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J Zhai

Publications and source records attributed to J Zhai.

At least 19 recordsLinked to original sources
PubMed2001

Identification of a novel interaction of 14-3-3 with p190RhoGEF.

Activation of Rho GTPases by guanine nucleotide exchange factors (GEFs) mediates a broad range of cytoskeletal alterations that determine cell shape. In the nervous system, Rho GTPases are essential for establishing highly asymmetrical neuronal forms and may fine-tune the shape of dendrites in differentiated neurons. p190RhoGEF is a brain-enriched, RhoA-specific GEF whose highly interactive C-terminal domain provides potential linkage to multiple pathways in the cell. In the present study, a yeast two-hybrid screen was used to identify 14-3-3eta and 14-3-3epsilon as additional binding partners of p190RhoGEF. Interactions between p190RhoGEF and 14-3-3eta were confirmed biochemically and by colocalization of the respective proteins when fused to fluorescent markers and transfected in neuronal cells. We also mapped a unique phosphorylation-independent binding site (I(1370)QAIQNL) in p190RhoGEF. Deletion of the binding site abolished interactions in vitro as well as the ability of 14-3-3eta to alter the cytoplasmic aggregation of p190RhoGEF in cotransfected cells. The findings suggest a potential role for 14-3-3 in modulating p190RhoGEF activity or in linking p190RhoGEF to the activities of other pathways in the neuron.

14-3-3 Proteins↗
PubMed2001

p190RhoGEF Binds to a destabilizing element in the 3' untranslated region of light neurofilament subunit mRNA and alters the stability of the transcript.

Stabilization of neurofilament (NF) mRNAs plays a major role in regulating levels of NF expression and in establishing axonal size and rate of axonal conduction. Previous studies have identified a 68-nucleotide destabilizing element at the junction of the coding region and 3' untranslated region of the light NF subunit (NF-L) mRNA. The present study has used the destabilizing element (probe A) to screen a rat brain cDNA library for interactive proteins. A cDNA clone encoding 1068 nucleotides in the C-terminal domain of p190RhoGEF (clone 39) was found to bind strongly and specifically to the RNA probe. The interaction was confirmed using a glutathione S-transferase/clone 39 fusion protein in Northwestern, gel-shift, and cross-linkage studies. The glutathione S-transferase/clone 39 fusion protein also enhanced the cross-linkage of a major 43-kDa protein in brain extract to the destabilizing element. Functional studies on stably transfected neuronal cells showed that p190RhoGEF expression increased the half-life of a wild-type NF-L mRNA but did not alter the half-life of a mutant NF-L mRNA lacking the destabilizing element. The findings reveal a novel interactive feature of p190RhoGEF that links the exchange factor with NF mRNA stability and regulation of the axonal cytoskeleton.

3' Untranslated Regions↗
PubMed2001

Superinhibition of sarcoplasmic reticulum function by phospholamban induces cardiac contractile failure.

To determine whether selective impairment of cardiac sarcoplasmic reticulum (SR) Ca(2+) transport may drive the progressive functional deterioration leading to heart failure, transgenic mice, overexpressing a phospholamban Val(49) --> Gly mutant (2-fold), which is a superinhibitor of SR Ca(2+)-ATPase affinity for Ca(2+), were generated, and their cardiac phenotype was examined longitudinally. At 3 months of age, the increased EC(50) level of SR Ca(2+) uptake for Ca(2+) (0.67 +/- 0.09 microm) resulted in significantly higher depression of cardiomyocyte rates of shortening (57%), relengthening (31%), and prolongation of the Ca(2+) signal decay time (165%) than overexpression (2-fold) of wild type phospholamban (68%, 64%, and 125%, respectively), compared with controls (100%). Echocardiography also revealed significantly depressed function and impaired beta-adrenergic responses in mutant hearts. The depressed contractile parameters were associated with left ventricular remodeling, recapitulation of fetal gene expression, and hypertrophy, which progressed to dilated cardiomyopathy with interstitial tissue fibrosis and death by 6 months in males. Females also had ventricular hypertrophy at 3 months but exhibited normal systolic function up to 12 months of age. These results suggest a causal relationship between defective SR Ca(2+) cycling and cardiac remodeling leading to heart failure, with a gender-dependent influence on the time course of these alterations.

