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Biomedical subjects

J F Conway

Publications and source records attributed to J F Conway.

45 records · Page 3Linked to original sources
PubMed1986

Structural studies on lamin. Similarities and differences between lamin and intermediate-filament proteins.

Analysis of the amino acid sequences of lamins A and C has revealed that each chain has an almost continuous heptad-containing coiled-coil domain containing structural regularities in the linear disposition of the acidic and the basic residues. The data suggest that the lamin molecules are two-stranded ropes, that the two chains are parallel to one another and in axial register, and that the molecules aggregate in vivo through periodic ionic interactions. These results indicate that significant changes in stability of the nuclear envelope may be achieved between interphase and mitosis through changes in the degree of phosphorylation of the lamin proteins.

Amino Acid Sequence↗
PubMed1984

Penile horns: report of 2 cases.

We report 2 cases of penile horns, including 1 in which verruca carcinoma developed in the base. Treatment of this disease and its potential malignant degeneration are discussed.

Aged↗
PubMed1983

Scrotal ultrasonography.

Scrotal ultrasonography was performed on 43 patients with a diagnostic accuracy rate of 88 per cent. With a small parts 7.5 MHz. real-time ultrasound scanner a clear distinction between gonadal and epididymal pathologic conditions can be achieved in the majority of cases.

Genital Diseases, Male↗
PubMedDate not supplied

The effects of radiation damage on the structure of frozen hydrated HSV-1 capsids.

Radiation damage imposes stringent limits on the information content of electron micrographs of biological specimens. In this study, we have investigated its effects on frozen, hydrated specimens and three-dimensional reconstructions calculated from cryomicrographs using capsids of herpes simplex virus as a model system. Multiple-exposure series of micrographs of both B-capsids (which contain no DNA) and C-capsids (which are fully packaged) were recorded and reconstructions were calculated from the first exposures, corresponding to a cumulative electron dose of 6-7 e-/A2, and from later exposures (25-40 e-/A2). Experimental procedures were standardized to ensure that perceived changes in the micrographs and reconstructions would be attributable to radiation damage alone. The effects of the higher doses in both the micrographs and the reconstructions were expressed as a progressive blurring of the finer details, corresponding to a delocalization of structure in the ice-embedded specimens. The resolutions of the reconstructions were quantified according to a form of the Fourier ring correlation coefficient criterion, according to which the first-exposure reconstructions had resolutions of 30-36 A. The fifth-exposure B-capsid reconstruction had comparable nominal resolution, although it exhibited progressively lower correlations at higher spatial frequencies. Qualitatively similar changes in the series of C-capsid reconstructions were observed although they were more pronounced, presumably because these micrographs had lower contrast and signal-to-noise ratios. We infer that the observed changes in the images and reconstructions and the concomitant loss in contrast in the immediate vicinity of the capsid surface may reflect radiation-induced perturbation of molecular structure and/or the release of peptide fragments. Nevertheless, the observed changes are relatively subtle, at least at the operational resolution of this study; overall, our results support earlier indications (M. F. Schmid et al. J. Struct. Biol. 108, 62-68, 1992) that prospects are quite good for tilt-series reconstructions from cryoelectron micrographs, including six to eight views of the same specimen.

Capsid↗
PubMedDate not supplied

Digital image processing of electron micrographs: the PIC system-III.

The PIC system is an integrated package of image processing software written in Fortran and C. Throughout its 16 years of continuous development, PIC has been designed for the processing of electron micrographs with emphasis on the particular requirements for structural analysis of biological macromolecules. PIC has been implemented on successive generations of Digital Equipment Corporation dedicated minicomputers and workstations. The latest version, PIC-III, runs on Alpha workstations and represents a substantial upgrading in functionality compared with PIC-II, the VAX version previously described (B.L. Trus et al. (1992), Scanning Microsc. Suppl. 6, 441-451). PIC now possesses an X-windows menu-driven graphical user interface that many be utilized from both local or remote X-window terminals or workstations. Other new features include dynamic memory allocation; an open systems approach to interfacing with other image processing software packages; interface options with visualization software; and programs to reconstruct three-dimensional density maps of both helical filaments and free-standing particles with and without symmetry.

Computer Simulation↗
PubMedDate not supplied

Visualization of three-dimensional density maps reconstructed from cryoelectron micrographs of viral capsids.

Full evaluation of three-dimensional density maps calculated from cryoelectron micrographs of complex supramolecular structures requires that the maps be sifted by a variety of complementary visualization techniques. We present here a primer for a number of such techniques in current widespread use, including surface rendering; serial sections; simulated motion; and real-time manipulation of tiled surfaces displayed on an advanced workstation. The principles on which these techniques operate are briefly reviewed, as are their advantages and limitations, with emphasis on the requirements for visual representation of viral capsid structures. These methods are illustrated in application to a density map of herpes simplex virus type 1 (HSV-1) capsid at 24 A resolution, which reveals more detailed information than heretofore concerning the inner surface of the icosahedral capsid shell and the 150-A-long channels that pass through each of the 162 capsomers.

Animals↗