Search PubMed⌕ Search

Biomedical subjects

W C Phillips

Publications and source records attributed to W C Phillips.

At least 19 recordsLinked to original sources
PubMed1992

Correlations of atomic movements in lysozyme crystals.

Diffuse scattering data have been collected on two crystal forms of lysozyme, tetragonal and triclinic, using synchrotron radiation. The observed diffraction patterns were simulated using an exact theory for simple model crystals which relates the diffuse scattering intensity distribution to the amplitudes and correlations of atomic movements. Although the mean square displacements in the tetragonal form are twice that in the triclinic crystal, the predominant component of atomic movement in both crystals is accounted for by short-range coupled motions where displacement correlations decay exponentially as a function of atomic separation, with a relaxation distance of approximately 6 A. Lattice coupled movements with a correlation distance approximately 50 A account for only about 5-10% of the total atomic mean square displacements in the protein crystals. The results contradict various presumptions that the disorder in protein crystals can be modeled predominantly by elastic vibrations or rigid body movements.

Crystallization↗
PubMed1991

Osteoarthritis: with emphasis on primary osteoarthritis of the shoulder.

Fifty-three shoulders in 35 patients were found to have osteoarthritis (OA) of the shoulder using radiographic criteria to establish the diagnosis. Thirty of these shoulders did not exhibit any predetermined signs of secondary OA and were labeled primary OA. The average age of the patients was 79 years. This article discusses OA, with special emphasis on primary OA of the shoulder. Primary OA of the shoulder appears to occur in older individuals and may not be as rare as many observers have stated.

Aged↗
PubMed1990

Diffraction diagnosis of protein folding in gap junction connexons.

To diagnose the regular polypeptide conformation in gap junction membranes, the x-ray intensities diffracted from oriented specimens have been separated into a modulated component due to the coherently ordered portion of the channel-forming pairs of connexon hexamers and a diffuse component due to the disordered parts. The spherically averaged ordered protein diffraction, in the resolution range 15-4 A, was compared with intensity curves calculated from the Fourier transforms of proteins representative of the major tertiary structural classes. From this comparison the alpha-helical content of the ordered portion of the connexon was estimated to be approximately 60%. Calculation of cylindrically averaged patterns for oriented distributions of alpha-helical and beta-sheet proteins demonstrated that the ratio of the modulated diffracted intensity near 5 A spacing on the meridian and 10 A spacing on the equator observed from the gap junctions can be accounted for by alpha-helical segments inclined relative to the connexon axis. Model dimers of connexonlike hexamers were constructed from alpha-helix bundle proteins to correlate features in the calculated diffraction patterns with the model parameters. On the basis of these correlations, the ordered gap junction diffraction data indicate that alpha-helical segments centered at 38 A from the midplane of the gap have a mean radial location approximately 24 A from the hexamer axis, and an axial projected length of approximately 35 A. Thus, these alpha-helical segments traverse the hydrocarbon core of the lipid bilayer, as expected for the four hydrophobic sequences of the connexin molecule.

Animals↗
PubMed1989

Intercalary bone allografts: radiographic evaluation.

The authors retrospectively evaluated the clinical records and radiographs of 20 patients with a variety of neoplasms in the long bones treated with local resection and allograft replacement. All of the tumors were peridiaphyseal and required an interposed (intercalary) segmental allograft replacement. Postoperative complications developed in 40% of the patients. However, the eventual clinical outcome was good or excellent in 85% of all cases. Various factors appeared to be responsible for the development of complications or the eventual clinical outcome, including union of the graft with the host tissue, soft-tissue swelling, callus formation, and type of allograft (hemi or full). Knowledge of these factors and the relationship between complications and radiographic findings may lead to an early diagnosis and appropriate treatment.

Adolescent↗
PubMed1986

Giant cell tumor of bone: radiographic changes following local excision and allograft replacement.

The authors retrospectively evaluated the clinical records and radiographs obtained from 41 patients who had giant cell tumor of bone and who were treated by local resection and allograft replacement. Postoperative complications developed in 41% of the patients. However, the eventual clinical outcome was considered to be satisfactory in 85% of all cases. There were no instances of tumor recurrence, and surprisingly, postoperative arthritis was not a major problem. The major complications encountered were infection and allograft fracture; bone infection accounted for most of the clinical failures. All infections were associated with the increasing soft-tissue swelling and bone resorption detected on radiographic studies. Other radiographic parameters that were associated with an increased rate of complications included osteopenia, increased periosteal reaction, and decreased bone formation at the host-donor junction site. The clinical outcome was distinctly less favorable in those cases in which the patient had had a pathologic fracture or a previous resection, or in whom the graft was implanted at the distal radius.

