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M A Lieberman P Rothenberg D M Raben L Glaser 《Biochemical and biophysical research communications》1980,92(2):696-702
Epidermal growth factor (EGF) induced DNA synthesis in non-confluent, G0-arrested Swiss 3T3 fibroblasts is partially blocked by plasma membranes isolated from the EGF receptor deficient NR-6 Swiss 3T3 cell line. This inhibition could be due to either a steric block of the receptor by the membranes, a membrane induced down regulation of the EGF receptor, or a signal generated by membrane binding which is antagonistic towards the mitogenic signal generated by EGF. Binding measurements utilizing 125I-labeled EGF demonstrated that membranes do not block either the EGF induced down regulation of the receptor or alter the number of receptors on the surface. These results suggest that the membranes exert their inhibitory effect via generation of a signal which is antagonistic to the EGF induced mitogenic signal, with the result expressed as a reduced mitogenic response. 相似文献
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Heparin potentiates the action of plasma membrane-associated growth stimulatory activity 总被引:1,自引:0,他引:1
Plasma membranes prepared from mouse liver have been previously shown to contain growth stimulatory activity as determined with cultured mouse fibroblasts. This growth stimulatory activity, termed plasma membrane-associated growth stimulatory activity (PMGA), is highly mitogenic in the presence of platelet-poor plasma. We now demonstrate that the growth stimulatory action of PMGA is dramatically enhanced by the addition of heparin. The half-maximal effect of heparin was observed at 1-3 micrograms/ml. The synergistic effect was seen in two distinct assays; the stimulation of DNA synthesis in quiescent cells, and an increase of cell number over a 3-day culture period. Heparin, by itself, does not have any measurable influence on the growth of fibroblasts. The action of heparin is not unique to this glycosaminoglycan, as several other highly sulfated polysaccharides, including dextran sulfate, pentosan polysulfate, and fucoidan, also exhibited the highly synergistic effect. Among other glycosaminoglycans examined, chondroitin sulfate B and heparan sulfate had a small, but significant, effect on enhancing the growth stimulatory action of PMGA. Chondroitin sulfate A, chondroitin sulfate C, hyaluronic acid dextran, and poly-L-glutamic acid, however, had no detectable effect. Further experiments suggested that the effect of heparin is twofold, namely, both a potentiation of growth stimulatory activity and a protection of PMGA activity. The data presented here suggest that the association of various cell surface components, such as PMGA and specific proteoglycans, can modulate the growth potential of a cell. 相似文献
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Carboxypeptidase Y digestion of band 3, the anion transport protein of human erythrocyte membranes 总被引:1,自引:0,他引:1
The exposure of the carboxyl-terminal of the Band 3 protein of human erythrocyte membranes in intact cells and membrane preparations to proteolytic digestion was determined. Carboxypeptidase Y digestion of purified Band 3 in the presence of non-ionic detergent released amino acids from the carboxyl-terminal of Band 3. The release of amino acids was very pH dependent, digestion being most extensive at pH 3, with limited digestion at pH 6 or above. The 55,000 dalton carboxyl-terminal fragment of Band 3, generated by mild trypsin digestion of ghost membranes, had the same carboxyl-terminal sequence as intact Band 3, based on carboxypeptidase Y digestion. Treatment of intact cells with trypsin or carboxypeptidase Y did not release any amino acids from the carboxyl-terminal of Band 3. In contrast, carboxypeptidase Y readily digested the carboxyl-terminal of Band 3 in ghosts that were stripped of extrinsic membrane proteins by alkali or high salt. This was shown by a decrease in the molecular weight of a carboxyl-terminal fragment of Band 3 after carboxypeptidase Y digestion of stripped ghost membranes. No such decrease was observed after carboxypeptidase Y treatment of intact cells. In addition, Band 3 purified from carboxypeptidase Y-treated stripped ghost membranes had a different carboxyl-terminal sequence from intact Band 3. Cleavage of the carboxyl-terminal of Band 3 was also observed when non-stripped ghosts or inside-out vesicles were treated with carboxypeptidase Y. However, the digestion was less extensive. These results suggest that the carboxyl-terminal of Band 3 may be protected from digestion by its association with extrinsic membrane proteins. We conclude, therefore, that the carboxyl-terminal of Band 3 is located on the cytoplasmic side of the red cell membrane. Since the amino-terminal of Band 3 is also located on the cytoplasmic side of the erythrocyte membrane, the Band 3 polypeptide crosses the membrane an even number of times. A model for the folding of Band 3 in the erythrocyte membrane is presented. 相似文献
