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Biomedical subjects

B Guo

Publications and source records attributed to B Guo.

At least 19 recordsLinked to original sources
PubMed2006

Role of salicylic acid in alleviating oxidative damage in rice roots (Oryza sativa) subjected to cadmium stress.

Time-dependent changes in enzymatic and non-enzymatic antioxidants, and lipid peroxidation were investigated in roots of rice (Oryza sativa) grown hydroponically with Cd, with or without pretreatment of salicylic acid (SA). Exposure to 50 microM Cd significantly decreased root growth, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), but increased the concentrations of H(2)O(2), malondialdehyde (MDA), ascorbic acid (AsA), glutathione (GSH) and non-protein thiols (NPT). However, pretreatment with 10 microM SA enhanced the activities of antioxidant enzymes and the concentrations of non-enzymatic antioxidants, but lowered the concentrations of H(2)O(2) and MDA in the Cd-stressed rice compared with the Cd treatment alone. Pretreatment with SA alleviated the Cd-induced inhibition of root growth. The results showed that pretreatment with SA enhanced the antioxidant defense activities in Cd-stressed rice, thus alleviating Cd-induced oxidative damage and enhancing Cd tolerance. The possible mechanism of SA-induced H(2)O(2) signaling in mediating Cd tolerance was discussed.

Antioxidants↗
PubMed2006

Pooled analysis of data from multiple quantitative trait locus mapping populations.

Quantitative trait locus (QTL) analysis on pooled data from multiple populations (pooled analysis) provides a means for evaluating, as a whole, evidence for existence of a QTL from different studies and examining differences in gene effect of a QTL among different populations. Objectives of this study were to: (1) develop a method for pooled analysis and (2) conduct pooled analysis on data from two soybean mapping populations. Least square interval mapping was extended for pooled analysis by inclusion of populations and cofactor markers as indicator variables and covariate variables separately in the multiple linear models. The general linear test approach was applied for detecting a QTL. Single population-based and pooled analyses were conducted on data from two F(2:3) mapping populations, Hamilton (susceptible) x PI 90763 (resistant) and Magellan (susceptible) x PI 404198A (resistant), for resistance to soybean cyst nematode (SCN) in soybean. It was demonstrated that where a QTL was shared among populations, pooled analysis showed increased LOD values on the QTL candidate region over single population analyses. Where a QTL was not shared among populations, however, the pooled analysis showed decreased LOD values on the QTL candidate region over single population analyses. Pooled analysis on data from genetically similar populations may have higher power of QTL detection than single population-based analyses. QTLs were identified by pooled analysis on linkage groups (LGs) G, B1 and J for resistance to SCN race 2 whereas QTLs on LGs G, B1 and E for resistance to SCN race 5 in soybean PI 90763 and PI 404198A. QTLs on LG G and B1 were identified in both PI 90763 and PI 404198A whereas QTLs on LG E and J were identified in PI 90763 only. QTLs on LGs G and B1 for resistance to race 2 may be the same or closely linked with QTLs on LG G and B1 for resistance to race 5, respectively. It was further demonstrated that QTLs on G and B1 carried by PI 90763 were not significantly different in gene effect from QTLs on LGs G and B1 in PI 404198A, respectively.

Chromosome Mapping↗
PubMed2005

Identification of QTLs associated with resistance to soybean cyst nematode races 2, 3 and 5 in soybean PI 90763.

Soybean cyst nematode (SCN) is a major soybean pest throughout the soybean growing regions in the world, including the USA. Soybean PI 90763 is an important SCN resistance source. It is resistant to several SCN populations including races 2, 3 and 5. But its genetics of resistance is not well known. The objectives of this study were to: (1) confirm quantitative trait loci (QTLs) for resistance to SCN race 3 in PI 90763 and (2) identify QTLs for resistance to SCN races 2 and 5. QTLs were searched in Hamilton x PI 90763 F(2:3)populations using 193 polymorphic simple sequence repeats (SSRs) covering 20 linkage groups (LGs). QTLs for resistance to SCN were identified on LGs A2, B1, E, G, J and L. The same QTL was suggested for resistance to different SCN races where their 1-LOD support intervals of QTL positions highly overlapped. The QTL on LG G was associated with resistance to races 2, 3 and 5. The QTL on LG B1 was associated with resistance to races 2 and 5. The QTL on LG J was associated with resistance to races 2 and 3. The QTLs on LGs A2 and L were associated with resistance to race 3. The QTL on LG E was associated with resistance to race 5. We conclude that LGs A2 and B1 may represent an important distinction between resistance to SCN race 3 and resistance to SCN races 2 and 5 in soybean.