Aging↗
PubMed2001

Positive modulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors in prefrontal cortical pyramidal neurons by a novel allosteric potentiator.

Positive modulators of glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors can enhance cognitive function in several species. The present experiments compared the actions of a novel biarylpropylsulfonamide compound, LY404187, with the prototypical benzoylpiperidine, 1-(quinoxalin-6-ylcarbonyl)-piperidine (CX516), on AMPA receptors of prefrontal cortex (PFC) pyramidal neurons. LY404187 (0.03-10 microM) selectively enhanced glutamate-evoked currents through AMPA receptor/channels of acutely isolated pyramidal neurons with considerably greater potency (EC50 = 1.3 +/- 0.3 microM) and efficacy (Emax = 45.3 +/- 8.0-fold increase) than did CX516 (EC50 = 2.8 +/- 0.9 mM; Emax = 4.8 +/- 1.4-fold increase). Both LY404187 and CX516 increased the potency of the glutamate concentration-response profile by 6- and 3-fold, respectively. Rapid perfusion experiments demonstrated that LY404187 produced a marked suppression in the magnitude but no change in the kinetics of receptor desensitization; whereas CX516 produced little change in the degree and a modest deceleration of the desensitization process. In PFC slices, both spontaneous and stimulus-evoked AMPA receptor-mediated excitatory postsynaptic potentials were enhanced by nanomolar concentrations of LY404187. Voltage-sensitive N-methyl-D-aspartate (NMDA) receptor-dependent synaptic responses also were indirectly augmented as a consequence of greater postsynaptic depolarization. Consistent with the in vitro data, LY404187 was 1000-fold more potent than CX516 in enhancing the probability of discharge of PFC neurons in response to stimulation of glutamatergic afferents from hippocampus in vivo. This potentiation by LY404187 was reduced by both selective AMPA (LY300168, 1 mg/kg, i.v.) and NMDA (LY235959, 5 mg/kg, i.v.) receptor antagonists. Collectively, these results demonstrate that LY404187 is an extremely potent and centrally active potentiator of native AMPA receptors and has a unique mechanism of action. The therapeutic implications of AMPA receptor potentiators are discussed.

Allosteric Regulation↗
PubMed2000

A single site (Ser16) phosphorylation in phospholamban is sufficient in mediating its maximal cardiac responses to beta -agonists.

Phospholamban (PLB) can be phosphorylated at Ser(16) by cyclic AMP-dependent protein kinase and at Thr(17) by Ca(2+)-calmodulin-dependent protein kinase during beta-agonist stimulation. A previous study indicated that mutation of S16A in PLB resulted in lack of Thr(17) phosphorylation and attenuation of the beta-agonist stimulatory effects in perfused mouse hearts. To further delineate the functional interplay between dual-site PLB phosphorylation, we generated transgenic mice expressing the T17A mutant PLB in the cardiac compartment of the null background. Lines expressing similar levels of T17A mutant, S16A mutant, or wild-type PLB in the null background were characterized in parallel. Cardiac myocyte basal mechanics and Ca(2+) kinetics were similar among the three groups. Isoproterenol stimulation was associated with phosphorylation of both Ser(16) and Thr(17) in wild-type PLB and Ser(16) phosphorylation in T17A mutant PLB, whereas there was no detectable phosphorylation of S16A mutant PLB. Phosphorylation of Ser(16) alone in T17A mutant PLB resulted in responses of the mechanical and Ca(2+) kinetic parameters to isoproterenol similar to those in wild-type myocytes, which exhibited dual-site PLB phosphorylation. However, those parameters were significantly attenuated in the S16A mutant myocytes. Thus, Ser(16) in PLB can be phosphorylated independently of Thr(17) in vivo, and phosphorylation of Ser(16) is sufficient for mediating the maximal cardiac responses to beta-adrenergic stimulation.

