Biomedical subjects

R Sullivan

Publications and source records attributed to R Sullivan.

At least 145 records · Page 8Linked to original sources

PubMed1987

Multiple forms of basic fibroblast growth factor: amino-terminal cleavages by tumor cell- and brain cell-derived acid proteinases.

Basic fibroblast growth factor (FGF) was purified by heparin-Sepharose chromatography from two sources, brain and hepatoma cells. Brain cell-derived basic FGF (brFGF) and hepatoma cell-derived basic FGF (heFGF) were found to exist in multiple forms whose molecular weights depended on whether they were extracted from their respective tissue or cells at neutral or acid pH. When extracted at pH 7.0 brFGF and heFGF comigrated on NaDodSO4/PAGE with a Mr of approximately 18,400. When extracted at pHs 3.5-4.5, acid proteinases cleaved brFGF and heFGF to lower molecular weight forms but to different extents. brFGF was cleaved to a Mr 18,000 form at acid pH by a brain-derived acid proteinase that could be inhibited by pepstatin. heFGF was cleaved mostly to a Mr 16,500 form at acid pH by a hepatoma cell-derived acid proteinase that was inhibited by leupeptin. Electrophoretic transfer blot analysis using site-specific anti-FGF antibodies suggested that the cleavages occurred at the amino-terminal ends of brFGF and heFGF. Cleavage to lower molecular weight forms of brFGF and heFGF did not affect growth factor activity or chromatographic behavior on heparin-Sepharose columns.

Amino Acid Sequence↗

PubMed1987

Endothelial cell-derived basic fibroblast growth factor: synthesis and deposition into subendothelial extracellular matrix.

Bovine aortic and corneal endothelial cells synthesize a growth factor that remains mostly cell-associated but can also be extracted from the subendothelial extracellular matrix (ECM) deposited by these cells. The endothelial cell-derived growth factors extracted from cell lysates and from the extracellular matrix appear to be structurally related to basic fibroblast growth factor by the criteria that they bind to heparin-Sepharose and are eluted at 1.4-1.6 M NaCl, have a molecular weight of about 18,400, cross-react with anti-basic fibroblast growth factor antibodies when analyzed by electrophoretic blotting and immunoprecipitation, and are potent mitogens for bovine aortic and capillary endothelial cells. It is suggested that endothelium can store growth factors capable of autocrine growth promotion in two ways: by sequestering growth factor within the cell and by incorporating it into the underlying extracellular matrix.

Animals↗

PubMed1987

Seroepidemiologic study of giardiasis patients and high-risk groups in a midwestern city in the United States.

Serum antibodies to Giardia lamblia were measured in giardiasis patients, in groups at high risk for intestinal parasite infection, and in controls by an indirect fluorescent antibody (IFA) technique. Symptomatic patients had the highest antibody titers, and antibodies remained present for up to 18 months in persons with chronic infection. Indochinese refugees and male homosexuals with the acquired immunodeficiency syndrome (AIDS) and pre-AIDS had higher mean antibody levels than did healthy controls, whereas sewer and highway maintenance workers had levels similar to those of controls. Serum antibodies to Entamoeba histolytica measured by an indirect hemagglutination antibody technique were detected in only a few Indochinese refugees. We conclude that serology is a promising tool in G. lamblia epidemiology and that further population studies would be of interest.

Entamoeba histolytica↗

PubMed1987

Acquisition of formyl peptide receptors during normal human myeloid differentiation.

