[Insulinotropic factors in health and disease]. / Insulinotropnye faktory v norme i pri patologii.

Reviews in brief the studies of the effects of some non-glucose regulators of various origins on pancreatic insulin secretion mediated by endocrine, paracrine, and neurocrine mechanisms, carried out in this laboratory. Model experiments with primary monolayer cultures of isolated islet cells have helped demonstrate a direct insulinotropic effect of STH, TRH, C-terminal tetrapeptide cholecystokinin, opioid peptides and blood plasma of patients with insulin-dependent diabetes mellitus. The findings evidence that the insulinotropic effect of the blood serum of patients with type I diabetes may be associated with both stimulation and suppression of the functional activity of the cultivated islet cells. This latter type of effect influences the basal and glucose-stimulated secretion of insulin. The destructive effect of the plasma of patients with insulin-dependent diabetes on the function of islet cell culture is confirmed by the presence of autoantibodies to islet cell surface antigens in the plasma of 53-55% of the examined patients and by a cytotoxic effect in 45% of cases.

[Hypoinsulinemia, hyperglycemia and circulating antibodies to the islet cells during the development of streptozotocin diabetes in rats]. / Gipoinsulinemiia, giperglikemiia i tsirkuliruiushchie antitela k ostrovkovym kletkam pri razvitii streptozototsinovogo diabeta u krys.

The time course of metabolic parameters and islet cell surface antibodies (ICSA) in low-dose streptozotocin (STZ)-induced diabetes in rats was studied, a total STZ dose being 160 mg/kg body weight. Two-phase diabetes development was observed. Initial mild hypoinsulinemia and hyperglycemia turned to more severe diabetes after day 24 which was preceded by the first ICSA peak at day 13. The second ICSA peak occurred at day 35. The data obtained suggest that in this model of diabetes the toxic STZ effect induces both the diabetic syndrome and humoral autoimmunity to beta-cells, and the latter leads to further impairment of diabetes.

Islet cell transplantation in type I diabetes mellitus: evaluation of humoral immune response.

Four males and three females ranging in age from 20 to 35 years and afflicted with complicated Type 1-diabetes for more than 8 years underwent islet cell allotransplantation (ATx, 6 cases) and xenotransplantation (XTx, 1 case). Precultured islet cells derived from human or bovine fetal pancreata were injected into the m. rectus abdominis. Immunosuppression was not applied. Plasma C-peptide and islet cell surface antibodies (ICSA) were continually measured both before and until the twentienth week following islet cell transplantation. All recipients were subdivided as "responsive" (RR, 3 males) or "non-responsive" (NRR, 1 male and 3 females), according to the dynamics of their ICSA levels. All 3 RR (1XTx and 2 ATx) showed a peak of ICSA two weeks after cell injection. Subsequent ICSA levels had the tendency to either diminish or increase. Heterogeneity of preoperative antibody level, especially in NRR, was also observed. No associations between ICSA and ATx or XTx, age at diabetes onset, or duration of the disease was found. Only one RR with XTx had a reduced daily insulin requirement and a significant C-peptide response similar to the dynamics of ICSA levels. A greater mass of available bovine islet cells might be responsible for this effect.

The effects of sera obtained from children with insulin-dependent diabetes mellitus on cultivated islet cells: cytotoxicity and insulin release.

Sera were obtained from 24 patients with newly-diagnosed insulin-dependent diabetes mellitus (IDDM) and 14 children with a high risk of diabetes. The influence of the decomplementated sera on basal and stimulated insulin secretion was studied in a mixed culture of newborn rat islet cells. In addition, complement-dependent antibody-mediated cytotoxicity (C'AMC) was measured by 51Cr-release from pre-labelled islet cells. Incubation of the islet cells with sera from ten IDDM patients did not affect the basal insulin release. Sera from other children with IDDM (n = 14) either significantly increased (n = 7) or inhibited (n = 7) basal IRI secretion was compared with the sera of control donors. Nearly half of the sera from the high-risk children was found to be insulin-stimulating. Preincubation of islet cells with sera from IDDM children caused a significant decrease of insulin response to 16.5 mM glucose plus 5 mM theophylline (P less than 0.001). Sera from the high-risk children did influence the response of pancreatic cells to secretagogues. C'AMC was found in 45% of the patients with IDDM and in 33% of the high-risk children, however, there was no correlation between C'AMC and serum effect upon basal insulin secretion. These results suggest the presence of B-cytotropic factors in serum from children with IDDM or with a risk of diabetes. Opposite effects of different sera on insulin secretion may reflect the variety of pathogenetic mechanisms involved in islet cell destruction.

[Mechanisms of the regulation of insulin secretion]. / Mekhanizmy reguliatsii sekretsii insulina.

The endocrine, paracrine, and neurocrine influences of the non-glucose insulin secretion regulators on the pancreatic islets are analysed. Experiments on rats using the primary monolayer culture of isolated islet cells proved that insulin secretion is directly modulated by the growth hormone (GH), C-terminal tetrapeptide of cholecystokinin, thyroliberin, and met-enkephalin, and by certain blood plasma factors of diabetes I patients. In addition, GH is showed to stimulate the islet cell proliferation by intensifying 3H-thymidine incorporation into DNA synthesis. The blood plasma factors of IdDM patients influence the islets of Langerhans activity by either stimulating or depressing the secretory function of insulin producing cells. The aspects of functional organization of the islet cells and complex regulation of insulin secretion are discussed.

[Simulation of diabetes mellitus in rats: Latent and manifest forms]. / Modelirovanie sakharnogo diabeta u krys: Latentnaia i manifestnaia formy.

The paper is concerned with the investigation of problems of the etiology and pathogenesis of diabetes mellitus and simulation of this disease in animals in order to study its preclinical stages. Experiments were performed on adult male rats using i.v. GTT, a radioimmunoassay for determination of blood insulin, immunoenzymatic detection of autoantibodies to pancreatic islet cell surface, and determination of complement dependent cytotoxicity. Fractionated intraperitoneal administration of subdiabetic doses of streptozocin was shown to cause the destruction of the insular apparatus in rats with the involvement of the immune system. Five injections of B-cytotoxin (40 mg/kg) caused the development of manifest diabetes mellitus, two injections led to a decrease in function of the insular apparatus and the appearance of autoantibodies to the surface of islet cells with cytotoxic features. Problems of the pathogenetic role of factors of humoral immunity in the development of type I diabetes mellitus are under discussion.

[Effect of fibroblast growth factor and nerve growth factor on the cellular proliferation and functional activity of isolated islands of Langerhans]. / Vliianie faktora rosta fibroblastov i nervnogo rostovogo faktora na proliferatsiiu i funktsional'nuiu aktivnost' kletok izolirovannykh ostrovkov Langergansa.

The effects of fibroblast growth factor (FGF) and nerve growth factor (NGF) on DNA synthesis and insulin secretion were studied in 4-5-day cultures of the isolated neonatal rat islets. FGF (0.1 ng/ml) stimulated significantly the incorporation of 3H-thymidine into DNA of the isolated islets, but failed to change either insulin content in the islets or the rate of insulin secretion. NGF (0.1-1000 ng/ml) did not affect the above parameters. The responses of the islets of Langerhans to increasing concentrations of glucose and isobutylmethylxanthine were not modified after prolonged exposure to NGF. The role of FGF and NGF in the regulation of proliferation and secretory process in pancreatic islet cells is discussed.

[Immunoenzyme detection of autoantibodies to the surface of pancreatic islet cells in diabetes mellitus and in increased risk of its development]. / Immunofermentnoe vyiavlenie autoantitel k poverkhnosti ostrovkovykh kletok podzheludochnoi zhelezy pri sakharnom diabete i pri povyshennom riske ego razvitiia.

The authors described the use of an enzyme-linked immunosorbent assay to determine islet cell surface antibodies (ICSA) in persons at high risk of developing insulin dependent diabetes (IDD) and different types of manifest disease. Among I degree healthy relatives of probands with IDD antibodies were detected in 16%. In disorder of the oral GTT (a small group) ICSA were found in 57% of examinees. In the group of IDD patients which was heterogeneous in duration of disease and age at its onset, the frequency of ICSA was 38%. The least frequency (10%) of antibodies was observed in patients with non-insulin dependent (NIDD) compensated by a diet and oral hypoglycaemic drugs. Among non-compensated NIDD patients 62% were ICSA-positive. Thus, ICSA determined by the enzyme-linked immunosorbent assay, could be employed as a marker of autoimmune damage of the insular apparatus for prognosis of the development of "primary" and "secondary" insulin dependence.

[Effect of nutrient medium perfusion on the secretory activity of rat hepatocytes and pancreatic islet cells]. / Vliianie perfuzii pitatel'noi sredoi na sekretornuiu aktivnost' gepatotsitov i ostrovkovykh kletok podzheludochnoi zhelezy krys.

