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M M Lerch

Publications and source records attributed to M M Lerch.

At least 55 records · Page 3Linked to original sources
PubMed2000

Early trypsinogen activation in acute pancreatitis.

This article discusses zymogen activation within the acinar cell. The authors review advances in respect to the cellular mechanism involved in a premature intrapancreatic protease activation. Critical factors that determine the onset of premature protease activation appear to be the molecular structure of trypsinogen, the presence or absence of functionally intact lysosomal hydrolases, the pH in intracellular compartments, and the calcium signaling cascade in the pancreatic acinar cell.

Calcium Signaling↗
PubMed2000

The double duct sign in patients with malignant and benign pancreatic lesions.

BACKGROUND: The double duct sign, a simultaneous stenosis of the common bile duct and the pancreatic duct by endoscopic retrograde cholangiopancreatography (ERCP), has been reported to predict the presence of pancreatic cancer with a high degree of certainty. METHODS: To test the specificity of the double duct sign for pancreatic cancer in patients with malignant and benign pancreatic lesions, we have reviewed all ERCP films obtained during a 24-month period (n = 1209) and corresponding clinical follow-up data obtained during a period of 4 years. RESULTS: Forty-three patients were identified as having a double duct stenosis on ERCP, 15% of whom did not have pancreatic carcinoma. In 4 patients chronic pancreatitis was confirmed by serial histologic sections of the surgical specimen. Data on the lengths of the stenotic segment in either the pancreatic duct or the bile duct did not contribute to a better discrimination between benign and malignant disease. CONCLUSION: The specificity of the double duct sign in predicting the presence of pancreatic cancer appears to be lower than previously reported. Better discrimination between malignant and benign disease of the pancreas will be difficult to achieve with existing imaging techniques.

Aged↗
PubMed2000

Role of cathepsin B in intracellular trypsinogen activation and the onset of acute pancreatitis.

Autodigestion of the pancreas by its own prematurely activated digestive proteases is thought to be an important event in the onset of acute pancreatitis. The mechanism responsible for the intrapancreatic activation of digestive zymogens is unknown, but a recent hypothesis predicts that a redistribution of lysosomal cathepsin B (CTSB) into a zymogen-containing subcellular compartment triggers this event. To test this hypothesis, we used CTSB-deficient mice in which the ctsb gene had been deleted by targeted disruption. After induction of experimental secretagogue-induced pancreatitis, the trypsin activity in the pancreas of ctsb(-/-) animals was more than 80% lower than in ctsb(+/+) animals. Pancreatic damage as indicated by serum activities of amylase and lipase, or by the extent of acinar tissue necrosis, was 50% lower in ctsb(-/-) animals. These experiments provide the first conclusive evidence to our knowledge that cathepsin B plays a role in intrapancreatic trypsinogen activation and the onset of acute pancreatitis.

Acute Disease↗
PubMed1999

Protein tyrosine dephosphorylation and the maintenance of cell adhesions in the pancreas.

Cell-cell contacts are important regulatory elements in tissue development, organ morphogenesis and malignant tumor invasion. In recent in vivo studies we have identified the members of the cadherin/catenin family of cell adhesion proteins that are differentially expressed in the pancreas and have determined their cell biological dynamics during dissociation and repair of adherens junctions. To further characterize these events, epithelial cell culture systems were used and a number of type II protein tyrosine phosphatases (PTPs) were found to colocalize and interact with the cadherin/catenin complex. These observations suggest that tyrosine dephosphorylation in general and PTPs in particular are involved in cell contact formation. Our most recent experiments indicate 1) that inhibition of PTPs alone dissociates pancreatic adherens junctions, 2) that cytosolic and transmembrane PTPs are differentially expressed in acinar cells, and 3) that a subset of them can associate with proteins of the cadherin/catenin complex at pancreatic cell-cell adhesions.

Cell Adhesion↗
PubMed1999

Palliative transhepatic biliary drainage and enteral nutrition.

