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Biomedical subjects

S C Quay

Publications and source records attributed to S C Quay.

At least 37 records · Page 2Linked to original sources
PubMed1983

Conformational studies of aqueous melittin: thermodynamic parameters of the monomer-tetramer self-association reaction.

The self-association reaction in which four melittin molecules associate to form an aqueously soluble tetramer was studied by fluorescent spectroscopy. At 23 degrees C, pH 7.15, gamma/2 0.50, the dissociation constant, Kd, is 3.20 x 10(-16) M3. At 23 degrees C, gamma/2 0.60, melittin has an amino acyl group with a proton ionization constant at ca. 10(-6) M, which must be un-ionized for tetramer formation to occur. The change in Kd with temperature indicates the forward reaction (tetramer formation) proceeds primarily by entropic changes, with delta H degrees = -20.3 kJ/mol of monomer and delta S degrees = 211 J/(K . mol of monomer). The observed enthalpic and entropic values for the tetramerization reaction are consistent with the expected contributions of both nascent hydrogen bonds and hydrophobic stabilization to the reaction. The ionic strength dependence of the tetramerization reaction was found to be consistent with an Edsall-Wyman treatment of activity coefficients. Specifically, the calculated charge of melittin varied from 2.5 (pH 10.53, gamma/2 less than 0.08) to ca. 6 (pH 7.15, gamma/2 greater than 0.3) and showed a strong dependence on gamma/2.

Animals↗
PubMed1983

Biochemical studies of immune complexes. I. Isolation of circulating immune complexes using a bifunctional exclusion chromatography matrix.

A simple and rapid method of isolating immune complexes from serum is described. The method utilizes the binding properties of a bifunctional chromatography matrix consisting of diethylaminoethyl and Cibacron blue F3GA functional groups linked to agarose beads. This column matrix binds all normal serum proteins except IgG and transferrin, excluding these proteins, and permitting them to be collected in the wash-through, void volume. Immune complexes prepared in vitro with human serum albumin were rapidly isolated from starting serum by this method. This method may have general application for the purification of immune complexes from serum in pathological conditions and should foster subsequent biochemical and immunological studies, including identification and characterization of immune complex antigens.

Animals↗
PubMed1983

Biochemical studies of immune complexes. II. Purification of immune complexes from sera of patients with malignant melanoma.

Circulating immune complexes (CICs) from serum samples of patients with malignant melanoma were isolated in high yield utilizing a bifunctional chromatography matrix that binds all normal serum proteins except IgG-containing immune complexes (ICs), IgG, and transferrin. Protein fractions were subsequently analyzed by polyacrylamide gel electrophoresis (PAGE) and characterized by molecular weight. By this method, one common and several unique component nonimmunoglobulin proteins of the ICs were identified. These proteins possess similar molecular weights to several previously described human melanoma antigens. This technique should permit biochemical and immunological characterization of the component antigens of CICs in melanoma and other malignancies.

Antigen-Antibody Complex↗
PubMed1982

Renin synthesis by canine aortic smooth muscle cells in culture.

Angiotensin-I generating activity has been detected in homogenates of arterial tissue but it remains unclear whether this enzymatic activity results from the presence of renin itself or from the action of other proteases such as cathepsin D. In an assay system employing anephric dog plasma as substrate and buffered to pH 7.4, we detected angiotensin-I generating activity in homogenates of canine aortic smooth muscle cells. This enzymatic activity was in large part inhibitable by renin-specific antisera raised to pure canine renal renin. Immunofluorescent study of cultured arterial smooth muscle cells was also performed using renin specific antiserum. Granular cytoplasmic immunofluorescence was detected when specific antirenin serum was used but not when preimmune serum was employed. The addition of pure canine renin to the renin antiserum during staining suppressed the granular immunofluorescence confirming the specificity of staining. Finally, biosynthetic radiolabelling studies were performed. Immunoprecipitation of newly synthesized proteins with antirenin serum and staphylococcal protein A followed by gel electrophoresis and autoradiography demonstrated the synthesis of an immunoreactive protein with the molecular weight of renin. Pretreatment of the antirenin serum with pure canine renin resulted in the disappearance of this immunoreactive protein band. Thus these studies provide multiple lines of evidence to indicate the in situ synthesis of renin by vascular smooth muscle cells.

Animals↗
PubMed1981

Papillary carcinoid tumor of the lung.

