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Biomedical subjects

B Yu

Publications and source records attributed to B Yu.

At least 19 recordsLinked to original sources
PubMed2007

Immune effect of heat-killed multistrain of Lactobacillus acidophilus against Salmonella typhimurium invasion to mice.

AIMS: This study attempted to determine whether lactic acid bacteria (LAB) could have a better probiotic function when used as a multistrain mixture, i.e. Mix-LAB, than when used as a monostrain. To this end, three strains of Lactobacillus acidophilus, specifically strain LAP5, LAF1 and LAH7, were heat-killed and mixed. This heat-killed Mix-LAB was used to evaluate the effectiveness of multistrain in inhibiting Salmonella invasion into cultured cells and into organs (spleen and liver) of live mice. METHODS AND RESULTS: BALB/c mice were orally administered with heat-killed Mix-LAB or sterile normal saline (control) for seven consecutive days and then challenged with orally administered Salmonella typhimurium on day 8. Results showed that, at day 6 after the challenge, the mice which had received Mix-LAB exhibited lower rates (P < 0.05) of Salmonella invasion into liver and spleen than did the control mice. Also, before the Salmonella challenge, the serum tumour necrosis factor-alpha (TNF-alpha) levels were not significantly different (P > 0.05) between these two groups of mice. After the challenge, however, the serum TNF-alpha level was significantly elevated (P < 0.05) in the control group, but not significantly changed in the Mix-LAB fed mice. To investigate possible factors involved in heat-killed Mix-LABs antagonistic effect on Salmonella invasion of mouse organs, heat-killed single strain and Mix-LAB were evaluated for ability to inhibit Salmonella invasion into cultured human intestinal Int-407 and Caco-2 cells. Results showed that none of the heat-killed strains were able to protect these cultured cells from Salmonella invasion, even though strains of LAP5 and Mix-LAB were adherent to them. However, study of the activation of murine macrophage Raw 264.7 cells showed that heat-killed Mix-LAB stimulated TNF-alpha production, nitric oxide release, and increased phagocytic activity in macrophages. CONCLUSIONS: Our findings suggest that heat-killed Mix-LAB can inhibit Salmonella invasion of mouse organs through the immunomodulating role of activated macrophage. SIGNIFICANCE AND IMPACT OF THE STUDY: The ability of heat-killed Mix-LAB to prevent bacterial infection in mice was found to be more significant than that of viable monostrain. This effect may be due to the activation of the immune system rather than to the adherence of LAB to the intestine epithelium.

Animals↗
PubMed2006

Macrophage activation by polysaccharide biological response modifier isolated from Aloe vera L. var. chinensis (Haw.) Berg.

A mannose-rich polysaccharide biological response modifier (BRM), derived from Aloe vera L. var. chinensis (Haw.) Berg., was demonstrated to be a potent murine B- and T-cell stimulator in our previous study. We here report the stimulatory activity of PAC-I on murine peritoneal macrophage. The polysaccharide when injected into mice enhanced the migration of macrophages to the peritoneal cavity. Peritoneal macrophage when treated by PAC-I in vitro had increased expression of MHC-II and FcgammaR, and enhanced endocytosis, phagocytosis, nitric oxide production, TNF-alpha secretion and tumor cell cytotoxicity. The administration of PAC-I into allogeneic ICR mice stimulated systemic TNF-alpha production in a dose-dependent manner and prolonged the survival of tumor-bearing mice. PAC-I is thus a potent stimulator of murine macrophage and the in vitro observed tumoricidal properties of activated macrophage might account for the in vivo antitumor properties of PAC-I. Our research findings may have therapeutic implications in tumor immunotherapy.

Aloe↗
PubMed2006

Potential of diffusion tensor MRI in the assessment of periventricular leukomalacia.

