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Biomedical subjects

W T Murakami

Publications and source records attributed to W T Murakami.

13 recordsLinked to original sources
PubMed1992

Inside polyomavirus at 25-A resolution.

Empty capsids and complete virions of polyomavirus crystallize isomorphously. Here we use difference Fourier analysis of X-ray diffraction data at 25-A resolution from these crystals to obtain an electron-density map of the inside of the virion. The polyomavirus capsid is built from 72 pentamers of VP1 that form three different types of connections in the T = 7d icosahedral surface lattice. Self-assembly of purified recombinant VP1 into capsid-like aggregates has shown that switching of the bonding specificity to form the unanticipated non-equivalent connections is an inherent property of the VP1 pentamers. Our map of the inside of the virion displays 72 prongs of electron density extending from the core into the axial cavities of the VP1 pentamers. We identify these prongs with the VP2 and VP3 molecules, which may function to guide the assembly of the highly ordered capsid on the nucleohistone core. The atomic structure of the closely related simian virus-40 capsid has been determined from the high-resolution diffraction data. Our polyomavirus map, calculated using all the low-resolution diffraction data, shows no indication of regular order inside the spherical core.

Capsid↗
PubMed1983

Fatal epistaxis in craniofacial trauma.

Facial trauma often results in minor and infrequently results in major bleeding in the structures of the face. We have recently observed two patients who suffered fatal hemorrhages which could have been controlled using relatively simple measures. Treating physicians often overlook this serious and potentially life-threatening source of hemorrhage until the patient has been in shock for long periods of time and irreversible ischemic brain damage and renal failure have occurred. With careful attention to examination of the face and oropharynx, hemorrhage from these sites can be identified early and the appropriate measures taken to control epistaxis.

Adolescent↗
PubMed1983

Tip suspension suture for superior tip rotation in rhinoplasty.

Superior tip rotation is sometimes necessary to relieve functional obstruction as well as improve the esthetic appearance in the aging nose and the thick skinned heavy tip nose. Conventional techniques including thinning resection, rim strip, lateral crural flap and even external skin excisions are often inadequate to obtain and maintain sufficient superior tip rotation. A technique is described to permanently suture the lower lateral crus to the upper lateral cartilages and to the cartilaginous septum. Long-term follow-up supports this technique's cosmetic and functional effectiveness.

Humans↗
PubMed1982

Polyoma virus capsid structure at 22.5 A resolution.

X-ray diffraction data from polyoma capsid crystals were phased by refinement of low-resolution starting models to obtain a self-consistent structural solution. The unexpected result that the hexavalent morphological unit is a pentamer shows that specificity of bonding is not conserved among the protein subunits in the icosahedrally symmetric capsid.

Capsid↗
PubMed1982

Applications of the biomechanical behavior of cartilage to nasal septoplastic surgery.

The biomechanics of septal cartilage as they apply to septoplasty are studied. The original investigations on septal cartilage are reviewed and summarized. Biomechanical principles of the behavior of cartilage are reviewed and applied to the principles of septoplasty surgery. Using pigs' ears, theoretical predictions are investigated and verified. Incorporating this information, an approach to septoplastic surgery is described.

Adolescent↗
PubMed1979

Polyoma virion and capsid crystal structures.

X-ray diffraction shows that complete virus particles and empty capsids crystallize isomorphously. The surface morphology of the protein coat, as revealed by electron microscopy, is the dominant structural feature determining the intensity of x-ray reflections to a resolution of approximately 30 angstroms. The structure and variability of the viral chromatin core can now be analyzed by comparison of electron density maps.

Crystallization↗
PubMedDate not supplied

Polyoma virus 'hexamer' tubes consist of paired pentamers.

The discovery that the 72 capsomeres of the icosahedrally symmetric polyoma virus capsid are all pentamers shows that the expected quasi-equivalent bonding specificity is not conserved in the assembly of this virus coat protein. Tubular particles produced by polyoma and other papovaviruses seem to be polymorphic aggregates of capsomeres that may arise through variation in switching of the bonding specificity. Electron micrographs of wide and narrow classes of tubes were analysed by Kiselev and Klug using optical diffraction and optical filtering methods. The wide type were called 'hexamer' tubes because they consist of approximately hexagonally arrayed capsomeres that were assumed to be hexamers, in accord with the quasi-equivalence theory of icosahedral virus particle construction. The narrow type were called 'pentamer' tubes because the capsomeres are arrayed in a particular 'pentagonal tesselation' which arises from the pairing of pentamers across 2-fold axes of the surface lattice. Our reexamination of negatively-stained polyoma virus tubes by digital image processing of low-irradiation electron micrographs shows that all tubes are assemblies of paired pentameric capsomeres. We report here that the packing arrangement of the pentamers in the hexamer tubes is simply related to the pentagonal tessellation respresenting the packing in the narrow pentamer tubes. In all the tube structures examined, at least one pairwise contact between neighbouring pentamers closely resembles the contact between the pentavalent and hexavalent capsomeres in the icosahedral capsid.

Microscopy, Electron↗