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651.
Calpain 总被引:1,自引:0,他引:1
Perrin BJ Huttenlocher A 《The international journal of biochemistry & cell biology》2002,34(7):722-725
The calcium-dependent thiol proteases, calpains, are widely expressed with ubiquitous and tissue specific isoforms. Calpains have been implicated in basic cellular processes including cell proliferation, apoptosis and differentiation. The focus of the current review is to summarize recent findings implicating calpains in cytoskeletal rearrangements and cell migration. Calpain cleaves many cytosolic proteins and therefore to be effective and limited in its scope, calpain activity has to be tightly regulated both temporally and spatially. Some mechanisms of regulation include calcium, growth factor-mediated phosphorylation and membrane targeting. Calpain inhibition reduces migration rates and inhibits cell invasiveness. Two putative mechanisms of calpain action during migration include its role as a signaling intermediate, acting upstream of Rho, and its effects on focal adhesion structure and disassembly. Therefore, calpains and downstream signaling molecules may be future targets for therapeutic interventions to treat cancer or chronic inflammation. 相似文献
652.
Perrin RM 《Current biology : CB》2001,11(6):R213-R216
Many questions remain about the biosynthesis of cellulose, the major plant cell wall component, not least of which is why plants have so many genes for the cellulose synthase catalytic subunit. Perhaps multiple isoforms of cellulose synthase are needed in the same cell for the formation of functional dimeric complexes. 相似文献
653.
With the cancellation of fenamiphos in the near future, alternative nematode management tactics for plant-parasitic nematodes (PPN) on golf courses need to be identified. The use of entomopathogenic nematodes (EPN) has been suggested as one possible alternative. This paper presents the results of 10 experiments evaluating the efficacy of EPN at managing PPN on turfgrasses and improving turf performance. These experiments were conducted at various locations throughout Florida over the course of a decade. In different experiments, different EPN species were tested against different species of PPN. Separate experiments evaluated multiple rates and applications of EPN, compared different EPN species, and compared single EPN species against multiple species of PPN. In a few trials, EPN were associated with reductions in certain plant-parasite species, but in other trials were associated with increases. In most trials, EPN had no effect on plant parasites. Because EPN were so inconsistent in their results, we conclude that EPN are not acceptable alternatives to fenamiphos by most turf managers in Florida at this time. 相似文献
654.
Ultrasonic calling during male-female encounters between individuals of the same species was investigated in six taxa of southern African gerbils, namely Tatera brantsii, Gerbillurus paeba paeba, G. p. cxilis, G. tytonis, G. setzeri, and G. vallinus. Vocalizations were detected by means of a bat detector utilizing a superheterodyne signal converter and a countdown circuit. Signals were recorded at audible frequencies and analysed with a sonograph. All taxa vocalized at ultrasonic frequencies by means of strongly modulated frequency “sweep” calls, which differed among taxa in duration, maximum and minimum frequency. “Clicks” were emitted by G. p. paeba and G. p. exilis, and G. tytonis emitted a “stutter” vocalization which consisted of a series of clicks. Long modulated “whistles” were identified from G. vallinus and T. brantsii at lower frequencies than “sweep” calls. Only one call type, a “sweep” call which differed in duration and frequency from all other taxa, was identified in G. setzeri. Cluster analysis was applied to the data using 7 acoustic characters. G. p. paeba and G. p. exilis displayed the highest similarity level between taxa and differed only in frequency of “sweep” vocalizations. G. paeba, G. tytonis and G. setzeri formed one cluster, while G. vallinus and T. brantsii formed a separate cluster. Numbers of calls in interspecific encounters were non-significantly less than in intraspecific encounters in all taxa except G. p. paeba, in which more vocalizations were recorded in inter- than intraspecific encounters. It is not clear whether species discrimination, measured by numbers of vocalizations in interspecific encounters, occurs. 相似文献
655.
The use of a monoclonal antibody specific for the envelope glycoprotein of rabies virus has been used in a direct enzyme immunoassay to quantify the glycoprotein content of rabies vaccines produced in two kinds of cell culture. The results of this direct enzyme immunoassay are well correlated with the in vivo NIH potency test. This test may be a useful tool to rapidly and accurately control the antigenic value of a vaccine. It could also be used for the "in process' control of vaccine production before deciding whether a vaccine batch may reasonably be subjected to the NIH potency test. 相似文献
656.
