Biomedical subjects

S Sandler

Publications and source records attributed to S Sandler.

At least 163 records · Page 9Linked to original sources

PubMed1987

The partial protective effect of branched chain amino acids against streptozotocin-induced cytotoxicity to mouse pancreatic islets in vitro.

Recent experiments suggested that injections of branched chain amino acids (BCAA) immediately followed by streptozotocin (SZ), induced a partial protection against the diabetogenic action of SZ in vivo. In the present investigation, isolated mouse pancreatic islets were exposed in vitro to SZ (2.2-4.4 mM), with or without preincubation in a mixture of BCAA (15 mM leucine, 15 mM isoleucine and 15 mM valine). In order to evaluate the toxic action of SZ on the beta-cell, the islets were studies after culture for 3 days following SZ exposure. In control islets which had not been pretreated with BCAA, 4.4 mM SZ induced a 47% diminution in the islet number, while only 20% were lost after pretreatment with BCAA. There was also a greater total islet DNA content recovered in the islets pretreated with BCAA before SZ exposure. The BCAA islets furthermore maintained a slightly higher insulin release to the culture medium, insulin content and insulin response to an acute glucose stimulus. Preincubation with each of the amino acids alone did not protect against the SZ action. The present data are consistent with previous in vivo findings and suggest that a direct BCAA-induced decrease in the beta-cell sensitivity to SZ can explain the partial protective effect of these amino acids against the diabetogenic action of SZ.

Amino Acids, Branched-Chain↗

PubMed1987

Blood flow measurements in autotransplanted pancreatic islets of the rat. Impairment of the blood perfusion of the graft during hyperglycemia.

No information is available on the rate of blood flow in transplanted islets. In this study, adult rats were partially depancreatized, and islets from the excised pancreas were then isolated, maintained for 7 d in tissue culture, and subsequently transplanted back to the animal, beneath the renal capsule. Some rats were rendered diabetic with streptozotocin before transplantation. A month after transplantation the blood flow of the grafts was measured by a microsphere technique. Autotransplantation to streptozotocin-diabetic rats of approximately 500 islets did not revert the hyperglycemia, and the blood flow of these grafts was approximately 25% of that in the normoglycemic-transplanted rats. However, in insulin-treated diabetic rats the blood flow of the pancreatic graft was similar to that in the normoglycemic rats. The present results suggest that the blood flow in transplanted islets is markedly diminished by hyperglycemia and that this can be enhanced by insulin administration.

Animals↗

PubMed1987

Inhibitory effects of interleukin 1 on insulin secretion, insulin biosynthesis, and oxidative metabolism of isolated rat pancreatic islets.

Recent observations suggest a role for interleukin 1 (IL-1), a macrophage-derived cytokine, in the autoimmune B cell destruction, which is observed in type 1 diabetes. In the present study we have investigated the effects of IL-1 and two other cytokines, namely tumor necrosis factor (TNF) and interferon-gamma (IFN-gamma) on the pancreatic B cell paying particular attention to insulin production and glucose metabolism. Rat pancreatic islets were isolated and kept in tissue culture for 5 days. The islets were subsequently transferred to media containing medium RPMI 1640 plus 0.5% human serum with or without additions of human recombinant preparations of either IL-1 (25 U/ml), TNF (1000 U/ml), or IFN-gamma (500 U/ml), and cultured for another 48 h. After the culture period the islets were subjected to light microscope examination and different functional tests in short-term incubations in the absence of cytokines. IL-1 was found to reduce insulin release in culture and totally inhibit glucose-stimulated insulin release in short-term incubations. Islet (pro)insulin biosynthesis, glucose oxidation, and oxygen uptake at 16.7 mM glucose were partially inhibited by IL-1. The DNA content of islets cultured with IL-1 was decreased and may partly explain these latter findings. However, inhibition of glucose oxidation could not be seen in islets exposed to IL-1 in short-term experiments only. By light microscopy there were marked signs of degeneration in IL-1 treated islets. TNF and IFN-gamma were essentially without effect on islet morphology or function. The results of this study indicate that IL-1 may be cytotoxic to islet B cells. The primary toxic action of IL-1 seems to involve factors other than an impaired islet glucose metabolism.

Animals↗

PubMed1987

Tissue culture of human fetal pancreas: growth hormone stimulates the formation and insulin production of islet-like cell clusters.

