PubMed Health⌕ Search

Biomedical subjects

P Boer

Publications and source records attributed to P Boer.

At least 91 records · Page 5Linked to original sources
PubMed1984

Determination of plasma oxalate with oxalate oxidase.

A method for the determination of plasma oxalate using oxalate oxidase (EC 1.2.3.4) and deproteinised plasma is described. Reference values are 1.2-6.4 mumol/l (n = 24, mean +/- SD 3.3 +/- 1.5 mumol/l). The sensitivity is 6-7 nmol, the accuracy 3-5 nmol, and the coefficient of variation 10.4% (at a level of 23 nmol). The recovery from plasma spiked with oxalate was 105 +/- 8% (n = 8). Allowing blood to stand for 4 h at room temperature had no effect on plasma oxalate levels; inhibitors of glyoxylate converting enzymes interfered with oxalate oxidase.

Humans↗
PubMed1984

Poliomyelitis outbreak in South Africa, 1982. I. Epidemiology.

An epidemic of type 1 poliomyelitis in Gazankulu, which is a self-governing National State in the north-eastern part of South Africa, is described. 260 cases of paralytic poliomyelitis, included 42 deaths, were recorded between 1st May and 3rd September 1982. 92% of cases, who were all admitted to hospital, were in the age group 0 to 5 years. The vaccination status of cases was found to be low: 69% said they had received no vaccination and a further 15% were unsure. Recommendations on the steps to be taken to prevent a recurrence can be gleaned from the discussion in Part II of this article, Laboratory and vaccine aspects (see pp. 24-29 below).

Adolescent↗
PubMed1984

Plasma oxalate concentration in chronic renal disease.

Plasma oxalate was measured with use of the enzyme oxalate oxidase (EC 1.2.3.4; normal values 3.3 +/- 1.5 mumol/L, n = 24) in 50 patients with different degrees of renal failure. The following mean concentrations +/- SD (in mumol/L) were found: for glomerular diseases, 12.7 +/- 7.8 (n = 21); tubular diseases, 20.4 +/- 14.0 (n = 16); chronic renal failure before dialysis, 32.5 +/- 13.5, and after dialysis, 17.8 +/- 3.8 (n = 10); and primary hyperoxalemia, 72.2 +/- 14.5 14.5 (n = 2). The course of plasma oxalate was followed in one of these two patients after renal transplantation and in a patient recovering from acute tubular necrosis. No significant differences were found between patients with glomerular and tubular disorders. Overall, plasma oxalate was correlated with plasma creatinine in patients with glomerular and tubular diseases and dialysis patients (r = .84, P less than .001). Patients with primary hyperoxalemia had values outside the 95% confidence area of the regression line. It is concluded that the values obtained with this method, although probably still tending to overestimate the true oxalate concentration to some extent, provide reliable information about relative differences in plasma oxalate levels. In patients with terminal renal failure, plasma oxalate sometimes rises to levels at which deposition of calcium oxalate in tissues can occur.

Adolescent↗
PubMed1984

Functional relationships in the nephrotic syndrome.

An analysis of 70 observations in patients with the nephrotic syndrome (NS) on a low sodium diet is presented. The following parameters were determined: plasma volume, plasma renin activity, plasma aldosterone concentration, serum albumin, urinary sodium and protein excretion, and creatinine clearance. In 41 instances glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined on the basis of 51Cr-EDTA and 125I-hippuran clearances, and the filtration fraction (FF) was calculated. The results in patients with minimal lesions (ML) and those with histological glomerular lesions (HL) were compared to determine whether these groups can be separated on the basis of signs of hypovolemia and primary renal sodium retention. Although a higher proportion of the ML patients showed extreme sodium retention and elevated plasma renin and aldosterone levels, these values tended to overlap and no differences were found for blood volume, blood pressure, and overall renal function between the groups. FF was markedly and equally depressed in both groups: 13.5 +/- 1.6% in the ML and 14.2 +/- 1.1% SEM in the HL group (NS). Analysis of the within-group relationships between the parameters under study revealed relatively few correlations, which supports the hypothesis that primary impairment of renal water and salt excretion is an important if not overruling factor in patients with the NS.

Adolescent↗
PubMed1984

Absorption kinetics of oxalate from oxalate-rich food in man.

The absorption of oxalate was investigated in a healthy subject after ingestion of oxalate-rich meals (spinach and rhubarb) with and without addition of 14C-labeled oxalic acid and calcium oxalate, and after oxalate-free meals with addition of nonlabeled sodium oxalate and calcium oxalate. Under these conditions, calcium oxalate was absorbed to the same extent as soluble oxalate; only a small percentage (2.4 +/- 0.7) of the total oxalate load was absorbed. Significant oxalate absorption occurred within 1 to 8 h after ingestion. The results suggest that under normal conditions the proximal part of the small bowel is a major absorption site.

