共查询到20条相似文献,搜索用时 46 毫秒
1.
Christopher D. Gregory John D. Pound 《Apoptosis : an international journal on programmed cell death》2010,15(9):1029-1049
The apoptosis program of physiological cell death elicits a range of non-phlogistic homeostatic mechanisms—“recognition, response and removal”—that regulate the microenvironments of normal and diseased tissues via multiple modalities operating over short and long distances. The molecular mechanisms mediate intercellular signaling through direct contact with neighboring cells, release of soluble factors and production of membrane-delimited fragments (apoptotic bodies, blebs and microparticles) that allow for interaction with host cells over long distances. These processes effect the selective recruitment of mononuclear phagocytes and the specific activation of both phagocytic and non-phagocytic cells. While much evidence is available concerning the mechanisms underlying the recognition and responses of phagocytes that culminate in the engulfment and removal of apoptotic cell bodies, relatively little is yet known about the non-phagocytic cellular responses to the apoptosis program. These responses regulate inflammatory and immune cell activation as well as cell fate decisions of proliferation, differentiation and death. Here, we review current knowledge of these processes, considering especially how apoptotic cells condition the microenvironments of normal and malignant tissues. We also discuss how apoptotic cells that persist in the absence of phagocytic clearance exert inhibitory effects over their viable neighbors, paying particular attention to the specific case of cell cultures and highlighting how new cell-corpse-clearance devices—Dead-Cert® Nanoparticles—can significantly improve the efficacy of cell cultures through effective removal of non-viable cells in the absence of phagocytes in vitro. 相似文献
2.
Numerous biological interactions, such as interactions between T cell receptors or antibodies with antigens, interactions
between enzymes and substrates, or interactions between predators and prey are often not strictly specific. In such less specific,
or “sloppy,” systems, referred to here as degenerate systems, a given unit of a diverse resource (antigens, enzymatic substrates,
prey) is at risk of being recognized and consumed by multiple consumers (lymphocytes, enzymes, predators). In this study,
we model generalized degenerate consumer-resource systems of Lotka–Volterra and Verhulst types. In the degenerate systems
of Lotka–Volterra, there is a continuum of types of consumer and resource based on variation of a single trait (characteristic,
or preference). The consumers experience competition for a continuum of resource types. This non-local interaction system
is modeled with partial differential-integral equations and shows spontaneous self-structuring of the consumer population
that depends on the degree of interaction degeneracy between resource and consumer, but does not mirror the distribution of
resource. We also show that the classical Verhulst (i.e. logistic) single population model can be generalized to a degenerate
model, which shows qualitative behavior similar to that in the degenerate Lotka–Volterra model. These results provide better
insight into the dynamics of selective systems in biology, suggesting that adaptation of degenerate repertoires is not a simple
“mirroring” of the environment by the “fittest” elements of population. 相似文献
3.
During normal kidney function, there are routinely wide swings in proximal tubule fluid flow and proportional changes in Na+ reabsorption across tubule epithelial cells. This “glomerulotubular balance” occurs in the absence of any substantial change
in cell volume, and is thus a challenge to coordinate luminal membrane solute entry with peritubular membrane solute exit.
In this work, linear optimal control theory is applied to generate a configuration of regulated transporters that could achieve
this result. A previously developed model of rat proximal tubule epithelium is linearized about a physiologic reference condition;
the approximate linear system is recast as a dynamical system; and a Riccati equation is solved to yield the optimal linear
feedback that stabilizes Na+ flux, cell volume, and cell pH. The first observation is that optimal feedback control is largely consigned to three physiologic
variables, cell volume, cell electrical potential, and lateral intercellular hydrostatic pressure. Parameter modulation by
cell volume stabilizes cell volume; parameter modulation by electrical potential or interspace pressure act to stabilize Na+ flux and cell pH. This feedback control is utilized in a tracking problem, in which reabsorptive Na+ flux varies over a factor of two, in order to represent a substantial excursion of glomerulotubular balance. The resulting
control parameters consist of two terms, an autonomous term and a feedback term, and both terms include transporters on both
luminal and peritubular cell membranes. Overall, the increase in Na+ flux is achieved with upregulation of luminal Na+/H+ exchange and Na+–glucose cotransport, with increased peritubular Na+–3HCO3− and K+–Cl− cotransport, and with increased Na+, K+–ATPase activity. The configuration of activated transporters emerges as a testable hypothesis of the molecular basis for
glomerulotubular balance. It is suggested that the autonomous control component at each cell membrane could represent the
cytoskeletal effects of luminal flow. 相似文献
4.
