Comparative morphology and biochemistry of pancreatic tissue fragments transplanted into the anterior eye chamber and subcutaneous regions of the rat

The present study was designed to compare the morphological changes occurring in pancreatic tissue fragments transplanted into the anterior eye chamber (AEC) and the subcutaneous (SC) regions of the rat. Pancreatic tissue segments were removed from the tail end of the pancreas of neonatal rats and transplanted into the AEC and SC region of the neck of homologous rats. Five weeks after transplantation, the grafts were removed and processed for light microscopy, immunohistochemistry and radioimmunoassay. In both pancreatic tissue grafts, the acinar cells degenerated completely after transplantation. In contrast to this, insulin-, glucagon-, somatostatin- and pancreatic polypeptide-positive cells and pancreatic ducts survived equally well in both the AEC and SC grafts. The pattern and percentage distribution of insulin-, glucagon-, somatostatin- and PP-producing cells in the AEC and SC grafts was similar to that observed in normal pancreas. However, the percentage distribution of glucagon- and PP-containing cells was significantly (p < 0.03) lower in SC grafts when compared to normal. Radioimmunoassay showed that the AEC and SC pancreatic tissue grafts contained large quantities of insulin and glucagon. However, the insulin content of AEC was slightly but not significantly higher than that of SC grafts. The protein content of pancreatic tissue grafts in these transplantation sites was still significantly (p < 0.05) lower compared to normal. Lymphatic infiltration was also more conspicuous in SC grafts compared to AEC grafts. This infiltration by lymphatic cells was confined only to the endocrine portion of the graft. In conclusion, pancreatic tissue grafts survived in both the AEC and SC regions of rats but the AEC appears to be more conducive to graft survival than the SC region.     

Effect of subcutaneous pancreatic tissue transplants on streptozotocin-induced diabetes in rats. I. Morphological studies on normal, diabetic and transplanted pancreatic tissues.

The present study examines the morphological changes occurring in subcutaneous pancreatic tissue grafts (SPTG) and its effect on the host pancreatic islet cells in streptozotocin (STZ)-induced diabetic rats using morphological techniques. SPTG survived after 15 weeks of transplantation. Its acinar cells degenerated but the ducts and endocrine cells survived. The surviving and newly formed pancreatic tubules and endocrine cells filled the spaces left by degenerated acinar cells. Compartmentalization of the surviving parenchymatic tissues was observed, with the pancreatic tubules lying in the periphery of the graft and the endocrine tissue in the inner portion of the graft. Lymphocytes invaded the inner portion of the graft, conglomerating around endocrine cells. It was interesting, however, that, lymphocytes where not observed in the periphery of the grafts where most of the surviving pancreatic tubules lie. In addition to this, necrotic tissues were observed in the inner part of the graft. Fifteen weeks after transplantation into the subcutaneous region, insulin, glucagon, somatostatin and pancreatic polypeptide-immunoreactive cells were observed in many parts of the graft. In the peripheral parts of the grafts, large numbers of pancreatic tubules differentiated into endocrine cells. In conclusion, the ductal and endocrine cells of pancreatic tissue fragments survived in the subcutaneous region of rat with normal pattern of distribution.     

The hippocampus and neuro-transplantation

A review of the author's histological and electron-microscopic studies of differentiation of hippocampal transplants with different levels of the graft/host integration. The grafts developing in the anterior eye chamber were the experimental model of complete isolation from the brain. The effects of various factors (age of the donor fetal tissue, host age and strain, degree of the integration with the recipient brain) on the growth and neural organization of grafts were studied. Analysis of fine structure of intraocular and intracortical grafts, as a rule, showed mature highly differentiated neurons and glia and normal density of typical synaptic contacts. However, morphological features suggesting both hyperactivity of some neurons and continuous growth of some neural processes were observed. The expression of nonsynaptic and transport-metabolic interactions between the cells was increased. The observed ultrastructural deviations can be regarded as a compensatory adaptation of the tissue to the deficit of specific afferent signals. It was shown that in the absence of normal cellular targets, axons of the grafted neurons establish functional synaptic contacts with improper neural elements in the host brain.     

