Biomedical subjects

B Yao

Publications and source records attributed to B Yao.

At least 19 recordsLinked to original sources

PubMed2006

Introduction of a disulfide bridge enhances the thermostability of a Streptomyces olivaceoviridis xylanase mutant.

Substitution of the N-terminus of Streptomyces olivaceoviridis xylanase XYNB to generate mutant TB has been previously shown to increase the thermostability of the enzyme. To further improve the stability of this mutant, we introduced a disulfide bridge (C109-C153) into the TB mutant, generating TS. To assess the effect of the disulfide bridge in the wild-type enzyme, the S109C-N153C mutation was also introduced into XYNB, resulting in XS. The mutants were expressed in Pichia pastoris, the recombinant enzymes were purified, and the effect of temperature and pH on enzymatic activity was characterized. Introduction of the disulfide bridge (C109-C153) into XYNB (XS variant) and TB (TS variant) increased the thermostability up to 2.8-fold and 12.4-fold, respectively, relative to XYNB, after incubation at 70 degrees C, pH 6.0, for 20 min. In addition, a synergistic effect of the disulfide bridge and the N-terminus replacement was observed, which extended the half-life of XYNB from 3 to 150 min. Moreover, XS and TS displayed better resistance to acidic conditions compared with the respective enzymes that did not contain a disulfide bridge.

Disulfides↗

PubMed2006

A genetic algorithm design for microcalcification detection and classification in digital mammograms.

In this paper, we propose a genetic algorithm design to automatically classify and detect micocalcification clusters in digital mammograms. The proposed GA technique is characterised by transforming input images into a feature domain, where each pixel is represented by its mean and standard deviation inside a surrounding window of size 9 x 9 pixel. In the feature domain, chromosomes are constructed to populate the initial generation and further features are extracted to enable the proposed GA to search for optimised classification and detection of microcalcification clusters via regions of 128 x 128 pixels. Extensive experiments show that the proposed GA design is able to achieve high performances in microcalcification classification and detection, which are measured by ROC curves, sensitivity against specificity, areas under ROC curves and benchmarked by existing representative techniques.

Algorithms↗

PubMed2006

Combination of MIG (CXCL9) chemokine gene therapy with low-dose cisplatin improves therapeutic efficacy against murine carcinoma.

MIG (monokine induced by interferon-gamma) is a CXC chemokine ligand (CXCL9) that can potently inhibit angiogenesis, and displays thymus-dependent antitumor effects. The effectiveness of a treatment combining gene therapy with plasmid-borne MIG (pORF-MIG) and low-dose cisplatin chemotherapy was determined using colon carcinoma (CT26) and Lewis lung carcinoma (LL/2c) murine models. The program was carried out via intramuscular delivery of pORF-MIG at 100 mug/mouse twice a week for 4 weeks, and/or intraperitoneal delivery of cisplatin at 0.6 mg/kg/mouse every 3 days for 48 days. Tumor volume and survival time were evaluated after treatment. CD31 immunohistochemical staining in tumor tissues and alginate capsule models in vivo was used to evaluate angiogenesis. Induction of apoptosis and cytotoxic T-lymphocyte (CTL) activity were also assessed. The combination of pORF-MIG and low-dose cisplatin produced significant antitumor activity, with complete tumor regression in 4/10 of CT26 colon carcinomas and 3/10 of LL/2c lung carcinomas, low vascularity, in alginate capsules, apparently degraded tumor microvessel density, and increased induction of apoptotic and CTL activities compared with either treatment alone. This study suggests that the combination of pORF-MIG plus cisplatin augments the inhibition of angiogenesis and the induction of apoptosis or CTL activity, all of which enhance antitumor activity. These findings may prove useful in further explorations of the application of combinatorial approaches to the treatment of solid tumors.

Animals↗

PubMed2006

Differential effects of Th1, monocyte/macrophage and Th2 cytokine mixtures on early gene expression for immune-related molecules by central nervous system mixed glial cell cultures.