AIM: To investigate magnetic resonance (MR) diffusion tensor imaging (DTI) and fibre tractography in the assessment of altered major white matter (WM) fibre tracts in periventricular leukomalacia (PVL). MATERIALS AND METHODS: Twelve children (male:female = 7:5, age range 3-10 years; mean age = 6.5 years) who had suffered PVL were included in this study. Meanwhile, Twelve age-matched normal controls (male:female = 6:6, age range 4-12 years; mean age = 7.3 years) with normal MRI findings and no neurological abnormalities were recruited for comparison. DTI was performed with 15 different diffusion gradient directions and DTI colour maps were created from fractional anisotropy (FA) values and the three vector elements. To identify alteration of WM fibre tracts in patient of PVL quantitatively, FA values on diffusion tensor colour maps were compared between the patients and controls. Quantitative analysis was performed using the regions of interest (ROI) method settled on the central part of all identifiable WM fibres, including the corticospinal tract (CST) in the brainstem, middle cerebellar peduncle (MCP), medial lemniscus (ML), anterior/posterior limb of internal capsule (ICAL/ICPL), arcuate fasciculus (AF), posterior thalamic radiation (PTR), genu of corpus callosum (GCC), splenium of corpus callosum (SCC), corona radiata (CR), cingulum (CG), and superior longitudinal fasciculus (SLF). The averaged FA value of each WM fibre was measured and summarized as the mean +/- standard deviation (SD). All data were analysed by paired Student's t-test. A p-value of less than 0.05 was considered to indicate statistical significance. RESULTS: Visual investigation of WM fibre tracts showed that the ICAL, brainstem CST, ML, MCP, and external capsule (EC) was similar in controls and subjects. However, the ICPL, AF, PTR, CR, CG, SLF and corpus callosum, were all attenuated in size. All 12 cases of PVL showed a significant mean FA reduction in the ICPL, AF, PTR, CR, CG, SLF, SCC, and GCC in comparison with the ipsilateral regions of healthy controls (p<0.05). However, there were no statistically significant differences of the ICAL, ML, MCP, and brainstem CST when analysed using a two-tailed Student's t-test for paired data (p>0.01). CONCLUSION: DTI can provide more information for understanding the pathophysiology of motor disability and associated sensory handicap in PVL.

Anisotropy↗
PubMed2005

Placental deficiency of interleukin-10 (IL-10) in preeclampsia and its relationship to an IL10 promoter polymorphism.

The placenta is pivotal in the acceptance of the feto-placental unit by the maternal immune system. Imbalance at the maternal-fetal interface of tissue pro- and anti-inflammatory cytokines may be partly involved in disease causation. Previous work has shown conflicting levels of IL-10. IL-10 levels have been shown to increase, decrease, or remain unchanged in women with preeclampsia. This study examines the difference in serum and placental IL-10 expression in women with preeclampsia and investigates if the IL10 (-1082) A promoter polymorphism contributes to lower concentrations. In a prospective case-control study of 12 women with preeclampsia and 31 controls we assessed serum IL-10 by ELISA, placental mRNA by quantitative PCR and protein by immunohistochemistry as well as placental IL10 promoter genotype. Comparisons were made with non-parametric tests where necessary and chi-square. We found a significant reduction in placental IL-10 mRNA and protein expression in women with preeclampsia compared to controls. Women with the AA IL-10 promoter genotype expressed less placental IL-10 mRNA compared to women with AG or GG genotype. There was no difference in serum IL-10 concentrations between different genotypes. Preeclampsia is associated with a deficiency of placental IL-10. Placental AA genotype in the promoter region results in significantly less placental IL-10.

Adult↗
PubMed2005

Effects of trans-resveratrol from Polygonum cuspidatum on bone loss using the ovariectomized rat model.

trans-Resveratrol (resveratrol) has been shown in several studies to significantly modulate biomarkers of bone metabolism. But, there is no direct evidence supporting its inhibitory effect towards bone loss. In the present study, effects of resveratrol on bone mineral density (BMD) and bone calcium content (BCC) were examined in the ovariectomized (OVX) rat model. Female Wistar rats were divided into four groups: SHAM group (sham-operated), OVX group (OVX control), OVX + ALD group (OVX and treated with 1.0 mg/kg of body weight of alendronate sodium), and OVX + RES group (OVX and treated with 0.7 mg/kg of body weight of resveratrol). Tested materials were given by gavage for 12 weeks after ovariectomy. Results showed that rats in the OVX, OVX + ALD, and OVX + RES groups had significantly higher body weights and feed efficiency than those in the SHAM group (P < .01). The OVX group had significantly lower femoral epiphysis BMD than the SHAM group, and epiphysis BMD in the OVX + ALD and OVX + RES groups was significantly greater than that in the OVX group (P < .05). However, the femoral midpoint BMD was not significantly different among the four groups. Additionally, animals in the OVX group had significantly lower BCC compared with the SHAM group, while the BCC of the OVX + ALD and OVX + RES groups was significantly higher than that of the OVX group (P < .05). These results indicated that resveratrol could increase epiphysis BMD and inhibit the decrease of femur BCC in OVX rats, suggesting that it could play a role in protecting against bone loss induced by estrogen deficiency.