Neurofilament-like and glial fibrillary acidic protein-like immunoreactivities in rat and guinea-pig sympathetic ganglia in situ and after perturbation

Summary The presence of neurofilament (NF)-like and glial fibrillary acidic protein (GFAP)-like immunoreactivities was studied in sympathetic ganglia of adult rats and guinea pigs during normal conditions and after perturbation. In the superior cervical ganglion (SCG) of normal rats, many ganglion cells and nerve fibers show NF immunoreactivity. Some of these nerve fibers disappear after preganglionic decentralization of SCG; this indicates the presence of a mixture of preand postganglionic NF-positive nerves in the ganglion. Cuts in both preand postganglionic nerves result in a marked increase in GFAP immunoreactivity in SCG, whereas NF immunoreactivity increases in nerve cell bodies after preganglionic cuts. Only a few ganglion cells show NF immunoreactivity in the normal SCG of guinea pig. All intraganglionic NF-positive nerves are of preganglionic origin; decentralization abolishes NF immunoreactivity in these nerve fibers. The inferior mesenteric ganglion, the hypogastric nerves and colonic nerves in guinea pigs contain large numbers of strongly NF-immunoreactive nerve fibers.When the SCG of adult rat is grafted to the anterior eye chamber of adult rat recipients, both ganglionic cell bodies and nerve fibers, forming on the host iris from the grafted ganglion, are NF-positive. As only the perikarya of these neurons normally exhibit NF immunoreactivity, and the terminal iris arborizations are NF-negative, it appears that the grafting procedure causes NF immunoreactivity to become more widespread in growing SCG neurons.     

The differentiation of the nerve and glial cells of neocortical transplants placed into the brain of adult rats

Embryonal neural tissue of 17-day-old rat embryos was transplanted into the brain of adult Wistar rats to test the differentiation of transplants with reference to the normal cerebral cortex development. The control and the experimental rats were decapitated 2, 5, 7, 10, 15, 20, 25, and 35 days after the transplantation. Differentiation of neural tissue was studied using monoclonal antibodies against neurofilaments as well as by counting the proportion of differentiated neurons. The glial differentiation was studied by immunohistochemical method using monoclonal antibodies against acid glial fibrillar protein and vimentin. The differentiation of neural cells of transplants proved to be synchronous with the normal ones while the differentiation of glial cells accelerates.     

Immunocytochemical localization of elastase 1 in human pancreas

By light and electron microscopic immunocytochemistry the distribution is described of human pancreatic elastase 1 (E1) during ontogenesis, in adults, in cases of acute and chronic panceatitis, acute pancreatic ischaemia as well as pancreatic tumours. E1-positive cells were first detected in ductal sprouts in the 14th gestational week. Complete acini expressing E1 could be found from the 17th to the 20th week of gestation onwards. Scattered distinct E1-positive epithelia could be found in the ducts of fetal and adult pancreas. By immunoelectron microscopy, E1 was localized in rough endoplasmic reticulum, condensing vacuoles, zymogen granules of acinar epithelia and in acinar lumina. E1 appeared to be distributed homogeneously in zymogen granules. As specific markers of acinar cells, both monoclonal antibodies under study identified heterotopic pancreatic acini in peribiliar glands of the liver and also helped to visualize different damage patterns in pancreatitis. The acinar epithelia surrounding acute lipolytic necroses initially reacted more intensely with the E1-antibodies than undamaged pancreatic tissue. In acute ischaemia, acinar cells which are dissociated from intercalated ducts lost their immunocytochemical reactivity for E1. Pancreatic parenchyma involved in advanced acute pancreatitis as well as in chronic inflammation was detected only weakly by both E1-antibodies. However, atrophic lobules in post-inflammatory scars were stained more intensely by the E1-antibodies than normal parenchyma. Pancreatic tumours (adenomas, adenocarcinomas, solid-cystic tumours and islet cell tumours) were not labelled by these antibodies.     

Expression of nerve growth factors in pancreatic neural tissue and pancreatic cancer.

