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S Bonner-Weir

Publications and source records attributed to S Bonner-Weir.

At least 109 records · Page 6Linked to original sources
PubMed1991

Correlations of in vivo beta-cell function tests with beta-cell mass and pancreatic insulin content in streptozocin-administered baboons.

In vivo beta-cell function tests are used increasingly in humans during the preclinical phase of insulin-dependent diabetes mellitus (IDDM), but the severity of the beta-cell loss responsible for the abnormalities seen in these tests is unknown. We have measured several physiological beta-cell function tests--fasting plasma glucose, glucose disappearance constant, fasting insulin, acute insulin responses to arginine (AIRarginine) and glucose (AIRglucose), and glucose potentiation of AIRarginine (delta AIRarginine/delta G) and two direct objective measurements (pancreatic insulin content [PIC] and quantitative beta-cell mass)--in adolescent male baboons (Papio anubis/cyanocephalus). We have correlated in vivo measurements obtained within 3 days after the animals were killed with in vitro estimates of PIC and beta-cell mass in 15 animals, (2 nondiabetic requiring insulin treatment and 13 after varying doses of streptozocin to induce degrees of beta-cell damage ranging from normoglycemia to severe hyperglycemia). There was a strong linear correlation between beta-cell mass and PIC (r = 0.79, P less than 0.001). Physiological measures of beta-cell function were significantly correlated with both PIC and beta-cell mass. The correlations between physiological measures and beta-cell mass were linear and intercepted the beta-cell mass axis at 0.15-0.2 g, suggesting that in vivo measures of beta-cell function approach 0 when there is still approximately 40-50% of the beta-cell mass detectable histologically. With PIC, the linear correlations intercepted the axes close to 0. These findings provide considerable validity to the measurements of beta-cell function used in preclinical IDDM in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Reduced expression of the liver/beta-cell glucose transporter isoform in glucose-insensitive pancreatic beta cells of diabetic rats.

Rats injected with a single dose of streptozocin at 2 days of age develop non-insulin-dependent diabetes 6 weeks later. The pancreatic beta islet cells of these diabetic rats display a loss of glucose-induced insulin secretion while maintaining sensitivity to other secretagogues such as arginine. We analyzed the level of expression of the liver/beta-cell glucose transporter isoform in diabetic islets by immunofluorescence staining of pancreas sections and by Western blotting of islet lysates. Islets from diabetic animals have a reduced expression of this beta-cell-specific glucose transporter isoform and the extent of reduction is correlated with the severity of hyperglycemia. In contrast, expression of this transporter isoform in liver is minimally modified by the diabetes. Thus a decreased expression of the liver/beta-cell glucose transporter isoform in beta cells is associated with the impaired glucose sensing characteristic of diabetic islets; our data suggest that this glucose transporter may be part of the beta-cell glucose sensor.

Animals↗
PubMed1990

Islet mass and function in diabetes and transplantation.

The concept of pancreatic beta-cell mass is fundamental to the understanding of normal metabolism, the pathogenesis of diabetes, and the transplantation of beta-cell tissue. The amount of beta-cell tissue present in the pancreas is a major determinant of the quantity of insulin that can be secreted, and its mass will vary according to the size of the individual and the degree of insulin resistance present. Not all insulin-producing cells are the same, and the dimensions of this heterogeneity remain to be defined. Pancreatic beta-cell mass is markedly reduced in insulin-dependent diabetes mellitus and moderately reduced in non-insulin-dependent diabetes mellitus. In both forms of diabetes, there are qualitative and quantitative abnormalities of insulin secretion that cannot be explained entirely by changes in beta-cell mass. The amount of beta-cell tissue needed for successful transplantation has only been partially defined. Segmental (approximately 50% of the pancreas) transplantation can normalize plasma glucose levels in humans. Difficulty obtaining sufficient amounts of beta-cell tissue is expected to remain a barrier to successful islet transplantation for the immediate future. More should be learned about the function and fate of grafted islet cells.

