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Biomedical subjects

H Orskov

Publications and source records attributed to H Orskov.

At least 199 records · Page 11Linked to original sources
PubMed1986

Glucose uptake and pulsatile insulin infusion: euglycaemic clamp and [3-3H]glucose studies in healthy subjects.

To test the hypothesis that insulin has a greater effect on glucose metabolism when given as pulsatile than as continuous infusion, a 354-min euglycaemic clamp study was carried out in 8 healthy subjects. At random order soluble insulin was given intravenously either at a constant rate of 0.45 mU/kg X min or in identical amounts in pulses of 1 1/2 to 2 1/4 min followed by intervals of 10 1/2 to 9 3/4 min. Average serum insulin levels were similar during the two infusion protocols, but pulsatile administration induced oscillations ranging between 15 and 62 microU/ml. Glucose uptake expressed as metabolic clearance rate (MCR) for glucose was significantly increased during pulsatile insulin delivery as compared with continuous administration (270-294 min: 8.7 +/- 0.7 vs 6.8 +/- 0.9 ml/kg X min, P less than 0.01, and 330-354 min: 8.9 +/- 0.5 vs 7.4 +/- 0.9 ml/kg X min, P less than 0.05). The superior efficacy of pulsatile insulin delivery on glucose uptake was not consistently found until after 210 min of insulin administration. In both infusion protocols, endogenous glucose production as estimated by the [3-3H]glucose infusion technique was suppressed to insignificant values. Finally, the effect of insulin on endogenous insulin secretion and lipolysis as assessed by changes in serum C-peptide and serum FFA was uninfluenced by the infusion mode. In conclusion, insulin infusion resulting in physiological serum insulin levels enhances glucose uptake in peripheral tissues in healthy subjects to a higher degree when given in a pulsed pattern mimicking that of the normal endocrine pancreas than when given as a continuous infusion.

Adult↗
PubMed1986

Synthetic pancreatic growth hormone-releasing factor (GRF-40) stimulates the secretion of the endocrine pancreas.

The effects on islet hormone secretion of the synthetic replicates of two peptides with potent GH-releasing activity isolated from human pancreatic islet cell tumors (GRF-40 and GRF-44) were studied using the isolated, perfused dog pancreas. GRF-40 produced a dose-dependent stimulation of insulin, glucagon, and somatostatin secretion. The responses to GRF-40 were modified by the prevailing glucose level: higher insulin and somatostatin and lower glucagon responses were obtained at high rather than low glucose. In contrast, GRF-44 did not produce any stimulation of the endocrine pancreas. In vivo GRF-40 and GRF-44 elicited identical pronounced growth hormone responses in the rat. The findings reported here provide support that pancreatic insulin and glucagon are modulated by GRF-40 with somatostatin as its inhibitory counterpart. The question, whether GRF-40 is of physiologic relevance in the regulation of the endocrine pancreas, must await evidence that it is present and releasable from the pancreas.

Animals↗
PubMed1986

Ultrafiltration method for direct radioimmunoassay measurement of free thyroxine and free tri-iodothyronine in serum.

Ultrafiltration at physiological pH and temperature of undiluted serum followed by direct radioimmunological determination of T3 and T4 in the protein-free ultrafiltrate offers the best possible approach towards estimation of in vitro plasma levels of free T3 and free T4. The major technical difficulties in meeting this apparently simple proposition are: establishing adequately sensitive radioimmunoassays; avoidance of adhesion to ultrafilters and glassware; removal from the ultrafilters of compounds which would cross-react or interfere in the radioimmunoassays; and avoidance of co-filtration of thyroid hormone binding proteins in serum, which would obviously imply spurious data. This methodological study describes the magnitude and significance of each of these obstacles and how to circumvent them. Practically all other available methods, including equilibrium dialysis, imply dilution of serum samples with buffer often leading to alterations in ionic composition to which thyroid hormone binding to proteins is peculiarly sensitive. Dilution itself alters the fraction of free thyroid hormones in serum especially when pharmaca or compounds are present which compete for the binding sites. These pitfalls are avoided in ultrafiltration of undiluted serum. This is illustrated through measurements on serum containing therapeutic concentrations of Fenclofenac which was found to displace 120% more T4 in undiluted than in diluted (1:28) serum. Using the described technique FT3 was 8.8 +/- 1.7 pmol/l and FT4 30.8 +/- 8.2 (SD) pmol/l in serum from 29 normal subjects. Pregnant women in their third trimester had lower levels: FT3 7.1 +/- 2.1 and FT4 17.6 +/- 5.8 pmol/l (SD, n = 24).

