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L Steyn

Publications and source records attributed to L Steyn.

10 recordsLinked to original sources
PubMed2001

The cold-shock stress response in Mycobacterium smegmatis induces the expression of a histone-like protein.

The response of Mycobacterium smegmatis to a cold shock was investigated by monitoring changes in both growth and cellular protein composition of the organism. The nature of the cellular response was influenced by the magnitude of the temperature reduction, with the shock from 37 degrees C to 10 degrees C having the most widespread effect on growth, metabolism and protein composition. This 27 degrees C temperature reduction was associated with a lag period of 21-24 h before increases were seen in all the measured cellular activities. The response to cold shock was adaptive, with growth resuming after this period, albeit at a 50-fold slower rate. The synthesis of at least 15 proteins was induced during the lag period. Two distinct patterns of cold-induced synthesis were apparent, namely transient and continuous, indicating the production of both cold-induced and cold-acclimation proteins. One of these cold-shock proteins, CipMa, was identified as the histone-like protein, Hlp, of M. smegmatis, which is also induced during anaerobic-induced dormancy. The corresponding gene demonstrated transient, cold-inducible expression with a five- to sevenfold increase in mRNA occurring 9-12 h after temperature shift. Although bacterial survival was unaffected, CipMa/Hlp knock-out mutants were unable to adapt metabolically to the cold shock and resume growth, thus indicating a key role for CipMa in the cold-shock response.

Amino Acid Sequence↗
PubMed2000

Thalidomide-induced antigen-specific immune stimulation in patients with human immunodeficiency virus type 1 and tuberculosis.

Thalidomide, which inhibits monocyte tumor necrosis factor (TNF)-alpha production and costimulates T cells, was tested for immune modulation in patients with human immunodeficiency virus (HIV) infection and tuberculosis (TB) in a placebo-controlled study. Thalidomide therapy resulted in increased levels of plasma interleukin (IL)-2 receptor, soluble CD8, interferon-gamma, and IL-12, indicating immune stimulation. TNF-alpha levels were not reduced. Thalidomide treatment increased CD4+ and CD8+ T cell counts and lymphocyte proliferation to purified protein derivative. Immune stimulation was not associated with an increase in plasma HIV levels. In vivo, a thalidomide dose-dependent costimulatory effect on T cell proliferation and HIV replication was observed after stimulation with antigens or anti-CD3, respectively. Thalidomide-induced increased viral replication in CD4+ T cells was abrogated by adding back autologous CD8+ T cells. Thus, in the presence of thalidomide, antigen-specific immune responses in vitro and in patients with HIV/TB were enhanced.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Ischemic heart disease in black South African stroke patients.

BACKGROUND AND PURPOSE: Stroke patients in western countries frequently have coronary artery disease (CAD). In black Africans, CAD has been reported as being rare in both stroke patients and the general population. In this study, an attempt has been made to determine the prevalence of CAD in a black South African stroke population. METHODS: The prevalence of CAD was determined by indicators identified through a series of 5 observational studies in black patients diagnosed with stroke. CAD indicators included (1) bedside diagnosis in 741 patients; (2) resting ECG in 555 consecutively admitted patients; (3) a combination of clinical examination, cardiac ultrasound, radionuclide scintigraphy, and multigated blood pool studies in 102 consecutively admitted patients; (4) thallium scintigraphy in 60 patients; and (5) necropsy in 23 patients. RESULTS: On bedside questioning, only 0.7% complained of previous angina. There was no history given of myocardial infarction (MI), but documentation of this was found in the clinical notes of 0.7% of the patients. In the resting ECG study, evidence of myocardial ischemia was present in 14.6% and MI in 2.1%. In the combined study, cardiac ischemia was documented on ECG in 12.7% of patients and evidence of previous MI in 5.8%. Cardiac scintigraphic studies revealed changes of myocardial ischemia in 31.7% and MI in 13.3% of the 60 patients studied. Four (17.4%) of 23 patients in the necropsy study had histological evidence of previous MI, and 50% of all patients had evidence of >50% atherosclerotic stenosis in 1, 2, or 3 coronary arteries. CONCLUSIONS: The prevalence of CAD in black African stroke patients is significantly higher than has been documented in the general nonstroke black population as well as in stroke patients. Black stroke patients may have a risk for CAD similar to that of their white counterparts.

Adult↗
PubMed1998

Selective increase in plasma tumor necrosis factor-alpha and concomitant clinical deterioration after initiating therapy in patients with severe tuberculosis.

The initiation of antituberculosis treatment in patients with severe tuberculosis may be accompanied by clinical deterioration and even death before any improvement occurs. To investigate this phenomenon, newly diagnosed human immunodeficiency virus-negative adults with severe tuberculosis were followed for the first 42 days of standard short-course therapy. Clinical status, serum lactate, plasma cytokine, and plasma cytokine receptor levels were monitored on days 0, 3, and 7 and then weekly for up to 42 days. Following 7 days of antituberculosis therapy, a significant transient decrease in mean Karnofsky score (P < .001), a concomitant increase in serum lactate (P = .06), a decrease in patient weight (P = .02), and an increase in plasma tumor necrosis factor-alpha (TNF-alpha) concentrations (P = .04) were observed. Plasma levels of soluble interleukin-2 receptor, interferon-gamma, interleukin-6, and TNF-alpha receptor decreased over the 42-day study period. These observations suggest that increases in plasma TNF-alpha levels may be associated with clinical deterioration observed early in the treatment of severe tuberculosis.

