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Biomedical subjects

P O'Brien

Publications and source records attributed to P O'Brien.

At least 235 records · Page 13Linked to original sources
PubMed1975

Alpha1-antitrypsin phenotypes in sex chromosome mosaicism.

We report the alpha1-antitrypsin phenotypes of 21 patients with sex chromosome mosaicism and their parents. The proportion of heterozygotes in the group of parents is significantly greater (p less than 0.01) than that proportion in both control groups. The maternal or paternal contribution to the statistical significance of this observation cannot be distinguished in our small sample of families.

Adolescent↗
PubMed1975

The effect of carbenoxolone on changes in canine and human gastric mucosa caused by taurocholate and ethanol.

The effect of carbenoxolone on taurocholate-induced changes in gastric mucosal permeabiity was assessed in three dogs, each of which was prepared with an antrectomy and a vagally denervated gastric pouch. Perfusion of the canine pouches with sodium taurocholate (40 mM) was associated with an increase in hydrogen ion back diffusion. This effect was not diminished by 10 days of carbenoxolone treatment. The effect of carbenoxolone on ethanol-induced changes in gastric mucosal permeability was assessed in six normal human subjects. A significant increase of gastric mucosal permeability was observed in six normal human subjects after instillation of ethanol (20 percent v/v). After 3 weeks of oral ingestion of carbenoxolone, there was inconsistent protection against ethanol-induced increases in gastric mucosal permeability. Basal secretion of hydrogen ion and postethanol hydrogen ion secretion appear to be diminished by carbenoxolone. These studies suggest that carbenoxolone does not protect against taurocholate- and ethanol-induced increases in gastric mucosal permeability in the dog and in man. It seems unlikely that carbenoxolone exerts its beneficial effect on the healing of gastric ulcers in man by an effect on gastric mucosal permeability.

Administration, Oral↗
PubMed1971

Inhibition of growth of leukemia cells by enzymic folate depletion.

A new bacterial enzyme, designated as carboxypeptidase G(1), inhibited growth of the L5178Y and L1210 murine leukemias, as well as the Walker carcinoma and the human lymphoblastoid line (RPMI 4265), propogated in vitro. This enzyme hydrolyzes the glutamate moiety from both oxidized and reduced folate forms, and thus it may prove to be of value in creating rapid folate depletion in vivo.

Animals↗
PubMedDate not supplied

Spectral karyotyping, a 24-colour FISH technique for the identification of chromosomal rearrangements.

Spectral karyotyping (SKY) is a new fluorescence in situ hybridisation (FISH) technique that refers to the molecular cytogenetic analysis of metaphase preparations by means of spectral microscopy. For SKY of human metaphase chromosomes, 24 chromosome-specific painting probes are used in just one FISH experiment. The probes are labelled by degenerate oligonucleotide-primed PCR using three fluorochromes and two haptens. Each probe is differentially labelled with one, two, three or four fluorescent dyes, resulting in a unique spectral signature for every chromosome. After in situ hybridisation and immunodetection, a spectral image is acquired using a conventional fluorescence light microscope equipped with a custom-designed triple-bandpass filter and the SpectraCube, which is able to retrieve spectral information for every pixel in a digital CCD image. The 24-colour display and chromosome classification are based on the unique emission spectra of the chromosomes. Together with chromosome banding information from an inverted DAPI or a G-banded metaphase, a comprehensive overview of chromosomal aberrations is presented.

Color↗
PubMedDate not supplied

Characteristics of electron beams from a new 25-MeV linear accelerator.

Clinically useful electron fields are produced on the Atomic Energy of Canada, Limited Therac 25 linear accelerator by computer-controlled scanning of the electron beam. Measurements were made to determine the properties of these electron fields. Central axis percentage depth dose and bremsstrahlung background were compared for these fields and for the fields from selected machines that use scattering foils. Dose calibrations were made in both water and polystyrene using the American Association of Physicists in Medicine Task Group 21 protocol. Measurements were made to determine the relative output factors, virtual source position, and the attenuation of the electron fields by lead.

Electrons↗
PubMedDate not supplied

Radiation protection aspects of a new high-energy linear accelerator.

The Therac-25 is a new 25-MeV linear accelerator manufactured by Atomic Energy of Canada, Ltd. The first two units have recently been installed in Toronto, Ontario and Halifax, Nova Scotia. Calculations and measurements of primary and secondary radiation levels were made. Neutron dose-equivalent rates were measured inside and outside the room. The maximum leakage rate at 1 m from the accelerator target was 0.4% Sv per peak photon Gy. The tenth value layer for neutrons from the Therac-25, at the entrance to a one-legged maze was found to be 5.5 cm of polyethylene. Measurements were done to estimate daily technologist exposure due to induced activity in the treatment room.

Electrons↗