The human fetal pancreas (HFP) is a potential source of insulin-producing B-cells for transplantation to insulin-dependent diabetic patients. We recently described a technique for culturing HFP tissue in vitro which results in the development of islet-like cell clusters (ICC). These clusters exhibited (pro)insulin biosynthesis and a modest rate of insulin secretion, and immunocytochemical staining indicated the presence of insulin-positive cells in the cell clusters. In this study this technique was used to evaluate the effects of the addition of 1000 micrograms/L GH to HFP cultured in medium RPMI-1640 plus 10% human serum. ICCs developed in 21 of 33 consecutive cultures. GH increased the yield of ICC by 35% compared to explants supplemented with human serum alone. The insulin content of the ICCs also was increased, but the size of individual ICCs was not affected by GH, as reflected by an unchanged DNA content. GH also caused increased insulin release when the ICCs were stimulated with 16.7 mM glucose plus 5 mM theophylline. However, (pro)insulin biosynthesis was not affected by the addition of GH. These results suggest that GH stimulates the formation of both ICCs and insulin production within the explants. These observations are relevant both for the production of human fetal B-cells intended for transplantation into insulin-dependent diabetic patients and for our knowledge of the growth regulation of the HFP B-cell.

Culture Techniques↗

PubMed1987

Tissue culture of human fetal pancreas. Effects of human serum on development and endocrine function of isletlike cell clusters.

The human fetal pancreas represents a source of insulin-producing beta-cells with a potential for transplantation to diabetic patients. It has previously been shown that such cells can be viably maintained in tissue culture media containing fetal calf serum (FCS) and that these explants continue to synthesize and release insulin. In this study the effects of human serum (HS) on the growth and function of human fetal pancreatic explants have been compared with those of FCS. For this purpose, pancreatic glands, obtained after prostaglandin-induced abortions, were briefly exposed to collagenase, and the digest was cultured in RPMI-1640 medium plus 10% pooled HS or FCS. The outgrowth of isletlike cell clusters (ICCs) was monitored. In 31 of 58 consecutively explanted glands, development of ICCs was observed. In the presence of FCS the outgrowth of ICC took place on top of a fibroblast monocellular cell layer; HS effected less growth of fibroblasts and increased the formation of ICCs about sevenfold compared with explants from the same glands maintained in FCS. However, in the explant cultures with HS, the cell number per ICC, expressed as DNA content, was reduced by 50%. In both FCS and HS the insulin content of the medium showed great variability and progressively declined from day 2 to day 5. The medium glucagon concentration also decreased but not to the same extent as that of insulin. Immunocytochemical-stained ICCs showed insulin- and glucagon-positive cells scattered among most nonstained, presumably nonendocrine cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood↗

PubMed1987

Cryopreservation of mouse pancreatic islets: effects of human serum on islet survival.

The aim of this study was to compare the survival of cryopreserved mouse pancreatic islets frozen in the presence of either a simple salt solution (Hanks' balanced salt solution) or a complete tissue culture medium (RPMI 1640). Moreover, the addition of 10% human serum to the freezing solutions was evaluated. Collagenase isolated islets were kept in culture for three days, before being cooled at a rate of 5 degrees C/min or 25 degrees C/min to -70 degrees C, at which temperature the islets were transferred to liquid nitrogen. All freezing media were supplemented with 2 M dimethylsulphoxide as cryoprotectant. The islets were rapidly thawed at 37 degrees C and subsequently cultured for another three days. The recovery of islets was higher when the more rapid cooling rate was used and the addition of serum further improved the recovery. Compared to non-frozen cultured islets there was a loss of cells in all groups of cryopreserved islets, as measured by their DNA content, and this was accompanied by a lowered insulin content. All groups of frozen-thawed islets responded to a high glucose stimulus in vitro with a 5-9 fold increase in insulin secretion. There was no obvious advantage of using a complete tissue culture medium for islet cryopreservation, but the addition of serum had some beneficial effects. Data obtained from non-frozen control islets suggest that human serum slightly impairs the function of mouse pancreatic B-cells.

Animals↗

PubMed1986

Regulation of RNA metabolism in relation to insulin production and oxidative metabolism in mouse pancreatic islets in vitro.

