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Extracellular nucleotides affect pericyte-mediated regulation of rat in situ vasa recta diameter
Get PDFAim: We hypothesized that extracellular nucleotides, established as being released from renal tubular epithelial cells, act at pericytes to regulate vasa recta capillary diameter.
Methods: A rat live kidney slice model and video imaging techniques were used to investigate the effects of extracellular nucleotides on in situ (subsurface) vasa recta diameter at pericyte and non-pericyte sites. In addition, RT-qPCR was used to quantify P2 receptor mRNA expression in isolated vasa recta.
Results: Extracellular ATP, UTP, benzylbenzyl ATP (BzATP) or 2-methylthioATP (2meSATP) evoked a significantly greater vasoconstriction of subsurface vasa recta at pericytes than at non-pericyte sites. The rank order of agonist potency was BzATP = 2meSATP > ATP = UTP. The vasoconstriction evoked at pericyte sites by ATP was significantly attenuated by the P2 receptor antagonists suramin, pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS) or Reactive Blue-2 (RB-2). UTP-evoked vasoconstriction at pericytes was attenuated by suramin or RB-2 but not PPADS. Interestingly, suramin or PPADS, when applied in the absence of a P2 receptor agonist, evoked a weak but significant vasoconstriction of vasa recta at pericyte sites, suggesting tonic vasodilation by nucleotides. Significant levels of P2X(1, 3 and 7) and P2Y(4 and 6) receptor mRNA were detected in vasa recta.
Conclusion: Extracellular nucleotides act at pericytes to cause vasoconstriction of in situ vasa recta. Pharmacological characterization, supported by RT-qPCR data, suggests that P2X(1 and 7) and P2Y(4) receptors mediate nucleotide-evoked vasoconstriction of vasa recta by pericytes. We propose that nucleotides released from renal tubular epithelial cells, in close proximity to vasa recta capillaries, are key in regulating renal medullary blood flow
Food, drink and ritualised communication in the household of Eleanor de Montfort, February to August 1265
No full textThis article investigates the use of feasts and gifts of food in the household of Eleanor de Montfort between February and August 1265. In his influential The dangers of ritual, Philippe Buc argued, through a study of early medieval chronicles, that rituals in medieval Europe were regularly targets for disruption and aggressive manipulation either in practice or in the texts reporting the rituals. This article tests Buc's thesis against administrative records from thirteenth-century England. The evidence from Eleanor's household accounts is illuminated through a study of contemporary literary sources and didactic texts. It concludes that the administrative records indicate that rituals in practice were less habitually the subject of manipulation and conflict than the literary evidence indicates
Action
No full textPhilosophical study of human action owes its importance to concerns addressed in metaphysics and philosophy of mind about the status of reasoning beings who make their impact in the natural causal world, and concerns addressed in ethics and legal philosophy about human freedom and responsibility. This encyclopedia entry provides an overview of philosophical approaches to the nature of human action
'Barbara Hepworth: The Plasters'
Get PDFA review of *Barbara Hepworth, The Plasters: The gift to Wakefield* edited by Sophie Bowness
Structural realism: Continuity and its limits
Get PDFStructural realism comes in various shapes and sizes. First there is the epistemic kind which holds that at best we can have knowledge of the structure of the world. This comes in two main flavours: à la Ramsey (e.g. John Worrall and Elie Zahar 2001) claiming that the structure of the world is reflected in the Ramsey sentence of successful scientific theories and à la Russell (e.g. Ioannis Votsis 2005) claiming that we can infer certain things about the structure of the world from the structure of our perceptions. Then there is the ontic kind which also comes in a multitude of flavours, three of which stand out: (i) the ‘no objects view’ (e.g. James Ladyman 1998) according to which there exist no objects only structures, (ii) the ‘no individuals view’ (e.g. Steven French and Decio Krause 2006) which maintains that there exist no individuals but only structures and objects lacking individuality and (iii) the ‘no intrinsic
natures view’ (e.g. Ladyman 2007) which eliminates intrinsic natures in favour of haecceity-free individuals and structures. Finally, there is the methodological kind which concentrates on the role shared structure plays in characterising scientific theories, in relating high-level theory to low-level data, and in identifying links between predecessor and successor theories (see Katherine Brading and Elaine Landry 2006)
EU–Russia energy negotiations: a choice between rational self-interest and collective action
No full textMaking contact with observations
Get PDFJim Bogen and James Woodward’s ‘Saving the Phenomena’, published only 20
years ago, has become a modern classic. Their centrepiece idea is a distinction between data and phenomena. Data are typically the kind of things that are publicly observable or measurable like “bubble chamber photographs, patterns of discharge in electronic particle detectors and records of reaction times and error rates in various psychological experiments” (p. 306). Phenomena are “relatively stable and general features of the world which are potential objects of explanation and prediction by general theory” and are typically unobservable (Woodward 1989, p. 393). Examples of the latter category include “weak neutral currents, the decay of the proton, and chunking and recency effects in human memory” (Bogen and Woodward 1988, p. 306). Theories, in Bogen and Woodward’s view, are utilised to systematically explain and predict phenomena, not data (pp. 305–306). The relationship between theories and data is rather indirect. Data count as evidence for phenomena and the latter in turn count as evidence for theories. This view has been further elaborated in subsequent papers (Bogen and Woodward 1992, 2005; Woodward 1989) and is becoming increasingly influential (e.g., Basu 2003; Psillos 2004; Mauricio Su´arez 2005).
In this paper I argue contrary to Bogen and Woodward that data serve as evidence for theories, not only for phenomena. Bogen and Woodward seem to forget the old Duhemian dictum that ‘theories cannot be tested in isolation’. That is, they seem to forget that theories require the help of auxiliary hypotheses to make contact with data. When augmented with suitable auxiliaries, theories do entail, predict and potentially explain the data. I say ‘potentially explain the data’ because my focus in this paper is only on the inferential and predictive relations between theories, phenomena and data. To demonstrate my claim I examine four cases from physics, chemistry and astronomy: (i) a controversy between Lavoisier and Priestley, (ii) the calculation of lead’s melting point, (iii) the prediction of the Poisson spot, and (iv) the discovery of Neptune. The first of these is discussed in Basu (op. cit.) and the second in Bogen and Woodward (1988). The last two have not yet been discussed in the context of Bogen and Woodward’s work but they are widely discussed in confirmation theory as paradigmatic examples of novel predictions. The choice of cases reflects my desire to assess Bogen and Woodward’s view (1) under the best light by considering one of their principal examples as well as a meticulously discussed example from one of their devotees and (2) under the most stringent confirmation criteria by considering two exemplary cases of novel prediction
'Words of les jeunes'
Get PDFA review of *A Crisis of Brilliance: 5 Young British artists and the Great War* by David Boyd Haycock