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Biomedical subjects

M Luo

Publications and source records attributed to M Luo.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Preliminary study on citral impaires the Aspergillus flavus membrane].

Compared with the normally growing A. flauas, the content as below was determined: the utilization ratio to protein and reducing sugar of hyphostroma poisened by citral, the activity of [Na+, K+]-ATPase capable of decomposition ATP, and the seepagevity ratio of electrolyte. In addition, the shape change in spore was observed via the scanning electron microscope (SEM) and the fast multi-channel micro-spectrophotomer (FMCM). The result above all suggested facts as following after it's poised by the citral in MIC. The surface of hyphostroma and spore turned into be porous and rough. The pass trace on spore shriveled and closed. The rate of conduct electricity increased by 52.8%. The utilization ratio to protein and reducing sugar respectively decreased 61.5% and 44.3%. The rate of spore's sprout dropped to 61.4%. The molecular structure of membrane was so distinctly changed that it lost the selective permeability. There was inhibition on hyphostroma growth and spore sprout.

Absorption↗
PubMed2001

[Study on inhibitory effect of ampelopsin on melanoma by serologic pharmacological method].

OBJECTIVE: To study the inhibitory effect of ampelopsin on melanoma. METHODS: Using a serologic pharmacological method, the inhibitory effects of different dose of ampelopsin on B16 melanoma cells were evaluated by a MTT assay and a flow cytometry. RESULTS: The serums of C57BL/6 mices, which were administered by 0.420 mmol/kg dose and 0.560 mmol/kg dose of ampelopsin, could obviously suppress the B16 melanoma cells, and the inhibitory rate was equal to that of the vacant serum adding same consistency ampelopsin. The drug serums of the two doses groups reduced the cleavage and proliferation index of B16 melanoma cells to 19.1% and 21.7% respectively. CONCLUSION: Ampelopsin possibly acts on melanoma B16 cells by original form drug at the period with a peak of the drug concentration, and inhibits the DNA synthesis of B16 cells.

Animals↗
PubMed2000

Human immunodeficiency virus type 1-infected women exhibit reduced interferon-gamma secretion after Chlamydia trachomatis stimulation of peripheral blood lymphocytes.

Epidemiologic, animal, and in vitro models suggest an important role for interferon (IFN)-gamma in the clearance of Chlamydia trachomatis infection. IFN-gamma in the supernatants of in vitro-stimulated peripheral blood mononuclear cells (PBMC) from 22 human immunodeficiency virus type 1 (HIV-1)-infected and 73 uninfected women at high risk for C. trachomatis acute pelvic inflammatory disease (PID) was studied. PBMC were stimulated with C. trachomatis purified major outer membrane protein (MOMP) and whole elementary bodies (EBs) from the 4 predominant serovars (E, F, K, and L2) that circulate in Nairobi. PBMC IFN-gamma secretion after stimulation with C. trachomatis EBs was significantly decreased in HIV-1-infected women. Among HIV-1-infected women, CD4 T cell depletion was associated with lower IFN-gamma secretion from PBMC stimulated with either C. trachomatis MOMP or EB antigen. Decreased antigen-specific IFN-gamma production may enhance the susceptibility of HIV-1-infected women to C. trachomatis PID.

Acute Disease↗
PubMed2000

Expression and parent-of-origin effects for FIS2, MEA, and FIE in the endosperm and embryo of developing Arabidopsis seeds.