Cytokines secreted within the central nervous system (CNS) are important in the development of multiple sclerosis (MS) lesions. The balance between Th1, monocyte/macrophage (M/M) and Th2 cytokines in the CNS may be pivotal in determining the outcome of lesion development. We examined the effects of mixtures of cytokines on gene expression by CNS glial cells, as mixtures of cytokines are present in MS lesions, which in turn contain mixtures of glial cells. In this initial analysis by gene array, we examined changes at 6 hours to identify early changes in gene expression that represent primary responses to the cytokines. Rat glial cells were incubated with mixtures of Th1, M/M and Th2 cytokines for 6 hours and examined for changes in early gene expression employing microarray gene chip technology. A minimum of 814 genes were differentially regulated by one or more of the cytokine mixtures in comparison to controls, including changes in expression in a large number of genes for immune system-related proteins. Expression of the proteins for these genes likely influences development and inhibition of MS lesions as well as protective and regenerative processes. Analysing gene expression for the effects of various combinations of exogenous cytokines on glial cells in the absence of the confounding effects of inflammatory cells themselves should increase our understanding of cytokine-induced pathways in the CNS.

Animals↗

PubMed2005

Linear correlation between fractal dimension of EEG signal and handgrip force.

Fractal dimension (FD) has been proved useful in quantifying the complexity of dynamical signals in biology and medicine. In this study, we measured FDs of human electroencephalographic (EEG) signals at different levels of handgrip forces. EEG signals were recorded from five major motor-related cortical areas in eight normal healthy subjects. FDs were calculated using three different methods. The three physiological periods of handgrip (command preparation, movement and holding periods) were analyzed and compared. The results showed that FDs of the EEG signals during the movement and holding periods increased linearly with handgrip force, whereas FD during the preparation period had no correlation with force. The results also demonstrated that one method (Katz's) gave greater changes in FD, and thus, had more power in capturing the dynamic changes in the signal. The linear increase of FD, together with results from other EEG and neuroimaging studies, suggest that under normal conditions the brain recruits motor neurons at a linear progress when increasing the force.

Adult↗

PubMed2005

LARALink: a web application for cytogenetic linkage analysis.

Genomic and expression data have increased dramatically over the last several years. This is primarily due to the completion of the human genome project as well as an upsurge in the use of various high-throughput technologies. Recent attempts to correlate genomic and expression data have stimulated the scientific community to determine how this data can be used within a clinical setting (P Khatri et al., Genomics 2002: 79: 266; LJ van't Veer et al., Nature 2002: 415: 530). LARALink (Loci Analysis for Rearrangements Link) is a database-driven web application that utilizes several public datasets to analyze clinical cytogenetic data to identify candidate genes. LARALink allows UniGene clusters or single-nucleotide polymorphisms (SNPs) to be queried for multiple patients by cytoband, chromosome marker, or base pair. The results can be further refined with the use of an anatomical site, developmental stage, pathology, or cell-type expression filter. Once a set of UniGene clusters (expressed genes) has been identified either for a single patient or for a shared region among multiple patients, the expression-distribution profile, expressed sequence tags (ESTs), or online mendelian inheritance in man (OMIM) entries are displayed. The utility of this tool is shown by its application to both research and clinical medicine. LARALink is a public resource available at: http://www.laralink.bioinformatics.wayne.edu:8080/unigene.

Alzheimer Disease↗

PubMed2003

[Treatment of vesicovaginal fistulas using the musculofascial flap of the levator ani muscle: 26 case reports].

OBJECTIVE: The authors reported the preliminary results of levator ani muscle flap in the treatment of vesicovaginal fistula. MATERIALS AND METHODS: Twenty-six patients whose age varied between 13 and 18 years (mean: 30 years) are selected. All the patients are treated by the vaginal approach using the part of superficial rectal fibers of the levator ani muscle. RESULTS: Among the 26 patients, 14 are free after the first cure of vesicovaginal fistula (54%), and 4 patients (15%), after the treatment of some complications. CONCLUSION: The musculofascial levator ani flap with its vascular pedicle and its mobilisation can successfully close the vesicovaginal fistula. The preliminary results obtained (88%) tie up with that previously described in the literature.

Adolescent↗

PubMed2003

[Urogenital tuberculosis: diagnostic difficulties in 5 cases].

