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Biomedical subjects

R D Hall

Publications and source records attributed to R D Hall.

At least 55 records · Page 3Linked to original sources
PubMed1986

Evaluation of the control of Myobia musculi infestations on laboratory mice with permethrin.

The efficacy of permethrin against Myobia musculi (Schrank) (Acari:Myobiidae) infestations on mice was evaluated using four different dose delivery methods. In all methods, an attempt was made to deliver 0.5 mg of active permethrin weekly to each mouse. Successful control was achieved with topical or environmental treatment with 0.25% permethrin dust and by dipping the mice into a 0.6 g/l permethrin emulsion. The use of an emulsion applied to the bedding produced the least satisfactory control. Untreated mice had an average infestation rate of 57.3% throughout the study. No significant differences were seen between treated and untreated groups in either body weight or histopathology of the liver, lung, or kidney.

Animals↗
PubMed1985

Activation of nonspecific lipase (EC 3.1.1.-) by bile salts.

The enzyme nonspecific lipase (EC 3.1.1.-) from rat pancreas has been isolated and its amino acid composition determined. The amino acid composition confirms more indirect evidence that nonspecific lipase is not the same enzyme as cholesteryl ester hydrolase. Activation of the enzymatic activity by bile salts has been studied by equilibrium dialysis, gel filtration, light scattering, circular dichroism and fluorescence polarization. The binding of bile salt by the enzyme is saturable and is associated with a conformational change. Upon binding cholate, the protein experiences a decrease in beta-structure with no significant change in alpha-helix content, an increase in apparent Stokes radius, a decrease in light scattering properties, and a slight decrease in polarization of the intrinsic tryptophan fluorescence. Attachment of bile salt is associated with decreased reactivity of essential sulfhydryl groups, but no detectable change in reactivity of amino groups. A change to a more nearly spherical shape upon binding bile salt would be consistent with the experimental observations, but the exact sites of binding remain uncertain.

Amino Acids↗
PubMed1984

The role of body size in climbing and locomotor behavior of protein-malnourished and well-nourished rats.

Behavioral comparisons of malnourished and well-nourished rats often involve animals of different sizes--even after rehabilitation of malnourished animals. The role of body size in two kinds of behavior affected by early malnutrition was investigated. Rats subjected to protein restriction during the preweaning period (LH) or during the pre- and postweaning periods (LL) climbed more than well-nourished rats (HH) at the ages of 35-225 days. This difference reflected differences in body weight; at comparable body weights LH and LL rats climbed no more than HH rats. Females climbed more than males, which also reflected differences in size, but decreases with age did not depend entirely on growth. LH rats were more active in running wheels than HH rats. For both LH and LL rats, the overall changes with diet and age resembled those in climbing, except that the effects of sex, but not age, were partly independent of size.

Age Factors↗
PubMed1984

Acoustic startle responses of protein malnourished rats.

Acoustic startle responses were measured as part of a systematic attempt to determine if early protein malnutrition leads to a general hyperreactivity to aversive stimulation. In Experiment 1 startle responses transduced by floor movements were not reliably influenced by protein restriction in the preweaning or postweaning periods. The magnitude of the startle response, however, was positively correlated with body weight, partly as a consequence of the transduction method. Thus, differences in body weight might have obscured diet-related differences in startle amplitude. In Experiment 2 startles were recorded as electromyographic responses of the neck muscles and were larger in rats fed the low protein diet postweaning, especially in rats switched from high to low protein conditions at weaning. There was no indication that rats subjected to preweaning protein malnutrition were hyperreactive to aversive stimulation. In Experiment 1 it was also found that mean startle amplitudes were larger in young adults, 60 or 90 days old, than in 35-day-old rats, partly because there was less habituation in the adults.

Age Factors↗
PubMed1984

A new in-cage treatment system for control of northern fowl mites on laying hens.

Commercially available plastic and other types of flexible tubing were tested to determine their relative permeability to an emulsifiable concentrate (EC) of permethrin acaricide. Bioassays employing northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), indicated that .3 mg permethrin/cm2 surface area penetrated vinyl plastic tubing that had been filled with 42.5% active ingredient EC for 14 days. Vinyl tubing circuits were installed in wire poultry cages, either in the form of suspended loops or woven through the rear cage wall, and permethrin EC was introduced by means of a small pump. Significant reductions in northern fowl mite populations on hens caged therein were apparent after 48 days posttreatment. This approach has merit as a long-term, labor-economical form of mite control on caged poultry.

Animals↗
PubMed1983

Is hippocampal function in the adult rat impaired by early protein or protein-calorie deficiencies?

Much of the development of the rat's hippocampal formation occurs postnatally, which suggests that this structure, like the cerebellum, may be especially vulnerable to early postnatal malnutrition. Radial-maze performance and spontaneous alternation, two kinds of behavior requiring the integrity of the hippocampus, were assessed to determine whether hippocampal function in the adult rat is impaired as a result of protein restriction in either the preweaning, the postweaning or both stages of development. In three experiments the performance of protein-malnourished rats in 8- and 12-arm mazes did not differ significantly from that of well-nourished rats. In a fourth experiment levels of spontaneous alternation in protein-malnourished rats were like those of normal well-nourished animals. Thus, the present experiments provide no evidence that hippocampal function is impaired as a consequence of early protein deprivation. For the most part, a critical review of earlier studied of undernourished rats supports a similar conclusion.

