Biomedical subjects

P X Chen

Publications and source records attributed to P X Chen.

At least 19 recordsLinked to original sources

PubMed2006

Role of the JAK-STAT pathway in protection of hydrogen peroxide preconditioning against apoptosis induced by oxidative stress in PC12 cells.

The aim of this study was to investigate the role of JAK-STAT pathway in the cytoprotection afforded by preconditioning with H(2)O(2). It was shown that (1) Preconditioning with 100 micromol/L H(2)O(2) can markedly protect PC12 cells against apoptosis and cytotoxicity induced by 300 micromol/L H(2)O(2); (2) The expression and tyrosine phosphorylation of JAK2, not JAK1 were rapidly increased at 5 min after H(2)O(2) preconditioning; (3) The expression of STAT1 and STAT3 were significantly increased at 15 min after H(2)O(2) preconditioning, and the pTyr-STAT1 and pTyr-STAT3 were markedly increased at 60 min after H(2)O(2) preconditioning; (4) Pretreatment with the JAK inhibitor AG-490 (10 micromol/L) 20 min before H(2)O(2) preconditioning blocked not only the activation of JAK2, STAT1 and STAT3, but also the cytoprotection of H(2)O(2) preconditioning against apoptosis and cytotoxicity induced by oxidative stress. These findings suggested that preconditioning with H(2)O(2) activated the JAK-STAT pathway that played an important role in the cytoprotection induced by H(2)O(2) preconditioning.

Animals↗

PubMed2006

Curcumin protects PC12 cells against 1-methyl-4-phenylpyridinium ion-induced apoptosis by bcl-2-mitochondria-ROS-iNOS pathway.

The aim of present study is to explore the cytoprotection of curcumin against 1-methyl-4-phenylpridinium ions (MPP(+))-induced apoptosis and the molecular mechanisms underlying in PC12 cells. Our findings indicated that MPP(+) significantly reduced the cell viability and induced apoptosis of PC12 cells. Curcumin protected PC12 cells against MPP(+)-induced cytotoxicity and apoptosis not only by inducing overexpression of Bcl-2, but also reducing the loss of mitochondrial membrane potential (MMP), an increase in intracellular reactive oxygen species (ROS) and overexpression of inducible nitric oxide synthase (iNOS). The selective iNOS inhibitor AG partly blocked MPP(+)-induced apoptosis of PC12 cells. The results of present study suggested that the cytoprotective effects of curcumin might be mediated, at least in part, by the Bcl-2-mitochondria-ROS-iNOS pathway. Because of its non-toxic property, curcumin could be further developed to treat the neurodegenerative diseases which are associated with oxidative stress, such as Parkinson's disease (PD).

1-Methyl-4-phenylpyridinium↗

PubMed2001

Assessment of fetal status in multiple gestation pregnancies using interphase FISH.

The use of fluorescence in situ hybridization (FISH) for women with multiple gestation pregnancies has been evaluated. Women were referred for chromosome analysis because of advanced maternal age, abnormal ultrasound findings or a positive family history and/or prior to fetal reduction. FISH was successfully applied to all specimens obtained by amniocentesis or chorionic villus sampling (CVS). Based on FISH results, fetal-fetal contamination of specimens following CVS was 11.5% in twin pregnancies and 16% in triplet or higher multiples. FISH detected trisomy 21 in three cases with no false negatives or positives. Whereas FISH may provide rapid and useful assessment of fetal status in decision-making regarding fetal reduction, the present study also highlighted the obstetrical difficulty of ensuring a sample representative of each fetus following CVS in addition to the possibility of not identifying clinically significant chromosome aberrations using currently available FISH probes.

Amniotic Fluid↗

PubMed2000

The clinical application of interphase FISH in prenatal diagnosis.

