Histophysiology of the obesity-diabetes syndrome in sand rats.

Insulin, glucagon, somatostatin, and PP cells were found by immunotopochemical and electron-optical techniques in the islets of Langerhans of the sand rat, proving that the islets in this species also contain the four basic cell types known to be found in the islets in mammals in general. The ratio of A cells to B cells was 1:4 (19.1% A cells to 80.9% B cells). The pancreas of the sand rat contained assemblages of various numbers of neurons in the intralobal and interlobular connective tissue. They did not seem related in any regular fashion to specific blood vessels or branches of the pancreatic ducts. No bundles of nerve fibers were found by either light or electron microscopy. Nonmyelinated nerve fibers were detected by electron microscopy in the stroma of the islets. In the sand rat the neuroinsular complexes are formed by the penetration of single nerve cells into the pancreatic islets. In the NH or long-term group the islets exhibited signs of stimulation. The number of islets was higher than normal (polynesia), with the islets themselves enlarged (macronesia). Double islets in the secretory ducts of the exocrine pancreas were frequent. The increase in islet size was due to hyperplasia of the B cells. The numbers of beta-granules in the B cells varied considerably. Glycogen was demonstrated in some islets. The fusion of beta-granules was shown in electron microscopic pictures. The electron-opaque centers of these granules were brighter than the others and appeared to have partly dissolved. The organelles of the B cells (ER, Golgi apparatus, and mitochondria) were well developed, this also being a sign of cell stimulation. No changes were observed in the B and PP cells. Stimulation of the islet cells was even more pronounced in the diabetic group. Due to hyperplasia, the islets in this group were significantly larger not only than those in the control group, but also than those in the NH group. The pancreata of this group of sand rats contained numerous small islets. Although necrotic B cells were found in the large islets of the pancreas, none were discovered in the small islets. The small islets were considered to be "regenerated" islets. Granulation was slight in the remaining functioning B cells. The hypophyses of the control group contained the GH, LTH, FSH, LH, and TSH cell types typical of this organ in other species. In the sand rat the granules of these cell types are of about the same size as has been stated for other rodents.(ABSTRACT TRUNCATED AT 400 WORDS)

Presence and regulation of a truncated proopiomelanocortin gene transcript in rat pancreatic islets.

The demonstration of proopiomelanocortin-(POMC-) derived peptides in the endocrine pancreas suggests a local biosynthesis of these peptides. Using Northern blot analysis we demonstrated a 800 nucleotide POMC-like mRNA species. The POMC-like mRNA was demonstrable in a part of the pancreatic islets by the in situ hybridization technique. A small number of single cells within the exocrine pancreas were also found to give positive hybridization signals. Isolated islets were incubated under normoglycemic conditions with dibutyryl-cAMP (3mM) or dexamethasone (0.1mM) for 4 h. Dibutyryl-cAMP significantly (p < 0.01) increased the POMC-like mRNA content to 177 +/- 39.1% of the control whereas dexamethasone decreased it to 66.9 +/- 11.4% of the control. In vivo treatment of adult rats with 80 micrograms dexamethasone over 3 days showed also a reduction of the POMC-like mRNA level in the islets. In conclusions, the POMC gene is expressed in adult rat islets and can be regulated by dexamethasone and dibutyryl-cAMP. Whether the truncated POMC-like mRNA reported here is the source of the biosynthetic POMC-like products detected in the islets is not yet known.

Subcutaneous glucose monitoring by means of electrochemical sensors: fiction or reality?

Amperometric glucose oxidase/hydrogen peroxide sensors were inserted subcutaneously into the neck of normal and diabetic dogs (n = 10), to elucidate the conditions for stable long-term functioning. Their output current was observed in parallel with measurements of plasma glucose concentrations and their function was checked by means of induced alterations in glycaemia. After between 14 and 96 h the experiments were terminated due to losses in the apparent sensitivity of implanted sensors and/or increasing oscillations following stable measurements. This was accompanied by an inflammatory reaction which was analysed on the basis of the clinical picture and histology. In most cases there was a bacterial ingrowth from the normal skin flora of dogs. The inflammatory exsudate contained only 23 +/- 17% of the simultaneous steady state plasma glucose concentration, which was significantly different from the glucose level in the fluid obtained from non-irritate subcutaneous tissue (95 +/- 12%, separate set of experiments). The in vitro calibration of sensors exhibited essentially comparable sensitivities before and after the in vivo application. No differences in reported findings related to the biomaterials used (polyurethane versus cellulose acetate), the presence of diabetes, the history of individual electrodes and the effective duration of a given experiment were discernible. We conclude that the functional bioinstability of subcutaneous glucose sensors is largely due to the inflammatory tissue reaction which alters the effective glucose concentration within the measuring compartment of the electrodes; these drawbacks may be overcome by further miniaturization including implantable telemetric devices allowing the closure of the skin.

