Biomedical subjects

Lin Chen

Publications and source records attributed to Lin Chen.

At least 37 records · Page 2Linked to original sources

PubMed2006

Karyotypic characteristics of human uterine leiomyoma and myometrial cell lines following telomerase induction.

Uterine leiomyomas are the most frequently diagnosed tumors of the female genital tract and the primary cause of hysterectomy in premenopausal women in the United States. In vitro model systems for studying these tumors are limited, due to poor culture growth. For the present study, myometrial (UtSMC) and uterine leiomyoma (UtLM) cell lines and their human telomerase reverse transcriptase (hTERT) immortalized counterparts were evaluated by GTL-banding and spectral karyotyping. UtSMC, at passage 9 showed the normal female karyotype, 46,XX. UtSMC-hTERT at passage 13 (population doubling [PD] 22 post immortalization) had two cell clones: 46,XX,der(13)t(10;13)(q11.2;p13)]/46,XX. UtLM, at passage 14, and the immortalized counterpart UtLM-hTERT (passage 13, PD 20 post immortalization), had the reciprocal translocation t(12;14)(q14;q23) in all cells and monosomy X in a fraction of cells. UtLM also displayed genomic instability with 15% of cells showing structural abnormalities involving chromosome arms 1p and 5q. UtLM-hTERT was karyotypically more stable than the parental line, thereby reflecting the inhibition of the accumulation of cytogenetic abnormalities by the maintenance of telomere integrity. This phenomenon was not observed in the UtSMC cells.

Cell Line↗

PubMed2006

Amiloride attenuates glycine-induced currents in cultured neurons of rat inferior colliculus.

Amiloride, a potassium sparing diuretic, is well known to interact with many ion transport systems and modulate the activity of several membrane receptors. However, relatively little information is available as to how amiloride affects membrane receptors of neurons in the brain areas. In the present study, we investigated the effects of amiloride on glycine-induced currents (I(Gly)) in cultured neurons of rat inferior colliculus with whole-cell patch-clamp recordings. Amiloride itself did not activate any current across the neuronal membrane but it reversibly inhibited the amplitude of the I(Gly) in a reversible and concentration-dependent manner, with an IC(50) of 487.4+/-25.3microM (n=5). Amiloride shifted the concentration-response relationship to the right without changing Hill coefficient and without changing the maximum response of the I(Gly). The pre-perfusion of amiloride produced an inhibitory effect on the I(Gly). In addition, amiloride was shown with a voltage ramp protocol to significantly reduce the conductance induced by glycine but not to change the reversal potential of the I(Gly). These results demonstrate that amiloride competitively inhibits the I(Gly) in rat inferior colliculus neurons by decreasing the affinity of glycine to its receptor. Our finding suggests that attention should be paid to the possible side effects of amiloride used as a drug on brain functions in the case of a defective blood-brain barrier and in the case of direct application of this drug into the cerebrospinal fluid for treatment of brain tumors.

Amiloride↗

PubMed2006

Effects of nimodipine, an L-type calcium channel antagonist, on the chicken's cochlear potentials.

At most synapses in the brain, neurotransmitter release depends on N-type or P/Q-type calcium channels. However, available in vitro experimental data suggest that there exist almost exclusively L-type calcium channels in sensory hair cells of most species. To test whether chicken hair cells depend on L-type calcium channels for neurotransmitter release, we examined the effects of nimodipine, a selective L-type calcium channel antagonist, on acoustically evoked cochlear potentials in 10-15 week old chickens in vivo. Diffusion of nimodipine into scala tympani significantly elevated threshold, dramatically decreased the amplitude and increased the latency of the compound action potential within 20 min of drug application. The summating potential was also significantly reduced in amplitude, but the cochlear microphonic was relatively less affected. All the effects were reversible after nimodipine was washed out with artificial perilymph except that the cochlear microphonic amplitude remained decreased. Application of omega-conotoxin GVIA, an N-type calcium channel antagonist and agatoxin Tk, a P-type calcium channel antagonist had no observable effects on the cochlear potentials. These results suggest that L-type calcium channels control neurotransmitter release from avian hair cells.

