Biomedical subjects

X Liu

Publications and source records attributed to X Liu.

At least 343 records · Page 19Linked to original sources

PubMed2001

Calpains mediate acute renal cell death: role of autolysis and translocation.

The goals of this study were to determine 1) the expression of calpain isoforms in rabbit renal proximal tubules (RPT); 2) calpain autolysis and translocation, and calpastatin levels during RPT injury; and 3) the effect of a calpain inhibitor (PD-150606) on calpain levels, mitochondrial function, and ion transport during RPT injury. RT-PCR, immunoblot analysis, and FITC-casein zymography demonstrated the presence of only mu- and m-calpains in rabbit RPT. The mitochondrial inhibitor antimycin A decreased RPT mu- and m-calpain and calpastatin levels in conjunction with cell death and increased plasma membrane permeability. No increases in either mu- or m-calpain were observed in the membrane nor were increases observed in autolytic forms of either mu- or m-calpain in antimycin A-exposed RPT. PD-150606 blocked antimycin A-induced cell death, preserved calpain levels in antimycin A-exposed RPT, and promoted the recovery of mitochondrial function and active Na+ transport in RPT after hypoxia and reoxygenation. The present study suggests that calpains mediate RPT injury without undergoing autolysis or translocation, and ultimately they leak from cells subsequent to RPT injury/death. Furthermore, PD-150606 allows functional recovery after injury.

Acrylates↗

PubMed2001

Localisation of the subthalamic nucleus using Radionics Image Fusion and Stereoplan combined with field potential recording. A technical note.

Subthalamic nucleus stimulation is an effective therapy for alleviating parkinsonian tremor, rigidity and bradykinesia. Although microelectrode recording is said to be essential for accurate targeting, this often prolongs the operation and the multiple recording tracts required may increase the incidence of complications, particularly haemorrhage. We describe a technique for implantation of deep brain electrodes in the subthalamic nucleus using MRI/CT fusion for anatomical localisation followed by bipolar recording of focal field potentials via the implanted stimulating electrode for neurophysiological confirmation of the stimulation site. The technique is effective, safe and requires much less time, and can be used as an alternative method to microelectrode recording.

Electric Stimulation Therapy↗

PubMed2001

Human ribonucleotide reductase M2 subunit gene amplification and transcriptional regulation in a homogeneous staining chromosome region responsible for the mechanism of drug resistance.

In our previous publication it was shown that a Gemcitabine-resistant KBGem clone derived from step-wise exposure to Gemcitabine resulted in overexpression of the human Ribonucleotide Reductase M2 subunit (hRRM2) mRNA and protein (Goan et al., 1999). In this study we confirm these results and show that the hRRM2 gene amplification arises in a homogeneous staining region (hsr) derived from chromosome translocation. The hydroxyurea-resistant clone (KBHURs) was studied as a comparison. PCR analysis of the hRRM2 gene promoter confirmed the amplification. Northern and Western blots were further employed to confirm the gene amplification and hRRM2 mRNA and protein expression were compatible with the level of drug resistance. Cells synchronized by serum starvation and then returned to serum-containing growth conditions showed a rapid induction of high levels of transcription of the hRRM2 gene. To clarify whether expression of hRRM2 mRNA was regulated at a transcriptional level, several transcription factors, including AP-1, Sp1, AP-2, CREB, NF-kappa B, and OCT1, were examined by gel-shift assay. Interestingly, the KBGem clone was regulated by different transcription factors than the KBHURs clone. Compared to the wild-type KB cells (KBwt), the KBGem clone exhibited a different binding pattern for Sp1 and NF-kappa B. The KBHURs clone, however, demonstrated a unique binding pattern with AP-1 and CREB, different from the KBwt control as well as the KBGem clone. Therefore, we conclude that the drug-resistant phenotype is associated with human RRM2 gene amplification from a homogeneous staining chromosome region and altered transcription regulation. Each clone demonstrated a unique pattern of transcription factor binding that may play a vital role in the mechanism of drug resistance.

Chromosome Banding↗

PubMed2001

Targeting the subthalamic nucleus.

