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Biomedical subjects

A B Fulton

Publications and source records attributed to A B Fulton.

At least 73 records · Page 4Linked to original sources
PubMed1990

Hyperopia in complicated Leber's congenital amaurosis.

We studied the refractive status of 13 children with Leber's congenital amaurosis. Seven had the disease complicated by neurological or other systemic abnormalities, while the other 6 patients had only ophthalmic abnormalities. All 13 patients were hyperopic. The magnitude of hyperopia did not differ significantly between the complicated and uncomplicated groups. Therefore, one cannot, as previously suggested, use the presence of high hyperopia to differentiate an uncomplicated form of Leber's congenital amaurosis from one complicated by neurologic or other systemic abnormalities. The concurrence of hyperopia with Leber's congenital amaurosis should not steer the physician away from careful neurologic systemic or biochemical evaluation of the child.

Age Factors↗
PubMed1990

The quantity of rhodopsin in human eyes.

The content of rhodopsin in the eyes of 15 donors (30 eyes) was determined. Both retinal and pigment epithelial fractions were collected from each globe, extracted using 1% CTAB, and the rhodopsin difference spectrum of each fraction was obtained separately. The total amount of rhodopsin, obtained by summing the amounts recovered from the retinal and PE fractions, ranged from 2.00 to 11.94 (median: 6.40) nmoles/eye. Previously reported mean values of about 3.5 to 4.0 nmoles per retina have been obtained using a variety of methods. The present higher values, perhaps largely dependent on procedural details described herein, appear plausible given the known concentrations of rhodopsin in rod outer segments, rod outer segment volumes, and number of rods in the human retina.

Adult↗
PubMed1989

Assembly of vimentin in cultured cells varies with cell type.

To examine how vimentin assembles into the cytoskeletons of cultured cells, we used pulse labeling with [35S]methionine, cell fractionation with Triton X-100, and immunoprecipitation with a monoclonal antibody that binds both nascent and full-length vimentin polypeptides. In embryonic muscle cells, fibroblasts, and erythroid cells, we find two populations of newly synthesized vimentin. One population is found on the cytoskeleton immediately after a 2-min pulse with labeled methionine; the other is delayed in its association with the cytoskeleton and has a measurable rate of disappearance from the extractable pool. This rate varies with cell type, being over 3-fold faster in muscle and fibroblast cells than in erythroid cells. By using [3H]puromycin to specifically label nascent chains, we detect nascent vimentin chains that are bound to the cytoskeleton independently of ribosomes. The fraction of newly synthesized, full-length vimentin that associates with the cytoskeleton immediately correlates in these cell types with the fraction of nascent vimentin chains that are not released from the cytoskeleton by puromycin, RNase, or 0.6 M NaCl. Over one-half of the newly synthesized vimentin associates immediately in muscle and fibroblasts, whereas this value is less than 15% in erythroid cells. These data suggest that the process of vimentin assembly may vary both kinetically and mechanistically in different cell types.

Animals↗
PubMed1989

Electrophysiologic testing techniques for children.

This practical article for clinical electrophysiologists discusses the evaluation of infant and child patients' visual systems using electroretinographic (ERG), electrooculographic (EOG), and visually evoked potential (VEP) techniques. These techniques not only help to secure specific diagnoses, but by systematic assessment of function along the visual pathways can also localize dysfunction underlying visual deficits of pediatric patients. Among children, development as well as disease can affect electrophysiological parameters. Therefore diagnosis of normal or abnormal depends critically on an adequate description of normal responses for age. Procedures that the authors have found feasible, reliable, and valid are summarized. Standardization of pediatric testing appears to be an important next step. The power of ERG, EOG and VEP recordings to demonstrate the neurophysiological basis for pediatric visual impairment is predicted to stimulate further research in this area.

Adult↗
PubMed1989

Psychophysical estimates of ocular media density of human infants.

The ocular media densities of eleven 10-week-old infants and of 10 adults were estimated from dark adapted thresholds measured using a two alternative forced choice preferential looking method. The estimated media density at 400 nm derived from these thresholds ranged from 0.55 to 1.00 (median 0.75) log units for infants, and from 1.35 to 1.69 (median 1.46) log units for young adults. This indicates media density increases significantly (0.71 log units) between infancy and adulthood. These data allow more complete specification of the retinal stimulus for quantitative analysis of infants' retinal function.

Adult↗
PubMed1989

Biosynthesis of titin in cultured skeletal muscle cells.