Adult↗
PubMed1984

Antihypertensive effect and degree of beta-adrenoceptor blockade after short-term and semi-chronic propranolol therapy.

In patients with normal-renin, mild (n = 6) or moderate (n = 6) hypertension, the antihypertensive effects of propranolol (80 mg/day) for 1 day or for 2 weeks were evaluated in relation to the degree of beta-adrenoceptor blockade induced. A significant and similar fall in systolic blood pressure was observed after 1 day and 2 weeks on propranolol in both groups of patients. In contrast, diastolic blood pressure showed only a minor decrease after 1 day of therapy (-2 +/- 2 and -3 +/- 1 mm Hg) but a significant drop (-7 +/- 3 and -9 +/- 3 mm Hg) after 2 weeks in the mild and moderate hypertension groups, respectively. Plasma propranolol levels and decreases in resting heart rate and PRA were similar after 1 day and 2 weeks of treatment. Isoprenaline dose-response curves for systolic and diastolic blood pressure, heart rate and PRA showed similar parallel shifts after 1 day and 2 weeks of treatment. The effect of graded bicycle exercise on these parameters were also similarly blunted. These results indicate that over time, systolic blood pressure decreases rapidly whereas diastolic blood pressure shows a delayed fall following initiation of low-dose propranolol therapy, despite the same degree of beta-adrenoceptor blockade.

Adrenergic beta-Antagonists↗
PubMed1984

Plasma volumes, noradrenaline levels and renin activity during posture changes in end-stage renal failure.

In nine normal subjects and nine patients with end-stage chronic renal failure (CRF) we studied the effect of prolonged (110 min) postural changes on the plasma volume, intrathoracic volume, plasma noradrenaline concentration, haemodynamic variables, and plasma renin activity (PRA). Upon standing, plasma volume decreased rapidly by about 11% in both groups as measured from the control volume and changes in haematocrit. This was accompanied by identical increments of plasma colloid osmotic pressure. The changes in intrathoracic volume (monitored by measurement of the electrical impedance of the thorax), as well as the alterations in plasma noradrenaline, blood pressure, and heart rate, were also comparable in the two groups. These similarities were in contrast with divergent responses of PRA. The increase in PRA on standing was significantly blunted in the CRF patients compared with the normal response (to 1.4 +/- 0.4 fold of the supine value in CRF v. 6.0 +/- 3.2 fold in the normals, P less than 0.0004). It is concluded that the attenuated increase in PRA upon standing in patients with CRF is not a consequence of diminished sympathetic stimulation or an altered response of the intravascular volume. Second, the unabated decrease in plasma volume upon standing pleads against a decrease of tissue compliance in CRF.

Adult↗
PubMed1984

Estimated lean body mass as an index for normalization of body fluid volumes in humans.

Blood volume was measured in 66 healthy subjects (38 males, 28 females), and extracellular fluid volume in 54 subjects (31 males, 23 females). Volumes were normalized against body weight, height, body surface area, leanness index, and lean body mass (estimated from body weight and height). The regression lines of body fluid volumes against lean body mass passed through the origin on extrapolation and were not different for males and females. None of the other indices fulfilled these criteria. It is concluded that estimated lean body mass is a suitable index for normalization of body fluid volumes. A single set of normal reference values can be used for males and females.

Blood Volume↗
PubMed1984

Effects of plasma volume expansion on renal salt handling in patients with the nephrotic syndrome.

In 10 patients with the nephrotic syndrome (NS) and edema persisting despite a NaCl-poor diet, the effect of a single infusion of hyperoncotic albumin (75 g) on NaCl excretion was studied. 6 patients had minimal lesions, and 2 patients were studied twice. On half of the occasions the glomerular filtration rate was reduced. Blood volume (BV), calculated from plasma volume and hematocrit, was slightly elevated before infusion, and increased to 136 and 120% of normal at 4 and 20 h after it, respectively. Plasma renin activity (PRA) and plasma aldosterone (PA) both decreased to suppressed levels at 20 h after infusion. Sodium excretion increased from 9.2 +/- 7.6 muEq/min before, to 3.10 +/- 22.4 (0-4 h) and 43.1 +/- 36.3 muEq/min (4-20 h) after infusion. In 6 of these patients clearance studies were done before and after the infusion, maximal free water clearance being used as marker for distal NaCl reabsorption. Proximal fractional NaCl reabsorption was elevated before (94.9 +/- 1.4%) and decreased after the infusion (92.8 +/- 1.7%). Distal fractional NaCl reabsorption was also elevated before (93.0 +/- 6.4%), but unaltered after infusion (93.0 +/- 5.6%). Thus, after marked expansion of BV and suppression of PRA and PA, sodium excretion remained low despite the present edema. The results indicate that in many patients with the NS, including minimal lesion NS, intravascular hypovolemia is not the sole cause of sodium retention.

