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Biomedical subjects

E L Smith

Publications and source records attributed to E L Smith.

At least 163 records · Page 9Linked to original sources
PubMed1983

Effects of chronic atropinization on visual acuity in kittens.

Atropine was instilled daily from the time of eye-opening until 14 weeks of age into either one or both eyes of developing kittens. Following a 4 week recovery period, grating visual acuity was determined using behavioral techniques under both monocular and binocular viewing conditions. The monocularly treated kittens behaviorally demonstrated an amblyopia in the treated eye and an absence of binocular summation. In contrast, the binocularly treated kittens appeared to show normal visual acuity in both eyes and their performance improved during binocular viewing conditions. Single-unit recordings in striate cortex indicated that binocular atropinization did not alter cortical binocularity, however, monocular atropinization resulted in a decrease in the proportion of binocularly excited neurons and a shift in ocular dominance to the untreated eye.

Amblyopia↗
PubMed1983

Binocular neurons and binocular function in monkeys and children.

Electrophysiologic studies have shown that binocular neurons of the striate cortex of monkeys are irreversibly lost when the visual axes of the eyes are optically dissociated during the first weeks of life. The present study was a behavioral investigation of monkeys reared with optical dissociation. After brief periods of experimental strabismus, the monkeys showed poor binocular summation performance and were unable to see random dot stereograms even after two years of post-treatment normal binocular vision. These monkeys' performance on the stereopsis task was virtually identical to the stereoperformance of clinically diagnosed stereoblind children.

Adolescent↗
PubMed1982

Color vision is altered during the suppression phase of binocular rivalry.

Increment-threshold spectral sensitivity functions were determined during the dominance and suppression phases of binocular rivalry. The shapes of the functions obtained during the dominance phase exhibited three maxima at approximately 440, 530, and 610 nanometers and resembled functions obtained for nonrivalrous control conditions. However, the functions measured during suppression had a single broad peak near 555 nanometers and were adequately described by functions measured with flicker methods during nonrivalrous conditions. The results indicate that binocular rivalry differentially attenuates opponent-color information relative to achromatic information.

Color Perception↗
PubMed1982

Further field testing of the more heat-stable measles vaccines in Cameroon.

Two of the more heat-stable measles vaccines were field tested in Cameroon. Both maintained the minimum required infectivity titre and the ability to induce seroconversion after storage unreconstituted at 37 degrees C for 14 days. One of the vaccines, studied after reconstitution, maintained its ability to induce seroconversion after reconstitution and storage at 25 degrees C for 48 hours and at 37 degrees C for at least four hours. The increased heat stability of the studied vaccines will not eliminate the need for a well-monitored system of vaccine conservation and distribution but will ease the rigid cold-storage requirements of conventional measles vaccines.

Antibodies, Viral↗
PubMed1982

Decrease in hepatic cytochrome P-450 by cobalt. Evidence for a role of cobalt protoporphyrin.

Exposure of cultured chick-embryo hepatocytes to increasing concentrations of CoCl2 in the presence of allylisopropylacetamide results in formation of cobalt protoporphyrin, with a reciprocal decrease in haem and cytochrome P-450. Treatment of rats with CoCl2 (84 mumol/kg) and 5-aminolaevulinate (0.2 mmol/kg) also results in formation of cobalt protoporphyrin and a decrease in cytochrome P-450 in the liver. Hepatic microsomal fractions from rats treated with phenobarbital, CoCl2 and 5-aminolaevulinate were analysed by polyacrylamide gel electrophoresis. Cobalt protoporphyrin was associated mainly with proteins of 50000-53000 mol.wt. The results suggest that the formation of cobalt protoporphyrin occurred at the expense of the synthesis of haem, leading to a decrease in cytochrome P-450. Furthermore, the cobalt protoporphyrin that was formed may itself have been incorporated into apocytochrome P-450.

Animals↗
PubMed1982

Lewis blood group fucolipids and their isomers from human and canine intestine.

