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21.
22.
This study was essentially an in vivo protection experiment designed to test further the hypothesis that stress induces release of endogenous opioids which then act at opioid receptors. Rats that were either subjected to restraint stress for 1 hr or unstressed were injected ICV with either saline or 2.5 micrograms of beta-funaltrexamine (beta-FNA), an irreversible opioid antagonist that alkylates the mu-opioid receptor. Twenty-four hours later, subjects were tested unstressed for morphine analgesia (tail-flick assay) or were sacrificed and opioid binding in brain was determined. [3H]D-Ala2NMePhe4-Gly5(ol)enkephalin (DAGO) served as a specific ligand for mu- opioid receptors, and [3H]-bremazocine as a general ligand for all opioid receptors. Rats injected with saline while stressed were significantly less sensitive to the analgesic action of morphine 24 hr later than were their unstressed counterparts. Beta-FNA pretreatment attenuated morphine analgesia in an insurmountable manner. Animals pretreated with beta-FNA while stressed were significantly more sensitive to the analgesic effect of morphine than were animals that received beta-FNA while unstressed, consistent with the hypothesis that stress induces release of endogenous opioids that would protect opioid receptors from alkylation by beta-FNA. beta-FNA caused small and similar decreases in [3H]-DAGO binding in brain of both stressed and unstressed animals. Stressed rats injected with saline tended to have increased levels of [3H]DAGO and [3H]-bremazocine binding compared to the other groups. This outcome may be relevant to the tolerance to morphine analgesia caused by stress. 相似文献
23.
Generation of altered transcripts by retroviral insertion within the c-myb gene in two murine monocytic leukemias 总被引:14,自引:2,他引:12
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Two murine monocytic leukemia cell lines, WEHI-265 and WEHI-274, were found to carry a rearranged c-myb gene. The rearrangements are due to insertion of a deleted Moloney murine leukemia virus (Mo-MLV) provirus in the 5' region of the c-myb gene and thus are similar to rearrangements in the ABPL tumors (G. L. C. Shen-Ong, M. Potter, J. F. Mushinski, S. Lavu, and E. P. Reddy, Science 226:1077-1080, 1984). In each cell line, the retroviral insertion has induced high levels of two aberrant RNA species, which, as in the ABPL tumors (G. L. C. Shen-Ong, H. C. Morse, M. Potter, and J. F. Mushinski, Mol. Cell. Biol. 6:380-392, 1986), contain both viral (Mo-MLV) and cellular (myb) sequences. Both species lack the sequences encoding the amino terminus of the c-myb protein and thus could encode a protein which, like the v-myb gene products (and the predicted ABPL myb proteins), is truncated at the amino terminus. We have found that the larger (5.3 kilobase [kb]) and more abundant of the tumor-specific myb RNAs was predominantly nuclear, while the smaller species (3.9 kb) was cytoplasmic. Furthermore, our data imply that the 3.9-kb RNA was derived from the 5.3-kb RNA by an additional splice which utilized a cryptic splice acceptor site within the viral gag sequences. On the basis of subcellular distribution and predicted translational potential, we conclude that the 3.9-kb RNA is probably the mRNA which encodes a truncated myb protein. We also show that, due to different insertion points in W265 and W274, the W274 myb RNAs contained sequences from a c-myb exon upstream of the exons represented in the W265 (and ABPL) RNAs. The significance of our findings with regard to transformation by myb in these tumors is discussed. 相似文献
24.
Amino-terminal processing of proteins by N-myristoylation. Substrate specificity of N-myristoyl transferase 总被引:40,自引:0,他引:40
D A Towler S R Eubanks D S Towery S P Adams L Glaser 《The Journal of biological chemistry》1987,262(3):1030-1036
Using synthetic octapeptides, we examined the amino-terminal sequence requirements for substrate recognition by myristoyl-CoA:protein N-myristoyl transferase (NMT). NMT is absolutely specific for peptides with amino-terminal Gly residues. Peptides with Asn, Gln, Ser, Val, or Leu penultimate to the amino-terminal Gly were substrates, whereas peptides with Asp, D-Asn, Phe, or Tyr at this position were not myristoylated. Peptides with aromatic residues at this position competitively inhibited myristoylation of substrates, introducing the possibility of developing specific in vivo inhibitors of NMT. Peptides having sequences which correspond to those of known N-myristoyl proteins, including p60src, appear to be recognized by a single enzyme, and yeast and murine NMT have identical substrate specificities. The catalytic selectivity of NMT for myristoyl transfer accounts for the remarkable acyl chain specificity of this enzyme. 相似文献
25.