Female↗
PubMed1985

Aspects of glucose homeostasis in uremia as assessed by the hyperinsulinemic euglycemic clamp technique.

A three-step hyperinsulinemic euglycemic clamp was performed in 14 nondialyzed uremic and ten age-matched healthy subjects. Nine of the uremics were restudied for a mean of 42 days (range, 21 to 88 days) after initiation of dialysis therapy. Insulin was infused at the following three rates: 0.5 mU X kg-1 X min-1, 2.0 mU X kg-1 X min-1, and 4.0 mU X kg-1 X min-1. Each dose was given for 120 minutes. Glucose uptake during the last 30 minutes of each clamp were consistently lower in uremic patients pre-dialysis than in controls (2.3 +/- 0.3 v 6.6 +/- 0.8 mg X kg-1 X min, 7.8 +/- 0.6 v 13.2 +/- 1.1 mg X kg-1 X min-1 and 9.6 +/- 0.7 v 15.5 +/- 1.0 mg X kg-1 X min-1, all P less than 0.001). Serum insulin levels were similar in the two groups, and blood glucose values during steady state were maintained at 79 +/- 2.77 +/- 2, and 77 +/- 2 mg/100 mL in uremic subjects and at 72 +/- 3, 73 +/- 2, and 75 +/- 2 mg/100 mL in healthy subjects. The insulin levels required to elicit half-maximal biological response in uremics (82 +/- 5 microU/mL) were markedly higher than in controls (54 +/- 8 microU/mL, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The effect of vasopressin infusion on glucose metabolism in man.

Studies on intact animals and isolated rat hepatocytes have shown that arginine vasopression (AVP) stimulates glycogen phosphorylase to break down glycogen and raise plasma glucose concentrations. Since no similar work has been performed on healthy human adults, the effect of moderate (25 pmol/min) and high (75 pmol/min) dose AVP infusion on plasma glucose, intermediary metabolites, glucose kinetics, and circulating glucagon and insulin concentrations was investigated. After AVP infusion, plasma glucose rose from 4.9 +/- 0.1 to a peak of 5.7 +/- 0.2 mmol/l (P less than 0.001), but no changes in blood lactate, pyruvate, alanine, glycerol or 3-hydroxybutyrate concentrations were observed. The glucose rise was accounted for entirely by an increase in the rate of appearance of glucose from 11.19 +/- 0.43 to 13.38 +/- 0.63 mu mol/kg/min (P less than 0.001). Infusion of AVP also increased plasma glucagon concentrations from 38 +/- 8 to 79 +/- 20 pg/l (P less than 0.01). The hyperglycaemic effect of AVP may be mediated solely by stimulation of glucagon release, but we cannot exclude direct stimulation of glycogen phosphorylase activity.

Adult↗
PubMed1985

The interaction of human pancreatic growth hormone releasing factor 1-44 with somatostatin in vivo in normal man.

The interaction between the stimulatory effects of hpGRF 1-44 and the inhibitory effects of somatostatin on GH release have been investigated in six normal male subjects receiving continuous 4 h infusions of these peptides alone and in combination. hpGRF 1-44 0.3 microgram/kg/h alone produced a peak GH response of 27.0 +/- 7.6 mU/l (mean +/- SEM). Somatostatin 1.0 microgram/kg/h markedly inhibited the GH response to hpGRF 1-44 with mean levels less than 4.0 mU/l during the infusion, though a rebound rise in GH levels to 26.1 +/- 9.0 mU/l was observed at the end of the infusion period. Somatostatin 0.2 microgram/kg/h inhibited the GH response to hpGRF 1-44 to a lesser degree (peak GH during the infusion 11.7 +/- 2.5 mU/l) and the rebound rise in GH levels (maximum 13.2 +/- 4.3 mU/l) was less than that observed with high dose somatostatin. During somatostatin 1.0 microgram/kg/h alone GH levels were suppressed less than 1.0 mU/l followed by a rebound at the end of the infusion in only two subjects. These data demonstrate a dose-dependent inhibition of hpGRF 1-44 by somatostatin in vivo in man.

Adult↗
PubMed1985

End-state renal failure in diabetic nephropathy: pathophysiology and treatment.