Although significant progress has been made regarding the structure and function of titin, little data exist on the biosynthesis of this large protein in developing muscle. Using pulse-labeling with [35S]methionine and immunoprecipitation with an anti-titin mAb, we have examined the biosynthesis of titin in synchronized cultures of skeletal muscle cells derived from day 12 chicken embryos. We find that: (a) titin synthesis increases greater than 4-fold during the first week in culture and during this same time period, synthesis of muscle-specific myosin heavy chain increases greater than 12-fold; (b) newly synthesized titin has a t1/2 of approximately 70 h; (c) titin is resistant to extraction with Triton X-100 both during and immediately after its synthesis. These observations suggest that newly synthesized titin molecules are stable proteins that rapidly associate with the cytoskeleton of developing myotubes.

Animals↗
PubMed1989

Dark adaptation in hyperprolactinemic women.

In a study to test the hypothesis that hyperprolactinemia is caused by subclinical zinc deficiency, dark-adaptation curves of seven women with primary hyperprolactinemia and seven normal women were measured to assess tissue zinc status. Although plasma zinc levels, final dark-adapted thresholds, and the time courses of rod dark-adaptation did not differ significantly between patients and normal subjects, the median cone plateau of the hyperprolactinemic patients was significantly higher (0.66 log units) than that of normal subjects. It appears unlikely that derangements of vitamin A metabolism, for which zinc is a cofactor, explains this unanticipated and subtle abnormality in dark adaptation of the hyperprolactinemic women.

Adult↗
PubMed1988

Visual acuities and dark-adapted thresholds of children with Bardet-Biedl syndrome.

We studied the visual acuities and dark-adapted sensitivities of 12 children with Bardet-Biedl syndrome. All except one child, who was seen only once, were tested serially. In the first decade of life, all visual acuities were within 2 octaves of normal. All but two final visual acuities obtained from patients in their second and third decades were more than 2 octaves poorer than normal. Dark-adapted sensitivities of all patients were, or became, significantly less than normal even in those patients whose period of follow-up was limited to the first decade of life. Of the 11 patients measured serially, seven showed decreases in dark-adapted sensitivities of at least 0.5 log unit during the follow-up period, and the last measured sensitivities of all patients were at least 2 log units less than the normal mean.

Child, Preschool↗
PubMed1988

The relation of rhodopsin and scotopic retinal sensitivity in sector retinitis pigmentosa.

We used reflection retinal densitometric, psychophysical, and electroretinographic techniques to study the scotopic retinal function of a mother and her three daughters who had clinical evidence of a sectoral type of retinitis pigmentosa. Retinal regions with, and those without, ophthalmoscopic signs of degeneration were investigated. During dark adaptation, the time courses of rhodopsin regeneration and recovery of scotopic sensitivity were similar to normal as was the relation of rhodopsin to scotopic threshold. In dark-adapted eyes, threshold increases were not proportional to rhodopsin loss. The results of psychophysical tests of background adaptation and temporal summation, and analysis of the relation of electroretinographic a- to b-wave amplitudes, led to the conclusion that abnormalities of photoreceptor cell function central to the rhodopsin-bearing outer segments accounted for the increased thresholds.

Adult↗
PubMed1988

The development of scotopic retinal function in human infants.

Scotopic retinal function undergoes age-related changes early in human infancy. Electroretinographic psychophysical, and pupillographic responses have been used in the study of normal development. Various components of the electroretinographic responses index distal and proximal retinal function. Changes in pupillary diameter, measurable in infants under carefully selected conditions, represent rhodopsin regeneration in the infants under carefully selected conditions, represent rhodopsin regeneration in the photoreceptor outer segment. From psychophysical data, inferences can be drawn about scotopic retinal control of visual performance. These data constrain theories about the determinants of sensitivity, about the flow of signals from the distal, rhodopsin-bearing, outer segments to the proximal retina, and about modulations of straight-through flow by feedback or inhibitory circuits. The results indicate that the post natal development of human scotopic function is due mainly to reorganization of processes central to the photoreceptors.

Adaptation, Physiological↗
PubMed1988

Esotropic children with amblyopia: effects of patching on acuity.

The rates of improvement of acuity in response to full-time occlusion therapy of 30 esotropic patients with amblyopia were determined. The children's ages at the time of full-time patching ranged from about 3 to 10 years. In keeping with clinical experience, the rate of acuity improvement during patching was slower for older than younger patients. The age-related changes in responsiveness to patching were modeled nonlinearly to provide quantitative guidelines for management of occlusion therapy of esotropic children with amblyopia.

Amblyopia↗
PubMed1988

Optokinetic nystagmus thresholds of dark-adapted RCS rats.

