Aspects of the structure and phenology of two fynbos communities

Data on the floristics, biomass, pattern, growth forms and regeneration modes of two tall, mid-dense, proteoid shrublands are analysed. The phenology of a number of species in different growth forms is examined in terms of current hypotheses about growth form related timing of shoot growth, and general patterns of periodicity in nutrient-poor mediterranean environments. Taxa typical of the fynbos flora are dominant in both communities, but the drier Cedarberg community has fewer species in these taxa and more annuals than the moister Kogelberg environment. These floristic changes are reflected also in the growth form spectra and the stratification of the communities. The biomass of the cedarberg community is higher at 1820 g/m2 against 1100 g/m2 for the Kogelberg community. This difference is discussed in terms of the greater effectiveness of the rainfall at the Cedarberg (664 mm/yr), than at the Kogelberg (1016 mm/yr), and the availability of soil nutrients. There are more sprouting plants, excluding annuals, in the flora of the Cedarberg site. This is in line with the prediction that, within limits, the drier the climate, the more reliable the investment in vegetative regrowth after fire. The similarity in community physiognomy is confirmed by the quantitative analyses which show that there are differences and also strong similarities between the communities. The overstorey Proteaceae grow from spring to mid-summer, as do the Restionaceae, but the other growth forms follow a variety of patterns, including opportunistic summer growth. The sequence of phenological events is partly related to morphological sequences in plant development and partly to resource partitioning. The current hypotheses concerning community structure and phenology in mediterranean environments cannot be refuted, but they do not account for the variations observed within and between growth forms and need to be critically examined

Assessment of the contribution of groundwater discharges to rivers using monthly flow statistics and flow seasonality

Groundwater discharge is believed to dominate dry season flows in perennial river systems and to sustain aquatic biodiversity. River flow statistics, extracted from the SPATSIM modelling system, were used to estimate the contribution of groundwater to river flow regimes. The flow statistics were compared for the principal aquifer types (based on major geological formations) in South Africa. This analysis focused on seasonal variation in flows rather than the annual totals or Baseflow Index. Groundwater discharge is expected to reduce flow variability and sustain flows, making flow concentrations lower than rainfall concentrations. Catchments dominated by carbonates have the greatest proportion of baseflow (37%), followed by basement complex (31%) and extrusive aquifer types (31%). The weak relationships between river flow indexes (particularly the Baseflow Index, Coefficient of Variation and Hydrological Index) and the seasonality or concentration statistics imply that catchment storage characteristics and other non-climatic factors play an important role in flow regulation. The geographic distribution of total flow concentrations differs markedly from rainfall concentrations, further evidence that non-climatic factors are important determinants of flow regimes. Karoo dykes and sills, extrusives and unconsolidated deposits are under-represented and the TMG sub-type, carbonates and basement complex and younger granites are over-represented among catchments with evenly distributed baseflows. The Baseflow Index and groundwater-fed baseflow are ecologically meaningful variables but lack clear thresholds that correspond with ecologically important changes in river flow regimes, for example perennial versus seasonal flow. Flow concentrations and percentage zero flows are useful and potentially ecologically important variables and should be tested as predictors of the aquatic and riparian biodiversity of river systems at a range of scales.Keywords: river flow statistics, baseflow, flow concentration, principal aquifer types, groundwater discharg

An approach to determining anthocyanin synthesis enzyme gene expression in an evolutionary context: an example from Erica plukenetii

Background and Aims: Floral colour in angiosperms can be controlled by variations in the expression of the genes of the anthocyanin pathway. Floral colour shifts influence pollinator specificity. Multiple shifts in floral colour occurred in the diversification of the genus Erica (Ericaceae), from plesiomorphic pink to, for example, red or white flowers. Variation in anthocyanin gene expression and its effects on floral colour in the red-, pink- and white-flowered Erica plukenetii species complex was investigated. Methods: Next generation sequencing, reverse transcriptase PCR and real-time reverse transcriptase quantitative PCR were used to quantify anthocyanin gene expression. Key Results: Non-homologous mutations causing loss of expression of single genes were found, indicating that the cause was likely to be mutations in transcription factor binding sites upstream of the 5′-untranslated region of the genes, and this was confirmed by sequencing. Conclusions: Independent evolution and subsequent loss of expression of anthocyanin genes may have influenced diversification in the E. plukenetii species complex. The approach developed here should find more general application in studies on the role of floral colour shifts in diversification.acceptedVersio

