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Biomedical subjects

E R Hall

Publications and source records attributed to E R Hall.

At least 37 records · Page 2Linked to original sources
PubMed1989

Serological studies of peptostreptococci using an indirect fluorescent antibody test.

Members of the genus Peptostreptococcus are frequent isolates from periodontal lesions. A study was undertaken for determination of the serological relationships of oral and non-oral strains of several species of this genus. Eighty-nine strains of peptostreptococci representing seven species were tested by means of an indirect fluorescent antibody technique (IFA), with rabbit antisera to Peptostreptococcus anaerobius ATCC 27337, Peptostreptococcus micros VPI 2618-A, and Peptostreptococcus productus ATCC 27340. Each antiserum showed positive fluorescence when reacted with homologous cells. When anti-P. micros VPI 2618-A serum was added to suspensions of P. micros ATCC 33270 and clinical isolates of P. micros in the IFA, positive fluorescence was observed to a titer of 1:64 with 26 out of 29 strains. Positive fluorescence was also seen when P. anaerobius VPI 5737 and clinical isolates of P. anaerobius were tested with anti-P. anaerobius ATCC 27337 serum; a titer of at least 1:64 was observed in 10 out of 14 strains. These results support the presence of two serological groups of P. anaerobius, rabbit anti-P. anaerobius ATCC 27337 serum reacting with Group II organisms. No interspecies cross-reactivity was observed except with four strains of Peptostreptococcus magnus, which reacted with several antisera as well as with normal rabbit serum and the saline controls. These results indicate that rabbit antisera and the use of an IFA are useful in the identification of P. anaerobius and P. micros from oral lesions.

Fluorescent Antibody Technique↗
PubMed1988

Prostaglandin production by murine tumors as a predictor for therapeutic response to indomethacin.

We investigated whether there is a relationship between the production of eicosanoids by murine solid tumors and their response to the prostaglandin H (PGH) synthase inhibitor indomethacin. Three sarcomas, designated FSA, NFSA, and SA-NH, and two carcinomas, designated MCA-K and HCA-I, syngeneic to C3Hf/Kam mice were used. In general, FSA and NFSA produced more PGH synthase products than lipoxygenase products, whereas HCA-I produced both types of metabolites in large quantities. All three tumors responded well to indomethacin treatment by slowing their growth. In contrast, MCA-K and SA-NH tumors produced insignificant quantities of PGH synthase products, but substantial amounts of lipoxygenase products. Their growth was not affected by treatment with indomethacin. Indomethacin did not influence tumor cell survival either in vitro or in vivo, but it reduced the proportion of S-phase cells in the tumors. The antitumor effect of indomethacin was not reduced by immunosuppression of the tumor host and was independent of tumor immunogenicity, implying that indomethacin acted through nonimmunological mechanisms. Thus, the effectiveness of indomethacin was directly related to the ability of tumors to produce PGs. Consequently, the eicosanoid profile of tumors could serve as a valuable way to select patients likely to respond to indomethacin and other PGH synthase inhibiting agents.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

The stimulation of arachidonic acid metabolism in human platelets by hydrodynamic stresses.

Even though shear-induced platelet activation and aggregation have been studied for about 20 years, there remains some controversy concerning the arachidonic acid metabolites formed during stress activation and the role of thromboxane A2 in shear-induced platelet aggregation. In this study, platelets were labelled with [1-14C]arachidonic acid to follow the metabolism of arachidonic acid in stimulated platelets using HPLC and scintillation counting. Platelets activated by thrombin formed principally thromboxane A2, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE). In contrast, for platelets activated by shear--though arachidonic acid metabolism was stimulated--only 12-HETE was formed and essentially no cyclooxygenase metabolites were detected. This indicates that physical forces may initiate a different pathway for eicosanoid metabolism than most commonly used chemical stimuli and perhaps also implies that regulation of the cyclooxygenase activity may be a secondary level of regulation in eicosanoid metabolism.

