Biomedical subjects

S Sandler

Publications and source records attributed to S Sandler.

At least 145 records · Page 8Linked to original sources

PubMed1989

Human interleukin 1 beta stimulates islet insulin release by a mechanism not dependent on changes in phospholipase C and protein kinase C activities or Ca2+ handling.

Isolated islets from adult rats or obese hyperglycemic (ob/ob) mice were incubated with human recombinant interleukin 1 beta in order to study whether the acute effects of the cytokine on islet insulin release are associated with changes in islet phospholipase C activity, Ca2+ handling or protein phosphorylation. The cytokine stimulated insulin release both at low and high glucose concentrations during one hour incubations. In short-term incubations (less than 1 min) interleukin 1 beta did not affect the production of inositoltrisphosphate. Addition of interleukin 1 beta affected neither the cytoplasmic free Ca2+ concentration at rest nor that observed subsequent to stimulation with a high concentration of glucose. Furthermore, the endogenous protein kinase C activity, as visualized by immunoprecipitation of a 32P-labelled substrate for this enzyme, was not altered by interleukin 1 beta. Separation of 32P-labelled proteins by means of 2-dimensional gel electrophoresis failed to reveal any specific effects of the cytokine on the total protein phosphorylation activity. These results suggest that the stimulatory effects on insulin release exerted by interleukin 1 beta are not caused by acute activation of phospholipase C and protein kinase C or by an alteration of islet Ca2+ handling of the B-cells.

Animals↗

PubMed1989

Persistent impairment of the insulin response to glucose both in vivo and in vitro after streptozotocin exposure: studies with grafted pancreatic islets and islets maintained in culture.

The functional responses of the pancreatic B-cells after cytotoxic damage are still largely unknown. Using in vitro models to clarify this issue, we have recently observed a preferential reduction of glucose-stimulated insulin production and release in mouse pancreatic islets maintained in culture after in vitro exposure to streptozotocin. In order to evaluate the relevance of these findings in vivo, two sets of experiments were performed. First, mouse pancreatic islets were exposed in vitro to 2.2 mmol/l streptozotocin or vehicle alone, cultured for 6 days, and finally grafted under the kidney capsule of normoglycemic nude mice. Two weeks after transplantation there was no difference in the total DNA and insulin content between the two groups of islet grafts, but the insulin concentration, as expressed per microgram DNA, was decreased by 40% in the streptozotocin-treated islets. The insulin release of the grafts, during perfusion of the graft-bearing kidney in situ with 16.7 mmol/l glucose was diminished in the streptozotocin group, whilst perfusion with 16.7 mmol/l glucose plus 5 mmol/l theophylline was able partially to counteract the reduction in insulin release. In the second set of experiments, NMRI mice were injected iv with 160 mg/kg streptozotocin or vehicle alone, and their islets isolated 15 min after the injections. After 6 days in culture, there was no decrease in DNA, glucagon and somatostatin contents, but the insulin content was decreased by 40% in the streptozotocin exposed islets. These islets also showed a 60% decrease in the insulin response to glucose, which was partly counteracted by incubation with 16.7 mmol/l glucose plus 5 mmol/l theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Sustained exposure of toxically damaged mouse pancreatic islets to high glucose does not increase beta-cell dysfunction.

The aim of this study was to clarify whether prolonged in-vitro exposure of either normal or damaged beta cells to a high glucose environment can be toxic to these cells. For this purpose NMRI mice were injected intravenously with a diabetogenic dose of streptozotocin (SZ; 160 mg/kg) or vehicle alone (controls). Their islets were isolated 15 min after the injection and subsequently maintained in culture for 21 days in the presence of 11.1 or 28 mmol glucose/l. After this period, during acute glucose stimulation, the control islets showed a marked increase in their insulin release in response to a high glucose stimulus. In the SZ-exposed islets there was a decrease in DNA and insulin contents, and a deficient insulin secretory response to glucose. However, in the SZ-damaged islets as well as in the control islets, culture with 28 mmol glucose/l compared with 11.1 mmol glucose/l did not impair islet retrieval after culture, islet DNA content or glucose-induced insulin release. Thus, the degree of damage was similar in the SZ-treated islets cultured at the two concentrations of glucose. These results suggest that glucose is not toxic to normal or damaged mouse pancreatic islets over a prolonged period in tissue culture.

