Pub Date : 2021-08-30DOI: 10.1080/0035919X.2021.1964105
R. Mugandani, C. Murewi, T. Chitata, F. Chipepa, B. Mudereri, Liboster Mwadzingeni, P. Mafongoya
The objective of the study was to use the item response theory to improve the quality of survey items used in research on the human fingerprint of climate change in the Beitbridge district, Zimbabwe. Data were collected using questionnaires to 365 randomly selected participants and analysed using the 1; 2- and 3-parameter models. The 1-parameter model showed that concerning item difficulty level, all the survey items on knowledge of human fingerprint on climate change are in the “good” category. Meanwhile, results of the 2-parameter model show that in terms of item discrimination, all the tests were fairly “good”, with a relatively flat slope. The 3-parameter model shows that all the survey items were in the “good” class with a guessing factor of 0% as well as improved discrimination values on most of the items. Therefore, item response theory is an appropriate approach to improve survey-based research methodology and outputs.
{"title":"Can the application of item response theory improve the quality of survey items for assessing human fingerprints on climate change?","authors":"R. Mugandani, C. Murewi, T. Chitata, F. Chipepa, B. Mudereri, Liboster Mwadzingeni, P. Mafongoya","doi":"10.1080/0035919X.2021.1964105","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1964105","url":null,"abstract":"The objective of the study was to use the item response theory to improve the quality of survey items used in research on the human fingerprint of climate change in the Beitbridge district, Zimbabwe. Data were collected using questionnaires to 365 randomly selected participants and analysed using the 1; 2- and 3-parameter models. The 1-parameter model showed that concerning item difficulty level, all the survey items on knowledge of human fingerprint on climate change are in the “good” category. Meanwhile, results of the 2-parameter model show that in terms of item discrimination, all the tests were fairly “good”, with a relatively flat slope. The 3-parameter model shows that all the survey items were in the “good” class with a guessing factor of 0% as well as improved discrimination values on most of the items. Therefore, item response theory is an appropriate approach to improve survey-based research methodology and outputs.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"283 - 290"},"PeriodicalIF":0.0,"publicationDate":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43308237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-23DOI: 10.1080/0035919X.2021.1947921
T. Bolaniran, A. Jamiu, T. Garuba, A. Wudil, H. Adeola, S. Sabiu
Mushrooms are universally valued for their dietary and therapeutic significance. Their importance could be attributed to numerous nutritive and dietary substances including polysaccharides, terpenoids, phenolics and other light molecular bioactive compounds. These compounds offer optimal health benefits and have been identified as a potential source of nutritional and medicinal products against several debilitating and food-related disorders. Here, we present an updated synopsis of the medicinal attributes of mushrooms, while also highlighting the technological advancements in their cultivation that have led to the birth of engineered species with improved traits that could alleviate malnourishment and contribute towards food security, offer health benefits, and provide efficient ways of waste management.
{"title":"An appraisal of the metabolites, pharmacological and biotechnological significance of edible mushrooms","authors":"T. Bolaniran, A. Jamiu, T. Garuba, A. Wudil, H. Adeola, S. Sabiu","doi":"10.1080/0035919X.2021.1947921","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1947921","url":null,"abstract":"Mushrooms are universally valued for their dietary and therapeutic significance. Their importance could be attributed to numerous nutritive and dietary substances including polysaccharides, terpenoids, phenolics and other light molecular bioactive compounds. These compounds offer optimal health benefits and have been identified as a potential source of nutritional and medicinal products against several debilitating and food-related disorders. Here, we present an updated synopsis of the medicinal attributes of mushrooms, while also highlighting the technological advancements in their cultivation that have led to the birth of engineered species with improved traits that could alleviate malnourishment and contribute towards food security, offer health benefits, and provide efficient ways of waste management.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"257 - 272"},"PeriodicalIF":0.0,"publicationDate":"2021-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0035919X.2021.1947921","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44969465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-23DOI: 10.1080/0035919X.2021.1934184
Talent Murwendo, A. Murwira, M. Masocha