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P. Lieberman 《Human Evolution》1988,3(1-2):3-18
The evolution of human speech and syntax, which appear to be the defining characteristics of modern human beings, is discussed. Speech depends on the morphology of the mouth, tongue, and larynx which yield the human «vocal tract», and neural mechanisms that facilitate the perception of speech and make possible the control of the articulatory gestures that underly speech. The neural mechanisms that underly human syntax may have derived by means of the Darwinian process of preadaption from the structures of the brain that first evolved to facilitate speech motor control. Recent data consistent with this theory are presented; deficits in the comprehension of syntax of normal aged people are correlated with a slowdown in speech rate. 相似文献
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D J Orlicky R Lieberman C Williams L E Gerschenson 《Prostaglandins, leukotrienes, and essential fatty acids》1988,31(2):73-81
We have proposed that two of the endogenously synthesized endometrial prostaglandins, prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E1 (PGE1), play a regulatory role in growth control of the endometrium. PGF2 alpha increases DNA synthesis and PGE1 inhibits that effect. Primary cultures of rabbit endometrial cells were used here to examine the effects of the tumor-promoting, diacylglycerol mimicking, phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate (TPA), on the prostaglandin control of cell proliferation. TPA treatment of these cultures results in: a decrease in control levels of proliferation and complete inhibition by TPA of PGF2 alpha stimulated DNA synthesis; a reduction in [3H]PGF2 alpha binding with short term treatment but an increase to above control binding level with long term treatment; an inhibition of the normal PGF2 alpha stimulated inositol polyphosphate synthesis; and a small increase in accumulation of PGF2 alpha in the culture media. Furthermore, in this culture system, TPA does not down regulate [3H]PGE1 binding; it does not alter the normal PGE1 stimulation of cAMP synthesis; and it has no effect on the normal endogenous PGE1 synthesis by these cultures. The above results are consistent with our previous observations that PGF2 alpha works through the intracellular messengers inositol polyphosphate/diacylglycerol whereas PGE1 works through cAMP. 相似文献
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Development of captive bongos (Tragelaphus eurycerus): Activity budgets and developmental milestones
Debra L. Forthman Lorraine A. Perkins Joan I. Mead Nicolette S. Miller 《Zoo biology》1992,11(3):197-207
The development of changes in visual orientation, posture, activity budgets, and behavioral milestones was examined in five bongo calves which were observed from birth to 4 or 6 months of age. The only significant change in the calves' visual orientation was an increase in orientation to food. Reclining declined significantly over weeks, while standing increased and moving did not change. Overall, stationary behaviors dominated the activity budget, but decreased significantly over the study. The category that included locomotion, object exploration, and auto-play did not change, while forage and rumination increased significantly. Contrary to expectation, the decline in suckling was not significant. Affiliative interactions with the dam decreased significantly during the study, but increases in affiliation with other bongos were not significant. Levels of agonistic behavior between the calves and their dams and other herd members were low throughout the study, and did not change significantly. One female calf achieved several developmental milestones later than the others. It is suggested that these differences may have been influenced by the dominance status of her dam. The results conform to the general developmental pattern of “hider” bovids. Bongos, however, show somewhat different patterns of social development than eland, which are reported to be more precocial in expression of aggressive and sexual behaviors. © 1992 Wiley-Liss, Inc. 相似文献