Simultaneous intestinal and biliary obstruction is a rare but agonizing complication of metastatic abdominal cancer. Although endoscopic procedures exist that relieve jaundice or restore enteral nutrition, they can be impossible to perform for technical or anatomical reasons. We propose a palliative approach for these patients that includes transcutaneous common bile duct drainage, progressive dilation of the transhepatic channel over 1 wk, and, finally, insertion of a permanent silicon catheter that drains bile into the duodenum and is combined with an enteral feeding line. We report three patients whose metastatic abdominal tumors had led to simultaneous jaundice and gastric outlet obstruction, neither of which could be treated endoscopically. In all patients, the transcutaneous bile drainage catheter combined with the enteral feeding line was inserted and tumor symptoms resolved rapidly. As a result, the patients chose to return to home care with enteral nutrition and pain medication. The creation of a transhepatic access for simultaneous enteral bile drainage and nutrition is a technically simple procedure that causes little discomfort to a terminally ill patient. It relieves the symptoms of tumor obstruction, and the option of enteral nutrition and medication can obviate the need for intravenous infusions.

Aged↗
PubMed1998

Infection of an intravenous port system with Metschnikowia pulcherrima Pitt et Miller.

A patient with short bowel syndrome as a consequence of multiple intestinal resections for Crohn's disease, had a port system implanted to improve her nutritional status. One year later she presented with fever, weakness and nighttime sweating. Metschnikowia pulcherrima Pitt et Miller was grown in blood cultures from the port system. After antifungal chemotherapy using fluconazole and removal of the implant, the patient's condition improved markedly and her fever and sweating disappeared. We conclude that Metschnikowia pulcherrima can turn into a human pathogen in patients with indwelling catheters for parenteral nutrition. Chemotherapy with fluconazole and, whenever possible, removal of the implant, appear to be adequate treatment.

Adult↗
PubMed1998

Intra-acinar cell activation of trypsinogen during caerulein-induced pancreatitis in rats.

Supramaximal stimulation of the pancreas with the CCK analog caerulein causes acute edematous pancreatitis. In this model, active trypsin can be detected in the pancreas shortly after the start of supramaximal stimulation. Incubation of pancreatic acini in vitro with a supramaximally stimulating caerulein concentration also results in rapid activation of trypsinogen. In the current study, we have used the techniques of subcellular fractionation and both light and electron microscopy immunolocalization to identify the site of trypsinogen activation and the subsequent fate of trypsin during caerulein-induced pancreatitis. We report that trypsin activity and trypsinogen-activation peptide (TAP), which is released on activation of trypsinogen, are first detectable in a heavy subcellular fraction. This fraction is enriched in digestive enzyme zymogens and lysosomal hydrolases. Subsequent to trypsinogen activation, both trypsin activity and TAP move to a soluble compartment. Immunolocalization studies indicate that trypsinogen activation occurs in cytoplasmic vacuoles that contain the lysosomal hydrolase cathepsin B. These observations suggest that, during the early stages of pancreatitis, trypsinogen is activated in subcellular organelles containing colocalized digestive enzyme zymogens and lysosomal hydrolases and that, subsequent to its activation, trypsin is released into the cytosol.

Acute Disease↗
PubMed1998

Zymogen proteolysis within the pancreatic acinar cell is associated with cellular injury.

The pathological activation of digestive zymogens within the pancreatic acinar cell probably plays a central role in initiating many forms of pancreatitis. To examine the relationship between zymogen activation and acinar cell injury, we investigated the effects of secretagogue treatment on isolated pancreatic acini. Immunofluorescence studies using antibodies to the trypsinogen-activation peptide demonstrated that both CCK (10(-7) M) hyperstimulation and bombesin (10(-5) M) stimulation of isolated acini resulted in trypsinogen processing to trypsin. These treatments also induced the proteolytic processing of procarboxypeptidase A1 to carboxypeptidase A1 (CA1). After CCK hyperstimulation, most CA1 remained in the acinar cell. In contrast, the CA1 generated by bombesin was released from the acinar cell. CCK hyperstimulation of acini was associated with cellular injury, whereas bombesin treatment did not induce injury. These studies suggest that 1) proteolytic zymogen processing occurs within the pancreatic acinar cell and 2) both zymogen activation and the retention of enzymes within the acinar cell may be required to induce injury.

