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Biomedical subjects

D B Archer

Publications and source records attributed to D B Archer.

At least 145 records · Page 8Linked to original sources
PubMed1987

Electrical injury of the eye.

A 17-year-old male suffered superficial and deep facial burns after coming into contact with a high tension electrical cable with his head and right side of the face. The right eye sustained severe thermal coagulative injuries and subsequently was enucleated. Histopathological examination showed that the retinal neuropile was relatively intact although the retinal and choroidal circulations were severely compromised. The left eye was less affected but a dense cataract developed and required lensectomy. Visual acuity remained poor in the left eye due to retinal atrophy, retinal vascular attenuation and optic nerve degeneration. Electroretinographic tests and pseudo-random binary stimulus visually evoked responses were useful in predicting the visual outcome.

Adolescent↗
PubMed1987

An in-vitro study of irradiated vitreo-retinal membranes.

Standard perforating injuries were created in the right eye of 30 rabbits. Twenty of these had the site of injury irradiated using the radioactive ophthalmic 60Cobalt applicator. Vitreo-retinal membranes obtained from non-irradiated and irradiated eyes were propagated in vitro. The morphology and viability of the cells that grew as a monolayer was studied using phase, light and electron microscopy. The proportions of the different cell types that constituted the monolayer was determined using immunofluorescent staining techniques. Non-irradiated membranes elaborated an abundant outgrowth of healthy cells that were predominantly fibroblasts. Irradiated membranes developed a sparse outgrowth of cells with vacuolated cytoplasm and pyknotic nuclei indicating cell destruction. The majority of the surviving cells were glial, with fibroblasts and retinal pigment epithelial cells forming the remainder.

Animals↗
PubMed1987

An experimental study of quinine blindness.

An experimental model of quinine induced blindness is presented. Electrophysiological, angiographical and morphological examinations were made. The occurrence of blindness and any recovery from blindness was dependent upon the dose of quinine taken. As no evidence of acute retinal ischaemia was found it is concluded that quinine is retinotoxic.

Animals↗
PubMed1987

Ocular larva migrans: a case report.

A case of intraocular toxocara larva migrans occurring in a 12-year-old boy is presented. Motility is inferred from the nature of multiple intraocular lesions observed. Possible mechanisms preventing a conclusive immunological response to the organism are discussed.

Child↗
PubMed1986

Compression keratopathy.

A 31-year-old man developed a localized corneal epithelial lesion after exposure to a high-pressure fire extinguisher jet. Visual acuity was temporarily decreased from 20/20 to 20/40 and intraocular pressure was increased to 28 mm Hg. Both values returned to normal within 18 hours after treatment. This represents an extreme form of anterior corneal mosaic associated with microsplits of the corneal epithelium.

Adult↗
PubMed1986

Long term observations on an anterior chamber Ridley intraocular lens.

In 1965 the patient, aged 6, sustained a perforating eye injury which was repaired and a traumatic cataract was aspirated within five weeks. Five years later a Ridley Mk 2 A/C intraocular lens was inserted. Several episodes of blunt trauma occurred over a three year period following this procedure. This paper reports the clinical, corneal pachometric and specular microscopic findings of both traumatized and normal fellow eyes 18 years after the initial incident. The corneal endothelial mosaic of the traumatized right eye was very irregular in the vicinity of the initial site of perforation. These marked variations in cell size and shape were less apparent at peripheral corneal areas. The estimated cell loss to the traumatized eye was in the region of 74% although in spite of this corneal function was maintained. The effects of trauma on the corneal endothelium are discussed and a brief review of the literature presented.

Anterior Chamber↗
PubMed1986

Does unidirectional vesicular transport occur in retinal vessels?

This paper challenges the hypothesis that the smooth 80 nm plasmalemmal caveolae found in abundance at the abluminal aspect of the endothelium in retinal blood vessels participate in a unidirectional vesicular transport mechanism. Evidence is presented which indicates that horseradish peroxidase, when introduced to the extracellular space of the retina via the vitreous body, may enter the intravascular compartment through junctional incompetence which occurs at or after enucleation of the eye. It is proposed that the plasmalemmal caveolae at the abluminal plasma membrane of endothelial cells in retinal blood vessels are static structures which facilitate the transport of small solutes and ions across the blood retinal barrier.

Animals↗
PubMed1986

Endocytosis in the retinal and choroidal microcirculation.

The endocytosis of horseradish peroxidase (HRP) by the vascular cells of retinal and choroidal blood vessels was compared in immersion and perfusion fixed eyes from individual rats. The mechanisms of endocytosis of HRP appeared identical in both retinal and choroidal vessels. The bulk of internalised tracer occurred in macropinosomes 300-400 nm in diameter. Tracer was localised to a 20-30 nm layer on the internal aspect of the limiting membrane. This layer was coincident with the glycocalyx of the luminal plasma membrane as revealed by ruthenium redosmium tetroxide staining. Horseradish peroxidase was also internalised by a small scattered population of vesicles (100-130 nm in diameter). The size of these vesicles suggested that they may have arisen from clathrin coated regions of the plasma membrane. It is suggested that the endocytosis of HRP in retinal and choroidal vascular endothelium occurs as a function of plasma membrane recycling. Horseradish peroxidase may also be internalised as a 'contaminant' of the glycocalyx in coated pits involved in receptor mediated endocytosis. The smooth 80 nm plasmalemmal caveolae of the retinal and choroidal vascular endothelial cells did not appear to participate either in absorptive endocytosis or vesicular transport.