Acylcoenzyme A:estradiol-17 beta acyltransferase in microsomes of bovine placenta cotyledons was strongly membrane bound. The enzyme was solubilised from microsomes by sodium cholate and was reconstituted into phospholipid vesicles. The apparent Km for estradiol-17 beta was 11 microM which was close to the value of 8 microM previously found with the membrane-bound enzyme. Testosterone was also a substrate for the reconstituted enzyme (apparent Km 62 microM) and was a competitive inhibitor (Ki 74 microM) of the acylation of estradiol-17 beta. Although various long-chained fatty acyl CoAs acted as acyl donors, these proved to have widely differing apparent Km values with palmitoleoyl CoA having the highest affinity (Km 24 microM) and arachidonoyl CoA the lowest affinity (Km 330 microM). 相似文献
26.
An antibody to the receptor for insulin-like growth factor I inhibits the growth of MCF-7 cells in tissue culture 总被引:12,自引:0,他引:12
Q T Rohlik D Adams F C Kull S Jacobs 《Biochemical and biophysical research communications》1987,149(1):276-281
Alpha IR-3, a monoclonal antibody to the insulin-like growth factor I receptor which blocks insulin-like growth factor I binding and inhibits its activity, inhibits the binding of 125I-insulin-like growth factor I to MCF-7 cells (an estrogen dependent human breast carcinoma cell line) with an IC-50 of approximately 100 ng/ml. It also inhibits the growth of MCF-7 cells cultured in 5% calf serum with approximately the same IC-50. Inhibition of growth occurs both when cells are cultured in the presence and absence of estrogen and is more pronounced when cells are grown at a low density. These findings demonstrate a requirement for insulin-like growth factor I for optimal growth of MCF-7 cells and suggest that it is an autocrine growth factor in these cells. 相似文献
27.
28.
The yeast retrotransposon Ty encodes proteins that assemble into virus-like particles (Ty-VLPs) which can be readily purified. We have recently shown that expression of the pl protein encoded by the TYA gene of Ty is sufficient for particle formation. In this paper we show that when a heterologous coding sequence, human interferon-alpha 2 (IFN), is fused in frame to the TYA gene, the resulting p1-IFN fusion protein is still assembled into VLPs. These Ty:IFN-VLPs can be easily purified to near homogeneity and furthermore, they induce an antibody response to interferon when they are injected into rabbits. Therefore, these data show that hybrid Ty-VLPs can be used as a convenient system for the efficient purification of fusion proteins in yeast. 相似文献
29.
30.
King penguins are important consumers of marine resources, throughout the year, at the Prince Edward Islands. Meal size varied from 8.5–12.6% of adult mass, depending on the method of determination. In spite of the biases in the analysis favouring the overestimation of squid, fish and, in particular, myctophid fish accounted for the largest proportion of the stomach samples, 87% by wet mass, 75% by numbers and 69% by reconstituted mass. The relative abundance of fish in the diet dropped markedly in winter followed by a subsequent rise to nearly 100% in summer. This rise coincided with an increase in the chick growth rate and the king penguin population at the island and suggests the rise in relative abundance offish reflects a real increase in the availability of fish around the islands.
Juvenile and adult Krefftichthys anderssoni/Protomyctophum tenisoni and adult Electrona carlsbergi were the most common fish consumed. There was an increase in the modal size of K. anderssoni/P. tenisoni throughout the year which we interpret as growth of a single fish population. Juvenile Kondakoviu longimana was the important squid species taken by king penguins. Crustaceans were only rarely recorded in the diet and may have come from digestion of fish and squid stomachs.
This is the first study of the diet of a Southern Ocean pelagic predator that has identified myctophid fish as a major component of its diet. All three important fish species taken by king penguins at Marion Island have a wide distribution throughout the Southern Ocean and consequently may prove to be important dietary components of other Southern Ocean pelagic predators. 相似文献
Juvenile and adult Krefftichthys anderssoni/Protomyctophum tenisoni and adult Electrona carlsbergi were the most common fish consumed. There was an increase in the modal size of K. anderssoni/P. tenisoni throughout the year which we interpret as growth of a single fish population. Juvenile Kondakoviu longimana was the important squid species taken by king penguins. Crustaceans were only rarely recorded in the diet and may have come from digestion of fish and squid stomachs.
This is the first study of the diet of a Southern Ocean pelagic predator that has identified myctophid fish as a major component of its diet. All three important fish species taken by king penguins at Marion Island have a wide distribution throughout the Southern Ocean and consequently may prove to be important dietary components of other Southern Ocean pelagic predators. 相似文献