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Biomedical subjects

D O Lightfoot

Publications and source records attributed to D O Lightfoot.

12 recordsLinked to original sources
PubMed1991

Lens capsule and epithelium in age-related cataract.

On the basis of preoperative assessment of patient characteristics, intraoperative obtainment of a lens-capsule and epithelium specimen, histopathologic investigation of lens capsule and epithelium, and biochemical analysis of glutathione reductase in lens epithelium, age-related cataract was studied in 50 adult patients who underwent consecutive extracapsular cataract-posterior chamber lens implant surgery. Patients (25 men and 25 women; age range, 41 to 91 years; mean age, 75 years) had a wide range of systemic and ocular disease; 17 of 50 (34%) patients had a history of severe vision-impairing cataract in a first-degree relative. Anterior lens-capsule thickness ranged from 10 to 22 microns, with a mean of 17 microns. Statistical analysis of lens-epithelium ultrastructure in 41 of 50 specimens documented mixing of normal and abnormal cells, verified a gradation in the degree of abnormal ultrastructural features, and demonstrated a statistically significant decrease in epithelial cytologic activity with advancing age (P = .038). Biochemical analysis documented a severe glutathione reductase deficiency in nine of 39 (23%) lens-epithelium specimens, possibly reflecting a dietary deficiency of riboflavin.

Adult↗
PubMed1987

Glutathione reductase in human lens epithelium: FAD-induced in vitro activation.

Glutathione reductase (GR) activity was measured with and without the addition of flavin adenine dinucleotide (FAD) in freshly excised human lens epithelium following cataract surgery, and in control eye bank lens epithelium. Large individual variations in activity were found in both groups. Out of 32 epithelia obtained from cataractous lenses, 14 showed no measurable GR activity. Activity in eight of these 14 epithelia was restored after FAD was added, implying that the apo-enzyme in these 8 epithelia was functional but FAD was not available. Another group of 8 active epithelia showed a significant increase in GR activity upon the addition of FAD, suggesting a mixed population of active enzyme and available fraction of apo-enzyme which was reactivated by the addition of FAD. Unusually high GR activities were observed in epithelia of several patients. This correlated principally with daily intake of thyroxine which is known to have a direct effect on the metabolism of riboflavin. The fact that in a significant number of cataract patients epithelial GR was not active, and the observation that activity could be restored by adding in vitro FAD, demands that more attention should be given to riboflavin nutritional status and FAD synthesis in the eye.

Cataract↗
PubMed1985

Reticular degeneration of the pigment epithelium.

A clinicopathologic study of reticular degeneration of the pigment epithelium (RDPE) was done on 750 eyes of 396 consecutive autopsy cases and on 100 eyes of 50 consecutive patients with RDPE. The clinical, angiographic, macroscopic, and histopathologic characteristics of RDPE and its correlation with macular degenerative abnormalities in the autopsy and clinical eyes are presented. Reticular degeneration of the pigment epithelium and macular degeneration were found to be concomitant manifestations of the aging process, and RDPE may be a significant risk factor associated with age-related macular degeneration. Evaluation of the peripheral fundus is of value in assessing patients with macular degenerative abnormalities.

Aged↗
PubMed1984

Clinicobiochemical correlations in aging-related human cataract. The Pan American Association and American Journal of Ophthalmology lecture.

In a series of 50 consecutive adult patients (24 men and 26 women) we studied aging-related cataract by means of comprehensive presurgical examination of the patient, the eyes, and the cataractous lens; cataract sample collection from predetermined sites during surgery; biochemical analyses with high-performance liquid chromatography of each individual lens sample; and computer-assisted biostatistical data analysis. Compared with normal values established on clear human lenses obtained from a donor eye program, the ratios of 23,000 (23K) crystallin to total beta, gamma, and low molecular weight soluble proteins were statistically significantly lower in the anterior axial lens cortex (P less than .001) and in the lens nucleus (P less than .001). Increased grades of cortex opacification and nucleus opacification were generally associated with progressively decreased 23K crystallin ratios. In this series of patients with diverse cataract-associated systemic diseases, family histories, ophthalmic disorders, and drug-use patterns, decreased 23K crystallin ratios were a sensitive marker for aging-related cataract. Similar biochemical abnormalities in patients with multiple cataract-associated factors may have important clinical implications.

Adult↗
PubMed1983

Presence of low molecular weight polypeptides in human brunescent cataracts.

