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Biomedical subjects

C Wright

Publications and source records attributed to C Wright.

At least 379 records · Page 21Linked to original sources
PubMed1980

A method for assessing the physiologic significance of coronary obstructions in man at cardiac surgery.

The functional significance of coronary narrowings of intermediate severity is often difficult to assess from preoperative coronary arteriograms. To complement the anatomic data obtained by arteriography, a method for measuring phasic coronary velocity and reactive hyperemia in man at cardiac surgery has been developed. The method uses a single-crystal Doppler probe coupled to surface coronary vessels with a small suction pad. The validity of the measurements has been documented in a series of in vitro and animal experiments. Because physiologically significant coronary narrowings invariably attenuate reactive hyperemic responses, this approach can be used to determine the functional importance of coronary obstruction before placement of coronary bypass grafts. Initial experience in 50 patients indicates that the measurements can be obtained safely and that the functional significance of coronary obstructions can be readily assessed.

Animals↗
PubMed1978

Somatomedin bioactivity in serum and amniotic fluid during pregnancy.

Somatomedin bioactivity (SMA) in maternal serum, as measured by hypophysectomized rat cartilage assays, was low during early and late pregnancy but was similar to normal nonpregnant control levels near 28 weeks and at term pregnancy. At term, the mean level of SMA in cord serum was significantly less than in maternal serum, and greater than in amniotic fluid. The mean level of SMA in amniotic fluid was higher at term than in early pregnancy. No significant correlation was noted between SMA levels in amniotic fluid, maternal serum or cord serum, or between the SMA levels in these samples and the usual amniotic fluid parameters used as indices of fetal maturity.

Amniotic Fluid↗
PubMed1977

The interaction of protein A and Fc fragment of rabbit immunoglobulin G as probed by complement-fixation and nuclear-magnetic-resonance studies.

Protein-A-Fc-fragment complexes were observed in sedimentation-velocity experiments by ultracentrifugation. The interaction was studied by protein-fluorescence-quenching titrations of the Fc fragment with protein A, allowing the dissociation constant to be determined under a variety of conditions. The first component of the complement pathway, C1, is activated by complexes of protein A with rabbit IgG (immunoglobulin G), and the structural basis for this interaction was studied by using n.m.r. (nuclear magnetic resonance). The four Fc-fragment binding sites on protein A were shown to contain aromatic amino acids, and to be connected by mobile hydrophilic regions. Neither n.m.r. nor proton-relaxation-enhancement studies show evidence of a large conformational change of the Fc fragment on binding protein A, and this suggests that the cross-linking of the Fc fragments may be primarily responsible for the activation of component C1. This is supported by the inability of a univalent tryptic fragment of protein A to activate complement fixation by rabbit IgG.

Animals↗
PubMed1977

Platelet and plasma amine oxidase inhibition and urinary amine excretion changes during phenelzine treatment.

The treatment of depressed patients with the monoamine oxidase (MAO)-inhibiting antidepressant, phenelzine, was found to be accompanied by an 82 per cent reduction in platelet MAO activity and a 91 per cent reduction in plasma amine oxidase activity. Maximum reductions in enzyme activity occurred after 7 to 14 days of treatment; recovery of enzyme activity posttreatment required an average of 14 days for the platelet MAO and greater than 6 weeks for the plasma enzyme. Marked elevations in urinary tryptamine excretion occurred in conjunction with MAO inhibition during phenelzine treatment, but the magnitidue of urinary tryptamine change in individual patients was not closely correlated with the magnitude of enzyme activity reduction. Changes in platelet serotonin content serotonin content and in urinary catecholamine metabolites also occurred in response to phenelzine treatment.

Blood Platelets↗
PubMed1976

Interactions of the lanthanide- and hapten-binding sites in the Fv fragment from the myeloma protein MOPC 315.

