Biomedical subjects

Lei Zhang

Publications and source records attributed to Lei Zhang.

At least 289 records · Page 16Linked to original sources

PubMed2004

Mood stabilizer valproate promotes ERK pathway-dependent cortical neuronal growth and neurogenesis.

Manic-depressive illness has been conceptualized as a neurochemical illness. However, brain imaging and postmortem studies reveal gray-matter reductions, as well as neuronal and glial atrophy and loss in discrete brain regions of manic-depressive patients. The roles of such cerebral morphological deficits in the neuropathophysiology and therapeutic mechanisms of manic-depressive illness are unknown. Valproate (2-propylpentanoate) is a commonly used mood stabilizer. The ERK (extracellular signal-regulated kinase) pathway is used by neurotrophic factors to regulate neurogenesis, neurite outgrowth, and neuronal survival. We found that chronic treatment of rats with valproate increased levels of activated phospho-ERK44/42 in neurons of the anterior cingulate, a region in which we found valproate-induced increases in expression of an ERK pathway-regulated gene, bcl-2. Valproate time and concentration dependently increased activated phospho-ERK44/42 and phospho-RSK1 (ribosomal S6 kinase 1) levels in cultured cortical cells. These increases were attenuated by Raf and MEK (mitogen-activated protein kinase/ERK kinase) inhibitors. Although valproate affects the functions of GSK-3 (glycogen synthase kinase-3) and histone deacetylase (HDAC), its effects on the ERK pathway were not fully mimicked by selective inhibitors of GSK-3 or HDAC. Similar to neurotrophic factors, valproate enhanced ERK pathway-dependent cortical neuronal growth. Valproate also promoted neural stem cell proliferation-maturation (neurogenesis), demonstrated by bromodeoxyuridine (BrdU) incorporation and double staining of BrdU with nestin, Tuj1, or the neuronal nuclei marker NeuN (neuronal-specific nuclear protein). Chronic treatment with valproate enhanced neurogenesis in the dentate gyrus of the hippocampus. Together, these data demonstrate that valproate activates the ERK pathway and induces ERK pathway-mediated neurotrophic actions. This cascade of events provides a potential mechanism whereby mood stabilizers alleviate cerebral morphometric deficits associated with manic-depressive illness.

Animals↗

PubMed2004

Structure of adsorbed n-dodecyl-beta-D-maltoside layers on hematite.

The composition, structure, and thickness of n-dodecyl-beta-D-maltoside self-assembled layers on hematite have been evaluated using infrared external reflection spectroscopy and spectral simulation techniques. From the qualitative and quantitative analysis of the reflection spectra of the same sample recorded at different specific angles of incidence and two polarizations, the orientation of the sugar ring and hydrocarbon chain were obtained. Both of these molecular groups are positioned parallel to hematite surface, the adsorbed molecules being at low (2.2-nm-thick layer) as well as higher (11-nm) coverages. The maltoside is adsorbed through interaction of sugar ring OH groups with hematite surface hydroxyl groups. The adsorption of maltoside is not very strong and desorption takes place easily from acidic and low-basic solutions but with more difficulty from strong-basic solution.

Ferric Compounds↗

PubMed2004

Aberrant gene expression in organs of bovine clones that die within two days after birth.

