Biomedical subjects

Long Ma

Publications and source records attributed to Long Ma.

11 recordsLinked to original sources

PubMed2007

SRC-family kinases are activated in non-small cell lung cancer and promote the survival of epidermal growth factor receptor-dependent cell lines.

The role of Src-family kinases (SFKs) in non-small cell lung cancer (NSCLC) has not been fully defined. Here we addressed this question by examining SFK phosphorylation in NSCLC biopsy samples and using genetic and pharmacological approaches to inhibit SFK expression and activity in cultured NSCLC cells. Immunohistochemical analysis of NSCLC biopsy samples using a Tyr416 phosphorylation-specific, pan-SFK antibody revealed staining in 123 (33%) of 370 tumors. Because c-Src is known to be both an upstream activator and downstream mediator of epidermal growth factor receptor (EGFR), we next investigated SFK phosphorylation in a panel of NSCLC cell lines, including ones that depend on EGFR for survival. The EGFR-dependent NSCLC cell lines HCC827 and H3255 had increased phosphorylation of SFKs, and treatment of these cells with an SFK inhibitor (PP1 or SKI-606) induced apoptosis. PP1 decreased phosphorylation of EGFR, ErbB2, and ErbB3 and strikingly enhanced apoptosis by gefitinib, an EGFR inhibitor. HCC827 cells transfected with c-Src short hairpin RNA exhibited diminished phosphorylation of EGFR and ErbB2 and decreased sensitivity to apoptosis by PP1 or gefitinib. We conclude that SFKs are activated in NSCLC biopsy samples, promote the survival of EGFR-dependent NSCLC cells, and should be investigated as therapeutic targets in NSCLC patients.

Aniline Compounds↗

PubMed2006

Transplantation of primed human fetal neural stem cells improves cognitive function in rats after traumatic brain injury.

Traumatic brain injury (TBI) often produces cognitive impairments by primary or secondary neuronal loss. Stem cells are a potential tool to treat TBI. However, most previous studies using rodent stem or progenitor cells failed to correlate cell grafting and cognitive improvement. Furthermore, the efficacy of fetal human neural stem cells (hNSCs) for ameliorating TBI cognitive dysfunction is undetermined. This study therefore characterized phenotypic differentiation, neurotrophic factor expression and release and functional outcome of grafting hNSCs into TBI rat brains. Adult Sprague-Dawley rats underwent a moderate parasagittal fluid percussion TBI followed by ipsilateral hippocampal transplantation of hNSCs or vehicle 1 day post-injury. Prior to grafting, hNSCs were treated in vitro for 7 days with our previously developed priming procedure. Significant spatial learning and memory improvements were detected by the Morris water maze (MWM) test in rats 10 days after receiving hNSC grafts. Morphological analyses revealed that hNSCs survived and differentiated mainly into neurons in the injured hippocampus at 2 weeks after grafting. Furthermore, hNSCs expressed and released glial-cell-line-derived neurotrophic factor (GDNF) in vitro and when grafted in vivo, as detected by RT-PCR, immunostaining, microdialysis and ELISA. This is the first direct demonstration of the release of a neurotrophic factor in conjunction with stem cell grafting. In conclusion, human fetal neural stem cell grafts improved cognitive function of rats with acute TBI. Grafted cells survived and differentiated into neurons and expressed and released GNDF in vivo, which may help protect host cells from secondary damage and aid host regeneration.

Animals↗

PubMed2006

A disk-pivot structure micro piezoelectric actuator using vibration mode B11.

Micro piezoelectric actuator using vibration mode B(11) (B(mn), where m is the number of nodal circles, n is the nodal diameters) is designed. Different from conventional wobble-type ultrasonic motor using piezoelectric rod or cylinder, piezoelectric disc is used to excite wobble modes and metal cylinder stator is used to amplify the transverse displacement, metal rod rotor is actuated to rotate. The outer diameter of the actuator is 14mm. There are features such as low drive voltage, micromation, and convenient control of wobble state by modifying the structure of stator, etc. Finite element analysis (FEA) of the stator has been made. It is found that the resonant frequency of vibration mode B(11) is 49.03kHz, which is measured at 45.7kHz by the laser vibrometer and impedance analyzer. The rotation speed has been measured, which could be as high as 10,071rpm under an alternating current 100V. Such piezoelectric actuator can be optimized and adjusted to fit practical conditions. It can be applied in the fields of precise instrument, bioengineering and other micro actuator system.

Journal Article↗

PubMed2006

Akt phosphorylates and suppresses the transactivation of retinoic acid receptor alpha.

