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The pancreas has an abundant nerve supply. Sympathetic, parasympathetic, and sensory nerves permeate the pancreas to participate in its normal activities. Pancreatic nerves modulate the secretions of the endocrine pancreas, playing a role in carbohydrate metabolism. They control exocrine pancreatic secretion, and their coordinated activity serves to provide a smooth reaction to the intake of food. Pancreatic blood flow is modulated by the nerves as a part of the normal response. When pathological changes take place, the nerves are involved. Afferent nerves are activated to cause pain. They may be altered locally and at some distance from the pancreas. Chronic inflammatory cells invade and damage nerves in patients with chronic pancreatitis. Acute inflammation causes pain through processes including acute inflammatory cells/products as well as breakdown and release of pancreatic cellular components. Cancer invades and spreads along pancreatic nerves. The role of nerves in initiating pathological change is less certain, but it seems likely that hyperstimulation via cholinergic nerves would lead to alteration of acinar cell membranes, producing an influx of calcium ions and changes consistent with pancreatitis.

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.

Background & Aims: Smooth muscle cells in the walls of the gastrointestinal tract are thought to derive solely from mesoderm surrounding the primitive gut. A population of neuroepithelial cells has recently been shown to migrate from the ventral part of the neural tube in the region joined by the vagus nerve. We sought to determine if these cells contributed to the development of the stomach and intestine. Methods: Cells of the ventral hindbrain of chick embryos were tagged by replication-deficient retroviral vectors containing the lacZ gene, providing a permanent label that is transmitted without dilution as the cells divide. Embryos were processed for detection of labeled cells. Specific markers were used to determine differentiation of progeny in the gastrointestinal tract. Results: Cells labeled in the ventral neural tube migrate in association with the vagus nerve. Labeled cells are found in the intestine and stomach after time for further migration and differentiation. Using a specific marker, they were clearly identified as smooth muscle cells. Conclusions: Some of the smooth muscle cells of the gastrointestinal tract are derived from precursor cells that originate in the ventral part of the hindbrain neural tube. Their developmental importance and functional significance remain to be determined. GASTROENTEROLOGY 1998;114:878-882

Proper development of the thymus is critical for an individual to acquire full immune capability. A full complement of the components that participate in thymic development, interacting with each other at the correct time, is required for maturation. In order to establish the microenvironment necessary for T-cell differentiation, the epithelial primordium of the thymus must expand from pharyngeal endoderm with the aid of contributions from the ectoderm. Experimental studies have established the importance of mesenchymal derivatives from the neural crest in functional development of the epithelial primordium. Interfering with this process inhibits thymic development in a manner similar to that observed in congenital conditions such as the DiGeorge syndrome and the fetal alcohol syndrome. These observations provide clues to understanding the origin of defects in thymus-dependent immunity, and point the way to studies that will expand our understanding of the controls that are involved in genetic and environmental factors impacting on this process.

It has been assumed in the past that pancreatic acinar cells represent an irreversible end stage in development. Consequently, when there was an increase in structures that had the morphology of ductules, the interpretation was that they were derived from the proliferation of stem cells and/or pre-existing ductular cells. Pancreatitis, however, is regressive in nature [Bockman (1984) In: Pancreatitis: Concepts and Classification. Gyr, K.E., Singer, M.V., Sarles, H., eds. Elsevier, Amsterdam, pp. 11-15]. That is, it is characterized by parenchymal destruction and loss, rather than by expansion of parenchyma. Furthermore, it was assumed that the organization of the pancreatic parenchyma is like bunches of grapes, with spheroidal acini representing the grapes, and the ductules representing the stems. Given this organization, it would be difficult to understand how regressive changes could lead to clusters of ductular structures. Investigations using three-dimensional reconstruction and retrograde injections have altered our idea of pancreatic organization. In addition to spheroidal acini, there also are other shapes, including tubular acini. Moreover, ductules do not necessarily stop when they encounter an acinus. They may emerge on the other side. Combined ductular and acinar lumina may anastomose with each other. It is now clear that pancreatic acini may undergo redifferentiation, taking on the morphology of ductules and forming tubular complexes during pancreatitis, as well as in response to pancreatic cancer, cystic fibrosis, or blockage of the ductal system. With this understanding of pancreatic architecture and morphological plasticity, it is easier to understand the changes one sees with pancreatic diseases.