Alien plant invasions in South Africa: Driving forces and the human dimension

Invasive alien plants pose a substantial threat to the rich biodiversity of South Africa, and to the sustained delivery of a wide range of ecosystem services. Biological invasions are driven by human activities and mediated by culturally shaped values and ethics. This paper explores the human dimensions of alien plant invasions in South Africa. We consider four primary forces, those which directly influence the likelihood and rate of invasion — arrival of propagules; changes in disturbance regimes; changes in the availability of limiting factors; and fragmentation of the landscape — and the roles of 22 secondary driving forces in shaping the outcomes of the four primary driving forces. Human societies and their dynamics and activities are an integral part of each of the secondary driving forces. A map of the interactions between and among the primary and secondary driving forces shows how they are interlinked and influence each other — either positively or negatively, or switching between the two. There are two key points for intervention: prevention of the introduction of propagules of potentially invasive species and developing collaborative initiatives with enterprises that rely largely on alien species (for example, horticulture, agriculture and forestry, including community forestry) to minimize the introduction and use of potentially invasive species. An example of the first type of intervention would be to implement more effective inspection systems at international border and customs posts. This type of intervention can only be effective if those who are directly affected — whether businessmen, tourists or migrants — understand the requirement for these measures, and collaborate. The need to build public awareness of the critical importance of the human dimension of invasions emerges as a key theme from this analysis and is the basis for better-informed decisions, more effective control programmes and a reduction of further invasions

Hydroxyapatite nanoparticle injectable hydrogel scaffold to support osteogenic differentiation of human mesenchymal stem cells

Bone loss associated with degenerative disease and trauma is a clinical problem increasing with the aging population. Thus, effective bone augmentation strategies are required; however, many have the disadvantages that they require invasive surgery and often the addition of expensive growth factors to induce osteoblast differentiation. Here, we investigated a Laponite crosslinked, pNIPAMDMAc copolymer (L-pNIPAM-co-DMAc) hydrogel with hydroxyapatite nanoparticles (HAPna), which can be maintained as a liquid ex vivo, injected via narrowgauge needle into affected bone, followed by in situ gelation to deliver and induce osteogenic differentiation of human mesenchymal stem cells (hMSC). L-pNIPAMco-DMAc hydrogels were synthesised and HAPna added post polymerisation. Commercial hMSCs from one donor (Lonza) were incorporated in liquid hydrogel, the mixture solidified and cultured for up to 6 weeks. Viability of hMSCs was maintained within hydrogel constructs containing 0.5 mg/mL HAPna. SEM analysis demonstrated matrix deposition in cellular hydrogels which were absent in acellular controls. A significant increase in storage modulus (G’) was observed in cellular hydrogels with 0.5 mg/mL HAPna. Semi-quantitative immunohistochemistry and histological analysis demonstrated that bone differentiation markers and collagen deposition was induced within 48 h, with increased calcium deposition with time. The thermally triggered hydrogel system, described here, was sufficient without the need of additional growth factors or osteogenic media to induce osteogenic differentiation of commercial hMSCs. Preliminary data presented here will be expanded on multiple patient samples to ensure differentiation is seen in these samples. This system could potentially reduce treatment costs and simplify the tre

Mesenchymal stem cell therapies for intervertebral disc degeneration: consideration of the degenerate niche

