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1.
A radioimmunoassay has been developed for the detection and quantification of a human serum polypeptide that has growth-promoting activity for confluent Balb/c-3T3 cells. Antiserum to this growth factor does not recognize antigens in mouse, guinea pig, or bovine serum but does detect some crossreacting antigen in the serum of the New World monkey Cebus albifrons and more in the serum of the Old World rhesus monkeys Macaca mulatta and M. fascicularis, demonstrating that the antigenic determinants of the growth factor have a degree of species specificity. Serum derived from whole human blood contains approximately 770 pg of the growth factor per mg of protein; serum derived from platelet-poor blood contains about 112 pg of the growth factor per mg of protein. As much as 1 microng of the growth factor per mg of protein has been recovered from human platelets by heating them at 100 degrees for 2 min. Approximately 1-2 ng of the growth factor, in either whole serum or platelets, stimulates 5 to 10 X 10(3) confluent Balb/c-3T3 cells to replicate. The heat treatment of platelets allows the purification and quantitative recovery of the growth factor from blood.  相似文献   

2.
Porcine aortic endothelial cells were isolated and maintained in Dulbecco's modified Eagle's medium (DME medium)/10% citrate-treated human plasma. They were stimulated by DME medium/10% human serum to grow from a density of 10,100 ± 500 per well to a final density of 83,000 ± 1,800 per well over a 9-day period. On the other hand these cells grew poorly (11% increase) in DME medium/10% human platelet-poor plasma prepared without chelating agents and containing platelet factor 4 at 18 ng/ml by radioimmunoassay. Dialysis of the human serum (Mr cutoff, 3,500) eliminated all the stimulatory activity. The activity recovered from the dialysate stimulated growth when added to endothelial cultures in conjunction with either dialyzed serum or platelet-poor plasma alone. The dialyzable factor could be obtained directly from platelets; both acetic acid extracts and boiled NaCl extracts stimulated porcine aortic endothelial cell replication. Gel filtration chromatography on Sephadex G-15 showed that the endothelial growth factor had a molecular weight of 700. Partially purified material induced a concentration-dependent stimulation of porcine aortic endothelial cell replication in the presence of DME medium alone; however, simultaneous incubation with platelet-poor plasma resulted in a much greater response. Fibroblast growth factor isolated from bovine brain was found to be mitogenic only in the presence of nondialyzed serum or of the dialyzable factor together with plasma. In the absence of this serum factor, fibroblast growth factor had no effect. We conclude that human serum contains a potent endothelial cell mitogen of platelet origin. Human plasma that is devoid of platelet content does not stimulate endothelial cell growth. This growth factor may be an important stimulant of the endothelial cell response to vascular wall injury.  相似文献   

3.
OBJECTIVE: Vascular smooth muscle cell hyperplasia plays a role in atherosclerosis and restenosis. While heparin has shown promise as an inhibitor of smooth muscle cell proliferation in vitro and in some animal models, it has failed to reduce restenosis in clinical trials. We have previously shown that human smooth muscle cells grown in the presence of human serum are heparin resistant, whereas in the presence of bovine serum they are heparin sensitive. In this report, we demonstrate that the heparin resistance factor is present in human plasma as well as serum, and characterise it further. METHODS: Human vascular smooth muscle cells were cultured as explants from the media of redundant adult internal mammary or umbilical cord arteries. They were tested for sensitivity to heparin at 100 microg/ml in the growth medium, in the presence of foetal bovine serum, human-plasma-derived serum, human whole blood serum, or fractions derived from these. RESULTS: In the presence of foetal bovine serum, heparin inhibited cell proliferation, while human-plasma-derived or whole blood sera conveyed heparin resistance. This activity was contained within the fraction of plasma/serum which bound to heparin Sepharose, and the sub-fraction which was retained by a membrane filter of molecular weight cut off of 100000. All the heparin resistance in this latter fraction was supplied by lipoproteins. LDL prepared directly from human plasma conveyed similar heparin resistance to the lipoproteins from the above sub-fraction. CONCLUSION: LDL in human plasma/serum conveys resistance to the anti-proliferative effects of heparin upon vascular smooth muscle cells. This activity may interfere with potential therapeutic effects of heparin as an anti-restenosis agent.  相似文献   

