The cell types in the endocrine pancreas of the human fetus

Summary Morphological and histochemical studies of the developing human islet cells are facilitated by the characteristic localization of the different islet cell types from about the third intrauterine month. By combining light microscopical analyses of silver impregnated and granule stained pancreatic sections with electron microscopy of osmium fixed material, the following four types of islet cells could be identified: (1) A₁ cells containing faint globular granules. These granules could be visualized only with the electron microscope. (2) A₂ cells containing electron-dense globular granules. It is uncertain whether the observation of a light and a dark variety of the A₂ cells reflects different stages of maturation or signifies cells with different secretion products. (3) B cells with irregular granules, which were often accumulated at the capillary pole of the cells. (4) Agranular islet cells. Mixed forms of A cells containing both faint and dense granules were also encountered. The difficulties in evaluating in the light microscope what may be called D cells in the human fetal islets were obvious from the observation of more cells stained with light-green than A₁ cells. Except for acid phosphatases, the histochemical tests for different phosphatases and esterases revealed rather weak or negative reactions in the islet cells. The development of phosphatase and esterase activities in the islets seemed far from complete, when morphologically differentiated islet cells could be recognized.Supported by the United States Public Health Service [grants RF-83(01) and TW-83(02)] and the Swedish Medical Research Council. The authors are indebted to Professor Carl Gemzell and Dr. Ulf Elvkull at the Department of Obstetrics and Gynecology, University Hospital, Uppsala, for the generous supply of the fetal pancreatic material.     

Morphological aspects on pancreatic islets of non-obese diabetic (NOD) mice

The pancreatic islets of female non-obese diabetic (NOD) mice (a model of insulin-dependent diabetes mellitus), have been examined by both light and electron microscopy. At about the age of 2 weeks, mononuclear cells began to infiltrate in or near the islets and some of these cells were in contact with the islet cells. Following this degeneration of islet B-cells took place, the process occurring in two ways. In many cells numerous secretory granules with extremely dense cores occupied the cytoplasm. Other cells, however, were filled with low-density secretory granules and the nuclei of these cells became pycnotic. After degeneration of B-cells, the islets were effaced by numerous mononuclear cells. With the onset of the diabetic state these mononuclear cells gradually disappeared, and thereafter small islets remained. By electron microscopy, retrovirus-like particles were observed in cisternae of the rough endoplasmic reticulum in islet B-cells at all stages. With an anti-retrovirus serum (goat anti-KiMSV-NIHxeno serum), positive immunofluorescence was observed in some pancreatic islet cells of NOD mice aged 1 day and 4, 6, 8, 9, 10 and 14 weeks. It is suggested that these virus particles may be intimately related to the inflammatory reaction occurring in the islets and to the development of diabetes mellitus.     

Light and electron microscopic study on the endocrine cells of the pancreas in a marine teleost,Fugu rubripes rubripes

Summary The pancreatic endocrine tissue of Fugu rubripes rubripes consists of numerous round principal islets (Brockmann bodies) of various sizes scattered around the gall-bladder. The endocrine cells are divided into A-, B-, D-, and F_f-cells. Each cell type was identified by comparing thick and thin sections in both light and electron microscopy. Aldehyde-fuchsin positive B-cells contain numerous round secretory granules (average diameter 300 nm) each of which has a round compact core of moderate density; a narrow space exists between this core and the limiting membrane. Grimelius' silver positive A cells contain round secretory granules (average diameter 360 nm) with a hexagonal or tetragonal crystalline core (average diameter 170 nm) of high density; the silver grains preferentially appear in the space between the limiting membrane and the core. The crystalline core of each -granule often contains an appendix-like structure of variable shape. D cells blackened by the silver impregnation method of Hellman and Hellerström (1960) have round secretory granules (average diameter 320 nm) filled with a flocculent material of low density. The fourth cell type (F_f-cell) has a clear cytoplasm after differential staining for light microscopy. By electron microscopy, this cell has elongated fusiform secretory granules (520 nm average length × 230 nm average width) filled with numerous filaments arranged in parallel with the longitudinal axis. Figures suggesting granule formation in the sacs of the Golgi apparatus were obtained in all of islet cell types. Equivalents of emiocytotic release of secretory granules were encountered in the A and F_f cells.     