OBJECTIVES: The aim of this study is: to emphasize the difficulties of diagnosing genito-urinary tuberculosis because of its non specific symptoms; to incite the physician to seek it more frequently. MATERIAL AND METHOD: Five cases of genito-urinary tuberculosis have been diagnosed within a 10-years period and included in a retrospective study. RESULTS: We found one location in the kidney and one location in the bladder with 2 women diagnosed by repeated urianalysis and 3 cases of location in epididymis diagnosed after surgery. CONCLUSION: Symptoms of genito-urinary tuberculosis are misleading, pathologic findings are taking a more and more important place in the diagnosis, which the new techniques of serologic tests will surely improve.

Adult↗

PubMed2003

[Heavy hematuria with shock caused by bladder pheochromocytoma].

The authors report a case of pheochromocytoma of the bladder revealed by an important gross hematuria with shock. The diagnosis has been established by the pathologist after a partial cystectomy. This location mimmicks a bladder tumor. The diagnosis is difficult; conservative surgery is the rule.

Adult↗

PubMed2001

Immunohistochemical and in situ hybridization studies of gonadotropin releasing hormone (GnRH) and its receptor in rat digestive tract.

GnRH(LH-RH) is first discovered in the hypothalamus and found to have a role in regulation of reproduction. With the study on it deepening, GnRH was demonnstrated that it also exists in a number of organs beyond the hypothalamus and acts on extrapituitary organs. To study whether digestive tract synthesizes GnRH and its receptor and, if it does, by what cells. In the experiment, the locallizations of GnRH and its receptors in rat digestive tract were studied using immunohistochemistry and in situ hybridization. The parietal cells of gastric gland, the villous and glandular epithelium in small and large intestine and parasympathetic ganglion cells of myenteric plexus showed GnRH immunoreactivity; GnRH mRNA hybridization signal was detected. The epithelium of gastric pit and the cells above in digestive tract showed GnRH receptor immunoreactivity; GnRH receptor mRNA hybridization signal was detected. The immunoreactive and signal materials distributed in cytoplasm of all positive cells, with nuclei being immunonegative and with no hybridization signal. These results suggested that the digestive tract can produce GnRH and express GnRH receptor; GnRH may also be a gastrointestinal hormone.

Animals↗

PubMed2001

Presence of gonadotropin-releasing hormone (GnRH) and its mRNA in rat pancreas.

Gonadotropin-releasing hormone (GnRH) has been reported to exist in many non-hypothalamic tissues, such as the placenta, gonads, and mammary glands, while there still have been no reports concerning the existence and expression of GnRH in the mammalian digestive system. Immunocytochemistry and in situ hybridization results show that GnRH molecule and GnRH mRNA are both exclusively distributed in exocrine pancreas, and RT-PCR result further proves that GnRH transcription units do exist in the pancreas, which possess the same sequence as the hypothalamus GnRH mRNA. Quantitative analysis indicates that mRNA levels in rat pancreas remain at a low level (less than 10% of that in hypothalamus) without sexual or developmental difference. This is the first report suggesting the existence and gene expression of GnRH in rat pancreas.

Animals↗

PubMed2001

Neuron tolerance during hydrocephalus.

Whether or not neuron death plays a major role in pathophysiology during hydrocephalus is not well known. The goals of this study were to determine if neural degeneration occurred during hydrocephalus, and to determine if neuron tolerance developed during this pathophysiologic procedure.Neural damage as visualized by a sensitive staining technique, silver impregnation, was observed in three experimental groups: (1) adult hydrocephalic rats induced by kaolin injection into the cisterna magna, (2) adult rats with chronic hydrocephalus for 10 weeks subjected to acute forebrain ischemia induced by four-vessel occlusion, and (3) adult rats without hydrocephalus subjected to acute forebrain ischemia. The magnitude of hydrocephalus was also evaluated during this time. In mild or moderate hydrocephalus, little cell death was found. In severe hydrocephalus, axon and neuropil degeneration was extensively distributed, but cell death was still rarely observed. Although some neuron degeneration was found after acute forebrain ischemia in hydrocephalic rats, the extensive cell death in cortical layers III and V, and in hippocampal areas CA1 and CA4 that is commonly observed in the ischemic brain without hydrocephalus, was not seen. This study suggests that neuron death was not a major pathological change in the brain during hydrocephalus, with cerebral ventricles being enlarged during the development of hydrocephalus. Less neuron death in hydrocephalic rats after acute forebrain ischemia suggests that neuronal tolerance to ischemia occurs during hydrocephalus.