Absorptiometry, Photon↗
PubMed2005

Denaturing high performance liquid chromatography: high throughput mutation screening in familial hypertrophic cardiomyopathy and SNP genotyping in motor neurone disease.

AIMS: To evaluate the usefulness of denaturing high performance liquid chromatography (DHPLC) as a high throughput tool in: (1) DNA mutation detection in familial hypertrophic cardiomyopathy (FHC), and (2) single nucleotide polymorphism (SNP) discovery and validation in sporadic motor neurone disease (MND). METHODS: The coding sequence and intron-exon boundaries of the cardiac beta myosin heavy chain gene (MYH7) were screened by DHPLC for mutation identification in 150 unrelated patients diagnosed with FHC. One hundred and forty patients with sporadic MND were genotyped for the A67T SNP in the poliovirus receptor gene. All DHPLC positive signals were confirmed by conventional methods. RESULTS: Mutation screening of MYH7 covered 10 kb with a total of 5700 amplicons, and more than 6750 DHPLC injections were completed within 35 days. The causative mutation was identified in 14% of FHC cases, including seven novel missense mutations (L227V, E328G, K351E, V411I, M435T, E894G, and E927K). Genotyping of the A67T SNP was performed at two different temperatures both in MND cases and 280 controls. This coding SNP was found more frequently in MND cases (13.6%) than in controls (6.8%). Furthermore, 19 and two SNPs were identified in MYH7 and the poliovirus receptor gene, respectively, during DHPLC screening. CONCLUSIONS: DHPLC is a high throughput, sensitive, specific, and robust platform for the detection of DNA variants, such as disease causing mutations or SNPs. It enables rapid and accurate screening of large genomic regions.

Algorithms↗
PubMed2005

Effect of progesterone on calcium activated potassium currents and intracellular calcium in guinea pig colon myocytes.

AIMS: To study the effects of progesterone on contractile activity of smooth muscle strips and on ion currents and intracellular Ca2+ ([Ca2+]i) intensity in single colonic myocytes in guinea pig proximal colons. METHODS: Strips and single cells were dissected from female guinea pig proximal colon. Contraction of strips through an isotonic transducer was assessed and the responsible currents to progesterone were recorded with EPC-9 amplifier in nystatin perforated whole-cell configuration. Detection of [Ca2+]i fluorescence loading fura-2 acetoxymethylester (fura-2/AM) was measured with confocal microscope. RESULTS: Progesterone significantly inhibited contraction of guinea pig colon strips in a dose-dependent pattern. Inhibitory concentration 50 (IC50) of progesterone in longitudinal strips and circular strips was, respectively, 9.7 microM and 1.0 nM. Iberiotoxin (IbTX) partially blocked inhibition of progesterone in both oriented smooth muscle strips. Ca2+ activated K+ (K(Ca)) channel currents recorded by depolarizing pulse protocol were enhanced by progesterone to 138% +/- 13% (n = 9, p < 0.01), and to 143% +/- 12% (n = 8, p < 0.01) when perfused with 10 mcM onapristone. Progesterone reduced L-Ca2+ currents to 67% +/- 6% (n = 7, p < 0.01) and had no effect with 5 microM nicardipine in bath solution. [Ca2+]i fluorescence was reduced by progesterone to 75% +/- 12% (n = 8, p < 0.01). CONCLUSION: Progesterone decreases the contraction of colonic smooth muscles by enhancing K(Ca) currents and reducing Ca2+ influx.

Animals↗
PubMed2004

In vitro and in vivo enzyme studies of polyhemoglobin-tyrosinase.