Animals↗

PubMed1989

Tissue culture of human fetal pancreas. Effects of nicotinamide on insulin production and formation of isletlike cell clusters.

Human fetal pancreas (HFP) is a potential source of beta-cells for transplantation to insulin-dependent diabetic patients. We have previously described a method for tissue culture of HFP that results in the in vitro development of isletlike cell clusters (ICCs) containing a minority of insulin-positive cells. Recently we found that nicotinamide, an inhibitor of poly(ADP-ribose) synthetase, induces an increased islet cell DNA replication both in vivo and in vitro. In this study, this culture technique was used to evaluate the effects of addition of 10 mM nicotinamide on HFP explants cultured in RPMI-1640 medium plus 10% human serum. ICCs developed in 11 of 19 consecutive cultures with nicotinamide increased the yield of ICCs by 40%. Also, the insulin content of ICCs increased approximately 50% with nicotinamide supplementation, although measurements of DNA indicated an unchanged number of cells in each ICC. Neither the rates of insulin release in response to 16.7 mM glucose plus 5 mM theophylline nor the (pro)insulin or total protein biosynthesis rates were affected by nicotinamide addition. The combined results of this study suggest that nicotinamide is useful for stimulating the formation of ICCs from HFP.

Culture Techniques↗

PubMed1989

Influence of hyperglycemia on blood perfusion of autotransplanted pancreatic islets in diabetic rats.

One week after a partial pancreatectomy, which did not affect glucose homeostasis, adult rats were autotransplanted with 500 isolated pancreatic islets beneath the renal capsule. Some rats were rendered diabetic with streptozocin (STZ) before being implanted with the islets, and other rats received no STZ and thus remained normoglycemic. The number of implanted islets was insufficient to revert hyperglycemia, but the STZ-induced diabetic animals were treated with insulin according to one of the following protocols: 1) one daily subcutaneous insulin injection for 28 days after transplantation; 2) insulin injection on days 1-14; 3) insulin injection on days 15-28; or 4) no insulin. Four weeks after transplantation, the blood perfusion of the islet grafts was determined by a microsphere technique. Continuous hyperglycemia after implantation of the islets significantly decreased the volume of the graft and the blood flow per volume compared with normoglycemic animals also receiving islet transplants. Insulin treatment counteracted the decrease in both of these values. This result was achieved regardless of whether the insulin treatment was maintained throughout the 4-wk period or only during the first or second half. The mechanism behind the impaired blood perfusion of the grafts during continuous hyperglycemia is unknown, but it may reflect an effect on the revascularization of the graft or on the intrinsic regulation of the blood perfusion of the graft.

Animals↗

PubMed1989

Effects of culture conditions on formation and hormone content of fetal porcine isletlike cell clusters.

To establish methods for stimulation of the growth and differentiation of fetal endocrine pancreatic cells, a technique for the in vitro production of fetal porcine isletlike cell clusters (ICCs) was used. By varying the composition of the culture medium with different glucose concentrations and the addition to the culture medium of insulin, growth hormone (GH), amino acids, or nicotinamide, we estimated the formation of ICCs and their hormone content. High glucose content (28.0 mM) stimulated the formation of abundant ICCs that contained decreased amounts of insulin. In contrast, culture at a low (5.6-mM) glucose concentration increased the ICC insulin content but decreased the number of ICCs formed. Addition of seven times the normal amount of amino acids hampered both the formation of ICCs and their insulin content. Neither insulin nor GH supplementation of the medium influenced the ICC insulin content, but GH stimulated an abundant outgrowth of ICCs containing relatively high insulin concentrations. However, ICCs formed under these circumstances contained less than 10% of the insulin content of adult islets, and further work has to be carried out to identify factors responsible for further differentiation of the fetal porcine pancreas.

Animals↗

PubMed1989

Pancreatic and islet blood flow in the regenerating pancreas after a partial pancreatectomy in adult rats.