[Quantitative histologic studies of the gonads of sand rats (Psammomys obesus) during the development of diabetes mellitus]. / Quantitativ-histologische Untersuchungen an Gonaden von Sandratten (Psammomys obesus) während der Ausbildung eines Diabetes mellitus.

Quantitative-histological investigations (point counting method) are pointed out in 27 male and 15 female sand rats. The animals are divided in the IGT (impaired glucose tolerance), the diabetic and the control group. The LEYDIG cells are in the IGT-group increased, and in the diabetic group decreased. The female sand rats are characterized by the tendency of increase of size and number of follicles in the IGT-group. Corpora lutea are reduced but atretic follicles are increased in the diabetic group. The ovaries are greater in diabetic sand rats.

[Hyperinsulinemia and B-cell proliferation in rats treated postnatally with L-glutamate]. / Hyperinsulinämie und B-Zellproliferation in postnatal mit L-Glutamat behandelten Ratten.

Development of hyperinsulinemia was investigated which appeared late in the obese state in rats postnatally treated with L-glutamate. Insulin concentrations were estimated in the blood plasma of the caval and portal vein, and morphometric and immunohistochemical measurements of cells in the islets of Langerhans were performed, and also glucose tolerance tests. Not earlier than at 3 months hyperinsulinemia is shown in glutamate obese rats (GOR) in the peripheral blood plasma. Also in the portal blood plasma the insulin concentration is higher (167%) in GOR relative to controls. The insulin concentrations in the portal vein rise further in both animal groups whereas insulin concentration in the peripheral blood remains at the different levels in both animal groups. Impaired glucose tolerance was observed for GOR only. Islets of Langerhans in the Pancreas show enlargement and increased proliferation of B-cells in GOR. In contrast the number of D-cells is diminished. The hyperplasia of islets differs remarkably to hypoplasia of other organs in GOR. We conclude that the peripheral hyperinsulinemia is caused by a permanent hypersecretion of insulin.

Immunocytes in the human fetal pancreas--a contribution to developmental immunoendocrinology concerning diabetes mellitus and organ cultivation.

The studies were performed on 103 samples of human fetal pancreas tissue (10th to 26th week of gestation). Of the mothers, 14 had insulin dependent type I diabetes mellitus (IDDM), and 33 of the samples were examined before and after cultivation for 14 days. 3 samples taken from fetuses in the 14th week of development (mothers without metabolic disorders) were examined in the electron microscope. Lymphocytes are generally irregularly distributed within the tissue. Groups of 3 to 5 lymphocytes are found in addition in the 12th week of development, and larger clusters (10 to 15 lymphocytes) appear from the 14th week onward. Relating these quantitative results to the 3 phases of early fetal islet organ development, it can be seen that lymphocyte numbers increase from the 10th to the 26th week of development. The significance of this is discussed in connection with the development of the immune system. In view of the contemplated transplantation of fetal pancreas tissue as treatment for IDDM, it means that a relatively low immunogenicity can be expected up to the 14th week of development. Thymic differentiation is not complete before the 17th week, and differentiation of the lymph nodes and spleen continues until weeks 20 to 23. Although IgG antibodies are transferred across the placental barrier already in about the 8th week, this flux does not reach its maximum until the 32nd week. Endogenous antibody synthesis in the fetus does not start until the 18th week. IDDM of the mother during fetal development (10th to 26th week) does not increase the lymphocyte number in the pancreas. This also applies to tissue that has been cultivated for 14 days after reaching the same stage of development.

