Complete nucleotide sequence of a Coxsackievirus B-4 strain capable of establishing persistent infection in human pancreatic islet cells: effects on insulin release, proinsulin synthesis, and cell morphology.

The aim of the present investigation was to study the effect of infection of human pancreatic islet cells with a strain (VD2921) of Coxsackie B virus serotype 4 capable of establishing persistent infection in these cells, as well as to sequence the strain, to study the determinants of virulence and persistence. Groups of islets were infected and assessments of proinsulin, insulin content, and virus replication were made. Insulin release in response to high glucose was measured.

The pancreatic islets in spontaneously hypertensive rats: islet blood flow and insulin production.

The aim of the study was to investigate if hypertension affects pancreatic islet blood flow and endocrine function. For this purpose, spontaneously hypertensive rats (SHR) were compared with normotensive control Wistar-Kyoto rats (WKY). Both islet size and islet cell replication in 4-month-old SHR was increased compared with WKY.

Engraftment and growth of transplanted pancreatic islets.

Transplantation of pancreatic islets may provide a cure for type 1 diabetes. However, this treatment can currently be offered only to very few patients. To improve transplantation success we need to understand better the mechanisms of how the implanted islets survive, grow and/or maintain adequate function.

Novel experimental strategies to prevent the development of type 1 diabetes mellitus.

Type 1 diabetes is an autoimmune disease leading to extensive destruction of the pancreatic beta-cells. Our research focusses on the role of beta-cells during the course of the disease, aiming at finding novel strategies to enhance beta-cell resistance against the cytotoxic damage inflicted by the immune system. Special attention has been paid to the possibility that cytokines released by the immune cells infiltrating the pancreatic islets can directly suppress and kill beta-cells.

Differences in amyloid deposition in islets of transgenic mice expressing human islet amyloid polypeptide versus human islets implanted into nude mice.

Islet amyloid polypeptide (IAPP)-derived amyloid is frequently deposited in the islets of Langerhans in patients with chronic non-insulin-dependent diabetes mellitus (NIDDM). When human islets were implanted under the renal capsule in nude mice, amyloid occurred in 73% of the grafts within 2 weeks. In this study, we compare the deposition of amyloid in islets from a transgenic mouse strain expressing human IAPP (hIAPP) and in normal human islets after implantation in nude mice.

Glucose metabolism in vitro of cultured and transplanted mouse pancreatic islets microencapsulated by means of a high-voltage electrostatic field.

The aim of this study was to assess the function of mouse pancreatic islets microencapsulated using a high-voltage electrostatic field. Islets were microencapsulated in alginate/poly-L-lysine/alginate (APA) capsules and maintained in tissue culture. Rates of glucose oxidation and insulin release were then assessed.

Appearance of glucose-induced insulin release in fetal rat beta-cells.

Fetal rat pancreatic cells were isolated from pancreatic primordia on days 12-14 of pregnancy and cultured for 48 h in the presence of 5 mmol/l glucose. Insulin accumulation in the medium over the next 24 h was measured. Cultured cells from day 12 fetuses secreted about 1 fmol insulin per pancreas in response to 5 or 15 mmol/l glucose irrespective of whether 1 mmol/l tolbutamide, 400 mumol/l diazoxide, 5 mmol/l theophylline or 10 mmol/l mannoheptulose was present.

Mechanisms of defective glucose-induced insulin release in human pancreatic islets transplanted to diabetic nude mice.

We have previously observed that human islets, transplanted under the kidney capsule of hyperglycemic nude mice, show a longlasting impairment in glucose-induced insulin release. To investigate the cause(s) of this phenomenon, we transplanted human islets into normoglycemic or alloxan-diabetic nude mice for a 4- to 6-week period. In a third experimental group, aimed at evaluating reversibility of hyperglycemia effects, diabetic nude mice bearing a human islet graft were cured by a second intrasplenic transplant of mouse islets, and the human islets were exposed to a further 2 weeks of normoglycemia.

Assessment of insulin secretion in vitro from microencapsulated fetal porcine islet-like cell clusters and rat, mouse, and human pancreatic islets.

Background: The possibility of transplanting microencapsulated pancreatic islets into patients with insulin-dependent diabetes mellitus, either as allografts or xenografts, has attracted great interest. A critical evaluation of the results obtained reveals that the success has been very limited. The aim of the present study was to compare the in vitro function of microencapsulated islets obtained from adult humans, adult mice, adult rats, and fetal pigs.

In vitro regulation of insulin release and biosynthesis of fetal rat pancreatic cells explanted on pregnancy day 16.

Although the morphological development of the fetal pancreatic B cell has been studied in considerable detail, knowledge about the functional maturation, particularly in early stages of development, is still poor. The present paper describes a method for monolayer culture of fetal rat islet cells which allows a study of the regulation of insulin biosynthesis, release and content during critical stages of embryonic and fetal development. Suspensions of pancreatic cells were prepared from rat fetuses on pregnancy day 16 and cultured for 3 days.

Diet-induced obesity and pancreatic islet blood flow in the rat: a preferential increase in islet blood perfusion persists after withdrawal of the diet and normalization of body weight.