Microdissected sections from opaque & brunescent lens nuclei contain low molecular weight (4,000-8,000 dalton) polypeptides not found in microdissected sections of transparent lens nuclei. Tryptic digestion of these polypeptides from different cataracts reveal similar peptide maps. Together, these results support the involvement of proteolysis in human cataractogenesis, and suggest the possibility of similar molecular mechanisms occurring in cleavage of lens polypeptides during formation of the opaque & brunescent human cataract.

Aged↗
PubMed1983

Posterior chamber intraocular lens implantation by ophthalmology residents. A prospective study of cataract surgery.

The UCLA Cataract Surgery Study Group evaluated extracapsular cataract extraction with posterior chamber intraocular lens implantation (ECCE-posterior chamber IOL) performed by eight senior ophthalmology residents with faculty supervision and five faculty ophthalmologists experienced in intraocular lens surgery. The first 18 consecutive ECCE-posterior chamber IOL operations performed by each resident and faculty surgeon after July 1, 1981, were analyzed. All 234 operations and follow-up conformed to a predetermined protocol. Resident surgery achieved 20/40 or better final visual acuity in 88% of eyes; faculty surgery achieved 20/40 or better in 89%. Excluding cases with macular degeneration or other pre-existing eye disease, resident surgery achieved 20/40 or better final visual acuity in 95% of eyes; faculty surgery achieved 20/40 or better in 96%. There was no statistically significant difference between the results of resident surgery and faculty surgery. With supervision, ophthalmology residents achieved results generally equivalent to results obtained by experienced ophthalmic surgeons.

Aged↗
PubMed1980

Rod and cone inputs to bipolar cells in goldfish retina.

Five morphological types of bipolar cells which make synaptic contact with rods and cones are distinguished in the retina of adult goldfish (Carassius auratus) by characteristics readily observable in the light microscope. Cells were designated type a or type b according to whether their axons terminate in the distal part (sublamina a) or proximal part (sublamina b) of the inner plexoform layer, respectively. Analysis of serial semi-thin sections of Golgi-impregnated cells demonstrates that each subtype of bipolar contacts rods and a characteristic set of chromatic subtypes of cones: types a1 and b1 cells contact rods and red-sensitive cones, while types a2, b2 and b3 contact rods and red- and green-sensitive cones. Comparison with published descriptions of cells stained with Procion Yellow after intracellular recordings had been made suggests that type a cells should be off-center types and type b on-center. Furthermore, it is suggested that the receptive fields of cell types a1 and b1 should be non-color-coded, and those of a2, b2, and b3 color-coded.

Animals↗
PubMed1977

Structural basis for on-and off-center responses in retinal bipolar cells.

Electron microscopy of Golgi preparations of goldfish retina shows that dendrites of type a (hyperpolarizing, off-center) bipolar cells make wide cleft junctions unassociated with synaptic ribbons, while those of type b (depolarizing, on-center) bioplar cells make narrow cleft junctions and synaptic ribbon contacts, with rods and cones. This suggests that wide cleft junctions are the site of sign-conserving, and narrow cleft junctions or ribbon contacts (or both) are the site of sign-inverting synaptic transmission from photoreceptors to bipolars.

Animals↗
PubMed1975

Color-specific interconnections of cones and horizontal cells in the retina of the goldfish.

In Golgi preparations of goldfish retina we have observed three types of horizontal cell which receive exclusively from cones and one which receives exclusively from rods. The cone horizontal cells were designated H1, H2 and H3, in order of increasing dendritic spread, increasing separation from the outer synaptic layer, decreasing size of perikaryon, and decreasing density of cone contacts. Slender appendages with knobby terminal enlargements project horizontal cells by alalyzing serial 1 mum sections with the light microscope. The probable inputs, in terms of visual pigments in the cones which contact them, are: H1, red+green+blue; H2, green+blue; H3, blue. Analysis of previously published work suggests (1) that H1 cells generate monophasic or L-type responses, H2 cells generate biphasic or C1-type responses, and H3 cells generate triphasic or C2-type responses; (2) that H1 cells receive direct functional input at least from red-sensitive cones, H2 cells from green-sensitive cones, and H3 cells from blue-sensitive cones, and (3) that H1 constitute pathways from cones to H2 cells, and H2 cells, and H2 cells constitute pathways from cones and H1 cells to H3 cells. The precise location and route of the transfers, from H1 to H2 and from H2 to H3, are not yet known.

Animals↗