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Biomedical subjects

D R Justesen

Publications and source records attributed to D R Justesen.

At least 19 recordsLinked to original sources
PubMed1985

Ototoxicity of intraventricularly administered gentamicin in adult rabbits.

To determine whether daily intraventricular injection of gentamicin sulfate is ototoxic, adult male rabbits were given 0.2 ml of saline (group 1; n = 8) or 0.25 mg/kg of gentamicin sulfate in 0.2 ml of saline (group 2; n = 7) by intraventricular infusion once a day for 21 d. All rabbits were also given intramuscular gentamicin sulfate, 2 mg/kg, twice daily. Before and after antibiotic treatment, brainstem auditory evoked responses (BAERs) were recorded. During the experimental period, neurologic examinations were performed on all rabbits. After treatment, the animals were euthanized; brain tissue and cochleas were then removed for histopathologic examination. The ratios of neurologic abnormalities observed in group 1 and 2 animals, respectively, were 0/8 and 5/7; of abnormal BAERs, 0/8 and 5/7; of abnormal brain morphology, 2/5 and 6/6; and of abnormal cochlear morphology, 0/6 and 7/7. The electrophysiologic evidence of auditory deficit and the structural evidence of ototoxic insult are significantly associated (p less than or equal to 0.006) with intraventricularly administered gentamicin sulfate. These data suggest that intraventricular gentamicin should be used with caution.

Animals↗
PubMed1977

Limits to conceptual rule-learing by schizophrenic patients.

Two studies of conceptual rule-learning by 36 hospitalized psychiatric patients revealed that (a) while all were clinically diagnosed as schizophrenic, they differed widely in their ability to discover abstract rules; (b) the Whitaker Index of Schizophrenic Thinking (WIST) strongly predicted the patients' ability to learn and to apply a conceptual rule; and (c) regardless of severity of conceptual impairment, the patients were unaffected by modest levels of externally generated irrelevant information as presented through the modality of vision. Deficits in abstractive ability, when they exist, are believed to be due to a schizophrenic patient's inability to prevent task-irrelevant information that originates in long-term memory from spilling into and despoiling the operations of working memory.

Adult↗
PubMed1975

Teratology, survival, and reversal learning after fetal irradiation of mice by 2450-MHz microwave energy.

In the first of two factorially designed studies, 80 primigravid mice of the C3H-HeJ strain were subjected to 2450-MHz sinusoidally modulated microwave radiation or to sham radiation (with or without an accompanying injection of 5 mg of cortisone as a teratological marker) on the 11th, 12th, 13th or 14th day of gestation. The radiation treatment consisted of a single intense dosing of microwave energy (38 mW/g for 600 sec.= 22.8 J/g) in a multi-mode cavity. On the 19th day of gestation fetuses were taken via Caesarean section and were observed for gross structural abnormalities. While radiation of dams failed reliably to increase the incidence of fetal mortality or morbidity above that of controls, the dams treated with cortisone gave birth to reliably greater numbers of stillborn and deformed fetuses. In the second experiment and during their 14th day of gestation 60 primigravid mice received the radiation of sham-radiation treatment, half with, half without, the accompanying injection of cortisone. A virtually complete failure to survive to weaning characterized the pups born of the sham-radiated cortisone-treated group of dams, but the incidence of cortisone-induced mortality was reliably reduced in pups whose dams were also radiated by microwave energy. Pups sampled from all but the depleted group were observed later as young adults for competency in mastering a series of reversal habits in a water maze. No differences in maze performances were observed in the mice as a function of their placement in the control or the radiation condition, but offspring of cortisone-treated, radiated dams made reliably more errors. Careful measurement of elevations of colonic temperatures of radiated dams shortly after treatment with cortisone revealed an averaged deltaT that is close to that observed in a comparably radiated volume of water of equivalent mass. If the finding has generality beyond the gravid mouse-it, that is, cortisone effectively and reversibly renders the mammal ectothermic-an important advance in biological dosimetry of non-ionizing radiation may be at hand.

Abnormalities, Drug-Induced↗
PubMed1971

Behavioral sensitivity to microwave irradiation.

Rats assayed by the technique of conditional suppression were able to detect the presence of 12.25-centimeter microwaves at doses of power approximating 0.5 to 6.4 milliwatts per gram. The assay, which controlled for sensitization, for pseudo and temporal conditioning, and for several possible sources of artifactual cueing, revealed that irradiation by microwaves, although lacking the saliency of an auditory stimulus, can function as a highly reliable cue. Efficiency of detection was strongly and positively related to the amount of microwave energy to which the rats were exposed.

Animals↗
PubMed1970

Pharmacological differentiation of allergic and classically conditioned asthma in the guinea pig.

A whole-body plethysmographic technique was developed and then used to detect experimentally induced asthma in guinea pigs and to assess pharmacological treatments of allergic and classically conditioned attacks. Inhalation of a beta adrenergic compound (isoproterenol) controlled both forms of attack. Atropine and methscopolamine, parasympathetic blocking agents, prevented conditional but not allergic attacks; diphenhydramine, an antihistamine, prevented allergic attacks; and methysergide, which blocks serotonin (which is believed to trigger human asthma), prevented neither. The guinea pig's allergic reaction is probably the result of a bronchospasm induced by histamine released in tissue of the airway by a local combination of allergen and antibody. The conditional attack is believed to be a constriction of the airway mediated by parasympathetic fibers of central origin.

Animals↗