Diabetes Mellitus↗
PubMed1989

Insulin receptor recycling in vascular endothelial cells. Regulation by insulin and phorbol ester.

Endothelial cell insulin receptors mediate the transcytosis of insulin from luminal to abluminal cell surface. We have investigated the kinetics of insulin receptor translocation by immunoprecipitation of radiolabeled receptors at various times before and after trypsin treatment of intact endothelial cells. Insulin receptors were constitutively internalized with t1/2 = 18 +/- 2 min and were recycled to the cell surface. Insulin stimulated receptor internalization and externalization rates 2.6- and 2.4-fold, respectively. Changes in cell-surface binding of 125I-insulin were consistent with the receptor translocation rates observed in surface-labeling experiments. Phorbol myristate acetate (PMA) treatment increased the rate of insulin-stimulated receptor externalization 1.7-fold. PMA treatment increased the constitutive externalization rate 3.5-fold without affecting the constitutive internalization rate, suggesting that recycling might occur via a mobilization of receptors from intracellular sites in a manner independent of internalization rate. Analysis of the intracellular distribution of receptors by 125I-insulin binding and immunogold electron microscopy revealed that less than one-third of the total insulin receptor pool resided on the cell surface. In summary, endothelial cell insulin receptors are constitutively recycled, and internalization and externalization rates are increased by receptor occupancy and PMA treatment.

Animals↗
PubMed1989

Production of insulin antibodies by mice rejecting insulin transfected cells.

Antibodies to insulin appear prior to the development of Type I diabetes and their concentration may correlate with the rate of autoimmune beta cell destruction. In order to study potential mechanisms involved in the production of antibodies to insulin, we transplanted different strains of mice with histoincompatible non-islet cells (AtT20-Ins and NIH-3T3-Ins) synthesizing homologous insulin, in contrast to immunization with non-transfected cells and insulin in Freund's adjuvant. The pituitary cell line (AtT20) and the fibroblast cell line (NIH-3T3) were transfected with the rat insulin-II gene (which encodes an insulin molecule identical to that of mouse insulin-II). No antibodies to insulin were found after subcutaneous injection of AtT20-control cells (without the integrated rat insulin gene) or after injection of rat insulin complete Freund's adjuvant. After subcutaneous injections of living AtT20-Ins or NIH-3T3-Ins cells producing insulin (40 to 60 ng insulin/10(6) cells per injection) in two strains (BALB/cJ, C3H/HeJ) but not in a third (SJL/J), antibodies to insulin rapidly appeared. In addition, when AtT20-Ins cells were transplanted into Wistar-Furth rats, insulin antibodies appeared in three out of four animals. The level of antibodies induced was similar to the concentrations of insulin antibodies of prediabetic NOD mice. This finding suggests that during the immune destruction of a cell synthesizing insulin, humoral 'tolerance' to insulin can be rapidly abrogated. Genetic control of this response is suggested by the difference between response of BALB/cJ and C3H/He vs SJL/J.

Animals↗
PubMed1989

Compensatory adaption to partial pancreatectomy in the rat.

The aim of the present study was to determine if compensatory adaptions in pancreatic B-cell mass and/or function occur when B-cell mass is reduced without altering glucose tolerance. Islet mass and insulin secretory responses (both in vivo and in vitro) were assessed 19 days after a 40% pancreatectomy (Px) in 5-week-old rats. Plasma glucose and insulin values were unchanged by the 40% Px, both in the fed state and after ip glucose. Also, glucose potentiation of arginine-induced insulin secretion was fully intact when assessed with the in vitro perfused pancreas. Islet mass, assessed using point-counting morphometrics, was 84% of the sham value, not the expected 60%. In contrast, there was no compensatory change in acinar tissue, as judged by pancreatic weight. To determine if the insulin secretory reserve capacity was reduced after the 40% Px, dexamethasone was given on days 14-18. On day 18, the Px rats were midly hyperglycemic, but by the next day, glucose tolerance post-ip glucose was normal, and the insulin responses to the ip glucose in vivo and arginine in vitro were identical in the dexamethasone-treated Px and sham rats. These data show no discernible change in quantitative or qualitative B-cell secretory responses after 40% Px. A key mechanism contributing to this maintenance of normal function was regrowth of much of the excised islet tissue.

