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A van Zyl

Publications and source records attributed to A van Zyl.

11 recordsLinked to original sources
PubMed1992

Effects of therapy on renal impairment in essential hypertension.

The effect of hydrochlorothiazide 50 mg, amiloride 5 mg (HCTZ-A) (Moduretic; MSD) and its combination with pindolol and nadolol on renal function were compared in patients with mild to moderate essential hypertension (mean untreated supine blood pressure 179 +/- 5.7/108 +/- 2.6 mmHg) with compromised renal function (glomerular filtration rate (GFR) < 85 ml/min). After randomisation to a beta-blocker plus diuretic, the beta-blocker was washed out (diuretic-only period) and the other beta-blocker added. Eleven patients completed the randomised cross-over comparative study, 5 receiving pindolol 15 mg plus 1 dose of HCTZ-A daily for 6 weeks, and 6 nadolol 120 mg plus 1 dose of HCTZ-A daily. The beta-blocker was then withdrawn for 4 weeks, after which each group of patients received 1 dose of HCTZ-A plus the alternative beta-blocker daily for 6 weeks. The GFR was measured using chromium-51-ethylenediamine-tetra-acetic acid at the end of each treatment phase. The mean GFR (+/- SE) fell from 69.6 +/- 5.8 to 60.6 +/- 5.1 ml/min (P < 0.01) during HCTZ-A therapy, whereas the addition of pindolol or nadolol caused no further drop in the GFR. We conclude that mild degrees of renal impairment in essential hypertension may be aggravated by HCTZ-A therapy when given as one tablet of Moduretic daily.

Adult↗
PubMed1981

The control of peroxidase-catalysed iodination and de-iodination.

It has been demonstrated that the H2O2/l ratio is a critical factor in the control of iodination and de-iodination of covalently bound tyrosyl residues in proteins and free iodotyrosines by peroxidase enzymes. This has been shown for myeloperoxidase (MPO) isolated from normal human polymorphonuclear lymphocytes in particular, and also for peroxidase of animal origin such as thyroid peroxidase (TPO) and lactoperoxidase (LPO). It has been shown that the H2O2/l ratio exerts a controlling influence on MPO-catalysed reactions of fully iodinated tyrosines, e.g. di-iodotyrosine, and of partially and completely iodinated thyronines such as thyroxine and tri-iodothyronine. Using an in vivo model system it has been shown that MPO catalyses the sequential events of iodination, iodine exchange and de-iodination of tyrosines and, furthermore, that all three reactions are influenced by the rate of H2O2 generation and the iodide concentration of the reaction medium. The action of MPO on iodothyronine substrates only affects de-iodination irrespective of whether the iodothyronine is partially iodinated, as in tri-iodothyronine, or completely iodinated, as in thyroxine. This MPO-catalysed de-iodination of thyroxine and tri-iodothyronine can also be regulated by the H2O2/l ratio. Moreover, the results show that MPO-catalysed iodine exchange can only occur in completely iodinated tyrosines such as di-iodotyrosine (DIT). Iodine exchange in partially iodinated tyrosines such as mono-iodotyrosine (MIT) or in iodothyronines (T3 and T4) cannot be catalysed by MPO irrespective of the H2O2/l ratio. These results introduce a new concept which may be important in understanding the control of thyroid activity in thyroid disease and the control of MPO activity in biological defence mechanisms in man.

Animals↗
PubMedDate not supplied

Autosomal recessive inheritance of congenital goiter in Afrikander cattle.

Congenital goiter was reported in a number of herds of Afrikander cattle in the 1950's. Some affected animals were assembled and maintained as a closed herd. Although considerable biochemical research into the nature of the disease has been conducted, no definitive report has described the mode of inheritance of the defect. This paper presents the results of breeding studies that indicate the defect is inherited as an autosomal recessive. Southern blot analysis of the thyroglobulin gene confirms this finding. In addition, serum levels of TSH (thyroid stimulating hormone, thyrotropin), T3 (3,4,3'-tri-iodothyronine), T4 (thyroxine), rT3 (3,3',5'-tri-iodothyronine), and DIT (diiodotyrosine) of goitrous animals are compared with normal animals.

Africa, Southern↗