Langerhans In Mice Research Articles

Virus-induced diabetes mellitus. XX. Polyendocrinopathy and autoimmunity.

Mice infected with reovirus type 1 developed transient diabetes and a runting syndrome. The diabetes was characterized by hyperglycemia, abnormal glucose tolerance tests, and hypoinsulinemia. Inflammatory cells and viral antigens were found in the islets of Langerhans, and virus particles were seen in alpha, beta, and delta cells. The runting syndrome consisted of retarded growth, oily hair, alopecia, and steatorrhea. Inflammatory cells and viral antigens were found in the anterior, but not posterior pituitary. Electron microscopy revealed virus particles in growth hormone (GH)-producing cells and radioimmunoassay showed that the concentration of GH in the blood was decreased. Examination of sera from infected mice revealed autoantibodies that, by immunofluorescence, reacted with cytoplasmic antigens in the islets of Langerhans, anterior pituitary, and gastric mucosa of uninfected mice. Absorption studies and enzyme-linked immunosorbent assays designed to identify the reactive antigens showed that some of the autoantibodies were directed against insulin and others against GH. Reovirus type 3, in contrast to reovirus type 1, did not induce autoantibodies to GH. By use of recombinant viruses, the segment of the reovirus genome responsible for the induction of autoantibodies to GH was identified. Virus containing the S1 gene segment from reovirus type 1, which codes for the sigma 1 polypeptide (i.e., hemagglutinin), infected cells in the anterior pituitary and induced autoantibodies to GH, whereas virus containing the S1 gene segment from reovirus type 3 failed to infect cells in the anterior pituitary and did not induce autoantibodies to GH. We conclude that reovirus type 1 infection can lead to polyendocrinopathy and autoimmunity and that the S1 gene segment is required for the induction of autoantibodies to GH.

Biochemical and ultrastructural changes in A and B cells of the islets of Langerhans of mice infected with EMC virus

Infection of DBA2 mice with the M strain of EMC virus was used to study the effects of virusinduced diabetes on the A and B cells of the islets of Langerhans. A transient hypoglycaemia was seen in 48% of mice 2–3 days after infection and probably resulted from increased serum insulin concentrations together with inhibition of glucagon secretion at that time. Islets from hypoglycaemic mice showed no significant alterations from control level in basal or fluoride-stimulated adenylate cyclase activity. Overall, 70% of infected mice became hyperglycaemic with a maximum incidence 6 days after infection. Hyperglycaemia was accompanied by a dramatic reduction in the total pancreatic insulin content and in insulin secretory responses to glucose and theophylline, while A-cell structure and function appeared relatively unaffected in diabetic animals. Basal adenylate cyclase activity was increased in hyperglycaemic mice at 7 days after infection, while fluoride-stimulated adenylate cyclase activity was normal throughout the course of infection. Ultrastructural alterations were observed in a small proportion of B cells from two days after infection and included abnormalities of mitochondrial structure and increased electron opacity of the cytoplasm of affected cells, which subsequently led to complete necrosis. The results suggest that EMC virus specifically affects the B cells of the islets and that disturbances of A cell function may be secondary to B cell damage.

Alteration of Islet Cell Populations in Spontaneously Diabetic Mice

Endocrine-cell populations in the islets of Langerhans of mutant mice with a severe hypoinsulinemic diabetes (ob/ob or db/db on the C57BL/KsJ background) or with a mild hyperinsulinemic diabetes (ob/ob or db/db on the C57BL/6J background) were studied quantitatively by immunofluorescence and morphometry. In severely diabetic mice, islets presented a reduced proportion of insulin containing cells but increased glucagon-, somatostatin-, and pancreatic polypeptide (PP)-containing cells, as compared with islets of control (+/+) mice. An inverse change was observed in islets of mildly diabetic mice: islets were hypertrophic and composed mostly of insulin-containing cells, with decreased proportions of glucagon-, somatostatin-, and PP-containing cells. In both types of diabetic syndromes, the changes in cell populations induced a qualitative alteration of cellular interrelationships in the affected islets.

Enzymehistochemical studies on the pancreatic islets in mice injected with anti-insulin serum.

