Pancreatic polypeptide (PP) cells in the PP-rich lobe of the human pancreas are identified ultrastructurally and immunocytochemically as F cells

A metabolic-dysfunction associated steatotic liver acinus biomimetic induces pancreatic islet dysfunction in a coupled microphysiology system

Preclinical and clinical studies suggest that lipid-induced hepatic insulin resistance is a primary defect that predisposes to dysfunction in pancreatic islets, implicating a perturbed liver-pancreas axis underlying the comorbidity of T2DM and MASLD. To investigate this hypothesis, we developed a human biomimetic microphysiological system (MPS) coupling our vascularized liver acinus MPS (vLAMPS) with primary islets on a chip (PANIS) enabling MASLD progression and islet dysfunction to be quantitatively assessed. The modular design of this system (vLAMPS-PANIS) allows intra-organ and inter-organ dysregulation to be deconvoluted. When compared to normal fasting (NF) conditions, under early metabolic syndrome (EMS) conditions, the standalone vLAMPS exhibited characteristics of early stage MASLD, while no significant differences were observed in the standalone PANIS. In contrast, with EMS, the coupled vLAMPS-PANIS exhibited a perturbed islet-specific secretome and a significantly dysregulated glucose stimulated insulin secretion (GSIS) response implicating direct signaling from the dysregulated liver acinus to the islets. Correlations between several pairs of a vLAMPS-derived and a PANIS-derived secreted factors were significantly altered under EMS, as compared to NF conditions, mechanistically connecting MASLD and T2DM associated hepatic factors with islet-derived GLP-1 synthesis and regulation. Since vLAMPS-PANIS is compatible with patient-specific iPSCs, this platform represents an important step towards addressing patient heterogeneity, identifying complex disease mechanisms, and advancing precision medicine.

Small Molecule-Induced Pancreatic β-Like Cell Development: Mechanistic Approaches and Available Strategies

Diabetes is a metabolic disease which affects not only glucose metabolism but also lipid and protein metabolism. It encompasses two major types: type 1 and 2 diabetes. Despite the different etiologies of type 1 and 2 diabetes mellitus (T1DM and T2DM, respectively), the defining features of the two forms are insulin deficiency and resistance, respectively. Stem cell therapy is an efficient method for the treatment of diabetes, which can be achieved by differentiating pancreatic β-like cells. The consistent generation of glucose-responsive insulin releasing cells remains challenging. In this review article, we present basic concepts of pancreatic organogenesis, which intermittently provides a basis for engineering differentiation procedures, mainly based on the use of small molecules. Small molecules are more auspicious than any other growth factors, as they have unique, valuable properties like cell-permeability, as well as a nonimmunogenic nature; furthermore, they offer immense benefits in terms of generating efficient functional beta-like cells. We also summarize advances in the generation of stem cell-derived pancreatic cell lineages, especially endocrine β-like cells or islet organoids. The successful induction of stem cells depends on the quantity and quality of available stem cells and the efficient use of small molecules.

Pancreatic islet of Langerhans' cytoarchitecture and ultrastructure in normal glucose tolerance and in type 2 diabetes mellitus

While a number of structural and cellular abnormalities occur in the islet of Langerhans in diabetes, and in particular in type 2 diabetes, the focus has been mostly on the insulin producing β-cells and only more recently on glucagon producing α- and δ-cells. There is ample evidence that in type 2 diabetes mellitus (T2DM), in addition to a progressive decline in β-cell function and associated insulin resistance in a number of insulin-sensitive tissues, alterations in glucagon secretion are also present and may play an important role in the pathogenesis of hyperglycemia both in the fasting and in the postprandial state. Recently, a number of studies have showed that there are also functional and structural alterations in glucagon-producing α-cells and somatostatin-producing δ-cells. Thus, it is becoming increasingly clear that multiple cellular alterations of multiple cell types occur, which adds even more complexity to our understanding of the pathophysiology of this common and severe disease. We believe that persistent efforts to increase the understanding of the pathophysiology of hormone secretion in the islets of Langerhans will also improve our capability to better prevent and treat diabetes mellitus.

Altered levels of blood proteins in Alzheimer's disease longitudinal study: Results from Australian Imaging Biomarkers Lifestyle Study of Ageing cohort

INTRODUCTION

A blood-based biomarker panel to identify individuals with preclinical Alzheimer's disease (AD) would be an inexpensive and accessible first step for routine testing.

METHODS

We analyzed 14 biomarkers that have previously been linked to AD in the Australian Imaging Biomarkers lifestyle longitudinal study of aging cohort.