Fluorescence in situ hybridization (FISH) for five chromosomes (13, 18, 21, X and Y) detected 87 of 107 (81%) of the chromosome aberrations identified by conventional chromosome analysis applied to fetal interphase cells obtained by chorionic villus sampling or amniocentesis. The choice of FISH was solely determined by prospective parents after formal genetic counselling concerning the advantages and disadvantages of FISH analysis. Excluding known familial chromosome aberrations, if FISH analysis revealed normal signals, there was an overall residual risk of 1 in 149 for an undetectable chromosome aberration. This risk varied according to the indication for prenatal diagnosis: 1 in 177 for women of advanced maternal age; 1 in 60 for women at increased risk for Down syndrome based on maternal serum screening; and, 1 in 43 for women whose ultrasound examination revealed fetal anomalies. There were 20 cases of discordance between the FISH results and standard karyotype analysis: four were the outcome of a failure to apply the appropriate FISH probe; 16 were not detectable by the available FISH probes. Of these 16, nine were chromosome abnormalities with clinical significance and seven were familial. If FISH is to become a standard part of prenatal genetic diagnosis, genetic counselling that is sensitive to patient health needs must be based on accurate information about the biological and obstetrical implications of the results of FISH analysis.

Adult↗

PubMed1998

Hybridization of chromosome 18 alpha-satellite DNA probe to chromosome 22.

Fluorescence in situ hybridization (FISH) of uncultured chorionic villus diploid cells with a chromosome 18 alpha-satellite DNA probe (D18Z1) revealed a third small signal in addition to two large signals. FISH analysis of diploid metaphase cells from cultured chorionic villus cells and from maternal lymphocytes revealed that the third signal resulted from hybridization to the centromere of chromosome 22. This is the first report of a variant involving D18Z1 detected by FISH and of hybridization of alpha-satellite from a sub-metacentric chromosome to the centromere of an acrocentric chromosome. We propose that this inherited variant resulted from insertion of chromosome 18 specific alpha-satellite DNA sequences into the centromeric region of chromosome 22.

Adult↗

PubMed1998

Factors associated with maternal cell contamination in amniocentesis samples as evaluated by fluorescent in situ hybridization.

OBJECTIVE: To determine which patient- and procedure-related factors contribute to maternal cell contamination in uncultured amniocentesis fluid. METHODS: One hundred thirty amniotic fluid (AF) samples were obtained by three operator groups: maternal-fetal medicine faculty (n=50), general obstetrician gynecologists (n=50), and obstetrics and gynecology residents supervised by maternal-fetal medicine faculty (n=30). These groups were designated "most," "intermediate," and "least experience," respectively. Study variables were recorded at the time of the procedure. Amniotic fluid cells from male fetuses underwent fluorescent in situ hybridization. Maternal cell contamination was calculated by analyzing 100 cells and determining the number of XX and XY cells. A control system was created to validate the methods used for AF processing and cell counting. RESULTS: Median maternal cell contamination was 2.0%. Maternal cell contamination did not vary with body mass index (r=-.13, P=.14), gestational age (r=.08, P=.35), or placental location (P=.55). Maternal cell contamination was significantly elevated with placental penetration (6.0% compared with 1.0%, P < .001), two passes (27.5% compared with 2.0%, P=.002), blood-tinged fluid color (14.0% compared with 2.0%, P < .001), and operator inexperience ("intermediate experience" compared with "most experience," 4.5% compared with 1.0%, P=.026). Maternal cell contamination did not differ between the "most experience" and "least experience" groups (1.0% compared with 2.0%, not significant). Concordance between detected and actual maternal cell contamination in the control system was extremely high (concordance coefficient=0.98, P=.008), confirming the validity of the techniques used. CONCLUSION: Our techniques of cell counting and maternal cell contamination calculation are accurate. Maternal cell contamination is increased with placental penetration, two passes, and operator inexperience. However, with expert supervision, inexperienced physicians can perform amniocentesis without an increase in maternal cell contamination.

Amniocentesis↗

PubMed1998

Unusual degradation of alpha-beta complexes in Xenopus oocytes by beta-subunits of Xenopus gastric H-K-ATPase.

