bluuebunny/crossref_metadata_2025 huggingface dataset:
Prolongation of Islet Xenograft Survival (Rat to Mouse)
Authors: Lacy Paul E , Davie Joseph M , Finke Edward H
Published: September 2013

The portal vein technique was modified to permit transplantation of isolated islets via the portal vein into diabetic mice. Transplants of BALB/c islets, via the portal vein, into diabetic BALB/c mice maintained normoglycemia for > 200 days. Morphologic studies of the liver of the recipients at 203–210 days revealed intact islets with a normal degree of beta granulation. A marked prolongation of islet xenograft survival was obtained by maintaining isolated rat islets (Wistar-Furth) in vitro at 24°C for 7 days, transplanting the islets into diabetic recipients (BALB/c) via the portal vein, and administering one i.v. injection of antiserum to mouse and rat lymphocytes at the time of transplantation. Seventy percent of the recipients were normoglycemic at 100 days and 33% were normoglycemic at 200 days after transplantation. Omitting the single injection of rat antilymphocyte serum from this protocol and using only mouse antilymphocyte serum and 1 wk of culture (24°C) resulted in a 10% survival of the islet xenografts at 100 and 200 days after transplantation. Morphologic studies on normoglycemic recipients (BALB/c) from 63 to 200 days after transplantation of rat islets revealed normal islets in the livers of the recipients with focal aggregates of lymphoid cells adjacent to the islets. The mechanism for induction of these lymphoid aggregates is unknown. Regardless of the mechanism of induction, the lymphoid aggregates did not interfere with the function of the islet transplants since the recipients were normoglycemic. Rejection of an established islet xenograft of rat islets was induced by the i.v. injection of 107 rat spleen cells into the recipient 57 days after transplantation. The mechanisms involved in obtaining marked prolongation of islet xenograft survival without the continuous use of immunosuppressive agents are not clearly established. The simplest explanation of the findings is that the pretreatment regimens destroyed or altered passenger lymphoid cells which are required for the induction of immune rejection of the islet xenografts by the recipient.
Gastrointestinal Insulinotropic Hormones in Normal and Gestational-Diabetic Pregnancy: Response to Oral Glucose
Authors: Hornnes Peter J , Kühl Claus , Lauritsen Keld B
Published: September 2013

The responses of gastric inhibitory polypeptide (GIP), gut glucagon-like-immunoreactivity (gut GLI), insulin, and pancreatic glucagon to a 50-g oral glucose load were studied in late pregnancy and postpartum in 11 normal women, 10 normal weight gestational diabetics, and 10 overweight gestational diabetics. The GIP response to glucose was impaired in pregnancy in all three groups. In pregnancy, the GIP response was smaller in both groups of gestational diabetics than in normal women, whereas postpartum, the GIP response was lower than normal in the normal weight gestational diabetics only. In pregnancy, the gut GLI response to glucose was reduced in the overweight gestational diabetics and abolished in the normal women. The insulin response to glucose was increased in pregnancy in all three groups. Moreover, it was higher in the overweight gestational diabetics than in the other two groups in pregnancy and postpartum. In the normals, the suppression of glucagon levels after glucose ingestion was more marked in pregnancy than postpartum, whereas no such effect was seen in gestational-diabetic pregnancy. It is concluded that pregnancy—normal as well as gestational-diabetic—is accompanied by profound changes in the secretion of gastrointestinal insulinotropic hormones after glucose ingestion. These findings may be important for the understanding of changes in metabolism and gastrointestinal physiology in gestation.
Effect of Insulin Therapy on Insulin Resistance in Type II Diabetic Subjects: Evidence for Heterogeneity
Authors: Ginsberg Henry , Rayfield Elliot J
Published: September 2013

Insulin resistance has been demonstrated previously in both glucose-intolerant and untreated type II diabetics. Although the former group had hyperinsulinemia in the fasting state and after an oral glucose load, the hyperglycemic type II subjects were relatively insulin deficient after carbohydrate ingestion. In an attempt to define the role that insulin deficiency might have played in the pathophysiology of insulin resistance in this latter group, we measured the steadystate plasma glucose level (SSPG) during a constant infusion of glucose (6 mg/kg/min) and insulin (80 mU/min) in 15 nonobese insulin-deficient type II diabetics before and after insulin replacement therapy. Hepatic glucose output (HGO) and plasma clearance of glucose (PCG) during these studies were also determined using an infusion of 3-3H-glucose.

Before insulin treatment, 13 of 15 subjects had SSPG levels above the range reported in normal subjects. Two type II patients appeared to be normally sensitive to insulin. Although all subjects were more sensitive to insulin after 1–8 wk of insulin therapy, they could be clearly divided into two groups. Thus, five patients were now normally sensitive to insulin (SSPG:75 ± 5.3 mg/dl) while 10 patients were still significantly resistant (SSPG: 227±11.3 mg/dl). HGO during the infusion studies was high in the resistant group pretreatment and did not change posttreatment (3.54 ± 0.32 vs. 3.14 ± 0.78 mg/kg/min). HGO was lower before insulin therapy and decreased by > 50% after therapy in the sensitive group (1.93 ± 0.07 vs. 0.71 ± 0.32 mg/kg/min). PCG determinations revealed a similar pattern of response. Retrospective analysis of the two groups revealed no significant differences in their baseline characteristics. Fasting plasma glucose and hemoglobin A1c levels also did not differ between the two groups before or after insulin therapy.

