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Biomedical subjects

A H Rahi

Publications and source records attributed to A H Rahi.

At least 37 records · Page 2Linked to original sources
PubMed1983

Lymphoproliferative disorders of the orbit: an immunological approach to diagnosis and pathogenesis.

A prospective immunological study of patients with proptosis due to intraorbital lesions composed largely or exclusively of lymphoid tissue indicates that the use of antisera to specific heavy and light chain antibody components can be helpful in distinguishing between polyclonal and truly neoplastic monoclonal disorders. On the basis of combined histological and immunological information it is possible to delineate 4 categories of patient: those with unequivocal chronic inflammation, those with a virtually pure lymphoproliferative lesion and a polyclonal profile, and those with a monoclonal lymphomatous disorder which may be histologically comparable to the previous category or, in a fourth group, be unmistakably malignant on cytological grounds. The first of these groups will normally respond to corticosteroid treatment, but the others, including the polyclonal lymphoproliferative masses, need radiotherapy. The finding of reduced numbers of circulating T cells in the presence of low plasma levels of IgA, and of autoantibodies in the serum of a third of the patients, could mean that individuals developing lymphoproliferative lesions in the orbit, whether hyperplastic or neoplastic, are partially immunodeficient.

Adult↗
PubMed1983

Epiretinal membranes in vitro.

Monolayers of cells were grown from epiretinal membranes using standard tissue culture techniques. The growing cells were filmed by time-lapse cinephotomicrography to record their locomotory characteristics and cell-to-cell interactions. The established layers of cells were examined in the scanning electron microscope. In addition, the cultured cells were studied immunohistochemically to identify specific cell types and the distribution of contractile elements (e.g. actin). The locomotory patterns, the topography and the immunohistochemistry of cells from epiretinal membranes were compared to the movement, appearance and staining characteristics of a wide range of normal cells in culture. From the growth characteristics in tissue culture, early membranes appeared more hypercellular than longer standing membranes. Cell outgrowth was established more quickly and was more widespread in the young epiretinal membranes than in older, more fibrous, specimens. The locomotory and immunohistochemical studies demonstrated that a wide variety of cell types may contribute to epiretinal membranes. A remarkably wide range of cell forms were observed in cultures of individual membranes. Epithelial and glial cells were found in many of the monolayers. However, they did not constitute the majority of cells in the cultures. The predominating cell types had the morphological and locomotory characteristics of fibroblasts or macrophages.

Animals↗
PubMed1983

Autoimmunity and the outer retina.

Structurally and therefore antigenically the retina is a complex tissue. Since it develops as an extension from the neural tube it shares with the brain several cell membranes and cytoplasm associated antigens including those present in neurofilaments of the various neurones and the glial filaments of the astrocytes. The advent of monoclonal antibodies has helped to dissect, in detail, the antigenic makeup of the retina. Nervous system antigens (NS-3, 4 and 7) are generously represented in the retina. At least in the chick eye there seems to be a concentration gradient of retinal antigens along a dorsoventral axis which is believed to provide means by which neurones of developing retinal signal and receive the positional information necessary for the formation of specific synapses. It now seems certain that organ-specific antigens are presented not only in the photoreceptors and the retinal pigment epithelium but also in the retinal ganglion cells and the astrocytes. Photoreceptor outer-segment contains soluble antigens which when injected in rats, rabbits, guinea-pigs or monkeys produce varying degrees of intraocular inflammation leading to uveitis, retinal detachment, photoreceptor degeneration and occasionally retinal vasculitis. Both cell-mediated and humoral immunity to photoreceptor antigen has been demonstrated in various types of uveitis (including toxoplasmosis and sarcoidosis), pars planitis, vitriitis, Behçets disease, sympathetic ophthalmitis, Vogt-Koyanagi-Harada syndrome, birdshot retinopathy, retinitis pigmentosa and retinal vasculitis. Retinal autoimmunity is also found in retinal detachment and diabetic retinopathy, particularly after Argon laser photocoagulation. Antibodies to retinal antigens are also found in patients with systemic lupus erythematosus and other systemic immune disorders without ocular involvement. The precise pathogenetic role of retinal autoimmunity in eye disease is therefore uncertain. It may simply represent an epiphenomenon which develops afer retinal damage due to physical, micro-organismal or immunological insult. Alternatively it is possible that although autoimmunity does not initiate ocular inflammation it perpetuates and maintains the inflammatory state and produces further damage to ocular tissues.

