136 research outputs found
Correction to: Antithrombotic Therapy for Symptomatic Peripheral Arterial Disease: A Systematic Review and Network Meta-Analysis
No full textThe 9th author currently listed as Barend M. W. Mees Should be listed as Barend M. E. Mees The original article has been updated.</p
A Stacked Segmented Adaptive Power Amplifier in 22nm FD-SOI
No full textThis work was supported by Soitec. (Corresponding author: Aritra Banerjee.
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Experience Effects on Risk Perception and Protective Action Decision Making when Facing a Rare Tornado Threat
No full textDamaging tornadoes are possible in all U.S. regions beyond the traditionally recognized "tornado alleys" in the southern plains and mid-south. Hence, this research examines how study participants respond to rare tornado events. Specifically, how disaster experiences affect risk perceptions and protective actions when facing a rare tornado event. This study used the protective action decision model (PADM) as the theoretical lens to investigate this issue. The PADM shows that personal characteristics, including personal disaster experience, could affect risk perceptions and how protective action decisions are made. This study applies the theory by recruiting 136 human subjects from the state of Washington to participate in a social experiment. The participants take part in a study that includes hypothetical tornado scenarios, ranging from thunderstorm warning to a tornado emergency then answering questions regarding the presented scenarios. Findings suggest that disaster experience and demographics influence how people perceive and respond to tornado disasters. Overall, people with direct and indirect tornado experiences showed significantly lower risk perceptions in the early stages of the threat when compared with those without any tornado experiences. Their tornado risk perceptions later increased when the threats were higher, and they tended to be more complacent regarding protective actions. This study applies the PADM as a theoretical basis for decision making and could assist emergency managers in creating better plans for risk information dissemination. The study could also potentially aid in gauging preparedness in different areas of a city or population, which can help with appropriate tornado protective actions
Synergistic in-vitro effects of combining an antiglycolytic, 3-bromopyruvate, and a bromodomain-4 inhibitor on U937 myeloid leukemia cells
No full textThis project investigated the in-vitro effects of a glycolytic inhibitor, 3-bromopyruvate (3-BrP), in combination with and a new in silico-designed inhibitor of the bromodomain-4 (BRD-4) protein, ITH-47, on the U937 acute myeloid leukemia cell line. 3-BrP is an agent that targets the altered metabolism of cancer cells by interfering with glucose metabolism in the glycolytic pathway. ITH-47 is an acetyl-lysine inhibitor that displaces bromdomain 4 proteins from chromatin by competitively binding to the acetyl-lysine recognition pocket of this bromodomain and extraterminal (BET) BRD protein, thereby preventing transcription of cancer-associated genes and further cell growth. Cell growth studies determined the IC50 after 48 h exposure for 3-BrP and ITH-47 to be 6 and 2 μmol/l, respectively. When combined, 2.4 and 1 μmol/l of 3-BrP and ITH-47, respectively, inhibited 50% of the cell population, yielding a synergistic combination index of 0.9. Subsequent mechanistic studies showed that the IC50 concentrations of ITH-47 and 3-BrP and the combination increased observable apoptotic bodies and cell shrinkage in U937 cells treated for 48 h. Cell cycle analysis showed an increase in the sub-G1 fraction in all treated cells, suggesting that cell death was increased in the treated samples. Annexin-V-FITC apoptosis analysis showed a statistically significant increase in the number of cells in early and late apoptosis, indicating that cell death occurred through apoptosis and not necrosis. Only U937 cells exposed to ITH-47 showed a decrease in mitochondrial membrane potential compared with the vehicle control. Reactive oxygen species production was decreased in all treated samples. ITH-47-exposed cells showed a decrease in c-Myc, Bcl-2, and p53 gene expressions. 3-BrP-treated cells showed an increase in c-myc and p53 gene expressions. The combination of ITH-47 and 3-BrP lead to downregulation of c-myc and Bcl-2 genes. ITH-47 exposure conditions yielded a marked decrease in c-myc protein levels as well as a decrease in Ser70 phosphorylated Bcl-2. Analysis of 3-BrP and the combination of ITH-47 and 3-BrP test conditions indicated an increase in p53 protein levels. This novel study is the first to investigate the in-vitro synergistic therapeutic effect of ITH-47 and 3-BrP. The current study contributes toward unraveling the in-vitro molecular mechanisms and signal transduction associated with a novel combination of BRD inhibitors and antiglycolytic agents, providing a basis for further research on these combinations.The Research and Development Programme of the University of Pretoria (A0W716), the University of Pretoria and National Research Foundation Thuthuka fund (A0X456 and N00521, respectively), and the Creative Flavors International fund (A0X444).https://journals.lww.com/anti-cancerdrugs/pages/default.aspx2019-06-01hj2018PhysiologySurger
