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Biomedical subjects

Y Zhou

Publications and source records attributed to Y Zhou.

At least 91 records · Page 5Linked to original sources
PubMed2003

Single nucleotide polymorphism discrimination assisted by improved base stacking hybridization using oligonucleotide microarrays.

Efficiencies of mismatch discrimination using size-varied capture probes were examined at various hybridization temperatures. The probes were 17, 15, 13, 11, 9, and 7 nucleotides long and contained single-base mismatches at their 3' ends. The optimal signal intensity and efficiency of base stacking hybridization on mismatch discrimination were observed for capture probes with a melting temperature (Tm) value of 36 degrees C, in the detection of DNA sequence variations at 40 degrees C. We employed asymmetric PCR to prepare single-stranded target DNA labeled with a fluorescent dye, and the PCR product was hybridized on the DNA microarray with no further purification. Our efforts have enhanced the sensitivity and simplified the procedures of base stacking hybridization on mismatch discrimination. As a model experiment, this improved technology was used to identify plasmid templates of human leukocyte antigen (HLA)-A alleles 2601, 2902, and 0206 on oligonucleotide microarrays. It is now possible to apply this simple, rapid, sensitive, and reliable base stacking hybridization technology to detect DNA sequence variations on microarrays in clinical diagnosis and other applications.

Alleles↗
PubMed2002

Theoretical analyses of dispersed-drug release from planar matrices with a boundary layer in a finite medium.

Analytical solutions for the kinetics of dispersed-drug release from planar matrices with a boundary layer in a well-stirred finite external medium were derived in a general and a simplified form. The general solutions are applicable for a broad range of the ratio of initial drug loading to drug solubility (e.g. C(0)/C(s)> or =3) till all dispersed drug is dissolved, while the simplified solutions describe the entire release process for higher C(0)/C(s) ratios (e.g. C(0)/C(s)> or =10). As the C(0)/C(s) ratio increased, the general solutions approached the exact solution from the lower bound, and the simplified solution from the upper bound. This property could be useful to find the lower and upper bound of an exact solution for the sink condition without a boundary layer when it is unknown. The current solutions can cover more scenarios than the existing analytical and approximate solutions. The formulas, with explicit expressions, can be readily applied to analyze determinants of release kinetics, including volume of external medium, initial drug loading, and boundary layer thickness. With the criterion established for finding the conditions of drug saturation in a medium, minimal liquid volume and maximal time for refreshing the medium can be determined.

Algorithms↗
PubMed2002

Comparison of fumaric acid production by Rhizopus oryzae using different neutralizing agents.

Fumaric acid fermentation in a 10-L bubble column fermenter using different neutralizing agents [CaCO(3), Ca(OH)(2), NaHCO(3)] by Rhizopus oryzae ATCC 20344 was examined. It was found that in the fermentation using CaCO(3 )as the neutralizing agent the highest fumaric acid weight yield and volumetric productivity were obtained, 53.4% and 1.03 g/L x h(-1) respectively. In the NaHCO(3) case, the fumaric acid weight yield and volumetric productivity were 33.7% and 0.69 g/L x h(-1), respectively, much lower than the CaCO(3) case. However, the NaHCO(3) alternative has advantages of cell reuse and simple downstream processing because of the high solubility of sodium fumarate. These advantages may offset the disadvantages of using NaHCO(3) as the neutralizing agent, and the overall fumaric acid weight yield and volumetric productivity will increase.

Journal Article↗
PubMed2002

Intersubband transport in quantum wells in strong magnetic fields mediated by single- and two-electron scattering.

We show theoretically that in quantum wells subjected to a strong magnetic field the intersubband current peaks at magnetic field values, which reveal the underlying specific intersubband scattering mechanism. We have designed and grown a superlattice structure in which such current oscillations are clearly visible, and in which the transition from the purely single-electron to the mixed single- and two-electron scattering regimes can be observed by tuning the applied voltage bias. The measurements were conducted in ultrahigh magnetic fields (up to 45 T) to obtain the full spectrum of the current oscillations.

Journal Article↗
PubMed2002

Fuzzy rules to predict degree of malignancy in brain glioma.