RESULTS

Levels of apolipoprotein J (apoJ) were higher in AD individuals compared with healthy controls at baseline and 18 months (P = .0003) and chemokine-309 (I-309) were increased in AD patients compared to mild cognitive impaired individuals over 36 months (P = .0008).

DISCUSSION

These data suggest that apoJ may have potential in the context of use (COU) of AD diagnostics, I-309 may be specifically useful in the COU of identifying individuals at greatest risk for progressing toward AD. This work takes an initial step toward identifying blood biomarkers with potential use in the diagnosis and prognosis of AD and should be validated across other prospective cohorts.

A case of annular pancreas with Wirsung's duct encircling the duodenum: embryological hypothesis based on cholangiopancreatographic and immunohistochemical findings

We present a resected case of annular pancreas in which Wirsung's duct encircled the duodenum and continued directly to the main pancreatic duct in the body and tail. Furthermore, Wirsung's duct coursed along the right side of the lower bile duct near the major duodenal papilla. Histologically, the islets of Langerhans in the annular pancreas were irregular in shape and were characterized by a striking abundance of pancreatic polypeptide (PP)-positive cells. The PP-rich area that encircled the duodenum was fused with the PP-poor area in the head of the pancreas. The following embryological hypothesis is proposed. The tip of the ventral pancreatic anlage adhered to the duodenal wall and stretched to form a ring during clockwise rotation. The rotation was incomplete, and the pancreatic duct did not cross over the lower bile duct. Since there was adequate ventral anlage in the lower part of the head of the pancreas, fusion between the ducts of the ventral and dorsal anlagen did not occur. The tip of the ventral anlage overgrew and adhered to the dorsal anlage, and the annular duct fused with the main duct of the dorsal anlage.

Recent advances in the regulation of pancreatic secretion

PURPOSE OF REVIEW

This review highlights recent progress made in the field of pancreatic secretion.

RECENT FINDINGS

This review summarizes a number of recent studies demonstrating the intracellular pathways by which hormones and neural inputs regulate pancreatic exocrine and endocrine secretion. In particular, the effects of vasoactive intestinal peptide and secretin on intra-acinar cell adenosine 3',5'-cyclic monophosphate are explored. Considerable attention is paid to regulation of β-cell function and includes studies detailing the mechanisms of regulation of insulin by somatostatin, serotonin, and melanocortins. These studies emphasize the critical role that hormonal, paracrine, and neural factors play in glucose homeostasis.

SUMMARY

Exocrine and endocrine pancreatic secretions are regulated by hormonal and neural mechanisms, and understanding these pathways will enable the discovery and design of new and improved therapies for prevention and control of diabetes and perhaps exocrine insufficiency.

Maturation of stem cell-derived beta-cells guided by the expression of urocortin 3

Type 1 diabetes (T1D) is a devastating disease precipitated by an autoimmune response directed at the insulin-producing beta-cells of the pancreas for which no cure exists. Stem cell-derived beta-cells show great promise for a cure as they have the potential to supply unlimited numbers of cells that could be derived from a patient's own cells, thus eliminating the need for immunosuppression. Current in vitro protocols for the differentiation of stem cell-derived beta-cells can successfully generate pancreatic endoderm cells. In diabetic rodents, such cells can differentiate further along the beta-cell lineage until they are eventually capable of restoring normoglycemia. While these observations demonstrate that stem cell-derived pancreatic endoderm has the potential to differentiate into mature, glucose-responsive beta-cells, the signals that direct differentiation and maturation from pancreatic endoderm onwards remain poorly understood. In this review, we analyze the sequence of events that culminates in the formation of beta-cells during embryonic development. and summarize how current protocols to generate beta-cells have sought to capitalize on this ontogenic template. We place particular emphasis on the current challenges and opportunities which occur in the later stages of beta-cell differentiation and maturation of transplantable stem cell-derived beta-cells. Another focus is on the question how the use of recently identified maturation markers such as urocortin 3 can be instrumental in guiding these efforts.

