摘要:

AbstractMacromolecules are sulfated during the vegetative growth ofDictyostelium discoideum.A characterisation of the structures of sulfated oligosaccharides associated with these macromolecules indicates that the oligosaccharides are heterogeneous. Endoglycosidase and pronase digestion were used with gel‐filtration chromatography to obtain two different Oligosaccharide fractions and a glycopeptide fraction; these were further characterised by ion‐exchange and lectin‐affinity chromatography and by acid hydrolysis. The data indicate that up to 43% of the sulfate is associated with typicalN‐linked oligosaccharides, that up to 5% is associated withN‐linked oligosaccharides that are either very large or extremely highly charged, and that the remaining sulfate is associated with oligosaccharides non‐N‐linked to protein. Each fraction was also shown to be heterogeneous at most other structural levels. Electrophoretic analyses following the endoglycosidasc and pronase treatments indicated that all of the macromolecules are glycoproteins and suggested further that at least two of the Oligosaccharide fractions are located on different groups of

ISSN:0730-2312    

DOI:10.1002/jcb.240380202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractMultidrug‐resistant human neuroblastoma cell lines obtained by selection with vincristine or actinomycin D from two independent clonal lines, SH‐SY5Y and MCIXC, have 3‐ to 30‐fold more cell surface epidermal growth factor (EGF) receptors than the drug‐sensitive parental cells as indicated by EGF binding assays and immunoprecipitation, affinity‐labeling, and phosphorylation studies. Reversion to drug sensitivity in one line was accompanied by a return to the parental level of EGF receptor. SH‐EP cells, a clone derived from the same neuroblastoma cell line as SH‐SY5Y but which displays melanocyte rather than neuronal lineage markers, also express significantly more EGF receptor than SH‐SY5Y cells. By nucleic acid hybridization analysis with a molecularly cloned probe, increased receptor level in multidrug‐resistant cells was shown to be the result of higher levels of EGF receptor mRNA in drug‐resistant than in drug‐sensitive cells. The increased steady state amount of specific RNA did not result from amplification of receptor‐encoding genes. A small difference was observed in the electrophoretic mobility under denaturing conditions of EGF receptor immunoprecipitated from drug‐resistant and drug‐sensitive cells. Quantitative and qualitative modulation of the EGF receptor might reflect alterations in the transformation and/or differentiation phenotype of the resistant cells or might result from unknown selective pressures associated with the develo

ISSN:0730-2312    

DOI:10.1002/jcb.240380203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA major protein in detergent extracts of skeletal muscle appears at 38,000 daltons in electrophoretic separations. Previous investigations have provided indirect evidence that a 38‐kD skeletal muscle protein is membrane associated, and this inference has served as the basis for speculations on 38‐kD protein function. In the present study, affinity purified, polyclonal antisera against 38‐kD protein from skeletal muscle are produced for immunolocalization and biochemical assays. Immunoblots of two dimensional electrophoretic separations show that this protein is heterogenously charged at pI ∼6.4. This 38‐kD protein is not extracted from muscle in low ionic strength or high ionic strength buffers, in isotonic buffers from pH 4 to pH 8 or in buffers containing 5 mM EGTA. The 38‐kD protein is extracted, however, by isotonic, pH 7.0 buffer containing 1.0% Triton‐X. Light microscope observations using indirect immunofluorescence of anti‐38‐kD labeled tissue show the protein distributed in a reticular pattern within cross‐sectioned muscle but not at the cell surface. Longitudinal sections show the protein concentrated in periodic, transverse bands. Purified fractions of muscle plasma membrane analyzed by immunoblotting contain 38‐kD protein. Immunoblots using anti‐38 kD show that this protein is present in all vertebrate skeletal muscle examined, however, the protein is present only in cardiac muscle that contains transverse tubules. The antibody does not recognize aldolase, another 38‐k

ISSN:0730-2312    

DOI:10.1002/jcb.240380204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractWestern blotting and immunoprecipitation data indicated that lysosomal enzymes represent a subset of the sulfated macromolecules present in vegetativeDictyostelium discoideumamoebae and account for less than 2.5% of the total sulfate incorporated during vegetative growth. These data suggest that the majority of the highly sulfated macromolecules of vegetativeD. discoideumamoebae are not related to the lysosomal enzymes.