The aim of the present study was to evaluate the effects of diet-induced obesity on pancreatic islet blood perfusion in normal Wistar rats. Furthermore, we investigated to what extent any obesity-associated changes in islet blood flow could be reversed after reversion to a normal diet with normalization of body weight. Young adult female Wistar rats were offered a palatable mixed high-caloric diet (cafeteria diet) in addition to standard pelleted chow.

Human pancreatic beta-cell deoxyribonucleic acid-synthesis in islet grafts decreases with increasing organ donor age but increases in response to glucose stimulation in vitro.

Human pancreatic beta-cell proliferation may be crucial for the success of islet transplantation. The aim of this study was to test the hypothesis that adult human beta-cells proliferate in vitro and in vivo and respond with increased rates of replication to factors known to promote rodent islet-cell proliferation, i.e.

Structure and function of macroencapsulated human and rodent pancreatic islets transplanted into nude mice.

Macroencapsulation of human pancreatic islets inside biomembranes is a promising approach to maintain islet allografts in the diabetic recipient without immunosuppression. In order to test this possibility islets isolated from human pancreata were kept in culture before macroencapsulation in a tissue chamber device. The device consisted of two titanium rings, which supported two flat membranes.

Nitric oxide donors decrease the function and survival of human pancreatic islets.

Nitric oxide (NO) has been proposed as a possible mediator of beta-cell damage in human IDDM. This hypothesis is based on in vitro studies with rodent pancreatic islets. In the present study we examined whether human beta-cells are affected by NO.

Differences in the expression of heat-shock proteins and antioxidant enzymes between human and rodent pancreatic islets: implications for the pathogenesis of insulin-dependent diabetes mellitus.

Background: It has previously been observed that the insulin-producing cells of human pancreatic islets are more resistant to alloxan-, streptozotocin-, nitroprusside-, or cytokine-induced injury than those of mouse and rat islets.

Materials And Methods: Human pancreatic islets were obtained from heart-beating organ donors. The expression of the stress proteins heat shock protein 70 (hsp70) and heme oxygenase and the anti-apoptosis gene bcl-2 was determined in isolated rat, mouse, and human islets, either cultured in vitro or transplanted under the kidney capsule of nude mice, using immunoblot analysis.

Insulin-like growth factor I does not inhibit insulin secretion in adult human pancreatic islets in tissue culture.

Insulin-like growth factor I (IGF-I) has been found to increase insulin sensitivity and suppress insulin secretion, thereby having a potential interest as a therapeutic agent for non-insulin-dependent diabetes mellitus (NIDDM). The aim of the present study was to investigate the direct actions of IGF-I (400 ng/ml) on human pancreatic islets, or on rat pancreatic islets, during a 48 h period in tissue culture. Insulin-like growth factor I did not affect medium insulin accumulation, DNA or insulin content or short-term glucose-induced insulin release of human islets.

Impairment of glucose-induced insulin secretion in human pancreatic islets transplanted to diabetic nude mice.

Hyperglycemia-induced beta-cell dysfunction may be an important component in the pathogenesis of non-insulin-dependent diabetes mellitus. However, most available data in this field were obtained from rodent islets. To investigate the relevance of this hypothesis for human beta-cells in vivo, human pancreatic islets were transplanted under the renal capsule of nude mice.

Immunosuppression, macroencapsulation and ultraviolet-B irradiation as immunoprotection in porcine pancreatic islet xenotransplantation.

Membrane encapsulation or ultraviolet-B irradiation, with or without mild immunosuppressive treatment, was applied in order to prolong the survival of xenogeneic porcine foetal pancreatic grafts. Non-diabetic C57BL/6 mice were transplanted with porcine islet-like cell clusters, either membrane-encapsulated in the epididymal fat pad, or non-encapsulated under the kidney capsule. The animals were treated with daily subcutaneous injections of either cyclosporin A (12.

Rapid deposition of amyloid in human islets transplanted into nude mice.

Human islets of Langerhans were transplanted to the subcapsular space of the kidneys of nude mice which were either normoglycaemic or made diabetic with alloxan. After 2 weeks, the transplants were processed for light and electron microscopical analyses. In all transplants, islet amyloid polypeptide (IAPP)-positive cells were found with highest frequency in normoglycaemic animals.

Transplantation of porcine fetal pancreas to diabetic patients.

Transplantation of fetal porcine islet-like cell clusters (ICC) reverses diabetes in experimental animals. We have now transplanted porcine ICC to ten insulin-dependent diabetic kidney-transplant patients. All patients received standard immunosuppression and, at ICC transplantation, antithymocyte globulin or 15-deoxyspergualin.

Major species differences between humans and rodents in the susceptibility to pancreatic beta-cell injury.

The ability of beta cells to endure assaults may be relevant in the development of insulin-dependent diabetes mellitus. This study examines the susceptibility of human pancreatic islets to agents that are cytotoxic for rodent beta cells--i.e.

Cytokines suppress human islet function irrespective of their effects on nitric oxide generation.

Cytokines have been proposed as inducers of beta-cell damage in human insulin-dependent diabetes mellitus via the generation of nitric oxide (NO). This concept is mostly based on data obtained in rodent pancreatic islets using heterologous cytokine preparations. The present study examined whether exposure of human pancreatic islets to different cytokines induces NO and impairs beta-cell function.