The ductal origin of structural and functional heterogeneity between pancreatic islets

Islets form in the pancreas after the first endocrine cells have arisen as either single cells or small cell clusters in the epithelial cords. These cords constitute the developing pancreas in one of its earliest recognizable stages. Islet formation begins at the time the cords transform into a branching ductal system, continues while the ductal system expands, and finally stops before the exocrine tissue of ducts and acini reaches its final expansion. Thus, islets continuously arise from founder cells located in the branching and ramifying ducts. Islets arising from proximal duct cells locate between the exocrine lobules, develop strong autonomic and sensory innervations, and pass their blood to efferent veins (insulo-venous efferent system). Islets arising from cells of more distal ducts locate within the exocrine lobules, respond to nerve impulses ending at neighbouring blood vessels, and pass their blood to the surrounding acini (insulo-acinar portal system). Consequently, the section of the ductal system from which an islet arises determines to a large extent its future neighbouring tissue, architecture, properties, and functions. We note that islets interlobular in position are frequently found in rodents (rats and mice), whereas intralobularly-located, peripheral duct islets prevail in humans and cattle. Also, we expound on bovine foetal Laguesse islets as a prominent foetal type of type 1 interlobular neuro-insular complexes, similar to neuro-insular associations frequently found in rodents. Finally, we consider the probable physiological and pathophysiological implications of the different islet positions within and between species.

Pancreatographic investigation of pancreatic duct system and pancreaticobiliary malformation

To clarify the anatomy of the pancreatic duct system and to investigate its embryology, we reviewed 256 pancreatograms with normal pancreatic head, 81 with pancreas divisum and 74 with pancreaticobiliary maljunction. Accessory pancreatograms were divided into two patterns. The long-type accessory pancreatic duct forms a straight line and joins the main pancreatic duct at the neck portion of the pancreas. The short-type accessory pancreatic duct joins the main pancreatic duct near its first inferior branch. The short-type accessory pancreatic duct is less likely to have a long inferior branch arising from the accessory pancreatic duct. The length of the accessory pancreatic duct from the orifice to the first long inferior branch was similar in the short- and long-type accessory pancreatic ducts. The first long inferior branch from the long-type accessory pancreatic duct passes though the main pancreatic duct near the origin of the inferior branch from the main pancreatic duct. Immunohistochemically, in the short-type accessory pancreatic duct, the main pancreatic duct between the junction with the short-type accessory pancreatic duct and the neck portion was located in the ventral pancreas. The long-type accessory pancreatic duct represents a continuation of the main duct of the dorsal pancreatic bud. The short-type accessory pancreatic duct is probably formed by the proximal main duct of the dorsal pancreatic bud and its long inferior branch.

Y(4) receptors mediate the inhibitory responses of pancreatic polypeptide in human and mouse colon mucosa

The antisecretory effects of several Y agonists, including pancreatic polypeptide (PP), indicate the presence of Y(1), Y(2), and Y(4) receptors in mouse and human (h) colon mucosae. Here, we used preparations from human and from wild-type (WT), Y(4), and Y(1) receptor knockout ((-/-)) mice, alongside Y(4) receptor-transfected cells to define the relative functional contribution of the Y(4) receptor. First, rat (r) PP antisecretory responses were lost in murine Y(4)(-/-) preparations, but hPP and Pro(34) peptide YY (PYY) costimulated Y(4) and Y(1) receptors in WT mucosa. The Y(1) antagonist/Y(4) agonist GR231118 [(Ile,Glu,Pro,Dpr,Tyr,Arg,Leu,Arg,Try-NH(2))-2-cyclic(2,4'),(2',4)-diamide] elicited small Y(4)-mediated antisecretory responses in human tissues pretreated with the Y(1) antagonist, BIBO3304 [(R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N(2)-(diphenylacetyl)-argininamide trifluoroacetate)], and attenuated Y(4)-mediated hPP responses in mouse and human mucosa. GR231118 and rPP were also antisecretory in hY(4)-transfected epithelial monolayers but were partial agonists compared with hPP at this receptor. In Y(4)-transfected human embryonic kidney (HEK) 293 cells, Y(4) ligands displaced [(125)I]hPP binding with orders of affinity (pK(i)) at human (hPP = rPP > GR231118 > Pro(34)PYY = PYY) and mouse (rPP = hPP > GR231118 > Pro(34)PYY > PYY) Y(4) receptors. GR231118- and rPP-stimulated guanosine 5'-3-O-(thio)triphosphate binding through hY(4) receptors with significantly lower efficacy than hPP. GR231118 marginally increased basal but abolished further PP-induced hY(4) internalization to recycling (transferrin-labeled) pathways in HEK293 cells. Taken together, these findings show that Y(4) receptors play a definitive role in attenuating colonic anion transport and may be useful targets for novel antidiarrheal agents due to their limited peripheral expression.