Cloning by somatic nuclear transfer is an inefficient process in which some of the cloned animals die shortly after birth and display organ abnormalities. In an effort to determine the possible genetic causes of neonatal death and organ abnormalities, we used real-time quantitative reverse transcription-polymerase chain reaction to examine expression patterns of eight developmentally important genes (PCAF, Xist, FGFR2, PDGFRa, FGF10, BMP4, Hsp70.1, and VEGF) in six organs (heart, liver, spleen, lung, kidney, and brain) of both cloned bovines that died soon after birth (n=9) and normal control calves produced by artificial insemination. In somatic cloning of cattle, fibroblasts have often been used for doner nuclei, and the effect of the age of the fibroblast donor cells on gene expression profiles was investigated. Aberrant expressions of seven genes were found in these clones. The majority of aberrantly expressed genes were common in clones derived from adult fibroblast (AF) and in clones derived from fetal fibroblast (FF) compared to controls, whereas some genes were dysregulated either in AF cell-derived or in FF cell-derived clones. For the studied genes, kidney was the organ least affected by gene dysregulation, and heart was the organ most affected, in which five genes were aberrant. Most dysregulations (12 of 19) were up-regulation, but PDGFRa only showed down-regulation. VEGF, BMP-4, PCAF, and Hsp70.1 were extremely dysregulated, whereas the other four genes had a low level of gene dysregulation. Our results suggest that the aberrant gene expression occurred in most tissues of cloned bovines that died soon after birth. For each specific gene, aberrant expression resulting from nuclear transfer was tissue-specific. Because these genes play important roles in embryo development and organogenesis, the aberrant transcription patterns detected in these clones may contribute to the defects of organs reported in neonatal death of clones.

Abnormalities, Multiple↗

PubMed2004

The serine/threonine kinase cyclin G-associated kinase regulates epidermal growth factor receptor signaling.

Cyclin G-associated kinase (GAK) is a serine/threonine kinase that features high homology outside its kinase domain with auxilin. Like auxilin, GAK has been shown to be a cofactor for uncoating clathrin vesicles in vitro. We investigated epidermal growth factor (EGF) receptor-mediated signaling in cells, in which GAK is down-regulated by small hairpin RNAs. Here, we report that down-regulation of GAK by small hairpin RNA has two pronounced effects on EGF receptor signaling: (i) the levels of receptor expression and tyrosine kinase activity go up by >50-fold; and (ii) the spectrum of downstream signaling is significantly changed. One very obvious result is a large increase in the levels of activated extracellular signal-regulated kinase 5 and Akt. These two effects of GAK down-regulation result from, at least in part, alterations in receptor trafficking, the most striking of which is the persistence of EGF receptor in altered cellular compartment along with activated extracellular signal-regulated kinase 5. The alterations resulting from GAK down-regulation can have distinctive biological consequences: In CV1P cells, down-regulation of GAK results in outgrowth of cells in soft agar, raising the possibility that loss of GAK function may promote tumorigenesis.

Cell Division↗

PubMed2004

[Integrins mediate the increase of concentration of intracellular free calcium in mouse eggs].

For studying the effect of integrin on the [Ca(2+)](i) of mouse eggs and its transmembrane signaling mechanism, zona-free mouse eggs were loaded with calcium probe Fluo-3/AM and the intensity of fluorescence of the eggs treated with different factors was measured through laser confocal microscopy. The results showed that the [Ca(2+)](i) of zona-free mouse eggs was increased when the eggs were treated with RGD peptide, fibronectin (Fn) and anti-mouse integrin subunit alpha(6) and beta(1) monoclonal antibodies, respectively. The [Ca(2+)](i) of the mouse eggs was also increased when the eggs were placed in calcium-free medium and treated with RGD peptide or Fn. The changes in the mouse egg [Ca(2+)](i) caused by RGD and Fn were similar to those caused by sperm. However, the concentration of Ca(2+) of the zona-free mouse eggs pretreated with tyrosine kinase inhibitor was not increased when the eggs were treated in the same way, and, neither was the intracellular calcium increased in those eggs pretreated with PKC inhibitor when the eggs were treated with RGD peptide. It is therefore suggested that the occupancy of integrins on the membrane of mouse eggs by their ligands mediates the release of Ca(2+) and then the increase in the [Ca(2+)](i) of eggs, which is one of the early events of egg activation. The tyrosine kinase signaling pathway and PKC are involved in this process as well.

Animals↗

PubMed2004

Expression of cysteinyl leukotriene receptor 1 in human traumatic brain injury and brain tumors.

