Hz). The monophasic action potential was recorded in Langendorff-perfused guinea pig hearts. In spontaneously beating preparations, HMR 1556, at 0.1 micromol/l and 1 micromol/l, prolonged the MAPD90 by 3% and 10%, respectively, with no further prolongation at 10 micromol/l. The prolongation was much greater at low pacing rates [25% at 100 beats per min (bpm) and 13% at 150 bpm] than at fast pacing rates (9% at 350 bpm). The left ventricular pressure LVPmax was not affected at 1 micromol/l HMR 1556, but it decreased by 15% at 10 micromol/l. Other parameters, like the heart rate and coronary flow, were only slightly decreased at 1 micromol/l HMR 1556. In conclusion, HMR 1556 is a potent and selective inhibitor of the IKs current in guinea pig ventricular myocytes. The prolongation of the action potential duration is maintained at fast pacing rates.

Animals↗
PubMed2000

Electropharmacological characterization of cardiac repolarization in German shepherd dogs with an inherited syndrome of sudden death: abnormal response to potassium channel blockers.

OBJECTIVES: This study sought to determine whether abnormal ventricular repolarization is implicated in cardiac arrhythmias of German shepherd dogs with inherited sudden death. BACKGROUND: Moïse et al. (9) have identified German shepherd dogs that display pause-dependent lethal ventricular arrhythmias. METHODS: Ventricular repolarization was studied both in vivo using electrocardiogram recordings on conscious dogs and in vitro with a standard microelectrode technique performed on endomyocardial biopsies and Purkinje fibers. Pharmacological manipulation was used to evaluate the role of potassium channels. RESULTS: In control conditions, electrocardiogram parameters were similar in both groups of dogs, except for the PR interval (18% longer in affected dogs, p < 0.05). Injection of d,l-sotalol (2 mg/kg) prolonged QT interval more in affected dogs (+14%, n = 9) than it did in unaffected dogs (+6%, n = 6, p < 0.05) and increased the severity of arrhythmias in affected dogs. In vitro, in control conditions, action potential duration (APD90) of endomyocardial biopsies and Purkinje fibers were significantly longer in affected dogs (respectively 209 +/- 3 ms, n = 30 and 352 +/- 15 ms, n = 17) than they were in unaffected dogs (197 +/- 4 ms, n = 25 and 300 +/- 9 ms, n = 30) at a pacing cycle length (PCL) of 1,000 ms. This difference increased with PCL. The kinetics of adaptation of APD90 to a change in PCL was faster in affected dogs. D,l-sotalol (10(-5) and 10(-4)M) increased APD90 in both groups of dogs, but this increase was greater in affected dogs, with the occurrence of triggered activity on Purkinje fibers. E-4031 (10(-7) and 10(-6) M), an I(Kr)-blocker, increased APD90 similarly in both groups of dogs. Chromanol 293B (10(-6) and 10(-5)M), an I(Ks)-blocker, increased significantly APD90 in unaffected dogs but had no effect in affected dogs. CONCLUSIONS: These results support the hypothesis of an abnormal cardiac repolarization in affected dogs. The effects of 293B suggest that I(Ks) may be involved in this anomaly.

Animals↗
PubMed2000

Molecular impact of MinK on the enantiospecific block of I(Ks) by chromanols.

Slowly activating I:(Ks) (KCNQ1/MinK) channels were expressed in Xenopous: oocytes and their sensitivity to chromanols was compared to homomeric KCNQ1 channels. To elucidate the contribution of the ss-subunit MinK on chromanol block, a formerly described chromanol HMR 1556 and its enantiomer S5557 were tested for enantio-specificity in blocking I:(Ks) and KCNQ1 as shown for the single enantiomers of chromanol 293B. Both enantiomers blocked homomeric KCNQ1 channels to a lesser extent than heteromeric I:(Ks) channels. Furthermore, we expressed both WT and mutant MinK subunits to examine the involvement of particular MinK protein regions in channel block by chromanols. Through a broad variety of MinK deletion and point mutants, we could not identify amino acids or regions where sensitivity was abolished or strikingly diminished (>2.5 fold). This could indicate that MinK does not directly take part in chromanol binding but acts allosterically to facilitate drug binding to the principal subunit KCNQ1.

