Biomedical subjects

Ya Li

Publications and source records attributed to Ya Li.

26 records · Page 2Linked to original sources

PubMed2004

Elevation of intracellular cAMP evokes activity-dependent release of adenosine in cultured rat forebrain neurons.

Adenosine is an important regulator of neuronal excitability. Zaprinast is a cyclic nucleotide phosphodiesterase inhibitor, and has been shown in the hippocampal slice to suppress excitation. This action can be blocked by an adenosine receptor antagonist, and therefore is presumably due to adenosine release stimulated by exposure to zaprinast. To explore the mechanism of this phenomenon further, we examined the effect of zaprinast on adenosine release itself in cultured rat forebrain neurons. Zaprinast significantly stimulated extracellular adenosine accumulation. The effect of zaprinast on adenosine appeared to be mediated by increasing intracellular cyclic adenosine monophosphate (cAMP) and activation of protein kinase A (PKA): (i) zaprinast stimulated intracellular cAMP accumulation; (ii) a cAMP antagonist (Rp-8-Br-cAMP) significantly reduced the zaprinast effect on adenosine; (iii) an inhibitor of phosphodiesterase (PDE)1 (vinpocetine) and an activator of adenylate cyclase (forskolin) mimicked the effect of zaprinast on adenosine. We also found that zaprinast had no effect on adenosine in astrocyte cultures, and tetrodotoxin completely blocked zaprinast-evoked adenosine accumulation in neuronal cultures, suggesting that neuronal activity was likely to be involved. Consistent with a dependence on neuronal activity, NMDA receptor antagonists (MK-801 and D-APV) and removal of extracellular glutamate by glutamate-pyruvate transaminase blocked the effect of zaprinast. In addition, zaprinast was shown to stimulate glutamate release. Thus, our data suggest that zaprinast-evoked adenosine accumulation is likely to be mediated by stimulation of glutamate release by a cAMP- and PKA-dependent mechanism, most likely by inhibition of PDE1 in neurons. Furthermore, regulation of cAMP, either by inhibiting cAMP-PDE activity or by stimulating adenylate cyclase activity, may play an important role in modulating neuronal excitability. These data suggest the existence of a homeostatic negative feedback loop in which increases in neuronal activity are damped by release of adenosine following activation of glutamate receptors.

Adenosine↗

PubMed2004

[Visualization technology and its application in medical image].

There are many noise disturbances in ultrasound image, and the surgical treatments are in great request for medical image, but the three dimensional image based on traditional surface graphics method cannot satisfy the request. Nevertheless, researches on visualization technology involves the denotation, operation and vision of the volume data the object contains, and the volume data contains ampler and more intact information than does the surface, therefore visualization technology will be widely used in the field of three dimensional medical image.

Computer Graphics↗

PubMed2003

NMDA receptor-mediated extracellular adenosine accumulation in rat forebrain neurons in culture is associated with inhibition of adenosine kinase.

The effect of N-methyl-d-aspartate (NMDA) on regulation of extracellular adenosine was investigated in rat forebrain neurons in culture. NMDA evoked accumulation of extracellular adenosine with an EC50 value of 4.8 +/- 1.2 microM. The effect of NMDA was blocked by (+)-5-methyl-10,11-dihydro-5H-dibenzo [a, d] cyclohepten-5,10-imine hydrogen maleate indicating that NMDA receptor activation was involved. The NMDA effect was also blocked by chelation of extracellular Ca2+ indicating that influx of calcium was required. The nitric oxide-cyclic GMP signalling pathway was not involved, as nitric oxide synthase inhibitors were unable to block, and cGMP analogs were unable to mimic, the effect of NMDA. The source for extracellular adenosine was likely to be intracellular adenosine as the ecto-5'-nucleotidase inhibitor alpha beta-methylene-ADP was unable to block the effect of NMDA. One possible cause of intracellular adenosine accumulation might be NMDA receptor-mediated inhibition of mitochondrial function and ATP hydrolysis. We found that NMDA caused a concentration dependent depletion of intracellular ATP with an EC50 value of 21 +/- 8 microM. NMDA also caused a significant decrease in adenosine kinase activity, assayed by two different methods. Consistent with the hypothesis that inhibition of adenosine kinase is sufficient to cause an increase in extracellular adenosine, inhibition of adenosine kinase by 5'-iodotubercidin resulted in elevation of extracellular adenosine. However, in the presence of a concentration of 5'-iodotubercidin that inhibited over 90% of adenosine kinase activity, exposure to NMDA still caused adenosine accumulation. These studies suggest that several possible mechanisms are likely to be involved in NMDA-evoked extracellular adenosine accumulation.

