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Biomedical subjects

R A Alexander

Publications and source records attributed to R A Alexander.

At least 19 recordsLinked to original sources
PubMed1992

Oxytalan fibres in proliferative vitreoretinopathy.

The distribution of elastic and related fibres was studied in 29 fibrocellular membranes associated with proliferative vitreoretinopathy using histochemical, immunohistochemical and ultrastructural techniques. Ten subretinal and ten epiretinal membranes were subjected to light microscopical investigation, whilst the remaining nine membranes were examined by transmission electron microscopy. Oxytalan fibres, an elastic fibre precursor that is found in a variety of normal and pathological connective-tissue matrices, were identified in all of the specimens. Mature elastic fibres were not observed in any of the 29 membranes. The demonstration that oxytalan connective-tissue fibres contribute to the infrastructure of PVR membranes adds further evidence to the suggestion that this proliferative tissue might be the result of a repair mechanism.

Adolescent↗
PubMed1991

Oestrogen receptors in conjunctival malignant melanoma: immunocytochemical study using formalin fixed paraffin wax sections.

In a group of 15 women with conjunctival malignant melanoma six cases (40%) were shown to have oestrogen receptor positivity using a monoclonal antibody to oestrogen receptor related antigen (ER-D5, Amersham RPN.710) on formalin fixed, paraffin wax sections. Receptors were also present in the epithelium of these six cases but not in controls and cases without ER-D5 positivity in their tumours. A subset of these aggressive, intractable unilateral tumours may therefore be amenable to hormone treatment.

Adolescent↗
PubMed1989

The effect of argon laser trabeculoplasty upon the normal human trabecular meshwork.

The effect of argon laser trabeculoplasty (ALT) upon the normal human trabecular meshwork, as determined by scanning and transmission electron microscopy is reported. The lower nasal and temporal quadrants of an eye received ALT 5 and 1 day, respectively, prior to enucleation. Laser impact sites were identified as focal disruptions of trabeculae, together with connective tissue and cellular debris. Surviving trabecular endothelial cells near the laser lesions exhibited signs of phagocytic and migratory activity. Exogenous macrophages also contributed to the clearance of debris. Activated trabecular cells were observed leaving the meshwork by migrating over the corneal endothelium. By 5 days post-ALT increased amounts of trabeculae lacked an endothelial covering. More activated trabecular cells but fewer macrophages were noted. A laser lesion sited close to Schwalbe's line induced, within 5 days, a local corneal endothelial wave front to advance towards it, thus reflecting many late failed ALT specimens that we have seen.

Humans↗
PubMed1989

Sorsby's fundus dystrophy. A light and electron microscopic study.

The light and electron microscopic changes in both eyes of a patient with Sorsby's fundus dystrophy are reported. The most striking finding was a 30-microns thick deposit present within Bruch's membrane that stained positive for lipids. The deposit has several unique features when compared with those found in other retinal dystrophies and in aged eyes. In addition, there was gross loss of the outer retina, the retinal pigment epithelium was discontinuous, and there was atrophy of the choriocapillaris. These findings are discussed in relation to the published clinical observations of other members of this pedigree.

Choroid↗
PubMed1989

Morphological effects of argon laser trabeculoplasty upon the glaucomatous human meshwork.

Thirty four trabeculectomy specimens from open angle glaucoma patients who had under argon laser trabeculoplasty as part of their treatment, were studied by scanning electron microscopy. Three of these were also examined by transmission electron microscopy. The intervals between laser therapy and surgery ranged from one month to five years. A sub-group consisted of six patients who had received laser treatment on more than one occasion prior to surgery. Electron microscopy revealed distortion of trabecular beams, loss of trabecular endothelial cells and the development of a cellular sheet extending from the region of Schwalbe's line and covering the anterior surfaces of the anterior portion of the uveal meshwork. The sheet occluded the trabecular spaces of the region; thus, when extensive, contributing to laser trabeculoplasty failure. It is concluded that argon laser trabeculoplasty induces a repair process, in the form of repopulating a cellular deficient meshwork, but which can become detrimental as a consequence of its success.

Adult↗
PubMed1988

The retinal pigment epithelium and other tissues immunocytochemical studies using hybridoma supernatants.

We describe the production of hybridomas producing antibody reactive with retinal pigment epithelium. The patterns of reactivity obtained when supernatants from these hybrids were used to immuno-stain ocular and non-ocular tissues are described. From the patterns of reactivity obtained we suggest that the RPE shares common features with simple and glandular epithelia as well as myoepithelial cells. These findings may lend support to the hypotheses of RPE cell migration and contraction in the formation of epiretinal membranes and retinal detachment.

Animals↗
PubMed1987

The viscous layer overlying the corneal posterior epithelium of the domestic cat.

