bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence that Bacitracin Alters Intracellular Insulin Metabolism in Isolated Rat Hepatocytes
Authors: Peavy Daniel E , Hamel Frederick G , Kincke Victoria L , Duckworth William C
Published: September 2013

The effect of bacitracin on intracellular insulin degradation was investigated using an isolated rat hepatocyte preparation In which essentially all insulin degradation was due to cell-mediated processes. Bacitracin produced a concentration-dependent decrease in the degradation of insulin to products soluble in trichloroacetic acid, with a half-maximal effect at approximately 0.5 mM. These results were confirmed by analysis of extracted cell-bound radioactivity by Sephadex G-50 molecular sieve chromatography. Radioactive material eluting in the position of intact insulin from the G-50 column was further analyzed by reversed-phase, highperformance liquid chromatography. In addition to intact insulin, two peaks of radioactive material less hydrophobic than insulin were evident. Incubation of cells in the presence of 0.5 mM bacitracin significantly (P < 0.05) altered the distribution of radioactivity in these two peaks. These results indicate that bacitracin significantly affects hepatocyte insulin metabolism and suggest that the continued use of bacitracin in studies of hepatocyte-insulin interaction should be avoided.
Abnormal Myocardial Calcium Uptake in Streptozocin-diabetic Rats: Evidence for a Direct Insulin Effect on Catecholamine Sensitivity
Authors: Gøtzsche Ole
Published: September 2013

Myocardial calcium uptake after isoproterenol (ISO) in the isolated, perfused heart was investigated at 24-h intervals after the injection of streptozocin (STZ) in rats. After 4 days, when hyperglycemia had persisted for 3 days, myocardial calcium uptake in response to this strong β-adrenergic agonist fell significantly to the level of unstimulated hearts, which also was the level of propranolol-pretreated hearts exposed to ISO. Insulin, when given in vivo 60–90 min before perfusion, led to a complete normalization of this ISO response in diabetic rats (duration 8 days), while in vitro addition of insulin to the perfusate (0.1 U/ml) significantly increased, while not completely normalizing, the ISO-induced myocardial calcium uptake. Insulin, therefore, has a direct effect on this β-adrenergic response in diabetic rats and streptozocin in itself does not cause the desensitization. Considering the essential role of this calcium transport for the electromechanical coupling in the heart, such rnetabolically induced changes in catecholamine sensitivity might hypothetically have relevance for the increased incidence of heart failure in diabetes.
The Pump Life: Patient Responses and Clinical and Technological Problems
Authors: Pickup John C , Sherwin Robert S , Tamborlane William V , Rizza Robert A , Service F John ,   The Kroc Collaborative Study Group
Published: September 2013

As part of a randomized, prospective trial in subjects with insulin-dependent diabetes assigned to either continuous subcutaneous insulin infusion (CSII) or to their unchanged conventional insulin treatment (CIT) for 8 mo, patients completed questionnaires dealing with general responses and clinical and technological problems.

Although there was no significant difference between treatment groups with respect to the number of patients experiencing severe hypoglycemia (i.e., requiring intravenous glucose or intramuscular glucagon injection), there were nine episodes in six patients during CSII compared with one episode during CIT. Diabetic ketoacidosis occurred significantly more often in the CSII group (nine episodes in eight patients) than in the CIT group (no episodes).

A number of CSII-related failures occurred, including omission of premeal bolus, needle dislodgement, pump accidentally turned off, and leakage at the infusion site. At 8 mo, 85% of CSII-treated patients wished to continue indefinitely on the pump, and almost all would continue with self-monitoring of blood glucose even if they Stopped CSII.
Demonstration that the Vitamin D Metabolite 1,25(OH)2-Vitamin D3 and Not 24R,25(OH)2-Vitamin D3 Is Essential for Normal Insulin Secretion in the Perfused Rat Pancreas
Authors: Kadowaki Seizo , Norman Anthony W
Published: September 2013

It has previously been shown that vitamin D deficiency impairs arginine-induced insulin secretion from the isolated, perfused rat pancreas (Science 1980; 209:823–25). Since vitamin D is known to be metabolized to 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) and 24R,25-dihydroxyvitamin D3 (24,25[OH]2D3), it is essential to clarify which vitamin D metabolite has the important role of enhancing insulin secretion. In this report, a comparison is made of the relative efficacy of 3-wk repletion with vitamin D3 (980 pmol/day), 1,25(OH)2D3 (39 pmol/day or 195 pmol/day), and 24,25(OH)2D3 (650 pmol/day) on arginine-induced insulin secretion from the isolated, perfused rat pancreas; in this experiment, the daily caloric intake of the animals receiving vitamin D or its metabolites was controlled by pair feeding to the caloric intake of the vitamin D-deficient rats. 1,25(OH)2D3 repletion was found to completely restore insulin secretion to the levels seen in vitamin D3-replete, pair-fed controls in both the first and second phases, while 24R,25(OH)2D3 only partially improved insulin secretion, and then only in the first phase.

Changes of both serum calcium levels and dietary caloric intake after vitamin D metabolite administration are concluded to play a lesser role on the enhancement of insulin secretion, since, in a separate experiment, vitamin D-deficient rats with normal serum calcium levels did not show recovery of insulin secretion equivalent to the vitamin D-replete animals under conditions of dietary pair feeding. These results suggest that 1,25(OH)2D3but not 24,25(OH)2D3 plays an essential role in the normal insulin secretion irrespective of the dietary caloric intake and prevailing serum calcium levels.
Anti-islet Cellular and Humoral Immunity, T-Cell Subsets, and Thymic Function in Type I Diabetes
Authors: Quiniou-Debrie M C , Debray-Sachs M , Dardenne M , Czernichow P , Assan R , Bach J F
Published: September 2013

Peripheral lymphocyte subsets were enumerated, using OKT monoclonal sera, in 56 diabetic (43 adults and 13 children) and 20 control subjects. Concomitantly, anti-islet humoral and cellular immunity was tested in vitro and serum thymulin level was measured.