Melanoma is now the fifth most common type of cancer in North America. At present, there is no optimal treatment for this cancer. However, the lowering of the tyrosine level can inhibit the growth of melanoma. Unfortunately, this diet restriction cannot be humanly tolerated and causes vomiting, nausea, and severe body weight loss. To prevent these problems, we are studying a new approach involving the preparation intermolecularly crosslinked hemoglobin and tyrosinase for intravenous injection. In this article we describe the method of preparation and the structural and functional properties of polyhemoglobin-tyrosinase. We evaluate the effects of varying glutaraldehyde ratio, crosslinking time, and enzyme concentration on the enzyme activity of polyhemoglobin-tyrosinase. We also optimize the molecular weight distribution of polyhemoglobin-tyrosinase. The stability of polyhemoglobin-tyrosinase at 37 degrees C is much more stable when compared to noncrosslinked tyrosinase solution. Animal studies show that a higher degree of polymerization correlates with a longer circulation time of polyhemoglobin-tyrosinase, and the optimal crosslinking time is 24 hours. One intravenous injection of polyhemoglobin-tyrosinase lowers the plasma tyrosine to about 10% of its original level within one hour.

Aldehydes↗
PubMed2004

Structural study of the type II 3-dehydroquinate dehydratase from Actinobacillus pleuropneumoniae.

The structure of the type II dehydroquinate dehydratase (DHQase) from Actinobacillus pleuropneumoniae, the third enzyme of the shikimate pathway, has been determined. Crystals diffracting to 1.7 A were obtained in space and on earth using the counter-diffusion technique. The structure was solved using molecular replacement and refined to high resolution. The overall structure of the dodecameric enzyme is described and compared with structures of DHQases from other bacteria. DHQases contain a flexible loop that presumably closes over the active site upon substrate binding. The enzyme can exist in an open or closed conformation. The present structure displays the open conformation, with a sulfate anion bound in the active site. The availability of this structure opens a route to structure-based antibiotics targetting this pathogenic bacterium.

Actinobacillus pleuropneumoniae↗
PubMed2004

Chemical and biological characterization of a polysaccharide biological response modifier from Aloe vera L. var. chinensis (Haw.) Berg.

Three purified polysaccharide fractions designated as PAC-I, PAC-II, and PAC-III were prepared from Aloe vera L. var. chinensis (Haw.) Berg. by membrane fractionation and gel filtration HPLC. The polysaccharide fractions had molecular weights of 10,000 kDa, 1300 kDa, and 470 kDa, respectively. The major sugar residue in the polysaccharide fractions is mannose, which was found to be 91.5% in PAC-I, 87.9% in PAC-II, and 53.7% in PAC-III. The protein contents in the polysaccharide fractions was undetectable. NMR study of PAC-I and PAC-II demonstrated the polysaccharides shared the same structure. The main skeletons of PAC-I and PAC-II are beta-(1-->4)-D linked mannose with acetylation at C-6 of manopyranosyl. The polysaccharide fractions stimulated peritoneal macrophages, splenic T and B cell proliferation, and activated these cells to secrete TNF-alpha, IL-1 beta, INF-gamma, IL-2, and IL-6. The polysaccharides were nontoxic and exhibited potent indirect antitumor response in murine model. PAC-I, which had the highest mannose content and molecular weight, was found to be the most potent biological response modifier of the three fractions. Our results suggested that the potency of aloe polysaccharide fraction increases as mannose content and molecular weight of the polysaccharide fraction increase.

Aloe↗
PubMed2004

Torsional vibrational modes of tryptophan studied by terahertz time-domain spectroscopy.

The low-frequency torsional modes, index of refraction, and absorption of a tryptophan film and pressed powders from 0.2 to 2.0 THz (6.6-66 cm(-1)) were measured by terahertz time-domain spectroscopy at room temperature. It was found that there were two dominated torsional vibrational modes at around 1.435 and 1.842 THz. The associated relaxation lifetimes ( approximately 1 ps) for these modes of the tryptophan molecule were measured. Using a density-functional calculation, the origins of the observed torsional vibrations were assigned to the chain and ring of the tryptophan molecule.

Coated Materials, Biocompatible↗
PubMed2004

A sterically stabilized immunolipoplex for systemic administration of a therapeutic gene.