Amino Acid Substitution↗
PubMed2000

Cardiac-specific overexpression of a superinhibitory pentameric phospholamban mutant enhances inhibition of cardiac function in vivo.

Phospholamban is a regulator of the Ca(2+) affinity of the cardiac sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) and of cardiac contractility. In vitro expression studies have shown that several mutant phospholamban monomers are superinhibitory, suggesting that monomeric phospholamban is the active species. However, a phospholamban Asn(27) --> Ala (N27A) mutant, which maintained a normal pentamer to monomer ratio, was shown to act as a superinhibitor of SERCA2a Ca(2+) affinity. To determine whether the pentameric N27A mutant is superinhibitory in vivo, transgenic mice with cardiac-specific overexpression of mutant phospholamban were generated. Quantitative immunoblotting revealed a 61 +/- 6% increase in total phospholamban in mutant hearts, with 90% of the overexpressed protein being pentameric. The EC(50) value for Ca(2+) dependence of Ca(2+) uptake was 0.69 +/- 0.07 microM in mutant hearts, compared with 0.29 +/- 0.02 microM in wild-type hearts or 0. 43 +/- 0.03 microM in hearts overexpressing wild-type PLB by 2-fold. Myocytes from phospholamban N27A mutant hearts also exhibited more depressed contractile parameters than wild-type phospholamban overexpressing cells. The shortening fraction was 52%, rates of shortening and relengthening were 46% and 38% respectively, and time for 80% decay of the Ca(2+) signal was 146%, compared with wild-types (100%). Langendorff-perfused mutant hearts also demonstrated depressed contractile parameters. Furthermore, in vivo echocardiography showed a depression in the ratio of early to late diastolic transmitral velocity and a 79% prolongation of the isovolumic relaxation time. Isoproterenol stimulation did not fully relieve the depressed contractile parameters at the cellular, organ, and intact animal levels. Thus, pentameric phospholamban N27A mutant can act as a superinhibitor of the affinity of SERCA2a for Ca(2+) and of cardiac contractility in vivo.

Amino Acid Substitution↗
PubMed2000

Costuslactone B.

Explore the source record for details and available documents.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Fabrication and Characterization of a New Self-Assembled Monolayer of Fullerene Dicarboxylic Acid Derivative and Its Photoelectric Conversion Property.

A new fullerene self-assembled monolayer (SAM) which has the property of photoelectric conversion is reported here. The SAM was fabricated on hydrophilic substrates by an esterification reaction. The SAM is characterized by contact angle, AFM, UV spectrum, and cyclic voltammetry. A cathodic photocurrent of 226 nA/cm(2) was obtained. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Behavioral and emotional problems in Chinese children of divorced parents.

OBJECTIVE: This study examined the behavioral problems in Chinese children of divorced parents. METHOD: A total of 58 children of divorce and 116 gender-, age-, and school class-matched controls were ascertained from a general population sample of children aged 6 through 15 years. Parents completed the Child Behavior Checklist (CBCL), and teachers completed the Teacher's Report Form (TRF) and Conners Hyperkinesis Index. RESULTS: Parent-reported problem scores on the CBCL total scale and each subscale, and prevalence of all CBCL syndromes except for Somatic Complaints, were significantly higher in children of divorce than in controls. Teacher-reported problem scores on the TRF total scale and Social and Attention Problems and prevalence of Attention Problems were significantly different for the 2 groups of children. Social competence was rated significantly lower in children of divorce than in controls. Discriminant function analysis showed that behavioral problems in children of divorce were characterized by aggressive behavior, withdrawal, and social problems. CONCLUSIONS: The findings emanating from China provide the first evidence of the link between parental divorce and children's psychopathology and clarify the psychopathological dimensions in Chinese children of divorced parents.

Adolescent↗
PubMed2000

[Effects of adenovirus-mediated p16 and p53 genes transfer on apoptosis and cell cycle of lung carcinoma cells].