Islets of Langerhans in white mice with a diabetic syndrome after single and repeated injections of anti-insulin serum were studied by enzymehistochemical methods and compared with controls. Changes in activity of some enzymes were noted in the islet area in accordance with the histopathological findings of severe degranulation and hypersecretory changes of the beta cells. — The α-glycerophosphate oxidase (GPOX) showed the most sensitive and severe decrease of activity whereas the acid phosphatase (ACPase) was only slightly decreased. Compared with the enzyme activity in normal mice, no significant changes of glucose-6-phosphate dehydrogenase (G-6-PD) could be observed. The only enzyme showing an increased activity was the glucose-6-phosphatase (G-6-Pase). The studies of the cytochrome oxidase (CCOX), lactic dehydrogenase (LDH), succinic dehydrogenase (SDH), acid phosphatase (ACPase), alkaline phosphatase (APase) and adenosine triphosphatase (ATPase) revealed no alterations of the enzyme patterns under these experimental conditions. The findings are discussed with regard to the hypothetical relations between the pentose phosphate shunt (indicator enzyme: G-6-PD), the glycerophosphate cycle (indicator enzyme: GPOX) and the phosphorylation of glucose (indicator enzyme: G-6-Pase) to insulin synthesis and release.

Ultrastructural studies of the hyperplastic islets of Langerhans of spiny mice (Acomys cahirinus) before and during the development of hyperglycemia.

Acomys Cahirinus, the spiny mouse, is a small rodent living in the semi-desertic areas of the Eastern Mediterranean. The observation that diabetes may occur spontaneously in this species, at least under laboratory conditions, has led to its breeding at the Institut de Biochimie Clinique, where a colony has been maintained over the last 3 years. Diabetes occurs in approximately 15% of the animals reaching one year of age; some of these are obese, but not all. Diabetes occurs in the presence of, and despite a striking hyperplasia of the endocrine pancreas, which may make up as much as 15% of the total organ in adult mice. This hyperplasia is present in all animals, whether hyperglycemic or not. — The islets of Langerhans of 22 spiny mice have been examined with the electron microscope and form the basis for an analysis of the different cell types observed, at different times relative to the onset of diabetes. Findings in the B cells of this species have included the generally high degree of development of the Golgi complex, the great variability of glycogen accumulation in diabetic animals, the frequent fusion of the granular sacs, and the occurrence of grossly hyper-granulated cells. — The hyperplasia of the islets of Langerhans in spiny mice is associated with a remarkable cellular polymorphism. However, the authors do not feel that this is the result of the presence in these islets of many distinct cell types. It would seem much more likely, that they represent different functional states of a small number of distinct types of cells, among which only A, B and perhaps D cells have been securely identified. Another feature of this cellular polymorphism is thefrequent presence of mixed or intermediate cells (exocrine-endocrine, or endocrine A-B), which suggests that the stimulation leading to hyperplasia of the endocrine cells in this species might result in the removal of some part of the nuclear inhibition usually associated with fully differentiated cells.

Effect of tolbutamide on postnatal neogenesis of the islet of Langerhans in mouse.

Tolbutamide stimulates postnatal neogenesis of the islets of Langerhans as demonstrated by enumeration of the islets, in vivo studies and radioautography. This drug first causes transient dilatation of insular vessels and rapid blood flow, followed by de granulation of the beta cells. Reappearance of granules, proliferation of the small pancreatic ducts, formation of new islets and an increased number of small islets occur during chronic administration of tolbutamide. The implications of these findings for the management of juvenile diabetes are discussed.

Obesity and diabetes mellitus with striking congenital hyperplasia of the islets of langerhans in spiny mice (Acomys Cahirinus)

Spiny mice (Acomys) are a group of small rodents indigenous to the Eastern Mediterranean and Africa. The Acomys Cahirinus strain reported on here is indigenous to Israel. The strain is characterized by striking and congenital hyperplasia of the islets of Langerhans, primarily of the beta cells. The endocrine tissue contributes up to 15 per cent of the pancreatic mass in adults, up to 25 per cent in the newborn. Pancreatic insulin content may be as high as 100 units per gram wet weight. When fedad libitum in the laboratory approximately one-half of the animals become obese, while approximately 15 per cent develop a diabetes mellitus-like state with moderate hyperglycemia, glucosuria, and, less frequently, ketonuria accompanied by weight loss and, ultimately, death. The development of the diabetic state is associated with degranulation and, later, striking glycogenic degeneration of the beta cells of the islets of Langerhans. There is also severe glycogenic nephrosis and myocardosis and preliminary observations suggest the presence of thickening of the capillary basement membrane of the renal glomeruli and in the endocrine pancreas. The interrelationships of hyperplasia of the islets of Langerhans, obesity, and diabetes mellitus are as yet to be established, as are the genetic characteristics of each of these entities. An important area of potential usefulness derives from the degree of the hyperplasia of the endocrine tissue, since this should greatly facilitate ultrastructural studies, microdissection and transplantation, as well as organ or tissue culture work. Also, the association of anomalies observed in these spiny mice may, through their systematic study, provide clues for the study of the association of diabetes and obesity with relative hyperinsulinism in man.