Cysteinyl leukotrienes (CysLTs) are potent proinflammatory mediators. CysLT receptor 1 (CysLT(1)) is one of the two CysLT receptors that has been cloned. Although the expression of CysLT(1) in the brain has been demonstrated by Northern blot and RT-PCR analyses, the location of CysLT(1) in the brain remains unknown. The objective of this study was to examine the distribution of CysLT(1) by immunohistochemical analysis in human brains with traumatic injury or tumors. CysLT(1) was expressed intensely in the microvascular endothelial cells in both normal and abnormal conditions. At 8 days after traumatic injury, microvascular regeneration was found and all of the endothelial cells highly expressed CysLT(1). In gray and white matters of the normal regions of the brain, CysLT(1) was expressed weekly or not at all. However, the CysLT(1) expression increased in the neuron- and glial-appearing cells in gray and white matters after traumatic brain injury. CysLT(1) was also detected in astrocytoma, ganglioglioma and metastatic adenocarcinoma, and the expression in the neuron- and glial-appearing cells around brain tumors increased robustly.

Adult↗

PubMed2004

Microtubule-stabilizing agents based on designed laulimalide analogues.

Laulimalide is a potent, structurally unique microtubule-stabilizing agent originally isolated from the marine sponge Cacospongia mycofijiensis. Laulimalide exhibits an activity profile different from other microtubule-binding agents, notably including effectiveness against paclitaxel-resistant cells, but it is intrinsically unstable. Five analogues of laulimalide were designed to exhibit enhanced chemical stability yet retain its exceptional biological activities. Evaluations of these analogues showed that all are effective inhibitors of cancer-cell proliferation yet differ substantially in potency with an IC(50) range of 0.12-16.5 microM. Although all of the analogues initiated cellular changes similar to laulimalide, including increased density of interphase microtubules, aberrant mitotic spindles, and ultimately apoptosis, differences among the analogues were apparent. The two most potent analogues, C(16)-C(17)-des-epoxy laulimalide and C(20)-methoxy laulimalide, appear to have a mechanism of action identical to laulimalide. The C(16)-C(17)-des-epoxy, C(20)-methoxy laulimalide derivative, which incorporates both chemical changes of the most potent analogues, was significantly less potent and initiated the formation of unique interphase microtubules unlike the parent compound and other analogues. Two C(2)-C(3)-alkynoate derivatives had lower potency, and they initiated abnormal microtubule structures but did not cause micronucleation or extensive G(2)/M accumulation. Significantly, paclitaxel- and epothilone-resistant cell lines were less resistant to the laulimalide analogues. In summary, analogues of laulimalide designed to minimize or eliminate its intrinsic instability have been synthesized, and some have been found to retain the unique biological activities of laulimalide.

Animals↗

PubMed2004

Large-Scale, solution-phase growth of single-crystalline SnO2 nanorods.

Small-diameter (<5 nm), single-crystalline SnO2 nanorods were synthesized in solution with a mean length of 17 +/- 4 nm (mean aspect ratio of 4:1) with the [001] direction along the major axis. Two characteristic peaks at 576 and 356 cm-1 in the Raman spectrum further confirmed the small crystal size. The SnO2 nanorods exhibit a red emission at 580 nm.

Journal Article↗

PubMed2004

A tobacco calcium/calmodulin-binding protein kinase functions as a negative regulator of flowering.