银染技术在生殖细胞研究中的应用

新近对传统的银染技术作出改良,以氨银反应观察精子发生及受精过程中碱性蛋白的更替,以Ａｇ－Ａｓ反应观察精子发生过程中ＮＯＲ,嗜银细胞器,细胞骨架及其它嗜银成份的变化以及皮层皮应中嗜银成分的变化。     

New cell types of the pancreatic islets in the crucian carp,Carassius carassius

Summary The pancreatic islets ofCarassius carassius have been studied by electron microscopy. 1. Besides A-, B- and D-cells, two new cell types, the fourth and the fifth, have been identified. The fourth cell type is numerous; it occurs interposed among the other types of islet cells or in small clusters. The secretory granules (90–280 mg in diameter) are round or oval and usually with much lower electron density than α- and δ-granules. The secretory granules of the fifth type of cell (approximately 140–240 mμ in diameter) contain finely granular material and an electron dense core that is round or often tetra- or hexagonal. 2. The islet cells with clear cytoplasmic matrix generally contain large numbers of fine, agranular and cored vesicles 400–680 ? in diameter. They appear, in bead-like chains, or randomly scattered throughout the cytoplasm, or often clustered in aggregates close to the secretory granules and show evidence of incorporation into the secretory granules. The two types of vesicles may be formed by constriction or pinching-off of the tubular smooth endoplasmic reticulum.     

The ultrastructural basis for the identification of cell types in the pancreatic islets

Summary The pancreatic islets of rabbit, dog and opossum have been studied by light and electron microscopy. Silver-positive cells in the rabbit are predominantly sandwiched between the peripheral A and central B cells, and by electron microscopy are identified as D cells. Pancreatic islets in the tail of the dog pancreas have A, B, and D (silver-positive) cells, but the islets in the uncinate process of the dog pancreas lack phosphotungstic acid hematoxylin-positive A cells. By electron microscopy the characteristic D cells are found in both tail and uncinate process, but A cells are confined to the tail islets, confirming the identification of cell types. A unique cell type termed the F cell is found in the dog uncinate islets and it is characterized by secretory granules of angular profiles. In the opossum, the A cells contain considerable amounts of glycogen demonstrable by both light and electron microscopy. A unique cell type is also present in the opossum islets termed an E cell (Thomas, 1937), which has large secretory granules (400–500 m). The physiological implications of a multiplicity of cell types in pancreatic islets is discussed.This investigation was supported in part by United States Public Health Service research grants GM-10102 and GM-03784 from the Institute of General Medical Sciences, and AM-01226 from the Institute of Arthritis and Metabolic Diseases. The authors wish to acknowledge the valuable technical assistance of Mrs. Aileen Sevier and Mrs. Lidia Donahue.     

Silver staining analysis on spermatozoa of Nucella lapillus (Gastropoda,Prosobranchia)

Summary

Sperm of Nucella lapillus was studied by electron microscopy, including the application of a cytochemical silver method. Using silver impregnation a dense precipitation of Ag granules in spermatocyte II nucleoli was seen over the fibrillar component and a slight one in the granular component. On longitudinal sections of the spermatozoon the results demonstrate that argyrophilic proteins are located in the external limiting zone of the acrosome in the anterior portion of the nucleus between the cytoplasmic and the nuclear membranes, in the posterior end of the nucleus and in the terminal portion of the middle region. These data indicate an affinity for silver in areas of the cytoplasm containing microtubules and in zones of transition.     

Selective fluorescence of zymogen granules of pancreatic acinar cells stained with hematoxylin and eosin

Following staining with hematoxylin and eosin Y, paraffin sections of mouse pancreas were examined by transmitted light, epifluorescence and confocal laser scanning microscopy. Light microscopy revealed that the nuclei of pancreatic acinar cells were located basally, while the apices of the cells appeared eosinophilic, although the secretory granules were difficult to visualize. Under violet-blue light excitation, the zymogen granules at the apices of the acinar cells showed strong yellowish fluorescence; the other part of the cytoplasm was only faintly fluorescent and the nuclei and the supporting tissues were nonfluorescent. Confocal laser scanning microscopy resulted in clear pictures of the zymogen granules and their distribution within the cell. The fluorescent emission of zymogen granules was certainly the result of eosin Y staining, because hematoxylin is not a fluorochrome and the zymogen granules are not autofluorescent. Staining with eosin Y alone, however, did not result in clear fluorescent images of zymogen granules or any other cellular structures. Our observation shows that the fluorescence emission of eosin Y allows easy and precise recognition of zymogen granules of pancreatic cells.     