Arachidonic Acids↗
PubMed1988

Immobilization of catalytically active thromboxane synthase.

Thromboxane synthase has been immobilized on phenyl-Sepharose beads by adsorption. The immobilized enzyme is catalytically active and has a slightly lower apparent Km for PGH2 than the detergent-solubilized enzyme. However, both imidazole- and pyridine-based inhibitors are equally effective in inhibiting the immobilized and solubilized enzyme preparations. Although the immobilized enzyme appears to be less stable than the solubilized enzyme it is sufficiently stable to be used as a model for studying the properties of the enzyme.

Animals↗
PubMed1988

Prostaglandin production by human promyelocytic leukemia (HL-60) cells.

A comparative analysis of prostaglandin production was carried out on human promyelocytic leukemia (HL-60) cells treated with either PMA or DMSO. When incubated with [1-14C]arachidonic acid these cells produced significant amounts of 6-keto prostaglandin F1 alpha, thromboxane B2, prostaglandin F2 alpha, prostaglandin E2, prostaglandin D2 and 12-hydroxy-5,8,10-heptadecatrienoic acid via the cyclooxygenase pathway. The major cyclooxygenase metabolite synthesized by these cells was prostaglandin F2 alpha. Its production increased significantly when the HL-60 cells were treated with PMA and decreased when treated with DMSO as compared to untreated control cells. This change in the production of prostaglandin F2 alpha appears to reflect alterations in cyclooxygenase activity. Another unidentified arachidonic acid metabolite was routinely observed in C18 high pressure liquid chromatography. The synthesis of this compound was inhibited by indomethacin. The unidentified metabolite was also seen in the human macrophage-like cell line U937.

Arachidonic Acid↗
PubMed1987

Selective internalization of arachidonic acid by endothelial cells.

The asymmetric distribution of phospholipids in bovine endothelial-cell membranes was probed with 2,4,6-trinitrobenzenesulphonate and purified phospholipase A2. The data suggest that phosphotidylethanolamine is primarily located in the inner lipid bilayer, as reported for other cell types. Stearic acid is taken up by the endothelial cells and is randomly distributed among the membrane phospholipids. In contrast, the polyunsaturated fatty acids (arachidonic, eicosatrienoic and eicosapentaenoic acids) have initial incorporation into the phosphatidylcholine fraction. These fatty acids then undergo a time-dependent transfer from phosphatidylcholine to phosphatidylethanolamine. Thus we propose that endothelial cells possess a mechanism for the selective internalization of polyunsaturated fatty acids.

8,11,14-Eicosatrienoic Acid↗
PubMed1987

Localization of estrogen-induced DNA adducts and cytochrome P-450 activity at the site of renal carcinogenesis in the hamster kidney.

Renal carcinoma in male Syrian hamsters, induced by chronic administration of estradiol for 5-7 months, is known to arise in the cortex at the cortico-medullary junction. In this in vivo model for hormonal carcinogenesis, estrogen-induced covalent DNA adducts have previously been observed in whole kidney and have been postulated to be involved in tumor induction. In the present study, the intrarenal distribution of estrogen-induced DNA modification and estrogen metabolizing enzymes were investigated in male Syrian hamsters to ascertain a role of metabolism and adduct formation in estrogen-induced carcinogenesis. The highest estrogen-induced DNA adduct concentrations as measured by 32P-postlabeling analysis were found in the renal cortex of hamsters treated with estradiol for 7 months. Total adduct levels in medullary DNA were approximately one-half of those found in cortex. Cytochrome P-450 enzymes were detected only in microsomes of kidney cortex (approximately 0.8 +/- 0.6 nmol P-450/mg protein) but not medulla of untreated male Syrian hamsters. Prostaglandin endoperoxide synthase activity in kidney cortical microsomes was 1/5 of the activity found in medullary microsomes. Thus, microsomal cytochrome P-450 levels and estrogen-induced DNA adduct formation were highest in hamster kidney cortex, the origin of renal tumorigenesis. It is postulated that estrogen metabolism by cytochrome P-450 enzymes leading to covalent DNA modification plays a role in hormonal carcinogenesis in the hamster kidney.