The promoters of MEA (FIS1), FIS2, and FIE (FIS3), genes that repress seed development in the absence of pollination, were fused to beta-glucuronidase (GUS) to study their activity pattern. The FIS2GUS product is found in the embryo sac, in each of the polar cell nuclei, and in the central cell nucleus. After pollination, the maternally derived FIS2GUS protein occurs in the nuclei of the cenocytic endosperm. Before cellularization of the endosperm, activity is terminated in the micropylar and central nuclei of the endosperm and subsequently in the nuclei of the chalazal cyst. MEAGUS has a pattern of activity similar to that of FIS2GUS, but FIEGUS protein is found in many tissues, including the prepollination embryo sac, and in embryo and endosperm postpollination. The similarity in mutant phenotypes; the activity of FIE, MEA, and FIS2 in the same cells in the embryo sac; and the fact that MEA and FIE proteins interact in a yeast two-hybrid system suggest that these proteins operate in the same system of control of seed development. Maternal and not paternal FIS2GUS, MEAGUS, and FIEGUS show activity in early endosperm, so these genes may be imprinted. When fis2, mea, and fie mutants are pollinated, seed development is arrested at the heart embryo stage. The seed arrest of mea and fis2 is avoided when they are fertilized by a low methylation parent. The wild-type alleles of MEA or FIS2 are not required. The parent-of-origin-determined differential activity of MEA, FIS2, and FIE is not dependent on DNA methylation, but methylation does control some gene(s) that have key roles in seed development.

Arabidopsis↗
PubMed2000

Changes of reliability and efficiency of micronucleus bioassay in Vicia faba after exposure to metal contamination for several generations.

Mitotic root micronucleus (MCN) frequency in Vicia faba as a bioassay, is primarily based on the extent of the sentinel Vicia response in terms of cytogenetic damage quantitatively or qualitatively to indicate the presence of mutagenic contaminants. This paper describes an investigation designed to assess changes in MCN frequencies of Vicia faba from three generation plants obtained, respectively from a reference site (RS) and a metal-contaminated experimental field (EF) in the bioassay of mutagenic Cd(2+) and NaN(3). The background value, dose-response to Cd(2+) and to NaN(3) in three generation (F(1), F(2) and F(3)) plants of the EF and the initial (F(0)) plants were determined in terms of MCN frequencies. With more generations of growing Vicia plants in the EF, a higher background value of MCN frequency, a lower slope value in the regression equation, a smaller ratio of MCN frequency between the control and treatment in the same generation and larger perturbation values were observed. This denotes that the decreased reliability and efficiency are represented in Vicia plants from the EF if the plants are used as sentinels in the bioassay of mutagenic Cd(2+) and NaN(3). It was concluded that the Vicia MCN bioassay should be used as an endpoint biomarker acceptable in biomonitoring environmental mutagens when the sentinel plants were collected from clean areas. Because no place is absolutely without pollutants, it is suggested that several seed stock centers should be established for providing sentinel Vicia if Vicia MCN bioassay is used as a biomarker to identify the global environmental status.

Journal Article↗
PubMed2000

Effect of thyroid hormone deficiency on developmental expression of goalpha gene in the brain of neonatal rats by competitive RT-PCR and in situ hybridization histochemistry.

Goalpha is a guanine nucloetide-binding regulatory protein alpha subunit which is mainly distributed in the central nervous system, but it has not previously been reported how it is regulated by thyroid hormone in the brain of neonatal rat at transcriptional levels. In this report, we used quantitative competitive reverse transcriptional PCR to quantify the effects of TH deficiency on Goalpha gene expression in the brain of neonatal rat at mRNA levels. It was found that Goalpha mRNA levels in the brain of 14-day-old rats significantly increased over 3-fold after induction of perinatal hypothyroidism, and declined markedly after treatment of thyroxine replacement. In situ hybridization histochemistry was further employed to observe the time-course and spatial expression of Goalpha gene in the brain of neonatal rats affected by thyroid hormone deficiency during the developmental period. The data showed that perinatal hypothyroidism can enhance Goalpha mRNA levels in the temporal cortex, sensorimotor cortex, piriform cortex, amygdala, hippocampal CA1-4 subfields, dentate gyrus, arcuate nucleus (AR) and ventromedial hypothalamic nucleus (VMH) of hypothalamus, but not in the striate cortex, cingulate cortex, claustrum, caudate/putamen and thalamus in the brain of rat at 7-21 days post-partum. The results suggest that up-regulation of Goalpha gene expression may be one kind of common mechanism responsible for neurological deficits in some brain areas arising from thyroid hormone deficiency in the critical periods of neonatal rats.

