Biomedical subjects

X Zeng

Publications and source records attributed to X Zeng.

At least 55 records · Page 3Linked to original sources

PubMed2001

[Phospholipase activities of Candida albicans isolates from oral pre-malignant lesions and oral cancers].

OBJECTIVE: The aim of this study is to compare activities of phospholipase of Candida albicans isolates from oral cavities of two groups of patients, including oral pre-malignant lesions and oral cancers. METHODS: A total of 55 isolates, including oral pre-malignant lesions (21), oral cancers (15), and normal health control (19), were studied using the precipitate zone assay on the egg yolk agar. RESULTS: No significant difference was found in phospholipase activities between these isolates from normal controls and oral pre-malignant lesions, while the activities of phospholipase of isolates from oral cancers were higher than those of the normal controls. CONCLUSION: Candida albicans may play different roles in different manners in these two closely related diseases.

Candida albicans↗

PubMed2001

[An analysis of the results of central masking effect on healthy ears].

OBJECTIVE: To investigate the mechanism of Central Masking Effects(CME) and its effects on audiometry measurement. METHOD: The pure tone threshold was measured when the notest ear was masked or was in quiet respectively. We investigated the different results while giving different level maskers at the same frequency, or giving the same masker at different frequencies to find out their rules. RESULT: The CME has frequency-selective properties and sound level-selective properties. The CME appears apparently at 1 kHz and 2 kHz. At 2 kHz, the CME get the highest. When the masker was lower than 60 dB HL, the CME became higher as the masker was tuned higher; when the masker was 60 dB HL, the CME get the highest[(11.53 +/- 4.38)dB HL]. If the masker was higher than 70 dB HL, overmasking appeared. CONCLUSION: Our observations come to the conclusion that central masking correction should be made clinically when the masker is higher than 40 dB HL. 60 dB HL masker at 2 kHz can make the CME higher than 10 dB HL, thereby can be used to identify false deafness.

Adult↗

PubMed2001

[Comprehensive quality appraisal of "maidong"].

According to the contents of 14 kinds of constituents, 6 samples of Maidong from various habitats were comprehensively appraised by the weighted method with factor analysis and fuzzy mathematic method. The results showed that certified Maidong (Ophiopogon japonicus) was superior to its substitute Shanmaidong(Liriope spp.), and the sample from Xiaoshan county was the best in 3 samples of certified goods. Being consistent with the result of the traditional appraisal, the method used in this paper may provide a new means for appraising traditional medicinal materials.

Drugs, Chinese Herbal↗

PubMed2001

[Characteristics in frequency domain by inductively coupled plasma atomic emission spectrometry with charge injection detection].

The characteristics of two-dimension spectra obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) with charge injection detection (CID) in frequency domain were studied in the present paper. The measurement spectra were Fourier transformed and the frequency distribution of the spectra was obtained. Results showed that the spectra in frequency domain could be divided into two parts: high frequency and low frequency signals. The later stood for measurement spectra and the former for background and noises. However, the high frequency signals could not be smoothed simply to reduce noises because the background was deteriorated even though the spectral signal did not change significantly.

Mass Spectrometry↗

PubMed2000

MDM2 inhibits p300-mediated p53 acetylation and activation by forming a ternary complex with the two proteins.

p300 acetylates and activates the tumor suppressor p53 after DNA damage. Here, we show that MDM2, a negative-feedback regulator of p53, inhibited p300-mediated p53 acetylation by complexing with these two proteins. First, we purified a p300-MDM2-p53 protein complex from HeLa nuclear extracts, which was inactive in p53 acetylation, but active in histone acetylation. Also, wild-type, but not N-terminally deleted, MDM2 inhibited p53 acetylation by p300 in vitro and in vivo. This inhibition was specific for p53, because MDM2 did not affect acetylation of histones or the C terminus of p73 by p300. Consequently, wild-type, but not the mutant, MDM2 repressed the p300-stimulated sequence-specific DNA-binding and transcriptional activities of p53. These results demonstrate that an additional mechanism of p53 inactivation by MDM2 is to inhibit p53 acetylation by p300.

Acetylation↗

PubMed2000

Chemoenzymatic synthesis of glycopolypeptides carrying alpha-Neu5Ac-(2-->3)-beta-D-Gal-(1-->3)-alpha-D-GalNAc, beta-D-Gal-(1-->3)-alpha-D-GalNAc, and related compounds and analysis of their specific interactions with lectins.

