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Biomedical subjects

R A Davidoff

Publications and source records attributed to R A Davidoff.

At least 73 records · Page 4Linked to original sources
PubMed1976

GABA and glycine transport in frog CNS: high affinity uptake and potassium-evoked release in vitro.

Slices of frog cerebrum, optic tectum, medulla and spinal cord rapidly accumulate [3H]GABA and [3H]glycine from the surrounding medium so that after 10 min tissue:medium ratios as high as 113 for GABA (optic tectum) and 18.5 for glycine (medulla) may be achieved. Kinetic analysis revealed two distinct saturable uptake systems for each amino acid in the 4 CNS areas. The high affinity systems (apparent Km: 9-22 muM for GABA; 5-35 muM for glycine) required sodium ions in the medium and were relatively substrate specific. Significant release of [3H]GABA and [3H]glycine, but not of L-[3H]leucine, was evoked by exposure to medium containing potassium ions in a concentration of 40 mM. The process of release was calcium-dependent. The importance of these results with regard to the roles of GABA and glycine as neurotransmitters in both spinal and supraspinal levels of the amphibian neuraxis is discussed.

Alanine↗
PubMed1976

Dacrystic epilepsy.

We observed a 69 year old patient who had spontaneous paroxysmal attacks of weeping with lacrimation, contorted facies, and (usually) head-turning to the right. These episodes were followed by confusion and amnesia. During a pentylenetetrazol-evoked attack the EEG showed a right temporal delta rhythm. Atrophy, particularly of the right temporal regions, was noted on pneumoencephalography. We propose the term "dacrystic epilepsy" for this rare type of seizure disorder.

Aged↗
PubMed1976

Phenytoin-induced ophthalmoplegia.

Total external ophthalmoplegia was observed in five patients consequent to the oral or intravenous administration of phenytoin. Coincident with the ophthalmoplegia, the state of consciousness varied from drowsiness to coma and the blood levels of phenytoin ranged from 36 to 55 mug per milliliter. Initially, the eyes were fixed in midposition, and oculocephalic and oculovestibular stimulation failed to evoke either horizontal or vertical eye movements. The return of vestibulo-ocular responsiveness lagged behind the return of consciousness and other reflex activity. The mechanism underlying this ophthalmoplegia may be related to the ability of phenytoin to potentiate inhibitory synapses in the vestibulo-oculomotor pathway which utilize gamma aminobutyric acid, and to increase the discharge rate of Purkinge cells which exert an inhibitory influence on the same structures.

Adolescent↗
PubMed1975

Effects of synthetic buffers on reflexes in the isolated frog spinal cord.

Substitution of synthetic buffers (Tris, TES, HEPES, or 3,3-dimethylglutarate) for CO2-bicarbonate buffer in Ringer solution perfusing the isolated in vitro frog spinal cord preparation altered membrane properties and reflex activity. Perfusion with Ringer solution gassed with O2 and containing synthetic bu,fers consistently produced a depolarization of motoneurons and dorsal root fibers, decreased the amplitude (and usually the duration) of ventral and dorsal root potentials, and had variable effects on motoneuron and dorsal root reflex discharges. With Tris-Ringer these discharges decreased in amplitude; with Ringer containing one of the other synthetic buffers, these discharges were augmented. All changes were reversible when the cord was returned to bicarbonate-buffered Ringer aerated with 95% O2/5% CO2. The use of a combined buffer system-one containing a synthetic buffer and bicarbonate-induced smaller or minimal changes in bioelectric activity. At present the data are insufficient to allow firm conclusions concerning the mechanisms underlying these results; but it is evident 1) that changes in PCO2 and bicarbonate concentration and 2) that the pharmacological properties of synthetic buffers are important variables.

Animals↗
PubMed1972

Gamma-aminobutyric acid antagonism and presynaptic inhibition in the frog spinal cord.

The convulsant alkaloid bicuculline blocked presynaptic inhibition, dorsal root potentials, primary afferent depolarization, and depolarizing effects of gamma-aminobutyric acid on dorsal root terminals of the amphibian spinal cord, but did not block effects of other putative amino acid transmitters. These actions of bicuculline suggest that gamma-aminobutyric acid may be the transmitter involved in spinal presynaptic inhibition.

Action Potentials↗