One of the characteristics of pancreatic cancer is its tendency to invade neural tissue. We hypothesized that the affinity of cancer cells for nerve tissue is related to the presence of growth factors in neural tissue and their receptors in cancer cells. Sections of pancreatic cancer and normal pancreatic tissue were examined by immunohistochemistry for the expression of the neurotrophins NGF, BDNF, NT-3, NT-4, and their receptors TrkA, TrkB, and TrkC, as well as the low-affinity receptor, p75NTR. TrkA expression was found in duct, islet, and cancer cells; TrkB was found in the alpha-cells of the islet only. The anti-pan-Trk antibody (TrkB3), which is presumed to recognize all three receptors, immunoreacted with duct and acinar cells in normal tissue and with cancer cells. The staining with TrkC was similar to that of TrkA. The low-affinity receptor p75NTR was expressed in the neural tissue and in scattered duct cells of the normal tissue only. Duct and acinar cells, as well as neural tissue and cancer cells, showed weak to strong immunoreactivity with NGF. NT-3 expression was noted in capillary endothelia and erythrocytes. NT-4 showed specific staining for ductule cells. The expression and distribution of neurotrophins and their receptors suggest their role in the potential of pancreatic cancer cells for neural invasion.     

Characterization of ducts isolated from the pancreas of the rat

Rat pancreases were minced and treated with collagenase or collagenase supplemented with chymotrypsin to yield a mixture of ducts, islets, acinar cell clusters, blood vessels, and nerves. Histologically and ultrastructurally, the isolated tissues resembled their in situ counterparts in most respects, the major difference being the destruction of the basement membranes (basal laminae). Ducts ranging in size from the common bile/main pancreatic duct to the intercalated ducts were identified in the digest, although interlobular ducts were most frequently observed. Acinar tissue fragments were separated from nonacinar structures either by flotation through discontinuous gradients of Ficoll or by sieving, the latter technique being the more efficient. Common bile/main ducts, interlobular ducts, and blood vessels were selected manually from the nonacinar fractions. Biochemical analyses showed that the entire nonacinar fraction, as well as isolated ducts and blood vessels, contained larger alkaline phosphatase, carbonic anhydrase, and Mg-ATPase specific activities than acinar tissue, whereas acinar tissue contained larger gamma-glutamyltranspeptidase and amylase activities. However, greater than 63% of the total recovered activity of each enzyme was associated with the acinar tissue. Both the association of the majority of each of these enzyme activities with the acinar tissue and the similarity in specific activities associated with ducts and blood vessels indicate that none of the enzymes tested is a unique marker for interlobular and larger ducts of the pancreas of the rat.     

Pancreatic cell proliferation in normal rats studied by in vivo autoradiography with 3H-thymidine

In vivo 3H-Thymidine autoradiographic investigations of DNA synthesis in acinar, islet and duct cells in the pancreas of normal rats showed that activity was dependent on age. The proliferation of acinar and islet cells, which was high in young animals, decreased exponentially with age; proliferation of the ductal cells on the other hand, increased until the animals became mature. These findings suggest that the physiological regeneration of acinar and islet cells, as well as their replacement after injury in adult animals commences from pancreatic ducts.     

Changes in the distribution of intermediate filament proteins and collagen IV in fetal and adult human pancreas

Summary The expression patterns of individual cytokeratin polypeptides in foetal and adult human pancreatic tissues were examined using monoclonal antibodies. We demonstrated that human pancreatic epithelia in early stages of development (14 weeks of gestation) contain cytokeratins 7, 8, 18 and 19, which are typical of simple epithelia, as well as cytokeratin 4 and 17, which are characteristic of stratified epithelia. In the pancreatic ducts, most of these cytokeratins appeared to be expressed together. Cytokeratins 1, 5, 10, 13, 16 and 20 were not detectable. In contrast, the pancreatic parenchyma was only positive for cytokeratins 8 and 18, except a transient expression of cytokeratins 7 and 19 in pancreatic islets and acinar cells during the foetal development. A focal cytokeratin 7 staining of single acinar cells was seen in newborn and in adult islets. In the stromal tissue, vascular smooth muscle cells were partly reactive with cytokeratin 8 and 18 specific antibodies. The results are discussed in the light of differentiation-dependent changes in the expression of individual cytokeratin polypeptides in developing epithelia.     

