bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Modeling of Insulin Binding to Receptors and Degradation In Vivo in the Rabbit
Authors: Berman Mones , McGuire Elizabeth A , Roth Jesse , Zeleznik Anthony J
Published: September 2013

In vivo metabolism of insulin, with emphasis on the distribution, binding, and degradation from receptor and nonreceptor sites, has been studied in rabbits by analyzing the kinetics of antibody-bindable, TCA-precipitable, and TCA-soluble components in plasma. Tracer amounts of 125I-and 131I-labeled high affinity (pork) and low affinity (guinea pig) insulins were injected simultaneously into rabbits in the basal state or after a large bolus of unlabeled pork insulin. In one series of experiments, a bolus of unlabeled pork insulin was given from 5 to 30 min after the tracers. Based on the kinetic curves derived in these experiments, a model is developed for insulin metabolic pathways in vivo. A number of features are contained in the model. First, some of the kinetics are caused by distribution spaces in the body and some by specific binding sites, presumably receptors. Two equilibration phases between plasma insulin and receptors can be detected. The first and major one occurs within about one minute. The second one takes about 15 or 20 min. Partial degradation of the insulin molecule can be detected rapidly by the kinetics and is associated with the rapid (1 min) receptor phase. About 27% of the labeled insulin molecules are partially degraded via this pathway. There is, also, irreversible loss of insulin from the receptors without significant return of label to plasma during the experiment. This loss could be a result of internalization of insulin by the cells. About 48% of the insulin injected follows this pathway. The remaining degradation of insulin (∼24%) takes place at other sites in the body. The results of the kinetic analysis also suggest that there are two populations of receptors. The high affinity population has an equilibrium dissociation constant equal to about 9 × 10−9 M, a value comparable to that observed in vitro (∼5 × 10−9 M). The low affinity population has an equilibrium dissociation constant about 100 times greater than that of the high affinity population; its capacity, however, is about 30 times greater. It is, further, concluded that the TCA-soluble degradation products observed in plasma could not be accounted for by the partial and irreversible degradation pathways identified in the insulin model. They could be accounted for, however, by a 5%–15% subpopulation of injected labeled TCA-precipitable molecules that decay monoexponentially from plasma.
The Histocompatibility (HLA) Antigen Distribution in Diabetes in Southern African Blacks (Xhosa)
Authors: Briggs Brian R , Jackson W P U , DuToit Ernette D , Botha Martin C
Published: September 2013

The frequency distributions of HLA antigens in 25 juvenile-onset diabetics (JOD) and 56 maturity-onset diabetics (MOD) belonging to a southern African black tribe (Xhosa) were compared with those of 153 non-diabetic Xhosa blacks. Unlike the findings in white JODs, there was no increase of B8 or B15 nor a reduced frequency of B7 but an apparently, significantly increased frequency of Bw35 and A2 in both Xhosa JODs and Xhosa MODs, respectively.

This is the first ethnic group in which an HLA antigen marker has been found for MOD. Furthermore, these findings suggest that diabetes, both JOD and MOD, in white people is a different genetic disease from the diabetes among the Xhosa tribe.
Alternatives in Pancreatic Islet Transplantation: Tissue Culture Studies
Authors: Reemtsma Keith , Weber Collin J , Pi-Sunyer F Xavier , Lerner Roger L , Hardy Mark A
Published: September 2013

Culture Of Islets Isolated from the pancreas of neonatal rats successfully preserved function for 6 days, as indicated by release of insulin into the culture medium and reversal of experimental diabetes by cultured islet isografts. Release of insulin into the culture medium correlated with lowering of fasting blood glucose in the diabetic recipient. Intravenous glucose tolerance was normal in recipients of immediate and 24-h cultured islets but abnormal in recipients of 6-day cultured islets.

Culture of the islets isolated from human pancreases (cadaveric) resulted in islet purification but at the expense of loss of islets, with only 1–5% surviving 1 wk of culture. During 8–10 days in culture, insulin release declined, and histological examination revealed only a few viable islets. Islets isolated from surgical specimens survived the culture conditions as demonstrated by viable cell clumps and insulin secretion. After an 85% pancreatectomy in the patient with chronic pancreatitis, islets were isolated, cultured for 7 days, and then autografted into muscle pockets and the subcutaneous space of the forearm. There was no evidence of function.
Culture and Function in Vitro
Authors: Ågren A , Andersson A , Björkén C , Groth C G , Gunnarsson R , Hellerström C , Lindmark G , Lundqvist G , Petersson B , Swenne I
Published: September 2013

Human fetal pancreas, obtained at prostaglandin-in-duced legal abortions, was maintained in organ culture for 6–14 days in medium TCM 199 (5.5 mM glucose) or RPMI 1640 (11.1 mM glucose) supplemented with 20% calf serum and antibiotics. Light microscopic examination indicated that the cultured explants were composed of fibrous tissue and well-preserved ducts and islets, whereas acinar cells had disappeared. The hormone content (insulin, C-peptide, glucagon, somatostatin) per milligram wet pancreatic weight increased 10–35 times during the culture period.

In static incubations of cultured explants there was a poor insulin response to glucose (16.7 mM). By contrast, insulin release was markedly stimulated in the presence of both glucose (16.7 mM) and theophylline (10 mM). The maximal rate of insulin release in response to glucose plus theophylline was observed after 11 days of culture. When pancreatic explants were incubated in a perifusion system after 7 days in culture, 25% of the fetuses showed a low and monophasic insulin response to glucose alone (15 mM), whereas the remaining ones failed to respond. When perifusions were performed with glucose (15 mM) plus theophylline (5 mM), the insulin response was high in about 25% of the fetuses, intermediate in 40%, and low in 35%. Neither in the static incubations nor in the perifusions was there any clear correlation between the rates of insulin release and the tissue culture medium used.