Animals↗
PubMed1999

Rate- and site-dependent effects of propafenone, dofetilide, and the new I(Ks)-blocking agent chromanol 293b on individual muscle layers of the intact canine heart.

BACKGROUND: Recent in vitro studies have demonstrated regional differences in electrophysiological properties of individual left ventricular muscle layers. Controversy exists on the relevance of these findings for the situation in vivo. Thus, this study was designed to determine whether the in vivo canine heart exhibits regional differences in left ventricular refractoriness and in the susceptibility to sodium and potassium channel blockers. METHODS AND RESULTS: In 16 dogs, 36 needle electrodes (12 mm long, 4 bipolar electrodes, interelectrode distance 2.5 mm) were inserted into the left ventricular wall. By use of a computerized multiplexer-mapping system, the spread of activation in epicardial, endocardial, and midmyocardial muscle was reconstructed during ventricular pacing at 300- and 850-ms basic cycle length (BCL). Effective refractory periods (ERPs) were determined at baseline and after application of propafenone (2 mg/kg), dofetilide (30 microg/kg), or chromanol 293b (10 mg/kg) by the extrastimulus technique (BCL 300 and 850 ms). At baseline, activation patterns and ERPs were uniform in all muscle layers. Propafenone homogeneously decreased conduction velocity and moderately prolonged ERPs without any regional differences. Dofetilide and chromanol 293b did not affect the spread of activation. Dofetilide exhibited reverse use-dependent effects on ERP, still preserving transmural homogeneity of refractoriness. Chromanol 293b led to a regionally uniform but more pronounced increase in local ERPs at faster than at slower pacing rates. CONCLUSIONS: At the heart rates applied, the in vivo canine heart does not exhibit regional differences in electrophysiological properties. Given the homogeneity of antiarrhythmic drug effects, induction of local gradients of refractoriness is obviously not a common mechanism of proarrhythmia in normal hearts.

Animals↗
PubMed1997

KVLQT channels are inhibited by the K+ channel blocker 293B.

Previous data have indicated that the chromanol 293B blocks a cAMP activated K+ conductance in the colonic crypt, a K+ conductance in pig cardiac myocytes and the K+ conductance induced by IsK protein expression in Xenopus oocytes. We have also shown that cAMP-activated cystic fibrosis transmembrane conductance regulator (CFTR) up-regulates, apart from the typical Cl- current, a 293B- inhibitable K+ current. Very recently it has been shown that the IsK protein interacts with KVLQT subunits to produce a K+ channel. These data have prompted us to ask the following questions: Is the 293B-inhibitable current in oocytes expressing CFTR and activated by cAMP caused by an endogenous Xenopus KVLQT (XKVLQT), and is mouse KVLQT (mKVLQT) expressed in oocytes inhibited by 293B? Antisense and sense probes for XKVLQT were coinjected with CFTR cRNA into oocytes. After 3-4 days the oocytes were examined by two electrode voltage clamp. It was found that in control oocytes expressing CFTR and stimulated by isobutylmethylxanthine (IBMX, 1 mmol/l) 293B (10 micromol/l) reduced the conductance (Gm). In oocytes coinjected with the sense probe for XKVLQT and pretreated with IBMX 293B still reduced Gm, whilst the 293B-inhibitable Gm was almost completely absent in oocytes coinjected with XKVLQT antisense. In another series a full length clone for mKVLQT was generated by PCR techniques and the cRNA was injected into oocytes. After several days these oocytes, unlike water injected ones, were found to be strongly hyperpolarized and their Gm was increased significantly. The oocytes were depolarized significantly and their Gm was reduced reversibly by 10 micromol/l 293B. These data indicate that CFTR activation by IBMX indeed co-activates an endogenous oocyte XKVLQT channel and that this channel is inhibited by a new class of channel blockers, of which 293B is the prototype.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Basement membrane proteins in synovial membrane: distribution in rheumatoid arthritis and synthesis by fibroblast-like cells.

