Dale E. Bockman

Analysis of nerves in chronic pancreatitis

We sought to identify characteristics of pancreatic nerves that were altered in chronic pancreatitis. Pancreatic tissue removed from patients with chronic pancreatitis was analyzed for the number and size of nerves, their association with inflammatory infiltrates, and their fine structure. The mean diameter of nerves in these patients was significantly greater than in controls, whereas the mean area of tissue served per nerve was significantly less than in controls. Foci of inflammatory cells, prominent in some specimens, sometimes were associated with nerves and ganglia, but inflammatory foci and neural elements also existed separately. Invasion of nerve tissue by inflammatory cells was observed but was not massive. Ultrastructural changes were detected in nerves. Individual nerve fibers showed evidence of damage, and there was evidence of edema in the nerve bundle. The perineurial sheath was altered so that it no longer provided a barrier between the surrounding connective tissue and the internal neural components. The results of this study indicate that nerves are preferentially retained while parenchyma degenerates and is replaced by fibrosis during chronic pancreatitis, but that they are retained in an altered condition. Increased mean diameters of nerves in chronic pancreatitis argues against pain being caused by constriction due to fibrosis. It is likely that both sensory and motor nerve fibers are affected by this alteration.

A thymus candidate in lampreys

Immunologists and evolutionary biologists have been debating the nature of the immune system of jawless vertebrates—lampreys and hagfish—since the nineteenth century. In the past 50 years, these fish were shown to have antibody-like responses and the capacity to reject allografts but were found to lack the immunoglobulin-based adaptive immune system of jawed vertebrates. Recent work has shown that lampreys have lymphocytes that instead express somatically diversified antigen receptors that contain leucine-rich-repeats, termed variable lymphocyte receptors (VLRs), and that the type of VLR expressed is specific to the lymphocyte lineage: T-like lymphocytes express type A VLR (VLRA) genes, and B-like lymphocytes express VLRB genes. These clonally diverse anticipatory antigen receptors are assembled from incomplete genomic fragments by gene conversion, which is thought to be initiated by either of two genes encoding cytosine deaminase, cytosine deaminase 1 (CDA1) in T-like cells and CDA2 in B-like cells. It is unknown whether jawless fish, like jawed vertebrates, have dedicated primary lymphoid organs, such as the thymus, where the development and selection of lymphocytes takes place. Here we identify discrete thymus-like lympho-epithelial structures, termed thymoids, in the tips of the gill filaments and the neighbouring secondary lamellae (both within the gill basket) of lamprey larvae. Only in the thymoids was expression of the orthologue of the gene encoding forkhead box N1 (FOXN1), a marker of the thymopoietic microenvironment in jawed vertebrates, accompanied by expression of CDA1 and VLRA. This expression pattern was unaffected by immunization of lampreys or by stimulation with a T-cell mitogen. Non-functional VLRA gene assemblies were found frequently in the thymoids but not elsewhere, further implicating the thymoid as the site of development of T-like cells in lampreys. These findings suggest that the similarities underlying the dual nature of the adaptive immune systems in the two sister groups of vertebrates extend to primary lymphoid organs.

Interaction of pancreatic ductal carcinoma with nerves leads to nerve damage

BACKGROUND/AIMS Perineural extension of pancreatic adenocarcinoma has been explained as a mechanical extension along planes of least resistance. This study tests whether the cancer is limited to following these planes and if substances involved in cell signaling are involved in the interaction of cancer cells with nerves. METHODS Samples of tissue from patients undergoing resection of pancreatic cancer were studied by electron microscopy and light microscopy. Transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) were localized in sections. RESULTS The adenocarcinoma is not confined to the periphery of nerves. It penetrates the perineurium and becomes intimately associated with Schwann cells and axons in the endoneurium. Neural elements are damaged. Neural invasion likely is a factor in associated pain. TGF-alpha is abundant in nerves in the pancreas. EGFR is prominent in the cells of the adenocarcinoma. CONCLUSIONS The interaction of pancreatic cancer with nerves involves more than the cancer following a perineural space. Interaction of TGF-alpha in nerves with EGFR on cancer cells constitutes a possible paracrine mechanism that provides a growth advantage for pancreatic adenocarcinoma and serves as an example of potential interactions that might be active in biological interaction of cancer with nerves.

Nuclear aryl hydrocarbon hydroxylase and interaction of polycyclic hydrocarbons with nuclear components.

