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Biomedical subjects

B Thorsteinsson

Publications and source records attributed to B Thorsteinsson.

At least 55 records · Page 3Linked to original sources
PubMed1986

Frequency of daytime biochemical hypoglycaemia in insulin-treated diabetic patients: relation to daily median blood glucose concentrations.

The frequency and distribution of daytime biochemical hypoglycaemia (capillary blood glucose concentration below 3 mmol/l) was assessed in type 1 diabetic patients on conventional twice daily insulin therapy (n = 79) and on continuous subcutaneous insulin infusion (n = 20). Patients collected and mailed to the hospital blood for seven-point blood glucose profiles. For both treatment regimens the frequency of biochemical hypoglycaemia on individual days was inversely related to the median blood glucose concentration in a curvilinear manner (p less than 0.001). Hypoglycaemia was more frequent pre-prandially than post-prandially (p less than 0.01), and was evenly distributed during the day in patients on continuous subcutaneous insulin infusion. In patients on conventional therapy, however, pre-lunch hypoglycaemia was four times more frequent than pre-breakfast or pre-dinner hypoglycaemia (p less than 0.0001).

Adolescent↗
PubMed1985

Nocturnal hypoglycaemia in patients receiving conventional treatment with insulin.

The prevalence of nocturnal biochemical hypoglycaemia--that is, blood glucose concentrations below 3 mmol/l (55 mg/100 ml)--was evaluated in a random sample of 58 insulin dependent diabetics receiving twice daily insulin. Seventeen patients had at least one blood glucose value below 3 mmol/l (55 mg/100 ml) and five a value below 2 mmol/l (36 mg/100 ml) during the night. Both bedtime (2300) and fasting morning (0700) blood glucose concentrations were significantly lower in the group with nocturnal hypoglycaemia compared with the group without (p less than 0.00001). If the bedtime blood glucose concentration was below 6 mmol/l (108 mg/100 ml) the risk of nocturnal hypoglycaemia was 80% (95% confidence limits 51-96%). If the bedtime blood glucose concentration was above 6 mmol/l the likelihood of hypoglycaemia not occurring during the night was 88% (74-96%). The mean glycosylated haemoglobin A1c (HbA1c) concentration in the group with nocturnal biochemical hypoglycaemia (8.2 (range 5.0-12.4)%) was significantly lower than that in the group without (9.4(7.0-14.2)%) (p less than 0.02). The prevalence of nocturnal hypoglycaemia in the patients receiving twice daily insulin (29%) was compared with that in 15 patients receiving thrice daily insulin (47%) and was not found to be significantly different. The likelihood of this risk being greater with thrice daily insulin was, however, 88%. No patient with nocturnal biochemical hypoglycaemia woke up during the night with symptomatic hypoglycaemia. Nocturnal biochemical hypoglycaemia is common during twice daily treatment with insulin, and low values of HbA1c might be associated with a higher risk of such hypoglycaemia. The blood glucose concentration at bedtime is a significant predictor of nocturnal biochemical hypoglycaemia, and HbA1c values might be of help in identifying patients at risk.

Adolescent↗
PubMed1985

Kinetic models for plasma disappearance of insulin in normal subjects.

Three theoretical kinetic models for plasma disappearance of insulin were examined in six normal men. The models allowed for the existence of non-saturable and/or saturable mechanisms. Constant infusion of porcine insulin at different rates was used to achieve different levels of steady state plasma insulin concentrations, while normoglycaemia was secured by a glucose clamp technique. Appropriate validation procedures demonstrated that one of the three models was superior to the others in describing the relationship between the exogenous insulin infusion rate Iex and the steady state plasma insulin concentration C: Iex = -Iend + k2 X C/(k3 + C), where Iend is the endogenous post-hepatic insulin delivery rate. Thus, only saturable mechanism(s) could be demonstrated. The median value of k2 (the maximal insulin disappearance rate) and k3 (the plasma insulin concentration at which the insulin disappearance rate is half maximal) were 7.31 nmol X min.-1 and 3.89 nmol X 1-1. The median value of k2/k3 (the clearance rate of insulin for infinitesimal plasma insulin concentrations) was 25.0 ml X kg-1 X min.-1. Thus, at physiological levels of plasma insulin concentrations the metabolic clearance rate of insulin is higher than insulin clearance estimates previously reported in studies based on the assumption of first order kinetics.

