Biomedical subjects

L-X Yang

Publications and source records attributed to L-X Yang.

4 recordsLinked to original sources

PubMed2006

Anomalous electronic state in CaCrO3 and SrCrO3.

Comprehensive measurements of electrical transport properties under pressure, thermal conductivity, magnetic susceptibility, and room-temperature compressibility have been used to characterize SrCrO3 and CaCrO3 perovskites synthesized under high pressure. Comparison with other narrow-band perovskite oxides suggests that their anomalous physical properties are correlated with bond-length instabilities caused by the crossover from localized to itinerant electronic behavior.

Journal Article↗

PubMed2006

Unilateral low-frequency stimulation of central piriform cortex delays seizure development induced by amygdaloid kindling in rats.

Low-frequency stimulation of the kindling site interferes with the course of kindling epileptogenesis. The present study examined the effect of unilateral low-frequency stimulation of the central piriform cortex on seizure development induced by amygdaloid kindling in rats. The ipsilateral or contralateral central piriform cortex received low-frequency stimulation (15 min train of 0.1 ms pulses at 1 Hz and 50-150 muA) immediately after termination of once daily kindling stimulation (2 s train of 1 ms pulses at 60 Hz and 150-300 microA) in the right amygdala for 30 days. Low-frequency stimulation of either the ipsilateral or contralateral central piriform cortex significantly suppressed the progression of seizure stages and reduced afterdischarge duration throughout the course of amygdaloid kindling. The marked suppression induced by low-frequency stimulation of the central piriform cortex on either side was predominantly due to the significant retardation of progression from stage 0 to stage 1 and stage 3 to stage 4 seizures. In addition, the suppressive effect of low-frequency stimulation did not disappear when the stimulation was stopped; it could persist for at least 10 days. These findings indicate that brain areas other than the kindling focus, such as the central piriform cortex on both sides, can also be used as reasonable targets for low-frequency stimulation to retard seizure development induced by amygdaloid kindling. Secondly, like the ipsilateral central piriform cortex, the contralateral central piriform cortex may also participate in the progression and secondary generalization of focal seizures. The study suggests that unilateral low-frequency stimulation of the central piriform cortex may have a significant antiepileptogenic effect, and may be helpful for exploring effective and long-lasting therapies for human temporal lobe epilepsy.

Amygdala↗

PubMed2005

Effects of carnosine on amygdaloid-kindled seizures in Sprague-Dawley rats.

The effects of carnosine (beta-alanyl-L-histidine) on amygdaloid-kindled seizures were investigated in rats. I.p. injection of carnosine (500, 1000, 1500 mg/kg, i.p.) significantly decreased seizure stage, afterdischarge duration and generalized seizure duration, and significantly prolonged generalized seizure latency of amygdaloid-kindled seizures, in a dose-dependent, and time-related manner. The protective effect of carnosine (1500 mg/kg) was completely antagonized by histamine H1-antagonists pyrilamine (2, 5 mg/kg, i.p.) and diphenhydramine (5, 10 mg/kg, i.p.), but not by histamine H2-antagonist zolantidine even at a high dose of 10 mg/kg. Carnosine (1500 mg/kg, i.p.) caused a significant increase of carnosine and histidine levels in the hypothalamus, thalamus, hippocampus, amygdala and cortex, as well as histamine levels in the hippocampus and amygdala. I.c.v. injection of alpha-fluoromethylhistidine (50 microg, i.c.v.), a selective and irreversible histidine decarboxylase inhibitor, only partially reversed the inhibition of amygdaloid-kindled seizures induced by carnosine. In addition, carnosine significantly decreased glutamate contents in the amygdala and hippocampus. These results indicate that carnosine could protect against amygdaloid-kindled seizures in rats, and its action may be due to the activation of histamine postsynaptic H1-receptors via two different mechanisms, one being carnosine's direct action, and the other being indirectly mediated by histaminergic pathway. The study suggests that carnosine may be an endogenous anticonvulsant factor in the brain and could be used as a new antiepileptic drug in the future.

Amygdala↗

PubMed2004

Glia cell line-derived neurotrophic factor regulates the distribution of acetylcholine receptors in mouse primary skeletal muscle cells.

It was recently reported that glia cell line-derived neurotrophic factor (GDNF) facilitates presynaptic axonal growth and neurotransmitter release at neuromuscular synapses. Little is known, however, whether GDNF can also act on the postsynaptic apparatus and its underlying mechanisms. Using biochemical cold blocking of existing membrane acetylcholine receptors (AchRs) and biotinylation of newly inserted receptors we demonstrate that GDNF increases the insertion of AChRs into the surface membrane of mouse primary cultured muscle cells and that this does not require protein synthesis. Quantitative data from double-label imaging indicate that GDNF induces a quick and substantial increase in AchR insertion as well as lateral movement into AchR aggregates, relative to a weak effect on reducing the loss of receptors from pre-existing AchR aggregates, which in contrast to the effect of PMA. These effects occur in both innervated and un-innervated muscles, and GDNF affects nerve-muscle co-cultures more than it affects muscle-only cultures. Neurturin, another member of GDNF-family ligands has similar effects on AchRs as GDNF but the unrelated growth factor, EGF does not. Studies on protein phosphorylation and specific inhibitors of cell signal transduction indicate that GDNF function is mediated by receptor GFRalpha1 and involves MAPK, cAMP/cAMP responsive element-binding factor and Src kinase activities. GDNF may signal through c-Ret as well as NCAM-140 pathways since both the signaling receptors are expressed in the neuromuscular junction (NMJ). These data suggest that GDNF is an autocrine regulator of NMJ to promote the insertion and stabilization of postsynaptic AchRs. In vivo, GDNF may function as a synaptotrophic modulator for both pre- and postsynaptic differentiation to strengthen the functional and structural connections between nerve and muscle, and contribute to the synaptogenesis and plasticity of neuromuscular synapses.

Animals↗