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1.
The incidental catch of northern sea lions ( Eumetopias jubatus ) in the walleye pollock ( Theragra chalcogramma ) joint-venture fishery in Shelikof Strait, Alaska, was studied during 1982–1984 to assess the nature and magnitude of the catch. Data were obtained by placing U.S. observers on foreign processing vessels. Dead sea lions recovered from trawl nets were counted, sexed and measured, teeth were removed for age determination by dental laminae; and stomach contents were analyzed. Although the fishery has continued to expand both in number of boats and estimated total catch (74,136 metric tons [t] in 1982 to 171,539 t in 1984), the estimated incidental catch of northern sea lions has declined (ranging from 958 to 1,436 in 1982, 216 to 324 in 1983 and 237 to 355 in 1984). Of the sea lions processed, 73 percent were caught between 2000 and 0500 h, probably during net retrieval. Most caught sea lions were females ranging in age from 1–25 yr with a mean age of 6.43 yr; 79 percent of the females were sexually mature and probably part of the reproducing population. Males had a mean age of 4.8 yr and only 12 percent were old enough to obtain and defend territories. Analysis of stomach contents showed that the sea lions consumed pollock the same size as that taken by the commercial fishery. The impact of the incidental catch on the Gulf of Alaska sea lion population is unknown. 相似文献
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Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
4.
Differential allelic expression of the type II collagen gene (COL2A1) in osteoarthritic cartilage. 总被引:2,自引:0,他引:2 下载免费PDF全文
J Loughlin C Irven N Athanasou A Carr B Sykes 《American journal of human genetics》1995,56(5):1186-1193
Osteoarthritis (OA) is a common debilitating disease resulting from the degeneration of articular cartilage. The major protein of cartilage is type II collagen, which is encoded by the COL2A1 gene. Mutations at this locus have been discovered in several individuals with inherited disorders of cartilage. We have identified 27 primary OA patients who are heterozygous for sequence dimorphisms located in the coding region of COL2A1. These dimorphisms were used to distinguish the mRNA output from each of the two COL2A1 alleles in articular cartilage obtained from each patient. Three patients demonstrated differential allelic expression and produced < 12% of the normal level of mRNA from one of their COL2A1 alleles. The same allele shows reduced expression in all three patients, and this allele is more frequent in a well-defined OA population than in a control group, suggesting the possible existence of a rare COL2A1 allele that predisposes to OA. 相似文献
5.
cysK mutants, deficient in O-acetylserine sulphydrylase A [O-acetyl-L-serine acetate-lyase (adding hydrogen-sulphide); EC 4.2.99.8], were isolated as strains resistant to selenite or giving a black colour reaction on bismuth citrate indicator medium. All were resistant to the inhibitor I,2,4-triazole. Four independent mutants were found which possessed lowered levels of O-acetylserine sulphydrylase activity and also partially constitutive levels of NADPH-sulphite reductase [hydrogen-sulphide: NADP+ oxidoreductase; EC I.8.I.2]. Strains containing both a cysE mutation and a cysK mutation lacked the constitutive levels of NADPH-sulphite reductase showing that these levels were due to the in vivo concentration of the inducer, O-acetylserine. The cysK locus was found to be 81% cotransducible with the ptsI gene. 相似文献
6.
Investigations into the parameters affecting the enantiomeric separation of an intermediate in the synthesis of a drug targeted for cardiac arrhythmia is presented. The separation was achieved under subcritical fluid chromatography using CO2 modified with methanol and co-modifiers isopropyl amine and methylene chloride. The stationary phase was a cellulose based stationary phase manufactured under the trade name Chiracel OB. The results showed the addition of methylene chloride had a noticeable effect on resolution while the separation factor, α, remained constant. The co-modifier, isopropyl amine, did not considerably influence the resolution, or separation factor. Temperature studies were performed in order to establish the thermodynamic parameters of the interaction between the enantiomers and the stationary phase. Plots of In k′ vs. 1/T proved to be curved, while plots of In α vs. 1/T were linear. © 1996 Wiley-Liss, Inc. 相似文献
7.
Two promoter-detection vectors have been constructed which enable the cloning and characterization of promoters recognized by the RNA polymerase of Escherichia coli K-12. The intergenic region of phage M13 DNA, present in opposite orientations in the two vectors, permits the preparation of single-stranded DNA of either strand of the insert thus facilitating oligodeoxyribonucleotide heteroduplex mutagenesis and sequencing of both strands by the dideoxy method of chain termination. After mutagenesis, isolates can be screened for changed function by replica-plating colonies to plates containing XGal. Selected isolates can be characterized by nucleotide sequence analysis, to determine the change in structure, and by beta-galactosidase assays, thus measuring the effect of mutagenesis on promoter function. The vectors could also be used like other protein-fusion vectors. 相似文献
8.
Williams DD Price NT Loughlin AJ Proud CG 《The Journal of biological chemistry》2001,276(27):24697-24703
Initiation factor eIF2B mediates a key regulatory step in the initiation of mRNA translation, i.e. the regeneration of active eIF2.GTP complexes. It is composed of five subunits, alpha-epsilon. The largest of these (epsilon) displays catalytic activity in the absence of the others. The catalytic mechanism of eIF2B and the functions of the other subunits remain to be clarified. Here we show that, when present at similar concentrations to eIF2, mammalian eIF2B can mediate release of eIF2-bound GDP even in the absence of free nucleotide, indicating that it acts as a GDP dissociation stimulator protein. Consistent with this, addition of GDP to purified eIF2.eIF2B complexes causes them to dissociate. The alternative sequential mechanism would require that eIF2Bepsilon itself bind GTP. However, we show that it is the beta-subunit of eIF2B that interacts with GTP. This indicates that binding of GTP to eIF2B is not an essential element of its mechanism. eIF2B preparations that lack the alpha-subunit display reduced activity compared with the holocomplex. Supplementation of such preparations with recombinant eIF2Balpha markedly enhances activity, indicating that eIF2Balpha is required for full activity of mammalian eIF2B. 相似文献
9.
DAZ family proteins exist throughout male germ cell development and transit from nucleus to cytoplasm at meiosis in humans and mice 总被引:17,自引:0,他引:17
Reijo RA Dorfman DM Slee R Renshaw AA Loughlin KR Cooke H Page DC 《Biology of reproduction》2000,63(5):1490-1496
The human DAZ gene family is expressed in germ cells and consists of a cluster of nearly identical DAZ (deleted in azoospermia) genes on the Y chromosome and an autosomal homolog, DAZL (DAZ-like). Only the autosomal gene is found in mice. Y-chromosome deletions that encompass the DAZ genes are a common cause of spermatogenic failure in men, and autosomal homologs of DAZ are essential for testicular germ cell development in mice and DROSOPHILA: Previous studies have reported that mouse DAZL protein is strictly cytoplasmic and that human DAZ protein is restricted to postmeiotic cells. By contrast, we report here that human DAZ and human and mouse DAZL proteins are present in both the nuclei and cytoplasm of fetal gonocytes and in spermatogonial nuclei. The proteins relocate to the cytoplasm during male meiosis. Further observations using human tissues indicate that, unlike DAZ, human DAZL protein persists in spermatids and even spermatozoa. These results, combined with findings in diverse species, suggest that DAZ family proteins function in multiple cellular compartments at multiple points in male germ cell development. They may act during meiosis and much earlier, when spermatogonial stem cell populations are established. 相似文献
10.
Sean Martin Andrew Vincent Anne W. Taylor Evan Atlantis Alicia Jenkins Andrzej Januszewski Peter O’Loughlin Gary Wittert 《PloS one》2015,10(10)