Adenosine↗

PubMed2003

Germacrane sesquiterpene esters from Salvia roborowskii.

From the whole plant of Salvia roborowskii, four new germacrane sesquiterpene esters, 3beta,6beta,8alpha-triacetoxy-4beta,5alpha-epoxy-1-oxogermacr-10(14)-ene, 3beta,6beta,8alpha-triacetoxy-4beta,5alpha-epoxygermacr-1 (10) E-ene, 3beta,6beta,8alpha-triacetoxy-4beta,5alpha:1alpha,10beta-diepoxygermacrane and 6beta-acetoxyglechomafuran were isolated, and their structures were elucidated by spectroscopic methods including 2D NMR techniques (1H-1H COSY and 1H-1H NOESY for 1).

Esters↗

PubMed2003

Phenolic compounds from Anaphalis aureo-punctata.

From the ethanolic extract of the whole plant of Anaphalis aureo-punctata, a new acylated flavonoid glycoside 3-O-kaempferol-3-O-acetyl-6-O-(p-coumaroyl)-beta-D-glucopyranoside (1), and five known phenolic compounds were isolated. Their structures were established by spectral methods (UV, IR, MS, 1D, 2D-NMR). The flavonoid glycosides, 1, 2 and 3 showed markedly inhibited oxidative DNA strand breaks induced by Fenton reaction and NADH/PMS in a concentration-dependent manner.

Asteraceae↗

PubMed2003

Lupane triterpenoids from Salvia roborowskii Maxim.

A new lupane type triterpenoid, 3beta, 11alpha-dihydroxy-30-norlupan-20-one and 6 known lupane triterpenoids were isolated from the petroleum ether (60-90 degrees C) extract of the whole plant of Salvia roborowskii Maxim. Their structures were elucidated by means of spectral methods including NMR and MS techniques.

Indicators and Reagents↗

PubMed2002

Neural and marrow-derived stromal cell sphere transplantation in a rat model of traumatic brain injury.

OBJECT: This study was designed to investigate the effect of treatment with a novel composite material consisting of embryonic neurospheres and bone marrow-derived stromal cell spheres (NMSCSs) in a rat model of traumatic brain injury (TBI). METHODS: The NMSCS composite was injected into the TBI contusion site 24 hours after injury, and all rats were killed on Day 14 after the transplantation. The Rotarod test and the neurological severity score were used to evaluate neurological function. The transplanted NMSCS was analyzed in recipient rat brains by using histological staining and laser scanning confocal microscopy. The lesion volumes in the brains were also calculated using computer image analysis. CONCLUSIONS: Rats that received NMSCS transplants had reduced lesion volume and showed improved motor and neurological function when compared with control groups 14 days after the treatment. These results suggest that transplantation of this novel biological material (NMSCS) may be useful in the treatment of TBI.

Animals↗

PubMed2001

Analysis of Human Platelet Antigen Genotypic Frequencies in Chinese Population by PCR Amplification with Sequence Specific Primers.

In present study, a method for genotyping for human platelet antigen (HPA) systems by means of the polymerase chain reaction amplification with sequence-specific primers (PCR-SSP) technique was developed and employed to determine the human platelet antigen frequencies in the Chinese population. Primers sets were designed to allow PCR amplification for five systems using the same assay conditions. Platelets from 110 random Chinese blood donors were typed for human platelet alloantigens HPA-1 to -5 by the method. The results showed that the HPA genotypic frequencies observed in the 110 donors were 0.91 and 0.09 for HPA-1a and HPA-1b, 0.86 and 0.14 for HPA-2a and HPA-2b, 0.60 and 0.40 for HPA-3a and HPA-3b, 0.92 and 0.08 for HPA-4a and HPA-4b, and 0.85 and 0.15 for HPA-5a and HPA-5b, respectively. In conclusion the method is feasible and practical and may be available to typing for HPA in the clinical laboratories.

Journal Article↗