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Biomedical subjects

C Niederau

Publications and source records attributed to C Niederau.

At least 91 records · Page 5Linked to original sources
PubMed1995

Lazaroids protect isolated rat pancreatic acinar cells against damage induced by free radicals.

Lazaroids, 21-aminosteroids without gluco- and mineralocorticoid activity, protect against oxidative injury in nervous system cells and may therefore also have a potential for treatment of pancreatitis, where oxidative stress contributes to cell injury. The present study evaluates the protective potential of the lazaroids U-78518F, U-74500A, and U-74389F against damage to isolated pancreatic acinar cells exposed to two models of oxidative stress: (a) a XOD/HX model, consisting of xanthine oxidase, hypoxanthine, and chelated FeCl3; and (b) an ADP/Fe model, consisting of FeSO4 and the reducing agent ADP. Both models caused time-dependent cell injury as assessed by uptake of trypan blue and release of lactate dehydrogenase. Short-term peak production of free radicals in the XOD/HX model--as monitored by the deoxyribose assay--was more injurious to cells than continuous radical generation at lower levels in the ADP/Fe model. In general, lazaroids at 1-10 microM reduced oxidative damage and deoxyribose oxidation in both models. The degree of reduction of cell damage and deoxyribose oxidation depended on the type and concentration of the lazaroid and the model used. Lazaroid concentrations < 0.1 microM were ineffective, and concentrations > 50 microM even accelerated cell injury, although lazaroids still served as scavengers at high concentrations. At least part of the noxious effects of high lazaroid concentrations is due to nonspecific membrane damage because these concentrations caused cell injury also in the absence of oxidative stress. The limited range of protective concentrations has to be observed in further in vivo studies. Interestingly, acinar cells in the absence of lazaroids also reduced radical-induced deoxyribose degradation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1995

Energy metabolism in mouse pancreas in response to different dosages of a CCK analogue.

Stimulation of the exocrine pancreas with cholecystokinin analogues leads to a variety of intraacinar processes, many coupled to energy consumption. It was hypothesized that extensive ATP depletion could play a role in the pathophysiology of acute pancreatitis, especially in the hyperstimulation (cerulein) model. Mice received seven intraperitoneal injections of cerulein at hourly intervals, at doses ranging from physiological (0.1 micrograms/kg) to pharmacological (50 micrograms/kg). A single dose of cerulein induced a 28-33% decrease in ATP, whereas a complete course of injections led to a nadir as low as 45% of the control value. The overall pattern of ATP tissue content during the observed time course was surprisingly similar in all four groups and statistically not different at any time point. Until 12 h, ATP levels in all groups remained below the control value. In contrast, serum amylase and light microscopy reflected a degree of pancreatitis in a close dose-response pattern to the administered cerulein dose. These findings suggest that ATP depletion--although probably facilitating acinar damage--does not seem to play a causal or primary role in the pathophysiology of acute pancreatitis.

Acute Disease↗
PubMed1995

Effects of CCK-receptor antagonist on colonic motor activity in dogs.

This study employed a cholecystokinin (CCK) antagonist to evaluate whether endogenous CCK regulates fasted and fed motor patterns of the colon. Experiments were performed in six conscious dogs, each in duplicate. Motor activity was recorded by four strain gauge transducers implanted on the colon. The effects of the CCK-analogue caerulein and the CCK-antagonist loxiglumide (Rotta, Italy) were studied in fasted and fed states. The motor activity was computed for the area under contractions. Caerulein given as an intravenous bolus of 50 ng kg-1 during a quiescent state caused a burst of phasic and tonic contractions resembling a regular non-migrating motor complex. Physiological doses of 10 ng kg-1 caerulein, which increases plasma CCK-immunoreactivity to postprandial levels, had no effect. Continuous intravenous infusion of 10 mg kg-1 h-1 loxiglumide completely abolished the effects of 50 ng kg-1 caerulein. The motor activity stimulated by the cholinesterase inhibitor neostigmine (10 micrograms kg-1) was not altered by loxiglumide. Loxiglumide given in the fasted state reduced the area under contractions in the proximal colon by 26.8 +/- 12.8% compared to the control without loxiglumide (P < 0.05). The postprandial increase in motor activity in the distal colon, the gastrocolonic response, was significantly inhibited by loxiglumide. Moreover, loxiglumide reduced the area under contractions in the fed state by 25.4 +/- 10.7% and 19 +/- 7.2% in the proximal and distal colon, respectively (P < 0.05). The present results show that loxiglumide acts as a specific antagonist of the actions of CCK on colonic motor activity in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Intrapancreatic zymogen activation and levels of ATP and glutathione during caerulein pancreatitis in rats.