By using a newly developed immune rosetting technique to isolate highly purified populations of myeloid precursor cells from normal human bone marrow and then inducing their differentiation with granulocyte and macrophage colony-stimulating factors (G/M-CSFs) in vitro, we studied the surface expression of chemotactic peptide receptors as the cells matured from the stage of the myeloblast to that of the mature, segmented neutrophil. We used ethylene glycol bis(succinimidyl succinate) to link N-formyl-Nle-Leu-Phe-Nle-[125I]iodo-Tyr-Lys to chemotactic peptide receptors on the surface of myeloid cells at sequential stages of maturation and then determined the density of receptor-radioligand complexes by autoradiography after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Specific, saturable formyl peptide receptors were not detectable at the level of the myeloblast but gradually emerged through progressive stages of neutrophil maturation. The specific receptors for formyl peptide that appeared during cellular maturation had a mol wt of 55 to 70 kiloDalton (kD), corresponding to those present on the surface of peripheral blood neutrophils, and binding of the radioligand was highly specific in that it was completely inhibited by a 1,000-fold excess of F-Met Leu Phe. These data correlate with and provide insight into our recent observation that F-Met Leu Phe-induced membrane depolarization and transient increases in cytosolic free calcium are gradually acquired as neutrophils mature. This report represents to our knowledge the first description of the maturational development of chemotactic peptide receptor expression in normal human myeloid cells.

Bone Marrow↗

PubMed1986

Purification and characterization of heparin-binding endothelial cell growth factors.

Thirteen endothelial cell growth factors have been purified to homogeneity by heparin affinity and reversed-phase high performance liquid chromatography, and their chromatographic and electrophoretic properties were compared. The amino acid compositions of 10 of these mitogens have also been determined. The results indicate that these heparin-binding growth factors (HBGFs) can be subdivided into two classes. Class 1 HBGFs are anionic mitogens of molecular weight 15,000-17,000 found in high levels in neural tissue and include acidic brain fibroblast growth factor and retina-derived growth factor. Class 2 HBGFs are cationic mitogens of molecular weight 18,000-20,000 found in a variety of normal tissues and are typified by pituitary fibroblast growth factor and cartilage-derived growth factor. Typical class 2 HBGFs have also been isolated from a rat chondrosarcoma, a human melanoma, and a human hepatoma, suggesting that tumors do not make a structurally distinct HBGF class. These results provide a sound basis for the evaluation of the HBGFs purified from a variety of tissues and species and for the delineation of their normal and pathological functions in vivo.

Amino Acids↗

PubMed1986

Human tumor cells synthesize an endothelial cell growth factor that is structurally related to basic fibroblast growth factor.

A human hepatoma cell line synthesizes, as evidenced by metabolic labeling, an endothelial cell mitogen that is found to be mostly cell associated. The hepatoma-derived growth factor (HDGF) has been purified to homogeneity by a combination of Bio-Rex 70, heparin-Sepharose, and reverse-phase chromatography; it is a cationic polypeptide with a molecular weight of about 18,500-19,000. HDGF is structurally related to basic fibroblast growth factor (FGF). Immunological analysis demonstrates that antiserum prepared against a synthetic peptide corresponding to the amino-terminal sequence of basic FGF cross-reacts with HDGF when analyzed by electrophoretic blotting and by immunoprecipitation. Sequence analysis of tryptic fragments demonstrates that HDGF contains sequences that are homologous to both amino-terminal and carboxyl-terminal sequences of basic FGF.

Amino Acid Sequence↗

PubMed1986

Production of erythroid burst-promoting activity (BPA) and granulocyte-monocyte colony-stimulating activity (GM-CSA) by isolated human T-lymphocyte subpopulations.