This study was undertaken to investigate the long-term effects of different substrates, in particular glucose, on the regulation of islet RNA metabolism and the relationship of this regulation to the metabolism and insulin production of the islet B-cell. For this purpose collagenase-isolated mouse islets were used either in the fresh state or after culture for 2 or 5 days in RPMI 1640 plus 10% calf serum supplemented with various test compounds. Islets cultured with 16.7 mM glucose contained more RNA than those cultured with 3.3 mM glucose. Culture of islets in glucose at low concentrations inhibited glucose-stimulated RNA synthesis and this inhibitory effect was reversed by prolonged exposure to high glucose concentrations. Culture with 10 mM leucine and 3.3 mM glucose or with 10 mM 2-ketoisocaproate and 3.3 mM glucose increased the total RNA content of islets as compared to that of islets cultured with 3.3 mM glucose alone. Islets cultured with 5 mM theophylline maintained a high RNA content in the presence of 3.3 mM glucose. Theophylline also increased the islet RNA content when added together with 16.7 mM glucose, as compared to 16.7 mM glucose alone. Theophylline probably exerted this effect by decreasing the rate of RNA degradation. Changes in islet RNA metabolism showed a close correlation to changes in islet total protein biosynthesis, whereas islet (pro)insulin biosynthesis and insulin release exhibited different glucose-dependency patterns. The response of islet oxygen uptake to glucose was similar to that of islet RNA and protein biosynthesis. It is concluded that the RNA content of the pancreatic islets is controlled at the levels of both synthesis and degradation. Glucose stimulates the RNA synthesis and inhibits its degradation. Moreover, the results suggest that regulation of RNA synthesis may be mediated through islet metabolic fluxes and the cAMP system.

Animals↗

PubMed1986

Alloxan-induced diabetes in the mouse: time course of pancreatic B-cell destruction as reflected in an increased islet vascular permeability.

The extent to which injections of the pancreatic B-cytotoxin alloxan in C57BL/Ks mice induced an increase in islet vascular permeability, and the time course of this increase, were studied. The vascular permeability was monitored by administration of the dye Monastral blue B, which is entrapped in leaky blood vessels with intact basement membranes. The islets were visualized by a freeze-thawing technique which allows identification of stained islets. Not until four hours after the alloxan injections was there an increase in islet uptake of Monastral blue B when compared with saline-treated control animals. Thereafter the islet staining increased further. The process was accompanied by gradual development of hyperglycaemia and a reduction of number of the islets identified in the pancreatic preparations. It is concluded that alloxan causes an increase in islet vascular permeability, which appears to become manifest at a later stage than the cytotoxic B-cell degeneration.

Alloxan↗

PubMed1986

Long-term effects of exposure of pancreatic islets to nicotinamide in vitro on DNA synthesis, metabolism and B-cell function.

Using 3H-thymidine labeling techniques, we found that rates of DNA synthesis in islet cells doubled when mouse pancreatic islets were cultured for 1 week with 10 mmol/l nicotinamide, a potent poly(ADP-ribose) synthetase inhibitor. Culture with nicotinamide partially inhibited glucose-stimulated insulin release, whereas the islet insulin content and rate of (pro)insulin biosynthesis remained unchanged. Long-term exposure to nicotinamide decreased glucose oxidation and ATP content in the islets. The findings support the view that poly(ADP-ribose)synthetase inhibitors stimulate islet cell replication, but may be accompanied by significant inhibitory effects on islet cell function.

Adenosine Triphosphate↗

PubMed1986

Cognitive and affective changes after myelography: a comparison of metrizamide and iohexol.

A battery of brief cognitive tests and a mood scale were administered to 42 patients before and after cervical myelography with either metrizamide (20 patients) or iohexol (22 patients). The patients receiving metrizamide experienced a deterioration in mood after myelography and a relatively greater decline in cognitive test performance than did those receiving iohexol. These two side effects tended to occur together in the metrizamide group, suggesting a common underlying cause; but there was no correlation between changes in mood and cognitive function after myelography with iohexol. These results suggest that metrizamide has a greater neurotoxic effect than iohexol.

Adult↗

PubMed1986

Cryopreservation of mouse pancreatic islets. Effects of fast cooling on islet B cell function and on the outcome of islet transplantation.