The data are reported on albumin secretion by rat hepatocytes and insulin secretion by pancreatic beta-cells of newborn rats during cell cultivation on flat synthetic membrane in conditions of continuous medium perfusion. Albumin and insulin secretion by the appropriate cultures was higher in continuous medium perfusion than in the control. Enhanced sensitivity of pancreatic beta-cells to glucose, as compared to the control was revealed. It is concluded that continuous medium perfusion of hepatocytes and pancreatic beta-cells in the primary culture had a favourable effect on albumin and insulin secretion by the appropriate cultures.

[Properties of (Ala5, Orn9)-somatostatin. The inhibition of pancreatic and hypophyseal hormone secretion in cell culture]. / Izuchenie svoistv (Ala5, Orn9)-somatostatina. Ingibirovanie sekretsii pankreaticheskikh i gipofizarnykh gormonov v kul'ture kletok.

Ability of Ala5, Orn9-somatostatin to inhibit the secretion of insulin, glucagon, somatotropic hormone (STH) and prolactin was tested on the model of primary monolayer culture of isolated insular pancreatic and adenohypophyseal cells. Chemical substitution performed between positions 5 and 9 in somatostatin molecule failed to change essentially hormone's biologic activity in suppression of insulin and glucagon in the culture of pancreatic insular cells isolated from newborn rats. Somatostatin analog revealed its natural hormonal ability to inhibit STH secretion but failed to affect that of prolactin. The results are suggestive of the principal possibility to produce somatostatin biologically active analog through lyzine residue substitution in position 9 with obligatory simultaneous substitution amino acid residue in position 5.

[Immunoenzyme determination of antibodies to the surface of islands of Langerhans in autoimmune destruction of the insular apparatus]. / Immunofermentnoe opredelenie antitel k poverkhnosti ostrovkovykh kletok podzheludochnoi zhelezy pri autoimmunnoi destruktsii insuliarnogo apparata.

Enzyme-linked immunosorbent assay (ELISA) was applied for detection of human islet cell surface antibodies (ICSA) to rat islet target cells. In 23 healthy controls without hereditary diabetes the findings were on the upper normal limit (mean value of optical density + 3 SEM). The results above the limit were considered positive. 11 out of 18 insulin-dependent (Type I) diabetics with the disease duration less than 5 years were ICSA-positive. All 9 patients with insulin-independent (Type 2) diabetes were ICSA-negative. 3 out of 18 healthy subjects (siblings and children of probands with type II diabetes) were strongly ICSA-positive, although all the members of this risk group had unimpaired oral glucose tolerance test. Thus, ELISA screening of ICSA may be useful for discriminating patients with different types of diabetes and revealing nonaffected individuals at high risk according to their beta-cell integrity.

[Natural peptides and their analogs. XXXV. Synthesis and properties of [Ala5, Orn9]somatostatin]. / Prirodnye peptidy i ikh analogi. XXXV. Sintez i svoistva [Ala5, Orn9]somatostatina.

A total chemical synthesis of [Ala5, Orn9]somatostatin has been performed. This structural analogue of natural somatostatin inhibits the release of somatotropin, insulin and glucagon, but shows no inhibitory effect on secretion of prolactin.

[Effect of thyroliberin on pancreatic islet cell function in rats]. / Vliianie tiroliberina na funktsiiu ostrovkovykh kletok podzheludochnoi zhelezy krys.

A study was made of the TRH effect on insulin and glucagon secretory function of a 4-day neonatal rat pancreatic islet cell culture. The TRH effect was determined in the range of 10-1000 ng/ml concentrations within 30 min and 3 h of cell cultivation with the hormone. TRH stimulated insulin and glucagon secretion within the range of the above doses. No dose dependence was revealed in the TRH stimulation of insulin and glucagon secretion. The data obtained suggest that TRH produces an direct effect on islet cell function stimulating insulin and glucagon secretion.

[Effect of somatotropin and prolactin on functional activity and proliferation of cultured islet cells of newborn rats]. / Vliianie somatotropnogo gormona i prolaktina na funktsional'nuiu aktivnost' i proliferatsiiu ostrovkovykh kletok v kul'ture podzheludochnoi zhelezy novorozhdennykh krys.

