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101.
M. Leigh Carson Henry Merchant 《Journal of experimental marine biology and ecology》2005,314(2):187-201
In this laboratory study, the frequency of locomotor behaviors for two grass shrimp species, Palaemonetes pugio and Palaemonetes vulgaris, and the killifish Fundulus heteroclitus were determined. Additional behaviors, such as grouping of grass shrimp, and pursuit by killifish, the grass shrimp's common predator, were also analyzed. The results show that mean behavioral frequencies for the two shrimp species were rarely significantly different statistically. Each shrimp species altered its behavior differently in the presence of the other shrimp species, but responded similarly to the presence of the predator. The results indicate that the response of each shrimp species to the predator was dependent upon the predator's size and health. In situations involving the large health predator, both grass shrimp species significantly reduced swimming, but did not show a significant difference in walking. Behavioral frequencies of large and small healthy killifish were not significantly different from each other when alone, but were significantly different in the presence of prey, while the large unhealthy killifish's behavior was significantly decreased in all situations compared to both the large and small health killifish. 相似文献
102.
103.
F. W. van Glnkel W. B. van Muiswinkel ; B. Merchant E. F. Lizzio O. W. Dixon D. P. Anderson 《Journal of fish biology》1985,27(3):265-272
Anterior kidney and splenic cells were taken from rainbow trout and splenic cells from BALB/c mice immunized with a T-dependent (sheep red blood cells) or T-independent (DNP-Ficoll) antigen. The cells were incubated at different temperatures in Jerne plaque assays (direct or passive haemolytic plaque assays). The optimum numbers of in vitro plaque-forming cells (PFC) after incubation with homologous complement were directly correlated with normal body temperatures of the respective species. The optimum incubation temperature was 37°C for mouse cells and 10°C for fish cells. Incubation of mouse cells at lower temperatures of 30, 20, 10, 4 or 0°C appeared to yield a direct line reduction in numbers of PFC. Trout cells developed significantly fewer PFC at 4 and 20°C and none at 30°C or above; however, significant numbers still appeared at 0°C. More PFC per million white blood cells were obtained from the anterior kidney; however, related to temperatures, no differences in development of numbers of PFC could be seen between the spleen and anterior kidney cells of trout. When the incubation time was lengthened for both trout and mouse cells held at low temperatures, the numbers of PFC approached those of the cells incubated at the optimum temperatures for 10 h. 相似文献
104.
Jesse C. Traller Shawn J. Cokus David A. Lopez Olga Gaidarenko Sarah R. Smith John P. McCrow Sean D. Gallaher Sheila Podell Michael Thompson Orna Cook Marco Morselli Artur Jaroszewicz Eric E. Allen Andrew E. Allen Sabeeha S. Merchant Matteo Pellegrini Mark Hildebrand 《Biotechnology for biofuels》2016,9(1):258
Background
Improvement in the performance of eukaryotic microalgae for biofuel and bioproduct production is largely dependent on characterization of metabolic mechanisms within the cell. The marine diatom Cyclotella cryptica, which was originally identified in the Aquatic Species Program, is a promising strain of microalgae for large-scale production of biofuel and bioproducts, such as omega-3 fatty acids.Results
We sequenced the nuclear genome and methylome of this oleaginous diatom to identify the genetic traits that enable substantial accumulation of triacylglycerol. The genome is comprised of highly methylated repetitive sequence, which does not significantly change under silicon starved lipid induction, and data further suggests the primary role of DNA methylation is to suppress DNA transposition. Annotation of pivotal glycolytic, lipid metabolism, and carbohydrate degradation processes reveal an expanded enzyme repertoire in C. cryptica that would allow for an increased metabolic capacity toward triacylglycerol production. Identification of previously unidentified genes, including those involved in carbon transport and chitin metabolism, provide potential targets for genetic manipulation of carbon flux to further increase its lipid phenotype. New genetic tools were developed, bringing this organism on a par with other microalgae in terms of genetic manipulation and characterization approaches.Conclusions
Functional annotation and detailed cross-species comparison of key carbon rich processes in C. cryptica highlights the importance of enzymatic subcellular compartmentation for regulation of carbon flux, which is often overlooked in photosynthetic microeukaryotes. The availability of the genome sequence, as well as advanced genetic manipulation tools enable further development of this organism for deployment in large-scale production systems.105.