The presence, nature, and composition of a layer of transparent mucinous material overlying the posterior epithelium (called here, 'the viscous layer of the posterior epithelium') was investigated in material from domestic cats. A number of different techniques were used. (a) A variety of different fixatives and histochemical stains was used to preserve and visualise the layer of examination by light microscopy. Frozen sections of fresh material were also examined after on-slide fixation. The preservation and appearance of the viscous layer was critically dependent on the type of fixative used and on minimal agitation during tissue processing. It appeared to contain sulphated acid GAGs, the staining of which was histochemically masked around pH 2.5. The use of frozen sections produced the most reliable preservation of the layer. (b) Ruthenium red or cetylpyridinium chloride was used to preserve the viscous layer for examination by transmission electron microscopy. It appeared in a dispersed form after stabilisation by ruthenium red and in a condensed form after stabilisation by cetylpyridinium chloride. (c) Freeze-dried tissue was examined by scanning electron microscopy. The viscous layer usually appeared as a band of coral- or moss-like material which was often many times the thickness of the posterior epithelium. Usually, the areas of the layer adjoining the posterior epithelium and the anterior chamber appeared more condensed when compared to the material between these two regions. The physiological significance of the viscous layer is discussed.

Animals↗
PubMed1986

Histochemistry of elastic and related fibres in the human eye in health and disease.

Although the presence of mature elastic fibres in the sclera, trabecular meshwork and Bruch's membrane of the human eye has been recognized for many years, it is only latterly that the existence of the elastic-related fibres oxytalan and elaunin has been appreciated. The microfibrillar component of elastic, oxytalan, which is present in several ocular structures in infancy, can either mature to fully-developed elastic tissue or, as in the cornea, disappear in subsequent years. Deposition of elastic fibres, particularly the incomplete forms, can occur in the post-developmental period in a variety of disease states but the stimulus and functional significance in most situations is obscure. The evidence suggests, however, that the capacity to form elastic-related tissue is not confined to any one cell type.

Contractile Proteins↗
PubMed1986

Scrolls of Descemet's membrane as unusual giant nodules on the posterior cornea: histochemical and ultrastructural findings.

Unusual giant nodules on the posterior surface of Descemet's membrane were observed in two out of over 400 corneae examined during routine histopathological reporting. Both of the patients, a 60-year-old man and a 26-year-old woman, had histories of corneal trauma. Neither was associated with chronic keratitis or corneal dystrophy. Light microscopy showed these nodules to be composed of material resembling Descemet's membrane. Histochemical and electron microscopical preparations identified oxytalan fibres within the outer layers of the nodules. These fibres are not a feature of the normal adult Descemet's membrane. The findings are discussed and compared with other nodular lesions of Descemet's membrane.

Adult↗
PubMed1986

Optimum split-half reliabilities for the Rorschach: projective techniques are more reliable than we think.

A new technique for optimizing split-half reliability estimates yielded substantial and comparable increases in indexes of internal reliability for some major Rorschach variables across two diverse samples. Practical suggestions for applying this method to other projective tests were advanced. The inadvisability of computing odd-even reliability coefficients without regard to split-half distributional anomalies is addressed.

Adult↗
PubMed1985

Maximizing split-half reliability estimates for projective techniques.

Hand Test data from comparable sets of clinical samples were analyzed for reliability using the usual odd-even split and then also calculating all possible (126) split-half combinations. Maximum stable reliabilities were obtained which were substantially superior to the odd-even method. It was concluded that projective tests are probably more internally reliable than has heretofore been reported.

Adaptation, Psychological↗
PubMed1985

Lipid keratopathy and atheromatosis in an SPF laboratory rabbit colony attributable to diet.

Sporadic cases of corneal opacity occurred in an SPF rabbit colony fed on a diet containing 10% white fish-meal. Routine histological monitoring also revealed atheromatous lesions involving the intima of the aorta, coronary arteries and the arteries of other organs in 29 rabbits examined. Serum cholesterol levels above 10 mmol/l were found in 7 rabbits, including 4 affected with corneal lesions, which proved to be lipid keratopathy on histochemical and electron microscopical examination. The serum cholesterol level was found to be within normal range (below 2.27 mmol/l) in 10 rabbits reared entirely on a modified version of the diet, where the 10% fish-meal content was replaced with 10% grass-meal. No more ocular or atheromatous lesions have been found since the adoption of the new diet for the colony.

Age Factors↗
PubMed1978

Selected Hand Test personality variables related to accidents in female drivers.

The Hand Test was administered to 170 females ranging in age from 17 to 72 years to determine if specific personality tendencies measured by the Hand Test would be significantly related to incidence of automotive accidents. Results indicated that the personality characteristic associated with DIR was significantly correlated with accidents, but that relationships differed somewhat with age.

Accidents, Traffic↗
PubMed1978

Note on preference for stimulus complexity across the life-span.

Preference for stimulus complexity across the life-span was investigated with 175 females ranging in age from 17 to 72 yr. of age. Preference for complexity appeared to be age-invariant and monotonic function. Relationships to previous findings are discussed.

Adolescent↗