A 60% partial pancreatectomy or a sham operation was performed in adult, male Sprague-Dawley rats. Measurements of pancreatic blood flow (PBF) and islet blood flow (IBF) were achieved by a microsphere technique either before surgery or 1, 2, 4, 8, or 16 weeks after the operation. An intraperitoneal glucose tolerance test (2 gm glucose/kg body weight) was made 2 days before the blood flow measurements. There were no aberrations in glucose homeostasis at any time point after the partial pancreatectomy. The sham-operated animals had both PBF and IBF values similar to those of nonoperated animals at all time points. The rats that underwent partial pancreatectomy, however, showed significantly increased PBF values 2 and 4 weeks after surgery but values similar to those of the sham-operated rats 1, 8, and 16 weeks after surgery. The IBF values of the animals that underwent pancreatectomy were significantly increased from week 2 onward when expressed per gram of pancreas and from week 4 onward when expressed as a fraction of PBF. Compared with the sham-operated animals, the total blood perfusion of the islet organ was increased in the rats that underwent partial pancreatectomy despite a reduction in total pancreatic mass. It is concluded that a partial pancreatectomy induces both a transient increase in PBF and a more long-lasting increase in IBF. It is conceivable that these observations reflect the regeneration of exocrine and endocrine cells and an increased functional load on these tissues.

Animals↗

PubMed1988

Culture of mouse pancreatic islets in different glucose concentrations modifies B cell sensitivity to streptozotocin.

There have previously been divergent data published regarding the effects of glucose on the diabetogenic effects of streptozotocin. In order to further explore this issue, two separate sets of experiments were performed. In the first, mouse pancreatic islets were maintained in culture for 3 days at different glucose concentrations (5.6, 11.1 and 28 mmol/l) and then exposed to streptozotocin. After another 3 days in culture at 11.1 mmol/l glucose, the B cell function was evaluated by measurement of glucose-stimulated insulin release, the number of islets recovered after culture, and the islet DNA and insulin contents. In the second group of experiments islets were first maintained in culture at 11.1 mmol/l glucose, then treated with streptozotocin and subsequently cultured for 6 days at the different glucose concentrations given above. It was found that islets maintained in a medium containing 28 mmol/l glucose before or after streptozotocin exposure showed less signs of damage than islets cultured in 11.1 mmol/l glucose. A similar, but less pronounced, decreased sensitivity to streptozotocin was found in islets precultured in 5.6 mmol/l glucose, in comparison with those islets cultured in 11.1 mmol/l glucose. Culture at 5.6 mmol/l glucose just after streptozotocin treatment did not induce any improvement in islet survival or function. It is suggested that the increased damage induced by streptozotocin to islets precultured at 11.1 mmol/l glucose, in comparison with 5.6 mmol/l glucose, can be related to the fact that an increased metabolic activity of B cells render them more susceptible to the toxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

The influence of cyclosporin A on the vascular permeability of the pancreatic islets and on diabetes induced by multiple low doses of streptozotocin in the mouse.

The aim of the present study was to investigate the influence of cyclosporin A on the course of multiple low dose streptozotocin induced diabetes in mice, an animal model for human type I diabetes mellitus. C57BL/Ks mice were treated on five consecutive days with intraperitoneal injections of streptozotocin or citiric acid buffer. Thirty min before the injections the animals were given cyclosporin A (10 or 50 mg/kg body weight) or saline. Cyclosporin A did not protect against the hypoglycaemia and at the higher dose it potentiated the diabetogenic effect. Furthermore, cyclosporin A did not affect the development of insulitis when the pancreatic glands were examined by light microscopy. Using a technique for monitoring vascular permeability in vivo with the aid of the pigment Monastral Blue B, it was found that the development of diabetes was accompanied by an increased vascular leakage. Control animals treated with cyclosporin A also showed an increased islet staining with Monastral Blue B. The data indicate that cyclosporin A potentiates diabetes induced by low doses of streptozotocin. This can be attributed to a direct toxic effect of cyclosporin A on the pancreatic B-cells and may also be due to an increased vascular leakage induced by cyclosporin A. The latter would allow an increased migration of inflammatory cells into the islets and the consequent release of B-cytotoxic substances.

Animals↗

PubMed1988

Functional characteristics of cultured mouse pancreatic islets following exposure to different streptozotocin concentrations.