We have previously reported a synthetic Laponite® crosslinked pNIPAM‐co‐DMAc (NPgel) hydrogel, which induces nucleus pulposus (NP) cell differentiation of human MSCs (hMSCs) without the need for additional growth factors. Furthermore NP gel supports integration following injection into the disc and restores mechanical function to the disc. However, translation of this treatment strategy into clinical application is dependent on the survival and differentiation of hMSC to the correct cell phenotype within the degenerate IVD. Here, we investigated the viability and differentiation of hMSCs within NP gel within a catabolic microenvironment. Human MSCs were encapsulated in NPgel and cultured for 4 weeks under hypoxia (5% O2) with ± calcium, IL‐1β and TNFα either individually or in combination to mimic the degenerate environment. Cell viability, and cellular phenotype was investigated. Stem cell viability was maintained within hydrogel systems for the 4 weeks investigated under all degenerate conditions. NP matrix markers: Agg and Col II and NP phenotypic markers: HIF‐1α, FOXF1 and PAX1 were expressed within the NPgel cultures and expression was not affected by culture within degenerate conditions. Alizarin red staining demonstrated increased calcium deposition under cultures containing CaCl2 indicating calcification of the matrix. Interestingly MMP's, ADAMTS 4 and Col I expression by hMSCs cultured in NPgel was upregulated by calcium but not by pro‐inflammatory cytokines IL‐1β and TNFα. Importantly IL‐1β and TNFα, regarded as key contributors to disc degeneration, were not shown to affect the NP cell differentiation of MSCs in the NPgel. In agreement with our previous findings, NPgel alone was sufficient to induce NP cell differentiation of MSCs, with expression of both aggrecan and collagen type II, under both standard and degenerate culture conditions; thus could provide a therapeutic option for the repair of the NP during IVD degeneration

Estimates of the impacts of invasive alien plants on water flows in South Africa

The adverse impacts of alien plant invasions on water flows have been a prime motivation for South Africa’s Working for Water Programme. The approach used in this study builds on a previous national assessment in 1998 by incorporating factors that limit plant water-use, information from recent research and improved flow reduction models. The total reduction in flows is estimated to be 1 444 million m3·yr−1 or 2.9% of the naturalised mean annual runoff (MAR), less than half of the 3 300 million m3·yr−1 estimated in 1998. Two main factors account for this difference: (a) a decrease in the estimated unit-area flow reduction to 970 m3·ha−1·yr−1 compared with 1 900 m3·ha−1·yr−1 estimated in 1998, largely due to the new model being based on more representative reduction factors; and (b) the updated estimate of the condensed invaded area of 1.50 million ha (previously 1.76 million ha), although the taxa mapped for this assessment only accounted for 1.00 million of the 1.76 million ha reported in 1998. Reductions due to invasions in Lesotho are estimated to be about 161 million m3·yr−1 and those in Swaziland about 193 million m3·yr−1. The taxon with the greatest estimated impact was wattles (Acacia mearnsii, A. dealbata, A. decurrens) with 34.0% of the total reductions, followed by Pinus species (19.3%) and Eucalyptus species (15.8%). The revised estimate is considered on the low side largely because the extent and impacts of riparian invasions have been underestimated. If the current estimates that 4–6% of Acacia mearnsii, Eucalyptus, Populus and Salix invasions are riparian, are adjusted to a more representative 20%, 50%, 80% and 80%, respectively, the total reductions increase by nearly 70% to ~2 444 million m3·yr−1. Producing these estimates involved a number of assumptions and extrapolations, and further research is needed to provide more robust estimates of the impacts.Keywords: plant water-use, flow reduction, mean annual runoff, riparian invasions, Working for Water Programm

Thermally Triggered Hydrogel Injection Into Bovine Intervertebral Disc Tissue Explants Induces Differentiation Of Mesenchymal Stem Cells And Restores Mechanical Function.

