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Biomedical subjects

P Boer

Publications and source records attributed to P Boer.

At least 145 records · Page 8Linked to original sources
PubMed1979

Measurement of cardiac output by impedance cardiography under various conditions.

The suitability of impedance cardiography as a method to follow changes in cardiac output (CO) was investigated by comparing it with thermodilution and by measurements in conditions with predictable effects on CO. The correlation between absolute CO values obtained by impedance and thermodilution techniques was moderate (r = 0.61), but the percentage changes showed a good correlation (r = 0.84). Head-up tilting decreased CO by 25% in 5 normal subjects. Bloodletting in three subjects caused a 20% decrease, reinfusion in one subject a 16% increase. Occlusion of artificial large flow arteriovenous shunts in 6 dialysis patients caused a 12% decrease in CO, whereas the effect was less with moderate and absent with small flow shunts. Ultrafiltration caused a 28% decrease in two dialysis patients. In 20 hypertensive patients CO dropped 25% after salt depletion; propranolol administered intravenously gave a 15% decrease (n = 13), diazoxide intravenously a 30% increase (n = 6). It is concluded that, provided conditions are strictly defined, impedance cardiography is a reproducible method and suitable for the measurement of intrapatient changes in cardiac output.

Adult↗
PubMed1979

De novo synthesis of purine nucleotides and metabolic availability of phosphoribosylpyrophosphate in leukemic leukocytes.

Among normal peripheral blood leukocytes, lymphocytes were found to contain most of the de novo purine synthesizing capacity. The rate of purine synthesis de novo was accelerated in leukocytes from patients with acute and chronic myelocytic leukemias, chronic monocytic leukemia, myelofibrosis and plasma cell leukemia, but was normal in most patients with chronic lymphocytic leukemia. The rate of de novo purine synthesis exhibited positive correlation with the percentage of immature cells in the leukocyte population. The metabolic availability of phosphoribosylpyrophosphate (PRPP) exhibited positive correlation with the state of de novo purine synthesis. These finding suggest that the accelerated rate of de novo purine synthesis and the increased metabolic availability of PRPP are characteristic properties of the immature leukemic granulocyte.

Humans↗
PubMed1979

"Outpatient hyperkalemia" syndrome in renal and hypertensive patients with suppressed aldosterone production.

"Outpatient hyperkalemia" is a new clinical syndrome in which high serum potassium levels (SK) are found in the outpatient condition returning toward normal without any specific treatment after admission to the hospital. We report here of six patients with high blood pressure of various origin (chronic glomerulonephritis, interstitial nephritis, diabetic nephropathy, Gordon syndrome) in whom dietary and postural factors were found to be responsible for the outpatient hyperkalemia. The Na content of the "ad libitum" outpatient diet was definitely higher than that of the regular hospital diet. Increasing the Na intake from 120 mEq to 300 mEq induced a marked elevation of SK (from 5.21 +/- 0.16 to 6.34 +/- 0.40 mEq/l; p less than 0.001) in two hospitalized, recombent patients. On the other hand, Na restriction induced a dramatic improvement in hyperkalemia (from 5.89 +/- 0.11 mEq/l to 4.79 +/- 0.08 mEq/l:; p less than 0.001) in 4 patients in whom the effect was studied in the outpatient state. Although the mean plasma aldosterone (PA) was significantly lower in the patient group than in the healthy group, during normal Na intake there was a considerable overlap. A clearer distintion was made by using the new index of PA per SK ratio expressing the diminution in the apparently normal PA when related to the abnormally high SK. During high Na intake, PA was definitely suppressed and during Na restriction there was a dramatic relief from suppression. The present studies confirmed the previously described phenomenon of "upright hyperkalemia" which may have played an additional role in the development of outpatient elevation of SK. The knowledge of the clinical syndrome of "outpatient hyperkalemia" may be important to single out certain cases of easily correctable insufficient (suppressed) aldosterone production.

Adult↗
PubMed1979

Increase of serum potassium in the upright posture in selective hypoaldosteronism.

