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Biomedical subjects

M Luo

Publications and source records attributed to M Luo.

At least 19 recordsLinked to original sources
PubMed2006

Storage protein profiles in Spanish and runner market type peanuts and potential markers.

BACKGROUND: Proteomic analysis has proven to be the most powerful method for describing plant species and lines, and for identification of proteins in complex mixtures. The strength of this method resides in high resolving power of two-dimensional electrophoresis (2-DE), coupled with highly sensitive mass spectrometry (MS), and sequence homology search. By using this method, we might find polymorphic markers to differentiate peanut subspecies. RESULTS: Total proteins extracted from seeds of 12 different genotypes of cultivated peanut (Arachis hypogaea L.), comprised of runner market (A. hypogaea ssp. hypogaea) and Spanish-bunch market type (A. hypogaea ssp. fastigiata), were separated by electrophoresis on both one- and two-dimensional SDS-PAGE gels. The protein profiles were similar on one-dimensional gels for all tested peanut genotypes. However, peanut genotype A13 lacked one major band with a molecular weight of about 35 kDa. There was one minor band with a molecular weight of 27 kDa that was present in all runner peanut genotypes and the Spanish-derivatives (GT-YY7, GT-YY20, and GT-YY79). The Spanish-derivatives have a runner-type peanut in their pedigrees. The 35 kDa protein in A13 and the 27 kDa protein in runner-type peanut genotypes were confirmed on the 2-D SDS-PAGE gels. Among more than 150 main protein spots on the 2-D gels, four protein spots that were individually marked as spots 1-4 showed polymorphic patterns between runner-type and Spanish-bunch peanuts. Spot 1 (ca. 22.5 kDa, pI 3.9) and spot 2 (ca. 23.5 kDa, pI 5.7) were observed in all Spanish-bunch genotypes, but were not found in runner types. In contrast, spot 3 (ca. 23 kDa, pI 6.6) and spot 4 (ca. 22 kDa, pI 6.8) were present in all runner peanut genotypes but not in Spanish-bunch genotypes. These four protein spots were sequenced. Based on the internal and N-terminal amino acid sequences, these proteins are isoforms (iso-Ara h3) of each other, are iso-allergens and may be modified by post-translational cleavage. CONCLUSION: These results suggest that there may be an association between these polymorphic storage protein isoforms and peanut subspecies fastigiata (Spanish type) and hypogaea (runner type). The polymorphic protein peptides distinguished by 2-D PAGE could be used as markers for identification of runner and Spanish peanuts.

Amino Acid Sequence↗
PubMed2006

Characterization of HLA-B*5516, -B*1313, -B*9512, and -DRB1*1457 alleles identified in a southwest Chinese population.

The human leukocyte antigen (HLA)-B*5516 allele differs from the B*5502 by a single 97 T --> C substitution (His to Tyr at position 33) in exon 2. The B*1313 allele results from 419 T --> A and 420 A --> C substitutions, encoding a Leu to Tyr substitution at 140 in exon 2 of the B*1301 allele. The B*9512 allele differs from B*1502 by a single 360 G --> C substitution (Gln to His at 120) in exon 3. The DRB1*1457 allele appears to be a hybrid molecule generated by recombination between the DRB1*13 and DRB1*14 alleles. The serological equivalents of these new alleles are HLA-B22, -B13, -B15, and DR13, respectively. Family studies detected two rare haplotypes: A*11, B*9512, DRB1*14 and A*24, B*52, Cw*07, DRB1*1457, DRB3*020201, DQB1*050301. The gene frequencies of these alleles in the Chinese population are less than 0.0001.

Alleles↗
PubMed2006

The visfatin gene is associated with glucose and lipid metabolism in a Chinese population.

