Great theoretical value has always been attached toBoveri's discovery as regards chromatin diminution inAscaris, for this discovery appeared to expose the mechanism causing the propagative cells, in which all chromatin remains, to originate an entirely new organism, whereas the soma cells of which the chromosomes have been diminished are only capable of specific differentiation.Boveri was further able to show that, not only do the soma and propagative nuclei differ from each other, but that rather the character of the cell-plasma decides (...) whether the nucleus diminishes or not. Considerations are brought forward to prove that the “diminisher” hypothesis as given byKing andBeams, is untenable. Diminution has always been supposed to result in the loss of the totipotence of the diminished nuclei. In the light of recent chromosome research this course of events does not seem probable. Therefore the following theory is brought forward: When the egg ofAscaris is split, blastomeres originate, which differ from each other as to the plasma. In proportion to the quality of the surrounding plasma, now these now other genes of the totipotent nucleus react in different cells, thus originating the specific differentiation of the cell in question. This cooperation between plasma and nucleus is, however, at first obstructed in the large collective chromosomes ofAscaris, by the presence of their thickened ends. In order to keep up this cooperation a certain quality of plasma is needed, situated in a certain horizontal zone of the egg. As soon as, in the course of the division, nuclei come to rest in different zones, a diminution occurs, and differentiation of the cells in question sets in. Towards the end of the embryonic development the ends of the chromosomes are lost in the propagative cells, and also in these cells differentiation occurs.On a toujours attribué une haute signification théorique à la découverte deBoveri, de la diminution des chromatines chez l'ascaris puisqu'elle semblait expliquer le mécanisme qui cause que les cellules propagatrices où séjourne, la totalité de l'effectif des chromatines, font de nouveau sortir d'elles-mêmes un organisme entier, pendant que les cellules somatiques, dont les chromosomes ont été diminués, ne sont plus capables qu'à produire une différenciation spécifique. De plus,Boveri a pu démontrer, que les noyaux somatiques et propagateurs ne sont pas, à peu de chose près, différents, mais que c'est bien plus la qualité du plasme des cellules qui décide si les noyaux qui leur ont été distribués, diminuent ou non. Des arguments sont apportés, qui démontrent que l'hypothèse du „diminisher” échafaudée parKing etBeams est insoutenable. En général on s'est représenté. l'action de la diminution de telle façon que la totipotentialité des noyaux diminués a été perdue. Cependant, le fait n'est pas acceptable quand on le considère à la lumière de la recherche moderne sur les chromosomes. Par conséquent, nous proposons l'opinion suivante: Dans l'œuf de l'ascaris, des blastomères différant plasmatiquement les uns des autres prennent naissance pendant le fendage. Selon l'état du plasme environnant, dans les cellules individuelles on voit réagir certain gène, dans les autres un autre gène du noyau totipotentiel, causant ainsi la différenciation des cellules visées. Cette collaboration entre le plasme et le noyau est cependant premièrement bloquée dans les grands chromosomes collectifs de l'ascaris par la présence des bouts de chromosomes épaissis. Pour leur conservation une certaine qualité de plasme est requise qui se trouve dans une zone horizontale déterminée de l'œuf. Dès que, dans le procès du fendage, des noyaux arrivent dans d'autres zones du plasme, la diminution a lieu, et la différenciation des cellules visées s'opère. Cependant, après la conclusion du développement embryonal, les bouts des chromosomes se perdent dans les cellules propagatrices et la différenciation a lieu aussi dans ces cellules. (shrink)

Darwins bahnbrechendes Werk 'Über die Entstehung der Arten' (1859) löste eine neue Debatte aus, die weniger durch wissenschaftliche Forschung als durch weltanschauliche Proklamationen geprägt war. Sie nahm in Deutschland einen anderen Verlauf als in England: Die dort noch starke Physikotheologie war in Deutschland bereits einflußlos geworden, und der vorangegangene Materialismus-Streit hatte den Boden für die Rezeption der Lehre Darwins vorbereitet. Von Seiten des weltanschaulichen Materialismus wurde der Darwinismus wegen seiner Eliminierung eines zwecksetzenden göttlichen Verstandes als unverhoffte Bestätigung angesehen und als (...) eine neue und zudem wissenschaftlich abgesicherte "Schöpfungstheorie" rezipiert und zum Schlüssel für die Lösung aller wissenschaftlichen und philosophischen Rätsel stilisiert. (shrink)