In the newly diagnosed patients (<30 days; 18 cases), the percent of OKT4+ and OKT8+ cells was reduced, the OKT8+ depletion being particularly pronounced in children. Tests for cellular immunity were positive in 83% of the newly diagnosed diabetic subjects and anti-islet cytotoxic antibodies were detected in 50%. The serum thymulin level was decreased in 2 children. Later on in the course of the disease, a marked reduction in OKT3+, OKT4+ and OKT8+ cell percentage was observed, the mean OKT4/OKT8 ratio being normal or lower than normal. The percent of antibody-positive sera rose to 64%, while anti-islet cellular immunity was detectable in 54%. When extrapancreatic manifestations of probable autoimmune nature were present, anti-islet cellular immunity was detected in 100% of cases, accompanied by cytotoxic antibodies in 54%.

(1) the magnitude of T-cell depletion and/or imbalance in diabetic subjects depended mainly on the duration of the disease, (2) anti-islet cellular immunity was the anomaly most frequently detectable, and (3) a decrease in serum thymulin level was infrequently detected.
Plasma Apolipoproteins AI, AII, B, CI, and E Are Glucosylated in Hyperglycemic Diabetic Subjects
Authors: Curtiss Linda K , Witztum Joseph L
Published: September 2013

Nonenzymatic posttranslational glucosylation of the free amine of lysine residues can occur in hyperglycemic diabetic subjects. Using monoclonal antibodies that specifically bind the reduced conjugate of glucose covalently bound to the epsilon amine of lysine, glucitollysine, plasma lipoprotein glucosylation was demonstrated by radioimmunoassays in all subjects tested. Lipoproteins isolated from the plasma of diabetic subjects in poor metabolic control contained up to 33-fold increases in glucitollysine residues/mg of isolated lipoprotein protein, and on an absolute basis contained between 36 and 383 nmol of glucitollysine in their total lipoprotein fraction compared with normals, who had a mean of 2.9 ± 0.06 nmol. The majority of the glucosylated protein in the d < 1.125 g/ml fraction was present in the triglyceride-rich lipoproteins of hyperglycemic subjects, whereas the majority of the glucosylated protein in the d < 1.125 g/ml fraction of euglycemic subjects was present in the high-density lipoproteins (HDL). A number of immunochemical approaches were used to demonstrate that, in diabetic plasma, apo Al, apo All, apo B, apo Cl, apo E, and albumin were glucosylated. Detailed studies of the apoproteins of a d ≤ 1.019 g/ml lipoprotein fraction and of an HDL fraction isolated from a hyperglycemic diabetic subject indicated that glucitollysine-specific antibodies can be sed to preparatively isolate proteins containing glucosylated amino acid residues so that the extent of glucosylation in specific proteins can be measured. The results indicate that some of the lysine residues of the apoproteins can be modified in hyperglycemic diabetic subjects by the covalent attachment of glucose. The possible significance of these observations is discussed.
Renal Hypertrophy in Experimental Diabetes: Changes in Pentose Phosphate Pathway Activity
Authors: Steer Keith A , Sochor Milena , McLean Patricia
Published: September 2013

An examination was made of the effect of different periods of experimental diabetes on the activity of the pentose phosphate pathway in rat kidney. A rapid increase in kidney weight, expressed both in absolute terms and in terms of body weight, occurred shortly after the induction of diabetes. The activity of the enzymes of the oxidative segment of the pentose phosphate pathway and the flux of glucose through the pathway were both increased during the first 7 days after induction of diabetes. Thereafter, enzyme activity returned toward control levels, but the increased functional activity of the pathway, as measured using specifically labeled glucose, persisted. In contrast, transketolase was significantly depressed at the time of most rapid kidney growth. A positive correlation was found between the rate of kidney growth and the change in activity of glucose-6-phosphate dehydrogenase and a negative correlation with changes in transketolase activity. The possible roles of the oxidative and nonoxidative segments of the pentose phosphate pathway in the kidney in early diabetes-induced renal hypertrophy are discussed.
Recognition and Uptake of Human Diabetic Peripheral Nerve Myelin by Macrophages
Authors: Vlassara Helen , Brownlee Michael , Cerami Anthony
Published: September 2013

Macrophages recognize and ingest several human proteins whose amino groups have beenmodified in vitro by specific chemical reagents. Because amino groups of human peripheral nerve myelin proteins become covalently modified in vivo by products of nonenzymatic glycosylation, we examined myelin/macrophage interactions using peripheral nerve myelin prepared from diabetic and nondiabetic patients.

Intracellular accumulation of diabetic myelin increased with concentration in an apparently saturable fashion, reaching levels 3—4 times higher than those of age-matched nondiabetic samples.Low-temperature inhibition of cellular myelin accumulation further suggested that diabetic myelin uptake was associated with adsorptive endocytosis. Macrophage recognition and accumulationof nondiabetic myelin glycosylated in vitro increased with duration of sugar incubation, to a level nearly nine times that of the same sample incubated in buffer alone. Data from competition experiments with albumin and myelin glycosylated in vitro showed that recognition of human peripheral nerve myelin proteins by macrophages is specific for proteinbound products of nonenzymatic glycosylation.

