Biomedical subjects

G W Ireland

Publications and source records attributed to G W Ireland.

At least 37 records · Page 2Linked to original sources

PubMed1981

Inversion in Volvox tertius: the effects of con A.

During the development of Volvox tertius spheroids, a single-celled gonidium enlarges and undergoes multiple incomplete cleavages to give an embryo which is 'inside-out' with respect to the adult organism. A morphogenetic movement, termed 'inversion', turns this hollow ball of cells 'inside-out' through a hole, the phialopore. In V. tertius this phialopore possesses 4 inwardly directed lips. Normal inversion was studied in vitro in slide chambers and involved cell-shape changes accompanied by the production of pseudopodia and the bending backwards of the phialopore lips. 100 micrograms/ml Con A specifically and reversibly blocked inversion. Despite the inhibitory effect on cell division, the blocking of inversion was not due to the blocking of the last cell division some 50-100 min prior to inversion. Neither did the first cell-shape change from pear- to spindle-shape appear blocked. A feature of inhibition by Con A was the enhanced production of pseudopodia by embryos blocked at inversion, and the abnormal production of pseudopodia by embryos blocked at earlier stages. Non-inverting embryos showed internal flagella. We suggest that the Con A block to inversion, which may be reversed by alpha-methyl mannoside, arises from the prevention of backwards-bending of the phialopore lips. Fluorescein-isothiocyanate-Con A bound to embryo and cell coat, ane more strongly to the embryo at pre-inversion. SDS-polyacrylamide gel analysis of proteins isolated from embryos showed 4 glycoprotein bands, but Con A binding to these bands could not be demonstrated.

Cell Division↗

PubMed1981

Polygonal networks in living chick embryonic cells.

Regular polygonal networks have been found in explants and dissociated cells of early chick embryos. These networks are readily observable in live cells with phase-contrast optics thus allowing time-lapse cinemicroscopy. They consisted of a regular pattern of nodes and radiating struts found predominantly in the lamelliplasm of the free edges of the cells bordering explants. At the outer edge, the network was terminated by radial struts associated with substrate-attached retraction processes whilst toward the centre of the cells it faded out. The network was also associated with stress fibres running across the cell and with microextensions on the dorsal surface. Even within one cell the network varied in size. Time-lapse films showed that microvilli were protruded from the dorsal surface over the nodes. Although the cells containing the networks were poorly motile the network itself was a mobile structure. Many explants from regions differing in prospective fates developed these networks after 2-4 days in culture. They appeared earlier in the smaller less yolky cells of definitive endoblast and epiblast. Experiments with dissociated and reaggregated cells confirmed their occurrence mainly in free edges of cells. The relationship between these networks seen in living chick embryo cells and those seen in other cell types using immunofluorescent techniques is discussed and a mechanism is proposed for their formation.

Animals↗

PubMed1981

The behaviour of embryonic chick and quail tissues in culture.

Pieces of tissue were dissected from early chick and quail embryos (Stages XIII and XIV of Eyal-Giladi & Kochav, 1976; and stages 3-5 of Hamburger & Hamilton, 1951). These tissues were taken from three different regions of the early embryos, and from eight different regions of the older ones, and were derived mainly from the lower layer. Epiblast tissues were also used. The experiments were designed to test the ability of one tissue to penetrate another. A single tissue was grown in culture in a Falcon dish for 18-24 h until it had formed a coherent sheet of cells (Explant I). A second tissue was then combined with it in one of two ways: (a) A small piece of tissue (Explant II) was explanted on top of Explant I. In most cases Explant II penetrated through Explant I and spread on the Falcon dish. (b) Another small piece of tissue (Explant III) was explanted beside (in confrontation with) Explant I. Usually, Explant III penetrated into Explant I rather than vice versa. The results were analysed to see if there were any variations in behaviour of the different tissues. The main result was that important differences were found to exist between certain types of chick and quail cells when grown in culture; the implications of this finding for the widely used technique of xenoplastic grafting are mentioned. Another result was that Explant I was more likely to be penetrated when the second tissue was placed on top of it (Explant II) than when it was confronted with it (Explant III). The significance of these results is discussed.

Age Factors↗

PubMed1980

A method for studying the effect of inhibitors on the development of the isolated gonidia of Volvox tertius.

During asexual reproduction in Volvox tertius, a single cell, the gonidium, contained within the parental spheroid, undergoes enlargement followed by multiple cleavages. A method has been developed for the isolation and maintenance of gonidia in vitro in paraffin chambers. In these chambers development of the gonidium to a multicellular spheroid and subsequent inversion was apparently normal. The paraffin chambers allowed the monitoring of the effects of inhibitors on development without the possible interference of the parental spheroid. Enlargement and division of isolated gonidia was prevented by actinomycin D, cycloheximide and streptomycin. Division but not enlargement was inhibited by 5-fluorouracil, mitomycin C and ethidium bromide. Colchicine at high concentrations prevented inversion, as did streptomycin, cycloheximide and actinomycin D.

Anti-Bacterial Agents↗

PubMed1977

Vesical endometriosis in a postmenopausal woman: a case report.

A case of endometriosis of the bladder extending into the bowel in a postmenopausal woman is reported. The origin of the tissue is mere conjecture. Five years before the onset of bleeding the patient had had an abdominal hysterectomy that may have seeded the adjacent vesical and small bowel tissue. It is hypothesized that the exogenous estrogen stimulated this tissue until it penetrated the bladder mucosa.

Aged↗

PubMed1974