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1.
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
2.
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
3.
Miho Iijima Kazuhiro Aiba Yoshimasa Tanaka Hideko Urushihara 《Journal of plant research》1998,111(1):93-96
Two cDNA fragments induced in developing zygotes ofDictyostelium discoideum were isolated by mRNA differential display. the relevant genes were also found to be expressed during asexual development,
suggesting that sexual and asexual development share common molecular mechanisms inD. discoideum. 相似文献
4.
Mutant spores of Dictyostelium discoideum, strain SG-10, differ from wild type spores in their ability to spontaneously germinate, to be activated with 5% dimethyl Sulfoxide (DMSO), and to be deactivated with 0.2 M sucrose. Both heat-activated wild type and mutant spores began to swell after a lag of 60–75 min at ambient temperature. Suspension of heat activated spores in 5% DMSO resulted in blockage of spore swelling and a concomitant severe inhibition of respiration; removal of 5% DMSO allowed resumption of respiration and the spores began to swell after a lag of only 15 min. It was concluded that 5% DMSO allowed the early reactions (M) to proceed but blocked the later reactions (R) of post-activation lag.Treatment of one day old spores with 20% DMSO solution for 30–120 min quantitatively activated the population. The post-activation lag time was directly dependent on the time of 20% DMSO treatment. Spores activated with 20% DMSO treatment could be deactivated by incubation at 0°C; the spores most quickly deactivated at 0°C were those within 10 min of swelling. Mitochondrial transport inhibitors such as azide and cyanide caused deactivation in an analogous manner. It is hypothesized that spores proceed to the second portion of the lag phase called (R) before the environment determines if dormancy is reimposed or if germination will proceed. The sensitive strain (SG-10) showed a greater degree of damage than the wild type after supraoptimal treatment with 40% DMSO. The spores became more resistant with age to the damaging action of 40% DMSO. All the observed effects of DMSO treatment were compatible with our multistate model of activation which suggests that the early portion of the lag phase (M) may involve a relative uncoupling of oxidative phosphorylation while the later portion (R) may require tight coupling. 相似文献
5.
Guanine nucleotides modulate the function of chemotactic cyclic AMP receptors inDictyostelium discoideum 总被引:3,自引:0,他引:3
Pim M. W. Janssens Peter L. J. van der Geer Jos C. Arents Roel van Driel 《Molecular and cellular biochemistry》1985,67(2):119-124
Summary Guanosine di- and triphosphates specifically decrease the affinity of chemotactic cAMP receptors in isolatedDictyostelium discoideum membranes. The K0.5 was increased from 50 nM to 150 nM. Receptors were shown to be heterogeneous in dissociation kinetics. In the absence of
guanine nucleotides three dissociation processes could be resolved, having first order rate constants of 8.7 x 10−4, 1.3 X 10−2, and higher than 0.1 s−1. Guanine nucleotides decreased the affinity for cAMP by transforming the slowest dissociating receptor form (KD is 8 nM) to forms dissociating more rapidly. Our data indicate that a guanine nucleotide binding protein (G-protein) is involved
in the transduction of the cAMP signal inD. discoideum. 相似文献
6.
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
7.
The localization of fluorescent substance was observed microscopically in livingDictyostelium discoideum cells. The fluorescence was localized in the vacuoles of the vegetative cells. The fluorescent vacuoles were not observed
in the dead cells. The fluorescent vacuoles in the cytoplasm were lost in starved cells which are able to form an aggregate
and to differentiate. The fluorescent vacuoles were not lost but decreased slightly in the cytoplasm of full grown cells and
of cells grown in liquid nutrient medium for an extended period of time (stationary phase cells). On a solid substratum, fluorescent
vacuoles were also lost from the cells, where the vegetative cells aggregate and form a slug-shaped mass of cells. The whole
slug showed homogeneous fluorescence. In a finally constructed fruiting body, the spore mass showed fluorescence. In a spore
mass, the fluorescence was not observed in the spores but in the interspore space of the spore mass. It is suggested that
vegetative cells secrete fluorescent substance into the inter-cellular space in the mass of cells during development. 相似文献
8.