The small size and surrounding neuronal structures and fibre tracts make the STN a difficult stereotactic target. In this article we present the technique used by us to target the STN. Our combined experience from two centres comprises 18 lesions and 27 stimulator implants in the STN. Our criteria for patient selection and the use of MRI, frame-on CT and volumetric image fusion are presented. The role of a movement disorder specialist neurologist in the operating theatre, local field potential recording, impedance monitoring, macrostimulation, post-operative CT/MRI and test stimulation are detailed.

Electric Stimulation Therapy↗

PubMed2001

Retinoic acid attenuates cytokine-driven fibroblast degradation of extracellular matrix in three-dimensional culture.

Proteolytic degradation of extracellular matrix is thought to play an important role both in emphysema and in tissue development and repair. Retinoic acid has been suggested to modify tissue injury, and in an animal model of emphysema may induce alveolar repair. Since cytokines can induce matrix metalloproteinase (MMP) production in fibroblasts and neutrophil elastase (NE) can activate MMPs, we hypothesized that retinoic acid could attenuate collagen degradation by modifying MMP production and activation. To evaluate this, human lung fibroblasts were cast into native type I collagen gels and floated in medium containing cytomix (TNF-alpha, IL-1beta, and IFN-gamma) alone or in combination with NE in the presence and absence of retinoic acid (1 microM). After 5 d, cytomix with elastase induced significant degradation of the collagen gels assessed by quantifying total hydroxyproline (41.6 +/- 1.6 microg versus 3.3 +/- 1.5 microg, P < 0.01). Retinoic acid significantly inhibited this degradation (23.3 +/- 1.5 microg versus 3.3 +/- 1.5 microg, P < 0.01). Gelatin zymography and Western blot revealed that MMP-1, MMP-3, and MMP-9 were induced by cytomix and that co-exposure to NE resulted in increased production of activated forms of these enzymes. Retinoic acid attenuated the induction and activation of MMP-1 and MMP-3. The current study, therefore, suggests that in addition to stimulating anabolic effects, retinoic acid may modulate proteolytic processes thought to contribute to tissue destruction in emphysema.

Animals↗

PubMed2001

Cigarette smoke inhibits human bronchial epithelial cell repair processes.

By interfering with the ability of airway epithelial cells to support repair processes, cigarette smoke could contribute to alterations of airway structures and functions that characterize chronic obstructive pulmonary disease (COPD). The current study assessed the ability of cigarette smoke extract (CSE) to alter human airway epithelial cell chemotaxis, proliferation, and contraction of three-dimensional collagen gels, a model of extracellular matrix remodeling. The volatile components contained in cigarette smoke, acetaldehyde and acrolein, were able to inhibit all three processes. Nonvolatile components contained within lyophilized CSE also inhibited chemotaxis but displayed no activity in the other two bioassays. CSE also inhibited the ability of airway epithelial cells to release transforming growth factor (TGF)-beta and fibronectin. Exogenous fibronectin was unable to restore epithelial cell contraction of collagen gels. Exogenous TGF-beta partially restored the ability of airway epithelial cells to contract collagen gels and to produce fibronectin. This supports a role for inhibition of TGF-beta release in mediating the inhibitory effects of cigarette smoke. Taken together, the results of the current study suggest that epithelial cells present in the airways of smokers may be altered in their ability to support repair responses, which may contribute to architectural disruptions present in the airways in COPD associated with cigarette smoking.

Acetaldehyde↗

PubMed2001

Factors associated with use of mental health services for depression by children and adolescents.

OBJECTIVE: This study examined patterns of mental health service use among depressed children and adolescents and factors associated with help seeking and treatment modalities. METHODS: The sample consisted of 206 children and adolescents aged 9 to 17 years who were assessed as part of a larger survey of mental health service use in five service systems and in the community and who met DSM-III-R criteria for depressive disorders (major depression or dysthymia). RESULTS: Among the 206 children, 75 (36 percent) never received professional help for depressive symptoms. Among the 131 children who received professional help for depression, antidepressants were prescribed for 40 (31 percent) in the year before the interview. The findings indicate possible undertreatment of depression among children and adolescents, especially among African Americans. Socioeconomic factors, such as the mother's education and the child's health insurance, were not associated with receiving professional help for depressive symptoms but were associated with receiving antidepressants. Parental perception of a child's mental health service need was associated with receiving professional help but not with receiving antidepressants. Also, depressed children were more likely to receive antidepressants when they had life-threatening or severe symptoms, such as a suicide attempt or drug abuse. CONCLUSIONS: Whether a depressed child receives mental health services and the types of treatment received are influenced by different individual and family factors and by the type of symptoms exhibited. Better understanding of these factors will help in meeting the service needs of depressed children and adolescents.