These results indicate that heterogeneity exists among subjects with type II diabetes mellitus. One-third of the subjects studied appear to have only insulin deficiency as the basis of their diabetes, while two-thirds seem to have an underlying resistance to insulin that is not corrected by insulin therapy.
Effect of the Membrane Lipid Environment on the Properties of Insulin Receptors
Authors: Ginsberg Barry H , Brown Thomas J , Simon Ido , Spector Arthur A
Published: September 2013

We have altered the fatty acid composition of the Friend erythroleukemia cells and studied the effect on the binding parameters of the insulin receptor. Cells were grown for about five generations in media enriched with oleate (a monounsaturated fatty acid) or linoleate (a polyunsaturated fatty acid). The microsomal phospholipids normally contained about 40% saturated, 40% monounsaturated, and 20% polyunsaturated fatty acids. In cells grown with oleate, monounsaturates rose to 63% and in cells grown with linoleate, the polyunsaturated component rose to 52%. Fluidity determination by electron spin resonance similarly indicated that the membranes of cells grown in linoleic acid were more fluid than those grown in oleic. Control cells demonstrated the least membrane fluidity.

The cells enriched in unsaturated fatty acids had an increased number of insulin receptors and decreased receptor affinity, but the exact interpretation of the change was dependent on the method of data analysis. When analyzed assuming negative cooperativity among a single class of receptors, there was an increase in receptor number from 23,000/cell in the control cells to 39,000/cell in the oleate-enriched and to 81,000/cell in the linoleate-enriched cells. These changes were accompanied by reciprocal decreases in the affinity of both the unoccupied form of the receptor (Ke) and the occupied form of the receptor (Kf). When analyzed assuming two independent classes of sites, there was no major change in the number or affinity of the high affinity receptors (6000–8000/cell). There was, however, a marked increase in the number of low affinity receptors from 15,000/cell in the control cells to 32,000/cell in the oleate-enriched and 74,000/cell in the linoleate-enriched cells. This increase in receptor concentration was again accompanied by a reciprocal decrease in the affinity of the low affinity receptor.

These studies thus demonstrate a relationship between the cellular fatty acid composition and the properties of insulin receptors. The observed changes could be due to alterations in the quaternary structure Of the receptor.
Experimental Chemical Diabetes and Pregnancy in the Rat: Evolution of Glucose Tolerance and Insulin Response
Authors: Triadou Nicole , Portha Bernard , Picon Luc , Rosselin Gabriel
Published: September 2013

The effect of pregnancy on the course of experimental chemical diabetes (CD) has been studied in the rat. Glucose tolerance tests (0.5 g/kg i.v.) have been performed serially in the virgin state (2 mo), late pregnancy (20.5 day of gestation), and 1 and 2 mo after delivery, in control and in CD female rats. During gestation in the controls basal plasma glucose is decreased, and plasma glucose levels after glucose load, and also lower than levels found in the virgin state. Glucose tolerance is not significantly affected. Nevertheless, glucose-induced insulin secretion in pregnant animals is increased compared with the virgin state. Glucose tolerance remains unchanged 1 and 2 mo postpartum, but insulin response to glucose becomes significantly lower than in the virgin state. In the pregnant CD rats basal plasma glucose is decreased, but plasma glucose levels after glucose load are similar to values found in the virgin state, thus suggesting decreased glucose tolerance. Glucose-induced insulin secretion is increased compared with the virgin state. Glucose tolerance remains deteriorated 1 and 2 mo postpartum, but insulin secretion is no longer significantly different.
Central and Peripheral Nervous System Complications
Authors: Brown Marvin R , Dyck Peter J , Mcclearn Gerald E , Sima Anders A F , Powell Henry C , Porte Daniel
Published: September 2013

Symptomatic neuropathy is a common manifestation of diabetes mellitus, and sensory, motor, or autonomic symptoms occur in approximately 10% of all diabetic patients. Animal models may be useful to study the metabolic and electrophysioiogic abnormalities peculiar to diabetic neuropathy. Genetic animal models, including the Chinese hamster, ob/ob mouse, db/db mouse, BB-wistar rat, and SSDR rat or chemically induced or nutritional models of diabetes mellitus provide the potential to use animals to study human neuropathy; however, to date, few characteristics of human diabetic neuropathy have been clearly demonstrated in any of these animal models. Better characterization of the neuropathy of existing animal models with emphasis on evaluation over long periods of time is recommended. These studies should include a cross-disciplinary approach using biochemical, electrophysioiogic and morphologic techniques. Specific future approaches to study diabetic neuropathy using chemical models is outlined in this chapter.
Can Future Type I Diabetes Be Predicted? A Study in Families of Affected Children
Authors: Gorsuch A N , Spencer K M , Lister J , Wolf E , Bottazzo G F , Cudworth A G
Published: September 2013

This article examines the risk of type I (insulin-dependent) diabetes in siblings of affected children, in relation to HLA genotypes. The 288 available siblings of 160 diabetic probands were grouped according to the number of HLA haplotypes in common with their probands. HLA-identical siblings (both haplotypes in common) have an approximately 100 times greater risk of developing the disease than that in the general population, and this risk is significantly higher than that in haplo-identical siblings (one haplotype in common) P = 0.008). Thus, in Northern European populations, some 30% of HLA-identical siblings are expected to be diabetic by the age of 30 yr. The risk in nonidentical siblings (neither haplotype in common) is not significantly increased. These findings carry implications for genetic counseling and research.
Quantitative Aspects of Glucose Production and Metabolism in Healthy Elderly Subjects
Authors: Robert J -J , Cummins J C , Wolfe R R , Durkot M , Matthews D E , Zhao X H , Bier D M , Young V R
Published: September 2013