Adolescent↗
PubMed1984

Absorption of soluble and isophane semi-synthetic human and porcine insulin in insulin-dependent diabetic subjects.

A double-blind cross-over study of the sc absorption of radiolabelled semi-synthetic human (SHI) and purified porcine (PPI) insulin was made. Absorption of both isophane (n = 10) and soluble insulin (n = 8) was studied. There was no significant difference between the disappearance from the injection site, the plasma free insulin concentrations, or blood glucose levels after sc injection of the isophane preparations. A faster disappearance of the soluble SHI (as judged from T/50 and AUC) was found (both P-values less than 0.01). However, no difference was observed between the plasma insulin concentrations at any time point (P less than 0.05). Blood glucose levels showed no statistical differences between the two soluble preparations. The data indicate minor differences between the pharmacokinetics of SHI and PPI, but these seem of no clinical importance.

Absorption↗
PubMed1983

Long-term insulin-dependent diabetes mellitus with secondary pituitary insufficiency and regression of retinopathy.

Three women with insulin-dependent diabetes mellitus (IDDM) from childhood and early development of diabetic retinopathy are described. Insulin requirement was reduced to 5-12 IU daily in all three after relatively uncomplicated births and all had very brittle diabetes on this dosage. At re-examination 16-22 years after these births and after 34-42 years of IDDM, regression of retinopathy was observed in two patients, while the third had a light retinopathy at the same level as initially. Other diabetic complications were few and none of the patients had nephropathy. Pituitary examination revealed incomplete hypopituitarism in all cases, human growth hormone (HGH) being the sole common factor lacking. These findings and a review of four similar cases reported previously lend some support to the hypothesis of HGH as a possible pathogenetic co-determinant in the development of diabetic retinopathy.

Adult↗
PubMed1982

The relationship between plasma concentration and plasma disappearance rate of immunoreactive insulin in normal subjects.

To investigate the mechanism of insulin degradation in normal subjects, a kinetic model of insulin disappearance was constructed: insulin was assumed to be extracted from plasma by two independent processes, one saturable and one non-saturable. On the basis of these assumptions, a linear (non-proportional) relationship between steady-state plasma insulin concentration and steady-state plasma disappearance rate was predicted over the concentration range studied. Constant infusion experiments were performed on eight healthy normal subjects, normoglycaemia and fasting plasma C-peptide concentrations being maintained during the experiments. Agreement was found between the predictions of the model and the experimental results, and it is concluded that insulin degradation in normal subjects may be described in terms of two processes: one that is saturated at physiological plasma insulin concentrations and one that is apparently non-saturable over a wide concentration range.

Antigens↗
PubMed1976

The content of water and potassium in fat cells.

The distribution spaces at equilibrium for 3H2O, [14C]urea and s-O-[14C]-methylglucose were measured in white fat cells using centrifugation through silicone oil at 2500 X g; no significant differences were observed. L-[14C]Glucose added immediately before the centrifugation was used as a marker for the extracellular water space. The calculated intracellular water content of the cells after the centrifugation through oil (e.g. 3H2O space minus L-[14C]glucose space) is an unbiased measure of the water content of the fat cells in suspension as judged by the following criteria: (1) The intracellular distribution space for 3-O-[14C]'methylglucose at equilibrium (methylglucose space minus L-glucose space) was not different from that calculated from a methylglucose wash-out curve. (2) The intracellular content of L-[14C]glucose (half time of efflux about 60 min) in cells preloaded during incubation of the tissue with collagenase was not different in cells recovered by (a) centrifugation through oil at 2500 X g, (b) centrifugation through oil at 600 X g, (c) centrifugation at 600 X g in the absence of oil and (d) filtration on Millipore filters. The intracellular content of water determined on cells from single rats weighing 120-150 g was 2.75 +/- 0.55 mul/100 mul fat cells (+/- S.D., n = 30). The intracellular content of potassium, determined on cells from the same rats, was 252 +/- 62 nmols/100 mul fat cells (+/- S.D., n = 30). The concentration of potassium in the intracellular water was calculated as 104 +/- 15 mM (+/- S.D., n = 30).

Animals↗