A tobacco calcium/calmodulin-binding protein kinase (NtCBK1) was isolated and identified. The predicted NtCBK1 protein has 599 amino acids, an N-terminal kinase domain, and shares high homology with other calmodulin (CaM)-related kinases. Whereas NtCBK1 phosphorylates itself and substrates such as histone IIIS and syntide-2 in the absence of CaM, its kinase activity can be stimulated by tobacco CaMs. However, unlike another tobacco protein kinase designated NtCBK2, NtCBK1 was not differentially regulated by the different CaM isoforms tested. The CaM-binding domain of NtCBK1 was located between amino acids 436 and 455, and this domain was shown to be necessary for CaM modulation of kinase activity. RNA in situ hybridization showed that NtCBK1 was highly regulated in the transition to flowering. Whereas NtCBK1 mRNA was accumulated in the shoot apical meristem during vegetative growth, its expression was dramatically decreased in the shoot apical meristem after floral determination, and in young flower primordia. The expression of NtCBK1 was up-regulated to high levels in floral organ primordia. Fluctuations in NtCBK1 expression were verified by analysis of tobacco plants expressing green fluorescent protein under the control of the NtCBK1 promoter, suggesting a role of NtCBK1 in the transition to flowering. This conclusion was confirmed by overexpressing NtCBK1 in transgenic tobacco plants, where maintenance of high levels of NtCBK1 in the shoot apical meristem delayed the switch to flowering and extended the vegetative phase of growth. Further work indicated that overexpression of NtCBK1 in transgenic tobacco did not affect the expression of NFL, a tobacco homologue of the LFY gene that controls meristem initiation and floral structure in tobacco. In addition, the promotion of tobacco flowering time by DNA demethylation cannot be blocked by the overexpression of NtCBK1.

Amino Acid Sequence↗

PubMed2004

Preparation of single rice chromosome for construction of a DNA library using a laser microbeam trap.

We report the development of a laser micromanipulation system and its application in the isolation of individual rice chromosomes directly from a metaphase cell. Microdissection and flow sorting are two major methods for the isolation of single chromosome. These methods are dependent on the techniques of chromosome spread and chromosome suspension, respectively. In the development of this system, we avoided using chromosome spread and cell suspension was used instead. The cell wall of metaphase rice cell was cut by optical scissors. The released single chromosome was captured by an optical trap and transported to an area without cell debris. The isolated single chromosome was then collected and specific library was constructed by linker adaptor PCR. The average insert size of the library was about 300 bp. Two hundred inserts of chromosome 4 library were sequenced, and 96.5% were aligned to the corresponding sequences of rice chromosome 4. These results suggest the possible application of this method for the preparation of other subcellular structures and for the cloning of single macromolecule through a laser microbeam trap.

Chromosomes, Plant↗

PubMed2004

Expression, purification and preliminary crystallographic studies of a single-point mutant of Mos1 mariner transposase.

A soluble single-point mutant of full-length Mos1 mariner transposase (MW = 40.7 kDa) has been overexpressed in Escherichia coli, purified to 95% homogeneity and crystallized. This provides the first example of the crystallization of a eukaryotic transposase. The native crystals diffract to 2.5 A resolution and show tetragonal symmetry, with unit-cell parameters a = b = 44.5, c = 205.6 A. Multiple-wavelength anomalous data from a selenomethionyl form of the protein and data from a heavy-atom derivative have been collected.

Amino Acid Sequence↗

PubMed2004

Engineering tropane biosynthetic pathway in Hyoscyamus niger hairy root cultures.

Scopolamine is a pharmaceutically important tropane alkaloid extensively used as an anticholinergic agent. Here, we report the simultaneous introduction and overexpression of genes encoding the rate-limiting upstream enzyme putrescine N-methyltransferase (PMT) and the downstream enzyme hyoscyamine 6 beta-hydroxylase (H6H) of scopolamine biosynthesis in transgenic henbane (Hyoscyamus niger) hairy root cultures. Transgenic hairy root lines expressing both pmt and h6h produced significantly higher (P < 0.05) levels of scopolamine compared with the wild-type and transgenic lines harboring a single gene (pmt or h6h). The best line (T(3)) produced 411 mg/liter scopolamine, which was over nine times more than that in the wild type (43 mg/liter) and more than twice the amount in the highest scopolamine-producing h6h single-gene transgenic line H(11) (184 mg/liter). To our knowledge, this is the highest scopolamine content achieved through genetic engineering of a plant. We conclude that transgenic plants harboring both pmt and h6h possessed an increased flux in the tropane alkaloid biosynthetic pathway that enhanced scopolamine yield, which was more efficient than plants harboring only one of the two genes. It seems that the pulling force of the downstream enzyme (the faucet enzyme) H6H plays a more important role in stimulating scopolamine accumulation in H. niger whereas the functioning of the upstream enzyme PMT is increased proportionally. This study provides an effective approach for large-scale commercial production of scopolamine by using hairy root culture systems as bioreactors.

Alkaloids↗

PubMed2004

An fMRI study with semantic access in low proficiency second language learners.

Brain activity was measured with fMRI in twelve 10- to 12-year-old Chinese children who began learning English when they were 8 years old in order to find out whether there is a common or a distinct neural semantic system for native language (L1) and second language (L2) in low proficiency bilingual subjects. Although they performed less well in L2 in the semantic decision task administered during fMRI measurement, these subjects showed similar robust activation, for both languages, in brain areas involved in semantic processing (e.g. the left inferior frontal cortex). Within-subject and group analyses revealed no significant difference in the activation patterns for L1 and L2 in these regions. These results suggest that at least at single-word level, there are shared neural substrates for semantic processing of L1 and L2 even when one is at a very low L2 proficiency level.

Brain↗

PubMed2004

Structural features of the rice chromosome 4 centromere.

A complete sequence of a chromosome centromere is necessary for fully understanding centromere function. We reported the sequence structures of the first complete rice chromosome centromere through sequencing a large insert bacterial artificial chromosome clone-based contig, which covered the rice chromosome 4 centromere. Complete sequencing of the 124-kb rice chromosome 4 centromere revealed that it consisted of 18 tracts of 379 tandemly arrayed repeats known as CentO and a total of 19 centromeric retroelements (CRs) but no unique sequences were detected. Four tracts, composed of 65 CentO repeats, were located in the opposite orientation, and 18 CentO tracts were flanked by 19 retroelements. The CRs were classified into four types, and the type I retroelements appeared to be more specific to rice centromeres. The preferential insert of the CRs among CentO repeats indicated that the centromere-specific retroelements may contribute to centromere expansion during evolution. The presence of three intact retrotransposons in the centromere suggests that they may be responsible for functional centromere initiation through a transcription-mediated mechanism.

Base Sequence↗

PubMed2004

Prolonged hypotensive effect of human tissue kallikrein gene delivery and recombinant enzyme administration in spontaneous hypertension rats.

To evaluate the feasibility of treating hypertension by human tissue kallikrein gene (KLK1) delivery and by enzyme (rK1) administration, two recombinant vectors expressing KLK1 cDNA were constructed for gene delivery (pcDNA-KLK1) and recombinant enzyme preparation (pOV-KLK1). Expression of the pcDNA-KLK1 vector in COS-1 cells was confirmed by immunofluorescence and in spontaneous hypertension rats (SHR) by enzymatic detection. Following intramuscular or intravenous injection with the pcDNA-KLK1 vector, systolic pressure of SHR was significantly decreased, which lasted for 20 d to two months depending on dose, route and/or time of injection. Egg white containing recombinant hK1 was prepared by injection of egg-laying hens with the oviduct-specific expression vector pOV-KLK1 and administered into SHR via oral gavage. Following administration, systolic pressure of the SHR was decreased to that of normal rats, which lasted for 3-5 d depending on the dosage used. These data suggest that both hKLK1 gene delivery and recombinant enzyme administration can be used as alternative strategies for treating human hypertension.

Animals↗

PubMed2004

A high-throughput approach for subcellular proteome: identification of rat liver proteins using subcellular fractionation coupled with two-dimensional liquid chromatography tandem mass spectrometry and bioinformatic analysis.