Albumin, the major circulating protein in blood, can undergo increased glycation in diabetes. One of the main properties of this plasma protein is its strong affinity to bind many therapeutic drugs, including warfarin and ketoprofen. In this study, we investigated whether or not there were any significant changes related to in vitro or in vivo glycation in the structural properties and the binding of human albumin to both therapeutic drugs. Structural parameters, including redox state and ketoamine contents of in vitro and in vivo glycated purified albumins, were investigated in parallel with their affinity for warfarin and ketoprofen. High-performance liquid chromatography was used to determine the free drug concentrations and dissociation constants according to the Scatchard method. An alternative method based on fluorescence spectroscopy was also used to assess drug-binding properties. Oxidation and glycation levels were found to be enhanced in albumin purified from diabetic patients or glycated with glucose or methylglyoxal, after determination of their ketoamine, free thiol, amino group and carbonyl contents. In parallel, significant impairments in the binding affinity of in vitro and in vivo glycated albumin, as indicated by the higher dissociation constant values and confirmed by higher free drug fractions, were observed. To a lesser extent, this alteration also significantly affected diabetic albumin affinity, indicated by a lower static quenching in fluorescence spectroscopy. This work provides useful information supporting in vivo diabetic albumin could be the best model of glycation for monitoring diabetic physiopathology and should be valuable to know if glycation of albumin could contribute to variability in drugs response during diabetes. 相似文献
5.
Serological identification and molecular characterization of B (A) 02 subtype
in patients and blood donors from Eastern China 下载免费PDF全文
Wen Wu Yecui Zhang Xingying Guo Peng Wu Zhibo Zhang Xiangyan Huang 《Asia-Pacific Journal of Blood Types and Genes》2017,1(1):55-59
This study was designed to identify the rare?type?ABO?blood?groups, B(A) 02, from Eastern China. Three samples with discordant serological results during routine blood type identification and four samples from one sample’ family were selected. All of them were detected by serological method. The exon 6 and 7 of the ABO genes were amplified by PCR and sequenced. They were typed as AsubB by serology and as BO by genotype. In AsubB samples, nt 700C>G mutation was detected in B gene, which was previously defined as B(A)02 alleles. In these seven samples, six showed B(A)02/O01 and one showed B(A)02/O02.B(A)02 allele was found to be more common in this study than B(A)04 which is considered to be more frequent than B(A)02. The careful identification of rare blood types is important for the safety of clinical blood transfusion. 相似文献
6.
7.
8.
It is a common medical folk-practice for parents to encourage their children to contract certain infectious diseases while
they are young. This folk-practice is controversial, in part, because it contradicts the long-term public health goal of minimizing
disease incidence. We study an epidemiological model of infectious disease in an age-structured population where virulence
is age-dependent and show that, in some cases, the optimal behavior will increase disease transmission. This provides a rigorous justification of the concept of “endemic stability,” and demonstrates that
folk-practices may have been historically justified. 相似文献
9.
10.
The analysis of data usage in a large set of real traces from a high-energy physics collaboration revealed the existence of
an emergent grouping of files that we coined “filecules”. This paper presents the benefits of using this file grouping for
prestaging data and compares it with previously proposed file grouping techniques along a range of performance metrics. Our
experiments with real workloads demonstrate that filecule grouping is a reliable and useful abstraction for data management
in science Grids; that preserving time locality for data prestaging is highly recommended; that job reordering with respect
to data availability has significant impact on throughput; and finally, that a relatively short history of traces is a good
predictor for filecule grouping. Our experimental results provide lessons for workload modeling and suggest design guidelines
for data management in data-intensive resource-sharing environments.
相似文献
Gabriele GarzoglioEmail: |
11.
12.
