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131.
Scribano Vittorio Simakov Sergei K. Finocchiaro Claudio Correale Alessandra Scirè Salvatore 《Origins of life and evolution of the biosphere》2019,49(1-2):19-47
Origins of Life and Evolution of Biospheres - Pyrite and organic matter closely coexist in some hydrothermally-altered gabbroic xenoliths from the Hyblean Plateau, Sicily. The representative sample... 相似文献
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Elizabeth M. McDowell Richard F. Hoyt Jr. Sergei P. Sorokin 《Cell and tissue research》1994,275(1):143-156
The ontogeny of protein gene product 9.5 (PGP 9.5), serotonin (5–HT), calcitonin gene-related peptide (CGRP), and calcitonin (CT) immunoreactivity was evaluated in small-granule endocrine cells of hamster laryngotracheal epithelium from fetal day 11 to adulthood. Two centrifugal (proximal-to-distal) patterns of differentiation occur. The first pattern begins during fetal life. Endocrine cells, single and clustered in groups (presumptive- or protoneuroepithelial bodies, pNEBs), initially co-localize immunostaining for PGP 9.5, 5–HT, and CGRP in the larynx and proximal 2/3 of the trachea on day 12 and spread to the caudal trachea on day 13. 5–HT disappears fleetingly during the 24 h preceding birth; otherwise immunoreactivity for all three substances persists into adulthood. The clusters of endocrine cells survive beyond birth but are so diluted by expansion of the nonendocrine epithelium as to become inconspicuous. Since innervation was not actually observed, these clusters may persist as pNEBs, without developing connections to afferent or efferent nerve fibers. The second pattern concerns single small-granule cells stainable for CGRP but not for 5–HT. These cells first appear in the larynx and cartilaginous part of the cranial trachea on postnatal day 3, and in the middle and caudal trachea, on day 5. The cells increase in number on day 7. In adults, they predominate among endocrine cells of the cartilaginous region. A subset of these cells begins to co-express CT proximally on postnatal day 10, reaching the caudal end of the trachea by 3 weeks. A few elements of the older 5–HT-positive population may also become immunoreactive for CT in juvenile hamsters. 相似文献
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In August of 2021, several cysts with juveniles and eggs were discovered during a vegetation survey conducted at the Arlington National Cemetery, Virginia. Eight soil samples were collected from the rhizosphere region of the common grass (Festuca arundinacea L.) and processed at the Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL). Cysts were light to dark brown in color, and oval to pear-shaped without bullae in young cysts but present in older cysts and with prominent vulval cone. The juveniles had slightly concave stylet knobs projecting sometimes anteriorly, tail tapering gradually to a narrowly rounded terminus, and hyaline tail terminus conspicuous at least twice the length of stylet. The molecular analysis included the analysis of three gene sequence fragments: D2–D3 of 28S rRNA, ITS rRNA, and COI. The nematode species was identified by both morphological and molecular means as Stone''s cyst nematode, Punctodera stonei. Detection of P. stonei in Virginia represents a new record of this species in the United States, and a second report after Canada in North America. 相似文献
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Biological control has been attracting an increasing attention over the last two decades as an environmentally friendly alternative
to the more traditional chemical-based control. In this paper, we address robustness of the biological control strategy with
respect to fluctuations in the controlling species density. Specifically, we consider a pest being kept under control by its
predator. The predator response is assumed to be of Holling type III, which makes the system’s kinetics “excitable.” The system
is studied by means of mathematical modeling and extensive numerical simulations. We show that the system response to perturbations
in the predator density can be completely different in spatial and non-spatial systems. In the nonspatial system, an overcritical
perturbation of the population density results in a pest outbreak that will eventually decay with time, which can be regarded
as a success of the biological control strategy. However, in the spatial system, a similar perturbation can drive the system
into a self-sustained regime of spatiotemporal pattern formation with a high pest density, which is clearly a biological control
failure. We then identify the parameter range where the biological control can still be successful and describe the corresponding
regime of the system dynamics. Finally, we identify the main scenarios of the system response to the population density perturbations
and reveal the corresponding structure of the parameter space of the system.
A. Morozov is on leave from Shirshov Institute of Oceanology, Russian Academy of Science, Nakhimovsky Prosp. 36, Moscow 117218,
Russia. 相似文献
139.
Arabidopsis phosphatidylglycerophosphate synthase 1 is essential for chloroplast differentiation,but is dispensable for mitochondrial function 总被引:3,自引:0,他引:3
Babiychuk E Müller F Eubel H Braun HP Frentzen M Kushnir S 《The Plant journal : for cell and molecular biology》2003,33(5):899-909
Genetic dissection of the lipid bilayer composition provides essential in vivo evidence for the role of individual lipid species in membrane function. To understand the in vivo role of the anionic phospholipid, phosphatidylglycerol, the loss-of-function mutation was identified and characterized in the Arabidopsis thaliana gene coding for phosphatidylglycerophosphate synthase 1, PGP1. This mutation resulted in pigment-deficient plants of the xantha type in which the biogenesis of thylakoid membranes was severely compromised. The PGP1 gene coded for a precursor polypeptide that was targeted in vivo to both plastids and mitochondria. The activity of the plastidial PGP1 isoform was essential for the biosynthesis of phosphatidylglycerol in chloroplasts, whereas the mitochondrial PGP1 isoform was redundant for the accumulation of phosphatidylglycerol and its derivative cardiolipin in plant mitochondrial membranes. Together with findings in cyanobacteria, these data demonstrated that anionic phospholipids play an important, evolutionarily conserved role in the biogenesis and function of the photosynthetic machinery. In addition, mutant analysis suggested that in higher plants, mitochondria, unlike plastids, could import phosphatidylglycerol from the endoplasmic reticulum. 相似文献
140.
We consider a single-species model of population dynamics allowing for migrations and the Allee effect. Two types of migration are taken into account: one caused by environmental factors (e.g., a passive transport with the wind or water current) and the other associated with biological mechanisms. While the first type is apparently density-independent, the speed of migration in the second one can depend on the population density. Mathematically, this model consists of a non-linear partial differential equation of advection-diffusion-reaction type. Using an appropriate change of variables, we obtain an exact solution of the equation describing propagation of travelling population fronts. We show that, depending on parameter values and thus on the relative intensity of density-dependent and density-independent factors, the direction of the propagation can be different thus describing either species invasion or species retreat. 相似文献