OBJECTIVE: To explore the synergistic inhibition effect and apoptosis induction of p16 and p53 genes on lung carcinoma cells. METHODS: E1-deficient and replication-defective recombinant p16 and p53 adenoviruses were generated by liposome-mediated co-transfection of recombinant plasmid pAdCMV-p16 or pAdCMV-p53 along with pJM17 and homologous recombination in 293 packaging cell. The lung cancer cell line H358, which had a homozygous deletion of p53 gene and no expression of p16 mRNA and protein, was infected with recombinant p16 and p53 adenovirus either individually or together. RESULTS: Immunohistochemical analysis showed that recombinant adenovirus could transfer p53 gene into tumor cell with 98% efficiency. Western blot indicated that p16 and p53 proteins were expressed at a high level in infected H358 cell. Inhibition effect of p53 gene on proliferation of H358 cell was weaker than that of p16 gene, and the combined use of both genes could completely prevent the proliferation of H358 cell. In situ end-labeling and flow cytometry indicated that p16 could result in G(1) arrest of cell cycle and did not induce H358 cells to undergo apoptosis; p53 also induced apoptosis of few cells besides G(1) arrest; and the simultaneous use of p16 and p53 genes could induce marked apoptosis of H358 cells. CONCLUSION: p16 and p53 genes possess the synergistic inhibiting effect on growth of lung cancer cells and can cooperate to induce apoptosis of H358 cell. The combined application of recombinant p16 and p53 adenoviruses can be used as a new strategy for cancer gene therapy.

Adenoviridae↗
PubMed1999

Serotonin receptor subtypes that depolarize guinea pig inferior mesenteric ganglion neurons.

Our previous studies indicated that serotonin (5-HT) depolarized a majority of guinea pig inferior mesenteric ganglion (IMG) neurons and may be another transmitter for the noncholinergic late slow excitatory postsynaptic potential (ls-EPSP) in the IMG. However, the subtypes of 5-HT receptor mediating these responses have not yet been identified. Using intracellular recording, we examined the effect of 5-HT receptor antagonists with specificity to various 5-HT receptor subtypes on the 5-HT-mediated depolarization and ls-EPSP in IMG neurons in vitro. Cyproheptadine, a 5-HT(1/2) receptor antagonist, reversibly inhibited the slow, but not the fast, depolarization and ls-EPSP in the 5-HT-sensitive neurons. Both mianserin and spiperone, 5-HT(2) and 5-HT(1A) receptor antagonists, did not significantly alter either the fast or slow depolarizing responses or the ls-EPSP. The 5-HT(3) receptor antagonist MDL 72222 (Bemesetron) completely inhibited the fast depolarization with little diminution of the slow depolarization and ls-EPSP. Superfusion of putative 5-HT(1P) receptor antagonist, BRL 24924 (Renzapride), reversibly attenuated both the depolarization and ls-EPSP. However, 5-HT-insensitive neurons with ls-EPSP were found to be insensitive to both cyproheptadine and BRL 24924. In most 5-HT-sensitive neurons, the 5-HT(3) receptor agonist, 2-methyl-5-HT, and the selective 5-HT(1P) agonist, MCPP or 5-OHIP, evoked a fast and a slow depolarization in 55.6 and 71.4% of the neurons, respectively, without a significant effect on the membrane potential in 85.7 and 100% of the 5-HT-insensitive neurons. In 5-HT-sensitive neurons, MDL 72222 reversibly abolished the fast depolarization induced by 2-methyl-5-HT; BRL 24924 significantly inhibited the slow depolarization induced by MCPP or 5-OHIP, but not by SP. Prolonged superfusion of 5-HT-sensitive neurons with MCPP abolished the evoked ls-EPSP without inhibition of action potential. These results suggest that the fast and slow depolarizations in these neurons are mediated by 5-HT(3) and 5-HT(1P) receptor subtypes, respectively. The latter may also mediate the ls-EPSP in 5-HT-sensitive neurons.

Animals↗
PubMed1999

Inward currents in neurons from newborn guinea pig intestine: mediation by 5-hydroxytryptamine type 3 receptors.