9.
Summary NADP-dependent glutamate dehydrogenase from Dictyostelium discoideum was purified 9300 fold with a yield of 4.6%. The enzyme is a hexamer of apparent molecular weight 294 kDa on Sephacryl S400 and a subunit molecular weight of 52 kDa as determined by SDS gel electrophoresis. The apparent KmS for -ketoglutarate, NADPH and NH
inf4
sup+
are 1.2 mM, 9.7 µM and 2.2 mM respectively, and the purified enzyme has a broad pH optimum with a peak at pH 7.75. GTP has a slight stimulatory effect (22% at 83 µM) as does ADP (11% at 1 mM), and AMP is slightly inhibitory (9% at 1 mM) whereas adenosine, ATP and cAMP have little or no effect. Neither the Zn2+ chelating compound 1,10-phenanthroline nor EDTA have any effect on the enzyme while p-hydroxymercuribenzoic acid inhibits enzyme activity (50% at 80 µM) yet N-ethylmaleimide does not.In addition, the NADP-GDH activity varies little during the various stages of morphogenesis.Abbreviations EDTA
Ethylenediamine Tetraacetic Acid
- Tris
Tris(hydroxymethyl)aminomethane
- Bis-tris
bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane
- TRITON X-100
iso-octylphenoxypoly-ethoxyethanol
-
pHMB
p-Hydroxymercuribenzoic acid 相似文献
10.
The implication of histone H1 kinase activity for the G2/M transition during the cell cycle was investigated usingDictyostelium discoideum Ax-2. Histone H1 kinase with its activity was purified from cell extracts by the use of p13suc1 affinity gel. In the vegetative cell cycle, the activity of histone H1 kinase including Cdc2 kinase was found using synchronized
Ax-2 cells to be highest just before the entry into mitosis. The activity also was markedly enhanced just prior to the M phase
from which developing cells (possibly prespore cells) reinitiate their cell cycle at the mound-tipped aggregate stage. These
results strongly suggest the importance of Cdc2 kinase activity in the G2 to M phase transition during the cell cycle, as
the case for other eukaryotic cells. 相似文献
11.
Denis Drainas 《Molecular biology reports》1995,22(2-3):135-138
Ribonuclease P (RNase P) is a key enzyme involved in tRNA biosynthesis. It catalyses the endonucleolytic cleavage of nearly all tRNA precursors to produce 5-end matured tRNA. RNase P activity has been found in all organisms examined, from bacteria to mammals. Eubacterial RNase P RNA is the only known RNA enzyme which functionsin trans in nature. Similar behaviour has not been demonstrated in RNase P enzymes examined from archaebacteria or eukaryotes. Characterisation of RNase P enzymes from more diverse eukaryotic species, including the slime moldDictyostelium discoideum, is useful for comparative analysis of the structure and function of eukaryotic RNase P.Abbreviations RNase P
ribonuclease P
- MN
micrococcal nuclease 相似文献
12.
The role of the cell cycle in differentiation of the cellular slime mould Dictyostelium discoideum 总被引:3,自引:0,他引:3
Summary During development and differentiation of the cellular slime mould Dictyostelium discoideum there appears to be a relationship between the cell cycle and cell fate: amoebae halted in G2 phase during early development differentiate into spores whereas stalk cells are formed from amoebae halted in GI phase. It is proposed that this is because a major effect of the cell cycle is to generate heterogeneity in the cell surface properties of the developing amoebae. 相似文献
13.