Alfonso Cuesta-Marcos Ernesto Igartua Francisco J. Ciudad Primitiva Codesal Joanne R. Russell José L. Molina-Cano Marian Moralejo Peter Szűcs María Pilar Gracia José M. Lasa Ana M. Casas 《Molecular breeding : new strategies in plant improvement》2008,21(4):455-471
Heading date is a key trait for the adaptation of barley to Mediterranean environments. We studied the genetic control of
flowering time under Northern Spanish (Mediterranean) conditions using a new population derived from the spring/winter cross
Beka/Mogador. A set of 120 doubled haploid lines was evaluated in the field, and under controlled temperature and photoperiod
conditions. Genotyping was carried out with 215 markers (RFLP, STS, RAPD, AFLP, SSR), including markers for vernalization
candidate genes, HvBM5 (Vrn-H1), HvZCCT (Vrn-H2), and HvT SNP22 (Ppd-H1). Four major QTL, and the interactions between them, accounted for most of the variation in both field (71–92%) and greenhouse
trials (55–86%). These were coincident with the location of the major genes for response to vernalization and short photoperiod
(Ppd-H2 on chromosome 1H). A major QTL, near the centromere of chromosome 2H was the most important under autumn sowing conditions.
Although it is detected under all conditions, its action seems not independent from environmental cues. An epistatic interaction
involving the two vernalization genes was detected when the plants were grown without vernalization and under long photoperiod.
The simultaneous presence of the winter Mogador allele at the two loci produced a marked delay in heading date, beyond a mere
additive effect. This interaction, combined with the effect of the gene responsive to short photoperiod, Ppd-H2, was found responsible of the phenomenon known as short-day vernalization, present in some of the lines of the population.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
Abstract The main objective of the current research was to study the reproductive behaviour of artificial triploid potato hybrids between wild Solanum commersonii and the cultivated potato Solanum tuberosum. When used in 3x × 2x crosses, triploids gave aneuploid progenies with somatic chromosome number ranging from 29 to 36. Fertilization fitness data suggested that the survival rate of gametes produced by the triploid parents may be related to their chromosome number. In addition, consistent with molecular data, our results indicated that fitness of gametes and chromosome number of progenies are influenced by the genome dosage of interspecific triploids. Since a main route to polyploidy formation is via 2n gametes and triploids, our study may contribute to a better understanding of polyploid plant reproduction, evolution and breeding. 相似文献
14.
Many populations live and disperse in advective media. A fundamental question, known as the “drift paradox” in stream ecology,
is how a closed population can survive when it is constantly being transported downstream by the flow. Recent population-level
models have focused on the role of diffusive movement in balancing the effects of advection, predicting critical conditions
for persistence. Here, we formulate an individual-based stochastic analog of the model described in (Lutscher et al., SIAM
Rev. 47(4):749–772, 2005) to quantify the effects of demographic stochasticity on persistence. Population dynamics are modeled as a logistic growth
process and dispersal as a position-jump process on a finite domain divided into patches. When there is no correlation in
the interpatch movement of residents, stochasticity simply smooths the persistence-extinction boundary. However, when individuals
disperse in “packets” from one patch to another and the flow field is memoryless on the timescale of packet transport, the
probability of persistence is greatly enhanced. The latter transport mechanism may be characteristic of larval dispersal in
the coastal ocean or wind-dispersed seed pods. 相似文献
15.
Selenoprotein W gene regulation by selenium in L8 cells 总被引:3,自引:0,他引:3
16.
Epidemic transmission is one of the critical density-dependent mechanisms that affect species viability and dynamics. In a
predator-prey system, epidemic transmission can strongly affect the success probability of hunting, especially for social
animals. Predators, therefore, will suffer from the positive density-dependence, i.e., Allee effect, due to epidemic transmission
in the population. The rate of species contacting the epidemic, especially for those endangered or invasive, has largely increased
due to the habitat destruction caused by anthropogenic disturbance. Using ordinary differential equations and cellular automata,
we here explored the epidemic transmission in a predator-prey system. Results show that a moderate Allee effect will destabilize
the dynamics, but it is not true for the extreme Allee effect (weak or strong). The predator-prey dynamics amazingly stabilize
by the extreme Allee effect. Predators suffer the most from the epidemic disease at moderate transmission probability. Counter-intuitively,
habitat destruction will benefit the control of the epidemic disease. The demographic stochasticity dramatically influences
the spatial distribution of the system. The spatial distribution changes from oil-bubble-like (due to local interaction) to
aggregated spatially scattered points (due to local interaction and demographic stochasticity). It indicates the possibility
of using human disturbance in habitat as a potential epidemic-control method in conservation. 相似文献
17.
