Publications by authors named "N Vlok"

11 Publications

Saved by the pump: Two successful resuscitations utilising emergency department-initiated extracorporeal cardiopulmonary resuscitation in South Africa.

S Afr Med J 2021 Mar 2;111(3):208-210. Epub 2021 Mar 2.

Emergency medical officer, private practice, Pretoria, South Africa.

Extracorporeal life support is the utilisation of advanced techniques to sustain circulatory and/or ventilatory functions in critically ill patients when standard therapies fail. It is well established in developed countries. There is increasing literature supporting its application in refractory cardiac arrest with a potential reversible cause, a procedure also known as extracorporeal cardiopulmonary resuscitation (eCPR). Two cases where eCPR was successfully utilised in a busy (>30 000 visits per year) private South African emergency department are described here, the first such cases to be reported on the African continent. The first patient had a life-threatening cardiac arrhythmia due to toxin ingestion, and the second a refractory ventricular fibrillation due to acute myocardial infarction. In both these cases the cardiac arrest was witnessed, occurred in the emergency department, and failed to respond to standard advanced resuscitative measures. Both the patients were discharged neurologically intact. Although it is effective, the benefit of this advanced method of resuscitation in a low- to middle-income country is debated.
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http://dx.doi.org/10.7196/SAMJ.2021.v111i3.15366DOI Listing
March 2021

Helicopter Emergency Medical Services Response to a Major Incident.

Air Med J 2020 Nov - Dec;39(6):506-508. Epub 2020 Oct 16.

HALO Aviation, Johannesburg, Gauteng, South Africa.

Major incidents account for a vast number of consequences, whether it be individual morbidity and mortality or economic disruption and expense. Because of the infrequent nature, it poses a variety of unique risks and challenges for individual emergency medical services systems. Air ambulances are usually dispatched based on the clinical presentation of an individual patient who needs emergent critical care intervention. The response to a major incident is unusual and infrequent, but the benefit of tasking air ambulances to such incidents has been described by various authors. Here, such a response is described in a low- to middle-income country that saw the immediate tasking of 2 separate air ambulances to a single, multivehicle collision with multiple injured patients that occurred near a small, rural hospital not capable of treating critically ill patients. The benefits of tasking of the air ambulance in the sense of additional expertise as well as potential other nonclinical benefits are discussed and described here.
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http://dx.doi.org/10.1016/j.amj.2020.09.007DOI Listing
October 2020

Novel kinase platform for the validation of the anti-tubercular activities of Pelargonium sidoides (Geraniaceae).

BMC Biotechnol 2020 09 29;20(1):50. Epub 2020 Sep 29.

Council for Scientific and Industrial Research, Pretoria, South Africa.

Background: Pelargonium sidoides is an important traditional medicine in South Africa with a well-defined history of both traditional and documented use of an aqueous-ethanolic formulation of the roots of P. sidoides (EPs 7630), which is successfully employed for the treatment of respiratory tract infections. There is also historical evidence of use in the treatment of tuberculosis. The aim of this study was to develop a platform of Mycobacterium tuberculosis (Mtb) kinase enzymes that may be used for the identification of therapeutically relevant ethnobotanical extracts that will allow drug target identification, as well as the subsequent isolation of the active compounds.

Results: Mtb kinases, Nucleoside diphosphokinase, Homoserine kinase, Acetate kinase, Glycerol kinase, Thiamine monophosphate kinase, Ribokinase, Aspartokinase and Shikimate kinase were cloned, produced in Escherichia coli and characterized. HPLC-based assays were used to determine the enzyme activities and subsequently the inhibitory potentials of varying concentrations of a P. sidoides extract against the produced enzymes. The enzyme activity assays indicated that these enzymes were active at low ATP concentrations. The 50% inhibitory concentration (IC) of an aqueous root extract of P. sidoides against the kinases indicated SK has an IC of 1.2 μg/ml and GK 1.4 μg/ml. These enzyme targets were further assessed for compound identification from the P. sidoides literature.