Spatial and temporal patterns of vegetation productivity in semi-arid savanna national parks are influenced by differences in land cover and changes in time series trends. The main purpose of this paper is to analyse patterns of vegetation productivity metrics of base value, peak value, amplitude, and small and large integrals in Gonarezhou National Park (GNP) in south-eastern Zimbabwe from 1981 to 2015. Three sample sites comprising shrublands, deciduous broadleaved forested woodlands and mixed cover (shrublands, broadleaved deciduous forested woodlands and grasslands) were selected to show existing patterns of vegetation productivity for GNP. We used remotely sensed Normalised Difference Vegetation Index (NDVI) data which was further processed in the TIMESAT 3.3 program to derive productivity metrics. We then tested differences in land cover using analysis of variance and changes in time-series trends using Mann–Kendall and Theil–Sen’s tests. We note significant differences in land cover (P< 0.01) in selected samples. There are significant downward trends in the base value in shrublands (P< 0.01) and broadleaved deciduous forested woodlands (P= 0.04). Significant upward trends in the amplitude in the shrublands (P< 0.01) and mixed cover areas (P= 0.01) were noted. However, there are no changes in vegetation productivity, as indicated by the peak value and large and small integral indices. Shrublands are becoming vulnerable in terms of energy and vegetation productivity and need constant monitoring. Long-span coarse-resolution images are important stepping stones in providing a baseline for further studies from moderate and fineresolution imagery. Research on vegetation productivity using fine-resolution imagery is more suitable for GNP.
{"title":"Vegetation phenology dynamics as an indicator of energy and productivity functions in semi-arid savannah protected areas: a case study of Gonarezhou National Park in south-eastern Zimbabwe","authors":"Talent Murwendo, A. Murwira, M. Masocha","doi":"10.1080/0035919X.2021.1934184","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1934184","url":null,"abstract":"Spatial and temporal patterns of vegetation productivity in semi-arid savanna national parks are influenced by differences in land cover and changes in time series trends. The main purpose of this paper is to analyse patterns of vegetation productivity metrics of base value, peak value, amplitude, and small and large integrals in Gonarezhou National Park (GNP) in south-eastern Zimbabwe from 1981 to 2015. Three sample sites comprising shrublands, deciduous broadleaved forested woodlands and mixed cover (shrublands, broadleaved deciduous forested woodlands and grasslands) were selected to show existing patterns of vegetation productivity for GNP. We used remotely sensed Normalised Difference Vegetation Index (NDVI) data which was further processed in the TIMESAT 3.3 program to derive productivity metrics. We then tested differences in land cover using analysis of variance and changes in time-series trends using Mann–Kendall and Theil–Sen’s tests. We note significant differences in land cover (P< 0.01) in selected samples. There are significant downward trends in the base value in shrublands (P< 0.01) and broadleaved deciduous forested woodlands (P= 0.04). Significant upward trends in the amplitude in the shrublands (P< 0.01) and mixed cover areas (P= 0.01) were noted. However, there are no changes in vegetation productivity, as indicated by the peak value and large and small integral indices. Shrublands are becoming vulnerable in terms of energy and vegetation productivity and need constant monitoring. Long-span coarse-resolution images are important stepping stones in providing a baseline for further studies from moderate and fineresolution imagery. Research on vegetation productivity using fine-resolution imagery is more suitable for GNP.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0035919X.2021.1934184","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48887329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-09DOI: 10.1080/0035919X.2021.1927882
A. Katunga, Edilegnaw Wale Zegeye, G. Ortmann
Farm household survey data collected in rural districts of central and northern Malawi were used to investigate factors that influenced smallholders to replace groundnut varieties. The results of the study showed that smallholders have not entirely replaced conventional varieties with modern ones. For the group of smallholders that replaced conventional with the modern varieties, few reverted to the former. Further results of a bivariate probit regression model indicated that the production of groundnuts for food and income increased the probability of replacing both conventional and modern varieties. Farmers’ perception of the relevance of agricultural extension services to groundnut production and land allocated to the cultivation of groundnuts increased the likelihood to replace conventional varieties. Conversely, poor rural road infrastructure decreased the probability of replacing the same. In other results, experience in groundnut production, education level of the farmer, membership of farmer organisations, and inadequate access to quality seed increased the likelihood of replacing modern varieties. The study's findings suggest that promoting an integrated seed system of groundnut varieties is critical for the adoption and conservation of improved and conventional varieties and could contribute to the food and income security of farm households.