Animals↗
PubMed1986

Experimental posterior perforating ocular injury: a controlled study of the gross effects of localised gamma irradiation.

A pilot study on the effect of localised irradiation applied to the site of a standard perforating injury in the rabbit eye, showed that gamma rays limited the formation of post-traumatic vitreoretinal membranes. A controlled study was therefore undertaken to confirm this observation. Twenty-four pairs of rabbits underwent a standard perforating injury in the right eye. One rabbit of each pair received a radioactive ophthalmic Cobalt applicator and the other a dummy applicator. Nineteen of 24 non-irradiated eyes developed vitreoretinal membranes, with associated traction retinal detachment. Only four of 24 irradiated eyes developed traction retinal detachment.

Animals↗
PubMed1986

Prognostic factors in malignant melanoma of the choroid: a retrospective survey of cases occurring in Northern Ireland between 1965 and 1980.

In Northern Ireland between 1965 and February 1980 one hundred eyes were enucleated following diagnosis of malignant melanoma of the choroid. The pathology of 87 cases was available for re-examination. Data on those patients still alive were examined together with the post-mortem reports of those deceased. A mathematical model was constructed to assess tumour volume more accurately. Survival was analysed using univariate and multivariate methods. Actuarial survival curves were constructed and two multivariate regression models were used--the proportional hazards model and the log-logistic model. In addition person years at risk analysis was used to compare survival with the Northern Ireland population. When the data were examined univariately, the location of the tumour, cell type, degree of invasion and the parameters of size (height, diameter and volume) were all significant prognostic indicators. When multivariate analysis was employed, the degree of invasion did not contribute significantly to the model, this being accommodated by tumour size. Cell type was also shown to be of less importance in the multivariate models. The various prognostic indicators together with the person years at risk analysis are discussed.

Adolescent↗
PubMed1985

A morphologic and autoradiographic study of cell death and regeneration in the retinal microvasculature of normal and diabetic rats.

Cell loss and regeneration were investigated and compared in the retinal microvasculature of age- and sex-matched normal and streptozotocin diabetic rats. Selective pericyte loss in the diabetic rat was characterized by changes in the pericyte to endothelial cell ratio in retinal capillaries isolated for microscopy by the trypsin digest technique. A comparison of 3- and 9-month-old normal rats showed no significant change in the pericyte to endothelial cell ratio (1:2.7). In diabetic animals the ratio was reduced to 1:4.03, which was statistically significant (P less than .001). Premitotic retinal vascular cells in normal and diabetic rats were labelled with tritiated thymidine and the labelling indices calculated from cell counts of trypsin digest preparations. Methyl H3 thymidine was infused continuously over an eight-day period using osmotic mini pumps. The labelling index of endothelial cells (0.33%) in normal rats increased to 0.91% in diabetic animals (P less than .05). The labelling index of pericyte cells in normal animals (0.16%) did not increase significantly (P greater than .05) in diabetic animals (0.19%). A special stain was used to exclude labelled polymorphonuclear leukocytes from the cell counts.

Animals↗
PubMed1985

Uncoupling of Methanogenesis from Growth of Methanosarcina barkeri by Phosphate Limitation.

Production of methane by Methanosarcina barkeri from H(2)-CO(2) was studied in fed-batch culture under phosphate-limiting conditions. A transition in the kinetics of methanogenesis from an exponentially increasing rate to a constant rate was due to depletion of phosphate from the medium. The period of exponentially increasing rate of methanogenesis was extended by increasing the initial concentration of phosphate in the medium. Addition of phosphate during the constant period changed the kinetics to an exponentially increasing rate of methanogenesis, indicating the reversibility of phosphate depletion. The relation between methanogenesis and growth of M. barkeri was investigated by measuring the incorporation of phosphorus, supplied as KH(2)PO(4), in the medium. At a low (1 muM) initial concentration of phosphate in the medium and during the constant period of methanogenesis, there was no net cell growth. At a higher (10 muM) initial concentration of phosphate, cell growth proceeded linearly with time after phosphate had been removed from the medium by uptake into cells.

Journal Article↗
PubMed1985

Three-dimensional architecture of the cell sheath and septa of Methanospirillum hungatei.

The methanogenic bacterium Methanospirillum hungatei exists as filaments which have a very unusual cell wall architecture, comprising a long cylindrical sheath within which there may be many individual cells arranged in a line. The sheath has a two-dimensional crystalline structure, and the cells are separated within the tube by septa which also have a crystalline structure. We have used computer image processing of tilted-view electron micrographs to analyze the structure in negative stains of both of these components in three dimensions. The repeating unit of the sheath consists of four approximately spherical domains ca. 2.5 nm in diameter arranged in a row. Based on observations of the type of lattice imperfections that occur, we suggest that each of the domains represents a separate polypeptide subunit and that the subunits are incorporated into the wall one by one. The septa are circular plates of remarkably constant size. They are normally found as double layers. They are hexagonally symmetrical and consist of trimerically associated subunits which interact about dimer axes to form an open network containing large pores ca. 15 nm in diameter.

Cell Division↗
PubMed1985

Congenital fistulae of the lacrimal gland.

A 15-year-old female was found on routine clinical examination to have bilateral asymptomatic congenital fistulae of the lacrimal glands. The fistulae opened into the conjunctival sac at the external canthus of both eyes. Temporary occlusion of these openings produced an immediate and significant reduction in tear secretion in both eyes.

Adolescent↗
PubMed1985

The seed-corn.

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Attitude to Health↗