Aryl hydrocarbon hydroxylase (AHH) activity has been demonstrated in the nucleus by a specific histofluorescent technique. The nuclear AHH is present at 15–20% of the activity of the microsomal enzyme. The properties of the nuclear and microsomal AHH have been compared. Cytochrome P-450 is also present within the nucleus as demonstrated by the CO-binding spectrum. Both the AHH and hemopigment are induced by prior treatment of the rats with 3-methylcholanthrene (3MC). The ratio of induced/ control in nuclei and microsomes was identical. Other inducing agents of the nuclear AHH included pregnenolone 16α-carbonitrile, phenobarbital, arochlor 1254, arochlor 1260, β-naphthoflavone, and benzo(α)pyrene (BP). The control nuclear and microsomal AHH were inhibited to a similar degree by 1-benzylimidazole, diethylmaleate, SKF 525A, and metyrapone; α-naphthoflavone inhibited the induced nuclear and microsomal enzymes to a similar degree. Lung nuclear AHH was induced by 3MC in AKR/J, DBA/J, A/J, C3H/J, and C57B1/6J mice; the most inducible strain was the C57B1/6J, while the least inducible was the DBA/J. High-pressure liquid Chromatographic analysis of the microsomal and nuclear metabolites did not indicate any substantial qualitative differences. [3H]BP was incubated with liver nuclei and a NADPH-generating system. Aralkylation of DNA, histones, and nonhistone components was demonstrated in these in vitro systems. The aralkylation of each of these macromolecules was stimulated by prior treatment of the rats with 3MC. The HIV histones were aralkylated to the least extent. Gel electrophoretic and radioisotopic analysis indicated that the nonhistone components were generally aralkylated. The implications of the nuclear enzyme are discussed.

Cytological changes in the pancreas of transgenic mice overexpressing transforming growth factor α

Transgenic mice overexpressing human transforming growth factor alpha (TGF-alpha) predictably develop an enlarged, firm pancreas. The present study investigated the changes that occur in the different components of the pancreas in these animals. The increase in size of the pancreas may be accounted for by increased connective tissue. The added collagen is mainly type I. Thin, elongate fibroblasts are frequently bordered by a basal lamina, a relationship that is normally restricted to the perineurium. Collagen is intimately associated with epithelial cells. Fingers of connective tissue extend close to acinar lumina. Redifferentiation of acinar cells produces tubular complexes. In some cases, acinar cells take on the appearance of ductular cells. In some, there is a transition to mucin-producing cells. Intermediate forms between acinar and mucin-producing cells are present. The growth factor is localized in acinar cells and decreases with redifferentiation. The pancreas of these animals routinely displays characteristics that also are observed in diseases of the exocrine pancreas in humans, including fibrosis and redifferentiation. It is likely that the changes are the result of both direct and indirect effects of TGF-alpha, some of which may parallel altered control mechanisms in human pancreatic disease. Study of this model may provide clues to understanding the initiation of fibrosis and redifferentiation in human pancreas.

Pancreatic Acinar Cell Function and Morphology in Rats Chronically Fed an Ethanol Diet

The aim of the present study was to determine the effect of prolonged ethanol intake on the morphology and protein metabolism in the rat pancreatic acinar cells. Weight-matched triplets of Sprague-Dawley rats were fed Lieber-DeCarli diet containing 5% (wt/vol) concentration of ethanol, isocaloric amounts of Lieber-DeCarli diet, or rat chow ad libitum for 6, 12, and 18 mo. In the ethanol-fed group, histologic studies by light microscopy showed absence of protein plugs in the pancreatic ducts and/or pancreatitis, but electron-microscopic evaluation revealed progressive accumulation of lipid droplets in acinar and ductal cells. No definite changes in the mitochondria and endoplasmic reticulum were noticed. Biochemical studies revealed increased specific activity of trypsinogen, chymotrypsinogen, and lipase, and decreased specific activity of amylase. Trypsin-inhibiting capacity was decreased in the tissue and in the medium in a progressive fashion. There was no increase in the secretion of total protein. These data show a complex and a nonparallel alteration of specific digestive enzymes and trypsin inhibitor in this model of chronic ethanol intoxication that may be of relevance to occurrence of pancreatitis.

Origin and development of the precursor lesions in experimental pancreatic cancer in rats

