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Biomedical subjects

W C Hutton

Publications and source records attributed to W C Hutton.

At least 127 records · Page 7Linked to original sources
PubMed1978

Spondyloysis. The role of the posterior elements in resisting the intervertebral compressive force.

Compressive tests were carried out on cadaveric lumbar intervertebral joints, before and after the neural arch was fractured. The results show that although the neural arch can play some part in resisting the intervertebral compressive force, there is no bony contact between the downward projecting tips of the inferior articular processes and the laminae of the vertebra below.

Adolescent↗
PubMed1977

Phospholipid head-group conformations; intermolecular interactions and cholesterol effects.

The predominant orientation of the phosphorylcholine polar head group in phosphatidylcholine and sphingomyelin bilayers and cholesterol perturbations of that orientation have been identified by exploiting the 31P (1H) nuclear Overhauser effect (NOE) in the 31P NMR spectra of phospholipid bilayers. In pure egg phosphatidylcholine bilayers, a NOE of 40% is observed. The magnitude of the NOE has been measured as a function of continuous-wave proton-decoupler frequency in order to identify the proton source of the NOE. In pure egg phosphatidylcholine bilayers, the maximum NOE occurs at the N-methyl proton resonance position of the choline moiety. In a modified phosphatidylcholine in which all the N-methyl protons were replaced by deuterium, the NOE arose from methylene protons next to the phosphate. In mixed systems of phosphatidylcholine and phosphatidylethanolamine, and phosphatidylcholine and diphosphatidylglycerol, both phospholipid resonances attained maximum NOE at the position of the N-methyl proton resonance of phosphatidylcholine. An analogous result was obtained with pure sphingomyelin. These results are explained by orienting the phosphorylcholine portion of the molecule parallel to the surface of the bilayer so that the positively charged N-methyl moiety is located close to the negatively charged phosphate on a neighboring phospholipid in an intermolecular interaction. Addition of cholesterol is shown to disrupt the intermolecular interaction in phosphatidylcholine bilayers.

Chemical Phenomena↗
PubMed1977

Molecular dynamics of the local anesthetic tetracaine in phospholipid vesicles.

Upon introduction into phosphatidylcholine vesicles, the 13C magnetic resonance peaks of the aromatic resonances of tetracaine are broadened while the T1 relaxation times show little change. Addition of tetracaine to vesicles containing 30% cholesterol produces a similar broadening in the 13C NMR spectrum of tetracaine. Nuclear magnetic resonance parameters of phosphatidylcholine in vesicles which are unchanged by the addition of equimolar tetracaine include 13C T1 relaxation time and 31P linewidth, T1 relaxation time, and nuclear Overhauser effect enhancement. These results are interpreted as indicating a hydrophobic interaction between hydrocarbon portions of the anesthetic and phospholipid bilayer. The rotational correlation time of tetracaine about its long axis in the vesicles has been calculated from the 13C NMR spin lattice relaxation times to be about 10(-10.3) s and is unchanged by incorporation into the phospholipid bilayer. The positively charged ammonium group of tetracaine interacts with the negatively charged phosphate group of the vesicle lipids. Using shift reagents and 31P NMR, tetracaine has been shown to displace cations from the bilayer surface, and does not undergo fast flip-flop across the vesicle bilayer.

Anesthetics, Local↗
PubMed1977

The structure of vesicular stomatitis virus membrane. A phosphorus nuclear magnetic resonance approach.

The proton decoupled 40.48 M Hz 31P NMR spectrum of intact and unperturbed membrane-enclosed vesicular stomatitis virus (sterotype Indiana) exhibited two distinct maxima. These can be resolved into a narrow, symmetric line and a broad asymmetric line. The 31P NMR spectrum of a multilamellar (unsonicated) preparation of the extracted viral lipids exhibited a line shape similar to that of the intact virus. A sonicated vesicle preparation of the extracted viral lipids exhibited a narrow symmetric line. The narrow component in the intact virus spectrum may be attributed to small membrane fragments. Phospholipase C digestion of the intact virus resulted in substantial reduction in intensity of both components which suggests that much of the contribution to both peaks is due to phosphate in the phospholipid polar head groups. The phospholipid phosphates in both sonicated and unsonicated preparations of the extracted viral lipids exhibited substantially longer relaxation times than did those in the intact virus. The short relaxation time emanating from the intact virus preparation is caused by immobilization of the phospholipid head groups which could be due to lipid-protein interactions. Trypsin treatment of vesicular stomatitis virions, which results in complete removal of the exterior hydrophilic segment of the membrane glycoprotein, increased the 31P relaxation time to a value similar to that observed in the protein-free total lipid extracts; this finding provides supporting evidence for the role of virus glycoprotein in shortened relaxation times. A reversible temperature-dependent change in apparent line width and absence of an effect of cholesterol on the 31P phospholipid spectrum were also demonstrated.

Cell Line↗
PubMed1977

The interaction of lanthanide and calcium salts with phospholipid bilayer vesicles: the validity of the nuclear magnetic resonance method for determination of vesicle bilayer phospholipid surface ratios.

Contrary to a recent report (B. Sears et al., Biochemistry 15 (1976) 1635), it has been determined that the ratio of the number of phospholipids on the inner and outer surfaces of phospholipid bilayer vesicles can be accurately determined by NMR paramagnetic ion shift reagent studies of vesicles. It is concluded that the metal interacts with all of the phospholipid on the exposed bilayer surface. A ratio of outer phospholipid to inner surface phospholipid of 2.1 +/- 0.1 is obtained regardless of the nucleus studied, position of the nucleus relative to the metal ion binding site, molar ratio of metal to phospholipid over three orders of magnitude, or location of the metal ion of the inside or outside of the vesicle. Additionally, P-31 NMR studies using LaC13 and CaC12 indicate that Ca2+ weakly interacts with egg PC vesicles and that the lanthanides are adequate substitutes for Ca2+ since neither metal is found to perturb measurably the average polar head group conformation.

