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Biomedical subjects

X Yu

Publications and source records attributed to X Yu.

At least 163 records · Page 9Linked to original sources
PubMed2000

[Determinations and analysis of masticatory performance in unilateral cleft lip and palate].

OBJECTIVE: Masticatory function is one of the most important physical functions in craniomaxilla system. Masticatory performance is evaluated with the degree of broken dawn tested food in a limited period of time. Unilateral cleft lip and palate (UCLP) is a congenital abnormality in craniofacial growth and developing. It seriously damages face esthetics and masticatory function in UCLP patients. METHODS: 28 UCLP patients (male 17, female 11, permanent teeth) were selected, which all had received plastic operation treatments and never received any orthodontic therapy. The masticatory performance was determined by the advanced light absorbtion method and took peanuts as tested food. Meanwhile, malocclusal patterns and castings were identified in clinic. All of the data were treated with t-test and step wise-regression in statistics. RESULTS: 1. Masticatory performance of male was higher than that of female in normal people, but there was no sexual difference in UCLP. 2. Masticatory performance in UCLP was lower about 53.97% than that in normal people. 3. Different masticatory times within limited time had no effects on masticatory performance. 4. Different Patterns of malocclusion had different effects on masticatory performance. CONCLUSION: Orthodontic therapy is necessary to improve masticatory function in UCLP after plastic surgery.

Adolescent↗
PubMed2000

[A novel method for preparation of C18 ester-bond RP-HPLC packing].

RP-HPLC packings have found widespread application in the fields of biology, chemistry and pharmaceutical industry, etc. C18-bonded phase is one of the most important packing. In order to avoid using toxic and unstable chloro-containing silane as derivatization reagent, a new practical and economic procedure had been developed to prepare RP packing. Octadecyl group was bound onto YQG80, 5 microns silica (Tsingdao Oceanic Chemical Factory, particle size d.p. 5 microns) with gamma-glycidoxypropyltrimethoxysilane as coupling agent. Elemental analysis and chromatographic evaluation confirmed the feasibility of the procedure and RP behavior of the packing. After eluting with 500 column volume of mobile phase at different pH (2, 5 and 8), the column still showed good performance (> 64,000 theoretical plates/m) and stability.

Carbon↗
PubMed2000

[The modulation of type I collagen and its receptor system on biological characteristics of osteoblasts].

This paper addresses the question whether type I collagen-receptor system is necessary for the functional activity of osteoblasts. Through blocking type I collagen-receptor system by type I collagen antibody or integrin alpha 2 beta 1 antibody, the proliferation of osteoblasts was studied by cell count, the apoptosis was studied by flow cytometry, and the mRNA expressions of type I collagen, integrin alpha 2 beta 1 and osteocalcin were also detected by RT-PCR techniques. When type I collagen-receptor system was blocked, osteoblasts showed high apoptosis rate, lower growth kinetics and weak mRNA expression of type I collagen, integrin alpha 2 beta 1 and osteocalcin; the blocking effect was reversible. It suggests that type I collagen-receptor system is necessary for osteoblastic phenotype. The biomaterials for bone tissue engineering should be constructed according to the extracellular matrix of osteoblasts, which supply normal extracellular environment for osteoblasts.

Apoptosis↗
PubMed2000

[The establishment of a computerized growth prediction system].

Natural craniofacial growth plays an important role in the etiology of malocclusion. So, craniofacial growth prediction is very necessary in orthodontics. The present author have developed a new-typed computerized craniofacial growth predition system, which was designed in the general sense of craniofacial growth. According to a unique method, the system could automatically predict of craniofacial growth to different craniofacial growth pattern. It can be used as an auxilliary tool in clinical, teaching and researches in orthodontics.

Adolescent↗
PubMed2000

[Studies on biosorption of Au3+ by Bacillus megaterium].