The metabolic basis for the reduced glucose tolerance that occurs during aging in humans has been explored with the aid of a primed constant intravenous infusion method of labeled glucose (6-3H; 6,6,2H- and U-13C-glucose). Healthy young adult men and women (24 ± 3 yr) and elderly men and women (75 ± 4 yr) participated in a series of studies designed to quantify rates of plasma glucose appearance, oxidation, and recycling while subjects were in the postabsorptive (basal) state and to determine rates of hepatic glucose production and glucose disappearance in response to intravenous glucose at approximately 1 and 2 mg · kg−1min−1 and also 4 mg · kg−1min−1 without or with a simultaneous infusion of insulin to maintain normoglycemia. Basal rates of glucose production were 2.41 ± 0.06 and 2.18 ± 0.05 mg · kg−1min−1 in the young adults and elderly, respectively (P < 0.05). Recycling of glucose carbon and glucose oxidation rates did not differ significantly between the two age groups. Infusion of unlabeled glucose reduced hepatic glucose production to the same extent in the two groups, indicating that the mechanisms responsible for altered hepatic glucose production with intravenous glucose administration remain intact during human aging. Plasma insulin changes were similar in young adult and elderly subjects receiving 4 mg · kg−1min−1 unlabeled glucose except that the higher plasma glucose levels in the elderly were associated with higher insulin levels. For elderly subjects, the amount of exogenous insulin required to maintain normoglycemia at the 4 mg · kg−1min−1 glucose infusion rate was about twice that necessary in young adults.
Nonenzymatic Glycosylation of Serum and Plasma Proteins
Authors: Kennedy Laurence , Mehl Thomas D , Elder Elizabeth , Varghese Matthew , Merimee Thomas J
Published: September 2013

Albumin and other serum and plasma proteins may be nonenzymatically glycosylated in vitro and in vivo. Chromatographie and colorimetrie measurement of these nonenzymatically glycosylated proteins shows that levels are approximately two to three times higher in diabetic than nondiabetic subjects. In diabetic patients levels appear to reflect glycemia in the preceding several days and correlate with other established parameters of glycemia such as fasting serum glucose, mean of several capillary blood glucose measurements, and glycosylated hemoglobin. Because serum and plasma proteins have shorter half-lives than hemoglobin, nonenzymatically glycosylated proteins are altered more rapidly than glycosylated hemoglobin in response to prolonged decreases or increases in blood glucose levels.

Acetylsalicylic acid significantly inhibits in vitro glycosylation of albumin and other serum proteins incubated for up to 7 days in glucose. It is not known whether such inhibition occurs in vivo.

Glycosylation of albumin appears to reduce its solubility, and glycosylation of low-density lipoprotein may increase its catabolism. Whether nonenzymatic glycosylation of other serum proteins alters their functions or may contribute to some of the long-term complications of diabetes is unknown at present.
Sorting of Pancreatic Islet Cell Subpopulations By Light Scattering Using a Fluorescence-activated Cell Sorter
Authors: Nielsen David A , Lernmark Åke , Berelowitz Michael , Bloom Gunnar D , Steiner Donald F
Published: September 2013

Methods have been developed for the preparation of suspensions of viable rat pancreatic islet cells and their analysis and sorting in the fluorescence-activated cell sorter (FACS III or IV). Histograms of cell number versus light scattering in a near forward angle (1–15°) demonstrated that viable islet cells produce a broad peak that is distinctly separated from the peaks generated by exocrine cells, erythrocytes, and nonviable cells. Electron microscopic examination and radioimmunoassay of hormone content in fractions collected across the peak showed that glucagon-containing (A) cells scatter less intensely and are concentrated within the left side of the islet cell peak, while somatostatin-containing (D) cells are localized to the far right side, indicating a higher intrinsic light scattering property of the D-cells. The more abundant insulin-containing (B) cells define the center of the islet cell peak. Sodium dodecyl sulfate slab gel electrophoresis and radioautography of 35S-methionine labeled cellular proteins confirmed that sorted cells are viable. Cells from the far left region contained increased amounts of labeled 18 Kd proglucagon and its 13-Kd and 10-Kd conversion intermediates, while cells from the right side were relatively enriched in labeled 12.5 Kd prosomatostatin. These results demonstrate that intrinsic light scattering alone can be used to prepare A- or D-cell enriched fractions from islets for biochemical analysis.
Expression of HLA-DR Antigens in Human Fetal Pancreas Tissue
Authors: Danilovs John A , Hofman Florence M , Taylor Clive R , Brown Josiah
Published: September 2013

The expression of HLA-DR antigens in human fetal pancreas tissue was studied using four independently derived monoclonal antibodies recognizing nonpolymorphic HLA-DR antigens. Immunoperoxidase staining of frozen sections revealed numerous DR-antigenpositive cells. Two major cell types could be distinguished. Large, strongly DR-positive cells with dendritic morphology were distributed throughout the pancreatic parenchyma and interstitial connective tissue. Dual staining of DR antigens and insulin using a two-color immunoperoxidase technique clearly showed that some of these DR-positive dendritic cells were located within and in close association with insulin-producing islets.