Binding of C3 and C3dg to the CR2 complement receptor induces growth of an Epstein-Barr virus-positive human B cell line 总被引:4,自引:0,他引:4
A Hatzfeld E Fischer J P Levesque R Perrin J Hatzfeld M D Kazatchkine 《Journal of immunology (Baltimore, Md. : 1950)》1988,140(1):170-175
The effect of ligand interactions with the C3d/C3dg complement receptor (CR2) on proliferation of human B lymphoblastoid cells was investigated by using cell cultures performed at low density (1 to 1.5 x 10(3) cells/ml) in a serum-free defined medium to which only transferrin had been added. This medium does not allow proliferation of Raji cells which die within 48 hr with formation of polykaryons. Addition of purified human C3 to the cultures resulted in a dose-dependent proliferation of the cells. A steady growth of Raji cells with a doubling time of 36 hr was observed in cultures containing 10 micrograms/ml of C3. A growth rate similar to that observed in the presence of native C3 was found in the presence of equimolar concentrations of purified C3dg but not of C3c. F(ab')2 anti-C3d but not F(ab')2 anti-C3c antibodies inhibited the mitogenic effect of C3. Preincubation of Raji cells with monoclonal antibody OKB7 which directly inhibits the binding of C3dg to CR2, totally suppressed C3-induced growth of the cells. C3 did not enhance growth of the T lymphoma-derived cell line JM and monocytic cell line U937 which do not express CR2. These results provide direct evidence that the interaction between CR2 and C3 fragments stimulates proliferation of human cells of the B lineage. Because CR2 also acts as a receptor for Epstein-Barr virus on B cells, our results may pertain to the B cell mitogenic properties of the virus. 相似文献
657.
S M Phillips P J Perrin D J Walker N G Fathelbab G P Linette M A Idris 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(5):1728-1733
These studies explore auto-anti-idiotypic mechanisms as potential regulators of the protective immune response against Schistosoma mansoni. Anti-idiotypic responses were stimulated by immunization of mice with lymphoblasts, bearing specific idiotypic receptors. These receptors were produced in vitro by stimulation of Ag-reactive T cells by soluble cercarial immunogen, keyhole limpet hemocyanin, or Con A. The animals were then exposed to irradiated cercariae, keyhole limpet hemocyanin, or SRBC. The results indicate that the soluble cercarial immunogen lymphoblast recipient mice demonstrated reduction in a number of parameters of their immune response to schistosome Ag, including resistance to challenge by parasites. These changes were immunologically specific. Anti-idiotypic antibodies and anti-clonotypic T cell reactivity was demonstrated in the lymphoblast immunized mice. The suppression of reactivity in LBM was mediated by Lyt-1-, L3T-4-, and Lyt-2+ lymphocytes. These studies suggest that idiotypically dependent pathways might be important for the regulation of resistance to schistosomiasis. 相似文献
658.
Using inbreeding theory as applied to neutral alleles inherited maternally,
we generate expected probability distributions of times to identity by
descent for random pairs of mitochondrial genotypes within a population or
within an entire species characterized by high gene flow. For comparisons
with these expectations, empirical distributions of times to most recent
common ancestry were calculated (by conventional mtDNA clock calibrations)
from mtDNA haplotype distances observed within each of three vertebrate
species--American eels, hardhead catfish, and redwinged blackbirds. These
species were chosen for analysis because census population size in each is
currently large and because both genetic and life-history data are
consistent with the postulate that historical gene flow within these
species has been high. The observed molecular distances among mtDNA
lineages were two to three orders of magnitude lower than predicted from
census sizes of breeding females, suggesting that rate of mtDNA evolution
is decelerated in these species and/or that long-term effective population
size is vastly smaller than present-day population size. Several
considerations point to the latter possibility as most likely. The genetic
structure of any species is greatly influenced by historical demography;
even for species that are currently abundant, mtDNA gene lineages appear to
have been channeled through fairly small numbers of ancestors.
相似文献
659.
J Belfaiza Y Guillou D Margarita D Perrin I Saint Girons 《Journal of bacteriology》1987,169(2):670-674
660.
A new method for the isolation of lipid droplets from rat liver has been devised. The procedure involves tissue homogenization and discontinuous density gradient centrifugation. Six discrete bands of lipid particles, rich in triglyceride and cholesterol, are visible following 30 min of centrifugation at 25,770 g (max) in a swinging bucket rotor. An entire rat liver can be processed in 1-2 hr. Differences in the density of these liver lipid particles correlate with their triglyceride, sterol, phospho-lipid, and protein contents. The separation of these distinct populations of intracellular particulate neutral lipids provides an approach to the study of their origin and metabolism. This procedure may also be useful in the isolation of various populations of lipid-rich particles from other tissues. 相似文献