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M M Lerch

Publications and source records attributed to M M Lerch.

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

Failure of a prolyl 4-hydroxylase inhibitor to alter extracellular matrix deposition during experimental pancreatitis.

In chronic pancreatitis the exocrine pancreatic tissue is replaced by extracellular matrix deposits from fibroblasts. We have stimulated fibrogenesis in the pancreas by inducing a single episode of cerulein pancreatitis (10 microg/kg/h for 12 h). We have used a spectrophotometrical assay to measure the tissue hydroxyproline content and immunohistochemistry to study the transient deposition of extracellular matrix in the pancreas. We have investigated whether a potent prolyl 4-hydroxylase inhibitor (HOE-077) can influence the deposition of extracellular matrix in the pancreas. Three days after the induction of the pancreatitis we found the maximum increase in pancreatic hydroxyproline content (by 63%), the maximum decrease in total protein content and amylase activity (by -39 and -86%, respectively), as well as a significant increase in DNA content and the deposition of interstitial collagen fibers on electron microscopy. By immunohistochemistry the largest expansion of extracellular matrix components was found for fibronectin. HOE 077, regardless of the concentration administered, failed to affect any of these parameters. We conclude that the induction of a single episode of cerulein pancreatitis and the serial determination of pancreatic hydroxyproline content represents a simple method to induce and monitor experimental fibrogenesis in the pancreas. Prolyl 4-hydroxylase inhibition did not affect the course of extracellular matrix deposition in the pancreas.

Acute Disease↗
PubMed1996

Association of human protein-tyrosine phosphatase kappa with members of the armadillo family.

We have identified a human receptor-like protein-tyrosine phosphatase (PTP) in the mammary carcinoma cell line SK-BR-3, which represents the human homolog of murine PTPkappa (Jiang, Y.-P., Wang, H., D'Eustachio, P., Musacchio, J. M., Schlessinger, J., and Sap, J. (1993) Mol. Cell. Biol. 13, 2942-2951) and was therefore termed hPTPkappa. We show here that hPTPkappa expression is dependent on cell density and find it colocalized with two members of the arm family of proteins, beta-catenin and gamma-catenin/plakoglobin, at adherens junctions. Using both in vitro and in vivo binding assays, we demonstrate specific complex formation between endogenous hPTPkappa and beta- and gamma-catenin/plakoglobin. In addition, we present evidence that suggests that beta-catenin may represent a substrate for the catalytic activity of hPTPkappa. The identification of specific binding partners for this receptor-like PTP provides insight into the mechanisms of its biological action and suggests a role for hPTPkappa in the regulation of processes involving cell contact and adhesion such as growth control, tumor invasion, and metastasis.

Amino Acid Sequence↗
PubMed1996

Characterization of PCP-2, a novel receptor protein tyrosine phosphatase of the MAM domain family.

DNA sequences encoding a novel member of the receptor protein tyrosine phosphatase (R-PTP) family, termed PCP-2, were identified in a human pancreatic adenocarcinoma cDNA library. Human PCP-2 cDNA predicts a protein of 1430 amino acids with a calculated Mr of 160 kDa. The predicted PCP-2 enzyme consists of a 740 amino acid extracellular region, a single transmembrane domain, and a 666 amino acid intracellular portion. The extracellular sequence contains a MAM (meprin/A5/PTPmu) domain, an immunoglobulin-like domain and four fibronectin type III-like repeats, suggesting that it is a member of the PTPkappa and PTPmu subfamily. The intracellular region contains two tandemly-repeated protein tyrosine phosphatase domains. Northern blot analyses revealed a single transcript of 5.5 kilobases, which is expressed at different levels in many human tissues except spleen and placenta. Upon transfection of PCP-2 cDNA into human embryonic kidney fibroblast 293 cells, a protein with an apparent Mr of 180 000 was detected by immunoblot analysis. This size was reduced to the predicted Mr upon treatment with endoglycosidase F, indicating that PCP-2 is glycosylated and, hence, expressed at the cell surface. A potential role of PCP-2 in cell-cell recognition and adhesion is supported by its co-localization with cell adhesion molecules, such as catenin and E-cadherin, at sites of cell-cell contact.