AIMS: Visfatin is a newly discovered adipokine found in abundance in visceral fat. It lowers plasma glucose in humans and mice. In this study, we explored the relationships between the plasma level of visfatin and genetic single nucleotide polymorphisms (SNPs) and Type 2 diabetes mellitus (T2DM) and anthropometric and metabolic parameters in Chinese subjects. METHODS: Oral glucose tolerance tests (OGTT) and biochemical assays for plasma insulin, lipid profiles and serum visfatin were performed in 241 newly diagnosed T2DM patients, subjects with impaired glucose regulation (IGR), and normal glucose tolerant subjects more than 40 years of age. Genotyping for three SNP loci: -1535C/T, rs2058539 and rs10953502 were performed using the allele-specific real-time PCR method. RESULTS: Visfatin levels were similar in T2DM patients, IGR and normal glucose tolerant subjects. However, visfatin levels were significantly lower in obese than normal-weight subjects (13.66 +/- 0.87 vs. 15.46 +/- 0.47 ng/ml, P = 0.03). There was suggestively significant correlation between visfatin level and body mass index (r = -0.17 P = 0.07) and waist-hip ratio (r = 0.16 P = 0.08) in male subjects, but not in female subjects. Allele and common haplotype frequencies of the three SNP loci were similar in T2DM patients, IGR and normal glucose tolerant subjects. However, significant associations were found between these three SNP loci and plasma glucose concentration at 0 and 120 min during OGTT, the area under the response curve for plasma glucose, and triglyceride and total cholesterol levels. CONCLUSIONS: Serum visfatin levels may be related to visceral obesity in men, and the visfatin gene may account for variation of glucose and lipid parameters in Chinese subjects.

Adult↗
PubMed2005

Upstream regions of the estrogen receptor alpha proximal promoter transcript regulate ER protein expression through a translational mechanism.

Estrogen receptor alpha (ER) mRNA is primarily transcribed from two promoters, the two transcripts share identical sequence encoding the same ER protein but differ in upstream regions. The 5' region of the two transcripts contain upstream open reading frames (uORFs) encoding potential peptides of 20 and 18 amino acids. The peptides have five C-terminal residues in common. These studies were undertaken to determine if the uORFs and encoded peptides differentially affected expression of ER. Expression of green fluorescent protein (GFP) reporter constructs containing upstream proximal promoter transcript sequences with the first 18 codons of ER fused to GFP was tested in HeLa cells. The cells expressed reduced levels of GFP as compared to the pEGFP-N1 parent vector; the effect was dependent on the presence of an intact proximal ER transcript uORF. Similar regulation by the uORF was seen in transfected MCF-7, MDA MB-231 and Ishikawa cells. Only protein expression was affected by eliminating the uORF; RNA levels were unchanged. This indicates the mechanism is translational rather than being an effect of the introduced point mutations on either mRNA stability or transcription. Eliminating the uORF did not significantly increase expression from similar distal promoter transcript ER-GFP constructs. However, study of in-frame fusions of GFP to the entire proximal and distal uORFs and to their translational start motifs showed that the translational start region of the distal uORF was inherently better at initiating translation than the AUG environment of the proximal promoter transcript uORF. The data indicate there are regulatory properties suppressing expression from the ER translation start which are specific to the unique regions of the ER proximal promoter transcript and these are likely associated with the proximal transcript uORF peptide product.

5' Untranslated Regions↗
PubMed2005

Identification of four novel HLA-B alleles, B*1590, B*1591, B*2726, and B*4705, from an East African population by high-resolution sequence-based typing.

We report here four novel HLA-B alleles, B*1590, B*1591, B*2726, and B*4705, identified from an East African population during sequence-based HLA-B typing. The novel alleles were confirmed by sequencing two separate polymerase chain reaction products, and by molecular cloning and sequencing multiple clones. B*1590 is identical to B*1510 at exon 2 and exon 3, except for a difference (GCCGTC) at codon 158. Sequence differences at codon 152 (GAGGTG) and codon 167 (TGGTCG) differentiate B*1591 from B*1503 at exon 3. B*2726 is identical to B*2708 at exon 2 and exon 3, except for a difference (AAGCAG) at codon 70. B*4705 was identified in three Kenyan women. The allele is identical to B*47010101/02 at exon 2 and exon 3, except for differences at codon 97 (AGGAAT) and codon 99 (TTTTAT). These new alleles have been named by the WHO Nomenclature Committee. Identification of these novel HLA-B alleles reflects the genetic diversity of this East African population.

Base Sequence↗
PubMed2005

High-resolution sequence-based DPA1 typing identified two novel DPA1 alleles, DPA1*010303 and DPA1*0303, from a Kenyan population.