Adolescent↗

PubMed2001

Identification of differentially expressed genes in human papillomavirus type-16 infected oral cancer cells.

OBJECTIVE: The goal of this study was to determine the genes required for head and neck cancer development. STUDY DESIGN AND SETTING: Differential mRNA display analysis was performed using human papillomavirus Type-16 infected immortalized human oral keratinocytes (HOK-16B) and its benzo(a)pyrene-exposed tumorigenic derivative (HOK-16B-BaP-T). RESULTS: Twenty-one differentially expressed cDNA clones were identified between the 2 cell lines. Clone 4 with no known homology showed lower expression in tumorigenic cells compared with either normal or immortalized oral keratinocytes. Clone 6 expression was elevated in several head and neck cancer cells, in addition to Burkitt's lymphoma Raji harboring latent Epstein-Barr virus. CONCLUSION: These findings suggested that clone 6 may be involved in the oncogenic transformation whereas clone 4 may potentially function as a tumor suppressor gene. SIGNIFICANCE: Differential mRNA analysis using the in vitro oral carcinogenesis model may help to identify important genetic markers for the early detection and progression of head and neck cancer.

Blotting, Northern↗

PubMed2001

Identification of an SAS (Sp1c adjacent site)-like element in the distal 5'-flanking region of the rat lutropin receptor gene essential for cyclic adenosine 3',5'-monophosphate responsiveness.

One of the hallmarks of the differentiation of granulosa cells is the estradiol and FSH/cAMP-dependent induction of the LH receptor (LHR). Previous studies using granulosa cells isolated from diethylstilbestrol-pretreated immature rats identified a novel cAMP-responsive element termed the SAS site (Sp1c adjacent site) in the promoter region of the rat (r) LHR gene. The studies presented herein show that there is an additional distal site located at nucleotide (nt) -933/-924 that appears to interact with the same transcription factor that binds to the promoter SAS site. Similar to the SAS site, the complex formed between granulosa cell nuclear extracts and this distal site is enhanced by cAMP treatment of the granulosa cells. The core sequence required for the formation of the DNA/protein complex at this distal rLHR site was determined to be AGTGG(A)GGGG. With the exception of adenine at -928, substitution of any residue within this sequence prevented formation of this complex. The core sequence of this distal site differs from that of the proximal SAS site, which is GGGGG, and hence the distal site has been termed a SAS-like site. Reporter gene assays using constructs containing the -2,109/-1 region of the rLHR demonstrate that mutation of the distal SAS-like site abolishes the cAMP-induced transcription of the rLHR gene in rat granulosa cells, underscoring the functional significance of this site. Given the lack of sequences in the 5'-flanking region of the rLHR gene consistent with known cAMP-responsive elements, the identification of the novel SAS and SAS-like sites in the rLHR gene provides important clues toward understanding the mechanisms by which the rLHR gene is induced by FSH/cAMP.

Animals↗

PubMed2001

Potentiation of estrogen receptor activation function 1 (AF-1) by Src/JNK through a serine 118-independent pathway.

Estrogen receptor (ER) is activated either by ligand or by signals from tyrosine kinase-linked cell surface receptors. We investigated whether the nonreceptor Src tyrosine kinase could affect ER activity. Expression of constitutively active Src or stimulation of the endogenous Src/JNK pathway enhances transcriptional activation by the estrogen-ER complex and strongly stimulates the otherwise weak activation by the unliganded ER and the tamoxifen-ER complex. Src affects ER activation function 1 (AF-1), and not ER AF-2, and does so through its tyrosine kinase activity. This effect of Src is mediated partly through a Raf/mitogen-activated ERK kinase/extracellular signal-regulated kinase (Raf/MEK/ERK) signaling cascade and partly through a MEKK/JNKK/JNK cascade. Although, as previously shown, Src action through activated ERK stimulates AF-1 by phosphorylation at S118, Src action through activated JNK neither leads to phosphorylation of S118 nor requires S118 for its action. We therefore suggest that the Src/JNK pathway enhances AF-1 activity by modification of ER AF-1-associated proteins. Src potentiates activation functions in CREB-binding protein (CBP) and glucocorticoid receptor interacting protein 1 (GRIP1), and we discuss the possibility that the Src/JNK pathway enhances the activity of these coactivators, which are known to mediate AF-1 action.