Adenocarcinoma↗
PubMed1996

Characterization of a non-invasive, vascular model of acute necrotizing pancreatitis.

One of the vasoactive peptides that has been implicated in the progression from edematous to necrotizing pancreatitis is bradykinin. We have investigated the effect of bradykinin administration and bradykinin inhibition on an edematous model of acute pancreatitis in rats (10 micrograms/kg/h of caerulein i.v.). Within six hours i.v. bradykinin reduced circulating serum amylase levels significantly but neither affected tissue edema nor morphology. A bradykinin antagonist (HOE-140), on the other hand, reduced pancreatic edema by 70% and converted edematous pancreatitis into a hemorrhagic and necrotizing variety of the disease. In further experiments we determined the time course and the minimal dosage required for the induction of this severe and non-invasive disease variety. A single dose of caerulein (40 micrograms/kg i.p.) together with a single administration of the bradykinin antagonist HOE-140 (100 micrograms/kg s.c.) consistently resulted in hemorrhagic necrosis of the pancreas within six hours. We conclude that this simple protocol allows for the non-invasive induction of a vascular model of necrotizing pancreatitis and appears ideally suited to study the development of this severe form of the disease.

Acute Disease↗
PubMed1995

Cloning, characterization, and differential expression of MDK2 and MDK5, two novel receptor tyrosine kinases of the eck/eph family.

Using a polymerase chain reaction-based strategy for the cloning of developmentally regulated receptor tyrosine kinases, we identified two novel members of the eck/eph-related subfamily which, in analogy with the recently identified mouse developmental kinase 1 (MDK1), were designated MDK2 and MDK5. MDK2 is highly homologous to the mouse kinase Myk-1 and the human kinase Htk, whereas MDK5 represents the mouse homologue of human Hek2. Northern blot analyses of adult mouse tissues revealed a 4.7 kb transcript of MDK2 and a 4.8 kb transcript of MDK5 in various organ systems, including lung, liver, kidney, intestine, muscle, heart, and, in the case of MDK5, also the brain. In addition to the full-length transcripts, smaller fragments were identified that probably represent truncated receptors. Northern blot analysis and in situ hybridization of mouse embryos indicated abundant expression during embryonic development, with preferential involvement of tissues of epithelial and endothelial origin for both kinases and of the spinal cord gray matter for MDK5. Unlike most other members of the eck/eph-related subfamily, the expression of MDK2 and MDK5 is not primarily restricted to neuronal structures, and their abundant presence in various organ systems during embryonic development suggests an important role in gestational growth and differentiation.

Amino Acid Sequence↗
PubMed1995

The role of nitric oxide in hemodynamic and metabolic alterations induced by prostaglandin F2 alpha in the perfused rat liver.

