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The Anemia monica Verrill population in Mono Lake, Californiahas two generations per year. Despite similarities in the year-to-yearlife history patterns, some important differences developedbetween 1979 and 1981. The first generation hatches from overwinteringcysts in early spring and reaches maturity by the end of May.The first-generation females reproduce ovoviviparously, givingrise to a second generation which matures between mid-July andAugust. In July, both first and second generation females beginproducing overwintering cysts. The population reaches it maximumin late summer, then declines to low numbers by November. Theabundance of the first generation in June declined from a meanof 20 000 m2 to 2400 m2. Despite the smaller firstgeneration, the second generation in 1980 and 1981 was at leastas abundant as in 1979. These differences are indicative ofa change in the Artemia population dynamics in Mono Lake.
1Address for correspondence: Hawaii Institute of Marine Biology,University of Hawaii, P.O. Box 1346 Kaneohe, HI 96744-1346,USA. 相似文献
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Cultures of the unicellular green alga Chlamydomonas reinhardii can be synchronized by light/dark cycling not only under photoautotrophic but also under mixotrophic growth conditions. We observed that cultures synchronized in the presence of acetate continue to divide synchronously for one cell-cycle period when transferred to heterotrophic growth conditions. This finding enabled us to investigate the differential effects of light on cell growth and cell division. When cells were exposed to continuous light at the beginning of the growth period they entered the division phase earlier than dark-grown cells as a consequence of an increased growth rate. Illumination at the end of the growth period, however, caused a considerable delay in cell division and an extended growth period. The light-induced delay in cell division was also observed in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. This finding demonstrates that cell division is directly influenced by a light/dard-responsive cell-cycle switch rather than by light/dark-dependent changes in energy metabolism. The importance of this light/dark control to the regulation of the Chlamydomonas cell cycle was investigated in comparison with other control mechanisms (size control, time control). We found that the light/dard-responsive cell-cycle switch regulates the transition from G1-to S-phase. This control mechanism is effective in cells which have attained the commitment to at least one round of DNA replication and division but have not attained the maximal cell mass which initiates cell division in the light.Abbreviations dCTP
deoxycytidine 5-triphosphate
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea 相似文献
5.
M A Tukalo M D Kubler D Kern M Mougel C Ehresmann J P Ebel B Ehresmann R Giegé 《Biochemistry》1987,26(16):5200-5208
A new approach allowing detection of contact points between RNAs and proteins has been developed using trans-diamminedichloroplatinum(II) as the cross-linking reagent. The advantage of the method relies on the fact that the coordination bonds between platinum and the potential acceptors on proteins and nucleic acids (mainly S of cysteine or methionine residues; N of imidazole rings in histidine residues; N7 of guanine, N1 of adenine, and N3 of cytosine residues) can be reversed, so that the cross-linked oligonucleotides or peptides in contact within a complex can be analyzed directly. The method was worked out with the ribosome from Escherichia coli and the tRNAVal/valyl-tRNA synthetase system from the yeast Saccharomyces cerevisiae. In the first system the platinum approach permitted detection of ribosomal proteins cross-linked to 16S rRNA within the 30S subunits (mainly S18 and to a lower extent S3, S4, S11, and S13/S14); in the second system major oligonucleotides of tRNAVal cross-linked to valyl-tRNA synthetase were detected in the anticodon stem and loop, in the variable loop, and in the 3' terminal amino acid accepting region. These results are discussed in light of the current knowledge on ribosome and tRNAs and of potential applications of the methodology. 相似文献
6.
