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Biomedical subjects

E W Russell

Publications and source records attributed to E W Russell.

At least 37 records · Page 2Linked to original sources
PubMed1986

Single-channel studies on linear gramicidins with altered amino acid side chains. Effects of altering the polarity of the side chain at position 1 in gramicidin A.

The modulation of gramicidin A single-channel characteristics by the amino acid side chains was investigated using gramicidin A analogues in which the NH2 terminal valine was chemically replaced by other amino acids. The replacements were chosen such that pairs of analogues would have essentially isosteric side chains of different polarities at position 1 (valine vs. trifluorovaline or hexafluorovaline; norvaline vs. S-methyl-cysteine; and norleucine vs. methionine). Even though the side chains are not in direct contact with the permeating ions, the single-channel conductances for Na+ and Cs+ are markedly affected by the changes in the physico-chemical characteristics of the side chains. The maximum single-channel conductance for Na+ is decreased by as much as 10-fold in channels formed by analogues with polar side chains at position 1 compared with their counterparts with nonpolar side chains, while the Na+ affinity is fairly insensitive to these changes. The relative conductance changes seen with Cs+ were less than those seen with Na+; the ion selectivity of the channels with polar side chains at position 1 was increased. Hybrid channels could form between compounds with a polar side chain at position 1 and either valine gramicidin A or their counterparts with a nonpolar side chain at position 1. The structure of channels formed by the modified gramicidins is thus essentially identical to the structure of channels formed by valine gramicidin A. The polarity of the side chain at position 1 is an important determinant of the permeability characteristics of the gramicidin A channel. We discuss the importance of having structural information when interpreting the functional consequences of site-directed amino acid modifications.

Amino Acids↗
PubMed1985

Comparison of the TPT 10 and 6 hole form board.

The 10 hole (Adult Version) Tactile Performance Test (TPT) or Form Board is too difficult for patients with moderate to severe brain damage. A series of studies were done to enable an examiner to substitute the simpler 6 hole board (TPT 6 - Child's Version) for such patients. Eighty subjects (61 brain damaged and 19 controls) were given both boards in a counter-balanced order. It was found that: (1) the TPT 10 was inadequate for severe damage; (2) the TPT 6 can be used with severe impairment; (3) a method of prorating blocks into time was developed; (4) the TPT 10 and TPT 6 are strongly correlated; (5) there were no order effects when both boards were given; (6) both boards significantly separated controls from brain-damaged subjects; (7) criteria for substitution of the TPT 6 were established; and (8) comparable scales were established for both boards so that an examiner can substitute either TPT for the other.

Adult↗
PubMed1985

MMPI correlates of verbal-intellectual deficits in patients with left hemisphere lesions.

This study investigated the emotional adjustment of patients (N = 31) with left hemisphere damage (LHD) as a function of the degree of impairment in verbal intelligence as measured by the Wechsler Adult Intelligence Scale. A multivariate comparison was made of the composite MMPI profiles of three groups of LHD patients classified according to Verbal IQ. The three groups produced fairly similar composite profiles, which indicated the presence of mild dysphoria, dissatisfaction, withdrawal, decreased initiative, and mild somatic preoccupations. Significant correlations emerged between the degree of verbal-intellectual disability and MMPI F, PT, SC, and SI. However, when the variance in MMPI scores due to premorbid status (education) was partialled out, these correlations dropped to nonsignificant levels. These findings failed to support previous studies that linked verbal deficits with emotional disturbance, and they underscore the importance of premorbid intelligence in the psychological adjustment to organic impairment.

Adult↗
PubMed1982

Difference in the ratio of dominant-lethal mutations to heritable translocations produced in mouse spermatids and fully mature sperm after treatment with triethylenemelamine (TEM).

The relative induction of dominant-lethal mutations and heritable translocations in triethylenemelamine-treated postmeiotic germ cells of mice was determined depending on the stage treated. Males were mated either 11.5-14.5 days after treatment (middle spermatids) or less than 2.5 hours after treatment (fully mature sperm). Results clearly showed that, even through similar levels of dominant-lethal mutations were induced in fully mature sperm and in middle spermatids, the frequency of heritable translocations induced in mature sperm was markedly lower than that induced in middle spermatids. This observation was used, together with earlier ones, to suggest a mechanism by which dominant-lethal mutations and heritable translocations are produced following chemical treatment of male postmeiotic germ cels.

Animals↗
PubMed1982

Factor analysis of the Revised Wechsler Memory Scale tests in a neuropsychological battery.

The Revised Wechsler Memory Scale (4 scales) along with 13 subtests from the WAIS and Halstead-Reitan battery were subjected to a principal components factor analysis. 9 tests of memory loaded on 5 of the 6 factors indicating that 5 types of memory were isolated. These were immediate verbal memory, recent verbal memory, recent figural memory, figural learning, verbal learning storage. Loading of memory and nonmemory tests on the same factors indicates a closer relationship between some memory and nonmemory processes than between kinds of memory.