Animals↗

PubMed2001

Accuracy and reproducibility of coronary flow rate assessment by real-time contrast echocardiography: in vitro and in vivo studies.

Real-time myocardial contrast echo (MCE) provides the potential to assess myocardial blood flow from time-intensity refilling curves after high-energy bubble destruction. This study validated the accuracy of this approach and the effect of specific examination variables and instrument settings on results. The effects of examination depth and angle as well as dynamic range, pulse repetition frequency, and line density were assessed with the use of in vitro incremental flow rates produced in an in vitro tissue phantom. In vivo recordings of real-time imaging with an infusion of a contrast agent (Optison) were obtained in 7 open-chest dogs with graded left anterior descending artery stenosis at baseline and during adenosine hyperemia, and were compared with flow probe measurements. After bubble destruction, time-intensity data were fitted to an exponential function, and the rate of intensity increase (b) and peak plateau intensity (A) were derived from refilling curves. In vivo real-time values for b, but not A, correlated closely with flow probe measures (r = 0.93). A similar correlation for b was observed in vitro (r = 0.98). The correlation between flow rate and b was influenced by several examination variables, including depth, angle, and instrument settings. Real-time MCE provides accurate quantification of coronary flow by assessing the rate of microbubble refilling. However, this parameter may be affected by several examination and instrument variables. Therefore, real-time MCE refilling measures are best applied by comparing baseline values with those of stress studies.

Animals↗

PubMed2001

Electrophysiologic and antiarrhythmic effects of the new class III antiarrhythmic drug KCB-328 in experimental canine atrial flutter.

BACKGROUND: The electrophysiologic and antiarrhythmic effects of a new class III antiarrhythmic drug (KCB-328), a delayed rectifier potassium current (IKr) blocker with minimal reverse use-dependent effect on atrial repolarization, were evaluated in the canine night atrial crush-injury model of atrial flutter (AFL). METHODS: Ten anesthetized, open-chest dogs, were studied after right atrial crush-injury. Atrial effective refractory period (ERP), conduction velocity (CV), wavelength, and dispersion of refractoriness were determined during programmed stimulation (S1S2 at S1S1 = 200, 300, 400, and 500 msec) at four sites via a mapping plaque sutured on the right atrial free wall. Right and left ventricular ERP were similarly measured at single sites. Electrophysiological parameters were determined at baseline and following sequential cumulative doses of KCB-328 (10, 30, 100, and 300 microg/kg). RESULTS: Sustained AFL was inducible in 7/10 dogs by rapid pacing following baseline electrophysiologic measurements. KCB-328 significantly prolonged sinus cycle length, but had no effect on PR interval, and prolonged QTc only at the highest dose level. KCB-328 significantly prolonged atrial ERP and wavelength and ventricular ERP, and significantly reduced dispersion of atrial refractoriness. KCB-328 significantly prolonged AFL cycle length, and increasing doses progressively terminated sustained AFL and prevented its reinduction by pacing. No adverse hemodynamic or ventricular proarrhythmic effects were observed. CONCLUSIONS: The electrophysiologic profile of KCB-328 in this canine model of AFL, particularly its lack of reverse use-dependent effect on atrial refractoriness, suggests that it may have significant antiarrhythmic potential in treatment of atrial arrhythmias.

Animals↗

PubMed2001

Axonal damage associated with enlargement of ventricles during hydrocephalus: a silver impregnation study.

