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1

Digitale Medien

Patterns of DNA Synthesis and Cell Division in Marine Dinoflagellates (1983)

KARENTZ, DENEB

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 30 (1983), S. 0

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ISSN: 1550-7408

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: Changes in mean cell size, DNA and cell density were monitored at 6-h intervals for 72 h in populations of six species (eight clones) of marine dinoflagellates to determine the temporal relationships between the cell cycle events of DNA replication and cytokinesis. Batch cultures were maintained at 15 or 20°C on a 12-h light: 12-h dark photoperiod. Cell densities and size frequency distributions were determined conductimetrically and the amount of DNA within populations was measured fluorometrically. A variety of intra- and interspecific relationships were observed, ranging from parallel phasing of cell cycle processes to variations which involved the temporal uncoupling of DNA synthesis from the phased pattern of cell division which is characteristic of dinoflagellate cell cycles. Daily growth rates of individual populations varied from 0.05 (Gymnodinium nelsoni) to 2.08 (Amphidinium carteri) cell divisions day-1 and DNA doubling rates ranged from 0 to 1.14 day-1. Mean doubling rates for DNA were usually 30–40% lower than those for cells. The degree of difference in these rates and the amount of variability evident in cell cycle sequences may be major factors in determining the rate and extent of development of dinoflagellate populations in nature.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1550-7408.1983.tb01426.x

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2

Digitale Medien

Mutation and expression of theXPA gene in revertants and hybrids of a xeroderma pigmentosum cell line (1994)

Cleaver, James E. ; McDowell, Mindy ; Jones, Christopher ; [weitere]

Springer

Somatic cell and molecular genetics 20 (1994), S. 327-337

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ISSN: 1572-9931

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract A series of ultraviolet (UV)-resistant cell lines have been generated from a UV-sensitive XP group A cell line homozygous for a stop codon (TGA) in the chromosome 9XPA gene. Three lines generated by chemical mutagenesis acquired the ability to excise (6–4) photoproducts but not cyclobutane dimers from the whole genome; two lines generated by a fusion procedure with hamster cells acquired the ability to excise both (6–4) photoproducts and cyclobutane dimers from the whole genome. A central region of the hamsterXPA gene was cloned and sequenced. With the use of species-specific primers in the polymerase chain reaction, we found that the hybrid cell lines do not contain a hamsterXPA gene. Sequence analysis showed that all of the UV-resistant cell lines contain reversions of the human stop codon, resulting in missense mutations (glycine or leucine for arginine) or wild-type sequences. The concentration of XPA protein in revertant cell lines was about one-half that in normal cells, which would be expected from heterozygous cells; there was no evidence that the mutant proteins were less stable than the wild-type proteins. These results are consistent with the idea that the XPA protein initiates repair by binding to damaged sites with various affinities, depending on the photoproduct and the transcriptional state of the region. A concentration of XPA protein near 50% is needed before repair can proceed into nontranscribed regions of the genome. The revertant cell lines represent a class of missense mutations in theXPA gene that may have altered specificity and that can be used to understand some of the regulatory differences in repair of photoproducts in various regions of the genome.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02254721

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Digitale Medien

Correction of excision repair in xeroderma pigmentosum by hamster chromosome fragments involves both classes of pyrimidine dimers (1987)

Karentz, Deneb ; Mitchell, David ; Cleaver, James E.

Springer

Somatic cell and molecular genetics 13 (1987), S. 621-625

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ISSN: 1572-9931

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Medizin

Notizen: Abstract The ultraviolet light-sensitive phenotype of xeroderma pigmentosum (XP) has been corrected by the incorporation into XP cells of small chromosome fragments from Chinese hamster ovary cells. Like normal human and hamster cells, these XP-hamster hybrids are able to excise both of the photoproducts produced by ultraviolet light: cyclobutane pyrimidine dimers and the minor photoproduct, (6−4) pyrimidine-pyrimidone dimers. This excision capacity contrasts with that of an XP revenant, of the same cell line used in this study, which is able to excise only the (6−4) photoproducts. The excision defect of XP has been fully corrected in the hybrids; therefore, the small hamster chromosome fragments they contain should carry the gene for complementation group A of XP.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01534482

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4

Digitale Medien

DNA repair in man: Regulation by a multigene family and association with human disease (1987)

Cleaver, James E. ; Karentz, Deneb

New York, NY : Wiley-Blackwell

BioEssays 6 (1987), S. 122-127

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ISSN: 0265-9247

Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Medizin

Notizen: The major mechanism of repair of damage to DNA involves a conceptually simple process of enzymatic excision and resynthesis of small regions of DNA. In man and other mammals, this process is regulated by several gene loci; up to 15 mutually complementary genes or gene products may be involved. Repair deficiency results in an array of clinical symptoms in skin, central nervous system, and hematopoietic and immune systems, the major example being xeroderma pigmentosum (XP), a disease with a high incidence of cancer. Cloning repair genes by straightforward methods has proved difficult, but we have begun the effort by demonstrating that correction of a human repair deficiency can be achieved by transferring very small fragments of DNA from normal hamsters into XP cells. One of the complementation groups of XP cells (group C) appears to express a change in gene regulation such that these cells repair only a small clustered region of the DNA with high efficiency.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bies.950060307

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Global distributions of Phaeocystis sp. abundance and biomass - Gridded data product (NetCDF) - Contribution to the MAREDAT World Ocean Atlas of Plankton Functional Types (2012)

Vogt, Meike ; O'Brien, Colleen J ; Peloquin, Jill M ; [weitere]

PANGAEA

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Publikationsdatum: 2023-03-27

Beschreibung: The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global biogeochemical cycling of carbon and sulphur, but little is known about its global biomass distribution. We have collected global microscopy data of the genus Phaeocystis and converted abundance data to carbon biomass using species-specific carbon conversion factors. Microscopic counts of single-celled and colonial Phaeocystis were obtained both through the mining of online databases and by accepting direct submissions (both published and unpublished) from Phaeocystis specialists. We recorded abundance data from a total of 1595 depth-resolved stations sampled between 1955-2009. The quality-controlled dataset includes 5057 counts of individual Phaeocystis cells resolved to species level and information regarding life-stages from 3526 samples. 83% of stations were located in the Northern Hemisphere while 17% were located in the Southern Hemisphere. Most data were located in the latitude range of 50-70° N. While the seasonal distribution of Northern Hemisphere data was well-balanced, Southern Hemisphere data was biased towards summer months. Mean species- and form-specific cell diameters were determined from previously published studies. Cell diameters were used to calculate the cellular biovolume of Phaeocystis cells, assuming spherical geometry. Cell biomass was calculated using a carbon conversion factor for Prymnesiophytes (Menden-Deuer and Lessard, 2000). For colonies, the number of cells per colony was derived from the colony volume. Cell numbers were then converted to carbon concentrations. An estimation of colonial mucus carbon was included a posteriori, assuming a mean colony size for each species. Carbon content per cell ranged from 9 pg (single-celled Phaeocystis antarctica) to 29 pg (colonial Phaeocystis globosa). Non-zero Phaeocystis cell biomasses (without mucus carbon) range from 2.9 - 10?5 µg l-1 to 5.4 - 103 µg l-1, with a mean of 45.7 µg l-1 and a median of 3.0 µg l-1. Highest biomasses occur in the Southern Ocean below 70° S (up to 783.9 µg l-1), and in the North Atlantic around 50° N (up to 5.4 - 103 µg l-1).

Schlagwort(e): MAREMIP; MARine Ecosystem Model Intercomparison Project

Materialart: Dataset

Format: application/zip, 3.6 MBytes

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