Four fractions from rat liver (a crude mitochondria (CM) and cytosol (C) fraction obtained with differential centrifugation, a purified mitochondrial (PM) fraction obtained with nycodenz density gradient centrifugation, and a total liver (TL) fraction) were analyzed with two-dimensional liquid chromatography tandem mass spectrometry analysis. A total of 564 rat proteins were identified and were bioinformatically annotated according to their physicochemical characteristics and functions. While most extreme alkaline ribosomal proteins were identified in the TL fraction, the C fraction mainly included neutral enzymes and the PM fraction enriched alkaline proteins and proteins with electron transfer activity or oxygen binding activity. Such characteristics were more apparent in proteins identified only in the TL, C, or PM fraction. The Swiss-Prot annotation and the bioinformatic prediction results proved that the C and PM fractions had enriched cytoplasmic or mitochondrial proteins, respectively. Combination usage of subcellular fractionation with two-dimensional liquid chromatography tandem mass spectrometry was proved to be a high-throughput, sensitive, and effective analytical approach for subcellular proteomics research. Using such a strategy, we have constructed the largest proteome database to date for rat liver (564 rat proteins) and its cytosol (222 rat proteins) and mitochondrial fractions (227 rat proteins). Moreover, the 352 proteins with Swiss-Prot subcellular location annotation in the 564 identified proteins were used as an actual subcellular proteome dataset to evaluate the widely used bioinformatics tools such as PSORT, TargetP, TMHMM, and GRAVY.

Animals↗

PubMed2004

A C-type lectin associated and translocated with cortical granules during oocyte maturation and egg fertilization in fish.

Oocyte maturation and egg fertilization in both vertebrates and invertebrates are marked by orchestrated cytoplasmic translocation of secretory vesicles known as cortical granules. It is thought that such redistribution of cellular content is critical for asymmetrical cell division during early development, but the mechanism and regulation of the process is poorly understood. Here we report the identification, purification and cDNA cloning of a C-type lectin from oocytes of a freshwater fish species gibel carp (Carassius auratus gibelio). The purified protein has been demonstrated to have lectin activity and to be a Ca(2+)-dependent C-type lectin by hemagglutination activity assay. Immunocytochemistry revealed that the lectin is associated with cortical granules, gradually translocated to the cell surface during oocyte maturation, and discharged to the egg envelope upon fertilization. Interestingly, the lectin becomes phosphorylated on threonine residues upon induction of exocytosis by fertilization and returns to its original state after morula stage of embryonic development, suggesting that this posttranslational modification may represent a critical molecular switch for early embryonic development.

Amino Acid Sequence↗

PubMed2004

Accurate qualitative and quantitative proteomic analysis of clinical hepatocellular carcinoma using laser capture microdissection coupled with isotope-coded affinity tag and two-dimensional liquid chromatography mass spectrometry.

Laser capture microdissection (LCM) is a powerful tool that enables the isolation of specific cell types from tissue sections, overcoming the problem of tissue heterogeneity and contamination. This study combined the LCM with isotope-coded affinity tag (ICAT) technology and two-dimensional liquid chromatography to investigate the qualitative and quantitative proteomes of hepatocellular carcinoma (HCC). The effects of three different histochemical stains on tissue sections have been compared, and toluidine blue stain was proved as the most suitable stain for LCM followed by proteomic analysis. The solubilized proteins from microdissected HCC and non-HCC hepatocytes were qualitatively and quantitatively analyzed with two-dimensional liquid chromatography tandem mass spectrometry (2D-LC-MS/MS) alone or coupled with cleavable ICAT labeling technology. A total of 644 proteins were qualitative identified, and 261 proteins were unambiguously quantitated. These results show that the clinical proteomic method using LCM coupled with ICAT and 2D-LC-MS/MS can carry out not only large-scale but also accurate qualitative and quantitative analysis.

Affinity Labels↗