The current pre-operative assessment of the degree of malignancy in brain glioma is based on magnetic resonance imaging (MRI) findings and clinical data. 280 cases were studied, of which 111 were high-grade malignancies and 169 were low-grade, so that regular and interpretable patterns of the relationships between glioma MRI features and the degree of malignancy could be acquired. However, as uncertainties in the data and missing values existed, a fuzzy rule extraction algorithm based on a fuzzy min-max neural network (FMMNN) was used. The performance of a multi-layer perceptron network (MLP) trained with the error back-propagation algorithm (BP), the decision tree algorithm ID3, nearest neighbour and the original fuzzy min-max neural network were also evaluated. The results showed that two fuzzy decision rules on only six features achieved an accuracy of 84.6% (89.9% for low-grade and 76.6% for high-grade cases). Investigations with the proposed algorithm revealed that age, mass effect, oedema, postcontrast enhancement, blood supply, calcification, haemorrhage and the signal intensity of the T1-weighted image were important diagnostic factors.

Brain Neoplasms↗
PubMed2002

In vitro bioactivity of a biocomposite fabricated from HA and Ti powders by powder metallurgy method.

Traditionally, hydroxyapatite was used as a coating material on titanium substrate by various techniques. In the present work, a biocomposite was successfully fabricated from hydroxyapatite and titanium powders by powder metallurgy method. Bioactivity of the composite in a simulated body fluid (SBF) was investigated. Main crystal phases of the as-fabricated composite are found to be Ti2O, CaTiO3, CaO, alpha-Ti and a TiP-like phase. When the composite is immersed in the simulated body fluid for a certain time, a poor-crystallized, calcium-deficient, carbonate-containing apatite film will form on the surface of the composite. The time required to induce apatite nucleation is within 2 h. In addition, the apatite is also incorporated with a little magnesium and chlorine element. It is found that Ti2O has the ability to induce the formation of bone-like apatite in the SBF. And a dissolve of the CaO phase could also provide favorable conditions for the apatite formation, by forming open pores on the surface of the composite and increasing the degree of supersaturation of the SBF with respect to the apatite.

Apatites↗
PubMed2002

Molecular cloning and developmental expression of Tlx (Hox11) genes in zebrafish (Danio rerio).

Tlx (Hox11) genes are orphan homeobox genes that play critical roles in the regulation of early developmental processes in vertebrates. Here, we report the identification and expression patterns of three members of the zebrafish Tlx family. These genes share similar, but not identical, expression patterns with other vertebrate Tlx-1 and Tlx-3 genes. Tlx-1 is expressed early in the developing hindbrain and pharyngeal arches, and later in the putative splenic primordium. However, unlike its orthologues, zebrafish Tlx-1 is not expressed in the cranial sensory ganglia or spinal cord. Two homologues of Tlx-3 were identified: Tlx-3a and Tlx-3b, which are both expressed in discrete regions of the developing nervous system, including the cranial sensory ganglia and Rohon-Beard neurons. However, only Tlx-3a is expressed in the statoacoustic cranial ganglia, enteric neurons and non-neural tissues such as the fin bud and pharyngeal arches and Tlx-3b is only expressed in the dorsal root ganglia.

Amino Acid Sequence↗
PubMed2002

Changes of TGFbeta1 and TGFbetaRII expression in esophageal precancerous and cancerous lesions: a study of a high-risk population in Henan, northern China.

The level of transforming growth factor beta1 (TGFbeta1) and transforming growth factor betaII receptor (TGFbetaRII) was determined immunohistochemically in normal tissues and tissues with different severities of lesions (basal cell hyperplasia, BCH; dysplasia, DYS; carcinoma in situ, CIS; and squamous cell carcinoma, SCC) from surgically resected human esophagi and esophageal biopsies of symptom-free subjects. The samples were from an area with high esophageal cancer incidence in northern China (Linzhou, formerly Linxian, and nearby county Huixian in Henan Province). Peroxidase immunostain (ABC) and conventional hematoxylin and eosin stain were used. The tissue sections were incubated with antibodies of TGFbeta1 and TGFbetaRII overnight. The immunoreactivity was observed in cytoplasm of the esophageal specimen. From normal to BCH to DYS to CIS and to SCC, the positive immunostaining rates for TGFbeta1 increased significantly (P < 0.05). A linear correlation between the positive immunostaining rates of TGFbeta1 and the different lesions was observed (P < 0.05). From well- to moderately- and poorly differentiated SCC, the positive immunostaining rates for TGFbeta1 decreased gradually, but the difference was not significant (P > 0.05). In contrast, with the lesions progressing from normal to BCH to DYS to CIS and to SCC, the positive immunostaining rates for TGFbetaRII decreased significantly (P < 0.05). From well- to moderately- and poorly differentiated SCC, the positive immunostaining rates for TGFbetaRII decreased significantly (P < 0.05). There was a linear correlation between the positive rates of TGFbetaRII and different lesions and SCC differentiation (P < 0.05). The present results indicated that the alterations of TGFbeta1 and TGFbetaRII is a frequent event in esophageal multistage carcinogenesis, the absent or lower expression of TGFbetaRII may lead to the loss of cell proliferation control by TGFbeta1 and the overexpression of TGFbeta1 may be a negative feedback response caused by the lower expression of TGFbetaRII protein.

