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Recent Submissions

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    Serum levels of transforming growth factor Beta 1 in Systemic Lupus Erythematosus patients
    (MDPI, 2023-12) Gómez-Bernal, Fuensanta; Quevedo-Abeledo, Juan Carlos; García-González, María; Fernández-Cladera, Yolanda; González-Rivero, Agustín F.; de Vera-González , Antonia; Martín-González, Candelaria; González-Gay, Miguel Á.; Ferraz-Amaro, Iván
    Transforming growth factor beta (TGF-β) is a highly pleiotropic cytokine that has broad anti-inflammatory and immunosuppressive effects. In patients with systemic lupus erythematosus (SLE), the immunosuppressive effect of TGF-β1 is thought to be dysfunctional. In the present work, we aimed to study the relationship between the serum levels of TGF-β1 with the characteristics of the disease as well as with the patterns of activity, damage, or severity of the disease. Two hundred and eighty-four patients with well-characterized SLE were recruited. The serum levels of TGF-β1 were assessed. A multivariable linear regression analysis was performed to analyze the relation of disease characteristics to TGF-β1. The Katz severity index (beta coefficient 179 [95% confidence interval 7–350] pg/mL, p = 0.041) and SLEDAI activity index (beta coefficient 96 [95% CI 20–171] pg/mL, p = 0.014) were associated with higher serum levels of TGF-β1 after the multivariable analysis. When the disease-specific features were studied, ocular and cardiovascular manifestations were positively associated with serum TGF-β1 levels. In contrast, gastrointestinal and musculoskeletal involvements were associated with lower levels of circulating TGF-β1. Among patients with SLE, the serum levels of TGF-β1 were highly associated with disease-related manifestations.
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    Full characterization of the three pathways of the complement system in patients with systemic lupus erythematosus
    (Frontiers Media, 2023-04) Garc´ıa-Gonza´lez, Mar´ıa; Go´ mez-Bernal, Fuensanta; Quevedo-Abeledo, Juan C.; Ferna´ndez-Cladera, Yolanda; Gonza´lez-Rivero, Agust´ın F.; de Vera-Gonza´lez, Antonia; de la Rua-Figueroa, Iñigo; Lo´pez-Mejias, Raquel; D´ıaz-Gonza´lez, Federico; Gonza´lez-Gay, Miguel A.; Ferraz-Amaro, Ivan
    Background: To date a complete characterization of the components of the complement (C) pathways (CLassical, LEctin and ALternative) in patients with systemic lupus erythematosus (SLE) has not been performed. We aimed to assess the function of these three C cascades through functional assays and the measurement of individual C proteins. We then studied how they relate to clinical characteristics. Methods: New generation functional assays of the three pathways of the C system were assessed in 284 patients with SLE. Linear regression analysis was performed to study the relationship between the activity, severity, and damage of the disease and C system. Results: Lower values of the functional tests AL and LE were more frequent than those of the CL pathway. Clinical activity was not related to inferior values of C routes functional assays. The presence of increased DNA binding was negatively linked to all three C pathways and products, except for C1-inh and C3a which were positively related. Disease damage revealed a consistent positive, rather than a negative, relationship with pathways and C elements. Anti-ribosomes and anti-nucleosomes were the autoantibodies that showed a greater relationship with C activation, mainly due to the LE and CL pathways. Regarding antiphospholipid antibodies, the most related with C activation were IgG antib2GP, predominantly involving the AL pathway Conclusion: Not only the CL route, but also the AL and LE are related to SLE features. C expression patterns are linked to disease profiles. While accrual damage was associated with higher functional tests of C pathways, anti-DNA, anti-ribosomes and antinucleosomes antibodies, were the ones that showed a higher relationship with C activation, mainly due to the LE and CL pathways.
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    How energy and thermal landscapes influence habitat use in chacma baboons (Papio ursinus)
    (University of the Witwatersrand, Johannesburg, 2025-10) Botha, Katinka; Hetem, Robyn; McFarland, Richard
    Landscape heterogeneity drives chacma baboon movement, behaviour and habitat use. Here, baboons alter their responses to the changing environment to balance thermoregulation and resource acquisition. This study incorporated historical data from multiple habituated troops within the Swebeswebe Wildlife Estate, along with more current field data collected while following a troop of 69 individuals. Behavioural data were collected in 30-minute scan sampling intervals to assess activity budgets and shade use, while corresponding GPS data tracked movement. Climatic conditions were recorded through an onsite weather station along with miniglobe thermometers placed in representative microhabitats, including one carried while tracking the troop. Landscape features, and food and water availability were mapped to analyse how biotic and abiotic factors influenced troop movement, behaviour and habitat use. Baboons travelled further under high heat loads and low water availability. They, however, only expanded their home ranges, particularly along the main river system, during periods of water scarcity. In contrast to travel distance, the frequency of travel behaviour, as well as rest behaviour, increased with higher temperatures and water availability. As a result, a trade-off was observed in foraging behaviour, highlighting prioritisation between thermoregulation and energy acquisition with differing environmental drivers. Social behaviour decreased under higher water availability but, in contrast, increased with higher vegetation greenness. Vegetation greenness was a key driver to shade use, a behaviour critical for thermoregulation, particularly under higher heat loads. In line with thermoregulatory activity, baboons selected stable microclimates, preferring cooler, densely vegetated habitats, particularly during peak heat loads in the day and in the wet season. Baboon distribution shifted seasonally, with troops found closer to their main cave sleep site and rivers during the dry season and being found further away from fence lines. This indicated a more constrained spatial use pattern in times of resource scarcity. These findings highlight the flexible responses of baboons to thermal and resource landscapes. The understanding of these patterns is crucial for their conservation through the protection of heterogeneous landscapes, and a broader understanding of their ecological resilience in the face of worsening climate change.