In vivo, such macrophage recognition of and interaction with nonenzymatic glycosylation products on diabetic peripheral nerve myelin could contribute to the pathogenesis of segmental demyelination.
Chlorozocin: A Diabetogenic Analogue of Streptozocin with Dissimilar Mechanisms of Action on Pancreatic Beta Cells
Authors: Mossman Brooke T , Wilson Glenn L , Craighead John E
Published: September 2013

Chlorozotocin (chlorozocin, CLZ), the 2-chloroethyl analogue of streptozocin (STZ), was evaluated in three species of rodents. The drug is currently being used in phase II chemotherapeutic trials in man, and appears to be effective in the treatment of certain tumors. In our studies, hyperglycemia was induced in hamsters as early as 2 days after a single intraperitoneal (i.p.) injection of 30–60 mg/kg and was most striking at 4 days. Greater concentrations of CLZ (≥50 mg/kg) were required to produce hyperglycemia in CD-1 mice. Degranulation and necrosis of beta cells developed in hamsters and mice, whereas alpha and acinar cells of the pancreas revealed no morphologic changes. Hyperglycemia was not induced in rats at any concentration tested; however, animals showed abnormal carbohydrate tolerance after administration of 100 mg/kg CLZ (LD50 dosage).

The nature of damage by CLZ to beta cells was investigated both in vivo and in vitro. Pretreatment of hamsters with nicotinamide (500 mg/kg, i.p.) failed to alter the extent of CLZ-induced beta cell injury and associated hyperglycemia, but decreased the amount pf beta cell necrosis and hyperglycemia in animals receiving STZ. The nonmetabolizable sugar, 3-O-methylglucose (3–O-MG), and 3-aminobenzamide, an inhibitor of the nuclear enzyme, poly AD Pribose synthetase, prevented STZ-associated damage to beta cells in islet cell cultures, but only 3–O-MG reduced CLZ-induced toxicity. Thus, in comparison to STZ, CLZ appears to be a diabetogenic agent with different species specificity and alternative mechanisms of cytotoxicity. The glucose moiety of both drugs appears critical in the induction of beta cell damage.
Altered Growth Kinetics of Dermal Fibroblasts and Arterial Smooth Muscle Cells from Spontaneously Diabetic BB Rats
Authors: Bowersox Jon C , Sorgente Nino
Published: September 2013

We cultured arterial smooth muscle cells and dermal fibroblasts from spontaneously diabetic BB rats and normoglycemic litter mate controls. Although there were no detectable differences in the morphology of cells obtained from diabetic rats, significant differences existed in growth parameters of the diabetic smooth muscle cells. These cells grew more rapidly than smooth muscle cells from normal rats (population doubling times: normal = 42.6 ± 3.2 h, diabetic = 31.8 ± 3.7 h) and attained greater densities at confluence. The growth rates of the diabetic smooth muscle cells were dependent on the initial seeding density of cells, a characteristic not observed in cells from normal rats. Although growth rates of the diabetic smooth muscle cells were increased, their plating efficiencies were reduced. Dermal fibroblasts from diabetic rats grew at the same rates as fibroblasts from control animals and the plating efficiencies of the diabetic fibroblasts were increased rather than reduced. In these studies, we have shown that vascular-derived cells from diabetic rats have growth defects not detected in dermal fibroblasts from the same animals. This emphasizes the importance of using blood vessel cells to probe the pathophysiology of diabetic vascular disease. Furthermore, our results establish the validity of using spontaneously diabetic rats as a model system for examining inherent cell defects in insulin-dependent diabetes mellitus.
Unresponsiveness to Glucose in a Streptozocin Model of Diabetes: Inappropriate Insulin and Glucagon Responses to a Reduction of Glucose Concentration
Authors: Leahy John L , Weir Gordon C
Published: September 2013

The neonatal streptozocin (STZ) rat model of NIDDM has been previously found to have a markedly reduced insulin response to an acute increase in glucose concentration. We studied the effect of an acute reduction in glucose concentration on insulin and glucagon secretion in this model and contrasted the results with the effects of epinephrine and somatostatin using the in vitro isolated, perfused pancreas.

The reduction in perfusate glucose concentration from 11.1 to 2.8 mM caused a rapid suppression of insulin release in the control rats, but had no inhibitory effect in the STZ group. Epinephrine (55 nM) and somatostatin (110 nM) caused similar decreases in insulin secretion in both groups. The glucose reduction also caused an increase in glucagon release in the controls, but had no effect in the STZ rats. Epinephrine, however, stimulated glucagon secretion in both groups in a similar fashion, and inhibition by somatostatin was also comparable. The baseline insulin and glucagon concentrations were enhanced in a separate series of experiments by the addition of arginine (5 mM) to the perfusate, and while the insulin and glucagon responses to the glucose reduction remained lost, appropriate inhibition of insulin secretion was demonstrated in the STZ rats with epinephrine.

These data indicate that A- and B-cells in this rat model of NIDDM are selectively unresponsive to both increases and decreases in glucose concentration, while the responsiveness to nonglucose agents remains intact.
Characteristics of the Interaction of the Glucagon Receptor, cAMP, and Insulin Secretion in Parent Cells and Clone 5F of a Cultured Rat Insulinoma
Authors: Korman L Y , Bhathena S J , Voyles N R , Oie H K , Recant L
Published: September 2013

Rat insulinoma cells, which grow in culture and secrete insulin, were used to study the mechanism of stimulation of insulin release by glucagon. The parent cell line (RIN-m) and a clone that secretes high levels of insulin (5F) had been shown to possess specific receptors for glucagon. Glucagon (1 μM) stimulated a rapid increase in cyclic adenosine 3'5'-monophosphate (cAMP) that was followed by an increase in insulin secretion in both cell lines. The concentration of glucagon necessary for half-maximal stimulation of cAMP was 50 μM in parent and approximately 0.5 μM in 5F, whereas the concentration required to inhibit binding by 50% was 0.5 nM and 30 nM, respectively. In 5F, the dose-response relationships for cAMP and insulin secretion were superimposable. The glucagon effects on insulin secretion and cAMP did not require either glucose or amino acids in the incubation media. No refractoriness to glucagon stimulation of cAMP or insulin was noted.