In most previous studies of cryopreserved isolated pancreatic islets, a slow cooling rate has been employed. We recently observed that faster cooling (5 degrees C/min) resulted in better functional islet preservation than cooling at 0.5 degrees C/min. We found that a culture period after the collagenase isolation of the islets, but prior to freezing, is crucial for the preservation of the islet B cell function. In the present investigation the function of isolated mouse pancreatic islets cooled in Hanks' solution supplemented with 2 M dimethylsulphoxide was compared with that of nonfrozen, cultured islets prepared from the same donors. The islets were cultured in RPMI 1640 + 10% calf serum for 3 days before freezing, and for 3 days after rapid thawing at 37 degrees C. Islets were cooled at rates of 5, 15, or 25 degrees C/min to 70 degrees C and then plunged into liquid nitrogen. All three groups of cryopreserved islets responded with insulin secretion when challenged with high glucose concentrations in batch-type incubations. In further experiments it was found that glucose-stimulated (pro)insulin biosynthesis in islets frozen at 25 degrees C/min was the same as that in the controls. Similar observations were made with respect to glucose-stimulated insulin release in perifusion experiments. However, a 30% reduction in insulin content was observed in the rapidly frozen islets. There was no difference in the replicatory capacity of the islets cells in vitro, as determined by an autoradiographic technique, between control islets and islets cooled at 5 degrees C or 25 degrees C/min. Intrasplenic implantation of 600-800 cryopreserved syngeneic islets into alloxan-diabetic mice led to complete or partial normalization of the hyperglycemia in seven of nine mice. When splenectomy was performed in five animals the serum glucose concentrations increased promptly. We conclude that relatively rapid cooling rates may be useful for cryopreservation of isolated pancreatic islets.

Animals↗

PubMed1985

Vascular permeability of pancreatic islets after administration of streptozotocin.

In the present study we have investigated whether the pancreatic B-cell toxic agent streptozotocin (SZ) induces increased vascular permeability as an indicator of lesions in the pancreatic islets. SZ was given either in multiple low doses, providing an animal model for Type I diabetes mellitus with signs of autoimmunity, or by a single diabetogenic dose to C57BL/KsJ mice. The vascular reactions were detected by administration of Monastral blue B and the pancreatic islets were visualized by a freeze-thawing technique which made it possible to count the number of stained and unstained islets. This proved to be a rapid and sensitive technique for detection of early lesions within the islets after administration of SZ. It was found that the islets showed an increased vascular staining before the animals had become diabetic by either mode of SZ treatment and also before signs of pancreatic insulitis were found after the multiple low-dose injections of SZ. It is suggested that both types of SZ administration induce a B-cytotoxic reaction, essential for the development of hyperglycaemia. This leads to an activation of cells dealing with the disposal of cell debris, a process which probably also involves the release of substances mediating increased vascular permeability.

Animals↗

PubMed1985

Mechanisms of pancreatic B-cell degeneration during the course of insulin-dependent diabetes mellitus.

This paper presents a review of different mechanisms possibly responsible for the degeneration of the pancreatic B-cell in insulin-dependent diabetes mellitus. The genetic dependence probably located in the HLA DR-locus of the sixth chromosome and its role in an autoimmune reaction against antigenically altered pancreatic B-cells is discussed. The actions of alloxan and streptozotocin in the induction of experimental diabetes, as models for postulated human B-cytotoxins, are described.

Alloxan↗

PubMed1985

Experimental studies of transplantation and regeneration of endocrine pancreatic cells.

Replacement of destroyed B-cells with new "healthy" ones appears to be the most physiological approach to treatment of insulin-dependent (type 1) diabetes. This could be achieved either by transplantation of isolated islets or pancreatic segments or by stimulation of the replicatory activity in the islet cells surviving the acute toxic or infectious insult. The results of our experimental investigations indicate that adult, mature insulin-producing cells can replicate very actively when challenged with a proper stimulus, such as when implanted into obese-hyperglycaemic mice. The growth of transplanted islets is, however, dependent on the site of implantation. Thus, the subcapsular space of the kidney is more favourable than the spleen. Furthermore, immunosuppressive therapy may impair islet cell replicatory activity, as demonstrated in this study for Cyclosporin A. In a search for factors stimulating islet cell replication, we found that the hepatotoxic agent galactosamine enhanced this process as observed autoradiographically one week after the injection. This fits in with previous case reports demonstrating increased mitotic activity in islets of patients suffering from various acute liver diseases. Altogether this series of experiments demonstrates that islet cell replication is a more dynamic process than has hitherto been believed. Obviously many conditions influence this process so significantly that an impact on the diabetic state of the patients can well be expected.

Animals↗

PubMed1985

Modulation of streptozotocin-induced insulitis and hyperglycaemia in the mouse.