Changes in the distribution of intermediate filament proteins and collagen IV in fetal and adult human pancreas. I. Localization of cytokeratin polypeptides

The expression patterns of individual cytokeratin polypeptides in foetal and adult human pancreatic tissues were examined using monoclonal antibodies. We demonstrated that human pancreatic epithelia in early stages of development (14 weeks of gestation) contain cytokeratins 7, 8, 18 and 19, which are typical of simple epithelia, as well as cytokeratin 4 and 17, which are characteristic of stratified epithelia. In the pancreatic ducts, most of these cytokeratins appeared to be expressed together. Cytokeratins 1, 5, 10, 13, 16 and 20 were not detectable. In contrast, the pancreatic parenchyma was only positive for cytokeratins 8 and 18, except a transient expression of cytokeratins 7 and 19 in pancreatic islets and acinar cells during the foetal development. A focal cytokeratin 7 staining of single acinar cells was seen in newborn and in adult islets. In the stromal tissue, vascular smooth muscle cells were partly reactive with cytokeratin 8 and 18 specific antibodies. The results are discussed in the light of differentiation-dependent changes in the expression of individual cytokeratin polypeptides in developing epithelia.     

Estrogen as a growth factor to central nervous cells: Estrogen treatment promotes development of acetylcholinesterase-positive basal forebrain neurons transplanted in the anterior eye chamber

3n a previous report, we demonstrated in vivo ameliorating effects of conjugated estrogen in women suffering from senile dementia-Alzheimer's type. To investigate the effects of estrogen on the growth of cholinergic neurons, the present study was performed using rat cholinergic tissue implanted into the anterior chamber of the eye. Fetal diagonal band tissue containing cholinergic neurons was grafted into the anterior eye chamber of adult female rats that had either been treated or not with 2 mg estradiol valerate injected every 3 days after oophrectomy. Two and four weeks after transplantation, the axonal and/or dendritic growth of cholinergic neurons in the graft was studied using acetylcholinesterase histochemistry. At both times, acetylcholinesterase positive processes were densely distributed in the grafts of estradiol valerate treated rats, while in rats without estradiol valerate treatment acetylcholinesterase positive reaction was essentially localized only on the cell bodies. These findings were more obvious at 2 weeks after transplantation than at 4 weeks. These results suggest that estrogen acts on cholinergic neurons as a growth factor.     

Copper deprivation in rats induces islet hyperplasia and hepatic metaplasia in the pancreas

BACKGROUND INFORMATION: Prolonged copper deprivation in rats followed by refeeding with a normal diet has previously been used to induce the appearance of hepatocyte-like cells in the pancreas, but the effects on islet size and morphology have not been determined. RESULTS: In the present study we investigated the distribution of pancreatic alpha- and beta-cells and of hepatocytes in adult rats fed a copper-deficient diet followed by refeeding with a normal diet. Immunohistochemical staining for insulin and glucagon showed that the islets of the copper-deficient group were up to 2.4 times larger in mass compared with controls. The islets were disorganized, with alpha-cells found in multiple layers at the periphery of the islet and sometimes deep in the core. Isolated alpha- and beta-cells were also found in increased numbers in the ductular system. Copper deprivation caused almost complete ablation of the acinar cells, and refeeding induced adipogenesis, acinar regeneration and hepatocyte-like cells. Ductular proliferation and nerve hyperplasia were also present. The hepatocytes tended to be associated with islets or with ducts, rather than with residual pancreatic exocrine tissue. CONCLUSIONS: These data show that copper deficiency in rats, as well as inducing the appearance of hepatocytes, is capable of causing islet hyperplasia.     

Endodermally-derived and neural crest-derived differentiation antigens expressed by a human lung tumor.

The plasma membrane antigens of an undifferentiated small cell (oat cell) carcinoma of the lung were studied by the indirect immunofluorescence method on frozen section substrates with a rabbit antiserum prepared to the tumor plasma membrane fraction. After appropriate absorption of the antiserum, at least two differentiation antigens present on the tumor cells but undetectable on normal lung surface or glandular epithelial cells were identified. One antigen(s) was characteristic of certain normal, endodermally-derived epithelial cells of the digestive system, including those of colonic mucosa, hepatic ducts, pancreatic ducts and acini, and islets of Langerhans. The other antigen(s) was characteristic of certain normal, neural crest-derived cells in the peripheral nervous system, including cells in peripheral nerve, dorsal root ganglion, and anterior roots of the spinal cord; parasympathetic ganglion cells in the colon; and small nerves and nerve processes in the lung, colon, and skin. It was concluded that the presence of these differentiation antigens on the tumor cells resulted from the expression of gene products repressed in the normal cell of origin of the tumor.     