Grundlagen Obwohl chronische Oberbauchschmerzen das Hauptsymptom der chronischen Pankreatitis darstellen, ist ihre Pathophysiologie bisher nur unzureichend verstanden.

The perception of pain depends upon signals carried by nerves to appropriate locations in the central nervous system. It is well known that when stretch receptors in the gastrointestinal tract are sti

Background/Aims: Transforming growth factor (TGF) α affects the growth of gastric mucosa. Its overexpression alters the mucosa. The aim of this study was to test the possibility that it regulates differentiation of gland cells. Methods: Transgenic mice that overexpress TGF-α were used to detect its effect on zymogenic (chief) cells in the stomach. To test for a general regulatory role of TGF-α in differentiation of zymogen-producing cells, salivary glands from transgenic mice were studied. Results: In these mice, messenger RNA for pepsinogen C is present in the stomach at normal levels during the neonatal period and then decreases markedly. Zymogenic cells are present in the stomach during the neonatal period but are missing in transgenic adults. The bases of gastric glands, normally rich in zymogenic cells, are occupied by undifferentiated cells and mucous neck cells, the precursors of zymogenic cells. Zymogen granules in submandibular glands of transgenic female mice are reduced in number. Zymogen granule-containing cells in the parotid gland undergo redifferentiation to form tubular complexes, collections of ductularlike structures like those formed in the transgenic pancreas. Conclusions: TGF-α is a major participant in the regulation of terminal differentiation of zymogenic cells in the stomach and salivary glands.

Chronic pancreatitis is a regressive disease, sometimes progressing to the point of insufficient secretion from both the exocrine and the endocrine pancreas. Functional decline is matched by morpholog

Immunologists and evolutionary biologists have been debating the nature of the immune system of jawless verte-brates--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 micro-environment 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.

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.

Cell membrane disruption take place in different cell systems under physiological and pathological conditions. We tested the hypothesis that disruption of acinar cell membranes take place in the onset of acute pancreatitis.

The purpose of this study was to correlate the contributions by derivatives of the neural crest with the development of the epithelial primordium of the thymus. The monoclonal antibody E/C8 was used to localize derivatives of the neural crest in chick embryos. Neural crest was ablated by microcautery of neural folds. Evaluation of thymic development was carried out on serial sections of embryos sacrificed on the sixth day of incubation. The size of the epithelial thymic primordium was smaller in experimental animals than in shams. E/C8-immunoreactivity was concentrated around the periphery of the primordium. It was determined, by quantifying reaction product using the Core-SCAN computer color analysis program, that the amount of immunoreactivity was decreased after ablation of neural crest. Statistical analysis showed that the quantity of reaction product was positively and significantly correlated with the size of the thymic primordium. It is concluded that mesenchymal derivatives of the neural crest, through participation in the early development of the epithelial primordium, play an important role in thymic development, and therefore with development of the immune system.

It has become obvious that the traditional assumptions about the transition from normal pancreas to pancreatic cancer are incomplete. Experimental studies reveal that the earliest changes during transition to pancreatic adenocarcinoma involve premalignant lesions that are derived from acinar, islet, and ductal cells.Changes are rapid, occurring in days. As part of redifferentiation and transformation to adenocarcinoma, cells regain the characteristics of developing pancreas. Elements significant in identifying precursor cell types include Pdx1, hedgehog signaling, notch signaling, and nestin, an intermediate filament expressed by precursor cell types.Thus pancreatic carcinogenesis is not simply a matter of transition of ductal cells to cancer cells months after insult by the carcinogen; ductal cells are not the sole source transitioning to cancer, and PanINs are not the sole route to adenocarcinoma. Tubular complexes, derived from multiple cell sources, are included in routes to pancreatic cancer. Markers characteristic of developing pancreas are consistent with this transition. Cells previously thought to be terminally differentiated become, in effect, stem cells.

