Biomedical subjects
B W Turner
Publications and source records attributed to B W Turner.
Treatment of sexual offenders in an outpatient community-based program.
The components of a court-mandated outpatient treatment program in Florida for adult sex offenders are discussed. Selection and treatment factors are presented, in addition to the success rate, in terms of recidivism for program participants (N = 202) over a 5-year time span. This study is an extension of the 1989 work of Bingham and Piotrowski.
Mutagenic dissection of hemoglobin cooperativity: effects of amino acid alteration on subunit assembly of oxy and deoxy tetramers.
Free energies of oxygen-linked subunit assembly and cooperative interaction have been determined for 34 molecular species of human hemoglobin, which differ by amino acid alterations as a result of mutation or chemical modification at specific sites. These studies required the development of extensions to our earlier methodology. In combination with previous results they comprise a data base of 60 hemoglobin species, characterized under the same conditions. The data base was analyzed in terms of the five following issues. (1) Range and sensitivity to site modifications. Deoxy tetramers showed greater average energetic response to structural modifications than the oxy species, but the ranges are similar for the two ligation forms. (2) Structural localization of cooperative free energy. Difference free energies of dimer-tetramer assembly (oxy minus deoxy) yielded delta Gc for each hemoglobin, i.e., the free energy used for modulation of oxygen affinity over all four binding steps. A structure-energy map constructed from these results shows that the alpha 1 beta 2 interface is a unique structural location of the noncovalent bonding interactions that are energetically coupled to cooperativity. (3) Relationship of cooperativity to intrinsic binding. Oxygen binding energetics for dissociated dimers of mutants strongly indicates that cooperativity and intrinsic binding are completely decoupled by tetramer to dimer dissociation. (4) Additivity, site-site coupling and adventitious perturbations. All these are exhibited by individual-site modifications of this study. Large nonadditivity may be correlated with global (quaternary) structure change. (5) Residue position vs. chemical nature. Functional response is solely dictated by structural location for a subset of the sites, but varies with side-chain type at other sites. The current data base provides a unique framework for further analyses and modeling of fundamental issues in the structural chemistry of proteins and allosteric mechanisms.
Physiologic abnormalities in the paranasal sinuses during experimental rhinovirus colds.
Six (18%) of 34 healthy, asymptomatic young adults had mucosal thickening or fluid in the paranasal sinuses on screening magnetic resonance imaging (MRI) examination. When 19 of these subjects were challenged with rhinovirus, 18 became infected. Twelve of the 18 infected subjects had technically satisfactory serial MRI examinations, and four (33%) of these developed MRI abnormalities of the ethmoid or antral sinuses that were temporally associated with the acute infection. The mean total nasal secretion weights were 22 gm/5 days in the four subjects whose MRI abnormalities were associated with the acute infection compared with 5.5 gm/5 days in the eight subjects who had normal MRI examinations during the acute infection (p = 0.06). Abnormalities of the paranasal sinuses, which were associated with increased volumes of nasal secretion, were detected by MRI examination during rhinovirus infection. These abnormalities may have a role in the pathogenesis of acute sinusitis associated with colds.
Laboratory outbreak of Q fever.
An outbreak of Q fever in a university department where sheep placentas were being used for research is described. Of six persons exposed to the sheep, four had positive titers with only one person developing an acute febrile illness and liver disease. This report illustrates the value of the family physician obtaining an occupational history and conducting an outbreak investigation.
Subunit association of enzyme I of the Salmonella typhimurium phosphoenolpyruvate: glycose phosphotransferase system. Temperature dependence and thermodynamic properties.