Rheumatoid arthritis is a complex disease of unknown origin. In consequence of some immunological reactions, proliferative invading synovial tissue leads to destruction of normal joint architecture. The aim of this study was to investigate qualitative changes in extracellular matrix distribution of proliferating rheumatoid synovium and their cellular origin. Synovial tissues from 57 clinically indicated arthrotomies were investigated with immunofluorescence, using specific antibodies against extracellular matrix proteins in tissue slides and cultured cells, which were also studied for collagen biosynthesis. Results indicated that synovial fibroblast-like cells synthesize and secrete basement membrane proteins laminin and collagen type IV as e.g. endothelial cells or organogenic fibroblasts. Laminin and collagen type IV were specifically demonstrated pericellularly in the hyperplastic lining layer of active rheumatoid synovitis. These findings are discussed with respect to the possible implication of altered cell-matrix interactions in rheumatoid synovial proliferation.

Arthritis, Rheumatoid↗
PubMed1992

[Roentgen studies of the skull in head injuries--a multicenter study].

The multi-center study presented reveals that 76% of the conventionally performed X-ray investigations of the skull can be avoided without any relevance concerning the non-diagnosis of severe injuries. Only in 3.2% of all patients investigated a skull X-ray had instantaneous therapeutically consequences. Thus routinely performed skull X-rays are no longer acceptable in the light of cost reduction and radiation load. The clinical-neurological investigations however are inevitable to perform the state of the art treatment of patients with head injuries today, leading to computerized tomography if necessary. A check-list of clinical findings is presented to get the indications for conventional X-rays of the skull and to manage an effective use of such investigations in appropriate clinical situations.

Adolescent↗
PubMed1991

Joint occurrence of collagen mRNA containing cells and macrophages in human atherosclerotic vessels.

Cells with enhanced levels of collagen type I and III mRNA were identified and localized in frozen tissue sections from samples of human atherosclerotic renal and common iliac arteries by in situ hybridization using complementary 35S-labeled RNA probes. Serial sections were immunohistochemically stained for smooth muscle cells, monocytes, and differentiated macrophages. In the fibromuscular intima and in the fibrous plaques, cells with enhanced transcriptional activity were located mainly in the vicinity of differentiated macrophages. In three patients, lack of enhanced transcriptional activity in a proliferated intima was connected with complete absence of macrophages, thus indicating a quiescent stage of atherosclerosis. Immunohistochemical staining of serial sections for smooth muscle cells (SMC) revealed the presence of this cell type throughout the proliferated intima in atherosclerotic arteries including those areas in which enhanced collagen mRNAs were detected. The present results support the idea that macrophages play an important role in the activation of collagen synthesis in SMC of atherosclerotic vessel walls.

Adolescent↗
PubMed1991

[Alpha-amylase isoenzymes in serum and saliva of patients with anorexia and bulimia nervosa].

In the serum and saliva of 45 patients with eating disorders and in 30 normal controls, alpha-amylase activity and isoamylase levels were measured. Of the 45 patients evaluated, 12 had restrictive anorexia nervosa, 13 were bulimic anorectics and 20 had bulimia nervosa. In all these groups, the mean alpha-amylase values in serum and saliva were higher than that of the control group. The proportion of pancreatic (P)- and salivary (S)-alpha-amylase isoenzymes in serum were within the normal range for the patient group with restrictive anorexia nervosa, whereas the bulimic anorexia nervosa and bulimia nervosa patients showed significantly greater increases in S- than P-isoamylase activity. The correlation of the salivary alpha-Amylase isoenzym pattern in serum and saliva pointed to the salivary glands as origin of the elevated salivary isoamylase levels in serum. Hyperamylasemia was found in 10 (25%) of the 45 patients with eating disorders. Three of these patients showed besides an increased S-alpha-amylase activity also pathologically elevated P-alpha-amylase and lipase activity in serum; however there were no abdominal symptoms, laboratory data or ultrasonic signs of pancreatitis. In all patients with eating disorders, the mean concentration and secretion of alpha-amylase in saliva were increased. Swelling of the salivary glands was present in 14 patients. In these cases the percentage of salivary-isoamylase activity in total serum alpha-amylase activity was increased significantly, whereas the alpha-amylase secretion in the resting saliva was decreased.