Absorption↗
PubMed1984

Relation between plasma aldosterone concentration and renal handling of sodium and potassium, in particular in patients with chronic renal failure.

In normal subjects a relation was found between the log plasma aldosterone concentration (PAC) and the ratio of renal potassium excretion (UK) and sodium delivery to the sodium-potassium exchange site (UNa + K). This relationship was independent of plasma renin activity (PRA). On these grounds, the UK/UNa + K ratio disturbance was considered to be a function of the PAC, and this relation was considered to reflect an altered sensitivity of the distal tubule to aldosterone. In several pathological conditions involving the kidney, the relation between the PAC and UK/UNa + K remained normal while the glomerular filtration rate was within normal limits. Under these conditions, however, the serum potassium concentration had some influence on this relation, in that a low potassium concentration was accompanied by an elevated (though still normal) PAC relative to the UK/UNa + K ratio. The relation was completely abolished when the effect of endogenous aldosterone was impaired by chronic renal disease made it possible to classify them according to the pathophysiological disturbance in question. We conclude that determination of the UK/UNa + K ratio and its relation to the PAC, PRA, and serum potassium level is very useful for the analysis of disorders of potassium metabolism.

Adolescent↗
PubMed1984

Plasma and blood volumes in patients with the nephrotic syndrome.

In 88 patients with the nephrotic syndrome (NS) we estimated plasma volume (PV) with 131I-albumin (RISA) and calculated blood volume (BV) from PV and whole body hematocrit (Ht). To assess whether this method gives erroneously high values in the NS, the transcapillary escape rate of albumin (TER) and large vessel Ht/whole body Ht ratio (F-cell ratio) were measured in two subsets of these patients (n = 19 and 24, respectively). Although TER appeared to be increased and F-cell ratio slightly decreased in the NS as compared to normals, it could be calculated that overestimation of PV and BV from these sources will not exceed +/- 1%. Taking these errors into account PV and BV appeared normal or increased in the NS (62.8 +/- 9.6 and 94.9 +/- 15.1 ml/kg vs. 56.0 +/- 7.1 and 88.5 +/- 10.1 ml/kg lean body mass in 51 normal controls). We conclude that PV can be measured reliably in the NS with 131I-albumin, and that even after appropriate corrections are made, PV and BV are normal or increased in most patients with the NS.

Adolescent↗
PubMed1984

Intrarenal sodium handling during chronic spironolactone treatment.

Intrarenal sodium handling was studied in 8 patients with essential hypertension before spironolactone treatment (200 mg/day), on the 4th day of treatment, and after 3 months of treatment. The results were compared with similar studies with chlorthalidone (50 mg/day). Renal sodium handling was assessed by simultaneous determination of the glomerular filtration rate, sodium, and potassium excretion, and maximal free-water clearance (CH2O). We took CH2O as an index of 'distal' sodium chloride reabsorption from which the proximal sodium reabsorption was calculated. During the first days of spironolactone treatment a natriuresis and increase in urinary flow rate was found. It resulted in a decrease of the extracellular fluid volume amounting to 0.9 liters and a 2.5-fold increase in the plasma renin activity. Potassium excretion showed a small but significant rise. After 3 months, virtually the same degree of volume depletion was found, which was comparable to that obtained after 3 months of chlorthalidone treatment. CH2O, as a fraction of glomerular filtration rate, decreased by 24% both after 3 days and 3 months, whereas proximal sodium reabsorption increased from 87.8 to 90.4% of the filtered load. CH2O, corrected for the 'distal' delivery of sodium, decreased from 85.3 to 80.7%. These changes were nearly the same as those found after 3 months of chlorthalidone treatment. It is concluded from these calculated values that spironolactone inhibits sodium chloride reabsorption in the diluting segment of the nephron and that the resulting increase in sodium delivery or urinary flow to the potassium excretory site partly counteracts the blocking effect of spironolactone on this part of the nephron, thus increasing potassium excretion during the acute administration of this drug.