Forty percent of patients with insulin-dependent diabetes will develop nephropathy during the course of their disease, thus being the most important single disorder leading to end-stage renal failure (ESRF). Intensive metabolic control delays onset of diabetic nephropathy, the first omen of which is appearance of subclinical albuminuria, also termed microalbuminuria. Moreover, it is now established that intensive treatment of hypertension reduces rate of decline in GFR and thus postpones ESRF. When uremia eventually sets in, a range of biochemical and endocrine abnormalities can be included among those characteristics of diabetes mellitus per se. These include elevated plasma levels of growth hormone, glucagon and free fatty acids, which may participate in the uremic insulin resistance superimposed on the preexisting diabetic carbohydrate intolerance. Hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) are two established modalities of renal replacement therapy in diabetes mellitus. Controlled clinical trials for comparison of CAPD versus HD treatment of diabetics are, however, still needed. The survival rate is approximately 80 and 65-95% in insulin-dependent diabetic patients at 1 year during treatment with HD and CAPD, respectively. However, it is general experience that diabetics on CAPD exhibit a glycemic control, superior to that attained during HD. It has not been proved that patient survival after cadaveric renal transplantation is better than on dialysis. The degree of vascular heart disease seems to be the major determinant for survival of kidney-transplanted diabetic patients.

Adult↗
PubMed1985

In vivo insulin action in type 1 (insulin-dependent) diabetic pregnant women as assessed by the insulin clamp technique.

To determine the influence of pregnancy on insulin sensitivity in patients with type 1 diabetes mellitus in more detail, a hyperinsulinemic euglycemic clamp study was performed in six pregnant type 1 diabetic women and eight nonpregnant women with type 1 diabetes mellitus. All of the pregnant women were studied three times: in early pregnancy (mean, week 13), late pregnancy (mean, week 34), and within a week after delivery. Insulin was infused in a constant rate of 1.0 mU/kg X min, which resulted in steady state serum free insulin levels (I) of 44 +/- 3 (+/- SEM), 56.6 +/- 6, and 55 +/- 8 microU/ml in the pregnant diabetic women and 52 +/- 4 microU/ml in the nonpregnant women. Mean glucose disposal (M) was 5.6 +/- 0.3 mg/kg X min early in pregnancy and 3.4 +/- 0.5 mg/kg X min late in pregnancy (P less than 0.02). However, in the early postpartum period, M was again higher (7.2 +/- 0.7 mg/kg X min; P less than 0.02) and similar to values in early pregnancy and nonpregnant diabetic women (7.2 +/- 0.6 mg/kg X min). When tissue sensitivity to insulin was expressed as the M to I ratio, similar results were obtained (nonpregnant women, early stage of gestation, and postpartum vs. late stage of gestation: 0.13 +/- 0.01, 0.13 +/- 0.01, and 0.15 +/- 0.03 mg/kg X min per microU/ml vs. 0.06 +/- 0.1 mg/kg X min per microU/ml; P less than 0.03 in all). There tended to be an inverse relationship between serum levels of human placental lactogen and the M to I ratio during pregnancy (r = -0.74; P = 0.09). However, we found no association between changes in the impairment of insulin action and serum estradiol, progesterone, or cortisol levels. In conclusion, pregnant type 1 diabetic women have insulin resistance in peripheral tissues in the late stage of gestation. Insulin sensitivity returns to values found in nonpregnant diabetic women within the first week after delivery.

Adult↗
PubMed1985

Higher plasma somatomedin A (biological) and C (immunological) levels with sc than with im growth hormone replacement therapy.

In a short-term cross-over study the effect of daily sc human growth hormone was compared with that of thrice weekly im treatment. At the end of each 6-week treatment period the 10 growth hormone deficient children were admitted to hospital for evaluation of diurnal plasma levels of hormones and intermediary metabolites. Somatomedin A as well as C levels were higher in 9 of 10 children after sc than after im growth hormone therapy. This may be the basis for previous observations of improved growth after change to sc treatment.

Adolescent↗
PubMed1985

Body temperature elevation, exercise and serum prolactin concentrations.

Ten young healthy normal-weight males were studied in four test situations designed to elucidate the relative role of body temperature increase vs that of exercise per se for pituitary hormone release. Tympanic temperature was recorded continuously during the tests. Elevation of body temperature at rest induced by external heating resulted in parallel changes in serum prolactin (Prl), also found when temperature spontaneously returned towards normal. In contrast, temperature elevation of the same magnitude through exercise (450 kpm/min for 40 min) induced no change in Prl secretion. It is concluded that increase in core temperature is a stimulus of Prl secretion and suggested that exercise apparently inhibits the stimulatory effect.