Multiple low-dose injections of streptozotocin (SZ) induce a gradually developing hyperglycaemia and pancreatic insulitis in certain inbred mouse strains. In the present investigation nicotinamide, which is known to protect against SZ-induced diabetes, was given prior to a single diabetogenic dose of SZ to C57BL/KsJ mice. Nicotinamide protected against SZ-induced hyperglycaemia in the acute phase but 13 of the 18 animals in this group became diabetic during the second week of observation. Nine of these mice had insulitis, seven of which showed overt diabetes. Since nicotinamide increased the serum glucose concentration at the time of the SZ-administration ten minutes later, the possibility that glucose mediated the protective action was evaluated. Glucose-pretreatment, however, was found to potentiate the diabetogenic action of SZ. It is obvious from the present data that another type of diabetes than that induced by a single high dose of SZ can be evoked if the immediate B-cytotoxic effects of SZ are reduced. It may be speculated that islet B-cells of mice given nicotinamide before SZ, for a time retain SZ-induced DNA injuries, which may lead to the expression of neoantigens and an autoimmune reaction.

Animals↗

PubMed1985

Pancreatic islet circulation in relation to the diabetogenic action of streptozotocin in the rat.

A possible relationship between pancreatic islet blood flow (IBF) and the diabetogenic action of streptozotocin (STZ) has been investigated in rats injected ip with saline, glucose, propranolol, phentolamine, yohimbine, or adrenaline. A low dose (25 mg/kg BW) of STZ was given iv 10 min later, and serum glucose concentrations were determined after 3 and 7 days. Measurements of IBF were performed in separate experiments with a microsphere technique 10 min after injection of the drugs. Administration of phentolamine, glucose, or yohimbine was followed by overt diabetes, whereas animals injected with saline, adrenaline, or propranolol failed to become diabetics. Blood flow measurements showed an increase in IBF 10 min after the injection of glucose or propranolol, while there were no significant effects of the other drugs. It is concluded that changes in IBF are of minor importance for the action of agents modulating the diabetogenic effect of STZ. However, the potentiated hyperglycemic effects by glucose, phentolamine, or yohimbine in combination with STZ seemed to coincide with increased insulin secretion, as reflected by elevated serum insulin concentrations at the time of STZ administration.

Animals↗

PubMed1985

Tissue culture of human fetal pancreas. Development and function of B-cells in vitro and transplantation of explants to nude mice.

The present study evaluates the development and function of human fetal B-cells in vitro with a view to using such cells in future attempts for transplantation of human fetal pancreas to diabetic patients. A method previously described in our laboratory for preparing islets in vitro from the fetal rat pancreas has been applied and modified for use with human fetal pancreas. Pancreatic glands of different gestational ages were obtained from 37 consecutive prostaglandin-induced abortions. After a mild collagenase treatment, the partially disintegrated tissue was maintained in culture for 7 days in tissue culture medium RPMI 1640 plus 20% fetal calf serum to permit cell attachment and out-growth of endocrine cells. In 17 of the 37 consecutively cultured fetal pancreatic glands, islet-like cell clusters were formed. The 20 remaining glands were lost because of either bacterial contamination or lack of viability already before dissection had occurred. Sections of the newly formed cell clusters revealed well-preserved pancreatic cells showing frequent mitotic figures. The tissue exhibited a high rate of (pro)insulin biosynthesis and a modest insulin response to secretory stimuli, suggesting that the mechanism of glucose regulation by the fetal B-cells is not yet fully developed. Electron micrographs showed a large number of granule-containing cells, some of which were identified as B-cells. In nine cases, harvested cell clusters were implanted beneath the kidney capsule of nude mice. When these animals were killed after 2 mo, seven mice showed a considerable growth of the grafts with numerous islet-like structures containing insulin- and glucagon-positive cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

DNA repair synthesis in the pancreatic islets of streptozotocin-treated mice.

We have investigated the ability of the diabetogenic drug streptozotocin (SZ) to induce DNA repair synthesis following DNA lesions in the cells of the islets of Langerhans of mice. Following intravenous injection of SZ, the pancreatic islets were isolated and incubated with tritiated thymidine. The incorporation of the isotope into cells performing DNA repair synthesis was analyzed using quantitative autoradiography. SZ induced an acute hyperglycemia in the mice together with a significant DNA repair synthesis (an increased tritiated thymidine incorporation) in the islet cells. In similar experiments performed with alloxan, the islet cells degenerated rapidly preventing the detection of DNA repair synthesis. The results support the view that SZ acts on the B cell by causing DNA damage followed by DNA repair synthesis. However, the rapid islet cell degeneration observed following alloxan administration suggests that this B cytotoxin has a different primary mechanism of action, from that of SZ.

Animals↗