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J I Garrels

Publications and source records attributed to J I Garrels.

46 records · Page 3Linked to original sources
PubMed1983

A diversified set of testicular cell proteins specified by genes within the mouse t complex.

We have conducted a comparative high-resolution, two-dimensional gel analysis of testicular cell proteins synthesized by inbred mice congenic for a series of t haplotypes on the 129/SvJ background. At least nine t haplotype-specific proteins can be identified within the 1000 most prominent proteins observed. Apparent allelic wild-type forms of six of these t complex proteins (TCPs) have also been identified, and evidence from cell-free translation experiments indicates that all of these are coded for directly by genes within the t complex. Eight of the mutant t-haplotype-specific proteins are expressed in an identical form by testicular cells carrying any one of the complete t haplotypes analyzed. The ninth protein is polymorphic among different t haplotypes, as well as among different inbred strains of mice. Partial t haplotypes were used to map the genes specifying the expression of each TCP protein to a subregion of the t complex. The accumulated data suggest a subset of TCP proteins that are most likely to be involved in t haplotype effects on germ cell differentiation and fertility.

Animals↗
PubMed1979

Post-translational modification of actins synthesized in vitro.

It has been shown in two different ways that beta and gamma actins synthesized in vitro are acetylated and that the minor species of actin, delta and epsilon, are nonacetylated forms of beta and gamma actin, respectively. Firstly, additon of acetyl-CoA to the wheat germ system translating poly(A)-containing RNA from unfused rat L6 myoblasts, resulted in an increase in the synthesis of beta and gamma actins at the expense of delta and epsilon actins. Secondly, beta and gamma actins were labeled when synthesized in vitro in the presence of [3H]acetyl-CoA. No label was detectable in delta and epsilon actins. By extrapolation this indicates that beta and gamma actin are acetylated in vivo, probably at the N-terminus. beta and gamma actins synthesized in vivo contain a N tau-methylhistidine residue, but no methylation of beta and gamma actins synthesized in vitro was detectable, using S-[3H]adenosylmethionine as a methyl donor.

Acetyl Coenzyme A↗
PubMed1979

Modulation of protein synthesis by nerve growth factor.

The effects of nerve growth factor (NGF) and two analogs of cAMP have been studied in the PC12 line of rat pheochromocytoma cells. We have used two-dimensional gel electrophoresis to detect more than 800 proteins from control and NGF-treated cells. Of these proteins, none were qualitatively repressed in response to NGF, and no new proteins appeared after NGF treatment. Visual inspection of the gels showed that approximately 5% of the proteins were detectably increased or decreased in rate of synthesis by NGF, and each of these changes was mimicked by both cAMP analogs. The two-dimensional gel data were further analyzed by a computerized scanning system. This analysis has revealed many significant changes that are smaller than those detected by eye. Approximately 25 to 30% of the proteins analyzed were found to be altered in rate of synthesis by 30% or more. Statistical analysis has shown that the response to NGF and the response to dibutyryl cAMP are highly correlated, even down to changes as small as 30%. No proteins were found to be significantly altered by both dibutyryl cAMP and 8-bromo cAMP, but not by NGF. These results show that NGF causes only quantitative modulations of protein synthesis in PC12 cells, and these data strongly suggest that the response of PC12 cells to NGF is mediated by cAMP.

Animals↗
PubMed1979

Two dimensional gel electrophoresis and computer analysis of proteins synthesized by clonal cell lines.

