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Biomedical subjects

R L Isaacson

Publications and source records attributed to R L Isaacson.

At least 91 records · Page 5Linked to original sources
PubMed1976

Anatomical and behavioral effects of colchicine administration to rats late in utero.

Offspring from pregnant rats injected with 4mg/kg body weight colchicine on Embryonic Days 18, 19, and 20 were found to have isocortical and hippocampal structures greatly reduced in mass when examined at birth. Cells with pyknotic nuclei were found in Layers 5, 4, and 3 of the cerebral isocortex, the habenula, and anterior medial nuclei of the thalamus. Brains taken at Postnatal Days 22 and 132 were reduced in overall size, and had a 20-30% reduction of cells at the vertex of the neocortex with up to 50% reduction in the thickness of the corpus callosum. A decrease in activity, an increase in fearfulness and/or decreased tendency to explore, reduced error scores on the Hebb-Williams maze, poor performance on the Maier elevated maze, and a lessened sensitivity to sound-induced seizures were correlated with these anatomical changes.

Animals↗
PubMed1975

An economical operant space interface for the PDP-8 computer.

An inexpensive input/output transfer system between a PDP-8/1 Digital Equipment Corporation computer and two operant stations is described. An interrupt facility is included. Slight modification of this interface will also permit it to work with the newer PDP-8 series computers.

Animals↗
PubMed1975

Epileptogenic effects of several penicillins and penicillin-related compounds in rat neocortex.

Several penicillins and penicillin-related compounds were tested for their ability to produce epileptiform activity in rat neocortex. (1) Alterations in the side chain of penicillin G decreased epileptogenic capability in all the compounds tested in this study: Phenoxymethylpenicillin produced a primary focus but no mirror focus, suggesting a dissociation of the mechanisms underlying these two processes. Ampicillin, 6-aminopenicillanic acid, and potassium 6-aminopenicillanic acid, and potassium 6-aminopenicillanic acid produced little or no epileptiform activity. All these compounds have free amino grounds and are amphoteric. (2) Breaking the beta lactam ring of penicillin G (potassium penicillin G penicilloate) eliminated epileptogenic capability. (3) Potassium salts of penicillin or its derivatives (potassium penicillin G, propicillin, potassium 6-aminopenicillanic acid, potassium penicillin G penicilloate) consistently suppressed cortical activity, regardless of the ability of the compound to produce spike discharges. Thus, mechanisms underlying these two properties can be dissociated. (4) Antibiotic activity of penicillins bears no relationship to epileptogenic capability.

Ampicillin↗
PubMed1975

Effects of differential hippocampal damage upon rhythmic and stress-induced corticosterone secretion in the rat.

The effects of dorsal, ventral, and near-total hippocampal lesions upon both rhythmic and stress-induced corticosterone secretion in adult male rats were examined. All hippocampally-damaged, cortically-damaged, and intact rats showed rhythmic corticosterone secretion as measured in 4 blood samples for each animal taken at 6-h intervals at least 1 week apart. There were no significant differences among the groups. In addition, there were no significant differences in the amount of stress-induced corticosterone across experimental groups.

Animals↗