Steroid and thyroid hormones modulate a changing brain.
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Animals↗
Biomedical subjects
S Mendelson
Publications and source records attributed to S Mendelson.
Intermale social aggression: suppression by medial preoptic area lesions.
The intermale social aggressive behavior of male rats cohabiting with a female rat was quantitatively scored weekly in response to the introduction of an unfamiliar intruding male. Resident male rats whose aggressiveness toward an intruder reached a criterion level were subjected to either sham lesions or bilateral lesions in the region of the medial preoptic area. The lesioned rats continued to exhibit levels of piloerection and lateral attack that were not significantly lower than those of sham-lesioned animals. However, the lesioned animals did emit significantly fewer bites and spent significantly less time in the "on-top" position than did sham-lesioned animals. The lesioned animals also displayed significantly less sexual behavior than the sham-lesioned animals but were not different in terms of defensiveness toward the experimenter. It is suggested that bilateral lesions in the region of the medial preoptic area cause a decrease in the intensity of intermale social aggression but do not prevent external stimuli from eliciting the aggression.
Aggression↗
Increased blood-brain barrier permeability to tetracycline in rabbits under dysbaric conditions.
Alteration of the blood-brain barrier (BBB) by dysbaric exposure may have relevance in several areas of hyperbaric medicine. Drugs administered to persons exposed to dysbaric conditions, e.g., divers, compressed air workers, may penetrate the brain in amounts that could produce toxic or undesirable effects. Modification of the BBB may also have pathogenetic implications in decompression sickness. Furthermore, increased BBB permeability to certain potentially useful antitumor agents, antibiotics, and other compounds under dysbaric conditions may provide the basis for a new therapeutic approach. This report concerns the influence of dysbaric exposure on BBB permeability to an antibiotic. Tetracycline (5-40 mg/kg) was intravenously injected in 22 experimental rabbits (subjected to air compression-decompression) and 17 controls (kept at ambient pressure). Fluorescence microscopy and spectrometry revealed significantly greater tetracycline concentrations in 72.7% of the experimental brains. With the 5 mg/kg dose, the mean tetracycline concentrations was 0.17 micrograms/g in control brains and 0.33 micrograms/g in experimentals. These results indicate that dysbaric exposure increases BBB permeability to tetracycline. It appears that BBB alteration is related to intravascular gas bubbles but is independent of the development of decompression sickness. The conclusions of this investigation are pertinent to brain pharmacotherapy and may provide some new insight into the mechanism of decompression sickness. They also point to potential risks connected with drug administration under dysbaric conditions that can alter BBB permeability.
Animals↗
Decarboxylation of (1-14C) L-DOPA after intravenous and intraventricular administration to rats as measured by expired 14CO2.
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Animals↗
Effect of cane use on tibial strain and strain rates.
The effect of cane ambulation on hip biomechanics has been well studied, but its effect on tibial strains and strain rates is not known. To test the hypothesis that cane use may lower tibial strain and strain rates during walking, percutaneous axial extensometers were mounted on the right medial cortex of the midtibial diaphysis in seven male volunteers. In vivo peak-to-peak axial tibial strains and strain rates were measured for ipsilateral and contralateral cane usage and compared with a no cane control. Cane-assisted ambulation was not found to significantly lower strain magnitudes; however, tibial strain rates were significantly lowered by both ipsilateral and contralateral cane usage. We conclude that either ipsilateral or contralateral cane usage may be beneficial when lowering tibial strain rate is desired, such as in the treatment of tibia stress fracture or osteoarthrosis of the knee.
Adult↗
Anatomic considerations of the foot and leg in tibial hemimelia.
Five lower extremities from four patients with tibial hemimelia were available for dissection. Multiple tendon anomalies were present. The ankle articulation was found to have a nonfunctional uniplanar motion. Multiple coalitions of the osseous structures of the foot were found, with subtalar coalition the most common.
Amputation, Surgical↗
Comparison of low-dose subcutaneous heparin calcium and heparin sodium on ecchymosis formation.
Ecchymosis formation in patients receiving identical concentrations of heparin calcium or heparin sodium was compared in a double-blind study. Sixty-three patients admitted to a coronary-care unit with orders to receive heparin 5000 units subcutaneously every 12 hours were randomly assigned to receive either heparin calcium or heparin sodium. The drugs were administered identically. The presence and size of any ecchymosis were recorded by a single observer. The 44 patients on whom data were collected received 86 heparin sodium and 102 heparin calcium injections. While there were no difference between salts in the percentage of patients with documented ecchymosis , significantly more injection sites with ecchymosis were reported for the calcium salt. No significant difference was found in bruise size between the calcium and sodium salts of heparin. In a subgroup of patients who were not receiving other drugs known to prolong bleeding, there was no significant difference between the salts in the percentage of patients and injection sites with ecchymosis . The subcutaneous administration of heparin calcium resulted in significantly more injection sites with ecchymosis than did heparin sodium, but the size of the reported ecchymosis was not different between the two groups.
Aged↗