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排序方式: 共有495条查询结果,搜索用时 265 毫秒
1.
A naphthalene-degrading strain of corynebacteria, Corynebacterium renale, harbors multiple small plasmids designated pCR1, pCR2, pCR3, and pCR4 with sizes of 1.4, 3.2, 4.4, and 5.7 kb, respectively. Plasmid pCR1 of 1.4 kb is the smallest plasmid reported in this group of bacteria and is present in high copy number. Attempts to clone whole pCR1 in Escherichia coli were unsuccessful but two of its fragments (750 and 650 bp) could be separately cloned in it. The 4.4-kb plasmid, pCR3, bears considerable restriction pattern similarity to a 4.4-kb plasmid belonging to the pBL1 group of cryptic plasmid of corynebacteria but has no sequence homology, suggesting that pCR3 represents a new member of the 4.4-kb group of corynebacterial plasmids. 相似文献
2.
A 5.7-kb vector plasmid pBK2 was constructed by ligating the kanamycin resistance gene from Escherichia coli plasmid pACYC177 to an endogenous cryptic 4.4-kb plasmid of Brevibacterium lactofermentum ATCC 21086. The vector replicates efficiently and is stably maintained in the host and other coryneforms. However, the copy number varied from 50 to 10 per chromosome-equivalent under different culture conditions. Continuous culture studies showed instability when low dilution rates were used. Co-culture experiments were performed at various dilution rates to measure the growth rate ratio (alpha) of the plasmid-free cells to the plasmid-containing cells. It was observed that at low dilution rates the value of alpha was higher than that at high dilution rates. Thus, the instability of the plasmid can be attributed to the increase in alpha at low dilution rates. Modelling of instability using a random partitioning model of plasmid segregation and experimentally obtained values of alpha showed agreement with experimental data. This demonstrated that active partitioning is not the operative mechanism for plasmid segregation in this case. 相似文献
3.
Wayne K. Hoffman Peter Lalley Jean Deb Butler Sheldon Orloff Joseph D. Schulman Anil B. Mukherjee 《In vitro cellular & developmental biology. Plant》1981,17(8):735-740
Summary Using lipochromosomes (phospholipid-entrapped chromosomes) we have transferred the human HGPRT gene into HGPRT deficient mouse
cells (A9) with a frequency of approximately 1×10−5 (Mukherjee et al., Proc. Natl. Acad. Sci. USA 75: 1361–1365; 1978). Two other genes located on the long arm of the human
X-chromosome were also expressed in two independently derived populations of transferents (A9/GT3 and A9/GT4). We report here
the chromosomal and enzymatic composition of human HGPRT-positive clones from each subpopulation analyzed in detail with alkaline
Giemsa-11 staining.
All the clones expressed human PGK and HGPRT, but one (A9/GT4C6) lacked human G6PD. In each of four clones examined microscopically,
a small piece of presumptive human chromatin was visible in the karyotypes of most cells. The chromatin fragment was free
or attached in each cell of an individual clone. When integrated, the human chromosomal fragment in each clone appeared associated
with the centromere of the same telocentric A9 chromosome (No. 6 by Q-banding).
These data suggest that: (a) substantial human chromosomal fragments can be transferred into recipient cells using the lipochromosome
technique; (b) clones from human HGPRT positive A9 transferent subpopulations may or may not possess other human X-linked
markers; (c) the stability of lipochromosomally transferred genes varied from clone to clone and stability is generally poor
in the absence of continuous selection pressure (e.g., HAT); (d) when multiple X-linked human genes were transferred to mouse
cells a cytologically detectable human chromosomal fragment was identified free or attached to a host chromosome; and (e)
integration of transferred human chromosomal material into mouse chromosomes may occur at preferential site(s) in the recipient
genome.
This research was sponsored in part by the Office of Health and Environmental Research U.S. Department of Energy under Contract
W-7405-eng-26 with the Union Carbide Corporation. 相似文献
4.
Molecular cloning and characterization of prolactin-like protein C complementary deoxyribonucleic acid. 总被引:2,自引:0,他引:2
S Deb K F Roby T N Faria C Szpirer G Levan S C Kwok M J Soares 《The Journal of biological chemistry》1991,266(34):23027-23032
In this report, we describe the isolation and characterization of a full length cDNA clone for rat prolactin-like protein C (PLP-C) and describe the expression of PLP-C mRNA in the developing rat placenta. Nucleotide sequence analysis of the PLP-C cDNA clone predicted a mature protein of 238 amino acids, including a 30-amino acid signal sequence. The predicted PLP-C amino acid sequence contains seven cysteine residues, three tryptophan residues, and two putative N-linked glycosylation sites. Six of the cysteine residues in PLP-C are located in positions homologous to the cysteines of pituitary prolactin (PRL). Additional sequence similarities with pituitary PRL and other members of the rat placental PRL family are evident. The PLP-C gene was localized to rat chromosome 17. Northern blot analysis showed that the PLP-C cDNA clone specifically hybridized to a 1.0-kilobase mRNA. PLP-C mRNA was first detectable between days 13 and 14 of gestation, peaked by day 18 of gestation, and remained elevated until term. In situ hybridization analysis indicated that PLP-C mRNA was specifically expressed by spongiotrophoblast cells and some trophoblast giant cells in the junctional zone region of rat chorioallantoic placenta. 相似文献
5.