Immunohistochemical, morphometric, and ultrastructural investigations of the early development of insulin, somatostatin, glucagon, and PP cells in foetal human pancreas.

Fresh autopsy specimens of pancreas, taken from 18 human foetuses at the 10th (n = 4), 12th (n = 7), and 14th (n = 7) weeks of gestation, were analyzed immunohistochemically for the presence of islet parenchymal cells, immunoreactive with antisera raised against insulin (B cells), somatostatin (D cells), glucagon (A cells), and pancreatic polypeptide (PP cells). All four islet cell types were found sporadically within or near the epithelium of the small excretory ducts at the 10th week of development. At the 12th week, their presence appeared to be no longer restricted to the duct epithelium, as some B cells were found also in small clusters outside the ducts. At the 14th week of development, the B cells formed large clusters in the neighborhood of the excretory ducts. It is at this stage that the first parenchymal cells with Grimelius argyrophilia could be found. They were supposed to represent A cells. The B cells were found to be the predominating type of islet cells (about 50%) at the 10th week of gestation. The relative volume density was about 25% for the D cells, about 15% for the A cells, and about 10% for the PP cells. At the 12th and 14th weeks of development, the relative numbers of B and PP cells decreased somewhat (to 36 and 6%, respectively), whereas those of the D and A cells were found to increase (to 30 and 27%, respectively). The relative volume density of the total islet parenchyma was about 2, 6, and 21% at the 10th, 12th, and 14th weeks of development, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Streptozotocin diabetes in spontaneously hypertensive rats.

The aim of our experiments was to find out to what extent male spontaneously hypertensive (SH) as well as normotensive Wistar-Kyoto (WKY) and Wistar-Schönerlinde (WS) rats developed changes of the endocrine pancreas function in response to streptozotocin (SR). 4 week old WS, WKY and SH rats were given ip. injections of 70 or 100 mg SR/kg and were killed at an age of 8 weeks, after which blood glucose, and in isolated islets, insulin-leakage, insulin secretion and insulin biosynthesis were determined; histologically the relative volume density of islet tissue was estimated. The results demonstrated that the intensity of the SR-caused damage to the endocrine pancreas differs considerably in the three strains of rats. The damage increases in the order WS, WKY, SH rats. These findings are indicative of the role played by genetic predisposition and of an increase in damage to the endocrine pancreas due to hypertension.

Syngeneic transplantation of thyroid tissue encapsulated in a cellulose sulphate membrane.

A new, simple encapsulation method, the precipitation of a polyelectrolyte complex membrane of cellulose sulphate and poly(dimethyldiallylammoniumchloride) was investigated in syngeneic thyroid transplantation. Half a thyroid gland was placed beneath the kidney capsule either after being encapsulated or as a non-encapsulated control graft. In normo-thyroid as well as hypothyroid recipients, the grafted tissue was viable for up to 12 weeks. Furthermore, the hypothyroid state, which was characterized by a markedly diminished 125iodine incorporation into the thyroid, no body weight gain and undetectable serum thyroxin concentrations, was compensated by the grafted tissue. The encapsulated grafts showed lower iodine incorporation, T4 secretion and body weight gain when compared with non-encapsulated control grafts. This may be due to a partial restriction of TSH by the capsule membrane. It was concluded that the cellulose sulphate membrane is biocompatible and enables the functional survival of syngeneic grafted tissue.

Phases in the early development of the human islet organ.

The study included morphometric examination and biochemical investigation of 41 human pancreata taken from 14th to 26th weeks of fetal development. 3 phases of development were observed. Phase I (weeks 14 to 16) is characterized by the presence of mainly islet buds. They were originated from the ducts and are vascularized during week 16. During phase II (17th to 20th weeks) the islet buds were detached from the ducts and they formed new mantled islets with the B cells in the centre. Non-B cells are situated on the periphery around the insulin producing cells. Phase III lasts from week 21 to week 26. During this phase B cells and non-B cells become more irregularly positioned within the islet, a cytology, which is similar approximating that of as also found in adult human islets. The changes of islet structure during pancreatic development are accompanied by other typical phenomena: Islet size increases during phases I and II, but decreases again during phase III. The proportion of isolated B cells outside of the islets varies during this stage of fetal development, but they generally account for about 15% of the total islet organ. This should be taken into account when assessing the islet function De Pablo et al. (1985) on a morphological basis.

