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Biomedical subjects

H R Wilson

Publications and source records attributed to H R Wilson.

At least 145 records · Page 8Linked to original sources
PubMed1983

Spatial frequency tuning of orientation selective units estimated by oblique masking.

Threshold elevations were measured as a function of the spatial frequency of high contrast cosine masks using spatially localized test stimuli with a 1.0 octave bandwidth. The cosine masks were oriented at 14.5 degrees relative to the vertical test patterns in order to average out spatial phase effects. The experiment was repeated for each of 14 test frequencies spanning the range 0.25-22.0 c/deg in 0.5 octave steps. The resulting threshold elevation curves fell into a small number of distinct groups, suggesting the existence of discrete spatial frequency mechanisms in human central vision. The data are shown to be consistent with a model having just six distinct classes of spatial frequency mechanisms in the fovea. Spatial frequency bandwidths of these mechanisms ranged from 2.5 octaves at low frequencies to as narrow as 1.25 octaves at high spatial frequencies. These results require revision of the Wilson and Bergen (1979) [Vision Res. 19, 19-32] model for spatial vision.

Form Perception↗
PubMed1983

Shifts in perceived size due to masking.

It has been suggested that perceived size depends upon the distribution of responses among a localized population of different size-tuned mechanisms. If so, then spatial frequency masking, which alters the distribution of responses, should produce shifts in a test pattern's perceived size. We have found this to be the case. The magnitude and direction of the shifts depend only on the frequency difference in octaves (delta omega) between mask and standard. The results are not antisymmetric about the point delta omega = 0, however, as they would be if perceived size were based purely on local size-tuning properties. Our results suggest that size perception depends both on these local properties and on the spatial distribution of mechanism responses.

Adaptation, Ocular↗
PubMed1983

Spatial-frequency adaptation affects spatial-probability summation.

The effects of spatial-frequency adaptation on spatial-probability summation were investigated by two techniques: the measurement of the dependence of cosine grating sensitivity on the number of cycles presented and the determination of the frequency-of-seeing curve for a cosine grating. Both measurements indicate that the contribution of spatial-probability summation to adapted grating thresholds is reduced in comparison with unadapted conditions. This reduction in the effects of spatial-probability summation, together with the decrease in local sensitivity, which depends on the spatial inhomogeneity of the visual system, is sufficient to account for the threshold elevation aftereffect measured when adapting and testing with cosine gratings.

Adaptation, Ocular↗
PubMed1983

Sodium chloride for broiler breeders.

Two experiments, each of 224 days duration, were conducted with Cobb broiler breeders, 32 weeks of age, to determine their response to supplemental dietary sodium chloride levels ranging from .12 to .48% in a corn-soybean meal diet. Average hen-day egg production, daily feed intake, feed required per dozen eggs, and egg specific gravity were not significantly influenced by any level of supplemental sodium chloride. Egg weights from hens receiving .36% sodium chloride were significantly heavier than those of birds that consumed .12 and .24% sodium chloride but not those of the .18 and .48% sodium chloride treatments. Egg fertility was significantly depressed by .48% sodium chloride and numerically reduced by .36%. Hatchability of fertile eggs was not found to be affected, but overall hatchability of eggs from .36 and .48% supplemental sodium chloride treatments was significantly lower than that supported by the least sodium chloride level provided, .12%. These data indicate that current National Research Council (1977) sodium requirements for heavy breeders (200 mg/day) may provide at least 23% more sodium than is required (less than or equal to 154 mg/day) and that daily sodium intakes in the range of 320 to 420 mg may reduce fertility in broiler breeders.

Animals↗
PubMed1983

Choline supplementation in the diets of aged White Leghorn hens grouped according to body weight.