Brain Damage, Chronic↗
PubMed1981

The chronicity effect.

The chronicity effect is derived from two other general principles that underlie clinical neuropsychological test interpretation. These are (1) localization principle: elementary functions are related to specific cortical areas; (2) Diaschisis: functions located at a distance from an acute lesion may be affected by that lesion. The chronicity effect states that as a nonprogressive lesion becomes chronic, diaschisis tends to recede. In an illustrative detailed case study, a man with encephalitis concentrated in the left temporoparietal area was tested five times over a 6-year period. In the first testing at 5 weeks many of his abilities were impaired. In subsequent months, all abilities except reading returned to the normal range. His dyslexia became permanent, while other abilities not related to the area of tissue damage returned to normal functioning.

Adult↗
PubMed1980

Tactile sensation--an all-or-none effect of cerebral damage.

Compared the Von Frey Hair scores of 158 brain-damaged Ss and 40 normals to scores on Speech Perception, Block Design and Trail Making B tests, in order to examine the distribution of organically affected tactile sensation. Organic impairment produced an all-or-none distribution pattern on the tactile test in that almost all scores fell either within the normal range or in the severely impaired range. By contrast, scores of the cognitive functions formed a graded continuous distribution. These results are related to Luria's concept of diminishing modality specificity. In addition, the neurological examination evidently is designed to measure all-or-none functions, while the neuropsychological examination is concerned with graded continuous functions.

Adult↗
PubMed1980

Fluid and crystallized intelligence: effects of diffuse brain damage on the WAIS.

In the 1940's two forms of intelligence, fluid and crystallized, were postulated. Active mental processing (WAIS performance subtests) were fluid while well learned abilities (WAIS verbal subtests) were crystallized. Brain damage was considered to affect fluid abilities more than crystallized. WAIS scores comparing normal and diffusely organically damaged subjects indicated that, as hypothesized, the verbal subtests were more affected than the performance subtests.

Atrophy↗
PubMed1979

Three patterns of brain damage of the WAIS.

Compared four groups of matched Ss (40 each) in order to examine different subtest patterns of brain damage on the WAIS, using F-tests and age mean profiles. The groups were: Normals, diffuse cortical degeneration, right and left hemisphere damage. The results indicated three patterns: (1) a normal pattern; (2) a diffuse degenerative and right hemisphere pattern; and (3) a left hemisphere pattern. The diffuse degenerative results were not significantly different from the right hemisphere results. The left hemisphere pattern had no large verbal vs. performance differences. These patterns appear to be produced by the interaction of three brain damage effects: (1) a general effect; (2) a right hemisphere effect; and (3) a left hemisphere effect. Verbal tests are both "hold" and left hemisphere tests, while three Performance Tests are "don't hold" and right hemisphere tests. The WAIS requires other specific tests of brain damage for an adequate assessment of brain damage.

Brain Damage, Chronic↗
PubMed1977

MMPI profiles of brain-damaged and schizophrenic subjects.

MMPI mean profiles for matched groups of 50 brain-damaged and 50 schizophrenic Ss from a short-term hospital were compared. The profiles are quite different. F tests demonstrated that the Sc scale best differentiated the two groups at far beyond the .01 level, and scales F, PA and PT also differentiated the two groups beyond the .01 level. A cut-off point of 80 on the SC scale correctly classified 78% of the two groups. Neither the 2-9 nor the 1-3-9 profile occurred a sufficient number of times in either group to be of any help in diagnosis.

Adult↗
PubMed1976

The Bender-Gestalt and the Halstead-Reitan battery: a case study.

A single case with severe static left hemisphere cerebral damage was used to illustrate some deficiencies in the Bender-Gestalt (B-G) test and to compare its results with the Halstead-Reitan battery. The B-G did not indicate the existence of any brain damage because visuoconstructional tests evidently are related directly only to the right parietal area. The Halstead indicated the existance of brain damage, the amount of impairment to various mental functions, the location, process status, and general type of pathology and provided an evaluation of residual functions. Used as a screening test, the B-G is useful because it measures nondominant functions and is a "don't hold" test. The Halstead should be used when a more complete evaluation or critical test for brain damage is required.

Aphasia↗
PubMed1975

Validation of a brain-damage vs. schizophrenia MMPI key.

Since neuropsychologic tests largely have failed to separate schizophrenic from brain-damaged patients, an MMPI key was constructed to make such a separation. When cross-validated, this key provided a 76% correct separation and achi2 significant beyond the .001 level for 50 schizophrenic and 50 brain-damaged profiles. Neuropsychologic tests should be used to separate normals from brain-damaged patients and the MMPI to separate schizophrenic from brain-damaged patients.

Adjustment Disorders↗