Search PubMed⌕ Search

Biomedical subjects

J L Roberts

Publications and source records attributed to J L Roberts.

At least 235 records · Page 13Linked to original sources
PubMed1981

Evidence for a signal sequence at the N terminus of the common precursor to adrenocorticothrophin and beta-lipotropin in mouse pituitary cells.

The precursor to corticotropin and beta-endorphin was synthesized in a reticulocyte cell-free system under the direction of mRNA from mouse AtT-20 pituitary tumor cells in the presence of [3H]proline, [3H]phenylalanine, [3H]leucine, [3H]valine, [3H]isoleucine or [35S]methionine. Automatic Edman degradation of the radioactive cell-free product showed the following N-terminal sequence: Pro-1, Met-2, Leu-11, Leu-12, Leu-13, Leu-15, Leu-16, Leu-17, Ile-21 and Val-23. The corticotropin-endorphin precursor was also labeled in AtT-20 cells with [3H]valine, [3H]leucine, [3H]tryptophan, [3H]serine, [35S]methionine or [35S]cysteine. Automatic Edman degradation of the radioactive intact cell form gave the following N-terminal sequence: Trp-1, Cys-2, Leu-3, Ser-5, Ser-6, Val-7, Cys-8, Leu-11, Leu-17, Leu-18 and tentatively Met-27. The sequence of the intact cell form from AtT-20 cells matches the sequence of the cell-free form of bovine pituitary precursor beginning at Trp-27, as determined by recombinant DNA technology [Nakanishi, S., Inoue, A., Kita, T., Nakamura, M., Chang, A. C. Y., Cohen, S. N., and Numa, S. (1979) Nature (Lond.) 278, 423-427]. The sequence of the mouse pituitary mRNA-directed cell-free translation product also matches the bovine precursor beginning at Pro-2. The results suggest that both the mouse and bovine precursors possess a signal sequence of 26 amino acids which is cleaved in intact cells. CNBr cleavage of [35S]cysteine-labelled intact cell precursor gave rise to an N-terminal fragment of a size compatible with the presence of a methionyl residue at or near position 27.

Adrenocorticotropic Hormone↗
PubMed1981

The proopiocortin (adrenocorticotropin/beta-lipoprotein) gene is located on chromosome 2 in humans.

The proopiocortin gene is located on chromosome 2 in humans. A 13-kb DNA fragment containing proopiocortin gene sequences was identified in human cells while proopiocortin-related genes sequences of 9.8 and 6.2 kb were present in mouse cells. In human-mouse cell hybrids which contained reduced numbers of human chromosomes and a complete set of mouse chromosomes, the 9.8- and 6.2-kb fragments were always present while the 13-kb fragment segregated with human chromosome 2 and the chromosome 2 enzyme markers acid phosphatase-1 (ACP1), malate dehydrogenase-1 (MDHI), and isocitrate dehydrogenase-1 (IDH1). Analysis of a single cell hybrid with a broken chromosome 2 indicates that the proopiocortin and ACP1 genes are closely linked and in the distal region of the short arm of chromosome 2.

Animals↗
PubMed1981

A serum C3-activating factor: its characterization and its presence in glomerular deposits.

A non-IgG C3 activating factor (C3AF) isolated from the serum and plasma of a patient with membranoproliferative glomerulonephritis with subendothelial and subepithelial deposits (type III) was studied to define its molecular structure, functional characteristics, and presence in renal biopsies. Alternative complement pathway (ACP) activation of C3 was comparable to that of zymosan, but significantly less than that of IgG C3 nephritic factor (C3NeF). Functionally active isolate contained beta 1H globulin (beta 1H) and the C3AF protein, which had a gamma-electrophoretic migration. beta 1H present in the isolate exhibited an altered gamma-beta electrophoretic mobility. The function of this complex is heat labile. Time/temperature studies demonstrated that inactivated preparations of this isolate show a return to the normal beta migration of beta 1H followed by the development of an alpha 2 electrophoretic migration of the previously gamma-migrating material of functionally active isolate. Normal human serums contain an alpha 2 protein that shows complete antigenic identity with the gamma protein of C3AF, but this alpha 2 protein lacks C3 activating function. On polyacrylamide gel electrophoresis, the C3AF isolate contains a high m.w. protein of 500,000 to 590,000 that is composed of 2 major subunits. Carbohydrate is not demonstrable, and the protein is antigenically distinct from plasma fibronectin. Immunofluorescence studies of renal biopsies of patients with types I and III MPGN revealed the presence of C3AF antigen in granular deposits in 10 of 16 cases. The presence of this antigen in glomerular deposits was associated with C3 and beta 1H, but was independent of Ig. These studies suggest that the mechanism of ACP activation by C3AF results from interference with beta 1H function. The presence of this material in renal biopsies from some MPGN patients further suggests a pathogenetic role in mediating glomerular pathology.