The whole-cell patch-clamp technique was used to analyze the effects of 5-hydroxytryptamine (5-HT) and alosetron on cultured myenteric neurons from newborn guinea pigs. All neurons responded to 5-HT (EC(50) approximately 38.7 microM) with a concentration-dependent inward current (reversal potential = 7.1 +/- 1.7 mV) with a short latency and rapid decay. Because the 5-HT-induced inward current was mimicked by 2-methyl-5-hydroxytryptamine (50 microM) and blocked by ondansetron (5.0 microM) and MDL 72222 (0.05 microM), it was 5-HT(3)-mediated. Alosetron blocked (IC(50) approximately 0.05 microM; Hill coefficient approximately 1.24) the 5-HT- and 2-methyl-5-hydroxytryptamine-induced inward currents. This effect was independent of membrane potential and was not seen when alosetron was delivered to the inside of cells. Alosetron-sensitive sites are, thus, accessible only on the ectodomain of the plasmalemma. The effect of alosetron was reversible, but not surmountable. Although nicotine (100 microM) mimicked the 5-HT-induced inward current, the response was antagonized by hexamethonium (100 microM), but not by alosetron, implying its potential to be a selective 5-HT(3) antagonist. Hexamethonium did not affect responses to 5-HT. Most neurons in the cultures were 5-HT-immunoreactive and immunostained with an antibody raised against 5-HT(3) receptors. The 5-HT-selective uptake inhibitor, fluoxetine (30 microM), gradually reduced the amplitude of the current induced by 5-HT; the residual response was abolished by alosetron (0.2 microM). The effect of fluoxetine could have been caused by either the desensitization of 5-HT(3) receptors or by a nonspecific 5-HT(3) antagonistic effect of fluoxetine. It is concluded that alosetron is a potent and noncompetitive 5-HT(3) antagonist on myenteric neurons.

Acetylcholine↗
PubMed1999

[A study of the relationship between dynamic blood rheologic changes and the fluid resuscitation in burn patients].

OBJECTIVE: To further study the relationship between hemor rheologic changes and fluid resuscitation in patients with burn and treatment of anemia after burns. METHODS: 238 case of burn patients were divided into four groups. In which patients with major burn were allocated to group C and D according to different methods of fluid resuscitation and treatment of anemia. RESULTS: Abnormal hemorrheologic parameters could be corrected when transfusion of fresh whole blood and traditional herb medicines were given within 24-48 hours after burn injury. CONCLUSION: Dynamic observation of hemorrheologic changes is one of important index in monitoring burn shock and guiding fluid resuscitation. Blood transfusion and traditional medicine can improve abnormal blood rheologic parameters, effectively correct anemia when given early.

Adolescent↗
PubMed1999

[Retroviral transfer of a human beta-globin gene linked to beta locus control region hypersensitive site 2 into murine hematopoietic stem cells].

OBJECTIVE: To examine the in vivo properties of retroviral recombinants carrying partially deleted human beta-globin gene (delta beta) and truncated erythroid enhancer (292 bp and 341 bp of 5'HS2) at the mRNA levels following short- and long-term reconstitution in mice with infected marrow cells. METHODS: First ecotropic virus producer cell lines with higher virus titers were isolated using "ping-pong" procedures. Then the human beta-globin gene was transferred into murine hematopoietic progenitor cells and the integration and expression of transferred gene were analyzed by southern blot and RNase protection assay or RT-PCR. RESULTS: The virus titers of both recombinants increased obviously after "ping-pong" procedures. The transferred human beta-globin gene was detected in murine CFU-S12 and the expression level was about 0.5%-5% of endogenous mouse alpha-globin gene. In 3 of 14 mice surviving long-term transplanted with bone marrow cells transduced with high-titer virus, bone marrow, spleen and thymus from two mice and bone marrow and spleen from another mouse contained the intact proviral genome. Long-term expression of the transferred gene was seen in one mouse at level of 7% of endogenous murine alpha-globin gene. CONCLUSIONS: The transferred human beta-globin gene can stably integrate into murine hematopoietic stem cells mediated by retroviral vectors and express in an erythroid-specific manner.

3T3 Cells↗
PubMed1999

[One-time operation in infant cleft lip and palate plus alveolar process].