CREB-Binding Protein↗

PubMed2001

Pleiotropic effects of substitutions of a highly conserved leucine in transmembrane helix III of the human lutropin/choriogonadotropin receptor with respect to constitutive activation and hormone responsiveness.

It has been shown previously that a naturally occurring mutation of the human LH/CG receptor (hLHR), which replaces L457 in helix III with arginine, results in a receptor that constitutively elevates basal cAMP but does not respond to human CG (hCG) with further cAMP production. In the present study, substitutions of L457 with several amino acids were examined. The constitutive activation of cAMP production was observed only when L457 was replaced with a positively charged residue. Although constitutive activation of the inositol phosphate pathway could not be detected when measuring inositol phosphate production, the use of a more sensitive reporter gene assay for protein kinase C activation revealed the constitutive activation of this pathway by the R- and K-substituted mutants. Therefore, L457 of the hLHR plays a key role in stabilizing the receptor in an inactive conformation. Molecular modeling shows that the insertion of R, K, or H at position 457 triggers the receptor transition toward an active state due to the proximity of an anionic amino acid, D578, in helix VI. These substitutions cause perturbations in helix III-helix VI and helix III-helix VII interactions that culminate in the opening of a solvent-accessible site in the cytosolic domains potentially involved in Gs recognition. Interestingly, L457R was completely unresponsive and the K- and H-substituted L457 hLHR mutants were significantly blunted in their cAMP responses to hCG stimulation. Cells expressing L457R were also unresponsive to hCG with regards to increased inositol phosphate production. Other substitutions of L457 were identified, though, that selectively permit the hormonal stimulation of only one of the two signaling pathways. These results suggest a pivotal role for L457 in hormone-stimulated signal transduction by the hLHR.

Adenylyl Cyclases↗

PubMed2001

Müllerian inhibiting substance signaling uses a bone morphogenetic protein (BMP)-like pathway mediated by ALK2 and induces SMAD6 expression.

Signal reception of Müllerian inhibiting substance (MIS) in the mesenchyme around the embryonic Müllerian duct in the male is essential for regression of the duct. Deficiency of MIS or of the MIS type II receptor, MISRII, results in abnormal reproductive development in the male due to the maintenance of the duct. MIS is a member of the transforming growth factor-beta (TGFbeta) superfamily of secreted protein hormones that signal through receptor complexes of type I and type II serine/threonine kinase receptors. To investigate candidate MIS type I receptors, we examined reporter construct activation by MIS. The bone morphogenetic protein (BMP)-responsive Tlx2 and Xvent2 promoter-driven reporter constructs were stimulated by MIS but the TGFbeta/activin-induced p3TP-lux or CAGA-luc reporter constructs were not. The induction of Tlx2-luc was dependent upon the kinase activity of MISRII and was blocked by a dominant negative truncated ALK2 (tALK2) receptor but not by truncated forms of the other BMP type I receptors ALK1, ALK3, or ALK6. MIS induced activation of a Gal4DBD-Smad1 but not a Gal4DBD-Smad2 fusion protein. This activation could also be blocked by tALK2. The BMP-induced inhibitory Smad, Smad6, was up-regulated by MIS endogenously in Leydig cell-derived lines and is expressed in male but not female Müllerian duct mesenchyme. ALK6 has been shown to function as an MIS type I receptor. Investigation of the pattern of ALK2, MISRII, and ALK6 in the developing urogenital system demonstrated overlapping expression of ALK2 and MISRII in the mesenchyme surrounding the duct while ALK6 was observed only in the epithelium. Examination of ALK6 -/- male animals revealed no defect in duct regression. The reporter construct analysis, pattern of expression of the receptors, and analysis of ALK6-deficient animals suggest that ALK2 is the MIS type I receptor involved in Müllerian duct regression.

