1,721,008 research outputs found
Tournaisian (early carboniferous) palynology of the West Mains Farm Borehole, UK
No full textAs part of the study of the tetrapod world in the Scottish Borders during the earliest Carboniferous, a fully cored 500 m science borehole was drilled through most of the Tournaisian Ballagan Formation. Both miospores and megaspores have been studied throughout the section and give new insight into the recovery of the terrestrial vegetation following the End Devonian Mass Extinction event. The persistent assemblage throughout the section is from the CM spore biozone, as typified by Schopfites claviger and Auroraspora macra. However, quantitative counts of the miospores shows that other spores became dominant and tell us much about how terrestrial vegetation was re-established. These spores include Anapiculatisporites delicatus (from the creeping lycopod Oxroadia) and Prolycospora claytonii that is presumed to come from an arborescent lycopod. These lycopods successively recolonised the Ballagan environment – a pattern that is mirrored in the megaspore distribution. The quantitative counts also reveal a changing pattern of Schopfites/Auroraspora that represent drier climatic conditions, whereas the lycopods support a progressively more humid environment. These changes in the dominant spore assemblage are also matched by a changing environment as shown by the distribution of key facies, such as different types of palaeosol and cementstones<br/
Post-extinction recovery of terrestrial vegetation following the End Devonian Mass Extinction: integrated palynological and palaeobotanical evidence from the Tournaisian (Early Carboniferous) of the UK
No full textAs part of an investigation into the earliest Carboniferous tetrapod world, palynomorphs have been studied from a fully cored 500 m science borehole (West Mains Farm) in the Scottish Borders. Together with an outcrop section at Burnmouth, these encompass most of the Tournaisian Ballagan Formation. Both miospores and megaspores have been examined throughout, with quantitative abundances of key spore taxa enabling a robust correlation between Burnmouth and the borehole. In total, some eight distinct assemblages can be recognised through a CONISS analysis of the data. These assemblages map onto the palaeosol types present and reveal an inter-connection, with changes in climate ultimately driving a succession of vegetation types. The immediate post-extinction pattern of recovery was a simple flora, followed by increasing spore diversity. The vegetation then became dominated by the creeping lycopod Oxroadia conferta (Anaplanisporites baccatus), including abundant megaspores (Setispora pannosa). This was replaced by an assemblage dominated by Prolycospora claytonii, which new evidence suggests had an affinity with the seed plants. The palaeosols indicate that this may represent a wetter interval with more permanent vegetation and, hence, increased landscape stability. Further upsection, Oxroadia returned in abundance but was succeeded by larger arborescent lycopods with established Stigmaria root systems. But these were not lepidodendroid lycopods as they appeared significantly below the inception of Lycospora. A considerable increase in the abundance of Spelaeotriletes crustatus towards the top of the section, reveals a further change in the dominant vegetation to the ?progymnosperms. Significantly, the eight-fold subdivision of the Tournaisian can now be mapped onto long Milankovitch cycles identified in shallow marine sections
Tournaisian (Early Carboniferous) recovery of terrestrial vegetation following the End Devonian Mass Extinction in the United Kingdom
No full textThe pulsed End Devonian Mass Extinction (EDME) affected marine biota initially, followed by terrestrial plant life at the Devonian–Carboniferous Boundary. To investigate the recovery of the early Carboniferous vegetation after the EDME, an interval associated with the evolution of the first terrestrial vertebrate animals (tetrapods), palynomorphs from the West Mains Farm, Norham (NWMF) borehole core of the Tournaisian Ballagan Formation were examined.Using the abundances of key spore taxa, we found that following the EDME, the depleted flora recovered to produce a stratified ecosystem with a diversity of plants. The initial simple (r-selected) survival flora was replaced by an increasingly complex (K-selected) recovery assemblage that diversified to produce a stepwise progression in the dominance of different plants. The first of these, the ground-creeping lycopod Oxroadia conferta (Anaplanisporites baccatus and Setispora pannosa), was adapted to form high-density populations in unstable conditions. It was replaced by a recovery assemblage dominated by a seed plant, represented by Genomosperma kidstoni (Prolycospora claytonii), which indicates the environment becoming more stable. The pteridosperm then declined and the fern Stauropteris burntislandica (Didymosporites scottii) became dominant. The return of O. conferta indicated a second phase of instability, until G. kidstoni once again became dominant. Additionally, the background flora of two pteridosperms, the shrubby Lyrasperma scotica (Colatisporites denticulatus) and the tree-sized Pitus primaeva (Colatisporites decorus), a sphenophyte Cheirostrobus pettycurensis (Retusotriletes incohatus) and the intermittent progymnosperm Protopitys scotica (Remysporites magnificus) indicate a diverse floral assemblage throughout this time.To investigate the driving forces behind the recovery of the Ballagan environment, we performed a CONISS analysis of 8 outgroup taxa and 4 taxa with recognised parent plant affinities. This produced distinctive natural assemblages which were grouped together to track palaeoclimatic changes through the Tournaisian. Applying the grouped clusters to the fluctuating abundance of Schopfites claviger, revealed a repeating pattern of drier and wetter climate intervals, which suggests periodicity.Adding the S. claviger climate information to the distribution of the borehole’s megaspores, studied