Browsing by Author "Van der Merwe, Andre"

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    African KhoeSan ancestry linked to high-risk prostate cancer
    (BMC (part of Springer Nature), 2019-06-04) Petersen, Desiree C.; Jaratlerdsiri, Weerachai; Van Wyk, Abraham; Chan, Eva K. F.; Fernandez, Pedro; Lyons, Ruth J.; Mutambirw, Shingai B. A.; Van der Merwe, Andre; Venter, Philip A.; Bates, William; Bornman, M. S. R.; Hayes, Vanessa M.
    Backgrounds: Genetic diversity is greatest within Africa, in particular the KhoeSan click-speaking peoples of southern Africa. South African populations represent admixture fractions including differing degrees of African, African-KhoeSan and non-African genetic ancestries. Within the United States, African ancestry has been linked to prostate cancer presentation and mortality. Together with environmental contributions, genetics is a significant risk factor for high-risk prostate cancer, defined by a pathological Gleason score ≥ 8. Methods: Using genotype array data merged with ancestry informative reference data, we investigate the contribution of African ancestral fractions to high-risk prostate cancer. Our study includes 152 South African men of African (Black) or African-admixed (Coloured) ancestries, in which 40% showed high-risk prostate cancer. Results: Genetic fractions were determined for averaging an equal African to non-African genetic ancestral contribution in the Coloured; we found African ancestry to be linked to high-risk prostate cancer (P-value = 0.0477). Adjusting for age, the associated African ancestral fraction was driven by a significant KhoeSan over Bantu contribution, defined by Gleason score ≥ 8 (P-value = 0.02329) or prostate specific antigen levels ≥20 ng/ml (Pvalue = 0.03713). Additionally, we observed the mean overall KhoeSan contribution to be increased in Black patients with high-risk (11.8%) over low-risk (10.9%) disease. Linking for the first time KhoeSan ancestry to a common modern disease, namely high-risk prostate cancer, we tested in this small study the validity of using KhoeSan ancestry as a surrogate for identifying potential high-risk prostate cancer risk loci. As such, we identified four loci within chromosomal regions 2p11.2, 3p14, 8q23 and 22q13.2 (P-value = all age-adjusted < 0.01), two of which have previously been associated with high-risk prostate cancer. Conclusions: Our study suggests that ancient KhoeSan ancestry may be linked to common modern diseases, specifically those of late onset and therefore unlikely to have undergone exclusive selective pressure. As such we show within a uniquely admixed South African population a link between KhoeSan ancestry and high-risk prostate cancer, which may explain the 2-fold increase in presentation in Black South Africans compared with African Americans.
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    Penile allotransplantation for total phallic loss due to ritual circumcision: Proof of concept
    (Stellenbosch : Stellenbosch University, 2020-12) Van der Merwe, Andre; Moosa, Mohammed Rafique; Stellenbosch University. Faculty of Health Sciences. Dept. of Surgical Sciences: Urology.