We report here two novel DPA1 alleles, DPA1*010303 and DPA1*0303, identified from a Kenyan population during sequence-based HLA-DPA1 typing. Molecular cloning and sequencing of multiple clones confirmed that one of the new DPA1 alleles is identical to DPA1*010301 at exon 2, except for a single nucleotide substitution (ACG ACC) at codon 15. The new allele has been named by the WHO Nomenclature Committee as DPA1*010303. The second novel DPA1 allele is identical to DPA1*0301, except for a single nucleotide difference (GAA GAC) at codon 28 that changed the amino acid from Glu to Asp. The new allele has been named by the WHO Nomenclature Committee as DPA1*0303. Identification of the two novel DPA1 alleles reflects the genetic diversity of this East African population.

Base Sequence↗
PubMed2005

Development of a pyrosequencing approach for rapid screening of rifampin, isoniazid and ethambutol-resistant Mycobacterium tuberculosis.

SETTING: The need to minimize the transmission of drug-resistant Mycobacterium tuberculosis requires rapid identification procedures. OBJECTIVE: To develop a pyrosequencing approach for rapid screening of rifampin, isoniazid and ethambutol-resistant M. tuberculosis based on characterization of resistance-associated hot mutations. DESIGN: Three pairs of PCR primers and three pyrosequencing sequencing primers for detecting mutations at codon 526 and 531 of the rpoB gene, codon 315 of the katG gene, and codon 306 of the embB gene were chosen. The sensitivity of the pyrosequencing approach was determined by assaying PCR products generated from 10-fold serial dilutions of the DNA from the H37Rv strain. The efficacy of the pyrosequencing approach was evaluated by analyzing clinical isolates with a known antibiotic phenotype. RESULTS: Resistance-associated hot mutations could be determined within 2 h after PCR amplification using pyrosequencing. About 45 fg DNA per reaction was required to obtain sufficient PCR products to produce a clear, accurate pyrosequencing pattern. No mutations were found in all 20 drug-susceptible clinical isolates, while all isolates with mutations showed corresponding drug resistances. CONCLUSION: This pyrosequencing approach can be used for rapid screening of rifampin-, isoniazid- and ethambutol-resistant M. tuberculosis prior to standard drug susceptibility testing.

Antibiotics, Antitubercular↗
PubMed2004

Structural genomics of Caenorhabditis elegans: structure of the BAG domain.

Binding of the BAG domain to the eukaryotic chaperone heat-shock protein (Hsp70) promotes ATP-dependent release of the protein substrate from Hsp70. Although the murine and human BAG domains have been shown to form an antiparallel three-helix bundle, the Caenorhabditis elegans BAG domain is formed by two antiparallel helices, while the third helix is extended away and stabilized by crystal-packing interactions. A small beta-sheet between helices 2 and 3 interferes with formation of the intramolecular three-helix bundle. However, intermolecular three-helix bundles are observed throughout the crystal packing and suggest that stable functional dimers and tetramers can be formed in solution. The structure may represent a new folding type of the BAG domain.

Animals↗
PubMed2004

Identification of a novel HLA-DQA1 null allele, DQA1*0403N, from an East African woman.

We report a novel DQA1 allele (DQA1*0403N) identified during sequence-based HLA-DQA1 typing of a Kenyan population. The new allele is identical to DQA1*0401 at exon 2 except for a single-nucleotide substitution at codon 53, changing it from lysine to a stop codon (CAA-->TAA). The substitution at codon 53 was confirmed by sequencing two separate polymerase chain reaction products and by sequencing multiple clones obtained following TOPO-TA cloning. The resulting stop codon at position of codon 53 in exon 2 is predicted to produce a non-functional DQA1 alpha-chain. The new allele has been named by the WHO nomenclature committee as DQA1*0403N. This is the first report of a null allele detected in the DQA1 gene.

Adult↗
PubMed2004

Detection of the differentially expressed gene IGF-binding protein-related protein-1 and analysis of its relationship to fasting glucose in Chinese colorectal cancer patients.

