Biomedical subjects

Li Ni

Publications and source records attributed to Li Ni.

13 recordsLinked to original sources

PubMed2007

Toll-like receptor ligands and CD154 stimulate microglia to produce a factor(s) that promotes excess cholinergic differentiation in the developing rat basal forebrain: implications for neurodevelopmental disorders.

Maternal inflammation plays a role in the etiology of certain neurodevelopmental disorders including autism and schizophrenia. Because maternal inflammation can lead to activation of fetal microglia, we have examined effects of inflamed microglia on cultured neural progenitors from rat embryonic septal region and basal forebrain. These cells give rise to cholinergic neurons projecting to cortex and hippocampus. Microglia stimulated with lipopolysaccharide (LPS), peptidoglycan, Poly I:C and CD154 produce conditioned media (CM) that promotes excessive numbers of cholinergic neurons and levels of choline acetyltransferase (ChAT) activity 6-8 times that of untreated cultures. Expression of the neural-specific transcription factor MATH1 increases substantially within 1 h of plating in LPS-CM. Untreated cultures do not attain equivalent levels until 6 h. By contrast, expression of glial-related transcription factors in LPS-CM-treated cultures never attains the elevated levels of untreated cultures. LPS-CM-treated clones derived from individual progenitors labeled with a LacZ-expressing retrovirus showed >2.5-fold increase in the percentage of cholinergic cells compared with untreated clones. Thus, CM from activated microglia prompts excess cholinergic differentiation from undifferentiated progenitors suggesting that microglial inflammation during critical stages can lead to aberrant brain development.

Acetylcholine↗

PubMed2007

Small-molecule inhibitors of ser/thr protein phosphatases: specificity, use and common forms of abuse.

Natural product extracts have proven to be a rich source of small molecules that potently inhibit the catalytic activity of certain PPP-family ser/thr protein phosphatases. To date, the list of inhibitors includes okadaic acid (produced by marine dinoflagelates, Prorocentrum sp. and Dinophysis sp.), calyculin A, dragmacidins (isolated from marine sponges), microcystins, nodularins (cyanobacteria, Microcystis sp. and Nodularia sp.), tautomycin, tautomycetin, cytostatins, phospholine, leustroducsins, phoslactomycins, fostriecin (soil bacteria, Streptomyces sp.), and cantharidin (blister beetles, approx 1500 species). Many of these compounds share structural similarities, and several have become readily available for research purposes. Here we will review the specificity of available inhibitors and present methods for their use in studying sensitive phosphatases. Common mistakes in the employment of these compounds will also be addressed briefly, notably the widespread misconception that they only inhibit the activity of PP1 and PP2A. Inhibitors of PP2B (calcineurin) will only be mentioned in passing, except to state that, in our hands, cypermethrin, deltamethrin, and fenvalerate, which are sold as potent inhibitors of PP2B, do not inhibit the catalytic activity of PP2B.

Cantharidin↗

PubMed2006

Extraction of berberine from rhizome of Coptis chinensis Franch using supercritical fluid extraction.

Supercritical fluid was used to extract berberine from rhizome of Coptis chinensis Franch. The recovery of berberine was compared with various modifiers, i.e. methanol and 95% ethanol with and without surfactant Tween 80, and 1,2-propanediol. The results show that the yield obtained after 3 h extraction with 1,2-propanediol-modified supercritical carbon dioxide was the highest (from 6.91%, w/w at 200 bar to 7.53%, w/w at 500 bar), while that obtained with 95% ethanol modified-supercritical carbon dioxide was the lowest (from 0.15%, w/w at 300 bar to 0.19%, w/w at 600 bar). The recovery of berberine was not improved by adding 5% Tween 80 in supercritical fluid.

Berberine↗

PubMed2006

Functional genomics of genes with small open reading frames (sORFs) in S. cerevisiae.