Also observed as a regular feature of fetal pancreas tissue sections were large clusters of DR-positive cells with lymphoid morphology. Positive staining of many cells within these clusters with monoclonal antibodies against T-cell marker (Leu-1) and T-cell subset markers (Leu-2 and -3) supported their classification as lymphoid cells. In contrast, no positive staining with anti-T-cell antibodies was observed outside of lymphoid cell clusters, confirming the distinction between these cells and the DR-positive cells distributed throughout the pancreas. The presence of other DR-bearing cell types in fetal pancreas could not be excluded, but most endothelial cells appeared to be DR-negative.

The demonstration of numerous DR-bearing cells associated with fetal pancreas tissue may require that we alter our views on DR-antigen ontogeny and develop new strategies for fetal pancreas transplantation.
Skin Collagen Metabolism in the Streptozotocin-induced Diabetic Rat: Enhanced Catabolism of Collagen Formed Both Before and During the Diabetic State
Authors: Schneir Michael , Ramamurthy Nangavaram , Golub Lorne
Published: September 2013

Collagen catabolism has been measured in skins of streptozotocin-induced diabetic rats. For measuring catabolism of collagen synthesized de novo during the diabetic state, we measured the amounts of [3H]hydroxyproline-containing degradation products in skins of diabetic rats, killed 4 h after [3H]proline injection (protocol 1); degradation products were isolated in TCA-soluble fractions of skin homogenates. For measuring catabolism of collagen preexisting before the induction of the diabetic state, we measured the 21-day loss of [3H]hydroxyproline (and hydroxyproline) in entire skins of rats that were streptozotocin-treated after [3H]proline injection (protocol 2).

A 2.5-fold increase in the relative amounts of [3H]hydroxyproline-containing degradation products was measured in the TCA-soluble fractions of skins from diabetic rats (protocol 1). These degradation products had a low molecular weight (as evident from their diffusibility), and they were derived from recently synthesized collagen, possibly procollagen (as evident from their high [3H]hydroxyproline specific activity). Furthermore, they were not derived from the degradation of [3H]hydroxyproline-labeled collagen present before induction of the diabetic state (protocol 2). Evidence for this conclusion is as follows: the amounts of [3H]hydroxyproline-containing degradation products in skins of diabetic rats were not greater than that in skins of control rats, despite a 50% resorption of collagen in skins of diabetic rats.

Overall, the catabolism of collagen formed de novo during the diabetic state was distinguished from the catabolism of collagen formed before, and both catabolic processes were enhanced in rat skins of streptozotocin-induced diabetic rats.
Pupil Size in Insulin-dependent Diabetes: Relationship to Duration, Metabolic Control, and Long-Term Manifestations
Authors: Hreidarsson A B
Published: September 2013

The pupil area was measured in complete darkness by infrared TV-videopupillography in 109 insulin-dependent diabetics, aged 25–43 yr, diabetes duration 0–35 yr, and 39 control subjects, aged 26–41 yr. In darkness the pupil was 19.6% ± 4.2 (SEM) smaller in diabetics than in controls (2 P < 10−5. There was an inverse relationship between diabetes duration and pupil area (Kendall's coefficient of correlation, τ = −0.33, 2 P < 10−4. There was also an inverse correlation between pupil size and vibratory perception threshold (τ = 0.32, 2 P < 10−3. Long-term diabetics (duration ≥ 15 yr) with proliferative retinopathy had a 28.4% ± 8.1 (SEM) smaller pupil than those without (2 P = < 10−3. Likewise, long-term diabetics with nephropathy had a 19.8% ± 9.1 smaller pupil than those without nephropathy (2 P = 0.035). In the long-term diabetics there was an inverse relationship between the level of blood glucose throughout the years and pupil area (τ = −0.49, 2 P < 10−3. Also, high blood glucose levels throughout the years were correlated to severity of retinopathy (τ = 0.43, 2 P < 10−3 and nephropathy (τ = 0.30, 2 P = 0.024). There was no correlation between biomicroscopic changes in the iris and the diminished pupil area. Pupil area in light was measured in 85 patients and 31 controls. In continuous light only the long-term diabetics had a smaller pupil size than the controls. Both the absolute and relative change in pupil size from darkness to light was less in the diabetic group. Measuring the pupil size in darkness is a simple, noninvasive and reproducible method that may yield information about autonomic nervous involvement in diabetes.
Virus-Induced Diabetes Mellitus: Glucose Abnormalities Produced in Mice by the Six Members of the Coxsackie B Virus Group
Authors: Toniolo Antonio , Onodera Takashi , Jordan George , Yoon Ji-Won , Notkins Abner Louis
Published: September 2013

The capacity of Coxsackie B viruses (CBVs) to produce diabetes in mice was studied before and after passage in various cell types. CBVs that had been passaged in monkey kidney cells or in mouse embryo fibroblasts failed to produce abnormal glucose tolerance tests, whereas virus passaged five or more times in the pancreata of mice or in beta-cell cultures p oduced transient abnormal glucose tolerance tests. Immunofluorescence and histologic studies revealed that passage of CBVs in cultured beta-cells changed the tropism of these viruses from the acinar pancreas to the islets of Langerhans. Although all six CBV serotypes that had been passaged in beta-cell cultures behaved very similarly, substantial variation was observed with the different virus passages and in some experiments, beta-cell damage and the glucose abnormalities were minimal. From these and other experiments, we conclude that the six members of the CBV group have the potential for infecting and damaging pancreatic beta-cells in mice.
Insulin, Glucagon, and Somatostatin Receptors on Cultured Cells and Clones from Rat Islet Cell Tumor
Authors: Bhathena Sam J , Oie Herbert K , Gazdar Adi F , Voyles Nancy R , Wilkins Samuel D , Recant Lillian
Published: September 2013