Calcium↗
PubMed1977

The effects of split dose radiations on the mechanical properties of the skin.

A series of split dose experiments in which the interval between doses was varied from 1 to 7 d is reported. In vitro measurements of the mechanical properties of skin are made 50 and 120 d after the first irradiation. The variation of the skin thickness, load at rupture, extension at rupture, stress at rupture and skin stiffness with dose and with time interval between doses is examined. The results suggest that after the highest doses of irradiation the skin is matted in structure and the fractionation pattern is insignificant. Different fractionation patterns only influence the radiation effects at lower doses where the skin retains an open mesh structure. The experiments indicate that a maximum skin sparing effect is obtained with a two day interval between the split doses.

Animals↗
PubMed1977

A method of in vivo measurement of the elastic properties of skin in radiotherapy patients.

A portable apparatus which measures the force-displacement or elastic characteristics of skin in vivo has been constructed. A displacement transducer between two arms measures the extension of the skin as the arms are driven apart by means of a lead screw, and the force exerted on the skin is measured by means of two electrical resistance strain gauges attached at a reduced section on each of the arms. The apparatus was designed for compactness and lightness to enable it to be hand held. Illustrative results obtained on patients during and after courses of radiotherapy are presented.

Breast Neoplasms↗
PubMed1977

Effects of radiation on the visual appearance and mechanical properties of mouse skin.

A study of the long term effects of radiation on the visual appearance and mechanical properties of mouse skin is presented. The effects associated with the hair follicle (greying and alopecia) increase monotonically with exposure. Other effects (load, extension and stress at rupture and scarring of the skin) all show a reversal at the highest exposures. The skin thickness changes little with exposure, while the skin stiffness exhibits a shoulder on the response curve. Possible mechanisms underlying these effects are discussed.

Alopecia↗
PubMed1976

Structure in the polar head region of phospholipid bilayers: A 31P [1H] nuclear Overhauser effect study.

The structure of the head-group region of some phospholipid bilayers in vesicle form has been studied and an intermolecular association of the N-methyl protons of phosphatidylcholine (PC) with the phosphate of phosphatidylethanolamine (PE) in mixed vesicles has been identified. Observation of a 31P[1H] nuclear Overhauser effect (NOE) in the phosphorus nuclear magnetic resonances of both PC and PE in mixed vesicles demonstrates an intimate dipolar interaction between some protons and the phosphorus nuclei. Substitution of deuterium for the N-methyl protons of PC eliminated the majority of the effect and necessitated the construction of a model of the bilayer surface in which the N-methyl protons of PC could interact closely with the phosphates of neighboring PE molecules. The predominant orientation of the head group must then be parallel to the bilayer surface. The amino protons of PE do not contribute significantly to the observed NOE. A corollary of these results is that there is little if any tendency for either PC or PE in the mixed vesicles to segregate into separate domains. A decrease in NOE in sphingomyelin vesicles on going from H2O to D2O suggests that an exchangeable proton contributes to the NOE. In addition the low value of the NOE observed in D2O suggests that the head-group conformation of sphingomyelin differs from that of PC.

Binding Sites↗
PubMed1976

Effects of paramagnetic shift reagents on the 13C nuclear magnetic resonance spectra of egg phosphatidylcholine enriched with 13C in the N-methyl carbons.

Effects of paramagnetic shift reagents on the 13C NMR spectra obtained from single-walled vesicle dispersions of egg phosphatidylcholine enriched with 13C in the N-methyl carbons are investigated. Spectra obtained at 25.1 MHz show that, at Yb3+ to phospholipid molar ratios as low as 0.06, complete resolution of the N-methyl carbon resonances is obtained from molecules on the inner and outer faces of the vesicle bilayer. No precipitation of the vesicles is caused by Yb3+ at these concentrations nor is appreciable line broadening observed. Other paramagnetic shift reagents frequently used in proton NMR investigations of phosphatidylcholine vesicles do not give complete separation of the N-methyl 13C signals from the two bilayer surfaces. K3Fe(CN)b,Eu3+, and Pr3+ cause precipitation of the phosphatidylcholine vesicles at concentrations, which give only incomplete resolution of these signals. T1 measurements of the resonances separated by Yb3+ indicate that the choline groups on the inner bilayer surface are less mobile than are the same groups in the outer surface. Gated proton decoupling measurements, which show that the nuclear Overhauser effect is 2.8 +/- 0.1, indicate that the dominant mode of relaxation is dipolar interaction.

Carbon Isotopes↗
PubMed1976

Transmembrane asymmetry of vesicle lipids.

The role of fatty acyl chain unsaturation in promoting asymmetry in phospholipid vesicle bilayers was investigated in mixed lipid systems with differing acyl chains and a constant phosphatidylcholine headgroup. Ratios of outside to inside components were determined by nuclear magnetic resonance spectroscopy of 13C-enriched egg phosphatidylcholine. An asymmetry or disproportionation ratio is defined and used to express quantitatively how a mixture of two lipids distributes in the outer and inner vesicle surfaces. In mixed systems with 13C-enriched egg phosphatidylcholine as one component, increasing fatty acyl unsaturation in the other component results in an increasing preference of the unsaturated chains for the outer surface.

Binding Sites↗
PubMed1976

Spondylolytic fractures.

A method is described whereby fractures of the neural arch similar to those in spondylolysis are produced experimentally. The forces, bending moments and displacements required to initiate the fractures are given; The mechanical aspects in the aetiology of spondylolysis are explained by a simplified two-dimensional force analysis.

Aged↗