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Biomedical subjects

G de Klerk

Publications and source records attributed to G de Klerk.

15 recordsLinked to original sources

[Cystic adventitial degeneration of the popliteal artery; an unexpected cause of intermittent claudication].

Three men, aged 48, 44 and 51 years, were referred to the vascular surgery outpatient clinic because of acute intermittent claudication in one leg. The first patient had no medical history and no vascular risk factors, the second patient was receiving drug treatment for hypercholesterolaemia and diabetes mellitus and the third patient smoked. After additional radiological diagnostics, cystic adventitial degeneration of the popliteal artery was diagnosed in all patients. All 3 patients were operated. Only circumferential resection of the cystic adventitia and the outer layer of the media, so-called exarteriectomy, was performed in the second patient. The other 2 patients underwent resection of the affected popliteal artery followed by an autologous vein graft. The post-operative course was uncomplicated. The diagnosis of cystic adventitial degeneration was confirmed histopathologically. Cystic adventitial degeneration is localised only in the popliteal artery in 85-90% of cases. It is probably caused by incorporation of mesenchymal cells in the wall of the popliteal artery during embryogenesis. The disease is often progressive and, if left untreated, may lead to critical ischaemia due to arterial occlusion. Surgical intervention is therefore necessary, with exarteriectomy as the preferred technique, especially because the patients are often young.

Adult↗

[Hypokalemic periodic paralysis as the sole manifestation of hyperthyroidism].

Hypopotassaemic periodic paralysis as the sole manifestation of hyperthyroidism. Hypopotassaemic periodic paralysis is a rare disorder that is found in certain families, sporadically or in association with certain diseases. The association with hyperthyroidism is almost wholly restricted to south-east Asian males. It is characterized by attacks of subacute paralysis, starting most often early in the morning and lasting some hours to a few days. We present a 42-year-old patient of Indonesian origin, who experienced four attacks of paralysis before underlying hyperthyroidism was diagnosed. The mechanism is based on potassium shift into the muscle cell due to higher activity of the Na-K-ATP-ase pump, under the influence of beta-adrenergic stimulation and thyroid hormone. Treatment with antithyroidal medication and beta-blockers led to the complete abolition of attacks.

Adult↗

Serum erythropoietin (ESF) titers in anemia of chronic renal failure.

ESF titers were determined in 99 patients of various stages of chronic renal failure, by using the fetal mouse liver cell bioassay. Of these patients 45 were receiving conservative therapy and 54 on maintenance hemodialysis. ESF levels were significantly below normal in both groups of patients. A significant inverse relationship was found between hemoglobin concentration and ESF level in the predialysis patients with chronic glomerulonephritis. No correlation was found between both parameters in the predialysis patients with chronic nonglomerular renal disease. A significant positive correlation was found between hemoglobin concentration and ESF level in nephric dialysis patients who were transfusion independent. Transfusion-dependent nephric dialysis patients had lower hemoglobin concentrations and lower ESF levels before transfusion than did nephric dialysis patients who were transfusion independent. In nephric dialysis patients ESF levels fell sharply after blood transfusion, whereas in anephric dialysis patients such a physiologic ESF response was not found. It was concluded that despite the presence of an absolute ESF deficiency in all anemia uremic patients, this anemia cannot be explained by ESF deficiency alone. The increasing degree of anemia found in predialysis patients with deteriorating renal function appears to be primarily caused by factors other than ESF deficiency, the most likely being accumulation of uremic inhibitors of erythropoiesis. In dialysis patients in whom inhibitor levels are relatively homogeneous, the degree of anemia appears to be directly related to the residual capability of the kidney or the extrarenal sites to produce ESF.

Adult↗

Comparative study on the circulatory and respiratory effects of buprenorphine and methadone.

A comparative study on the effects on circulation and respiration of buprenorphine and methadone was performed on a group of four healthy volunteers in a double blind way. Both drugs were given by continuous slow i.v. infusion. Before and after administration of the drugs, the subjects breathed in an open, resp. closed system, gas mixtures of 50% O2 / 50% N2 resp. 50% O2 / 43% N2 / 7% CO2. After each breathing/rebreathing period pupil diameters were measured photographically. The effects on respiration were calculated as shifts in vol. % CO2 necessary to obtain a standard respiratory minute volume. Analysis of variance showed a dose-independent inhibition of respiration of buprenorphine and a dose-dependent inhibition of methadone. Both drugs caused a weakly dose-dependent miosis. There were no significant dose-dependent effects on circulation and both drugs caused a similar side effect profile.

Adult↗

Serum erythropoietin (EST) titers in anemia.

