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131.
Evolution of the Ribosomal DNA Spacers of Drosophila melanogaster : Different Patterns of Variation on X and Y Chromosomes 总被引:4,自引:3,他引:1
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Length variation of the ribosomal gene spacers of Drosophila melanogaster was studied. Analysis of 47 X chromosomal and 47 Y chromosomal linked rDNA arrays collected from five continents indicates that the arrays on the two chromosomes differ qualitatively. The Y-linked arrays from around the world share little or no similarity for either their overall length or the organization of their spacers. Most of the X-linked arrays do, however, share a major length spacer of 5.1 kb. In addition, those X-linked arrays that have a major 5.1-kb band have similar spacer organization as demonstrated by genomic DNA digestions with several restriction enzymes. These data strongly support the hypothesis that spacer length patterns on only X-linked genes are maintained primarily by natural selection. 相似文献
132.
Protein kinase C-dependent and -independent pathways of proto-oncogene induction in human astrocytoma cells 总被引:8,自引:0,他引:8
P J Blackshear D J Stumpo J K Huang R A Nemenoff D H Spach 《The Journal of biological chemistry》1987,262(16):7774-7781
We compared the abilities of the muscarinic agonist carbachol, epidermal growth factor (EGF), and phorbol 12-myristate 13-acetate (PMA) to induce proto-oncogene mRNA accumulation and other cellular responses in normal and protein kinase C-deficient 1321-N1 human astrocytoma cells. PMA, carbachol, and EGF all stimulated rapid accumulation of mRNA for the proto-oncogenes c-fos and c-myc in the normal cells; in the protein kinase C-deficient cells, carbachol and EGF, but not PMA, retained this effect, which was not mimicked by the calcium ionophore A23187. Both carbachol and PMA activated protein kinase C in these cells, as evidenced by the stimulated phosphorylation of an acidic Mr 80,000 protein kinase C substrate protein with phosphoamino acid and peptide map identity. This response was mimicked by several other neurotransmitters in these cells, including epinephrine, histamine, oxotremorine, and serotonin, and was abolished in cells made protein kinase C-deficient by preincubation with high concentrations of PMA. Both PMA and carbachol promoted the phosphorylation of the ribosomal protein S6 and activated an S6 protein kinase in the normal but not in the protein kinase C-deficient cells. EGF, in contrast, did not appear to activate protein kinase C, but promoted the phosphorylation of S6 and activation of the S6 kinase in both normal and protein kinase C-deficient cells. We conclude that, in 1321-N1 cells, induction of c-fos and c-myc mRNA can occur through a protein kinase C-dependent pathway and one or more independent pathways, exemplified by the responses to carbachol and EGF in the protein kinase C-deficient cells. 相似文献
133.
Purification and characterization of proteolytic fragments of lipocortin I that inhibit phospholipase A2 总被引:3,自引:0,他引:3
K S Huang P McGray R J Mattaliano C Burne E P Chow L K Sinclair R B Pepinsky 《The Journal of biological chemistry》1987,262(16):7639-7645
Human lipocortin I is a 38.5-kDa phospholipase A2 inhibitor that has been produced in Escherichia coli in large quantities by recombinant DNA technology (Wallner, B.P., Mattaliano, R.J., Hession, C., Cate, R. L., Tizard, R., Sinclair, L.K., Foeller, C., Chow, E.P., Browning, J.L., Ramachandran, K.L., and Pepinsky, R.B. (1986) Nature 320, 77-80). To localize the region within the protein responsible for its inhibitory activity, we generated a series of fragments of the recombinant product by limited proteolysis with elastase and characterized their structure by sequencing and peptide mapping. Five active fragments have been analyzed in detail. The smallest is an 18-kDa fragment derived from the amino-terminal half of lipocortin. Three of the larger fragments contain this region. The fifth fragment is missing 83 amino acids from the amino terminus. A region common to all the active fragments (amino acid residues 97-178) is 70% homologous with the corresponding region from a second member of the lipocortin family which recently was cloned (Huang, K-S., Wallner, B.P., Mattaliano, R.J., Tizard, R., Burne, C., Frey, A., Hession, C., McGray, P., Sinclair, L.K., Chow, E.P., Browning, J.L., Ramachandran, K.L., Tang, J., Smart, J.E., and Pepinsky, R.B. (1986) Cell 46, 191-199) and thus presumably is important for activity. In addition to inhibitory fragments, we have isolated a 3-kDa proteolytic fragment from the amino terminus of lipocortin I that contains the known phosphorylation site for protein-tyrosine kinases. Because of sequence homology of the 3-kDa fragment with biologically active synthetic peptides from pp60v-src and middle T antigen, its release by proteases may represent an important part of the activity of lipocortin. 相似文献
134.