The Rho GTPases—Rho, Rac and Cdc42—act as molecular switches, cycling between an active GTP‐bound state and an inactive GDP‐bound state, to regulate the actin cytoskeleton. It has recently become apparent that the Rho GTPases can be activated in subcellular zones that appear semi‐stable, yet are dynamically maintained. These Rho GTPase activity zones are associated with a variety of fundamental biological processes including symmetric and asymmetric cytokinesis and cellular wound repair. Here we review the basic features of Rho GTPase activity zones, (...) suggest that these zones represent a fundamental signaling mechanism, and discuss the implications of zone properties from the perspective of both their function and how they are likely to be controlled. BioEssays 28: 983–993, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Among recent developments in the anthropological sciences, hardly any have found so much attention and led to so much controversy as have the views advanced by the late Benjamin Whorf.The hypothesis offered by Whorf is,“that the commonly held belief that the cognitive processes of all human beings possess a common logical structure which operates prior to and independently of communication through language, is erroneous. It is Whorf's view that the linguistic patterns themselves determine what the individual perceives in this world (...) and how he thinks about it. Since these patterns vary widely, the modes of thinking and perceiving in groups utilizing different linguistic systems will result in basically different world views”.“We are thus introduced to a new principle of relativity which holds that all observers are not led by the same physical evidence to the same picture of the universe, unless their linguistic backgrounds are similar. … We cut up and organize the spread and flow of events as we do largely because, through our mother tongue, we are parties to an agreement to do so, not because nature itself is segmented in exactly that way for all to see”. (shrink)

Two studies document that people are more willing to express emotions that reveal vulnerabilities to partners when they perceive those partners to be more communally responsive to them. In Study 1, participants rated the communal strength they thought various partners felt toward them and their own willingness to express happiness, sadness and anxiety to each partner. Individuals who generally perceive high communal strength from their partners were also generally most willing to express emotion to partners. Independently, participants were more willing (...) to express emotion to particular partners whom they perceived felt more communal strength toward them. In Study 2, members of romantic couples independently reported their own felt communal strength toward one another, perceptions of their partners’ felt communal strength toward them, and willingness to express emotions to each other. The communal strength partners reported feeling toward the participants predicted the participants’ willingness to express emotion to those partners. This link was mediated by participants’ perceptions of the partner’s communal strength toward them which, itself, was a joint function of accurate perceptions of the communal strength partners had reported feeling toward them and projections of their own felt communal strength for their partners onto those partners. (shrink)

Chaque époque se caractériserait par des dispositifs rituels de rassemblement des publics qui reflètent une certaine configuration socio-politique : du rassemblement collectif de la tradition théâtrale au modèle individualisé de l’exposition dans le contexte moderne. Comment rassembler des publics face aux défis de notre siècle?

In children experiencing pain, the study of the social context of facial expressions might help to evaluate evolutionary and conditioning hypotheses of behavioural development. Social motivations and influences may be complex, as seen in studies of children having their ears pierced, and in studies of everyday pain in children. A study of opposing predictions of the long-term effects of parental caregiving is suggested.