Activin Receptors, Type I↗

PubMed2001

Identification of two distinct structural motifs that, when added to the C-terminal tail of the rat LH receptor, redirect the internalized hormone-receptor complex from a degradation to a recycling pathway.

We show that most of the internalized rat LH receptor is routed to a lysosomal degradation pathway whereas a substantial portion of the human LH receptor is routed to a recycling pathway. Chimeras of these two receptors identified a linear amino acid sequence (GTALL) present near the C terminus of the human LH receptor that, when grafted onto the rat LH receptor, redirects most of the rat LH receptor to a recycling pathway. Removal of the GTALL sequence from the human LH receptor failed to affect its routing, however. The GTALL sequence shows homology with the C-terminal tetrapeptide (DSLL) of the beta2-adrenergic receptor, a motif that has been reported to mediate the recycling of the internalized beta2-adrenergic receptor by binding to ezrin-radixin-moesin-binding phosphoprotein-50. Addition of the DSLL tetrapeptide to the C terminus of the rat LH receptor also redirects most of the internalized rat LH receptor to a recycling pathway but, like the recycling of the human LH receptor, this rerouting is not mediated by ezrin-radixin-moesin-binding phosphoprotein-50. We conclude that most of the internalized rat LH receptor is degraded because its C-terminal tail lacks motifs that promote recycling and that two distinct, but homologous, motifs (DSLL at the C terminus or GTALL near the C terminus) can reroute the internalized rat LH receptor to a recycling pathway that is independent of ezrin-radixin-moesin-binding phosphoprotein-50.

Amino Acid Motifs↗

PubMed2001

SHP-2 complex formation with the SHP-2 substrate-1 during C2C12 myogenesis.

Myogenesis is a highly ordered process that involves the expression of muscle-specific genes, cell-cell recognition and multinucleated myotube formation. Although protein tyrosine kinases have figured prominently in myogenesis, the involvement of tyrosine phosphatases in this process is unknown. SHP-2 is an SH2 domain-containing tyrosine phosphatase, which positively regulates growth and differentiation. We show that in C2C12 myoblasts, SHP-2 becomes upregulated early on during myogenesis and associates with a 120 kDa tyrosyl-phosphorylated complex. We have identified that the 120 kDa complex consists of the SHP-2 substrate-1 (SHPS-1) and the Grb2-associated binder-1 (Gab-1). SHPS-1, but not Gab-1, undergoes tyrosyl phosphorylation and association with SHP-2 during myogenesis, the kinetics of which correlate with the expression of MyoD. Either constitutive expression or inducible activation of MyoD in 10T(1/2) fibroblasts promotes SHPS-1 tyrosyl phosphorylation and its association with SHP-2. It has been shown that p38 mitogen-activated protein kinase (MAPK) activity is required for the expression/activation of MyoD and MyoD-responsive genes. Inhibition of p38 MAPK by SB203580 in differentiating C2C12 myoblasts blocks MyoD expression, SHPS-1 tyrosyl phosphorylation and the association of SHPS-1 with SHP-2. These data suggest that SHPS-1/SHP-2 complex formation is an integral signaling component of skeletal muscle differentiation.

Adaptor Proteins, Signal Transducing↗

PubMed2001

DSM-IV alcohol dependence and sustained reduction in drinking: investigation in a community sample.

OBJECTIVE: A common clinical conception of alcohol dependence is that it is chronic, and the idea of impaired control figures prominently in an influential definition of alcohol dependence. We investigated the meaning of a diagnosis of DSM-IV alcohol dependence in untreated individuals. METHOD: Household residents screened for elevated drinking were assessed for DSM-IV alcohol dependence and re-interviewed 1 year later. We report on 115 subjects with and 460 subjects without current DSM-IV alcohol dependence at baseline. Follow-up drinking indicators included a measure of sustained reduction in drinking. RESULTS: No support was found for a lower probability of sustained reduction in drinking at follow-up among the group with baseline DSM-IV alcohol dependence. Significant group differences indicated that the dependent group was more likely to reduce drinking. CONCLUSIONS: A diagnosis of DSM-IV alcohol dependence among untreated individuals implies a prognosis that is different from that for the same diagnosis among those seen in treatment settings. This does not necessarily indicate that the diagnosis is invalid, but rather suggests that risk factors for chronic course are more applicable to cases of DSM-IV alcohol dependence seen in treatment settings.