Carcinoid tumors of the lung have a wide histologic spectrum. The histologic differential diagnosis of papillary tumors in the lung generally does not include carcinoid. A carcinoid tumor that formed a discrete coin lesion on chest radiograph is presented in this report. On gross examination the center appeared and felt spongy. On microscopic examination delicate, compacted papillae were separated by a serpentine space continuous with air spaces at the periphery of the tumor. The papillae were each composed of a fibrovascular core, an undulating basement membrane separating stroma from epithelial cells, and cuboidal clear and dark cells that proved to be, respectively, healthy and degenerate cells of carcinoid tumor with neurosecretory granules. Upon the carcinoid cells, draped in the manner of an umbrella, were nonciliated, respiratory cells that proved to be Clara cells. The various histologic patterns of bronchopulmonary carcinoids and the differential diagnosis of papillary tumors within the lung are tabulated.

Aged↗
PubMed1981

Tumor shedding and coagulation.

Three syngeneic carcinomas from two species shed plasma membrane vesicles when cultured in vitro or grown in the ascites tumor form in vivo. Shed vesicles carry procoagulant activity that can account for the activation of the clotting system and the fibrin deposition associated with these and many other types of malignancy in animals and man.

Animals↗
PubMed1981

Incorporation of photosensitive fatty acids into phospholipids of Escherichia coli and irradiation-dependent cross-linking of phospholipids to membrane proteins.

In an approach to the study of phospholipid-protein interactions in biological membranes, the photoactivable fatty acids, omega-(m-azidophenoxy)-undecanoic acid (I) and omega-(m-diazirinophenoxy)-hexadecanoic acid (II), were incorporated biosynthetically into the phospholipids of the Escherichia coli fatty acid auxotroph, strain K1060-B5. The extent of incorporation of the two fatty acids was 43% and 21%, respectively, of the total fatty acid content of the phospholipids. Membrane vesicles prepared from cells grown on the fatty acid supplements and [32P]H3PO4 were irradiated at suitable wavelengths to generate the reactive nitrene or carbene intermediates. Subsequent analysis of solubilized membrane proteins by two-dimensional isoelectric focusing-polyacrylamide gel electrophoresis indicated cross-linking between radioactive phospholipids and an number of proteins. A corresponding experiment with cells grown on oleic acid showed only trace amounts of covalently cross-linked phospholipid-protein adducts. While the extent of cross-linking in vesicles from cells grown on I was only 3 times the background level observed for oleic acid-grown cells, cells grown on II showed 30 times this amount. The present results, together with the previously observed nonreactivity of the nitrene generated from I to undergo C-H insertion, show that the use of carbene precursors such as II is promising for chemical analysis of specific phospholipid-protein interactions in bacterial membranes under biologically meaningful conditions.

Cell Membrane↗
PubMed1981

Contamination of Hodgkin's disease cell cultures.

Several laboratories have recently reported the establishment and characterization of long-term cell lines thought to be related to the neoplastic cell of Hodgkin's disease. Here, Harris et al. discuss evidence that some of these lines are, in fact, not related to Hodgkin's disease but are non-human contaminants.

Animals↗
PubMed1981

Role for membrane potential in the secretion of protein into the periplasm of Escherichia coli.

The leucine-specific binding protein of Escherichia coli is a periplasmic protein that is synthesized as a precursor and subsequently is processed during its secretion into the periplasmic space. The processing of both the leucine-specific binding protein and a plasmid-coded beta-lactamase is inhibited by phenethyl alcohol and by the proton ionophore, carbonylcyanide m-chlorophenylhydrazone (CCCP). The levels of CCCP that inhibit processing also produce significant decreases in the membrane potential. Valinomycin, a potassium ionophore, also inhibits processing of the leucine-specific binding protein in spheroplasts. Processing can be restored in CCCP-treated cells and in valinomycin-treated spheroplasts by dilution of the treated cells in fresh medium. These results suggest a role for membrane potential in the secretion of periplasmic proteins. A model is presented which suggests that membrane potential plays a primary role in the proper orientation of the precursor signal sequence within the membrane, thus promoting processing and secretion.

Bacterial Proteins↗
PubMed1981

Carcinosarcoma of the skin. Case report and review.

A carcinosarcoma of the skin in a 74-year-old man is reported. The epithelial element consisted of a highly anaplastic basal cell carcinoma with focal keratinization. The mesenchymal component included elements of fibrosarcoma, chondrosarcoma, osteogenic sarcoma, and synovial sarcoma. This is, to our knowledge, the second reported case of carcinosarcoma arising in the skin.

