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Biomedical subjects

A B Fulton

Publications and source records attributed to A B Fulton.

At least 109 records · Page 6Linked to original sources
PubMed1984

Assembly associated with the cytomatrix.

Assembly in vivo has been studied both for endogenous cytoskeletal proteins and for several classes of viruses. Autoradiography of cytoskeletal proteins has shown that many associate with the cytoskeletal framework close to the time and place of synthesis. The cytoskeletal proteins rearrange after association with the cytoskeletal framework. Rearrangement in symmetrical giant cells occurs in a centrifugal and coherent pattern. Many of the cytoskeletal proteins associate cotranslationally, as shown by their puromycin resistance in a cell-free translation system. The assembly of several groups of viruses has been shown to be associated with various components of the cytoskeleton; whether such assembly is cotranslational has not yet been addressed directly.

Autoradiography↗
PubMed1984

Cycloplegic refractions of infants and young children: the axis of astigmatism.

Review of the cycloplegic refractions of all children who were first examined at Children's Hospital Medical Center in Boston between 1968 and 1978 revealed that 281 children between the ages of 0 and 9.5 years had astigmatism of 1 diopter (D) or greater but no other ophthalmological or neurological problems. In the 85 children under 3.5 years of age, against-the-rule astigmatism was 2.5 times more common than with-the-rule astigmatism, whereas in the 103 children over 5.5 years of age, with-the-rule astigmatism was three times as common as against-the-rule astigmatism. Eleven children who had been astigmatic as infants were recalled; follow-up refraction at ages 5-11 years revealed that all but three had at least a 0.75 D decrease in astigmatism. The remaining three had astigmatism equal in magnitude and axis to the astigmatism they had as infants. Thus, there is a high prevalence of against-the-rule astigmatism in infants and toddlers, which disappears by the time the children reach school age.

Accommodation, Ocular↗
PubMed1984

The relation of retinal sensitivity and rhodopsin in developing rat retina.

The authors have studied the relations of rhodopsin and retinal sensitivity in developing albino rats, (1) in the dark-adapted state and (2) after exposure to light that bleaches greater than 90% of rhodopsin. Developmental increases in dark-adapted b-wave sensitivity and rhodopsin content were related directly as has been reported previously for rhodopsin and PIII sensitivity of other developing retinas. During dark-adaptation, infant rat log a-wave and log b-wave sensitivities and adults' log b-wave sensitivity were related linearly to the proportion of rhodopsin present. The authors suspect that the sensitivity-rhodopsin relations of infant rat retina are determined mainly by photoreceptor processes. Thus, the infant rat provides a model for investigation of mechanisms underlying both (1) the direct relation of sensitivity and rhodopsin and (2) the log sensitivity-rhodopsin relation.

Animals↗
PubMed1984

Assessment of acuity in human infants using face and grating stimuli.

In a variety of ocular disorders, square-wave gratings yield more optimistic estimates of visual acuity than more complex stimuli such as letters. However, for clinical vision testing of preverbal patients, square-wave gratings are usually employed in conjunction with preferential looking procedures. We developed a complex stimulus--a schematic face--for use in preferential looking procedures. Using the method of constant stimuli, the acuities of 1-, 3-, and 5-month-old infants with normal eyes were estimated using schematic faces and square-wave gratings. Within each age group, thresholds for face and grating stimuli were not significantly different, but psychometric functions obtained with faces were significantly steeper than those obtained with square-wave gratings. This suggests that complex stimuli such as the schematic face could yield more precise acuity estimates than gratings in some pediatric eye patients.

Age Factors↗
PubMed1983

Many cytoskeletal proteins associate with the hela cytoskeleton during translation in vitro.

Observations that cytoskeletal proteins assemble in vivo close to the time and site of synthesis have been confirmed and extended by an in vitro translation system. HeLa cytoskeletons prepared with Triton in a translation-extraction buffer without reticulocyte or wheat germ lysate efficiently incorporate 35S-methionine into polypeptides, and are stable during this translation. Cytoskeletal proteins translated in this way associate with the HeLa cytoskeleton independent of the concentration of soluble proteins. These associations are puromycin-resistant before the proteins are complete; the protein associations made in vitro show only minor differences from those made in vivo. The protein associations are not simply a consequence of protein solubility in the buffers used, as the associations require initiation in vivo. These results indicate that many cytoskeletal proteins associate with the cytoskeleton during translation.

Cell Fractionation↗
PubMed1983

Retinal sensitivity and adaptation in pediatric patients.

