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Biomedical subjects

H H Parving

Publications and source records attributed to H H Parving.

At least 235 records · Page 13Linked to original sources
PubMed1984

Haemodynamic changes in insulin-induced hypoglycaemia in normal man.

Haemodynamic variables (plasma volume, heart rate, blood pressure, cardiac output, stroke volume, pulmonary tissue volume, total peripheral vascular resistance, hepato-splanchnic vascular resistance, lower extremity vascular resistance and plasma catecholamines) were measured before and after insulin-induced hypoglycaemia in seven healthy men. Plasma volume decreased significantly at the nadir of glucose (mean decrease 222 +/- 41 ml) and subsequently increased to pre-hypoglycaemic values within 30 min. Cardiac output increased in response to hypoglycaemia (mean increase 2.8 +/- 0.61/min). The early rise in cardiac output was primarily due to an increase in heart rate, but later mainly due to increased stroke volume. Since pulmonary tissue volume was constant, the observed changes in cardiac output are unlikely to be due to a Frank-Starling mechanism but rather to increased sympatho-adrenal activity. Total peripheral vascular resistance as well as lower extremity vascular resistance decreased, whereas hepato-splanchnic vascular resistance was unaffected. Thus insulin-induced hypoglycaemia has marked transient effects on the circulation.

Adult↗
PubMed1984

Impaired autoregulation of glomerular filtration rate in type 1 (insulin-dependent) diabetic patients with nephropathy.

The effect of acute lowering of arterial blood pressure upon kidney function in nephropathy was studied in 13 patients with long-term Type 1 (insulin-dependent) diabetes. Ten normal subjects (six normotensive and four hypertensive) and five short-term Type 1 diabetic patients without nephropathy served as controls. Renal function was assessed by glomerular filtration rate (single bolus 51Cr-EDTA technique) and urinary albumin excretion rate (radial immunodiffusion). The study was performed twice within 2 weeks, with the subjects receiving an intravenous injection of either clonidine (225 micrograms) or saline (0.154 mmol/l). The arterial blood pressure was similar in the diabetic patients with nephropathy (mean 136 +/- 11 divided by 88 +/- mmHg) and in the non-diabetic control subjects (mean 140 +/- 25 divided by 92 +/- 15 mmHg). The clonidine injection induced similar reductions in mean arterial blood pressure in all three groups (16-18 mmHg). While glomerular filtration rate and urinary albumin excretion rate remained unchanged in both control groups after clonidine injection, glomerular filtration rate diminished from 78 to 71 ml/min per 1.73 m2 (p les than 0.01), and urinary albumin excretion declined from 1707 to 938 micrograms/min (p less than 0.01) in the patients with diabetic nephropathy. Our results suggest that an intrinsic vascular (arteriolar) mechanism underlying the normal autoregulation of glomerular filtration rate, i.e. the relative constancy of glomerular filtration rate that occurs in response to rather wide variations in perfusion pressure, is defective in diabetic nephropathy.

Adult↗
PubMed1984

Loss of autoregulation of blood flow in subcutaneous tissue in juvenile diabetes.

The autoregulation of blood flow in subcutaneous tissue was investigated at the level of the lateral malleolus by the local 133Xenon washout technique. We have investigated eight long-term insulin-dependent diabetics and seven healthy controls. All diabetics had moderate diabetic nephropathy and retinopathy. The blood flow remained constant in all normal subjects, when the arterial perfusion pressure was varied between 70 and 150 mm Hg. All diabetics had impaired or reduced autoregulation of the subcutaneous blood flow. The blood flow increased and decreased almost linearly with the changes in arterial perfusion pressure. The mechanism underlying the defect autoregulation of blood flow in diabetics is uncertain; possibilities include structural changes of the arterioles and/or alterations of local metabolic factors.

Adult↗
PubMed1984

Quantitative studies of glomerular ultrastructure in human and experimental diabetes.

A brief review is given of glomerular structural changes in diabetes mellitus and in rats with induced diabetes. The stereological methods for obtaining quantitative structural data are mentioned, and references are given to the underlying theories as well as to more detailed descriptions of the practical performance. In short-term diabetes a glomerular hypertrophy is found with increase in the surface area of the capillaries, in parallel with an increase in glomerular filtration. In long-term diabetes mellitus the picture is dominated by accumulations of basement membrane: thickening of the peripheral basement membrane and expansion of the mesangial regions which hold large amounts of basement membrane material. Rats with a moderate diabetes show the early hypertrophy as well as long-term basement membrane thickening. Severely diabetic rats develop basement membrane thickening but do not show the early hypertrophy, which is therefore not a necessary condition for basement membrane thickening to occur.