Erythropoietin (ESF) titers were determined in sera from patients with different types of anemia using the fetal mouse liver cell bioassay. An inverse relationship was found between hemoglobin concentration and ESF titer. However, ESF titers differed markedly between patients at comparable degrees of anemia. Several groups of patients were distinguished on the basis of the activity of their erythroid bone marrow. In each of these groups, a significant negative correlation was found between the hemoglobin concentration and the logarithm of the ESF titer. ESF titers in patients with pure red cell aplasia were fourfold higher than those in patients with iron-deficiency anemia and tenfold higher than those in patients with megaloblastic anemia and homozygous sickle cell anemia at comparable hemoglobin concentrations. Following the initiation of specific therapy in patients with pernicious anemia and patients wit iron-deficiency anemia, serum ESF titers were found to decrease prior to any substantial rise in hemoglobin concentrations. In the patients with pernicious anemia, the lowest ESF levels were found 1 day after administration of vitamin B12, whereas in the patients with iron-deficiency anemia, the lowest ESF levels were reached in the second week of oral iron therapy. ON the basis of these data it was concluded that serum ESF titers in anemic patients are not only inversely related to the hemoglobin concentration but also to the activity of the erythroid bone marrow.

Anemia↗

Serum erythropoietin (ESF) titers in polycythemia.

Serum ESF titers were measured in 42 polycythemic patients using the fetal mouse liver cell bioassay. ESF titers in patients with secondary polycythemia differed significantly from those in patients with polycythemia vera (p less than 0.0001). Among the 21 patients with secondary polycythemia, 1 patient had an ESF titer less than 10 mU/ml (the lower limit of sensitivity) and 20 had ESF titers that ranged between 11 and 112 mU/ml, with a mean titer of 56 mU/ml. Among the 21 patients with polycythemia vera, 13 patients had ESF titers less than 10 mU/ml and 8 had ESF titers ranging between 12 and 55 mU/ml, with a mean titer of 26 mU/ml. The mean hemoglobin concentration in the 8 patients with ESF titers greater than 10 mU/ml was significantly below that in the 13 polycythemia vera patients with ESF titers less than 10 mU/ml (p less than 0.03). If ESF titers less than 10 mU/ml had been indicative of polycythemia vera and ESF titers greater than 10 mU/ml had been indicative of secondary polycythemia in patients with hemoglobin concentrations greater than 17.7 g/dl, but not indicative of either condition in patients with hemoglobin concentrations less than 17.7 g/dl, 71.5% of the polycythemic patients in this study would have been diagnosed correctly, 9.5% incorrectly, and in the 19% the diagnosis would have remained uncertain. It was concluded that measurement of serum ESF titers using this in vitro bioassay can be of clinical importance in differentiating between polycythemia vera and secondary polycythemia.

Adult↗

Comparison of the hemagglutination inhibition assay kit for erythropoietin (ESF) with the fetal mouse liver cell bioassay in vitro.

The commercially available hemagglutination inhibition (HAI) assay kit for erythropoietin (ESF) was compared with the fetal mouse liver cell (FMLC) bioassay. No correlation was obtained ESF levels determined by both methods in a variety of pathologic sera. The HAI kit showed a great batch variability. Significant immunoreactivity was found in those fractions of a normal human serum and a human urinary ESF preparation that were not active in the FMLC bioassay. A very poor recovery of immunoreactivity was found when the international reference preparation for erythropoietin (second IRPE) was added to a normal human serum.

Absorption↗

Modified method of erythropoietin (ESF) bioassay in vitro using mouse fetal liver cells. I. Effect of serum iron on 59Fe incorporation into heme.

Investigations on the mouse fetal liver cell bioassay for erythropoietin (ESF) have revealed that iron present in test sera significantly dilutes the radiolabel (59Fe) and thus decreases 59Fe incorporation into heme. A method of correction for the influence of iron on the dose-response relationship of human sera is presented. Application of this method made it possible to assay human sera up to culture concentrations of 150 microliter/ml. It was shown that a corrected serum dose-response curve showed parallelism to the curve of an ESF standard preparation. This suggests similarity of the active principles and allows valid estimation of a potency ratio.

Dose-Response Relationship, Drug↗

Modified method of erythropoietin (ESF) bioassay in vitro using mouse fetal liver cells. II. measurement of ESF in human serum.

A modification of the mouse fetal liver cell bioassay for erythropoietin (ESF) that allows quantitative detection of ESF in human serum is described. The modification consists of (1) correction for the effect of serum iron on 59Fe incorporation into heme and (2) the use of an "internal standard," i.e., a standard ESF preparation dissolved in the assayed test serum. As a result of this modification the statistical method of bioassay analysis had to be changed fundamentally. The mean serum concentration of ESF measured in 20 normal males was 48 microunit/ml, as compared to 29 microunit/ml in 18 females. The difference was significant at p = 0.017. The stimulatory activity of a human serum on 59Fe incorporation into heme could be neutralized by an anti-human ESF immune serum.

Cells, Cultured↗