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Biomedical subjects

A Harrison

Publications and source records attributed to A Harrison.

At least 253 records · Page 14Linked to original sources
PubMed1977

Identification of Rickettsia rickettsii in a guinea pig model by immunofluorescent and electron microscopic techniques.

Moribund guinea pigs infected with Richettsia rickettsii were examined by necropsy, histology, immunofluorescence, electron microscopy, and serology. Untreated animals died at 9 and 10 days after inoculation. Animals given saline subcutaneously survived from 1 to 4 days longer. Prolonged survival was accompanied by more severe lesions: scrotal necrosis; infarction of ears; and swollen, hemorrhagic footpads, epididymis, and cremaster muscle. Histopathologic examination demonstrated that acute, necrotizing vasculitis, perivascular hemorrhage, and focal necrosis were more extensive. Direct immunofluorescence indicated many more rickettsiae in endothelium and vascular wall of saline recipients. Ultrastructurally, typical rickettsiae were present focally in the cytoplasm of endothelial and vascular smooth muscle cells. Cytopathology in infected and adjacent cells included swelling, mitochondrial enlargement with decrease in matrix density and loss of cristae, and increased pinocytosis. In addition, treated animals had more cytonecrosis, thrombosis, extravascular fibrin deposition, prominent inflammatory cells with polymorphonuclear phagocytosis of rickettsiae, and antibody production.

Animals↗
PubMed1976

Clinical results of the measurement of occlusal wear of complete dentures.

This study supports the clinical impression that acrylic resin teeth wear down faster than porcelain teeth but does not support Myerson's view that the total wear of acrylic resin opposing porcelain teeth is less than that of acrylic resin opposing acrylic resin teeth. There was a wide range of rate of wear in acrylic resin teeth opposing acrylic resin teeth. Dentures of the four subjects in the porcelain-only group showed considerably less wear. The dentures with acrylic resin teeth opposing porcelain teeth showed the same general trend, i.e., a high rate of wear for the acrylic resin teeth with very little for the porcelain teeth. Conclusive proof is given for the differing wear rates of acrylic resin and porcelain teeth when opposing like materials.

Acrylic Resins↗
PubMed1976

Abrasive wear, tensile strength, and hardness of dental composite resins--is there a relationship?

The in vitro abrasive wear resistance, tensile strength, and hardness of seven widely used composite restorative resins have been measured. Findings indicate that the values of tensile strength and hardness are not related to the measured abrasion rates. It is apparent that abrasive wear is a complex phenomenon and that materials which have high values for strength and/or hardness do not necessarily have high resistance to abrasive wear.

Composite Resins↗
PubMed1976

Masticatory function - a review of the literature. III. Masticatory performance and efficiency.

A review and evaluation of the literature on mastication has been undertaken. Part I discusses the form of the masticatory cycle in the natural and artificial dentitions, including the controversial question of whether tooth contact occurs during function. Part II reviews the literature concerning the speed of movement of the mandible, rate of chewing, and the forces developed in chewing. Part III describes masticatory efficiency and performance, the effect of food on masticatory function, and incorporates a summary of all these three papers.

Adaptation, Physiological↗
PubMed1976

A survey of accredited dental technology education programs in the United States.

A study was made of current educational methods and prosthetic technology used in the accredited dental technology education programs in the United States. Some of the results have been compared with the findings of a similar study in Britain and several differences have been noted. The results of this study and of the British one refer to accredited educational programs and do not necessarily reflect the procedures used in dental practice or in commercial dental laboratories.

Accreditation↗
PubMed1976

Lymphoreticular and myeloid pathogenesis of Venezuelan equine encephalitis in hamsters.

Ultrastructural, histopathologic, and virologic studies of adult hamsters infected with virulent Venezuelan equine encelphalomyelitis (VEE) virus (Subtype I-B) demonstrated precise chronologic and topographic progression of lesions and viral replication in extraneural sites. Thymus contained the earliest lesions and the highest initial and subsequent viral titers. No particular cytotropism was observed as highly efficient viral replication and severe cytonecrosis proceded. Early cortical necrosis of splenic periarteriolar lymphocytic sheath was followed by lymphoblastoid repopulation of the peripheral zone. Massive bone marrow necrosis was accompained by ultrastructural evidence of VEE viral particle production in reticulum cells, rubricytes, myeloid cells, lymphoblastoid cells, and megakaryocytes. Speed, efficiency, destructiveness, and relative sensitivity of virtually all lymphoreticular and hematopoetic cells were hallmarks of virulent VEE infection in the hamster.

Animals↗
PubMed1975

The development of an abrasion testing machine for dental materials.

Wear testing should be an important part of the investigation into the physical and mechanical properties of some dental materials. It has, however, largely been ignored because of conflicting and unreproducible results. It was decided, therefore, to review the work done by other researchers and to examine the human masticatory cycle, and then present new parameters to design and construct a new dental abrasion testing machine. This new machine is described in detail and its capabilities briefly illustrated.

Dental Materials↗
PubMed1975

Masticatory function--a review of the literature. 1. The form of the masticatory cycle.

Recently, the authors realized that an evaluation of the literature on mastication had never been undertaken, and it is hoped that this review presented in three parts, will be of value, not only to the dental clinician, but to other scientists working in associated fields. The first paper discusses the form of the masticatory cycle in the natural and artificial dentitions, including the controversial question of whether tooth contact occurs during function. The second paper reviews the literature concerning the speed of movement of the mandible, rate of chewing and the forces developed in chewing. The final paper describes masticatory efficiency and performance, the effect of food on masticatory function, and incorporates a summary of all these three papers.

Cineradiography↗
PubMed1975

The isolation and characterization of a temperate phage, Y46/(E2), from Erwinia herbicola Y40.

A temperate phage was induced from exponential phase cells of Erwinia herbicola Y46 by treatment with mitomycin C. The phage was purified by single plaque isolation, and produced in bulk by successive cultivation in young cultures of E. herbicola Y 178. Phages were concentrated from culture filtrates by rate zonal centrifugation and resuspension in 0.02 M Tris buffer, pH 7.2, twice, yielding suspensions of about 5 times 10(11) PFU/ml. Purification was achieved by centrifugation in buffered sucrose solutions. The band at the 30/40% sucrose interface yielded intact particles having regular hexagonal heads and lonb contractile tails, with base plates. Fibers were not seen. The mean dimensions were head, 51 nm; neck length, 11 nm; overall tail length, extended, 98 nm and contracted, 75 nm; diameter of tail sheath, 24 nm. The phage was stable from pH 4.0 to 11.0, but unstable at pH 3.0, the response being independent of the suspending medium used. At pH 3.0, a survival curve having biphasic appearance was observed, which was not due to a mixed population of phages. Stability to heat was good up to 45 degrees C, above which a logarithmic decline with temperature increase occurred. The average inactivation rate constant at 50 degrees C and pH 6.8 was 0.15 min-1. Adsorption to E. herbicola Y 178 cells exhibited first-order kinetics, the adsorption rate constant being 2.5 times 10(-10) ml/min. One-step growth-curve experiments indicated a burst size of 35-40, and a minimum latent period of 80 min. Probit analysis gave a mean latent period of 140 min (SD 25). The phage caused lysis of only E. herbicola strains Y178 and Y186.

Adsorption↗
PubMed1975

Role of the dental technician in professional education.

This survey has documented the current role of dental technicians in dental schools in the United States. This role is still rather minor, but it is significant. Some suggestions for improving the situation have been made. A further survey of this kind should be made again in 3-5 years, at which time a comparison with this survey may reveal a developing pattern and some better clues to the future.

Dental Technicians↗