Publications by authors named "HC Davies"

Background: Endocrine surgery (ES) is a relatively young subspecialty of general surgery, and prior research has shown low public awareness of these specialists' roles. We hypothesized that a video-based intervention could increase public knowledge of the specialty in an effective and efficient manner.

Methods: Participants were recruited at three public locations (a farmer's market, a public park, and a university hospital) and were given a three-question survey to assess baseline knowledge of ES.

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The behaviour of six replicates of broilers obtained from commercial farms, fed ad-libitum and housed on 23-h light:1-h dark schedule at 20 lx was observed using scan sampling. Comparisons were made between sound birds and those of varying degrees of lameness between 39 and 49 days of age. Sound broilers averaged 76% of their time lying and this increased significantly to 86% in lame birds (gait score 3).

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Our suggestions for experiments demonstrating electron-transport-chain composition and reactions all exploit bacteria which can be prepared quickly, easily and cheaply from cells grown in Erlenmeyer flasks. While they have been designed from a cytochrome oxidase point of view using organisms of our own prejudice, strains containing mutations in other sites could be just as educational. Most bacteria that can grow aerobically have features in common with the mitochondrial respiratory chain.

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Electron transport in the Paracoccus denitrificans respiratory chain system is considerably more rapid when it includes the membrane-bound cytochrome c552 than with either soluble Paracoccus c550 or bovine cytochrome c; a pool function for cytochrome c is not necessary. Low concentrations of Paracoccus or bovine cytochrome c stimulate the oxidase activity. This observation could explain the multiphasic Scatchard plots which are obtained.

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A mutant of Paracoccus denitrificans which is deficient in c-type cytochromes grows aerobically with generation times similar to those obtained with a wild-type strain. The aa3-type oxidase is functional in the mutant as judged by spectrophotometric assays of cytochrome c oxidation using the membrane particles and cytochrome aa3 reduction in whole cells. The cytochrome c oxidase (aa3-type) of the c-less mutant oxidizes soluble cytochrome c at rates equivalent to those obtained with the wild-type.

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We have devised a relatively simple method for the purification of cytochrome aa3 of Paracoccus denitrificans with three major subunits similar to those of the larger subunits of the mitochondrial cytochrome oxidase. This preparation has no c-type cytochrome. Studies were made of the oxidation of soluble cytochromes c from bovine heart and Paracoccus.

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We have studied the reactions of the oxidase of Paracoccus dentrificans with its membrane-bound cytochrome c and with soluble cytochrome c550 of Paracoccus and of bovine heart. The turnover rate of Paracoccus oxidase with membrane-bound cytochrome c is high, approaching 1000/sec. at 25 degrees.

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A monoclonal antibody has been produced to an antigenic site on human cytochrome c which includes amino acid number 58 (isoleucine). This area is on the bottom back of the cytochrome, removed from the postulated binding/reaction sites for oxidase and reductase, but in the area of the molecule where an appreciable change in conformation is seen on oxidation-reduction. In spectrophotometric assays, where binding of cytochrome c to the oxidase or reductase is rate-limiting, the antibody gave stimulation of the reductase reaction under some conditions, where the oxidase reaction was inhibited.

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The effect of a monoclonal antibody to a soluble cytochrome c from Paracoccus denitrificans was tested on the membrane-bound electron-transport system of this bacterium. This antibody (F3-10.2) and one previously described (F3-29.

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The effects of monoclonal antibodies to bovine and Paracoccus denitrificans cytochromes c (Kuo, L.M. and Davies, H.

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The reaction of the cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.

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Hybridoma cell lines secreting monoclonal antibodies which bind beef heart cytochrome c or Paracoccus denitrificans cytochrome c have been produced using spleen cells from BALB/c mice immunized with cytochrome c. Immunization was performed with either the native cytochrome c, succinylated hemocyanin-conjugated cytochrome c, or beef heart cytochrome c polymerized with glutaraldehyde. Of 10 such fusions, the hybridization frequency ranged from 0 to 42%.

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The kinetics of oxidation of horse cytochrome c and the trifluoromethylphenylcarbamylated lysine-13 derivative by cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.

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Adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), and inorganic pyrophosphate partially inhibit the oxidation of exogenous cytochrome c by cytochrome c oxidase of submitochondrial particles (with or without detergent treatment) or by a purified preparation when it is assayed polarographically in buffers of nonbinding ions at pH 7.8. ATP is somewhat more inhibitory than ADP.

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Strains of type 6 (S 43) and type 14 group A streptococci were grown with M-protein production in the presence of chemically defined synthetic media slightly modified from that previously employed for the growth of a nonproducer of M protein (type 4). The M protein, which is associated with virulence in group A streptococcus, was previously produced in growing cultures only with complex media. The bacterial growth with the biosynthesis of M protein in synthetic medium was obtained by successive adaptation in steady-state culture with decreasing amounts of Todd-Hewitt broth.

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Davies, Helen C. (University of Pennsylvania, Philadelphia), Fred Karush, and Joanne H. Rudd.

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