Animals↗
PubMed2003

Multi-wavelength mid-infrared micro-spectral imaging using semiconductor lasers.

Infrared (IR, 3-12-microm) microscopic spectral imaging is an important analytical technique. Many current instruments employ thermal IR light sources, which suffer the problem of low brightness and high noise. This paper evaluates the system engineering merit in using semiconductor lasers, which offer orders-of-magnitude-higher power, brightness, and lower noise. A microscopic spectral imaging system using semiconductor lasers (quantum cascade) as illuminators, and focal plane array detectors demonstrated a high signal-to-noise ratio (> 20 dB) at video frame rate for a large illuminated area. The comparative advantages of laser vs. thermal light source are analyzed and demonstrated. Microscopic spectral imaging with fixed-wavelength and tunable lasers of 4.6-, 5.1-, 6-, and 9.3-microm wavelength was applied to a number of representative samples that consist of biological tissues (plant and animal), solid material (a stack of laminated polymers), and liquid chemical (benzene). Transmission spectral images with approximately 30-dB dynamic range were obtained with clear evidence of spectral features for different samples. The potential of more advanced systems with a wide coverage of spectral bands is discussed.

Animals↗
PubMed2002

A matrix-assisted laser desorption/ionization time-of-flight based method for screening the 1691G --> A mutation in the factor V gene.

A point mutation, 1691 G --> A in the coagulation factor V gene results in an Arg506 --> Gln amino acid substitution in the factor V molecule. This mutation, defined as factor VLEIDEN, results in activated protein C (APC) resistance and is the most common genetic risk factor for familial thrombophilia. A new mini-sequencing method using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was developed for the screening of the 1691G --> A substitution in factor V. In this method, a fragment of genomic DNA containing the 1691st base is first amplified, followed by mini-sequencing in the presence of dGTP and ddATP, ddCTP, and ddTTP. In this manner, the primer is extended by one base from one allele and two bases from the other allele. The extended products are analyzed using MALDI-TOF mass spectrometry. The base at position 1691 is identified based on the number of nucleotides added. We have used this method to genotype 16 APC-resistant patients previously identified by conventional methods and 11 normal control samples. The genotypes of all samples were correctly identified. This method is accurate, fast, and potentially allows for simultaneous multiplex genotyping of a number of mutation sites associated with thrombophilia and clot formation.

Activated Protein C Resistance↗
PubMed2001

Earliest presence of humans in northeast Asia.

The timing of the earliest habitation and oldest stone technologies in different regions of the world remains a contentious topic in the study of human evolution. Here we contribute to this debate with detailed magnetostratigraphic results on two exposed parallel sections of lacustrine sediments at Xiaochangliang in the Nihewan Basin, north China; these results place stringent controls on the age of Palaeolithic stone artifacts that were originally reported over two decades ago. Our palaeomagnetic findings indicate that the artifact layer resides in a reverse polarity magnetozone bounded by the Olduvai and Jaramillo subchrons. Coupled with an estimated rate of sedimentation, these findings constrain the layer's age to roughly 1.36 million years ago. This result represents the age of the oldest known stone assemblage comprising recognizable types of Palaeolithic tool in east Asia, and the earliest definite occupation in this region as far north as 40 degrees N.

Animals↗
PubMed2001

Viral interleukin 6 stimulates human peripheral blood B cells that are unresponsive to human interleukin 6.

Cellular responsiveness to human interleukin 6 (hIL6) requires the expression of two receptor molecules: IL6-specific receptor (CD126'IL6R') and a nonspecific signal-transducing molecule (CD130'gp130'). Regulation of responsiveness to hIL6 is generally controlled by CD126'IL6R' expression. A viral homologue of hIL6 (vIL6) is encoded by human herpesvirus-8 and has biologic activity similar to hIL6 on a number of cell lines. vIL6 differs from hIL6 in its receptor utilization, requiring only CD130'gp130'. Total human B cells isolated from peripheral blood, which are predominantly CD126'IL6R'-negative, as well as sorted CD126'IL6R'-negative B cells, could be stimulated by recombinant vIL6, but not by hIL6, as indicated by induction of IL6-like signaling (STAT3 phosphorylation). This suggests that the ability of vIL6 to stimulate B cells expressing little or no CD126'IL6R' allows it to act on a larger pool of target B cells, compared to human IL6.

Adult↗
PubMed2001

The Chk1-Cdc25C regulation is involved in sensitizing A253 cells to a novel topoisomerase I inhibitor BNP1350 by bax gene transfer.