{"title":"Smallholders’ replacement of groundnut varieties in Malawi: implications for adoption and conservation of improved and conventional varieties","authors":"A. Katunga, Edilegnaw Wale Zegeye, G. Ortmann","doi":"10.1080/0035919X.2021.1927882","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1927882","url":null,"abstract":"Farm household survey data collected in rural districts of central and northern Malawi were used to investigate factors that influenced smallholders to replace groundnut varieties. The results of the study showed that smallholders have not entirely replaced conventional varieties with modern ones. For the group of smallholders that replaced conventional with the modern varieties, few reverted to the former. Further results of a bivariate probit regression model indicated that the production of groundnuts for food and income increased the probability of replacing both conventional and modern varieties. Farmers’ perception of the relevance of agricultural extension services to groundnut production and land allocated to the cultivation of groundnuts increased the likelihood to replace conventional varieties. Conversely, poor rural road infrastructure decreased the probability of replacing the same. In other results, experience in groundnut production, education level of the farmer, membership of farmer organisations, and inadequate access to quality seed increased the likelihood of replacing modern varieties. The study's findings suggest that promoting an integrated seed system of groundnut varieties is critical for the adoption and conservation of improved and conventional varieties and could contribute to the food and income security of farm households.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"273 - 282"},"PeriodicalIF":0.0,"publicationDate":"2021-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0035919X.2021.1927882","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42260963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-10DOI: 10.1080/0035919X.2021.1938283
J. Carruthers
Author Lesley Green is an Associate Professor of Social Anthropology and founding Director of Environmental Humanities South at the University of Cape Town. Her major over-arching project is to bring together disparate fields and to create an integrative and interdisciplinary network that interrogates and explores the variety of knowledges about our contemporary environment. Environmental justice, or eco-justice, lies at the heart of her work. Green is well published in her field, and her publications are concerned not only with southern Africa but, with David Green, she has also written about Amerindian, as well as Amazonian indigenous knowledge in Brazil. This book, written in the voice of the engaged-researcher, in the first person and with many autobiographical inclusions – “she cannot accept the comfort of academic distancing” (Foreword by Isabelle Stengers, p. xiii) – contains interesting ideas and stories that readers who have an interest in the “environment” in its broadest sense need to consider in our current era and in this particular moment in South Africa. The book is divided into three parts, each comprising two chapters – the arrangement is explained on pp. 17–19. In Part 1, “Pasts Present”, Chapter 1 (Rock) engages with geology, water supply, and the city of Cape Town and Chapter 2 (Water) with fracking in the karoo. Part II, “Present Futures” contains Chapter 3 (Life) that explores knowledge of Namaqua plant medicine and Chapter 4 (Rock), access to and use of land. Part III, “Futures Imperfect”, includes Chapter 5 (Life) baboon management and Chapter 6 (Water) marine resource and sewage disposal in the city of Cape Town and its surroundings. There is an Introduction, entitled “Different Questions, Different Answers” and a “Coda: Composing Ecopolitics”. All the chapters discuss highly contested issues that cry out for fresh perspectives if there is to be any resolution to them. Some of the chapters have enjoyed previous iterations (in the South African Journal of Science and elsewhere) and they can be read as standing alone, as they do not flow into one another as an integrated narrative. It is the introduction and the Coda that tie them together. In summarising the book, the Coda, in particular, makes interesting connections that demand attention and careful thought if South Africa and South Africans are to fare well in a time of global change. The ideas that permeate Rock | Water | Life may be helpful in charting any way forward but the author refrains from giving any blueprint or from offering comparison with other former colonised countries. The major thrust of the book is that there are different ways of knowing, each demanding respect for the insight into the issue that the others can provide. These diverse pathways to knowing – if acknowledged and understood – may create fresh concepts that advance understanding, although synthesis may well never be accomplished. Perhaps it should not be sought, the author asserts, but rath