Some characteristics of Au3+ biosorption and bioreduction by Bacillus megaterium D01 biomass were reported. The optimum pH value of Au3+ biosorption by strain D01 was 3.0. The biosorption was a rapid process, reaching 95% of the maximal capacity within the first 5 min of contact. Temperature did not affect the biosorption. The biosorptive efficiency(99.1%) and capacity (302.0 mg Au3+/g dry weight biomass) were achieved under the conditions of pH 3.0 and 30 degrees C, both concentration with an initial Au3+/biomass radio of 305 mg/g dry weight for 30 min of the contact. The D01 biomass could reduce Au3+ in the solution to Au0, Au0 on the cells surface and in the contact solution could be crystallized to different forms gold crystals, Au3+ impregnated on SiO2 and alpha-Fe2O3 could be reduced to Au0 by D01 biomass. The results of electrochemical reaction indicated that the strain D01 exhibited a high selectivity for Au3+.

Adsorption↗
PubMed2000

Preparation of anti-idiotypic antibodies specific for anti-HEL and analysis of their functional mimicry.

OBJECTIVE: This study is to investigate the functional mimicry by using anti-idiotypic antibodies of enzymes. METHODS: Monoclonal anti-idiotypic antibodies against anti-HEL (hen egg-white lysozyme, HEL) antibodies were obtained by fusion of Sp2/0 myeloma cells with spleen cells of syngeneic mice immunized with monoclonal anti-HEL antibodies against HEL's different antigenic epitopes. Then bacteriolysis of the anti-idiotypic antibodies were observed. RESULTS: Eight hybridomas strains secreting anti-idiotypic antibodies were selected and characterized. It was shown that two of eight anti-idiotypic antibodies secreted by two hybridomas (1A10C9 and 2A11C1B3) could mimic HEL catalytic activity to lyse Micrococcus lysodeikticus and that the catalytic effect of mixed anti-idiotypic antibodies of 1A10C9 and 2A11C1B3 was stronger than that of one of them, but less than HEL. CONCLUSION: The results demonstrated that the anti-idiotypic antibodies that could mimic enzyme activity existed in the idiotype network during anti-enzymatic immune response.

Animals↗
PubMed2000

[Study on neodymium complexes by broad wavelength range photoacoustic spectroscopy].

Neodymium complexes were studied by photoacoustic(PA) spectroscopy from UV-Vis to mid-IR. According to the PA spectra, low excited energy levels, relaxation processes and fluorescence properties were discussed. Then the influence of interaction between Nd(III) and ligands in solid complexes was investigated on the basis of band shifts and intensity change.

Chelating Agents↗
PubMed2000

[The synthesis and spectral study of multicomponent heteropoly compounds with Keggin structure].

The Multicomponent heteropoly compounds [Me4N]3 + x[PVxMoyW12-x-yO40]. n(H2O) with Keggin structure have been synthesized, and have been characterized by FTIR and NIR FT-Raman. The vibrational regularity of oxygen-containing bonds (P-Oa, M = Od, M-Ob-M and M-Oc-M) in these heteropoly compounds have been studied. The vibrational frequencies nu as (M = Od) and nu as (M-Ob-M) was shown to prove the reason why the acidity of the heteropoly compounds descended and the oxidization increased by the substitution of V atoms.

English Abstract↗
PubMed2000

[Study on the photoacoustic phase of rare earth complexes].

The theory of the photoacoustic (PA) phase has been studied. The PA phase spectra of rare earth complexes with dibenzoylmethide have been explained basing on the theory. The phase shifts of Tb complexes at the ligand absorption peak have been calculated. The phase shifts and their intramolecular relaxation processes have been studied also.

Acoustics↗
PubMed2000

[Clinical evaluation of the paste of erythromycin ethylsuccinate-metronidazole CP for root canal sterilization].

OBJECTIVE: The infected root canal was sterilized by anti-bacteria compound paste and the efficacy was compared with FC. METHODS: According to the mixed infection in infected root canal of anaerobic bacteria and obligate anaerobe, the paste made of erythromycin ethylsuccinate, metronidazole and CP was selected to seal and sterilize the root canal. RESULTS: The clinical observation of 180 patients with entirely developed root apex of acute and chronic apical periodontitis shown that there was no significant difference comparing erythromycin ethylsuccinate metronidazole-CP with FC in root canal sterilization, therefore, the irritability and poisonousness of the paste can be reduced by using erythromycin ethylsuccinate metronidazole CP instead of FC. CONCLUSION: The root canal sterilization drug of erythromycin ethylsuccinate metronidazole-CP was a safe and effective method to promote the restoration of root apex diseases.