The catalytic alpha-subunit of oligomeric P-type ATPases such as Na-K-ATPase and H-K-ATPase requires association with a beta-subunit after synthesis in the endoplasmic reticulum (ER) to become stably expressed and functionally active. In this study, we have expressed the beta-subunit of Xenopus gastric H-K-ATPase (betaHK) in Xenopus oocytes together with alpha-subunits of H-K-ATPase (alphaHK) or Na-K-ATPase (alphaNK) and have followed the biosynthesis, assembly, and cell surface expression of functional pumps. Immunoprecipitations of Xenopus betaHK from metabolically labeled oocytes show that it is well expressed and, when synthesized without alpha-subunits, can leave the ER and become fully glycosylated. Xenopus betaHK can associate with both coexpressed alphaHK and alphaNK, but the alpha-beta complexes formed are degraded rapidly in or close to the ER and do not produce functional pumps at the cell surface as assessed by 86Rb uptake. A possible explanation of these results is that Xenopus betaHK may contain a tissue-specific signal that is important in the formation or correct targeting of functional alpha-beta complexes in the stomach but that cannot be recognized in Xenopus oocytes and in consequence leads to cellular degradation of the alpha-beta complexes in this experimental system.

Amino Acid Sequence↗

PubMed1998

[Changes of K+ channel current in cerebellar cortical neuron of apoptosis induced with H2O2].

The neurons dissociated from the cerebellar cortex of neonatal SD rat were cultured, while the growth of non-neuron cells were suppressed by Ara-c. Apoptosis of the neurons were induced with H2O2. The changes of Ik were studied during apoptosis using the patch clamp technique in cell-attached configurations. The results are as follows: (1) the Ik amplitudes of the neurons were lower than that of normal at various corresponding clamp voltages; (2) the conductances, mean open time, open probability, long and short opening time constants were all lower, as compared with normal neurons. All these results indicate that the activities of K+ channels on cerebellar neurons decrease during apoptosis.

Animals↗

PubMed1998

[Effects of 17 beta-estradiol on delayed rectifier potassium channels in hippocampal pyramidal neurons of the rat].

In the present study, both cell-attached and inside-out patch-clamp techniques were used to detect the effects of 17 beta-estradiol (E2) on 42 pS delayed rectifier potassium channels in acutely dissociated hippocampal neurons of new-born SD rats. The results indicated that after application of 1.0 and 10.0 nmol/L E2, the open probabilities of K+ channels were decreased from (67.4 +/- 18.2)% to (41.2 +/- 12.5)% and from (56.3 +/- 15.8)% to (13.2 +/- 12.6)% respectively, the open frequencies were reduced from (43.40 +/- 6.7) Hz to (27.68 +/- 9.1) Hz and from (38.19 +/- 10.1) Hz to (15.79 +/- 3.5) Hz respectively. Meanwhile, there was a shortening of the mean open time and a lenghtening of the mean close time of the channels. The above results suggest that E2 has suppressive effects on the activities of the channels, which might be exerted through a direct action on the cellular membrane.

Animals↗

PubMed1997

[Effect of pregnenolone sulfate on delayed rectifier K+ channel in pyramidial neuron of cerebral cortex].

Recent studies have shown that endogenous brain metabolites of steroids may exert important nongenomic modulatory effects on neuronal mechanisms. In this work the effect of pregnenolone sulfate (PS) on delayed rectifier K+ channel (IK) was studied in acutely dissociated rat cerebral cortical pyramidial neurons by means of cell-attached and inside-out patch clamp techniques. The open probability and mean open time of the IK channels were increased by PS in a concentration-dependent manner over the range of 30-100 mumol/L. but without changing the IK amplitude.

Animals↗

PubMed1996

Dopamine-induced ionic currents in acutely dissociated rat neurons of CNS.

AIM: To determine whether or not the dopamine (DA) can induce ionic current in single neuron acutely dissociated from different central areas including striatum, ventral tegmental area (VTA), substantia nigra pars compacta (SNC) and hippocampal CA1 area. METHODS: Using a new patch-clamp whole-cell recording technic, namely nystatin-perforated whole-cell configuration under voltage-clamp mode. RESULTS: In 36 single neurons isolated from the striatum and VTA, DA 10-1000 mumol.L-1 was quite diverse to elicit ionic current responses. In 19 SNC neurons, 5 neurons (26%) response to 1 mmol.L-1 DA represented as a small outward current (11.3 +/- 2.4 pA) at a holding potential (V(H)) of -20 mV. In 25 of 69 (36%) examined hippocampal CA1 pyramidal neurons, however, application of DA induced 3 types of current responses: outward current (8 neurons) accompanied with an increase of membrane conductance, slow inward current (5 neurons) with an decrease of membrane conductance and outward-following inward current (12 neurons) at a V(H) of -20 mV. The concentration-response relationship of DA-induced currents showed the typical sigmoid shape with the threshold dose, being the maximum response dose are 3 mumol.L-1 and 1 mmol.L-1 respectively. The current-voltage (I-V) relationship of DA-induced responses did not show any voltage-dependent manner and the reversal potential (E(DA)) was close to the equilibrium potential of potassium (E(K)) calculated with the Nernst equation. TEA 5 mol.L-1 effectively inhibited the DA-induced response. CONCLUSION: These results suggest that DA-induced outward current is carried by K+ in single hippocampal CA1 pyramidal neuron.

