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Biomedical subjects

B Wallace

Publications and source records attributed to B Wallace.

At least 55 records · Page 3Linked to original sources
PubMed1991

Effect of imagery ability on letter-level and word-level processing.

In a letter-identification task, subjects matched a probe letter to the initial letter of a subsequently presented probe word. We varied word frequency and predicted that the performance of vivid imagers would resemble that of typical young adults, whereas the performance of poor imagers would fall in between that of typical young adults and of older adults, or would simply resemble the performance of typical older adults (a linear decrease in reaction time [RT] with word frequency; see Allen & Madden, 1989). The in-between function for young and older adults combined predicts a dip in RT for very-high-frequency words compared to medium-high-, low-, and very-low-frequency words. As predicted, vivid imagers exhibited increased latencies for medium-high-frequency words relative to the other three word-frequency categories, whereas poor imagers exhibited a dip.

Adult↗
PubMed1991

The importance of internal marketing: the case of geriatric services.

Hospitals seeking to become more aggressive often are tempted to introduce programs prematurely. Using the example of a geriatric services program at a large hospital, the authors illustrate the dangers of neglecting internal marketing and offer recommendations for ensuring internal coordination prior to introduction of a product externally.

Aged↗
PubMed1990

Male-male interactions and mating kinetics in Drosophila.

Male-male interaction (K) has been estimated from data on the attrition rate of virgin females per minute in a study of the mating kinetics in Drosophila. K is expressed as the time males expend on other males relative to that expended while searching for, courting, and copulating with females. The value of K in these studies ranged from 0 (approximately) to .695; it was affected both by strain (sepia or ebony D. melanogaster and wild-type D. simulans) and by size of the mating chamber. Host-parasitoid models of ecologists appear to be appropriate for examining mating kinetics in Drosophila.

Analysis of Variance↗
PubMed1990

Imagery vividness, hypnotic susceptibility, and the perception of fragmented stimuli.

Two experiments were conducted to determine the role of hypnotic susceptibility level (high or low) and imaging ability (vivid or poor) in the performance of gestalt closure tasks. In Experiment 1, subjects were required to identify fragmented stimuli in the Closure Speed Test and in the Street Test. In Experiment 2, subjects reported on fragmented stimuli that were projected to the right eye and subsequently produced an afterimage. Individuals were asked to identify the composite if possible and to report on the duration of the afterimage. In both experiments, hypnotic susceptibility level and imaging ability affected reports of gestalt closure. The greatest number of correct closures was reported by those who were both high in hypnotic susceptibility and vivid in imaging ability. In addition, in the second experiment, this group also reported the longest enduring afterimage. These results are discussed in terms of the processes required to perform in a gestalt closure task.

Adult↗
PubMed1990

Components of fitness become effectively neutral in equilibrium populations.

If, because of trade-offs or similar considerations, components of fitness are negatively correlated in equilibrium populations, they may then exhibit no correlation with total fitness. Lack of correlation with fitness is a fundamental characteristic of selective neutrality. Hence, selectively important traits become subsumed under neutral traits when the definition of neutrality is extended to include factors (genetic or phenotypic) that "behave as if they are neutral."

Mathematics↗
PubMed1990

Hypnotizability and the modification of cognitive search strategies.

An experiment was conducted to determine if Ss judged to be low in hypnotizability could be taught the efficient search strategies used by high hypnotizable Ss in the performance of a cognitive search task. Ss were requested to find objects embedded within a variety of pictorial scenes. High hypnotizable Ss were found to be more adept than low hypnotizables at finding more objects correctly. When low hypnotizable Ss were taught the efficient search strategies used by the high hypnotizables, their performance improved and was not significantly different from that of the high hypnotizable Ss. Implications of these results for teaching search strategies are discussed.

Cognition↗
PubMed1990

Effects on prism adaptation of duration and timing of visual feedback during pointing.

