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Biomedical subjects

C F Schaefer

Publications and source records attributed to C F Schaefer.

36 records · Page 2Linked to original sources
PubMed1984

Laryngoscopic endotracheal intubation of rats for inhalation anesthesia.

Endotracheal intubation of the rat under direct vision is described together with the details of procedures and apparatus for conducting inhalation anesthesia in this species. Our intubation method requires no special manufacture of equipment, because it employs the human laryngoscope equipped with an infant blade (size 0). Using inhalation anesthetics such as enflurane or halothane for induction, clear laryngoscopic visualization of the glottis is reliably obtained, allowing rapid and routine intubation of the rat in a highly predictable amount of time. In contrast, the injected anesthetics such as ketamine or pentobarbital sodium seem unsuited to laryngoscopic intubation as a result of problems of variable induction times, copious oral secretions, and strong pharyngeal-laryngeal reflexes.

Anesthesia, Inhalation↗
PubMed1984

Anesthetic-induced changes in cardiovascular and small intestinal responses to endotoxin in the rat.

The influence of anesthesia on endotoxin shock patterns in the rat was examined. Blood pressure, heart rate, arterial blood gases, glucose, lactate, and pathology of the small intestine were measured before and after endotoxin (40 mg/kg) challenge in male Sprague-Dawley rats. The three groups studied were: (1) enflurane anesthetized (N = 10), (2) ketamine anesthetized (N = 10), and (3) awake and unrestrained (N = 13). Measurements were made during 30 min prior to endotoxin injection (IV) and for 240 min afterward. Reflex tachycardia, which occurred in the awake group simultaneously with the initial endotoxin-induced hypotension, was not present during either enflurane or ketamine anesthesia. Significantly less gross intestinal pathology was found at 4 hr after endotoxin in the anesthetized groups compared to the awake group. These results suggest that the response of the sympathoadrenal system to the hypotension following endotoxin may be blunted in the anesthetized animal.

Anesthesia↗
PubMed1983

The benefits of corticosteroid given after the onset of hypotension during endotoxin shock in the conscious rat.

We have shown that prophylactic treatment with a high dose of corticosteroid stabilizes the cardiovascular system, prevents hemorrhage of the small intestine, and improves survival. In this study we evaluated the effect of corticosteroid administered early after the manifestation of shock induced by endotoxin on blood pressure, heart rate, respiration rate, hematocrit, blood glucose, acid-base parameters, small-intestinal hemorrhage, and survival in the conscious rat. Male Sprague-Dawley rats were anesthetized with 2% enflurane and cannulae were placed in the carotid artery and jugular vein. Following recovery the animals were challenged with endotoxin (20 mg/kg). After the mean blood pressure had fallen to below 70 mm Hg the animals received corticosteroid (300 mg/kg) or an equivalent volume of saline. Supplemental doses of 30 mg/kg were given 90 min and 180 min after the initial dose. In groups other than those dealing with survival, rats were sacrificed after 4 h for pathological examination. When endotoxin was administered to untreated animals, 0/10 were alive at 15 h. In the treated group, 6/10 were alive at 24 h. Treatment shortened the early hypotensive period, but resulted in lower blood pressure from + 60 min to sacrifice. Heart rates in the treated animals were lower, pulse pressures were higher, and respiration rates were the same. Corticosteroid treatment prevented hypoglycemia, hemoconcentration, and acidemia, and markedly inhibited hemorrhage of the small intestine. Large-dose corticosteroid treatment is highly effective even when administered after the first evidence of shock induced by endotoxin in the conscious rat.

Animals↗
PubMed1983

The role of vasopressin in the maintenance of cardiovascular function during early endotoxin shock.

This study was conducted as an initial step to elucidate the role of vasopressin in the events leading to irreversible shock. The influence of vasopressin on the maintenance of cardiovascular and respiratory function during early endotoxin shock was evaluated. Conscious, unrestrained male Sprague-Dawley rats (SD) and male homozygous Brattleboro rats (B) lacking vasopressin were anesthetized with 2% enflurane and cannulas were placed in the carotid artery and jugular vein. After recovery from anesthesia, endotoxin (20 mg/kg) was administered. Endotoxin in the B caused an immediate drop in blood pressure to below 40 mm Hg with no recovery. This resulted in death for all ten animals within 3 1/2 hours; eight of ten had expired within 90 min. In contrast, the blood pressure response of the SD dropped to 70 mm Hg but recovered to values near control until sacrificed 240 min after endotoxin. Corticosteroid treatment (300 mg/kg) administered 30 min before endotoxin in the B prevented the severe decrease in blood pressure with values falling to and remaining near 70 mm Hg for the 240-min observation period. All treated animals survived this period. Heart rates in the SD increased sharply after endotoxin and continued to rise, whereas both treated and untreated B increased slowly. Respiration rates for the untreated B were severely depressed until death after endotoxin, whereas the SD and treated B remained at or above control. The results implicate vasopressin in the maintenance of cardiovascular function during the early phase of shock induced by endotoxin, and demonstrate the ability of corticosteroid to substantially improve cardiovascular integrity in the absence of vasopressin.