Animals↗
PubMed1983

Hyposensitivity to serotonergic stimulation in protein malnourished rats.

Rats subjected to early protein malnutrition have higher levels of brain serotonin (5-HT) than well-nourished rats. In the present study we asked whether the elevated 5-HT levels of associated with any changes in sensitivity to serotonergic stimulation. In four different behavioral tets the effects of the 5-HT agonist N,N-dimethyltryptamine (DMT) were, with only a few exceptions, smaller in rats malnourished during both pre- and postweaning stages of development or during just one period or the other. In Experiment 1 the 5-HT syndrome induced by DMT was weaker in malnourished rats than in well-nourished ones. In Experiments 2 and 3, DMT was not a disruptive to malnourished rats in two motor tasks, rotating rod and treadmill, as it was to rats reared under high protein conditions. In Experiment 4 reductions in acoustic startle amplitudes induced by DMT were not as large in malnourished as in well-nourished rats. The hyposensitivity to DMt in protein malnourished rats may reflect a diminished sensitivity of 5-HT receptors resulting from the abnormally high levels of the neurotransmitter.

Animals↗
PubMed1983

Olfactory bulbectomy impairs the rat's radial-maze behavior.

Previous studies had shown that transection of the lateral olfactory tracts and lesions of the septohippocampal system were similar in the deficits they engendered in nest building and food piling or hoarding by hamsters. The present investigation asked whether olfactory lesions would also produce deficits in radial-maze behavior like those associated with septo-hippocampal lesions. Radical olfactory bulbectomy led to a marked deterioration in preoperatively trained behavior in an 8-arm radial maze. The behavioral changes resembled those resulting from septo-hippocampal lesions in three ways: (1) There were fewer choices of adjacent arms and more choices of more distant arms. (2) Choice accuracy as a function of successive choices within a trial declined more rapidly. (3) The probability of repeating choice sequences was abnormally high. Earlier studies had shown that the rat does not require olfactory cues to perform efficiently in radial mazes. It therefore seems likely that the deficits described here resulted from the disruption of interconnections between the olfactory and septo-hippocampal systems rather than from the loss of olfactory sensitivity.

Animals↗
PubMed1983

Comparative efficacy of plastic strips impregnated with permethrin and permethrin dust for northern fowl mite control on caged laying hens.

Established populations of northern fowl mites, Ornitonyssus sylviarum (Canestrini and Fanzago), on caged laying hens were effectively controlled within 77 days by application of two plastic strips impregnated with permethrin per cage. Such strips contained 9.6% active ingredient (wt/wt), were ca. 20.5-cm long, and were affixed to the top cage wires. Use of only one strip per cage resulted in less control, approximating that obtained with .25% permethrin dust. Egg mass, expressed as gram egg per hen per day, was significantly greater in all treated groups.

Administration, Topical↗
PubMed1981

Erythrocyte protoporphyrin levels in Aotus trivirgatus.

High levels of the heme precursor, protoporphyrin, were found in a sample of 36 Aotus trivirgatus. The owl monkeys were of five different karyotypes and from three separate colonies. In many animals, a significant proportion of the protoporphyrin was not bound to zinc, as is normal, but existed as the free base protoporphyrin IX. The protoporphyrinemia may be related to major pathologies of captive Aotus.

Anemia, Hemolytic↗
PubMed1981

Application phenomena and efficacy of concentrated acaricide dusts for northern fowl mite control on caged laying hens.

Fluorescent pigments were used to measure plumage coverage when caged laying hens were dusted for northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), control. Carriage type electrostatic or high velocity backpack equipment produced superior coverage 2 hr posttreatment when the rates of 454 g (1 lb) dust per 100 or 500 hens was employed. A redistribution of dust was noted 48 hr posttreatment, and a subsequent experiment demonstrated that this phenomenon resulted from intracage cross contamination dependent upon bird caging density. Carbaryl 80% wettable powder (WP) at 454 g/1600 hens and tetrachlorvinphos 50% WP at 454 g/1000 hens provided northern fowl mite control for 11 and 5 weeks posttreatment, respectively.

Animals↗
PubMed1980

Comparative evaluation of four registered acaricides for field control of northern fowl mites on caged laying hens.

Carbaryl and tetrachlorvinphos provided longer lasting control of northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), than did coumaphos or malathion when the materials were applied to caged laying hens as aqueous sprays. The average duration of residual control was ca. 5 weeks for carbaryl, 4.3 weeks for tetrachlorvinphos, 3.5 weeks for coumaphos, and 2 weeks for malathion. No presumptive evidence of northern fowl mite resistance to carbaryl or tetrachlorvinphos was encountered. In contrast, malathion often failed to produce satisfactory control, and difficulty with adequate dispersion of coumaphos wettable powder was noted.

Animals↗