Biomedical subjects

Lei Zhang

Publications and source records attributed to Lei Zhang.

At least 307 records · Page 17Linked to original sources

PubMed2004

Thermosensitive transient receptor potential channels in vagal afferent neurons of the mouse.

A number of transient receptor potential (TRP) channels has recently been shown to mediate cutaneous thermosensitivity. Sensitivity to warm and cool stimuli has been demonstrated in both human and animal gastrointestinal tract; however, the molecular mechanisms that underlie this have not been determined. Vagal afferent neurons with cell bodies in the nodose ganglion are known to mediate nonnociceptive sensation from the upper gut. In this study, isolated cultured nodose ganglion from the mouse neurons showed changes in cytoplasmic-free Ca(2+) concentrations over a range of temperatures, as well as to icilin (a TRPM8 and TRPN1 agonist) and capsaicin (a TRPV1 agonist). RT-PCR was used to show the presence of six temperature-sensitive TRP channel transcripts (TRPV1-4, TRPN1, and TRPM8) in whole nodose ganglia. In addition, RT-PCR of single nodose cell bodies, which had been retrogradely labeled from the upper gut, detected transcripts for TRPV1, TRPV2, TRPV4, TRPN1, and TRPM8 in a proportion of cells. Immunohistochemical labeling detected TRPV1 and TRPV2 proteins in nodose ganglia. The presence of TRP channel transcripts and proteins was also detected in cells within several regions of the gastrointestinal tract. Our results reveal that TRP channels are present in subsets of vagal afferent neurons that project to the stomach and may confer temperature sensitivity on these cells.

Animals↗

PubMed2004

Dopamine-induced synaptic depression in the parabrachial nucleus is independent of CTX- and PTX-sensitive G-proteins, PKA and PLC signalling pathways.

We have previously reported that dopamine (DA) depresses non-NMDA receptor-mediated glutamatergic transmission in the rat parabrachial nucleus (PBN), an interface between brainstem and forebrain that is implicated in autonomic regulation. This work examined cellular signalling pathways that might underlie this DA-induced synaptic depression. Direct activation of adenylyl cyclase with 10 microM forskolin increased the evoked EPSC but did not occlude DA-induced EPSC depression. Similarly, a preferential protein kinase A inhibitor, H-7 (10 microM), did not block DA's synaptic effects. Incubation of slices with cholera toxin (CTX; 1 microgram/ml) or pertussis toxin (PTX; 0.5 microgram/ml) for 20 h, procedures used to irreversibly activate or disable the G(s) and G(i) proteins, respectively, did not change DA's effects. The putative phospholipase C inhibitor, U-73122 (10 microM) and its inactive analogue U-73343 (10 microM) did not alter DA-induced reduction in the EPSCs. Alterations in signalling molecules downstream of phospholipase C including depleting internal calcium stores by thapsigargin and cyclopiazonic acid and blocking protein kinase C with chelerythrine, had no effect on DA-induced synaptic depression. Furthermore, DA's depression of the non-NMDA response was not blocked by APV, an NMDA receptor antagonist. Finally, DA depressed evoked, pharmacologically isolated NMDA receptor-mediated synaptic responses while increasing NMDA-induced inward currents in the PBN. These results indicate that DA-induced synaptic effects in the PBN are not through the activation of cholera or pertussis toxin sensitive G proteins. Furthermore, it does not employ the adenylyl cyclase-cAMP-PKA cascade, the phospholipase C signalling pathway and NMDA receptor-coupled mechanisms to depress excitatory synaptic transmission in the PBN.

Adjuvants, Immunologic↗

PubMed2004

Evidence from brain imaging with fMRI supporting functional specificity of acupoints in humans.

