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Biomedical subjects

W C Hutton

Publications and source records attributed to W C Hutton.

At least 145 records · Page 8Linked to original sources
PubMed1975

Headgroup conformation and lipid--cholesterol association in phosphatidylcholine vesicles: a 31P(1H) nuclear Overhauser effect study.

The nuclear Overhauser effect has been observed in the nuclear magnetic resonance spectra of 31P. The information content of the nuclear Overhauser effect has been applied to the structure and dynamic properties of phosphatidylcholine vesicles. In the vesicles only 1/3 of the theoretical maximum nuclear Overhauser effect enhancement is observed. This result is accounted for by dipolar interactions between the N-methyl protons and the phosphate of phosphatidylcholine, and a correlation time for internal motion of 1.4 X 10(-9) sec. Addition of up to 30% cholesterol does not change the nuclear Overhauser effect enhancement or spin-lattice relaxation time of the vesicles. It is argued that the OH group of cholesterol is hydrogen bonded to the ester carbonyl oxygen of the phosphatidylcholine molecules.

Cholesterol↗
PubMed1975

The effects of x-irradiation on the mechanical properties of skin.

The elastic properties of rat skin previously irradiated with single doses form 1000 to 3000 rad have been studied. The measurements were made 50 and 120 d after irradiation on skin specimens immersed in saline at 37 degrees c. The tests were carried out on a tensile testing machine. The load extension curve, which was plotted to the point of rupture, exhibits two portions which are identified with the aligment of the collagen fibres and then their subsequent stretching. The elastic properties associated with fibre alignment are little affected by these doses of radiation but the stiffness of the collagen itself tends to decrease with increasing dose, exhibiting a shoulder in the dose response curve.

Animals↗
PubMed1975

The neuropathic ulcer and loads on the foot in diabetic patients.

Normal subjects and diabetic patients with and without food ulcers have been studied using an apparatus which measures the loads on the foot during walking. Diabetic patients have alterations in loading which show as a lateral shift of the highest maximum load on the forefoot and a decrease in the load carried by the toes. There is a significant progression of these changes between normal subjects, diabetic patients with deformity of the foot but no ulcer, and diabetic patients with foot ulcers. All the patients with ulcers exerted maximum loads at the site of the ulcer.

Adolescent↗
PubMedDate not supplied

Biomechanical comparison of hybrid external fixators.

OBJECTIVES: To determine the stiffness characteristics of the hybrid ring fixator in the treatment of (OTA 41-C) proximal metaphyseal and shaft tibial fractures. DESIGN: Five identical composite tibiae were fixed with a Synthes, ACE Fischer, Howmedica Monticelli-Spinelli, or Smith & Nephew Trauma Ilizarov hybrid external fixator or with the conventional Ilizarov wire fixator. The Synthes and Monticelli-Spinelli fixators were tested twice, the first time with the connectors on the outside of the ring and the second time with the connectors on the inside of the ring. MAIN OUTCOME MEASUREMENTS: A materials testing machine was used to apply pure compression, anterior and posterior bending, medial and lateral bending, and torsion. Stiffness values were calculated from the load deformation and torque angle curves. RESULTS: Overall, the Synthes and Monticelli-Spinelli fixators were the most rigid of the fixators when the wire-to-ring connectors were placed inside the ring. In general, the fixators were stiffest in axial compression and least stiff in posterior bending. Wire length had a significant effect on overall stiffness. CONCLUSIONS: This study suggests that the four hybrid external fixators in standard configuration have stiffness characteristics similar to those of the conventional Ilizarov fixator when used to treat proximal metaphyseal and shaft fractures of the tibia.

Biomechanical Phenomena↗
PubMedDate not supplied

A comparison of mechanical strength of the femoral neck following locked intramedullary nailing using oblique versus transverse proximal screws.