The bacterial phosphoenolpyruvate:glycose phosphotransferase system plays an essential role in diverse physiological phenomena. To perform these functions, the system is stringently regulated, although the underlying molecular regulatory mechanisms have not been established. A potential target for this type of regulation is the first protein in the phosphotransfer sequence, Enzyme I, which catalyzes the following reaction: P-enolpyruvate + Enzyme I Mg2+ in equilibrium phospho-I + pyruvate. We reported previously that Enzyme I from Salmonella typhimurium consists of identical subunits which associate in a temperature-dependent manner; the mode of association was found to be either monomer-dimer or isodesmic. The association reaction has now been investigated by analytical gel chromatography at 8, 11, and 23 degrees C. At each temperature, the mode of association was strictly monomer-dimer. The apparent association equilibrium constant, K'a, increased dramatically with temperature, with an enthalpy of 54.8 +/- 6.3 kcal/mol. At 23 degrees C, K'a decreased slightly when the enzyme solution contained either Mg2+ or phosphoenolpyruvate. However, when both ligands were present, i.e. under conditions where Enzyme I is phosphorylated, K'a decreased significantly (25-fold at 11 degrees C and 50-fold at 23 degrees C). These results are in accord with a model for the action of Enzyme I which involves a cycle of association and dissociation. This model has potentially important implications for regulating Enzyme I and the bacterial phosphoenolpyruvate:glycose phosphotransferase system.
A quantitative model for the cooperative mechanism of human hemoglobin.
A quantitative model has been developed for the cooperative oxygenation of human hemoglobin. The model correlates the structural and energetic features of ligand-linked subunit interactions within the tetrameric molecule and the coupling of these interactions to the binding of oxygen and Bohr protons. Recent findings are incorporated regarding (i) the sites of regulatory energy change within the tetrameric molecule, (ii) the nature of the Bohr effect for tetramers and dimers, (iii) the fractional Bohr proton release at each stage of oxygenation, (iv) relative probabilities of binding to the alpha and beta chains within the tetramer, and (v) an extensive data base recently obtained on the linked processes of oxygenation, proton binding, and subunit interactions [Chu, A. H., Turner, B. W. & Ackers, G. K. (1984) Biochemistry 23, 604-617]. Least squares minimization was used to evaluate from these data the free energies for the various processes. A special feature of the model lies in the synchronization of Bohr proton release with changes in quaternary structure. This leads to the striking prediction that a major fraction (as much as 30%) of tetramers are in the oxy quaternary structure after the first oxygen is bound. The model provides a rationale for the essential features of regulatory energy control, and it defines several kinds of additional information that are needed for a more complete understanding of the hemoglobin mechanism.
Probing the energetics of proteins through structural perturbation: sites of regulatory energy in human hemoglobin.
The sites of energy transduction within the human hemoglobin molecule for the regulation of oxygen affinity have been determined by an extensive study of the molecule's energetic response to structural alteration at individual amino acid residues. For 22 mutant and chemically modified hemoglobins we have determined the total free energy used by the tetrameric molecule for alteration of oxygen affinity at the four binding steps. The results imply that the regulation of oxygen binding affinity is due to energy changes which are mostly localized at the alpha 1 beta 2 interface. They also indicate a high degree of "internal cooperativity" within this contact region--i.e., the structural perturbations at individual residue sites are energetically coupled. Cooperativity in ligand binding is thus a reflection of cooperativity at a deeper level--that of the protein-protein interactions within the alpha 1 beta 2 interfacial domain.
Measurement and analysis of ligand-linked subunit dissociation equilibria in human hemoglobins.
Explore the source record for details and available documents.
Fractures of the clavicle.
Three hundred and forty-two patients with fractures of the clavicle attended the Fractrure Clinic at Bridgend General Hospital between 1957 and 1972. The history of injury was recorded in the notes at the first visit but in only 215 cases was the exact mechanism of the injury clearly stated. Of these, 91 per cent were caused by a fall or a blow on the point of the shoulder. All patients were treated symptomatically. A triangular sling was applied to support the weight of the arm and early use of the limb was encouraged. One hundred unselected patients were followed up, the longest period being 15 years and the shortest, 1 year. None had any loss of function of muscle power at the shoulder. Only 15 per cent were left with any noteworthy deformity at the site of fracture.