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Biomedical subjects

J Ofstad

Publications and source records attributed to J Ofstad.

At least 55 records · Page 3Linked to original sources
PubMed1979

Intrarenal venous and cortical catheter pressures in the dog kidney.

To examine the validity of intrarenal venous pressure (IRVP) as a measure of peritubular capillary pressure when obtained with a method applicable in man, IRVP was measured with a 0.9 mm o.d. catheter introduced retrograde into interlobar veins of anesthetized dogs and was compared with a modified needle pressure (cortical catheter pressure = RCCP) measured simultaneously in the same kidneys. In twelve dogs with a mean experimental kidney control sodium excretion of 91 +/- 15 (SEM) micronmol/min IRVP averaged 16.0 +/- 1.1 mmHg and was significantly lower than the average RCCP of 22.6 +/- 1.1 mmHg (P less than 0.001). These pressures compare well with the reported micropuncture pressures in the peritubular capillaries and proximal tubules, respectively, at comparable levels of sodium excretion. IRVP fell significantly during reduction of renal perfusion pressure within the range of autoregulation of renal blood flow and increased during elevation of renal pelvic pressure (PP). At at PP of 60 mmHg, when urine flow had stopped, the PP-IRVP gradient was 22.7 +/- 3.1 and increased to 36.7 +/- 3.8 (P less than 0.001) at a PP of 80. Acute renal vein constriction always increased IRVP before renal vein pressure reached the preceeding control level of IRVP. Increased urine flow during saline volume expansion and furosemid infusion was associated with increased IRVP. The results when compared with micropuncture data indicate that IRVP is a satisfactory expression of peritubular capillary pressure in the experimental conditions included in the study.

Animals↗
PubMed1979

Postglomerular vascular hydrostatic and oncotic pressures during acute saline volume expansion in normotensive man.

The importance of the peritubular physical factors as mediators of the natriuretic response to saline volume expansion was examined in twenty normotensive, hydropenic indivduals. Intrarenal venous pressure (IRVP), used as a measure of peritubular capillary hydrostatic pressure, and efferent arteriolar colloid osmotic pressure, calculated from arterial colloid osmotic pressure and the filtration fraction, were measured before and during sustained volume expansion with 0.9% NaCl, increasing the body weight by 3% and plasma volume about 20%. During expansion there was a significant increase in urine flow from 1.1 +/0 0.1 to 3.1 +/- 0.4 ml/min and sodium excretion from 161 +/- 12 to 551 +/- 61 microEq/min. Efferent colloid osmotic pressure fell from 31.9 +/- 0.6 to 23.6 +/- 0.5 mmHg (P less than 0.001) while IRVP changed from 24.8 +/- 0.8 to 25.1 +/- 0.9 mmHg (P greater than 0.10). In eight individuals IRVP increased during saline loading but later fell during sustained expansion. Glomerular filtration rate and renal blood flow did not change significantly. It is concluded that increase in peritubular capillary hydrostatic pressure is not necessary either to induce or to maintain the natriuresis of a moderate saline volume expansion. Although the fall in postglomerular vascular colloid osmotic pressure is a possible mediator of the natriuretic response, the change in peritubular transcapillary net driving force produced by a modest saline volume expansion is probably small.

Adult↗
PubMed1979

Suppressed development of experimental glomerulonephritis in lactating rats.

Five of six lactating rats did not develop proteinuria after an injection of nephrotoxic serum, whereas four out of five non-lactating, non-pregnant rats showed the usual proteinuric response (P = 0.06). The amount of heterologous IgG deposits was similar in both groups, but the lactating rats had significantly less autologous IgG (P = 0.004) in the glomerular basal membrane. It is suggested that hormonal factors influence the development of experimental glomerulonephritis in lactating rats.

Animals↗
PubMed1978

Diameter of afferent arterioles during autoregulation estimated from microsphere data in the dog kidney.

Afferent arteiolar diameters, relative flow distribution, and flow conductance factors are estimated by nonlinear regression analysis of the sieving effect on microspheres in different vascular structures of the dog renal cortex. The data presented are from experiments in which microspheres of 10-30 microgram were injected into the abdominal aorta during normotension and after lowering the blood pressure to the lower limit of autoregulation. Microscopic examination of the spheres trapped in the glomeruli and the renal arteries showed an increasing exclusion of microspheres greater than 15 micrometer from the afferent arterioles during normotension. This effect was most pronounced for the deeper cortical layers and can be explained mainly as geometrical exclusion of spheres from afferent arterioles. During hypotension, progressively larger microspheres entered glomeruli and afferent arterioles, presumably due to vasodilation of the vessels. There was a significant redistribution of microspheres larger than 15 micrometer from the outer to the inner cortex during hypotension without a corresponding redistribution of smaller spheres or the estimated blood flow. Approximately the same degree of dilation of afferent arterioles was observed during autoregulatory hypotension in three cortical layers.

Animals↗
PubMed1977

Membrane filtration in microscopical examination of urinary sediment.

Microscopical examination of the urinary sediment has been performed after membrane filtration and after routine centrifugation, and the results were compared. Various quantities of urine were filtered through a membrane with pore size of 3 micrometer, stained with Shorr stain and made translucent with xylol. All granular and cellular casts were counted on a trimmed membrane, 15 X 20 mm. The routine centrifugation was carried out on 10 ml urine at 1500 rpm for 3 min. Among 11 patients with glomerulonephrits and recurrent hematuria, casts were found in 9 after filtration but in only 2 after routine centrifugation. Casts were detected by the filter method in the urine after angiography of the kidneys in 8 of 12 patients, after centrifugation in only one of them. No casts were found in 6 patients with hematuria due to urological disorders and in 21 healthy persons. The diagnostic sensitivity of microscopical examination of urine was greatly increased by the filter method. This may be due to larger amount of urine examined by the filter method, but an additional cause may be that routine centrifugation destroys red cell casts.

Adolescent↗
PubMed1976

Cadmium and zinc in human liver and kidney.

Liver and kidney samples obtained from 76 autopsies were analyzed for cadmium and zinc content. The patients had died of various internal diseases. None of them had any known occupational exposure to cadmium. A record was made of age, sex, place of residence, diagnosis, and smoking habits of each patient. The results showed no significant correlation between cadmium accumulation and hypertension or cardiovascular disease. There was, however, a significantly higher kidney cadmium level in smokers than in nonsmokers.

Adolescent↗
PubMed1976

Effect of steric restriction on the intracortical distribution of microspheres in the dog kidney.

The effect on the intracortical distribution of microspheres and radioactivity caused by steric hindrance of the free movement of spheres into afferent arterioles are described by two mathematical models. The results are compared with corresponding experimental data obtained in six kidneys from normotensive dogs. The first model (A) assumes that spheres are distributed as blood flow, regardless of their size, except for those having diameters greater than that of an afferent arteriole and which do not enter this vessel. The second model (B) includes the Ferry correction. The experimental data show that the percent recovery of spheres with diameters of 20-25 mum was significantly greater in the outer cortex and significantly less in the juxtamedullary cortex than recovery of the smaller spheres, and that the distribution of spheres with diameters of 10 mum to about 17 mum seems uninfluenced by the sphere size. The experimental results we have obtained fit best with model A. We found that according to both models steric restriction is a factor of major importance in relation to the intracortical distribution of spheres, and the analysis shows that the blood flow in the inner part of the renal cortex is grossly underestimated by the method of isotope labeled microspheres when diameters of 15 +/- 5 mum are used in the dog. Furthermore we found that dilation of the afferent arterioles will change the steric hindrance so that a redistribution of spheres and radioactivity may occur without any redistribution of blood flow. It is suggested that the results interpreted as redistribution of blood flow can be explained as due to altered steric hindrance alone, i.e., as a methodological artifact.

Animals↗
PubMed1975

Retroperitoneal fibrosis during treatment with methydopa.

Retroperitoneeal fibrosis (R.P.F.) and a positive direct Coombs test developed in a patient who had received 1.4 kg. of alpha-methyldopa over a period of 5 years. Immunofluorescence microscopy demonstrated deposits of IgG, IgM, and IgA on the collagen fibres of the R.P.F. Biopsy speciments of the temporal artery, the right kidney, and the R.P.F. did not show signs of general arterial disease on light, immunofluorescence, and electron microscopy. Drugs which provoke autoimmunisation and interfere with nervous transmission are known to induce deposition of collagen or R.P.F. This suggests that R.P.F. in this patient was probably caused by alpha-methydopa.

Biopsy↗
PubMed1975

Diameter of the afferent arteriole in the dog kidney estimated by the microsphere method.

Microspheres with diameters of from 10 to 30 mum were injected into the renal arteries of three anesthetized dogs. The six kidneys were studied by light microscopy. The diameters of the spheres trapped in the afferent arterioles and of all spheres recovered in the kidneys were recorded. On the basis of the distribution of diameters in these two populations of spheres, the average diameter of the afferent arteriole and the distribution of the afferent arteriolar diameters were estimated. The average diameter of the afferent arterioles was 16.3 mum (S.D. 2.2 mum), without any difference between three cortical layers of equal thickness. The mean diameter of spheres trapped in the interlobular arteries was 25.7 mum (S.D. 2.6). It is suggested that the pressure drop along some interlobular arteries may be of physiological importance, affecting the autoregulation of blood flow in the renal cortex.

Animals↗
PubMed1975

Distribution of the renal cortical blood flow in man.

The distribution of the radioactivity following an interaarterial injection of (-131-labeled macroalbumin (MA) was observed in 7 human kidneys and compared with the renal distribution of MA and microspheres in the dog. In the renal cortex the radioactivity per gram of dry tissue in the juxtamedullar and middle cortex was 20.5 and 44.2 per cent of that observed in the outer cortex. The relative radioactivity in the juxtamedullary cortex was significantly (P is less than 0.01) greater in the human than in the dog kidney. In the renal columns the radioactivity was similar to that observed in the middle and outer cortex with incresing values towards the renal hilus. Only traces of radioactivity were observed in the renal medulla. The findings indicate that the distribution of the renal cortical blood flow is similar in the human and the dog kidney with the exception of a greater relative blood flow in the juxtamedullary part of the human kidney.

Aged↗