Promotion of apoptosis may potentiate the sensitivity of tumor cells to chemotherapeutic agents, thus improving the efficacy of cancer treatment. The transfection of the proapoptotic bax gene, which results in the overexpression of bax protein, augments the growth inhibition of A253 cells by BNP1350. Increased drug response was associated with the induction of DNA fragmentation in the size of 30-200 Kb, generating a cleaved fragment of 18 kDa from full-length 21 kDa bax and the cleavage of PARP. A253/vec cells treated with 0.07 microM(IC50) of BNP1350 accumulated in G2 phase at 24 h after drug removal. In contrast, A253/Bax cells treated with an equimolar concentration of BNP1350 primarily displayed a G1 phase accumulation with a concurrent decrease in G2 phase. Certain cell cycle regulatory protein expression and activities were altered following drug exposure in both cell lines under similar conditions. Cdk2- and cdc2-associated H1 kinase activities were markedly increased in the A253/Bax cell line with marginal increased activity in the A253/vec cell line. A chk1 activity assay was performed with GST-cdc25C (200-256) or GST-cdc25C(S216A) (200-256) fusion proteins as the substrate. Increased chk1 activity was observed in the A253/vec cell line, with little change in the A253/Bax cell line, when exposed to equimolar concentrations of BNP1350 (0.07 microM). A Western blot of immunoprecipitated chk1 indicated that increased chk1 phosphorylation following DNA damage induced by BNP1350 was accompanied by the observed G2 accumulation in the A253/vec cell line, while only a slight increase in chk1 phosphorylation was seen in the A253/Bax cell line. A decreased expression of cdc25C was observed in the BNP1350-treated A253/Bax cells, but not in the A253/vec cell line. Following exposure to BNP1350, increased binding of 14-3-3 proteins to chk1 occurred in both cell lines, with more being observed in the A253/vec cell line. The data have shown that inhibition of the chk1 pathway accompanied by the abrogation of G2 arrest is involved in sensitizing A253 cells to BNP1350 by bax gene transfer. These findings suggest that bax gene transfer sensitizes A253 cells to BNP1350 through apoptosis promoting and G2/M DNA damage checkpoint regulatory pathways.

Apoptosis↗
PubMed2001

Cloning and characterization of Chinese hamster homologue of yeast DBF4 (ChDBF4).

The Dbf4 protein is the regulatory subunit of Cdc7 serine/threonine kinase, which is essential for entry into S phase. We report here the cloning and initial characterization of the Chinese hamster homologue of yeast DBF4. The deduced ChDbf4 protein contains 676 amino acids with a predicted molecular mass of 75.8 kDa, and shares extensive identity overall with those of human (68%) and mouse (73%). The ChDBF4 mRNA level was barely detectable in the cells arrested in the quiescent stage (G(0)) by isoleucine starvation. When cells in G(0) were released into the cell cycle, the ChDBF4 mRNA level did not significantly change until the cells reached the G(1)/S boundary, when the level rapidly increased and reached approximately 70% of the maximum level that was observed in mid to late S phase. Interestingly, gamma-irradiation rapidly and transiently downregulated the level of ChDBF4 mRNA in asynchronous cell populations. Since Dbf4-Cdc7 kinase is involved in the regulation of replication initiation, which can be transiently downregulated by irradiation (Larner et al., 1994. Mol. Cell. Biol. 14, 1901, our data raise the possibility that the downregulation of DBF4 (and, thus, the Cdc7 kinase activity) by irradiation may play a role in the cell-cycle checkpoint that functions at the G(1)/S transition and in S phase (Lee et al., 1997. Proc. Natl. Acad. Sci. USA 94, 526).

Amino Acid Sequence↗
PubMed2001

Angiogenesis in breast cancer: the role of transforming growth factor beta and CD105.

The progression of breast cancer depends on the establishment of a neovasculature, by a process called angiogenesis. Angiogenesis is an invasive cellular event that requires the co-ordination of numerous molecules including growth factors and their receptors, extracellular proteins, adhesion molecules, and proteolytic enzymes. TGFbeta has emerged to be a major modulator of angiogenesis by regulating endothelial cell proliferation, migration, extracellular matrix (ECM) metabolism, and the expression of adhesion molecules. It is a potent growth inhibitor of normal mammary epithelial cells and a number of breast cancer cell lines. It seems that TGFbeta exerts pleiotropic effects in the oncogenesis of breast cancers in a contextual manner, i.e., it suppresses tumourigenesis at an early stage by direct inhibition of angiogenesis and tumour cell growth. However, over-production of TGFbeta by an advanced tumour may accelerate disease progression through indirect stimulation of angiogenesis and immune suppression. The cell membrane antigen CD105 (endoglin) binds TGFbeta1 and TGFbeta3 and is preferentially expressed in angiogenic vascular endothelial cells. The reduction of CD105 levels in HUVEC leads to in vitro angiogenesis inhibition and massive cell mortality in the presence of TGFbeta1. CD105 null mice die in utero with impaired vasculature, indicating the pivotal role of CD105 in vascular development. The administration of an immunotoxin-conjugate, mab to CD105, induces long-term and complete regression of breast cancer growth in SCID mice. Therefore, CD105 is a promising vascular target for antiangiogenic therapy.