OBJECTIVE: The objective of the present study was to determine whether the 130-degree oblique or transverse proximal locking technique significantly enhances or diminishes the strength of the intramedullary nail-to-bone construct in a "stancelike" loading configuration. DESIGN: Six paired fresh frozen femora were randomized to locked intramedullary nailing with either the 130-degree proximal locking technique or the transverse locking technique and tested in axial compressive loading. Torsion, shear, and impact loading were not tested. PATIENTS/PARTICIPANTS: Six paired adult fresh frozen cadavers. INTERVENTION: An unreamed eleven-millimeter by thirty-eight-centimeter intramedullary nail was placed under direct visualization in each femur. Proximal locking was randomly performed on each pair with either two transverse screws or a single oblique screw. Each femur was loaded to failure at a rate of 50.8 millimeters per minute (two inches per minute) by using an Instron tensiometer. Radiographs after nail insertion and after failure were obtained. MAIN OUTCOME MEASURES: Load to fracture and fracture pattern. RESULTS: A significant difference between load to fracture was observed across femora of different donors (p < 0.001). No significant difference was observed in paired femora from the same donor when using either 130-degree or transverse proximal locking (p > 0.05). This result was based on nonanatomical axial loading that approximated loading during stance, without hip abductor loads to help stabilize the femur. CONCLUSION: Neither technique preferentially predisposed the construct to failure for the loading pattern tested. The mode of failure was the same in all cases, with failure beginning at the nail insertion site.

Aged↗
PubMedDate not supplied

Variations in the amount and distribution of cortical bone across the partes interarticulares of L5. A predisposing factor in spondylolysis?

The possible role of the physical and mechanical properties of the neural arch as contributing factors in the etiology of spondylolysis was tested by comparing two groups of vertebral specimens obtained at necropsy. Group I specimens had been subjected to repetitive cyclic force which they withstood without fracturing. Group II specimens were randomly selected. The cross-sectional distribution of cortical and cancellous bone in the partes interarticulares were measured, and the two groups compared. The previously stressed group was found to have a greater percentage of cortical bone than the random group. The data are interpreted to suggest that thin partes interarticulares may predispose to spondylolysis through the mechanism of fatigue failure.

Adolescent↗
PubMedDate not supplied

Articular tropism and stability of the lumbar spine.

Lumbar intervertebral joints were subjected to compressive and shear forces calculated to simulate walking with a heavy pack on the back. The joints with articular tropism were found to rotate toward the side of the more oblique facet. The mechanics relating the orientation of the articular facets with joint forces and stability of the lumbar spine are discussed.

Adolescent↗
PubMedDate not supplied

The resistance to flexion of the lumbar intervertebral joint.

Cadaveric lumbar intervertebral joints were subjected to physiologic loads to simulate flexion. The resistance to bending was measured first with the joint intact and again after cutting in turn through the supraspinous/interspinous ligaments, the ligamentum flavum, and the capsular ligaments of the apophyseal joints. In this way the part played by each of these structures, and the intervertebral disc, in resisting and limiting flexion was determined. The results show that at the limit of flexion the supraspinous and interspinous ligaments sprain first and that the capsular ligaments and the intervertebral disc offer considerably more resistance than the ligamentum flavum and the supraspinous/interspinous ligaments. The intervertebral joint was found, on average, to be sufficiently stiff to balance about half the bending moment exerted by the trunk in full flexion.

Biomechanical Phenomena↗
PubMedDate not supplied

The relevance of torsion to the mechanical derangement of the lumbar spine.

Cadaveric lumbar intervertebral joints were loaded simultaneously in torsion and compression, and load-deformation curves were obtained. These were repeated after each of the following structures were cut through in turn: the supra/interspinous ligaments, the apophyseal joint in compression, and the apophyseal joint in tension. From the differences in the curves, it was possible to deduce the role of each structure and of the intervertebral disc in resisting and limiting torsion. The results show that torsion of the lumbar spine is resisted primarily by the apophyseal joint that is in compression, although the intervertebral disc does play a major role. The capsular ligaments of the tension facet and the supra/interspinous ligaments are unimportant. The compression facet is the first of rotation in joints with nondegenerated intervertebral discs. Much greater angles are required to damage the intervertebral disc, so torsion seems unimportant in the etiology of disc degeneration and prolapse.

Adolescent↗
PubMedDate not supplied

Can the lumbar spine be crushed in heavy lifting?

Cadaveric lumbar intervertebral joints were wedged to simulate forward flexion and then compressed to failure. The compressive strengths of the young male specimens tested were compared with the forces calculated to act when average young men perform maximum lifts from the flexed posture. It is concluded that the spine has a considerable margin of safety when such lifts are performed.

Adult↗