Plato and Peirce on Likeness and Semblance

In his well-known essay, ??What Is a Sign???(CP 2.281, 285) Peirce uses ??likeness?? and ??resemblance?? interchangeably in his definition of icon. The synonymity of the two words has rarely, if ever, been questioned. Curiously, a locus classicus of the pair, at least in F. M. Cornford??s English translation, can be found in a late dialogue of Plato, namely, the Sophist. In this dialogue on the myth and truth of the sophists?? profession, the mysterious ??stranger??, who is most likely Socrates?? persona, makes the famous distinction between eikon (likeness) and phantasma (semblance) (236a,b). For all his broad knowledge in ancient philosophy, Peirce never mentioned this parallel; nor has any Peircean scholar identified it. There seems to be little problem with eikon as likeness, but phantasma may give rise to a puzzle which this paper will attempt to solve. Plato uses two pairs of words: what eikon is to phantasma is eikastikén (the making of likeness [235d]) to phantastikén (semblance making [236c]). In other words, icons come into being because of the act of icon-making, which is none other than indexicality. Witness what Peirce says about the relationship between photographs and the objects they represent: ??But this resemblance is due to the photographs having been produced under such circumstances that they were physically forced to correspond point by point to nature.?? (Ibid.) Thus the iconicity which links the representamen (sign) and its object is made possible not only by an interpretant, but also by idexisation. Their possible etymological and epistemological links aside, the Peircean example of photographing and the Platonic discussion of painting and sculpturing in the Sophist, clearly show the physio-pragmatic aspect of iconicity. The paper will therefore reread the Peircean iconicity by closely analysing this relatively obscure Platonic text, and by so doing restore to the text its hidden semiotic dimension.     

Nuclear envelope‐associated dynein drives prophase centrosome separation and enables Eg5‐independent bipolar spindle formation

The microtubule motor protein kinesin‐5 (Eg5) provides an outward force on centrosomes, which drives bipolar spindle assembly. Acute inhibition of Eg5 blocks centrosome separation and causes mitotic arrest in human cells, making Eg5 an attractive target for anti‐cancer therapy. Using in vitro directed evolution, we show that human cells treated with Eg5 inhibitors can rapidly acquire the ability to divide in the complete absence of Eg5 activity. We have used these Eg5‐independent cells to study alternative mechanisms of centrosome separation. We uncovered a pathway involving nuclear envelope (NE)‐associated dynein that drives centrosome separation in prophase. This NE‐dynein pathway is essential for bipolar spindle assembly in the absence of Eg5, but also functions in the presence of full Eg5 activity, where it pulls individual centrosomes along the NE and acts in concert with Eg5‐dependent outward pushing forces to coordinate prophase centrosome separation. Together, these results reveal how the forces are produced to drive prophase centrosome separation and identify a novel mechanism of resistance to kinesin‐5 inhibitors.     

A physiological analogy of the niche for projecting the potential distribution of plants

Aim  To develop a physiologically based model of the plant niche for use in species distribution modelling. Location  Europe. Methods  We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results  We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions  We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants.     

Short hairpin RNAs against eotaxin or interleukin‐5 decrease airway eosinophilia and hyper‐responsiveness in a murine model of asthma

Background

Eosinophilia plays the major role in the pathogenesis of asthma and correlates with the up‐regulation of eotaxin, which, together with interleukin (IL)‐5, is important for differentiation, chemo‐attraction, degranulation, and survival of eosinophils in local tissue. In a previous study, we found that administration of lentivirus‐delivered short hairpin RNA (shRNA) to suppress the expression of IL‐5 inhibited airway inflammation. The present study aimed to investigate the role of eotaxin shRNA and the synergistic effect of eotaxin and IL‐5 shRNAs on airway inflammation in an ovalbumin (OVA)‐induced murine model of asthma.

Methods

Lentivirus‐delivered shRNAs were used to suppress the expression of eotaxin and/or IL‐5 in local tissue in an OVA‐induced murine asthma model.

Results

Intra‐tracheal administration of lentivirus containing eotaxin shRNA expressing cassette (eoSEC3.3) efficiently moderated the characteristics of asthma, including airway hyper‐responsiveness, cellular infiltration of lung tissues, and eotaxin and IL‐5 levels in bronchio‐alveolar lavage fluid. Administration of lentiviruses expressing IL‐5 or eotaxin shRNAs (IL5SEC4 + eoSEC3.3) also moderated the symptoms of asthma in a mouse model.

Conclusions

Local delivery of lentiviruses expressing IL‐5 and eotaxin shRNAs provides a potential tool in moderating airway inflammation and also has the potential for developing clinical therapy based on the application of shRNAs of chemokines and cytokines involved in T helper 2 cell inflammation and eosinophilia. Copyright © 2008 John Wiley & Sons, Ltd.