bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Central Biochemistry Laboratory in the Multicenter Kroc Study: Problems and Proposals
Authors: Home Philip D , Alberti K George M M , Rodger N Wilson , Burrin Jacqueline M ,   The Kroc Collaborative Study Group
Published: September 2013

The advantages of a multicenter trial can easily be lost if results from individual centers cannot be safely combined for statistical analysis. One objective of the Kroc Study was to develop methods that would allow valid amalgamation of results from laboratories at the six clinical centers and a central biochemical laboratory at the University of Newcastle upon Tyne. Responsibilities of the local laboratories, in addition to measurement of plasma glucose, creatinine, and glycosylated hemoglobin, were to obtain and prepare samples for measurement of plasma glucose, glycosylated hemoglobin, and serum lipids at the central laboratory, of C-peptide at the University of Chicago, and to collect and prepare samples for measurement of urinary albumin excretion at Guy's Hospital. The central laboratory was additionally to provide a system to ensure the comparability of plasma glucose determinations between and within centers, and to advise on common procedures for sample handling.
Major problems were encountered with sample labeling, dispatch, and transport to the central laboratory. Although central determinations of plasma glucose and serum lipids were still possible in transported specimens, central assay of glycosylated hemoglobin proved inaccurate and useless. Compliance with the plasma glucose quality control program was variable among centers. Although the difference between the centers recording the highest and lowest values was 24.6% of the mean estimate of plasma glucose level, correlation between local and central plasma glucose determinations was good (r = 0.99, see pages 22–26).
From this experience, we suggest that for satisfactory performance of a multicenter trial an individual is given responsibility for coordinating efforts between laboratories, supervising and auditing local procedures of sample preparation and quality control, and ensuring adequate communication between the central laboratory, local centers, and the data collation center. A biochemist at each local laboratory should in turn be personally responsible for the specimens generated by each experiment, and preparation and dispatch of samples to the central laboratory. Duplication of assays of critical variables, namely at local and central laboratories, is recommended. Blood glucose and glycosylated hemoglobin assays should be by a single method using one type of instrument, the methods chosen being selected by their ability to produce reliable and comparable results in different hands.
These measures should minimize the likelihood of loss of critical information due to poor sample management, and the variability inherent in the combined use of biochemical data derived from multiple laboratories.
Comparison of Stereofundus Photographs in Patients with Insulin-dependent Diabetes During Conventional Insulin Treatment or Continuous Subcutaneous Insulin Infusion
Authors: Canny C L B , Kohner E M , Trautman J , Puklin J , Morse P ,   The Kroc Collaborative Study Group
Published: September 2013

Sixty-five patients with mild to moderate nonproliferative diabetic retinopathy who enrolled in a prospective controlled clinical trial had stereofundus photographs assessed for change over an 8-mo period. The entire study group showed a worsening of retinopathy with time (P &lt; 0.001). The worsening was greater in the pump-treated group (15/32) than in the conventionally treated group (9/33). The significance of this difference ranged from P = 0.67, if changes in mean retinopathy level for each patient were compared, to P = 0.177 if a grading system keyed to the worse eye was compared. The difference in rates of change between treatment groups was found to be related to the baseline mean retinopathy level (P = 0.031), but less significantly so if baseline retinopathy keyed to the worse eye was used as a covariate (P = 0.08). Worsening occurred more frequently in those patients starting with the lower retinopathy levels.
Progression was associated with the appearance of retinal infarcts (cotton-wool spots, soft exudates) and/or intraretinal microvascular abnormalities, with the pump patients showing a significant increase in these individual retinal lesions compared with the conventionally treated patients over 8 mo (P &lt; 0.025).
Improved Insulin Sensitivity in Patients with Type I Diabetes Mellitus After CSII
Authors: Simonson Donald C , Tamborlane William V , Sherwin Robert S , Smith J Douglas , DeFronzo Ralph A ,   The Kroc Collaborative Study Group
Published: September 2013