Animals↗
PubMed2000

Endothelial vasodilator function is related to low-density lipoprotein particle size and low-density lipoprotein vitamin E content in type 1 diabetes.

OBJECTIVES: We sought to determine whether endothelial vasodilator function (EVF) in patients with type 1 diabetes was related to low-density lipoprotein (LDL) particle size (LDLPS), LDL vitamin E content (LDLVE) or the susceptibility of LDL to oxidation (OxLDL). BACKGROUND: Impaired EVF is an early feature of diabetic vascular disease and may be related to oxidant stress. Although small, dense LDL and oxidized LDL are features of type 2 diabetes and predict the development of coronary artery disease, their role in type 1 diabetes is less clear. METHODS: Endothelium-dependent vasodilation was assessed in the brachial artery (flow-mediated vasodilation [FMD]) and in the forearm resistance circulation using venous occlusion plethysmography in response to graded doses of intrabrachial acetylcholine (ACh). Thirty-seven patients with type 1 diabetes mellitus (DM) and 45 matched controls underwent flow-mediated dilation, while a subset of 19 DM and 20 controls underwent plethysmography. RESULTS: Total, LDL and high-density lipoprotein cholesterol or triglycerides were not different in DM compared with controls, but LDLPS was smaller (25.6 +/- 0.06 vs. 26.1 +/- 0.1 nm, p < 0.05) and LDLVE was reduced (2.0 +/- 0.25 vs. 2.6 +/- 0.18 micromol/mmol LDL, p < 0.05). Oxidative susceptibility of LDL was not different. Flow-mediated vasodilation was impaired in DM compared with controls (3.6 +/- 0.6% vs. 7.1 +/- 0.5%, p < 0.005), as was the vasodilator response to ACh (p < 0.05). Flow-mediated vasodilation was directly related to LDLPS and LDLVE in both the entire study cohort and DM alone (p < 0.05), but not to other parameters of the standard lipid profile. Similarly, endothelium-dependent vasodilation in the resistance circulation was directly related to LDLPS and LDLVE, but not to OxLDL. CONCLUSION: These results suggest, but do not prove, that LDL particle size and LDL vitamin E may be determinants of conduit and resistance vessel endothelial vasodilator function in type 1 diabetes. Further work will be required to prove cause and effect.

Acetylcholine↗
PubMed2000

Genome organization and phylogenetic distribution of a novel family of ancient murine endogenous proviruses with evidence for transposition-mediated proliferation.

A new family of murine endogenous proviruses (VL6.0) is described here. The intact provirus is near 6 kb in length and shows a genomic organization of 5' LTR, gag, pol, env, and 3' LTR. The primer binding site (PBS) is that of a tRNA(gly). The lack of functional open reading frames and occurrence of significant gaps in most, if not all, members of this group show it to be ancient. Our estimate of copy number per haploid genome is 30+. Members of this group have been isolated from Mus musculus domesticus, M. m. casteneus, M. m. hortulanus, M. caroli, and M. spretus. The occurrence of these sequences throughout such diverse members of the genus Mus may indicate that the date of the original infection predated the divergence of the extant Mus lineages at around 2.5 million years ago. Analysis of gap (deletion/insertion) patterns indicates that these sequences may have proliferated within the Mus genome by a mechanism of reverse transcriptase-mediated transposition. As yet, there are no closely related murine retroviruses described. The closest mammalian retrovirus based on sequence similarity is from the miniature swine (Sus scrofa).

Amino Acid Sequence↗
PubMed2000

Genomic organization of the human and mouse stau genes.