Notwithstanding the importance of understanding how pancreatic ductal adenocarcinoma develops, the process remains controversial. A key question is whether the cells of origin of the tubular complexes that constitute precursor lesions are derived from a single cell type or from multiple types. Suggestions that they arise solely from centroacinar cells or ductal cells have been based on inference due to their morphologic appearance in tissue from patients or investigation of limited numbers of tubular complexes in animal models later in the carcinogenic process. The present study establishes clearly that two steps are involved; rapid transdifferentiation to produce tubular complexes followed later by transformation of the component cells. Animals were killed at intervals beginning 1 day after implantation of the carcinogen dimethylbenzanthracene. Transdifferentiation of acinar cells to ductal cells does not require cell division. Transition of lobules to tubular complexes begins by 2 days after implantation of carcinogen. Within 4 days after implantation well-developed tubular complexes are present. Islets participate in the process. Ductal adenocarcinoma is observed by 1 month after implantation of carcinogen. Chymotrypsin and cytokeratin localized by immunocytochemistry indicate acinar and ductal cell characteristics. Acino-ductal transdifferentiation persists in carcinogen-implanted animals, but not in controls implanted with sodium chloride crystals or subjected to sham implantation. The precursor lesions (tubular complexes) are formed by the transdifferentiation of acinar cells and to a lesser extent islet cells, with the incorporation of the duct cells pre-existing in the lobules. Therefore, cells that at one time were acinar cells, islet cells, and duct cells, provide the precursor cells for the ductal adenocarcinoma that develops from tubular complexes. The results raise the question whether the transdifferentiated cells in the tubular complexes of patients with chronic pancreatitis are more susceptible to carcinogenic influences, resulting in the increased rate of pancreatic cancer.

Pancreatic Extracellular Matrix Alterations in Chronic Pancreatitis

The proliferation of pancreatic extracellular matrix, which characterizes chronic pancreatitis, has been analysed using immunohistochemistry. The relationship of matrix components to intraductal precipitates and the presence of serum proteins in precipitates were also studied to investigate the suggestion that ductal permeability increases in chronic pancreatitis. Pancreatic tissue from organ donors was compared with that from patients with chronic calcifying or chronic obstructive pancreatitis. Frozen sections were labeled with monospecific antibodies to collagen types I, III, pro-III and IV, laminin, fibronectin, IgG, IgA, and IgM and then visualized by indirect immunofluorescence. In chronic pancreatitis, interstitial collagens and fibronectin appeared increased and disorganized in both fibrous tissue and areas that appeared histologically normal. Type IV collagen distribution was abnormal and in some sites was present with interstitial collagen. In addition, intraductal precipitates were shown to contain immunoglobulins, and defects were identified in the duct basal lamina associated with precipitates. These results demonstrate that in chronic pancreatitis interstitial collagens are extensively disorganized, the fibrosis possibly being relatively labile. The presence of serum proteins in intraductal precipitates confirms an increase in ductal permeability, and associated defects in the basal lamina appear to define a route via which serum proteins may enter the intraluminal compartment.

Cells of origin of pancreatic cancer: experimental animal tumors related to human pancreas.

Human pancreatic adenocarcinoma is traditionally believed to be ductal in origin, primarily due to the presence of complexes of tubules interpreted as being derived from ductular proliferation. Although observations in various animal models of pancreatic tumors suggested that acinar cells were undergoing dedifferentiation to form tubular complexes, this process was difficult to reconcile with an acinar arrangement of the pancreas. Using three‐dimensional reconstructions and retrograde injections, it was concluded that the normal pancreas actually has a tubular arrangement. The tubules branch, curve, and anastomose. By losing zymogen granules and decreasing in height, acinar units become recognized as ductule‐like structures. Therefore, the presence of tubular complexes should not be taken to indicate that carcinogenesis has taken place or to eliminate acinar cells as possible cells of origin of adenocarcinoma, which by present criteria would be classified as ductal.

Localization of peptide transporter in nuclei and lysosomes of the pancreas

SummaryConclusionsThese studies show for the first time the localization of a H+/peptide cotransporter in nuclei of vascular smooth muscle cells and Schwann cells and its localization in lysosomes of the exocrine pancreas. It is likely that the transporter functions to move small peptides from the lysosome to the cytoplasm following intralysosomal protein degradation. The nature of the transporter function in the nucleus remains to be determined, including the possibility that peptide signaling molecules may be transmitted between nucleus and cytoplasm.BackgroundPEPT1 transports di- and tripeptides through plasma membranes. Peptides are cotransported with H+, thus deriving the energy for the active transport process from an electrochemical H+ gradient. The main regions in which PEPT1 has been thought to function are the plasma membranes of the small intestinal epithelial cells for absorption of protein digestion products and in the kidney tubules for recovery of small peptides from the glomerular filtrate.MethodsPancreas was removed from rats and quick frozen with liquid nitrogen. Frozen sections were fixed in cold acetone. Sections were incubated with primary antibody against PEPT1, followed by a secondary antibody conjugated with fluorescein, then examined with a fluorescence microscope.ResultsThree major structures were immunopositive with the antibody to PEPT1: the nuclei of smooth muscle cells in the wall of arterioles, the nuclei of Schwann cells in unmyelinated pancreatic nerves, and lysosomes in acinar cells.