The properties of batrachotoxin-modified cardiac Na channels, including state-dependent block by tetrodotoxin 总被引:6,自引:2,他引:4
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Batrachotoxin (BTX) modification and tetrodotoxin (TTX) block of BTX-modified Na channels were studied in single cardiac cells of neonatal rats using the whole-cell patch-clamp recording technique. The properties of BTX-modified Na channels in heart are qualitatively similar to those in nerve. However, quantitative differences do exist between the modified channels of these two tissues. In the heart, the shift of the conductance-voltage curve for the modified channel was less pronounced, the maximal activation rate constant, (tau m)max, of modified channels was considerably slower, and the slow inactivation of the BTX-modified cardiac Na channels was only partially abolished. TTX blocked BTX-modified mammalian cardiac Na channels and the block decreased over the potential range of -80 to -40 mV. The apparent dissociation constant of TTX changed from 0.23 microM at -50 mV to 0.69 microM at 0 mV. No further reduction of block was observed at potentials greater than -40 mV. This is the potential range over which gating from closed to open states occurred. These results were explained by assuming that TTX has a higher affinity for closed BTX-modified channels than for open modified channels. Hence, the TTX-binding rate constants are considered to be state dependent rather than voltage dependent. This differs from the voltage dependence of TTX block reported for BTX-modified Na channels from membrane vesicles incorporated into lipid bilayers and from amphibian node of Ranvier. 相似文献
135.
H Hagiwara H J Huang N Arai L A Herzenberg K Arai A Zlotnik 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(8):2514-2519
136.
D J McCormick G E Griesmann Z X Huang E H Lambert V A Lennon 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(8):2615-2619
This study reports the synthesis of a disulfide-looped peptide corresponding to residues 125-147 (Cys 128-Cys 142) of the nicotinic acetylcholine receptor (AChR) of human skeletal muscle, H alpha 125-147 (Lys-Ser-Tyr-Cys-Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu-Gln- Asn-Cys-Ser-Nle-Lys Leu-Gly), and a nondisulfide-looped analogue, H alpha 125-147(S) (Lys-Ser-Tyr-Ser-Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu- Gln-Asn-Cys-Ser-Nle-Lys-Leu-Gly), in which the amino acid Cys 128 was replaced with serine. Both peptides induced antigen-specific helper T cell responses, as evidenced in vitro by lymph node cell proliferation and in vivo by production of anti-AChR antibodies. Rats immunized with 100 micrograms of either synthetic peptide, without conjugation to a carrier, produced anti-peptide antibodies which bound to native AChR in immunoprecipitation assays and induced modulation of membrane-bound AChR from cultured human myotubes. Both peptides also induced electrophysiologic and biochemical signs of experimental autoimmune myasthenia gravis. Thus, region 125-147 of the AChR alpha-subunit is at least partly exposed extracellularly in human muscle and contains one or more autoantigenic sites capable of stimulating T cells and B cells. Disulfide-linkage between residues Cys 128 and Cys 142 is not essential for myasthenogenicity. 相似文献
137.
Species specificity of bacterial palindromic units 总被引:8,自引:0,他引:8
Eric Gilson David Perrin William Saurin Maurice Hofnung 《Journal of molecular evolution》1987,25(4):371-373
We described previously a family of dispersed palindromic sequences highly repeated in Escherichia coli and Salmonella typhimurium genomes. These sequences, called PU (palindromic units), are located outside structural genes. We report here observations suggesting that PU may have a role in bacterial speciation. 相似文献
138.
139.
利用 XAD-4憎水性吸附树脂采集墨红头香,以毛细管气相色谱双柱保留指数和 GC/MS/DS 联用方法鉴定头香的化学成份。共分离鉴定或初步鉴定了45种组份,其中含量较大的有乙酸芳樟酯(14.98%),柠檬烯(12.07%),甲基苯甲醚(9.88%),香茅醇(4.82%),乙酸巳酯(3.98%),β-石竹烯(4.55%),芳樟醇(3.18%),正巳醇(3.17%)等. 相似文献
140.
Vertical distributions and relations of euphausiid populations off Elephant Island,March 1984 总被引:4,自引:3,他引:1
Summary Distributional relationships are described for post-larval and larval Euphausia superba and Thysanoessa sp. (probably macrura) and post-larval Euphausia frigida collected in 0–70/80 m and 0–175/200 m depth ranges with a MOCNESS sampler north of Elephant Island (61°S, 55°W) during 17–23 March 1984. Larval E. superba (predominantly calyptopes stage 2 and 3) were rare shallower than 80 m at night. Day catches of post-larval E. suberba were small and night catches were primarily near the top of the thermocline above 50 m depth. Thysanoessa sp. occurred throughout the 0–200 m depth range and was abundant in the upper 80 m both night and day. E. frigida migrated to the upper 80 m at night from deeper day depths. Larval stages of E. superba and bost-larval stages of all three species demonstrated independent and variable vertical distribution patterns both night and day. Changes in E. superba abundance and distributional patterns could to a certain extent be associated with observed environmental changes. An increase in larval and decrease in post-larval E. superba abundances between 0–80 m was associated with an intrusion of cold water at depth. At night, vertically restricted concentrations of post-larval E. superba were associated with shallow mixed layer depths, and a significant vertical separation of developmental stages and size categories was observed only during periods of stratification in the upper 80 m. Fluctuations in the distribution and abundance of Thysanoessa sp. and distribution of E. frigida did not appear to be influenced by physical parameters within the upper 80 m. Within the 0–80 m depth range, the distributions of these two species differed from each other and from E. superba and showed large tow to tow variability that could not be related to physical parameters in the upper water column. 相似文献