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991.
992.
The incertae sedis Carpathoporella Dragastan, 1995, reported from the Lower Cretaceous of the Western Tethyan domain, is usually interpreted as remains of calcareous algae
(Dasycladales or Characeae). New thin-section material from the Aptian of Albania sheds light not only on its biogenic nature
but also on the morphological variability of this taxon. In fact, Carpathoporella represents the debris of colonial, bushy, most likely gorgonid octocorals with tuberculated spheroids that may be fused at
least near the basal root-like holdfast. Colony branching originates from longitudinally grooved calcareous branches or internodes.
Possible relationships to other Upper Cretaceous to Palaeogene genera are discussed and a revised critical inventory of Cretaceous
octocorals is presented. Due to the evidenced morphological features, Carpathoporella could either represent an ancestral isidid octocoral of the order Alcyonacea such as Moltkia Steenstrup or, due to the likely primary aragonitic skeletal mineralogy, a representative of Epiphaxum Lonsdale of the order Helioporacea. Due to morphological analogies, the new combination Carpathoporella elliotti (Radoičić) is proposed. In any case, the Lower Cretaceous record from Tethyan peri-reefal shallow-water carbonates is highlighted
since numerous skeletal findings of fossil gorgonid Octocorallia were so far only known from Upper Cretaceous and younger
strata of outer shelf environments of the boreal realm. The origin of deep-water Upper Cretaceous octocorals from Lower Cretaceous
shallow-water taxa such as Carpathoporella is proposed as a possible further example of onshore/offshore evolutionary pattern. 相似文献
993.
Plasmonic nanorods and their clusters are the fundamental units in plasmonic nanoantenna engineering. A theory that can predict the resonance of single nanorod already exists but is in lack for a heterodimer. Here, we propose a model combining the effective circuit theory for the response of spherical nanoparticles together with standard transmission line theory for hemispherically capped nanorod antennas. The resonances of multiple orders are predictable by defining the reflection phase at the terminals of such antennas, in both symmetric and asymmetric coupled nanorods. The theoretical results compare favorably with full-wave finite element numerical calculations. By the analytical formula, it is easy to control the length of the antennas for regulating the cooperative resonant properties and consequently the radiation characteristics of a nearby electric dipole. Consequently, we obtain both commensurate and incommensurate resonance features in such nanorod-based heterodimer antennas, showing respectively cumulative and selective responses from the individual nanorods. 相似文献
994.
RICHARD M. WEINSHILBOUM RICHARD KVETNANSKY JULIUS AXELROD IRWIN J. KOPIN 《Nature: New biology》1971,230(17):287-288
THE formation of the neurotransmitter noradrenaline from 3,4-dihydroxyphenylethylamine (dopamine) is catalysed by the enzyme dopamine-β-hydroxylase (DBH)1. This enzyme is associated both with the catecholamine-containing chromaffin granules in the adrenal medulla2,3 and with the vesicular structures in sympathetic nerve terminals which contain catecholamines4. Furthermore, DBH activity is released with catecholamines into the perfusate after stimulation of either the isolated perfused adrenal gland5 or the isolated perfused spleen6–8. DBH activity has been reported in the serum of both man and the rat9,10. This activity is similar to adrenal and sympathetic nerve DBH activity with regard to cofactor requirements, oxygen requirement and kinetic characteristics9,10. It has been suggested that serum DBH activity might be present as a result of release of enzyme with catecholamines from the adrenal glands and sympathetic nerves. If this is the case, serum DBH activity might be a useful and convenient index of sympathetic-adrenal activity. The work described here was undertaken to investigate both the source of the serum DBH and the effect on this activity of forced immobilization, a procedure which has been used as a model of stress and which has been shown to release catecholamines from the adrenal gland and increase catecholamine excretion11. 相似文献
995.
Protein is one of the three main storage chemical components in maize grains, and is negatively correlated with starch concentration
(SC). Our objective was to analyse the influence of genetic backgrounds on QTL detection for protein concentration (PC) and
to reveal the molecular genetic associations between PC and both SC and grain weight (GWP). Two hundred and eighty-four (Pop1)
and 265 (Pop2) F2:3 families were developed from two crosses between one high-oil maize inbred GY220 and two normal maize inbreds 8984 and 8622
respectively, and were genotyped with 185 and 173 pairs of SSR markers. PC, SC and GWP were evaluated under two environments.