Adult↗
PubMed2002

Endoscopic screening and determination of p53 and proliferating cell nuclear antigen in esophageal multistage carcinogenesis: a comparative study between high- and low-risk populations in Henan, northern China.

The objective of this study was to characterize the histologic changes from endoscopic screening for early esophageal cancer (EC) on subjects at high-incidence area (HIA) and low-incidence area (LIA) in Henan, China, and to further compare the changes in p53 and proliferating cell nuclear antigen (PCNA) in the multistage of human esophageal carcinogenesis from these two populations. The detection rate of basal cell hyperplasia (BCH) and dysplasia (DYS) was higher in the subjects from HIA than in those from LIA. Out of the 1568 symptom-free subjects examined at HIA, 10 (0.6%) cases with early squamous cell carcinoma (SCC) were identified. Immunoreactivity of p53 and PCNA was observed in cell nuclei of esophageal biopsies and surgically resected esophageal cancer specimens both in HIA and LIA. With the lesions progressed from normal epithelium to BCH to DYS to SCC, the positive-immunostaining cells expanded from basal layer to superficial layer, and the number of positive cells/mm2 for p53 and PCNA increased, and was significantly higher in HIA than in LIA among the similar morphological lesions (P < 0.01). The number of p53 positive cells/mm2 in SCC from HIA was almost fivefold higher than SCC from LIA (P < 0.01). The remarkable difference was also observed between HIA and LIA in DYS and BCH. The present results indicate that p53 protein accumulation is an important early biomarker for identifying high-risk subjects for EC.

Adult↗
PubMed2002

Genetically engineered analogs of ascomycin for nerve regeneration.

The polyketides FK506 (tacrolimus) and FK520 (ascomycin) are potent immunosuppressants that function by inhibiting calcineurin phosphatase through formation of an FKBP12-FK506/520-calcineurin ternary complex. They also have calcineurin-independent neuroregenerative properties in cell culture and animal models of nervous system disorders. Based on the crystal structure of the FKBP12-FK506-calcineurin complex, we deduced that the 13- and 15-methoxy groups of FK506 or FK520 are important for inhibition of calcineurin phosphatase but not for binding to FKBP12. By genetic modification of the FK520 gene cluster, we generated 13- and 15-desmethoxy analogs of FK520 that contain hydrogen, methyl, or ethyl instead of methoxy at one or both of these positions. These analogs bind FKBP12 tightly, have decreased calcineurin phosphatase inhibition and immunosuppressive properties, and enhance neurite outgrowth in cell cultures. A representative compound was also shown to accelerate nerve regeneration and functional recovery in the rat sciatic nerve crush model.

Acetyltransferases↗
PubMed2002

Bovine herpesvirus 5 (BHV-5) Us9 is essential for BHV-5 neuropathogenesis.