We tested whether the stimulation of acupoints in the same spinal segments could induce different central responses with functional magnetic resonance imaging (fMRI) study. Stimulation of acupoints ST36/SP6 (Zusanli/Sanyinjiao) or GB34/BL57 (Yanglingquan/Chengshan) both activated primary and secondary somatosensory area, insula, ventral thalamus, parietal Brodmann Area 40, temporal lobe, putamen, and cerebellum, while de-activated amygdala. Nevertheless, ST36/SP6 stimulation specifically activated orbital frontal cortex and de-activated hippocampus. Alternatively, stimulation of GB34/BL57 activated dorsal thalamus and inhibited those of primary motor area and premotor cortex. Thus, stimulation of acupoints in the same spinal segments induced distinct though overlapped cerebral response patterns, which indicated the existence of acupoint specificity.

Adult↗

PubMed2004

Birth of calves expressing the enhanced green fluorescent protein after transfer of fresh or vitrified/thawed blastocysts produced by somatic cell nuclear transfer.

The present study examined effects of genetic manipulation and serum starvation on in vitro developmental potential of bovine somatic cell nuclear transfer (SCNT) embryos and vitrification on in vivo developmental competence of transgenic SCNT blastocysts. Fetal oviduct epithelial cells (FOECs) were isolated from the oviduct of a Day 147 bovine fetus and transfected with a plasmid (pCE-EGFP-IRES-NEO) containing the enhanced green fluorescent protein (EGFP) and neomycin-resistant (Neor) genes. There were no significant differences (P > 0.05) in cleavage rates or development rates to the blastocyst stage for SCNT embryos derived from FOECs (72.5 and 47.8%, respectively) or transfected FOECs (TFOECs, 73.8 and 47.7%, respectively); nor from serum-fed (73.6 and 47.2%, respectively) or serum-starved (72.7 and 48.3%, respectively) cells. Seventeen of Day 7 GFP-embryos (eight fresh blastocysts and nine vitrified/thawed blastocysts ) were transferred to recipients with one embryo per recipient. Two (25%) recipients were confirmed pregnant at Day 60 in fresh blastocysts group, and three recipients (33%) were confirmed pregnant at Day 60 in vitrified/thawed blastocysts group. Two healthy calves (25%) were obtained from fresh blastocysts and one (11%) from vitrified/thawed blastocysts. Microsatellite analysis confirmed that the three clones were genetically identical to the donor cells. Moreover, PCR and Southern blot demonstrated integration of transgene in genomic DNA of all three cloned calves. Expression of GFP in skin biopsies isolated from transgenic cloned calves and fibroblasts derived from the skin biopsies revealed the activity of EGFP gene, and G418 resistance in vitro of these fibroblasts confirmed the activity of Neor gene. Our results show that genetic manipulation and serum starvation of donor cells (FOECs) do not affect in vitro developmental competence of bovine SCNT embryos, and vitrified transgenic SCNT blastocysts can develop to term successfully.

Animals↗

PubMed2004

Isolation and characterization of a new mannose-binding lectin gene from Taxus media.

In this paper, we report the cloning and characterization of the first mannose-binding lectin gene from a gymnosperm plant species, Taxus media. The full-length cDNA of T. media agglutinin (TMA) consisted of 676 bp and contained a 432 bp open reading frame (ORF) encoding a 144 amino acid protein. Comparative analysis showed that TMA had high homology with many previously reported plant mannose-binding lectins and that tma encoded a precursor lectin with a 26-aa signal peptide. Molecular modelling revealed that TMA was a new mannosebinding lectin with three typical mannose-binding boxes like lectins from species of angiosperms. Tissue expression pattern analyses revealed that tma is expressed in a tissue-specific manner in leaves and stems, but not in fruits and roots. Phylogenetic tree analyses showed that TMA belonged to the structurally and evolutionarily closely related monocot mannose-binding lectin superfamily. This study provides useful information to understand the molecular evolution of plant lectins.

Amino Acid Sequence↗

PubMed2004

Quantification of thrombospondin-1 secretion and expression of alphavbeta3 and alpha3beta1 integrins and syndecan-1 as cell-surface receptors for thrombospondin-1 in malignant glioma cells.