In the liver prostaglandins have been shown to be potent regulators of portal blood flow, carbohydrate metabolism and bile secretion. It is not known whether these effects represent a direct action of prostaglandins, and it has been suggested that nitric oxide (NO) might be a critical mediator for prostaglandin induced hepatic events. We have studied whether nitric oxide formation or inhibition alters the action of prostaglandin F2 alpha (PG F2 alpha) in a single-pass liver perfusion model. The liver of untreated rats (constitutive NO-synthase) or after pretreatment with endotoxin (inducible form of NO-synthase) was perfused at a constant pressure via the portal vein. Effluate were collected in 1-min intervals and bile in 5-min intervals. In both groups the addition of PG F2 alpha (10 microM) to the perfusate for 5 min resulted in a significant increase of glucose and lactate production, and in a significant decrease in portal blood flow (-0.56 +/- 0.04 ml/g per min), in bile flow (-60.7%) and in bile acid release (-60.6%). Inhibition of NO synthase by adding NG-monomethyl-L-arginine (L-NMMA, 100 microM) to the perfusate did not affect any of the alterations induced by PG F2 alpha. Substitution of the endogenous substrate for the NO synthase L-arginine (500 microM) in the perfusate completely prevented the hemodynamic alterations induced by PG F2 alpha in endotoxin pretreated livers and limited the flow reduction (0.15 +/- 0.04 ml/g per min) in the untreated group. The substitution of L-arginine in the perfusate of endotoxin pretreated livers raised nitrite (from 1.5 +/- 0.3 to 3.6 +/- 0.7 nmol/g per min) and urea release (from 65 +/- 25 to 294 +/- 68 nmol/g per min), but had no effect on any of the other metabolic parameters and bile secretion. We conclude that PG F2 alpha increases glucose and lactate production in the perfused rat liver and decreases portal flow bile secretion. The metabolic effects induced by PG F2 alpha appear to be independent of NO mediation and hemodynamic alterations. Portal flow alone can be influenced by endogenous NO formation.

Animals↗
PubMed1995

Expression and in-situ localization of genes coding for extracellular matrix proteins and extracellular matrix degrading proteases in pancreatic cancer.

Pancreatic cancer shows a strong desmoplastic reaction characterized by a remarkable proliferation of interstitial connective tissue (collagens type I and III, fibronectin). In this study we have analyzed the balance of expression of mRNAs encoding extracellular matrix components (collagens I, III and IV, laminin, fibronectin), extracellular matrix-degrading metalloproteinases (MMP-1, -2, -3 and -9) and tissue inhibitors of metalloproteinases (TIMP-1 and -2) in pancreatic cancer and control pancreatic tissue by Northern-blot analysis and mRNA in situ hybridization. Transcripts for MMP-1 (interstitial collagenase) and MMP-3 (stromelysin-1) were not detectable in pancreatic cancer and control tissues. Steady-state levels of transcripts encoding extracellular matrix proteins, MMP-2 (72-kDa collagenase IV), MMP-9 (92-kDa collagenase type IV), TIMP-1 and TIMP-2 were elevated in the majority of pancreatic-cancer tissue samples as compared to control pancreatic tissue. A good correlation was seen between overexpression of these MMPs and TIMPs and the steady-state levels of transcripts coding for extracellular matrix proteins, the amount of collagen protein and the severity of the desmoplastic reaction. In situ hybridization studies localized transcripts coding for collagens type I and III to spindle-shaped stromal cells, whereas transcripts for MMP-2, MMP-9, TIMP-1 and TIMP-2 were found in both stromal and tumor cells. However, MMP-2 transcripts appeared to be more abundant in stromal cells, TIMP-1 and TIMP-2 transcripts were evenly distributed over tumor and stromal cells and relatively more MMP-9 transcripts were found in tumor cells. We conclude that, in human pancreatic cancer, MMP-2, MMP-9, TIMP-1 and TIMP-2 may be involved in processes leading to the strong desmoplastic reaction observed in these tumors. Both stromal and tumor cells appear to be the source of MMPs and TIMPs in human pancreatic cancer.

Blotting, Northern↗
PubMed1995

Prevention of postoperative adhesions by single intraperitoneal medication.