T-lymphocytes and monocytes are prominent among the classes of normal human cells that have been implicated in the production of the hemopoietic growth factors granulocyte-macrophage colony-stimulating activity (GM-CSA) and erythroid burst-promoting activity (BPA). To investigate the nature of the cooperativity that occurs during the elaboration of these growth factors by activated T-lymphocytes and monocytes in vitro, and to define the subsets of T cells involved in this response, we studied the production of GM-CSA and BPA by populations of T-lymphocytes isolated by fluorescence-activated cell sorting, using the monoclonal antibodies OKT3, OKT4, and OKT8. When OKT3+, OKT4+, or OKT8+ cells were incubated for five days in liquid suspension cultures, their production of GM-CSA and BPA was undetectably low. When 5% autologous monocytes were added to the cultures, no increase in the secretion of either of these classes of growth factors was noted. In the presence of concanavalin A (Con A), measurable quantities of both GM-CSA and BPA were elaborated by all three populations of T cells in the absence of monocytes; however, when autologous monocytes were added to the Con A-stimulated T cells, the secretion of both GM-CSA and BPA was markedly enhanced. In addition, we found that supernates of unfractionated T cells incubated with Con A contained not only GM-CSA and BPA but also a potent inhibitor(s) of BPA that could be demonstrated by dilution of the media and removed by gel filtration. In contrast, no inhibitor of GM-CSA was found. By molecular sieve chromatography of the supernates, GM-CSA and BPA coeluted as a single peak. However, the two biologic activities could be separated on the basis of heat stability, since GM-CSA proved to be heat labile whereas BPA did not. Our data indicate that GM-CSA and BPA derived from human T cells are similar in their apparent molecular weights and in the pattern of their production in suspension cultures in response to lectin stimulation. The secretion of both GM-CSA and BPA by Con A-stimulated T cells is facilitated by the presence of autologous monocytes, and is not restricted to either the OKT4- or the OKT8-defined subset.

Antibodies, Monoclonal↗

PubMed1985

Effect of bacterial endotoxin on the transmembrane electrical potential and plasma membrane fluidity of human monocytes.

In order to gain insight into the physical interaction between bacterial endotoxins and the surface of human monocytes, we investigated the effects of Salmonella typhi endotoxin and lipid A on two functional properties of the plasma membrane of these cells: (1) the transmembrane electrical potential and (2) the fluidity of the lipid bilayer. Using the fluorescent lipophilic cationic probe 3,3'-dipropylthiodicarbocyanine (di-S-C3(5] to monitor the transmembrane electrical potential, we found that neither endotoxin nor lipid A induced depolarization of the monocyte's plasma membrane or impeded its ability to undergo depolarization in response to phorbol myristate acetate. When the resting transmembrane potential of the monocyte was analyzed by exposing di-S-C3(5)-labeled cells suspended in media containing incremental concentrations of potassium ion (K+) to valinomycin, no difference between the response of control cells and cells pretreated with endotoxin was noted. We next examined the effect of endotoxin and lipid A on the fluidity of the monocyte's plasma membrane by monitoring the intensity of the fluorescence of 1,6-diphenyl-1,3,5-hexatriene. By quantifying the intensity of parallel and perpendicular polarized light emitted by this membrane-embedded probe between 8 and 56 degrees C, measurements of molecular anisotropy were used to identify temperature-dependent phase transitions within the hydrocarbon region of the plasma membrane and to estimate the relative microviscosity of the lipid bilayer before and after exposing the cells to endotoxin or lipid A. Although the temperature at which phase transitions occurred was the same in all experimental groups of cells, preincubation of monocytes with either endotoxin or lipid A appeared to increase both the apparent microviscosity of the cell membrane and the order of the lipid bilayer as reflected by a decrease in its flow-activation energy. Our data indicate that when endotoxin molecules contact the surface of the monocyte, the lipid A moiety appears to become incorporated into the plasma membrane, increasing the microviscosity of the lipid bilayer without significantly altering its ionic permeability. We therefore conclude that the metabolic activation of monocytes by endotoxin is not coupled to, or initiated by, membrane depolarization.

Endotoxins↗

PubMed1985

Purification of cartilage-derived growth factor by heparin affinity chromatography.

Cartilage-derived growth factor (CDGF) was found to bind tightly to columns of immobilized heparin and could be eluted with concentrations of salt in the order of 1.6-1.8 M NaCl. The molecular weight of CDGF was estimated to be 18,000-20,000 by high performance liquid-size exclusion chromatography. The affinity of CDGF for heparin greatly facilitated its purification. Highly purified CDGF active at about 1-2 ng/ml was obtained when crude cartilage extract was applied to heparin-Sepharose and the growth factor activity was recycled over heparin-Sepharose two more times. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver stain visualization of highly purified CDGF showed one major polypeptide band with a molecular weight of about 19,000 containing over 95% of the protein and one minor polypeptide band containing the rest of the protein. Only the Mr 19,000 polypeptide was active after elution from the polyacrylamide gel. Although CDGF bound tightly to immobilized heparin, it did not bind to immobilized chondroitin sulfate or hyaluronic acid. In addition, CDGF bound to heparin much more tightly than did platelet-derived growth factor even though these two growth factors had similar isoelectric points of about 10. These results suggest that the binding of CDGF to heparin was due to a specific affinity of the 2 molecules for each other.