{"title":"Rock | water | life: ecology and humanities for a decolonial South Africa","authors":"J. Carruthers","doi":"10.1080/0035919X.2021.1938283","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1938283","url":null,"abstract":"Author Lesley Green is an Associate Professor of Social Anthropology and founding Director of Environmental Humanities South at the University of Cape Town. Her major over-arching project is to bring together disparate fields and to create an integrative and interdisciplinary network that interrogates and explores the variety of knowledges about our contemporary environment. Environmental justice, or eco-justice, lies at the heart of her work. Green is well published in her field, and her publications are concerned not only with southern Africa but, with David Green, she has also written about Amerindian, as well as Amazonian indigenous knowledge in Brazil. This book, written in the voice of the engaged-researcher, in the first person and with many autobiographical inclusions – “she cannot accept the comfort of academic distancing” (Foreword by Isabelle Stengers, p. xiii) – contains interesting ideas and stories that readers who have an interest in the “environment” in its broadest sense need to consider in our current era and in this particular moment in South Africa. The book is divided into three parts, each comprising two chapters – the arrangement is explained on pp. 17–19. In Part 1, “Pasts Present”, Chapter 1 (Rock) engages with geology, water supply, and the city of Cape Town and Chapter 2 (Water) with fracking in the karoo. Part II, “Present Futures” contains Chapter 3 (Life) that explores knowledge of Namaqua plant medicine and Chapter 4 (Rock), access to and use of land. Part III, “Futures Imperfect”, includes Chapter 5 (Life) baboon management and Chapter 6 (Water) marine resource and sewage disposal in the city of Cape Town and its surroundings. There is an Introduction, entitled “Different Questions, Different Answers” and a “Coda: Composing Ecopolitics”. All the chapters discuss highly contested issues that cry out for fresh perspectives if there is to be any resolution to them. Some of the chapters have enjoyed previous iterations (in the South African Journal of Science and elsewhere) and they can be read as standing alone, as they do not flow into one another as an integrated narrative. It is the introduction and the Coda that tie them together. In summarising the book, the Coda, in particular, makes interesting connections that demand attention and careful thought if South Africa and South Africans are to fare well in a time of global change. The ideas that permeate Rock | Water | Life may be helpful in charting any way forward but the author refrains from giving any blueprint or from offering comparison with other former colonised countries. The major thrust of the book is that there are different ways of knowing, each demanding respect for the insight into the issue that the others can provide. These diverse pathways to knowing – if acknowledged and understood – may create fresh concepts that advance understanding, although synthesis may well never be accomplished. Perhaps it should not be sought, the author asserts, but rath","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"307 - 308"},"PeriodicalIF":0.0,"publicationDate":"2021-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/0035919X.2021.1938283","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42531848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-04DOI: 10.1080/0035919X.2021.1902878
A. Famuyiwa, S. Ande, A. Adeboye, O. Kehinde, Nasirudeen Sulaiman, Oyindamola Otaniyi, Abayomi G. Taiwo
Rapid developments in industrialisation and urbanisation have resulted in serious environmental pollution. It is therefore imperative to evaluate contamination levels, sources, and ecological and human health risks of potentially toxic elements (PTEs) in soils. This work examined the degree of PTE pollution in soils collected from Ikorodu Industrial Layout in Lagos, Nigeria. Concentrations of PTEs were determined by digesting the soil samples with aqua regia and analysing them using an atomic absorption spectrophotometer (ICE 3000 series). The results showed that the majority of the PTEs analysed did not exceed the guideline values, but Zn was enriched at about 27% of the sampling locations. The enrichment and contamination factor computations revealed Zn and Ni as the highest and lowest contaminants, respectively. Pollution assessment tools employed Enrichment factor and Contamination factor (EF and CF) showed a similar PTE pattern (in descending order): Zn > Pb > Cd > Cu > Fe > Mn > Ni. Ecological risk assessment revealed that about 70% of sampling locations had significant potential ecological risks. Correlation and hierarchical clustering identified geogenic, anthropogenic and mixed contributions to soil PTE load. Hazard index indicators for children and adults wer less than 1, which suggests there was no potential for significant toxicity risks. Carcinogenic risks were estimated for Cd, Ni and Pb and results were within acceptable risk levels, but children are more vulnerable to cancer and non-cancer risks than adults.
