28 resultados para Homeostatic Epistemology
Resumo:
This paper is an examination of evidential holism, a prominent position in epistemology and the philosophy of science which claims that experiments only ever confirm or refute entire theories. The position is historically associated with W.V. Quine, and it is at once both popular and notorious, as well as being largely under-described. But even though there’s no univocal statement of what holism is or what it does, philosophers have nevertheless made substantial assumptions about its content and its truth. Moreover they have drawn controversial and important conclusions from these assumptions. In this paper I distinguish three types of evidential holism and argue that the most oft-cited and controversial thesis is entirely unmotivated. The other two theses are much overlooked, but are well-motivated and free from controversial implications.
Resumo:
Cytokines are important modulators of homeostatic processes such as development, haematopoiesis and host defence, A recently identified family of proteins, the supressors of cytokine signalling (SOCS) act as negative regulators of the key cytokine-activated signalling pathway, the Janus kinase/signal transducers and activators of transcription (JAK/STAT) cascade, In the current review, the discovery, structural features, regulation of expression, mechanisms of JAK/STAT inhibition and putative role in health and disease of the SOCS family are discussed.
Resumo:
In normal populations of the common grass Holcus lanatus there is a polymorphism for arsenate resistance, manifested as suppressed phosphate uptake (SPU), and controlled by a major gene with dominant expression. A natural population of SPU plants had greater arbuscular-mycorrhizal colonization than wild type, nonSPU plants. It was hypothesized that, in order to survive alongside plants with a normal rate of phosphate (P) uptake, SPU plants would be more dependent on mycorrhizal associations. We performed an experiment using plants with SPU phenotypes from both arsenate mine spoils and uncontaminated soils, as well as plants with a nonSPU phenotype. They were grown with and without a mycorrhizal inoculum and added N, which altered plant P requirements. We showed that grasses with SPU phenotypes accumulated more shoot P than nonSPU plants, the opposite of the expected result. SPY plants also produced considerably more flower panicles, and had greater shoot and root biomass. The persistence of SPU phenotypes in normal populations is not necessarily related to mycorrhizal colonization as there were no differences in percentage AM colonization between the phenotypes. Being mycorrhizal reduced flower biomass production, as mycorrhizal SPU plants had lower shoot P concentrations and produced fewer flower panicles than non-mycorrhizal, nonSPU plants. We now hypothesize that the SPU phenotype is brought about by a genotype that results in increased accumulation of P in shoots, and that suppression of the rate of uptake is a consequence of this high shoot P concentration, operating by means of a homeostatic feedback mechanism. We also postulate that increased flower production is linked to a high shoot P concentration. SPU plants thus allocate more resources into seed production, leading to a higher frequency of SPU genes. Increased reproductive allocation reduces vegetative allocation and may affect competitive ability and hence survival, explaining the maintenance of the polymorphism. As mycorrhizal SPU plants behave more like nonSPU plants, AM colonization itself could play a major part in the maintenance of the SPU polymorphism.
Resumo:
The eye and the brain are prototypical tissues manifesting immune privilege (IP) in which immune responses to foreign antigens, particularly alloantigens are suppressed, and even completely inhibited. Explanations for this phenomenon are numerous and mostly reflect our evolving understanding of the molecular and cellular processes underpinning immunological responses generally. IP is now viewed as a property of many tissues and the level of expression of IP varies not only with the tissue but with the nature of the foreign antigen and changes in the limited conditions under which privilege can operate as a mechanism of immunological tolerance. As a result, IP functions normally as a homeostatic mechanism preserving normal function in tissues, particularly those with highly specialized function and limited capacity for renewal such as the eye and brain. However, IP is relatively easily bypassed in the face of a sufficiently strong immunological response, and the privileged tissues may be at greater risk of collateral damage because its natural defenses are more easily breached than in a fully immunocompetent tissue which rapidly rejects foreign antigen and restores integrity. This two-edged sword cuts its swathe through the eye: under most circumstances, IP mechanisms such as blood-ocular barriers, intraocular immune modulators, induction of T regulatory cells, lack of lymphatics, and other properties maintain tissue integrity; however, when these are breached, various degrees of tissue damage occur from severe tissue destruction in retinal viral infections and other forms of uveoretinal inflammation, to less severe inflammatory responses in conditions such as macular degeneration. Conversely, ocular IP and tumor-related IP can combine to permit extensive tumor growth and increased risk of metastasis thus threatening the survival of the host.
Resumo:
Recent debates and controversies have highlighted several issues surrounding sociological research, which relate to the general conditions under which it is undertaken and how this is changing. There is a pressing need to respond to these issues as a whole, in particular by examining what they tell us about research practices. This article argues that a consideration of themes raised by the American television drama The Wire is useful for facilitating such a response, since it may be read as a discussion of working conditions within neoliberal societies. The following themes are pertinent here: the need to reflect upon the terms by which research is framed by funders, to take adequate time to conduct and complete research, and to encourage critical debate within research. Whilst these relate to influential epistemological discussions by Pierre Bourdieu and Michael Burawoy, this reading of The Wire is particularly helpful for highlighting the practical and inter-relational situations in which sociological research is carried out but which tend not to receive the systematic attention they deserve.