IGF-binding protein-related protein-1 (IGFBP-rP1) is a member of the IGF axis. In our previous work, we separated cDNA fragments of IGFBP-rP1 from colonic adenocarcinoma and normal mucosa cDNA subtraction libraries. In this study, we compared the expression of IGFBP-rP1 by semi-quantitative RT-PCR and immunohistochemistry among colorectal cancer, adenoma, normal tissue adjacent to cancer site, and normal tissue. Associations between IGFBP-rP1 and plasma glucose were further explored. We found that the mRNA level of IGFBP-rP1 was highest in cancer, moderate in adenoma and tissue adjacent to the cancer site and lowest in normal tissue (P<0.05). A significant difference was found in the immunoreactivity of IGFBP-rP1 between paired normal and cancer tissue (P<0.05). Tumor samples with upregulated expression of IGFBP-rP1 in invading tumor cells showed an increased frequency of metastasis to the lymph node, an increased depth of infiltration and stronger staining of IGFBP-rP1 compared with other samples (P<0.05). The fasting glucose level was significantly correlated with the staining of IGFBP-rP1 in cancer tissue (Spearman's rho=0.4, P<0.000). Thus, we concluded overexpression of IGFBP-rP1 might play an important role in the initiation and promotion of colorectal cancer. IGFBP-rP1 expression may also be associated with fasting glucose level and the presence of diabetes mellitus.

Adenocarcinoma↗
PubMed2003

High resolution sequence-based DPB1 typing identified two novel DPB1 alleles, DPB1*9401 and DPB1*9501, from a Kenyan population.

Two novel DPB1 alleles, DPB1*9401 and DPB1*9501, were identified from a Kenyan population during sequence-based HLA-DPB1 typing. Molecular cloning and sequencing of multiple clones confirmed that one of the new DPB1 alleles is identical to DPB1*0402 at exon 2 except for a single nucleotide substitution (CGG -->TGG), changing codon 70 from Arg to Trp. The new allele has been named DPB1*9401. This is the first report of polymorphism at codon 70 of HLA-DPB1 alleles. New codon combinations have been identified in another novel DPB1 allele named DPB1*9501. The extensive diversity at DPB1 locus of this East African population is being revealed by high resolution sequence-based DPB1 typing.

Amino Acid Sequence↗
PubMed2003

Leukotriene synthesis by epithelial cells.

Leukotrienes (LTs) are intercellular signaling molecules that evoke a variety of responses. They are best known as potent promoters of inflammation. Normally, LTs are produced primarily by leukocytes. As a result, current models regarding the production of LTs in the context of disease focus on the leukocytes as the site of production. Structural cells, including epithelial cells, are typically relegated to supportive roles. It is recognized that epithelial cells normally contain all the components necessary for LT synthesis except the enzyme 5-lipoxygenase (5-LO). There is accumulating evidence that some populations of epithelial cells normally express low levels of 5-LO and can synthesize LTs autonomously. Moreover, certain factors, including bacterial and viral infection, can promote the expression of 5-LO in airway, gastrointestinal and skin epithelial cells. The appearance of active 5-LO enzyme in epithelial cells at these sites may contribute to diseases like cancer, colitis and psoriasis. This paper reviews the state of our knowledge regarding the expression of 5-LO in epithelial cells, the factors that modify that expression, and the implications regarding pathogenesis.

Animals↗
PubMed2002

New genomic resources for the honey bee(Apis mellifera L.): development of a deep-coverage BAC library and a preliminary STC database.

We have constructed a bacterial artificial chromosome (BAC) library for a European honey bee strain using the cloning enzyme HindIII in order to develop resources for structural genomics research. The library contains 36,864 clones (ninety-six 384-well plates). A random sampling of 247 clones indicated an average insert size of 113 kb (range = 27 to 213 kb) and 2% empty vectors. Based on an estimated genome size of 270 Mb, this library provides approximately 15 haploid genome equivalents, allowing >99% probability of recovering any specific sequence of interest. High-density colony filters were gridded robotically using a Genetix Q-BOT in a 4 x 4 double-spotted array on 22.5-cm2 filters. Screening of the library with four mapped honey bee genomic clones and two bee cDNA probes identified an average of 21 positive signals per probe, with a range of 7-38 positive signals per probe. An additional screening was performed with nine aphid gene fragments and one Drosophila gene fragment resulting in seven of the nine aphid probes and the Drosophila probe producing positive signals with a range of 1 to 122 positive signals per probe (average of 45). To evaluate the utility of the library for sequence tagged connector analysis, 1152 BAC clones were end sequenced in both forward and reverse directions, giving a total of 2061 successful reads of high quality. End sequences were queried against SWISS-PROT, insect genomic sequence GSS, insect EST, and insect transposable element databases. Results in spreadsheet format from these searches are publicly available at the Clemson University Genomics Institute (CUGI) website in a searchable format (http://www.genome.clemson.edu/projects/stc/bee/AM__Ba/).

