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1.
Summary Intracellular free calcium ion concentrations ([Ca2+]i) in the anterior prestalk and posterior prespore cells of theDictyostelium discoideum slug were determined, using the highly selective Ca2+ indicators, quin-2/AM and fura-2/AM. Temporal changes in [Ca2+]i in response to chemotactic stimulation with cAMP were also monitored at the single-cell level and compared between the two types of cells. The results obtained showed that resting [Ca2+]i in the prestalk cells is considerably higher than that in the prespore cells. Moreover, transient increase in [Ca2+]i upon stimulation with a low concentration of cAMP (20 nM) was noticed only in the prestalk cells, but not in the prespore cells. These facts are discussed in relation to the polarized movement and cellular differentiation in the migrating slug.Abbreviations cAMP
3,5-cyclic adenosine monophosphate
- DIF
differentiation-inducing factors
- IP3
inositol 1,4,5-triphosphate 相似文献
2.
We showed previously that ifDictyostelium discoideum cells are sucked up into a small glass capillary with air at one end and plugged with mineral oil at the other, a sharp band
of fast moving cells with prestalk characteristics formed within a minute at the air end of the cell mass. We now demonstrate
that oxygen inside the capillary is responsible for the initiation and positioning of the sharp division line between prestalk-like
and prespore-like cells, and that the length of the prestalk zone is regulated by the oxygen concentration. Our results are
compared to a quantitative theory, showing good agreement with the experiments. We also discuss the relevance of these observations
to the differentiation of prestalk and prespore zones in normal slugs and the origins of polarity in this organism. 相似文献
3.
Astrid Rugendorff Amelia Younossi-Hartenstein Volker Hartenstein 《Development genes and evolution》1994,203(5):266-280
We have followed the normal development of the different cell types associated with the Drosophila dorsal vessel, i.e. cardioblasts, pericardial cells, alary muscles, lymph gland and ring gland, by using several tissue-specific markers and transmission electron microscopy. Precursors of pericardial cells and cardioblasts split as two longitudinal rows of cells from the lateral mesoderm of segments T2-A7 (cardiogenic region) during stage 12. The lymph gland and dorsal part of the ring gland (corpus allatum) originate from clusters of lateral mesodermal cells located in T3 and T1/dorsal ridge, respectively. Cardioblast precursors are strictly segmentally organized; each of T2-A6 gives rise to six cardioblasts. While moving dorsally during the stages leading up to dorsal closure, cardioblast precursors become flattened, polarized cells aligned in a regular longitudinal row. At dorsal closure, the leading edges of the cardioblast precursors meet their contralateral counterparts. The lumen of the dorsal vessel is formed when the trailing edges of the cardioblast precursors of either side bend around and contact each other. The amnioserosa invaginates during dorsal closure and is transiently attached to the cardioblasts; however, it does not contribute to the cells associated with the dorsal vessel and degenerates during late embryogenesis. We describe ultrastructural characteristics of cardioblast differentiation and discuss similarities between cardioblast development and capillary differentiation in vertebrates.
Correspondence to: V. Hartenstein 相似文献
4.
Skindersoe ME Ettinger-Epstein P Rasmussen TB Bjarnsholt T de Nys R Givskov M 《Marine biotechnology (New York, N.Y.)》2008,10(1):56-63
With the global emergence of multiresistant bacteria there is an increasing demand for development of new treatments to combat
pathogens. Bacterial cell–cell communication [quorum sensing (QS)] regulates expression of virulence factors in a number of
bacterial pathogens and is a new promising target for the control of infectious bacteria. We present the results of screening
of 284 extracts of marine organisms from the Great Barrier Reef, Australia, for their inhibition of QS. Of the 284 extracts,
64 (23%) were active in a general, LuxR-derived QS screen, and of these 36 (56%) were also active in a specific Pseudomonas aeruginosa QS screen. Extracts of the marine sponge Luffariella variabilis proved active in both systems. The secondary metabolites manoalide, manoalide monoacetate, and secomanoalide isolated from
the sponge showed strong QS inhibition of a lasB::gfp(ASV) fusion, demonstrating the potential for further identification of specific QS antagonists from marine organisms. 相似文献
5.