Tissue sensitivity to insulin was studied using the euglycemic insulin clamp technique (Δ plasma insulin above basal 90 μU/ml) in eight patients with type I diabetes mellitus (IDDM) before and after 4–8 mo of continuous subcutaneous insulin infusion (CSII) and in 36 age-matched control subjects. Institution of CSII was associated with significant improvements in glycosylated hemoglobin (HbA1) (11.2 ± 0.6% versus 8.1 ± 0.4%; P &lt;0.001) and mean 24-h plasma glucose concentrations (239 ± 23 mg/dl versus 106 ± 18 mg/ dl ; P &lt; 0.001).
Insulin-mediated glucose metabolism in the diabetic patients pre-CSII (3.92 ± 0.36 mg/kg min) was reduced by 44% compared with controls (7.03 ± 0.22 mg/kg min; P &lt; 0.001). After 4–8 mo of improved glycemic control, improved tissue sensitivity to insulin was observed (5.33 ± 0.75 mg/kg·min; P &lt; 0.05 versus pre- CSII). However, insulin-mediated glucose utilization still remained significantly below control values (P &lt; 0.01). During hyperinsulinemia, hepatic glucose production (3-3H-glucose) was suppressed by over 90% in diabetic patients (pre- and post-CSII) and in control subjects.
We conclude that near-normalization of glucose metabolism with CSII partially corrects, but does not restore to normal, insulin-stimulated glucose uptake in IDDM. Our failure to totally reverse the impaired response of peripheral tissues to insulin in IDDM patients may be attributed to inadequate metabolic correction, the peripheral route of insulin administration, or a primary defect in glucose metabolism.
Ketone Body Production and Disposal in Diabetic Ketosis: A Comparison with Fasting Ketosis
Authors: Féry Françoise , Balasse Edmond O 
Published: September 2013

This work compares the metabolism of total ketone bodies in 13 insulin-deprived, type I diabetic subjects and 26 control subjects fasted for 15 h to 23 days, with the two groups showing a similar range of ketone body levels (1–12 mM). Ketone turnover rate was measured using a primed, constant infusion of either 14C-acetoacetate or 14C-β-hydroxybutyrate, both tracers yielding comparable results.
The major conclusions of this study are the following: the kinetics of ketone bodies are comparable in the two groups within the range of concentrations tested. The hyperketonemia of fasting and diabetes is primarily caused by an increased production of ketone bodies, but the phenomenon is amplified by a progressive limitation in the ability of tissues to remove ketones from blood as the concentration rises. The inverse relationship between the metabolic clearance and the plasma levels of ketones, which underlies this process, represents a general characteristic of ketone body metabolism that applies to both types of ketosis. A maximal metabolic disposal rate of about 2.3 mmol/min/1.73 m2 is attained in both groups at concentrations of 10–12 mM, which correspond to the highest ketone body levels encountered during prolonged fasting. Thus, up to these levels, there is no evidence for the existence of a ketone body removal defect specific to diabetes.
The Effect of In Vivo Glucose Administration on Human Erythrocyte Ca2+-ATPase Activity and on Enzyme Responsiveness In Vitro to Thyroid Hormone and Calmodulin
Authors: Davis Faith B , Davis Paul J , Nat Gerard , Blas Susan D , Macgillivray Margaret , Gutman Steven , Feldman Mary Jane 
Published: September 2013