Animals↗
PubMed2001

Simulation of biomass gasification with a hybrid neural network model.

Gasification of several types of biomass has been conducted in a fluidized bed gasifier at atmospheric pressure with steam as the fluidizing medium. In order to obtain the gasification profiles for each type of biomass, an artificial neural network model has been developed to simulate this gasification processes. Model-predicted gas production rates in this biomass gasification processes were consistent with the experimental data. Therefore, the gasification profiles generated by neural networks are considered to have properly reflected the real gasification process of a biomass. Gasification profiles identified by neural network suggest that gasification behavior of arboreal types of biomass is significantly different from that of herbaceous ones.

Biomass↗
PubMed2001

TIP41 interacts with TAP42 and negatively regulates the TOR signaling pathway.

In Saccharomyces cerevisiae, the rapamycin-sensitive TOR kinases negatively regulate the type 2A-related phosphatase SIT4 by promoting the association of this phosphatase with the inhibitor TAP42. Here, we describe TIP41, a conserved TAP42-interacting protein involved in the regulation of SIT4. Deletion of the TIP41 gene confers rapamycin resistance, suppresses a tap42 mutation, and prevents dissociation of SIT4 from TAP42. Furthermore, a TIP41 deletion prevents SIT4-dependent events such as dephosphorylation of the kinase NPR1 and nuclear translocation of the transcription factor GLN3. Thus, TIP41 negatively regulates the TOR pathway by binding and inhibiting TAP42. The binding of TIP41 to TAP42 is stimulated upon rapamycin treatment via SIT4-dependent dephosphorylation of TIP41, suggesting that TIP41 is part of a feedback loop that rapidly amplifies SIT4 phosphatase activity under TOR-inactivating conditions.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Dinucleotide repeat polymorphism of matrix metalloproteinase-9 gene is associated with diabetic nephropathy.

BACKGROUND: Although genetic susceptibility has been proposed as an important factor for the development and progression of diabetic nephropathy, the definitive gene has not been identified. To identify the genetic marker for diabetic nephropathy, we examined the association between the (A-C)n dinucleotide repeat polymorphism upstream of the matrix metalloproteinase-9 (MMP-9) gene and diabetic nephropathy in a group of Japanese patients with type 2 diabetes. METHODS: Patients were divided into three groups based on their urinary albumin excretion rate (AER) and the stage of diabetic retinopathy as follows: uncomplicated group (U), normal albuminuria (AER <20 microg/min) without proliferative retinopathy and with the duration of diabetes more than 20 years (N = 32); microalbuminuria group (M), 20 < or = AER < 200 microg/min (N = 155); overt nephropathy group (O), AER > or = 200 microg/min (N = 63). The region containing the dinucleotide repeat upstream of MMP-9 gene was amplified by polymerase chain reaction (PCR). The amplified products were analyzed with 7% formamide/urea acrylamide gel electrophoresis. The promoter constructs of the MMP-9 gene were transfected with the CMV-beta-galactosidase construct into 293 cells using the liposome method. Twenty-four hours after transfection, cells were harvested, and luciferase and beta-galactosidase activities were measured. RESULTS: Nine alleles of the dinucleotide repeat polymorphism (17 to 25 repeats) were identified, and the frequency of each allele in diabetic subjects was not different from that in nondiabetic controls. The frequency of the allele containing 21 repeats (A21) was most abundant (42.4% in control and 45.6% in diabetic subjects), followed by the allele with 23 repeats (A23; 35.4% in control and 27.6% in diabetic subjects). The A21 allele was less frequent in M and O than U (O, 38.9%; M, 45.5%; U, 59.3%, chi2 = 7.18; P < 0.05, O vs. U), while the frequency of the alleles other than A21 was not different among each group. The calculated odds ratio for nephropathy in the noncarrier, heterozygote, or homozygote of A21 allele was 3.38, 1.97, and 0.2, respectively. Furthermore, the promoter assay for the MMP-9 gene revealed that the A21 allele had a higher promoter activity compared with other alleles. No significant correlation was observed between serum MMP-9 concentrations and the MMP-9 gene polymorphism. CONCLUSION: These results indicate that the patients with A21 allele of the MMP-9 gene may be protected from the development and progression of diabetic nephropathy. Thus, the microsatellite polymorphism upstream of the MMP-9 gene could be a useful genetic marker for diabetic nephropathy.