Malignant glioma cells secrete thrombospondin-1 (TSP-1) which participates in the motility of glioma cells, and binds to cell surface alphavbeta3 and alpha3beta1 integrins, and syndecan-1. This study evaluated the amount of TSP-1 secretion from malignant glioma cells, and the expression of alphavbeta3 and alpha3beta1 integrins, and syndecan-1. The amounts of TSP-1 in the supernatants from 10 malignant glioma cell lines and eight non-glioma malignant tumor cell lines were measured by enzyme-linked immunosorbent assay. Expression of alphavbeta3 and alpha3beta1 integrins, and syndecan-1 were examined by flow cytometry. The amounts of TSP-1 secreted by malignant glioma cells were 43 to 2431 ng/l x 10(6) cells/24 h (mean +/- SD = 626 +/- 792). Seven of 10 glioma cell lines secreted more than 100 ng of TSP-1 and three of these cell lines secreted more than 1 microg. Seven of eight non-glioma cell lines secreted less than 100 ng of TSP-1. All glioma cell lines expressed alpha3beta1 integrin and syndecan-1, and seven of 10 glioma cell lines expressed alphavbeta3 integrin. Treatment of the glioma cell lines with TGF-beta2 did not change the expression of alphavbeta3 integrin. These results suggest that malignant glioma cells secrete high levels of TSP-1, which may be important in the migration of glioma cells via interactions with alphavbeta3 and alpha3beta1 integrins, and syndecan-1.

Brain Neoplasms↗

PubMed2004

Cholinergic augmentation with donepezil enhances recovery in short-term memory and sustained attention after traumatic brain injury.

OBJECTIVE: To examine effects of donepezil on short-term memory and sustained attention in postacute patients with traumatic brain injury (TBI). DESIGN: A 24-week, randomized, placebo-controlled, double-blind crossover trial. SETTING: Outpatient clinics in 2 teaching hospitals. PARTICIPANTS: Eighteen postacute TBI patients with cognitive impairment. INTERVENTION: Patients were randomly assigned to group A or group B. Patients in group A received donepezil for the first 10 weeks and then a placebo for another 10 weeks. The 2 treatment phases were separated by a washout period of 4 weeks. Patients in group B received the preparations in the opposite order. MAIN OUTCOME MEASURES: Short-term memory and sustained attention were assessed by 2 indexes (Auditory Immediate Index [AII], Visual Immediate Index [VII]) of the Wechsler Memory Scale-III and the Paced Auditory Serial Addition Test (PASAT), at baseline, week 10, and week 24 of the trial. RESULTS: Intragroup comparison of different phases of the trial in both groups showed that donepezil significantly increased the testing scores of the AII and VII, as well as PASAT scores, compared with baseline. There was no significant change in the testing scores between assessment at baseline and the end of the placebo phase in group B. Intergroup comparison at the 10-week assessment showed significantly improved testing scores in group A with donepezil over group B with the placebo. The improved testing scores with donepezil in group A were sustained after the washout period and placebo phase, suggesting a carry-over effect of the medication. CONCLUSIONS: Donepezil increased neuropsychologic testing scores in short-term memory and sustained attention in postacute TBI patients. Cholinergic augmentation may be a viable approach to restore memory and attention after TBI.

Adult↗

PubMed2004

Enhancement of the effectiveness of electroporation-augmented cutaneous DNA vaccination by a particulate adjuvant.

DNA vaccines are attracting increased attention due to multiple advantages over conventional vaccines. Attempts to improve these vaccines focus on enhancing DNA delivery and employing novel immunoadjuvants. Electroporation (EP) has emerged as an effective method for delivering DNA vaccines, significantly enhancing humoral and cellular responses. To further improve EP-augmented DNA vaccination, we used micron-size gold particles as a particulate adjuvant. DNA is not bound, or adsorbed, to the particles. Gold particles were coinjected intradermally with plasmid DNA encoding the hepatitis B virus surface antigen (HBsAg) into mice, both in the absence and presence of noninvasive EP. The particles enhanced the percentage of responding animals, and shortened the time for reaching maximal antibody titers by 2 weeks. Subtyping of the produced antibodies revealed a predominantly Th1-like response which did not change significantly with the absence or presence of particles. The particles likely function as an attractant for antigen-presenting cells (APCs), and probably do not affect EP or antigen expression to a significant extent. We conclude that micron-size gold particles injected intradermally together with DNA followed by EP give rise to an accelerated, potent immune response with a strong cellular component. This method may become important for the development of fast-acting therapeutic and prophylactic vaccines.