It is concluded that human fetal B cells may retain viability in organ culture for more than a week. The fetal pancreatic material prepared and stored by this means may be used in attempts to cure human diabetes by transplantation.
Cryopreservation of Human Fetal Pancreas
Authors: Brown Josiah , Kemp John A , Hurt Susan , Clark William R
Published: September 2013

To determine the optimal conditions for successful cryopreservation of the human fetal pancreas, techniques developed for the rat organ were modified. The parameters studied were the conditions of exposure to the cryopreservation agent dimethyl sulfoxide (DMSO), the rate of cooling and thawing, and the effect of in vitro culture. A total of 33 pancreases, obtained after fetal death due to prostaglandin-induced abortion, was studied. Survival of the pancreas is based on incorporation of 3H-amino acids into protein by pancreas pieces (2 mm3) during a 4-h incubation compared with nonfrozen control pieces from the same pancreas. Toxicity of DMSO at 37°C was found to be severe after a 4-h exposure. Varying the effects of temperature, time of exposure, and concentrations of DMSO on survival after freeze-thaw revealed that 1.5 M DMSO for 1 h at room temperature was optimal. The cooling rate was 0.22°C/min and thawing was at room temperature. Since these conditions resulted in only 50% survival, a period of culture before exposure to DMSO was added. The optimal duration of culture was 12–16 h. Using this method with addition of culture for 24 h after thawing, survival has varied from 70 to 120% of control. If a functional test for growth and insulin production by the frozen-thawed pancreas is positive, permanent shortage of the human fetal pancreas will be possible.
Transplantation of Human Fetal Pancreas: Experience in Thymusaplastic Mice and Rats and in a Diabetic Patient
Authors: Usadel K H , Schwedes U , Bastert G , Steinau U , Klempa I , Fassbinder W , Schöffling K
Published: September 2013

The aim of the present study was to investigate if thymusaplastic nude mice and rats are favorable as recipients for transplantation of human fetal pancreas. Twenty human fetal pancreases were transplanted subcutaneously to 20 nude mice, and six human fetal pancreases were transplanted to six rats. The xenografts showed histotypical development of islets of Langerhans. Insulin, glucagon, somatostatin, and pancreatic polypeptide immunoreactivities were also seen in very early stages of the transplant development within the monolayered ducts.

With the described “epigastric pouch technique” in rats, we could demonstrate a new in vivo method for selective stimulations and simultaneous blood sampling from tissue-isolated xenografts.

Transplantation of human fetal pancreas to the brachioradial muscle of an insulin-dependent patient in combination with a kidney transplant revealed that rejection crises of the kidney led to necrosis of the pancreas transplant, whereas rejection of the kidney was overcome by steroid pulse therapy.
Transplantation of Fetal Pancreatic Microfragments via the Portal Vein to a Diabetic Patient
Authors: Groth C G , Andersson A , Björkén C , Gunnarsson R , Hellerström C , Lundgren G , Petersson B , Swenne I , Östman J
Published: September 2013

Human fetal pancreas preserved in culture was used as a donor organ in a 45-yr-old man with diabetes of 14-yr duration complicated by severe retinopathy and nephropathy. Renal failure had been successfully treated by a cadaveric renal transplant 2 yr earlier. Six fetal pancreases, obtained within 30 min of delivery after prostaglandin-induced abortion at 14–20 wk of gestation, were minced and placed in tissue culture for 3 h at the earliest and 15 days at the longest duration. The cultures were harvested 2–3 h before transplantation. Approximately 3 ml of tissue was infused into a right portal vein branch. Azathioprine was continued at 2 mg/kg and prednisolone increased from 10 mg to 100 mg/day on the day of transplantation and gradually reduced to 25 mg/day. Only two doses of antilymphocytic globulin were given because of a severe reaction. During the 40 days since transplantation, insulin requirements have not changed, but C-peptide has appeared in the urine, suggesting function of the transplanted tissue.
Effect of Culture on Islet Rejection
Authors: Lacy Paul E , Davie Joseph M , Finke Edward H
Published: September 2013

In order to diminish or prevent rejection of transplanted allogeneic islets of Langerhans, in vitro culture was used. After digestion of the rat pancreas and Ficoll separation, islets were handpicked to be free of vascular and ductal tissue. Phenol red in the culture medium imparted a pink color to the islets when observed with a diffuse green light against a black background. Islets cultured at room temperature (24°C) remained functionally and morphologically intact for 1–4 wk. Insulin secretion was 1–3 μU per islet per hour, increasing to 16 μU per islet per hour at 37°C, Culture alone resulted in a modest prolongation of function across a major histocompatibility barrier, Wistar Furth to Lewis (mean survival time, 11.6 ± 1.2 vs. 7.2 ± 0.5 days). However, one injection of antilymphocytic serum (ALS) into 10 recipients at the time of transplantation prolonged survival to greater than 100 days in nine rats. In the combination ACI to Lewis, also a major barrier, the same regimen prolonged function to greater than 100 days in five out of five recipients. Injection of donor peritoneal exudate cells resulted in prompt rejection of islets. These results suggest that culture and ALS either damage or alter passenger leukocytes in the donor tissue, thereby preventing rejection Of the islets.
Beneficial Effect of Chromium-rich Yeast on Glucose Tolerance and Blood Lipids in Elderly Subjects
Authors: Offenbacher Esther G , Pi-Sunyer F Xavier
Published: September 2013