Selective fluorescence of zymogen granules of pancreatic acinar cells stained with hematoxylin and eosin

Following staining with hematoxylin and eosin Y, paraffin sections of mouse pancreas were examined by transmitted light, epifluorescence and confocal laser scanning microscopy. Light microscopy revealed that the nuclei of pancreatic acinar cells were located basally, while the apices of the cells appeared eosinophilic, although the secretory granules were difficult to visualize. Under violet-blue light excitation, the zymogen granules at the apices of the acinar cells showed strong yellowish fluorescence; the other part of the cytoplasm was only faintly fluorescent and the nuclei and the supporting tissues were nonfluorescent. Confocal laser scanning microscopy resulted in clear pictures of the zymogen granules and their distribution within the cell. The fluorescent emission of zymogen granules was certainly the result of eosin Y staining, because hematoxylin is not a fluorochrome and the zymogen granules are not autofluorescent. Staining with eosin Y alone, however, did not result in clear fluorescent images of zymogen granules or any other cellular structures. Our observation shows that the fluorescence emission of eosin Y allows easy and precise recognition of zymogen granules of pancreatic cells.     

Selective fluorescence of zymogen granules of pancreatic acinar cells stained with hematoxylin and eosin.

Following staining with hematoxylin and eosin Y, paraffin sections of mouse pancreas were examined by transmitted light, epifluorescence and confocal laser scanning microscopy. Light microscopy revealed that the nuclei of pancreatic acinar cells were located basally, while the apices of the cells appeared eosinophilic, although the secretory granules were difficult to visualize. Under violet-blue light excitation, the zymogen granules at the apices of the acinar cells showed strong yellowish fluorescence; the other part of the cytoplasm was only faintly fluorescent and the nuclei and the supporting tissues were nonfluorescent. Confocal laser scanning microscopy resulted in clear pictures of the zymogen granules and their distribution within the cell. The fluorescent emission of zymogen granules was certainly the result of eosin Y staining, because hematoxylin is not a fluorochrome and the zymogen granules are not autofluorescent. Staining with eosin Y alone, however, did not result in clear fluorescent images of zymogen granules or any other cellular structures. Our observation shows that the fluorescence emission of eosin Y allows easy and precise recognition of zymogen granules of pancreatic cells.     

Improvement in the staining and in the visualization of the argyrophilic proteins of the nucleolar organizer region at the optical level

Summary The argyrophilic proteins of the nucleolar organizer region (Ag-NOR proteins) were specifically localized at the optical level with a modified one-step silver technique performed at 20° C.This method was applied to various materials including cells in smears, chromosomes, semi-thin sections of plastic-embedded cells and sections of paraffin-embedded human pathological tissues.In order to improve the visualization of the silver deposits we tested various modes of imaging, including bright-field, Nomarski contrast, reflected light and combined Nomarski contrast with reflected light. The use of Nomarski contrast is useful to define precisely the phases of mitosis. The use of reflected light, which is based on the ability of silver to reflect incident light specifically, gives images with an improved resolution compared to bright-field.     

ELECTRON MICROSCOPE STUDIES OF EPIDERMAL MELANOCYTES, AND THE FINE STRUCTURE OF MELANIN GRANULES

Melanocytes and melanin granules have been studied by electron microscopy in normal human and cat skin, and in hyperplastic human skin lesions. The melanocytes have always been found as free cells within the epidermis,i.e., on the epidermal side of the dermal membrane. Melanocytes frequently rest on the dermal membrane or bulge towards the dermis. In such cases the uninterrupted dermal membrane is uniformly thin and smooth in appearance, in contrast with the regions alongside Malpighian cells, where it appears appreciably thicker and seemingly anchored to the basal cell layer. Two types of melanin granules have been distinguished according to their location in the melanocytes and to morphological characteristics which may only express different stages in the maturation of the granules: (a) light melanin granules in which a structure resembling a fine network is apparent; (b) dense melanin granules which, in osmium-fixed preparations, appear as uniformly dense masses surrounded by a coarsely granular, intensely osmiophilic shell. Treatment of sections of osmium-fixed tissues with potassium permanganate has revealed within the dense granules the existence of an organized framework in the form of a regular, crystalline-like lattice. It is suggested that this basic structure is protein in nature and may include the enzymatic system capable of producing melanin. The existence is reported of fine filaments located in the cytoplasm of melanocytes and morphologically distinct from the tonofilaments found in Malpighian cells.     