Studies in acutely inflamed pancreatic tissue in humans and animals suggest that premature activation of proteases within the gland plays a key role in its pathophysiology. The present study aimed to detect such protease activation in relation to protease inhibition and to changes in the concentrations of the vital cellular compounds ATP and glutathione in pancreatic tissue during caerulein-induced pancreatitis in rats. Within 1 h after supramaximal stimulation by intraperitoneal caerulein injection, pancreatic tissue activities of enzymatically active trypsin and elastase showed significant increases, accompanied by a twofold increase in trypsin inhibitory capacity. Over the same time course pancreatic ATP and glutathione concentrations dropped to 38% and 47%, respectively, after 1 h and reached a nadir of 22% and 28%, respectively, after 4-8 h. Intrapancreatic trypsin activation in this model, despite increasing trypsin inhibitory capacity, indicates concealed liberation of even more protease or enzyme-inhibitor complex instability. It is hypothesized that early acinar glutathione depletion, in part due to diminished ATP, could play a role in the premature activation of digestive enzymes by impairment of the integrity of the cytoskeleton and cell organelles or lowered defense capabilities against oxidant stress, finally leading to acute pancreatitis.

Adenosine Triphosphate↗
PubMed1995

[Diagnosis and therapy of autoimmune hepatitis].

Thorough differential diagnosis in patients with autoimmune hepatitis is important since other liver disorders need different treatment regimen. Elevated transaminases and gamma-globulines and autoantibodies should make one think of autoimmune hepatitis. Liver biopsy is helpful but usually not a definitive proof of the diagnosis. Immunosuppressive therapy has to be administered for years and possibly leads to serious side effects. Therapy should only be discontinued if a complete remission is induced. Relapses after cessation of medical treatment occur frequently. If no remission is achieved lifelong immunosuppressive therapy has to be given. In decompensated disease liver transplantation offers a treatment with good prognosis.

Autoantibodies↗
PubMed1995

Active pancreatic digestive enzymes show striking differences in their potential to damage isolated rat pancreatic acinar cells.

Active digestive enzymes are involved in the pathophysiology of acute pancreatitis. Previous studies have mainly focused on the role of trypsin in the autodigestive process. The present study compares the noxious potential of different pancreatic enzymes to damage acinar cells. Acinar cells were isolated from rat pancreas by collagenase digestion. Cell viability was studied by (1) exclusion of trypan blue, (2) release of lactate dehydrogenase, and (3) release of newly synthesized proteins identified with methionine labeled with sulfur 35. Cells were then incubated in oxygenated N-2-hydroxyethylpiperazine-N-'-2-ethanesulfonic acid-Ringer solution containing different concentrations of various active digestive enzymes. Uptake of trypan blue was the most sensitive and reliable test of cell damage when compared with release of lactate dehydrogenase or radiolabeled newly synthesized proteins. All active digestive enzymes studied caused dose-dependent cell damage. The noxious potential, however, was strikingly different for the various enzymes. Pancreatic elastase in nanomolar concentrations caused marked cell damage after 45 to 90 minutes of incubation. Lipase and chymotrypsin caused a similar damage only at micromolar concentrations, whereas even millimolar concentrations of trypsin failed to cause significant damage. The present results confirmed recent work showing that lipase and phospholipase A2 probably cause cell damage through release of free fatty acids and lysolecithin. Although activation of trypsin might be the trigger to start the activation cascade in acute pancreatitis, trypsin itself is markedly less noxious to acinar cells when compared with other digestive enzymes. Elastase by far had the greatest noxious potential of all enzymes evaluated. Studies analyzing therapeutic effects of protease inhibitors should evaluate not only the inhibitory potential against trypsin but also that against other digestive enzymes, particularly elastase.

Acute Disease↗
PubMed1995

[HIV infection and the lower gastrointestinal tract--characteristics of endoscopic diagnosis].

In the course of HIV infection intestinal complaints, particularly diarrhoea, are frequent. As a result of the HIV-induced immunosuppression infections with unusual viral, mycobacterial and protozoan pathogens occur. In addition usually self-limiting intestinal infections become frequently persistent in HIV-positive patients with advanced cellular immunodeficiency. Intestinal manifestation of HIV-associated neoplasm is not rare. In combination with microbiological examination of stool specimen endoscopy of the lower gastrointestinal tract is a valuable diagnostic method, especially for the diagnosis of viral infections and neoplasm.

AIDS-Related Opportunistic Infections↗
PubMed1995

[Ultrasound findings in HIV patients].

A wide range of abnormal findings can be seen at abdominal ultrasonography in patients with HIV infection. The most frequent findings, hepatomegaly, splenomegaly, and enlarged lymph nodes, are nonspecific, however. Increased echogenicity or focal lesions of parenchymal organs, dilated bile ducts, nephromegaly, gut wall thickening or abscesses are uncommon findings. If there is clinical suspicion for a treatable disease, abnormalities seen on ultrasound examination of HIV-infected patients need to be confirmed by guided biopsy.