工业化和城市化的快速发展造成了严重的环境污染。因此，必须评估土壤中潜在有毒元素(pte)的污染水平、来源以及生态和人类健康风险。这项工作检查了从尼日利亚拉各斯的Ikorodu工业布局收集的土壤中PTE污染的程度。用王水消化土壤样品，用ICE 3000系列原子吸收分光光度计测定pte的浓度。结果表明，分析的大部分pte未超过指标值，但约27%的采样点Zn富集。富集和污染因子计算表明，Zn和Ni分别是最高和最低的污染物。采用富集因子和污染因子(EF和CF)的污染评价工具显示出相似的PTE模式(由高到低):Zn > Pb > Cd > Cu > Fe > Mn > Ni。生态风险评价显示，约70%的采样地点存在显著的潜在生态风险。相关分析和层次聚类分析确定了地质、人为和混合因素对土壤PTE负荷的影响。对儿童和成人的危害指数均小于1，说明不存在显著的潜在毒性风险。对镉、镍和铅的致癌风险进行了估计，结果在可接受的风险水平范围内，但儿童比成人更容易患癌症和非癌症。
{"title":"Pollution characterisation, ecological and human health risks assessment of potentially toxic elements in soils of Ikorodu industrial area of Lagos, Southwestern, Nigeria","authors":"A. Famuyiwa, S. Ande, A. Adeboye, O. Kehinde, Nasirudeen Sulaiman, Oyindamola Otaniyi, Abayomi G. Taiwo","doi":"10.1080/0035919X.2021.1902878","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1902878","url":null,"abstract":"Rapid developments in industrialisation and urbanisation have resulted in serious environmental pollution. It is therefore imperative to evaluate contamination levels, sources, and ecological and human health risks of potentially toxic elements (PTEs) in soils. This work examined the degree of PTE pollution in soils collected from Ikorodu Industrial Layout in Lagos, Nigeria. Concentrations of PTEs were determined by digesting the soil samples with aqua regia and analysing them using an atomic absorption spectrophotometer (ICE 3000 series). The results showed that the majority of the PTEs analysed did not exceed the guideline values, but Zn was enriched at about 27% of the sampling locations. The enrichment and contamination factor computations revealed Zn and Ni as the highest and lowest contaminants, respectively. Pollution assessment tools employed Enrichment factor and Contamination factor (EF and CF) showed a similar PTE pattern (in descending order): Zn > Pb > Cd > Cu > Fe > Mn > Ni. Ecological risk assessment revealed that about 70% of sampling locations had significant potential ecological risks. Correlation and hierarchical clustering identified geogenic, anthropogenic and mixed contributions to soil PTE load. Hazard index indicators for children and adults wer less than 1, which suggests there was no potential for significant toxicity risks. Carcinogenic risks were estimated for Cd, Ni and Pb and results were within acceptable risk levels, but children are more vulnerable to cancer and non-cancer risks than adults.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"189 - 199"},"PeriodicalIF":0.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43540479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-04DOI: 10.1080/0035919X.2021.1966550
D. V. van Niekerk, M. Oosthuizen, F. du Toit, J. Snoep
During its asexual growth, Plasmodium falciparum undergoes a number of 48 h intra-erythrocytic cycles, punctuated by reinvasion events. The biomass formation dynamics can be described by three key parameters: the period of the growth cycle (for P. falciparum, typically 48 h), the merozoite release number (variable between 8 and 32), and the reinvasion efficiency (variable between 20 and 40% in cell cultures). An accurate estimation of these parameters is important to describe growth dynamics, and for evaluating working mechanisms of anti-malaria drugs. Standard techniques for the estimation of merozoite release number and reinvasion efficiency are based on interpretation of microscope images, typically involve fairly low numbers of observations and are laborious. Here, we employ a combined experimental and mathematical modelling approach that is based on metabolic end-product formation and parasitaemia dynamics, to quantify the key parameters for Plasmodium biomass formation in cell cultures in vitro. We present experimental data for Plasmodium falciparum, together with a mechanistic model for the mathematical analysis, and finally an easy-to-use method for a direct analysis of the experimental data. The results are in agreement with previously published results, but – importantly – are average values for all cells in the culture, i.e. based on a large number of cells, and are reproducible between independent experiments.