Bovine herpesvirus 5 (BHV-5) is a neurovirulent alphaherpesvirus that causes fatal encephalitis in calves. In a rabbit model, the virus invades the central nervous system (CNS) anterogradely from the olfactory mucosa following intranasal infection. In addition to glycoproteins E and I (gE and gI, respectively), Us9 and its homologue in alphaherpesviruses are necessary for the viral anterograde spread from the presynaptic to postsynaptic neurons. The BHV-5 Us9 gene sequence was determined, and the predicted amino acid sequence of BHV-5 Us9 was compared with the corresponding Us9 sequences of BHV-1.1. Alignment results showed that they share 77% identity and 83% similarity. BHV-5 Us9 peptide-specific antibody recognized a doublet of 17- and 19-kDa protein bands in BHV-5-infected cell lysates and in purified virions. To determine the role of the BHV-5 Us9 gene in BHV-5 neuropathogenesis, a BHV-5 Us9 deletion recombinant was generated and its neurovirulence and neuroinvasive properties were compared with those of a Us9 rescue mutant of BHV-5 in a rabbit model. Following intranasal infection, the Us9 rescue mutant of BHV-5 displayed a wild-type level of neurovirulence and neural spread in the olfactory pathway, but the Us9 deletion mutant of BHV-5 was virtually avirulent and failed to invade the CNS. In the olfactory mucosa containing the olfactory receptor neurons, the Us9 deletion mutant virus replicated with an efficiency similar to that of the Us9 rescue mutant of BHV-5. However, the Us9 deletion mutant virus was not transported to the bulb. Confocal microscopy of the olfactory epithelium detected similar amounts of virus-specific antigens in the cell bodies of olfactory receptor neuron for both the viruses, but only the Us9 rescue mutant viral proteins were detected in the processes of the olfactory receptor neurons. When injected directly into the bulb, both viruses were equally neurovirulent, and they were transported retrogradely to areas connected to the bulb. Taken together, these results indicate that Us9 is essential for the anterograde spread of the virus from the olfactory mucosa to the bulb.

Amino Acid Sequence↗
PubMed2002

Undermethylated DNA as a source of microsatellites from a conifer genome.

Developing microsatellites from the large, highly duplicated conifer genome requires special tools. To improve the efficiency of developing Pinus taeda L. microsatellites, undermethylated (UM) DNA fragments were used to construct a microsatellite-enriched copy library. A methylation-sensitive restriction enzyme, McrBC, was used to enrich for UM DNA before library construction. Digested DNA fragments larger than 9 kb were then excised and digested with RsaI and used to construct nine dinucleotide and trinucleotide libraries. A total of 1016 microsatellite-positive clones were detected among 11 904 clones and 620 of these were unique. Of 245 primer sets that produced a PCR product, 113 could be developed as UM microsatellite markers and 70 were polymorphic. Inheritance and marker informativeness were tested for a random sample of 36 polymorphic markers using a three-generation outbred pedigree. Thirty-one microsatellites (86%) had single-locus inheritance despite the highly duplicated nature of the P. taeda genome. Nineteen UM microsatellites had highly informative intercross mating type configurations. Allele number and frequency were estimated for eleven UM microsatellites using a population survey. Allele numbers for these UM microsatellites ranged from 3 to 12 with an average of 5.7 alleles/locus. Frequencies for the 63 alleles were mostly in the low-common range; only 14 of the 63 were in the rare allele (q < 0.05) class. Enriching for UM DNA was an efficient method for developing polymorphic microsatellites from a large plant genome.

DNA Methylation↗
PubMed2002

Modeling stem cell development by retrospective analysis of gene expression profiles in single progenitor-derived colonies.

The process of development of various cell types is often based on a linear or deterministic paradigm. This is true, for example, for osteoblast development, a process that occurs through the differentiation of a subset of primitive fibroblast progenitors called colony-forming unit-osteoblasts (CFU-Os). CFU-O differentiation has been subdivided into three stages: proliferation, extracellular matrix development and maturation, and mineralization, with characteristic changes in gene expression at each stage. Few analyses have asked whether CFU-O differentiation, or indeed stem cell differentiation in general, may follow more complex and nondeterministic paths, a possibility that may underlie the substantial number of discrepancies in published reports of progenitor cell developmental sequences. We analyzed 99 single colonies of osteoblast stem/primitive progenitor cells cultured under identical conditions. The colonies were analyzed by global amplification poly(A) polymerase chain reaction to determine which of nine genes had been expressed. We used the expression profiles to develop a statistically rigorous map of the cell fate decisions that occur during osteoprogenitor differentiation and show that different developmental routes can be taken to achieve the same end point phenotype. These routes appear to involve both developmental "dead ends" (leading to the expression of genes not correlated with osteoblast-associated genes or the mature osteoblast phenotype) and developmental flexibility (the existence of multiple gene expression routes to the same developmental end point). Our results provide new insight into the biology of primitive progenitor cell differentiation and introduce a powerful new quantitative method for stem cell lineage analysis that should be applicable to a wide variety of stem cell systems.