Genes with small open reading frames (sORFs; <100 amino acids) represent an untapped source of important biology. sORFs largely escaped analysis because they were difficult to predict computationally and less likely to be targeted by genetic screens. Thus, the substantial number of sORFs and their potential importance have only recently become clear. To investigate sORF function, we undertook the first functional studies of sORFs in any system, using the model eukaryote Saccharomyces cerevisiae. Based on independent experimental approaches and computational analyses, evidence exists for 299 sORFs in the S. cerevisiae genome, representing approximately 5% of the annotated ORFs. We determined that a similar percentage of sORFs are annotated in other eukaryotes, including humans, and 184 of the S. cerevisiae sORFs exhibit similarity with ORFs in other organisms. To investigate sORF function, we constructed a collection of gene-deletion mutants of 140 newly identified sORFs, each of which contains a strain-specific "molecular barcode," bringing the total number of sORF deletion strains to 247. Phenotypic analyses of the new gene-deletion strains identified 22 sORFs required for haploid growth, growth at high temperature, growth in the presence of a nonfermentable carbon source, or growth in the presence of DNA damage and replication-arrest agents. We provide a collection of sORF deletion strains that can be integrated into the existing deletion collection as a resource for the yeast community for elucidating gene function. Moreover, our analyses of the S. cerevisiae sORFs establish that sORFs are conserved across eukaryotes and have important biological functions.

Conserved Sequence↗

PubMed2006

[The investigation of FFA fixative solution for retina].

PURPOSE: To search for an effective fixative solution for retina. METHODS: One group of retinas were fixed in an admixture of formalin, dehydrated alcohol and glacial acetic acid (FFA). The other group of retinas were fixed in 10% neutral formalin.HE and immunohistochemistry were performed. Then compare the difference under the light microscope. RESULTS: The structure of the retinas fixed in FFA fixative solution was clear. The cells were arranged and compacted. Few exfoliation of the tissue from the glass slide was observed. CONCLUSION: FFA fixative solution is superior to 10% neutral formalin for the fixation of retina.

Acetic Acid↗

PubMed2005

A procedure for assessing GO annotation consistency.

MOTIVATION: The Gene Ontology (GO) is widely used to annotate molecular attributes of genes and gene products. Multiple groups undertaking functional annotations of genomes contribute their annotation sets to the GO database resource and these data are subsequently used in comparative functional analysis research. Although GO curators adhere to the same protocols and standards while assigning GO annotations, the specific procedure followed by each annotation group can vary. Since differences in application of annotation standards would dilute the effectiveness of comparative analysis, methods for assessing annotation consistency are essential. The development of methodologies that are broadly applicable for the assessment of GO annotation consistency is an important issue for the comparative genomics community. RESULTS: We have developed a methodology for assessing the consistency of GO annotations provided by different annotation groups. The method is completely general and can be applied to compare any two sets of GO annotations. This is the first attempt to assess cross-species GO annotation consistency. Our method compares annotation sets utilizing the hierarchical structure of the GO to compare GO annotations between orthologous gene pairs. The method produces a report on the annotation consistency and inconsistency for each orthologous pair. We present results obtained by comparing GO annotations for mouse and human gene sets. AVAILABILITY: The complete current MGI_GOA GO annotation consistency report is available online at http://www.spatial.maine.edu/~mdolan/

Animals↗

PubMed2004

A co-translational model to explain the in vivo import of proteins into HeLa cell mitochondria.

The dual signal approach, i.e. a mitochondrial signal at the N-terminus and an ER (endoplasmic reticulum) or a peroxisomal signal at the C-terminus of EGFP (enhanced green fluorescent protein), was employed in transfected HeLa cells to test for a co-translational import model. The signal peptide from OTC (ornithine transcarbamylase) or arginase II was fused to the N-terminus of EGFP, and an ER or peroxisomal signal was fused to its C-terminus. The rationale was that if the free preprotein remained in the cytosol, it could be distributed between the two organelles by using a post-translational pathway. The resulting fusion proteins were imported exclusively into mitochondria, suggesting that co-translational import occurred. Native preALDH (precursor of rat liver mitochondrial aldehyde dehydrogenase), preOTC and rhodanese, each with the addition of a C-terminal ER or peroxisomal signal, were also translocated only to the mitochondria, again showing that a co-translational import pathway exists for these native proteins. Import of preALDH(sp)-DHFR, a fusion protein consisting of the leader sequence (signal peptide) of preALDH fused to DHFR (dihydrofolate reductase), was studied in the presence of methotrexate, a substrate analogue for DHFR. It was found that 70% of the preALDH(sp)-DHFR was imported into mitochondria in the presence of methotrexate, implying that 70% of the protein utilized the co-translational import pathway and 30% used the post-translational import pathway. Thus it appears that co-translational import is a major pathway for mitochondrial protein import. A model is proposed to explain how competition between binding factors could influence whether or not a cytosolic carrier protein, such as DHFR, uses the co- or post-translational import pathway.