Resumo:
Macrophage function is not restricted to the innate and adaptive immune responses, but also includes host defence, wound healing, angiogenesis and homeostatic processes. Within the spectrum of macrophage activation there are two extremes: M1 classically activated macrophages which have a pro-inflammatory phenotype, and M2 alternatively activated macrophages which are pro-angiogenic and anti-inflammatory. An important property of macrophages is their plasticity to switch from one phenotype to the other and they can be defined in their polarisation state at any point between the two extremes. In order to determine what stage of activation macrophages are in, it is essential to profile various phenotypic markers for their identification. This review describes the angiogenic role for myeloid cells: circulating monocytes, Tie-2 expressing monocytes (TEMs), myeloid-derived suppressor cells (MDSCs), tumour associated macrophages (TAMs), and neutrophils. Each cell type is discussed by phenotype, roles within angiogenesis and possible targets as a cell therapy. In addition, we also refer to our own research on myeloid angiogenic cells (MACs), outlining their ability to induce angiogenesis and their similarities to alternatively activated M2 macrophages. MACs significantly contribute to vascular repair through paracrine mechanisms as they lack the capacity to differentiate into endothelial cells. Since MACs also retain plasticity, phenotypic changes can occur according to disease states and the surrounding microenvironment. This pro-angiogenic potential of MACs could be harnessed as a novel cellular therapy for the treatment of ischaemic diseases, such as diabetic retinopathy, hind limb ischaemia and myocardial infarction; however, caution needs to be taken when MACs are delivered into an inflammatory milieu.
Resumo:
This article is a response to Ray Pawson’s critique of critical realism, the philosophy of science elaborated by Roy Bhaskar. I argue with Pawson’s interpretation of critical realism’s positions on both natural and social science and his charges concerning its totalizing ontology, its arrogant epistemology and its naive methodology. The differences between critical realism and realist evaluation are not as significant as Pawson contends. The main differences between the two realisms lie in their approaches to the relationship between social structures and human agency, and between facts and values. I argue that evaluation scientists need to clearly distinguish structure and agency. They should also make their values explicit. The uncritical approach of realist evaluation, combined with its underplaying of the importance of agency, leaves it open to implication in the abuses of bureaucratic instrumentalism.
Resumo:
Cystic fibrosis (CF) lung disease is an inherited condition with an incidence rate of approximately 1 in 2500 new born babies. CF is characterized as chronic infection of the lung which leads to inflammation of the airway. Sputum from CF patients contains elevated levels of neutrophils and subsequently elevated levels of neutrophil serine proteases. In a healthy individual these proteases aid in the phagocytic process by degrading microbial peptides and are kept in homeostatic balance by cognate antiproteases. Due to the heavy neutrophil burden associated with CF the high concentration of neutrophil derived proteases overwhelms cognate antiproteases. The general effects of this protease/antiprotease imbalance are impaired mucus clearance, increased and self-perpetuating inflammation, and impaired immune responses and tissue. To restore this balance antiproteases have been suggested as potential therapeutics or therapeutic targets. As such a number of both endogenous and synthetic antiproteases have been trialed with mixed success as therapeutics for CF lung disease.
Resumo:
The unfolded protein response (UPR) is a homeostatic mechanism to maintain endoplasmic reticulum (ER) function. The UPR is activated by various physiological conditions as well as in disease states, such as cancer. As androgens regulate secretion and development of the normal prostate and drive prostate cancer (PCa) growth, they may affect UPR pathways. Here, we show that the canonical UPR pathways are directly and divergently regulated by androgens in PCa cells, through the androgen receptor (AR), which is critical for PCa survival. AR bound to gene regulatory sites and activated the IRE1α branch, but simultaneously inhibited PERK signaling. Inhibition of the IRE1α arm profoundly reduced PCa cell growth in vitro as well as tumor formation in preclinical models of PCa in vivo. Consistently, AR and UPR gene expression were correlated in human PCa, and spliced XBP-1 expression was significantly upregulated in cancer compared with normal prostate. These data establish a genetic switch orchestrated by AR that divergently regulates the UPR pathways and suggest that targeting IRE1α signaling may have therapeutic utility in PCa.
Resumo:
Over the past decade the concept of ‘resilience’ has been mobilised across an increasingly wide range of policy arenas. For example, it has featured prominently within recent discussions on the nature of warfare, the purpose of urban and regional planning, the effectiveness of development policies, the intent of welfare reform and the stability of the international financial system. The term’s origins can be traced back to the work of the ecologist Crawford S. Holling and his formulation of a science of complexity. This paper reflects on the origins of these ideas and their travels from the field of natural resource management, which it now dominates, to contemporary social practices and policy arenas. It reflects on the ways in which a lexicon of complex adaptive systems, grounded in an epistemology of limited knowledge and uncertain futures, seeks to displace ongoing ‘dependence’ on professionals by valorising self-reliance and responsibility as techniques to be applied by subjects in the making of the resilient self. In so doing, resilience is being mobilised to govern a wide range of threats and sources of uncertainty, from climate change, financial crises and terrorism, to the sustainability of development, the financing of welfare and providing for an aging population. As such, ‘resilience’ risks becoming a measure of its subjects’ ‘fitness’ to survive in what are pre-figured as natural, turbulent orders of things.