A sterically stabilized immunolipoplex (TsPLP), containing an antitransferrin receptor single-chain antibody fragment (TfRscFv)-PEG molecule, has been developed to specifically and efficiently deliver a therapeutic gene to tumor cells. A postcoating preparation strategy was employed in which a DNA/lipid complex (lipoplex) was formed first and then sequentially conjugated with PEG and TfRscFv. The complex prepared by this method was shown to be superior in ability to deliver genes to tumor cells than when prepared by a common precoating strategy, in which DNA is mixed with TfRscFv-PEG conjugated liposome. Using prostate cancer cell line DU145, a comparison was made between the in vitro and in vivo gene delivery efficiencies of four complexes, Lipoplex (LP), PEG-Lipoplex (PLP), TfRscFv-PEG-Lipoplex (TsPLP) and our standard TfRscFv-Lipoplex (TsLP). In vitro, the order of transfection efficiency was TsLP>LP approximately TsPLP>PLP. However, in vivo the order of transfection efficiency, after systemic administration via the tail vein, was TsPLP>TsLP>LP or PLP with TsPLP-mediated exogenous gene expression in tumor being two-fold higher than when mediated by TsLP. This suggests that the in vitro transfection efficiency of TsPLP was not indicative of its in vivo efficiency. In addition, it was found that the level of exogenous gene expression in the tumor mediated by TsPLP was higher than that mediated by TsLP and did not decrease over the time. More importantly, high exogenous gene expression in tumor, but low expression in liver, was observed after an i.v. delivery of TsPLP carrying either the GFP reporter gene or the p53 gene, indicating that tumor preferential targeting was maintained by this complex in the presence of PEG. These findings show that incorporation of PEG into our targeted lipoplex results in a more efficient delivery of the complex to the tumor cells, possibly by inhibiting the first pass clearance observed with non-PEG containing liposomes. Therefore, these data demonstrate that TsPLP is a improvement over our previously established tumor targeted gene delivery complex for systemic gene therapy of cancer.

Animals↗
PubMed2004

Promoting of melanocyte adhesion and migration by Malytea Scurfpea fruit in vitro.

The aim of this study was to investigate the effect of Malytea Scurfpea Fruit (MSF) on melanocyte adhesion and migration. Human epidermal melanocytes were treated with MSF and examined for adhesion to bovine serum fibronectin-coated culture dishes. Control and treated cells were also examined for migration into micropore filters coated with the same protein. Compared with control, MSF-treated melanocytes adhered to the dishes more easily and migrated into the filters in a dose-dependent manner. MSF at a dose of more than 200 micro g/ml did not increase melanocyte adhesion and migration accordingly. With the exception of MSF 10 micro g/ml, at every concentration of MSF there were significant differences between treated and untreated melanocytes (p < 0.01) when the adhesion test was studied. Regarding migration, even at a concentration of MSF 10 micro g/ml, obviously increased cell numbers were found compared with MSF untreated melanocytes (p < 0.01). MSF promoted melanocyte adhesion and migration; this could explain, in part, the capacity of MSF to regulate melanocyte function in vitiligo.

Animals↗
PubMed2002

Adaptation to chronic PCP results in hyperfunctional NMDA and hypofunctional GABA(A) synaptic receptors.

Schizophrenia is currently thought to be associated with a hypoglutamatergic state that is mimicked by acute phencyclidine (PCP), an antagonist of the N-methyl-D-aspartate (NMDA) receptor subtype. In this study we tested the hypothesis that chronic treatment of rats with this antagonist may be a more appropriate animal model than acute exposure since it could result in adaptive synaptic responses that would model certain aspects of the schizophrenic state in humans. In vitro intracellular electrophysiological recordings employing brain slices from rats treated chronically in vivo with PCP demonstrated that chronic PCP caused a substantial increase in synaptic responses mediated by NMDA receptors without any significant changes in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate-mediated synaptic responses. At the same time, GABA(A) receptor-mediated inhibitory responses were depressed significantly. Pharmacological and paired-pulse facilitation experiments demonstrated that these adaptive responses following chronic PCP administration were not the result of altered glutamate or GABA release. Immunoblot analyses suggest that the hyperfunctional NMDA response is at least partially mediated by an increased synthesis of NR1 and NR2A subunits as well as a change in the subunit stoichiometry of the NMDA receptor. This change in receptor composition was also supported by pharmacological experiments with a subunit selective NMDA antagonist. Our data support a reconsideration of NMDA and GABA(A) receptor responsiveness following a chronic, not acute, exposure to PCP and the adaptations that persist after such a regimen.