To characterize endogenous control mechanisms for human erythrocyte membrane Ca2+-ATPase (“calcium pump”) activity, we studied the effect of changes in blood glucose concentration in vivo within the physiologic range on Ca2+-ATPase activity in red cells. Red cells obtained in the course of induced hyperglycemia were also studied to determine susceptibility of membrane Ca2+-ATPase to stimulation in vitro by thyroid hormone and calmodulin, both of which have been shown previously to enhance Ca2+-ATPase activity.
Oral glucose administration (75 g) to eight healthy, adult subjects induced predictable increases in concentrations of blood glucose and immunoreactive insulin. Basal levels of activity of Ca2+-ATPase in red cells obtained after glucose ingestion fell 55% (P &lt; 0.025) by 30 min after glucose with recovery of enzyme activity to levels not significantly different from basal by 60 min. Activity of red cell Ca2+-ATPase at time zero was significantly stimulated in vitro by thyroxine (T4, 10−10 M), triiodo-L-thyronine (T3, 10−10 M), and calmodulin (100 ng/mg membrane protein). In vivo glucose administration led to depression of red cell enzyme responsiveness in vitro to T4 and T3; recovery from this effect did not occur by 120 min after oral administration of glucose. Calmodulin responsiveness of the enzyme in vitro was less significantly reduced in red cells obtained after glucose ingestion.
Intravenous (i.v.) glucose administration (20 g) to five subjects also led to decreased basal enzyme activity (61% of fasting level at 20 min). A significant decrease in response of enzyme to T4 was achieved by 8 min after glucose administration (P &lt; 0.02), with recovery by 60 min. Calmodulin responsiveness showed an insignificant downward trend.
Exposure of red cell membranes to glucose (200 mg/ dl) or insulin (100 nil/ml) in vitro resulted in 26% and 17% reductions, respectively, in basal Ca2+-ATPase activity (P &lt; 0.001), together with a reduction in thyroid hormone stimulation of the enzyme. Tunicamycin, an inhibitor of enzymatic protein glycosylatioh, reversed these in vitro effects of glucose, but not of insulin, on erythrocyte Ca2+-ATPase activity.
These observations are relevant to the interpretation of clinical studies of Ca2+-ATPase activity and to the physiology of the enzyme. Glucose administration predictably decreases Ca2+-ATPase in the human red cell, an alteration in calcium pump activity that would allow pulsing Of Ca2+ into the cell.
Acute Reversal of the Enhanced Insulin Action in Trained Athletes: Association with Insulin Receptor Changes
Authors: Burstein R , Polychronakos C , Toews C J , MacDougall J D , Guyda H J , Posner B I 
Published: September 2013

We studied the effect of aerobic training and detraining on insulin-stimulated glucose disposal and on erythrocyte insulin receptor binding. Seven endurancetrained athletes were studied at 12 h, 60 h, and 7 days after cessation of training and compared with three untrained, age- and weight-matched controls.
The metabolic clearance rate of glucose as measured by the euglycemic clamp technique was 15.6 ± 1 . 8 ml/kg/min (mean ± SEM) in the trained subjects 12 h after the last bout of exercise compared with 7.8 ± 1.2 ml/kg/min in the untrained control group. When the trained subjects refrained from physical training, the metabolic clearance rate decreased to 10.1 ± 1 . 0 ml/kg/min at 60 h and further to 8.5 ± 0.5 ml/kg/min after 7 days of detraining.
The percentage of specific insulin binding to young erythrocytes (density 1.089–1.092), isolated by density gradient centrifugation, decreased from 10.4 ± 0.9 at 12 h after the last exercise to 8.1 ± 0.7%/3 × 109 cells after 60 h of detraining (P &lt; 0.001). The decrease in insulin binding to erythrocytes was almost entirely accounted for by a decrease in the number of insulin receptors.
We conclude that the increase in peripheral insulin action seen in trained athletes is rapidly reversed, possibly by a mechanism separate from other phenomena associated with chronic training. The parallel findings of decreased in vivo insulin action and decreased insulin binding in young erythrocytes suggest that modulation of in vivo insulin response by detraining may be at least partially mediated by changes in insulin receptor number. Isolated young erythrocytes are better indicators of acute insulin receptor modulation than are whole cell preparations.
Successful Long-Term Survival of Pancreatic Islet Allografts in Spontaneous or Pancreatectomy-induced Diabetes in Dogs: Cyclosporine-induced Immune Unresponsiveness
Authors: Alejandro Rodolfo , Cutfield Richard , Shienvold Frances L , Latif Zuhair , Mintz Daniel H 
Published: September 2013

Nineteen pancreatectomized beagles and three spontaneously diabetic dogs were recipients of canine islet allografts from one or more unrelated donors. The islets, enriched 30–45-fold for endocrine cells and contained in a packed cell volume of &lt;1.5 ml, were engrafted in the livers of recipient animals. Treatment of diabetic recipients with cyclosporine (CsA) was begun 3–5 days before islet transplantation and the initial dosage was adjusted to attain and maintain CsA serum trough levels between 400 and 600 ng/ml. Five dogs with CsA levels less than this (155 ± 35 SEM ng/ml) at the time of transplantation promptly rejected their grafts, whereas rejection was encountered in only 1 of 17 diabetic animals in which the initial level exceeded 400 ng/ml. CsA was discontinued 30, 60, or 90 days after continuous therapy in 10 animals. Graft failure was observed 2 mo after stopping CsA in 1 animal and 5 mo in the other. Eight other islet allograft recipients have sustained fasting euglycemia for 7 and 8 mo in 2 and for at least 2 mo in the remainder.
These results demonstrate that short-term CsA therapy prolongs survival of islet allografts and induces a state of immune unresponsiveness to islet alloantigens in dogs with experimental and spontaneous diabetes. The findings are unique for a nonrodent mammal and thus hold promise that similar results may be achieved for islet allografts of other mammalian species, including humans.
Continuous Subcutaneous Insulin Infusion
Authors:   American Diabetes Association
Published: September 2013