Action Potentials↗

PubMed2006

Dynamic analysis of ABA accumulation in relation to the rate of ABA catabolism in maize tissues under water deficit.

The plant hormone abscisic acid (ABA) accumulates in plant tissues which experience water deficit (stress ABA). This study analysed its accumulation as a function of both synthesis and catabolism in maize tissues. By following the disappearance of the stress ABA when ABA synthesis was blocked by nordihydroguaiaretic acid (NDGA), the rate of the catabolism of stress ABA was determined. When compared with the catabolic rate of baseline (non-stress) ABA, stress ABA showed a catabolic rate >11 times higher. With such an elevated catabolic rate, it is proposed that the xanthophyll precursor pool may not be able to sustain the ABA accumulation, and such a proposition has been substantiated by further experiments where fluridone is used to limit the availability of upstream ABA precursors. When fluridone was used, stress ABA accumulation could only be sustained for a few hours, i.e. approximately 5 h for leaf and 1 h for root tissues. In detached roots, stress ABA accumulation could not be sustained even if fluridone was not used, suggesting that stress ABA accumulation in root systems requires the continuous import of ABA precursors from the shoots. Such an assumption was substantiated by the observation that defoliation or shading significantly reduced ABA accumulation in intact roots. The present study suggests that ABA catabolism is rapid enough to play an important role in the regulation of ABA accumulation.

Abscisic Acid↗

PubMed2006

Taurine acts as a glycine receptor agonist in slices of rat inferior colliculus.

Taurine is an important endogenous amino acid for neural development and for many physiological functions, but little is known about its functional role in the central auditory system. We investigated in young rats (P10-P14) the effects of taurine on the neuronal responses and synaptic transmissions in the central nucleus of the inferior colliculus (ICC) with a brain slice preparation and with whole-cell patch-clamp recordings. Perfusion of taurine at 1mM reliably evoked a current across the membrane and decreased the input resistance in neurons of the ICC. Taurine also depressed the spontaneous and current-evoked firing of ICC neurons. All these effects were reversible after washout and could be blocked by 3 microM strychnine, an antagonist of glycine receptors, but not by 10 microM bicuculline, an antagonist of GABA(A) receptors. When the inhibitory receptors were not pharmacologically blocked, taurine reversibly reduced the postsynaptic currents/potentials evoked by electrically stimulating the commissure of the inferior colliculus or the ipsilateral lateral lemniscus. The results demonstrate that taurine reduces the neuronal excitability and depresses the synaptic transmission in the ICC by activating glycine-gated chloride channels. Our findings suggest that taurine acts as a ligand of glycine receptors in the ICC and can be involved in the information processing of the central auditory system similarly like the neurotransmitter glycine.

Animals↗

PubMed2006

Cortactin overexpression regulates actin-related protein 2/3 complex activity, motility, and invasion in carcinomas with chromosome 11q13 amplification.

Carcinoma cell motility and invasion are prerequisites for tumor cell metastasis, which requires regulation of the actin cytoskeleton. Cortactin is an actin-related protein 2/3 (Arp2/3) complex-activating and filamentous (F)-actin-binding protein that is implicated in tumor cell motility and metastasis, partially by its ability to become tyrosine phosphorylated. Cortactin is encoded by the CTTN gene and maps to chromosome 11q13, a region amplified in many carcinomas, including head and neck squamous cell carcinoma (HNSCC). CTTN gene amplification is associated with lymph node metastasis and poor patient outcome, and cortactin overexpression enhances motility in tumor cells lacking 11q13 amplification. However, a direct link between increased motility and invasion has not been reported in tumor cells with chromosome 11q13 amplification and cortactin overexpression. In this study, we have examined the relationship between CTTN amplification and tumor cell motility in HNSCC. In 11 of 39 (28%) HNSCC cases, cortactin overexpression determined by immunohistochemistry correlates with lymph node metastasis and CTTN gene amplification. HNSCC cells containing cortactin gene amplification and protein overexpression display increased binding and activation of Arp2/3 complex, and were more motile and invasive than HNSCC cells lacking CTTN amplification. Down-regulation of cortactin expression in CTTN-amplified HNSCC cells by small interfering RNA impairs HNSCC motility and invasion. Treatment of HNSCC cells with the epidermal growth factor receptor inhibitor gefitinib inhibits HNSCC motility and down-regulates cortactin tyrosine phosphorylation. These data suggest that cortactin may be a valid prognostic and therapeutic marker for invasive and metastatic HNSCC and other carcinomas with 11q13 amplification.