Adjuvants, Immunologic↗

PubMed2004

fMRI evidence for the automatic phonological activation of briefly presented words.

Functional magnetic resonance imaging was used to investigate whether people generate the phonology of briefly presented words that they do not attend. This was done in Chinese by examining the effect of orthography-phonology regularity (i.e., how predictable the phonology of a word is from its components rather than whole-word form) with high- and low-frequency words, and by using a task that diverted participants' attention to a mask, rather than the words. The results showed that there was a significant interaction between regularity and word frequency in blood oxygen level-dependent (BOLD) signal, which mirrored the pattern found in behavioral data. Specifically, for low-frequency characters, bilateral fusiform gyri, the posterior superior temporal gyrus, and inferior parietal regions were more active when using irregular compared to regular characters. There were no significant differences when high-frequency characters were used. These results support the possibility that at least for low-frequency words, phonology is automatically generated when reading, even when people do not attend to the words and even in a language where the orthography-phonology mapping is extremely irregular.

Adolescent↗

PubMed2004

Laurenditerpenol, a new diterpene from the tropical marine alga Laurenciaintricata that potently inhibits HIF-1 mediated hypoxic signaling in breast tumor cells.

The degree of tumor hypoxia correlates with advanced disease stages and treatment resistance. The transcription factor hypoxia-inducible factor-1 (HIF-1) promotes tumor cell adaptation and survival under hypoxic conditions. Therefore, specific HIF-1 inhibitors represent an important new class of potential tumor-selective therapeutic agents. A T47D human breast tumor cell-based reporter assay was used to examine extracts of plants and marine organisms for inhibitors of HIF-1 activation. Bioassay-guided fractionation of the lipid extract of the red alga Laurencia intricata yielded a structurally novel diterpene, laurenditerpenol (1). The structure of 1 was determined spectroscopically. The relative configurations of the substituents of each ring system were assigned on the basis of NOESY correlations. The absolute configuration of position C-1 was determined by the modified Mosher ester procedure (directly in NMR tubes). Compound 1 potently inhibited hypoxia-activated HIF-1 (IC50: 0.4 microM) and hypoxia-induced VEGF (a potent angiogenic factor) in T47D cells. Compound 1 selectively inhibits HIF-1 activation by hypoxia but not iron chelator-induced activation. Further, 1 suppresses tumor cell survival under hypoxic conditions without affecting normoxic cell growth. Compound 1 inhibits HIF-1 by blocking the induction of the oxygen-regulated HIF-1alpha protein. Mitochondrial respiration studies revealed that 1 suppresses oxygen consumption.

Antineoplastic Agents↗

PubMed2004

Sucrose regulates elongation of carrot somatic embryo radicles as a signal molecule.

Elongation of carrot somatic embryo radicles was inhibited by sucrose at or above 5% (145 mM). This effect would not be released until the sucrose concentration was lowered again. Morphological and cytological studies as well as determination of ABA content and analysis of the expression mode of a Lea gene, all point to its similarity to natural dormancy and germination of seeds. Use of monosaccharides (glucose and fructose), other disaccharide (maltose), and isomolar concentration of osmotica (mannitol and sorbitol), did not show similar regulatory effect. It is thus clear that the regulatory effect is not a result of simple osmotic stress. Hexokinase inhibitors such as glucosamine and N -acetyl-glucosamine did not exert any influence on the regulation-deregulation effects of sucrose. Mannose, which inhibits germination of Arabidopsis seeds, did not prevent carrot somatic embryo radicles from elongating. It is thus inferred that this sucrose-signaling pathway may be independent of hexokinase. As a first step to understand the molecular mechanism of this process, a carrot sucrose transporter gene ( cSUT ) expressed in the embryos and roots specifically was isolated. Studies on transformed yeast mutant with cSUT cDNA identified its sucrose transport activity. Northern hybridization and gel retardation experiment revealed that there is a marked increase in expression of cSUT at the beginning of somatic embryo germination, and this is attributed to regulation on the level of transcription. This suggested the possibility that cSUT has an important role in this sucrose signal regulation system.