Myxomycetes from the Kimberley Region, Western Australia 总被引:1,自引:0,他引:1
BRUCE ING F.L.S. BRIAN M. SPOONER 《Botanical journal of the Linnean Society. Linnean Society of London》1994,116(1):71-76
An account of the Myxomycetes of the Kimberley Region of north Western Australia is presented. It is based on collections obtained mainly from the Napier and Oscar Ranges during the Kimberley Research Project, 1988. The thirty-two collections represent eighteen species, four of which are new records for Australia and twelve new to Western Australia. All but one are new to the Kimberley region, from where only four species were previously known. 相似文献
6.
酪醇是一种多酚类天然产物,广泛应用于化工、医药和食品等领域。目前大肠杆菌(Escherichia coli)从头合成酪醇存在发酵菌体密度低和产量低等问题。为此,本研究将前期获得苯丙酮酸脱羧酶突变体ARO10F138L/D218G与不同来源的醇脱氢酶融合表达,最优组合ARO10F138L/D218G-L-YahK酪醇产量达到1.09 g/L。为进一步提高酪醇产量,敲除了4-羟基苯乙酸竞争途径关键基因feaB,使酪醇产量提高了21.15%,达到1.26g/L。针对酪醇发酵菌体密度低的问题,通过群体感应系统动态调控酪醇合成途径,减轻酪醇对底盘细胞的毒性作用,缓解生长抑制,使其产量提高了33.82%,达到1.74 g/L。在2 L发酵罐中,群体感应动态调控工程菌TRFQ5的酪醇产量达到4.22g/L,OD600值达到42.88,分别较静态诱导表达工程菌TRF5提高了38.58%和43.62%。本研究应用基因敲除技术,阻断了酪醇合成竞争途径;同时结合群体感应动态调控策略,减轻了酪醇毒性对底盘细胞的生长抑制,从而有效地提高了酪醇产量。本研究对其他高毒性化学品的生物合成具有良好的借鉴和应用价值。 相似文献
7.
H. J. Hoops 《Protoplasma》1997,199(3-4):99-112
Summary The colonial Volvocales are often said to be composed of Chlamydomonas-like cells, but there are substantial differences in motility and flagellar apparatus construction between the unicellular forms and the individual members of a colony or spheroid. These changes appear to be required for effective organismal motion and might possibly limit the rate at which new colonial forms evolve from unicellular ones. The flagellar-beat envelopes in colonial members are modified such that they beat in the same direction and in parallel planes with their effective strokes at right angles to the cellular anterior-posterior axis. These changes result from a series of developmental events of the flagellar apparatus of the colonial forms while the colony is still an embryo. Differences in the flagellar-apparatus structure in the members of the Goniaceae and Volvocaceae are not obviously correlated with the traditional placement of these algae in a simple volvocine lineage. Effective colonial motion clearly requires precise positioning and rotational orientation of the cells within the colony. Almost any arrangement where the cells are placed with rotational symmetry within the colony results in colonial progression with rotation. Such rotational symmetry is present from the time of embryogenesis. The mechanism that leads to organismal steering in behavioral responses (e.g., phototaxis) must likewise differ between colonial and unicellular forms. In at least some cases, this appears to result from changes in beat frequency in some parts of the spheroid, but changes in beat direction cannot be ruled out for all forms. 相似文献
8.
Kirk DL 《Current opinion in plant biology》1999,2(6):496-501
Recent studies reveal that relationships among the volvocine algae are more complex than was previously believed. Nevertheless, this group still appears to provide an unrivaled opportunity to analyze an evolutionary pathway leading from unicellularity (Chlamydomonas) to multicellularity with division of labor (Volvox). Significant progress in this regard was made in the past year when two genes playing key roles in Volvox cellular differentiation were cloned, and clues were uncovered regarding their mechanisms of action. 相似文献
9.
10.