It is well established that damage to the outer membrane of cells is a common phenomenon allowing abnormal transmission of substances into the cytosol. Penetration of albumin into acinar cells has been detected in experimental acute pancreatitis, raising the possibility that membrane damage is a very early event, potentially representing the first changes leading to pancreatitis. To determine if direct damage to the cell membrane is a key factor during induction of acute pancreatitis, thus altering the balance of extra- and intracellular substances, fluorescein-dextran was administered with supramaximal doses of caerulein via the jugular vein or by injection directly into the pancreas. This tracer rapidly penetrates into cells. Two patterns of tracer penetration are observed: cytosolic and vesicular/vacuolar. Fluorescein-dextran administered intravenously with caerulein penetrates into the cytosol of acinar cells within 10 min. Strong cytoplasmic fluorescence occurs within 5 min after direct injection. It may be concluded that supramaximal caerulein, administered in vivo, damages the cell membrane of acinar cells, allowing large molecules to enter the cytosol. Thus Ca(2+) and other substances may enter the cells in abnormally high concentrations, initiating the cellular changes characteristic of pancreatitis. The results raise the question whether membrane wounding may play a role in the initiation of human pancreatitis.

These studies show for the first time the localization of a H+/peptide cotrasporter 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.PEPT1 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.Pancreas 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.Three 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.

Trotz intensiver Forschung auf dem Gebiet der akuten Pankreatitis ist die Atiologie und Pathogenese auch heute noch nicht ausreichend geklart. Eine Zerstorung der Zellmembran mit Freisetzung von Zellorganellen und Pankreasenzymen in den Interzellularraum ist typisch im spateren Stadium der humanen akuten Pankreatitis [1]. Die strukturellen und funktionellen Beziehungen die die normale Pankreasphysiologie charakterisieren scheinen bereits im Fruhstadium der akuten Pankreatitis gestort zu sein. Eine Untersuchung dieser Zeitspanne der zellularen Ereignisse ist am Menschen nicht moglich. Deshalb werden eine Reihe von Tiermodellen zur Untersuchung der fruhen Ereignisse verwendet. Ein interzellulares Odem und die Formation von intrazellularen Vakuolen kann kurz nach der Induktion der akuten Pankreatitis gesehen werden, was auf eine Veranderung der normalen Kompartimentierung hinweist [2]. Hohe Serumenzymwerte von z. B. Amylase konnen Stunden nach der Pankreatitisinduktion gemessen werden, obgleich eine Erhohung von Amylase schon sehr viel fruher mesbar wird.

Chronic pancreatitis and restricted pancreatic outflow are accompanied by pathological changes in the ducts, including inflammation and alterations in the microvasculature. These changes and loss of epithelium provide a likely explanation for increased release of serum proteins, immunoglobulins, and lactoferrin into the juice, and the possibility of luminal contents entering the extracellular space and bloodstream.Enlargement of pancreatic ducts is a well-known phenomenon accompanying chronic pancreatitis and conditions restricting outflow of pancreatic juice. However, the relationship between ductal pathology and concomitant changes in the pancreatic juice is incompletely understood.Segments of pancreatic ducts removed at surgery from patients with chronic pancreatitis and conditions restricting outflow were studied by light and electron microscopy to assess the pathological changes.Pathological changes in ducts from patients with chronic pancreatitis include chronic inflammation in the wall, enlarged and numerous capillaries packed with erythrocytes and leukocytes close to the lumen, and loss of epithelium and sometimes basement membrane. Plasma cells provide a source for increased immunoglobulins. Ducts from patients with diseases restricting outflow show significant pathology.

Each year the American Pancreatic Association sponsors the Frank Brooks Memorial State of the Art Lecture. The following Frank Brooks Memorial Lecture was delivered at the combined meeting of the American Pancreatic Association and the International Association of Pancreatology, which was held in Chicago, Illinois, November 2-4, 1994. The presentation emphasizes the necessity for understanding the normal architecture of the pancreas, and the nature of the changes that occur, as important steps in understanding the origins and progression of pancreatic disease. A central theme is the plasticity of the cells that comprise the pancreas. Encouraging new insights are being derived from studies that determine the signaling molecules that regulate proliferation and differentiation, including those studies using transgenes.

