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Biomedical subjects

B Zinman

Publications and source records attributed to B Zinman.

At least 181 records · Page 10Linked to original sources
PubMed1977

Studies with an artificial endocrine pancreas.

Short-term studies with an artificial endocrine pancreas have provided insights into the pathophysiology of diabetes and demonstrated the ability of such a system to restore and maintain glucose homeostasis in human subjects given either their usual diet, a 50 gm oral glucose tolerance test, or a moderate level of physical exercise. Animals were used to demonstrate that a peripheral route of insulin delivery by the artificial pancreas is equivalent to the portal route.

Animals↗
PubMedDate not supplied

Glucose turnover in insulinoma--a case report.

To define glucose flux in a state of chronic endogenous insulin excess, a patient with an insulinoma was studied. Plasma glucose, insulin (IRI), glucagon (IRG) and glucose turnover ([3-3H]glucose infusion) were measured before and after insulinoma resection in the postabsorptive state (PA), during a glucose infusion adjusted to attain euglycemia (before insulinoma resection only) and following an intravenous glucagon bolus (1 mg). Before insulinoma resection, plasma glucose was 55 mg/dl, glucose production (Ra) and disappearance (Rd) were equal (1.6 mg/kg/min) and glucose clearance was elevated (2.8 ml/kg/min) in PA. When glycemia was raised with a glucose infusion to 77 mg/dl, Rd did not change; in contrast Ra dropped to zero. Plasma IRI and IRG concentrations were 0.7 ng/ml and 110 pg/ml respectively before glucose infusion and remained constant throughout. After resection of the insulinoma, glycemia in PA was 103 mg/dl, Ra and Rd were increased slightly to 1.9 mg/kg/min while the metabolic clearance of glucose was decreased by 25% (2.1 ml/kg/min). Glucagon stimulation pre- and postinsulinoma resection resulted in significant increases in glycemia and IRI. We conclude that hypoglycemia with insulinoma is a consequence of decreased glucose production and increased glucose clearance. Hepatic sensitivity to small increments in glycemia is markedly enhanced so as to fully suppress endogenous glucose production at euglycemic levels in the absence of any change in IRI and IRG. The mechanisms controlling hepatic Ra in insulinoma appear different from normal.

Adenoma, Islet Cell↗
PubMedDate not supplied

Controlled crossover study of subcutaneous and intravenous insulin infusion in type I diabetes.

Various routes of insulin infusion have been utilized to improve metabolic control in type I (insulin-dependent) diabetes. To determine the relative effectiveness of subcutaneous (SC) and intravenous (IV) systems of insulin-pump therapy, we studied five type I diabetic subjects aged 20-39 yr who were randomly assigned to a 3-mo period of either SC or IV insulin infusion and then crossed over to the alternate route for a similar period. After an initial 7- to 14-day period of in-hospital insulin-dose adjustment, all subjects were similarly followed as outpatients during both infusion periods, with a minimum of four daily preprandial self-measurements of blood glucose. Although the overall mean levels of blood glucose and HbA1c (116 +/- 6 vs. 114 +/- 5 mg/dl and 6.1 +/- 0.2 vs. 5.9 +/- 0.1% for the SC and IV systems, respectively) were similar, there was a greater incidence of low (less than 50 mg/dl) and high (greater than 180 mg/dl) preprandial blood glucose readings during SC- than during IV-pump therapy (P less than .05). Furthermore, the frequency of nocturnal and preprandial hypoglycemia was greater during SC-pump therapy (P less than .05 and P less than .02, respectively). Eight documented technical problems related to the pump and catheter occurred with the SC system, whereas 17 episodes occurred with the IV system. The number of episodes of ketosis (4 vs. 5 for SC and IV, respectively) was similar with both systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

For insulin infusion: a miniature precision peristaltic pump and silicone rubber reservoir.

This paper describes a miniature precision peristaltic pump and a silicone rubber reservoir developed for the infusion of insulin in diabetic subjects. The ability of the 100-ml reservoir to maintain sterility of its contents over 26 refilling cycles (48 days) is demonstrated. Accelerated bench tests on 10 pumps over 30 days indicate an accuracy of +/- 1% on flow rate whether measured over 10 min or 24 h and with or without 1 atm of outlet back pressure. Comparison of calibrations made before and after 58 animal and clinical tests of 6--71 days' duration showed a percentage difference in calibration that varied with a mean +/- SD of 0.05 +/- 3.09%. Microscopic examination of pump tube samples after 21 days of clinical use indicated redistribution of surface material without evidence of particle spallation. Samples subjected to accelerated wear equivalent to 620 days of clinical use showed extensive luminal surface modification and particulate deposits on downstream filters. These were identified by X-ray spectroscopy as silicon compounds.

Animals↗
PubMedDate not supplied

Electronic flow rate controller for a portable insulin infusion pump.