for the first time from a continuous succession through the entire Ballagan Formation, also revealed their parent plants’ preference for a drier climate, except for S. pannosa which was more often present in the wetter phases. This indicates that O. conferta exhibited a broad climate tolerance alongside withstanding unstable substrates. Additionally, analyses of the abundant megaspores of O. conferta and S. burntislandica from a thin coal seam from the core showed that it represented an enclosed pool surrounded by a highly restricted, ground-level flora of lycopods and ferns in a stable, wetland community.The common presence of roots in the palaeosols of the borehole and of intermittent Stigmaria ficoides at outcrop, indicate the presence of large, arborescent lycopsids, likely Sigillaria, growing on substrates that were stable for long enough to support more architecturally complex plants. Palaeosols provide a direct record of changes in the climate and landscape and the diversity of the borehole palaeosols, with the presence of deep vertic cracks and gypsum and anhydrite deposits, indicate a dynamic floodplain with a strongly seasonal climate with repeated cycles of wetting and drying, becoming increasingly dry towards the end of the Tournaisian. These findings agreed with the palynomorph data and a comparison of the CONISS dendrograms for the palaeosols and the palynomorphs revealed a correlation. This showed, for the first time, that fossil soils and palynomorphs can be related directly and revealed a diverse assemblage of palaeosols supporting a diverse assemblage of plant life. Evidence from the NWMF borehole core has shown how the flora of the Ballagan environment recovered from the EDME. We found that both the soil formation and the plant distribution were driven by changes in the climate, which ultimately effected a succession of vegetation types within the Tournaisian
The Tournaisian recovery of terrestrial vegetation following the end Devonian mass extinction
No full textTo understand how terrestrial vegetation was impacted by and recovered from the End Devonian Mass Extinction, a quantitative record of Tournaisian plant spores has been acquired from a 500 m borehole through the Ballagan Formation and related outcrop sections in the Scottish Borders. This is part of the NERC TW:eed project – an integrated study of the earliest Carboniferous tetrapods and their world. The immediate post-extinction vegetation was simple and then progressively increased in diversity, including inceptions and the return of some Devonian plant groups. After this initial reestablishment, the creeping lycopod Oxroadia (Anaplanisporites baccatus with its abundant megaspore Lagenicula subpilosa) became dominant, forming dense thickets on the floodplain. These thickets were repeatedly interspersed, on the tens of meters scale, by Prolycospora claytonii-dominated assemblages. Although not known in situ, a strong association with fragments of Genomosperma kidstoni indicates a seed plant affinity. Additionally, a marked increase in abundance of Spelaeotriletes crustatus in the late Tournaisian suggests an increasing abundance of progymnosperms. Quantitative abundance of selected spores correlates with palaeosol distribution, highlighting repeated climatic fluctuations between wetter and drier episodes. CONISS analysis reveals eight distinct assemblages that can be mapped onto long Milankovitch cycles, identified in marginal marine sections
Post-extinction recovery of terrestrial vegetation following the End Devonian Mass Extinction: palynological evidence from the Tournaisian (early Carboniferous) of the UK
No full textAs part of an investigation into the earliest Carboniferous tetrapod world, palynomorphs have been studied from a fully cored 500 m science borehole (West Mains Farm) in the Scottish Borders. Together with an outcrop section at Burnmouth, these encompass most of the Tournaisian Ballagan Formation. Both miospores and megaspores have been examined throughout, however, it is only at Burnmouth that the lowest palynological zone (VI) is present. Quantitative abundances of key spore taxa enable a robust correlation between Burnmouth and the borehole. In total, some eight distinct assemblages can be recognised through a CONISS analysis of the data. These assemblages map onto the palaeosol types present and reveal an inter-connection, with changes in climate ultimately driving a succession of vegetation types. The immediate post-extinction pattern of recovery was a simple vegetation represented by the VI palynomorphs, followed by increasing spore diversity. The vegetation then became dominated by the creeping lycopod Oxroadia (Anaplanisporites baccatus), including abundant megaspores (Lagenicula subpilosa). This was then replaced by an assemblage dominated by Prolycospora claytonii, which, although its parent plant is currently unknown, it was not necessarily a lycopod. Palaeosol evidence indicates that this may represent a wetter interval with more permanent vegetation and, hence, increased landscape stability. Further upsection, Oxroadia returned in abundance but was succeeded by larger arborescent lycopods with established Stigmaria root systems. However, this predates the first occurrence of Lycospora pusilla. In these younger parts of the succession, there are a number of inceptions of distinctive spore types that will further permit palynological sub-division of the interval. This eight-fold subdivision of the Tournaisian can now be mapped onto long Milankovitch cycles identified in shallow marine sections
Megaspores of the West mains farm borehole, tournaisian, England