Transforming growth factor alpha (TGFα) evokes diverse responses in transgenic mouse tissues in which it is over-expressed, including the gastric mucosa, which experiences aberrant growth and a coincident repression of hydrochloric acid production. Here we show that ectopically expressed TGFα induces an age-dependent cellular reorganization of the transgenic stomach, in which the surface mucous cell population in the gastric pit is greatly expanded at the expense of cells in the glandular base. Immunohistochemical analysis of BrdU incorporation into DNA demonstrated that although mature surface mucous cells were not proliferating, DNA synthesis was enhanced by approximately 67% in the glandular base and isthmus, where progenitor cells reside. RNA blot and in situ hybridization were employed to determine temporal and spatial expression patterns of specific markers representing a variety of exocrine and endocrine gastric cell types. Mature parietal and chief cells were specifically depleted from the glandular mucosa, as judged by a 6- to 7-fold decrease in the expression of genes encoding H+,K+-ATPase, which is required for acid secretion, and pepsinogen C, respectively. The reduction of these markers coincided in time with the activation of TGFα transgene expression in the neonatal stomach. The rate of cell death in the glandular region was not overtly different. Significantly, the loss of parietal and chief cells occurred without a concomitant loss of their respective cellular precursors. In contrast to exocrine cells, D and G endocrine cells were much less severely affected, based on analysis of somatostatin and gastrin expression. Analysis of these dynamic changes indicates that TGFα can induce selective alterations in terminal differentiation and proliferation in the gastric mucosa, and suggests that TGFα plays an important physiological role in the normal regulation of epithelial cell renewal.

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 α (TGF-α) 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-α 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-α 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.

Local or generalized alteration of microcirculation may be expected in diseases of the pancreas. Changes may range from increased permeability of capillaries to hemorrhage. Tissue necrosis may result from prolonged ischemia owing to intravascular coagulation and severely impaired blood flow. It is possible to observe early microvascular changes by intravital microscopy. Klar and coworkers have demonstrated by this method that isovolemic hemodilution improves blood flow under conditions that would otherwise lead to tissue damage. This paper presents the basic microcirculation of the pancreas and the changes that accompany pancreatic disease. It emphasizes that concentration on the changes in microcirculation that accompany the early manifestations of pancreatic diseases, particularly pancreatitis, may reveal important clues to their pathogenesis.

Although bisdiamine has been shown to affect the development of mammals, its effect on the nervous system has gone largely unrecognized. In the present study, rats were given bisdiamine by gavage on days 9 and 10 of pregnancy. They were sacrificed at intervals and the fetuses were prepared for study of serial sections stained with hematoxylin and eosin, or by immunohistochemical reaction with HNK-1 monoclonal antibody. HNK-1 reacted strongly with the nervous system, allowing precise analysis of the components and their relationships. Controls receiving no bisdiamine were prepared and studied in parallel with the experimental fetuses. Administration of bisdiamine inhibited development of the petrosal and nodose ganglia, altered associations of the glossopharyngeal, vagus, and hypoglossal nerves, and inhibited contributions of vagal nerve fibers to the developing enteric system. The proximal ganglia of the glossopharyngeal and vagus nerves developed normally. It is concluded that bisdiamine affects, directly or indirectly, the differentiation of nervous components derived from the epibranchial placodes. It seems likely that these placode-derived components serve as pioneer neurons in establishing the pathway for the posteriorly extending trunks of the glossopharyngeal and vagus nerves. The early changes in congenital conditions such as the DiGeorge syndrome may not be limited to alterations in neural crest derivatives. It may be worthwhile to investigate more closely whether there are alterations in the nervous system associated with these syndromes. © 1992 Wiley-Liss, Inc.