Actin-Related Protein 2-3 Complex↗

PubMed2006

Perceptual asynchrony: motion leads color.

It is widely accepted that motion and color are processed in separate brain areas of primates. Numerous studies on monkeys suggest that neural mechanisms responsible for motion processing respond faster than those for color. Recent studies on humans, however, provide contradictory evidence. Is this discrepancy due to a gap between species (animal vs. human), or between measures (neurophysiological vs. behavioral)? To help resolve this issue, event-related potentials were acquired as human participants viewed motion and color stimuli. Results indicated that the physiological response evoked by motion arose earlier than that by color, which is consistent with previous findings in animals. This temporal precedence of motion signal processing over color was corroborated in a parallel behavioral experiment.

Adult↗

PubMed2006

FOXP3 controls regulatory T cell function through cooperation with NFAT.

Antigen stimulation of immune cells activates the transcription factor NFAT, a key regulator of T cell activation and anergy. NFAT forms cooperative complexes with the AP-1 family of transcription factors and regulates T cell activation-associated genes. Here we show that regulatory T cell (Treg) function is mediated by an analogous cooperative complex of NFAT with the forkhead transcription factor FOXP3, a lineage specification factor for Tregs. The crystal structure of an NFAT:FOXP2:DNA complex reveals an extensive protein-protein interaction interface between NFAT and FOXP2. Structure-guided mutations of FOXP3, predicted to progressively disrupt its interaction with NFAT, interfere in a graded manner with the ability of FOXP3 to repress expression of the cytokine IL2, upregulate expression of the Treg markers CTLA4 and CD25, and confer suppressor function in a murine model of autoimmune diabetes. Thus by switching transcriptional partners, NFAT converts the acute T cell activation program into the suppressor program of Tregs.

Amino Acid Sequence↗

PubMed2006

The mechanism of involuntary visual spatial attention revealed by a new linear computation model.

EEG reveals brain electrical activities with high temporal resolution. Yet, multiple implicit variables may be involved in limited event related potential (ERP) measures. Special computation techniques are needed to recover these parameters. In the study of involuntary visual spatial attention, we may obtain the ERP in valid cued (V), invalid cued (I) and neutral cued (N) conditions. Usually, the effect of involuntary attention is computed by the subtraction model with the assumption that V/I and N are independent. Yet, they should be related. Treating V/I as a function of N, a linear model V(I) = W + GN is assumed, where W and G are implicit in the ERP measures. G is the gain control on the neutral function. Provided G and W are constant over a local brain region, we may use the Total Least Square (TLS) algorithm to compute their values. The values of W and G computed from an involuntary attention experiment data show that multiple implicit variables are involved in obtained ERPs. Here G acts as a "top-down" sensory modulator on the neutral ERPs and W is related to possible newly involved neural activities. The parameters derived from the new linear model also suggest that there are different mechanisms involved in involuntary attention and voluntary allocation of attention.

Adult↗

PubMed2006

Alphastatin downregulates vascular endothelial cells sphingosine kinase activity and suppresses tumor growth in nude mice bearing human gastric cancer xenografts.