An electronic controller is described that regulates the flow of infusate by controlling the fraction of time that a pump is energized. Using the integral programming capability of the device, any one of 256 possible basal rates between 0 and 49.6% of the maximum rate can be chosen. An externally triggerable single meal-associated pulse can also be configured. The rate during the meal pulse can be any one of the 255 equally spaced rates in the range of 0--99.7%. The duration of this pulse can be chosen in 3-min steps to a maximum of 12.75 h, after which the rate automatically returns to the basal value. The controller consumes a minimum amount of power and can continuously operate a dc motor-driven pump at 3.0 V for 36 h. It drives the pump in an on-off mode in order to control the average flow rate digitally. In this way a significant reduction in the power requirements is realized and the system can be run for many days using small rechargeable batteries. One year of experience with 20 of these controllers was obtained in the research laboratory and clinical investigation unit. The results of this experience indicated the reliability and precision of these controllers, gave insight into their modes of failure, and provided valuable biomedical data for their improvement.

Animals↗
PubMedDate not supplied

Overnight metabolic control with pulsed intermittent versus continuous subcutaneous insulin infusion.

Subcutaneous insulin pumps deliver insulin both as a premeal bolus and as a continuous basal rate. It has been shown that the effect of the basal component is primarily to maintain normoglycemia overnight, but it is not known whether an intermittent pulsed infusion would achieve similar metabolic control. Six type I diabetic subjects (19-31 yr) were studied for 2 wk. Glycemic control was maintained by premeal injections of regular insulin with subcutaneous infusion overnight. A constant basal flow rate of insulin was delivered either continuously or intermittently as pulses spaced at 30-, 60-, and 120-min intervals. With each type of infusion, given in a randomized order, plasma glucose levels at 0600 h were: 81 +/- 12, 89 +/- 11, 102 +/- 14, and 94 +/- 13 mg/dl (mean +/- SEM), respectively. These values are not significantly different and remained stable until 1000 h. In addition, the hormonal responses (immunoreactive glucagon and "free" insulin levels) and metabolite levels (lactate, pyruvate, 3-hydroxybutyrate, alanine, and glycerol) were the same with continuous and pulsed insulin. These findings are in keeping with the expected kinetics for subcutaneously injected insulin. They may be of considerable interest for the design of smaller and more efficient subcutaneous insulin infusion pumps and demonstrate the wide physiologic limits for subcutaneous basal insulin replacement.

3-Hydroxybutyric Acid↗
PubMedDate not supplied

Pathophysiology of beta cell failure after prolonged remission of insulin-dependent diabetes mellitus (IDDM).

The pathophysiology of beta cell failure in IDDM has not been well documented. Islet cell responsiveness (C-peptide and glucagon) to oral glucose (OGTT), intravenous glucose (IVGTT), and arginine infusion was studied sequentially in a 24-yr-old nonobese patient with IDDM in prolonged remission interrupted by an episode of diabetic ketoacidosis and followed by a second transient (6 mo) partial recovery of beta cell function. The earliest abnormality in glucose tolerance was demonstrated with the IVGTT (K = 0.77) although OGTT (F, 101: 1/2 h, 177; 7 h, 211; 1 1 h, 144; and 2 h, 111 mg/dl) and glucagon responses to glucose and arginine were normal. With the development of abnormal OGTT, glucagon failed to suppress with hyperglycemia although basal levels were not elevated. With the development of frank clinical diabetes, C-peptide did not respond to oral or i.v. glucose although stimulation in response to arginine infusion was still possible. Basal glucagon concentrations were now elevated. Thus, the failing beta cell shows a progressive deterioration in its responsiveness to various secretagogues in a sequential manner (i.v. glucose followed by oral glucose and then i.v. arginine). Abnormalities in glucagon secretion can be demonstrated early in the development of abnormal oral glucose tolerance. With more precise elucidation of the etiology of diabetes, it may be possible to intervene therapeutically in diabetic individuals who experience a remission in order to prevent further deterioration in beta cell function.

Adult↗
PubMedDate not supplied

Comparison of the acute and long-term effects of exercise on glucose control in type I diabetes.

To determine the long-term effect of exercise training on glucose control, 13 subjects with type I diabetes and 7 control subjects performed 45 min of cycle exercise three times per wk for 12 wk. The acute blood glucose response, the long-term effect on glucose control (glycosylated hemoglobin and fasting plasma glucose), and changes in nutrient intake were assessed. Fitness as measured by VO2 MAX increased in both control (33.8 +/- 1.7 to 43.2 +/- 3.5 ml/min/kg) and diabetic (38.7 +/- 3.3 to 46.5 +/- 3.6 ml/min/kg) (P less than 0.05) subjects although body weight remained unchanged. In the diabetic subjects, an acute glucose-lowering effect occurred with each exercise session throughout the 12-wk training period (225.8 +/- 16.1 to 148.5 +/- 16.8 mg/dl, P less than 0.001). However, fasting plasma glucose and glycosylated hemoglobin remained essentially unchanged (pretraining, 193.7 +/- 27.5 mg/dl and 10.7 +/- 0.3%; 6-wk training, 192.5 +/- 27.1 mg/dl and 10.7 +/- 0.03%; 12-wk training, 202 +/- 30.1 mg/dl and 10.3 +/- 0.8%). Total caloric intake as assessed by diet history increased significantly on exercising days (2569-2849 kcal, P less than 0.05). Although plasma glucose decreases acutely with exercise, increased caloric intake on exercising days obviates a long-term effect of training on glucose control. More precise guidelines and recommendations as to exercise timing and nutrient intake, likely based on self-monitoring of blood glucose, are required to achieve a beneficial effect of exercise training on metabolic control in type I diabetes.

Adult↗