Pancreatic atrophy in copper-deficient rats: Histochemical and ultrastructural evidence of a selective effect on acinar cells

Summary Copper deficiency had a differential effect between tissues in the rat pancreas. There was marked loss and atrophy of acinar cells, in which both hypertrophied and degenerating mitochondria were present. Cytochrome oxidase activity in acini was greatly depleted while monoamine oxidase activity was enhanced. Atrophy of acinar cells was accompanied by extensive degeneration of the rough endoplasmic reticulum, and by a failure of zymogen granule synthesis. These changes contrasted strongly with the appearance of non-acinar tissues, in which hypertrophy and degeneration of mitochondria were rarely observed. Islet tissue, pancreatic ducts and blood vessels showed no atrophic changes. Cytochrome oxidase activity in islet tissue, and in the epithelium of the main pancreatic ducts, appeared unaffected.     

The effect of estrogens on the development of rats solitary tract nucleus neutrons transplanted into the anterior eye chamber]

By means of some autoradiografic, light and electron microscopic methods were investigated estrogen effects on synaptogenesis and neural synthetic activity in nucleus tractus solitarii grafts developed in anterior eye chamber. Estrogen increased the RNA-polymerase activity in some neurons of the grafts and also affected synaptogenesis in the neurophil of the graft tissue.     

‘Neuropeptide tyrosine’ (NPY) is co-stored with noradrenaline in vascular but not in parenchymal sympathetic nerves of brown adipose tissue

By using immunohistochemistry it is shown that both the parenchymal and vascular sympathetic innervation in the interscapular depot of brown adipose tissue in the rat contain the catecholamine-synthesizing enzyme tyrosine-hydroxylase (TH). In contrast, 'neuropeptide tyrosine' (NPY) is selectively present in the vascular sympathetic nerves of the tissue--but not in nerves around brown fat cells. This is consistent with the presence of two populations of neurons (containing either TH alone or TH plus NPY) in the stellate ganglion, which is the probable origin of the sympathetic nerves in the interscapular brown adipose tissue. Furthermore, the perivascular NPY-positive nerves in the brown adipose tissue disappeared after 6-hydroxydopamine treatment, demonstrating their noradrenergic nature. Taken together, these findings suggest that sympathetic nerves to blood vessels and brown fat cells represent two separate subpopulations of autonomic neurons.     

Features of the development of homo- and heterotopic allotransplants of rat embryonal neocortex

Mechanisms of regulation of cell division in the developing neocortex are largely unknown. The aim of the present study was to investigate the influence of a microenvironment on the fetal neocortex histogenesis. The fetal neocortex from 15-day old Wistar rat embryo was grafted into the neocortex, crushed sciatic nerve and anterior chamber of eye of adult rats. A comparative study of graft development was carried out on 1, 3, 7, 10, 30 days using histological (Nissl stain, hematoxylin-eosin) and immunohistochemical (monoclonal antibody to proliferating cell nuclear antigen, and to glial fibrillary acidic protein) methods. Grafted neuroepithelial cells proliferated in grafts that developed in the neocortex and the anterior chamber of eye for 7 days, and in the sciatic nerve for 10 days. In all grafts differentiating neuroblasts, young neurons and mature neurons were observed 7, 10 and 30 days later, respectively. In 10 days, transplants in the nerve have a glial capsule, in contrast to other sites of grafting. The capsule consists of ependymocytes with microvilli and cilia 30 days later. These cells are GFAP-positive. Our results indicate epigenetic influence on the development of neuroepithelial precursors. The microenvironment of the peripheral nerve is suggested to promote glyogenesis in developing grafts. Afferent inputs do not influence the proliferative potency of brain cell precursors.     

Pancreatic neoplasia induced by ras expression in acinar cells of transgenic mice

Expression of an activated human c-H-ras oncogene under control of rat elastase I regulating elements leads to neoplasia of the fetal exocrine pancreas. In most transgenic mice bearing this gene construct, massive tumors involving all the pancreatic acinar cells develop within a few days of pancreatic differentiation. Expression of the normal c-H-ras proto-oncogene in acinar cells leads to more subtle anomalies, but no tumors develop. Thus modest amounts of the mutant ras proteins are sufficient, in an otherwise normal genetic background, to lead to neoplastic transformation of differentiating pancreatic acinar cells. In contrast, a comparable elastase-myc construct produces no pancreatic tumors in transgenic mice.