Ontogeny, postnatal development and ageing of endocrine pancreas in Bubalus bubalis

The ontogenesis, postnatal development and ageing of the endocrine pancreas in mammals have not been extensively studied. In order to improve understanding of this organ, we studied the buffalo pancreas during fetal and postnatal development. Glucagon, insulin and somatostatin immunoreactive cells (i.c.) were first seen in 2-mo-old embryos. Pancreatic polypeptide (PP) i.c. were observed during the 3rd month of gestation. The early embryo pancreas was almost totally composed of endocrine tissue. The endocrine portion only slightly increased in mass with animal growth, whereas the exocrine portion noticeably increased in mass during the late fetal and postnatal periods. In adults, therefore, the exocrine portion was more evident than the endocrine portion. Three types of islet were observed in fetal and young buffalos: small, large and PP-islets. The small islets were composed of insulin, glucagon, somatostatin and PP i.c. The large islets were primarily composed of insulin i.c. and a few glucagon, somatostatin and PP i.c. The PP islets were mostly composed of PP i.c. with a few somatostatin, insulin and glucagon i.c. The number of large islets greatly diminished by adulthood. Glucagon, insulin, somatostatin and PP i.c. were also seen scattered in the exocrine parenchyma and along the duct epithelium. In the duct epithelium, these cells were either single or grouped, and they sometimes formed a protrusion projecting towards the connective tissue. These morphological features were primarily observed in fetuses and young buffalos.

Ultrastructural classification of the endocrine cells of the large intestine of the calf. Cytochemical evidence of the presence of Viallis's pre-EC cells

GEP (Gastro-Entero-Pancreatic) endocrine cells were very numerous in the mucosal layer of the large intestine of the calf. Their frequence appeared to increase towards the distal portions of the gut. Endocrine cells were dispersed among epithelial cells lining intestinal glands and were frequently grouped together. Cellular shape was pyramidal or elongated; the cytoplasm was electron-lucent and contained highly characteristic secretory granules. Six different types of endocrine cells were identified on the basis of the ultrastructural aspect and cytochemical characteristics (silver-reactivity) of their secretory granules: EC, L, PP, A, D1 and D cells. EC and L cells were the most abundant in all localisations. They were especially numerous in the rectum. A subpopulation of EC cells was negative to Masson-Singh's reaction showing that they lack 5-HT. This observation enabled us to refer this latter cellular type to the "pre-EC" cells, described by Vialli as an earlier evolutive step of the EC cells population. Their presence in the calf gut might be linked to its possible "immaturity", due either to the age or to the alimentary diet.

Studies on co-localization of 7B2 and pancreatic hormones in normal and tumoural islet cells

The distribution of protein 7B2, a protein with structural characteristics of GTP-binding proteins, has been studied in normal pancreatic islets and in a series of 70 pancreatic endocrine tumours with emphasis on the co-localization of 7B2 and the different pancreatic hormones. Although all cell types of normal islets were found to store 7B2, variations from intense expression to absence of reaction were seen within each cell type. In particular, B cells showed intense immunostaining for 7B2 in small compact islets and weak or no staining in larger islets with lobular arrangement. Pancreatic polypeptide (PP) cells expressed 7B2 intensely in the PP-rich area of ventral embryological origin, but were mostly non-reactive in the PP-poor area. The A cells, located along intralobular blood vessels, were more frequently immunoreactive for 7B2 than those at the periphery of the islets. Immuno-electron microscopy revealed a preferential localization of 7B2 in secretory granules of islet cells, with more intense localization in the peripheral halo of alpha granules. Benign islet cell tumours more frequently expressed 7B2 than their malignant counterparts. Although often expressed in a lower number of tumour cells than the tumour-specific hormone, 7B2 was usually co-localized with the latter. In contrast, no relationship was found with the localization of proinsulin. It is concluded that 7B2 is a non-permanent component of the cell granule compartment, probably involved in events related to exocytosis and without relationship to intracellular prohormone processing.

Coexistence of glucagon and pancreatic polypeptide in human and rat pancreatic endocrine cells

Pancreatic islet cells containing both glucagon and pancreatic polypeptide simultaneously (glucagon/PP cells) were identified in the rat and human normal pancreas using immunocy-tochemical staining on consecutive serial sections and double-immunolabeling techniques on the same sections. Numerous glucagon/PP cells were found at the periphery of the islets in all regions of the pancreas, particularly in the rat. As a whole, these bipeptide-containing cells appeared in higher proportions than the cells secreting glucagon or PP separately. Double immunogold labeling performed on both surfaces of the thin tissue sections allowed differentiation between the glucagon/PP cells and the single-labeled glucagon or PP cells at the ultra-structural level. The pancreatic glucagon/PP cells displayed the morphological characteristics of either A cells or PP cells. Both peptides were found in the same secretory granules of the glucagon/PP cells and, in the human pancreas, the glucagon/PP cells displayed secretory granules with a dense core in which both peptides were rather concentrated. The coexistence of glucagon and PP is assumed to originate from the simultaneous expression of the two different genes in the same cell and suggests that the cellular processing through the rough en-doplasmic reticulum-Golgi apparatusgranule secretory pathway for both peptides takes place in parallel.