1. The interactions of lanthanide metals and dinitrophenyl spin-label haptens with the Fv fragment of the mouse myeloma protein MOPC 315 were investigated by the techniques of fluorescence, e.s.r. (electron spin resonance) and high-resolution n.m.r. (nuclear magnetic resonance). 2. The protein fluorescence of Fv fragment at 340nm is quenched by the haptens (fluorescence enhancement, epsilon=0.15) and enhanced by Gd(III) (epsilon=1.14) and other lanthanides. The binding of the haptens studied here is insensitive to pH in the range 5.5-7.0 (dissociation constant KH=0.3-1.0 muM) and shows 1:1 stoicheiometry. The binding of Gd(III) also shows 1:1 stoicheiometry, but is pH-dependent; the binding constant (KM) varies from 10 muM at pH7.0 to 700 muM at pH4.8. La(III) binding is less sensitive to pH. The pH-dependences of the metal-binding constants imply that a group in the protein with pKa greater than or equal to 6.2 is involved in the binding, and probably also other groups with lower pKa values. 3. The apparent binding of the haptens is weakened about 20-fold by Gd(III), and vice versa. An equilibrium scheme involving a ternary complex with an interaction between the two binding sites is derived in Appendix I to explain the experimental results at two pH values. 4. Time-dependent fluorescence changes are observed in the presence of Gd(III) at pH5.5. A two-state kinetic scheme involving a 'slow' conformational change in the Fv fragment is derived in Appendix II to explain this time-dependence. This scheme is consistent with the antagonistic equilibrium behaviour. 5. The e.s.r. changes in the spin-label haptens on binding to Fv fragment and on the subsequent addition of lanthanides are consistent with the binding scheme for haptens and lanthanides proposed from the fluorescence studies. A difference between the limiting quenching of the e.s.r. signal from the bound haptens in the presence of saturating concentrations of Gd(III) and La(III) is attributed to dipolar interactions between bound Gd(III) and the nitroxide moiety of the bound hapten. The residual quenching with Gd(III) allows an estimate of 1.2nm to be made for the distance between the two paramagnetic centres. 6. The 270 MHz proton difference spectrum of the Fv fragment resulting from the addition of La(III) suggests that any metal-induced conformational changes are small and involve relatively few amino acid residues on the Fv fragment...

Animals↗
PubMed1973

Bilateral traumatic renal artery thrombosis.

A case of bilateral traumatic renal artery thrombosis involving three renal arteries is presented. Four other cases of this entity are summarized for comparison. The recommended course of investigation is outlined, and the urgency of immediate surgical intervention is emphasized.

Accidents, Traffic↗
PubMedDate not supplied

Absorption kinetics of rectally and orally administered ibuprofen.

The bioavailability of rectally administered sodium ibuprofen solution and aluminum ibuprofen suspension was determined in eight normal subjects relative to the same treatments administered orally. The results indicate that the suspension was less bioavailable than the solution irrespective of the route of administration. Although not bioequivalent, rectally administered ibuprofen solution compared favourably with orally administered ibuprofen solution. The mean AUC and Cmax from rectal administration were 87 per cent and 62 per cent of the corresponding values achieved after oral administration. Mean residence times and peak times were 1-3 h longer with the rectal solution, indicating a slower rate of absorption. Absorption after rectal administration was zero order in some subjects while absorption after oral administration was first order. This may be due to the large differences in surface area between absorption sites. Since sodium ibuprofen solution is absorbed when given rectally, this route of administration could be used in patients unable to take oral ibuprofen.

Administration, Oral↗
PubMedDate not supplied

Patterns of hypothalamic-pituitary-gonadal dysfunction in men with liver disease due to differing etiologies.

The hypothalamic-pituitary-gonadal axis was evaluated in two groups of age-matched men with documented biochemical and histologic liver disease and compared to that of age-matched normal controls. Basal testosterone levels (p less than 0.05), spermatozoa concentrations (p less than 0.01), and seminal plasma volume (p less than 0.01) were reduced in the alcoholics studied with liver disease, but not the hemophiliacs with liver disease when compared to the normal controls. No difference in estradiol levels was noted between groups. Basal follicle-stimulating hormone and luteinizing hormone (LH) concentrations were increased (both p less than 0.01) in the alcoholics while only LH concentrations were increased (p less than 0.01) in the hemophiliacs compared to the normal controls. Gonadotropins (follicle-stimulating hormone and LH) and testosterone responses to clomiphene and to luteinizing hormone-releasing factor (LH only) in the alcoholic population studied, further distinguished the alcoholics from the hemophiliacs and the normal controls. The basal levels of the other anterior pituitary hormones (growth hormone and thyroid-stimulating hormone) as well as their provocative responses to thyrotropin-releasing hormone also distinguished the alcoholics from the hemophiliac population. Based upon these results, we propose that factors other than the liver disease per se are responsible for the disturbances of hypothalamic-pituitary-gonadal function observed in men with biochemically as well as histologically advanced stable liver disease.

Adult↗