Animals↗

PubMed1985

Accelerated wound repair, cell proliferation, and collagen accumulation are produced by a cartilage-derived growth factor.

Cartilage-derived growth factor (CDGF), a cationic polypeptide of approximately 18,000 mol wt, was prepared from bovine articular cartilage; other sources were bovine and human scapular and costal cartilage. Previous studies have shown that CDGF stimulates the proliferation of cultured mouse fibroblasts as well as chondrocytes and endothelial cells from various sources. In this study, CDGF was shown to stimulate dose-dependently the accumulation of DNA and collagen by rat embryo fibroblasts and a population of fibroblasts derived from granulation tissue. CDGF also stimulated the proliferation of cultured bovine capillary endothelial cells dose-dependently. To evaluate the effects of CDGF in vivo, we implanted polyvinyl alcohol sponges subcutaneously in rats. 6 d postimplantation, sponges were injected with 300 micrograms of partially purified CDGF, a dose which takes into account the cell numbers in the sponges as compared with cell cultures. CDGF rapidly disappeared from the sponges and only approximately 10% of the initial dose was present at 4 h. Despite its transient presence, CDGF caused a relative increase in sponge DNA content of 2.6-fold at 48 h and 2.4-fold at 72 h. We repeated the sponge experiment by using 500-ng injections of CDGF purified to near homogeneity by heparin-Sepharose chromatography. Purified CDGF caused significant increases in sponge collagen, protein, and DNA content at 48 and 72 h after a single injection. The effects of CDGF were abolished by heat and unaffected by reduction of disulfide linkages. Morphologically, CDGF did not evoke an inflammatory response, and its effect on proliferating endothelial cells and fibroblasts was, therefore, probably direct. However, increases in DNA content of sponges could not be fully accounted for by increased DNA synthesis, which suggests that recruitment may be an important component of the in vivo response. Taken together, the effects of CDGF on cultured cells and granulation tissue suggest that the sustained presence of CDGF in vivo may greatly enhance its effects upon wound repair.

Animals↗

PubMed1985

Compliance and policy issues and recommendations related to revision of the National Interim Primary Drinking Water Regulations for Radionuclides.

This paper summarizes the deliberations and conclusions of the Compliance and Policy Committee of the National Workshop for Radioactivity in Drinking Water. Prior to and during the workshop the committee considered a total of 32 possible compliance and policy issues and determined that 22 were valid. The committee developed positions on seven of these and these positions are presented herein. The remaining 25 issues are also listed with the committee's evaluation of each.

Legislation as Topic↗

PubMed1985

Clinical trial of the efficacy and safety of ticarcillin and clavulanic acid.

Forty-three hospitalized patients were treated with a new antibiotic combination containing ticarcillin plus the beta-lactamase inhibitor, clavulanic acid, in a fixed combination for intravenous use. A variety of infections were treated, including pneumonia, bacteremia, urinary tract infection, and osteomyelitis. Of 50 episodes of infection in 43 patients, 44 clinical cures were obtained, with 5 patients improving and 1 patient failing to respond to treatment. In vitro susceptibility testing of 101 clinical isolates was notable for the rarity of resistance to the combination antibiotic. Of specific interest, all 14 isolates of Staphylococcus aureus were susceptible to ticarcillin plus clavulanic acid, whereas only 2 of the 14 isolates were susceptible to ticarcillin alone. Adverse reactions to the study drug were minimal; eosinophilia, unaccompanied by other allergic phenomena, and oral candidiasis were most frequent. Overall, the combination of ticarcillin with the beta-lactamase inhibitor, clavulanic acid, appears to be a safe and effective drug for the treatment of infections caused by susceptible organisms.