Adolescent↗
PubMed1984

Gap junction structures. V. Structural chemistry inferred from X-ray diffraction measurements on sucrose accessibility and trypsin susceptibility.

X-ray diffraction patterns have been recorded from partially oriented specimens of gap junctions isolated from mouse liver and suspended in sucrose solutions of different concentration and thus of different electron density. Analysis of these diffraction patterns has shown that sucrose is excluded from the 6-fold rotation axis of the junction lattice for a length of about 100 A. This indicates that the aqueous channel of the junctions is in the closed, high resistance state in these preparations. Mapping of the sucrose-accessible space in the junction indicates that the cross-sectional area of the channel entrance on the cytoplasmic side of the membrane could be up to five times larger than the area of the transmembrane channel. Sucrose does not penetrate more than 20 A into the membrane along the channel. Apparently the aqueous channel, 8 to 10 A in radius for most of its length, is narrowed or blocked by a small feature about 50 A from the center of the gap. Very close interactions exist between the gap junction protein and the lipid polar head groups on the cytoplasmic surface of the membrane. In this region, the protein intercalates between the polar head groups. These results suggest that the gap junction protein may have a functional two-domain structure. One domain, with a molecular weight of about 15,000, spans one bilayer and half of the gap and is contained largely within a radius of 25 A from the 6-fold axis. The second domain is smaller and occupies the cytoplasmic surface of the gap junction membrane. Trypsin digestion removes about 4000 Mr from the cytoplasmic surface domain of the junction protein. Most of the material susceptible to trypsin digestion is located more than 28 A from the 6-fold axis.

Animals↗
PubMed1984

Gap junction structures. VI. Variation and conservation in connexon conformation and packing.

Correlation of structural changes in isolated gap junctions with the mechanism of channel gating is complicated by the effects of isolation procedures and the lack of a direct functional assay. The effect of variations in the isolation procedure are examined by comparison of the structures of gap junctions isolated by different protocols. X-ray diffraction data from over two hundren specimens are compared to provide a basis for identification of invariant aspects of the connexon structure and variable properties related either to functional switching or experimental modifications. We discuss the relationship between subunit tilt, lattice symmetry and packing, and membrane curvature and demonstrate that membrane curvature may be a natural consequence of the structure of the connexons and the patterns of interactions between them.

Animals↗
PubMed1983

Osteoid osteoma: an unusual cause of articular pain.

Twenty-five patients who had histologically proved osteoid osteoma and whose major symptom was joint pain were studied. Retrospective study of clinical data and radiographs revealed that almost all of the lesions were located near the painful joint and that there had been significant delay in determination of the correct diagnosis. The delay was related to the nonspecificity of symptoms, the latency between the onset of symptoms and the appearance of the lesion on radiologic study, and the evaluation sequence used in some patients. The relative effectiveness of various diagnostic modalities is discussed. Radionuclide bone scanning, plain radiography, and guided tomography are the most useful diagnostic studies.

Adolescent↗
PubMed1983

Severed body parts: radiologic evaluation following replantation.

Sixty-two replantations of totally severed body parts in 25 patients were followed via serial radiography. Most of these replantations were of digits. Uncomplicated digital replantation showed a definite temporal pattern consisting initially of decreasing mineral content followed by increasing mineral content, decreasing soft-tissue swelling, and increasing callus formation. Deviations from the expected patterns were helpful in predicting complications such as infection and/or osteonecrosis.

Adolescent↗
PubMed1983

CT in pyogenic osteomyelitis of the spine.

Six patients with bacteriologically proven pyogenic osteomyelitis of the spine were followed serially with computed tomography (CT). Initial evaluation of the involved vertebral bodies and adjacent soft tissues showed a drop in CT numbers when compared to normal cancellous bone and soft tissues. A soft-tissue mass was seen in all cases. After appropriate antibiotic therapy, all six patients showed an increase in bone density and a diminution of the soft-tissue mass (p less than 0.05). Five of the six patients showed a further decrease in soft-tissue CT numbers.

Adult↗
PubMed1983

Statistics for diagnostic procedures. I. How sensitive is "sensitivity"; how specific is "specificity"?

The terms of medical decision making (i.e., accuracy, sensitivity, specificity, predictive value, false positive/negative rates) are often seen in the radiologic literature. The interrelationships among these terms are explained, with special emphasis on the following: (1) How useful a procedure is for detecting/excluding disease depends on sensitivity, specificity, and prevalence of disease, and thus varies from practice to practice, and (2) "Accuracy" is often very misleading.

Decision Making↗