Cells grown in culture from rat islet cell tumor (parent cells) and clones obtained from them were used in this study. Parent cells secreted primarily insulin and somatostatin with very small quantities of glucagon. The clones, based on hormone content and secretion, were divided into three phenotypic groups: insulin secreting, somatostatin secreting, and nonsecreting clones. Specific receptors for insulin, glucagon, and somatostatin were demonstrated on parent cells and clones. Parent cells bound 4.12 ± 0.46% insulin, 2.11 ± 0.29% glucagon, and 2.49 ± 1.24% somatostatin per 2 × 106 cells. Characteristic hormone binding patterns were observed in insulin secreting versus somatostatin secreting clones. Insulin secreting clones bound less insulin than somatostatin and other noninsulin- secreting clones (P < 0.02). In contrast, somatostatin secreting clones bound more somatostatin than non-somatostatin-secreting clones (P < 0.05). Somatostatin-secreting clones had a significantly greater number of receptors for all three hormones. The difficulties involved in the interpretation of the quantitative aspects of binding in the presence of continued hormone secretion are discussed. Nonetheless, the presence of receptors on the cells for hormones secreted by the same cells strongly suggests autoregulation. The apparent low affinity of some of these receptors and the presence of receptors for all three islet cell hormones on all islet cells supports the likelihood of paracrine controls.
The Effect of Hyperinsulinemia on Glucose Homeostasis During Moderate Exercise in Man
Authors: Chisholm Donald J , Jenkins Arthur B , James David E , Kraegen Edward W
Published: September 2013

Moderate exercise in man for 1 h results in a two- to threefold increase in glucose disappearance (Rd) and hepatic glucose production (Ra) so that euglycemia is maintained. The mechanism controlling the increase in Ra is not known, although circulating levels of insulin and glucagon have been suggested as important regulatory factors.

To assess the importance of circulating insulin levels on exercise-induced glucose flux, we have examined the response to 60-min exercise on a bicycle ergometer at 60% maximal oxygen uptake (Vo2 max) in five normal male subjects on two occasions. A constant i.v. infusion of insulin (20 mU/kg/h) or saline was begun 60 min before exercise. Ra and Rd were measured by a non-steady-state constant [3-3H]glucose infusion technique.

During the control (saline) study serum insulin (IRI) fell from 6.4 ± 1.8 (SEM) to 4.4 ± 1.4 mU/L (P < 0.05). During the insulin infusion IRI was maintained at 23.0 ± 0.8 mU/L with a modest drop in plasma glucose before exercise, 5.4 ± 0.2 to 4.0 ± 0.4 mmol/L. Hyperinsulinemia during exercise did not affect peak responses of either Ra (control 1.88 ±0.25 versus 2.00 ± 0.17 mmol/min, NS) or Rd (control 1.89 ± 0.26 versus 1.94 ± 0.18 mmol/min, NS) nor did it result in a significant fall in plasma glucose (control −0.2 ± 0.2 versus −0.2 ± 0.4 mmol/L). Moreover, plasma glucagon (IRG) had not changed significantly after 30-min exercise during insulin infusion when Ra had increased to 195% of the pre-exercise level. Plasma cortisol, norepinephrine, and growth hormone rose during exercise, but the elevation was not significantly greater during insulin infusion than in the control study.

Thus, during moderate hyperinsulinemia in normal man, exercise does not cause a fall in plasma glucose and hepatic glucose output is undiminished. This study demonstrates that a decrease in IRI, elevation of IRG, or a change in IRI/IRG ratio are not important in initiating hepatic glucose output during exercise.
Autonomic Neuropathy and the Ventilatory Responses of Diabetics to Progressive Hypoxemia and Hypercarbia
Authors: Soler Norman G , Eagleton Lanie E
Published: September 2013

To investigate one suggested cause of unexplained deaths of diabetic patients with autonomic neuropathy, ventilatory responses to progressive hypoxemia and to progressive hypercarbia were compared among two groups of diabetic patients, with and without autonomic neuropathy, and a group of normal control subjects. Hypoxemia was induced gradually under isocapnic conditions and the arterial oxygen saturation was reduced to below 75%. In a separate test the end tidal CO2 was increased gradually to 55 mm Hg in subjects who could tolerate this degree of hypercarbia. The ventilatory responses to hypoxemia and to hypercarbia did not differ among groups nor did age, duration of diabetes, or presence of proliferative retinopathy and nephropathy have a significant effect on the ventilatory responses of diabetics. The authors conclude that defective ventilatory responses to hypoxemia or hypercarbia are not associated with the sudden unexplained deaths in diabetics with autonomic neuropathy.
Binding and Degradation of Insulin by Isolated Renal Brush Border Membranes
Authors: Rabkin Ralph , Petersen Jeffrey , Mamelok Richard
Published: September 2013