Aged↗

PubMed1985

Antimalarial activities and subacute toxicity of RC-12, a 4-amino-substituted pyrocatechol.

RC-12 [1,2-dimethoxy-4-(bis-diethylaminoethyl)-amino-5-bromobenzene] was evaluated for prophylactic, radical curative, and suppressive activities against infections with Plasmodium cynomolgi and subacute toxicity in rhesus monkeys. Applied as a prophylactic agent, RC-12, administered in doses of 6.25 to 25.0 mg/kg daily throughout the incubation period, provided near-complete to complete protection against 10(5) to 10(6) times the minimum infective dose of sporozoites. Applied as a suppressive agent, daily doses of 100.0 mg of RC-12 per kg did not eradicate blood schizonts regularly; hence, the need for concomitant administration of a blood schizonticide, such as chloroquine, in assessments of radical curative activity. In such appraisals, daily doses of 6.25 to 25.0 mg of RC-12 per kg for 14 days, in combination with 2.5 mg of chloroquine per kg daily for 7 days, effected cure of 69 and 93% of established infections, respectively. The curative activity of RC-12 was related to the total dose and could be achieved with a regimen as brief as 4 days. With respect to outward expressions of toxicity, daily doses of 50.0 mg/kg or lower for 15 to 225 days evoked no reactions. Doses of 100.0 or 200.0 mg/kg, scheduled for 15 days, evoked convulsions and depression and were, respectively, lethal to 4 of 17 and 7 of 7 recipients. Doses of 25.0 mg/kg or lower evoked no discrete reactions. Doses of 50.0 mg/kg and higher evoked hepatomegaly, vacuolation of hepatocytes, and elevations of glutamic oxalacetic and glutamic pyruvic transferase activities in serum, reactions related in intensity to dose but not duration of dosage.

Animals↗

PubMed1985

The kinetics of the production of granulocyte-monocyte colony stimulating activity (GM-CSA) by isolated human monocytes: response to bacterial endotoxin.

When mononuclear phagocytes are stimulated by bacterial endotoxins, they produce Granulocyte-Monocyte Colony-Stimulating Activity (GM-CSA). In order to study the kinetics of the production of GM-CSA by human monocytes, we prepared suspensions of these cells and studied their response to Salmonella typhi endotoxin. We found that when human monocytes were exposed to this preparation of endotoxin, they synthesized GM-CSA de novo and subsequently secreted it into the extracellular environment; however, within hours, the cells became highly refractory to further stimulation by endotoxin. The resistance to endotoxin which these cells rapidly acquired in vitro could not be accounted for by cell attrition, the accumulation of toxic metabolites in the cultures, negative feedback inhibition by newly synthesized GM-CSA, depolarization of the plasma membrane of the cells, or by degradation of endotoxin. When we studied the binding of tritium-labeled endotoxin to viable monocytes, we found that after monocytes were initially exposed to endotoxin, their subsequent ability to bind lipopolysaccharide molecules onto the surface of the plasma membrane was reduced. When we subjected concentrated supernates from endotoxin-stimulated monocyte cultures to gel filtration and isoelectric focusing, we noted that GM-CSA derived from human monocytes had an apparent molecular weight of approximately 42,000 daltons. Our results indicate that resistance to bacterial endotoxins acquired by mononuclear phagocytes may play a role in the immunologic phenomenon of immediate endotoxin tolerance observed in vivo and may in part be due to down-regulation of endotoxin binding to the outer surface of the cell.

Cells, Cultured↗

PubMed1984

Interaction of radiolabeled endotoxin molecules with human monocyte membranes.