Adult↗
PubMed1983

Early aggressive antihypertensive treatment reduces rate of decline in kidney function in diabetic nephropathy.

The effect of early aggressive antihypertensive treatment on kidney function in diabetic nephropathy was studied prospectively in ten insulin-dependent diabetics (mean age 29 years). During the mean pretreatment period of 29 (range 23-38) months the glomerular filtration rate (GFR) decreased significantly and the urinary albumin excretion rate and arterial blood pressure rose significantly. During the 39 month (range 28-48) period of antihypertensive treatment with metoprolol, hydralazine, and frusemide (furosemide) or thiazide, arterial blood pressure fell from 144/97 mm Hg (mean of all pretreatment values) to 128/84 mm Hg (mean of all post-treatment values), urinary albumin excretion from 977 micrograms/min to 433 micrograms/min, and GFR from 80 to 62 ml/min/1 . 73 m2. The rate of decline in GFR decreased from 0.91 ml/min/month before treatment to 0.39 ml/min/month (range 0.08 to 0.68 ml/min/month) during treatment.

Adult↗
PubMed1983

The effect of strict short-term metabolic control on retinal nervous system abnormalities in newly diagnosed Type 1 (insulin-dependent) diabetic patients.

The oscillatory potential of the electroretinogram and the initial 2-min phase of dark-adaptation were studied in seven newly diagnosed Type 1 (insulin-dependent) diabetic patients before and during initial insulin treatment. Strict metabolic control was achieved in all seven patients using multiple subcutaneous injections of insulin. Seven to 11 days of strict metabolic control improved the added amplitude value of the oscillatory potential from 236 +/- 8 to 268 +/- 8 microV (mean +/- SEM; p less than 0.01) and the dark-adaptation from 90 +/- 5 to 67 +/- 5 s (p less than 0.01). Our study has demonstrated reversible neurophysiological abnormalities in the diabetic retina which are related to metabolic control.

Adult↗
PubMed1983

Diabetic nephropathy and arterial hypertension.

The relationship between arterial blood pressure and diabetic nephropathy was examined in 61 Type 1 (insulin-dependent) diabetic patients (22 females and 39 males). All patients fulfilled the following criteria: persistent proteinuria (greater than 0.5 g/day), onset of diabetes before 31 years of age, age less than 42 years, serum creatinine less than 130 mumol/l, and no antihypertensive treatment. Thirty Type 1 diabetic patients without persistent proteinuria but matched for sex, age, ideal body weight and duration of diabetes, and 30 healthy subjects matched for sex, age and ideal body weight were also studied as controls. The diabetic patients with persistent proteinuria had elevated blood pressures (146/96 +/- 17/10 mmHg, mean +/- SD) compared with 123/75 +/- 11/8 mmHg in diabetic patients without persistent proteinuria, and normal subjects (120/77 +/- 6/6 mmHg; p less than 0.001 for each). Diastolic blood pressure greater than or equal to 95 mmHg was found in 51% of the group with persistent proteinuria. Elevated arterial blood pressure is frequently present in young Type 1 diabetic patients with diabetic nephropathy and normal serum creatinine.

Adult↗
PubMed1983

Impaired autoregulation of blood flow in skeletal muscle and subcutaneous tissue in long-term Type 1 (insulin-dependent) diabetic patients with microangiopathy.

Autoregulation of blood flow was studied in skeletal muscle and subcutaneous tissue in seven Type 1 (insulin-dependent) diabetic patients (median age: 36 years) with nephropathy and retinopathy and in eight normal subjects of the same age. Blood flow was measured by the local 133Xe washout technique. Reduction in arterial perfusion pressure was produced by elevating the limb 20 and 40 cm above heart level. Blood flow remained within 10% of control values when the limb was elevated in normal subjects. In five of the seven diabetic subjects blood flow fell significantly in both tissues when the limb was elevated 40 cm indicating impaired autoregulation. The results suggest that intrinsic vascular (arteriolar) mechanisms (myogenic and/or metabolic) underlying the normal autoregulatory response are defective in some diabetic patients with microangiopathy.

