摘要:

Recent advances in understanding the in vitro translocation of nascent polypeptides across the endoplasmic reticulum (ER) membrane have established a molecular basis for the initial reactions predicted by the signal hypothesis. The first two events involve a transient arrest of nascent chain elongation, followed by a docking maneuver with the ER membrane which releases this block. It is not clear, however, that such signal sequence‐mediated transfer occurs in the case of all proteins, or for that matter in all cell‐free translation syst

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00319.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Lesions of vascular human EC play an important role in the development of thrombi and atherosclerosis. The factors which control the repair of vascular lesions are not well known. In addition, they are difficult to study because vascular EC from large vessels are fastidious cells to grow in tissue culture. We have investigated some of the factors that may be important in human umbilical vein EC growth in primary culture. Because of reported species differences in EC culture, we have decided to culture human EC only in the presence of biological culture reagents of human origin. Human umbilical vein EC, at low seed density, can be grown to confluency on a human FN matrix or on human ECM providing the medium is supplemented with a high concentration (30%) of human serum. The optimal proliferation of EC (even when seeded at clonal density) is obtained if HBE is added. HBE cannot completely replace serum, but EC proliferate to a similar extent whether they are grown on FN or on ECM in the presence of 30% human serum of 10% human serum plus HBE. Thus, HBE contains a growth factor activity for human EC which stimulates cell growth and DNA replication. Further work is needed to purify HBE and to compare it to other endothelial cell growth factors isolated from bovine brain and bovine eye.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00320.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

After treatment with trypsin, chick embryo fibroblasts exhibited an age‐related difference in their capacity to readhere to the substratum, since 8‐day‐cells readhered more rapidly than 16‐day‐cells. Treatment with tunicamycin altered embryo cell readhesion to the substratum in varying degrees, depending on the duration of drug treatment and of readhesion assay. The effect of tunicamycin was not toxic and was totally reversible with time after its removal. These results indicated that embryo cell readhesion involved trypsin‐sensitive cell surface glycoproteins. During embryo development, the glycosylation of cell surface glycoproteins altered markedly. The ratio of N‐linked to O‐linked glycan chains dropped from 80/20 in 8‐day‐cells to 55/45 in 16‐day‐cells, indicating that the relative labelling of O‐linked glycan chains increased during embryo development. This result was confirmed by alkaline treatment of radiolabelled glycan chains, and by the fact that tunicamycin treatment reduced 14C‐glucosamine incorporation by greater than or equal to 80% in 8‐day‐cells but only 60% in 16‐day‐cells. Marked changes were observed during embryo development in the structure of the N‐linked glycan chains; concanavalin A‐Sepharose chromatography showed that these changes concerned the glycopeptides containing complex type carbohydrate chains. The ratio of tri‐ plus tetra‐antennary chains to bi‐antennary chains increased about 2.5‐fold between the 8th and 16th day of development. A correlation was noted between embryo cell readhesion to the substratum and N‐glycosylation of cell surface glycoproteins. The N‐linked glycoconjugates played a crucial part in cell readhesion. The possible role of

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00321.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Sponges grown in the presence of 12‐O‐tetradecanoyl phorbol‐13‐acetate (TPA) show deep alterations of their structure and development. Their aquiferous system (flagellated cells and canals) is largely altered and the tissues show an unusually high cell density. This focalized effect of TPA on the aquiferous system seems specific and is reversible at low concentrations (100 ng/ml). A toxic, non‐specific effect is also noted, particularly at high concentrations (5000 ng/ml). Using 3H‐phorbol‐12, 13‐dibutyrate (3H‐PDBu), we demonstrate a class of specific binding sites for phorbol esters in the homogenates of sponges. These binding sites have high affinity (Kd = 26.0 nM) for PDBu and at saturation about 20 pmoles of 3H‐PDBu is bound per mg protein of sponge homogenates. The binding of 3H‐PDBu was inhibited by other phorbol esters and their congeners, and there was a good correlation between their potency in binding inhibition and their tumor promoting activity. It is concluded that sponges have a class of specific saturable and high affinity receptors for phorbol esters and that there is a very high conservation of these receptors during evolution. Such specific binding may be responsible for subsequent biological eff

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00322.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Treatment of rats with colchicine administered intraperitoneally at a dosage of 0.5 mg per 100 g of body weight for 6 hr induces extensive accumulations of tubular‐vesicular and cisternal organelles in the absorptive cells of the small intestine. The formation of these organelle aggregates coincides with a reduction of microtubules and massive changes in the cellular organization including alterations of the Golgi apparatus and the plasma membrane. In most cases the accumulated tubules and vesicles contain a homogeneous electron‐dense matrix, the cisternae often having the character of rigid lamellae. The organelle aggregates mainly occupy apical cell portions subjacent to the terminal web as well as basal cellular regions close to the basolateral plasma membrane. Tubular‐vesicular as well as cisternal organelles react strongly for thiamine pyrophosphatase (TPPase), inosine diphosphatase (IDPase), acid phosphatase (AcPase) and trimetaphosphatase (TMPase). The staining pattern of TMPase differs from that of the other phosphatases in that the reaction is restricted to the colchicine‐induced tubular‐vesicular and cisternal aggregates, whereas TPPase, IDPase, and AcPase, respectively, also appear over Golgi stacks, multivesiculated bodies and plasma membrane. This phosphatase reactivity indicates the lysosomal character of the organelle a

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00323.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Determination of experimental conditions which allow the evaluation of the variations in the ratio of non polymerized and polymerized forms of actin and tubulin during the reorganization of the cytoskeletal cell system is of most valuable importance. In order to prepare cell homogenates which would reflect the in vivo situation, we tested in vitro a lysis medium which stabilized both microfilaments and microtubules, which were determined by DNase inhibition assays and colchicine binding assays respectively. This lysis medium containing 10 mM potassium phosphate, 1mM magnesium chloride, 5 mM EGTA, 1 M hexylene glycol, 1% Triton X‐100, pH 6.4, used at 4 degrees C a) diffused rapidly into the cells; b) did not denature actin and tubulin; c) did not displace the equilibrium between non polymerized and polymerized forms of actin and tubulin, allowing biochemical assays on cell homogenates; d) blocked the evolution of the cytoskeletal system and permitted structural studies; e) and allowed the decoration of microfilaments by heavy meromyosi

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00324.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY