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Biomedical subjects

Lei Chen

Publications and source records attributed to Lei Chen.

At least 91 records · Page 5Linked to original sources
PubMed2005

Phosphorylation of the A-kinase-anchoring protein Yotiao contributes to protein kinase A regulation of a heart potassium channel.

Regulation of the heart by the sympathetic nervous system, fundamental to the physiological response to stress and exercise, requires coordinated phosphorylation of multiple downstream molecular targets, including the I(Ks) (slowly activating potassium current) channel. Sympathetic nervous system stimulation increases intracellular cAMP for which targeted regulation is directed in large part by distinct scaffold or anchoring proteins. Yotiao is an A-kinase-anchoring protein (AKAP) that recruits the cyclic AMP-dependent protein kinase (protein kinase A (PKA)) and protein phosphatase 1 to the carboxyl terminus of the I(Ks) channel to form a molecular complex and control its phosphorylation state, crucial to the cardiac cellular response to sympathetic nervous system stimulation. Here we report that Yotiao itself is a substrate for PKA phosphorylation, and we identify a Yotiao amino-terminal (N-T) residue (Ser-43) that is PKA-phosphorylated in response to beta-adrenergic receptor stimulation. The replacement of Ser-43 by Ala ablates the PKA phosphorylation of N-T Yotiao and markedly diminishes the functional response of the wild type and pseudo-phosphorylated I(Ks) channel to cAMP but neither prevents the PKA phosphorylation of KCNQ1 nor its binding to Yotiao. These results suggest, for the first time, a critical role for the PKA phosphorylation of an AKAP in the functional regulation of an ion channel protein and postphosphorylation allosteric modulation of the I(Ks) channel by Yotiao.

A Kinase Anchor Proteins↗
PubMed2005

Centrally administered adrenomedullin 2 activates hypothalamic oxytocin-secreting neurons, causing elevated plasma oxytocin level in rats.

We examined the effects of intracerebroventricular (i.c.v.) administration of adrenomedullin 2 (AM2) on plasma oxytocin (OXT) and arginine vasopressin (AVP) levels in conscious rats. Plasma OXT levels were markedly increased 5 min after i.c.v. administration of AM2 (1 nmol/rat) compared with vehicle and remained elevated in samples taken at 10, 15, 30, and 60 min. By contrast, plasma AVP levels were not significantly elevated in samples taken between 5 and 180 min after i.c.v. administration of AM2 except at the 30-min time point. Fos-like immunoreactivity (Fos-LI) was observed in various brain areas, including the paraventricular (PVN) and the supraoptic nuclei (SON) after i.c.v. administration of AM2 (2 nmol/rat) in conscious rats (measured at 90 min post-AM2 infusion). Dual immunostaining for OXT/Fos and AVP/Fos showed that OXT-LI neurons predominantly exhibited nuclear Fos-LI compared with AVP-LI neurons in the PVN and the SON. In situ hybridization histochemistry showed that i.c.v. administration of AM2 (0.2, 1, and 2 nmol/rat) caused marked induction of the expression of the c-fos gene in the PVN and the SON. This induction was significantly reduced by pretreatment with both the calcitonin gene-related peptide (CGRP) antagonist CGRP-(8-37) (3 nmol/rat) and the AM receptor antagonist AM-(22-52) (27 nmol/rat). These results suggest that centrally administered AM2 mainly activates OXT-secreting neurons in the PVN and the SON, at least in part through the CGRP and/or AM receptors with marked elevation of plasma OXT levels in conscious rats.

Adrenomedullin↗
PubMed2005

Synthesis, crystal structure, and solid-state NMR spectroscopy of a new open-framework aluminophosphate (NH(4))(2)Al(4)(PO(4))(4)(HPO(4))xH(2)O.

A new three-dimensional open-framework aluminophosphate (NH(4))(2)Al(4)(PO(4))(4)(HPO(4)).H(2)O (denoted AlPO-CJ19) with an Al/P ratio of 4/5 has been synthesized, using pyridine as the solvent and 2-aminopyridine as the structure-directing agent, under solvothermal conditions. The structure was determined by single-crystal X-ray diffraction and further characterized by solid-state NMR techniques. The alternation of the Al-centered polyhedra (including AlO(4), AlO(5), and AlO(6)) and the P-centered tetrahedra (including PO(4) and PO(3)OH) results in an interrupted open-framework structure with an eight-membered ring channel along the [100] direction. This is the first aluminophosphate containing three kinds of Al coordinations (AlO(4), AlO(5), and AlO(6)) with all oxygen vertexes connected to framework P atoms. (27)Al MAS NMR, (31)P MAS NMR, and (1)H --> (31)P CPMAS NMR characterizations show that the solid-state NMR techniques are an effective complement to XRD analysis for structure elucidation. Furthermore, all of the possible coordinations of Al and P in the aluminophosphates with an Al/P ratio of 4/5 are summarized. Crystal data: (NH(4))(2)Al(4)(PO(4))(4)(HPO(4))xH(2)O, monoclinic P2(1) (No. 4), a = 5.0568(3) A, b = 21.6211(18) A, c = 8.1724(4) A, beta = 91.361(4) degrees , V = 893.27(10) A(3), Z = 2, R(1) = 0.0456 (I > 2 sigma(I)), and wR(2) = 0.1051 (all data).

Journal Article↗
PubMed2005

[Serum adiponectin concentration in relation to body fat distribution and tissue insulin sensitivity in the glucose clamp study].

OBJECTIVE: To study serum adiponectin level in relation to body fat distribution and tissue insulin sensitivity by using the extended hyperinsulinemic euglycemic clamp technique. METHODS: Extended hyperinsulinemic euglycemic clamp was performed in 44 Chinese individuals with normal glucose tolerance from Shanghai area, including 12 subjects with normal weight [body mass index (BMI) < 25 kg/m(2)], 19 with overweight (25 kg/m(2) < or = BMI < 30 kg/m(2)), and 13 with obesity (BMI > or = 30 kg/m(2)). The rate of insulin-mediated glucose disposal (Rd) during the steady state of glucose clamp was used to assess the peripheral tissue insulin sensitivity. Total body fat depots [BMI, percentage of body fat (FAT%), and body fat mass (FM)], regional body fat depots [waist circumference (W), hip circumference (H), W and H ratio (WHR), abdominal subcutaneous fat area (SA), intra-abdominal fat area (VA), and femoral subcutaneous fat area (FA)] were measured on all subjects. Fasting serum adiponectin level was determined by radioimmunoassay. RESULTS: (1) After the adjustment for age and sex, the serum adiponectin concentrations in the overweight and obesity groups were (8.7 +/- 4.8) mg/L and (6.7 +/- 0.8) mg/L, both significantly lower than that in the normal weight group [(15.7 +/- 1.8) mg/L, both P < 0.01]. (2) Serum adiponectin concentration was negatively correlated with BMI, W, WHR, FAT%, FM and VA, especially with W and VA (r = -0.46, P < 0.01, and r = -0.53, P < 0.01). (3) Serum adiponectin concentration was positively correlated with Rd (r = 0.52, P < 0.01) and the rate of glycogen synthesis (r = 0.36, P < 0.05), and was negatively correlated with free fatty acid level (r = -0.41, P < 0.05). (4) Stepwise regression analysis indicated that in addition to sex, BMI, WHR or VA and SA, serum adiponectin level was also the independent contributing factor for Rd, which explains 3.52% and 4.84% of the variance respectively (P all < 0.05). CONCLUSION: (1) The decrease in serum adiponectin level is associated with the increase of total body fat depot, especially the increase of total body fat depot in intra-abdominal fat area. (2) Serum adiponectin level is an independent contributing factor for insulin sensitivity.

Adiponectin↗
PubMed2005

C31 enhances voltage-gated calcium channel currents in undifferentiated PC12 cells.

C31, consisting of 31 amino acid residues, is generated from the carboxyl terminal fragments (CTFs) of amyloid precursor protein (APP). It has been shown that C31 causes apoptosis in neurons and is present in brains of Alzheimer disease (AD) patients. Using whole-cell patch clamp techniques, we investigated effects of C31 on voltage-gated calcium channel (VGCC) currents and the protective effects of beta-estradiol on PC12 cells. The results demonstrated that C31 induced a significant increase of the VGCC currents in PC12 cells, which was blocked by beta-estradiol. These results suggest that modulation of intracellular calcium levels by VGCC may in part be involved in C31 induced neuronal death associated with AD.

Animals↗
PubMed2005

Type VII collagen is required for Ras-driven human epidermal tumorigenesis.

Type VII collagen defects cause recessive dystrophic epidermolysis bullosa (RDEB), a blistering skin disorder often accompanied by epidermal cancers. To study the role of collagen VII in these cancers, we examined Ras-driven tumorigenesis in RDEB keratinocytes. Cells devoid of collagen VII did not form tumors in mice, whereas those retaining a specific collagen VII fragment (the amino-terminal noncollagenous domain NC1) were tumorigenic. Forced NC1 expression restored tumorigenicity to collagen VII-null epidermis in a non-cell-autonomous fashion. Fibronectin-like sequences within NC1 (FNC1) promoted tumor cell invasion in a laminin 5-dependent manner and were required for tumorigenesis. Tumor-stroma interactions mediated by collagen VII thus promote neoplasia, and retention of NC1 sequences in a subset of RDEB patients may contribute to their increased susceptibility to squamous cell carcinoma.

Adolescent↗
PubMed2005

Distribution, cloning and sequencing of GnRH, its receptor, and effects of gastric acid secretion of GnRH analogue in gastric parietal cells of rats.

Our objective was to study the distribution of gonadotropin-releasing hormone (GnRH) and its receptor, cloning and sequencing of GnRH and its receptor gene in cultured gastric parietal cells of rats. The distribution of GnRH and its receptor mRNA were investigated through immunocytochemical ABC methods and in situ hybridization methods in cultured gastric parietal cells of rats. After isolation of the total RNA from the parietal cells, RT-PCR was conducted to obtain GnRH and its receptor cDNA. Then, the products of PCR was purified, digested by the restriction enzyme of Hind III and EcoR I, and DNA fragments of interests were cloned into pUC19 vector. The products of PCR were analyzed by sequencing with Sanger's method after identified by PCR and digestion of restriction enzyme. Gastric parietal cells showed GnRH and its receptor immunoreactivity; positive material was located in cytoplasm other than in nuclei. GnRH and its receptor mRNA hybridized signals were also detected in cytoplasm with negative nuclei. The specific amplified band of GnRH and its receptor sequences were detected through Agarose gel electrophoresis, and GnRH gene sequence is identical to that of GnRH which has been reported in rat hypothalamus and GnRH receptor sequence is identical to that of the pituitary of rat. GnRH analogue (Alarelin) could inhibit the gastric acid secretion both by direct actions on parietal cells and by inhibiting vagous function. Our data suggest that GnRH could be produced by gastric parietal cells of rats and may modulate physiological function of gastric parietal cells of rats through autocrinal and paracrinal way.

Animals↗
PubMed2005

Novel polymer patterns formed by lithographically induced self-assembly (LISA).

A variety of self-assembly patterns, e.g., concentric rings, rods, and pillars, in polymer thin film have been achieved by lithographically induced self-assembly (LISA) in this study. The variations of the LISA patterns are controlled by many operation factors, such as the choice of the polymers, mask topology, process temperatures, surface tension, and so forth. It was found that as the inter- and intramolecular hydrogen bond interactions were incorporated into the polymer [poly(methyl methacrylate-co-methacrylic acid)], novel LISA patterns such as rods and corresponding arrays (concentric ring, triangle, hexagonal, etc.) were formed, in addition to the pillar arrays formed in poly(methyl methacrylate) under the same experimental conditions. The origins of the rod array are determined by the topology of the masks. Under a plain mask, the patterns developed from any nonuniform defects (spots) on the mask or polymer thin film and propagated outward. However, under a mask with protruding flat patterns, the rod patterns started along the edge of the protrusions and propagated inward. By increasing the process temperature, those novel rods and corresponding array patterns could transform back to pillar or pillar arrays.

Journal Article↗
PubMed2005

High-performance nanowire-grid polarizers.

We developed a new type of wire-grid polarizer that has achieved excellent optical performance and reliability. The nanowire-grid polarizer is based on a fully optimized innovative design structure that consists of not only the core nanowire grid but also the surrounding multilayer thin-film structures. The surrounding structures are designed for antireflectivity to provide the best possible efficiency as well as for device reliability to provide the best possible handling robustness and environmental durability. The core nanowire grid utilizes nanosized high-aspect-ratio dielectric walls as a support for forming a high-aspect-ratio metal nanowire grid that significantly reduces energy loss as a result of metal absorption for the transmitted beam while providing a high extinction ratio of the blocked beam. The developed high-quality nanowire-grid polarizer has potential for use in many integrated optical applications.

Journal Article↗
PubMed2005

Biological effect of velvet antler polypeptides on neural stem cells from embryonic rat brain.

BACKGROUND: Velvet antler polypeptides (VAPs), which are derived from the antler velvets, have been reported to maintain survival and promote growth and differentiation of neural cells and, especially the development of neural tissues. This study was designed to explore the influence of VAPs on neural stem cells in vitro derived from embryonic rat brain. METHODS: Neural stem cells derived from E12-14 rat brain were isolated, cultured, and expanded for 7 days until neural stem cell aggregations and neurospheres were generated. The neurospheres were cultured under the condition of different concentration of VAPs followed by immunocytochemistry to detect the differentiation of neural stem cells. RESULTS: VAPs could remarkably promote differentiation of neural stem cells and most neural stem cells were induced to differentiate towards the direction of neurons under certain concentration of VAPs. CONCLUSION: Neural stem cells can be successfully induced into neurons by VAPs in vitro, which could provide a basis for regeneration of the nervous system.

Animals↗
PubMed2005

Characterization of monoclonal antibody to L-homocysteic acid and its immunohistochemistry in rat hippocampus.

L-homocysteic acid (HCA) and other amino acids were conjugated to rat brain material (extracted rat brain protein) with glutaraldehyde to form HCA- and amino acids-brain material conjugates. The specificity of monoclonal antibody (McAb) was tested on serial dilution test and absorption test on enzyme-linked immunosorbent assay (ELISA) using these conjugates as antigens instead of amino acids-BSA (bovine serum albumin) conjugates used previously. The characterized McAb was applied for immunohistochemical staining using PAP (peroxidase antiperoxidase) technique in combination with silver enhancement of diamino-benzene (DAB) products. The results indicated that McAb to L-HCA reacted with L-HCA-brain material conjugates, but not with other amino acids-brain material conjugates so far tested. McAb absorbed with L-HCA-brain material abolished or decreased immunoreactivity of L-HCA-brain material with McAb. The antibody selectively stained subpopulation of cells and processes in the hippocampus fixed with glutaradehyde. Absorption of McAb with L-HCA-brain material abolished immunohistochemical staining. These results suggested that McAb was specific for L-HCA-brain materials and could be used for imuno-histocytochemistry. This would provide a new tool for immunohistochemical visualization and localization of L-HCA in the nervous system.

Animals↗
PubMed2005

Cloning and preliminary characterization of lh3 gene encoding a putative acetyltransferase from a rifamycin SV-producing strain Amycolatopsis mediterranei.

An ORF located immediately downstream of glnR gene was cloned from Amycolatopsis mediterranei U32 and was named lh3. Sequence analysis revealed that lh3 encodes a putative acetyltransferase, which shows high amino acid sequence similarities to the mycothiol synthase (MshD) from other actinomycetes. For functional analysis, mutation in lh3 gene was generated by gene replacement with an apramycin resistance gene through homologous recombination. Compared with the wild type strain, the resulting mutant was more sensitive to H2O2, apramycin and erythromycin by two- to three-fold. These results suggest that the lh3 gene plays an important role in the course of detoxification in A. mediterranei U32.

Acetyltransferases↗
PubMed2005

Resonance Raman characterization of Rhodobacter capsulatus reaction centers with lysine mutations near the accessory bacteriochlorophylls.

Lysine residues have been introduced into Rhodobacter capsulatus reaction centers at M-polypeptide position 201 and at L-polypeptide position 178. These positions are in the proximity of ring V of the accessory bacterochlorophylls BA and BB, respectively. Resonance Raman studies indicate that the introduction of a Lys residue at either position M201 or L178 results in structural perturbations to the BChl cofactors. Lys at L178 directly interacts with BB, most likely via a hydrogen bond. The hydrogen bonding interaction is consistent with enhanced B branch electron transfer that is observed in RCs from the S(L178)K/G(M201)D/L(M212)H triple mutant versus the G(M201)D/L(M212)H double mutant. In contrast, the introduction of a Lys at M201 does not result in hydrogen bonding to the BA cofactor, in contrast to the introduction of a His at M201. Accordingly, the alkyl ammonium head group of the side chain of the Lys at M201 residue appears to be distant from BA.

Bacteriochlorophylls↗
PubMed2005

Cloning and characterization of a novel G protein beta-subunit of pearl oyster (Pinctada fucata), and its interaction sites with calmodulin.

A cDNA clone encoding a novel G protein beta subunit of beta1 subclass, pfGbeta1 was isolated from the pearl oyster (Pinctada fucata). The deduced amino acid sequence of pfGbeta1 (341 amino acids) shares high homology to northern European squid (Loligo pealei) and great pond snail (Lymnaea stagnalis) pfGbeta1, while it has diverged from bovine (Bos taurus) and human. The well-conserved amino acid domains in G protein beta subunit, seven WD repeats, were founded in the deduced amino acid sequence. Alignment analysis showed that the beginning amino acid residues in variable fragment of the seventh WD motif are different from any other Gbeta. The prediction of 3D structure of pfGbeta showed that pfGbeta belongs to beta-propeller family proteins whose members contain 4-8 antiparallel beta-sheets resembling the blades of a propeller. In situ hybridization and Northern blotting analysis revealed that the pfGbeta mRNA hybridization signals were widely expressed in various tissues except muscle, with abundantly in epithelia of gill, gonad and outer fold of mantle. We also investigated the interactions between Gbetagamma and calmodulin (CaM), and specific amino acid residues that may be critical for the binding of Gbetagamma to CaM were also identified. Furthermore, the functional studies of the interaction showed that the binding of CaM and Gbetagamma increases the alkaline phosphatase (ALP) activity, an indicator for mineralization in MC3T3-E1 cells. The ALP activity of the mutants of pfGbetagamma that impaired the interactions of Gbetagamma with CaM is higher than the Control group; however, it is lower than the WTC group. Together, these results suggest that the Gbetagamma might interact with CaM and point to the important physiological function in modulating cellular functions.

Alkaline Phosphatase↗
PubMed2005

Tonic activation of presynaptic GABA(B) receptors on rat pallidosubthalamic terminals.

AIM: The subthalamic nucleus plays a critical role in the regulation of movement, and abnormal activity of its neurons is associated with some basal ganglia motor symptoms. We examined the presence of functional presynaptic GABA(B) receptors on pallidosubthalamic terminals and tested whether they were tonically active in the in vitro subthalamic slices. METHODS: Whole-cell patch-clamp recordings were applied to acutely prepared rat subthalamic nucleus slices. The effects of specific GABA(B) agonist and antagonist on action potential-independent inhibitory postsynaptic currents (IPSCs), as well as holding current, were examined. RESULTS: Superfusion of baclofen, a GABA(B) receptor agonist, significantly reduced the frequency of GABA(A) receptor-mediated miniature IPSCs (mIPSCs), in a Cd2+-sensitive manner, with no effect on the amplitude, indicating presynaptic inhibition on GABA release. In addition, baclofen induced a weak outward current only in a minority of subthalamic neurons. Both the pre- and post-synaptic effects of baclofen were prevented by the specific GABA(B) receptor antagonist, CGP55845. Furthermore, CGP55845 alone increased the frequency of mIPSCs, but had no effect on the holding current. CONCLUSION: These findings suggest the functional dominance of presynaptic GABA(B) receptors on the pallidosubthalamic terminals over the postsynaptic GABA(B) receptors on subthalamic neurons. Furthermore, the presynaptic, but not the postsynaptic, GABA(B) receptors are tonically active, suggesting that the presynaptic GABA(B) receptors in the subthalamic nucleus are potential therapeutic target for the treatment of Parkinson disease.

Animals↗
PubMed2005

Action of aluminum on high voltage-dependent calcium current and its modulation by ginkgolide B.

AIM: To investigate the effect of aluminum (Al) on high voltage-dependent calcium current (I(HVA)) and its modulation by ginkgolide B (Gin B). METHODS: The whole-cell, patch-clamp technique was used to record IHVA from acutely isolated hippocampal CA1 pyramydal neurons in rats. RESULTS: Al 0.1 mmol/L (low concentration) reduced I(HVA); Al 0.75 and 1.0 mmol/L (high concentrations) increased I(HVA), and Al decreased and increased I(HVA) at intermediate concentrations of 0.25 and 0.5 mmol/L. The increase of I(HVA) by Al 1.0 mmol/L was enhanced by the adenylyl cyclase (AC) agonist forskolin and was partly abolished by the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) antagonist H-89, whereas the decrease observed with Al 0.1 mmol/L was neither reversed by forskolin nor affected by H-89. Gin B had no effect on I(HVA) in normal neurons, but canceled the increase in I(HVA) by 1.0 mmol/L Al. CONCLUSION: The results indicate that the mechanism of Al affecting I(HVA) differs at different concentrations, and this may be attributed to its complex actions. Gin B could prevent neurons from injury by inhibiting calcium influx.

Aluminum Chloride↗