Adult↗

PubMed2001

[Cases-Control association study and transmission disequilibrium test of T102C polymorphism in 5HT2A and Tourette syndrome].

OBJECTIVE: To investigate whether T102C polymorphism in 5HT2A (serotonin receptor 2A) is associated with Tourette syndrome. METHODS: Both case-control association analysis and Transmission Disequilibrium Test(TDT), in addition to polymerase chain reaction and RFLP technique were used in 157 trios with Tourette syndrome (TS) and 120 controls. A semi-structured "Schedule for Tourette and other behavioral syndrome" was used in family history-collecting. Both the criteria of "Diagnostic and Statistical Manual of Mental Disorders"(DSM-IV) and that of Tourette syndrome association (TSA) were used in the diagnosis of Tourette syndrome and related disorders. RESULTS: The association between T102C polymorphism in 5HT2A and Tourette syndrome comorbided with obsessive compulsive disorder (OCD) was found by genotype-wise analysis (chi(2)=8.38,P=0.004) and allele-wise analysis (chi(2)=4.84,P=0.028), which was further confirmed by TDT analysis (chi(2)=5.12,P=0.02). No evidence of association or transmission disequilibrium between 102T/C polymorphism in 5HT2A and this disease in pure TS and total TS sample was found. CONCLUSION: 102T/C polymorphism in 5HT2A is exclusively associated with Tourette syndrome comorbided with DSM-IV OCD, which may constitute an independent subtype of Tourette syndrome.

Adolescent↗

PubMed2001

[Analysis on associations of cytochrome P450 1A1-Hinc II and glutathion S-transferase-theta with primary dysmenorrhea].

OBJECTIVE: To investigate the genetic susceptibility to primary dysmenorrhea. METHODS: Data of 499 female workers in a textile mill were collected. The associations of cytochrome P450 1A1-Hinc II(CYP 1A1-Hinc II) and glutathion S-transferase-theta(GSTT1) polymorphisms with heavy primary dysmenorrhea were evaluated by Logistic regression, with adjustment for potential confounders. RESULTS: The result showed variant of CYP1A1- Hinc II genotypes slightly reduced the risk of primary dysmenorrhea, but its OR value was not statistically significant (CYP1A1-Hinc II:OR=0.64, 95% CI 0.35-1.17). The GSTT1 genotype variant increased the risk of primary dysmenorrhea (GSTT1:OR=1.83, 95% CI 1.04-3.21). After potential confounders were adjusted, the data showed that CYP1A1-Hinc II variant had the trend of decreasing the risk of dysmenorrhea (CYP1A1-Hinc II:OR=0.58, 95% CI 0.31-1.08), but its decreasing scope was still not statistically significant. The GSTT1 variant genotypes showed a significantly increased risk of dysmenorrhea (GSTT1:OR=2.01, 95% CI 1.12-3.62). CONCLUSION: The results suggested that GSTT1 polymorphism be associated with heavy primary dysmenorrhea.

Adult↗

PubMed2001

[Effect of vitamin E on morphological variation of retinal ganglion cells after microwave radiation].

To determine the morphological variation in the primary cultured pig retinal ganglion cells induced by microwave and the protection of VE can supply some experiment foundation for study of effect of microwave and its protection. Retinal ganglion cells of pig were cultured in vitro and added VE of different concentration, Each group was taken after 30 mW/cm2 microwave intensity radiated for 1 h in shielded room by 2450 MHz continuous wave physiotherapy machine. Immediately after radiation, the morphological variation of cells was observed by optics microscope and transmission electronic microscope. The result showed that a portion of cells congregated, with their axon disappeared after radiation. Mitochondria and endoplasmic reticulum are detected swelling by transmission electronic microscope. The results showed that A poptosis cells can be observed. Cells of VE added groups had not obvious changes with optics microscope, but could be found that mitochondria swelling lightly and integrate mitochondria cristae by transmission electronic microscope. The results showed that microwave induced the morphological damage in primary cultured retinal ganglion cells, VE could reduced the damage of retina ganglion cells by microwave in some extent.

Animals↗