Twenty-four volunteers, mean age 78, including eight mildly non-insulin-dependent diabetics, were randomly allocated to one of two groups and were fed (daily for 8 wk) 9 g of either chromium-rich brewers' yeast (experimental) or chromium-poor torula yeast (control). Before and after yeast supplementation, the serum glucose and insulin response to 100 g oral glucose was measured at 30 min intervals for 2 h. Fasting serum cholesterol, total lipids, and triglycerides were also determined. In the total experimental group (normals + diabetics) and in both the diabetic and nondiabetic experimental subgroups, glucose tolerance improved significantly and insulin output decreased after supplementation. Cholesterol and total lipids fell significantly after supplementation in the total experimental group. The cholesterol decrease was particularly marked in hypercholesterolemic subjects (cholesterol > 300 mg/dl). In the control group, no significant change in glucose tolerance, insulin, triglycerides, or total lipids was found. Cholesterol was significantly lowered in the nondiabetic but not in the diabetic group. Thus, chromium-rich brewers' yeast improved glucose tolerance and total lipids in elderly subjects, while chromium-poor torula yeast did not. An improvement in insulin sensitivity also occurred with brewers' yeast supplementation. This supports the thesis that elderly people may have a low level of chromium and that an effective source for chromjum repletion, such as brewers' yeast, may improve their carbohydrate tolerance and total lipids. The improvement in serum cholesterol in some control subjects, as well as in the total experimental group, also suggests the presence of a hypocholesterolemic factor other than chromium in both brewers' and torula yeast.
Ventromedial Hypothalamic Lesions Increase Pancreatic Sensitivity to Streptozotocin in Rats
Authors: West David B , Seino Yutaka , Woods Stephen C , Porte Daniel
Published: September 2013

Rats with electrolytic lesions of the ventromedial hypothalamus (VMX rats) and sham-operated controls (SHAM rats) were injected with streptozotocin (STZ) at a dose of 50 mg/kg 48 h after the lesions were made. VMX rats were significantly more sensitive to STZ in that over 70% died within 6 wk, whereas none of the SHAM rats died. When smaller doses of STZ were given to VMX rats (30–35 mg/kg), a large percentage still died, although the survivors appeared equally as diabetic (in terms of hyperglycemia and hypoinsulinemia) as SHAM rats given a larger dose of STZ. At 25 mg/kg, the surviving VMX rats were more hyperglycemic than matched controls. We suggest that the increased B-cell activity known to occur in VMX animals might be the important factor in the increased sensitivity to STZ observed. We speculate that similar variation in pancreatic B-cell response to an environmental injury may be an important determinant of diabetes susceptibility in man.
Type I (Insulin-dependent) Diabetic Multiplex Families: Mode of Genetic Transmission
Authors: Walker Angela , Cudworth A G
Published: September 2013

HLA genotypes have been analyzed in 120 classic type I (insulin-dependent) diabetic sib pairs with an age of onset below 16 yr reported to the British Diabetic Association register (1972–78). By this age, siblings of diabetic children are 26 times more likely to develop type I diabetes than other children. There is a highly significant disturbance in the zygotic assortment of HLA haplotypes in these sib pairs, providing conclusive evidence for the existence of major susceptibility genes in the HLA complex.

The present data exclude a simple dominant or recessive mode of inheritance. It is likely that both parents contribute to the susceptibility, indicating the presence of two HLA-linked genes (or clusters of genes in linkage disequilibrium) that influence the predisposition to the disease. There is no evidence that type I diabetic multiplex families have an increased HLA risk or increased predisposition to autoimmunity compared with families with one affected child.
Arterial Procollagen Type I, Type III, and Fibronectin: Effects of Diabetic Serum, Glucose, Insulin, Ketone, and Growth Hormone Studied on Rabbit Aortic Myomedial Cell Cultures
Authors: Ledet Thomas , Vuust Jens
Published: September 2013

Arterial myomedial cell cultures were grown from thoracic aortas of normal rabbits. The effect of normolipemic serum from young nonobese male juvenile diabetics on the production of procollagen type I, type III, and fibronectin was studied on nearly confluent primary cultures not treated with trypsin and incubated in the presence of [U-14C]-proline. The macromolecules were isolated from the incubation medium by ammonium sulfate precipitation, fractioned by DEAEcellulose chromatography and SDS urea-polyacrylamide gel electrophoresis, and quantitated by liquid scintillation counting.

Media containing diabetic serum enhanced the production of procollagen type I (P < 0.05). There was no effect on the elaboration of procollagen type III. Diabetic serum, however, stimulated the production of fibronectin (P < 0.005). There was no relationship between the glucose level and the amount of either procollagen type I or fibronectin.

Growth medium supplemented with normal serum and extra glucose did not change the production of procollagen type III or fibronectin but decreased the elaboration of procollagen type I (P < 0.05). Addition of insulin (100 μU/ml) resulted in a significant decrease in procollagen type I, type III, and fibronectin elaboration (P < 0.05, P < 0.02). When ketones (0.2 mM) were added together with normal serum, no changes in the procollagens and fibronectin were observed.

Supplementation of normal serum with human growth hormone (1 ng/ml) resulted in a significant increase in the production of procollagen type I (P < 0.02) and fibronectin (P < 0.01).

