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Biomedical subjects

T L Petit

Publications and source records attributed to T L Petit.

47 records · Page 3Linked to original sources
PubMed1979

Electric membrane properties of human DRG neurons in cell culture and the effect of high K medium.

Cell cultures were prepared from human fetal and newborn dorsal root ganglia (DRG) and maintained in culture medium with normal (4 mM) and elevated (20 mM) potassium (K). Both types of cultures were transferred to 4 mM K, and the electrical membrane properties of the DRG neurons characterized by an extensive investigation of resting membrane potential, specific membrane resistance (Rm) and capacitance, time constant (tau), rheobasic current, and various aspects of the action potential, including overshoot, duration (DT), afterhyperpolarization and absolute refractory period (ARP). No previous quantitative determinations of these membrane properties for human neurons could be found. However, our values were in good agreement with those reported for the DRG neurons of other mammalian species both in vitro and in situ. Significant correlations occurred between membrane properties and the developmental age of each specimen used for culturing. However, the data must be interpreted cautiously due to the limited number of specimens used (4) and the possibility of differential responses of the specimens to the experimental situation. Precultivation in high K medium had profound effects on both passive and active membrane properties: the primary effect being to reduce Rm, and as a result tau, DT, and ARP were also reduced. These observations add further support to the hypothesis that high K in vitro can substitute to some extent for trophic factors normally present in situ.

Cells, Cultured↗
PubMed1979

Differential experience following developmental lead exposure: effects on brain and behavior.

Long Evans hooded rat pups were exposed to lead (Pb) via the maternal milk supply from Postnatal Day 1 (PN 1) to PN 25. Mothers were fed diets containing either 4% Pb CO3 (High Pb), 0.4% Pb CO3 (Low Pb) or 2.2% Na2 CO3 (Controls) throughout this period. Pups were weaned at PN 30 and littermates randomly assigned to either an Enriched or Isolated environment for a period of 30 days. Increases in activity levels and decreases in passive avoidance latencies were observed in Pb exposed animals. However, there were minimal effects due to Pb on symmetrical maze performance. Experience in the enriched environment had no effect on open field activity levels but resulted in a marked reduction in symmetrical maze errors. While enrichment had no effect on passive avoidance performance in High Pb animals, it was capable of raising latencies in Low Pb animals to Control values. Thus, the therapeutic value of environmental enrichment in Pb exposed animals depends on both the task employed and the severity of the pre-enrichment brain damage. From both brain regional analysis and behavioral testing results, it appeared that the hippocampus was a major site of Pb action. From comparison of blood Pb levels of our animals and those reported in children, it became apparent that the rat may have a greater tolerance for Pb, and as such, caution must be used in making direct comparisons between the two species in terms of blood Pb levels.

Animals↗
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

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↗