Aged↗
PubMed2001

Fluorescence produced by transfection reagents can be confused with green fluorescent proteins in mammalian cells.

The Aequorea victoria green fluorescent protein (GFP) reporter system is a convenient way to monitor gene expression and other cellular functions in mammalian cells. To study gene expression, a GFP-fusion plasmid construct is often transfected into mammalian cells using a variety of methods including calcium phosphate- and liposome-based DNA transfer. Subsequently, the expression of GFP-fusion protein is monitored by fluorescence microscopy or flow cytometry. Here, we report that certain transfection reagents can produce fluorescence that can be detected in a wide range of wavelengths, which can be confused with GFP-fusion protein. The fluorescence false positives can be a problem, particularly when the GFP expression levels are low. To improve the GFP-based detection or screening methods, it is imperative to include an appropriate negative control and to detect GFP using a narrow-wavelength emission filter corresponding to the emission spectrum around the GFP peak.

Animals↗
PubMed2001

[Effect of para-aminobenzoic acid on the adhesion of Streptococcus mutans].

OBJECTIVE: To investigate the effects of Para-aminobenzoic acid (PABA) on the adhesion of Streptococcus mutans to saliva-coated hydroxyapatite (S-HA). METHODS: The adhesion model in vitro established by Gibbons was adopted in this study to quantify adsorptive cells through [3H] thymidine labelling. RESULTS: PABA solution over a range of concentration from 10(-9) to 10(-3) g/L could inhibit the attachment of S. mutans to S-HA effectively, and the inhibition declined when the concentration of PABA solution was 10(-3) g/L. CONCLUSION: PABA can inhibit the adherence of Streptococcus mutans to S-HA effectively.

4-Aminobenzoic Acid↗
PubMed2001

[Effects of para-aminobenzoic acid (PABA) on growth of Streptococcus mutans].

OBJECTIVE: The aim of this study is to examine effects of para-aminobenzoic acid (PABA) on the growth of Streptococcus mutans (S. mutans). METHODS: Different concentrations of PABA (10(-10)-10(-3) g/L) were separately transferred to modified Carlsson medium. S. mutans (ATCC 25175) grew in modified Carlsson medium with different concentrations of PABA. All cultures were incubated at 37 degrees C anaerobically in an atmosphere of 80% of nitrogen (v/v), 10% of hydrogen (v/v) and 10% of carbon dioxide (v/v) for 48 hours. The absorbance values of S. mutans were measured by using a spectrometer (UV-1601). The colony forming units (CFU) were obtained by growing S. mutans in media with different concentrations of PABA (10(-10)-10(-3) g/L). RESULTS: Different concentrations of PABA had different stimulating effects on the growth of S. mutans (P < 0.05). But this kind of stimulating effects declined when the concentration of PABA was 10(-3) g/L. CONCLUSION: This experiment indicates PABA has stimulating effects on the growth of S. mutans, and PABA can promote growth of S. mutans.

4-Aminobenzoic Acid↗
PubMed2001

[Effects of para-aminobenzoic acid (PABA) on growth of Lactobacillus acidophilus].

OBJECTIVE: The aim of this study is to examine effects of para-aminobenzoic acid (PABA) on the growth of Lactobacillus acidophilus (L. acidophilus). METHODS: Different concentrations of PABA (10(-10)-10(-3) g/L) were separately transferred to the modified Carlsson medium. L. acidophilus (ATCC4356) grew in these Carlsson media. All cultures were incubated at 37 degrees C anaerobically in atmosphere of 80% of nitrogen, 10% of hydrogen, and 10% of carbon dioxide for 48 hours. Absorbance values (lambda = 540 nm) of bacterial suspensions were measured using a spectrometer (UV-1601). Colony forming units (CFU) were obtained by growing L. acidophilus in Carlsson media with different concentration of PABA (10(-10)-10(-3) g/L). RESULTS: Different concentrations of PABA (10(-10)-10(-4) g/L) had different stimulating effects on the growth of L. acidophilus (P < 0.05). But stimulating effects declined, when PABA concentration was 10(-5) g/L, and when the concentration of PABA reached 10(-3) g/L, the stimulating effect disappeared. CONCLUSION: This study indicates PABA stimulates the growth of L. acidophilus, and PABA can promote growth of L. acidophilus.

4-Aminobenzoic Acid↗