The present results demonstrate that the factor(s) in normolipemic diabetic human serum enhancing theproduction of procollagen type I and fibronectin by arterial myomedial cell cultures cannot be imputed to glucose, insulin, or ketones, but leaves growth hormone as one possible factor

The data may be relevant for the understanding of the development of human diabetic macroangiopathy.
Amino Acid Transport in Isolated Hepatocytes from Streptozotocin-diabetic Rats
Authors: Samson Michel , Fehlmann Max , Dolais-Kitabgi Jacqueline , Freychet Pierre
Published: September 2013

The enhanced ability of liver to extract glucogenic precursors from plasma in insulinopenic diabetes was investigated at the cellular level by measuring amino acid transport in isolated hepatocytes from streptozotocin-diabetic rats. The concentrative Na+-dependent uptake of α-amino[1-14C]isobutyric acid (AIB), a nonmetabolizable analog of alanine, was increased in hepatocytes from diabetic rats compared with controls. This increase was observed both at a low (0.1 mM) and high (30 mM) extracellular concentration of the amino acid. Analysis of the relationship between AIB influx and AIB concentration revealed that the increased uptake in diabetic rat hepatocytes was due to an enhanced capacity (i.e., a twofold increase in the Vmax) of the transport system whereas the apparent affinity (Km) for AIB was unaltered.

The increased amino acid transport activity in diabetic rat hepatocytes was due mainly to an increased transport through system A (alanine-preferring) and, to a much lesser extent, through system ASC (alanine, serine, cysteine). System L (leucine-preferring) and AIB entry through simple diffusion were not affected in diabetic rat hepatocytes compared with controls. Increased AIB transport of diabetic rat hepatocytes was returned to normal by insulin treatment.
Diabetes and Cell Growth—Lack of Differences in Growth Characteristics of Fibroblasts from Diabetic and Nondiabetic Pima Indians
Authors: Howard Barbara V , Fields Rose M , Mott David M , Savage Peter J , Nagulesparan M , Bennett Peter H
Published: September 2013

Skin biopsies were obtained from diabetic and nondiabetic Pima Indians and nondiabetic Caucasian controls to compare fibroblast growth characteristics. The Pima population were used because they have a high prevalence of well-characterized diabetes mellitus, and extensive clinical and demographic data are available for selection of subjects.Cultures were derived from 19 subjects between the ages of 20 and 42 yr. Seven were from Pimas with severe diabetes who had two diabetic parents and relatively early age of onset. Six were from Pima nondiabetics who had two nondiabetic parents. Six control cultures were established from Caucasian nondiabetics with no family history of diabetes. Cell density at confluence, plating efficiency, thymidine incorporation, and population doubling rates were monitored as a function of cell population doublings until the senescence of each culture. Fibroblast cultures from the Pima diabetics did not differ from those of the Pima nondiabetics in replicative life span or any of the measured culture parameters. When cultures from the Pimas were compared with those of the Caucasian controls, however, they had decreased cell density at confluence, slower population doubling times, decreased thymidine incorporation, shorter replicative life spans, and lower plating efficiency. The data suggest that altered growth properties of cultures from diabetics may not be a requisite of diabetic status; they may reflect a genetic background that accompanies the expression of diabetes.
Inhibition of Gastric Inhibitory Polypeptide (GIP) Release by Insulin and Glucose in Juvenile Diabetes
Authors: Creutzfeldt W , Talaulicar M , Ebert R , Willms B
Published: September 2013

The effect of glucose and insulin on fat- and glucose-induced gastric inhibitory polypeptide (GIP) release has been studied in insulin-dependent juvenile-type diabetics. Blood glucose and serum immunoreactive GIP (IR-GIP) were measured after an oral load of 100 g glucose or 100 g fat was given and during an infusion of one of the following: saline, glucose, glucose plus insulin, or insulin. The infusion of insulin alone (in the presence of elevated glucose levels) or together with glucose significantly suppressed the IR-GIP rise after fat ingestion, but it did not alter the GIP response to oral glucose. Intravenous infusion of glucose had a slight but significant inhibitory effect on fat-stimulated increase of IR-GIP, which cannot be related to endogenous insulin release in these insulin-deficient diabetics. It is suggested that an insulin-mediated increase of glucose utilization in the GIP cell interferes only with increased GIP secretion stimulated by the utilization of fatty acids but not of glucose. This could explain the existence of a negative feedback control between insulin and GIP secretion for fat but not for glucose-induced GIP release.
Transformation of Glicentin-containing L-Cells into Glucagon-containing Cells by Enzymatic Digestion
Authors: Ravazzola Mariella , Orci Lelio
Published: September 2013

Exposure of sections of ileal mucosa to enzymatic digestion with trypsin and carboxypeptidase B reveals a population of immunofluorescent cells after incubation with a specific C-terminally directed antiglucagon serum. These cells, unreactive before enzyme treatment, were identified as L-cells by their immunoreactivity to antiglicentin serum and to cross-reacting (N-terminal) antiglucagon sera. The presence in the L-cells of antigenic sites characteristic of the glucagon-containing cells (A-cells) emphasizes the close relationships between these two cell types, and it further supports the hypothesis of glicentin as a glucagon precursor.
Direct Evidence for Downregulation of Insulin Receptors by Physiologic Hyperinsulinemia in Man
Authors: Soman Vijay R , DeFronzo Ralph A
Published: September 2013

To directly examine whether physiologic hyperinsulinemia regulates insulin receptors in normal man, we studied the effect of insulin infusion (employing the euglycemic insulin clamp technique) on 125I-insulin binding to monocytes. In Study I (9 subjects), when the steady-state plasma insulin concentration was raised to approximately 100 μU/ml, insulin binding to monocytes remained unchanged at 1 h, but decreased significantly by 3 h (20%, P < 0.01) and fell further by 5 h (37%, P < 0.001) following the insulin infusion. In Study II (5 subjects) increments in plasma insulin concentration to 31 μU/ml resulted in no change in insulin binding at 3 h (P > 0.5) but resulted in a significant decrease at 5 h (25%, P < 0.01). The plasma glucose concentration was maintained at basal levels in both infusion protocols. The decrease in insulin binding in both studies was due to a decrease in insulin receptor concentration. No significant change in receptor affinity was observed. In a control study (5 subjects) 5 h of saline infusion had no effect on insulin binding to monocytes.

