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J McAvoy

Publications and source records attributed to J McAvoy.

9 recordsLinked to original sources
PubMed1984

Sequential structural response of lens epithelium to retina-conditioned medium.

When lens epithelium is cultured with retina-conditioned medium, many of the cells undergo fibre differentiation within 6-10 days. Here we report the temporal sequence of structural events that characterize this change in an organ culture model system. Within an hour of exposure to conditioned medium, some cells withdrew from the epithelial monolayer and began migrating over stationary cells still attached to the capsule. By 24 hr, migratory activity was largely responsible for causing the explant to become multilayered, increasing its thickness while at the same time reducing its surface area. Control cells attached to each other along their lateral boundaries through interdigitations of microvilli. After BRCM treatment, microvilli flattened out and the membranes had a crinkled appearance. Eventually, as the cultured cells developed into fibres, membranes straightened and developed knob and socket junctions and large numbers of their organelles underwent degradation within autophagic vacuoles. Nucleoli began to enlarge by 16 hr and by the time cells had been exposed for 24 hr, some nucleoli were enlarged to seven-fold their original area, as measured on electron micrographs. This nucleolar change was followed over the next few days by a gradual increase in cytoplasmic protein, and cells became plump or elongated. The ultrastructural changes that we observed in culture are similar to those that can be seen in the intact lens. Such fidelity of change indicates that this cultured lens explant system is an excellent model for experimental intervention and analysis of the processes involved in terminal lens fibre differentiation.

Animals↗
PubMed1984

Localisation of laminin and fibronectin during rat lens morphogenesis.

Immunofluorescence clearly localised laminin and fibronectin in the basement membranes of ocular epithelia through all stages of rat lens differentiation. Some fibronectin is also localised around the mesodermal cells associated with the epithelia. At 10 days of embryonic development, the presumptive lens ectoderm and optic vesicle are closely associated, and the "interspace" between the two tissues contains only a few mesodermal cells. Later, as the mesoderm is excluded and the lens placode invaginates to form the lens pit, there is a marked increase in the concentration of both laminin and fibronectin in the interspace. At about 13 days, the interspace widens, and there is fluorescence for both glycoproteins in the basement membranes of the optic cup and lens vesicle; as the lens capsule thickens, the fluorescence for laminin increases in the latter. The unlabelled peroxidase anti-peroxidase (PAP) method shows that 'blebs' and 'blisters' of basement membranes, particularly from the optic vesicle, appear to give rise to cords of fibronectin- and laminin-positive material. These cords extend into the interspace and are associated with flocculent and fibrillar material. Therefore, the glycoproteins probably combine with other extracellular matrix (ECM) constituents, e.g. collagen, to form a network of fibrils in the interspace. This network must provide good adhesion between the lens placode and the optic vesicle so that invagination is co-ordinated to form the lens pit and the optic cup, respectively. It is suggested that, in addition to providing good adhesion between the tissues, this laminin- and fibronectin-rich ECM may stimulate the formation of basal extensions and cytoplasmic processes, particularly from the lens placode, and therefore, initiate the ectoderm to form lens placode.

Animals↗
PubMed1977

Carcinoma arising in the wall of a breast cyst during pregnancy.

A 23-year-old patient developed a carcinoma in the wall of a breast cyst during the second trimester of an otherwise uncomplicated pregnancy. A review of the literature revealed 7 reported cases of carcinoma of the breast arising in a cyst wall. However, none of these these cases has been associated with pregnancy. The relationship of fibrocystic disease and carcinoma of the breast is discussed. The possible influence of pregnancy and age on the prognosis of this patient are also considered.

Adult↗