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Biomedical subjects

R A White

Publications and source records attributed to R A White.

At least 19 recordsLinked to original sources
PubMed1979

In vivo comparison of replamineform, Silastic, and bioelectric polyurethane arterial grafts.

The replamineform process allows fabrication of microporous prostheses with control of both pore diameter and structural geometry by means of a variety for biomaterials. Tubular prostheses 3 cm long, 6 mm inside diameter, and 1 mm wall thickness were made of Silastic or Bioelectric Polyurethane (BEP) with use of a template of the echinoderm Heterocentrotus mammillatus. Pore diameter of the prosthesis wall was 18 to 25 mu. Light and scanning-electron microscopy of grafts removed between 1 and 32 weeks demonstrated that organization and endothelialization of neointima were similar for both polymers, being complete by 4 to 8 weeks. However, the character of prosthesis wall ingrowth was strikingly different: the microporous lattice of BEP was completely ingrown early, but was apparently fragmented by continued granulomatous inflammation by 32 weeks, while Silastic generated minimal inflammatory response and slower fibrous tissue and capillary ingrowth. Thus, with Silastic and BEP, similarities in neointima organization appeared independent of distinct differences in wall ingrowth. The replamineform process is a unique means of studying surface healing and wall ingrowth of different biomaterials as microporous vascular prostheses in a controlled fashion.

Arteries↗
PubMed1979

"Cytogenetic" studies of spermatids of mice carrying Cattanach's translocation by flow cytometry.

The DNA content of spermatids of mice carrying Cattanach's translocation has been measured with high precision by flow cytometry. The observation that the two peaks of DNA content in the haploid region of the DNA histograms represent X- and Y-bearing spermatids was tested and confirmed. Using flow cytometry, the difference in DNA content between the X and Y chromosomes in these mice was measured to be 5.2 +/- 0.1% of the total haploid genome as compared to 3.4 +/- 0.1% in normal mice. These results demonstrated the precision of flow cytometry for cytogenetic studies. Additional information on spermatogenesis in mice bearing Cattanach's translocation was obtained and showed a gradual loss of cells during spermatogenesis in those bearing the balanced form of the translocation.

Animals↗
PubMed1979

The penetration of misonidazole into spontaneous canine tumours.

The hypoxic cell-radiosensitizing drug misonidazole (1-(2-nitroimidazol-1-yl)-3-methoxypropan -2 -ol, Ro 07-0582, MIS) was administered at a dose of 150 mg/kg i.v. to 6 dogs bearing spontaneous tumours, and the resulting tumour concentrations were measured to HPLC analysis. In 4 dogs it was possible to obtain serial biopsy specimens up to 5 h. With the exception of a brain tumour, the tumour concentrations ranged between 47% and 95% of the plasma concentration, most of the values falling within the range 50--70%. Concentrations in the brain tumour were markedly lower. Barbiturate anaesthesia was necessary for the removal of the serial biopsy specimens, and the effects of sodium pentobarbitone anaesthesia on the pharmacokinetics of MIS were investigated in 2 dogs. After barbiturate anaesthesia peak plasma concontrations were raised and the availability of MIS was increased, although the biological half-life remained unaltered. The metabolism of MIS to the O-demethylated metabolite, Ro 05-9963, was delayed initially. The concentrations of MIS AND Ro 05-9963 in cerebrospinal fluid were also recorded in these dogs; MIS concentrations were found to approach those of the plasma, whereas the metabolite concentrations were considerably lower (0--58% of the plasma concentration).

Adenocarcinoma↗
PubMed1979

Uniform microporous biomaterials prepared by the Relamineform technique.

The Replamineform process provides a technique for fabricating microporous ceramic, metal and polymer biomedical implant materials. A range of pore sizes can be made in the same material, thus allowing independent study of the effect of pore size and biomaterial on incorporation of implants. This new family of biomaterials shows promise for helping to determine the optimum characteristics to enhance tissue regeneration.

Aluminum Oxide↗
PubMed1978

T-lymphocyte heterogeneity in the rat: separation of functional subpopulations using a monoclonal antibody.

W3/25 antibody is the monoclonal product of a hybrid cell resulting from the fusion of a mouse myeloma cell line with spleen cells from a mouse immunized with rat thymocytes. Pure clones have been derived, and segregants free of parental myeloma chains have been isolated. Previous studies have shown that this antibody recognizes a subpopulation of T cells among rat thoracic duct lymphocytes. In the work reported here, three T-cell functions were assayed after separating rat thoracic duct lymphocytes on the fluorescence-activated cell sorter on the basis of labeling with W3/25 antibody. Two of the functional activities appeared to be completely segregated by this procedure. Thus, helper cell activity for an anti-hapten plaque-forming cell response was confined to the labeled population, whereas the allogeneic suppressive effect produced in a parental vector F1 adoptive transfer was mediated by cells in the unlabeled fraction. The third function, graft-versus-host activity, was almost entirely contained within the labeled subpopulation. It is concluded that the antigenic determinant recognized by the monoclonal antibody W3/25 is a differentiation marker for T-cell functional subpopulations.

Animals↗
PubMed1978

Induction of multiple cytochrome P-450 species in housefly microsomes--SDS-gel electrophoresis studies.

1. Microsomal fractions isolated from various housefly strains have been characterized with respect to multiple forms of cytochrome P-450 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. 2. Susceptible NAIDM houseflies were pretreated with known inducers of cytochrome P-450, and their microsomal electrophoretic profiles were compared to control NAIDM microsomes, using as standards partially purified cytochrome P-450s from noninduced NAIDM houseflies. 3. Tentatively, at least five different species of cytochrome P-450 may exist in the NAIDM housefly strain. 4. A comparison of the microsomal electrophoretic profile of different housefly strains also indicates the presence of at least two additional cytochrome P-450 species. 5. Induction with alpha-pinene and phenobarbital was expressed by a shift of the maximum absorbance at 452 nm in the CO-difference spectrum to lower wavelengths in the NAIDM strain; whereas, beta-naphthoflavone, although increasing the amount of cytochrome P-450, did not change the wavelength of maximum absorbance. 6. Cytochromes of the P-452 type appear to predominate in the susceptible NAIDM strain, while cytochromes of the P-450 and P-448 types predominate in resistant strains.

Animals↗