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    The relationship between landscape functional patch type and soil ecotoxicity along a pollution gradient
    (University of the Witwatersrand, Johannesburg, 2025-10) Bisnath, Celine; Situngu, Sivu; Weiersbye, Isabel
    Anthropogenic stressors such as mining and smelting disrupt soil processes and degrade landscape functionality, creating long-term barriers to ecological rehabilitation. The Landscape Function Analysis (LFA) model is widely used to monitor landscape recovery. It works by delineating a fixed portion of the landscape into regions of resource accumulation (patches) and areas of resource loss (interpatches). Each region is then visually and physically assessed for its soil-surface attributes, which relate to indices of landscape function (stability, infiltration, and nutrient cycling). However, the LFA model is field-based, so it cannot directly capture landscape function in terms of chemical and ecotoxicological degradation, and these are integral aspects of ecosystem function. This study aimed to determine whether complementing soil physicochemical and ecotoxicological indicators with LFA metrics could improve the assessment of ecosystem function in contaminated environments. This research was conducted along a heavy metal pollution gradient at an area next to a smelter complex, using the Trigger–Transfer–Reserve–Pulse (TTRP) model as a conceptual foundation. Three complementary approaches were applied: (1) measuring soil properties and deriving LFA indices in patches and interpatches; (2) assessing the toxicity of soil leachates to the euryhaline cladoceran Daphnia magna (D. magna) and the marine bacterium Aliivibrio fischeri (A. fischeri); and (3) evaluating soil and leachate phytotoxicity using vascular plant bioassays. The results indicated significant variation in soil chemistry along the gradient, with decreasing organic matter (p = 0.003) under higher contamination. The correlations between the LFA indices and soil parameters were weak, indicating that surface indicators were insufficient to reflect subsurface chemical impairment. For toxicity to D. magna and A. fischeri, the results revealed significant toxicity in leachates from highly contaminated sites, with increased immobilisation of D. magna (p = 0.021) and inhibition of A. fischeri luminescence (p < 0.001) corresponding to higher concentrations of Cu, Zn, and Pb. Some leachates from areas with moderate LFA scores still exhibited strong toxicity, indicating that the visual surface condition may underestimate chemical stressors. The vascular plant bioassays revealed strong inhibition of germination (p < 0.05) and root growth (p < 0.05) in soils and leachates from highly contaminated areas, with root elongation being the most sensitive endpoint. These vascular plant patterns were consistent with aquatic bioassay results and correlated with elevated metal concentrations and electrical conductivity (r = 0.67 and r = 0.92, respectively). Differences between patch and interpatch soils diminished with increasing contamination. Collectively, these findings showed that heavy metal contamination and salinity decouple surface structure from subsurface processes, disrupting the TTRP feedback that maintains landscape resilience. This study proposes an expanded LFA framework for smelter contaminated sites, incorporating chemical and ecotoxicological diagnostics alongside traditional surface metrics. The integrated approach captures both visible and latent dimensions of ecosystem function, offering a more mechanistic and sensitive tool for monitoring rehabilitation and ecological recovery in degraded areas.
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    Development of new radiation hard materials with high secondary electron emission yield for the nuclear industry
    (University of the Witwatersrand, Johannesburg, 2025-09) Baldwin, Cameron Lance; Sideras-Haddad, Elias
    Photomultiplier tubes (PMTs) play a crucial role in various research fields, particularly in particle physics, where they serve as highly sensitive detectors for light. These experiments often occur in environments with extreme radiation levels, exposing PMT components to prolonged radiation damage that can degrade their performance over time. A critical element in the PMT structure is the dynode system, which facilitates signal amplification through the secondary electron yield (SEY) mechanism. SEY is fundamental to enhancing the initial photoelectron signal, making it essential to the detection process. Therefore, materials used for dynodes must not only exhibit a high SEY but also possess significant radiation hardness to ensure long-term stability and minimize frequent replacements. In this study, Aluminum Oxide (Al2O3) and Magnesium Oxide (MgO) were selected for evaluation based on their potential to meet these criteria. The materials were subjected to controlled gamma irradiation from a Co-60 source at varying doses. Theoretical Monte Carlo simulations were conducted to assess the radiation damage in terms of displacements per atom (DPA), while SEY measurements were performed post-irradiation to quantify the impact of the radiation exposure on the SEY of the Al2O3 and MgO samples. SEY measurements were conducted at the 6 MeV Tandem Accelerator at the iThemba Laboratory for Accelerator-Based Sciences (LABS) in Johannesburg. The existing microprobe setup was adapted to enable electronic measurements of SEY from MgO and Al2O3 samples across different radiation doses. These adaptations allowed for precise quantification of SEY variations as a function of absorbed gamma radiation dose. The results indicate a clear inverse relationship between radiation dose and SEY: as the radiation dose increases, SEY decreases. This degradation is attributed to ionizing events induced by gamma rays, leading to the formation of vacancies and interstitial defects within the material. These structural defects alter the electronic properties of the dynodes, ultimately reducing their amplification efficiency (SEY). This study provides valuable insights into the radiation tolerance of dynode materials and highlights the importance of selecting robust materials to enhance the longevity and reliability of PMTs in radiation harsh environments.