Search PubMed⌕ Search

Biomedical subjects

B Wallace

Publications and source records attributed to B Wallace.

At least 127 records · Page 7Linked to original sources
PubMed1977

Stability of Wilkinson's linear model of prism adaptation over time for various targets.

Prism adaptation as measured by negative aftereffects (NA), proprioceptive shifts (PS), and visual shifts (VS) was assessed as a function of amount of exposure time and target specificity, whether an exposure and a test target background were the same or different, to determine the validity of Wilkinson's linear model (NA = PS + VS). With few exceptions the model was found to hold well up to 40 min of prism viewing regardless of type of exposure background. In addition target specificity affected magnitude of the NA component of adapation but not the PS and the VS components.

Adaptation, Ocular↗
PubMed1977

Computerized hematology: operation of a high-volume hematology laboratory.

Operation of automated hematology testing, on-line to a laboratory-dedicated computer, is described. The computer stores, retrieves and monitors the results of two Model S Sr. Coulter Counters, three Technicon platelet counters, one Electra 600-D, and six leukocyte differential consoles, which are interphased to the computer. All other hematology tests are batch-entered via the keyboard of cathode-ray tubes. The computer generates specimen labels, worksheets, and lists of incomplete tests, monitors all on-line instruments, and performs all the calculations used in the procedures of quality control. Results are available instantaneously on cathod-ray tubes strategically located in patient-related areas throughout the institution. These can be obtained as all of the results for a given day or as cumulative summaries or histogram-type plots of results for a given day.

Autoanalysis↗
PubMed1977

An analysis of motor coordination components for various localization tasks.

Localization abilities of subjects in three perceptual-motor tasks were considered before and after an exposure to a visual distortion. During this distortion the subject observed his hand ballistically point to an invisible but audible target while either receiving or not receiving knowledge of results (KR) concerning pointing accuracy. Also, subjects either received a 1- or a 4-sec rest period between each of 30 exposure ballistic pointing actions. The pre- and postexposure tasks involved the ability of a subject to accurately point to an occluded and stationary auditory target, to point to the straight-ahead position in space, and to indicate when a moving, auditory target was perceived as being in the straight-ahead position. For these tasks, the pre- vs. postexposure localization difference scores are referred to as the negative aftereffect, the proprioceptive shift, and the auditory shift, respectively. Wilkinson's (1971) two-component additive model (negative aftereffect = proprioceptive shift plus auditory shift) held when KR was given regardless of amount of rest between exposure pointing responses. With a 4-sec rest and no KR, the relationship between coordination components was nonadditive (negative aftereffect greater than proprioceptive shift plus auditory shift).

Journal Article↗
PubMed1976

On inverted repeat sequences in chromosomal DNA.

It is suggested that chromosomal DNA should contain a class of palindromic reverse repeats, comparable in number to that of genes themselves, which are formed as follows:(1) a transcription-termination signal that follows the gene plus (on the complementary strand and located as near to the "anti-gene" as possible); (2) a second termination signal which actively prevents the accidental transcription of the anti-gene. Thus, the adjacent termination-anti-termination region of one strand would complement the anti-termination-termination region of the other.

Chromosome Inversion↗
PubMed1976

Investigation of the organization of mammalian chromosomes at the DNA sequence level.

New developments in DNA sequencing techniques permit rapid progress in the determination of both repetitious and single-copy mammalian sequences. Three distinct families of highly repetitious satellite DNA's from the kangaroo rat Dipodomys ordii have been sequenced. With the MS satellite it was possible to show that the basic repeat sequence and its variants were arranged in a nonrandom order suggesting a hierarchy of repeats. The HS-alpha satellite from D. ordii was shown to resemble the guinea pig alpha satellite, a long term evolutionary persistence inconsistent with previous models. Sequences from hemoglobin mRNA were determined using hemoglobin complementary DNA as template for transcription in vitro. Seven of the largest fragments have been assigned to untranslated regions of the mRNA whereas 15 others have been tentatively located within the structural genes. From correlations with sequences from corresponding regions in the human hemoglobin mRNA's we have been able to make the first direct measurements of the rate of fixation of mutations that do not change the amino acid sequence. The minimum estimate for this rate is greater than the highest previously estimated rates of fixation of neutral mutations (calculated for fibrinopeptide A. A new technique, deoxysubstitution sequencing, which should speed determination of the complete mRNA sequences, is described.

Animals↗
PubMed1975

Apparent reversals for circular and elliptical stimuli.

Number of apparent reversals for various patterned ellipses and circles was investigated. Ellipses produced significantly more reversals than circles. Patterned stimuli produced a number of reversals dependent upon pattern orientation and corroborated predictions consistent with Power and Day's (1973) general constancy theory for apparent reversals.

Form Perception↗
PubMed1975

Outflow theory and autokinetic movement: color, viewing angle, and dark adaptation.

The number of reported changes in direction of autokinetic movement was assessed as a function of color of the light that served as stimulus, viewing angle (0, 30, or 60 deg of displacement from straight ahead), and dark adaptation. Color and dark adaptation had no significant main effect on the number of reported changes in direction for the red and yellow lights, but viewing angle was inversely related to the number of reported changes. For the blue-green light, atypical effects of viewing angle and dark adaptation were found.

Color Perception↗
PubMed1974

On the structure of gene control regions.

A model emphasizing the possible genetic role of tandem duplications of reverse repeats has been developed as an extension of Crick's (1971) general model for the chromosomes of higher organisms. Although developed initially (1) to explain why random differences in the control regions of individual gene loci might confer a selective advantage on heterozygous individuals as well as (2) to offer the species a means by which such differences might be effected without mutational harm, it seems that control regions built on a foundation of tandemly duplicated reverse repeats would exhibit many properties previously observed in studies on mutable loci in various organisms.

Alleles↗