Efficacy of Vickers indentation method to measure residual stress in additively manufactured IN718 specimens
No full textMEng (Mechanical Engineering), North-West University, Potchefstroom CampusSelective laser melting of Inconel 718 powder (a nickel-based superalloy) is regularly used to manufacture gas turbine parts for the aerospace industry. Residual stresses that remain in components after manufacturing are known to be detrimental, often resulting in geometric distortion and inadequate mechanical properties. It is therefore essential to be able to measure these residual stresses. Many non-destructive residual stress measuring techniques are used in the industry, and the Vickers indentation method has been proposed as a less expensive, rapid evaluation technique of residual stresses. The efficacy of the Vickers indentation method as a residual stress measurement technique was evaluated in the study.
It was observed that, for the conditions present in the study, the Vickers micro-indentation method provided inaccurate data. Residual stresses measured using this technique varied considerably across the surfaces of the specimens, with only slight tendencies observable. Compared to X-ray diffraction measurement on cubes manufactured under the same conditions, the residual stress values calculated from the Vickers micro-indentations were very low in magnitude. Differences in hatch distance overlap percentage did not show substantial differences in calculated surface residual stress values; however, slight increases in compressive stresses were observed with increasing hatch distance overlap. Sand-blasting of specimen surfaces preceded dry electrochemical polishing and resulted in increased compressive stresses calculated by the Vickers micro-indentation method. The ability to ensure even and smooth surfaces for Vickers micro-indentations would provide more accurate data on surface residual stress values. Ultimately, it was concluded that the Vickers micro-indentation method is not suitable for surface residual stress measurements of selective laser melted components because of the inability to provide adequately smooth surfaces for indentations to provide accurate data without removing substantial amounts of component surfaces.
Finally, the inherent strain method was employed to simulate residual surface stresses on the selective laser melted components. It was found that these values did not correlate with the values obtained from Vickers micro-indentation tests and X-ray diffraction tests. These discrepancies were attributed to the inability of the simulation software to account for certain processes used during the manufacturing and preparation of the specimens.Master
An investigation into the prevalence and risk factors of occupational low back pain amongst commercial pilots registered with the South African Civil Aviation Authority
No full textSubmitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, Durban, South Africa, 2014.Background
Occupational low back pain (LBP) has been described as a significant burden to society. Although there is uncertainty and conflicting studies on the exact causes and combination of causes of LBP, it has been found that occupations which require prolonged sitting periods and have exposure to physical factors such as whole body vibration (WBV) and / or awkward posture, results in increased likelihood for LBP. Pilots are not sheltered from the development of LBP, with the lifetime prevalence of LBP varying from 31.5% to a significant 82%. Additionally, point prevalence varies significantly between 5.1% and 68%, which illustrates that individual pilot and / or occupational factors may contribute to specific pilot subgroups.
This could apply to commercial pilots, who use seats that were found to be ineffective in terms of their depth and inclination, therefore limiting the height and impact of the lumbar support. There is a paucity of studies performed on LBP relating to commercial pilots, specifically, on their unique occupational setting. Research is therefore warranted to illustrate the possible risk factors to which they are exposed to, as impeded performance may lead to catastrophic consequences if a pilot’s ability to complete actions critical to flight becomes hindered.