We conclude that in normal humans, increments in the plasma insulin concentration in the physiologic range downregulates the number of insulin receptors in a dose- and time-dependent manner.
Prevention of Hypophosphatemia by Phosphate Infusion During Treatment of Diabetic Ketoacidosis and Hyperosmolar Coma
Authors: Keller Ulrich , Berger Willie
Published: September 2013

To assess the effect of phosphate replacement therapy on the course of diabetic coma, 24 patients with severe diabetic ketoacidosis and 16 patients with non-ketotic hyperosmolar coma were randomly assigned either to standardized conventional treatment alone or combined with phosphate infusions. Insulin and fluid therapy produced a rapid fall of plasma phosphorus; almost all patients not receiving phosphate infusions developed marked hypophosphatemia within 12 h. Hypophosphatemia was prevented by administration of 62 ± 5 mmol (range 35–140) sodium phosphate. Initial red blood cell 2,3-diphosphoglycerate (2,3-DPG) concentrations were markedly decreased in ketoacidotic patients. The recovery of 2,3-DPG upon institution of therapy was accelerated when phosphate replacement infusions were given. The increase in 2,3-DPG during the first 48 h was 56% greater (P < 0.02) when phosphate was administered, but later the difference between the two treatment groups disappeared. Non-ketotic hyperosmolar coma patients revealed normal 2,3-DPG concentrations on admission, and a similar decline of plasma phosphorus occurred, as in ketoacidosis, during treatment. 2,3-DPG levels remained unaffected by phosphate therapy. While plasma calcium levels declined during the initial 48 h in both groups, transient postinfusion hyperphosphatemia was noted in 7 of 17 patients. A favorable effect of phosphate therapy on the clinical course of diabetic ketoacidosis or hyperosmolar coma could not be demonstrated.
Insulin Resistance in Obesity as Analyzed by the Response of Glucose Kinetics to Glucagon Infusion
Authors: Vranic Mladen , Morita Soichiro , Steiner George
Published: September 2013

A new approach has been developed to examine insulin sensitivity and resistance in vivo in man. In it, tracer methods are used, which permit the assessment of nonsteady state glucose kinetics by a method that is noninvasive and does not use pharmacologic agents. Graded doses of glucagon, infused intravenously, are used to drive glucose out of steady state and to stimulate the release of insulin into the portal circulation. By relating the changes in the rates of glucose production, utilization, and fractional disappearance to immunoreactive glucagon and insulin, it is possible to assess the body's sensitivity to physiologic levels of these two hormones.

The utility of this approach was examined in obesity, a known human model of insulin resistance. The data demonstrated that glucose production in the obese subjects responded normally to glucagon. They also showed that insulin was much less effective in promoting glucose utilization in the obese persons than it was in the normal ones. In the obese subjects who were studied, the pancreatic B-cells were shown to be normally responsive to the stimulatory effects of either glucose or glucagon. Hence, they did not release sufficient insulin to overcome the insulin resistance, and these obese individuals had impaired glucose tolerance. Thus, it is suggested that, in the presence of insulin resistance, the responsiveness of B-cells will determine whether the glucose tolerance will be normal or abnormal in obese persons. This approach can now be used to explore glucose homeostasis in other conditions associated with glucose intolerance, the metabolic basis of which is undefined.
Ketonuria in Pregnancy—With Special Reference to Calorie-restricted Food Intake in Obese Diabetics
Authors: Coetzee E J , Jackson W P U , Berman P A
Published: September 2013

Early morning ketonuria, as judged by Ketostix testing, occurred in 19% of urine samples from insulin-independent diabetic pregnant women eating 1000 calorie diets, in 14% from diabetics on higher calorie diets, and in 7% of urines from nondiabetic pregnant women. Ketostix test was never found to be positive in blood, even when it was 2+ in urine samples, and acetoacetate levels were always below 1 mmol/L.

Enzymatic estimations of acetoacetate (AA) and beta-hydroxybutyrate (BB) in urine and plasma samples revealed (1) no significant differences in range or mean between the groups receiving different restricted diets or full diets, the highest value observed for plasma AA being 0.34 mmol/L; (2) that Ketostix became positive at a concentration of AA above 1 mmol/L and that such a value in urine corresponded to plasma levels of between 0.06 and 0.1 mmol/L, i.e., double the normal; and (3) a 50–100-fold increase in urine AA when blood levels exceeded 0.08 mmol/L.