The effect of a 4 hr upright posture on serum potassium (SK) levels was investigated in a certain group of hospitalized renal patients with selective hypoaldosteronism and in healthy subjects. Significant (p less than 0.001) postural increase in SK (0.4 MMol/L) was found only in the 3 young patients with chronic glomerulonephritis and hypoaldosteronism who presented with hyperkalemia (5.84 +/- 0.13 mMol/L) as outpatients, but showed a marked improvement toward normokalemia (4.95 +/- 0.13 mMol/L; p less than 0.001) within the hospital without any specific treatment. In healthy persons in the fastqng condition the influence of the upright position of short duration (45 min) was also studied on SK and a very small but significant increase (0.15 mMol/L) was found. It was concluded: 1. the postural SK INCREASE MAY OFFER AN--AT LEAST PARTIAL--EXPLANTATION FOR THE "OUTPATIENT HYPERKALEMIA", 2. The normal activity of renin-angiotensinaldosterone system may play a role in the counteraction of the trend for SK rise in the upright posture.

Adolescent↗
PubMed1979

Regulations of plasma aldosterone in young hyperkalemic patients with stable chronic renal failure.

In a group of four young patients with stable chronic renal failure and hyperkalemia sodium restriction induced a remarkable increase in plasma renin activity (PRA) and plasma aldosterone (PA), a decrease in the elevated serum potassium (SK) and a rise in potassium excretion. During high sodium intake the levels of PRA and PA were lower than those found in the healthy control group suggesting that enhanced suppressibility of the renin-angiotensin-aldosterone system (RAAS) was the main cause of hyperkalemia. During sodium restriction despite a marked increase in PRA and PA levels poor correlations were found between these variables indicating disorganisation within the RAAS and probably a diminished role for renin-angiotensin in the regulation of aldosterone production in three hyperkalemic patients with chronic glomerulonephritis. On the other hand, in the same patients significant correlations were found between fluctuations of SK and PA on constant normal and low sodium diets supporting the concept of an (at least) equal role of potassium and RAAS in the acute regulation of PA. A prominent role for SK was found in an unusual hyperkalemic patient with interstitial nephritis when PRA was suppressed and the elevated SK showed a definite postural rise inducing dramatic increases in PA in the upright posture. Reversion of the postural SK rise masked again the governing role of SK.

Adolescent↗
PubMed1979

Effect of DDAVP on plasma renin activity in man.

We have investigated in eight healthy persons the effect of a single intranasal dose of 40 microgram DDAVP on plasma renin activity (PRA) in the upright posture. During normal sodium intake there were no differences in the PRA values between the time-control and DDAVP studies. However, during sodium restriction in four subjects with higher initial PRA, DDAVP induced a 40% decrease, lasting no longer than 45 minutes. There was no change in PRA after DDAVP in the other four subjects with much lower initial levels. Although no major or consistent suppressive influence could be demonstrated in the present study, in certain persons with highly stimulated initial PRA levels a transitory slight depression may be expected after a pharmacological dose of DDAVP.

Arginine Vasopressin↗
PubMed1979

Oxalic acid concentration in serum measured by isotopic clearance technique. Experience in hyper- and normo-oxaluric subjects.

In a family from which two children suffered from primary hyperoxaluria the renal clearance of (14C) oxalate was studied. The (14C) oxalate/creatinine clearance ratio ranged from 1.76-2.63 (mean: 2.03) and appeared to be independent of glomerular filtration rate (GFR). The calculated plasma oxalate concentrations in normo-oxaluric subjects ranged from 0.1-0.9 mumol/L, whereas in hyperoxaluric subjects values between 3.2-16.3 mumol/L were found. The mean biological half-life of (14C) oxalate was 2.7hr in subjects with normal renal function and increased proportionally with renal functional impairment. Recovery of (14C) oxalate ranged from 87-112% (mean: 101%). All urine (14C) activity was found in the oxalate fraction.

Adolescent↗
PubMed1978

Regulation of de novo purine synthesis in chick liver slices. Role of phosphoribosylpyrophosphate availability and of salvage purine nucleotide synthesis.