In order to assess the capacity of neural crest from different sources to participate in thymic development, neural crest from selected axial levels was transplanted unilaterally from quail donors to the region in chick hosts from which neural crest cells normally migrate to interact with the primordial thymus. The greatest representation of donor cells was observed after isotopic transplantation and when donor tissue was taken from the hyoid and mesencephalic regions of the neural crest. The capacity for transplants to contribute cells decreased both anteriorly and posteriorly, so that neural crest close to the usual origin of mesenchyme-producing cells contributed a large number of donor cells around the developing thymus than neural crest from anterior and posterior regions. Cells from the transplant were inserted as an addition to the host chick cells. Thus, a special relationship and capacity for interaction in thymic development is expressed by neural crest at usual levels over a limited span of axial regions, but to some extent by all regions. This study has established that the capacity for neural crest cells from different axial levels to interact with developing organs is not uniform, but may vary, depending upon the nature of the interaction with a particular organ.

Impaired thymic development as a result of ablation of neural crest has been observed in embryos late in development. The present study was initiated to determine what changes are effected early in thymic development by neural crest ablation. The epithelial primordia of the thymus were studied in chick embryos on the sixth day of incubation. Embryos with neural crest ablations were compared with sham-operated and untreated controls. Neural crest ablation inhibited formation of epithelial thymic primordia. Primordia in experimental embryos were fewer in number and were smaller than in shams and untreated controls. When primordia from shams and controls were transplanted to the chorioallantoic membrane of chick hosts, they were able to develop into organs with the typical features of embryonic thymus. Similar transplantation from neural crest-ablated animals, on the other hand, led to small, predominantly epithelial structures with meager lymphoid development. These findings are consistent with the hypothesis that mesenchyme derived from cranial neural crest is critical in initiating and sustaining the development from pharyngeal pouches of epithelial structures competent to attract and support the proliferation and differentiation of lymphoid stem cells.

To determine the presence and extent of thrombus formation in the apparatus used for extracorporeal membrane oxygenation we studied various portions of the polyvinylchloride circuit from five infants who received extracorporeal membrane oxygenation for 70 to 330 hours. All infants had right-sided cannulation. Sections were cut from the circuit at the time of decannulation and subjected to light and scanning electron microscopy. The site that contained the most thrombus formation was the membrane oxygenator bypass circuit, which is subjected to repeated periods of unclamping and clamping to direct blood flow through the membrane oxygenator. Autopsy results from nonsurvivors showed evidence of pulmonary and renal infarcts, a left frontal lobe infarct, a thromboembolus of the left external and internal carotid arteries, and thrombi in the lungs, kidney, brain, and coronary arteries. One survivor had computed tomographic evidence of infarction of the left middle cerebral artery distribution. We suggest that the areas of the extracorporeal membrane oxygenation circuit subjected to repeated changes in flow dynamics may be the source of microemboli.

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 wee 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.

An increased proportion of ductulelike structures, sometimes dilated, occurs in association with pancreatic adenocarcinoma, chronic pancreatitis, cystic fibrosis, and pancreatic ectasia associated with conditions such as uremia. This frequently is interpreted as ductular proliferation, implying origin in ductal elements. Recent animal studies have provided an altered view of pancreatic architecture that is consistent with acinar dedifferentiation leading to the ductulelike structures, or tubular complexes. The architecture of pancreas from organ donors was studied by light and scanning electron microscopy and by wax reconstruction of serial sections. It is concluded that the zymogen granule-containing cells of normal human exocrine pancreas are arranged as branching tubules that vary in diameter and curve acutely. The tubules frequently end blindly to form acinar structures; less frequently they anastomose. This arrangement is consistent with the interpretation that tubular complexes associated with pancreatic disease result from dedifferentiative changes in acinar cells. Tubular complexes may reflect a defect or defects common to pancreatic disease rather than ductular proliferation specific to each one.

Cilia are found in acinar and ductular lumina. Most descriptions of human or dog pancreatic tissue have indicated that these are probably motile structures which move and/or mix pancreatic secretion. A recent study interpreted arrangements of microtubules within cilia which deviated from the classic 9 + 2 pattern as indicating pathological change. There have been suggestions, however, from studies on nonmammalian and human pancreas, that the structure of pancreatic cilia suggests a sensory function. The present paper reports studies on the ultrastructural organization of the specialized cilia in human and canine pancreatic tissue. The pattern of microtubular organization resembles that of cilia modified for chemoreception rather than that of classic kinocilia. It is concluded that pancreatic ductular cilia are sensory rather than motile, providing a mechanism for monitoring general or specific molecular concentrations.