Animals↗
PubMed2002

Molecular views and measurements of hemostatic processes using atomic force microscopy.

Hemostasis and thrombosis are highly complex and coordinated interfacial responses to vascular injury. In recent years, atomic force microscopy (AFM) has proven to be a very useful approach for studying hemostatic processes under near physiologic conditions. In this report, we review recent progress in the use of AFM for studying hemostatic processes, including molecular level visualization of plasma proteins, protein aggregation and multimer assembly, and structural and morphological details of vascular cells under aqueous conditions. AFM offers opportunities for visualizing surface-dependent molecular and cellular interactions in three dimensions on a nanoscale and for sensitive, picoNewton level, measurements of intermolecular forces. AFM has been used to obtain molecular and sub-molecular, resolution of many biological molecules and assemblies, including coagulation proteins and cell surfaces. Surface-dependent molecular processes including protein adsorption, conformational changes, and subsequent interactions with cellular components have been described. This review outlines the basic principles and utility of AFM for imaging and force measurements, and offers objective perspectives on both the advantages and disadvantages. We focus primarily on molecular level events related to hemostasis and thrombosis, particularly coagulation proteins, and blood platelets, but also explore the use of AFM in force measurements and surface property mapping.

Adsorption↗
PubMed2002

Biological effects of hyperbaric oxygen on human severe periodontitis.

This paper reports the effects of Hyperbaric Oxygen (HBO2) in a controlled study of periodontitis in 24 patients. The patients received either HBO2 or no HBO2, and study teeth were divided into 4 groups based on treatment: 1-HBO2 therapy, 2-HBO2 + scaling, 3-scaling, 4-control. We measured indices of periodontal disease and gingival blood flow (GBF). The microorganisms in a periodontal pocket were stained and the percentage of straight rods (Rods), curved rods (Cur), fusiforms (Fusi) and spirochetes (Spiro) were observed. The numbers of anaerobic organisms were measured by routine anaerobic culture. Highly significant differences in Gingival Indices (GI), Sulcus Bleeding Indices (SBI), Probing Depth (PD), Attachment Loss (AL), Plaque Index (PLI), and GBF were seen in the HBO2, the HBO2 + Scaling and the Scaling Groups compared to the Control Group (P < 0.01). The number of subgingival anaerobes as well as the number of Rods, Cur, Fusi, and Spiro were reduced markedly in these three treatment groups. Statistically greater differences in clinical indices, GBF, subgingival anaerobe number and number of Rods, Cur, Fusi and Spiro were found by comparison of HBO2 + Scaling and HBO2 Groups, as well as between the HBO2 + Scaling and Scaling Groups, but no significant differences were observed in GI, SBI, PD, or AL between the HBO2 and Scaling Groups. In conclusion, HBO2 had beneficial therapeutic effects on severe periodontitis. HBO2 therapy combined with scaling and root planing was the most beneficial in the treatment of periodontitis. Clinical follow-up suggests that this treatment effect could last more than 1 year.

Adolescent↗
PubMed2001

Characterization of an eukaryotic peptide deformylase from Plasmodium falciparum.

Ribosomal protein synthesis in eubacteria and eukaryotic organelles initiates with an N-formylmethionyl-tRNA(i), resulting in N-terminal formylation of all nascent polypeptides. Peptide deformylase (PDF) catalyzes the subsequent removal of the N-terminal formyl group from the majority of bacterial proteins. Until recently, PDF has been thought as an enzyme unique to the bacterial kingdom. Searches of the genomic DNA databases identified several genes that encode proteins of high sequence homology to bacterial PDF from eukaryotic organisms. The cDNA encoding Plasmodium falciparum PDF (PfPDF) has been cloned and overexpressed in Escherichia coli. The recombinant protein is catalytically active in deformylating N-formylated peptides, shares many of the properties of bacterial PDF, and is inhibited by specific PDF inhibitors. Western blot analysis indicated expression of mature PfPDF in trophozoite, schizont, and segmenter stages of intraerythrocytic development. These results provide strong evidence that a functional PDF is present in P. falciparum. In addition, PDF inhibitors inhibited the growth of P. falciparum in the intraerythrocytic culture.

Amidohydrolases↗