The differences between the uricotelic chick and the ureotelic rat, in the regulation of purine synthesis de novo, were studied in intact liver tissue. Chick liver, in comparison with rat liver, was found to contain a high activity of purine synthesis de novo, a high content and availability of 5-phosphoribosyl 1-pyrophosphate (PP-rib-P), comparable activity of PP-rib-P synthetase, and low activity of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and of adenine phosphoribosyltransferase (APRT). The results suggest that the intensive activity of the pathway of purine synthesis de novo in the chick liver is mediated by the high PP-rib-P concentration, which may be due at least in part to the relative partial deficiency of HGPRT.

Adenine↗
PubMed1978

The presence of dolichol in a lipid diphosphate N-acetylglucosamine from Saccharomyces cerevisiae (baker's yeast).

The lipid moiety of a lipid diphosphate N-acetylglucosamine, an intermediate in glycosylation of proteins, was studied. Ozonolysis of the compound gave evidence for an alpha-saturated isoprene unit. Alkaline hydrolysis of the glycolipid, followed by high-pressure liquid chromatography, showed the presence of a series of polyprenol homologues identical with those isolated directly from Saccharomyces cerevisiae (baker's yeast). No particular homologue was preferred in the enzymic transfer of N-acetylglucosamine 1-phosphate to endogenous dolichol monophosphate.

Acetylglucosamine↗
PubMed1978

Sodium intake and the effects of isoproterenol and exercise on plasma renin in man.

Changes in heart rate, blood pressure, and plasma renin activity (PRA) were assessed during infusion of increasing doses of isoproterenol and during increasing work loads of dynamic exercise in five normal young men. Studies were performed at three levels of dietary sodium restriction: normal, moderately, and more severely restricted. Isoproterenol induced the expected dose-related increases in heart rate, systolic blood pressure, and PRA and decreases in diastolic blood pressure. Changes in dietary sodium intake affected these changes only to a minor degree. Dynamic exercise also induced the expected work-load-related increases in heart rate, systolic blood pressure, and PRA and decreases in diastolic blood pressure. Also these changes were not significantly affected by changes in dietary sodium intake. Apparently dietary sodium restriction does not sensitize the renin-releasing mechanisms to sympathetic stimulation.

Adult↗
PubMed1978

Overproduction disease in man due to enzyme feedback resistance mutation. Purine overproduction in gout due to excessive activity of mutant feedback-resistant phosphoribosylpyrophosphate synthetase.

Physiologically superactive phosphoribosylpyrophosphate (PRPP) synthetase, due to feedback resistance mutation, was found in a family with excessive purine production, gout and uric acid lithiasis. The superactivity of the mutant enzyme was manifest in the propositus' erythrocytes and cultured fibroblasts, in increased generation, content and metabolic availability of PRPP, leading in the fibroblasts to acceleration of the rate of purine synthesis de novo. One of the propositus' two siblings was similarly affected, but the propositus' father, his second brother and four sons, were all clinically and biochemically normal. The mother was clinically normal and normouricemic, but hyperuricosuric. Cultured fibroblasts from her skin exhibited variability in PRPP content and availability and in the rate of purine synthesis de novo. The mother's cultures were found to contain a mosaicism of two cell populations, one with normal and the other with mutant PRPP synthetase, indicating an X-linked pattern of inheritance of the PRPP synthetase abnormality in this gouty family.

Adolescent↗
PubMed1978

Pharmacologic studies in Bartter's syndrome: opposite effects of treatment with antikaliuretic and antiprostaglandin drugs. Part I.

The effect of antikaliuretic agents (spironolactone, amiloride) and antiprostaglandin agents (indomethacin, ibuprofen) on plasma renin activity and potassium metabolism was studied in a patient with familial Bartter's syndrome. The decrease in renal potassium clearance in response to antikaliuretic treatment was only of a temporary nature, in contrast to the marked potassium retention seen after indomethacin therapy. Plasma renin activity showed a consistent increase after kaliuretics and a marked decrease in response to antiprostaglandin agents. The opposite effect of the drugs on plasma renin activity, due to their different sites of action on the pathophysiologic chain of events in Bartter's syndrome, given an explanation for the contrasting therapeutic results.