AIM: To investigate whether alphastatin could inhibit human gastric cancer growth and furthermore whether sphingosine kinase (SPK) activity is involved in this process. METHODS: Using migration assay, MTT assay and Matrigel assay, the effect of alphastatin on vascular endothelial cells (ECs) was evaluated in vitro. SPK and endothelial differentiation gene (EDG)-1, -3, -5 mRNAs were detected by reverse transcription-polymerase chain reaction (RT-PCR). SPK activity assay was used to evaluate the effect of alphastatin on ECs. Matrigel plug assay in nude mice was used to investigate the effect of alphastatin on angiogenesis in vivo. Female nude mice were subcutaneously implanted with human gastric cancer cells (BGC823) for the tumor xenografts studies. Micro vessel density was analyzed in Factor VIII-stained tumor sections by the immunohistochemical SP method. RESULTS: In vitro, alphastatin inhibited the migration and tube formation of ECs, but had no effect on proliferation of ECs. RT-PCR analysis demonstrated that ECs expressed SPK and EDG-1, -3, -5 mRNAs. In vivo, alphastatin sufficiently suppressed neovascularization of the tumor in the nude mice. Daily administration of alphastatin produced significant tumor growth suppression. Immunohistochemical studies of tumor tissues revealed decreased micro vessel density in alphastatin-treated animals as compared with controls. CONCLUSION: Downregulating ECs SPK activity may be one of the mechanisms that alphastatin inhibits gastric cancer angiogenesis. Alphastatin might be a useful and relatively nontoxic adjuvant therapy in the treatment of gastric cancer.

Animals↗

PubMed2006

Morphometry of otoliths in chicken macula lagena.

The macula lagena located at the apical end of the cochlea in birds is characterized by the presence of numerous otoliths with unclear sensory functions. These otoliths are reported to be similar to those in the vestibular system but their detailed features in morphology are unknown. In the present study, we examined the number, size and shape of otoliths from the macula lagena in Chinese domestic chickens (Gallus Ling Nan) with a scanning electron microscope for morphometry. For chickens aged 10-15 post-hatch days, the otoliths in each macula lagena were counted to be 16,055 +/- 4038 (mean +/- S.D., n = 4). The average length and width were 12.98 +/- 3.70 microm and 5.10 +/- 1.48 microm (n = 526 otoliths), respectively. The ratio of length to width for the otolith was 2.58 +/- 0.39 (n = 526 otoliths) and remained relatively constant despite their variations in physical size. Almost all the otoliths were in regular shape and appeared like isolated cylinders with smooth facets at each end, but a few of them (0.025% of 64,221 otoliths screened) were found to be in odd shapes, such as T-shape and cross-shape. The results suggest that otoliths in the macula lagena and those in the vestibular system of bird's inner ear have similar physical properties and may play a similar role in sensing gravitational and acceleration signals.

Acoustic Maculae↗

PubMed2006

DIXDC1 isoform, l-DIXDC1, is a novel filamentous actin-binding protein.

Ccd1, a DIX domain containing Zebrafish protein involved in neural patterning, is a positive regulator of the Wnt signaling pathway. DIXDC1, the human homolog of Ccd1, has two predominant isoforms. The short form (s-DIXDC1) has a similar amino acid sequence compared with Ccd1, while the long form (l-DIXDC1) contains an extra N-terminal sequence containing a calponin-homology (CH) domain, suggesting additional interaction with actin that we have performed detailed analysis in this report. We show that mRNA expression of both DIXDC1 isoforms can be detected in various adult tissues by Northern blot analysis and is most abundant in cardiac and skeletal muscles. Both endogenous and ectopically expressed l-DIXDC1, but not s-DIXDC1, in cultured mammalian cells is localized to actin stress fibers at the filament ends in focal adhesion plaques. More importantly, l-DIXDC1 can directly bind to filamentous actin both in vitro and in vivo and the binding is mediated via a novel actin-binding domain (ABD) from amino acid 127 to 300. Thus, our data provide the first evidence that l-DIXDC1 may act as a novel branching component in the Wnt signaling pathway targeting both beta-catenin-TCF complex for gene expression and cytoskeleton for regulating dynamics of actin filaments.

Actin Cytoskeleton↗

PubMed2006

Relaxed significance criteria for linkage analysis.