Identification and characterization of a new member of the prolactin family, placental lactogen-I variant 总被引:1,自引:0,他引:1
S Deb T N Faria K F Roby D Larsen S C Kwok F Talamantes M J Soares 《The Journal of biological chemistry》1991,266(3):1605-1610
This report describes the identification and characterization of a new member of the placental prolactin (PRL) family, termed placental lactogen-I variant (PL-Iv). PL-Iv was isolated from medium conditioned by late gestation placental explants. Rat PL-Iv was found to be closely related to rat PL-I. Amino-terminal sequence analysis indicated that PL-Iv shared approximately 88% sequence identity with the amino terminus of PL-I. PL-Iv proteins cross-reacted with antiserum to recombinant mouse PL-I and PL-Iv mRNA hybridized with a PL-I cDNA. Multiple PL-I and PL-Iv species were present in placental cytosol. Despite the structural similarities between PL-I and PL-Iv, distinct differences were also evident. Antibodies generated to the amino-terminal 19 amino acids of PL-Iv specifically recognized PL-Iv, while failing to recognize PL-I. Secreted PL-Iv had an affinity for concanavalin A, whereas secreted PL-I lacked affinity for the lectin. PL-I was predominantly secreted as a 36-40-kDa species and PL-Iv was predominantly secreted as a 33-kDa species. Furthermore, PL-I and PL-Iv were synthesized at different times during gestation and by different cell types. PL-I was synthesized by trophoblast giant cells during the first half of gestation, while PL-Iv was predominantly synthesized by spongiotrophoblast cells during the later stages of gestation. PL-Iv was shown to stimulate the proliferation of rat Nb2 lymphoma cells, an in vitro measure of lactogenic activity. In summary, PL-Iv shares structural similarities with PL-I; however, it shows other structural differences in addition to unique cell- and temporal-specific patterns of expression in the rat chorioallantoic placenta. 相似文献
6.
Dehydroascorbic acid reduction in human erythrocytes 总被引:1,自引:0,他引:1
S Basu S Som S Deb D Mukherjee I B Chatterjee 《Biochemical and biophysical research communications》1979,90(4):1335-1340
7.
8.
How cells regulate the size of intracellular structures and organelles is a longstanding question. Recent experiments suggest that size control of intracellular structures is achieved through the depletion of a limiting subunit pool in the cytoplasm. While the limiting pool model ensures organelle-to-cell size scaling, it does not provide a mechanism for robust size control of multiple co-existing structures. Here we develop a generalized theory for size-dependent growth of intracellular structures to demonstrate that robust size control of multiple intracellular structures, competing for a limiting subunit pool, is achieved via a negative feedback between the growth rate and the size of the individual structure. This design principle captures size maintenance of a wide variety of subcellular structures, from cytoskeletal filaments to three-dimensional organelles. We identify the feedback motifs for structure size regulation based on known molecular processes, and compare our theory to existing models of size regulation in biological assemblies. Furthermore, we show that positive feedback between structure size and growth rate can lead to bistable size distribution and spontaneous size selection. 相似文献
9.
10.
Jiban C. Deb Stuart Phinn Nathalie Butt Clive A. McAlpine 《Ecology and evolution》2017,7(7):2238-2248
Two ecologically and economically important, and threatened Dipterocarp trees Sal (Shorea robusta) and Garjan (Dipterocarpus turbinatus) form mono‐specific canopies in dry deciduous, moist deciduous, evergreen, and semievergreen forests across South Asia and continental parts of Southeast Asia. They provide valuable timber and play an important role in the economy of many Asian countries. However, both Dipterocarp trees are threatened by continuing forest clearing, habitat alteration, and global climate change. While climatic regimes in the Asian tropics are changing, research on climate change‐driven shifts in the distribution of tropical Asian trees is limited. We applied a bioclimatic modeling approach to these two Dipterocarp trees Sal and Garjan. We used presence‐only records for the tree species, five bioclimatic variables, and selected two climatic scenarios (RCP4.5: an optimistic scenario and RCP8.5: a pessimistic scenario) and three global climate models (GCMs) to encompass the full range of variation in the models. We modeled climate space suitability for both species, projected to 2070, using a climate envelope modeling tool “MaxEnt” (the maximum entropy algorithm). Annual precipitation was the key bioclimatic variable in all GCMs for explaining the current and future distributions of Sal and Garjan (Sal: 49.97 ± 1.33; Garjan: 37.63 ± 1.19). Our models predict that suitable climate space for Sal will decline by 24% and 34% (the mean of the three GCMs) by 2070 under RCP4.5 and RCP8.5, respectively. In contrast, the consequences of imminent climate change appear less severe for Garjan, with a decline of 17% and 27% under RCP4.5 and RCP8.5, respectively. The findings of this study can be used to set conservation guidelines for Sal and Garjan by identifying vulnerable habitats in the region. In addition, the natural habitats of Sal and Garjan can be categorized as low to high risk under changing climates where artificial regeneration should be undertaken for forest restoration. 相似文献