OBJECTIVE: To improve safety and viability of one-time operation in the therapy of cleft lip and palate and cleft alveolar process. METHODS: Under the air-vein anesthesia, one-time operations were performed in 42 patients with complete cleft lip and palate plus cleft alveolar process. After rehabilitation in ICU, all patients were put into wards, and left hospital 4-7 days after operation. RESULTS: The situation during anesthesia and operation was good. There were no statistically significant changes in blood pressure, oxygen saturation of blood, heart rate and cardiac rhythm before, during and after operation. No anesthetic accident and no complication happened. The loss of blood was about 42.7 +/- 6.5 ml and the duration of operation was about 139.2 +/- 18.6 minutes. The rehabilitation was successful after operations. First intention took place in almost all patients' incisions, and palatal fistulas appeared in only 2 cases. CONCLUSION: Under the control of provisioned pediatric anesthesia and rehabilitation, one-time complete cleft lip and palate plus cleft alveolar process closure is safe and viable.

Alveolar Process↗
PubMed1998

Phosphorylation of the GABAA receptor gamma2L subunit in rat sensory neurons may not be necessary for ethanol sensitivity.

The effect of ethanol on the current activated by 2.5 to 40 microM gamma-aminobutyric acid (GABA) was studied in freshly isolated rat dorsal root ganglion (DRG) neurons under voltage clamp in the whole-cell and perforated-patch recording configurations. Our results confirmed that GABAA-activated current in these neurons was insensitive to ethanol at concentrations from 2.5 to 100 mM [G. White, D.M. Lovinger, F.F. Weight, Ethanol inhibits NMDA-activated current but does not alter GABA-activated current in an isolated adult mammalian neuron, Brain Res. 507 (1990) 332-336.]. In addition, the ethanol sensitivity of GABA receptors was studied under conditions that promote phosphorylation of the PKC site on the gamma2L subunit. The presence of the gamma2L and other subunit mRNAs was detected by reverse transcription (RT) of total RNA purified from adult DRG followed by polymerase chain reaction (PCR) using subunit specific primer sets. We found that the GABA response remained insensitive to 2.5-100 mM ethanol despite: (i) the extracellular preapplication of 5, 20 or 500 nM phorbol 12-myristate 13-acetate (PMA); (ii) raising free intracellular Ca2+ ([Ca2+]i) from 7 to 100 or 600 nM by altering the intracellular Ca2+/EGTA ratio; (iii) intracellular application of PKC (0.247 U ml-1 ); and (iv) combining the intracellular application of 1 microM okadaic acid and 30 microM peptide 3 with the extracellular application of 20 nM PMA. These results suggest that phosphorylation of the gamma2L subunit is not the only requirement for ethanol sensitivity of GABAA receptors.

Animals↗
PubMed1998

Effects of ethanol on rat somatosensory cortical neurons.

In this study, we characterized the local effects of ethanol (EtOH) on postsynaptic potentials (PSPs) and membrane properties of layer II-III (L2-3) and layer V (L5) somatosensory cortical neurons. Intracellular recordings were done using the in vitro slice preparation of rat somatosensory cortex. Our results show that EtOH exerts local effects on cortical cell membrane at physiologically relevant concentrations. A predominant effect of EtOH was to reduce excitability of L2-3 and L5 neurons by increasing the rheobase, decreasing input resistance and repetitive firing, reducing PSPs amplitude and the probability of evoking action potentials. Early (6 ms) and late (18 ms) PSP components were affected differentially by EtOH, the late components being more suppressed. Overall, EtOH-mediated suppression of PSPs was stronger in L5 neurons. Cortical neurons were divided into three subtypes: regular spiking adapting (RS-A), regular spiking non-adapting (RS-NA) and bursting (D-IB) neurons. PSPs evoked in RS-A neurons were more sensitive to EtOH suppressant effects. EtOH effects on input resistance were distributed differentially among the three groups of neurons. These results support the notion that EtOH disrupts higher processing of somatosensory information via a differential alteration of cortical neuron's membrane properties and synaptic transmission.

Animals↗