Animals↗

PubMed1996

[ATP-activated single ion channel and its properties in cerebral cortical neurons of neonatal rat].

In the present study, single channel currents were recorded from single neurons dissociated from the cerebral cortex of neonatal SD rat by the cell-attached and inside- out modes of patch clamp technique. ATP-activated channels with a conductance of 32 pS were often recorded and permeable to Na+, K+ and Cs+, but not to Cl-. Most of open time distribution histograms were fitted by two exponential components and few by one, whereas closed time distribution histograms were fitted by two exponential components. Both mean open time and open probability were independent of membrane potential, but the latter increased with increasing ATP concentration. The channel activity was recorded only in the presence of pipette solution containing ATP, and its conductance and open probability were not affected by ACh N-receptor antagonist hexamethonium and mecamylamine. It is suggested that ATP-activated ion channels probably exist in the cerebral cortical neurons of neonatal rat.

Adenosine Triphosphate↗

PubMed1995

[Single channel properties of NMDA receptors in cortical neurons].

The cell-attached and inside-out configurations of the patch-clamp techniques were used to investigate single channel properties of NMDA receptors in cultured intact neurons mechanically isolated from rat cereberal cortex. Recordings were made in Mg(2+)-free solutions. A channel, with a conductance of 35 pS was studied in detail with either NMDA or L-aspartate in the patch pipette. NMDA channels were permeable to Na+ K+, but not to Cl-, the mean open times and open probabilities of these channels were decreased with increasing hyperpolarization. Distributions for the open times, closed times and burst durations required two-component fits. Channel openings were suppressed by APV. When Mg2+ was included in the pipette, the mean open times were significantly diminished in a concentration- and voltage-dependent manner. Decreasing the bath temperature prolonged channel open times and decreased current amplitudes. The results indicate that there is an intrinsic voltage dependence of NMDA channel kinetics in the intact neurons, suggesting that the normal function of the NMDA channel may be dependent on some intracellular biochemical processes.

Animals↗

PubMed1994

[Study on the collagen of the different region of disc and different sigmental disc].

With the method of the collagen decomposition producting special hyoroxyprolines (HYP), the collagens of the different region of discs and different segmental discs were studied. The results were as follow: The fibrous annulus had a higher collagen content than did the nucleus pulposus (P < 0.001). In fibrous annulus, the inner region had a lower collagen content was found at the postolateral part of the fibrous annulus (P < 0.05), especially at the poster-lateral inner zone (P < 0.001). The local low-collagen content at the particular location may be one of the factors, which was clinically susceptible to a disc herniation at the part. An increasing graduation of collagen content was found from thoracic disc12 to lumbar disc 5. But, there was no statistically significant difference (P > 0.05).

Adult↗

PubMed1994

[Spectrum analysis of cat si neurone discharges].