How cellular movement determines the collective force generated by the Dictyostelium discoideum slug
How the collective motion of cells in a biological tissue originates in the behavior of a collection of individuals, each of which responds to the chemical and mechanical signals it receives from neighbors, is still poorly understood. Here we study this question for a particular system, the slug stage of the cellular slime mold Dictyostelium discoideum (Dd). We investigate how cells in the interior of a migrating slug can effectively transmit stress to the substrate and thereby contribute to the overall motive force. Theoretical analysis suggests necessary conditions on the behavior of individual cells, and computational results shed light on experimental results concerning the total force exerted by a migrating slug. The model predicts that only cells in contact with the substrate contribute to the translational motion of the slug. Since the model is not based specifically on the mechanical properties of Dd cells, the results suggest that this behavior will be found in many developing systems. 相似文献
14.
Incubation ofDictyostelium discoideum cells with selenate is known to inhibit vegetative growth. In this paper we show that in the presence of selenate macromolecules accumulate which can be converted to sulphated products once the selenate is removed. The presence of cycloheximide, an inhibitor of protein synthesis, during the subsequent incubation does not prevent this conversion but tunicamycin, an inhibitor of glycosylation does. It is concluded that, in the presence of selenate, precursors accumulate as unglycosylated proteins, suggesting that feedback inhibition of glycosylation may be operated. 相似文献
15.
Bert Van Duijn Dirk L. Ypey Loek G. Van der Molen 《The Journal of membrane biology》1988,106(2):123-134
Summary Electrical membrane properties of the cellular slime moldDictyostelium discoideum were investigated with the use of intracellular microelectrodes. The rapid potential transients (1 msec) upon microelectrode penetration of normal cells had a negative-going peak-shaped time course. This indicates that penetration of a cell with a microelectrode causes a rapid depolarization, which can just be recorded by the microelectrode itself. Therefore, the initial (negative) peak potential transient valueE
p (–19 mV) should be used as an indicator of the resting membrane potentialE
m ofD. discoideum before impalement, rather than the subsequent semistationary depolarized valueE
n (–5 mV). Using enlarged cells such as giant mutant cells (E
p=–39 mV) and electrofused normal cells (E
p=–30 mV) improved the reliability ofE
p as an indicator ofE
m. From the data we concluded thatE
m ofD. discoideum cells bathed in (mm) 40 NaCl, 5 KCl and 1 CaCl2 is at least –50 mV. This potential was shown to be dependent on extracellular potassium. The average input resistanceR
i of the impaled cells was 56 M for normalD. discoideum. However, our analysis indicates that the membrane resistance of these cells before impalement is >1 G. Specific membrane capacitance was 1–3 pF/cm2. Long-term recording of the membrane potential showed the existence of a transient hyperpolarization following the rapid impalement transient. This hyperpolarization was associated with an increase inR
i of the impaled cell. It was followed by a depolarization, which was associated with a decrease inR
i. The depolarization time was dependent on the filling of the microelectrode. The present characterization of the electrical membrane properties ofDictyostelium cells is a first step in a membrane electrophysiological analysis of signal transduction in cellular slime molds. 相似文献
16.
We examined 12 important monoterpenes found on the forest floor underPinus thunbergii, and monitored their effect on the growth of a slime mold,Dictyostelium discoideum Ax-2. Four concentrations were tested for each compound (3.3, 0.33, 0.033, and 0.0033 μ/mL). Relative growth rates were determined
by comparing the cell counts of treated organisms with those from the controls. At a concentration of 3.3 μlml, (1S)-(-)-α-pinene,
(-)-menthone, (-)-camphene, (S)-(+)-carvone, and (1 R)-(-)-fenchone strongly inhibited the development of this slime mold.
In contrast, (+)-sabinene, (R)-(+)-limonene, and myrcene showed no inhibitory effects, even at the highest concentration tested.