Animals↗
PubMed1987

The effect of smokeless-tobacco extracts on the growth of oral bacteria of the genus Streptococcus.

Aqueous tobacco extracts were used to supplement a basic salts solution (BSS) and a microbial medium. Thin-layer chromatography revealed sucrose in only one of four extracts. Discs saturated with extracts (0.1-50 mg/ml) failed to inhibit growth of any of the micro-organisms. Supplementation (10 mg/ml) of BSS with the tobaccos lacking sucrose resulted in augmented growth of Streptococcus mutans, Streptococcus salivarius and Streptococcus sanguis whereas the sucrose-containing brand augmented only Strep. sanguis growth. Thus extracts of these smokeless tobaccos would serve as a growth substrate for three species of oral streptococci which are frequently associated with human dental caries.

Bacteriological Techniques↗
PubMed1987

Monoclonal antibody against TXB2: its use in solid and liquid phase radioimmunoassays.

Monoclonal antibodies to thromboxane B2 (TXB2) have been produced and characterized. Both liquid and solid phase radioimmunoassays have been developed using one of these monoclonal antibodies. The two assays gave similar results when used to quantitate TXB2 in 11 serum samples; however the solid phase assay was more sensitive than the liquid phase assay (i.e., 63 pg/ml vs 19 pg/ml) at a B/BO = 90%). Despite a difference in the sensitivity of the two assay systems, the cross-reactivity of the monoclonal antibody for PGD2, PGE2, PGF2 alpha and 6 keto-PGF1 alpha was the same.

Animals↗
PubMed1987

Biofilm reactors in anaerobic wastewater treatment.

Attached biofilm reactors provide the means for implementing energy-efficient anaerobic wastewater treatment at full scale. Progress has been made in the development of fixed, expanded and fluidized bed anaerobic processes by addressing fundamental reactor design issues. Several new biofilm reactor concepts have evolved from recent studies.

Journal Article↗
PubMed1987

Interaction between lymphocytes and platelets in the synthesis of prostacyclin.

To test the hypothesis that prostacyclin (PGI2) is formed via a biochemical interaction between platelets and lymphocytes, we measured eicosanoids by high performance liquid chromatography (HPLC) and radioimmunoassay (RIA). A distinct 6-keto-prostaglandin F1 alpha (6KPGF1 alpha) peak was noted when [14C]arachidonic acid ([14C]AA) was added to the mixed cell preparations which was increased by pretreating platelets with 1-benzylimidazole (1-BI). Lymphocytes prelabeled with [14C]AA failed to form 6KPGF1 alpha when stimulated with phytohemagglutinin (PHA) or ionophore A23187. When the prelabeled platelets were suspended together with aspirin-treated lymphocytes and stimulated with ionophore, thrombin, or collagen, a 6KPGF1 alpha peak was detected and enhanced by 1-BI. These results were supported by quantifying the 6KPGF1 alpha content in the HPLC-purified fraction by RIA. Adding prostaglandin H2 (PGH2) directly to lymphocytes led to 6KPGF1 alpha production. Platelet aggregation and release were inhibited by lymphocytes in a dose-related manner. We conclude that lymphocytes possess PGI2 synthase activity which is capable of converting platelet-derived PGH2 into PGI2. PGI2 formed is sufficient to inhibit platelet function.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Production of platelet thromboxane A2 inactivates purified human platelet thromboxane synthase.