Characterization of the endocrine cells in the pancreatic-bile duct system of the rat

Six types of endocrine cells showing immunolabelling against gut or pancreatic islet hormones were identified in the pancreatic-bile duct system of the normal adult rat at the light and electron microscopic levels. They were located within the epithelial lining of the duct system from the intercalated portion to its duodenal opening. However, the distribution and frequency of each endocrine cell varied along the length of the duct system. While insulin, glucagon, somatostatin, and pancreatic polypeptide cells were widely distributed along the entire duct system, small numbers of cholecystokinin and serotonin cells were confined to the terminal portion. A considerable number of somatostatin cells were concentrated in gland-like pouches of the terminal portion of the common pancreatic-bile duct. When the accessory pancreatic duct was present, insulin, glucagon, and somatostatin cells were also found in its epithelial lining. Electron microscopically, the specific content of the secretory granules of all endocrine cells was confirmed by immunolabelling or cytochemical staining. Further the characteristics of the secretory granules of each endocrine cell type corresponded to those present in the same kind of endocrine cells in gut or pancreatic islet. The duct endocrine cells displayed a particular ultrastructural appearance. The "open type cells" were highly polarized, with their apical cytoplasmic process reaching the duct lumen, whereas "closed type cells" showed long basal cytoplasmic processes with no connection with the duct lumen. In general, insulin, and somatostatin cells were of the "open type", while no morphological connection with the duct lumen was found for glucagon and pancreatic polypeptide cells. The presence of various duct endocrine cells with their particular ultrastructural appearance implies that they may take part in modulating the function of the duct system.

The morphology and neuroendocrine profile of pancreatic epithelial VIPomas and extrapancreatic, VIP-producing, neurogenic tumors

The histology, histochemistry, and ultrastructure of 43 VIP-producing tumors (34 from the pancreas, one jejunal, six retroperitoneal and two mediastinic), 37 of which were associated with the WDHA syndrome, have been investigated on paraffin sections of primary or metastatic tumor tissue. The pancreatic and jejunal tumors showed all structural and secretory patterns of epithelial endocrine tumors, including expression of cytokeratin, neuroendocrine markers like neuron-specific enolase, chromogranins and synaptophysin, peptides like VIP, PHM, GRH, PP, insulin, neurotensin, glucagon, somatostatin and enkephalin, secretory granules, small clear vesicles, peculiar osmiophilic bodies, and occasional formation of tubules or microacini with specialized luminal surfaces. All the remaining tumors were neurogenic, showing either neurons and nerve fibers together with Schwann cells (ganglioneuromas and ganglioneuroblastomas) or endocrine cells (pheochromocytomas) reacting with VIP, PHM, NPY, enkephalin, somatostatin, neuron-specific enolase, synaptophysin, and MAP2 (but not cytokeratin, PP, or GRH) antibodies. A possible origin of pancreatic VIPomas from transformed pancreatic PP cells or ductular stem cells partially committed to differentiation along the PP cell line is suggested.

Widespread expression of intestinal markers in gastric carcinoma: a light and electron microscopic study using BD-5 monoclonal antibody

BD-5 monoclonal antibody reacted with tumour cells in 262 of 316 cases of gastric cancers, including 121 of 134 early, 141 of 182 advanced tumours (p less than 0.01), and 113 of 146 glandular, 72 of 83 diffuse, 22 of 25 mucoid, and 55 of 59 mixed tumours. No difference in reactivity was observed between metastatic and non-metastatic advanced tumours. Immunocytochemical techniques applied to light and electron microscopical specimens of colorectal mucosa and gastric cancer showed that BD-5 immunoreactive material occurred in the Golgi complex, in small clear, to dense cored, cytoplasmic vesicles, and in the glycocalix of the luminal and lateral membranes of normal and neoplastic cells in the glands, as well as in the peripheral membrane of dispersed neoplastic cells. Mucin granules stored in the cytoplasm of goblet cells were unreactive or poorly reactive. Ultrastructural features consistent with colorectal type differentiation were observed in many reactive tumours. Unreactive tumours showing ultrastructural patterns consistent with intestinal differentiation, especially of small bowel type, were also observed. Signs of intestinal differentiation, including BD-5 immunoreactivity, often occur in gastric cancer, irrespective of histological type and stage of disease.