We previously reported a synthetic Laponite® crosslinked pNIPAM-co-DMAc (L-pNIPAM-co-DMAc) hydrogel which promotes differentiation of mesenchymal stem cells (MSCs) to nucleus pulposus (NP) cells without additional growth factors. The clinical success of this hydrogel is dependent on: integration with surrounding tissue; the capacity to restore mechanical function; as well as supporting the viability and differentiation of delivered MSCs. Bovine NP tissue explants were injected with media (control), human MSCs (hMSCs) alone, acellular L-pNIPAM-co-DMAc hydrogel or hMSCs incorporated within the L-pNIPAM-co-DMAc hydrogel and maintained at 5% O2 for 6 weeks. Viability of native NP cells and delivered MSCs was maintained. Furthermore hMSCs delivered via the L-pNIPAM-co-DMAc hydrogel differentiated and produced NP matrix components: aggrecan, collagen type II and chondroitin sulphate, with integration of the hydrogel with native NP tissue. In addition L-pNIPAM-co-DMAc hydrogel injected into collagenase digested bovine discs filled micro and macro fissures, were maintained within the disc during loading and restored IVD stiffness. The mechanical support of the L-pNIPAM-co-DMAc hydrogel, to restore disc height, could provide immediate symptomatic pain relief, whilst the delivery of MSCs over time regenerates the NP extracellular matrix; thus the L-pNIPAM-co-DMAc hydrogel could provide a combined cellular and mechanical repair approach

Cutibacterium acnes is present in non-herniated human discs; its positivity rate correlates with the patients age

Introduction: The presence of bacteria in the intervertebral discs (IVDs) and their role in disc degeneration is an area of controversy. Numerous studies have detected Cutibacterium acnes and other microbes with 16S DNA Sequencing and microbial cultures. However, those studies fail to determine whether the bacteria are in-vivo disc bacteria or perioperative contamination. Capoor et al. 1 performed confocal scanning laser microscopy for a limited number of herniated IVDs and detected C. acnes biofilms within the human specimens. Our study investigated the presence of Gram-positive bacteria C. acnes and Staphylococcus aureus in non-herniated human IVDs. Furthermore, expression of cellular recognition receptors Toll-like receptor (TLR) 2, TLR4 and NLR family pyrin domain containing 3 (NLRP3) and the pyroptosis marker Gasdermin D were investigated. Methods: Immunohistochemical staining for Gram-positive bacteria, S. aureus, C.acnes TLR2, TLR4, NLRP3 and Gasdermin D was performed on 75 non-herniated human IVD samples. Cell detection and classification was performed using QuPath. Fluorescently labelled S. aureus cells were co-cultured with human NP cells in monolayer across multiplicity of Infection (MOI) range (1:10- 1:100), and analysed by confocal imaging. Furthermore, human nucleus pulposus (NP) cells in monolayer were treated with Lipopolysaccharide (LPS) (5-50μg/ml) and Peptidoglycan (PGN) (5-50 μg/ml) for 48h, and cells in 3D alginate with PGN for up to 72h. Secretome analysis was performed using Luminex for cytokines, chemokines, matrix degrading enzymes and other secreted factors. Statistical analysis was performed using Kruskal-Wallis, Dunn’s multiple comparison test and Pearson correlation. Results Co-culture of S. aureus with NP cells showed internalisation of bacteria. Immunohistochemical staining demonstrated gram positive bacteria was solely detected within cells and not as biofilm within the tissue. The positivity rate of C. acnes ranged between 5-99%. The number of C.acnes positive cells showed a correlation with the age of the patients (r=0.41, p= 0.007). However, it did not correlate with grade of degeneration. The positivity rate of TLR2 ranged between 5-99% and TLR4 from 3-72%. TLR2 and TLR4 showed a strong correlation (r= 0.62, p= 1.5e-006). A significant decrease in TLR2 was observed in females showing a mid-degenerative grade compared to females showing no signs of degeneration. Investigation of the presence and the correlation between NLRP3, GasderminD, S. aureus and the above-mentioned factors is undergoing. Treatment of NP cells with LPS and PGN resulted in an increase of several catabolic cytokines such as IL-1, TNF, IL-6 and IFN-γ alongside increased production of chemokines, neurotrophic and angiogenic factors associated with IVD degeneration. Conclusion This study demonstrated the presence of Gram-positive bacteria such as C. acnes in non-herniated and cadaveric human disc samples. The internalisation of bacteria by human NP cells was demonstrated and aligns with previous publications. Furthermore, this shows a correlation between age and the presence of C. acnes as well as a strong correlation between the two TLRs. Moreover, bacterial cell membrane components triggered a catabolic response in human disc cells. Ongoing interaction studies between bacteria and NP cells will give us insight it to the potential role of bacteria in disc degeneration