Adrenal Cortex Hormones↗
PubMed1980

Reduced left ventricular hypertrophy following long-term water deprivation in the young spontaneously hypertensive rat.

Biochemical and physical parameters of cardiac hypertrophy accompanying hypertension were studied in water deprived versus non-deprived immature spontaneously hypertensive rats (SHR) and their normotensive progenitor strain, Wistar Kyoto (WKY). A 23.5 hour/day water deprivation schedule was maintained from 5 to 13 weeks of age in 23 SHR and 8 WKY rats to compare the non-deprived animals (16 SHR and 8 WKY controls). Water deprived SHR had lower left ventricular weight, lower total protein and hydroxyproline and the same total DNA as the non-deprived SHR. DNA concentration was higher in the deprived SHR than in the non-deprived SHR. No differences were found among the four groups in right ventricular weight or DNA concentration. Left to right ventricular weight ratio was significantly lower and left to right ventricular DNA concentration ratio significantly higher in the deprived SHR relative to non-deprived SHR. These data indicate that the water deprived SHR, which was less hypertensive than the non-deprived SHR, had less hypertrophy of their left ventricles. While water deprivation lowered mean arterial pressure in the WKY, also, there was no effect on left ventricular weight or biochemical indices of left ventricular cell size and cell number.

Animals↗
PubMed1977

Dose-related heart-rate, perceptual, and decisional changes in man following marihuana smoking.

Information processing was tested in 12 male subjects after smoking marihuana containing 0, 10, or 20 mg. of delta-9-tetrahydrocannabinol (THC) in three consecutive experimental sessions according to a Latin square protocol. Successful dose control was indicated both by the dose-related linear increase observed in heart rate and by preliminary assays of THC metabolites excreted in the urine. During tachistoscopic presentation of varying numbers of circles, statistically significant decrements in information processing occurred as a function of THC dosage. However, adding irrelevant information (triangles) to the display of circles eliminated effects of marihuana on accuracy of counting. Complex reaction times for oddity discrimination increased significantly only after the high dose. Nonetheless, both the social and high doses inappropriately inhibited the general tendency to respond to changing stimuli during oddity discrimination. Marihuana had no effect on field-dependence as measured by the Rod-and-frame test.

Adult↗
PubMedDate not supplied

Behavioral hyperreactivity in the spontaneously hypertensive rat compared to its normotensive progenitor.

The spontaneously hypertensive rat (SHR) is an excellent model of essential hypertensive disease. Hyperreactivity has been postulated as a contributing factor in the development of high blood pressure in the SHR and in man. In the maturing organism recurring hypertensive stesss responses may promote permanent vascular changes and result in a fixed hypertension. Simple behavioral activity and emotionality rating scales were used to compare a large number of SHR with equally large groups of closely-related and distantly-related normotensive rats. As predicted, the SHR were clearly more active and emotional than their ancestral Wistar Kyoto (WKY) strain. However, the distantly-related normotensive Wistars did not differ from the SHR in either activity or emotionality. These results indicate that behavior and hypertension are not necessarily related in the rat. Nonetheless, the behavioral differences between the SHR and their closest genetic match, the WKY, suggest that arousal and blood pressure levels may be causally linked in this case of naturally occurring hypertension.

Animals↗
PubMedDate not supplied

Lifelong hyperarousal in the spontaneously hypertensive rat indicated by operant behavior.

Instrumental conditioning techniques were used to obtain objective evidence of differences in behavioral arousal between the spontaneously hypertensive rat (SHR) and the normotensive ancestral Wistar Kyoto (WKY) strain. Subjective emotionality ratings previously indicated that the genetically hypertensive rats were more active and aggressive than their normotensive cousins. In a lengthy series of operant conditioning sessions using a small number of adult female SHR and WKY rats, hyperarousal in the SHR was confirmed by their significantly higher response outputs on either response contingent or time contingent schedules of reinforcement. Conditioned emotionality tests during this series of experiments also suggested hyperarousal and aggressiveness in the SHR, since the fear-conditioned stimulus suppressed bar-pressing in the SHR much less than in the WKY. Further experiments with young prehypertensive SHR rats provided the same evidence of hyperresponsivity in the SHR compared to the WKY strain. Furthermore, these young SHR failed to develop hypertension by the end of the study (14 weeks of age), while their nonconditioned SHR cousins had become clearly hypertensive by the same age. This suggests that factors related to the conditioning methods modified the development of high blood pressure in this animal model of essential hypertension.

Age Factors↗