Adaptation, Physiological↗
PubMed1989

Compensatory growth of pancreatic beta-cells in adult rats after short-term glucose infusion.

The extent to which adult pancreatic beta-cells can respond in vivo to a sustained glucose stimulus by increasing their mass through either hyperplasia or hypertrophy has remained unanswered. Therefore, we studied the in vivo effect of short-term (96-h) hyperglycemia on the growth of beta-cells by infusing adult rats with 35 or 50% glucose or 0.45% saline. After 96 h of glucose infusion, the beta-cell mass, quantified by point-counting morphometrics of immunoperoxidase-stained paraffin sections, showed a 50% increase (9.57 +/- 0.87 mg, n = 5, 50% glucose infused; 9.50 +/- 1.23, n = 7, 35% glucose infused; 6.15 +/- 0.55, n = 6, 0.45% saline infused). This growth was selective for beta-cells; the non-beta-cell mass was unchanged. The mitotic index, measured by accumulated mitotic frequency after a 4-h colchicine treatment, increased fivefold in glucose-infused animals compared to saline-infused animals. This enhanced replication of beta-cells provides evidence for increase in cell number or hyperplasia. In addition, hypertrophy of the beta-cell was also quantified. Mean cell volume, determined from the mean cell cross-sectional area measured planimetrically from low-magnification electron micrographs, increased to 150% of control values after 96 h of 50% glucose infusion. Seven days after the 96-h infusion, in reversal experiments, the beta-cell mass had not returned to saline-infused levels. In addition, the non-beta-cell mass of glucose-infused animals had increased. The mitotic index of the beta-cell of glucose-infused rats was, however, significantly lower than that of the saline controls, but the mean cell volume of the beta-cells remained elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Minimal chronic hyperglycemia is a critical determinant of impaired insulin secretion after an incomplete pancreatectomy.

We now describe experiments that allow one to determine the consequences of B cell reduction alone vs. those that result from superimposed mild hyperglycemia. Male CD rats underwent a 60% pancreatectomy (Px); controls were sham operated. 1 wk later, either 10% sucrose (SUC) was substituted as fluid supply or tap water was continued (WAT). Plasma glucose and insulin values in Px-WAT remained equal to the sham groups; in Px-SUC the values were euglycemic for 25 d, but then nonfasting plasma glucose rose 15 mg/dl. After 6 wk, B cell mass in Px-WAT was reduced by 45% and non-B cell mass by 57%. In contrast, in Px-SUC both masses were comparable to the sham groups. The insulin response to 27.7 mM glucose was measured using the in vitro perfused pancreas. The responses were reduced in Px-WAT but in proportion to their reduced B cell mass; in contrast, it was 75% less than expected in Px-SUC. Also, the response to arginine given at 16.7 mM glucose was reduced only in Px-SUC. These results show that a lowering of B cell mass that does not result in hyperglycemia has no adverse effect on the remaining B cells. On the other hand, if even mild hyperglycemia develops, B cell function becomes impaired and results in inappropriately reduced insulin stores and insulin responses to marked stimuli.

Animals↗
PubMed1988

Altered differentiated cell surface properties of transformed (RINm5F) compared with native adult rat pancreatic B cells.