Abscisic Acid↗

PubMed2004

Production and analysis of organic acids in hairy-root cultures of Isatis indigotica Fort. (indigo woad).

Hairy roots were induced from both cotyledon and hypocotyl explants of Isatis indigotica Fort. (indigo woad) through transformation with Agrobaterium rhizogenes strain A4, R1601 and ATCC15834. The results showed that the cotyledons were the preferred explants to hypocotyls and A4 was the most suitable A. rhizogenes strain for the transformation and induction of hairy roots of I. indigotica. High-voltage paper electrophoresis (HVPE) analysis demonstrated the production of mannopine in hairy roots and confirmed the successful transfer of Ri T-DNA (root-inducing transferred DNA) of A. rhizogenes into the I. indigotica genome. Five organic acids, namely CPQ [3-(2-carboxyphenol)-4(3 H )-quinazolinone], syringic acid, salicylic acid, benzoic acid and 2-aminobenzoic acid, which were considered as main antiviral components of I. indigotica, were detected in natural roots, hairy roots and liquid media with high-performance capillary electrophoresis. The results showed CPQ production in hairy roots was significantly higher than that in natural roots. Our results also revealed that all the five organic acids could be excreted from hairy roots into liquid media, and the concentrations of organic acids in the liquid media paralleled those in hairy roots. The hairy roots of I. indigotica grew fast and showed an S-shaped growth curve that reached its apex on the day 24 of culture with a 20-fold increase in fresh weight compared with the starting inoculums. The accumulation of the two organic acids CPQ and syringic acid in liquid media paralleled the growth of hairy roots. MS [Murashige, T. and Skoog, F. (1962) Physiol. Plant. 15, 473-497] medium or half-strength MS medium supplemented with 30 g/l maltose was found to be best for hairy-root culture and accumulation of CPQ.

Benzoic Acid↗

PubMed2004

Glutamate-induced over-expression of GAD is down-regulated by acetyl-L-carnitine in rat islet cells.

Glutamic acid decarboxylase (GAD65 and GAD67) in pancreatic beta cells is the target of autoantibodies and autoreactive T cells in insulin-dependent diabetes mellitus (IDDM). Regulating expression of GAD perhaps is a practical approach to treat IDDM. In this study, we established an in vitro system, in which GAD was expressed and glutamate treatment produced over-expression of GAD67 and GAD65 in rat islet cells. By using the system we were able to demonstrate basal level of expression of GAD and effects of glutamate and the antioxidant, acetyl-L-carnitine (ALC) on expression of GAD. We found that GAD67 expressed in 10% of islets cells, whereas GAD65 was localized in only 4% of the cells. Glutamate treatment resulted in significant over-expression of GAD67, but not GAD65. Such glutamate-induced overexpression of GAD67 was attenuated by pretreatment with ALC (100 microM). These findings suggest that the over-expression of GAD67 induced by glutamate in islet cells of rat may act as a suitable cellular model to study GAD autoreactivity during the development of IDDM. Meanwhile, it indicates that ALC, an ester of the trimethylated amino acid, can block glutamate-induced over-expression of GAD67, a key beta-cell autoantigen, suggesting a therapeutic potential of ALC in IDDM.

Acetylcarnitine↗

PubMed2004

Characterization of palmprints by wavelet signatures via directional context modeling.

The palmprint is one of the most reliable physiological characteristics that can be used to distinguish between individuals. Current palmprint-based systems are more user friendly, more cost effective, and require fewer data signatures than traditional fingerprint-based identification systems. The principal lines and wrinkles captured in a low-resolution palmprint image provide more than enough information to uniquely identify an individual. This paper presents a palmprint identification scheme that characterizes a palmprint using a set of statistical signatures. The palmprint is first transformed into the wavelet domain, and the directional context of each wavelet subband is defined and computed in order to collect the predominant coefficients of its principal lines and wrinkles. A set of statistical signatures, which includes gravity center, density, spatial dispersivity and energy, is then defined to characterize the palmprint with the selected directional context values. A classification and identification scheme based on these signatures is subsequently developed. This scheme exploits the features of principal lines and prominent wrinkles sufficiently and achieves satisfactory results. Compared with the line-segments-matching or interesting-points-matching based palmprint verification schemes, the proposed scheme uses a much smaller amount of data signatures. It also provides a convenient classification strategy and more accurate identification.