Filtered proteins including insulin are absorbed in the proximal tubule by means of pinocytosis. The first step in this process is binding of the protein to brush border membrane. As it is not known whether absorption exhibits specificity, we set out to determine whether specific binding sites for insulin are present in brush border membranes. Rabbit-isolated brush border membranes were incubated with 125I-insulin and varying concentrations of cold insulin or other peptide hormones. Binding and degradation of 125I-insulin occurred in a time- and temperature–dependent manner. Native insulin competitively inhibited 125I-insulin binding, but calcitonin, arginine vasopressin, glucagon, and growth hormone (10−6 M) were relatively ineffective. Nonspecific binding averaged one-third of the total radioactivity bound. Scatchard analysis of binding data revealed two classes of insulin receptors: high affinity, low capacity receptors and low affinity, high capacity receptors. Gel filtration analysis of 125I-insulin exposed to brush border membrane revealed the formation of low-molecular-weight products similar to that produced by intact kidneys. The degrading process exhibited some specificity, for cold insulin (10−6 M) was more effective than calcitonin, vasopressin, glucagon, or growth hormone in inhibiting degradation (32% versus <13% inhibition; P < 0.01). Whether this reflects inhibition of insulin specific binding before exposure to degradation or inhibition of specific enzymes is unclear. In summary, it appears that renal brush border membranes have a major insulin-specific receptor component that could potentially mediate tubular insulin absorption. In addition, there is a smaller nonspecific component that may also have the potential to mediate insulin absorption. Finally, it appears that brush border membranes have the ability to degrade insulin to low-molecular-weight products by a process that exhibits some specificity for insulin.
Quantitation of Glycosylated Hemoglobin: Elimination of Labile Glycohemoglobin During Sample Hemolysis at pH 5
Authors: Bissé Emanuel , Berger Willi , Flückiger Rudolf
Published: September 2013

A simple method for the elimination of labile glycohemoglobin in the chromatographic quantitation of glycosylated hemoglobin is described. Use is made of the instability of Schiff base adducts in acidic solution. Erythrocytes are lysed with a pH 5 buffer. At this pH dissociation reaches completion during sample preparation.
[125I]Diiodoinsulins: Binding Affinities, Biologic Potencies, and Properties of their Decay Products
Authors: Maceda Blanca Pérez , Linde Susanne , Sonne Ole , Gliemann Jørgen
Published: September 2013

Insulin was iodinated with 0.3–0.4 mol 125I/mol insulin using the lactoperoxidase method. About one-third of the radioactivity incorporated into insulin was in diiodoinsulins and about 40% of these molecules contained diiodotyrosine in residue 14 of the A chain. Most of the remaining molecules contained one A14-monoiodotyrosine and one monoiodotyrosine in either position A19, B16, or B26. The binding affinity and biologic potency of this heterogeneous diiodoinsulin preparation was not significantly different from that of A14-[125I]monoiodoinsulin in rat adipocytes, whereas it was slightly reduced in hepatocytes and IM-9 lymphocytes. From the iodine distribution and previous data on the binding affinity of each of the four monoiodoinsulin isomers it was calculated that A14-diiodotyrosine-insulin possesses full binding affinity and biologic potency in adipocytes.

Diiodoinsulins isolated from another iodoinsulin preparation (iodate method) contained 58% A19-diiodotyrosine-insulin, and most remaining molecules contained one A19-monoiodotyrosine. The binding affinity of this mixed diiodoinsulin preparation was approximately one-fourth of that of A14-monoiodoinsulin in adipocytes, IM-9 lymphocytes, and hepatocytes. It was calculated that A19-diiodotyrosine-insulin is nearly devoid of binding affinity.

The diiodoinsulins (lactoperoxidase method) decayed to iodide (probably from diiodotyrosine-insulin) or to polymers with little specific but a markedly increased nonspecific binding. In addition, the polymers had a marked tendency to adsorb to cellulose acetate filters.

Conclusions: 1. The binding affinities of diiodoinsulins range from very low values to values at least as high as that of insulin depending on the positions of the iodine moieties. 2. The relative binding affinities vary among tissues. 3. Polymeric decay products give high nonspecific binding.
Influence on Anion Transport on Glucose-induced Electrical Activity in the B-Cell
Authors: Pace Caroline S , Tarvin John T
Published: September 2013

We have previously shown that the effect of glucose on electrical activity (EA) in islet B-cells is altered by modification of pH. The regulation of intracellular pH (pHi) in nerve and muscle cells is coupled to anion exchange. In the present study we have examined the involvement of HCO3:Cl exchange across the plasma membrane in the maintenance of glucose-induced EA in B-cells. 4,4′-diisothiocyanostilbene-2,2′ disulfonic acid (DIDS), an inhibitor of anion exchange, elicited a dose-related stimulation of EA in the presence of 11.1 mM glucose. The increase in the relative duration of the active phase (constant spike activity) was first observed at 20 μM DIDS, and a nearly maximal effect was obtained at 200 μM. The substitution of HCO3− by a Hepes buffer elicited constant spike activity. The application of 0.25 μM tributyltin, an electroneutral Cl:OH exchanger, also enhanced EA as indicated by an increase in the duration of the active phase. The influence of HCO3− withdrawal, DIDS, and tributyltin all elicited electrical events similar to that obtained by a decrease in pHi. Our results suggest that anion exchange may be involved in the regulation of electrical events in the B-cell by influencing pHi, as has been documented to occur in invertebrate nerve and muscle.
Does Insulin Removal Rate from Plasma Decline with Age?
Authors: Reaven Gerald M , Greenfield Michael S , Mondon Carl E , Rosenthal Mark , Wright Diana , Reaven Eve P
Published: September 2013