S. C. Pratt 《Insectes Sociaux》2005,52(4):383-392
This paper examines the individual behavior underlying collective choice among nest sites by the ant Temnothorax (formerly Leptothorax) curvispinosus. Colonies can actively compare options, rejecting a mediocre site when it is paired with a good one, but accepting the same
mediocre design if it is instead paired with a worse site. This ability emerges from the behavior of an active minority of
workers who organize emigrations. When one of these finds a promising site, she recruits nest mates to it, but only after
a delay that varies inversely with site quality. Ants first recruit fellow active ants via slow tandem runs, but eventually
switch to speedier transports of the colony’s passive majority. Later transports grow faster still, as ants improve their
speed with experience. An ant’s choice of recruitment type is governed by a quorum rule, such that her likelihood of starting
to transport increases with the population of the new site. The size of the quorum depends on experience, with ants demanding
a larger population to launch immediately into transport than they do to switch to transport after first leading a few tandem
runs. Perception of quorum attainment requires direct contact between ants. The ants’ behavior qualitatively matches that
of T. albipennis, where models have shown that decentralized choice of the best site depends on quality-dependent recruitment delays, amplified
by a quorum rule for initiating transport. Parameter estimates for an agent-based model show significant quantitative differences
between the species, and suggest that T. albipennis may place relatively greater emphasis on emigration speed.
Received 11 February 2005; revised 10 May 2005; accepted 20 May 2005. 相似文献
11.
A. O. Shpakov 《Microbiology》2009,78(2):133-143
This review classifies and analyzes the literature data on bacterial autoinducers (AI), the signal molecules produced and secreted by bacterial cells and responsible for intercellular communication (quorum sensing, QS). The most important families of nonpeptide AI are discussed, including N-acyl homoserine lactones, derivatives of 2-methyl-2,3,4,5-tetrahydroxy tetrahydrofuran, indole and quinoline derivatives, and adrenalinerelated compounds. The data is provided on the intracellular and membrane receptors specifically binding to AI, as well as on the effector systems that are activated by AI and mediate their regulatory effects. The possible role of some vertebrate hormones (adrenergic agonists, serotonin, etc.) as AI and their effect on bacterial activity are discussed. The data are presented suggesting a high efficiency of AI-based antibacterial preparations, which selectively disrupt the bacterial information network and thus suppress bacterial infections. 相似文献
12.
Summary The iron storage protein, ferritin, is the major yolk protein in freshwater snails. In this report we show by in vitro labelling experiments that yolk ferritin of the snails Lymnaea stagnalis L. and Planorbarius corneus L. is an exogenous protein synthesized in the midgut gland and secreted into the hemolymph. Gonad and mantle tissue are inactive in the synthesis of yolk ferritin, but, together with the midgut gland, they synthesize another ferritin type (soma ferritin) which is not released into the hemolymph and which may be a housekeeping ferritin. Soma ferritin and yolk ferritin are not in a precursor/product relationship since subunits of both ferritins are synthesized as primary translation products in rabbit reticulocyte lysate programmed with poly (A)+ RNA from midgut gland and gonad. Results suggest that both ferritins are synthesized on different mRNAs (and possibly on different genes) so they may be regulated in a different way. 相似文献
13.
Reproduction and formation of resistant dormant spores in Volvox aureus (Ehr.) and V. tertius (Meyer) were studied in a biocoenosis of a transient pool in July–August 1996 and 1997. Under these conditions, the populations of two Volvox species had species-specific reproductive features. In the V. tertius population, a relatively small amount of male individuals and dormant spores (zygospores) appeared sporadically. On the contrary, in the V. aureus population, dormant parthenospores were formed, but male individuals were never observed. 相似文献
14.
A killer strain was discovered in cellular slime molds. The wild isolate CK-8 of Polysphondylium pallidum kills all other strains in Polysphondylium and Dictyostelium, as far as could be determined, except strain CK-8 itself and its complementary mating type strain CK-9. Growth-phase cells of CK-8 excrete a killer factor which is sensitive to heat, above 60°C for 5 min, and trypsin. The apparent molecular mass of the factor was determined at 10 000–12 000.Abbreviations BSS
Bonner's salt solution
- CM
conditioned medium 相似文献
15.