Synaptophysin immunoreactivity and small clear vesicles in neuroendocrine cells and related tumours

Synaptophysin (protein p38) immunoreactivity has been detected immunohistochemically in neuroendocrine cells of the human adrenal medulla, carotid body, skin, pituitary, thyroid, lung, pancreas and gastrointestinal mucosa as well as in 87 out of 93 neuroendocrine tumours investigated, including pheochromocytomas, chromaffin and non-chromaffin paragangliomas, ganglioneuromas, pituitary adenomas, thyroid medullary carcinomas, parathyroid adenomas, lung carcinoids and neuroendocrine carcinomas, pancreatic and gut endocrine tumours and cutaneous merkelomas. Parallel ultrastructural investigation of synaptophysin-reactive cells and tumours revealed the presence, in addition to dense-cored, secretory granules, of a population of pleomorphic, small, clear vesicles resembling synaptic vesicles of nerve terminals as well as the synaptophysin immunoreactive vesicles already described in rat adrenal medullary and pituitary cells. Synaptophysin immunoreactivity showed several differences in its distribution among tumour and non-tumour endocrine cells when compared to chromogranin A immunoreactivity, a well known marker of the core of endocrine granules. Synaptophysin represents a reliable general marker of neuroendocrine cells and tumours, which may be useful in diagnostic histopathology.

Immunocytochemistry of normal pancreatic islets and spontaneous islet cell tumors in dogs

Immunocytochemical studies of the distribution of glucagon, gastrin, insulin, and somatostatin in normal canine pancreatic islets and 20 canine islet cell tumors were done using the peroxidase-anti-peroxidase (PAP) technique. In the normal adult canine pancreas, islets typically consisted of clusters of 20-30 cells, but smaller foci and even individual cells were identified. Alpha cells (glucagon) were often peripherally located, beta cells (insulin) were centrally located and most numerous, and delta cells (somatostatin) were the least numerous and randomly located. Both juvenile and adult canine pancreases did not stain for gastrin. Of the 20 tumors examined, 18 had positive immunoreactivity for insulin, nine for glucagon, 14 for somatostatin, and one for gastrin. Two tumors were uninterpretable due to autolysis. Three tumors were pure insulinomas, but no pure somatostatinomas, glucagonomas, or gastrinomas were identified. Most tumors and metastases had mixed positive immunoreactivity; one neoplastic cell type predominated with lesser numbers of other cell types. Metastatic sites (liver and lymph node) stained for insulin and somatostatin, only. Foci of non-neoplastic islet cell tissue (nesidioblastosis), often located at the pancreatic-mesenteric junction, stained strongly positive for insulin, glucagon, and somatostatin but not for gastrin. The tumor staining pattern did not consistently correlate with tumor function, as determined by blood glucose and serum insulin assays. The PAP technique works well on paraffin-embedded, formalin-fixed tissue using rabbit or guinea pig antisera as the primary antibody. Staining occurred on sections of paraffin blocks stored for up to 7 years.

Glucagon, glicentin, proglucagon, PYY, PP and proPP-icosapeptide immunoreactivities of rectal carcinoid tumors and related non-tumor cells

Glucagon/PP-related peptides were detected immunohistochemically in 18 out of 22 cases of rectal tumors investigated. The reactive tumors showed prevalence of trabecular or mixed trabecular-acinar structure and moderate staining with Grimelius' silver and lead-hematoxylin. Three of the remaining 4 cases were characterized by reactivity for 5-hydroxytryptamine only, prevalence of a solid nest structural component and intense staining with Grimelius' silver technique and lead-hematoxylin. Fifteen of the 18 glucagon/PP-reactive cases were investigated immunohistochemically with a series of 6 sera directed against different sequences of glucagon, glicentin and proglucagon, and of 7 sera directed against PP, PYY and proPP-icosapeptide. A large spectrum of glucagon-related immunoreactivities, including C-terminus and mid-portion glucagon-immunoreactivity, N- and C-terminus glicentin-immunoreactivity, GLP1- and GLP2-immunoreactivity, were detected in human rectal L cells and most rectal carcinoids. With the exception of a few scattered cells in the rectal mucosa and in 3 tumors, C-terminus glucagon-immunoreactivity was obtained only after trypsin or subtilisin treatment of tissue sections. Both PYY and PP/proPP-like peptide(s) were detected in rectal L cells and carcinoids, with prevalence of PYY in normal cells and PP/proPP-like peptides in tumor cells. It is concluded that the same or closely related hormone/prohormone sequences are synthesized and stored in rectal endocrine cells and carcinoid tumors although differences of quantitative expression, post-translational cleavage or reactivity to antibodies may occur. The usefulness of protease treatments of tissue sections to unmask immunoreactivities of uncleaved propeptides or fixative-denatured peptides is outlined.