Jürgen Voigt Dieter Mergenhagen Petra Münzner Hans-Peter Vogeler Klaus Nagel 《Planta》1989,178(4):456-462
In light-dark-synchronized cultures of the unicellular green algaChlamydomonas reinhardtii, release of zoospores from the wall of the mother cell normally takes place during the second half of the dark period. The recently isolated mutant ls, however, needs light for the liberation of zoospores when grown photoautotrophically under a 12 h light-12 h dark regime. The light-induced release of zoospores was found to be prevented by addition of the photosystem-II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Furthermore, light dependence of this process was shown to be abolished when the mutant ls was grown either photoautotrophically under a 14 h light-10 h dark regime or in the presence of acetate. Our findings indicate that the light-dependency of zoospore liberation observed in cultures of this particular mutant during photoautotrophic growth under a 12 h light-12 h dark regime might be attributed to an altered energy metabolism. The light-induced release of zoospores was found to be prevented by addition of cycloheximide or chloramphenicol, antibiotics which inhibit protein biosynthesis by cytoplasmic and organellar ribosomes, respectively. Actinomycin D, an inhibitor of RNA synthesis, however, did not affect the light-induced liberation of zoospores.Sporangia accumulate in stationary cultures of the mutant ls. Release of zoospores was observed when these sporangia were collected by centrifugation and incubated in the light after resuspension in fresh culture medium. Since liberation of zoospores was not observed after dilution of the stationary cultures with fresh culture medium, we suppose that components which interfere with the action of the sporangial autolysin are accumulated in the culture medium of the mutant ls.Abbreviation DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea 相似文献
7.
Crosslinking of elongation factor Tu to tRNA(Phe) by trans-diamminedichloroplatinum (II). Characterization of two crosslinking sites on EF-Tu 总被引:4,自引:0,他引:4
In a preceding paper [(1987) Nucleic Acids Res. 15, 5787-5801], we have used trans-diamminedichloroplatinum (II) to induce reversible RNA-protein crosslinks within the ternary EF-Tu/GTP/Phe-tRNA(Phe) complex and have identified two crosslinking sites on the tRNA. The aim of the present paper is to determine the crosslinking sites on EF-Tu. Two tryptic peptides located in domain I could be identified, a major one (residues 45-74) and a minor one (residues 117-154). The use of Staphylococcus aureus V8 protease led to the isolation of two major peptides (residues 56-68 and 64-68) and one minor peptide (118-124). These results are discussed in the light of the current knowledge of the topography of the EF-Tu/tRNA complex. 相似文献
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In this study we compared the properties of cytochrome-c oxidase (COX) in cultured fibroblasts from two patients with Leigh Syndrome with COX from control fibroblasts. The fibroblasts from patients showed decreased growth reates and elevated lactate production. COX activity of patients fibroblasts was about 25% of control. Kinetic studies with isolated mitochondria showed a higher Km for cytochrome c and a markedly reduced molecular turnover of COX from patients, indicating a different structure of the enzyme. A biphasic change of COX activity was obtained by titration of dodecylmaltoside solubilized mitochondria from control fibroblasts with increasing concentrations of anions. With patient mitochondria we found only the inhibiting phase of COX activity and, in contrast to control mitochondria, irreversible inhibition of COX activity by guanidinium chloride. ELISA titrations with monoclonal antibodies to subunit II, IV, Vab, VIac and VIIab indicated a normal amount of mitochondrial coded subunit II, but a reduced amound of nuclear coded subunits. The data indicate incompletely assembled nuclear coded subunits of COX from patient fibroblasts. 相似文献
10.
Androgen receptor heterogeneity in LNCaP cells is caused by a hormone independent phosphorylation step 总被引:6,自引:0,他引:6
George G. J. M. Kuiper Petra E. de Ruiter Albert O. Brinkmann 《The Journal of steroid biochemistry and molecular biology》1992,41(3-8):697-700
Androgen receptor synthesis and modification were studied in the human LNCaP cell line. Immunoblotting showed that the androgen receptor migrated as a closely spaced 110–112 kDa doublet on SDS-PAGE gels. Most of the receptor protein is present in the higher molecular mass form. Labelling experiments with [35S]methionine showed that the androgen receptor is synthesized as a single 110 kDa protein which is rapidly converted to a 112 kDa protein. Upon alkaline phosphatase treatment a gradual elimination of the 112 kDa isoform with a concomitant increase of the 110 kDa isoform was seen, indicating that the observed 110 to 112 kDa upshift reflects androgen receptor phosphorylation. Furthermore, it is shown that both isoforms can bind hormone and undergo a hormone dependent transformation to a tight nuclear binding form, indicating that the 110 to 112 kDa conversion is not an obligatory step for hormone binding or receptor transformation. 相似文献