It may be concluded that (1) there are significant differences between glucagon binding and glucagon responses in parent cells and clone 5F, (2) there are glucagon receptors that are not coupled to adenylate cyclase, and (3) cAMP mediates glucagon-stimulated insulin release.
Phosphate Transport by Jejunal Brush Border Membrane Vesicles of the Streptozocin-diabetic Rat
Authors: Ghishan Fayez K , Borowitz Stephen , Mulberg Andrew
Published: September 2013

We studied the effects of acute diabetes mellitus on jejunal transport of phosphate (32P) by rat brush border membrane vesicles (BBMV) using a Millipore filtration technique. Diabetes was induced by an intravenous (i.v.) injection of 50 mg/kg of streptozocin (STZ). Control and diabetic rats were studied 4 days after the induction of diabetes. In both control and diabetic rats, the presence of a sodium gradient significantly enhanced the uptake of 32P at 20 s and at 1, 2, 5, and 60 min as compared with potassium gradient conditions. Na+-dependent 32P uptake at 20 s and at 1 and 2 min was significantly greater in the diabetic BBMV compared with controls. Na+-independent 32P uptake in both diabetic and control BBMV was similar. To determine whether the enhancement of Na+-dependent 32P uptake in diabetic BBMV is due to an induction of Na+ /phosphate cotransporter activity, or a change in Na+ permeability, two additional studies were conducted. Trans-stimulation studies nullifying all electrochemical gradients across the membranes were performed. In diabetic BBMV, 32P uptake at all time points was significantly greater than corresponding values in controls, indicating an increase in the activity of Na+ /phosphate cotransporters. 22Na uptake into BBMV at 30 s and at 1, 2, and 60 min was not different between diabetics and controls, indicating that Na+ permeability is not altered in diabetes. Furthermore, kinetic studies using phosphate concentrations between 0.05 and 2.5 mM indicate a significant increase in Vmax capacity of diabetic rats compared with controls without a change in Km values. We conclude that the reason for the increased uptake of 32P observed in 4-day diabetic BBMV is due to an increase in the activity of the Na+ /phosphate cotransporter.
Prostaglandin E2 Metabolite Levels During Diabetic Ketoacidosis
Authors: McRae John R , Day Richard P , Metz Stewart A , Halter Jeffrey B , Ensinck John W , Robertson R Paul
Published: September 2013

Insulin therapy was withdrawn from 15 well-controlled type I diabetic subjects for no longer than 18 h to examine the sequence with which 13,14-dihydro-15-keto-PGE2 (PGE-m), glucagon, norepinephrine, and epinephrine increased in circulating blood in diabetic subjects becoming ketoacidotic. Fourteen of 15 patients had increments in PGE-m; 12/12, 12/15, and 13/15 had increments in glucagon, norepinephrine, and epinephrine, respectively. Six of the 15 patients developed mild diabetic ketoacidosis (DKA) by 12–18 h; all had nonmeasurable C-peptide levels. This DKA group had significantly greater increments of PGE-m (835 ± 130 versus 276 ± 111 pg/ml, mean ± SEM, P < 0.01) but not glucagon, norepinephrine, or epinephrine compared with the 9 non-DKA patients. In the DKA group, there were significant PGE-m and glucagon increments in the circulation by 3 h, significant norepinephrine increments by 9 h, and epinephrine increments in 5/6 patients by 12 h (not statistically significant) of insulin withdrawal. These studies document that (1) PGE-m accumulates in the circulation during DKA, (2) PGE-m and glucagon increase before catecholamines, and (3) PGE-m, glucagon, and catecholamine levels promptly return to normal levels when insulin therapy is reinstituted. It is suggested that elevated PGE-m levels early in the onset of DKA may represent a host-defense mechanism.
Long-Term Prognosis After Myocardial Infarction in Men with Diabetes
Authors: Ulvenstam Göran , Åberg Anders , Bergstrand Robert , Johansson Saga , Pennert Kjell , Vedin Anders , Wilhelmsen Lars , Wilhelmsson Claes
Published: September 2013

Men (1306) who survived a first myocardial infarction (Ml) were studied. The mean follow-up time was 6.5 yr, and at the end of the follow-up period survival status was known for all patients. By the time of the Ml the prevalence of diabetes was 5.6%. Patients with and without diabetes were compared. There were no differences in the estimated primary or secondary risk. The cumulative survival rate 1, 2, and 5 yr after the Ml was 82, 78, and 58% among the diabetic subjects compared with 94, 92, and 82% among the nondiabetic subjects (P < 0.001). The difference remained even after allowance for age and estimated secondary risk in a multivariate regression analysis. There were no differences in mortality rates among patients with type I diabetes compared with type II diabetes, nor among patients treated with diet alone, sulfonylurea, or insulin, but the numbers were small. The cumulative rate of reinfarctions after 1, 2, and 5 yr was 18, 28, and 46% in diabetic subjects and 12,17, and 27% in nondiabetic subjects (P = 0.004).