By comparing individual growth rates with the control during the incubation period, we could classify these monoterpenes into
three groups: I., compounds that were able to inhibit Ax-2 growth at all concentrations; II., compounds that showed a strong
inhibitory effect at treatments between 3.3 and 0.033 μl/mL, and mild anti-microbial activity at the lowest concentration;
and III., compounds that inhibited growth at higher concentrations (3.3 and 0.33 μl/mL), but enhanced it at lower levels (0.033
and 0.0033 μ/ml.). Based on these results, we suggest that the inhibitory and enhancing effects of selected monoterpenes depend
upon the concentration of the individual compound. 相似文献
17.
M. Maniak 《Protoplasma》1999,210(1-2):25-30
Summary The cells ofDictyostelium discoideum are soil amoebae with a simple endocytic pathway: Particles or fluid are taken up at the plasma membrane in a process dependent on the actin cytoskeleton. After rapid acidification and subsequent neutralisation of the food vacuoles during which breakdown of the contents occurs, indigestible remnants are exocytosed. This tight coupling between endocytosis and exocytosis is thought to maintain membrane homeostasis. In spite of the apparent overall difference between the endocytic pathways of mammalian cells andD. discoideum, conserved proteins are involved in individual steps of endocytic transport, possibly indicating that in mammalian cells it is only the routing of marker that has evolved from a simple transit to a complex, branched pathway. 相似文献
18.
In the heterothallic strains NC4 and HM1 ofDictyostelium discoideum, sexual development is initiated by the formation of diploid zygotic giant cells produced through the fusion of these two
opposite mating-type haploid cells. For sexual cell fusion, amoeboid cells must first acquire fusion competence, which requires
culture under certain environmental conditions, such as darkness, excessive water, and sufficient bacteria as food. However,
in the subsequent stages of cell fusion and development of the giant cells into mature macrocysts, cells do not require the
above conditions. Cell fusion and development into macrocysts were able to occur even in light with minimum water and in the
absence of bacteria. For cell fusion calcium ions were required. 相似文献
19.
Proteins of the mitochondrial carrier family (MCF) mediate the transport of a large range of compounds, including metabolites and cofactors. They are localized mainly in the inner mitochondrial membrane, except for a few members found in the membranes of peroxisomes. Similarity searches among Dictyostelium discoideum protein sequences identified a total of 31 MCF members. All these are membrane proteins that possess three characteristic repeats of a domain of approximately 100 residues. Among them, three proteins have supplementary structural domains consisting of Ca(2+)-binding motifs made up of 2 or 4 EF-hand units localized on the N-terminal end, facing the mitochondrial intermembrane space. The nature of transported substrates is proposed on the basis of sequence comparison with orthologs characterized biochemically in other organisms, of phylogenetic analysis, and of the conservation of discriminating amino acid residues belonging to the substrate binding sites. Carriers have been grouped in subclasses based on their specificity for the transport of nucleotides, amino acids or keto acids. Furthermore, we have identified an iron carrier of the mitoferrin type, an inorganic phosphate carrier, and three carriers with similarity to uncoupler proteins. This study provides a focus for mitochondrial carrier analysis in Dictyostelium discoideum. 相似文献
20.
Dennis L. Welker Arturo De Lozanne James A. Spudich 《Molecular & general genetics : MGG》1989,216(2-3):498-502
Summary A mutation (mhcA1 in strain HMM) created by insertional gene inactivation was used to map the Dictyostelium discoideum myosin heavy chain gene (mhcA) to linkage group IV. Three phenotypic traits associated with this mutation (slow colony growth, inability of the mutant to develop past aggregation, and the presence of five to ten integrated vector copies) cosegregated as expected for the consequences of a single insertional event. This linkage was confirmed using a restriction fragment length polymorphism. The mhcA1 mutation was recessive to wild type and was nonallelic with mutations at the following loci on linkage group IV: aggJ, aggL, couH, minA, phgB and tsgB. This work demonstrates the ability to apply standard techniques developed for D. discoideum parasexual genetic analyses to mutants generated by transformation, which is of particular relevance to analysis of genes for which no classical mutations or restriction fragment length polymorphisms are available. 相似文献