Aim
To determine the prevalence of low back pain (LBP) in commercial pilots and identify possible risk factors that pilots are exposed to.
Study designs
The study transpired as a cross sectional questionnaire survey.
Participants
Study comprised of 100 commercial pilots registered with the South African Civil Aviation Authority (SACAA) and affiliated with the various participating companies utilizing O.R. Tambo International Airport.
Methodology
All commercial pilots registered with the SACAA and who make use of the O.R.Tambo International Airport (operate through or from) and affiliated with the participating companies during the research study, was approached for participation. Pilots were required to sign and agree to the letter of information and informed consent, as well as the confidentiality agreement. Questionnaires were distributed and all documents were collected, following completion thereof. Pilots were not allocated to more than one group during the data collection (recording) phase of the study. Subgroup analysis was however not excluded in the analysis. IBM SPSS version 21 was used for analysis. A p value <0.05 was considered as statistically significant. Demographics of the pilots were described in the same manner as in the case of categorical variables, and using summary statistics such as mean, standard deviation and range for quantitative variables. Prevalence and characteristics of the low back pain is described using relative frequency and percentages, with 95% confidence intervals.
Associations between risk factors and low back pain was identified with log linear regression analysis and tested using Pearson’s chi square test in the case of categorical variables and t-tests in the case of continuous variables.
Results
The lifetime prevalence of LBP amongst commercial pilots was 80.8%, with the annual prevalence reaching 68.7%. Majority of commercial pilots were white, married males, with nearly the entire population having reached similar educational levels. Considering the male predominance of this population, gender was significantly associated with LBP. Although the female population was much smaller than the male population, it was also found that females were six times more at risk of developing LBP; however the risk was not statistically significant. Awkward posture such as twisting and being stressed at work were found to be significantly related to LBP. Having a history as an ex-smoker or non-smoker was found to be a risk for LBP development. BMI was also significantly related to LBP; however, an inverse relationship is indicated. Having a subjective rating of good health versus excellent health was also an indicator of risk for LBP.
Conclusion:
Commercial pilots have a significant risk for LBP development. It was found that subjective ratings of own health was a good indicator of LBP whereby good health versus excellent health, was a significant risk factor. Although greater portions of the populace are white males, normally less at risk, a significant lifetime and annual prevalence of LBP was found. Furthermore, the small female population had potentially considerable contribution to the prevalence of LBP through their significant odds ratio. Being a current smoker carried less risk in comparison to a history of an ex-smoker or non-smoker, which further complicates the so often debated contribution of this proposed risk factor. Interesting results were found through the inverse proportional relationship that exists between BMI and LBP, whereby every unit increase in BMI results in a relative decreased risk for LBP development. Majority of the proposed risk factors of LBP was not found to be significant, except stress and twisting, which were found to be common risk factors amongst commercial pilots.
Evaluation of spirulina on the performance and pigmentation of rainbow trout
No full textThesis (MPhil)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: trout was conducted at the Jonkershoek trout research station of the Division of Aquaculture,
University of Stellenbosch. Treatments consisted of ten experimental diets containing increasing
levels of Spirulina (0%, 0.05%, 0.1%, 0.15%, 0.3%, 0.6%, 1.25%, 2.5%, 5% and 10%). The data
was analyzed through means of a one-way ANOVA and Tukey’s pair wise comparison test for
significant differences between treatments for the various parameters of flesh pigmentation and
growth.
The results indicates that the inclusion of Spirulina in the diets of rainbow trout will cause a
undesirable yellowing of fillets, particularly at levels of inclusion at 5 percent and above, which
may limit its use in diets for rainbow trout. There was an inconsistent increase in b* (yellowblue)
and Chroma values with increasing levels of Spirulina inclusion, which may indicate the
deposition of carotenoids (yellow-orange colour range) instead of the desired deposition of
xanthophylls (pink-red colour range) in the flesh of the rainbow trout. This increase in b*
(yellow-blue) values was significantly higher (P<0.05) at inclusion levels above 5 percent.