Glycolipids containing fucose linked to N-acetylglucosamine were isolated and characterized from 14 individual human and 13 individual dog intestines. From 8 of the dog intestines, Lewis a isomer fucolipids were isolated, all identical and having the structure Gal(beta 1 leads to 4)[Fuc alpha 1 leads to 3]GlcNAc(beta 1 leads to 3)Gal(beta 1 leads to 4)Glc-ceramide. Lewis b isomer fucolipids were isolated from 12 of the intestines, all identical and having the structure Fuc(alpha 1 leads to 2)Gal(beta 1 leads to 4)[Fuc alpha 1 leads to 3]GlcNAc(beta 1 leads to 3)Gal(beta 1 leads to 4)Glc-ceramide. Lewis a-active glycolipids were isolated as the sole major fucolipid in 6 of the human intestines and differed from the canine isomer only in the position of the linkage of galactose to N-acetylglucosamine, having the beta 1 leads to 3 (type 1) rather than the beta 1 leads to 4 (type 2) linkage. Lewis b-active fucolipids were isolated from 8 human intestines and differed from their canine isomer only in that they, too, had the type 1 rather than the type 2 oligosaccharide chain. Lewis a and b glycolipid isomers commonly co-existed in canine intestine as major fucolipids whereas Lewis a and b glycolipids did not so co-exist in human intestine. In all of the fucolipids, only hydroxylated fatty acids were present and phytosphingosine and sphingosine were the predominant long chain bases. These findings are of interest in the biosynthesis of these substances and in their genetic expression.

Animals↗
PubMed1982

Contrast increment thresholds of rhesus monkeys.

Increment contrast thresholds ware determined behaviourally as a function of background contrast for sinusoidal gratings with spatial frequencies between 0.5 and 8.0 c/deg. As has been previously reported for humans, the contrast discrimination functions ere characterized by a facilitation effect for low background contrasts and a masking effect for high background contrasts. The shapes of the functions varied with spatial frequency, but for all spatial frequencies, portion of the functions were adequately described by a power law. The shapes of the reaction time distributions obtained for near threshold stimuli suggested that at least two mechanisms with different spatio-temporal sensitivities were involved in detecting the stimulus and that the exact shape of the contrast discrimination function was dependent on which mechanism dominated detection.

Animals↗
PubMed1982

Optically induced anisometropia in kittens.

Anisometropia was simulated in 11 kittens during the critical period of visual system development by securing a high-powered minus lens in front of one eye. Behavioral determinations of monocular grating acuity indicated that the induced refractive error resulted in severe amblyopia in the defocused eye. Microelectrode recordings in striate cortex revealed that the deficits in visual acuity were paralleled by a decrease in binocularly innervated neurons and a marked shift in ocular dominance toward the nondeprived eye. "Position of paralysis" estimates revealed that all the anisometropic kittens exhibited anomalous interocular alignments that were indicative of estropia. There was also a significant reduction in the cross-sectional areas of dorsal lateral geniculate nucleus (LGNd) neurons in laminae innervated by the deprived eye. A 6 week period of binocular recovery initiated when three of the anisometropic kittens were approximately 16 weeks of age resulted in a partial recovery of visual acuity; however, there was little or no evidence for recovery of cortical binocularity, cortical ocular dominance, LGNd neuron cell size, or interocular alignment. In general the visual system alterations produced by the induced anisometropia appear to be qualitatively similar to the anomalies associated with prolonged unilateral lid suture.

Animals↗
PubMed1981

ERG off-effects produced by short duration stimuli.

Variable duration square wave pulses of 633-nm light were used to produce electroretinograms (ERG's) in a human subject. When the stimuli were presented on a white light background, the records obtained for stimulus durations greater than 70 msec showed a clearly separated off-response while those of shorter durations did not. By subtracting a common "on-effect" from the ERG's produced by short duration stimuli, the previously unseen off-effect was isolated from records produced by stimulus pulses as short as 5 msec. It appears that the marked increase in b-wave amplitude associated with these short duration stimuli can be attributed to an interaction between "on" and "off" components of the ERG.

Computers↗
PubMed1981

Physical activity and calcium modalities for bone mineral increase in aged women.

This study tested the hypothesis that physical activity and/or supplemental calcium (0.75 g/day) and vitamin D (400 IU) would effectively slow bone loss, and /or increase bone mineral content (BMC) in aged females (X = 81) over three years. In vivo BMC and width of the radius was determined by photon absorptiometry at two sites. Four groups were formed: a control, a drug, a physical activity, and a physical activity plus drug. A single tailed t-test was used to compared the slope of the linear regression of 10 data points collected on each subject. The BMC of the control group declined 3.29%, while the physical activity group and drug group demonstrated a 2.29% (p less than .05) increase and a 1.58% (p less than .07) increase respectively, during the study.