Adolescent↗
PubMed1990

[Ultrasonic findings in aggressive abdominal fibromatosis].

A case of aggressive abdominal fibromatosis is reported. Ultrasonography revealed multiple inhomogenous, hypoechoic tumours within the mesenterium and the anterior abdominal wall. Some of these lesions had a hyperechogenic margin.

Abdominal Muscles↗
PubMed1990

Immunoadsorbent plasma perfusion in patients with systemic lupus erythematosus.

Extracorporeal treatment of acute systemic lupus erythematous (SLE) by plasmapheresis has been reported for more than 10 years. Risks of plasmapheresis include unselective procedure, an immunoadsorbent plasma perfusion by IM-P column. Eight of 10 patients evaluated improved through 3 treatments of a 2-liter perfusion. Analysis of proteins removed during plasma perfusion showed a semiselectivity of the IM-P column for circulating immune complexes and anti-dsDNA antibodies. After perfusion of 2 liters of plasma, these substances were reduced by about 35-40%, whereas whole protein was lowered by less than 10% and immunoglobulins by about 18%. Our results in severe SLE indicate that immunoadsorption having the advantage of lowering side effects by dispensing wih foreign protein substitution.

Humans↗
PubMed1989

Significance of a sonographic secretin test in the diagnosis of pancreatic disease. Results of a prospective study.

In a prospective study the pancreatic duct diameter was measured sonographically before and after secretin stimulation in 20 healthy controls and 59 patients with upper abdominal pain, weight loss, and/or diarrhea. Whereas healthy controls and patients without pancreatic disease after secretin stimulation showed a distinct pancreatic duct dilatation of more than 90% of basal duct diameter, no distinct secretin-induced duct enlargement was observed in most patients with chronic pancreatitis. Patients with circumscript pancreatic duct stenosis even had a marked and longer-lasting duct dilatation after stimulation. In patients with anomalies of the pancreatic duct system, no uniform response was found after secretin injection. In this study the sonographic secretin test showed a sensitivity of 92% and a specificity of 95% for diagnosis of chronic pancreatitis. The results confirm that this diagnostic method can be recommended as a reliable screening test for pancreatic disease.

Adult↗
PubMed1989

Evaluation of serum laminin P1, procollagen-III peptides, and N-acetyl-beta-glucosaminidase for monitoring the activity of liver fibrosis.

Chronic liver diseases are characterized by an increase in connective tissue components in liver tissue. The determination of Col 1-3 peptide of type III procollagen (P-III-P) in serum of patients seems to be a useful parameter of hepatic fibroplasia. Specific radioimmunoassays are available for Col 1-3 (P-III-P) and the Col 1 and Col 1-3 (P-III-P-Fab) peptides of type III procollagen and for laminin P1 fragment. These proteins and the activity of N-acetyl-beta-glucosaminidase (beta-NAG) were measured in 94 patients with chronic liver diseases, and in 74 healthy controls. In addition, direct immunofluorescence studies were done for laminin P1 in normal and fibrotic liver tissues. In normal human liver, laminin was found in the basement membrane of bile ducts and in blood vessel walls. In fibrotic liver tissue, laminin additionally occurred in periportal areas and in sinusoids co-distributed with other connective tissue components. In serum concentrations of P-III-P, P-III-P-Fab and laminin were higher in patients than in healthy subjects. Laminin concentration was increased in early stages of chronic liver disease, possibly as a marker of regeneration; the highest concentrations were in active cirrhosis and chronic active hepatitis. The determination of P-III-P and P-III-P-Fab provided information on synthesis and degradation of type III collagen: In inactive cirrhosis, Col 1 peptide was increased in relation to Col 1-3 peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