    ENGLISH ABSTRACT:Ritual circumcision is an important tradition practiced by many African cultures in South Africa. These circumcisions occasionally result in severe penile mutilations, and many men are rendered aphallic as a result. Phalloplasty represents conventional treatment for these cases. However, this type of surgery has many challenges, which make it an undesirable treatment option, particularly in low- to middle-income settings, such as South Africa. Therefore, we considered alternatives to phalloplasty that were technically feasible and cost-effective. Penile allotransplantation was largely unexplored as a therapeutic option at the inception of the study in 2011, and it was uncertain if a penis transplant would restore all the functions of a normal penis. We undertook a proof of concept investigation and explored the feasibility of penile transplantation in our resource- constrained hospital setting. This is a prospective mixed-methods observational study. Following Human Research Ethics Committee approval, ritual circumcision related aphallic patients attending the Urology Clinic at Tygerberg Academic Hospital were invited to participate. Informed consent was obtained following the intense briefing of candidates over several visits. Various blood tests were conducted, after which selected patients werewaitlisted. The first donor became available in December 2014, and the most suitable recipient was selected based on blood group matching and a negative T-cell cross match. The donor penis was retrieved and transplanted by using the same basic principles of vascularised free flap surgery. Intense immunotherapy was initiated. Outcomes were recorded in terms of recovery from surgery, sexual function, standing to urinate, and general psychological recovery. In the first case-report at 24 months postoperatively, we used standardised pre-and post-surgery Short-Form (SF-36) health questionnaires as well as the International Index of Erectile Function (IIEF) scores to document erectile function outcomes. After that, we used lessons learned from the first case to construct a preliminary guidance manuscript on penile transplantation. We performed a second penile transplant case with 40 months follow-up using patient-reported outcomes as a measure of success in terms of erectile function, sexual satisfaction, and general well- being. We reviewed the ethics around penile transplantation in the context of our experience gained performing two penile transplantations and the societal and academic responses to these cases. Using a phenomenological approach, we conducted four in-depth interviews and performed a thematic analysis to describe study participants’ experiences of living with another person’s penis. Finally, we investigated the current state of penile transplantation by a review of the English literature using available primary databases. Additionally, we published two book chapters on penile transplantation and a manuscript of rebuttal to an argument against penile transplantation. These are attached as addenda to the current thesis. Patients with penile loss are suffering severely. Their self-image, as well as relationships, are destroyed with no effective treatment available to them. Penile transplantation offers hope for the restoration of their broken body image and relationships. Also, this study may pave the way for penile- or total genital transplantation in transmales.
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    Simulation procedure for marker and camera placement
    (Stellenbosch : Stellenbosch University, 2003-12) Van der Merwe, Andre; Muller, N.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    INTRODUCTION: The Medical Radiation department at iThemba LABS provides proton beam therapy facilities for irradiation of intracranial, head and neck lesions. Proton radiation treatment offers a number of advantages over alternative radiation therapy modal- ities. The most significant advantage is the ability to localize the dose to the lesion or target volume [16]. Lesions are located by means of medical imaging processes, such as Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) scans. Patient treatment commences at the existing treatment facility of iThemba LABS. The patient positioning system that is currently in use at this facility was designed for only one horizontal beam delivery system and a limited number of treatment positions. The possibility of acquiring an additional beam delivery system and im- proving the utilization of the system resulted in plans to expand the current proton therapy capabilities. These plans resulted in the development of a new treatment vault, complete with a new patient positioning system. The new vault will cater for two beam delivery systems and expand current treatment positions.
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    Time-driven activity-based costing related to digital twinning in additive manufacturing
    (Southern African Institute for Industrial Engineering, 2021-05) Anderson, Anje Marjorie; Van der Merwe, Andre
    ENGLISH ABSTRACT: Many businesses in the additive manufacturing industry have limited equipment capacity. This method of using time-driven activity-based costing in collaboration with digital twinning will be advantageous to optimise their use of time and their capacity. Optimising the use of time is essential to ensure efficient process flow and to waste less time and money. To optimise, we need to analyse system dynamics and model system responses, to enable us to consider various scenarios iteratively. This paper first considers activity-based costing, driven by its most precious resource, time. Standard time is defined as the base parameter by which cost is calculated. Charge-out rates of elements are based on the actual cost of equipment apportioned to activities, based on the time spent using such equipment. The process chain is broken into elements, each of which incurs full cost when started. The value chain develops accordingly, enabling us to predict the actual cost of production. Second, the use of digital twinning to model standard time is considered. Stochastic variation is evident, but standard time can be allocated to each element in the process chain, given a certain confidence level. Together, a cause—effect prediction model can be developed. The model would predict the time that a process chain, consisting of known elements, would take. However, in the event of an occurrence out of the norm, the updated expected time can be predicted. Using the same rates, the new cost can be determined immediately. We propose that the digital twin can predict production cost, based on a statistically measurable stochastic variation of element duration and the time-varying charge-out rate.