Spirulina had no significant effect on weight gain of rainbow trout at any level of inclusion. No
significant differences (P>0.05) were observed in any of the other production performance
parameters (growth rate, feed intake, feed conversion ratio, viscerosomatic index, hepatosomatic
index, and liver lipid content) that were evaluated. Low mortality rates were observed with no
significant differences between treatments. A trend of decreased feed intake with increased levels
of Spirulina inclusion became significant at the 2.5 percent level of inclusion, caused by
deterioration in the palatability of the feed. A significantly higher dress-out percentage was
observed at levels of Spirulina inclusion above 5 percent. A trend of decreased liver lipid content
with increased Spirulina inclusion was observed, though not significant at any level of Spirulina
inclusion. This observation justifies further investigation because of its potential to improved
carbohydrate metabolism in carnivorous fish
Results confirm that up to 10% Spirulina can effectively replaced soybean meal in the control
diets for rainbow trout while simultaneously improving carcass dress-out at high inclusion levels.AFRIKAANSE OPSOMMING: rantsoen van reënboog forel te evalueer. Die eksperiment is opgestel by die Akwakultuur Divisie,
van die Universiteit van Stellenbosch, se navorsingstelsel in Jonkershoek, buite Stellenbosch.
Reënboog forel (Oncorhynchus mykiss) vingerlinge van gemiddeld 20 gram is gebruik en
ingedeel in 20 ronde tenks volgens kommersieële digthede (250 per tenk).
Die rantsoene is gemeng met verskeie vlakke van Spirulina insluiting (0%, 0.05%, 0.1%, 0.15%,
0.3%, 0.6%, 1.25%, 2.5%, 5% en 10%). Twee herhalings van elke rantsoen is gevolg vir ‘n
periode van 3 maande. Die vis is ad lib (volgens behoefte) gevoer, drie maal per dag.
Daar was ‘n neiging tot ‘n verhoging in b* (geel-blou) en Chroma waardes met verhoogde
insluitingsvlakke van Spirulina. Hierdie is wel ‘n aanduiding van die deponeering van karoteen,
maar val in die geel-oranje kleur reeks en is nie die verlangde pienk-rooi (xantofil) kleur in die
spier weefsel van die vis nie. Die verhoging in b* (geel-blou) waardes was statisties betekenisvol
(P<0.05) bo die 5% insluitings vlak.
In vergelyking met die kontrole (0%) rantsoen, was daar geen betekenisvolle massa toename na
afloop van die proef tussen die verskeie behandelings nie. Behalwe vir ‘n verskil in voer inname,
was daar geen statisties betekenisvolle verskil (P>0.05) waarneembaar tussen die verskillende
behandelings ten opsigte van die verskeie produksie prestasie parameters nie. Daar was wel ‘n
afnemende neiging in voer inname met verhoogde vlakke van Spirulina wat betekenisvol geraak
het bo 2.5% insluitingsvlak. Smaaklikheid kan die moontlike rede hiervoor wees. Baie lae
mortaliteite is ervaar by al die insluitings vlakke. Daar was ook ‘n neiging in hoër uitslag
persentasie by verhoogde insluitingsvlakke van Spirulina wat betekenisvol geraak het bo 5 %
insluiting. ‘n Afnemende vlak van lewer lipied inhoud is waargeneem maar was nie betekenisvol
by enige van die insluitingsvlakke nie.
