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Biomedical subjects

N Ashton

Publications and source records attributed to N Ashton.

At least 55 records · Page 3Linked to original sources
PubMed1979

XXXV Edward Jackson Memorial Lecture. Allergic granulomatous nodules of the eyelid and conjunctiva.

Twenty-two cases of granulomas of the conjunctiva or eyelids were studied, and the clinical and pathologic features were tabled. All cases showed the histologic features of the Splendore-Hoeppli phenomenon, that is a giant cell and eosinophil granulomatous reaction to an antigen-antibody precipitate originally described in relation to parasites or fungi. Seven typical cases were selected for detailed description; in four of these cases, unidentified nematodes were the cause of the condition.

Adolescent↗
PubMed1979

Experimental retinal branch vein occlusion in rhesus monkeys. III. Histopathological and electron microscopical studies.

Experimental retinal vein occlusion in monkeys was followed by an immediate increase in capillary permeability which was accompanied by retinal oedema. This functional capillary change was followed at about 6 hours after occlusion by structural damage to the capillary wall. Thrombus formation occurred in the damaged vessels, and areas of stasis were thus produced with associated retinal haemorrhages. Finally, there was complete loss of the capillary endothelium and pericytes, and the acellular capillaries were invaded by proliferating glial cell processes, so producing permanent capillary closure.

Animals↗
PubMed1978

Contractile proteins in retinal endothelium and other non-muscle tissues of the eye.

The present study is the first investigation to demonstrate, by employing the combined approach of immunologically and electron microscope methods, the presence of actin-like contractile proteins in the mammalian retina, the corneal epithelium and endothelium, the iris, and the ciliary body, and to confirm their presence in lens epithelium. This is also the first report to demonstrate by these methods the presence of microfilaments and intermediate filaments in retinal vascular endothelium. Since we have shown that actin filaments are especially abundant in immature retinal endothelial cells, the question of their function arises, and we have discussed their possible relevance to the closure of immature retinal vessels when exposed to hyperoxia.

Actins↗
PubMed1977

Reticulum fibres in relation to retinal vessels.

Argyrophilic perivascular and intervascular fibres in the mammalian retina are shown by specific antireticulin immunofluorescence to consist of reticulin. The possible significance of these findings is briefly discussed.

Animals↗
PubMed1976

Encephalitozoonosis (nosematosis) causing bilateral cataract in a rabbit.

Bilateral cataract due to a microsporidan believed to be Encephalitozoon cuniculi (also called Nosema cuniculi) is described as an incidental finding in a laboratory rabbit. The route of infection and the significance of the findings are discussed. This is apparently the first report of cataract due to this cause.

Animals↗
PubMed1976

Experimental retinal branch vein occlusion in the monkey. Histopathological and ultrastructural studies.

Light and electron microscopical studies of monkey retinae after experimental branch vein occlusion by argon laser reveal that the immediate reaction in the corresponding region is one of capillary engorgement and dilatation followed by oedema (intra- and extracellular), and plasma leakage as shown by intravenous injection of horseradish peroxidase. Vascular stasis is characterized by packing of erythrocytes in the capillary lumen, early thrombus formation, and focal haemorrhages. Progressive degenerative changes in the endothelium and pericytes are seen in specimens taken a few hours to a few days after occlusion; within 3 to 4 weeks many vessels in the occluded region are reduced to basement membrane "ghosts" and the lumen and the cellular lodges of some vessels are subsequently invaded by proliferating glia, thus producing permanent capillary closure.

Animals↗
PubMed1975

Perivascular and intervascular reticular fibers of the retina.

We demonstrated the existence in the retina of an argyrophilic perivascular membrane comparable in all respects to that which exists throughout the vascular system. We compared our findings by light microscopy with those previously reported. We identified, by electron microscopy, the normal general location of the network between the basal laminae of the glial and vessel cells and demonstrated its selective staining with silver methenamine. These perivascular fibers, intercapillary strands, and bridges develop in relation to the process of retinal vascularization and the potential for forming these fibers is reactivated in senility and disease, as in diabetes. We summarized the evidence by concluding that these fibers are most likely composed of reticulin; it appears provable that in the past there may have been some confusion with neural fibers.

Age Factors↗
PubMed1975

Pathogenesis of hypertensive retinopathy. An experimental study in the monkey.

Retinal changes in accelerated hypertension were studied in seventeen monkeys with experimental hypertension by means of ophthalmoscopy and colour and flourescence photography during life, and by injection and digest preparations and light and electron microscopy after the animals had been killed. Cotton-wool spots developed in all but three monkeys. The arteries became tortuous and dilated and the light reflex decreased in those animals that became hypertensive. The earliest abnormality was a development of many points of fluorescein leakage on terminal arterioles or small arteries. Such leaking points were always present in relation to cotton-wool spots but were not confined to such areas. Focal narrowing of arteries was not observed but arteriolar occlusion and retrograde filling of the distal segment was present in three animals. Superficial linear haemorrhages were noted in five animals. Light microscopy revealed cotton-wool spots which were identical to those observed in man with a collection of swollen axons containing densely staining pseudonuclei. Study of the arterioles by electron microscopy showed findings ranging from normality to extensive necrosis. Many precapillary arteries were constricted and some were virtually occluded. Degenerative changes were present in smooth muscle cells in the wall of many of the constricted arterioles. Many arteries also showed insudation into their wall of plasma which had seeped into the muscular coat displacing and sometimes entirely replacing the smooth muscle cells. Except for arterioles with advanced necrosis, there was no indication of how plasma insudation occurred. Two arterioles with extensive necrosis showed a break within the endothelial cell cytoplasm through which penetration of plasma proteins had probably occurred. The extravascular tissues showed collections of amorphous material, sone of it with the typical banded configuration of fibrin. The sequence of events proposed to explain these features is as follows: (1) The arterioles constrict as the pressure rises, most likely as a result of vascular autoregulation. This may head to occlusion of the precapillary arterioles and is associated with necrosis of vascular smooth muscle. (2) Dilatation then occurs with insudation of plasma into the unsupported wall through a damaged endothelium. This stage probably corresponds to the autoregulatory break-point and is evidenced clinically by focal leakage of fluorescein. (3) Progressive plasma insudation into the vessel wall with further muscle necrosis results in secondary occlusion and the typical picture of advanced fibrinoid necrosis.

Animals↗
PubMed1975

Epithelial tumours of the lacrimal gland.

This paper reports a histopathological and follow-up study of 54 cases of epithelial tumours of the lacrimal gland. The findings confirm the view that accurate histological diagnosis is a reliable guide to the prognosis of these tumours and, therefore, to their clinical management. Since a thorough histological examination is of such clinical importance, treatment of these particular neoplasms should not be based upon evidence obtained from frozen sections of biopsies taken during operation. The histological criteria are described and illustrated and the follow-up analyzed in detail. Benign mixed tumours were the most common (55.5%) followed by adenoid cystic carcinoma (24.1%), other carcinomas, including two mucoepidermoid tumours (16.6%) and malignant mixed tumours (37.7%). In this series the prognosis for benign mixed tumours was excellent, despite occasional benigh recurrences, whereas the prognosis in the carcinoma group was correspondingly poor. Adenoid cystic carcinoma was the commonest form of carcinoma and commoner in the lacrimal gland than elsewhere. Although they run a highly malignant course, one case in this series is alive and well, without recurrence, after 17 years, indicating that the prognosis may well be favourable, providing the initial growth can be completely extirpated. The treatment of these tumours, already well described by SANDERS et al. [1962] is briefly summarized.

Adenocarcinoma↗