Aged↗
PubMed1980

Binocular interactions in normal and anomalous binocular vision.

Binocular interactions for grating patterns were investigated in humans with normal binocular vision and in humans with abnormal binocular visual experience due to strabismus and/or amblyopia via 1) comparison of monocular and binocular contrast thresholds; 2) interocular transfer of the threshold elevation aftereffect; and 3) dichoptic masking. Whereas the normal observers showed improved binocular over monocular contrast sensitivity (i.e., binocular summation) and substantial interocular transfer of the threshold elevation aftereffect, the abnormal observers showed an absence of binocular summation and no significant interocular transfer. The dichoptic masking experiments showed that a suprathreshold masking grating presented to one eye elevated the contrast threshold for gratings presented to the fellow eye, within a narrow range of spatial frequencies (about 1 octave wide at half height) and orientations, centered about the spatial frequency and orientation of the mask. The magnitude and bandwidth of this masking effect was similar in subjects with normal and abnormal binocular vision, occurring even when the masking grating was presented to the amblyopic eye. These effects depend upon the contrast of the masking grating. In individuals with normal binocular vision, a grating with subthreshold contrast presented to one eye reduces the contrast threshold for detection of gratings of similar spatial frequency and orientation presented to the fellow eye. No such subthreshold summation is evident in the amblyopic observers. We conclude that while strabismus and/or amblyopia disrupted the normal excitatory interactions between the two eyes, cortical inhibitory binocular connections were not disrupted.

Adult↗
PubMed1980

Nicotinamide adenine dinucleotide-specific glutamate dehydrogenase of Neurospora crassa. Isolation and sequences of several cyanogen bromide peptides from the NH2-terminal portion of the peptide chain.

Previous studies of the amino acid sequence of the NAD-specific glutamate dehydrogenase of Neurospora crassa (EC 1.4.1.2) resulted in the assignments of peptides to four fragments, the longest being the COOH-terminal 669 residues of the protein. A further study of peptides derived by cyanogen bromide cleavage by different separation methods has yielded additional peptides that have provided new information concerning the sequence and has given overlaps of previously known sequences. This has permitted establishment of 313 residues in one sequence (fragment II). This is in addition to a sequence of 43 residues (fragment I) at the NH2-terminal end and a sequence of 669 residues (fragment III) previously established at the COOH-terminal end of the molecule. The present status of our knowledge of the overall sequence is given in the accompanying papers, together with some views regarding the conformation of the protein (Haberland, M.E., Chen, C.-W., and Smith, E.L. (1980) J. Biol. Chem. 255, 7993-8000, and Austen, B.M., Haberland, M.E., and Smith, E.L. (1980) J. Biol. Chem. 255, 8001-8004).

Amino Acid Sequence↗
PubMed1980

Secondary structure predictions for the NAD-specific glutamate dehydrogenase of Neurospora crassa.

From the amino acid sequences of the three known fragments of the NAD-specific glutamate dehydrogenase of Neurospora crassa, the secondary structures have been predicted from the rules of Chou and Fasman (Chou, P.Y., and Fasman, G.D. (1979) Biophys. J. 26, 367-384). Comparison of these structures with those calculated for bovine glutamate dehydrogenase has shown that in the regions of homologous sequences containing identified functional regions, there is considerable homology of structure. From these predictions, it has been possible to identify a putative coenzyme-binding domain in the COOH-terminal part of the molecule similar to those of various NAD-specific dehydrogenases. Residues whose modification alters coenzyme binding are located in the putative coenzyme binding domain. The major sites of tryptic cleavage of the native enzyme, described in an accompanying paper (Haberland, M.E., Chen, C.-W., and Smith, E.L. (1980) J. Biol. Chem. 255, 7993-8000), are in regions of random coil structure.

Amino Acid Sequence↗
PubMed1980

Ocular dominance, eye alignment and visual acuity in kittens reared with an optically induced squint.

A horizontal concomitant strabismus produced optically in kittens with prisms caused a decrease in the proportion of binocularly excitable striate neurons with approximately equal percentages of neurons being driven by each eye. In addition, preventing fusion with prisms resulted in alterations in interocular alignment and in some cases a mild strabismic amblyopia. The changes in ocular dominance were dependent on the amount and direction of the prism induced deviation; however, regardless of the type of prisms worn, the kittens which demonstrated interocular misalignments were esotropic.

Animals↗