AIDS-Related Opportunistic Infections↗
PubMed1994

Effects of CCK on pancreatic function and morphology.

This report reviews the effects of CCK on the pancreas and in particular analyzes recent studies in which CCK antagonists were used to evaluate the physiological role of CCK in modulating pancreatic function and morphology. CCK is released from endocrine cells of the small intestine in response to a meal. In various animal species there are CCK receptors on pancreatic acinar cells with two sites; occupation of the high affinity site is thought to mediate pancreatic secretion and growth, whereas occupation of the low affinity site by high CCK concentrations is thought to be responsible for supramaximal inhibition of secretion and pancreatitis. Recently, CCK receptors were also found on postganglionic cholinergic neurons in the gastrointestinal tract. Administration of CCK agonists stimulates pancreatic secretion and growth. Although in some previous studies CCK was given at doses that mimic its postprandial increase in plasma, these studies did not prove that the actions of exogenous CCK were physiologically important. In addition, it was unclear if CCK primarily acts as a true hormone or as a neurotransmitter. The development of specific CCK receptor antagonists made it possible to better evaluate the physiological role of CCK. In humans, CCK-A antagonists like loxiglumide or L-364,718 at doses that completely inhibited the action of supraphysiological doses of exogenous CCK reduced meal-stimulated pancreatic enzyme secretion only by approximately 50%. On the other hand, atropine abolished the postprandial increase in pancreatic secretion and in addition markedly reduced the increase in pancreatic secretion due to infusion of "physiological" doses of CCK (i.e., CCK doses that mimic its postprandial increase in plasma). The increase in pancreatic bicarbonate secretion was only slightly reduced by CCK blockade. CCK antagonists failed to reduce the postprandial increase in plasma insulin, but markedly reduced the postprandial PP release. CCK-A antagonists caused slight hypotrophy and hypoplasia of the exocrine pancreas. However, even after 9 months of effective blockade of the CCK-A-receptor, mice had normal body weight and an almost normal pancreas. CCK antagonists were unable to alter short-term changes in pancreatic growth due to feeding and fasting. In some species, CCK agonists induced development of pancreatic nodules and increased the growth of malignant tumors. Studies about the effects of CCK antagonists on induction and growth of pancreatic tumors showed controversial results. In conclusion, CCK may act on the pancreas by three pathways: (1) At low doses it serves as a neurotransmitter by acting on cholinergic neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Epidemiology, clinical spectrum and prognosis of hemochromatosis.

EPIDEMIOLOGY: Eleven prospective epidemiological studies from various countries have as yet evaluated the gene prevalence of HLA-linked hemochromatosis. The estimated frequency ranged from 0.027-0.107, the frequency of homozygotes from 0.00074-0.0116, and the frequency of heterozygotes from 0.052-0.191. In a meta-analysis of the eleven surveys the frequency is 0.0016 (106/64758 subjects) for homozygotes which corresponds to a gene frequency of 0.041 and a frequency of heterozygotes of 0.078. Further analyses showed that some of these studies have probably underestimated the prevalence which in reality is probably two- to threefold higher than estimated by the meta-analysis. CLINICAL SPECTRUM: In the total group of 251 patients diagnosed with hemochromatosis in the University of Düsseldorf from 1959-1992, abnormality in liver function tests (75%), weakness and lethargy (74%), skin hyperpigmentation (70%), diabetes mellitus (48%), arthralgia (44%), impotence (45% in males), and ECG abnormalities (31%) were the most frequent findings and symptoms at diagnosis. In recent years about 50% of patients were detected without having liver cirrhosis and 20% of patients did not have any symptoms and pathology except iron overload. PROGNOSIS: Survival analysis in the 251 patients showed that in the absence of cirrhosis and diabetes iron removal by phlebotomy therapy prevents further tissue damage and guarantees a normal life expectancy. Sex and presence of arthropathy did not predict prognosis. However, patients with massive and long-lasting iron overload had a worse prognosis than patients with less severe iron excess. Iron removal in general ameliorated liver disease, weakness and cardiac abnormalities, and also prevented the progression of endocrine alterations. Therapy, however, did not influence arthropathy which even got worse in several patients. Iron removal also failed to reverse insulin-dependent diabetes. During a mean followup of 13.4 years 69 deaths occurred in the 251 patients. In 19 patients death was due to liver cancer, in 14 due to liver cirrhosis, in 5 due to cardiomyopathy, and in 3 due to diabetes mellitus (all causes significantly more frequent than expected for the general population). The other causes of death were as frequent as expected including extrahepatic malignancies. All liver cancers were seen in cirrhotic livers, but often occurred many years or even decades after complete iron removal. Further strategies have to evaluate the design of screening programs in order to diagnose more patients in the precirrhotic and asymptomatic stage.