In two experiments, we investigated the effects of duration of visual feedback of the pointing limb and the time (early to late) in the movement when the limb first becomes visible (timing of visual feedback). Timing, rather than duration of visual feedback, proved to have the greater effect on the relative magnitude of visual and proprioceptive adaptation. Visual adaptation increased smoothly with feedback delay, but corresponding decreases in proprioceptive adaptation underwent an additional sharp change when feedback was delayed until about three-fourths of the way to the terminal limb position. These results are consistent with the idea that visual and proprioceptive adaptation are mediated by exclusive processes. Change in the limb position sense (i.e., proprioceptive adaptation) may be produced by visual guidance of the pointing limb, and view of the limb early in the pointing movement seems to be critical for such visual guidance. The limb may be ballistically released as it nears the terminal position, and, thereafter, any opportunity for visual guidance (i.e., view of the limb) is not effective. On the other hand, change in the eye position sense (i.e., visual adaptation) may be mediated by proprioceptive guidance of the eye; the eyes may track the imaged position of the nonvisible limb. Such proprioceptive guidance seems to be solely a function of the distance moved before the limb becomes visible.

Journal Article↗
PubMed1990

Genes Responsible for Size Reduction of Marine Vibrios during Starvation Are Located on the Chromosome.

In a survey of 21 marine Vibrio spp., all responded to nutrient deprivation by undergoing a reduction in size (dwarfing). However, only 43% of these strains possessed one or more plasmids, suggesting that the genes responsible for dwarfing were located on the chromosome rather than on the plasmids. This conclusion was confirmed by the observation that fragmentation and subsequent size reduction occurred in three strains from which the plasmids had been removed by curing. The cured strains lost certain characteristics, such as resistance to some heavy metals and antibiotics, that were restored when the plasmids were reintroduced by either transformation or electroporation.

Journal Article↗
PubMed1990

Cloning and sequencing of a gene encoding a glutamate and aspartate carrier of Escherichia coli K-12.

A gene encoding a carrier protein for glutamate and aspartate was cloned into Escherichia coli K-12 strain BK9MDG by using the high-copy-number plasmid pBR322. The gene (designated gltP) is probably identical to a gene recently cloned from E. coli B (Y. Deguchi, I. Yamato, and Y. Anraku, J. Bacteriol. 171:1314-1319). A 1.6-kilobase DNA fragment containing gltP was subcloned into the expression plasmids pT7-5 and pT7-6, and its product was identified by a phage T7 RNA polymerase-T7 promoter coupled system (S. Tabor and C. C. Richardson, Proc. Natl. Acad. Sci. USA 82:1074-1078) as a polypeptide with an apparent mass of 38 kilodaltons. A portion of the gltP polypeptide was associated with the cytoplasmic membrane. The nucleotide sequence of the 1.6-kilobase fragment was determined. It contained an open reading frame capable of encoding a highly hydrophobic polypeptide of 395 amino acids, containing four possible transmembrane segments. Uptake of glutamate and aspartate was increased 5.5- and 4.5-fold, respectively, in strains containing gltP plasmids. Glutamate uptake was insensitive to the concentration of Na+ and was inhibited by L-cysteate and beta-hydroxyaspartate. These results suggest that gltP is a structural gene for a carrier protein of the Na(+)-independent, binding-protein-independent glutamate-aspartate transport system.

Amino Acid Sequence↗
PubMed1989

Analyzing variation in egg-to-adult viability in experimental populations of Drosophila melanogaster.

Selective culling in populations of most organisms is rank-order: individuals of low rank on a scale of potential fitnesses tend to be eliminated during early development, whereas surviving adults (whose number reflects the carrying capacity of the environment) are generally drawn from the distribution's upper end. Haldane pointed out [Haldane, J.B.S. (1932) The Causes of Evolution (Harper & Row, New York)] that selection which favors individuals in the upper tail of a composite distribution curve tends to favor members of the more variable of two populations, rather than members of a less variable one, even though the latter may possess the higher mean. In addition to reviewing earlier observations bearing on Haldane's argument, the present report describes an analysis of the comparative egg-to-adult viabilities of flies (Drosophila melanogaster) carrying combinations of second chromosomes obtained from one or another of eight experimental populations. Overall, the viabilities of flies carrying combinations of chromosomes one of which is shared (i/j vs. j/k) are as different as those of flies carrying combinations of independently sampled chromosomes (i/j vs. k/l). Episodes seemingly occurred within the populations during which flies carrying combinations that shared a chromosome differed more in their viabilities than flies carrying unrelated combinations. Such episodes could reflect the occurrence of selection of the sort described by Haldane.

Alleles↗
PubMed1989

Hypnotic susceptibility and familial handedness.

The possible relationship between hypnotic susceptibility and familiar handedness was examined. In a mass-testing session of students enrolled in introductory psychology classes, subjects were administered the Harvard Group Scale of Hypnotic Susceptibility, Form A and were also required to complete a questionnaire that ascertained information on their dominant handedness and that of their immediate family relatives. Subjects who had immediate sinistral relatives scored significantly lower in hypnotic susceptibility compared to those who had a history of familial dextrality. When immediate relatives of the original subject pool were tested on hypnotic susceptibility level, sinistral relatives scored lower in susceptibility than dextral relatives. This may indicate the existence of a familial component in hypnotic susceptibility.

Adolescent↗
PubMed1989

Improving cognitive search skills in resistant hypnotic subjects.

Subjects who were resistant (n = 20) and susceptible (n = 20) to hypnotic suggestion were asked to find the letter Z in an array of other straight-form letters. Susceptibles found the letter more quickly than resistants, and this superiority appeared to be related to their use of a more efficient search strategy. When resistants were taught this strategy, their performance was not significantly different from that of susceptibles. Implications of these results for teaching search strategies are discussed.

Adult↗
PubMed1989

One selectionist's perspective.

Following introductory comments expressing doubts about the validity of genetic load and Haldane's "cost of natural selection," the role of selection (expressed as the average number of adult daughters per female) on gene frequencies in populations has been partitioned into population and time arenas. The population arena (a geometric plane) deals with the fitnesses of different genotypes under the many situations encountered by individual members of the population in a single generation; average fitnesses of carriers of various genotypes are obtained by calculating across these many situations. The population arena includes the point signifying that, on the average, each mother leaves one daughter as her replacement within the population. It is the plane within which evolutionarily significant norms of reaction exist. The time arena is also a (geometric) plane, one that is composed of the edge-on limit (average fitness) of each successive population arena. It does not include the effects of individual situations on relative fitnesses within each population arena; it encompasses only the temporal sequence of average relative fitnesses. Amino acid substitutions in proteins and base-pair substitutions in DNA are events of concern in the time arena; within the population arena, however, gene action (not merely gene structure) is a matter of considerable concern. Thus, the discussions of the 1950s and 1960s regarding genetic variation which were reasonable within the population arena seem less so within the time arena where structural, rather than functional, variation is stressed. The function-structure dichotomy is entangled with the neutralist-selectionist controversy.

Alleles↗
PubMed1989

Growth of vegetarian children: The Farm Study.

To examine the effects of a vegetarian diet on child growth, height and weight data of 404 vegetarian children aged 4 months to 10 years who lived in a collective community in Tennessee were studied. Height for age, weight for age, and weight for height were compared with the US growth reference. Birth weights, infant feeding patterns, and parental heights were also evaluated in relation to growth. Most of the height for age, weight for age, and weight for height (n = 833) were within the 25th and 75th percentiles of the US growth reference. The mean height for age and weight for age, however, were slightly less than the median of the reference population. For different age groups, the mean height ranged from 0.2 to 2.1 cm and the mean weight ranged from 0.1 to 1.1 kg less than the reference median. The largest height difference was observed at 1 to 3 years of age and may be partly the result of intrinsic irregularities in the US growth reference at those ages. By 10 years of age, children from The Farm averaged 0.7 cm and 1.1 kg less than the reference median, representing only 0.1 and 0.3 SD from the reference. Thus, these children have adequate attained growth, even though it was modestly less than that of the reference population.

Adult↗