Spontaneous firing and the discharges evoked by A- and/or C-fiber inputs (A-ED, C-ED, AC-ED) of saphenous nerve were recorded in the somatosensory cortical (SI) neurons (n = 128) of the cats anesthetized with chloralose and paralysed by gallamine. Normalized power spectrum density function (NPSDF) was used to analyse the neuron discharges. The results showed that 1) all the NPSDFs for the spontaneous discharges were single-peak with a peak frequency of 3.91 +/- 1.63 Hz (spontaneous rhythm) and a peak value of 0.0154 +/- 0.0045; 2) the NPSDFs of A-ED showed a single peak (peak value 0.021 +/- 0.0054) and an overlapped double-peak (with spontaneous discharge) or a separate multi-peak (without spontaneous discharge); 3) the NPSDFs of C-ED showed a single peak (peak value 0.020 +/- 0.007) or a separate double-peak; 4) the NPSDFs of AC-ED have two patterns: a single peak (peak value 0.023 +/- 0.004) and an overlapped multi-peak. It is suggested that A-fiber input can potentiate the rhythms of the spontaneous discharge and induce specific rhythm; that C-fiber input can potentiate the spontaneous rhythm and induce characteristic C-rhythm. It is also observed that both spontaneous rhythm and evoked rhythm affect each other; that the evoked rhythms by A-fiber and C-fiber inputs also affect each other.

Animals↗

PubMed1993

[Amplification, cloning and sequence analysis of a SSUrRNA gene fragment of Plasmodium vivax isolates from Yunnan Province].

According to known SSUrDNA sequences of Plasmodium vivax, correlated protozoa and human being, sequences of oligonucleotide primers were defined with computer programming. Specific SSUrDNA fragment of P. vivax, about 640 bp in length, was directly amplified by two temperature point polymerase chain reaction from extracted genomic DNA of two blood samples of vivax malaria patients from Yunnan Province. Using dideoxynucleotide terminator method, the sequences of amplified DNA fragments were determined separately and showed no difference between the two samples. However, comparison of the sequence reported by Waters AP and McCutchan TF (1989) and that of amplified fragment of Yunnan P. vivax isolates revealed the existence of nucleotide substitution and deletion which occurred respectively in the sites 269 and 630, and resulted in the change of restriction map.

Animals↗

PubMed1993

[Effect of electrical stimulation of second somatosensory cortex on the response of primary somatosensory cortex to C-fiber inputs].

When the projecting point of saphenous nerve in second somatosensory cortex (S II) of cat was stimulated, the evoked potentials elicited by C-fiber inputs of saphenous nerve recorded in the primary somatosensory cortex (C-CEP) might be either inhibited or facilited according to whether the superficial and/or the deeper layer of the cortex was stimulated. The inhibition was expressed as a decrease of amplitude and prolongation of latency of C-CEP; while the facilitation, as an increase of amplitude and duration of C-CEP. When the superfaicial layer of S II was stimulated by weaker current, both inhibitory and facilitatory effects could be observed, but only inhibitory effect was observed, when the deep layer was stimulated. With the same intensity of stimulation, inhibitory effect was more pronounced when the deep layer rather than the superficial layer was stimulated. It is suggested that S II may play a role in the modulation of C-CEP of S I.

Animals↗

PubMed1992

[Simple spike response of cerebellar Purkinje cells to stimulation of C-fiber in saphenous nerve].

Simple spike of cerebellar Purkinje cells (PC-SS) was recorded with microelectrode. In the NCCVF (normalized cross-covariance function) histogram, spontaneous PC-SS does not show obvious peak. When the saphenous nerve is stimulated at lower intensities, which elicits the A-fiber input only, the discharge response (A-CED) consists of an early component with a latency of 16.7 +/- 0.9 ms and a late component with a latency of 270.8 +/- 12.8 ms. After A-fibers are blocked selectively by polarizing current, the stimulation at a suprathreshold strength for C-fiber evokes a characteristic response (C-CED) with a latency of 142.4 +/- 4.3 ms. However, the C-CED can not be evoked by the inputs of A- and C-fiber simultaneously. In NPSDF histogram, the spontaneous activities of PC-SS can be divided into two groups, the high and the low peak group. The high peak group (n = 15) has a peak energy value of 15.7 +/- 4.7 x 10(-3) and peak frequency of 4.07 +/- 1.69 Hz. A-fiber input causes an increase of the peak value, while C-fiber input causes a decrease. The low peak group (n = 16) has a peak energy value 8.4 +/- 1.4 x 10(-3) and peak frequency of 3.67 +/- 2.90 Hz. Both A-fiber and C-fiber inputs cause an increase of the peak value, but the effect of A-fiber input was more prominent. The results show that the pure C-fiber input can reach the cerebellar PC and elicit characteristic simple spike response.

Animals↗