A history of diabetes was an independent secondary risk factor among male survivors of a first Ml with respect to deaths and reinfarctions.
Insulin and Anti-Insulin Antibody Interaction: Evidence for the Formation of 7 S and 10 S Structures
Authors: Petersen Karl-Georg , Storch Max-Jürgen , Rother Krishna , Licht Thomas , Kerp Lothar
Published: September 2013

The clearing of monoclonal and polyclonal and antiinsulin antibodies from homogenous solutions at 100,000 × g was used to estimate the size of soluble insulin-antibody complexes at physiologic concentrations. Monoclonal antibodies cleared as a uniform population of 6.6 S independent of the insulin concentration. Polyclonal antibodies cleared as 6.6 S monomers at saturation and as 10 S particles when the amount of insulin bound decreased, suggesting that a soluble complex with two antibodies was formed. An increase of the affinity and a decrease of antibody valency can be related to the complex formation. The binding affinity of polyclonal sera depends on the composition of the affinities of the IgG monomers and on their ability to form 10 S complexes. The formation of insulin-antibody dimers precludes cross-linking and precipitation. Both types of insulin-antibody complexes have been found in the sera from patients treated with bovine insulin.
Biohybrid Artificial Pancreas Long-Term Insulin Secretion by Devices Seeded with Canine Islets
Authors: Araki Yoshimasa , Solomon Barry A , Basile Richard M , Chick William L
Published: September 2013

Long-term insulin secretion was investigated in seven biohybrid capillary devices seeded with canine islets. Approximately 50,000 islets could be isolated from a single canine pancreas using collagenase digestion in conjunction with the recently described Velcro technique. Devices were perfused with tissue culture medium 199 containing 300 mg/dl glucose. Insulin secretion fell during the first 1–2 days of culture from approximately 18 to 6 U/day. After 3–4 wk of perfusion, however, there was a gradual rise in insulin output that reached >15 U/day after 7 wk. Insulin output eventually stabilized at 18–20 U/day. Two of these devices were studied for 80 and 86 days, respectively, and continued to secrete these same amounts of insulin. Glucose-induced insulin release was studied after 1 and 4 wk of culture and was well preserved.
A Functional and Ultrastructural Analysis of Experimental Diabetic Rat Myocardium: Manifestation of a Cardiomyopathy
Authors: Jackson Charles V , McGrath Gail M , Tahiliani Arun G , Vadlamudi Rao V S V , McNeill John H
Published: September 2013

The effects of experimental diabetes on cardiac function and ultrastructure were studied in rats that had been diabetic for 6–24 wk. Experimental diabetes was produced by the intravenous (i.v.) injection of 65 mg/kg streptozocin (STZ) into rats 42–43 days old. Diabetic rat hearts perfused at 15 cm H2O on the working heart apparatus demonstrated depressed cardiac function (i.e., lower left ventricular pressure and ±dP/dt) at 6, 12, and 24 wk of diabetes. Electron microscopic analysis of ventricular myocardium revealed increased lipid deposition from 6 to 24 wk of diabetes and progressive deterioration of the myocardial cell integrityat 12 and 24 wk of diabetes. This deterioration was characterized by loss of contractile protein,vacuolization (swollen sarcoplasmic reticulum), myelin formations, myocytolysis, and contracture bands. These alterations paralleled the depression of cardiac function at 12 and 24 wk of diabetes. There was, however, depressed function at 6 wk of diabetes but no observable alterations in myocardial ultrastructure. Therefore, experimental diabetes produced ultrastructural alterations inthe rat heart that manifested themselves only after a demonstrable depression in cardiac function.
Effects of Intravenous and Oral Glucose Administration on Insulin Action in Human Fat Cells
Authors: Bounder Jan , Östman Jan , Arner Peter
Published: September 2013

The effects of various forms of glucose administration on insulin action were investigated in isolated human fat cells. Subcutaneous (s.c.) adipose tissue was obtained before and (1) 30 min (eight subjects) and 60 min (seven subjects) after an intravenous (i.v.) glucose load, and (2) after a 60-min continuous i.v. glucose infusion (five subjects). In addition, five subjects were reinvestigated before and 60 min after oral glucose ingestion. Lipolysis (glycerol release) and insulin receptor binding were determined. After all forms of i.v. glucose administration, adipocyte insulin binding was significantly reduced by 20% owing to a decrease in the high-affinity binding, whereas the concentrations of insulin producing the half-maximum inhibitions of basal and isoprenaline-induced rates of glycerol release were unaltered. Sixty minutes after oral glucose ingestion, insulin sensitivity increased 7–30-fold (P < 0.05–0.01) and high-affinityinsulin binding increased by 25% (P < 0.05). The maximum insulin-induced inhibitions ofbasal and isoprenaline-stimulated lipolysis were not altered after oral or i.v. glucose. The plasma level of glycerol was markedly and rapidly reduced after oral glucose, but the fall was slow and less pronounced after i.v. glucose. It is concluded that oral, but not i.v., glucose administration mediates a rapid increase in the antilipolytic potency of insulin in human fat cells in vitro. This may explain why antilipolysis in vivo is more pronounced after oral than after i.v. glucose challenge. Moreover, the lack of a clear correspondence between the observed changes in adipocyte insulin binding and sensitivity suggests the presence of separate short-term, glucose-mediated regulatory processes that operate both at the receptor and postreceptor levels of insulin action.
Streptozocin-induced Diabetes Affects Rat Urinary Bladder Response to Autonomic Agents
Authors: Kolta Malak G , Wallace Lane J , Gerald Michael C
Published: September 2013

The response of the urinary bladder body and base to autonomic agents was studied instreptozocin (STZ)-diabetic rats. The bladder body region from 6-wk diabetic rats showed no changes in response to acetylcholine, phenylephrine, or isoproterenol. In contrast, the bladder base region showed a 39% increase in contractile response to acetylcholine and a 37% increased response to phenylephrine. In tissues from 47-wk diabetic animals, the bladder body showed a 51% increased contractile response to acetylcholine and a 37% increased relaxation response to isoproterenol. The bladder base showed a 66% increased contraction to acetylcholine. Thus, in the bladder base, enhanced responses to acetylcholine are detected soon after induction of diabetes and continue to increase as the diabetic state progresses. Moreover, in the same bladder region, an increase in responsiveness to alphaadrenergic stimuli occurs. In the bladder body, enhanced responses to cholinergic and to beta-adrenergic stimuli occur, but are only observed in a more chronic diabetic state. The data suggest that an effect associated with autonomic diabetic neuropathy of the urinary bladder is an increased postsynaptic responsiveness to cholinergic stimuli in both regions.
Nonenzymatic Glycosylation Products on Collagen Covalently Trap Low-Density Lipoprotein
Authors: Brownlee Michael , Vlassara Helen , Cerami Anthony
Published: September 2013

