No abstract

No abstract

The aim of this study was to identify fibrogenic mediators stimulating activation, proliferation, and/or matrix synthesis of rat pancreatic stellate cells (PSC). PSC were isolated from the pancreas of normal Wistar rats and from rats with cerulein pancreatitis. Cell activation was demonstrated by immunofluorescence microscopy of smooth muscle alpha-actin (SMA) and real-time quantitative RT-PCR of SMA, fibronectin, and transforming growth factor (TGF)-beta(1). Proliferation was measured by bromodeoxyuridine incorporation. Matrix synthesis was demonstrated on the protein and mRNA level. Within a few days in primary culture, PSC changed their phenotype from fat-storing to SMA-positive myofibroblast-like cells expressing platelet-derived growth factor (PDGF) alpha- and PDGF beta-receptors. TGF-beta(1) and tumor necrosis factor (TNF)-alpha accelerated the change in the cells' phenotype. Addition of 50 ng/ml PDGF and 5 ng/ml basic fibroblast growth factor (bFGF) to cultured PSC significantly stimulated cell proliferation (4.37 +/- 0.49- and 2.96 +/- 0.39-fold of control). Fibronectin synthesis calculated on the basis of DNA was stimulated by 5 ng/ml bFGF (3.44 +/- 1.13-fold), 5 ng/ml TGF-beta(1) (2.46 +/- 0.89-fold), 20 ng/ml PDGF (2.27 +/- 0.68-fold), and 50 ng/ml TGF-alpha (1.87 +/- 0.19-fold). As shown by RT-PCR, PSC express predominantly the splice variant EIII-A of fibronectin. Immunofluorescence microscopy and Northern blot confirmed that in particular bFGF and TGF-beta(1) stimulated the synthesis of fibronectin and collagens type I and III. In conclusion, our data demonstrate that 1) TGF-beta(1) and TNF-alpha accelerate the change in the cell phenotype, 2) PDGF represents the most effective mitogen, and 3) bFGF, TGF-beta(1), PDGF, and, to a lesser extent, TGF-alpha stimulate extracellular matrix synthesis of cultured rat PSC.

Brush cytology and forceps biopsy have only limited sensitivity for the diagnosis of malignant hilar tumors. In our eyes, additional diagnostic techniques should be evaluated and should become routine in patients with negative cytological and histological findings.

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.

No abstract

Little is known about the pathophysiological factors that determine the clinical severity of acute pancreatitis. Because

No abstract