Localization of human pancreatic polypeptide in an argyrophilic fourth cell type in islets of the rat pancreas.

An argyrophilic fourth cell type in the rat pancreatic islet can be differentiated from other silver-staining cells by using a modification of the Grimelius aqueous silver nitrate technique. Restaining of the tissues using fluorescent techniques with anti-HPP (Human Pancreatic Polypeptide) serum results in bright fluorescence in the fourth cell type.     

On the ultrastructural localization of noradrenaline in the central nervous system of the rat

Summary Isolated cells were prepared from microdissected pancreatic islets of guinea-pigs. Phase-contrast microscopy of the fresh islet cells suspended in a balanced salt solution displayed a number of cellular details, including cytoplasmic secretion granules. There was morphologic evidence of the survival of islet cells in monolayer cultures for up to 3 weeks. A moderate proliferation of cells occurred during the first 2 weeks after explantation. Different types of islet cells could not be distinguished in the phase-contrast microscope.Research carried out with the financial support of the Swedish Medical Research Council (B 67-12 X-109-03), the Medical Faculty of Uppsala University and the U. S. Public Health Service (Grant AM-05759-05). We thank Assistant Professor Björn Sandström, M. D., for much advice on the tissue-culture method.     

The ultrastructural basis for the identification of cell types in the pancreatic islets I. Guinea pig

Summary The pancreatic islets of the guinea pig have been studied by light and electron microscopy. The B granules in glutaraldehyde-fixed tissue often are cup-shaped with an indentation visible on one side of the granule. Phosphotungstic acid hematoxylin (PTAH) positive cells have been characterized by electron microscopy as three subtypes based on the size of the secretory granules. A_a cells are the most common and have secretory granules around 200 m in diameter. A_b cells have large secretory granules around 300 m in diameter and are relatively infrequent. A_c cells are the least common and have small (160 m) granules. Characteristic D cells are identifiable by electron microscopy and, on the basis of the subsequent study (Munger, Caramia, and Lacy, 1965), are identified as the silver positive cells observed by light microscopy.This investigation was supported in part by United States Public Health Service research grants GM-10102 and GM-03784 from the Institute of General Medical Sciences, and AM-01226 from the Institute of Arthritis and Metabolic Diseases.-The authors wish to acknowledge the valuable technical assistance of Mrs. Aileen Sevier and Mrs. Lidia Donohue.     

Nonconventional innervation of the pancreatic islets of the teleost fish,Gillichthys mirabilis

Summary The innervation of the pancreatic islets of a teleost fish, Gillichthys mirabilis, was investigated with various techniques including axonal iontophoresis of cobalt, light microscopy, and electron microscopy. Two types of postganglionic neurons, the splanchnic and the vagus, innervate the islet parenchyma. The splanchnic fibers originate from the single coeliac ganglion, situated near the third spinal nerve on the right side, and pass caudally to the islet. Postganglionic vagal fibers reaching the islets arise from ganglion cells located at irregular intervals along the vagus nerve.Iontophoresis of cobaltous chloride revealed that both types of nerves send large numbers of fibers to the islet cells. Electron microscopy showed that the granules of the vagal fibers are polymorphic, large (130 mm diameter) and markedly electron dense, whereas the splanchnic granules are smaller (100 nm diameter) and less electron dense than those of the vagus.These granules do not correspond to those seen in postganglionic autonomic neurons of other vertebrates. Rather, they are more like classical neurosecretory granules. Although their chemical nature is unknown, the extent of islet innervation suggests that it must play an important regulatory role.Supported by a grant (AM 17161) from the National Institutes of Health     

Cytological Staining Procedures Applicable to Methacrylate-Embedded Tissues

Experiments indicate that osmic-fixed, plastic-embedded sections are suitable for examination in the light microscope. Nuclei, mitochondia, cellular membranes and cytoplasmic granules are readily demonstrable by phase microscopy. Connective tissue stains permit the identification of elastic and collagenous fibers. Glycogen and other carbohydrate-containing structures are demonstrable by the periodic acid-Schiff and the ammoniacal silver nitrate procedures. It is, therefore, possible to cross-check individual structures by comparing alternate thick and thin sections, examined in the light microscope and electron microscope respectively. Several other advantages pertain to plastic embedded tissues. The sections compare favorably in translucency and in their lack of distortion with material embedded in celloidin, yet the procedure is simpler and much more rapid. Sections of any desired thinness can be prepared, and alternate thick and thin sections are easily forthcoming. When examined in the phase-contrast microscope, mitochondrial preparations become routinely available without the uncertainties of most of the mitochondrial staining methods. It appears, therefore, that plastic embedding should find a useful place among the methods for light microscopy as well as in the armamentarium of the electron microscopist.     