Mammalian Staufen is a double-stranded RNA-binding protein potentially involved in mRNA transport and localization. Recently, we reported that the human gene is located on chromosome 20, region q13.1. We now report the genomic organization of both the human and mouse stau genes. Amplification of genomic DNA and sequencing of the resulting PCR products indicated that the human and mouse genes are fragmented into 15 and 12 exons, distributed over at least 65 and 17 kb of genomic DNA, respectively. The three additional exons found in the human gene are subjected to differential splicing, generating four different transcripts. Corresponding exons have not been found in mouse transcripts. Apart from those three exons, the overall organization of the stau gene is similar in the two species, and the positions of the exon-intron junctions are perfectly conserved. Even an alternative choice between two splicing acceptor sites, which causes an insertion of 18 nucleotides in exon 5, is conserved in both humans and mice. An extremely G+C-rich region lacking canonical TATA and CAAT boxes was found upstream of the most 5' RACE sequence, suggesting that a housekeeping-like promoter drives the broad expression of Staufen in mammalian cells. This work represents the first step toward production of knockout mice and the elucidation of putative Staufen-linked hereditary diseases in humans.

Alternative Splicing↗
PubMed2000

Crystallization and preliminary X-ray diffraction studies of human epidermal growth factor.

Human epidermal growth factor (hEGF), a 6.2 kDa protein of 53 amino acids with three internal disulfide bridges, has been crystallized by the hanging-drop method. hEGF crystallizes in space group P3(1)21 (or P3(2)21) using MgCl(2) as precipitant, with unit-cell parameters a = b = 61.4, c = 87.0 A. Another type of crystal, obtained using NaCl as precipitant, belongs to a tetragonal point group and has unit-cell dimensions a = b = 102.5, c = 166.6 A. The trigonal crystals with the smaller unit cell diffract X-rays better and a native data set from a single crystal has been collected to 3.0 A resolution.

Crystallization↗
PubMed2000

The double-stranded RNA-binding protein Staufen is incorporated in human immunodeficiency virus type 1: evidence for a role in genomic RNA encapsidation.

Human Staufen (hStau), a double-stranded RNA (dsRNA)-binding protein that is involved in mRNA transport, is incorporated in human immunodeficiency virus type 1 (HIV-1) and in other retroviruses, including HIV-2 and Moloney murine leukemia virus. Sucrose and Optiprep gradient analyses reveal cosedimentation of hStau with purified HIV-1, while subtilisin assays demonstrate that it is internalized. hStau incorporation in HIV-1 is selective, is dependent on an intact functional dsRNA-binding domain, and quantitatively correlates with levels of encapsidated HIV-1 genomic RNA. By coimmunoprecipitation and reverse transcription-PCR analyses, we demonstrate that hStau is associated with HIV-1 genomic RNA in HIV-1-expressing cells and purified virus. Overexpression of hStau enhances virion incorporation levels, and a corresponding, threefold increase in HIV-1 genomic RNA encapsidation levels. This coordinated increase in hStau and genomic RNA packaging had a significant negative effect on viral infectivity. This study is the first to describe hStau within HIV-1 particles and provides evidence that hStau binds HIV-1 genomic RNA, indicating that it may be implicated in retroviral genome selection and packaging into assembling virions.

Binding Sites↗
PubMed2000

Study of the assembly of vesicular stomatitis virus N protein: role of the P protein.