Chemical Precipitation↗
PubMed1980

Expression of cloned beta-endorphin gene sequences by Escherichia coli.

DNA coding for the opiate peptide beta-endorphin has been cloned into bacterial plasmids in such a way as to direct the synthesis of a hybrid beta-galactosidase/beta-endorphin protein. This hybrid protein can readily be cleaved in vitro to release biologically active beta-endorphin.

Animals↗
PubMed1980

Is autoimmunity a common denominator in immune complex diseases?

In normal circumstances, antibodies reactive with native DNA appear in the plasma during the course of many clinical conditions associated with inflammation. These antibodies seem to be elaborated in response to the release of exceptional amounts of DNA by nucleated cells. As a result, DNA/anti-DNA complexes can be demonstrated in the cryoprecipitable fraction of plasma from patients with various inflammatory diseases. A significant proportion of these immune complexes contain low-molecular-weight polynucleotide antigens. These polynucleotides are derived from DNA which has been degraded by plasma DNAase. Because of the digestion of DNA in the plasma a spectrum of antigen/antibody complexes forms. While large, relatively insoluble complexes would be expected to be rapidly cleared by the reticuloendothelial system, low-molecular-weight complexes are removed more slowly. It is proposed that the action of plasma DNAase upon both free and immune bound-DNA can lead to a preponderance of small, soluble, polynucleotide/anti-DNA complexes. Under appropriate conditions of vascular permeability, these soluble complexes may be deposited in vessel walls. Hence, regardless of the initiating infectious or inflammatory agent, polynucleotide antigen/anti-DNA antibody complexes form and can result in immune-mediated inflammatory phenomena in diverse disease states.

Animals↗
PubMed1980

Immunopathology of cardiac lesions in fatal systemic lupus erythematosus.

Immunopathologic studies were performed on cardiac tissue obtained at autopsy in 10 patients with severe systemic lupus erythematosus (SLE). The immunopathologic findings were correlated with histopathologic and clinical evidence of cardiac injury, and with clinical and serologic features of SLE. Immune reactants were demonstrated by direct immunofluorescence in nine patients in a granular deposition pattern suggesting immune complex aggregates. Histologic and gross anatomic findings of inflammation were generally more focal than was the distribution of immune reactants. Most of the immune deposits were present in the walls of the blood vessels of myocardium (eight of 10) or pericardium (two of three). In one patient with Libman-Sacks endocarditis, immunoglobulin and complement components were present in the valve stroma and the vegetations. The immune deposits around epicardial nerve fibers in two patients with severe neurologic manifestations contained immunoglobulin E(IgE). In general, the most intense and widespread immune deposits were observed in patients with persistently increased serologic and clinical evidence of activity of their systemic disease. These results suggest a role for immune complex deposition in the pathogenesis of the cardiac lesions of SLE.

Adolescent↗
PubMed1980

Processing of the precursor to corticotropin and beta-lipotropin in humans.

The biosynthesis of human corticotropin (ACTH) was studied in organ culture of pituitary adenomas and by translating mRNA from an ectopic ACTH-producing tumor in a cell-free system. Peptides similar to human ACTH, beta-lipotropin, and the amino-terminal glycopeptide are cleaved from a common precursor with an apparent molecular weight of 35,000 on sodium dodecyl sulfate/polyacrylamide gels. The precursors synthesized in pituitary and ectopic ACTH-producing tissues are indistinguishable. The cleavage sites of the peptide chain appear to be similar to those previously deduced for murine and bovine ACTH. Immunoprecipitation studies suggest that the primary structure of the precursor peptide is similar in all three species. However, glycosylation is different in the human and murine precursors: the precursor to human ACTH appears to be glycosylated only in the amino-terminal fragment, not in the ACTH or beta-lipotropin sequences. Studies with an autopsied normal human pituitary suggest that neither normal nor adenomatous pituitary tissue glycosylates the ACTH sequence.

Adrenocorticotropic Hormone↗