The present study was undertaken to investigate the acute and long-term effects of streptozotocin (SZ) on pancreatic islet function and survival in vitro. Isolated mouse pancreatic islets, that had been cultured overnight, were exposed to SZ (0.55-4.4 mM) or critic acid buffer in the case of the control group. The islets were examined either immediately after SZ exposure or after one week in culture. There was a marked loss of islets treated with 2.2 and 4.4 mM SZ during the culture; however, the DNA content of the remaining islets was unaffected. The islet insulin content was reduced 7 days after treatment with 2.2 and 4.4 mM SZ. At 4.4 mM the glucagon and somatostatin content of the islet was also decreased but not to the same degree as the insulin content. SZ-induced inhibition of glucose-stimulated insulin release and (pro)insulin biosynthesis was more pronounced on day 7 as compared to day 0. A similar pattern of inhibitory action of SZ was observed on islet glucose oxidation rates. Islet ATP contents were depressed on day 7 in islets exposed 4.4 mM SZ, but were otherwise similar to the control group. Islet NAD + NADH contents were decreased by 50% after exposure to 2.2 mM SZ, compared to the control islets on day 0. This decrease in NAD + NADH contents was to a large extent restored during the one-week culture. The present study shows that islets failed to completely repair the acute damage caused by SZ, and that the impairment of the islet glucose-stimulated insulin release induced by SZ seemed to progress in culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1988

Large-scale production of fetal porcine pancreatic isletlike cell clusters. An experimental tool for studies of islet cell differentiation and xenotransplantation.

A recently described method for the preparation of isletlike cell clusters (ICC) from human fetal pancreas has been applied to the fetal pig with the ultimate aim of large-scale production of ICC. Fetuses ranging in age from 51 to 77 days were used, and after a brief collagenase-incubation the pancreatic digest was plated into culture dishes containing medium RPMI 1640 supplemented with either 10% fetal calf serum (FCS) or human serum (HS). HS seemed to increase the number of ICC formed as compared to that obtained with FCS. A total of more than 100,000 ICC were produced from each of 3 litters, ages 67-77 days, after culture in the presence of HS. The DNA content of such ICC was reduced by about 50% as compared to those maintained with FCS supplementation. Immunocytochemical staining revealed insulin- and glucagon-positive cells scattered among a majority of nonstained cells within the cell clusters. ICC maintained in either FCS or HS displayed significant rates of (pro)insulin biosynthesis in vitro and an increased insulin release when exposed to 16.7 mM glucose plus 5 mM theophylline. Four weeks after implantation, ICC grafted under the kidney capsule of nondiabetic nude mice contained frequent insulin- and glucagon-positive cells. In 2 nude mice transplanted with ICC, the functional capacity of the graft was tested by perfusing the graft-bearing kidney. When the perfusion fluid was changed from one containing 2.8 mM glucose to one containing 16.7 mM glucose +/- 5 mM theophylline, the secretion of insulin increased within a few min. It is concluded that the fetal porcine pancreas can be used for large-scale production of ICC, which have a very consistent, but immature functional capacity. Because of their inherent growth and differentiation properties, fetal porcine ICC constitute a potential source of xenogenic islet grafts intended for human diabetics.

Animals↗

PubMed1988

Stimulation of cell replication in transplanted pancreatic islets by nicotinamide treatment.

A major obstacle for islet transplantation in insulin-dependent diabetes mellitus is to obtain a sufficient amount of islet tissue. This may partly be overcome if the cell replication in the grafted islet preparation could be stimulated in the recipient. In the present study adult mice were treated for 14 days with daily injections of nicotinamide (500 mg/kg body weight) or saline. Subsequently, the autoradiographic labeling index in the cells of the pancreatic islets were calculated in normal mice and in syngeneic islets transplanted into alloxan-diabetic mice. Treatment with nicotinamide caused a more than three-fold increase in the islet cell labeling index in the endogenous pancreatic islets, and also a 50% increase in the cell replication rates of the transplanted islets. It thus appears that nicotinamide enhances islet cell replication, possibly through an inhibition of poly(ADP-ribose) synthetase activities.

Animals↗

PubMed1988

Functional restoration of cultured mouse pancreatic islets after in vitro exposure to alloxan.

The molecular mechanisms behind the functional responses of the beta-cells after cytotoxic damage are still largely unknown. The aim of this study was to investigate to what extent the islet beta-cells are capable of repairing cellular injuries after acute treatment with increasing doses of alloxan. Isolated mouse pancreatic islets were exposed for 30 min. at 37 degrees to alloxan (1.0, 1.5 and 2.0 mM) or vehicle alone (controls). Immediately after alloxan exposure the islet glucose-stimulated insulin release was severely decreased, and there were morphological evidences of partial necrosis of the islets. After further six days in culture, there was a marked decrease in islet number in the groups of islets treated with 1.5 or 2.0 mM alloxan. However, the DNA and insulin contents of the remaining islets were similar to the values observed in cultured control islets. Furthermore, the insulin secretory response to glucose and the light microscopical appearance of these islets were largely restored on day 6. It is concluded that beta-cells surviving after an injury induced by alloxan may recover their functional capacity after an initial period of inhibited function.

Alloxan↗

PubMed1988

Preferential reduction of insulin production in mouse pancreatic islets maintained in culture after streptozotocin exposure.

The ability of the pancreatic beta-cell to repair itself after a cytotoxic injury and reassume its functional activities may be a key issue in affording protection from insulin-dependent diabetes mellitus. The molecular mechanisms behind the functional responses of the beta-cell after cytotoxic damage are still largely unknown. The present study in an attempt to elucidate this issue. Mouse pancreatic islets were isolated with collagenase and, after overnight culture, exposed for 30 min at 37 C to 2.2 mM streptozotocin (SZ) or vehicle alone (controls). The islets were subsequently cultured for 6 days in medium RPMI-1640 plus 10% calf serum. After the culture they were subjected to light microscopical examinations or different functional tests during short term incubations. The SZ-treated islets showed markedly diminished insulin release after stimulation with the beta-cell nutrients glucose and leucine plus glutamine. Compounds known to increase intracellular cAMP [theophylline and (Bu)2-cAMP] were able to partially counteract the SZ-induced reduction of insulin release. Stimulation with arginine could also slightly restore the impaired insulin release. Glucose-stimulated oxygen uptake, proinsulin biosynthesis, and insulin and insulin mRNA contents were also decreased, with values at about 50% of the controls. However, the cellular contents of DNA and RNA and total protein biosynthesis rates were essentially normal. Besides mild degranulation in some islets, the morphological appearance of the SZ-treated islets did not reveal any obvious differences compared to the control islets. The present observations suggest that after a toxic injury there remains a population of partially damaged beta-cells, which are able to maintain most of their basal metabolic functions, but fail to maintain adequate insulin biosynthesis and release.

Animals↗

PubMed1988

Defective catabolism of D-glucose and L-glutamine in mouse pancreatic islets maintained in culture after streptozotocin exposure.

We recently described a preferential reduction of the secretory response to nutrient secretagogues (glucose; leucine plus glutamine) in islets maintained in culture after in vitro exposure to streptozotocin (SZ). The present study is an attempt to further clarify the biochemical mechanisms behind this defective insulin response. Mouse pancreatic islets were collagenase isolated and, after 4-5 days in culture, exposed during 30 min at 37 C to 1.8 mM SZ or vehicle alone (controls). The islets were subsequently cultured for 7 days in medium RPMI 1640 plus 10% calf serum, before the enzymatic and metabolic studies were performed. The activities of the glycolytic enzymes, hexokinase, glucokinase, and glyceraldehyde 3-phosphate dehydrogenase, were similar in the control and SZ-exposed islets. The relative amount of cytosolic and mitochondria-bound hexokinase was also unaffected by SZ. However, there was a 30-40% decrease in the activity of NAD+- and NADP+-dependent glutamate dehydrogenase and glutamate-aspartate transaminase in the SZ-treated islets. This coincided with a 40% decrease in L-[U-14C]glutamine oxidation in the SZ-treated islets. The D-glucose catabolism was further examined in the presence of D-[5-3H] and D-[6-14C] glucose. There was no difference between control and SZ islets in terms of glucose utilization at either 1.7 or 16.7 mM glucose. The oxidation of D-[6-14C]glucose was nevertheless decreased by more than 50% in SZ islets incubated at 16.7 mM (but not 1.7 mM) glucose. Altogether, these converging observations suggest a perturbation of distal regulatory processes, apparently at the mitochondrial level, in the D-glucose and L-glutamine catabolism of SZ-exposed islets. Whether this reflects a primary action of SZ on the islet mitochondria, or an inhibitory effect of SZ on the synthesis of mitochondrial enzymes, as a result of nuclear DNA damage, remains to be elucidated.

Animals↗

PubMed1988

Functional characteristics of rat pancreatic islets maintained in culture after exposure to human interleukin 1.