{"title":"Estimating merozoite release number and reinvasion efficiency in Plasmodium falciparum cell culture","authors":"D. V. van Niekerk, M. Oosthuizen, F. du Toit, J. Snoep","doi":"10.1080/0035919X.2021.1966550","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1966550","url":null,"abstract":"During its asexual growth, Plasmodium falciparum undergoes a number of 48 h intra-erythrocytic cycles, punctuated by reinvasion events. The biomass formation dynamics can be described by three key parameters: the period of the growth cycle (for P. falciparum, typically 48 h), the merozoite release number (variable between 8 and 32), and the reinvasion efficiency (variable between 20 and 40% in cell cultures). An accurate estimation of these parameters is important to describe growth dynamics, and for evaluating working mechanisms of anti-malaria drugs. Standard techniques for the estimation of merozoite release number and reinvasion efficiency are based on interpretation of microscope images, typically involve fairly low numbers of observations and are laborious. Here, we employ a combined experimental and mathematical modelling approach that is based on metabolic end-product formation and parasitaemia dynamics, to quantify the key parameters for Plasmodium biomass formation in cell cultures in vitro. We present experimental data for Plasmodium falciparum, together with a mechanistic model for the mathematical analysis, and finally an easy-to-use method for a direct analysis of the experimental data. The results are in agreement with previously published results, but – importantly – are average values for all cells in the culture, i.e. based on a large number of cells, and are reproducible between independent experiments.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"147 - 155"},"PeriodicalIF":0.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41746486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-04DOI: 10.1080/0035919X.2021.1900950
A. B. Mapossa, M. Sibanda, D. Moyo, Taneshka Kruger, W. Focke, R. Androsch, R. Boldt, J. Wesley-Smith
Malaria remains a public health concern with vector control still the vital component of disease prevention, control, and elimination strategies. Recent years has seen a “stalling” in the progress made towards the reduction in the global malaria burden, highlighting the need to develop new, innovative, and safe alternative tools and delivery systems to achieve global malaria elimination. Interventions based on the use of indoor residual spraying (IRS) and long-life insecticidal bed nets (LLINs), i.e. insecticide-containing wall linings (IWLs), can contribute towards the reduction of malaria. Both LLINs and IWLs rely on the presence of insecticides on the fibre or filament surfaces. However, materials directly incorporating the insecticides into the polymer melt during extrusion, allows for effective killing of the mosquitoes when they come into contact with the surface of the material, only if there is insecticide present there. This means that the insecticide must migrate to the surface and precipitate there (bloom). Over time the internal concentration of insecticide will decay. This investigation was done using Fourier transform infrared spectroscopy (FTIR) in both the transmission and attenuated total reflection (ATR) modes to better understand the blooming of three World Health Organization-approved contact insecticides, i.e. alphacypermethrin, fipronil and chlorfenapyr, from mesh or film to better understand the likeliness of insecticides within the materials to migrate to the surface. Film-based samples were prepared in addition to wall lining mesh, because of their easier characterisation than the irregular shaped mesh filaments. FTIR, in ATR and in transmission modes, enabled the tracking of the migration of the three insecticides, over time to the surface of polyethylene mesh or film. This made it possible to estimate the apparent solubility of the insecticides in the polymer matrix. However, scanning electron microscopy (SEM) revealed that a portion of the insecticide is trapped, in a crystalline state, inside the polymer matrix. These results suggest the possibility of developing products-based insecticides for protection against infective mosquito bites in malaria-endemic regions.
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Pub Date : 2021-05-04DOI: 10.1080/0035919X.2021.1966551
J. Carruthers
{"title":"‘Africa forms the key’: Alex du Toit and the history of continental drift","authors":"J. Carruthers","doi":"10.1080/0035919X.2021.1966551","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1966551","url":null,"abstract":"","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"217 - 218"},"PeriodicalIF":0.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44797031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-04DOI: 10.1080/0035919X.2021.1964106
Charl Deacon
{"title":"Pollinators, predators & parasites","authors":"Charl Deacon","doi":"10.1080/0035919X.2021.1964106","DOIUrl":"https://doi.org/10.1080/0035919X.2021.1964106","url":null,"abstract":"","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"76 1","pages":"219 - 220"},"PeriodicalIF":0.0,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43664469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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