Neonates born to diabetic mothers with ketonuria had no fetal distress or asphyxia neonatorum. The lowest Apgar score at 5 min was 8; 80% of neonates had a score of 10. Hence, positive Ketostix tests in urine samples do not indicate toxic levels in the blood, and a 1000 calorie diet for obese pregnant diabetics appears to be safe as regards neonatal outcome.
Mode of Action of Clonidine Upon Islet Function: Dissociated Effects Upon the Time Course and Magnitude of Insulin Release
Authors: Leclercq-Meyer V , Herchuelz A , Valverde I , Couturier E , Marchand J , Malaisse W J
Published: September 2013

Clonidine (0.08 to 80.0 ng/ml) caused a dose-related inhibition of glucose-stimulated insulin release, but failed to affect glucose oxidation, glucose-stimulated 45Ca net uptake, and adenylate cyclase activity in isolated rat islets. Phentolamine antagonized the effect of clonidine upon insulin release. Despite profound inhibition of insulin secretion, the drug failed to affect the time course for the changes evoked by glucose in either 45Ca fractional outflow rate from perifused islets or insulin release from the isolated perfused pancreas. The latter changes were multiphasic, revealing an initial secretory peak, a period of low secretory activity, and a second secretory elevation before establishing a period characterized by a steadily and slowly increasing insulin output. In the clonidine-treated islets, the secretory rate was not significantly different from the basal value during the period after the initial secretory response. Thus, despite continuous stimulation with glucose, insulin release appears as a discontinuous phenomenon, even when little insulin is secreted during the initial phase of stimulation.
Effects of Exogenous Fatty Acid Concentration on Glucagon-induced Changes in Hepatic Fatty Acid Metabolism
Authors: McGarry J Denis , Foster Daniel W
Published: September 2013

Studies were conducted to clarify the relationship between the external fatty acid concentration and glucagon in the regulation of hepatic fatty acid metabolism. Hepatocytes from fed rats were incubated with increasing concentrations of oleate (up to 1 mM) in the presence and absence of glucagon and the time sequence of changes in cellular malonyl-CoA levels, fatty acid synthesis, fatty acid oxidation, and ketogenesis were measured. At low concentrations of fatty acid the effect of glucagon was to abolish malonyl-CoA synthesis and lipogenesis and to produce a marked stimulation of fatty acid oxidation and keto-genesis. Similar effects were obtained with high concentrations of fatty acid in the absence of glucagon and, under these conditions, the additional presence of the hormone produced little further response. The results are consistent with the concept that the rate of fatty acid oxidation in liver is dictated largely by the relative concentrations of long-chain acyl-COA (substrate for carnitine acyltransferase I) and malonyl-CoA (inhibitor of the transferase). They also indicate that the preemptive effect of fatty acids on glucagon-induced changes in fatty acid metabolism stems from their ability to reduce the tissue malonyl-CoA content, probably through long-chain acyl-CoA suppression of acetyl-COA carboxylase.
Metabolic Activity of Diabetic Monocytes
Authors: Kitahara Mitsuo , Eyre Harmon J , Lynch Robert E , Rallison Marvin L , Hill Harry R
Published: September 2013

There have been several reported abnormalities in the cellular components of the acute inflammatory response in diabetes mellitus. These studies have dealt primarily with polymorphonuclear leukocytes. In the present investigations, we have examined monocyte metabolic activity in diabetic patients and controls. Following particle ingestion, the microbicidal mechanisms of the monocyte are activated and excited molecular oxygen and carboxyl groups are generated. Upon decay to the ground state, these molecules emit photons, which can be measured as chemiluminescence. Chemiluminescence production was significantly increased in 27 patients with poorly controlled diabetes (blood glucose levels from 208 to 712 mg/dl). The mean peak in the diabetics was 31.3 ± 8.2 (SD) × 103 cpm versus 25.8 ± 3.8 × 103 cpm in controls. Hexose monophosphate shunt activity as determined by 14 C-I-glucose utilization was also increased (667 ± 284 percent increase in diabetics versus 425 ± 154 in controls). Superoxide dismutase-inhibitable superoxide production was also significantly augmented in diabetic monocytes (9.77 ± 3.06 nmol/106 monocytes/20 min versus 6.36 ± 1.10 nmol). Addition of glucose to whole blood from a normal individual, or to normal or diabetic monocyte suspensions, resulted in marked enhancement of chemiluminescence production. Increasing blood sugar levels appear, therefore, to be associated with monocyte metabolic activation in diabetic patients. Such activation could conceivably be detrimental to the diabetic host by contributing to cell damage through the release of toxic oxygen products.
Effects of Insulin and Pancreatic Polypeptide on Gastric Somatostatin Release
Authors: Chiba Tsutomu , Taminato Tomohiko , Kadowaki Seizo , Abe Hiromi , Chihara Kazuo , Matsukura Shigeru , Goto Yasuo , Seino Yutaka , Fujita Takuo
Published: September 2013

Effects of arginine and such pancreatic hormones as insulin and pancreatic polypeptide on gastric somatostatin release from the isolated perfused rat stomach were studied. The stomach was isolated from a fasted rat by a modification of the method of Lefébvre and was perfused with 4.6% dextran Krebs-Ringer bicarbonate buffer containing 5.5 mM glucose. Both insulin and pancreatic polypeptide (10−10, 10−9, and 10−8 M) caused a significant decrease in gastric somatostatin secretion. Insulin (10 −10 M), furthermore, inhibited the glucagon (5 × 10−8 M)-induced somatostatin response. Arginine (10 and 19 mM) failed to elicit any significant change of somatostatin release.