The pancreatic islet system of the mouse (Mus musculus)

Summary The pancreatic islet in the mouse has a highly complex and heterogeneous structure. It contains Aa, Ab, Ac, B, C, D, E, and F cells. The classification of cell types is primarily based on the shape, size and electron opacity of secretory granules and on the spatial relationship of the granules to their unit membranes. Morphological evidence is supported by a statistical analysis of the size distribution of granules and of their membranes. Experimental immunization of mice with insulin, provides additional data to support the existence of eight different cell types in the islet of the normal animal and reveales marked immunological stimulation of B cells, secondary stimulation of Aa, D and F cells, atrophy of Ac cells and hyperplasia of C cells. It is proposed that corresponding cell types exist in other mammals and man. The experimental insulin immunization process appears to perform an immunofunctional analysis of the islet, and suggests that in mice the Aa, D and F cells might be involved in cell energy supply. Lipocaic and some pancreatic factors with insulin-like activity (NSILA) will likely find their morphological equivalents. It is proposed that chemical solubility techniques represent the most promising avenues of approach to the isolation of secretory products from the endocrine pancreas, and that the assay of these extracts should primarily be conducted at the cell level.Dedicated to Prof. Dr. med. W. Masshoff on his 60th birthday.The author is indebted to Dr. med. H. J. Stolpmann for guidance in applying the techniques of electron microscopy and wishes to express his special appreciation to Mrs. Marjanne Hinz for her valuable assistance in completing different aspects of this work and for her competent technical aid.     

New types of islet cells in a cyclostome,Petromyzon marinus L.

Four types of acidophilic granular cells, in addition to B-cells, are identified in the islet organ of anadromous specimens of two subspecies of Petromyzon marinus by light and electron microscopy. Three of these acidophils (PI, PII and PIV-cells) occur in both the cranial and hepatic islets while a fourth type (PIII-cell) has only been found in the hepatic islet of some animals. The granules of the PI-cells stain with ponceau de xylidine, give a distinct tryptophan reaction and in ultrastructural examination show large, dense granules. The PII-cells contain unusual crystals and appear to be a non-secretory stage of the PI. The PIII-cells stain deep-red and acid fuchsin. They contain very large, dense granules and some lysosomes. PIV-cells stain selectively with phosphotungstic acid-hematoxylin and ultrastructurally, contain small, more or less dense granules. It appears that PI- and PIV-cells develop directly from B-cells, while the PIII-cells derive from PI-cells. despite their direct or indirect origin from B-cells, the PI-, PIII- and PIV-cells show characteristic features of functionally independent endocrine cells. Petromyzon marinus may be an ideal model for the understanding of phylogenetic and pathological interrelationships between islet and gastrointestinal hormones. It is clear that the interpretation of the islet organ of the cyclostomes, which has been generally considered a source of insulin only, requires a revaluation.     

Annexin XI may be involved in Ca2+ - or GTP-gammaS-induced insulin secretion in the pancreatic beta-cell

The aim of this study was to investigate possible involvement of annexin XI in the insulin secretory machinery. In fluorescence immunocytochemistry, annexin XI was found in the cytoplasm of pancreatic endocrine cells and a pancreatic beta-cell line, MIN6, in a granular pattern. MIN6 cells also possessed weak and diffused annexin XI immunoreactivity in the cytoplasm. Immunoelectron microscopy revealed annexin XI in the insulin granules. Insulin secretion from streptolysin-O-permeabilized MIN6 cells was inhibited by anti-annexin XI antibody, when the release was stimulated by either Ca2+ or GTP-gammaS, but not by a protein kinase C-activating phorbol ester. Inhibition of insulin release by anti-annexin XI antibody was reproduced in permeabilized rat islets. These findings suggest that annexin XI may be involved in the regulation of insulin secretion from the pancreatic beta-cells.