The thresholds of dark adapted RCS rats and controls were estimated from optokinetic responses to blue stimuli, and compared to thresholds derived from b-wave stimulus/response functions. The rats were tested at ages 25, 30 and 35 days, a period during which the RCS degeneration is evolving and normal retinal development is proceeding. At all ages the OKN thresholds of control rats were lower than those of the RCS rats, but only by age 30 days did b-wave thresholds discriminate RCS from controls. As the RCS disease progressed b-wave thresholds increased, but OKN thresholds did not change significantly. The discrepancy between the OKN and b-wave results may be due largely to the smaller OKN stimulus field, which probably stimulates mainly the posterior retina where the RCS degeneration is most advanced.

Animals↗
PubMed1988

Visual fields of young children.

A light-emitting diode (LED) perimeter and forced-choice procedures are described that enable quantitative assessment of peripheral visual fields of young children. The visual fields of normal children, aged 2-5 years, and adults are compared. There are no significant differences in the extent of the LED visual field of the children and the adults. For selected neuro-ophthalmology patients, results of LED and kinetic Goldmann perimetry have been compared. The patients' LED and Goldmann fields are similar in overall extent. In all cases, field defects demonstrated by Goldmann perimetry are detected by LED perimetry. However, discrepancies in the severity of quandrantanopic defects of a patient have been discovered that may be stimulus-dependent.

Adolescent↗
PubMed1988

Shedding of cytoplasmic actins by developing muscle cells.

Young myotubes develop spots or macules of actin and alpha actinin under and adjacent to slender actin strands. Macules are found only before sarcomere formation. They contain cytoplasmic actin, small amounts of alpha actin, and alpha actinin but are devoid of tubulin, myosin and vimentin. In the electron microscope, they are seen to contain small filaments but no other organelles. Macules are found on the culture dish and in the culture medium, as well as on the lower and lateral surfaces of the cells. Both emetine and cycloheximide, at doses that inhibit protein synthesis, accelerate formation and shedding of macules. This presents the first observation of a cellular system in which the changeover from a generalized cytoskeleton to a tissue-specific cytoskeleton involves shedding of the cytoplasmic isoforms of cytoskeletal proteins.

Actins↗
PubMed1988

Visual fields of infants assessed with a new perimetric technique.

The visual field of normal infants was assessed using a perimeter with LED stimuli and a forced-choice observation procedure. Central fixation was elicited by four central, pulsing LEDs and maintained with the aid of auditory stimuli. Field extent was derived from the four-alternative, forced-choice judgments of an adult who observed the infant's eye movements to peripherally illuminated LEDs. The binocular visual field of infants, ages 6-7 months, was similar to that of adults tested with the same apparatus. Area of the infants' binocular field was 93% that of the adults'. However, the infants' monocular fields were smaller than those of adults, averaging 74% of the adults' monocular field area. This may have been due to the distracting effect on infant behavior of the adhesive patch used for monocular testing. The visual fields of a young patient with hydrocephalus illustrate the potential clinical utility of this new perimetric technique for infants at risk of field defects.

Adult↗
PubMed1987

The relation of rhodopsin and scotopic sensitivity in choroideremia.

We examined two patients who had clinical characteristics typical of choroideremia using psychophysical and reflection retinal densitometric techniques. In the dark-adapted state, sensitivity was more compromised than would be predicted on the basis of the modest losses of rhodopsin. In the dark-adapted state, studies of spatial and temporal summation suggested that postreceptoral processes are similar to normal. The kinetics of rhodopsin regeneration after bleaching exposures were abnormal in some retinal regions.

Adult↗
PubMed1987

Foveal cone pigments and sensitivity in young patients with Usher's syndrome.

Psychophysical and reflection retinal densitometric techniques were used to investigate foveal function of three patients (ages 14, 16, and 19 years) with Usher's syndrome who had good central visual acuity and, by ophthalmoscopic examination, normal foveal areas. During dark adaptation foveal sensitivity and its relation to proportion of cone pigment present were normal, but the kinetics of regeneration of the pigments were markedly abnormal. Measurements were made to consider the possibilities that the disorders of regeneration were associated with altered light-catching capacities of the patients' cone pigments, deranged transport of visual cycle substances between the retinal pigment epithelium and photoreceptors, or lingering photoproducts. None of the mechanisms fully accounted for the observed kinetics. The results suggested that abnormal kinetics of regeneration are among the earliest signs of malfunction of the foveal photoreceptor-pigment epithelial complex in some of the retinal degenerative disorders.

Adolescent↗