A randomized block design experiment was conducted to determine if aged layers require supplemental choline when fed practical corn-soy diets adequate in methionine. Hisex hens (50 weeks old) were divided into four body weight groups containing 120 hens each. Six experimental treatments were prepared by addition of choline to a corn-soy basal diet at 0, 55, 110, 220, 440, and 880 mg/kg of diet. Each diet was fed to four replicates of 5 hens each within each body weight group. The nutrient content in the basal diet formulated for each body weight group was adjusted depending on daily feed intake. The experiment was conducted for four 28-day periods (January 21 to May 13). Hen-day egg production, feed conversion, egg specific gravity, and egg weight did not differ significantly for any level of choline supplementation. Liver lipid content was significantly different at no supplemental choline in extra heavy birds. Results of this experiment support the conclusion that, regardless of body weight, aged laying hens required very little, if any, supplemental choline when they are fed a corn-soy practical diet containing adequate methionine.

Animals↗
PubMed1983

Restricted feeding of broiler breeders.

Two experiments were conducted to compare the effects of various feed restriction programs during the growing and laying periods on body weight, egg production, fertility, and hatchability. In the first experiment, Cobb color-sexed broiler breeders were fed one of three grower programs (full feed, skip-a-day, or low protein) from 8 to 24 weeks of age. Two layer programs (full feed and restricted) were fed from 24 to 67 weeks of age. Overall the skip-a-day grower treatment gave the best results of the programs tested. This treatment resulted in the significantly lowest body weights, greatest delay in sexual maturity, and highest egg production and fertility. The restricted layer treatment resulted in lower body weight, delayed sexual maturity, lower egg production during the colder months, and higher fertility and hatchability of fertile eggs. In the second experiment, Cobb color-sexed broiler breeders were fed one of three skip-a-day grower treatments (control or breeder's recommendations, control minus 10%, control minus 20%) from 8 to 24 weeks of age. Two layer programs (full feed and restricted) were fed from 24 to 51 weeks of age. Overall, the control minus 20% treatment resulted in significantly delayed sexual maturity and significantly decreased body weight. The restricted layer treatment also significantly delayed sexual maturity and decreased body weight.

Animals↗
PubMed1983

Effect of high levels of Larvadex on reproduction in Leghorn breeders.

The insect growth inhibitor, Larvadex, was fed to egg type breeder hens for 8 weeks at levels of 0, 50, 100, 500, 1000, and 2000 ppm and to the same strain of males at 0 and 2000 ppm. All birds were kept in individual cages. Fertility was determined following artificial insemination. Egg production was significantly increased in Experiment 1 but numerically decreased in Experiment 2 by feeding 1000 ppm Larvadex. Feeding 2000 ppm significantly decreased egg production in both experiments. Egg weight was highest at 100 ppm and decreased with higher treatment levels. Specific gravity of eggs was improved with all Larvadex treatments. Fertility was not affected by treatment of females or males. Hatchability was reduced by the 1000 and 2000 ppm levels in the hen's diet. Semen quality was not significantly affected by feeding Larvadex at 2000 ppm.

Animals↗
PubMed1983

Improved performance of turkey hens from the addition of dietary fat.

An experiment was conducted to determine the influence of added fat on the performance of large turkey hens. The addition of 4% animal fat to the diet significantly increased energy consumption and increased egg production. A numerical decrease in feed consumption and significant increase in egg production were obtained by increasing added fat from 4 to 8%. Added fat did not influence specific gravity or fertility and hatchability of fertile eggs.

Animals↗
PubMed1983

Performance of broiler breeders on different feeding systems.

Two experiments were conducted in which broiler breeders were fed either at 0800, 1300, 1600 hr, ad libitum, or at 1300 hr followed by a calcium-phosphorus (Ca-P) supplement 3 hr later. The Ca-P supplement was 10.6 g/bird/day of pellets containing 5.2% P and 21.0% Ca. Experiment 1 was conducted with 64-week-old hens from July 27 to August 23. Experiment 2 was conducted with 32-week-old hens from November 5 to January 27. The birds that were fed at 1300 hr followed by Ca-P pellets at 1600 hr and those fed at 1600 hr laid eggs with higher specific gravity than did the birds fed at 0800 hr, 1300 hr, or ad libitum. The ad libitum-fed birds laid eggs with the lowest specific gravity. There were no significant differences in fertility or hatchability of fertile eggs attributed to different feeding times, although ad libitum-fed birds had lower fertility and hatchability. However, egg production was significantly higher for hens fed at 1300 hr with Ca-P pellets at 1600 hr than for birds fed ad libitum in Experiment 1. In Experiment 2, ad libitum-fed birds had significantly higher egg production than birds fed at 1300 hr. However, there were no significant differences in egg production among birds fed at different times.