Composite interval mapping (CIM) and multiple interval mapping (MIM) methods were used to detect single-trait QTL for PC,
and multiple-trait QTL for PC with both SC and GWP. No common QTL were shared between the two populations for their four and
one PC QTL. Common QTL with opposite signs of effects for PC and SC/GWP were detected on three marker intervals at bins 6.07–6.08,
8.03 and 8.03–8.04. Multiple-traits QTL mapping showed that tightly-linked QTL, pleiotropic QTL and QTL having effects with
opposite directions for PC and SC/GWP were all observed in Pop1, while all QTL reflected opposite effects in Pop2. 相似文献
996.
997.
Cells live in uncertain, dynamic environments and have many mechanisms for sensing and responding to changes in their surroundings. However, sudden fluctuations in the environment can be catastrophic to a population if it relies solely on sensory responses, which have a delay associated with them. Cells can reconcile these effects by using a tunable stochastic response, where in the absence of a stressor they create phenotypic diversity within an isogenic population, but use a deterministic response when stressors are sensed. Here, we develop a stochastic model of the multiple antibiotic resistance network of Escherichia coli and show that it can produce tunable stochastic pulses in the activator MarA. In particular, we show that a combination of interlinked positive and negative feedback loops plays an important role in setting the dynamics of the stochastic pulses. Negative feedback produces a pulsatile response that is tunable, while positive feedback serves to amplify the effect. Our simulations show that the uninduced native network is in a parameter regime that is of low cost to the cell (taxing resistance mechanisms are expressed infrequently) and also elevated noise strength (phenotypic variability is high). The stochastic pulsing can be tuned by MarA induction such that variability is decreased once stresses are sensed, avoiding the detrimental effects of noise when an optimal MarA concentration is needed. We further show that variability in the expression of MarA can act as a bet hedging mechanism, allowing for survival in time-varying stress environments, however this effect is tunable to allow for a fully induced, deterministic response in the presence of a stressor. 相似文献
998.
James P. Kehrer 《Cell biology and toxicology》2010,26(2):83-89
Survival and apoptosis signaling pathways are altered concomitantly in response to numerous endogenous and exogenous stressors.
The lipocalin family of small soluble proteins has been implicated in modulating apoptosis. However, the overall effect of
these proteins has been variable, showing both pro- and anti-apoptotic activities. The goal of this minireview is to summarize
the studies on lipocalins and apoptosis and consider what roles lipocalin-2 may play in cell death and survival. 相似文献
999.
Angiogenesis is the formation of new blood vessels from pre-existing vasculature. Pathologic angiogenesis in the eye can lead
to severe visual impairment. In our review, we discuss the roles of both pro-angiogenic and anti-angiogenic molecular players
in corneal angiogenesis, proliferative diabetic retinopathy, exudative macular degeneration and retinopathy of prematurity,
highlighting novel targets that have emerged over the past decade. 相似文献
1000.
Ian D. Stephen Miriam J. Law Smith Michael R. Stirrat David I. Perrett 《International journal of primatology》2009,30(6):845-857
Numerous researchers have examined the effects of skin condition, including texture and color, on the perception of health,
age, and attractiveness in human faces. They have focused on facial color distribution, homogeneity of pigmentation, or skin
quality. We here investigate the role of overall skin color in determining perceptions of health from faces by allowing participants
to manipulate the skin portions of color-calibrated Caucasian face photographs along CIELab color axes. To enhance healthy
appearance, participants increased skin redness (a*), providing additional support for previous findings that skin blood color enhances the healthy appearance of faces. Participants
also increased skin yellowness (b*) and lightness (L*), suggesting a role for high carotenoid and low melanin coloration in the healthy appearance of faces. The color preferences
described here resemble the red and yellow color cues to health displayed by many species of nonhuman animals. 相似文献