Animals↗
PubMed2002

Effects of sources of protein and enzyme supplementation on protein digestibility and chyme characteristics in broilers.

1. The purpose of this study was to evaluate the effects of protein source and enzyme supplementation on protein digestibility and chyme characteristics in broilers. 2. One hundred and twenty growing (13 d old) and 60 finishing (34 d old) Arbor Acre strain commercial male broilers were selected and placed into individual metabolic cages. 3. The experiment was a 5 x 2 factorial arrangement with 5 different sources of protein: casein, fish meal, soybean meal (SBM), soy protein concentrate (SPC), maize gluten meal (MGM) and two levels of protease (bromelain), 0 and 65 CDU/kg diets. 4. The diets were iso-nitrogenous and semi-purified, with Cr2O3 as an indicator for determination of ileal digestibility and chyme characteristics. 5. Apparent ileal protein digestibility (AIPD) in both growing and finishing chickens was highest on the casein diet, followed by fish meal, SBM, SPC and MGM. 6. Enzyme inclusion did not improve protein digestibility, but significantly decreased the digesta pH value in the gizzard and increased pH in the ileum in the 3-week-old broilers. 7. The digesta pH values in the gizzard and duodenum were significantly lower in the SBM and fish meal groups compared with the other protein groups. The molecular weight distribution pattern of the soluble protein in the chyme of the gastrointestinal (GI) segments showed a similar trend, regardless of the enzyme inclusion or the stage of growth. 8. The molecular weight profile of soluble protein changed dynamically in the casein fed broilers from the gizzard to ileum and the low molecular weight proteins, < 7 kDa, reached maximum levels at the ileum. The molecular weight profile of the soluble protein in the SBM and SPC changed between the jejunum and the ileum and in the intermediate molecular soluble protein weight (7 to 10 kDa) was significantly decreased. This indicated that the hydrolysis process began from the middle to the posterior end of the small intestine. 9. Similar profiles were also shown with fish meal protein. The pattern of distribution, however, did not show any prominent change in the GI segments of the MGM group. 10. The pepsin, trypsin and chymotrypsin protease activity in the gizzard and duodenum were highest in the casein group and lowest in the MGM group as compared with the other protein groups. 11. The rate change in the patterns of molecular weight distribution in soluble protein and the digestive enzyme activity provide indications of the partial digestibility of different protein sources. The exogenous enzyme, bromelain, did not show any beneficial effect on protein digestion.

Animals↗
PubMed2001

Mechanisms for intragenic complementation at the human argininosuccinate lyase locus.

Argininosuccinate lyase (ASL) is a homotetrameric enzyme that catalyzes the reversible cleavage of argininosuccinate to arginine and fumarate. Deficiencies in the enzyme result in the autosomal, recessive disorder argininosuccinic aciduria. Considerable clinical and genetic heterogeneity is associated with this disorder, which is thought to be a consequence of the extensive intragenic complementation identified in patient strains. Our ability to predict genotype-phenotype relationships is hampered by the current lack of understanding of the mechanisms by which complementation can occur. The 3-dimensional structure of wild-type ASL has enabled us to propose that the complementation between two ASL active site mutant subunits, Q286R and D87G, occurs through a regeneration of functional active sites in the heteromutant protein. We have reconstructed this complementation event, both in vivo and in vitro, using recombinant proteins and have confirmed this hypothesis. The complementation events between Q286R and two nonactive site mutants, M360T and A398D, have also been characterized. The M360T and A398D substitutions have adverse effects on the thermodynamic stability of the protein. Complementation between either the M360T or the A398D mutant and the stable Q286R mutant occurs through the formation of a more stable heteromeric protein with partial recovery of catalytic activity. The detection and characterization of a novel complementation event between the A398D and D87G mutants has shown how complementation in patients with argininosuccinic aciduria may correlate with the clinical phenotype.

Alanine↗