RINm5F cells, a line derived from a rat insulinoma, are frequently used as a model for studying pancreatic B cell structure and function. These transformed cells are known, however, to be different from native B cells in a number of biochemical respects. We have now compared the surface features of RIN cells and native B cells in two different ways: 1) Dispersed cells from islet obtained from adult rats can reassociate spontaneously in culture to form aggregates (pseudoislets) with cellular organization similar to that of intact native islets (a central B cell core surrounded by a discontinuous mantle of non-B cells). Native islet cells and RIN cells were mixed together and allowed to reaggregate. Examination by immunocytochemistry and transmission electron microscopy showed that the aggregates contained all cell types present in the original mixed cell suspension (native B- and non-B cells, and RIN cells). The native B cells were centrally located, surrounded by zones of non-B cells, as in islets. The RIN cells, however, were restricted to the periphery and as such not recognized as native B cells. 2) R2D6, a monoclonal antibody, binds selectively to a ganglioside on the surface of islet B, but not non-B, cells. The role of this ganglioside is not known. RIN cells were incubated with R2D6 followed by a fluorescently labeled second antibody. Analysis by flow cytofluorometry indicated that the monoclonal antibody had bound (stained) only 3-15% of the RIN cells. These R2D6 positive cells were sorted from R2D6 negative cells and subsequently shown to have a lower DNA content. Expression of the R2D6 target ganglioside on RIN cells thus appears to be cell cycle dependent. Based on two different criteria, RINm5F cells do not therefore share surface features in common with native B cells. The cell cycle dependent expression of a B cell surface antigen by the RIN cells might, however, be a useful model for studying the regulation of ganglioside turnover.

Animals↗
PubMed1988

beta----alpha----delta pancreatic islet cellular perfusion in dogs.

Intraislet communication between alpha-, beta-, and delta-cells and their secretory products may theoretically occur via the paracrine (interstitial) and/or vascular routes. Recently, we have shown that there is a directed microvascular circulation in the rat islet with a cellular order of perfusion of beta----alpha----delta. The direction of microvascular perfusion of cells within the dog islet has been controversial. Anterograde (arterial) perfusion and retrograde (reversed or venous) perfusion of a segment of isolated dog pancreas with potent insulin antibodies yielded results similar to those found in the rat pancreas (anterograde, 158 +/- 44% increase in glucagon and 65 +/- 20% increase in somatostatin; retrograde, no change in glucagon or somatostatin). Anterograde infusion of glucagon antibody (no change in insulin, -33.5 +/- 3% decrease in somatostatin) or somatostatin antibody (no change in insulin or glucagon) also yielded the same results as in the rat pancreas. Anterograde infusion of 500 pg/ml glucagon caused a larger increase in insulin secretion (245 +/- 10%) than retrograde infusion (45 +/- 4%), whereas somatostatin was stimulated more retrogradely (339 +/- 17%) than anterogradely (121 +/- 9%). Anterograde infusion of somatostatin produced a larger decrease in insulin and glucagon than did retrograde perfusion (P less than .0001 for both comparisons). The retrograde infusion of 0.3 mU/ml insulin caused a decrease in glucagon but was without effect anterogradely. The results from the infusion of exogenous hormones suggest that the sensitivity of the alpha-, beta-, and delta-cells to insulin, glucagon, and somatostatin is determined by the beta----alpha----delta order of perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Discordance of exocrine and endocrine growth after 90% pancreatectomy in rats.

As we have previously shown, by 8 wk after 90% pancreatectomy (PX) in the rat, there is considerable regeneration of both exocrine and endocrine pancreas. In this study we examine the growth of both the exocrine and endocrine tissue 3, 7, 14, and 21 days after PX by following the pancreatic content of insulin, glucagon, and amylase as well as the mitotic indices for exocrine and islet beta-cells. By 7 days the pancreatic remnant weighed more than the anatomically equivalent tissue in the sham, the remnant equivalent. The growth of the exocrine tissue and the endocrine beta-cells was discordant during these initial weeks after PX, as shown by the mitotic index. The mitotic index, measured as accumulated mitotic figures after a 4-h colchicine treatment, for both the exocrine and beta-cells in the sham animals was low and unchanging at the different time points (approximately 0.5%). At 3 and 7 days after PX, both the exocrine and beta-cells had mitotic indices three- to fourfold that of the sham animals. At 14 days after PX, the exocrine cells had a slightly, albeit significantly, elevated mitotic index, whereas that of the beta-cells was still double that of the shams. By 21 days there was no difference in mitotic index for exocrine tissue, but the beta-cells on the PX animals had a mitotic index still double that of the shams. Another index of growth, the cell birthrate, was estimated at 7 days from the slope of regression lines of the mitotic frequency accumulated 1, 2, 3, and 4 h after colchicine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Selective localization of factor VIII antigenicity to islet endothelial cells and expression of class II antigens by normal human pancreatic ductal epithelium.