The transactivation of nuclear receptors is regulated by both ligand binding and phosphorylation. We previously showed that RARalpha (retinoic acid receptor alpha) phosphorylation by c-Jun N-terminal kinase contributes to retinoid resistance in a subset of NSCLC cells (non-small cell lung cancer cells), but the aetiology of this resistance in the remainder has not been fully elucidated [Srinivas, Juroske, Kalyankrishna, Cody, Price, Xu, Narayanan, Weigel and Kurie (2005) Mol. Cell. Biol. 25, 1054-1069]. In the present study, we report that Akt, which is constitutively activated in NSCLC cells, phosphorylates RARalpha and inhibits its transactivation. Biochemical and functional analyses showed that Akt interacts with RARalpha and phosphorylates the Ser96 residue of its DNA-binding domain. Mutation of Ser96 to alanine abrogated the suppressive effect of Akt. Overexpression of a dominant-negative form of Akt in an NSCLC cell line decreased RAR phosphorylation, increased RAR transactivation and enhanced the growth-inhibitory effects of an RAR ligand. The findings presented here show that Akt inhibits RAR transactivation and contributes to retinoid resistance in a subset of NSCLC cells.

Animals↗

PubMed2005

Protein kinases mediate increment of the phosphorylation of cyclic AMP-responsive element binding protein in spinal cord of rats following capsaicin injection.

BACKGROUND: Strong noxious stimuli cause plastic changes in spinal nociceptive neurons. Intracellular signal transduction pathways from cellular membrane to nucleus, which may further regulate gene expression by critical transcription factors, convey peripheral stimulation. Cyclic AMP-responsive element binding protein (CREB) is a well-characterized stimulus-induced transcription factor whose activation requires phosphorylation of the Serine-133 residue. Phospho-CREB can further induce gene transcription and strengthen synaptic transmission by the activation of the protein kinase cascades. However, little is known about the mechanisms by which CREB phosphorylation is regulated by protein kinases during nociception. This study was designed to use Western blot analysis to investigate the role of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK 1/2), PKA and PKC in regulating the phosphorylation of CREB in the spinal cord of rats following intraplantar capsaicin injection. RESULTS: We found that capsaicin injection significantly increased the phosphorylation level of CREB in the ipsilateral side of the spinal cord. Pharmacological manipulation of MEK 1/2, PKA and PKC with their inhibitors (U0126, H89 and NPC 15473, respectively) significantly blocked this increment of CREB phosphorylation. However, the expression of CREB itself showed no change in any group. CONCLUSION: These findings suggest that the activation of intracellular MAP kinase, PKA and PKC cascades may contribute to the regulation of phospho-CREB in central nociceptive neurons following peripheral painful stimuli.

Animals↗

PubMed2005

TrkB signaling regulates the developmental maturation of the somatosensory cortex.

In the rodent central nervous system, the region of the cortex that responds to facial whisker stimulation is anatomically segregated into discrete regions called barrels. Each barrel is made up of layer IV cortical neurons that receive input from a separate whisker via innervation from the thalamus. It has been shown that neurotrophins play important roles in the development and plasticity of thalamic axon innervation into the visual and retrosplenial cortex. We now extend those findings to the investigation of the role of neurotrophin signaling in barrel cortex formation. We show that the neurotrophin receptor TrkB is expressed in the thalamus and cortex during the time of cortical innervation. The two TrkB ligands, brain derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4), are expressed in the cortex at this time. Mice lacking TrkB demonstrate a developmental delay in the segregation of thalamic axons within barrels. In TrkB mutants, thalamic axons are abnormally uniform within layer IV of the cortex at postnatal day 4 compared to their control littermates, but show clear segregation into barrels 2 days later. This phenotype is recapitulated in BDNF mutant mice, but not in NT-4 mutant mice. These results demonstrate that BDNF is the sole TrkB ligand responsible for this phenotype. Analysis of conditional knockout mice that lack TrkB within the cortex, and not the thalamus, does not show a delay in thalamic axon segregation. These results indicate that TrkB expression in thalamic axons is important for the appropriate timing of barrel cortex development.

Afferent Pathways↗

PubMed2005

Comparison of HER-2/neu, ER and PCNA expression in premenopausal and postmenopausal patients with breast carcinoma.