Advanced nonenzymatic glycosylation products capable of cross-linking proteins accumulate on collagen in vivo in proportion to time-averaged blood glucose concentration. In this report, we have evaluated the ability of advanced nonenzymatic glycosylation productsformed on collagen in vitro to covalently bind low-density lipoprotein (LDL) in a manner similar to that which occurs in human atherosclerotic lesions. At constant LDL concentration, covalent trapping increased linearly with the extent of advanced glycosylation product formation, from 1.42 ± 0.15 to 4.46 ± 0.36 μg LDL protein/mg collagen. At a constant level of collagen advancedglycosylation product, LDL binding increased as a function of increasing LDL concentration. At anLDL-cholesterol level of 103 mg/dl, covalent trapping of LDL by nonenzymatic glycosylation products on collagen averaged 3.2 times as much as control (P < 0.01).

These data indicate that LDL is bound specifically by reactive products generated by nonenzymatic glycosylation of collagen, and suggest that excessive LDL trapping by hyperglycemia-induced advanced glycosylation endproducts may contribute to the accelerated development of atherosclerosis in patients with diabetes mellitus.
An Immunohistochemical, Ultrastructural, and Physiologic Study of Pancreatic Islets from Copper-deficient, Penicillamine-treated Rats
Authors: Weaver Fr Cyprian , Sorenson Robert L , Kaung Hue-Lee C
Published: September 2013

Murine copper deficiency induced by diet and supplemented with a copper chelator is known to produce a progressive atrophy of pancreatic acinar tissue largely replaced by noninflammatory lipomatosis, while the ductal and endocrine systems appear to remain unaffected. The islets were studied morphologically and physiologically in animals rendered copper deficient by diet and supplemented with D-penicillamine. Using immunohistochemistry, the distribution of islet cell types from copper-deficient animals exhibited a normal cellular complement for A-, B-, D-, and PP-cells. Ultrastructural analysis showed the islet tissue remains normal in appearance during the course of the metal-deficient state. Physiologic data based on the response of islets to a low- and high-glucose load in perfused, isolated pancreata as well as intravenous glucose tolerance tests indicated that insulin-secreting B-cells were functionally normal. Because of the accessibility of islets enhanced by atrophy of acini, this model may be adopted for the isolation of viable islets and for in situ physiologic studies of islet hormone secretion.
Abnormalities of Insulin Responses After Ambient and Previous Exposure to Glucose in Streptozocin-diabetic and Dexamethasone-treated Rats: Role of Hyperglycemia and Increased B-Cell Demands
Authors: Grill V , Rundfeldt M
Published: September 2013

In NIDDM, B-cells are insensitive to glucose. We studied the specificity and evolution of this abnormality in 6–10-wk-old neonatally streptozocin-diabetic (STZ) and in dexamethasone-treated (DMT) rats. Not only the effect of ambient but also that of previous glucose (priming effect) was characterized in the perfused pancreas. In fed STZ, blood glucose was elevated to 9.2 ± 0.8 versus 5.3 ± 0.2 mM in control (C) rats. Ambient glucose (27 mM) in the perfusate induced a significant but reduced total response (11% of C) that was predominantly monophasic. Secretion was promptly induced (in <20 s) both in STZ and C. Other nutrients, i.e., glyceraldehyde (10 mM) and α-ketoisocaproic acid (KIC) (5 mM) also induced reduced and monophasic responses, whereas, in contrast, 3-isobutyl-1-methylxanthine (IBMX) induced an enhanced response that was 3.8-fold larger than in C. In DMT, blood glucose was normal (5.4 ± 0.3 mM). Ambient glucose (27 mM) in the perfusate induced a normal first phase and a moderately reduced second phase (52% of untreated rats). DMT rats were hyperresponsive to IBMX, this agent inducing 2.5-fold higher release than in untreated rats.

Previous perfusion with 27 mM glucose enhanced twofold the effect of a second stimulation period with glucose in C. This induction of priming by glucose could not be demonstrated in fed STZ or in DMT. However, when STZ were fasted or insulin treated for 36 h, induction of priming reappeared, i.e., the second pulse of glucose evoked 2–3-fold more insulin release than the first pulse.

We conclude that partial B-cell insensitivity to glucose in STZ alters time dynamics of the insulin response, includes loss of a priming effect, is influenced by hyperglycemia, and is nutrient but not glucose specific. Results in DMT indicate that increased demands on B-cell secretion can lead to hyperresponsiveness to nonmetabolic secretagogues as well as loss of induction of priming by glucose without concomitant loss of sensitivity to ambient glucose.
Body Composition, Adipocyte Size, Free Fatty Acid Concentration, and Glucose Tolerance in Children of Diabetic Pregnancies
Authors: Abbott W G H , Thuillez P , Howard B V , Bennett P H , Salans L B , Cushman S W , Reaven G M , Foley J E
Published: September 2013