The effect of age on the rate of insulin removal from plasma was studied in both rat and man. The experimental approach was based on measurement of the steady-state plasma insulin concentration achieved during a period in which endogenous insulin secretion was suppressed and exogenous insulin infused. Rats, 1½ and 12 mo of age, were infused with 2.5, 5.0, and 10.0 μU/kg of insulin during a 180-min period in which endogenous insulin secretion was suppressed by epinephrine and propranolol. Steady-state plasma insulin concentrations were approximately twice as high in the older rats at every insulin infusion rate. Similar results were seen in man; significant correlations were observed between height of steady-state plasma insulin concentration and advancing age during infusion of exogenous insulin and suppression of endogenous insulin with either exogenous insulin (r = 0.66, P < 0.001) or epinephrine and propranolol (r = 0.47, P < 0.01). Since infusion rates of exogenous insulin were identical in all studies, these results suggest that there is an age-related decrease in insulin catabolism.
Insulin Secretion by Fetal Human Pancreatic Islets of Langerhans in Prolonged Organ Culture
Authors: Mandel T E , Georgiou H M
Published: September 2013

Fetal human pancreata, obtained from legally-induced abortions, were placed in organ culture to study their capacity to produce insulin over periods in vitro of between 18 and 40 days. Specimens obtained by hysterotomy usually showed increasing insulin secretion as measured by the insulin content of the media at each twice-weekly medium change. In most instances, relatively little insulin was produced during the first 7–10 days, but thereafter insulin secretion rapidly increased. In contrast, most specimens from prostaglandin-induced abortions showed high levels of insulin in the medium early in the culture period but little thereafter, indicating rapid release of insulin from damaged tissue. In some instances, after early insulin release by damaged tissue, some recovery of islet function occurred and insulin secretion again increased. The presence of differentiated endocrine cells was confirmed histologically. Tissue from each fetus was placed in a number of petri dishes, and for each individual fetus a qualitatively similar pattern of secretion was noted in each dish. These data suggest that representative and nondestructive monitoring of islet function is possible and may be important before such tissue is considered for use in islet transplantation in insulin-dependent diabetes.
Insulin Secretion in the Obese (ob/ob) Mouse: The Effect of Oxytetracycline on Insulin Release
Authors: Dalpé-Scott Marthe , Heick H M C , Bégin-Heick Nicole
Published: September 2013

The effect of oxytetracycline (OTC) pretreatment on the response of the ob /ob mouse to insulin secretagogues in vivo and in vitro was investigated. With glucose loading in vivo, the peak glucose was twofold greater and the insulin levels threefold greater in obese than in lean mice. After OTC treatment, there was no significant difference in insulin levels between lean and obese mice although the peak glucose level was still 1.5 times as high. Glucagon increased plasma glucose 2.5-fold and plasma insulin 20-fold in the obese as compared with lean mice. After OTC treatment, the glycemie response of the obese was indistinguishable from that of the lean control. The insulin levels, while higher than those of lean mice, were only 25% of those found in the untreated obese. Aminophylline produced an 8- and a 20-fold increase in peak glucose and insulin levels, respectively, as compared with lean mice. In the OTC-treated obese mice, the injection of aminophylline produced a slower rise in plasma glucose than in the obese controls, but the levels were not significantly different from those of the untreated obese mice at 90 min. On the other hand, the insulin levels attained a plateau at a value which was one-fifth that found in the control obese group. In vitro, isolated islets from obese mice showed an exaggerated response to the secretagogues. Pretreatment with OTC attenuated this response. The fraction of insulin released at 10 mM glucose was less than one-fourth that in the obese controls. With glucagon added, the response was only one-eighth, and with aminophylline, one-half as great in the OTC-treated than in the obese control. The effects of OTC cannot be attributed to the effects of the drug on food consumption, since obese mice food restricted to the intake of the OTC-treated obese mice showed either no improvement or much smaller Changes.
A Controlled Trial of Sorbinil, an Aldose Reductase Inhibitor, in Chronic Painful Diabetic Neuropathy
Authors: Young Robert J , Ewing David J , Clarke Basil F
Published: September 2013

A double-blind, randomized, placebo-controlled crossover trial of the aldose reductase inhibitor sorbinil was undertaken in 15 patients (age 35–68 yr) with chronic painful diabetic neuropathy. Treatment was evaluated by subjective pain responses, clinical examination, vibration perception threshold, motor and sensory nerve electrophysiology, and cardiovascular reflex tests of autonomie nerve function. Among the many measurements, only pain, tendon reflex scores, and sural sensory potential amplitude improved significantly during sorbinil administration, while scores of clinical sensory examination deteriorated. Four patients experienced an idiosyncratic reaction that rapidly recovered on discontinuing the drug. This study suggests that aldose reductase inhibitor treatment with sorbinil may have an effect on symptomatic diabetic neuropathy in man.
The Development of Lesions in the Glomerular Basement Membrane and Mesangium After Transplantation of Normal Kidneys to Diabetic Patients
Authors: Mauer S Michael , Steffes Michael W , Connett John , Najarian John S , Sutherland David E R , Barbosa Jose
Published: September 2013