English Abstract↗
PubMed1999

Alternative splicing patterns of CYP2D genes in human brain and neurodegenerative disorders.

The expression patterns of alternatively spliced forms of the CYP2D (6, 7, 7A, 7B) gene were analyzed in the brains of individuals with Lewy body disease (LBD) and correlated with CYP2D6 polymorphisms. Five different alternatively spliced transcripts were identified. The most common was the deletion of exon 6 (87.3% of cases), followed by a 91-base pair fragment deletion at the 3' end of the gene (63.9% of cases). There was no correlation between the polymorphisms in the CYP2D6B gene or presence of LBD and these five alternatively spliced transcripts. Susceptibility to LBD may occur through mechanisms other than altered mRNA splicing of the CYP2D6 gene.

Aged↗
PubMed1999

A loss of function mutation of presenilin-2 interferes with amyloid beta-peptide production and notch signaling.

Presenilin-1 (PS1) facilitates gamma-secretase cleavage of the beta-amyloid precursor protein and the intramembraneous cleavage of Notch1. Although Alzheimer's disease-associated mutations in the homologous presenilin (PS2) gene elevate amyloid beta-peptide (Abeta42) production like PS1 mutations, here we demonstrate that a gene ablation of PS2 (unlike that of PS1) in mice does not result in a severe phenotype resembling that of Notch-ablated animals. To investigate the amyloidogenic function of PS2 more directly, we mutagenized a conserved aspartate at position 366 to alanine, because the corresponding residue of PS1 is known to be required for its amyloidogenic function. Cells expressing the PS2 D366A mutation exhibit significant deficits in proteolytic processing of beta-amyloid precursor protein indicating a defect in gamma-secretase activity. The reduced gamma-secretase activity results in the almost complete inhibition of Abeta and p3 production in cells stably expressing PS2 D366A, whereas cells overexpressing the wild-type PS2 cDNA produce robust levels of Abeta and p3. Using highly sensitive in vivo assays, we demonstrate that the PS2 D366A mutation not only blocks gamma-secretase activity but also inactivates PS2 activity in Notch signaling by inhibiting the proteolytic release of the cytoplasmic Notch1 domain. These data suggest that PS2 is functionally involved in Abeta production and Notch signaling by facilitating similar proteolytic cleavages.

Amyloid beta-Peptides↗
PubMed1999

2-Bromopropane causes ovarian dysfunction by damaging primordial follicles and their oocytes in female rats.

Ovarian dysfunction induced by 2-bromopropane (2-BP) has been described in female factory workers and experimental animals. However, the underlying mechanism is still unclear. To establish the reproductive target site and define mechanisms of 2-BP toxicity in adult female rats, we examined the effects of different doses and duration of exposure to 2-BP in female rats. In the dose-dependent experiments, female rats were exposed to 2-BP at 100, 300, or 1000 ppm or fresh air (n = 9 each) in exposure chambers for 8 h/day for 9 weeks. In the time-course experiments, female rats were exposed to 2-BP at 3000 ppm for 8 h (n = 7 each). The rats were then euthanized 1, 3, 5, and 17 days after exposure. Differential follicle counts and in situ terminal deoxynucleotidyl transferase assay were used to evaluate 2-BP effect on primordial, growing, and antral follicles. Exposure to 2-BP at 300 and 1000 ppm produced a significant reduction in the percentage of primordial, growing, and antral follicles in a dose-dependent manner. Significant reduction in the percentage of primordial follicles at 17 days after exposure was observed in time-course experiments. Exposure to 2-BP at 3000 ppm for 8 h resulted in histological changes in primordial follicles complex at 5 and 17 days after exposure. These changes consisted of distortion of the symmetry of oocytes and their nuclei at Day 5 after exposure and appearance of eccentric pyknotic cells and shrinkage of oocyte nuclei at Day 17 after exposure. In situ end labeling showed increased numbers of apoptotic oocytes and granulosa cells in primordial follicles at Days 5 and 17 after exposure. Our results suggested that ovarian dysfunction induced by 2-BP was caused by the destruction of primordial follicle and its oocyte due to the induction of apoptosis. Our studies also show that the follicle differential count is a more sensitive method than the vaginal smear in monitoring the female reproductive disorders induced by 2-BP.