Previous studies show that children of women who are diabetic during pregnancy are more obese and have a higher prevalence of non-insulin-dependent diabetes mellitus (NIDDM) than children of women who first developed NIDDM >1 yr after the pregnancy (prediabetic mothers) and children of women who have never developed diabetes (nondiabetic mothers). To determine whether lean and obese children of glucose-intolerant pregnancies can be distinguished from similar children of glucose-tolerant pregnancies, we measured body composition, abdominal and gluteal adipocyte size, fasting free fatty acid (FFA), and fasting and stimulated glucose and insulin concentrations during an oral glucose tolerance test in prepubertal children of glucoseintolerant and prediabetic mothers. Each group ranged in adipocity from 6 to 40% body fat. Age, weight, height, and percentage of body fat were similar in the two groups. There were no significant differences in adipocyte size or in glucose, FFA, C-peptide, and insulin concentrations between the groups. The correlation between abdominal adipocyte size and fasting insulin concentration (r = .91 and .18, t = 2.8, P = .01) was stronger in children from glucose-intolerant than from glucose-tolerant pregnancies, respectively. In terms of the parameters we measured, there are no major differences between children of glucose-intolerant and glucose-tolerant pregnancies.
Identification of Glucokinase as an Alloxan-Sensitive Glucose Sensor of the Pancreatic β-Cell
Authors: Meglasson M D , Burch P T , Berner D K , Najafi H , Matschinsky F M
Published: September 2013

Alloxan inactivated glucokinase in intact, isolated pancreatic islets incubated in vitro. Inactivation of glucokinase was antagonized by 30 mM glucose present during incubation of islets with alloxan. Glucokinase partially purified from transplantable insulinomas or rat liver was inactivated by alloxan with a half-maximal effect at 2–4 μM alloxan. Inactivation of purified glucokinase was antagonized by glucose, mannose, and 2-deoxyglucose in order of decreasing potency but not by 3-O-methylglucose. Glucose anomers at 6 and 14 mM were discriminated as protecting agents, with the α-anomer more effective than the β-anomer. Glucokinase was not protected from alloxan inactivation by N-acetylglucosamine, indicating that the reactive site for alloxan is not the active site; therefore, glucose may protect glucokinase by inducing a conformational change. Glucokinase is thought to be the glucose sensor of the pancreatic β-cell. The finding that glucokinase is inactivated by alloxan and protected by glucose with discrimination of its anomers similar to inhibition of glucose-stimulated insulin secretion by alloxan supports this hypothesis and appears to explain the mechanism for inhibition of hexose-stimulated insulin secretion by this agent and the unique role of glucose and mannose as protecting agents.
Expression of Class I MHC Proteins on RIN-m5F Cells Is Increased by Interferon-γ and Lymphokine-Conditioned Medium
Authors: Campbell I L , Harrison L C , Colman P G , Papaioannou J , Ashcroft R G
Published: September 2013

To examine whether products of the immune system interact with the pancreatic β-cell, rat insulinoma cells (RIN-m5F line) were cultured in the presence of conditioned medium from concanavalin A–activated mouse spleen cells (CAS medium). Indirect immunofluorescence and flow cytometry revealed that after culture in CAS medium, RIN-m5F cells had an 8- to 10-fold increase in class I major histocompatibility complex (MHC) proteins, whereas class II MHC proteins remained undetectable, and the level of insulin and/or insulin-like growth factor 1 receptors was unchanged. The stimulation of class I MHC expression on RIN-m5F cells by CAS medium could be mimicked by recombinant interferon-γ. Analysis of 125I–surface-labeled cells by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and autoradiography revealed that in the presence of CAS medium, there was a major increase in the expression of proteins of 48,000, 32,000, and 12,000 Mr and a minor increase in proteins of 17,000 and 9000 Mr. Precipitation with monoclonal antibody identified the 48,000- and 12,000-Mr proteins as the class I MHC protein and β2-microglobulin, respectively. The ability of lymphokine-conditioned medium to increase the expression of RIN-m5F cell surface proteins, including the class I MHC proteins, provides a potential mechanism for enhancing the immunemediated destruction Of the β-cell.
A New Case of Abnormal Insulinemia with Diabetes: Reduced Insulin Values Determined by Radioreceptor Assay
Authors: Iwamoto Y , Sakura H , Ishii Y , Yamamoto R , Kumakura S , Sakamoto Y , Matsuda A , Kuzuya T
Published: September 2013

A 44-yr-old Japanese woman was found to have diabetes with marked fasting hyperinsulinemia. Her fasting plasma glucose, serum insulin, and C-peptide levels were 137 mg/dl, 204 μU/ml, and 1.13 pmol/ml, respectively, and the C-peptide-to-insulin molar ratio was markedly reduced. Insulin antibodies and insulinreceptor antibodies were negative. Fasting levels of counter-insulin hormones were normal. She had normal hypoglycemic response to exogenous insulin injection. Binding of 125I-labeled insulin to erythrocytes was normal. Oral glucose-tolerance tests in eight members of her first-degree relatives revealed four members (mother, sister, brother, and daughter) with fasting hyperinsulinemia (111–314 μU/ml), and two of them (mother and sister) were overtly diabetic. Thus, the abnormality was thought to be an autosomal dominant trait. Reverse-phase high-performance liquid chromatograph analysis of immunopurified insulin obtained from her serum revealed two peaks of insulin immunoreactivity. The amount of the abnormal insulin peak was seven times greater than that of normal insulin. The abnormal insulin was eluted after bovine, human, and porcine insulins, indicating it has a more hydrophobic nature than normal human insulin. Radioreceptor assay (RRA) for serum insulin with guinea pig kidney membrane revealed that the binding activity of their serum insulin was markedly decreased. Discrepancies between the values measured by RRA and those measured by radioimmunoassay were also found in her family members with hyperinsulinemia but not in her family members without hyperinsulinemia and other hyperinsulinemic patients. Thus, this family represents a new case of abnormal insulinemia with diabetes.
Demonstration of Islet Cell Surface Antibodies in Sera of New Zealand Black Mice and Inhibitory Effect on Insulin Release
Authors: Yamada K , Hanafusa T , Fujino-Kurihara H , Miyazaki A , Nakajima H , Miyagawa J , Kono N , Nonaka K , Tarui S
Published: September 2013