Resultate van die proef dui daarop dat 10% Spirulina insluiting effektief kan dien as ‘n
gedeeltelike plaasvervanger vir soyaboon meel in forel rantsoene. Die hoër uitslag persentasies
hou belofte in. Die onverlangde vergeeling van die filette mag die gebruik van Spirulina beperk
by reënboog forel rantsoene veral bo 5 % insluitings vlakke. Die verlaging in lewer lipied vlakke
by ‘n verhoging van Spirulina insluiting regverdig vêrdere navorsing oor die potensiaal van
Spirulina om die metabolisme van koolhidrate te verbeter by karnivoor visspesies.Master
Evaluation of a catalytic fixed bed reactor for sulphur trioxide decomposition
No full textPhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2014The world energy supply and demand, together with limited available resources have resulted in the need to develop alternative energy sources to ensure sustainable and expanding economies. Hydrogen is being considered a viable option with particular application to fuel cells. The Hybrid Sulphur cycle has been identified as a process to produce clean hydrogen (carbon free process) and can have economic benefits when coupled to nuclear reactors (High Temperature Gas Reactor) or solar heaters for the supply of the required process energy. The sulphur trioxide decomposition reactor producing sulphur dioxide for the electrolytic cells in a closed loop system has been examined, but it is clear that development with respect to a more durable active catalyst in a reactor operating under severe conditions needs to be investigated. A suitable sulphur trioxide reactor needs to operate at a high temperature with efficient heating in view of the endothermic reaction, and has to consist of special materials of construction to handle the very corrosive reactants and products. This investigation was undertaken to address (1) the synthesis, characterisation, reactivity and stability of a suitable catalyst (2), determination the reaction rate of the chosen catalyst with a suitable micro reactor (3) construction and evaluation of a packed bed reactor for the required reaction, and (4) the development and validation of a reactor model using computational fluid dynamics with associated chemical reactions.
A supported catalyst consisting of 0.5 wt% platinum and 0.5 wt% palladium on rutile (TiO2, titania) was prepared by the sintering of an anatase/rutile supported catalyst with the same noble metal composition, synthesized according to an incipient impregnation procedure using cylindrical porous pellets (±1.7 mm diameter and ±5 mm long). Characterization involving: surface area, porosity, metal composition, - dispersion, - particle size, support phase and sulphur content was carried out and it was found from reactivity determinations that the sintered catalyst, which was very different from the synthesized catalyst, had an acceptable activity and stability which was suitable for further evaluation.
A micro pellet reactor was constructed and operated and consisted of a small number of pellets (five) placed apart from each other in a two-stage quartz reactor with sulphur trioxide generated from sulphuric acid in the first stage and the conversion of sulphur trioxide in the second stage, respectively. Attention was only confined to the second stage involving the conversion of sulphur trioxide with the supported catalyst. The overall reaction kinetics of the pellets involving momentum, heat and mass transfer and chemical reaction was evaluated and validated with constants obtained from literature and with an unknown reaction rate equation for which constants were obtained by regression. As result of the complexity of the flow, mass and heat transfer fields in the micro pellet reactor it was necessary to use a CFD model with chemical reactions which was accomplished with a commercial code COMSOL MultiPhysics® 4.3b. A reversible reaction rate equation was used and a least squares regression procedure was used to evaluate the activation energy and pre-exponential factor. The activation energy obtained for the first order forward reaction was higher than values obtained from literature for a first order reaction rate (irreversible reaction) for the platinum group metals on titania catalysts. Detailed analyses of the velocity, temperature and concentration profile revealed the importance of using a complex model for determination of the reaction parameters.
A fixed bed reactor system consisting of a sulphuric acid vaporizer, a single reactor tube (1 m length, 25 mm OD) heated with a surrounding electrical furnace followed, by a series of condensers for the analysis of the products was constructed and operated. Three process variables were investigated, which included the inlet temperature, the weight hourly velocity and the residence time in order to assess the performance of the reactor and generate results for developing a model. The results obtained included the wall and reactor centreline temperature profiles together with average conversion. As a result of the complexity of the chemistry and the phases present containing the products from the reactor a detailed calculation was done using vapour/liquid equilibrium with the accompanying mass balance (Aspen-Plus®) to determine the distribution of sulphur trioxide, sulphur dioxide, oxygen and steam. A mass balance was successfully completed with analyses including SO2 with a GC, O2 with a paramagnetic cell analyser, acid/base titrations with sodium hydroxide, SO2 titrations with iodine and measurement of condensables (mass and volume). The results obtained showed that a steady state (constant conversion) was obtained after approximately six hours and that it was possible to obtain sulphur trioxide conversion approaching equilibrium conditions for bed lengths of 100 mm with very low weight hourly space velocities.