Aldehyde Dehydrogenase↗

PubMed2004

Correction of defective early tyrosinase processing by bafilomycin A1 and monensin in pink-eyed dilution melanocytes.

Mutations in the human P gene result in oculocutaneous albinism type 2, the most common form of albinism. Mouse melan-p1 melanocytes, cultured from mice null at the homologous pink-eyed dilution (p) locus, exhibit defective melanin production. A variety of compounds including tyrosine, NH4Cl, bafilomycin A1, concanamycin, monensin, and nigericin are capable of restoring melanin synthesis in these cells. In the current study, we investigated the subcellular effects of bafilomycin A1 and monensin treatment of melan-p1 cells. Both agents play two roles in the processing of tyrosinase (Tyr) in melan-p1 cells. First, combined glycosidase digestion and immunoblotting analysis showed that these agents reduce levels of Tyr retained in the endoplasmic reticulum (ER) and facilitate the release of Tyr from the ER to the Golgi. Secondly, treatment with these compounds resulted in the stabilization of Tyr. Surprisingly, induction of melanin synthesis corresponds more closely with diminution of ER-retained Tyr, rather than the absolute amount of Tyr. Our results suggest that bafilomycin A1 and monensin induce melanin synthesis in melan-p1 cells mainly by facilitating Tyr processing from the ER to the Golgi by increasing the pH in either the ER or the ER-Golgi intermediate compartment.

Animals↗

PubMed2004

High-performance liquid chromatography-electrospray ionization mass spectrometric determination of nisoldipine in human plasma.

A selective and sensitive high-performance liquid chromatography-electrospray ionization mass spectrometry (MS) for the determination of nisoldipine in human plasma is first presented. With nimodipine as the internal standard, nisoldipine is extracted from plasma with ethyl acetate. The organic layer is evaporated and the residue is resuspended in the mobile phase of methanol-water (80:20, v/v). An aliquot of 40 microL is chromatographically analyzed on an Agilent ODS C18 reversed-phase column (5 microm, 250- x 4.6-mm i.d.) by means of selected-ion monitoring mode MS. The calibration curve of nisoldipine in plasma exhibits a linear range from 0.5 to 20.0 ng/mL with a correlation coefficient of 0.9995. The limit of detection is 0.2 ng/mL. The within- and between-day variations (relative standard deviation) are less than 9.28% and 11.13% (n = 5), respectively. The developed method is validated through successful use for the analysis of nisoldipine contained in biological fluids resulting from a phase-I human pharmacokinetic study.

Calcium Channel Blockers↗

PubMed2003

[Experimental study on spermatogenic and strengthening yang action of baxian capsule].

OBJECTIVE: To discuss spermatogenic and strengthening yang action of Baxian(BX) capsule and its possible mechanism. METHODS: Rats or mice were divided randomly into five groups: control group, Baxian groups(2.5 g/kg, 7.5 g/kg, 22.5 g/kg) and positive group. After the drug had been given for 14 days, the levels of serum testosterone and cortisol in the low-aged rats were measured by radioimmunoassay. The coefficient of the reproductive organs in rats, the quantity of sperm and interstitial cells in mice were investigated, and the change of the latency time of penis erection in castrated rats, the capture and ejaculation in normal rats were observed at the same time. RESULTS: BX capsule could obviously raise the concentration of serum testosterone and cortisol, and the coefficient of sex organ in rats, and increase the number of sperm and interstitial cells in mice. Also, it could improve the penis erection and sexual ability of the male rats. CONCLUSIONS: The spermatogenic and strengthening yang action of BX capsule could be attributed to the improvement of the actions of the axis of lower thalamus-hypophysis-sexual gland and the axis of lower thalamus-hypophysis-adrenal cortex.

Animals↗

PubMed2002

Functional profiling of the Saccharomyces cerevisiae genome.