Adult↗
PubMed1985

Reversal of D- and A-cell insensitivity to glucose in alloxan-diabetic dogs by treatment with the artificial beta cell (Biostator).

Insulin-deficient diabetes in man as well as in experimental diabetes is associated with islet cell insensitivity to glucose. The present study was designed to determine whether this abnormality could be counteracted either by increasing the intraislet insulin level or by normalizing the diabetic state by a glucose-controlled insulin infusion system (GCIIS: Biostator, Life Science Instruments, Elkhart, Indiana). Using the isolated, perfused pancreas of dogs with moderate, untreated alloxan diabetes of 4 days duration, we found that 5 mM arginine (N = 4) and 5 mM calcium (N = 4) stimulated D- and A-cell secretion, whereas an increment in glucose from 1.3 to 11 mM (N = 4) had no effect on islet hormone secretion. In the pancreas from untreated alloxan-diabetic dogs, acute infusion of large amounts of insulin (25 mU/ml) in vitro simultaneously with an elevation of perfusate glucose from 1.3 to 11 mM failed to restore the glucose from 1.3 to 11 mM failed to restore the glucose sensitivity. In contrast, treatment of alloxan-diabetic dogs (N = 3) by a GCIIS for 24 h revived some responsiveness of the glucagon, insulin, and somatostatin to glucose (1.3-11 mM) of the subsequently perfused pancreas. It is concluded that the insensitivity to glucose of islet cells in insulin-deficient diabetes is not ascribed to an intra-islet insulin deficiency per se but rather to an abnormal metabolic state secondary to insulin deficiency. The results also indicate that the glucose receptor dysfunction is not due to a direct lesion by the diabetogenic drug.

Animals↗
PubMed1985

A comparison of 3 methods for assessing insulin sensitivity in subjects with normal and abnormal glucose tolerance.

The euglycaemic clamp, insulin sensitivity test with somatostatin, and insulin sensitivity test without somatostatin, were compared as in vivo methods of assessing insulin sensitivity. Fifteen subjects with varying degrees of glucose tolerance were studied. Somatostatin was not found to influence the assessment of insulin sensitivity by the insulin sensitivity test. When glucose disposal was expressed as metabolic clearance rate significant strong correlations were found between the euglycaemic clamp technique and the insulin sensitivity test with (r = 0.90) and without (r = 0.83) somatostatin. The effects of the tests on intermediary metabolism were also similar, and all 3 tests showed a similar impairment of insulin sensitivity in subjects with abnormal glucose tolerance. The insulin sensitivity test without somatostatin thus provides a simple and economical tool for studying insulin sensitivity.

Adult↗
PubMed1985

A test strip method for visual and reflectometric reading of blood glucose.

A double field glucose oxidase test strip, B-M Haemoglucotest 1-44 R, was tested for stability of reaction and comparability of visual and reflectometric readings (evaluating four reflectometers) with a standard laboratory glucose oxidase analysis and showed excellent precision and accuracy within the whole range when estimated immediately. Readings after 1 and 7 days showed a systematic and increasing error with time, with spuriously high and low values in the lower (less than or equal to 4.0 mmol/l) and higher (greater than or equal to 8.1 mmol/l) part of the range, respectively. In the lower range, however, the error was in the order of 1 mmol/l only, thus stability of the reaction allows mailing the strips to the clinic for rechecking.

Blood Glucose↗
PubMed1985

Assessment of tissue sensitivity to insulin in uraemic patients on long-term haemodialysis therapy.

Glucose intolerance is a common concomitant of untreated chronic renal failure, but the effect of long-term treatment on the insulin resistance believed to be behind it is as yet not clarified. Peripheral tissue sensitivity to insulin was therefore examined in 7 dialyzed uraemic patients, 8 undialyzed uraemic and 8 matched healthy subjects using the hyperinsulinaemic euglycaemic clamp technique. The dialyzed subjects had been on maintenance haemodialysis for a mean of 4 yr (range, 3-131 months) and were studied both before and after a single random dialysis. The clamping was performed during 150 min using a glucose controlled insulin infusion system (Biostator). Insulin was infused at a rate of 2.0 mU/kg/min. Tissue sensitivity to insulin was expressed as glucose uptake (M) at steady state (90-150 min) over steady state serum insulin concentration (I). While M was significantly greater in healthy subjects (12.52 +/- 1.02 mg/kg/min, mean +/- 1 SEM) than in dialyzed uraemics (9.59 +/- 0.78 mg/kg/min and 9.36 +/- 0.70 mg/kg/min, both p less than 0.05), M/I was similar in chronically dialyzed patients (before and after dialysis: 0.098 +/- 0.017 mg/kg/min per microU/ml vs 0.104 +/- 0.020 mg/kg/min per microU/ml) and in controls (0.111 +/- 0.015 mg/kg/min per microU/ml; p greater than 0.20). In contrast M/I ratio of uraemic subjects who had never been dialyzed (0.062 +/- mg/kg/min per microU/ml) was significantly reduced (both p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