Conclusion: This study suggests P. sidoides is potentially a source of anti-tubercular compounds and the Mtb kinase platform has significant potential as a tool for the subsequent screening of P. sidoides extracts and plant extracts in general, for compound identification and elaboration by selected extract target inhibitor profiling.
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http://dx.doi.org/10.1186/s12896-020-00643-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7523293PMC
September 2020

Early-Ethanol Exposure Induced Region-Specific Changes in Metabolic Proteins in the Rat Brain: A Proteomics Study.

J Mol Neurosci 2018 Jul 18;65(3):277-288. Epub 2018 Jun 18.

Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.

In utero exposure to alcohol has been shown to cause a spectrum of cognitive and behavioral deficits. This study aimed to explore the long-term effects of early-ethanol exposure on proteins in the brain. Male Sprague-Dawley rat pups were exposed to 12% ethanol (4 g/kg/day i.p.) or volume-controlled saline during the third human trimester equivalent (P4-P9). At P31, prefrontal cortex (PFC) and dorsal hippocampus (DH) proteins were analyzed by isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography mass spectrometry (LC-MS). Early-ethanol exposure increased the capacity for metabolism of NADH and oxidative phosphorylation, as shown by an upregulation of NADH dehydrogenase (ubiquinone, 1 alpha subcomplex 9) while simultaneously decreasing the capacity to protect against oxidative stress in the PFC. Early-ethanol exposure decreased the capacity for ATP synthesis (> 2-fold down regulation of ATP synthase) and increased glycogen synthesis in the DH (> 2-fold decrease in glycogen synthase kinase-3β). The effects of early-ethanol exposure on glucose metabolism and ATP production appeared to be region specific. In addition, early-ethanol exposure decreased structural proteins in both the PFC and DH. A greater number of proteins were altered in the DH than in the PFC, indicating that the DH may be more susceptible to the effects of early-ethanol exposure. These proteomic profiles provide valuable insight into the long-term molecular changes in the brain induced by early-ethanol exposure.
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http://dx.doi.org/10.1007/s12031-018-1097-zDOI Listing
July 2018

An Electrospray Ionization Mass Spectrometry Study on the "In Vacuo" Hetero-Oligomers Formed by the Antimicrobial Peptides, Surfactin and Gramicidin S.

J Am Soc Mass Spectrom 2017 08 30;28(8):1623-1637. Epub 2017 May 30.

Department of Biochemistry, University of Stellenbosch, Stellenbosch, 7602, Republic of South Africa.

It was previously observed that the lipopeptide surfactants in surfactin (Srf) have an antagonistic action towards the highly potent antimicrobial cyclodecapeptide, gramicidin S (GS). This study reports on some of the molecular aspects of the antagonism as investigated through complementary electrospray ionization mass spectrometry techniques. We were able to detect stable 1:1 and 2:1 hetero-oligomers in a mixture of surfactin and gramicidin S. The noncovalent interaction between GS and Srf, with the proposed equilibrium: GS~Srf↔GS+Srf correlated to apparent K values of 6-9 μM in gas-phase and 1 μM in aqueous solution. The apparent K values decreased with a longer incubation time and indicated a slow oligomerization equilibrium. Furthermore, the low μM K values of GS~Srf↔GS+Srf fell within the biological concentration range and related to the 2- to 3-fold increase in [GS] needed for bacterial growth inhibition in the presence of Srf. Competition studies indicated that neither Na nor Ca had a major effect on the stability of preformed heterodimers and that GS in fact out-competed Ca and Na from Srf. Traveling wave ion mobility mass spectrometry revealed near symmetrical peaks of the heterodimers correlating to a compact dimer conformation that depend on specific interactions. Collision-induced dissociation studies indicated that the peptide interaction is most probably between one Orn residue in GS and the Asp residue, but not the Glu residue in Srf. We propose that flanking hydrophobic residues in both peptides stabilize the antagonistic and inactive peptide hetero-oligomers and shield the specific polar interactions in an aqueous environment. Graphical Abstract ᅟ.
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http://dx.doi.org/10.1007/s13361-017-1685-0DOI Listing
August 2017