Human platelet thromboxane synthase was partially purified by DEAE-cellulose, Affi-Gel Blue, and Sephacryl S-300 chromatography to a specific activity of 259 nmol of thromboxane B2/min per mg. Thromboxane synthase retained 75-90% of its enzymic activity when bound to phenyl-Sepharose. The immobilized enzyme was inactivated at pH 3.0 and inhibited by 1-benzylimidazole and U-63,557A. The ability of the enzyme to produce thromboxane A2 from prostaglandin H2 was dramatically reduced by multiple additions of prostaglandin H2. Our data suggest that the production of thromboxane A2 by the enzyme is self-limiting and that the enzyme is inactivated during the reaction.

Blood Platelets↗
PubMed1986

Ammonia (NH3 and N2H3) direct chemical ionization mass spectrometry of underivatized prostaglandin-H2 and other selected stable prostaglandins.

A study of the positive and negative ion, ammonia (NH3 and N2H3) direct chemical ionization mass spectrometry of highly purified prostaglandin endoperoxide (PGH2) is presented. The positive ion spectra were characterized by an intense [M + NH4]+ adduct at m/z 370 and several fragment ions, most notably a [M + NH4-H2O]+ ion at m/z 352 and an ion at m/z 298, assigned as the [M + NH4-72]+ ion of 12-hydroxy-5,8,10-heptadecatrienoic acid formed form PGH2 in the spectrometer. The negative ion spectra of PGH2 were characterized by a base peak at m/z 352 [M]- and by an ion at m/z 334 corresponding to the loss of water from the parent ion. A combination of negative ion and deuterated ammonia reagent gas was used in making assignments and in demonstrating that the spectra observed were due to intact PGH2 and its stable PGE2 and PGD2 isomers formed in the spectrometer. In addition, use of the latter reagent gas was shown to clearly distinguish between several arachidonic acid metabolites, differing in their number of exchangeable protons. Furthermore, preliminary results with several stable prostaglandins indicate that the spectra are sensitive to different functional groups that are present. Consequently, it would appear that negative and positive ion, NH3 (N2H3) direct chemical ionization mass spectrometry would be useful in the analysis of labile arachidonic acid metabolites, without the need for prior derivatization.

Ammonia↗
PubMed1986

A fast, nondestructive purification scheme for prostaglandin H2 using a nonaqueous, bonded-phase high-performance liquid chromatography system.

Arachidonic acid metabolism produces several biologically important compounds including the leukotrienes and prostaglandins. Prostaglandin H2 (PGH2) is the first metabolite in the arachidonic acid cascade leading to all other prostaglandins. Pivotal to our understanding of PGH2's biology is the ability to separate it in pure form from the numerous other arachidonic acid metabolites produced in a biological milieu. The extensive literature on PGH2 biology and metabolism has relied almost exclusively on the traditional method of separation using gravity flow silicic acid columns. In our hands, such PGH2 preparations were found to contain varying amounts of 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT), PGE2, PGF2 alpha and other minor impurities as determined by further chromatographic and mass spectral analyses. Analytical separation of PGH2 and other arachidonic acid metabolites has been accomplished using reversed-phase HPLC. However, the labile nature of this molecule in aqueous systems makes such techniques unacceptable for preparative isolation of high purity PGH2 and has necessitated the development of a totally nonaqueous separation. To this end, we attempted several stationary phases and found that the cyano-bonded phase showed the best selectivity for resolving PGH2 from its major contaminants. Separations were performed on self-packed columns using a hexane-isopropanol gradient. Peaks were detected both by liquid scintillation counting and uv spectrophotometry (214 nm). Structure assignments were made by chromatographic comparison with authentic standards (PGF2 alpha, PGE2), biological activity (PGH2--platelet aggregation), and by ammonia direct chemical ionization mass spectrometry (HHT, hydroxy-5,8,10,14-eicosatetraenoic acid, PGH2, PGE2, PGF2 alpha). The latter technique, which by its very nature volatilizes all organic material in the sample, was particularly useful in determining not only that the PGH2 preparations were free from the aforementioned side products, but that they were also free from lipid, protein, and other potential residues frequently found in biological preparations.

