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Biomedical subjects

P Monaghan

Publications and source records attributed to P Monaghan.

154 records · Page 9Linked to original sources
PubMed1979

The pathology of adrenocortical neoplasia: a correlated structural and functional approach to the diagnosis of malignant disease.

The structural and functional characteristics of nine functioning adrenocortical tumors (four adenomas and five carcinomas) causing Cushing's syndrome or virilization were studied. All tumors that we considered to show histologic evidence of malignant disease and that subsequently metastasized or recurred also showed in cell culture at least one significant functional or behavioral difference from benign tumors. No single defect was common to all carcinomas, but predominant changes included secretion of precursor steroids, such as 11-deoxycortisol (S) and a blunted or absent response to ACTH. All adenomase examined were normal in these respects in comparison with nondiseased cortical cells in culture. In carcinomas whose functions deviated only minimally from normal the presence of highly differentiated ultrastructural characteristics did not, however, confer a better prognosis.

Adenoma↗
PubMed1976

Differential sensitivity of rods and cones in Xenopus retina to hemicholinium-3.

Hemicholinium-3 (HC-3), a drug which prevents synthesis of acetylcholine in neurons, when injected intraperitoneally in doses as low as 2 X 5 mg/kg produces marked ultrastructural changes and damage in rod but not in cone photoreceptors. In rods it causes a reduction in cytoplasmic background density, swelling of the endoplasmic reticulum, ballooning of the outer membrane of the nucleus, leaching of the nucleoplasm and clumping of the nuclear chromatin. In dark-adapted rods HC-3 produces some loss of cytoplasmic synaptic vesicles but no reduction in numbers of those vesicles which lie adjacent to the synaptic ribbons. In light-adapted rods the drug does not cause such an apparent reduction of synaptic vesicles but does induce a considerable reduction in numbers of vesicles associated with the ribbons. These structural changes are discussed in the light of what is known about the pharmacology of HC-3 and neurotransmitter release from vertebrate photoreceptors.

Acetylcholine↗
PubMed1976

Effects of light and dark upon photoreceptor synapses in the retina of Xenopus laevis.

Photoreceptor synapses in Xenopus retina were studied after exposure to day/night cycles and continuous light or dark. In the rods, dense-core vesicles appear alongside the synaptic ribbons in animals exposed to light. In dark-adapted rods, electron-dense material is present in the synaptic clefts, but no dense-core vesicles are found associated with the synaptic ribbons. Cone photoreceptors do not show these ultrastructural changes in response to light and dark. Prolonged exposure to light (21 days) causes flattening of the synaptic vesicles associated with the synaptic ribbons in both rods and cones. The results are discussed in the light of what is known about transmitter release from photoreceptors.

Adaptation, Ocular↗
PubMed1975

Ultrastructural and pharmacological studies on the afferent synapse of lateral-line sensory cells of the African clawed toad, Xenopus laevis.

Lateral-line sensory cells of Xenopus show considerable similarity to central nervous system synapses in their responses to the zinc iodide-osmium tetroxide, and bismuth-iodide cytochemical staining techniques. Both reserpine and FLA-63 cause a reduction in the diameter and electron density of the synaptic bars, and a dramatic loss of synaptic vesicles surrounding the bars. Aminooxy acetic acid and 3-mercaptopropionic acid cause no significant changes in the sensory-cell afferent synaptic apparatus. The results are discussed in the light of the known effects of the drugs. It is concluded that a monoamine rather than an amino acid may act as the afferent transmitter.

Aminooxyacetic Acid↗
PubMedDate not supplied

Immunoperoxidase reactions in resin embedded sections.

A simple reproducible and reliable schedule for the immunoperoxidase demonstration of various substances in resin embedded sections is described. It has been applied to a variety of epithelial membrane antigens in carcinoma of the colon and to blood group substances. Preliminary work indicates that it may be applicable to most if not all of the antigens which survive conventional paraffin wax embedding.

Antigens, Neoplasm↗
PubMedDate not supplied

Keratinocyte differentiation of human buccal mucosa in vitro.

The process of differentiation in keratinocytes of human buccal mucosa is accompanied by a number of specific membrane and cytoplasmic changes. Using simple tissue culture techniques, it has been possible to establish an in vitro model for keratinocyte differentiation which closely resembles the in vivo situation. A multi-layered structure is formed with maturation towards the surface. The superficial cells are characterized by a thickening of the plasma membrane, an increased concentration of tonofilaments, loss of intercellular adhesions and the presence of membrane-coated granules. It is concluded that this represents a suitable in vitro model for the biological and pathological study of both normal and abnormal oral epithelium.

Cell Differentiation↗
PubMedDate not supplied

Asymmetrical distribution of epithelial membrane antigen on the plasma membranes of human breast cell lines in culture.

A technique for localizing antigens by immunoperoxidase staining on the surfaces of unfixed culture cells is described. The cells can subsequently be studied by light or electron microscopy. These methods have been used to localize epithelial membrane antigen (EMA) on human mammary carcinoma (MCF7) cells in culture. This antigen was expressed on the plasma membrane, being localized on the interface with the culture medium and absent from the other external cell surfaces. This heterogeneous distribution reflects the distribution observed in mammary epithelial cells in vivo.

Antigens, Surface↗