No full textFollowing the end Devonian Mass Extinction event, tetrapods seemed to disappear from the fossil record for a significant time interval (Romer's Gap). However, many have been discovered within intact ecosystems from a number of Tournaisian localities in Nova Scotia, Canada and in the Scottish Borders, UK. These tetrapods, and associated environments, are now being studied by the NERC funded TW:eed Project.The UK tetrapod sites are from a number of scattered localities in the poorly exposed Ballagan Formation. In an attempt to tie these localities together stratigraphically, the Ballagan Formation has been cored (501.33 m) in the West Mains Farm borehole at Norham, just inside the England border. This is a preliminary account of the megaspores from the borehole. Although megaspores are well known from a number of localities in the region, this is the first time they can be studied stratigraphically within a continuous section.After standard palynological processing, megaspores were hand-picked from the >150 μm fraction. The distribution of the megaspores through the Ballagan Formation shows that they occur in discrete zones that highlights an episodic return to a lycopod forested landscape. Abundant Didymosporites scottii megaspores together with rarer lycopods (Setosisporites sp.) support an environmental reconstruction of a low-level vegetation of the fern Stauropteris with higher, most distant lycopods
Antigen processing and immune regulation in the response to tumours
No full textThe MHC class I and II antigen processing and presentation pathways display peptides to circulating CD8+ cytotoxic and CD4+ helper T cells respectively to enable pathogens and transformed cells to be identified. Once detected, T cells become activated and either directly kill the infected / transformed cells (CD8+ cytotoxic T lymphocytes) or orchestrate the activation of the adaptive immune response (CD4+ T cells). The immune surveillance of transformed/tumour cells drives alteration of the antigen processing and presentation pathways to evade detection and hence the immune response. Evasion of the immune response is a significant event tumour development and considered one of the hallmarks of cancer. To avoid immune recognition, tumours employ a multitude of strategies with most resulting in a down-regulation of the MHC class I expression at the cell surface, significantly impairing the ability of CD8+ cytotoxic T lymphocytes to recognize the tumour. Alteration of the expression of key players in antigen processing not only affects MHC class I expression but also significantly alters the repertoire of peptides being presented. These modified peptide repertoires may serve to further reduce the presentation of tumour-specific/associated antigenic epitopes to aid immune evasion and tumour progression. Here we review the modifications to the antigen processing and presentation pathway in tumours and how it affects the anti-tumour immune response, considering the role of tumour-infiltrating cell populations and highlighting possible future therapeutic targets
The role of polymorphic ERAP1 in autoinflammatory disease
No full textAutoimmune and autoinflammatory conditions represent a group of disorders characterized by self-directed tissue damage due to aberrant changes in innate and adaptive immune responses. These disorders possess widely varying clinical phenotypes and etiology; however, they share a number of similarities in genetic associations and environmental influences. Whilst the pathogenic mechanisms of disease remain poorly understood, genome wide association studies (GWAS) have implicated a number of genetic loci that are shared between several autoimmune and autoinflammatory conditions. Association of particular HLA alleles with disease susceptibility represents one of the strongest genetic associations. Furthermore, recent GWAS findings reveal strong associations with single nucleotide polymorphisms in the endoplasmic reticulum aminopeptidase 1 (ERAP1) gene and susceptibility to a number of these HLA-associated conditions. ERAP1 plays a major role in regulating the repertoire of peptides presented on HLA class I alleles at the cell surface, with the presence of single nucleotide polymorphisms in ERAP1 having a significant impact on peptide processing function and the repertoire of peptides presented. The impact of this dysfunctional peptide generation on CD8+ T-cell responses has been proposed as a mechanism of pathogenesis diseases where HLA and ERAP1 are associated. More recently, studies have highlighted a role for ERAP1 in innate immune-mediated pathways involved in inflammatory responses. Here, we discuss the role of polymorphic ERAP1 in various immune cell functions, and in the context of autoimmune and autoinflammatory disease pathogenesis.</p
Vegetational recovery on an early carboniferous coastal plain following the end devonian mass extinction event
No full textFollowing the End Devonian Mass Extinction Event, tetrapods disappeared from the fossil record for a significant time interval (Romer’s Gap). However, many new specimens have been discovered within intact ecosystems from a number of Tournaisian localities in the Scottish Borders, UK. These tetrapods, and associated environments, are now being investigated by the NERC funded TW:eed project.The Scottish tetrapod sites are from a number of scattered localities in the poorly exposed Ballagan Formation. In an attempt to tie these localities together stratigraphically, the Ballagan Formation has been entirely cored to a depth of 501.33 m in the West Mains Farm borehole at Norham, which is just inside the England border. This is a preliminary account of the mio- and megaspores from the borehole. Although palynomorphs are well-known from a number of localities in the region, this is the first time they can be studied stratigraphically within a continuous section.After standard palynological processing, abundant miospore assemblages were identified which, as expected, belong to the CM biozone. Samples have been studied at 10 m intervals, and their distribution through the Ballagan Formation is not stable but indicates fluctuations in the diversity of the vegetation. The distribution of megaspores, hand-picked from the >150 μm fraction, shows that they occur in discrete zones. This highlights an episodic return to a lycopod forested landscape. Rare scolecodonts indicate marine flooding events and possibly reworked Devonian miospores suggest erosive periods of basin uplift
- …