Radiolabeled and biologically active endotoxin molecules were prepared, and their binding to monocyte plasma membranes was studied. The binding of 3H-endotoxin and 51Cr-lipid A to isolated membranes was found to be less specific and of lower apparent affinity than that observed using whole cells. Plasma membranes isolated from intact, viable 51Cr-lipid A-pretreated monocytes were found to contain a significant portion of the cell-associated 51Cr-lipid A following Percoll density gradient fractionation of post-nuclear homogenates. When monocytes were pretreated with 3H-endotoxin under the same experimental conditions, all of the label was recovered in the extracellular medium, and subcellular fractionation revealed no fractions which contained tritium. Taken together, our results suggest that specific and high affinity interactions between monocyte membranes and endotoxin molecules are likely to depend on plasma membrane structures which are assembled in intact monocytes but which are disrupted when plasma membranes are isolated from these cells.

Cell Fractionation↗

PubMed1984

Heparin affinity: purification of a tumor-derived capillary endothelial cell growth factor.

A tumor-derived growth factor that stimulates the proliferation of capillary endothelial cells has a very strong affinity for heparin. This heparin affinity makes it possible to purify the growth factor to a single-band preparation in a rapid two-step procedure. The purified growth factor is a cationic polypeptide, has a molecular weight of about 18,000, and stimulates capillary endothelial cell proliferation at a concentration of about 1 nanogram per milliliter.

Angiogenesis Inducing Agents↗

PubMed1984

Quantitation of serum suppressor factor, related to the erythrocyte receptor of human peripheral blood T lymphocytes as measured by radioimmunoassay.

A solid phase radioimmunoassay for a serum suppressor factor has been developed. The factor was previously purified from malignant ascites fluids and shown to be related to the sheep erythrocyte receptor of human peripheral blood T lymphocytes. This humoral suppressor factor has been termed suppressive E-receptor factor. Using this assay, it was demonstrated that both ascites fluids and sera derived from patients with solid tumors contain elevated levels of this factor compared to similar specimens from patients with a variety of nonmalignant diseases. The concentration of this SER factor does not correlate with serum immunoglobulin G levels but it does correlate with the ability of sera from individual patients to inhibit phytohemagglutinin-induced DNA synthesis by normal human peripheral blood T lymphocytes. Kinetically, this suppressive E-receptor factor directly competes with monoclonal antibody directed to the sheep erythrocyte receptor of human peripheral T lymphocytes and exhibits noncompetitive-type inhibition of DNA synthesis induced by phytohemagglutinin.

Antibodies, Monoclonal↗

PubMed1984

Interaction between endotoxin and human monocytes: characteristics of the binding of 3H-labeled lipopolysaccharide and 51Cr-labeled lipid A before and after the induction of endotoxin tolerance.

Salmonella typhi endotoxin (lipopolysaccharide, LPS) was labeled with tritium and purified by gel filtration. Using this preparation, we found that binding of 3H-labeled LPS (3H-LPS) to isolated human monocytes consisted of a rapid (t1/2 less than 5 min), reversible, temperature-independent phase of surface adsorption that was followed by a slower (t1/2 greater than 20 min) period of binding that was irreversible and temperature-dependent. The interactions between 3H-LPS and monocytes that we measured were dependent both on the concentration of LPS and the cell number. We observed an apparent decrease in 3H-LPS surface binding after initial treatment of the cells with LPS, which was most likely due to an acquired reduction in the number of sites on the monocyte membrane available for the binding of LPS. Estimates of the parameters of the binding of 3H-LPS were calculated from a double-reciprocal plot (1/bound vs. 1/free) of the surface binding data and suggest that the relative binding affinity (Kd) for 3H-LPS was unchanged after pretreatment of the monocytes with LPS; however, the total number of LPS binding sites appeared to be reduced by this manipulation. The results of competition binding experiments also suggest that the binding affinity for 3H-LPS was the same before and after incubation of the cells with LPS. Lipid A, which we extracted from LPS and labeled with chromium-51, exhibited a binding affinity similar to that of 3H-LPS and, like 3H-LPS, could be displaced from the cells by competing concentrations of unfractionated LPS; however, the kinetics of binding of the two labeled ligands differed considerably. Our results suggest that exposure of monocytes to LPS may alter the ability of these cells to interact with, and consequently respond to, LPS.

Biological Transport↗