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.

Few studies have been published on the ultrastructural changes which accompany human acute pancreatitis, and these have concentrated primarily on parenchyma. The present study concentrates on extraparenchymal changes, compares acute pancreatitis occurring alone with that on a background of chronic pancreatitis, and tests for similarity with observations made previously in an experimental model. Pancreatic tissue came from 16 patients undergoing surgery for pancreatic disease and five subjects without pancreatic disease. Regressive changes in parenchymal cells were consistent with ischemia, and with previously described studies. Polymorphonuclear leukocytes infiltrated into stroma and parenchyma. Platelets accumulated intra- and extravascularly. Fibrin deposits were common in the connective tissue, and could be observed in intercellular spaces at the base of acini, mingled with degenerating acinar cells and secretion product. Microthrombi occurred in blood vessels. These alterations were consistent with those in experimental acute pancreatitis. Similar changes were observed whether or not acute pancreatitis occurred on a background of chronic pancreatitis. The vascular component is important in acute pancreatitis, and altered epithelial barriers allow interaction between blood-borne material and pancreatic exocrine secretions.

Mesenchymal derivatives of the neural crest contribute to the connective tissues and blood vessels of the pharyngeal arches, and participate in the septation of the outflow tract of the heart. The present study was designed to determine the nature and timing of alterations in the development of the heart and arch arteries subsequent to diminished neural crest contributions. The neural crest contributing to the three caudalmost pharyngeal arches was ablated bilaterally in chick embryos and compared with sham or unoper-ated controls. Heart development was studied by scanning electron microscopy. Arch artery development was studied microscopically after intravascular injection of India ink and clearing of the specimen. Neural crest ablation caused morphological changes in most hearts. Hearts in experimental animals commonly were elongate and were subject to inappropriate development of ventricular and atrial areas. A surgical effect delayed the disappearance of arch arteries one and two, and removal of neural crest produced an additional delay. Neural crest ablation caused failure of arch arteries three, four (right), and six to develop to the proper size in some animals. Survival of those whose sixth arch arteries achieved the proper size caused group measurements to reach normal values again by stage 32. Closure of arch arteries in some animals and maintenance in others produced greater variability in experimental animals than in controls. It is significant that heart morphology was altered before septation of the outflow tract normally occurs. This indicates at the least that another factor, such as altered blood flow, contributes to the abnormal development. Altered flow may result from changes in pharyngeal arch mesenchyme and arch artery endothelium.

The mechanisms by which anti-µ chain antibodies suppress LPS-induced differentiation of murine B lymphocytes to plasma cells were examined as a function of age. Concentrations of anti-µ, sufficient to inhibit completely differentiation of adult B lymphocytes paradoxically enhanced cellular proliferation of LPS-stimulated cultures, whereas newborn cells, which are suppressed by much lower concentrations of anti-µ, failed to proliferate. Enhancement of proliferation of adult cultures was dependent upon both the concentration of anti-µ antibodies and the time they remained in culture. Proliferating lymphoblasts from anti-µ-treated cultures expressed H-2 and Ia alloantigens and receptors for Fc (IgG) and C3; they lacked rough endoplasmic reticulum and other ultrastructural characteristics of plasma cells and had no detectable membrane immunoglobulin. Small deposits of mouse IgM were identified in the perinuclear and Golgi regions in 95% of the cells. Cells recovered from suppressed newborn cultures lacked all of these characteristics. A population of cells, stimulated by LPS in the presence of anti-µ, appeared in the spleen between birth and 3 days, and, by 12 days of age, 35% of cells in suppressed cultures had Golgi-associated IgM. These results suggest that anti-µ inhibition of Ig synthesis in LPS-stimulated adult cells is highly specific, occurs subsequent to cross-linkage of surface IgM, and is mediated in intracellular sites by complexes of anti-µ chain antibody and IgM. Similar treatment of newborn spleen cultures results in elimination of immature B cells. These observations relate to the mechanisms of antigen-induced clonal elimination among immature B cells, as well as to the phenomenon of B cell tolerance and regulation of B cell function by anti-idiotypic antibodies in adults.