Islet cell surface antibodies (ICSAs) in sera of New Zealand Black (NZB) and New Zealand White (NZW) mice were detected by the indirect immunofluorescence method with cultured Balb/c mouse islet cells as antigens. Circulating ICSAs appeared in NZB mice from age 20 wk; at 30 wk, 73% of male mice and 88% of female mice had detectable ICSAs. The ICSAs were significantly absorbed with mouse islet cells but hardly absorbed with spleen cells or liver powder. The ICSAs also bound with islet cells of ICR mice, Sprague-Dawley rats, and NZB mice. NZB mice showed glucose intolerance especially at ages 10 and 30 wk. Although plasma glucose levels tended to be higher in NZB mice with strongly positive ICSAs, pancreatic insulin content was not reduced, and insulitis was rarely observed in the pancreases. On the other hand, 30-wk-old NZW mice had normal or mildly impaired glucose tolerance and only weak, if any, ICSAs. The ICSA-positive serum of NZB mice significantly suppressed glucose-induced insulin release by cultured islet cells. The ICSAs may be responsible, at least in part, for glucose intolerance in NZB mice after age 20 wk through the inhibitory effect on insulin secretion,
Combined Treatment With Nicotinamide and Desferrioxamine Prevents Islet Allograft Destruction in NOD Mice
Authors: Nomikos I N , Prowse S J , Carotenuto P , Lafferty K J
Published: September 2013

Nonobese diabetic (NOD) mice get spontaneous diabetes with clinical and pathological manifestations similar to those seen in human type I diabetes. NOD mice will destroy transplants of treated allogeneic islet tissue by a recurrence of the disease process that destroyed the original islet tissue. This may be prevented by treatment of the animals with combined desferrioxamine and nicotinamide. Transplanted animals become normoglycemic and remain so for the duration of the treatment. This suggests that oxygen-derived free radicals may be involved in islet damage in spontaneous diabetes.
Insulin Dose-Response Characteristics for Suppression of Glycerol Release and Conversion to Glucose in Humans
Authors: Nurjhan N , Campbell P J , Kennedy F P , Miles J M , Gerich J E
Published: September 2013

To compare the dose-response characteristics for suppression of lipolysis and suppression of glucose production by insulin, 13 normal nonobese individuals were infused with insulin at rates of 0.1, 0.2, 0.4, 0.8, and 1.6 mU · kg−1 · min−1 while normoglycemia was maintained with the glucose clamp technique. Glucose appearance and glycerol appearance (taken as index of lipolysis) were measured isotopically with simultaneous infusions of 3-[3H]glucose and U-[14C]glycerol. Baseline glucose and glycerol rates of appearance were 14 ± 0.5 and 1.7 ± 0.2 (μmol · kg−1 · min−1, respectively. Approximately 3% of plasma glucose originated from glycerol, and this accounted for ∼50% of glycerol disposal. During the insulin infusions, arterial insulin (basal, 9.8 ± 0.6 μU/ml) increased to 14 ± 0.5, 20 ± 0.5, 31 ± 1, 58 ± 2, and 104 ± 6 (μU/ml; calculated portal venous insulin (basal, 24 ± 2 μU/ml) increased to 26 ± 1, 32 ± 3, 70 ± 4, and 115 ± 6 JJLU ml. The rate of glucose appearance was suppressed 100%, whereas the rate of appearance of glycerol was maximally suppressed only 85%. Nevertheless, the insulin concentration that produced half-maximal suppression of glucose appearance was twice as great as that required for half-maximal suppression of glycerol appearance (26 ± 2 vs. 13 ± 2 μU/ml, P < .001). Insulin decreased both the absolute rate of glycerol conversion to plasma glucose and the percent of glycerol disposal appearing in plasma glucose (both P < .001). These results indicate that in normal humans the suppression of lipolysis is more sensitive to insulin than is the suppression of hepatic glucose production and that in addition to reducing glycerol availability, insulin suppresses glycerol incorporation into plasma glucose by another (presumably hepatic) mechanism.
Decreased Blood-Brain Barrier Permeability to Sodium in Early Experimental Diabetes
Authors: Knudsen G M , Jakobsen J , Juhler M , Paulson O B
Published: September 2013

Blood-brain barrier (BBB) permeability to 24Na+ 36CI−, and [3H] sucrose was studied in rats after 2 wk of streptozocin-induced diabetes. The PS (permeabilitysurface area product) for Na+ in the cortex of the frontal lobes was 5.4 ± 0.6 (105 cm3 g−1 · s−1; ± SD) in diabetic rats compared with 7.1 ± 1.7 in control rats. In the occipital cortex, the values were 7.6 ± 1.5 and 9.9 ± 1.6, respectively. In contrast, BBB permeability to Cl− and sucrose remained unchanged. We conclude that a selective alteration in BBB permeability to Na+ unrelated to changes in brain capillary surface area is present in experimental diabetes.
Definition of Streptozocin Toxicity for Primary Lymphoidal Tissues
Authors: Wellhausen S R
Published: September 2013

Hyperglycemia was induced in BALB/c mice with either streptozocin or alloxan to evaluate the effects of these drugs on primary lymphoidal tissues. Streptozocin but not alloxan 1) briefly inhibited in situ DNA synthesis in bone marrow and thymus, 2) elicited a transient selective depletion of circulating lymphocytes, and 3) elicited a transient selective depletion of cortical thymocytes. Streptozocin also inhibited in vitro DNA synthesis of bone marrow cells and thymocytes from normal mice. A single subdiabetogenic dose of streptozocin depleted circulating lymphocytes and thymocytes.