Aged↗
PubMed1979

Intermolecular crosslinking of fatty acyl chains in phospholipids: use of photoactivable carbene precursors.

Phospholipids containing photolysable carbene precursors (beta-trifluoro-alpha-diazopropionoxy and m-diazirinophenoxy groups) in omega-positions of sn-2 fatty acyl chains were prepared. Photolysis of their vesicles produced crosslinked products in 40-60% yields. Crosslinking was mostly intermolecular and occurred by carbene insertion into the C-H bonds of a second fatty acyl chain. Crosslinking products were characterized by (i) their gel permeation behavior, (ii) analysis of products formed by base-catalyzed transesterification, (iii) degradation with phospholipases A2 and C, (iv) gas chromatography/mass spectrometry, and (v) use of mixtures of phospholipids carrying the carbene precursors and a phospholipid containing radioactively labeled fatty acyl groups. Nitrenes generated from the aliphatic or aromatic azido groups in phospholipids were unsatisfactory for forming crosslinks by insertion in C-H bonds.

Chemical Phenomena↗
PubMed1979

The relA locus specifies a positive effector in branched-chain amino acid transport regulation.

The regulation of branched-chain amino acid transport and periplasmic binding proteins was studied in Escherichia coli strains which were isogenic except for the relA locus, the gene for the "stringent factor," which is responsible for guanosine tetraphosphate synthesis. The strain containing the relA mutation could not be derepressed for the synthesis of leucine transport or binding proteins when shifted from a medium containing all 20 amino acids in excess to one in which leucine was limiting. The relA+ strain showed normal derepression under these conditions.

Amino Acids, Branched-Chain↗
PubMed1979

Reaction of immune complexes with Hodgkin's disease tissue cultures: radioimmune assay and immunoferritin electron microscopy.

We examined the binding of soluble immune complexes in sera from patients with Hodgkin's disease to established tissue cultures derived from the tumor. Circulating immune complex levels were determined by the Raji cell assay, and the reaction of serum with cultured cells was examined with a radioimmune assay and by immunoferritin electron microscopy. Serum with elevated immune complexes was found to react with cells of Hodgkin's disease monolayers when tested with radioiodine-labeled antisera against human IgG heavy and light chains and the complement 3 (C3) component. When examined with the electron microscope, monolayers incubated with Hodgkin's disease serum containing immune complex and labeled with ferritin-conjugated antiserum to C3 contained surface-bound ferritin particles with a uniform but discontinuous pattern. Absorption of Hodgkin's disease serum with monolayer cells reduced immune complexes and decreased reactivity of the sample with cultured cells by radioimmune assay. Sera of patients with other disorders and aggregated gamma-globulin with complement, despite markedly elevated immune complex levels, did not react positively with monolayers derived from Hodgkin's disease tumors, and none of the sera reacted with normal cultured spleen. The approximate size of serum components reacting with Hodgkin's disease monolayers was estimated by sucrose density gradient centrifugation. Sedimentation fractions in the 19S region reacted with monolayer cells when tested with 125I-labeled antisera to both IgG and C3 and contained immunoglobulin-complement complexes by gel diffusion and immunoabsorption. A component sedimenting at 7-9S contained immunoglobulin not complexed with complement; this component reacted with monolayer cells when tested with anti-IgG antiserum but did not react when tested with antibody to C3. The reaction of Hodgkin's disease monolayers with serum containing immune complexes differed from that of two suspension culture lines composed of cells with surface complement and IgG Fc receptors. Inasmuch as cells of our long-term Hodgkin's disease monolayers do not contain these surface receptors, possibly the antibody component of the immune complex reacts with antigens on the surface of cultured cells.

Antigen-Antibody Complex↗
PubMed1978

Branched-chain amino acid transport regulation in mutants blocked in tRNA maturation and transcriptional termination.

The regulation of branched-chain amino acid transport and binding protein biosynthesis was studied in Escherichia coli strains containing hisT (the structural gene for pseudouridine synthetase) and rho (the structural gene for the mRNA transcriptional termination factor rho) mutations. The results indicate that the hisT strain cannot be fully derepressed for transport and that the hisT rho double mutant is partially derepressed under excess leucine conditions, but cannot be further derepressed by leucine deprivation. These data are consistent with a model in which fully mature tRNALeu is required for derepression and in which rho interacts with tRNALeu in regulating transport by terminating transcription, especially in excess-leucine growth conditions.

Amino Acids↗