To derive structural information about the vesicular stomatitis virus (VSV) nucleocapsid (N) protein, the N protein and the VSV phosphoprotein (P protein) were expressed together in Escherichia coli. The N and P proteins formed soluble protein complexes of various molar ratios when coexpressed. The major N/P protein complex was composed of 10 molecules of the N protein, 5 molecules of the P protein, and an RNA. A soluble N protein-RNA oligomer free of the P protein was isolated from the N/P protein-RNA complex using conditions of lowered pH. The molecular weight of the N protein-RNA oligomer, 513,879, as determined by analytical ultracentrifugation, showed that it was composed of 10 molecules of the N protein and an RNA of approximately 90 nucleotides. The N protein-RNA oligomer had the appearance of a disk with outer diameter, inner diameter, and thickness of 148 +/- 10 A, 78 +/- 9 A, and 83 +/- 8 A, respectively, as determined by electron microscopy. RNA in the complexes was protected from RNase digestion and was stable at pH 11. This verified that N/P protein complexes expressed in E. coli were competent for encapsidation. In addition to coexpression with the full-length P protein, the N protein was expressed with the C-terminal 72 amino acids of the P protein. This portion of the P protein was sufficient for binding to the N protein, maintaining it in a soluble state, and for assembly of N protein-RNA oligomers. With the results provided in this report, we propose a model for the assembly of an N/P protein-RNA oligomer.

Cloning, Molecular↗
PubMed2000

Sialylation of the host receptor may modulate entry of demyelinating persistent Theiler's virus.

Theiler's murine encephalomyelitis virus (TMEV) is a picornavirus of the Cardiovirus genus. Certain strains of TMEV may cause a chronic demyelinating disease, which is very similar to multiple sclerosis in humans, associated with a persistent viral infection in the mouse central nervous system (CNS). Other strains of TMEV only cause an acute infection without persistence in the CNS. It has been shown that sialic acid is a receptor moiety only for the persistent TMEV strains and not for the nonpersistent strains. We report the effect of sialylation on cell surface on entry and the complex structure of DA virus, a persistent TMEV, and the receptor moiety mimic, sialyllactose, refined to a resolution of 3.0 A. The ligand binds to a pocket on the viral surface, composed mainly of the amino acid residues from capsid protein VP2 puff B, in the vicinity of the VP1 loop and VP3 C terminus. The interaction of the receptor moiety with the persistent DA strain provides new understanding for the demyelinating persistent infection in the mouse CNS by TMEV.

Animals↗
PubMed2000

Mutation of predicted virion pit residues alters binding of Theiler's murine encephalomyelitis virus to BHK-21 cells.

Theiler's murine encephalomyelitis virus (TMEV), a natural pathogen of mice, is a member of the genus Cardiovirus in the family Picornaviridae. Structural studies indicate that the cardiovirus pit, a deep depression on the surface of the virion, is involved in receptor attachment; however, this notion has never been systematically tested. Therefore, we used BeAn virus, a less virulent TMEV, to study the effect of site-specific mutation of selected pit amino acids on viral binding as well as other replicative functions of the virus. Four amino acids within the pit, V1091, P1153, A1225 and P3179, were selected for mutagenesis to evaluate their role in receptor attachment. Three amino acid replacements were made at each site, the first a conservative replacement, followed by progressively more radical amino acid changes in order to detect variable effects at each site. A total of seven viable mutant viruses were recovered and characterized for their binding properties to BHK-21 cells, capsid stability at 40 degrees C, viral RNA replication, single- and multistep growth kinetics, and virus translation. Our data implicate three of these residues in TMEV-cell receptor attachment.

Animals↗
PubMed2000

A novel murine Staufen isoform modulates the RNA content of Staufen complexes.

Mouse Staufen (mStau) is a double-stranded RNA-binding protein associated with polysomes and the rough endoplasmic reticulum (RER). We describe a novel endogenous isoform of mStau (termed mStau(i)) which has an insertion of six amino acids within dsRBD3, the major double-stranded RNA (dsRNA)-binding domain. With a structural change of the RNA-binding domain, this conserved and widely distributed isoform showed strongly impaired dsRNA-binding ability. In transfected cells, mStau(i) exhibited the same tubulovesicular distribution (RER) as mStau when weakly expressed; however, when overexpressed, mStau(i) was found in large cytoplasmic granules. Markers of the RER colocalized with mStau(i)-containing granules, showing that overexpressed mStau(i) could still be associated with the RER. Cotransfection of mStau(i) with mStau relocalized overexpressed mStau(i) to the reticular RER, suggesting that they can form a complex on the RER and that a balance between these isoforms is important to achieve proper localization. Coimmunoprecipitation demonstrated that the two mStau isoforms are components of the same complex in vivo. Analysis of the immunoprecipitates showed that mStau is a component of an RNA-protein complex and that the association with mStau(i) drastically reduces the RNA content of the complex. We propose that this new isoform, by forming a multiple-isoform complex, regulates the amount of RNA in mStau complexes in mammalian cells.