Renal allograft biopsies at the time of transplantation (baseline) and 2 yr later were obtained in 6 type 1 diabetic and 12 nondiabetic patients and studied for glomerular basement membrane (GBM) and mesangial changes. Diabetic patients had significantly greater GBM thickness compared with nondiabetics at 2 yr (P = 0.05, rank sum test), and the increase in GBM thickness comparing baseline and 2-yr biopsies was greater in the diabetic compared with nondiabetic patients (P = 0.005, rank sum test). Similarly, diabetic patients developed significant mesangial thickening by light microscopy while no changes were observed in nondiabetic patients (P = 0.001). Electron microscopic morphometric analysis of the percentage of total mesangium was not different on comparing diabetic and nondiabetic patients at 2 yr. There was an increase in the matrix component of the mesangium in the diabetics at this time, although this did not reach statistical significance (P = 0.06). In addition, the surface density of the peripheral glomerular capillary wall, presumably reflecting mesangial expansion, was decreased in the diabetic and unchanged in the nondiabetic patients (P = 0.005). These studies document, for the first time, the development of GBM and mesangial lesions of diabetic nephropathy in normal living related donor and cadaver kidneys transplanted into diabetic patients and support the hypothesis that these lesions are secondary to the diabetic state.
Involvement of Ca2+ in the Impaired Glucose-induced Insulin Release from Islets Cultured at Low Glucose
Authors: Siegel Eberhard G , Wollheim Claes B , Janjic Danilo , Ribes Gérard , Sharp Geoffrey W G
Published: September 2013

Islet culture at a low glucose concentration results in a progressive impairment of glucose-induced insulin release. The role of Ca2+ in this defect was studied by comparing rat islets cultured for 6 days either at 8.3 mM (control) or 2.8 mM glucose. For measurement of 45Ca content and 45Ca2+ efflux, islets were kept in the presence of 45Ca2+ throughout. In islets cultured at 8.3 mM glucose, stimulation with 16.7 mM glucose during perifusion caused a typical biphasic pattern of insulin release paralleled by an increase in the rate of 45Ca2+ efflux. Both effects of glucose were markedly reduced in islets kept at 2.8 mM glucose, despite a similar insulin content. Islet 45Ca content was reduced. Both 45Ca content and insulin release were restored when islets were kept for an additional 24 h at 8.3 mM glucose. Insulin release induced by 3-isobutyl-1-methylxanthine (IBMX) or α-ketoisocaproic acid was not impaired, demonstrating that there is no generalized release defect. In contrast, glyceraldehyde- or K+-induced release was decreased. In islets maintained at 2.8 mM glucose, the stimulatory effect of glucose on Ca2+ uptake and the inhibitory effect on Ca2+ efflux (in the absence of Ca2+) were found to be operative. A defect may therefore lie distal to the Ca2+ uptake step involving either the mechanism by which glucose uses cellular Ca or another step yet to be identified.
Unanticipated Amyloidosis in Dogs Infused with Insulin
Authors: Albisser A M , McAdam K P W J , Perlman K , Carson S , Bahoric A , Williamson J R
Published: September 2013

Highly purified regular porcine insulin was given by portable insulin pumps through indwelling vena cavai catheters to 17 (13 normal, and 4 pancreatectomized) dogs initially weighing 15 ± 2 kg at rates ranging from 2 to 10 mU/min (total 17–250 mg) over time periods ranging from 37 to 252 days. During the course of the study, many of the animals lost weight and became anemic. Since these conditions persisted and weight loss progressed even after cessation of insulin infusion, as many of the dogs as possible (15 of 17) were autopsied for microscopic studies. Large amounts of amyloid were demonstrated in the liver, kidney, spleen, and/or pancreas in 55% (6/11) of normal, and in 75% (3/4) of pancreatectomized dogs. The amyloid deposits were Congo red positive, exhibited classical apple green fluorescence under polarized light, and possessed the characteristic ultrastructural features of amyloid. Massive deposits of amyloid were observed in animals receiving as little as 17 mg of insulin over a time span of 52 days. In those animals with hepatic amyloid, marked hepatomegaly was present (i.e., 1200 ± 250, X ± SD, versus 300 ± 25 g for normal animals) and preterminal serum alkaline phosphatase levels were markedly elevated (434 ± 285 versus 30 ± 14 IU/L for animals without hepatic amyloid). The magnitude of the hepatic amyloid deposits precludes the possibility that they represent insulin aggregates or insulin-derived products per se. No evidence of amyloid was present in any of the tissue biopsy specimens obtained prior to insulin infusion.

Moreover, the possibility that this represents an immune response to the injected porcine insulin has to be viewed in light of the fact that the amino acid sequences of dog and porcine insulins are identical. It is of particular interest that the affinity of the amyloid deposits for Congo red stain was totally abolished by prior permanganate treatment, suggesting that the amyloid was derived from serum amyloid A protein rather than from immunoglobulin light chains or insulin aggregates per se. Further evidence that the protein was of the AA-type came from the initial biochemical characterization. Gel filtration on Sephadex G100 in 6 M guanidine hydrochloride identified two small molecular weight peaks of about 13,000 and 25,000 daltons, both of which inhibited the radioimmunoassay for human AA protein.

The consistent finding that the insulin solutions recovered from the pump reservoirs were in an aggregated state suggests that under the conditions of these experiments insulin was physically altered in such a way as to render it amyloidogenic when administered to the dogs. Filters to trap such aggregates were not present. The relative importance of the route of administration, of the physicochemical state of the insulin, and of the status of the recipient's immune system in initiating amyloid deposition remain to be determined.