Animals↗
PubMed2002

HLA-A and HLA-B in Kenya, Africa: allele frequencies and identification of HLA-B*1567 and HLA-B*4426.

HLA-A and HLA-B alleles of a population from Kenya, Africa were examined by sequencing exon 2 and exon 3 DNA and typing using a Taxonomy-based Sequence-analysis (TBSA) method. Extensive diversities were observed at both HLA-A and HLA-B loci in this population. Forty-one HLA-A alleles were identified from 159 unrelated individuals. The most frequently observed alleles were A*6802 (11.64%), A*02011/09 (9.75%), A*7401/02 (9.43%), A*3001 (7.86%), A*3002 (7.23%) and A*3601 (6.6%). Forty-nine HLA-B alleles were identified in 161 unrelated individuals, including two novel alleles, B*1567 and B*4426. The most frequently observed HLA-B alleles were B*5301 (9.01%), B*5801 (8.38%), B*4201 (7.76%), B*1503 (7.14%), B*1801 (6.21%), and B*5802 (5.90%). The most frequently observed HLA-A-B haplotypes were A*3601-B*5301 (3.55%) and A*3001-B*4201 (3.19%), followed by A*7401/02-B*5801 (2.84%), A*7401/02-B*5802 (2.84%) and A*02011/09-B*1503 (2.13%). Linkage disequilibrium and chi2 analysis showed the association of these HLA-A-B haplotypes at the antigen level to be significant. The frequencies of HLA-A and HLA-B alleles from the Kenyan population were compared with that of a population from Cameroon. The difference in allele and haplotype frequency distributions partly reflected the different ethnic composition of these two African populations.

Adult↗
PubMed2001

Response correlation maps of neurons in the mammalian olfactory bulb.

To define the relationship between glomerular activation patterns and neuronal olfactory responses in the main olfactory bulb, intracellular recordings were combined with optical imaging of intrinsic signals. Response correlation maps (RCMs) were constructed by correlating the fluctuations in membrane potential and firing rate during odorant presentations with patterns of glomerular activation. The RCMs indicated that mitral/tufted cells were excited by activation of a focal region surrounding their principal glomerulus and generally inhibited by activation of more distant regions. However, the structure of the RCMs and the relative contribution of excitatory and inhibitory glomerular input evolved and even changed sign during and after odorant application. These data suggest a dynamic center-surround organization of mitral/tufted cell receptive fields.

Action Potentials↗
PubMed2001

The crystal structure of the influenza matrix protein M1 at neutral pH: M1-M1 protein interfaces can rotate in the oligomeric structures of M1.

The influenza matrix protein (M1) forms a protein layer under the viral membrane and is essential for viral stability and integrity. M1 mediates the encapsidation of the viral RNPs into the viral membrane by its membrane and RNP-binding activities. In order to understand the roles of M1-M1 protein interactions in forming the M1 layer, X-ray crystallographic studies of a M1 fragment (1-162) were carried out at neutral pH and compared with an acidic pH structure. At neutral pH the asymmetric unit was a stacked dimer of M1. A long molecular ribbon of neutral stacked dimers was formed by translation as dictated by the P1 space group. The elongated ribbon had a positively charged stripe on one side of the ribbon. A similar M1-M1 stacking interface was also found in the acidic asymmetric unit. However, within the acidic stacked dimer the molecules were not straight, but rotated in relation to each other by slightly changing the M1-M1 stacking interface. The acidic structure possessed an additional M1-M1 twofold interface. Protein docking confirmed that the M1-M1 stacking and M1-M1 twofold interfaces could be used to form a double ribbon of M1 molecules. By iterative repetition of the rotated relationship among the M1 molecules, a helix of M1 was generated. These studies suggest that M1 has the ability to form straight or bent elongated ribbons and helices. These oligomers are consistent with previous electron microscopic studies of M1, which demonstrated that isolated M1 formed elongated and flexible ribbons when isolated from what appeared to be a helical shell of M1 in the influenza virus.

Crystallography, X-Ray↗