Linkage analysis involves performing significance tests at many loci located throughout the genome. Traditional criteria for declaring a linkage statistically significant have been formulated with the goal of controlling the rate at which any single false positive occurs, called the genomewise error rate (GWER). As complex traits have become the focus of linkage analysis, it is increasingly common to expect that a number of loci are truly linked to the trait. This is especially true in mapping quantitative trait loci (QTL), where sometimes dozens of QTL may exist. Therefore, alternatives to the strict goal of preventing any single false positive have recently been explored, such as the false discovery rate (FDR) criterion. Here, we characterize some of the challenges that arise when defining relaxed significance criteria that allow for at least one false positive linkage to occur. In particular, we show that the FDR suffers from several problems when applied to linkage analysis of a single trait. We therefore conclude that the general applicability of FDR for declaring significant linkages in the analysis of a single trait is dubious. Instead, we propose a significance criterion that is more relaxed than the traditional GWER, but does not appear to suffer from the problems of the FDR. A generalized version of the GWER is proposed, called GWERk, that allows one to provide a more liberal balance between true positives and false positives at no additional cost in computation or assumptions.

Algorithms↗

PubMed2006

CCL27 is a critical factor for the development of atopic dermatitis in the keratin-14 IL-4 transgenic mouse model.

The keratin-14 IL-4 transgenic (Tg) mouse model of atopic dermatitis (AD) is characterized by skin infiltration of T cells, early up-regulation of T(h)2 cytokines and late surge of T(h)1 cytokines. In the present study, we investigated the role of CCL27, a T cell skin-homing chemokine known to be elevated in sera of human AD patients, in disease development in our animal model of AD. The results showed that the mRNA and protein levels of CCL27 in the skin and serum were significantly increased in IL-4 Tg mice. The percentage of T cells expressing CCR10 in skin draining lymph nodes of IL-4 Tg mice was increased, consistent with the findings of >80% of skin-infiltrating T cells in Tg mice expressing CCR10. Chemotaxis transmigration assay demonstrated that CCL27 promotes a greater degree of migration of T cells in diseased Tg mice. Subcutaneous injection of neutralizing anti-CCL27 to IL-4 Tg mice with early skin lesions resulted in reduced clinical progression of inflammation, accompanied with decreased T cell and mast cell infiltration in the skin, and down-regulation of inflammatory cytokines. In conclusion, CCL27 and CCR10 interaction is important for the development of skin inflammation in our AD model.

Animals↗

PubMed2006

Phase diagram of stigmasterol-dipalmitoylphosphatidylcholine mixtures dispersed in excess water.

As a simple model of rafts in plant cells, the effect of stigmasterol, one of the predominant sterols in plant plasma membranes, on the phase behavior of dipalmitoylphosphatidylcholine (DPPC) multilayers has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and freeze-fracture electron microscopy (FFEM) techniques. A partial phase diagram of the binary system has been constructed. Particularly, the stigmasterol concentrations of the "left endpoint" and "right endpoint" of the three-phase line have been determined using the newly developed linear and nonlinear fitting method. They are 6.2 and 23.7 mol%, respectively. Furthermore, the resemblance and difference of phase diagrams of DPPC/stigmasterol, DPPC/cholesterol, and DPPC/ergosterol have been compared and the efficiency of these sterols in promoting the formation of the liquid-ordered domains (rafts) have also been discussed.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Simultaneous determination of sorbic and benzoic acids in food dressing by headspace solid-phase microextraction and gas chromatography.

A facile headspace solid-phase microextraction (HS-SPME) procedure using 85 microm polyacrylate (PA) fiber is presented for the simultaneous determination of preservatives (sorbic and benzoic acids) in food dressing, including Thousand Island Dressing, HellMANN'S Salad Dressing and Tomato Ketchup, by gas chromatography (GC) with flame ionization detector (FID). The method presented preserves the advantages typical of HS-SPME such as simplicity, low intensity of labor, low cost and solvent free. The main factors affecting the HS-SPME process, such as extraction temperature and time, desorption temperature and time, the acidity and salt concentration of the solution, were optimized. Limits of detection (LODs) of the method were 2.00 microg/L for sorbic acid and 1.22 microg/L for benzoic acid. Relative standard deviations (RSDs) for quintuplicate analyses at three concentration levels of 0.10, 2.0 and 20 mg/L ranged between 3.86 and 14.8%. The method also showed good linearity n a range from 0.02 to 40 mg/L with correlation coefficients (R2) of 0.9986 for sorbic acid and 0.9994 for benzoic acid. Recoveries for the two analytes in all the samples tested ranged from 83.44 to 113.2%. Practical applicability was demonstrated through the simultaneous determination of sorbic and benzoic acids in the three complex samples.