A heterogeneous 2D model consisting of the relevant continuity, momentum, heat transfer and mass transfer and the reaction rate equation determined in this investigation was developed and solved with the use of the commercial code COMSOL MultiPhysics® 4.3b with an appropriate mesh structure. The geometry of the packed bed (geometry) was accomplished by generating a randomly packed bed with a commercial package DigiPac™. The model predicted results that agreed with experimental results with conversions up to 56%, obtained over the following ranges: weight hourly space velocity equal to 15 h-1, temperatures between 903 K and 1053 K and residence times between 0.1 and 0.07 seconds. The post-processing results were most useful for assessing the effect of the controlling mechanisms and associated parameters.Doctora
Evaluation of the neurotoxicity of pentachlorophenol and its active metabolites on SH-SY5Y neuroblastoma cells
No full textDissertation (MSc)--University of Pretoria, 2017.Pentachlorophenol (PCP) is an organochloride pesticide that is ubiquitous within the
environment due to its chemical stability. It is classified as a persistent organic
pollutant, and has been predominantly used in the wood preservation industry.
Workers and populations living close to PCP usage and production are exposed to it
via inhalation and dermal absorption, and ingestion of contaminated food and water.
It is lipophilic and is able to accumulate within various bodily systems, including the
brain. Adverse effects of PCP have been reported to varying degrees in the immune,
hepatic, and endocrine systems. Although neurological symptoms have been
associated with PCP exposure, knowledge of mechanisms of neurotoxicity is limited.
Elucidation of molecular mechanisms at a cellular level within neuronal cells is
required to contribute toward the current gap in the knowledge of PCP neurotoxicity.
The aim of the study was to evaluate the effects of PCP and its active metabolites,
tetrachloro-1,4-benzoquinone (TCBQ) and tetrachlorohydroquinone (TCHQ) in
human neuroblastoma SH-SY5Y cells.
Effects on cell proliferation were assessed using the sulforhodamine B (SRB) assay.
Flow cytometric analysis was employed to investigate effects on cell cycle using
propidium iodide (PI), mode of cell death using Annexin V-FITC and PI, reactive
oxygen species (ROS) using dichlorofluorescein, and mitochondrial membrane
potential (Δᴪm) using JC-1 fluorescence. Caspase-3 activity was assessed with Ac-
DEVD-AMC, and glutathione (GSH) with monochlorobimane fluorescence. Effects on
acetylcholinesterase (AChE) were assessed in vitro using the Ellman esterase
assay, as well as in silico via molecular docking and molecular dynamics simulation.
The IC50 concentrations of PCP, TCBQ and TCHQ were 80.0, 35.4, and 63.7 μM,
respectively. Cell cycle disruptions were revealed in the form of a G1 block and a
G2/M block as a result of PCP and TCHQ exposure, respectively, while TCBQ
resulted in a prolonged S phase traverse. The predominant mode of cell death of
PCP was necrosis, while TCBQ induced apoptosis. Exposure to TCHQ resulted in
one of two fates, being either predominantly apoptotic or necrotic cell death.
Decreased Δᴪm was an early event for all compounds, however, differed in their
involvement of inducing ROS. Oxidative stress was an evident mechanism of PCP
and TCBQ toxicity, as increased ROS was accompanied by lowered GSH, while reductive stress leading to subsequent oxidative stress was indicated by increased
ROS and GSH for TCHQ. All compounds yielded increased caspase-3 activity. The
fate of TCHQ exposed cells was postulated as a switch from apoptosis to necrosis
due to overwhelming ROS insult on apoptotic machinery, surpassing a threshold for
apoptosis capability. Inhibition of AChE was observed by only TCHQ in vitro, the
Ellman IC50 of which was 79.7 μM. In silico assessment supported a hypothesis of
TCHQ inhibition of AChE, with TCHQ-acetate bound ligands binding AChE receptors
with binding energies corresponding to the Ellman IC50. Binding stability was
confirmed by molecular dynamics.