Using a fluorospectrophotometer, we examined the fluorescence of a crude preparation from the spore masses ofDictyostelium discoideum. Fluorescence emission spectra and excitation spectra suggested that the fluorescence of the crude preparation was a lumazine-like
fluorescence rather than a pterin-like fluorescence. By using a microspectrophotometer, we observedin situ the fluorescence emission of a lumazine-like substance localized only in the spore mass of the fruiting body. 相似文献
16.
Perspective: the size-complexity rule 总被引:3,自引:0,他引:3
Bonner JT 《Evolution; international journal of organic evolution》2004,58(9):1883-1890
It is widely accepted that bigger entities have a greater division of labor than smaller ones and this is reflected in the fact that larger multicellular organisms have a corresponding increase in the number of their cell types. This rule is examined in some detail from very small organisms to large animals, and plants, and societies. Compared to other size-related rules, the size-complexity rule is relatively rough and approximate, yet clearly it holds throughout the whole range of living organisms, as well as for societies. The relationship between size and complexity is analyzed by examining the effects of size increase and decrease: size increase requires an increase in complexity, whereas size decrease permits, and sometimes requires, a decrease in complexity. Conversely, an increase or decrease in complexity permits, but does not require changes in size. An especially compelling argument for the close relation between size and complexity can be found in size quorum sensing in very small multicellular organisms. 相似文献
17.
K. Inouye 《Protoplasma》1984,121(3):171-177
Summary The motive force of the migrating slug of the cellular slime mouldDictyostelium discoideum was measured by the use of centrifugal force. Changes in shape of the slugs due to the use of centrifugal force were prevented by letting them migrate in an agar capillary. The motive force thus obtained was proportional to the slug volume, the value per unit volume being 5.8×106 dyne/cm3 (58 N/cm3). This is in good agreement with the value measured by the use of hydrostatic pressure. 相似文献
18.
To assess the role in cell-cell adhesion of gp64, a putative cell-cell adhesion molecule ofPolysphondylium pallidum, we treated the cells with tunicamycin (TM), a known inhibitor of the synthesis of the N-linked oligosaccharide precursor,
and examined TM's effect on cell-cell adhesion. The vegetative growth ofPolysphondylium cells was inhibited with TM in a dose-dependent manner. When cells were treated with TM (2.0 μg/ml) during only the first
4 hr of starvation and further starved for 8 hr without TM, the cells dissociated considerably, although even the growth phase
cells ofPolysphondylium normally show EDTA-resistant (Ca2+-independent) cell adhesions. In parallel with the above effects, the amounts of intact gp64 decreased considerably in time
with the lengths of incubation (0 hr>4 hr >8 hr). When TM-treated cells were washed free of TM, and shaken for a further 12
hr, the cells began to aggregate again, accompanied by an increase of gp64. In conclusion, TM affected cell-cell adhesion
ofPolysphondylium cells, but we were not able to distinguish whether the inhibition of cell aggregation was due to defects in glycosylation
on glycoproteins and/or due to reduced levels of glycoproteins themselves. 相似文献
19.
【目的】探究副溶血弧菌群体感应(quorum sensing,QS)系统核心调控子AphA和OpaR对mshH基因的转录调控。【方法】提取特定条件下副溶血弧菌野生株(wild-type,WT)和调控子基因突变株(ΔaphA和ΔopaR)的总RNA,采用实时定量PCR (quantitative real-time PCR,qPCR)研究AphA和OpaR对mshH基因的转录调控关系以及mshH基因的时相依赖性表达特性;将mshH启动子区DNA序列克隆入pHRP309质粒β-半乳糖苷酶基因的上游,构建LacZ重组质粒,并将其转入WT、ΔaphA和ΔopaR中,获得LacZ实验菌株,再通过LacZ报告基因融合实验研究AphA和OpaR对mshH基因的调控关系以及mshH基因的时相依赖性表达特性;PCR扩增mshH上游启动子区DNA序列,并纯化His-AphA和His-OpaR蛋白,通过凝胶阻滞实验(electrophoretic mobility shift assay,EMSA)和DNase I足迹实验,研究体外条件下His-AphA和His-OpaR对靶基因启动子区DNA片段是否具有直... 相似文献