Biomedical subjects

C LeBlanc

Publications and source records attributed to C LeBlanc.

8 recordsLinked to original sources

PubMed2001

Organized sports for children and preadolescents.

Participation in organized sports provides an opportunity for young people to increase their physical activity and develop physical and social skills. However, when the demands and expectations of organized sports exceed the maturation and readiness of the participant, the positive aspects of participation can be negated. The nature of parental or adult involvement can also influence the degree to which participation in organized sports is a positive experience for preadolescents. This updates a previous policy statement on athletics for preadolescents and incorporates guidelines for sports participation for preschool children. Recommendations are offered on how pediatricians can help determine a child's readiness to participate, how risks can be minimized, and how child-oriented goals can be maximized.

Age Factors↗

PubMed2001

Strength training by children and adolescents.

Pediatricians are often asked to give advice on the safety and efficacy of strength training programs for children and adolescents. This review, a revision of a previous American Academy of Pediatrics policy statement, defines relevant terminology and provides current information on risks and benefits of strength training for children and adolescents.

Adolescent↗

PubMed1999

An interaction between PPADS, an ATP antagonist, and a moderately intense sound in the cochlea.

In the organ of Corti ionotropic receptors for ATP (ATPRs) on cells that are bathed by perilymph have been suggested to modulate cochlear mechanics. The purpose of the present study was to test the hypothesis that endogenous extracellular ATP acting through ATPRs is involved in modulating cochlear mechanics during moderately intense sound exposure. Guinea pigs were exposed to either: (1) a perilymphatic administration of pyridoxal-phosphate-6-azophenyl-2', 4'-disulfonic acid (PPADS, 1 mM), an ATP antagonist; (2) a moderately intense sound (6.7 kHz tone, 95 dB SPL, 15 min); or (3) a combination of both the PPADS and the sound. The effects on cochlear potentials (cochlear microphonic, CM; negative summating potential, SP; compound action potential of the auditory nerve, CAP; and N(1) latency) evoked by a 10 kHz tone pip were monitored. PPADS alone reduced the CAP and the SP and increased N(1) latency. The intense sound alone reduced the CAP and SP. The combination of PPADS with the intense tone induced reversible effects on cochlear potentials that were greater than induced by either treatment alone. The effect on N(1) latency and low intensity CM was a potentiation since the effect was greater than a simple addition of the effect of either treatment alone. The effects of the combination treatment on CAP, SP and high intensity CM were not different from additive. Results are consistent with the hypothesis that ATPRs in the organ of Corti are involved in modulating cochlear mechanics during moderately intense sound exposure.

Adenosine Triphosphate↗

PubMed1997

Differences in the distribution of responses to ATP and acetylcholine between outer hair cells of rat and guinea pig.

Adenosine 5' triphosphate (ATP) and acetylcholine (ACh) are neurotransmitters (ACh) and/or modulators (ATP) in the mammalian cochlea. In guinea pig, it appears that both neurotransmitters have a similar response distribution, with larger responses being evoked by the ligands in short hair cells compared to long hair cells (e.g., Chen et al., 1995b. Noise exposure alters the response of outer hair cells to ATP. Hear. Res. 88, 215-221.; Erostegui et al., 1994. In vitro pharmacologic characterization of a cholinergic receptor on outer hair cells. Hear. Res. 74, 135 147). The purpose of the present study was to test whether the distribution of responses to ACh and ATP in the OHCs of rat is the same as guinea pig. The ligand-induced current was monitored using the whole-cell configuration of the patch-clamp technique. Results show that in guinea pig OHCs, extracellular application of 100 microM ATP induced a current response in a majority of the same cells that responded to the application of 100 microM ACh. In contrast in rat OHCs, 100 microM ATP did not induce a current in the majority of cells that responded to the application of 100 microM ACh. N-methyl-glucamine (NMG+) substituted for K+ in the pipette solution failed to unmask an ATP-evoked inward current in rat OHCs. In addition, no response was produced in rat or guinea pig OHCs by adenosine, adenosine 5'-monophosphate (AMP) or adenosine 5'-diphosphate (ADP) at 100 microM. Results suggest that in guinea pig ACh-gated channels are present on most of the same OHCs that have ATP-gated ion channels, whereas in rat ACh-gated ion channels are present without ATP-gated channels on some OHCs.

Acetylcholine↗

PubMed1996

Differences in cholinergic responses from outer hair cells of rat and guinea pig.