A study was made of the STH and prolactin effect on insulin secretion and 3H-thymidine incorporation in DNA by keeping them in 10.5 and 1% embryonic calf serum using a model of the primary monolayer culture of isolated pancreatic islet cells. It has been shown that STH preincubation of the islet cells for 16 hours resulted in a distinct stimulation of insulin secretion and cell proliferation in culture. Prolactin had a similar stimulating effect with STH preincubation of the cells for 24 hours. The STH and prolactin effect depended on the cultivation conditions and manifested itself to a large extent with a low content in the medium of the embryonic calf serum (1%). The results are indicative of the presence of the STH and prolactin direct specific effect on insulin secretory function and cultivated islet cell proliferation.

[Aspartame--the sweet-tasting dipeptide--does not affect the pancreatic insulin-secreting function]. / Aspartam--dipeptid sladkogo vkusa--ne vliiaet na insulinosekretornuiu funktsiiu podzheludochnoi zhelezy.

The action of a synthetic dipeptide aspartam (150 to 180 times as sweet as glucose) on pancreatic insulin-secretory function of rats was studied in vivo and in vitro. The drug was given orally while drinking (300 mg/kg body weight) or was added to the incubation medium of cultivated pancreatic cells (20 mM). It was shown that insulin content in the rat blood serum remained unchanged 10 and 35 minutes after aspartam administration. The drug did not exert any stimulating effect upon insulin secretion following the addition to the pancreatic cell culture medium. It is concluded that aspartam exhibits no direct or mediated action on pancreatic insulin-secretory function.

[Effect of C-terminal tetrapeptide cholecystokinin (CCK-4) on the function of the islands of Langerhans and the adenohypophysis]. / Vliianie C-kontsevogo tetrapeptida kholetsistokinina (CCK-4) na funktsiiu ostrovkov Langergansa i adenogipofiza.

A study was made of the action of C-terminal tetrapeptide cholecystokinin (CCK-4) on the secretory function of A-, B- and D-cells of the islets of Langerhans and on the lactotropic function of the hypophysis. Intravenous injection into rats of CCK-4 in doses of 5 and 50 micrograms/kg bw resulted within 2 min in increased blood immunoreactive insulin. Tetrapeptide also exerted a stimulant dose-dependent action on the function of insulin-, glucagon- and somatostatin-secreting pancreatic cells of the pancreatic islets in culture at concentrations ranging within 10(-9)-10(-6)M. When given in the same doses CCK-4 did not affect basal or dopamine-inhibited prolactin secretion by cultured adenohypophyseal cells. It is concluded that CCK-4 stimulates insulin, glucagon and somatostatin secretion by direct contact with target cells.

[Endocrine pancreas function in rats in the early postnatal period. The effect of feeding and litter size]. / Sostoianie éndokrinnogo apparata podzheludochnoi zhelezy u krysy v rannem postnatal'nom periode. Vliianie kormleniia i chisla plodov v pomete.

The rat pancreatic endocrine region during the early postnatal period was evaluated depending on the litter size. The body and pancreatic weight lowers and the blood glucose content tends to rise alongside with the litter size increasing. Insulin levels are augmented and glucagon content is reduced in the pancreas of newborn rats with the large litter. The feeding of the animals is accompanied by rapid enhancement of the gland hormone concentration. The per cent content of insulin-secreting cells in Langerhans' islets of newborn rats is rather higher than that of adult animals, being dependent on the litter size as well.

[Effect of whale somatotropin and its biologically active fragment on various indicators of carbohydrate metabolism in the rat diaphragm in vitro]. / Issledovanie vliianiia kitovogo somatotropina i ego biologicheski aktivnogo fragmenta na nekotorye parametry uglevodnogo obmena v diafragmal'noi myshtse krys in vitro.

The ability of somatotropin seival and its fragment 77-107, retaining a marked growth-stimulationg activity, to change the intensity of 14C-glucose consumption from the medium and 14C-glucose inclusion into glycogen by in vitro incubated semidiaphragm of hypophysectomized rats was studied. It was detected that somatotropin seival, contacting with the diaphragmatic muscle tissue, provokes "insulin-like" effect. (i.e. stimulates glucose consumption and glycogen synthesis by this tissue), similar to that of the other animal somatotropins studied. Somatotropin fragment 77-107, revealing growth-stimulating activity, is not able to intensify glucose consumption and glycogen synthesis in the muscle tissue, in contrast to the whole hormone, being indicative of dissociation between structural determinants of these effects in hormone molecule.