Adult↗
PubMed1983

Acute haemorrhagic conjunctivitis in Soweto, 1982. An epidemiological investigation.

In mid-March 1982 an epidemic of acute haemorrhagic conjunctivitis (AHC) broke out in Soweto. Over 34 000 people were treated before the epidemic subsided some 13 weeks later, the overall attack rate being 34,1/1 000. The records of 3 945 patients seen at St John's Eye Hospital were analysed, and the populations at greatest risk of contracting the disease were identified. Males were at greatest risk, with a male to female attack rate ratio of 1,8:1. The age-specific attack rates for both sexes show a similar pattern, peaking in the young adult age groups.

Acute Disease↗
PubMed1983

Urinary oxalate excretion, as determined by isotope dilution and indirect colorimetry.

A simple and reliable method for the determination of urinary oxalate excretion is described. Urinary oxalate is precipitated with calcium chloride, and the oxalate content of the precipitate is measured by an indirect colorimetric method developed by Neas and Guyon in 1972 [1]. For single urine samples, a correction is made for the incompleteness of the precipitation of calcium oxalate by isotope dilution. The range of normal values (5% limits) determined in 52 normal subjects was 0.121-0.325 mmol . 24 h-1 . m-2 for a 1-day collection period and 0.145-0.301 mmol . 24 h-1 . m-2 for a 3-day collection period. The within-assay CV of a control urine with a low oxalate concentration was 9% (n = 7) and the between-assay CV for the same control urine was 12% (n = 6). When the values obtained for oxalate excretion were normalized to body surface area, there was no significant difference between males and females; the main source of variation was the intra-individual variation.

Body Surface Area↗
PubMed1983

The inhibitory effect of some lectins on the differentiation of Friend erythroleukemia cells.

Growth and differentiation of Friend cells can be inhibited by treatment with concanavalin A and wheat-germ agglutinin. This inhibition is specific for cells that are in the early stages of the differentiation process (24-48 h after the addition of dimethyl sulfoxide) and is reversible upon treatment with the sugars competitive for these lectins. These results suggest a regulatory role for some plasma membrane-bound glycoproteins early in the differentiation of Friend erythroleukemia cells induced by dimethyl sulfoxide.

Animals↗
PubMed1983

A study on the distribution of body fluids after rapid saline expansion in normal subjects and in patients with renal insufficiency: preferential intravascular deposition in renal failure.

1. The effect of rapid intravenous infusion of 25 ml of isotonic sodium chloride solution (saline)/kg body weight on extracellular fluid volume (ECFV, 82Br distribution volume), plasma volume (131I-labelled albumin distribution volume) and blood volume (from plasma volume and packed cell volume) was studied in nine normal subjects and a group of 11 patients with end-stage renal disease (ESRD). 2. Immediately after the infusion, the increases in ECFV were equal in the two groups but the increases in plasma and blood volumes were significantly larger in the patients with ESRD. 3. Ninety minutes after the end of the infusion, the blood volume/ECFV ratio was significantly decreased from the control value in the normal subjects, but slightly increased in the patients with ESRD. 4. It is concluded that in severe renal failure the control of fluid distribution is changed in a way which leads to a preferential distribution of rapidly infused saline into the intravascular compartment.

Adult↗
PubMed1983

Antihypertensive effect of propranolol at rest and during exercise.

In eight patients with normal-renin, moderate hypertension, the antihypertensive effects of increasing doses of propranolol (80, 160, 320 and, in three patients, 640 mg/day, each dose for 2 weeks) were evaluated at rest and during exercise in relation to the degree of beta-adrenoceptor blockade induced. A significant decrease (11 +/- 4 mm Hg) in systolic blood pressure was found after propranolol 80 mg/day. Systolic blood pressure showed a fall of 16 +/- 4 mm Hg after 160 mg/day, but no further decrease was measured at higher doses. Diastolic blood pressure showed a significant drop (by 9 +/- 3 mm Hg) after propranolol 80 mg/day; a decrease by 12 +/- 3 mm Hg after propranolol 160 mg/day, but no further decreases at higher doses. PRA and the rise of systolic blood pressure during bicycle exercise were suppressed to a similar extent by propranolol 80 ng and the higher doses. At 80 mg daily exercise tachycardia was reduced by 18%, at 160 mg by 28%, and at the 2 higher doses by 32%. These results suggest that relatively low doses of propranolol (80-160 mg daily) induce most of the antihypertensive effect of propranolol not only at rest but also during exercise. Complete cardiac chronotropic beta-adrenoceptor blockade may not be necessary for the full hypotensive effect.

Adult↗