Animals↗
PubMed1982

Phacoallergy.

Explore the source record for details and available documents.

Autoantigens↗
PubMed1981

Structural basis of contraction in vitreal fibrous membranes.

A combined ultrastructural and immunofluorescent study was conducted on experimentally induced fibrous membranes in the vitreous of adult rabbits. Autochthonous tissue cultured fibroblasts were injected into the mid-vitreous of one eye of each of 25 rabbits. The animals were monitored routinely with an ophthalmoscope and slit-lamp and were killed at various time periods between 5 minutes and 6 months. Appropriate tissue was taken for light microscopy, transmission electron microscopy, scanning electron microscopy, and indirect immunofluorescence. With this model we were able to show that the contractile elements in fibrous membranes are probably modified fibroblasts called myofibroblasts which are most abundant 3 to 6 weeks after injection. This is the time when retinal detachment usually occurs. It is our impression that, as traction membranes develop, there is not so much an increase in the contractile elements of the constituent cells as a rearrangement of the existing cytoplasmic microfilaments into compact highly organised bundles called stress cables. The behaviour and ultrastructural characteristics of intravitreal fibroblasts compare with the action of fibroblasts in the healing of wounds.

Animals↗
PubMed1981

Human corneal endothelial cell repair in health and disease.

The human corneal endothelium which is exposed to a variety of physical and chemical insults can repair itself either by mitotic division, or by simple expansion and spreading of the neighbouring cells, or through an elaborate DNA repair system. The present study suggests that the ability of the corneal endothelium to repair its damaged DNA is fundamental to its survival and that a failure to do so may underlie a variety of corneal problems in which endothelial failure is a common feature.

Adult↗
PubMed1981

Immunoglobulin A (IgA) deficiency and eye disease.

The finding of a deficiency of immunoglobulin A (IgA) in serum is not uncommon. In order to determine whether low serum IgA levels were associated with any particular ocular conditions, the immunological investigations of over 4,000 patients with a variety of ophthalmological disorders, performed at the Department of Pathology of the Institute of Ophthalmology, London, were reviewed and analysed. The study showed an apparent tendency to low levels in patients with conjunctivitis and thyroid disease. These findings are of theoretical interest rather than diagnostic value.

Adolescent↗
PubMed1980

Tumors of the anterior uvea. I. Metastasizing malignant melanoma of the iris.

Although metastases from malignant melanomas of the ciliary body and choroid are common, similar tumors from the iris are rare. In this article seven such cases are described. They represent 3.5% of 196 cases in our files that were followed up for a minimum of five years where the tumor was confined to the iris and did not involve the ciliary body or the choroid. To our knowledge, this is the largest series to be described in the literature. Of the seven patients who died of metastases, six were male and autopsies were performed on four. There is evidence that diffusely infiltrating, heavily pigmented tumors, and tumors whose cell nuclei show prominent nucleoli are those most likely to metastasize.

Adolescent↗
PubMed1980

Tumours of the anterior uvea. III. Oxytalan fibres in the differential diagnosis of leiomyoma and malignant melanoma of the iris.

The diagnostic potential of oxytalan fibre demonstration in differentiating between leiomyomas and spindle-cell malignant melanomas of the iris was investigated. It was found that oxytalan fibres were abundant in leiomyomata, both between and around the tumour cells, whereas they were found in small numbers only and usually near the iris muscle in malignant melanomata. Their presence and distribution, therefore, appear to offer a satisfactory method of differentiating between these tumours. Since the human choroid and ciliary body normally contain oxytalan fibres, the above findings are not relevant to malignant melanoma of these structures. Naevi and regressing aggregates of iris melanoma cells away from the main tumour mass may similarly be surrounded by misleading amounts of these fibres.

Connective Tissue↗
PubMed1980

Tumours of the anterior uvea. II. Intranuclear cytoplasmic inclusions in malignant melanoma of the iris.

