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Opposite Phenomenon (opposite + phenomenon)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Of coiled oysters and big brains: how to rescue the terminology of heterochrony, now gone astray

EVOLUTION AND DEVELOPMENT, Issue 5 2000
Stephen Jay Gould
SUMMARY During the past decade, the terminology of heterochrony, heretofore consistent and workable, has become internally illogical and incoherent as the unfortunate result of an extension of terms, properly devised to describe shifts in developmental timing of shapes and features, to the rates and timings that cause these shifts. All the resulting, and extensive, confusion in the literature arises as a pure consequence of this error in logic and nomenclature, and not at all from disagreement about the important empirical questions described by this central concept and phenomenon in the integration of evolution and development. In particular, the claim that the same feature in human evolution (the paedomorphic shape of the human cranium) expresses either neoteny or the apparently opposite phenomenon of hypermorphosis only records the terminological error, and not any factual disagreement,for this neotenic feature has probably arisen by a prolongation of juvenile growth patterns inappropriately designated as "hypermorphosis of rate." I show that a prominent and unchallenged case of neoteny in fossil oysters arises by exactly the same evolutionary mode. When we restore the terminology of heterochrony by the "paedomorphic" intellectual event of dropping these inadaptive terminal accretions (the illogical extension of shape categories to describe rates), then the concept of heterochrony will again make proper distinctions by designating a clearly meaningful category of evolutionary changes originating by shifts in timing for features already present in ancestors. "It's not all heterochrony",and this particular statement of "less is more" represents heterochrony's strength as an interesting subset with definite meaning, rather than an illogical hodge-podge apparently applicable to all phenomena, and therefore explaining nothing. [source]

Functionalized Siloles: Versatile Synthesis, Aggregation-Induced Emission, and Sensory and Device Applications

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2009
Zhen Li
Abstract The synthesis of functionalized siloles has been a challenge because of the incompatibility of polar functional groups with the reactive intermediates in the conventional protocols for silole synthesis. In this work, a synthetic route for silole functionalization is elaborated, through which a series of functionalized siloles are successfully prepared. Whereas light emissions of traditional luminophores are often quenched by aggregation, most of the functionalized siloles show an exactly opposite phenomenon of aggregation-induced emission (AIE). The siloles are nonemissive when dissolved in their good solvents but become highly luminescent when aggregated in their poor solvents or in the solid state. Manipulation of the aggregation,deaggregation processes of the siloles enables them to play two seemly antagonistic roles and work as both excellent quenchers and efficient emitters. The AIE effect endows the siloles with multifaceted functionalities, including fluorescence quenching, pH sensing, explosive detection, and biological probing. The sensing processes are very sensitive (with detection limit down to 0.1,ppm) and highly selective (with capability of discriminating among different kinds of ions, explosives, proteins, DNAs, and RNAs). The siloles also serve as active layers in the fabrication of electroluminescent devices and as photosensitive films in the generation of fluorescence patterns. [source]

ORIGINAL ARTICLE: The Role of IL-6, IL-10, TNF-, and its Receptors TNFR1 and TNFR2 in the Local Regulatory System of Normal and Impaired Human Spermatogenesis

AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 1 2009
gorzata Bia
Problem, To investigate the expression of genes coding for selected cytokines with antagonistic functions (IL-6, IL-10, TNF-,) as well as TNF-, receptors (TNFR1 and TNFR2) in correct spermatogenesis (normal proliferation), maturation arrest (proliferation inhibited) and testicular tumors (overgrowth). Method of study, Transcription levels of genes coding for IL-6, IL-10, TNF-,, TNFR1 and TNFR2 were quantitatively examined using a real-time RT-PCR. Results, Significantly higher amounts of IL-6 mRNA were observed in testicular tumor samples than in normal spermatogenesis or in some syndromes with maturation arrest (MA at spermatid level or SCOS), while IL-10 gene levels were fairly stable. In homogenates with maturation arrest, the expression of TNFR1 gene was markedly higher than in testicular tumors, while the opposite phenomenon was found in respect to TNFR2 gene. Conclusion, The results obtained indicate that changes in activities of intra-testicular cytokines may promote different distinct pathologies such as testicular cancer or infertility. [source]

Effects of lipopolysaccharide on vascular reactivity and mortality in rats

AUTONOMIC & AUTACOID PHARMACOLOGY, Issue 5-6 2002
J. P. L. Nunes
Summary 1 The effects of intraperitoneal (i.p.) lipopolysaccharide on vascular reactivity to noradrenaline in rat aorta under different conditions of passive tension, as well as on mortality in normotensive and hypertensive rats, were studied. 2 Concentration,response curves to noradrenaline were obtained in aorta rings, at two levels of passive tension: 3 and 0.5 g, from control and lipopolysaccharide-treated Wistar rats. Contractile responses were expressed as percentage of the maximal response to noradrenaline obtained in the beginning of the experiment at a resting tension of 2 g. The maxima were significantly larger (P < 0.05) at 3 g than at 0.5 g in both groups of rats: 117.8 vs. 62.3%, respectively, for control animals; 85.8 vs. 32.5%, respectively, for lipopolysaccharide-treated rats. 3 The 24-h mortality after the i.p. administration of lipopolysaccharide was lower in spontaneously hypertensive rats (1/12; 8%), when compared with control Wistar,Kyoto rats (5/11; 45%). However, mortality was higher in Wistar,Kyoto made hypertensive by 8-day administration of corticosterone (6/6; 100%). 4 We conclude that a differential sensitivity to noradrenaline of aortic smooth muscle at two different levels of passive tension is still present in lipopolysaccharide-treated animals. Chronic hypertension in SHR rats is associated with resistance to the lethal effects of lipopolysaccharide, whereas abrupt-onset hypertension induced by corticosterone leads to an increased mortality. 5 These results are compatible with the myofibrillary hypothesis, which explains vascular hyper-reactivity in chronic arterial hypertension, by postulating that a more favourable relative position (and/or proportion) for actin and myosin occurs, whereas in states of vascular hypo-reactivity, such as vasodilatory shock, the opposite phenomenon may exist. [source]