Gary D. Stoner Donald J. Merchant 《In vitro cellular & developmental biology. Plant》1972,7(6):330-343
Summary The amino acid requirements of strain L-M mouse cells grown in a chemically defined medium (2×Eagle) containing only the 13
essential amino acids (EAA) were investigated. Medium and acid hydrolysate samples were analyzed for amino acid content by
the method of ion exchange chromatography. The extent of utilization of the EAA differed;e.g. after 120 hr of cell growth without medium change, glutamine was exhausted from the medium; methionine, leucine, isoleucine,
cystine, arginine, and valine were depleted 60 to 80%; other EAA were used to lesser extents. Although the EAA were used in
excess of their requirements for protein synthesis, a correlation could generally be made between utilization and protein
amino acid composition.
Glutamine appeared to be, a growth-limiting factor. Use of U-14C-labeled glutamine indicated that over one-half of the metabolized glutamine was converted to carbon dioxide, 17% to cell
material, and 15% was extracted from the amino acid pools.
Nonessential amino acids (NEAA), viz. alanine, aspartic acid, glutamic acid, glycine, proline, and serine, were released into
the medium during growth, and some were reutilized. Exogenous provision of these did not improve cell growth. In contrast
to the other NEAA, only serine showed net utilization when provided exogenously. When glutamic acid largely replaced the glutamine
in the medium, it exerted a sparing effect on the glutamine requirement for protein synthesis. Suggestions are given for the
improvement of Eagle medium for cell growth.
Supported by Research Grants CA 03720 and CA 11802 from the National Institutes of Health.
Predoctoral, fellow supported, by Grant F01-GM-42156-02 from the National Institutes of Health. 相似文献
106.
VP4-specific intestinal antibody response to rotavirus in a murine model of heterotypic infection. 下载免费PDF全文
We have adapted a murine model of heterotypic rotavirus infection for the purpose of evaluating the intestinal antibody response to an infection that mimics human vaccination. Neonatal mice were infected with the rhesus rotavirus (RRV). The enzyme-linked immunospot assay was used in order to avoid common artifacts in the quantitation of intestinal immune responses inherent in measurements of luminal or serum immunoglobulins and to obtain easily quantifiable data in a flexible and convenient format. Functionally active lymphocytes were harvested from the spleen, small intestinal lamina propria, Peyer's patches, and mesenteric lymph nodes and processed into single-cell suspensions. Antibody-secreting cells (ASC) were quantitated from 5 to 50 days after infection for total, RRV-specific, baculovirus-expressed VP4-specific, and single-shell RRV-specific ASC secreting either immunoglobulin G (IgG), IgM, or IgA. The response to VP4 constituted less than 1.5% of the total virus-specific response, which was located almost exclusively in the gut and was 90% IgA. Intestinal ASC were directed overwhelmingly toward proteins incorporated in the single-shell particle, predominantly VP2 and VP6. We conclude that the antibody response to VP4, thought to be the site of the important neutralization sites conserved among several rotavirus serotypes, is an extremely small portion of the overall antibody response in the intestinal tract. 相似文献
107.
108.
Synthesis and Turnover of the Chloroplast Coupling Factor 1 in Chlamydomonas reinhardi 总被引:2,自引:1,他引:2 下载免费PDF全文
Studies on the biosynthesis of the chloroplast coupling factor 1 (CF1) in Chlamydomonas reinhardi have been initiated. The ratio of CF1 to chlorophyll in the cell was shown to be independent of the density of the culture. No turnover of assembled CF1 could be detected, thus suggesting that CF1 was synthesized at a rate equivalent to that of net chlorophyll synthesis. A lag of between 5 to 7 minutes in the incorporation of radioactive precursor sulfate into assembled CF1 was measureable. This puts an upper limit on the pool size of any precursor to the assembled CF1 complex. The pool size is estimated to be equivalent to 1% of the total CF1 in the cell. 相似文献
109.
Sea urchin Hox genes: insights into the ancestral Hox cluster 总被引:3,自引:0,他引:3
We describe the Hox cluster in the radially symmetric sea urchin and
compare our findings to what is known from clusters in bilaterally
symmetric animals. Several Hox genes from the direct-developing sea urchin
Heliocidaris erythrogramma are described. CHEF gel analysis shows that the
Hox genes are clustered on a < or = 300 kilobase (kb) fragment of DNA,
and only a single cluster is present, as in lower chordates and other
nonvertebrate metazoans. Phylogenetic analyses of sea urchin, amphioxus,
Drosophila, and selected vertebrate Hox genes confirm that the H.
erythrogramma genes, and others previously cloned from other sea urchins,
belong to anterior, central, and posterior groups. Despite their radial
body plan and lack of cephalization, echinoderms retain at least one of the
anterior group Hox genes, an orthologue of Hox3. The structure of the
echinoderm Hox cluster suggests that the ancestral deuterostome had a Hox
cluster more similar to the current chordate cluster than was expected Sea
urchins have at least three Abd-B type genes, suggesting that Abd-B
expansion began before the radiation of deuterostomes.
相似文献
110.