Benzoates↗

PubMed2006

Sodium salicylate reduces inhibitory postsynaptic currents in neurons of rat auditory cortex.

Sodium salicylate (SS) is a medicine for anti-inflammation and for chronic pain relief with a side effect of tinnitus. To understand the cellular mechanisms of tinnitus induced by SS in the central auditory system, we examined effects of SS on evoked and miniature inhibitory postsynaptic currents (eIPSCs and mIPSCs) recorded from layer II/III pyramidal neurons of rat auditory cortex in a brain slice preparation with whole-cell patch-clamp techniques. Both eIPSCs and mIPSCs recorded from the auditory cortex could be completely blocked by bicuculline, a selective GABA(A) receptor antagonist. SS did not change the input resistance of neurons but was found to reversibly depress eIPSCs in a concentration-dependent manner. SS reduced eIPSCs to 82.3% of the control level at 0.5 mM (n=7) and to 60.9% at 1.4 mM (n=12). In addition, SS at 1.4 mM significantly reduced the amplitude of mIPSCs from 24.12+/-1.44 pA to 19.92+/-1.31 pA and reduced the frequency of mIPSCs from 1.34+/-0.23 Hz to 0.89+/-0.13 Hz (n=6). Our results demonstrate that SS attenuates inhibitory postsynaptic currents in the auditory cortex, suggesting that the alteration of inhibitory neural circuits may be one of the cellular mechanisms for tinnitus induced by SS in the central auditory region.

Animals↗

PubMed2006

[Inhibition of alphastatin on angiogenesis in human endothelial cells and the mechanism thereof: an experimental study].

OBJECTIVE: To explore the effect of alphastatin on angiogenesis activity of human umbilical vein endothelial cells and mechanism thereof. METHOD: Human umbilical vein endothelial cells of the line ECV304 was cultured. Hepatic growth factor (HGF) and alphastatin of the concentrations of 10, 100, or 1000 nmol/L were use in migration test ECV304 cells at logarithmic stage were inoculated in a 96-well plate. Alphastatin of different concentrations was added, 24, 48, 72, and 96 hours later MTT was added to detect the A(490) nm values with and draw a growth curve. Phorbol 12-myristate 13-acetate (PMA) was used as positive group. The formation of capillary-like structure was examined with fluorescent microscopy. RT-PCR was used to examine the expression of sphingosine kinase (SPK) mRNA in the ECV304 cells. ECV304 cells were treated with alphastatin of 10 nmol/L, 100 nmol/L, or 1000 nmol/L respectively. SPK activity was examined by using [gamma-(32)P] ATP. RESULTS: The number of migrated cells treated with alphastatin of the concentrations of 10, 100, and 1000 nmol/L were (103 +/- 4), (75 +/- 3), and (13 +/- 1) respectively, all significantly lower than that of the HGF group (131 +/- 4, all P < 0.05). The values at different time points of the ECV304 cells treated with alphastatin of different concentrations were not significantly different from that of the HGF group. The area of capillary-like structure of the PMA group was 2996 +/- 31 microm(2)/field, and those of the groups of alphastatin of the concentrations of 100 and 1000 nmol/L were 1509 +/- 30 microm(2)/field and 1301 +/- 20 microm(2)/field respectively, all significantly less than that of the PMA group (2996 +/- 31 microm(2)/field, all P < 0.05). However, there was not a dose-dependent manner in the inhibitive activity of alphastatin on the formation of capillary-like structure. RT-PCR showed that quantity of SPK mRNA product was amplified from the ECV304 cells. The S1P activity of the ECV304 treated with alphastatin was significantly lower than that of the control group, especially when the concentration of alphastatin was 100 nmol/L and 12 hours after treatment. CONCLUSION: Alphastatin shows a potent antiangiogenic property, which may be closely associated with the downregulation of endothelial cells SPK activity.

Cell Line↗