Intranuclear cytoplasmic inclusions have been described previously in both human and animal tissue. So far as we are aware they are described in detail for the first time in this paper in 60 cases of malignant melanoma of the iris, usually in spindle cells. The light microscopic appearances are described, and electron microscopic studies of selected cases show clearly the genesis of these inclusions by cytoplasmic invagination of the nuclear membrane. Their significance is discussed. It is of interest that we have seen identical inclusions in malignant melanomas of the ciliary body, choroid, and conjunctiva but have not as yet reported our findings.

Cell Nucleus↗
PubMed1980

Histology of the camel eye.

The camel eye shows some distinct features such as a pigmented peripheral cornea, a remarkably thickened Descement membrane, and endothelial-lined pectinate ligament, a cleft ciliary body, long ciliary processes, a horizontally oval pupil with well-developed corpora nigra and a holangiotic retina. Some of these are characteristic of horses, cattle and sheep, whereas others are more commonly found in lower mammals such as the rabbit. The reason for this staggered evolution in the development of the camel eye remains obscure.

Animals↗
PubMed1980

Contractile proteins in ocular tissues. Their role in health and disease.

Various cytoskeletal and contractile filamentous systems are located within non-muscular eukaryotic cells including microtubules, intermediate filaments, myosin filaments, and actin microfilaments. Microtubules are a major component of cilia, flagella, axons, and the mitotic spindles, but apart from these more specialized roles they are cytoskeletal structures and are involved in the directional movement of organelles within the cytoplasm. Intermediate filaments are structurally and biochemically similar to neurofilaments and although they are present in most cells they are particularly prominent in mesenchymal cells. Their function is not fully understood but they probably have a supportive role and constrain organelles including the nucleus in position within the cell. The contractile proteins, actin and myosin, in their most complex forms are found as a variety of filamentous structures which are involved in such diverse processes as motility, adhesion, phagocytosis, endocytosis, and cytokinesis. In this study the distribution of cytoskeletal an contractile elements in the non-muscular tissues of the human and the rabbit eye were investigated both in vivo and in vitro using electron microscopy and indirect immunofluorescence. Particular emphasis was placed on the role of cytoplasmic filaments in normal tissue function and their possible significance in various pathological conditions.

Actins↗
PubMed1979

The nature of retest reaction in delayed hypersensitivity. I. Light microscopic changes in the skin of the eyelid.

The retest reaction is a variant of delayed hypersensitivity where in repeated application of an antigen at the same site leads to an intense eosinophil leucocytic infiltration. This reaction has been produced experimentally for the first time in the eyelids of rabbits and guinea-pigs and it is possible that such a mechanism is implicated in a variety of clinical ocular conditions in which IgE does not appear to feature. It was also found that tissue reaction was modified in the absence of suppressor cells, these having been temporarily inhibited by pretreatment of the animals with cyclophosphamide.

Animals↗
PubMed1979

Microfilaments in the cells of the human trabecular meshwork.

In this present study the results are presented of a combined ultrastructural and immunofluorescent investigation of 'smooth muscle' elements within the cytoplasm of human trabecular meshwork cells. The cytoplasm of human meshwork cells both in vivo and in vitro is replete with 10 nm intermediate filaments and also contains smaller 6 nm filaments which are particularly prominent in the cell processes. By immunofluorescence using sera rich in antibodies to contractile proteins, particularly actin, cultured meshwork cells showed strong cytoplasmic fluorescence. On occasion the cytoplasmic fluorescence was diffuse, but more often recognisable bundless (stress fibres) or a loose fibrillar framework was found. The possible role of structural and contractile cellular proteins in trabecular function was discussed.

Actins↗
PubMed1979

HLA and eye disease.

This review article discusses the evolution and function of the histocompatibility system, the nature of the HLA antigens and their classification, the phenomenon of linkage disequilibrium, and the mechanisms of HLA and disease susceptibility. The reported associations between HLA antigens and various eye diseases are analysed and their significance is discussed. Problems in designing studies on HLA and disease associations are highlighted and suitable statistical procedures for the analysis of the results are outlined.

Eye Diseases↗