Postoperative adhesions account for a significant morbidity after abdominal, gynecological, or cardiac surgery. A large number of compounds have been suggested to prevent such adhesions, but none is generally accepted. We have compared eight different substances that could be beneficial for the prevention of postoperative adhesions in a new standardized rabbit model with measurement of the areas of adhesion. In 10 groups of 20 rabbits an area of abrasion of the serosa of the ileum, the appendix, and the abdominal wall measuring 10,000 mm2 was created by an emery piston during celiotomy. The controls received no medication. The treatment groups received a single intraperitoneal administration of 1 ml per 100 g body wt of normal saline (NaCl), 5 mg taurolidine (T), 0.5 U plasmin/300 U DNase (PD), 2000 IU streptokinase/500 IU streptodornase (SS), 7 mg phosphatidylcholine (PC), 4 mg hyaluronic acid (HA), 7 mg sphingolipid (SL), 7 mg galactolipid (GL), or 0.5 ml tetrachlorodecaoxide (TCDO), respectively. Ten days later the extent of adhesions was quantified by morphometry. The total area of adhesions (+/- SEM) was found to be 1998 +/- 124 mm2 in controls. The application of NaCl reduced the adhesions to 1368 +/- 58 mm2, of T to 1012 +/- 48 mm2, of PD to 673 +/- 33 mm2, of SS to 360 +/- 44 mm2, of PC to 335 +/- 84 mm2, of HA to 328 +/- 76 mm2, of SL to 278 +/- 80 mm2, of GL to 261 +/- 67 mm2, and of TCDO to 240 +/- 45 mm2. The effects of PD, SS, PC, HA, SL, GL, and TCDO were significant in comparison to controls and NaCl. Our experimental data suggest that the two new lipid substances, SL and GL, are the most likely candidates for routine clinical use in the prevention of postsurgical adhesions.

Abdominal Muscles↗
PubMed1995

Supramaximal secretagogue stimulation enhances heat shock protein expression in the rat pancreas.

Heat shock or stress proteins (HSPs) are synthesized by various cell types in response to different metabolic insults (e.g., hyperthermia). Although the function of HSPs is not fully understood, they are believed to be an evolutionary conserved intracellular defense mechanism. In an attempt to characterize the autoprotective potential of pancreatic acinar cells, we investigated the regulation of HSPs of the 70-kD family and the small HSP ubiquitin in vitro and in vivo during supramaximal cerulein stimulation. Infusion of the secretagogue cerulein induces a mild edematous form of pancreatitis in vivo and is characterized by a marked disturbance of the intracellular transport and segregation of enzymes. Synthesis of HSP70 mRNA is upregulated in isolated pancreatic lobules by either cerulein (100 nM) or hyperthermia (42 degrees C for 60 min). In contrast, expression of ubiquitin mRNA was not altered by either secretagogue treatment or hyperthermia. This heat shock-like response of pancreatic acinar cells could be reproduced in vivo: Pancreatitis was induced in male Wistar rats by intravenous infusion of supramaximal doses of cerulein (10 micrograms/kg/h). Analysis of mRNA expression revealed a significant upregulation of HSP70 RNA during supramaximal secretagogue stimulation. mRNA levels encoding for ubiquitin remained unchanged. Western blot analysis demonstrated that the transcriptional upregulation of HSP70 in vivo was reflected on the protein level. This study demonstrates that the marked intracellular disturbance observed in secretagogue-induced pancreatitis is associated with enhanced expression and synthesis of a major stress protein. Given the autoprotective potential of HSPs, this upregulation may indicate a self-defense mechanism of pancreatic acinar cells in experimental pancreatitis.

Animals↗
PubMed1995

Vasoactive mediators and the progression from oedematous to necrotising experimental acute pancreatitis.

Little is known about the pathophysiological factors that determine the clinical severity of acute pancreatitis. Because impairment of pancreatic circulation and oxygenation is associated with greater disease severity and morphological damage in experimental pancreatitis it has been suggested that various vasoactive mediators might participate in the progression from the oedematous to the necrotising variety of the disease. This study used an animal model of acute pancreatitis induced by intravenous caeruleint (10 micrograms/kg/h for up to six hours), which does not entail either haemorrhage or significant necrosis of the pancreas. This study considered whether the administration or the inhibition of either nitric oxide, bradykinin, or adrenergic mediators can convert this mild variety into haemorrhagic and necrotising pancreatitis. Neither nitric oxide nor catecholamines were involved in the progression from oedematous to haemorrhagic pancreatitis. Their substitution, activation, and inhibition all failed to change the severity of the disease process. Bradykinin alone seemed to be critically involved in the pathogenesis of pancreatic haemorrhage and necrosis. However, the inhibition of bradykinin and not its activation or substitution increased the severity of the disease.