Determining the effect of gene deletion is a fundamental approach to understanding gene function. Conventional genetic screens exhibit biases, and genes contributing to a phenotype are often missed. We systematically constructed a nearly complete collection of gene-deletion mutants (96% of annotated open reading frames, or ORFs) of the yeast Saccharomyces cerevisiae. DNA sequences dubbed 'molecular bar codes' uniquely identify each strain, enabling their growth to be analysed in parallel and the fitness contribution of each gene to be quantitatively assessed by hybridization to high-density oligonucleotide arrays. We show that previously known and new genes are necessary for optimal growth under six well-studied conditions: high salt, sorbitol, galactose, pH 8, minimal medium and nystatin treatment. Less than 7% of genes that exhibit a significant increase in messenger RNA expression are also required for optimal growth in four of the tested conditions. Our results validate the yeast gene-deletion collection as a valuable resource for functional genomics.

Cell Size↗

PubMed2002

Cytokine activity contributes to induction of inflammatory cytokine mRNAs in spinal cord following contusion.

Injury of the spinal cord leads to an inflammatory tissue response, probably mediated in part by cytokines. Because a common therapy for acute spinal cord injury is the use of an antiinflammatory synthetic glucocorticoid (methylprednisolone), we sought to determine mechanisms contributing to inflammation shortly after acute injury. Cytokine mRNAs [interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor (TNF)-alpha, and IL-6] were increased during the first 2 hr following weight-drop compression injury by RNase protection assay, prior to the reported appearance of circulating lymphocytes. This immediate pattern of cytokine mRNA induction could be replicated in cultured, explanted spinal cord slices but not in whole blood of injured animals, which is consistent with a tissue source of cytokine mRNAs. Western blotting detected IL-1beta-like immunoreactivity released into culture medium following explantation and pro-IL-1beta-like immunoreactivity in freshly dissected spinal cord tissue. Pharmacologically blocking IL-1 and TNF-alpha receptors significantly reduced expression of IL-1alpha, IL-1beta, and TNF-alpha mRNAs. Finally, mice lacking both IL-1 and TNF-alpha receptors exhibited diminished induction of TNF-alpha, IL-6, and IL-1ra mRNAs following injury. Therefore, we conclude that contusion injury induces an immediate release of cytokines, which then contributes to the induction of cytokine mRNAs.

Animals↗

PubMed2002

Influence of the ORM1 phenotypes on serum unbound concentration and protein binding of quinidine.

BACKGROUND: Only unbound or free drug in plasma can be transported to its site of action. The fraction of unbound drug in plasma varies widely for highly bound drugs among individuals. The genetic polymorphism of orosomucoid (ORM) could be related to the interindividual variability in plasma binding of basic drugs, as ORM is the transport protein for these drugs in plasma. The ORM is a major binding protein in plasma for various basic drugs and is coded by two loci, ORM1 and ORM2, which are closely linked on chromosome 9q31-->34.1. ORM1 locus is highly polymorphic and the ORM2 locus is monomorphic in most population. METHODS: Twenty-eight healthy volunteers were selected with three ORM1 phenotypes, containing homozygotes ORM1 F1 (n=10) and ORM1 S (n=8), and heterozygote ORM1 F1S (n=10), identified by isoelectric focusing on polyacrylamide gels followed immunoblotting after desialylation of sera. After a single oral dose of quinidine 200 mg, serum total (HPLC) and unbound concentrations in ultrafiltrate (ultrafiltration/HPLC) were determined, and the pharmacokinetic parameters and protein binding rate were calculated. RESULTS: Serum concentrations of ORM (553.8-573.2 mg/l) and albumin proteins (57.5-58.4 mg/l) were similar in the three groups (P>0.05). Unbound quinidine concentration in ORM1 F1 phenotype subjects was higher than that in ORM1 S and ORM1 F1S phenotype; the free drug percentage for the subjects with ORM1 F1 phenotype (19.79%) was twice as high as that with ORM1 S phenotype (10.96%) (P<0.01) at 24 h after administration of oral quinidine when the state of disposition equilibrium occurred. The elimination t(1/2) values and the other pharmacokinetic parameters of quinidine were not affected by the different ORM1 phenotypes. CONCLUSIONS: Different ORM1 phenotypes may affect the disposition of quinidine, a basic drug, rather than its hepatic metabolism and elimination. The functional heterogeneity of ORM1 could be responsible for the differences in plasma binding of quinidine. Therefore, monitoring of the unbound quinidine concentration would be important for the patients with different ORM1 phenotypes who are treated with quinidine.

Adult↗