Motor and cognitive deficits are commonly associated with hydrocephalus. Although the mechanisms responsible for these impairments have not been confirmed, neuronal cell death and axon degeneration may play an important role, and have long lasting consequences on neuronal connectivity. The goal of this study was to determine if neural degeneration occurred during hydrocephalus in structures anatomically related to cognitive motor functioning, namely, the sensorimotor cortex, neostriatum, hippocampus and corpus callosum. Neural damage, as visualized by silver staining, was examined in adult rats 2-10 weeks after obstructive hydrocephalus was induced by kaolin injection into the cisterna magna. In mild or moderate hydrocephalus, mostly occurring 2-6 weeks after kaolin injections, silver-labeled axons were scattered in the white matter of the sensorimotor cortex, corpus callosum, neostriatum, and hippocampus. In severe hydrocephalus, 10 weeks after kaolin injections, axon degeneration was more extensive in these areas, as well as in layers IV through VI of the sensorimotor cortex. Axons in the subiculum and the fimbria were heavily labeled, suggesting damage to hippocampal afferent and efferent fibers. In contrast, neuron cell death was rarely observed at any stage of hydrocephalus. The major pathological change of brain regions involved in motor and learning functions during hydrocephalus is axon degeneration, and this degeneration is correlated with an enlargement of the cerebral ventricles.

Animals↗

PubMed2001

[Cloning of neutral phytase gene nphy from Bacillus subtilis and its expression in Escherichia coli].

The gene encoding the neutral phytase nphy was cloned from Bacillus subtilis by polymerase chain reaction (PCR). Nucleotide sequence analysis of nphy revealed the presence of an open reading frame of 1152 bp coding for 383 aa. The start codon was followed by a sequence coding for a putative signal peptide of 26 aa in length. The nphy without original signal peptide encoding sequence was cloned into E. coli expression plasmid pTYB40. The result of SDS-PAGE of the phytase expressed in E. coli showed that the nphy had been overexpressed. The expressed phytase was over 40% of the total soluble protein of E. coli, and has normal bioactivity.

6-Phytase↗

PubMed2001

Correlation between decrease of 11beta-hydroxysteroid dehydrogenase activity and hypokalemia induced by furosemide in rats.

AIM: To investigate the correlation between decrease of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) activity and hypokalemia induced by furosemide (Fur) in rats. METHODS: SD rats were given single dose or successive doses of Fur by gavage. The activity of 11beta-HSD was evaluated by measuring the ratio of 11-dehydrocorticosterone (A) and corticosterone (B) in urine and conversion rate of B to A in renal cortex microsome preparation was determined with HPLC. RESULTS: After giving single dose of Fur (40, 100, and 250 mg/kg) or multiple doses of Fur (10, 20, and 100 mg/kg, bid x 20 d), the ratio of A/B was reduced by 29.0 %, 58.6 %, and 60.9 % at 0 - 2 h; 14.4 %, 36.0 %, and 44.9 %, respectively; the conversion rate of B to A was decreased by 29 %, 33 %, and 37 %; 6 %, 17 %, and 23 %, respectively. The serum potassium was significantly reduced by multiple doses of Fur (20 and 100 mg/kg, bid x 20 d) (P < 0.01). The reduction in serum potassium was positively correlated with the lowering of A/B ratio and the conversion of B to A (P < 0.01). CONCLUSION: The inhibition of renal 11beta-HSD activity may be another new biochemical mechanism for hypokalemia induced by Fur.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2001

[GATA-2 gene expression in leukemia patients and its significance].

OBJECTIVE: To investigate GATA-2 gene expression in leukemia patients and its clinical significance. METHODS: GATA-2 gene transcripts were detected by reverse transcriptase polymerase chain reaction (RT-PCR), and bcr/abl or PML/RAR alpha transcripts were detected in patients with chronic myeloid leukemia (CML) and acute promyelocytic leukemia (APL), respectively. RESULTS: The GATA-2 transcripts were revealed in 93% of acute myeloid leukemia (AML), in 70% of acute lymphoblastic leukemia (ALL), and 83% of CML patients, but not in normal bone marrow and peripheral blood cells. GATA-2 expression in remission patients was similar to newly diagnosed or relapsed patients. In post-transplantation patients, GATA-2 expression was significantly decreased. In these cases GATA-2 transcripts could be detected with bcr/abl fusion gene disappeared in 2 of 12 CML, whereas neither GATA-2 nor PML/RARalpha transcripts could be detected in APL. CONCLUSION: GATA-2 transcripts was highly expressed in leukemia patients and had no change in remission but significantly decreased in post-transplantation patients. Detection of GATA-2 expression would give information about the residual leukemia stem cells.

Bone Marrow Cells↗