Peptide-hormone- and serotonin-immunoreactive cells in normal and hyperplastic prostate glands

Peptide-hormone- and serotonin-immunoreactive cells of endocrine type are present both in the normal prostatic gland and in the nodules of benign prostatic hyperplasia of man. They are located in the epithelium of the acini and the ducts of all the different parts of the gland, as well as in the urothelium of the prostatic part of the mucosa of the urethra. The endocrine cells are usually argyrophil, sometimes even argentaffin, and immunoreactive with neuron-specific enolase; they can be either of open or of closed type and usually occur widely scattered as single cells. Three kinds of endocrine cells were observed both in the normal gland and in the hyperplastic parenchyma. In the by far most prevalent type serotonin was found to co-exist with a peptide immunohistochemically related to the thyroid stimulating hormone (TSH). In a more rare type serotonin co-existed immunohistochemically with calcitonin. The third kind of endocrine cells was somatostatin-immunoreactive cells; they were also rather rare. The only difference observed between the normal and hyperplastic parenchyma was an increase in the number of all the three kinds of endocrine cells in the hyperplastic nodules. The endocrine cells could easily be visualized by means of silver-staining techniques, even using conventionally formalin-fixed, paraffin-embedded specimens.

Chromogranin A, B and C immunoreactivities of mammalian endocrine cells. Distribution, distinction from costored hormones/prohormones and relationship with the argyrophil component of secretory granules

Antibodies specific for chromogranin A, B or C have been used to detect immunohistochemically these three anionic proteins. Pancreatic A, B and PP cells, gut argentaffin EC, argyrophil ECL and gastrin G cells, thyroid C cells, parathyroid cells, adrenal medullary cells, pituitary TSH, FSH and LH cells as well as some axons of visceral nerves have been found to react with chromogranin A antibodies. Pancreatic A, gut EC and G, adrenal medullary and pituitary cells as well as some gut nerve fibers showed chromogranin B immunoreactivity. Chromogranin C immunoreactivity has been detected in pancreatic A, pyloric D1, intestinal L, thyroid C, adrenal medullary and pituitary cells, as well as in some gut neurons and nerve fibers. No crossreactivity has been found in immunohistochemical tests between chromogranins A, B or C and costored monoamines or peptide hormones/prohormones, from which chromogranins can be separated by selective extraction during fixation. On both morphological and chemical grounds a relationship seems to exist between chromogranin A and Grimelius' argyrophilia. Sialooligosaccharide chains of chromogranin A and, possibly, chromogranins' phosphoserine/phosphothreonine groups, seem to interact with guanidyl, amino, and/or imidazole groups of non-chromogranin components to form silver complexing sites accounting for granules' argyrophilia, which can be removed or blocked without affecting chromogranin immunoreactivities. The abundant anionic groups of the three proteins should contribute substantially to granules' basophilia, the partly "masked" pattern of which supports the existence of a close interaction of such groups with other components of secretory granules, including monoamines and peptide hormones or prohormones. Chromogranins could play a rôle in hormone postranslational biosynthesis and intragranular packaging.

Nesidioblastosis and islet cell changes related to endogenous hypergastrinemia

The endocrine pancreas from four hypergastrinemic patients with recurrent peptic ulceration has been studied by light and electron microscopy. Greatly increased numbers of ducts and centroacinar cells have been observed associated with a striking increase in the number of islets and endocrine cells scattered in the acinar tissue (nesidioblastosis). The islet cells scattered throughout the exocrine parenchyma are of all the known islet cell types, with a prevalence of B and especially A cells. Many islets, probably formed de novo, are of a considerable size, have irregular contours and are in close apposition to centroacinar cells and ducts. The degree of nesidioblastosis and islet hyperplasia does not seem to be related to the plasma gastrin levels. Cytological changes have also been found in the islet cells of the hypergastrinemic patients compared with controls. These changes mainly affect the B cells and consist of a striking decrease in the number of mature secretory granules associated with a fairly extended ergastoplasm and Golgi apparatus and with a relevant increase in the number of immature granules. In two of the four patients examined, who had more severe hypergastrinemia, cytological signs of enhanced secretion are also recognized in A cells. The features indicating hypersecretion of B and A cells seem to be related to the plasma gastrin levels. The above findings indicate that chronic endogenous hypergastrinemia promotes proliferation and differentiation of islet cells and stimulates the secretory function of B cells and, to a lesser extent, of A cells, thus providing evidence for a trophic and secretagogue action of gastrin on the endocrine pancreas.