A cholinergic receptor on outer hair cells (OHC) in guinea pig cochlea induces a K+ current when it is activated by acetylcholine and suberyldicholine but not by nicotine or muscarine (Bobbin, 1995). This unusual receptor may contain an alpha 9-subunit. However, the pharmacology of the alpha 9-subunit cloned from rat and expressed in Xenopus oocytes does not completely match that obtained for the ACh receptor in guinea pig OHCs. The response to 1,1-dimethyl-4-phenylpiperazinium (DMPP) is large in guinea pig OHCs and small in oocytes containing receptors of the alpha 9-subunit. Therefore, we compared the effects of cholinergic receptor agonists in rat and guinea pig OHCs using the whole-cell variant of the patch-clamp technique. ACh caused the largest outward K+ current in OHCs from both rat and guinea pig. Carbachol- and suberyldicholine-induced responses were similar in magnitude in OHCs of rat and guinea pig. However, DMPP produced a small response in OHCs from rat and a large response in OHCs from guinea pig. At a concentration of 100 microM, muscarine, oxotremorine M, nicotine and cytisine induced little response in guinea pig OHCs and none in rat OHCs. Results suggest that the ACh receptor on rat OHCs is similar to the alpha 9-subunit-containing receptor expressed in oocytes but different from the ACh receptor on guinea pig OHCs.

Acetylcholine↗

PubMed1995

Evidence that glutathione is the unidentified amine (Unk 2.5) released by high potassium into cochlear fluids.

An unidentified substance, Unk 2.5, may be important in the function of the cochlea. The efflux of Unk 2.5 into cochlear fluids is increased by intense sound (Bobbin and Fallon, 1992) and by exposure of the cochlear tissue to high concentrations of K+ (Bobbin et al., 1990,1991; Bobbin and Fallon, 1992). The unidentified chemical eluted at 2.5 min in chromatograms obtained by HPLC utilizing fluorescence detection and precolumn o-phthalaldehyde (OPA) derivatization of samples of effluent from the cochlea (e.g., Bobbin et al., 1990). The purpose of this investigation was to provide evidence as to the identity of this unidentified chemical we call Unk 2.5. Therefore, we carried out additional HPLC assays on samples obtained during perfusion of the cochlear perilymph compartment. Glutathione (GSH) was found to elute at the same time (@ 2.5 min) as Unk 2.5 in HPLC chromatograms utilizing precolumn derivatization with OPA and mercaptoethanol. In addition, both Unk 2.5 and GSH reacted with OPA without mercaptoethanol present in the reaction mixture to give a peak at 2.5 min in the chromatogram, but failed to show this peak if stored in solutions with a pH > 7 for several days before the reaction. Results indicate that Unk 2.5 is GSH or a closely related compound. Given this probable identification GSH, aka Unk 2.5, has been demonstrated to be released from tissue in the cochlea by high concentrations of K+ (Bobbin et al., 1990,1991) and by intense sound (124 dB SPL; Bobbin and Fallon, 1992).

Acoustic Stimulation↗

PubMed1994

DNA sequence analysis using hierarchical ART-based Classification Networks.

Adaptive resonance theory (ART) describes a class of artificial neural network architectures that act as classification tools which self-organize, work in realtime, and require no retraining to classify novel sequences. We have adapted ART networks to provide support to scientists attempting to categorize tandem repeat DNA fragments from Onchocerca volvulus. In this approach, sequences of DNA fragments are presented to multiple ART-based networks which are linked together into two (or more) tiers; the first provides coarse sequence classification while the subsequent tiers refine the classifications as needed. The overall rating of the resulting classification of fragments is measured using statistical techniques based on those introduced by Zimmerman, et al. (1994) to validate results from traditional phylogenetic analysis. Tests of the Hierarchical ART-based Classification Network, or HABclass network, indicate its value as a fast, easy-to-use classification tool which adapts to new data without retraining on previously classified data.

Algorithms↗

PubMedDate not supplied

Pig fetal septal neurons implanted into the hippocampus of aged or cholinergic deafferented rats grow axons and form cross-species synapses in appropriate target regions.

The anatomical specificity of axon growth from fetal pig septal xenografts was studied by transplanting septal cells from E30-35 pig fetuses into cholinergic deafferented (192-IgG-saporin-infused) rats or into aged rats (> 18 months). Cell suspensions (100,000 cells/microl) were injected bilaterally into the dorsal and ventral hippocampus of immunosuppressed rats (10 mg/kg/day cyclosporine A). To assess axonal growth and synapse formation, acetylcholinesterase histochemistry, an antibody to choline acetyltransferase (ChAT), and three pig-positive/rat-negative antibodies: bovine 70kD neurofilament (NF70), human low-affinity NGF receptor (hNGFr), and human synaptobrevin (hSB) were used. In rats with surviving grafts at 6 months, NF70 axonal labeling was more extensive than either ChAT or hNGFr labeling. All three markers demonstrated graft axons extending selectively through the hippocampal CA fields and the molecular layer of the dentate gyrus. Graft axons did not extend into adjacent entorhinal cortex or neocortex. The distribution of pig hSB-positive synapses correlated with AChE-positive fiber outgrowth in to the host. Electron microscopic analysis of hSB-immunostained hippocampal sections revealed pig presynaptic terminals in contact with normal rat postsynaptic structures in the CA fields and the dentate gyrus. These data demonstrate target-appropriate growth of pig cholinergic axons and the formation of cross-species synapses in the deafferented or aged rat hippocampus.

Afferent Pathways↗