Assessment of subcutaneous glucose concentration: validation of the wick technique as a reference for implanted electrochemical sensors in normal and diabetic dogs.

Employing saline-impregnated cotton threads, an implanted-wick technique was adopted in dogs to obtain specimen from the subcutaneous interstitial compartment in order to estimate its glucose concentration. By measuring the protein, potassium and haemoglobin contents, the centrifuged wick fluid was shown to contain the interstitial concentration of solutes after an equilibration time of approximately 15 min. In normal and in diabetic animals the steady state subcutaneous glucose concentration was almost identical to the circulating glucose level when ranged between 2 and 25 mmol/l. Slow alterations in the circulating glucose profile such as those which appear during an oral glucose tolerance test are closely mirrored by the respective levels in the wick fluid. Fast alterations, however, show deviations. The wick-based glucose levels are well paralleled by the current of Clark type glucose oxidase sensors implanted at the same site. Since, on the basis of in vitro calibrations the sensor outputs have only indicated apparent tissue glucose concentrations of between 70 and 90% of glycaemia, another reference is needed for calibration. Under steady state conditions, the wick method, and on this basis in routine measurements the blood glucose concentration, may be recommended as a reference of implanted sensors which can otherwise not be calibrated in situ.

Pancreatic endocrine tumours: histological, immuncytochemical and electronmicroscopical investigations.

Fifteen endocrine pancreatic tumours (8 insulinomas, 3 gastrinomas, 1 vipoma, 3 tumours without hormonal activity) and two cases with dysplasia of the endocrine pancreas are reported. Immunohistochemical and electronmicroscopical investigations produced evidence of multihormonality in adenomas that clinically appeared to be monohormonal. The S-phase fraction of such tumours is below 1% which indicates their low proliferative potential. The malignancy of endocrine pancreatic tumours cannot be seen from cytochemical or histological symptoms; it can be established with certainty only from the presence of metastases. Multiple endocrine adenomas should suggest the possibility of hereditary endocrine polyadenomatosis. Hyperplasia and distribution disorder of the endocrine tissue as well as pathologically increased nesidioblastic activity represent the morphologic substrate of dysplasia of the endocrine pancreas as a potential cause of hyperinsulinaemic hypoglycaemia in infancy.

Dietary effects on (pro)insulin biosynthesis and insulin-degrading activity in islets from sand rats.

Sand rats were fed either a vegetable (vegetable group) or a standard pellet diet. After 14-16 weeks, the normoglycemic subgroup selected (pellet group) from the animals that had been maintained on the standard diet showed a modest increase in body weight. Plasma immunoreactive insulin levels were not significantly increased, but glucose-stimulated insulin release was elevated from islets isolated from sand rats of the pellet group. Insulin biosynthesis was estimated in vitro by measuring [3H]leucine incorporation into (pro)insulin at 1.5 or 15 mmol/l glucose. The rate of (pro)insulin biosynthesis was elevated only at 15 mmol/l glucose in islets from those normoglycemic sand rats fed the pellet diet when compared with islets from the vegetable group. Specific insulin-degrading activity, as determined by measuring degradation of 125I-labeled insulin, was also increased for islets from the pellet group. The metabolic state of these sand rats is thus associated with normoglycemia in vivo, and increased stimulated rates of insulin biosynthesis and degradation in pancreatic islets in vitro.

[Heavy metals in the mammalian body with special reference to zinc and its methods of detection]. / Schwermetalle im Säugetierorganismus unter besonderer Berücksichtigung des Zinks und seiner Nachweismethoden.

In this study the presence of heavy metals in mammals with special regard of the zinc have been investigated. The methods of the detection of zinc were described too. The current methods for investigating heavy metals ( dithizon -, sulfid -silver- and fluorescence-method) are compared. The use of these methods is discussed. The occurrence of the heavy metals in tissues of various species is demonstrated. Metabolic functions of heavy metals are explained. The important role of zinc-ions in the storage of hormones and other substances as well as the importance of cobaltous-ions for the degranulation of mast cells are referred too.