PubMed Health⌕ Search

Biomedical subjects

L Pretorius

Publications and source records attributed to L Pretorius.

8 recordsLinked to original sources
PubMed2006

Ethambutol resistance testing by mutation detection.

OBJECTIVE: To identify chromosomal mutations that confer resistance to ethambutol (EMB) in Mycobacterium tuberculosis. DESIGN: Drug-resistant (n = 235) and drug-susceptible (n = 117) M. tuberculosis isolates collected from the Western Cape in South Africa were subjected to embB gene analysis and the results were compared to phenotypic EMB testing. RESULTS: Genotypic analysis identified mutations at codon 306 of the embB gene in 20% (47/235) of the resistant isolates in comparison to only 1.7% (4/235) of those that were phenotypically resistant to EMB by the agar diffusion method. No gene mutations were detected in susceptible isolates. Phenotypic retesting in BACTEC demonstrated that the 47 genotypically resistant isolates were phenotypically resistant to EMB. This implies that 91.4% (43/47) of EMB resistance had been phenotypically missed by routine laboratory procedures. EMB resistance was closely linked to multidrug resistance (MDR); 87.2% (41/47) of the EMB-resistant isolates were resistant to both isoniazid and rifampicin. A newly developed one-step amplification refractory mutation system polymerase chain reaction (ARMS-PCR) method correctly detected the EMB-resistant genotype. CONCLUSION: Implementation of more accurate diagnosis of EMB resistance may enhance patient management in South Africa, as standardised treatment of MDR-TB with second-line drugs is currently dependent on the outcome of the EMB resistance test.

Antitubercular Agents↗
PubMed1998

Numerical simulation of pulsating flow in the aortic arch.

In order to investigate the flow profiles in the aorta a numerical three-dimensional model of the aortic arch was created. The velocity fields were simulated by applying an inlet velocity corresponding to the physiological velocity of the pressure wave at the aortic valve. The velocity field distribution was found to be uniform throughout the model during the time of increasing inlet velocities. With decreasing inlet velocities a region of low flow developed in the descending portion of the model leading to recirculating flow at the inner wall. At this region of low flow the variation in velocity with time at the inner wall was approximately twice the variation at the outer wall. As a result of the recirculating flow, the wall shear stresses at the inner wall are low and oscillating, predisposing to the development of atherosclerosis. This model shows that transient fluid flow in the aortic arch can be simulated. Biological studies are needed to prove that this model can be used to predict sites of pathology.

Algorithms↗
PubMed1984

Splenectomy in onyalai. A report on 5 cases.

Onyalai is an acquired immune thrombocytopenia with 10% mortality. Conservative measures such as traditional medicines, corticosteroids and blood transfusion have not always controlled severe bleeding or prevented death. Five patients (2 male, 3 female) with onyalai who had uncontrollable haemorrhage, thrombocytopenia and documented previous attacks of severe bleeding, underwent splenectomy. The patients were screened for malaria, sickle-cell anaemia and bilharzia. Vitamin K and epsilon-aminocaproic acid were administered pre-operatively, and fresh blood was given during surgery. The duration of follow-up varied between 280 and 544 days. There were no operative complications. Bleeding stopped in all patients and the platelet counts increased within 24 hours. All achieved normal platelet counts, but these were not always sustained. Three patients remained free of disease with normal platelet counts up to days 539, 539 and 544 of follow-up. Two patients had a recurrence of bleeding and died from cerebral haemorrhage and haemorrhagic shock.

Adolescent↗
PubMed1983

Octamer reconstitution from acid-extracted chicken erythrocyte histones.

Histone octamers have been reconstituted from acid-extracted chicken erythrocyte histones. By the criteria of molecular size on exclusion chromatography as well as sedimentation velocity and conformational properties established by circular dichroism, fluorescence spectroscopy and imido-ester cross-linking, the reconstituted octamers have a structure identical to that of salt-extracted octamers.

Animals↗
PubMed1982

The effect of Ca2+ on the stability of chicken erythrocyte histone octamers.

Histones can be extracted from chicken erythrocyte chromatin with 2 M CaCl2 10 mM Tris (pH 7.4). The core histones so extracted exist as H3-H4 tetramers and H2A-H2B dimers since calcium at greater than 0.5 M result in dissociation of the histone octamer. Reconstitution of octamers occurs on removal of the Ca2+ by dialysis. Although less than 0.5 M calcium do not result in octamer dissociation, perturbations in the structure can be detected by CD and tyrosine fluorescence spectroscopy.

Animals↗
PubMed1981

The effect of intravenous amino acids on plasma amino acid concentration during total parenteral nutrition in infants with necrotizing enterocolitis.

Plasma aminograms of infants receiving total parenteral nutrition as part of the treatment for necrotizing enterocolitis were studied. Their ages varied from 2 to 60 days and their mean birth mass was 1 621 g (range 760-2 550 g). The intravenous administration of amino acids produced changes in plasma amino acid levels corresponding to the concentration of individual amino acid levels in the solution employed: higher levels of amino acids in the infusate produced increased plasma levels, whereas low plasma levels were obtained for amino acids not present or present in small amounts according to the solution used. The infants did not appear to suffer in any way, but the long-term effects still have to be evaluated. Pending further knowledge in this regard it is suggested that plasma amino acid levels should be maintained as near to normal values as possible. This could probably be achieved by the use of amino acid solutions specially formulated according to the amino acid profile of breast milk or the plasma amino acid profile of normal infants.

Amino Acids↗