Browsing by Author "Botha, Matthys Hendrik"

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    DNA damage response of haematopoietic stem and progenitor cells to high-LET neutron irradiation
    (Nature, 2021-10) Engelbrecht, Monique; Ndimba, Roya; De Kock, Maryna; Miles, Xanthene; Nair, Shankari; Fisher, Randall; Du Plessis, Peter; Bolcaen, Julie; Botha, Matthys Hendrik; Zwanepoel, Elbie; Sioen, Simon; Baeyens, Ans; Nieto-Camero, Jaime; De Kock, Evan; Vandevoorde, Charlot
    The radiosensitivity of haematopoietic stem and progenitor cells (HSPCs) to neutron radiation remains largely underexplored, notwithstanding their potential role as target cells for radiation-induced leukemogenesis. New insights are required for radiation protection purposes, particularly for aviation, space missions, nuclear accidents and even particle therapy. In this study, HSPCs (CD34+CD38+ cells) were isolated from umbilical cord blood and irradiated with 60Co γ-rays (photons) and high energy p(66)/Be(40) neutrons. At 2 h post-irradiation, a significantly higher number of 1.28 ± 0.12 γ-H2AX foci/cell was observed after 0.5 Gy neutrons compared to 0.84 ± 0.14 foci/cell for photons, but this decreased to similar levels for both radiation qualities after 18 h. However, a significant difference in late apoptosis was observed with Annexin-V+/PI+ assay between photon and neutron irradiation at 18 h, 43.17 ± 6.10% versus 55.55 ± 4.87%, respectively. A significant increase in MN frequency was observed after both 0.5 and 1 Gy neutron irradiation compared to photons illustrating higher levels of neutron-induced cytogenetic damage, while there was no difference in the nuclear division index between both radiation qualities. The results point towards a higher induction of DNA damage after neutron irradiation in HSPCs followed by error-prone DNA repair, which contributes to genomic instability and a higher risk of leukemogenesis.
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    Endocrine function and fertility preservation in women surviving cancer : a study on cancer treatment and fertility
    (Stellenbosch : University of Stellenbosch, 2010-12) Botha, Matthys Hendrik; Kruger, T. F.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Obstetrics and Gynaecology.
    ENGLISH ABSTRACT: Chapter 1 is a literature review investigating the incidence of cancer in children and young adults. It describes the most important treatment options including chemotherapy, radiotherapy and surgery and the effect of treatment on future endocrine development and fertility. Different primary cancer sites are discussed in more detail. Chapter 2 is a literature review on the effects of cancer surgery in women and the options for fertility sparing. Cervical cancer and pre-cancer are discussed in detail with options for more conservative surgery in selected patients. A summary of the available published cases of trachelectomy with pregnancy outcomes is included. Other gynaecological cancers requiring surgery are also discussed with reference to conservative options. Chapter 3 is a literature review about the medical (pharmacological) options for protection of ovarian function in patients undergoing oncotherapy. The role of gonadotrophin releasing hormone analogues and hormonal contraceptives in ovarian suppression is discussed in detail. Chapter 4 This chapter examines germ cell physiology with reference to cryopreservation. It includes two major parts. Part 1 is the description of germ cell- and follicle physiology, the principles of cryobiology followed by a review of oocyte cryopreservation and ovarian tissue preservation. Both slow freezing and vitrification techniques are described. The second part of chapter 4 is a report on a randomised controlled evaluation of two different slow freezing cryopreservation protocols. This experimental study compared ultrastructural changes in fresh and previously cryopreserved ovarian cortical tissue after equilibration and thawing using two different cryoprotectants. This is the first randomised investigation into DMSO and PROH as cryoprotectants. Chapter 5 is an investigation into cryopreservation of ovarian tissue as a strategy to protect hormonal function and fertility against gonadotoxic treatment. This chapter consists of two parts. The first part is a thorough literature review of all the published work about grafting of previously cryopreserved ovarian tissue. The largest case series found from a single institution was five patients. Another report of six patients included patients from various sites in Denmark. Part 2 is a description of a cohort of patients followed up after re-implantation of previously cryopreserved ovarian cortical tissue. Follow-up hormone levels of 13 individual cases are described in detail. This is the largest case series ever reported. The experimental study described in Chapter 4 and the clinical study described in Chapter 5 was approved by the ethical research committee of the Faculty of Health Sciences, Stellenbosch University, project number N05/10/182. Chapter 6 provides an integrated overview of the incidence and treatment of cancer in young women and how its negative effects may be prevented or mitigated. Aspects of chemotherapy, radiotherapy and surgery are evaluated where it may affect future reproductive health. The role of oocyte and ovarian tissue cryopreservation is discussed. Guidelines are provided for clinicians.