We evaluated the expression of factor VIII and class II histocompatibility antigens on frozen sections of normal human and rat pancreases. The immunohistologic studies were performed with directly fluoresceinated anti-human factor VIII and monoclonal antibodies A2B5, 3G5 (anti-islet), L-243, I-2, OK1 (anti-human Ia-DR), Leu-10 (anti-human HLA-DQ), anti-human HLA-DP, and OX6 (anti-rat Ia). Islet endothelial cells of humans and Wistar, CD, and BB diabetes-prone rats could be distinguished from intra-acinar endothelial cells by markedly enhanced factor VIII immunoreactivity. Factor VIII-antibody staining of islet endothelial cells was specifically absorbed by prior incubation of anti-human factor VIII antibody with normal human plasma but not by incubation with factor VIII-deficient plasma. By double indirect immunofluorescence, normal human pancreatic ductal epithelium expressed Ia in five of six pancreases studied.

Adolescent↗
PubMed1988

Morphological evidence for pancreatic polarity of beta-cell within islets of Langerhans.

Reconstructions from serial paraffin sections were used to define the relationships of the pancreatic endocrine cells and the microvasculature of the islets of Langerhans of the rat. We have reported that the afferent vessel to an islet, an arteriole, enters the islet directly in the beta-cell core. Immediately after entering the islet, this arteriole branches into capillaries. Herein, we report that beta-cells have two capillary faces. When viewed in cross section, 8-10 beta-cells form a tubelike structure around a central capillary. The outer side of each beta-cell also abuts a capillary. A clear polarity of secretory granules was seen on the ultrastructural level when the beta-cells were partially degranulated by prior in vivo treatment with glyburide. Of the remaining granules, 75.7 +/- 1.7% were accumulated in the apical portion of the cell, even though this portion was only 50.4 +/- 3.2% of the cytoplasm. beta-Cells around a particular cross-sectioned capillary shared the same orientation of granular accumulation. These findings provide morphological evidence of in situ beta-cell polarity that could be an anatomical basis for functional compartmentalization.

Animals↗
PubMed1987

Glucose utilization in islets of hyperglycemic rat models with impaired glucose-induced insulin secretion.

Under most experimental conditions islet glucose metabolism is well-correlated with short-term glucose-induced insulin secretion. Two hyperglycemic rat models (neonatal streptozotocin and glucose infusion) have been previously found to have markedly impaired insulin responses to glucose, and the glucose utilization of islets isolated from these models was therefore studied to see if reduced glucose metabolism might be related to the secretory abnormalities. It was found that glucose utilization in the islets of the two models was similar or higher than in comparable control islets. These data suggest that the secretory defect of these models, which is presumably induced by chronic hyperglycemia, is at a step in the secretion process distal to glucose metabolism.

Animals↗
PubMed1987

Reproducible high yield of rat islets by stationary in vitro digestion following pancreatic ductal or portal venous collagenase injection.