Use of continuous subcutaneous insulin infusion requires continuing available care by skilled professionals, careful selection of patients, meticulous patient monitoring, and provisions for recording and reporting experiences.
Insulin pumps prescribed by a physician within these guidelines are a part of treatment and should be covered by usual payment mechanisms.
Approved: Board of Directors, June 15, 1985.
Effects of Anti-Insulin Receptor Antibodies (AIRA) on Downregulation and Turnover of Insulin Receptors on Cultured Hepatocytes
Authors: Shimoyama R , Shelmet J J , Savage C R , Boden G 
Published: September 2013

We have studied the effects of two polyclonal anti-insulin receptor antibodies (AIRA) on insulin receptor downregulation and turnover in rat hepatocytes in primary culture. Downregulation was determined by measurement of insulin binding after acid washing of cells to remove AIRA. Insulin receptor turnover was estimated by measurement of insulin binding after inhibition of synthesis of functional receptors with tunicamycin (0.5 μg/ml). Exposure of hepatocytes to AIRA (both sera were of comparable effectiveness) resulted in progressive, time- and dose-dependent losses of insulin binding (maximal loss was about 55% after 24 h of incubation with AIRA diluted 1:25). Cycloheximide (100 μM) prevented AIRA-mediated downregulation.
The t½ of disappearance of cell surface insulin binding capacity determined with tunicamycin was 8.0 h. Addition of insulin (1000 ng/ml) or AIRA to tunicamycin reduced the t½ to 2.6 h (insulin), 2.2 h (patient B10), and 2.0 h (patient 1). These data suggest that (1) AIRA downregulated insulin receptors on cultured hepatocytes by accelerating their rate of disappearance, (2) inhibition of protein synthesis prevented AIRA-mediated downregulation, and (3) downregulation by AIRA of insulin binding may be partially responsible for the desensitization of target cells to some of the insulinlike actions of these autoantibodies.
Utilization of Oral Sucrose Load During Exercise in Humans: Effect of the α-Glucosidase Inhibitor Acarbose
Authors: Gerard J , Jandrain B , Pirnay F , Pallikarakis N , Krzentowski G , Lacroix M , Mosora F , Luyckx A S , Lefèbvre P J 
Published: September 2013

We investigated the hormonal and metabolic response to a 100-g sucrose load given 15 min after adaptation to moderate-intensity (50% Vmaxo2) long-duration (4-h) exercise in healthy volunteers. The effect of a 100-mg dose of the α-glucosidase inhibitor Acarbose ingested with the sucrose load was also investigated. “Naturally labeled [13C] sucrose” was used to follow the conversion to expired-air CO2 of the sugar ingested by isotope-ratio mass spectrometry. Circulating hormone and metabolite data were obtained in nine subjects, and indirect calorimetry and stable isotope methodology were applied to six of them. Under placebo, 93 ± 4 g sucrose were entirely oxidized during the 4 h of exercise, total carbohydrate utilization was 235 ± 14 g, endogenous carbohydrate utilization was 142 ± 13 g, and total lipid oxidation was 121 ± 7 g. A single oral dose of 100 mg Acarbose ingested with the sucrose load did not significantly modify total carbohydrate (239 ± 2 g/4 h) or lipid (122 ± 6 g/4 h) oxidation. In contrast, sucrose oxidation was reduced to 53 ± 6 g/4 h and endogenous carbohydrate utilization increased to 186 ± 7 g/4 h. Reduction of the rises in blood glucose and fructose and of the increases in plasma insulin and C peptide under Acarbose confirmed these effects, whereas lower circulating levels of alanine suggested a higher rate of gluconeogenesis.
These data show that a 100-g glucose load ingested soon after initiation of exercise is a perfect available metabolic substrate. Furthermore, the simultaneous ingestion of 100 mg Acarbose significantly reduces the availability of sucrose during exercise, a finding that has to be considered if this or other compounds with similar properties are envisaged for the treatment of diabetic patients.
The Limitations to and Valid Use of C-Peptide as a Marker of the Secretion of Insulin
Authors: Polonsky K , Frank B , Pugh W , Addis A , Karrison T , Meier P , Tager H , Rubenstein A 
Published: September 2013