Animals↗
PubMed1999

Human Dmc1 protein binds DNA as an octameric ring.

The bacterial RecA protein has been the most intensively studied enzyme in homologous genetic recombination. The core of RecA is structurally homologous to that of the F1-ATPase and helicases. Like the F1-ATPase and ring helicases, RecA forms a hexameric ring. The human Dmc1 (hDmc1) protein, a meiosis-specific recombinase, is homologous to RecA. We show that hDmc1 forms octameric rings. Unlike RecA and Rad51, however, hDmc1 protein does not form helical filaments. The hDmc1 ring binds DNA in the central channel, as do the ring helicases, which is likely to represent the active form of the protein. These observations indicate that the conservation of the RecA-like ring structure extends from bacteria to humans, and that some RecA homologs may form both rings and filaments, whereas others may function only as rings.

Bacteriophages↗
PubMed1999

Nitric oxide inhibits angiotensin II-induced activation of the calcium-sensitive tyrosine kinase proline-rich tyrosine kinase 2 without affecting epidermal growth factor receptor transactivation.

In a previous study, we showed that nitric oxide donors and N-acetylcysteine, either alone or in combination, inhibited the activation of several mitogen-activated protein kinases by angiotensin II in rat cardiac fibroblasts (Wang, D., Yu, X., and Brecher, P. (1998) J. Biol. Chem. 273, 33027-33034). In the present study, we have focused on the mechanism by which nitric oxide exerts this effect on the activation of extracellular signal-regulated kinase (ERK). We contrasted the effects of nitric oxide on ERK activation by angiotensin II and epidermal growth factor (EGF), since the transactivation of the EGF receptor has been implicated as a response to angiotensin II. We found that nitric oxide inhibited ERK activation by angiotensin II but did not inhibit the relatively slight but significant transactivation of the EGF receptor by angiotensin II. The tyrphostin AG1478, known to inhibit EGF receptor phosphorylation, also inhibited the angiotensin II and EGF-induced activation of ERK, the phosphorylation of the EGF receptor, and the subsequent association of Shc and Grb2. Nitric oxide did not affect either EGF receptor phosphorylation or Shc-Grb2 activation induced by either Ang II or EGF. However, the activation of the calcium-sensitive tyrosine kinase PYK2, which occurred in response to angiotensin II, but not EGF, was inhibited by nitric oxide. The data suggested that PYK2 activation may be an important inhibitory site in signaling pathways affected by nitric oxide.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Interaction of the P-glycoprotein multidrug transporter (MDR1) with high affinity peptide chemosensitizers in isolated membranes, reconstituted systems, and intact cells.

P-glycoprotein-mediated multidrug resistance can be reversed by the action of a group of compounds known as chemosensitizers. The interactions with P-glycoprotein of two novel hydrophobic peptide chemosensitizers (reversins 121 and 205) have been studied in model systems in vitro, and in a variety of MDR1-expressing intact tumor cells. The reversins bound to purified P-glycoprotein with high affinity (77-154 nM), as assessed by a quenching assay using fluorescently labeled purified protein. The peptides modulated P-glycoprotein ATPase activity in Sf9 insect cell membranes expressing human MDR1, plasma membrane vesicles from multidrug-resistant cells, and reconstituted proteoliposomes. Both peptides induced a large stimulation of ATPase activity; however, higher concentrations, especially of reversin 205, led to inhibition. This pattern was different from that of simple linear peptides, and resembled that of chemosensitizers such as verapamil. In both membrane vesicles and reconstituted proteoliposomes, 1-2 microM reversins were more effective than cyclosporin A at blocking colchicine transport. Reversin 121 and reversin 205 restored the uptake of [3H]daunorubicin and rhodamine 123 in MDR1-expressing cells to the level observed in the drug-sensitive parent cell lines, and also effectively inhibited the extrusion of calcein acetoxymethyl ester from intact cells. In cytotoxicity assays, reversin 121 and reversin 205 eliminated the resistance of MDR1-expressing tumor cells against MDR1-substrate anticancer drugs, and they had no toxic effects in MDR1-negative control cells. We suggest that peptides of the reversin type interact with the MDR1 protein with high affinity and specificity, and thus they may be good candidates for the development of MDR1-modulating agents to sensitize drug resistance in cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