Animals↗
PubMed1998

[Role of protease activation in pathophysiology of acute pancreatitis].

For over a century it has been assumed that acute pancreatitis represents an autodigestion of the pancreas by its own, physiologically inactive proteases. Whether, how and where digestive proteases are being activated in the pancreas has remained the topic of much controversy and speculation. We review a number of recent studies that have been undertaken to elucidate the mechanisms and identify the initial subcellular localization of this process. These studies suggest that a premature and intrapancreatic protease activation does, indeed, occur early in pancreatitis and can be experimentally induced in vivo and in vitro. Activation begins within minutes of the induction of pancreatitis and is initially confined to cytoplasmic vacuoles at the apical pole of acinar cells. From here trypsin activity as well as its activation peptide are transferred to the cytosol of acinar cells where autodigestion may begin.

Animals↗
PubMed1997

Cellular redistribution of protein tyrosine phosphatases LAR and PTPsigma by inducible proteolytic processing.

Most receptor-like protein tyrosine phosphatases (PTPases) display a high degree of homology with cell adhesion molecules in their extracellular domains. We studied the functional significance of processing for the receptor-like PTPases LAR and PTPsigma. PTPsigma biosynthesis and intracellular processing resembled that of the related PTPase LAR and was expressed on the cell surface as a two-subunit complex. Both LAR and PTPsigma underwent further proteolytical processing upon treatment of cells with either calcium ionophore A23187 or phorbol ester TPA. Induction of LAR processing by TPA in 293 cells did require overexpression of PKCalpha. Induced proteolysis resulted in shedding of the extracellular domains of both PTPases. This was in agreement with the identification of a specific PTPsigma cleavage site between amino acids Pro821 and Ile822. Confocal microscopy studies identified adherens junctions and desmosomes as the preferential subcellular localization for both PTPases matching that of plakoglobin. Consistent with this observation, we found direct association of plakoglobin and beta-catenin with the intracellular domain of LAR in vitro. Taken together, these data suggested an involvement of LAR and PTPsigma in the regulation of cell contacts in concert with cell adhesion molecules of the cadherin/catenin family. After processing and shedding of the extracellular domain, the catalytically active intracellular portions of both PTPases were internalized and redistributed away from the sites of cell-cell contact, suggesting a mechanism that regulates the activity and target specificity of these PTPases. Calcium withdrawal, which led to cell contact disruption, also resulted in internalization but was not associated with prior proteolytic cleavage and shedding of the extracellular domain. We conclude that the subcellular localization of LAR and PTPsigma is regulated by at least two independent mechanisms, one of which requires the presence of their extracellular domains and one of which involves the presence of intact cell-cell contacts.

Amino Acid Sequence↗
PubMed1997

A circus flea.

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Animals↗
PubMed1997

Dissociation and reassembly of adherens junctions during experimental acute pancreatitis.

BACKGROUND & AIMS: The initial pathophysiological events that characterize acute pancreatitis include the formation of pancreatic edema. An interstitial accumulation of fluid, however, is incompatible with the presence of intact intercellular junctions between acinar cells. This study examined the major components of adherens junctions, E-cadherin, alpha-catenin, beta-catenin, and actin, during the initial phase of experimental pancreatitis. METHODS: Pancreatitis was induced in rats by 10 micrograms.kg-1.h-1 intravenous cerulein for up to 12 hours. Adherens junction proteins were localized by immunocytochemistry for fluorescence microscopy or electron microscopy, their expression was studied by slot blot analysis, and their association was investigated by immunoprecipitation and Western blot. RESULTS: During a rapid increase of E-cadherin-encoding RNA, E-cadherin protein declined only moderately and, unlike its cytoskeletal binding partner actin, was not proteolytically cleaved during pancreatitis. Morphologically, E-cadherin and beta-catenin were localized at the basolateral cell membrane from where they rapidly dissociated early in pancreatitis and to where they slowly relocalized during the subsequent course. E-cadherin/beta-catenin complexes disintegrated and reassembled completely in parallel on immunoprecipitation experiments. CONCLUSIONS: The dissociation of adherens junctions and the internalization, relocalization, and reassembly of their major components seem to represent the critical biochemical event at cell-cell contacts during edema formation and resolution in acute pancreatitis.