A comparison of the artificial pancreas (glucose controlled insulin infusion system) and a manual technique for assessing insulin sensitivity during euglycaemic clamping.

Two main methods are available for assessing insulin sensitivity with the hyperinsulinaemic euglycaemic clamp technique: one employs a glucose-controlled insulin infusion system (the Biostator) with automatic feedback control; the second depends on frequent glucose measurement and the use of an algorithm and a pocket calculator ('manual') to determine the glucose infusion rate. The amount of glucose infused is a measure of insulin sensitivity. The efficiency of the two methods was compared in nine normal subjects (seven lean, two obese). After an overnight fast subjects were infused with insulin at 50 mU X kg-1 X h-1 for 2 h; this rate was doubled during the first 10 min for the manual technique. Blood glucose averaged 4.7 +/- 0.1 and 4.8 +/- 0.1 mmol/l from 0 to 120 min for Biostator and manual techniques and did not deviate significantly from the desired level. Variability of the clamp was also similar over the same period (coefficient of variation 5.1 +/- 0.6% and 6.4 +/- 0.7%, Biostator and manual). Glucose infused to maintain steady state from 60 to 120 min was higher, however, with the manual than the Biostator method (5.7 +/- 0.6 versus 4.4 +/- 0.6 mg X kg-1 X min-1, p less than 0.01) even when the loading dose was omitted, although the two methods correlated closely (p less than 0.05). Glucose infusion rate varied more from minute to minute with the Biostator (coefficient of variation 28.8 +/- 3% versus 12.2 +/- 2.1%). Steady-state serum insulin levels (30-120 min) were the same during both methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

The metabolic effects of dopamine in man.

The metabolic effects of dopamine have been investigated by its infusion in normal man with and without simultaneous somatostatin administration. Dopamine was infused into overnight fasted men at 1.5 microgram/kg/min (n = 6) and 3.0 micrograms/kg/min (n = 5) for 120 min. Plasma dopamine concentrations at 120 min were 78 +/- 9 nmol/l and 117 +/- 17 nmol/l respectively, associated with a marginal rise in plasma noradrenaline. Dopamine (1.5 microgram/kg/min) induced an early and sustained rise in plasma glucagon (48 +/- 9 pg/ml versus 19 +/- 6 pg/ml in saline controls at 10 min, p less than 0.01) and a transient elevation in serum growth hormone which peaked to 17.7 (range 4.5-71.8) mU/l at 60 min (7.2 (range 0.6-37.7) mU/l with saline, p less than 0.05) but did not alter serum insulin, blood glucose or other metabolite levels. At 3.0 micrograms/kg/min, dopamine in addition provoked mild and transient elevations in blood glucose and serum insulin. Somatostatin (250 micrograms/h) suppressed circulating insulin, glucagon, and growth hormone levels and abolished the small hyperglycaemic effect seen with the higher dopamine dose. Somatostatin alone induced a progressive rise in circulating non-esterified fatty acid and 3-hydroxybutyrate levels reflecting insulin deficiency. This rise in NEFA and 3-hydroxybutyrate was increased by dopamine particularly at the higher dosage (plasma NEFA; somatostatin alone, 1.08 +/- 0.13 mmol/l; somatostatin plus dopamine 3 micrograms/kg/min, 1.44 +/- 0.17 mmol/l at 120 min, p less than 0.01: blood 3-hydroxybutyrate; somatostatin alone, 0.32 +/- 0.04 mmol/l; somatostatin plus dopamine 3 micrograms/kg/min, 0.56 +/- 0.12 mmol/l at 120 min, p less than 0.05). Thus: 1) dopamine at pharmacological dosage has minor effects when other endocrine mechanisms are intact, 2) it enhances lipolysis and ketogenesis during somatostatin-induced insulin deficiency; 3) the hyperglycaemia effect of the higher dopamine dose is probably mediated through stimulated glucagon secretion.

3-Hydroxybutyric Acid↗