Animals↗
PubMed1983

Chloride requirement of the turkey breeder hen.

Two experiments were conducted to determine the chloride requirement of Nicholas Large White Turkey hens fed a corn soybean meal diet. No supplemental chloride over the .03% in the basal diet and 20 ppm in the water was required for maximum egg production, fertility, or hatchability. Supplemental chloride at .09% was necessary for maximum specific gravity.

Animals↗
PubMed1982

Localized effects of spatial frequency adaptation.

The spatially localized threshold-elevation aftereffect of spatial-frequency adaptation was measured by using localized, aperiodic test patterns that have bandpass Fourier transforms. At a given retinal location, the threshold-elevation curves are consistent with the fatigue of size-turned mechanisms with center-surround sensitivity profile. Only a few different sizes of such mechanisms were required to fit the local results. The local aftereffect was also measured as a function of eccentricity near the fovea. The results indicate that the threshold-elevation aftereffect of spatial-frequency adaptation is not spatially homogeneous.

Adaptation, Ocular↗
PubMed1981

Synthesis and antischistosomal activity of certain pyrazolo[1,5-a]pyrimidines.

Several 7-hydroxypyrazolo[1,5-a]pyrimidines (1-21), 7-mercaptopyrazolo[1,5-a]pyrimidines (37-49), and 4-alkylpyrazolo[1,5-a]pyrimidin-7-ones (50-55) and the corresponding 4-alkylpyrazolo[1,5-a]pyrimidine-7-thiones (56-60) were synthesized and tested for antischistosomal activity against Schistosoma mansoni. Of the compounds examined, the greatest degree of activity in vitro was found with the 7-mercaptopyrazolo[1,5-a]pyrimidines. In particular, compounds 37 and 47 proved lethal at 100 micrograms/mL after an exposure of only 1 h. The 7-hydroxypyrazolo[1,5-a]-pyrimidines were not as active. None of the compounds exhibiting in vitro activity were active against S. mansoni in vivo.

Animals↗
PubMed1981

Susceptibility of various poultry species to dietary aflatoxin.

1. The relative sensitivities of broiler chicks, White Leghorn chicks, quail chicks, goslings and turkey poults to increasing dietary contents of aflatoxin from 1 to 21 d of age were determined. Aflatoxin was included in the diets at three concentrations (0.7, 1.4 and 2.1 mg aflatoxin B1 equivalents/kg). 2. Data were analysed for species differences in food consumption, body weight, food utilisation, mortality and liver pathology. 3. There were no significant effects of aflatoxin in broiler and Leghorn chicks. Aflatoxin at 0.7 mg/kg decreased the body weight of turkey poults but tended to increase the growth rate of goslings. At 1.4 mg aflatoxin/kg food consumption, body weight and weight gain of goslings were adversely affected. 4. Liver damage occurred in goslings and quail chicks at all inclusions of aflatoxin and was extensive at 2.1 mg/kg. 5. Poults and goslings appeared to be the most sensitive, quail were intermediate and domestic chicks were most resistant.

Aflatoxins↗
PubMed1981

The performance of Bobwhite quail fed diets containing Lactobacilli.

Two experiments were conducted each consisting of two trials. Day-old Bobwhite quail were fed a starter diet containing a microbial preparation of Lactobacilli. In both experiments the experimental diets were fed for 5 weeks. No significant differences in growth, feed efficiency, or mortality were found between the control and Lactobacilli supplemented diets. Mortality was higher than normal within all treatments but unaffected by treatment.

Animal Feed↗
PubMed1980

A transducer function for threshold and suprathreshold human vision.

A nonlinear function is derived to describe the contrast transduction process for human visual mechanisms. This function is sigmoid in form, having an accelerating nonlinearity at low contrasts and a compressive nonlinearity at high contrasts. The resulting formulation is consistent with both signal detection theory and with Quick's (1974) equation for probability summation. Similarities between the present description of human vision and properties of complex cells in cat visual cortex are noted.

Animals↗