Adult↗
PubMed1997

rhuIL-2 adjunctive therapy in multidrug resistant tuberculosis: a comparison of two treatment regimens and placebo.

SETTING: Low-dose recombinant human interleukin 2 (rhuIL-2) adjunctive immunotherapy in multidrug resistant tuberculosis (MDR-TB) patients. OBJECTIVE: Evaluation of the effects of daily versus pulse-administered rhuIL-2 compared to placebo. DESIGN: MDR-TB patients on best available antituberculous chemotherapy received rhuIL-2 for 30 consecutive days (daily therapy), or for 5 days followed by a 9-day 'rest', for three cycles (pulse therapy). Placebo control patients received diluent. The cumulative total dose of rhuIL-2 given to each patient in either rhuIL-2 treatment group was the same. Patient immunologic, microbiologic, and radiologic responses were compared. RESULTS: The three treatment schedules induced different results. Immune activation was documented in patients receiving daily rhuIL-2 therapy. Numbers of CD25+ and CD56+ cells in the peripheral blood were increased in these patients, but not in patients receiving pulse rhuIL-2 or placebo. In addition, 5/8 (62%) patients receiving daily rhuIL-2 demonstrated reduced or cleared sputum bacterial load while only 2/7 (28%) pulse rhuIL-2 treated and 2/8 (25%) controls showed bacillary clearance. Chest radiographs of 7/12 (58%) patients receiving daily rhuIL-2 indicated significant improvement over 6 weeks. Only 2/9 (22%) pulse rhuIL-2-treated patients and 5/12(42%) placebo controls showed radiologic improvement. CONCLUSION: Daily low dose rhuIL-2 adjunctive treatment stimulates immune activation and may enhance the antimicrobial response in MDR-TB.

Adult↗
PubMed1993

Simple method for production of internal control DNA for Mycobacterium tuberculosis polymerase chain reaction assays.

A simple method for the production of internal control DNA for two well-established Mycobacterium tuberculosis polymerase chain reaction assays is described. The internal controls were produced from Mycobacterium kansasii DNA with the same primers but at a lower annealing temperature than that used in the standard assays. In both assays, therefore, the internal control DNA has the same primer-binding sequences at the target DNA. One-microgram quantities of internal control DNA which was not contaminated with target DNA could easily be produced by this method. The inclusion of the internal control in the reaction mixture did not affect the efficiency of amplification of the target DNA. The method is simple and rapid and should be adaptable to most M. tuberculosis polymerase chain reaction assays.

DNA, Bacterial↗
PubMed1992

A comparative study of the polymerase chain reaction and conventional procedures for the diagnosis of tuberculous pleural effusion.

Preliminary reports by ourselves and others suggest that amplification of mycobacterial DNA by the polymerase chain reaction (PCR) is a sensitive and rapid diagnostic test for tuberculosis. We recently described a PCR assay with a 336 bp repetitive sequence specific for Mycobacterium tuberculosis as the DNA target, which gave encouraging results in culture-positive smear-negative clinical specimens. In the present prospective study of patients with pleural effusions we compared PCR of the pleural fluid with conventional procedures. 84 adult patients with pleural effusions were divided into 4 groups. In group A (44 patients), M. tuberculosis was detected by culture of pleural fluid, pleural biopsy or extrapleural source. In group B (6 patients), tuberculous infection was confirmed by histology (group A excluded). Group C (3 patients) had clinical evidence of tuberculosis. Group D (31 patients) had no evidence of active M. tuberculosis infection. Analysis of the pleural fluid confirmed a sensitivity for PCR of 81%. The sensitivity of pleural fluid culture, culture of pleural biopsy, and histology of biopsy was 52.8%, 69.8% and 77.3% respectively. There were however 7 PCR positive results within group D; 6 of these were in patients with malignant effusions. We conclude that for the diagnosis of M. tuberculosis PCR is more sensitive than laboratory culture as determined by the analysis of pleural fluids. Positive PCR results among patients with malignant effusions may be false-positives or the result of latent tuberculous infections. PCR should remain an investigational procedure until prospective studies in high and low prevalence areas have critically evaluated the specificity of the assay.

Adult↗
PubMed1990

Direct detection of Mycobacterium tuberculosis in clinical specimens by DNA amplification.

A polymerase chain reaction assay was developed for the amplification of a 336-bp repetitive fragment in the chromosome of Mycobacterium tuberculosis. The assay is specific for M. tuberculosis and can be used to detect the amount of DNA present in less than 10 organisms. It was used to demonstrate M. tuberculosis DNA in 14 of 26 clinical specimens (from cerebrospinal fluids, pleural fluid aspirates and biopsies, pericardial fluid aspirates, and an open lung biopsy), and it was shown to be at least as sensitive as conventional culture techniques with these specimens.

Base Sequence↗