An improved method of two-dimensional gel electrophoresis has been developed which produces high resolution, reproducible images suitable for computer analysis. In the images that are presented, more than 800 proteins have been resolved without significant overlap, and many more proteins can be detected after longer exposures. To establish the usefulness of such methods for detailed quantitative comparisons of cultured cells, extensive controls have been carried out to test the reproducibility of the electrophoretic procedures, the sample preparation procedures, and the cell culture conditions. A computerized scanning system has been developed which can automatically detect and integrate the densities of the spots on a two-dimensional fluorogram or autoradiogram. The corresponding proteins from two or more samples can then be matched and their intensities compared. Several types of graphic output have been used to display the number and magnitude of the differences between the compared samples. These methods were used to study the patterns of protein synthesis in the nerve cell line B103 and the glial cell line B9. Both exponentially dividing and stationary cultures were analyzed and the relative rates of synthesis of approximately 300 proteins were compared by computer. For each cell line, no major qualitative differences were found between dividing and stationary phase cells although numerous quantitative differences of up to 15-fold were detected. The proteins that were increased or decreased in rate of synthesis as B103 cells became confluent were in general not the same proteins that were increased or decreased in rate of synthesis as B9 cells reached confluence, indicating that most of the changes do not reflect growth control responses common to all cells. When the two cell lines were analyzed in the same state of growth and compared by computer, qualitative differences were found in approximately 5% of the proteins analyzed, and at least 40% of the shared proteins were involved in quantitative differences of 2-fold or more. The rates of synthesis of the shared proteins were more divergent between the two cell lines than between dividing and stationary phase cells of either line. These studies show, therefore, that these cell lines can be distinguished, regardless of growth state, by their cell-specific proteins and by their characteristic rates of synthesis of many of the shared proteins.

Animals↗
PubMed1976

Identification and characterization of multiple forms of actin.

Multiple forms of actin have been found in a variety of mammalian cell lines and tissues by the use of high resolution, two-dimensional gel electrophoresis. One form (alpha actin) was found only in differentiated muscle cells, and its synthesis is induced during myogenesis in culture. Two other forms (beta and gamma actin) are present in all nonmuscle cell types examined, and they continue to be synthesized in cultured muscle cells after fusion. Tryptic peptide comparisons have shown that muscle actin is distinguished from the two "nonmuscle" actins by several peptide differences, and that the two non-muscle actins are nearly identical. All three forms contain equimolar amounts of N-methylhistidine, and extensive controls have shown no evidence of artifactual heterogeneity. In addition to the three major actins, two other proteins were identified as probably forms of actin by affinity for DNAase I-agarose. These proteins are similar in charge and molecular weight to the major actin forms, but are unstable and have lifetimes in the cell of less than 2 hr.

Actins↗
PubMedDate not supplied

Co-expression of vimentin and cytokeratins in parietal endoderm cells of early mouse embryo.

Of the five classes of intermediate filaments found in vertebrate tissues, the cytokeratins are considered unique to epithelial tissues, while vimentin is expressed by endothelial and mesenchymal cells. In neither case is the precise function of the filament system known. Epithelial cells in culture often express vimentin as well as cytokeratins, but co-expression in vivo, as reported for pleomorphic adenomas of the parotid gland and metastatic carcinoma cells in ascites or pleural fluid, is still controversial. Here we report the co-expression of cytokeratins and vimentin in situ, in the parietal endoderm of the mouse embryo 8.5-13.5 days old. This population of individual, motile cells seems to be derived from a conventional epithelium by migration and differentiation. Our results support the idea that vimentin expression is specifically related to reduced cell-to-cell contact, and to the independent existence of a cell following detachment from an epithelial sheet.

Animals↗
PubMedDate not supplied

Identity of the proliferating cell nuclear antigen and cyclin.

Studies of growth regulation and cellular transformation will be assisted by the identification of proteins that are preferentially synthesized in dividing cells. The 'proliferating cell nuclear antigen' ( PCNA ), distinguished by its apparent association with cell division, is defined by reaction with an antibody found in the autoimmune disease systemic lupus erythematosus (SLE). This antibody reacts with proliferating cells including tumour cells but gives weak or undetectable immunofluorescence with resting cells of normal tissues. Peripheral blood lymphocytes are devoid of PCNA until activated by mitogen in vitro. In synchronized cultures its level and distribution fluctuate through the cell cycle, with a striking accumulation in the nucleolus late in the G1 phase and early in the S phase. Many of these properties are shared by ' cyclin '. This nuclear protein, identified by its position in a two-dimensional separation of cell proteins, is also transformation-sensitive and is preferentially synthesized in the S phase. We establish here that PCNA and cyclin are identical, and show that PCNA is an acidic nuclear protein of apparent molecular weight 35,000.

Animals↗