Adult↗
PubMed1978

Pharmacologic studies in Bartter's syndrome: effect of DDAVP and indomethacin on renal concentrating operation. Part II.

We have investigated the effect of indomethacin and DDAVP on water excretion in a patient with familial Bartter's syndrome in whom urinary concentration was impaired during ad libitum fluid intake without any decrease in maximal concentrating ability. In response to indomethacin urine osmolality and free water reabsorption increased, simultaneously with the decrease in the excretion of prostaglandin E2. The indomethacin induced improvement was however less than that obtained after DDAVP with or without indomethacin. The results can be interpreted on the basis of either a direct "vasopressin-like" action of indomethacin or abolishment of the peripheral vasopressin--prostaglandin interaction. The clinical implication is that the theoretical possibility of indomethacin-induced inappropriate ADH syndrome should be borne in mind when a patient is treated with this drug on a long term basis.

Adult↗
PubMed1977

Glycolipid intermediates involved in the transfer of N-acetylglucosamine to endogenous proteins in a yeast membrane preparation.

A particulate membrane fraction from Saccharomyces cerevisiae contains transferases which catalyze the incorporation of N-acetylglucosamine from UDP-N-acetylglucosamine into a lipid fraction as well as into a protein fraction. The lipid fraction contains two alkali-stable lipids which can be separated on a silica G-60 column. The sugar moieties of these polyprenoid lipids are: N-acetylglucosamine and di-N-acetylchitobiose. The transfer of carbohydrate from isolated glycolipids to endogenous protein has been examined. After separation of protein and saccharide by hydrazinolysis and reacetylation only di-N-acetylchitobiose is found, and also when glycolipid containing only one N-acetylglucosamine is used as substrate. Maximum transfer of saccharides from glycolipids to protein is obtained at a Triton X-100 concentration of 1%. At this Triton X-100 concentration there is practically no transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to the phosphorylated lipid. Therefore, when polyprenyl diphosphate N-acetyl[3H]-glucosamine is incubated together with UDP-N-acetyl[14C]glucosamine with the membrane fraction in the presence of 1% Triton X-100, a doubly labelled di-N-acetylchitobiose linked to lipid is formed with N-acetyl[14C]glucosamine at the non-reducing end of the chain.

Acetylglucosamine↗
PubMed1977

Superactivity of phosphoribosylpyrophosphate synthetase, due to feedback resistance, causing purine overproduction and gout.

A mutant feedback-resistant, physiologically superactive, phosphoribosylpyrophosphate (PP-ribose-P) synthetase was found in a family with purine overproduction, gout and uric acid lithiasis. In haemolysates and cultured fibroblasts from the propositus, the mutant enzyme exhibited resistance to feedback inhibition by normal cell constituents, such as ADP and GDP; normal affinity to substrates and to activator Pi was demonstrated in the haemolysate. In both erythrocytes and cultured fibroblasts, the superactivity of the mutant enzyme was manifest in increased PP-ribose-P content and availability for nucleotide synthesis, leading to an acceleration of the rate of purine synthesis de novo in the fibroblasts. The enzyme abnormality and the resulting increase in PP-ribose-P content and generation were demonstrated in the erythrocytes of one of the propositus' two siblings who was similarly affected but not in the propositus' father, his second brother and four sons, who were all clinically and biochemically normal, nor in the erythrocytes of the clinically normal hyperuricosuric mother. However, cultured fibroblasts from her skin exhibited variability in PP-ribose-P content and availability and in the rate of purine synthesis de novo, these parameters being increased in most cultures. The mother's fibroblast cultures were found to contain two cell populations, one with normal and the other with mutant PP-ribose-P synthetase, indicating an X-linked pattern of inheritance of the synthetase superactivity in this gouty family.

Adolescent↗