ISSN:0730-2312    

DOI:10.1002/jcb.240380205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe murineIckgene encodes a membrane‐associated protein tyrosine kinase that has been implicated in lymphocyte oncogenesis. Here we report the structure of normal humanIcktranscripts and the pattern of expression of these transcripts in developing thymus and in peripheral T cell subsets. The humanIckgene encodes a 509 amino acid polypeptide that is closely related to the murineIckencoded protein throughout its length. Analysis of the deduced amino acid sequence of human p56Ickdemonstrates that an amino‐terminal domain, widely divergent among the seven knownsrcfamily members, has been conserved between murine and human p56Ick, and thus probably includes sequences crucial to the lymphocyte‐specific function of this molecule. HumanIcktranscripts were detected in CD4+and CD8+T cells, in partially purified B cells, and in Epstein‐Barr virus‐immortalized B cell lines, but not in monocytes, granulocytes, or in nonhematopoietic cell types. HumanIcktranscripts are readily detectable in fetal thymocytes at 70 days of gestation, but not at 57 days of gestation, indicating thatIckexpression appears coordinately with the appearance of lymphoid cells in the developing thymus. ThusIckgene expression is a marker for cells of the lymphocyte lineage in man. We conclude that theIckgene probably participates in a signal transduction pathway uniquely present in lymph

ISSN:0730-2312    

DOI:10.1002/jcb.240380206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractCombinations of low dosages of purified recombinant human (rh) macrophage colony stimulating factor (M‐CSF; also termed CSF‐1) and rh granulocyte‐colony stimulating factor (G‐CSF) were compared alone and in combination for their influence on the cycling rates and numbers of bone marrow and splenic granulocyte macrophage, erythroid, and multipotential progenitor cells in vivo in mice pretreated with iron‐saturated human lactoferrin (LF). LF was used to enhance detection of the stimulating effects of exogenously added CSFs. Concentrations of each CSF that were not active in vivo when given alone were active when given together, with the other CSF. The concentrations of rhM‐CSF and rhG‐CSF needed to increase progenitor cell cycling in the marrow and spleen were reduced by factors of 40‐200 when these CSFs were administered in combination with low dosages of the other CSF. At the concentrations of rhM‐CSF and rhG‐CSF tested, synergism was not noted on absolute numbers of progenitor cells or total nucleated cell counts per organ o circulating in the blood. These findings may have potential relevance when considered in a clinical setting where the CSFs might be used in combination with other biotherapy

ISSN:0730-2312    

DOI:10.1002/jcb.240380207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe dependency of normal cell proliferation on adequate extracellular Ca2+levels was further investigated by determining the role of Ca2+influx in epidermal growth factor (EGF)‐induced rat liver epithelial (T51B) cell DNA synthesis. Fura‐2‐loaded T51B cells responded with an increase in [Ca2+]ito EGF (5–50 ng/ml) that was blocked by low (25 μM) extracellular Ca2+or by pretreatment with 50 μM La3+to inhibit plasma membrane Ca2+flux. Confluent T51B cells treated for 24 h with EGF (0.1–50 ng/ml) dose‐dependently incorporated [3H]‐thymidine into cell nuclei. Low extracellular Ca2+or addition of La3+prevented the EGF stimulated rise in labeled nuclei, indicating that a movement of Ca2+into the cell was required for DNA synthesis. This was supported by our findings that bradykinin, which induced a rise in [Ca2+]iby opening plasma membrane Ca2+channels in T51B cells (but not A23187, thrombin or ATP, which raise [Ca2+]iprimary through mobilization of intracellular Ca2+stores), potentiated DNA synthesis stimulated by submaximal doses of EGF. Potentiation of the action of EGF by the tumor promoter 12‐0‐tctradecanoyl‐phorbol‐13‐acetatc (TPA), indicates that activation of protein kinase C and an influx of Ca2+share a common mechanism for

ISSN:0730-2312    

DOI:10.1002/jcb.240380208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0730-2312    

DOI:10.1002/jcb.240380201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY