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Biomedical subjects

M Cook

Publications and source records attributed to M Cook.

At least 91 records · Page 5Linked to original sources
PubMed1984

Relation between simultaneous spatial-discrimination thresholds and luminance in man.

Simultaneous spatial-discrimination thresholds of 6 human subjects were measured at luminances between 0.2 and 2000 cd/m2. Subjects were tested on a forced-choice discrimination task which required them to distinguish between test and control stimuli of high contrast square-wave gratings with similar space-average luminances. The form of the function depicting the relationship between acuity and luminance is similar to that obtained by other researchers. The estimated maximum acuity of 72 cycles/degree (c/deg) is higher than the commonly cited value of 60 c/deg and this is probably due to the combination of the high stimulus luminance and the psychophysical technique employed in this study.

Adult↗
PubMed1984

Representational drawings of solid objects by young children.

Two groups of children aged 6 and 8 years were given three tasks requiring graphical representations of solid geometric forms. These tasks were drawing from life models, copying from photographs, and copying from line drawings of these objects. Performance was assessed on the basis of level of approximation to correct perspective. Older children used more perspective features than younger children in their drawings. At all ages, the drawings from life were most difficult. Results on the two copying tasks were not consistent. Drawings made by copying photographs were either as advanced as or poorer than copies of line drawings. The results are explained in terms of the difficulties exhibited by young children in translating the three-dimensional scene to a two-dimensional picture plane and strategies adopted by them to cope with these problems.

Art↗
PubMed1983

The subcellular location of isozymes of NADP-isocitrate dehydrogenase in tissues from pig, ox and rat.

Antibodies against purified NADP-isocitrate dehydrogenase from pig liver cytosol and pig heart were raised in rabbits. The purified enzymes from these sources are different proteins, as demonstrated by differences in electrophoretic mobility and absence of crossreactivity by immunotitration and immunodiffusion. The NADP-isocitrate dehydrogenase in the soluble supernatant homogenate fraction from pig liver, kidney cortex, brain and erythrocyte hemolyzate was identical with the purified enzyme from pig liver cytosol, as determined by electrophoretic mobility and immunological techniques. The enzyme in extracts of mitochondria from pig heart, kidney, liver and brain was identical with the purified pig heart enzyme by the same criteria. However, the 'mitochondrial' isozyme was the major component also in the soluble supernatant fraction of pig heart homogenate. The 'cytosolic' isozyme accounted for only 1-2% of total NADP-isocitrate dehydrogenase in pig heart, as determined by separation of the isozymes with agarose gel electrophoresis and immunotitration. The mitochondrial isozyme was also the predominant NADP-isocitrate dehydrogenase in porcine skeletal muscle. The ratio of cytosolic/mitochondrial isozyme for porcine whole tissue extract, determined by immunotitration, was about 2 for liver and 1 for kidney cortex and brain. The distribution of isozymes in cell homogenate fractions from ox and rat tissues corresponded to that observed in organs of porcine origin. The mitochondrial and cytosolic isozymes from ox and rat tissues exhibited crossreactivity with the antibodies against the pig heart and pig liver cytosol enzyme, respectively, and the electrophoretic migration patterns were similar qualitatively to those found for the isozymes in porcine tissues. Nevertheless, there were species specific differences in the characteristics of each of the corresponding isozymes. NAD-isocitrate dehydrogenase was not inhibited by the antibodies, confirming that the protein is distinct from that of either isozyme of NADP-isocitrate dehydrogenase.

Animals↗
PubMed1982

The ability to see solid form in early infancy.

The perception of three-dimensional attributes of solid objects by twelve-week-old infants was studied. In the first experiment the rates of habituation of fixation to a cube in a fixed orientation, to one which changed in orientation between presentations, and to a sequence of photographs of cubes in different orientations were determined. Habituation rate was also determined for a photograph of a cube in a fixed orientation. No difference was found between the initial fixation times for solids and photographs, or between the habituation curves for the solids in fixed and varying orientation. For the photographs habituation was much greater for the fixed orientation than the varying orientation condition. These data were interpreted as providing strong evidence that the infants were responding to the stimuli on the basis of their three-dimensional attributes. In the second experiment the same discriminations were examined by a recovery-from-habituation technique. One group was habituated to a cube in a fixed orientation and tested for recovery of fixation to a new orientation. A second group was habituated to a photograph of a cube in a single orientation and tested for recovery to a photograph of a new orientation. Both groups showed recovery and the recovery was the same for both conditions. These data demonstrated that the subjects were, after all, capable of discriminating between different orientations of a solid cube, and they provided no further evidence that the infants were perceiving three-dimensional attributes of the stimuli.

Depth Perception↗
PubMed1982

Radiographic studies on bone in beagles subjected to low levels of dietary lead since birth.

This experiment studies the effects of low-level oral lead administration on bone in standardized colony-raised research male Beagles. Lead was administered to lactating mothers from parturition through weaning and directly to the pups thereafter. Results of bone radiographic morphometric and bone radiographic densitometric findings in five experimental and four control animals are reported. Total femoral length, and femoral diaphysal width, combined with cortical thickness, thickness/width ratio, and radiographic photodensitometry did not vary significantly between both groups, although bone lead and blood lead levels were significantly higher in the experimental group.

Absorptiometry, Photon↗
PubMed1982

Radiographic morphometry and radiographic photodensitometry of the femur in the Beagle at 13 and 21 months.

A study was made of x-ray morphometry and x-ray photodensitometry of bones of 2 small groups of healthy standardized colony-raised male research Beagles, ages 13 and 21 months. The morphometry and photodensitometry results were correlated to other variables of interest. The total width of the femur and its optical density to x-rays increased significantly with age and body weight, but not so the length of the femur nor the combined cortical thickness (CCT). This last measurement (CCT) did not increase in parallel with the whole length of the bone either. The CCT/width ratio decreased as body weight increased. The clear-cut increase in the optical density of the whole bone is therefore explained by the age-related variations in bone envelope activity.

Absorptiometry, Photon↗
PubMed1981

Anhedonia and schizophrenia.

Data from Chapman's anhedonia and perceptual aberration scales are presented for groups of schizophrenics and hospital staff control subjects. Differences between the two groups are found for both anhedonia scales and for the perceptual aberration scale, but the difference for physical anhedonia is only marginally significant. The anhedonia scales do not differentiate between the two groups sufficiently well to be useful diagnostically.

Adult↗
PubMed1979

Attentional deficit in the siblings of schizophrenics.

A study of attentional deficit in the relatives of schizophrenics and in a matched control group is reported, in which the relatives are found to have poorer scores on a vigilance test and on a choice reaction time test. It is concluded that this deficit points to one of the primary symptoms of schizoprenia, and suggestions for further research are made.

Adolescent↗
PubMed1979

Gaze patterns of mentally retarded adults in two contrasting environments.

Two matched samples of mentally retarded adults were video recorded on two occasions, before and after one group was transferred to a different type of hospital, and their gaze patterns analyzed. Overall, only slight changes after transfer were found, but analysis according to amount of looking at the interviewer on the first occasion showed that those transferred subjects who initially looked little of the time significantly increased their amount of looking after transfer. Some correlations with the Adaptive Behavior Scale were also reported.

Adult↗
PubMed1978

The perception of solid form in early infancy.

Day and McKenzie determined the rate of habituation of fixation of young infants to repeated visual presentations of a cube. They found the habituation rate to be the same when the stimulus orientation changed between presentations as when it was fixed, and they interpreted this as evidence of shape constancy. However, a failure to discriminate between cubes in different orientations is only evidence of shape constancy if the infant can at the same time discriminate the cube from other cubelike forms. The experiment described here contrasted the rate of habituation of fixation of 12-week-old infants to a homogenous stimulus series (a cube presented in different orientations) with the rates of habituation to various heterogeneous series, in each of which a cube was alternated with some other solid. It was found that, while the infant could distinguish a cube from a photograph of a cube and a concave solid (an L-form), there was no evidence of discrimination between the cube and either a wedge or a truncated pyramid. The results imply limits to the young infants capacity to resolve solid form.

Discrimination Learning↗