Pancreatic distension with collagenase solution followed by stationary in vitro digestion yields large numbers of intact islets. We compared in rats two routes of collagenase injection, pancreatic ductal (PD) and portal venous (PV), for islet yield, in vitro insulin secretory capacities, and in vivo functional viability. The islet yield in the PD method (n = 11) was greater than that in the PV method (n = 8) (682 +/- 27 vs. 417 +/- 39 per pancreas, P less than 0.025). The insulin release from the PD islets in response to 16.7 mM glucose increased gradually following culture, 3.2 +/- 0.8 ng/10 islets/30 min (fresh) to 12.3 +/- 2.1 (24-hr culture). In contrast, insulin release from the PV islets increased during the first 6 hr of culture, but decreased after 24 hr in culture. Under electronmicroscopic examination, the PD islets revealed a well preserved structure with healthy endocrine cells, while the PV islets showed a dilated capillary network and distorted endocrine cell continuity. When 100 PD islets were transplanted into streptozotocin-induced diabetic B6AF1 mice (n = 8), all the recipient mice restored normoglycemia (less than 200 mg/dl) within 1-4 days following transplantation and maintained it until rejection. However, the recipient mice given 100 PV islets showed a significant delay in restoring normoglycemia, and 3 of 8 mice given 100 PV islets were still hyperglycemic on day 4 postgrafting. In summary, pancreatic ductal collagenase injection followed by stationary in vitro digestion reproducibly yields higher numbers of intact and viable islets when compared with portal venous collagenase injection, indicating the superiority of this method to portal venous injection.

Animals↗
PubMed1987

Regulation of vascular permeability in cell culture.

Although one of the earliest findings of diabetic retinopathy is altered capillary permeability, metabolic factors in diabetes that may increase the permeability of capillaries to fluorescein are unknown. We have studied the effect of a variety of vascular and retinal cells and hyperglycemia on the diffusion rate of fluorescein. These studies were performed with a cell culture system that mimics the cross-section of a capillary by having two chambers separated with a porous membrane that can support the growth of cells on either side of the membrane. The addition of a confluent layer of endothelial cells or retinal pigmented epithelial (RPE) cells inhibited fluorescein diffusion between the two chambers 20- and 300-fold, respectively, after cells were cultured for greater than 5 days. Exposure of endothelial cells to 400 mg/dl glucose for either 3 or 100 days did not affect the barrier function of these cells. The barrier function of capillary endothelial cells isolated from BB rats with chronic diabetes and from nondiabetic animals did not differ. In contrast to endothelial cells and RPE cells, arterial smooth muscle and pericytes, which are not known to form tight junctions, did not inhibit the diffusion of fluorescein more than 2-fold. Surprisingly, the dual culture of endothelial cells with either retinal pericytes or smooth muscle cells resulted in a 50-fold increase in the rate of fluorescein diffusion, showing a disruption of the endothelial barrier. In summary, the intercellular connections between endothelial and epithelial cells that are responsible for the barrier to fluorescein diffusion are not functionally affected by chronic exposure to hyperglycemia or diabetic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Spontaneous reassociation of dispersed adult rat pancreatic islet cells into aggregates with three-dimensional architecture typical of native islets.

Islets of Langerhans consist of four major endocrine cell types assembled in a highly organized manner critical for their function. The molecular forces governing islet cellular architecture are not understood. We determined whether adult rat islet cells carry information necessary for orderly assembly. Dispersed cells from adult rat islets were maintained in static suspension culture for 6 days. During this time the cells reassociated to form numerous aggregates. These aggregates were approximately half the size of native islets with a commensurate reduction in DNA and insulin content. However, both cellular composition and organization were remarkably similar to that of adult rat islets, in which the beta-cells form a central core surrounded by a discontinuous mantle of non-beta-cells. Thus, immunoperoxidase staining showed that in the aggregates, just as in intact islets cultured in parallel, 26% of the cells were non-beta-cells and of these, 94% were clearly peripheral. Non-beta-cells were similarly found to be peripheral, with beta-cells located centrally, even when the ratio of non-beta-cells to beta-cells had been altered. This was achieved by sorting the two cell populations by fluorescence-activated flow cytometry, resulting in aggregates with 79% non-beta-cells and 21% beta-cells. Insulin release from the aggregates was stimulated approximately ninefold by raising glucose from 50 to 300 mg/dl, which was comparable to that found for intact islets. The spontaneous formation of isletlike aggregates displaying appropriate cellular architecture indicates that the signals (molecules) needed for such organization are intrinsic to islet cells and are still expressed by them in adult life.

Animals↗