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1.
A method by which virus penetration through condoms can be tested with simple, inexpensive equipment is described. The method uses chi X174 bacteriophage as the challenge virus and physiologically relevant pressure. Penetration by 0.1 microliters (or less) of challenge suspension can be readily detected. As examples, latex and natural-membrane condoms were examined. 相似文献
2.
Roy E. Crabtree Edward C. Cyr Renée E. Bishop Laura M Falkenstein John M. Dean 《Environmental Biology of Fishes》1992,35(4):361-370
Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration. 相似文献
3.
Neurons require a large amount of intracellular transport. Cytoplasmic polypeptides and membrane-bounded organelles move from
the perikaryon, down the length of the axon, and to the synaptic terminals. This movement occurs at distinct rates and is
termed axonal transport. Axonal transport is divided into the slow transport of cytoplasmic proteins including glycolytic
enzymes and cytoskeletal structures and the fast transport of membrane-bounded organelles along linear arrays of microtubules.
The polypeptide compositions of the rate classes of axonal transport have been well characterized, but the underlying molecular
mechanisms of this movement are less clear. Progress has been particularly slow toward understanding force-generation in slow
transport, but recent developments have provided insight into the molecular motors involved in fast axonal transport. Recent
advances in the cellular and molecular biology of one fast axonal transport motor, kinesin, have provided a clearer understanding
of organelle movement along microtubules. The availability of cellular and molecular probes for kinesin and other putative
axonal transport motors have led to a reevaluation of our understanding of intracellular motility. 相似文献
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7.
The delta psi- and Hsp70/MIM44-dependent reaction cycle driving early steps of protein import into mitochondria. 总被引:7,自引:4,他引:3
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New steps in the reaction cycle that drives protein translocation into the mitochondrial matrix have been defined. The membrane potential (delta psi)- and the mtHsp70/MIM44-dependent import machinery cooperate in the transfer of the presequence across the inner membrane. Translocation intermediates, arrested at a stage where only the presequence could form a complex with mtHsp70, still required delta psi for further import. Delta psi at this stage prevented retrograde movement, since mtHsp70 did not bind to the presequence with sufficient affinity. In contrast, mature regions of incoming chains adjacent to the presequence were bound by mtHsp70 tightly enough to stabilize them in the matrix. Cycling of the mtHsp70 on and off incoming chains is a continuous process in the presence of matrix ATP. Both MIM44-bound and free forms of mtHsp70 were found in association with the incoming chains. These data are consistent with a reaction pathway in which the mtHsp70/MIM44 complex acts as a molecular ratchet on the cis side of the inner membrane to drive protein translocation into the matrix. 相似文献
8.
Summary While reported interactions of elongation factor-1 (EF-1) with various other molecules involved in protein biosynthesis are abundant, its interactions with major cytoskeletal proteins have not been as extensively examined. Major roles for EF-1 in cytoskeletal organization emerge from a review of such interactions within species as diverse as slime molds and mammals, sea urchins and higher plants. Based on these studies, the integration of EF-1's cytoskeletal roles with those of translation is considered, and prospective mechanisms for regulation of EF-1's cytoskeletal associations are discussed.Abbreviations EF
elongation factor
- RNP
ribonucleoprotein particle
- MT
microtubule
- MA
mitotic apparatus
- CaM
calmodulin
- MAP
microtubule-associated protein 相似文献
9.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
10.
Genetically and phenotypically identical immune cell populations can be highly heterogenous in terms of their immune functions and protein secretion profiles. The microfluidic chip-based single-cell highly multiplexed secretome proteomics enables characterization of cellular heterogeneity of immune responses at different cellular and molecular layers. Increasing evidence has demonstrated that polyfunctional T cells that simultaneously produce 2+ proteins per cell at the single-cell level are key effector cells that contribute to the development of potent and durable cellular immunity against pathogens and cancers. The functional proteomic technology offers a wide spectrum of cellular function assessment and can uniquely define highly polyfunctional cell subsets with cytokine signatures from live individual cells. This high-dimensional single-cell analysis provides deep dissection into functional heterogeneity and helps identify predictive biomarkers and potential correlates that are crucial for immunotherapeutic product design optimization and personalized immunotherapy development to achieve better clinical outcomes. 相似文献