The fine structure of human appendix was studied from the earliest stages of lymphoid development in fetuses to the definitive relationships found in children up to 8 years old. Follicular accumulations of lymphocytes were observed first in the mesenchyme immediately beneath epithelium which contained a predominance of goblet cells on the surface and in the crypts. Larger accumulations of lymphoid cells in older fetuses were intimately related to surface epithelium but not to the epithelium of crypts. At the point of invasion of lymphoid cells into surface epithelium, the goblet cell population diminished and epithelial cells displaying a morphologically distinct form of differentiation were observed. They were characterized by the presence of irregular microvilli or microfolds and numerous apical micropinocytotic vesciles. This follicle-associated epithelium (FAE) appeared ultrastructurally identical with epithelium in chicken bursa of Fabricius, mouse Peyer's patch, and rabbit appendix, which has been shown to be capable of transporting ferritin and India ink tracer from the lumen to underlying tissue. It appeared identical to specialized epithelial cells of adult human Peyer's patches. FAE was maintained through the neonatal period into childhood. We speculate that the biological significance of FAE is to provide a channel through which antigens may stimulate clonal proliferation and seeding of B-lymphocytes throughout the lamina propria of internal mucous surfaces.

Several clinical syndromes, including the DiGeorge syndrome, are characterized by clusters of developmental defects of the heart and great vessels with structures derived from the embryonic pharyngeal apparatus including thymus and parathyroids. The connective tissue derivatives of neural crest are necessary for the normal development of these structures, and there is new experimental evidence that depletion of neural crest causes defects similar to these clinical syndromes. Therefore it is proposed that many of these syndromes are due to inappropriate development of neural crest. The implications of this hypothesis include the predictions (1) that asplenia and certain other anomalies have the same etiology, and (2) that it is possible to observe the effects of teratogenic agents upon a cellular population (neural crest) at the time when it is being altered, rather than waiting until definitive organs may be examined.

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.

The present study was done to determine interaction of ethanol and marginal zinc nutriture on morphology and function of rat pancreas. Sprague-Dawley rats were maintained on Wayne Rodent-Blox ad libitum; marginal zinc-deficient diet plus ethanol ad libitum and pair fed with animals fed marginal zinc-deficient liquid diet and zinc-supplemented liquid diet with ethanol for 33 (+/- 1 SEM) days. Body, pancreas, liver, heart, and kidney weights were determined, and studies of pancreatic DNA, RNA, total proteins and newly labeled proteins, amylase, lipase, trypsinogen, and chymotrypsinogen were done on pancreatic lobules in vitro. Ethanol feeding independent of the zinc content of the diet caused a decrease in zinc content of the liver, body weight, liver and pancreas weight, pancreatic DNA, total protein, and amylase concentration and an increase in lipase and trypsinogen concentrations and in secretion of amylase and lipase. Interaction of the marginal zinc diet and ethanol feeding resulted in a decreased synthesis of RNA and secretion of newly synthesized protein and an increase in secretion of serine proteases. Morphological studies revealed a reduction in the number of zymogen granules in animals fed low levels of zinc, also with an accumulation of lipid droplets when the diet contained ethanol. These studies confirmed our previous observations of specific injury to the pancreas due to marginal zinc nutriture or to ethanol, independent of each other. Marginal zinc nutriture in concert with ethanol resulted in impaired RNA synthesis and secretion of nascent proteins and increased secretion of serine proteases. These data indicate that altered zinc metabolism induced by ethanol per se may contribute to ethanol-induced disturbance of pancreatic function.

Wax reconstructions of zymogen-containing cells in rat show the arrangement of the exocrine pancreas to be a branching, anastomosing system of tubules which vary in diameter and end blindly. This arrangement is not that of a true acinar gland.

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.