The text of the tract De arcubus similibus was published for the first time by M. Curtze in 1887. However, after examining some more Latin manuscripts and the Arabic MS Oxford, Bodleian Library, Marsh 663 it appeared, that Curtze's edition was rather an adaptation. Also Curtze's suggestion that Jordanus Nemorarius was the author was very probably wrong. The author of the tract was the Egyptian mathematician Ahmed ibn Jusuf as appears from the Latin manuscripts, and its translator, very probably, Gerard (...) of Cremona. In the tract Ahmed tried to prove, that the assertion ‘similar arcs are also equal arcs’ was wrong . His starting points were the propositions Euclid III, 20 and 21. Consequently, the tract can be looked upon as a commentary on the third book of the Elements. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Caught Between History and ImaginationVico's Ingenium for a Rhetorical Renovation of CitizenshipAlessandra Beasley Von BurgCitizenship is usually thought of as synonymous with nationality and the rights and duties associated with the people who live, work, and participate politically, socially, and economically within the borders of their nation-state. In this conception, the main criterion used to decide who is and who is not a citizen is nationality. As the nature (...) of nation-state governance evolves and the acceleration of citizen mobility hastens interdependence, pressures for new definitions and paradigms of citizenship build. As Joseph Weiler argues, this pressure produces cognitive dissonance because "the traditional, classical vocabulary of citizenship is the vocabulary of the State, the Nation and Peoplehood" (qtd. in La Torre 1998, 1).1 The classical association of citizenship with nationality blocks our ability to grasp new, nonstatist conceptions of citizenship, even as postnational political visions take shape in institutions like the European Union (EU).2 In 1992, EU citizenship was established in the Treaty of Maastricht, which granted some additional rights to citizens of the member states in the same way that single nation-states grant their inhabitants special status as nationals, rights that are not nullified when citizens leave their home country to live and work in other member states.3 [End Page 26]The relationship between nationality and citizenship in the EU context is complicated by the fact that although Maastricht guidelines set postnational membership criteria for EU citizens, they also limit the scope of EU citizenship. In trying to reach beyond the nation while anchoring its very essence to the nation, EU citizenship remains limited as it relies on the traditional language of national membership to found its postnational concept of equality and inclusion for noncitizens. The contradictory elements of EU citizenship are exemplified in its current definition, which includes all member states' citizens and excludes millions who are living in Europe as third-country nationals (TCNs), defined as "any person who is not a citizen of one of the member states" of the EU but permanently and legally resides in one.4 The current debate over the status of legal, long-term TCNs challenges the relationship between citizenship and nationality, as advocates from EU institutions, national governments, nongovernmental organizations and academia argue that TCNs should be granted EU citizenship rather than be naturalized in the member states and push for a new, postnational mode of citizenship based on residency. Advocates for the inclusion of TCNs as EU citizens have to work with the limited vocabulary of national citizenship yet articulate a case for a new kind of citizenship divorced from nationality. They suggest that the EU should be viewed as a deliberative community, in which all long-term residents like TCNs are given an equal opportunity to practice citizenship. The deliberative community rationale is based on an idea of citizenship as performance with residents enacting citizenship by living together and deliberating with each other about common interests and concerns.5This reordering of the concept of community arising out of political practice calls for a full philosophical and rhetorical reimagining of the meaning of citizenship. The act of reimagining citizenship creates a new practice of citizenship and grounds citizenship in a philosophical context as well as a practical one. There is no better philosophical and rhetorical tradition to turn to for this purpose than that of Giambattista Vico. Vico, and to a larger extent the entire tradition of Italian humanism, has been overlooked in modern Western philosophy. Yet Vico embodies a seamless marriage of philosophy and rhetoric. Vico's philosophically grounded rhetoric provides the means in an investigation of EU citizenship as an innovative rhetorical practice beyond nationality, for understanding how new practices become persuasive through imaginative language, until citizens separate citizenship from nationality and accept residence and deliberative practices as legitimate criteria for citizenship. Vico argues that "every study method [End Page 27] may be said to be made up of three things: instruments, complementary aids, and aim envisaged" and notes that "the instruments presuppose and include a systematic, orderly manner of proceeding" (1990, 6). This essay proceeds in this fashion to reveal how a new vocabulary of citizenship... (shrink)

Mitochondrial dysfunction has long been considered a key mechanism in the ageing process but surprisingly little attention has been paid to the impact of mitochondrial number or density within cells. Recent reports suggest a positive association between mitochondrial density, energy homeostasis and longevity. However, mitochondrial number also determines the number of sites generating reactive oxygen species (ROS) and we suggest that the links between mitochondrial density and ageing are more complex, potentially acting in both directions. The idea that increased density, (...) especially when combined with mitochondrial dysfunction, might accelerate ageing is supported by a negative correlation between mitochondrial density and maximum longevity in an interspecies comparison in mammals, and by evidence for an intimate interconnection between cellular ROS levels, mitochondrial density and cellular ageing. Recent data suggest that retrograde response, which activates mitochondrial biogenesis, accompanies cellular ageing processes. We hypothesise that increased mitochondrial biogenesis, and possibly also impaired degradation and segregation of mitochondria, if occurring as adaptation to pre‐existing mitochondrial dysfunction, might aggravate ROS production and thus actively contribute to ageing. BioEssays 29:908–917, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

We examine the opportunities children have for interacting with others and the extent to which they are the focus of others’ visual attention in five societies where extended family communities are the norm. We compiled six video-recorded datasets collected by a team of anthropologists and psychologists conducting long-term research in each society. The six datasets include video observations of children among the Yasawas, Tanna, Tsimane, Huatasani, and Aka. Each dataset consists of a series of videos of children ranging in age (...) from 2 months to 12 years in their everyday contexts. We coded 998 videos and identified with whom children had opportunities to interact as well as the number of individuals and the proportion of observed time that children spent with these individuals. We also examined the proportion of time children received direct visual gaze. Our results indicate that children less than 5 years old spend the majority of their observed time in the presence of one female adult. This is the case across the five societies. In the three societies from which we have older children, we find a clear shift around 5 years of age, with children spending the majority of their time with other children. We also coded the presence or absence of a primary caregiver and found that caregivers remained within 2 ft of target children until 7 years of age. When they were in the company of a primary caregiver, children older than seven spent the majority of their time more than 2 ft from the caregiver. We found a consistent trend across societies with decreasing focal attention on the child with increasing child age. These findings show remarkable consistency across these societies in children’s interaction opportunities and that a developmental approach is needed to fully understand human development because the social context is dynamic across the lifespan. These data can serve as a springboard for future research examining social development in everyday contexts. (shrink)