Acute Disease↗
PubMed1995

Disassembly of rat pancreatic acinar cell cytoskeleton during supramaximal secretagogue stimulation.

In vivo stimulation of the exocrine pancreas with concentrations of secretagogue in excess of a maximally stimulating dose causes a marked disturbance of the intracellular segregation, transport, and exocytosis of digestive enzyme zymogens. Under physiological conditions elements of the cytoskeleton, most notably microtubules and microfilaments, are involved in the regulation of these intracellular events. We infused caerulein, a peptide analogue of cholecystokinin, at a supramaximal dose (10 micrograms.kg-1.h-1 for up to 6 h) intravenously in rats. To study the ultrastructural alterations of acinar cell microfilaments and microtubules by immunogold labeling, we used monoclonal antibodies directed against actin and beta-tubulin. As early as 30 min after the start of the secretagogue infusion we found a progressive disassembly of microtubules and microfilaments in exocrine cells. In immunoblot studies this disassembly of the cytoskeleton was paralleled by a degradation of its structural proteins actin and beta-tubulin. Our results indicate that the earliest morphological events during supramaximal secretagogue stimulation of the pancreas involve the disassembly and degradation of microtubules and microfilaments. This cell biological phenomenon offers an explanation for the disturbances of segregation, transport, and exocytosis of digestive enzymes, which are known to be associated with supramaximal stimulation of the pancreas and experimental models of pancreatitis.

Actin Cytoskeleton↗
PubMed1995

Effect of kinin inhibition in experimental acute pancreatitis.

Activation of the endogenous kinin system is a consistent observation in acute pancreatitis and has repeatedly been implicated in the pathophysiology of the disease. We have studied the effect of a potent bradykinin antagonist on the onset and development of acute pancreatitis in four unrelated animal models. Pancreatitis was induced in rats by either supramaximal stimulation with caerulein, intraductal injection of sodium taurocholate, or pancreatic duct ligation with secretin infusion, and in mice by feeding a choline-deficient, ethionine-supplemented diet. The potent, long-acting bradykinin antagonist HOE-140 was administered subcutaneously (0.1 mg/kg every 5 h). Effective kinin inhibition had no effect on pancreatitis-associated mortality, the extent of morphological damage and inflammation, or the intracellular distribution of lysosomal hydrolases. Pancreatic edema was only reduced in caerulein-induced pancreatitis, the only model in which edema formation was paralleled by increased vascular permeability. We conclude that, contrary to previous suggestions, kinins do not play a predominant role in the development of acute pancreatitis. Their participation is strictly limited to vascular events and does not involve the early cell biological alterations in pancreatic acinar cells.

Acute Disease↗
PubMed1995

Luminal endocytosis and intracellular targeting by acinar cells during early biliary pancreatitis in the opossum.

Cell necrosis in acute experimental pancreatitis is preceded by a redistribution of digestive enzymes into a lysosomal subcellular compartment. We have investigated whether endocytosis from the acinar cell lumen might contribute to this disturbance of intracellular compartmentation. In an animal model of pancreatitis involving pancreatic bile duct ligation in opossums, we have studied in vivo endocytosis of dextran 40 and [14C]dextran 70, cationized ferritin, and horseradish peroxidase from the apical surface of acinar cells before the onset of necrosis. Marker solutions were instilled into the pancreatic duct of anesthetized animals at physiological pressure. Tissue samples obtained at intervals of up to 60 min after instillation of markers were studied by electron microscopy and electron microscope autoradiography. All markers were taken up by acinar cells in control animals and in animals with obstructed pancreatic bile ducts. Markers for membrane-mediated endocytosis (cationated ferritin and horseradish peroxidase) were transported to lysosomes in both groups. In contrast, the fluid-phase tracer dextran was transported to the secretory pathway in controls but to lysosomes after duct ligation. Since dextran and luminally present secretory proteins can be expected to follow the same route after endocytosis, our findings suggest that altered intracellular targeting of endocytosed proteases might be one mechanism by which digestive zymogens reach an intracellular compartment in which premature activation can occur. This phenomenon may be a critical and early event in the pathogenesis of biliary pancreatitis.