Recent observations suggest a role for interleukin 1 beta (IL-1) in the autoimmune beta-cell destruction observed in type I (insulin-dependent) diabetes mellitus. We investigated the acute and long-term effects of IL-1 on pancreatic beta-cell function in vitro. Rat pancreatic islets were isolated and kept in tissue culture for 5 days. The islets were subsequently transferred to media containing RPMI-1640 plus 1% human serum with or without human recombinant IL-1 beta (300 pM) and cultured for another 48 h. The islets were examined either immediately after IL-1 exposure (day 0) or after an additional 6-day culture period without IL-1. On day 0, IL-1 was found to totally inhibit glucose-stimulated insulin release, partially inhibit glucose oxidation, and induce a decrease in islet DNA content. However, these islets were able to release insulin after stimulation with glucose plus theophylline, although the absolute rate of insulin secretion was lower than that of the control group. After 6 days in culture, the insulin-secretory response to glucose and the glucose oxidation rates of the IL-1-pretreated islets were completely restored, but there remained a reduced islet DNA content. We conclude that IL-1 is cytotoxic to islet beta-cells. However, surviving beta-cells are able to recover their functional capacity after a period of inhibited function.

Animals↗

PubMed1988

Use of liposomes to introduce substances into pancreatic islet cells.

The liposome technique is widely used to transport substances that cannot normally traverse the plasma membrane into the cell. The interactions of liposomes with the plasma membrane of pancreatic islet cells have not previously been studied. We evaluate the suitability of the liposome technique for introducing substances into the pancreatic beta-cell to which the cell membrane is impermeable. Liposomes were synthesized with an ether-injection method, and the cell-liposomal interactions were investigated by means of radioactive labeling and the fluorescent aqueous space marker 6-carboxyfluorescein. Experiments were performed on freshly isolated mouse pancreatic islets and on free islet cell preparations. With fluorescence microscopy, liposomes were observed to fuse spontaneously with islet cells, and the corresponding internalized volumes were quantified with spectrofluorometric measurements. The liposome association with islets and islet cell suspensions, as assessed by radioactive labeling, was found to increase with the liposome concentration. The effects of liposome membrane lipid composition on the fusion rate were found to be decreased in the presence of glucolipid. In addition, polyethylene glycol failed to affect the liposomal uptake. Freshly isolated islets incubated with liposomes containing glucose 6-phosphate were observed to release slightly more insulin than islets incubated with "empty" liposomes. In conclusion, liposomes fuse spontaneously with islet cells in vitro, and the uptake of liposomes is regulated by the lipid composition of the liposomal bilayer and the amount of liposomes present. The function of the beta-cell can be altered with the liposome technique, e.g., by addition of biologically active molecules such as glucose 6-phosphate.

Animals↗

PubMed1987

Cryopreservation of mouse pancreatic islets: effects of different glucose concentrations in the post-thaw culture medium on islet recovery.

It was the aim of this study to investigate the influence of the glucose concentration of the post-thaw culture medium on islet B-cell survival after cryopreservation by the combined assessments of islet recovery, islet DNA and insulin contents, and insulin release. Collagenase isolated mouse islets were kept in culture for 3 days in the presence of 11.1 mM glucose and then transferred to freezing ampoules containing Hanks' solution supplemented with 10% calf serum and 2 M dimethyl sulfoxide. After a 20-min incubation at 0 degrees C the islets were cooled at a rate of 25 degrees C/min to -70 degrees C and subsequently plunged into liquid nitrogen. After 2 hr the frozen islets were rapidly thawed at 37 degrees C, transferred to culture dishes, and cultured for another 3 days in the presence of 2.8, 5.6, 11.1, 16.7, or 28 mM glucose. Nonfrozen control islets were treated identically after a preceding 3-day culture at 11.1 mM glucose. The percentage recovery of cryopreserved islets was decreased compared to that of nonfrozen islets, but was increased when higher glucose concentrations were used in the post-thaw culture medium. Since the DNA content of the cryopreserved islets was slightly decreased, the overall survival rate of the cryopreserved B-cells, when cultured at the higher glucose concentrations after thawing, was found to be about 75%. The insulin content of the cryopreserved islets was decreased but the glucose-stimulated insulin release was essentially the same as that of the nonfrozen islets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