Algorithms↗

PubMed2004

Effects of antibody on viral kinetics in simian/human immunodeficiency virus infection: implications for vaccination.

Passive antibody treatment of macaques prior to simian/human immunodeficiency virus infection produces "sterilizing immunity" in some animals and long-term reductions in viral loads in others. Analysis of viral kinetics suggests that antibody mediates sterilizing immunity by its effects on the initial viral inoculum. By contrast, reduction in peak viral load later in infection prevents CD4 depletion and contributes to long-term viral control.

Animals↗

PubMed2004

Transient pancytopenia preceding T lineage acute lymphoblastic leukemia.

Transient pancytopenia preceding acute lymphoblastic leukemia (pre-ALL) is a rare occurrence usually affecting children with subsequent development of B lineage ALL. We report a case of pre-ALL characterized by a T cell immunophenotype and abnormal karyotype t (11; 14) (q10; q10). The patient achieved a transient complete remission after initial therapy, but relapsed within a few months and died of leukemic encephalopathy. To the best of our knowledge, this is the first report of T lineage pre-ALL.

Cell Lineage↗

PubMed2004

Signaling cascades implicated in muscarinic regulation of proliferation of neural stem and progenitor cells.

Muscarinic acetylcholine receptors (mAChRs) belong to the G-protein-coupled receptor superfamily that transduces signals through multiple intracellular signaling cascades to regulate a wide variety of physiological responses. Recently, it has been discovered that subtypes of mAChRs are expressed in proliferative neuroepithelial cells of the ventricular zone and in basic fibroblast growth factor-expanded neural stem and progenitor cell cultures. Activation of the mAChRs by ACh or its analogue carbachol leads to increased DNA synthesis and neurogenesis. The mitogenic effects of muscarinic agonists are likely mediated via mAChR-activated multisignaling pathways. The exact intracellular mechanisms underlying mAChR-modulated DNA synthesis and neurogenesis are not fully understood. However, several pathways through Ras-mitogen-activated protein kinase, phosphatidylinositol 3-kinase-Akt, protein kinase C, c-Src and Ca(2+) signaling have been shown to play roles in this dynamic process. These novel signaling cascades may improve our understanding of the intracellular mechanisms underlying mAChR-stimulated neural progenitor proliferation and provide insights for therapeutic drug development.

Animals↗

PubMed2004

Reorganization of cytoskeletal proteins of mouse oocytes mediated by integrins.

To study whether integrins on cell membrane ligate with intracellular cytoskeletal proteins and mediate their reorganization in egg activation, female mice were used for superovulation. The zona-free oocytes were incubated separately with specific ligand of integrins, an active RGD peptide, in vitro for certain period of time. RGE peptide and mouse capacitated sperm were used as controls. Freshly ovulated oocytes and those treated with different factors were immunostained with FITC-labeled anti-actin antibody, then detected with confocal microscope. The results demonstrated that freshly ovulated mouse oocytes, oocytes incubated for 2 h in vitro and those treated with control RGE peptide for 15 min showed hardly visible fluorescene or only thin fluorescence in plasma membrane region. Oocytes coincubated with sperms for 15 min and those treated with active RGD peptide for 10 min, 30 min and 2 hours respectively had strong and thick fluorescence in the plasma membrane and cortical region of oocytes, and some of them showed asymmetrically fluorescent distribution. It is proved that integrins on membrane are ligated directly with cytoskeletal protein. Integrins binding with their ligands regulate reorganization of cytoskelal protein, which may be involved in transmembrane signaling in egg activation.

Animals↗