Acute Disease↗
PubMed1994

Differential expression of heat shock proteins in pancreatic carcinoma.

In the present study we sought to determine by Northern blot analysis and mRNA in situ hybridization whether gene expression of heat shock proteins (HSPs) (HSP 89 alpha, HSP 89 beta, HSP 70, and ubiquitin) is altered in pancreatic carcinoma, compared to control tissues (normal pancreas and chronic pancreatitis tissue). HSP 89 alpha was selectively overexpressed in pancreatic carcinoma, and tumor cells were shown to contain the largest amount of HSP 89 alpha mRNA. Steady state levels of HSP 70 mRNA were increased in pancreatic carcinoma (tumor and connective tissue cells) and in chronic pancreatitis (connective tissue cells and residues of exocrine acinar cells). HSP 89 beta and ubiquitin B were constitutively expressed at high levels in pancreatic tissue from all three groups; HSP 89 beta mRNA was found in cells of parenchymal and stromal origin. A strong correlation was found between the expression of HSP 70 and the expression of transforming growth factor beta 1. The finding that HSPs are differentially expressed in pancreatic cancer, compared to normal pancreas and chronic pancreatitis tissue, and the cancer specificity of HSP 89 alpha suggest that HSPs play a specific role in the pathogenesis of pancreatic cancer, e.g., by participating in regulatory processes or in tumor immunity, as proposed previously.

Blotting, Northern↗
PubMed1994

Diagnostic value of indirect pancreatic function test in serum of anuric patients with chronic renal failure.

Although patients with chronic renal failure have a high incidence of chronic pancreatic disease, the condition is frequently overlooked. We have modified the pancreolauryl test--an indirect pancreatic function test--for anuric patients. The test permitted good discrimination between patients with chronic pancreatic disease and those with a normal pancreas when serum levels of fluorescein were measured 10 h after administration with a standard meal. The sensitivity at this time interval was 80% and the specificity 83%. We conclude that the pancreolauryl test with serum measurements provides a simple, noninvasive, and reliable diagnostic test for chronic pancreatic disease in anuric patients with chronic renal failure.

Anuria↗
PubMed1994

Pancreatic outflow obstruction as the critical event for human gall stone induced pancreatitis.

Opie suggested in 1901 that a common channel between the pancreatic duct and the common bile duct is created when a gall stone becomes impacted at the duodenal papilla. He proposed that bile would regurgitate into the pancreas and trigger pancreatitis. The case is reported of a 22 year old woman with an impacted stone at the duodenal papilla creating a common channel. The patient suffered from acute pancreatitis. Three days before the onset of pancreatitis, however, a T drain had been inserted into the common bile duct from which bile had been flowing freely and continuously. Moreover, amylase activity in fluid from the T drain was 49,000 U/l at the onset of pancreatitis pointing to reflux of pancreatic juice into the biliary tract. The amylase activity in bile decreased rapidly after endoscopic papillotomy and retrieval of the stone. The events participating in the development of acute gall stone induced pancreatitis in this patient with a common channel situation permitted reflux of pancreatic juice into the biliary tract rather than bile into the pancreas. Impairment of pancreatic outflow by a gall stone was probably the primary triggering event, rather than the regurgitation of bile into the pancreas. Preventive or therapeutic treatment in gall stone pancreatitis should be aimed at the urgent restoration of pancreatic flow rather than at the prevention of a hypothetical bile reflux.

Acute Disease↗