Actins↗
PubMed1997

Common biliary-pancreatic conduit stenosis induces pancreobiliary reflux.

A striking pancreatic juice reflux toward the biliary tree (PR) has frequently been found in subjects with common bile-pancreatic conduit (CBPC) and gallstone-induced acute pancreatitis (SAP). Our aim was to determine the role of the CBPC functional diameter as a potential trigger of PR. The CBPC was calibrated in three groups of patients: (A) patients with gallbladder stones using intraoperative direct cholangiometry (n = 24), (B) patients after surgical removal of common bile duct stones using postoperative cholangiometry via T-drain (n = 6), and (C) patients with SAP using the same procedures as in group B (n = 6). In all patients in groups B and C, aliquots of bile were collected and assayed for pancreatic amylase content. The mean functional diameter of the CBPC varied from 0.80 mm in patients in groups A and B to 0.47 mm in group C (p < 0.001). The bile samples of group B contained low concentrations of amylase, whereas high values could be found in all samples of group C. We conclude that PR is a frequent event occurring after bile duct revision concerning small amounts of pancreatic juice. However, CBPC functional stenosis as seen in patients with SAP obviously induces PR with high amounts of pancreatic juice.

Acute Disease↗
PubMed1997

Expression of the protooncogene jun is induced in the rat pancreas by cerulein infusion.

Cholecystokinin (CCK) can stimulate secretion and DNA synthesis in pancreatic acinar cells. Hyperstimulation with cerulein (a CCK analogue) induces acute edematous pancreatitis. To study the effects of in vivo pancreatic stimulation with cerulein, we analyzed the expression of the protooncogenes jun, myc, and fos on the mRNA and protein levels. RNA and protein were extracted from the pancreas of rats administered an infusion of cerulein, 10 micrograms/kg/h (Group A) or 0.25 microgram/kg/h (Group B), or saline (Group C) and sacrificed 2, 4, and 6 h after beginning the infusion and 0, 12, and 24 h and 2, 4, and 6 days after completing the infusion period. Transcript levels were studied using slot-blot analysis. Protein expression was studied using Western blot and immunohistochemistry. No changes were found for the expression of protooncogenes myc and fos on either the transcript or the protein levels. Higher jun mRNA levels were found in Group A than in Group B or C, particularly after 2 h of infusion and 12, 24, and 48 h after the end of a 12-h cerulein infusion. No significant difference was observed in Groups B and C. The jun protein behavior was similar in Groups A and B, revealing two peaks: one early during infusion and a second one after the end of a 12-h cerulein infusion. Jun protein was found mainly in the acinar cells. In conclusion, (1) acinar cells in the rat pancreas respond to cerulein stimulation by increasing the expression of jun; (2) in vivo high doses of cerulein increase the jun mRNA and jun protein levels, whereas low doses raise only the protein levels; and (3) myc and fos are apparently uninfluenced by cerulein administration.

Animals↗
PubMed1997

Combined treatment with C1 esterase inhibitor and antithrombin III improves survival in severe acute experimental pancreatitis.

BACKGROUND: Patients with severe acute pancreatitis die of complications closely related to the systemic activation of protease cascades. AIM: To examine the effects of human C1 esterase inhibitor (C1 INH) and antithrombin III (AT III) on two experimental models of acute pancreatitis. METHODS: Oedematous pancreatitis was induced by continuous intravenous infusion of caerulein and haemorrhagic pancreatitis by retrograde injection of sodium taurocholate into the biliopancreatic duct. C1 INH and AT III were given intravenously, either before or after the induction of pancreatitis. Treatment with C1 INH and AT III had no beneficial effect on oedematous pancreatitis. On the other hand, combined C1 INH and AT III therapy improved the survival in haemorrhagic pancreatitis compared with treatment with human serum albumin. This reduction in mortality was found regardless of whether the treatment was given prophylactically or therapeutically. CONCLUSIONS: Treatment with C1 INH and AT III represents a promising therapeutic concept for patients with severe haemorrhagic pancreatitis.

Acute Disease↗