These results suggest that gastric somatostatin release is affected by pancreatic hormones.
Complement-mediated Cytotoxic Effects on Pancreatic Islets With Sera from Diabetic Patients
Authors: Rittenhouse Harry G , Oxender Dale L , Pek Sumer , Ar Diane
Published: September 2013

Sera from 11/30 patients with juvenile-onset-type diabetes (JOD) had cytotoxic effects on isolated pancreatic islets from hamsters when guinea pig complement was present. The cytotoxic activity could be readily eliminated by heating the guinea pig complement at 56°C for 30 min, thus demonstrating a complement-dependent process. Complement-dependent cy totoxicity toward pancreatic islets was not observed with sera from 11 patients with maturity-onset-type diabetes, 4 nondiabetic hospital patient controls, and 28 healthy adult subjects. The presence of circulating complement-mediated cytotoxic factor(s) toward isolated islets indicates the potential importance of autoimmune pathogenic damage to pancreatic islets in some patients with diabetes.
Diurnal Episodic Pattern of Insulin Secretion in the Dog
Authors: Vanhelder Walter P , Sirek Anna , Sirek Otakar V , Norwich Kenneth H , Policova Zdenka , Vanhelder Tomas
Published: September 2013

Sampling portal blood every 15 min by means of indwelling cannulae, we have found evidence that basal insulin secretion in nonanesthetized dogs takes place in six or seven major secretory episodes over a 24-h period. Reproducible patterns were obtained in four experiments conducted on three normal animals. When frequency of peaks was plotted against the log of insulin concentration, a normal distribution was obtained (lognormal distribution). The means and variances were nearly the same in the three animals. Low levels of insulin (10–25 μU/ml) alternated with peaks which were occasionally higher than 200 μU/ml. The average duration of a peak was 30 min and seemed to be independent of ambient glucose levels. It is suggested that these peaks are the result of surges in plasma growth hormone concentrations and/or spontaneous repetitive discharges along neuronal pathways functionally related to insulin secretion.
A Comparison of Basal and Insulin stimulated Glucose Transport in Rat Adipocyte Plasma Membranes
Authors: Ludvigsen Carl , Jarett Leonard
Published: September 2013

Specific D-glucose transport in plasma membranes prepared from control and insulin-treated rat adipocytes was measured using a recently developed dual isotope ([3H]-D-glucose and [14C]-L-glucose), rapid filtration assay which allowed measurements of initial rates at 1 s and 37δ.1 Plasma membranes from insulintreated adipocytes showed an increase in glucose transport compared with control cells. Saturation kinetic data revealed that the plasma membranes from insulin-treated and control cells had the same Km (26 mM) for glucose transport, whereas insulin treatment increased the Vmax from 4433 pmol/mg protein/s to 9465 pmol/mg protein/s. Arrhenius plots showed no difference in the energy of activation between control and insulin-stimulated glucose transport states. The optimum pH of both control and insulin-stimulated glucose transport was 7.4. Lower or higher pHs progressively decreased both control and insulin-stimulated glucose transport proportionately. Calcium in the transport assay media did not affect basal or insulinstimulated glucose transport. However, omission of calcium from the adipocyte incubation media significantly lowered the insulin stimulation by 24% while basal levels were not significantly affected. Insulin specifically bound to the plasma membrane was carried through the fractionation procedure, but removal of this insulin did not alter the stimulated glucose transport. Glucose transport by plasma membranes from control or insulin-treated adipocytes was equally (percentage) inhibited by N-ethylmaleimide, dithiothreitol, reduced glutathione, or cytochalasin B. No inhibition of control or insulin-stimulated transport was seen with cytochalasin D or oxidized glutathione. The data presented are consistent with insulin causing the formation of new transport sites similar to the existing basal Sites.
Effects of Indomethacin on Acute Insulin Release in Man
Authors: Topol Eric , Brodows Robert G
Published: September 2013

Prostaglandin (PG) E2 stimulates glucose-induced insulin release from isolated rat pancreatic islets but inhibits acute insulin release to intravenous (i.v.) glucose in man. Since PGs act as intracellular messengers, we have studied the effect of endogenous PG inhibition with indomethacin (a potent PG synthesis inhibitor) to clarify these differences. The acute insulin response (AIR) to 5 g and 20 g j.v. glucose, 5 g i.v. arginine, and 1 mg i.v. glucagon before and one hour after ingestSbn of 50 mg indomethacin (INDO) or placebo was studied in healthy lean subjects. INDO significantly lowered basal insulin levels (pre, 9.5 ± 1.6; post, 6.4 ± 1,8 μU/ml, ± SE, p < 0.02, paired t-test) while placebo failed to alter basal insulin (pre, 8 ± 2.7; post, 6.9 ± 0.6 μU/ml). INDO substantially blunted the AIR to 5 g glucose (Δ3–5' IRI pre, 20.3 ± 3; post, 8.4 ± 2.4 μU/ml, P < 0.005), 20 g glucose (Δ3–5' IRI pre, 38.1 ± 9.7; post, 18.9 ± 8 μU/ml, P < 0.005), and 1 mg glucagon (0–10' IRI area pre, 375 ± 73; post, 149 ± 30 μU · min/ml, P < 0.05), but it failed to influence arginine-stimulated AIR (0–10' IRI area pre, 161 ± 34; post, 186 ± 31). Thus, PG inhibition with INDO lowers basal, glucose-, and glucagon-stimulated AIR, but it has ho effect on arginine-stimulated AIR. Our data suggest that endogenous PGs enhance insulin secretion.
Integrated Concentration of Growth Hormone in Juvenile-onset Diabetes
Authors: Hayford John T , Danney Mark M , Hendrix James A , Thompson Robert G
Published: September 2013