Adult↗
PubMed1983

Hemodynamic factors in the genesis of diabetic microangiopathy.

There are many candidate mechanisms to explain the phenomenon of delayed microvascular disease in the diabetic. All may play some part in determining the genesis, the evolution or the ultimate degree and form of the angiopathy. General metabolic and humoral factors may provide the pathogenetic background against which special local conditions, e.g., in the retina or renal cortex, will determine the morphology of the angiopathy and its functional and structural consequences. Some of the processes occurring in the diabetic person may, however, be of major importance in initiating and maintaining conditions for the evolution of microvascular disease. The hemodynamic changes and the vascular responses to them that we have described are, we suggest, very likely to be an important component of this sort. Unlike the later structural changes, these hemodynamic phenomena are to be found very early in the diabetic state. Of most clinical importance, perhaps, is that they appear, with the achievement of adequate metabolic correction, to be reversible.

Animals↗
PubMed1983

Plasma-to-ascitic fluid transport rate of albumin in patients with decompensated cirrhosis. Relation to intraperitoneal albumin.

Albumin-kinetics and haemodynamic studies were performed in 20 patients with decompensated liver cirrhosis in order to improve the knowledge on genesis and perpetuation of hepatic ascites, especially with respect to determinants of intraperitoneal protein. A positive relationship was found between the plasma-to-peritoneal transport rate of albumin (index of 'lymph-imbalance') and the mass of intraperitoneal albumin (rlog = 0.82, P less than 0.001), indicating a significant role of 'lymph-imbalance' to sequestration of protein in the peritoneal cavity. Ascitic fluid albumin concentration was on the average 0.22 of that of plasma and directly correlated to the plasma concentration (rlin = 0.68, P less than 0.01). The hydrostatic pressure difference across the splanchnic microvasculature (assessed as wedged hepatic vein minus inferior vena caval pressure) was directly correlated to the effective (plasma minus ascitic fluid) oncotic pressure (rlin = 0.74, P less than 0.001) but significantly higher than that (P less than 0.005), indicating a 'non-equilibrium' in the splanchnic Starling forces. The results point to a multivariate genesis and perpetuation of cirrhotic ascites as laid down in the 'lymph-imbalance' theory of ascites formation, whereas a 'fluid equilibrium' theory seems to be too simple, especially with respect to explain protein sequestration in the peritoneal cavity.

Adult↗
PubMed1983

The blood-retinal barrier permeability in essential hypertension.

In a series of 8 patients with recently discovered moderate essential hypertension the blood-retinal barrier permeability to fluorescein was determined by aid of quantitative vitreous fluorophotometry before and after normalization of the systemic blood pressure. The permeability before medical treatment was 1.69 X 10(-7) cm/sec (+/- SEM = 0.14) and after medical treatment and normalization of the blood pressure 1.27 X 10(-7) cm/sec (+/- SEM = 0.12), corresponding to the permeability in a normal population. Thus the blood-retinal barrier permeability is pathologically increased even in moderate degrees of essential hypertension, but this increase in permeability is reversible.

Adrenergic beta-Antagonists↗
PubMed1983

Diabetic nephropathy and arterial hypertension. The effect of antihypertensive treatment.

Our longitudinal study of urinary albumin excretion rate in long-term insulin-dependent diabetics without proteinuria (negative albustix) suggests that early detection of patients at high and low risk of developing persistent proteinuria, i.e., diabetic nephropathy, is possible by using a sensitive method for albumin determination. Our prospective studies in young insulin-dependent diabetics with diabetic nephropathy show that the rate of decline in glomerular filtration rate (GFR) varies considerably, with a mean of 0.75 ml/min/mo and a range from 0.1 to 1.50 ml/min/mo, and that an increase in arterial blood pressure to a hypertensive level is an early feature; 43% of the patients had diastolic blood pressure greater than 100 mm Hg. Early and aggressive antihypertensive treatment reduces both albuminuria and the rate of decline in GFR in young patients with diabetic nephropathy.

Adult↗
PubMed1982

Kidney function and size in type 1 (insulin-dependent) diabetic patients before and during growth hormone administration for one week.

Kidney function and size were studied in seven well-controlled male Type 1 (insulin-dependent) diabetic patients before and after administration of highly purified human growth hormone for one week. Glomerular filtration rate, renal plasma flow (steady state infusion technique with urinary collections using 125I-iothalamate and 131I-hippuran), kidney size (ultrasonic scanning) and urinary excretion rates of albumin and beta-2-microglobulin were measured. Highly purified growth hormone was injected subcutaneously, 2 IU in the morning and 4 IU in the evening. The growth hormone dosage applied induced an elevation in plasma growth hormone concentration from the normal level seen in these very well controlled diabetics to levels within the range previously demonstrated in normally controlled Type 1 diabetic patients. During the week of growth hormone administration, glycaemic control was maintained unchanged by increasing the insulin dose by 79 +/- 9% (mean +/- SEM). Glomerular filtration rate increased from 122 +/- 3 to 131 +/- 3 ml/min X 1.73 m2 (p less than 0.05) and renal plasma flow increased from 535 +/- 10 to 569 +/- 22 ml/min x 1.73 m2 (p less than 0.05). Kidney size changed from 128 +/- 5 to 133 +/- 5 ml/1.73 m2 (NS). Urinary excretion rates of albumin and beta-2-microglobulin were unchanged. The present findings suggest that the growth hormone elevation typically found in Type 1 diabetic patients with reasonable clinical control, contributes to the enhanced glomerular filtration rate and renal plasma flow present in that disease.

Adult↗
PubMed1982

Decreased distensibility of a passive vascular bed in diabetes mellitus: an indicator of microangiopathy?

This study was undertaken to determine whether the distensibility of a passive vascular bed is reduced in Type 1 (insulin-dependent) diabetic patients with microangiopathy. The change in blood flow induced by 45 degrees head-up tilting was studied in two systems: (a) following maximal ischaemic exercise and (b) in a vascular bed locally paralysed by the injection of papaverine. Five normal subjects, six patients with long-standing Type 1 diabetes and six non-diabetic patients with severe atherosclerosis affecting the legs were studied. Blood flow was measured in the anterior tibial muscle by the isotope washout technique. The median increase in blood flow produced by tilting was greater in normal subjects than in diabetic subjects in both the locally-relaxed bed (58% and 14% respectively) and after maximal ischaemic exercise (45% and 4% respectively). In the atherosclerotic subjects, the increase in blood flow in the locally relaxed bed was 77%. The results are consistent with the hypothesis that the reduced distensibility seen in the diabetic subjects was related to the presence of microvascular disease and that the behaviour of a vascular bed relaxed by the local injection of papaverine might be an appropriate model to study this condition.

Adult↗
PubMed1982

Kidney function and size in diabetics before and during initial insulin treatment.

GFR, RPF, and kidney size were measured in nine young recently diagnosed insulin-dependent diabetics before (days 0) and 3 and 8 days after the beginning of the initial insulin treatment and in comparable control subjects. Kidney function was measured by a constant infusion technique using I-125-iothalamate and 131-I-hippuran. Kidney size was determined by means of ultrasound. Before insulin treatment elevated values for GFR (+44%, P less than 0.01), RPF (+18%, P less than 0.05), and kidney size (+29%, P less than 0.01) were found. Near-normal metabolic control was achieved in all patients using either multiple subcutaneous injections of insulin or an artificial betacell. GFR decreased from 160 +/- 9 SEM to 141 +/- 6 ml/min X 1.73 m2 (P less than 0.01) and further to 133 +/- 5 ml/min X 1.73 m2 (P less than 0.01, compared to day 0). Renal plasma flow was 601 +/- 33 and 588 +/- 44 ml x 1.73 m2 at days 0 and 3, respectively (NS) and decreased to 558 +/- 35 ml/min x 1.73 m2 at day 0 (P less than 0.01). By contrast no statistically significant changes in kidney volume were observed; the results on day 0, 3 and 8 were 145 +/- 7, 162 +/- 11 and 143 +/- 9 ml/1.73 m2, respectively. The present study demonstrates that kidney size and function are elevated at the onset of insulin-dependent diabetes. Near-normal metabolic control; for 8 days induces a reduction but not a complete normalization in kidney function. From the present observations it is suggested that the rapidly reversible part of the elevation in GFR cannot be explained by concomitant changes in kidney and glomerular size (morphological origin) but is probably due to a reduction in renal plasma flow and to a decreased transglomerular pressure (functional origin).

Adult↗