We attempted to compare the pattern of HER-2/neu, ER and PCNA in premenopausal and postmenopausal patients with breast carcinoma to identify potential biological differences. Five hundred and forty-eight samples from 318 premenopausal and 230 postmenopausal women with invasive ductal carcinoma of the breast were evaluated for HER-2/neu, ER and PCNA expression by immunohistochemistry. HER-2/neu expression showed 27.4% positivity in premenopausal and 24.8% in postmenopausal women; there was no significant difference between the two groups (p>0.05). In contrast, HER-2/neu expression was found to be significantly associated with ER negativity in the two groups (p<0.05 in premenopausal, p<0.001 in postmenopausal patients). However, it was significantly associated with PCNA expression only in the postmenopausal group (p<0.001). 54.4% showed premenopausal tumor cell ER positivity, whereas 64.3% of the postmenopausal group showed positivity. ER expression showed a significant correlation with patient menopausal status (p<0.05). The prevalence of PCNA positivity in the tumor cell components is slightly higher in postmenopausal compared to premenopausal women (p>0.20). The current study is consistent with reports from other groups regarding the correlation of HER-2/neu with adverse pathologic features and with expression of other markers in carcinoma. We also observed there was no trend toward increased HER-2/neu expression in either premenopausal or postmenopausal patients, i.e. there was similar HER-2/neu expression in the two groups. This suggests that HER-2/neu status could be used to determine assignment to specific intensive adjuvant therapy and evaluation of biological behavior in both pre- and postmenopausal patients with breast carcinoma.

Biomarkers, Tumor↗

PubMed2003

Brn3a regulation of TrkA/NGF receptor expression in developing sensory neurons.

The TrkA/NGF receptor is essential for the survival and differentiation of sensory neurons. The molecular mechanisms regulating tissue and stage-specific expression of TrkA are largely unknown. The Brn3a POU-domain transcription factor has been implicated in the development of the PNS and proposed as a transcription regulator for TrkA. The molecular mechanisms underlying the regulation of TrkA by Brn3a is unclear. In this study, we provide genetic, transgenic and biochemical evidence that Brn3a binds to novel, specific sites in the 457 bp enhancer that regulates TrkA expression in embryonic sensory neurons. We employ Bax-knockout mice, in which sensory neurons no longer require neurotrophins for survival, to uncouple TrkA-dependent cell death from downregulation of TrkA expression. In addition, when mutagenized, the novel Brn3a-binding sites identified fail to drive appropriate reporter transgene expression in sensory neurons. Thus, TrkA, a gene that is crucial for the differentiation and survival of sensory nociceptive neurons, requires Brn3a to maintain normal transcriptional activity.

Binding Sites↗

PubMed2003

[Quantitative analysis of resveratrol from grape seeds and grape skins by high performance liquid chromatography method].

In order to perform a quantitative analysis of resveratrol from grape seeds, grape skins and waste residue of grape winery, acetonitrile-water (26:74) was applied as the fluxion phase. The detective wave-length (lambda) was 303 nm. Colume temperature was 35 degrees C. The type of chrimato pattern colume was SupelcosiLTMLC-18 (250 mm x 4.6 mm, 5 microns). Results showed that the contents of resveratrol from grape skins were higher than those of grape seeds. Among different kinds of grape skins, resveratrol contents varied. The reserveratrol content of Suo Suo grape skin was the lowest (0.9850 microgram/g). Among the same kinds of grape skins from the same production area, the resveratrol content was highest in the skin of waste residue of grape winery followed by the fresh grape skin and the old grape skin ranked thirdly, and the differences of resveratrol contents were statistically significant.

Chromatography, High Pressure Liquid↗

PubMed2002

Neurotrophin-3 is required for appropriate establishment of thalamocortical connections.

In the vertebrate brain, the thalamus serves as a relay and integration station for diverse neuronal information en route from the periphery to the cortex. Formation of the thalamocortical tract occurs during pre- and postnatal development, with distinct thalamic nuclei projecting to specific cortical regions. The molecular forces that underlie the invasion by axons into specific cortical layers followed by activity-dependent maturation of synapses are poorly understood. We show that genetic ablation of neurotrophin-3 (NT-3) in the mouse neocortex results in reduction of a set of anatomically distinct axonal bundles projecting from thalamus through cortical white matter. These bundles include thalamocortical axons that normally establish connections with retrosplenial and visual cortex, sites of early postnatal NT-3 expression. These results implicate neurotrophins in the critical stage of precise thalamocortical connections.

Animals↗

PubMed2002

[Survey of pharmacology of oleanolic acid].

OBJECTIVE: To summarize the pharmacological function of oleanolic acid. METHOD: Based on the documents and related achievements, the pharmacological function and its mechanism including its clinical use were summed up. RESULT AND CONCLUSION: Oleanolic Acid is a natural chemical which has wide-ranging function and abundant source. But we should place the emphasis on improving its biotic utilization and effect on clinical treatment.

Adjuvants, Immunologic↗