Twenty-four-hour patterns of plasma growth hormone concentrations were evaluated during 50 studies of 42 subjects with juvenile-onset diabetes mellitus. Blood was sampled continuously over 24 h using a portable peristaltic pump under conditions in which subjects remained ambulatory and maintained their daily dietary and insulin regimens. All diabetics showed diurnal patterns characterized by frequent episodes of secretion of growth hormone. The mean 24-h concentration of growth hormone, designated the integrated concentration, was significantly higher among juvenile-onset diabetics (P < 0.001) than it was in ageand sex-matched nondiabetic populations. Juvenileonset diabetics younger than 20 yr had significantly higher (P < 0.005) growth hormone integrated concentrations than did older juvenile-onset diabetics. There was no statistically significant correlation between the integrated concentrations of glucose and growth hormone; thus, the study failed to provide us with support for the hypothesis that elevated growth hormone concentrations in diabetics are a consequence of hyperglycemia. Variability of diurnal glucose concentrations was positively correlated (P < 0.015) with the growth hormone integrated concentration among juvenile-onset diabetics. Our observations indicate that rapid declines in plasma glucose concentration or episodes of absolute hypoglycemia were significant factors, contributing to both the elevated integrated concentration and the secretory spiking of growth hormone observed in the diabetic population,
Low Plasma Levels of Pancreatic Polypeptide in Obesity
Authors: Lassmann Véronique , Vague Philippe , Vialettes Bernard , Simon Marie-Christine
Published: September 2013

Plasma levels of pancreatic polypeptide (PP) were studied in a group of 22 normal and 22 obese subjects after an overnight fast. In a second group of 10 normal and 13 obese adults, PP secretion was stimulated by a protein-rich meal. The results indicate lower fasting PP values in the obese subjects and a decreased response during the second phase of the meal-induced secretion. This could suggest a possible role of PP in obesity.
The T Lymphocyte insulin Receptor in Diabetes and Obesity: An Intrinsic Binding Defect
Authors: Helderman J Harold , Raskin Philip
Published: September 2013

Based on in vitro studies of insulin receptors in a variety of tissues, it was postulated that circulating insulin levels govern receptor number in vivo ahd that the insulin resistance characteristic of adult-onset diabetics is the consequence of reduced receptor numbers secondary to hyperinsulinemia. The quiescent T lymphocyte in vivo uniquely does not bear a receptor for insulin. The receptor appears after activation by a mitogen or antigen. Thus, free from the influence of endogenous insulin levels, this cell is an excellent model to study the intrinsic relations between diabetes and the insulin receptor. Specific binding to T cells activated by lectin in culture from 20 juvenile-onset diabetics (26 yr, 109 ± 5% fat) was 1.52 ± 0.08 × 10−21 mol/cell, no different from the 1.55 ± 0.08 in 20 normal subjects (20 yr, 100 ± 3% fat) or than in an aged non-obese group. In contrast, binding was reduced to 1.23 ± 0.05 × 10−21 mol/cell in 11 obese subjects (38 yr, 143 ± 5% fat) and even further to 1.0 ± 0.06 × 10−21 mol/cell in 21 adult-onset diabetics (53 yr, 160 ± 10% fat). The appearance of the insulin receptor on cultured stimulated T cells was analyzed by Scatchard plots, which demonstrated that receptor affinity was normal (Kd = 3−5 nM) but the receptor number was distinctly fewer (6131 ± 465 vs 2904 ± 172 sites/cell). In summary, these data show that (1) T lymphocyte insulin receptor characteristics are normal in juvenile-onset diabetics and in elderly nonobese subjects, (2) obesity itself reduces insulin receptor numbers, (3) insulin receptor binding in adult-onset diabetics is significantly less than in. obese controls and represents a defect in receptor number unrelated to in vivo insulin concentrations. We conclude that, in both obesity and adult-onset diabetes, a reduction in T cell insulin receptors is produced by a novel mechanism not attributable to classic ligand-receptor interactions.
Insulin Released from Fetal Rat Pancreases Transplanted into Normal and Diabetic Animals During Perfusion
Authors: Weisman Harry , Mullen Yoko S , Brown Josiah
Published: September 2013

Insulin release from the pancreas in response to glucose appears at the end of gestation in the fetal rat and develops completely in the neonatal period. To determine when this response begins to occur in fetal pancreases transplanted into adult animals, in vitro perfusions were performed in normal and diabetic rats after varying periods of growth. Responsivity to a 300 mg/dl glucose as opposed to a basal medium (50 mg/dl) was not present in the transplanted organ after 3 or 5 wk of growth in normal rats, despite a rise in total insulin content from 88 ± 10 mU to 197 ± 10 mU per two pancreases. Transfer of the pancreases—after 3 wk in the normal—to a diabetic rat for 2 wk resulted in a greater insulin content (343 ± 15 mU) and more insulin being released during perfusion with the basal medium (1863 ± 56 vs. 1374 ± 113 μU/h). Insulin release from these pancreases doubled during perfusion with the high glucose medium rather than with the basal medium. When the transplanted pancreas was left in the normal rats for 5 wk before being transferred to the diabetic animal for 2 wk, the insulin content increased (450 ±10 mU) but there was no response to the glucose challenge during perfusion, despite good function, indicated by a response of all transplanted animals in the diabetic state. We conclude that glucose-induced insulin release will develop in the fetal rat pancreas transplanted into an adult animal after exposure to hyperglycemia, but optimal function requires a period of prior normoglycemia. Careful control of blood glucose with insulin may provide these conditions and will be required when this method is applied to diabetic patients.