Browsing by Author "Van Rensburg, Megan"
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- ItemChronic kidney diseases in mixed ancestry South African populations : prevalence, determinants and concordance between kidney function estimators(BioMed Central, 2013-04) Matsha, Tandi E.; Yako, Yandiswa Y.; Van Rensburg, Megan; Hassan, Mogamat S.; Kengne, Andre P.; Erasmus, Rajiv T.Background: Population-based data on the burden of chronic kidney disease (CKD) in sub-Saharan Africa is still very limited. We assessed the prevalence and determinants of CKD, and evaluated the concordance of commonly advocated estimators of glomerular filtration rate (eGFR) in a mixed ancestry population from South Africa. Methods: Participants were a population-based sample of adults selected from the Bellville-South community in the metropolitan city of Cape Town. eGFR was based on the Cockroft-Gault (CG), Modification of Diet in Kidney Disease (MDRD) and CKD Epidemiology Collaboration (CKD-EPI) equations (with and without adjustment for ethnicity). Kidney function staging used the Kidney Disease Outcome Quality Initiative (KDOQI) classification. Logistic regressions and kappa statistic were used to investigate determinants of CKD and assess the agreement between different estimators. Results: The crude prevalence of CKD stage 3–5 was 14.8% for Cockcroft-Gault, 7.6% and 23.9% respectively for the MDRD with and without ethnicity correction, and 7.4% and 17.3% for the CKD-EPI equations with and without ethnicity correction. The highest agreement between GFR estimators was between MDRD and CKD-EPI equations, both with ethnicity correction, Kappa 0.91 (95% CI: 0.86-0.95), correlation coefficient 0.95 (95% CI: 0.94-0.96). In multivariable logistic regression models, sex, age and known hypertension were consistently associated with CKD stage 3–5 across the 5 estimators Conclusions: The prevalence of CKD stages greater than 3 is the highest reported in Africa. This study provides evidence for support of the CKD-EPI equation for eGFR reporting and CKD classification.
- ItemLong-term storage of late season avocado cultivars Hass and Gem™(Stellenbosch : Stellenbosch University, 2021-12) Van Rensburg, Megan; Crouch, E. M.; Theron, K. I.; Thirupathi Karuppana P.; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.ENGLISH ABSTRACT: Avocados experience a physiological disorder known as mesocarp discolouration, also known as grey pulp, which is associated, but not limited, with storage and advanced maturity and leads to large amounts of waste. Avocados have heterogeneous maturities on the same tree, which make storage and marketing complicated. Ripening is essential in making fruit acceptable to consumers but finding the balance between extended storage periods and safe transit is key. The time it takes for the fruit to ripen after storage indicates what transport is possible and what the risk is for physiological disorders and rots to develop. Pathogenic rots are a quality concern that accompany the storage of fresh produce and are the cause of a large percentage of postharvest losses in the avocado industry. Therefore, the objective of this study was to determine the viability of long-term storage of ‘Hass’ and Gem™ to extend the supply of avocados to the local South African market. This was done by evaluating the effect of controlled atmosphere (CA) storage and temperature on grey pulp severity incidence, days to “cutting firmness” of fruit from arrival measured by densimeter, and pathogenic fungal growth. Fruit were stored at 1 and 3 °C in three different atmospheres including regular atmosphere (RA; air), CA (2% O2 and 6% CO2), and dynamic controlled atmosphere-chlorophyll fluorescence (DCA-CF; ≈0.4% O2 and 6% CO2) for various time intervals (4, 6, 7, and 8 weeks) to determine which storage conditions minimise the potential development of the grey pulp disorder, days to “cutting firmness” and pathogenic fungal occurrence. For grey pulp severity, it was possible to store fruit for extended periods (6-8 weeks) at 1 °C in both CA and DCA-CF with a reduced incidence of the disorder. For shorter storage periods, viz. 4 weeks, storing fruit at 1 °C (after step-down cooling) could negate the need for CA. Mesocarp discolouration / grey pulp severity incidence was worse when fruit were stored at higher storage temperatures (3 °C), for longer storage periods, and stored in RA. This study showed that fruit stored in both CA and DCA-CF took longer to soften to a “cutting firmness” and ripened more evenly than fruit stored in RA. It was also shown that where the temperature regime was statistically significant, fruit stored at lower temperatures (1 °C) softened slower to a “cutting firmness” than fruit stored at higher temperatures (3 °C). In the 2016-2017 season, DCA-CF treatment showed a lower incidence of stem-end and body rots compared to the CA and RA treatment. However, in the 2017-2018 season, both CA and DCA-CF treatment often controlled the incidence of stem-end rots and body rots better. Low temperature (1 °C) and both CA and DCA-CF treatment therefore reduced the incidence of stem-end and body rots, as well as the complex rot disorder development in the avocado fruit. This study showed that grey pulp severity or mesocarp discolouration, and decay are better controlled by low temperature and low oxygen environments in storage. These storage methods, combined with the right harvest maturity and transport, will allow longer storage and slower softening, thereby ensuring supply of good quality, late-season avocados to the local market.