Pentachlorophenol and its active metabolites exhibited different mechanisms of
toxicity toward neuronal cells, leading to different modes of cell death. A new
hypothesis for the molecular mechanism of TCHQ AChE inhibition was developed,
and sets a platform for further investigation.PhysiologyMScUnrestricte
Differential effects of Sutherlandia frutescens subs. microphylla on cell numbers, morphology, gene and protein expression in a breast adenocarcinoma and a normal breast epithelial cell line
No full textDissertation (MSc)--University of Pretoria, 2007.Sutherlandia frutescens is a South African herbal remedy traditionally used for various ailments and lately to improve the overall health in cancer and HIV/AIDS patients. Relatively little is known about the mechanisms of action of the constituents present in S. frutescens. The aim of this project was to examine the in vitro influence of crude ethanolic S. frutescens extracts in human breast adenocarcinoma (MCF-7) and non-tumorigenic breast epithelial (MCF-12A) cells after 48 h of exposure. Dose-dependent studies were conducted on cell numbers and metabolic activity by means of spectrophotometry. Morphological changes were determined with light-, fluorescent- and transmission electron microscopy (TEM). Cell cycle progression and apoptosis were analyzed using flow cytometry. The differential effects of S. frutescens extracts on gene expression levels in both the MCF-7 and MCF-12A cells were conducted utilizing micro array analysis. mTOR kinase activity was measured with an ELISA assay. S. frutescens reduced cell proliferation in both the non-tumorigenic MCF-12A and the tumorigenic MCF-7 cell line in a dose-dependent manner. The tumorigenic MCF-7 cells were more susceptible to S. frutescens treatment compared to the non-tumorigenic MCF-12A cells. Morphological characteristics of apoptosis and autophagy, including cytoplasmic shrinking, membrane blebbing and an increase in autophagic vacuoles were observed in both cell lines with the MCF-7 cells being more susceptible to autophagy and the MCF-12A cells less susceptible to autophagy and apoptotic cell death. TEM confirmed ultrastructural characteristics of autophagy in both cell lines. Flow cytometry revealed a G2/M arrest with no increase in apoptosis in MCF-7 cells and a G2/M arrest with an increase in apoptosis in MCF-12A cells treated with 1.5mg/ml S. frutescens extract. Microarray analyses revealed 325 statistically significantly differentially expressed genes in MCF-7 cells and 1467 genes in MCF-12A cells. The majority of S. frutescens-treated genes were down-regulated when compared to the vehicle-treated control in both cell lines. Several genes involved in DNA replication and repair were differentially expressed in response to S. frutescens exposure. These include Poly (ADP-ribose) polymerase family, member 2 (PARP-2) (down-regulated in both cell lines), PCNA (down-regulated in MCF-7 cells) and growth arrest and DNA-damage-inducible beta (GADD45B) (up¬regulated in MCF-12A cells). This suggests that abrogated expression of genes involved in DNA replication and repair play a role in inducing a G2/M cell cycle arrest in S. frutescens-treated cells. ELISA analysis of the mTOR kinase revealed a decrease in mTOR kinase activity in both cell lines after S. frutescens exposure. Therefore, attenuated mTOR kinase activity as a result of S. frutescens treatment in both cell lines is regarded as a central mediator in inducing autophagy suppressing gene expression and inhibiting ribosome biogenesis. Understanding of in vitro molecular mechanisms of S. frutescens enables researchers to focus on affected cellular mechanisms and identify active compounds with subsequent evaluation as possible candidates for use in anticancer therapy. The current study contributes to the unraveling of the in vitro molecular mechanisms and signal transduction associated with 70% ethanolic S. frutescens extracts, providing a basis for further research on this multi-purpose medicinal plant in Southern Africa.Physiologyunrestricte
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