Animals↗
PubMed1986

Platelet modulation of polymorphonuclear leukocyte shear induced aggregation.

A cone and plate viscometer and Coulter Counter were used to study platelet modulation of polymorphonuclear leukocyte (PMNL) aggregation caused by controlled shear stress. As an index of aggregation, the large-particle percentage (LPP) was calculated. This represents the ratio of aggregated cell count to total cell count. PMNL suspensions in buffer (1.0 X 10(7) cells per milliliter, final concentration) did not show any aggregate formation at shear stresses below 150 dynes/cm2 for one minute exposure time (LPP less than 3%). However, there was PMNL aggregation in mixed PMNL and platelet-rich plasma suspensions in this shear stress range. Supernatant plasma from sheared platelets initiated PMNL aggregation at moderate shear stress (150 dynes/cm2 for one minute; LPP, 20.3% +/- 2.5%). In contrast, platelet release factors, such as adenosine diphosphate (2 mumol/L) and serotonin (2 mumol/L) did not cause PMNL aggregation (LPP, 2.9% +/- 1.2% and 3.3% +/- 0.8%, respectively). The use of a cyclo-oxygenase inhibitor (acetylsalicylic acid, 50 mumol/L) did not suppress the aggregation of PMNLs after shear (LPP, 20.1% +/- 2.4%). However, preincubation with nordihydroguaiaretic acid (10 mumol/L), an inhibitor of C-5 and C-12 lipoxygenase, and 6,9-deepoxy-6,9-(phenylimino)-6,8-prostaglandin I1 (U-60257, 10 mumol/L), an inhibitor of C-5 lipoxygenase in human leukocytes, suppressed this aggregation (LPP, 9.1% +/- 2.5% and 10.4% +/- 3.2%, respectively). Also, the formation of lipoxygenase products (5-HETE, 12-HETE, 15-HETE, and LTB4) activated by shear stress was documented by reversed phase-high-performance liquid chromatography (RP-HPLC). These data support the possibility of a cooperation between platelets and leukocytes in shear-induced PMNL aggregation that is dependent on C-12 or C-5 lipoxygenase activity, or both.

Arachidonic Acid↗
PubMed1986

Stimulation of endothelial cell prostacyclin formation by interleukin-2.

The production of prostacyclin (PGI2) by the luminal surface of bovine aorta was significantly increased when incubated with 1 unit of interleukin-2 (IL-2). In separate experiments, confluent cultured bovine aortic endothelial cells were also shown to be stimulated to produce increased levels of PGI2 in a concentration-dependent manner by purified IL-2. This increase in prostacyclin biosynthesis was inhibited by cycloheximide. Since the recovery of prostacyclin production in aspirin treated cells was stimulated by interleukin-2, our results suggest that the stimulatory effect of interleukin-2 on prostacyclin synthesis is at least partially mediated by the de novo synthesis of cyclooxygenase.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Binding of prostacyclin by plasma glycoproteins.

The binding of prostacyclin (PGI2) to plasma proteins and the resulting increase in PGI2 stability was investigated. Using gel filtration to separate bound and free PGI2, we have found that Cohn Fraction VI can bind PGI2, and retard its hydrolysis to 6-keto-PGF1 alpha (6KPGF1 alpha). The biological activity of the bound PGI2 correlated well with the quantity of bound PGI2, measured as 6KPGF1 alpha by RIA. Fraction VI bound a greater percentage of PGI2 than the other eicosanoids tested (i.e., PGI2 greater than TXB2 greater than LTB4 greater than PGE1 greater than PGF2 alpha). The PGI2 binding activity of Fraction VI was lost after neuraminidase treatment. Our data suggest that Fraction VI glycoproteins may play an important role in the binding and stabilization of PGI2 by plasma proteins.

Epoprostenol↗