A two-alternative forced-choice preferential looking psychophysical procedure was used to measure dark-adapted thresholds of 79 patients whose medical and ophthalmological conditions raised the possibility of scotopic retinal disorders. The average dark-adapted threshold first obtained from 48 patients, who eventually manifested diseases affecting the scotopic retina, was higher than the average threshold of the 31 patients without scotopic disease. Among the 48 patients with scotopic disease, most (40 out of 48) had abnormal electroretinographic b-wave amplitudes; in 23 scotopic b-waves were present but attenuated to less than or equal to 30% of the normal mean; no scotopic b-wave responses could be elicited from 17. In only 6 of the 40 patients with abnormal scotopic b-waves were the psychophysical thresholds elevated greater than 2.5 log units. That is, the scotopic b-wave is often sensitive to the effects of the retinal disorders of our patients, but the wider range of psychophysical responses permits investigation and analysis of retinal function. In the 13 patients for whom b-wave thresholds could be determined, b-wave and psychophysical thresholds were not correlated, further suggesting that electroretinographic and psychophysical data provide complementary information about retinal function. Thus the psychophysical techniques are suitable for investigation of the functional organization of diseased pediatric retinas. In patients with retinal disorders psychophysical procedures have enabled description of temporal and spatial summation and adaptation to steady background lights. Examples of results of spatial summation and background adaptation studies are presented in this report.

Adolescent↗
PubMed1983

Preferential looking acuity of pediatric patients with developmental disabilities.

The grating acuity of 181 patients from 6 weeks to 18 years of age who had neurological abnormalities and documented developmental delay was assessed using preferential looking (PL) procedures. PL acuities were estimated by a staircase procedure in 79% of all patients (143 of 181) on the first attempt. PL acuities were poorer than normal on the average in all patient groups, including those without ophthalmological disorders. However, PL acuities varied systematically with the severity of the eye disorder in each category, with two exceptions, high refractive error and nystagmus. Interocular acuity differences were sensitive to such asymmetric eye disorders as strabismic amblyopia and unilateral ocular abnormalities and enabled monitoring of occlusion therapy for these conditions. Many patients who were 'visually inattentive' despite the absence of major ophthalmological abnormalities were testable but had very poor acuity. This study evaluates the clinical applicability of PL procedures for routine assessment of visual acuity in pediatric patients with developmental disabilities.

Adolescent↗
PubMed1983

Background adaptation in RCS rats.

The stimulus/response (S/R) relations of scotopic b-waves from dark-adapted RCS-p+ rats and those adapted to steady background lights were investigated in animals ages 14 to 50 days. The shapes of the S/R curves were normal at all ages and in all adaptation conditions. However, dark-adapted sensitivity, amplitude, and latency were abnormal in the second postnatal month. As the disease progressed, background lights varied amplitude and decreased sensitivity less than normal. Thus, the effects of the RCS degeneration on b-wave adaptation were different than previously found in the PCD mouse retinal degeneration studied in a similar fashion. A suggestion is made that investigations of b-wave background adaptation may contribute to elucidation of underlying retinal dysfunction in the human retinal degenerations.

Adaptation, Physiological↗
PubMed1982

The relation of myopia and astigmatism in developing eyes.

The relation of astigmatism and myopia was analyzed in 298 myopic children, ages birth to 10 years. The mean spherical equivalent, determined by cyclopentolate retinoscopy, for the entire group was--2.9 diopters and did not change significantly with age. However, in 3-year-old children and younger, myopia progressed in eyes with greater than or equal to 1 diopter of cylinder and tended to increase through age 8 years in those having greater than or equal to 3 diopters of cylinder. Also, astigmatic errors greater than or equal to 1 diopter, especially of oblique orientation, were associated with higher degrees of myopia than nonastigmatic errors. These data from myopic children suggest that uncorrected astigmatism during a period of visual immaturity influences the course of myopia. Thus, naturally occurring astigmatic errors, that are frequent among infants and young children, appear to have a role similar to the vision blurring perturbations that trigger the development of myopia in young animals. Ascertainment and full correction of these refractive errors in young children may be important in assuring the best possible vision.

Age Factors↗
PubMed1982

Interaction of the cytoskeletal framework with acetylcholine receptor on th surface of embryonic muscle cells in culture.

To monitor the interaction of cell surface acetylcholine (AcCho) receptors with the cytoskeleton, cultured muscle cells were labeled with radioactive or fluorescent alpha-bungarotoxin and extracted with Triton X-100, using conditions that preserve internal structure. A significant population of the AcCho receptors is retained on the skeletal framework remaining after detergent extraction. The skeleton organization responsible for restricting AcCho receptors to a patched region may also result in their retention after detergent extraction.

Animals↗
PubMed1982

Dark-adapted sensitivity, rhodopsin content, and background adaptation in pcd/pcd mice.