Bloodletting↗
PubMed1994

[Effect of resection or duct drainage on glucose stimulated beta cell function in chronic pancreatitis].

Chronic pancreatitis (CP) leads to deterioration of the endocrine pancreatic function by fibrotic destruction. The aim of the present study was to investigate whether resection or duct drainage in patients with CP would have a direct impact on the pancreatic beta cell function. An intravenous glucose tolerance test (IVGTT) was performed before, after and in some cases 3 months after operation in ten patients each of whom had been treated by either resection or duct drainage. Three patients undergoing pancreatic resection for cancer served as controls. Beta cell function was assessed by glucose elimination (K-values), insulin and C-peptide response. K-Values in patients with CP were not significantly influenced after resection (1.93 +/- 0.78/2.13 +/- 0.72; n.s.) or drainage (1.26 +/- 0.47/1.54 +/- 0.58; n.s.) but reduced in all three tumor patients (2.23 +/- 0.55/1.23 +/- 0.43). The initial insulin response [microU/ml] in CP patients was also not altered after resection (19.7 +/- 17.3/16.0 +/- 18.2; n.s.) or after drainage (16.7 +/- 16.5/13.0 +/- 9.0; n.s.), whereas all three resected tumor patients showed reduced values (42.9 +/- 15.7/17.5 +/- 3.8). Stimulated C-peptide synthesis [ngmin/ml] was not substantially lowered in patients resected for CP (90.5 +/- 85.6/73.8 +/- 48.9; n.s.) or in the drainage group (121.3 +/- 67.5/98.0 +/- 57.2; n.s.), but this parameter was decreased in every tumor patient postoperatively (157.8 +/- 66.9/125.1 +/- 69.6). Resection in patients with chronic pancreatitis did not inevitably result in loss of beta cell function. Parenchyma-preserving drainage procedures had no measurable advantage in this respect.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1994

Glutathione and ATP levels, subcellular distribution of enzymes, and permeability of duct system in rabbit pancreas following intravenous administration of alcohol and cerulein.

In order to reproduce what might occur during the initial phase in some cases of acute alcohol-induced pancreatitis, rabbits were infused with diluted ethanol and low-dose cerulein. The duct permeability was assessed by recovery of fluoresceinated dextran (molecular weight 19,500) in central venous blood following orthograde duct perfusion with this substance in the anesthetized animal. Serum ethanol, lipase, and amylase were measured; pancreatic duct morphology was examined by light microscopy and electron microscopy. ATP and glutathione were measured, as were amylase, trypsinogen/trypsin, cathepsin B, and DNA levels in differential centrifugates. As expected, acinar amylase and trypsinogen showed a significant decrease in the experimental group; cathepsin B activity was similarly diminished. Compared with the control group, the activity of serum amylase and lipase in the experimental group demonstrated a significant increase. However, no differences between saline-infused control animals and the treated group regarding pancreatic duct permeability, continuity of lumen-lining epithelium, ATP and glutathione levels, and the relative subcellular distribution of pancreatic digestive and lysosomal enzymes were observed. Thus, our findings do not support the relevance of some of the most common hypotheses on the pathophysiology of acute pancreatitis in its early stage for at least a certain subgroup of patients with acute alcohol-induced pancreatitis.

Adenosine Triphosphate↗
PubMed1994

Glucocerebrosidase for treatment of Gaucher's disease: first German long-term results.

Until recently, there was no specific therapy available for patients with Gaucher's disease. Since April 1991 a highly purified human placental preparation of glucocerebrosidase (Ceredase, Genzyme) has been available for clinical studies in Germany. Sequential deglycosylation of the native enzyme yields a mannose-terminated preparation that may preferentially bind to the plasma membrane of macrophages. The present report analyzes the first German (and European) long-term results with glucocerebrosidase therapy in five patients with type I Gaucher's disease (four women and one man, aged 29-40 years). All patients suffered from excessive enlargement of the liver and spleen with subsequent pancytopenia and from skeletal complications. Multiple pathological fractures had already occurred in three of the five patients, requiring several surgical procedures. Fatigue and asthenia were present in all patients. The initial dose of glucocerebrosidase was chosen according to the severity of complications in the individual patient (20-50 U/kg given i.v. every 2nd week) and was performed in the five patients for 12-18 months. After a few weeks all patients reported that fatigue and asthenia were markedly reduced. After 12 months, blood counts of erythrocytes, leukocytes and platelets had completely normalized in all but one of the patients. After 4-6 months a significant reduction in the sizes of liver and spleen could be observed in all patients. No further fractures occurred during treatment. Significant side-effects of glucocerebrosidase treatment did not occur. The new glucocerebrosidase preparation offers the first effective drug therapy for patients with Gaucher's disease. Although the treatment proved effective and harmless, it is, at least initially, very expensive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