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Biomedical subjects

A V Levin

Publications and source records attributed to A V Levin.

61 records · Page 4Linked to original sources
PubMedDate not supplied

Time courses for maturation of electroretinogram responses from infancy to adulthood.

The purpose of this study was to determine how responses in the normal human electroretinogram (ERG) change with subject age. We studied 62 children, 10 days to 15 years old, and 30 subjects 15-37 years old, using the standard protocol established by the International Society for Clinical Electrophysiology of Vision, with Burian-Allen bipolar contact-lens electrodes. We measured rod response, maximal response, oscillatory potentials (OPs), cone response, flicker response, and b-wave amplitude/log intensity (V/log I) curve. A logistic growth curve was used to describe the developmental changes. Dark- and light-adapted ERG a- and b-wave amplitudes reached adult levels by three to five years of age. although b-wave amplitudes of scotopic rod-mediated responses were slower to reach maturity than mixed rod-cone mediated responses. In early infancy OPs were the most immature of the ERG responses, although the rate of development thereafter exceeded that of the other responses such that OP amplitudes were within adult levels by two years of age. Amplitudes of the ERG responses in 21 children sedated with chloral hydrate did not differ significantly from 21 who had not been sedated. ERG responses developed at varying rates, reflecting different developmental stages in photoreceptors, middle retinal layers and more proximal retina.

Adolescent↗
PubMedDate not supplied

Ophthalmologic findings in the Cornelia de Lange syndrome.

Cornelia de Lange Syndrome (CDLS) is characterized by mental retardation, growth retardation, skeletal anomalies, and a characteristic facies. We examined 22 children with CDLS to ascertain the relative frequencies of oculofacial and ophthalmologic abnormalities. We confirm prior reports of the frequent findings of brow hypertrichosis, synophrys, and long arcuate eyelashes. In addition we documented the association with ptosis, nystagmus, and high myopia. Contrary to previous reports, we did not find blue sclera or corneal, pupillary, or retinal disorders to be part of this syndrome. Hypertelorism and telecanthus were found, but they were dependent on the method of calculation. Two children had optic nerve pallor. We also report the new findings of poor macular reflex, chin lifts induced by ptosis, hypertropia, and nasolacrimal duct fistula.

Adolescent↗
PubMedDate not supplied

Unilateral surgery for exotropia with convergence weakness.

We prospectively studied 14 patients whom we treated surgically for exotropia (XT) with convergence weakness measuring at least 8 delta for distance (6 m) that increased at least 8 delta at near (1/3 m). Surgery involved lateral rectus recessions and medial rectus strengthenings (advancements or resections) to eliminate distance and near deviations and simultaneously collapse near-distance differences. The medial rectus was strengthened more than the lateral rectus was recessed; amounts were based on the near deviation. Minimum follow-up was 6 months after surgery. Preoperatively, the mean XT at distance was 18.3 delta (range, 8 to 35 delta) and at near 30.1 delta (range, 16 to 50 delta). At latest follow-up evaluations the mean distance deviation was 0.1 delta XT and at near 1.8 delta XT. The near-distance differences were reduced by a mean of 10.2 delta; the mean postoperative difference was 1.7 delta. Unilateral surgery for XT with convergence weakness biased to medial rectus strengthening and geared to near deviation can successfully collapse the near-distance differences while satisfactorily aligning both distance and near fixation. This surgery has low risk of creating long-term postoperative esodeviations at distance.

Adolescent↗
PubMedDate not supplied

[Repetitious DNA in the genome of Drosophila lummei Hackman and its role in replication and chromosome behavior in mitosis].

The toromere previously found by other workers in the distal end of the sixth chromosome (microchromosome) of D. lummei was studied using differential staining of D. lummei giant chromosomes. The toromere which was first described as a quinacrine-bright structure appears as a C-positive body. Quantitative cytofluorometric analysis showed a significant increase in toromeric DNA under low temperature conditions. In situ hybridization of 125I nick-translated D. virilis sDNA (all three satellites were included in the sample) with polytene chromosomes of D. lummei larvae cultured at 12 degrees C revealed no label incorporation into the toromere region. However in situ hybridization of [3H]RNA complementary to highly repetitious DNA of D. lummei and D. virilis (C0t = 10(-1)--10(-2)) with polytene chromosomes of the larvae cultured at 12 degrees coupled with banding studies enable us to conclude that the toromere probably contains AT-rich repeated DNA. Well-developed toromere in the sixth chromosome of D. lummei was also demonstrated at normal temperature (25 degrees) in interspecific hybrids. The role of the toromere structure in the mitotic behaviour of microchromosomes and their replication pattern is discussed.

Animals↗