Adaptation to steady background lights has been investigated in pcd/pcd mice, a mutant strain with retinal degeneration. The hyperbolic stimulus/response functions of the scotopic b-wave of the electroretinogram show progressive changes. For the dark-adapted eyes the decrease in log sensitivity between ages 1 and 12 months is related linearly to the decreasing rhodopsin content. The observed decline in amplitude of maximum responses from dark-adapted eyes begins only after age 5 months and is accompanied by gradual prolongation of the time to the peak of half-maximum b-wave responses. At all ages, the sensitivity of response is changed little by increments of steady red background lights; the greatest slope of log sensitivity vs. log background plots is about +0.2. (In normal mice the slope is about +0.9.) The pcd/pcd b-wave results do not fit the normal empirical relation that is thought to reflect neural processing in the distal retina. Thus the present results suggest that neural processing is abnormal in pcd/pcd retinas.

Adaptation, Physiological↗
PubMed1982

Scotopic thresholds and plasma retinol in cystic fibrosis.

Patients with cystic-fibrosis (CF) often have low plasma concentrations of vitamin A. We have measured dark-adapted scotopic thresholds of 56 patients with CF, ages 4 to 34 years, either with a two-alternative forced-choice procedure or as the final threshold after a full dark-adaptation curve. Fasting plasma vitamin A alcohol (retinol) was measured in 34 of the 56 patients. The average thresholds were higher and retinol values lower in patients than in controls. In two patients with very low (less than 7 micrograms/dl) initial retinol levels and elevated thresholds, decreased rhodopsin densities were observed; rhodopsin density and thresholds returned to normal after treatment with oral vitamin A. Rhodopsin density and log sensitivity were linearly related. Only marked decreased in plasma retinol were associated with elevations of dark-adapted threshold and decreases in rhodopsin density, suggesting that the tissues of patients with CF sequester vitamin A to maintain retinal function.

Adolescent↗
PubMed1982

Preferential looking acuity obtained with a staircase procedure in pediatric patients.

Visual acuity of infants and young children with ophthalmologic disorders was assessed by adapting a transformed up-down staircase to preferential looking (PL) procedures. Eighty-five percent of pediatric patients between 11 days and 5 years of age were tested successfully. Acuity of infants and young children with normal eyes obtained by the PL staircase procedure agreed well with acuities obtained previously by the method of constant stimuli. In children with anisometropia, differences in acuity between eyes varied systematically with the amount of anisometropia. Monocular acuities of untreated patients with strabismus did not always agree with fixation preference. In general, test results from pediatric patients with structural ocular abnormalities were consistent with the severity of the disorder. By means of serial measurement of PL acuity, the therapy of patients with amblyopia was monitored. In our young patients, anisometropic amblyopia affected grating acuity differently than did strabismic amblyopia, as others have reported in older patients with these conditions. Our results indicate that the PL staircase procedure provides a useful measure of visual acuity in pediatric ocular disorders that can complement the clinical evaluation of infants and young children.

Age Factors↗
PubMed1981

Cone pigments in acute posterior multifocal placoid pigment epitheliopathy.

We measured cone pigment density and kinetics with a reflection retinal densitometer during the evolution and resolution of posterior pole lesions in a 17-year-old patient with acute posterior multifocal placoid pigment epitheliopathy. Three weeks after onset, density was markedly reduced and regeneration complex and nonexponential. Pigment density increased, and kinetics returned to normal as the disease resolved.

Acute Disease↗
PubMed1981

Cycloplegic refractions of premature infants.

Cyclopentolate refractions of 146 premature infants disclosed higher incidences of myopia and anisometropia than those reported for full-term infants. Also, more than 70% of the premature infants had I diopter or more of astigmatism; 83% of the astigmatism was against-the-rule. Infants with shorter gestational periods had more severe myopia and astigmatism. Infants born very prematurely should undergo follow-up refractions to determine whether they retain refractive errors large enough to interfere with visual function.

Age Factors↗
PubMed1981

Developmental reorganization of the skeletal framework and its surface lamina in fusing muscle cells.

The skeletal framework of cells, composed of internal structural fibers, microtrabeculae, and the surface lamina, is revealed with great clarity after extraction with detergent. When muscle cells fuse to form a multinucleated myotube, their skeletal framework reorganizes extensively. When myoblasts prepare to fuse, the previously continuous surface lamina develops numerous lacunae unique to this stage. The retention of iodinated surface proteins suggests that the lacunae are not formed by the extraction of lamina proteins. The lacunae appear to correspond to extensive patches that do not bind concanavalin A and are probably regions of lipid bilayer devoid of glycoproteins. The lacunae appear to be related to fusion and disappear rapidly after the multinucleated myotube is formed. When muscle cells fuse, their internal structural networks must interconnect to form the framework of the myotube. Transmission electron microscopy of skeletal framework whole mounts shows that proliferating myoblasts have well developed and highly interconnected internal networks. Immediately before fusion, these networks are extensively reorganized and destabilized. After fusion, a stable, extensively cross-linked internal structure is reformed, but with a morphology characteristic of the myotube. Muscle cells therefore undergo extensive reorganization both on the surface and internally at the time of fusion.

Animals↗