Moira L. Steyn-Ross D. A. Steyn-Ross J. W. Sleigh M. T. Wilson 《Bulletin of mathematical biology》2011,73(2):398-416
When the brain is in its noncognitive “idling” state, functional MRI measurements reveal the activation of default cortical
networks whose activity is suppressed during cognitive processing. This default or background mode is characterized by ultra-slow
BOLD oscillations (∼0.05 Hz), signaling extremely slow cycling in cortical metabolic demand across distinct cortical regions.
Here we describe a model of the cortex which predicts that slow cycling of cortical activity can arise naturally as a result
of nonlinear interactions between temporal (Hopf) and spatial (Turing) instabilities. The Hopf instability is triggered by
delays in the inhibitory postsynaptic response, while the Turing instability is precipitated by increases in the strength
of the gap-junction coupling between interneurons. We comment on possible implications for slow dendritic computation and
information processing. 相似文献
18.
M Pines R Das SJ Ellis A Morin S Czerniecki L Yuan M Klose D Coombs G Tanentzapf 《Nature cell biology》2012,14(9):935-943
Regulated assembly and disassembly,?or?turnover,?of integrin-mediated cell-extracellular matrix?(ECM)?adhesions is essential for dynamic cell movements?and?long-term tissue maintenance. For example, in Drosophila,?misregulation of integrin turnover disrupts muscle-tendon?attachment at myotendinous junctions (MTJs). We demonstrate that?mechanical force, which modulates integrin activity, also regulates integrin and intracellular adhesion complex (IAC) turnover in vivo. Using conditional mutants to alter the tensile force on MTJs, we found that the proportion of IAC components undergoing turnover inversely correlated with the force applied on MTJs. This effect was disrupted by point mutations in β-integrin that interfere with ECM-induced conformational changes and activation of β-integrin or integrin-mediated cytoplasmic signalling. These mutants also disrupted integrin dynamics at MTJs during larval development. Together, these data suggest that specific β-integrin-mediated signals regulate adhesion turnover in response to tension during tissue?formation. We propose that integrin-ECM adhesive stability is continuously controlled by force in vivo through integrin-dependent auto-regulatory feedback mechanisms so that tissues can quickly adapt to and withstand mechanical stresses. 相似文献
19.
Based on a seven-year study of pollen production and release in two different natural populations of Cedrus deodara from Garhwal Himalaya, India, we determined that pollen output follows a two-year cycle. Pollen productivity determinations
considered various sources of variability, including the number of pollen strobili per branch, strobili per tree, microsporophylls
per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and population effects. Microsporangium
dehiscence took from 2.5 to 3.5 days. Maximum dehiscence was observed between 12:00 and 14:00 h, which coincides with diurnal
highest temperature and lowest relative humidity. Annual production of pollen per tree varied from averages of 4.7 × 109, 7.2 × 109 and 5.1 × 109 in years of low production, with alternate high years, producing 12.6 × 109, 14.1 × 109, 13.3 × 109 and 14.0 × 109 pollen grains per tree. Annual pollen production in individual trees of C. deodara ranged from 1.4 × 109 to 22.3 × 109. 相似文献
20.
Francisco Carvallo-Chaigneau Cristina Trejo-Solís Celedonio Gómez-Ruiz Ernesto Rodríguez-Aguilera Lucía Macías-Rosales Edith Cortés-Barberena Carlos Cedillo-Peláez Isabel Gracia-Mora Lena Ruiz-Azuara Vicente Madrid-Marina Fernando Constantino-Casas 《Biometals》2008,21(1):17-28
The aim of this study was to evaluate the in vitro and in vivo effects of the new chemotherapy agent Casiopeina III-ia [(4,4′-dimethyl-2,2′-bipiridine)(acetylacetonate)
Copper (II) nitrate] on HCT-15 (p53–/-) colon cellular line. In vitro, the drug reduced the viability and induced necrosis
and apoptosis in a dose dependent manner, without affecting cell cycle phases. Apoptosis was related to Bax increasing levels,
suggesting a caspase-dependent mechanism of death, as verified by nucleosomal fragmentation of DNA. In vivo, the antitumor activity of Casiopeina III-ia was tested in HCT-15
cells transplanted to nude mice. In this study we will show that the novel antineoplastic agent Casiopeina III-ia is active
on this colon tumor line, setting out as a good candidate for the treatment of colon tumors refractory to chemotherapy.
Lena Ruiz-Azuara - Previously as Lena Ruiz-Ramirez. 相似文献