4.
OBJECTIVES--To investigate the role of platelet activation in the development of systemic sclerosis and the role of interferon-gamma (IFN gamma) in the inhibition of mitogenic activity induced by whole blood serum of patients with systemic sclerosis. METHODS--The mitogenic activity of whole blood serum in the absence or presence of different concentrations of IFN gamma (a potent inhibitor of induced collagen synthesis in dermal fibroblasts) and platelet-poor plasma derived serum were tested on human dermal fibroblasts by measuring incorporation of [3H]thymidine. Platelet activation was determined by quantification of plasma beta-thromboglobulin (beta-TG) using a beta-TG radioimmunoassay kit. RESULTS--The mitogenic activity was significantly increased in whole blood serum and in platelet-poor plasma derived serum of the patients compared with controls. In contrast, no significant increase in beta-TG concentration was observed in scleroderma platelet-poor plasma compared with control. Recombinant human IFN gamma had a greater inhibitory effect on the mitogenic activity induced by whole blood serum of patients than on that produced with control sera, at any concentration of IFN gamma tested. CONCLUSIONS--Our results suggest that mitogenic activity observed in the plasma of sclerodermic patients could originate from cells other than platelets and could be involved in the development of fibrosis. The potent inhibitory effect of IFN gamma on this proliferative activity may account for the beneficial effect of this cytokine in the treatment of progressive systemic sclerosis.  相似文献   

5.
Serum contains a growth factor derived from platelets and also growth factors derived from platelet-poor plasma. Extracts of heated (100 degrees ) human platelets function synergistically with platelet-poor plasma to induce DNA synthesis in quiescent, density-inhibited BALB/c 3T3 cells. Platelet-poor plasma alone did not induce DNA synthesis. Cells exposed to platelet extracts became competent to enter the cell cycle, but the rate of entry into the S phase depended upon the concentration of platelet-poor plasma. The time required for the induction of this competent state was a function of the concentration of the platelet extract. A 2-hr exposure to 100 mug of the platelet extract at 37 degrees caused the entire cell population to become competent to enter the S phase. At 4 degrees or 25 degrees the cells did not become competent to synthesize DNA. The platelet extract-induced competent state was stable for at least 13 hr after removal of the platelet extract; however, in the absence of platelet-poor plasma, these competent cells did not progress through the cell cycle. The addition of an optimal concentration of platelet-poor plasma (5%) to these competent cells initiated cell cycle traverse with a rapid, first-order entry of cells into the S phase beginning 12 hr after addition of the plasma. The addition of a suboptimal concentration of the plasma (0.25%) did not increase the rate of cell entry into the S phase. Thus, the induction of DNA synthesis in quiescent BALB/c 3T3 cells can be resolved into at least two phases, controlled by different serum components: (i) competence, induced by the platelet-derived growth factor; and (ii) progression of competent cells into the cell cycle, mediated by factors in platelet-poor plasma.  相似文献   

6.
Serum from two patients with abetalipoproteinemia, a rare disorder of lipid metabolism characterized by the absence of chylomicrons and very low density and low density lipoproteins, did not stimulate the proliferation and growth of human smooth muscle cells or dermal fibroblasts in vitro as effectively as normal serum. The growth-promoting activity of this serum was comparable to that observed for lipoprotein-deficient plasma from normolipidemic subjects. Although the mitogenic effect of abetalipoproteinemic serum was improved with supplementation of low density lipoproteins, it was still about half the activity achieved with normal serum. However, the growth-promoting activity of this serum was completely restored to normal levels after addition of a lysate of normal platelets. In contrast, the mitogenic activity of lipoprotein-deficient plasma remained unchanged after addition of a lysate from abetalipoproteinemic platelets, whereas a similar supplementation of normal platelets completely restored its growth-promoting activity to normal. Thus, the inability of abetalipoproteinemic serum to promote growth appears to be due both to a deficiency of a platelet-releasable growth factor(s) and to the absence of serum lipoproteins.  相似文献   