Glucagon- and PP-related peptides of intestinal L cells and pancreatic/gastric A or PP cells. Possible interrelationships of peptides and cells during evolution, fetal development and tumor growth

The immunohistochemical detection of six distinct sequences of proglucagon and its derivatives (GRPP, glicentin, glucagon-37, glucagon-29, GLP1, GLP2 and MPGF) in both intestinal L cells and pancreatic or gastric A cells of some mammals (dog, man, guinea pig) confirms that the two cell types produce the same proglucagon molecule, although the final step of its post-translational processing differs in the two cells. Immunohistochemical and ultrastructural patterns of glucagon/glicentin cells in the pancreas of lower vertebrates and early human fetuses, as well as tumor cell studies, suggest an evolution of gastropancreatic A cells from L cells. On the contrary, the PP-related peptide PYY of intestinal L cells, and PP with its C-terminal icosapeptide extension of pancreatic PP cells, likely originate from different prohormones. Although intermediate patterns of peptide expression can be observed, including some F-type PP cells of the dog pancreas (uncinate process) and pyloric mucosa showing PYY immunoreactivity or rare PYY and/or HPP immunoreactive cells of the human rectum lacking glicentin reactivity, no obvious relationship can be established between L cells and pancreatic (F-type) PP cells. However, some evolutionary, embryogenetic and oncogenetic link may exist between L cells and human D1-type PP cells, a minor population of PP cells scattered in the pancreatic tissue of dorsal pouch origin and a major fraction of tumor PP cells.

Light microscopic histochemistry on plastic sections

As compared with conventional paraffin, celloidin, and frozen sections, semithin plastic sections offer a superior quality of the light microscopic image in terms of better resolution, absence of distortion and shrinkage artifacts, and suitability for calcified tissues. Application of histochemical methods to such sections often encounters, however, serious difficulties resulting from a considerably reduced reactivity of plastic-embedded biological material. Factors involved include a poor penetration of reagents into plastic embedding media due to a steric or hydrophobic hindrance, as well as a blockade of the reactive chemical groups in the sample due to interactions with fixatives and plastics. Embedding in polar (hydrophilic) plastics, such as glycol methacrylate, permits carrying out a large number of histochemical reactions, including the demonstration of enzymatic activities, directly on sections, but is less suitable for combined light/electron microscopic studies because of an imperfect ultrastructural preservation of tissues. Embedding in nonpolar epoxy resins, particularly if combined with a double aldehyde-osmium fixation, results in a high quality ultrastructure but almost fully inhibits the histochemical reactivity of the embedded material. In order to restore this reactivity, i.e. to unmask chemical groups bound by the polymerized resin, semithin epoxy sections require the removal of the embedding matrix by alkoxides prior to the histochemical procedure. Additional steps are also often necessary: treatment of osmium-fixed sections with oxidative agents, e.g., hydrogen peroxide or periodate which reoxidize the bound osmium and remove it from tissue, and a controlled proteolytic digestion, especially useful in immunocytochemical studies, which probably cleaves the bonds between the primary aldehyde fixative, and the reactive sites. This article reviews histochemical methods which have been successfully applied to plastic-embedded material. Using polar methacrylates and/or nonpolar epoxy resins as embedding media, it has been possible to demonstrate proteins and aminoacid residues, carbohydrates, lipids, nucleic acids, biogenic amines, inorganic ions, and some enzymes, although the spectrum of methods found as suitable for plastic-embedded material is far narrower than that available for paraffin or frozen sections.(ABSTRACT TRUNCATED AT 400 WORDS)

Endocrine-paracrine cells of the prostate and prostatic urethra: an ultrastructural study

A remarkable morphologic diversity among the endocrine-paracrine (EP) cells of the prostate and prostatic urethra was found in this study. Based on granule morphology, a wide variety of EP cell "types" was discerned, although many intermediate and mixed cells, forming a continuum, were also observed. The EP cells were of both the open (containing luminal borders) and closed types. The latter often had long dendritic processes. Prominent lamellar bodies, possibly representing a form of crinophagy, were present in some EP cells. The variety and morphologic complexity of these prostatic and urethral EP cells suggest that they play an important role in both normal and pathologic conditions.