The ultrastructure of the islets of Langerhans in normal and obesehyperglycemic mice.

The islets of Langerhans in normal and obese-hyperglycemic mice were studied by electron microscopy. Two different types of islet cells with ultrastructural features well distinguished from the majority of B cells were observed. While one of them was provided with complete cell membranes, the other appeared to be arranged in a syncytium. It was postulated that these islet cells may be identified with the argyrophil A1 cells and the non argyrophil A2 cells demonstrated in different species with light microscopy. In the normal mouse the fine structure of the islet B cells corresponds in the main to what has been observed previously in the rat. However, in addition to the great majority of spherical B cell granules some appear rectangular, i.e. show similar morphological characteristics as described for the granules in the dog. The long termada ptation of the B cells to increased functional demands in the obese-hyperglycemic syndrome was associated with a pronounced degranulation with margination of the granules and with obvious changes of some organelles. The mechanisms for formation and liberation of insulin from the B cells are discussed in the light of the ultrastructural appearance of these cells in the obese-hyperglycemic mice.

HISTOCHEMICAL STUDIES ON GLUCOSE-6-PHOSPHATASE, ADENOSINE TRIPHOSPHATASE AND AMYLO PHOSPHORYLASE IN THE PANCREATIC ISLETS OF NORMAL AND OBESE-HYPERGLYCAEMIC MICE

ABSTRACT Histochemical methods for the detection of glucose-6-phosphatase (G-6-Pase), adenosine triphosphatase (ATPase) and amylo phosphorylase were applied to the islets of Langerhans in mice with hereditary obesity and hyperglycaemia (AO-mice) and in their lean litter mates (AN-mice). While the G-6-Pase activity was high in the hyperactive B cells of the AO-mice, it was only moderate in the AN-mice. In both types of mice ATP-hydrolyzing enzymes were observed in the islet capillaries and periinsular connective tissue, while the reaction in the islet cells was negative. From a study of the substrate specificity it was found that the enzyme activity was not dependent on specific ATPase, but probably mainly on less specific polyphosphatases. The reaction for amylo phosphorylase was negative in the islets of both the AN- and the AO-mice. The high G-6-Pase activity in the islets of the AO-mice is discussed in the light of the hypothesis that the activity of this enzyme represents an essential controlling factor in the insulin output of the B-cells.

Histochemical observations on the pancreatic islets in normal and obese-hyperglycemic mice

In the islets of Langerhans in mice with the American variety of the obese-hyperglycemic syndrome (AO) and their thin litter mates (AN) the following observations were made: 1. In cryostat sections of fresh pancreatic tissue from AN-mice, both more centrally situated islet cells with yellowish white granules, and peripherally situated cells with brighter silver white granules were found with dark field microscopy. While the central cells were considerably degranulated in the AO-mice, the peripheral cells were also well filled with granules in these animals. The technique described offers, especially in the AO-mice, better possibilities of differentiation of the islet cells than with the granule staining methods of fixed pancreatic material, which are now generally used. 2. After intravenous injection of dithizone, abundant orange yellow zinc dithizonate granules were found in all islet cells with dark field microscopy of cryostat sections from fresh pancreatic tissue of AN-mice. By dissolving out these granules, the zinc content could be related to the different types of islet cells. It was possible in this way to show that the zinc in the islets of the AO-mice was mainly situated in the peripheral cells, containing the silver white granulation typical of untreated animals in dark field. The occurrence of a lower zinc content in the centrally situated islet cells in the AO-mice was also evident from the so-called “sulphide-silver method”. 3. A positive islet reaction to both acid and alkaline phosphatases was obtained in the AN-mice. The alkaline phosphatase activity was high in the peripheral parts of the islets of AN-mice, but much lower in the AO-mice. While the majority of islet capillaries were strongly positive as regards alkaline phosphatases in the AN-mice, in the AO-mice they were for the most part completely negative. 4. In spite of the existence of a prolonged hyperglycemia, no storage of glycogen could be demonstrated in the islets of the AO-mice. With fluorescence microscopy, the occurrence of masked lipids in the islets was observed in the AN-mice, and to an even higher degree in the AO-mice. On the other hand the sudanophilic reaction was negative throughout. The raised functional activity in the islet B-cells of the AO-mice was reflected in an enlargement and fragmentation of the Golgi apparatus.