7.
Factor-XI activity of platelets has been studied in platelet-rich plasmas and isolated platelet suspensions. Fresh platelets in both environments had little or no measurable factor-XI activity. Frozen and thawed platelet-rich normal plasma had markedly elevated apparent factor-XI activity and factor-IX activity as compared to platelet-poor plasma. Frozen and thawed platelet-rich and platelet-poor normal plasmas had equivalent factor-XI antigen. Platelets isolated from normal blood and from factor-XI deficient blood had the same small amounts of apparent factor-XI activity, which increased slightly on freezing and thawing. The data indicates that minimal factor XI is associated with the platelet. The markedly elevated apparent factor-XI activity of frozen and thawed platelet-rich plasma is shown to reflect the interaction of a platelet activator with plasma clotting factors to produce a later activated-clotting-intermediate.  相似文献   

8.
The early state of atherosclerosis is characterized by a nodular proliferation of smooth muscle cells in the arterial intima. It has been suggested that this proliferation is initiated by platelet-derived growth factor (PDGF) released from aggregating platelets in connection with endothelial injury. In the present study platelet reactivity and mitogenic activity of plasma and serum were compared in young male survivors of myocardial infarction with angiographically demonstrable coronary atherosclerosis and in healthy subjects of similar age. Young post-infarction patients with coronary atherosclerosis had lower ED50 values of ADP-induced platelet aggregation. Furthermore plasma and serum from the patients contained increased amounts of mitogenic activity. Experiments using antibodies against platelet-derived growth factor indicated that the increase in mitogenic activity represented elevated concentrations of free PDGF growth factor in plasma. The results raise the possibility of a connection between increased levels of free PDGF and the proliferative reaction that characterizes early lesion progression.  相似文献   

9.
The insulin-like growth factors: their putative role in atherogenesis.   总被引:1,自引:0,他引:1  
G A Ferns  A S Motani  E E Angg?rd 《Artery》1991,18(4):197-225
Smooth muscle cell proliferation and leukocyte infiltration are characteristic features of all lesions of atherosclerosis. Although platelet derived growth factor (PDGF) is one of the major smooth muscle mitogens, other important mitogenic factors are found in plasma and in platelets. The insulin-like growth factors (IGF-I and IGF-II) are present in plasma complexed to one of a number of IGF-binding proteins (IGF-BP). They are also found at high concentrations within the alpha-granules of platelets. The IGFs are secreted by a number of cell types in-vitro and in-vivo, including smooth muscle cells and macrophages. The cellular effects of the IGFs are mediated by membrane bound high affinity receptors. IGF receptors are of two distinct types and are expressed by a wide variety of cells. The IGFs are potent smooth muscle cell mitogens and it is therefore possible that these polypeptides contribute to the formation of the atherosclerotic lesion by paracrine, autocrine or endocrine mechanisms.  相似文献   

10.
HJORT P  RAPAPORT SI  OWREN PA 《Blood》1955,10(11):1139-1150
1. Human platelets possess an accelerator activity equal to about six per centof the proaccelerin activity of normal citrated plasma. This accelerator activityis only slightly reduced by 10 washings.

2. Thrombin increases platelet accelerator activity as much as ten fold. Thismeans that platelet accelerator activity behaves like proaccelerin (plasma Acglobulin) rather than accelerin (serum Ac-globulin).

3. Platelets from a patient with parahemophilia (congenital proaccelerindeficiency) possess only a trace of accelerator activity. They acquire a normalamount of accelerator activity after contact with normal platelet-poor plasma.

4. Trypsin destroys 90 per cent or more of the platelet accelerator activityof normal platelets without altering their appearance. Trypsinized plateletsregain normal accelerator activity upon incubation with normal platelet-poorplasma.

5. These findings strongly suggest that the platelet accelerator (plateletfactor 1) is adsorbed plasma proaccelerin.

Submitted on April 15, 1955 Accepted on July 5, 1955  相似文献   

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