Alternative Splicing↗
PubMed2000

Chlamydia trachomatis mouse pneumonitis lung infection in IL-18 and IL-12 knockout mice: IL-12 is dominant over IL-18 for protective immunity.

BACKGROUND: Interferon (IFN)-gamma is a key to protective immunity against a variety of intracellular bacterial infections, including Chlamydia trachomatis. Interleukin (IL)-18, a recently identified Th1 cytokine, together with IL-12 is a strong stimulator for IFN-gamma production. We investigated the relative roles of IL-18 and IL- 12 in protective immunity to C. trachomatis mouse pneumonitis (MoPn) infection using gene knockout (KO) and wild-type (WT) mice. MATERIALS AND METHODS: Mice were intranasally infected with C. trachomatis MoPn and protective immunity was assessed among groups of mice by daily body weight changes, lung growth of MoPn, and histopathological appearances at day 10 postinfection. The corresponding immune responses for each group of mice at the same postinfection time point were evaluated by measuring antigen-specific antibody isotype responses and cytokine profiles. RESULTS: Our results showed that IL-18 deficiency had little or no influence on clearance of MoPn from the lung, although KO mice exhibited slightly more severe inflammatory reactions in lung tissues, as well as reduced systemic and local IFN-gamma production, compared with WT mice. Results with IL-18 KO mice were in sharp contrast to those observed with IL-12 KO mice that showed substantially reduced clearance of MoPn from the lungs, substantial reductions of antigen-specific systemic and lung IFN-gamma production, decreased ratio of MoPn-specific immunoglobulin G (IgG)2a/IgG1, and severe pathological changes in the lung with extensive polymorphonuclear, instead of mononuclear, cell infiltration. Exogenous IL-12 or IL-18 was able to increase IFN-gamma production in IL-18 KO mice; whereas, only exogenous IL-12, but not IL-18, enhanced IFN-gamma production in IL-12 KO mice. Caspase-1 is the key protease for activation of IL-18 precursor into the bioactive form, and caspase-1 KO mice also displayed similar bacterial clearance and body weight loss to that in WT mice at early stages of MoPn infection. This further confirmed that IL-18 was not essential for host defense against chlamydia infection. CONCLUSIONS: These results suggest that IL-12, rather than IL-18, plays the dominant role in the development of protective immunity against chlamydia lung infection, although both cytokines are involved in the in vivo regulation of IFN-gamma production.

Animals↗
PubMed2000

[The genetic effect of estrogen receptor(ESR) on litter size traits in pig].

Litter size is one of the most important economic traits in pig production, and the more piglet numbers per litter is capable to increase pork production and bring more economic profit for pig industry. ESR (estrogen receptor) gene has been determined to be one of the major genes affecting phenotype of litter size without any genetic negative correlation to growth and carcass traits. An optimized standard PCR-RFLP protocol is employed to type 262 sows from 5 different breeds in ESR loci, and then with the computation based on linear model ESR gene is confirmed to be a major locus significantly associated with litter size (P < 0.001). The genetic effect of ESR gene is quite large in these breeds, especially in these Chinese pig population. The sows of beneficial homozygote BB produce 1.40-3.37 total number born/litter and 0.63-3.58 number born alive/litter more than the sows of non-beneficial homozygote AA do. The information found in the present study is very important and could be utilized as DNA marker for improvement of reproduction trait in practice of pig breeding.

Animals↗