The accuracy with which the secretion rate of insulin can be calculated from peripheral concentrations of C-peptide was investigated in conscious mongrel dogs. Biosynthetic human C-peptide and insulin were infused intraportally and their concentrations measured in the femoral artery.
During steady-state infusions of C-peptide, the peripheral concentration changed in proportion to the infusion rate and the metabolic clearance rate (5.2 ± 0.3 ml/kg/min) remained constant over a wide range of plasma concentrations.
Application of a two-compartment mathematical model, in which the model parameters were estimated from analysis of C-peptide decay curves after intravenous bolus injections, allowed the intraportal infusion rate of C-peptide to be derived from peripheral C-peptide concentrations, even under non-steady-state conditions. Estimates of the intraportal infusion rate based on this model were 102.4 ± 2.6% of the actual infusion rate as it was increasing and 102.3 ± 5.5% of this rate as it was falling.
The peripheral C-peptide : insulin molar ratio was influenced by the rate at which equimolar intraportal infusions of C-peptide and insulin were changed. The baseline C-peptide : insulin molar ratio (4.1 ± 0.9) increased to peak values of 8.2 ± 0.6,10.3 ± 2.0, and 14.9 ±1.3 when the infusion rate was increased and then decreased rapidly. Peak values of only 5.7 ±1.2 were found if the intraportal infusion rate was changed slowly.
In conclusion: (1) under steady-state conditions the secretion rate of insulin can be calculated as the product of the peripheral concentration of C-peptide and its MCR; (2) under non-steady-state conditions, however, application of more complex mathematical models, such as the two-compartment model used in the present study, allows insulin secretion rates to be accurately calculated at discrete time points; and (3) under non-steady-state conditions the C-peptide:insulin molar ratio is influenced not only by the extent of hepatic insulin extraction but by other factors, including the rate of change of insulin secretion and the clearance rate of C-peptide. Changes in this ratio should therefore not be assumed to reflect changes in hepatic insulin extraction.
Growth and Hormonal Content of Human Fetal Pancreas Passaged in Athymic Mice
Authors: Tuch Bernard E , Grigoriou Samantha , Turtle John R 
Published: September 2013

While the usefulness of the human fetal pancreas transplanted into diabetic humans has yet to be realized, its transplantation into nude mice has revealed some of its potential. In this animal the organ grows in size, during which time differentiation of its endocrine component and maturation of the insulinogenic response to glucose occurs. The results reported in this article expand these results by providing data on the weight and both the insulin and glucagon content of these passaged organs.
Human fetal pancreata of gestational age 14–19 wk were implanted subcutaneously (s.c.) in nude mice and maintained in vivo for 5–54 wk (absolute age 19–68 wk). The implants were then removed and their insulin and glucagon content determined. Both the weight of these implants and their insulin content were positively correlated with the absolute age of the tissue (weight: r = 0.61, P &lt; 0.001; insulin content: r = 0.62, P = 0.0003). The glucagon content bore no relationship to the age. The maximum level of insulin extracted from 30 passaged human fetal pancreata was 0.8 U, a level far below the daily insulin requirements in adult humans. It is suggested that an explanation for this is the site of transplantation used. To compare the s.c. site with the renal subcapsular space, the explants of four fetal pancreata were evenly divided between these two sites. After 11–13 wk, the implants were removed. Those beneath the renal capsule were larger and contained a greater amount of insulin and glucagon than those transplanted s.c.
It is concluded that: (1) the human fetal pancreas implanted in the nude mouse grows and its insulin content increases with time, and (2) the renal subcapsular space is a better site for transplantation in these animals than a S.C. Site.