Glycopolypeptide (1) carrying the beta-D-Gal-(1-->3)-alpha-D-GalNAc unit as a kind model of asialo-type mucin was synthesized through three steps: enzymatic synthesis of p-nitrophenyl disaccharide glycoside, reduction of the p-nitrophenyl group, and coupling of the amino group with the carboxyl group of poly(L-glutamic acid)s (PGA). In a similar manner, glycopolypeptides (2-7) carrying beta-D-Gal-(1-->3)-beta-D-GalNAc, beta-D-Gal-(1-->3)-beta-D-GlcNAc, beta-D-Gal-(1-->6)-alpha-D-GalNAc, beta-D-Gal-(1-->6)-beta-D-GalNAc, alpha-D-GalNAc, and beta-D-GalNAc, respectively, were synthesized as analogous polymers of polymer 1. Glycopolypeptides 8 and 9 as a mimic of sialo-type mucin were further prepared from polymers 1 and 2 as the acceptor of CMP-Neu5Ac by alpha2,3-(O)-sialyltransferase, respectively. Interactions of these glycopolypeptides with lectins were investigated with the double-diffusion test and the hemagglutination-inhibition assay and in terms of an optical biosensor based on surface plasmon resonance. Polymers 1 and 2 reacted strongly with peanut (Arachis hypogaea) agglutinin (PNA) and Agaricus bisporus agglutinin (ABA). On the other hand, polymers 8 and 9 through sialylation from polymers 1 and 2 reacted with ABA, but did not with PNA. Other polymers 3-7 did not show any reactivity for both the lectins. These results show that PNA acts precisely in an exo manner on the beta-D-Gal-(1-->3)-D-GalNAc sequence, while ABA acts in an endo manner. Polymers 6 and 7 substituted with GalNAc reacted strongly with soybean (Glycine max) agglutinin and Vicia villosa agglutinin B4, regardless of the configuration of the glycosidic linkage. The interaction of all polymers with Bauhinia purpurea agglutinin was much stronger than that of the corresponding sugars. Polymers 8 and 9 reacted with wheat germ (Triticum vulgaris) agglutinin (WGA), to which Neu5Ac residues are needed for binding, but polymers 1 and 2 did not. These sugar-substituted glycopolypeptides interacted specifically with the corresponding lectins. Furthermore, polymers 4-7 reacted with WGA, but the corresponding sugars did not. It suggests that the N-acetyl group along the PGA backbone has a cluster effect for WGA. The artificial glycopolypeptides were shown to be useful as tools and probes of carbohydrate recognition and modeling in the analysis of glycoprotein-lectin interactions.

Hemagglutination Tests↗

PubMed2000

UV but not gamma irradiation accelerates p53-induced apoptosis of teratocarcinoma cells by repressing MDM2 transcription.

Induction of p53 by DNA damage results in apoptosis of teratocarcinoma cells, whereas MDM2, encoded by a p53-responsive gene, can reverse this phenotype by inhibiting p53 function. Here we report that UV (10 or 20 J/m2), but not gamma irradiation (7 or 10 Gy), caused a massive apoptosis of human teratoma Tera-2 or murine testicular carcinoma F9 cells, both of which contain wild-type p53, but not murine p53 null testicular carcinoma EB-16 cells. Most Tera-2 or F9 cells died overnight after UV but not gamma irradiation. Correlated with this phenotype was a dramatic and continuing accumulation of p53 proteins after UV but not gamma irradiation. This was attributable to UV-responsive repression of MDM2 expression, because both its protein and RNA were not detectable after UV irradiation. This UV-induced repression appeared to be specific to MDM2, because expression of other genes, such as p21, p53, or glyceraldehyde-3-phosphate dehydrogenase, was not reduced. Also, RNase protection analysis showed that a DNA region, excluding the p53 binding site, in the MDM2 promoter mediated transcriptional repression in response to UV. Thus, these results suggest that UV but not gamma irradiation can induce p53 by suppressing MDM2 expression in a p53-independent fashion and subsequently, massive cell death.

Animals↗

PubMed2000

Intramolecular interaction of yeast TFIIB in transcription control.

The general transcription factor TFIIB is a key component in the eukaryotic RNA polymerase II (RNAPII) transcriptional machinery. We have previously shown that a yeast TFIIB mutant (called YR1m4) with four amino acid residues in a species-specific region changed to corresponding human residues affects the expression of genes activated by different activators in vivo. We report here that YR1m4 can interact with several affected activators in vitro. In addition, YR1m4 and other mutants with amino acid alterations within the same region can interact with TATA-binding protein (TBP) and RNAPII normally. However, YR1m4 is defective in supporting activator-independent transcription in assays con-ducted both in vitro and in vivo. We further demonstrate that the interaction between the C-terminal core domain and the N-terminal region is weakened in YR1m4 and other related TFIIB mutants. These results suggest that the intramolecular interaction property of yeast TFIIB plays an important role in transcription regulation in cells.

DNA-Binding Proteins↗

PubMed2000

Vaccination of domestic pig with recombinant paramyosin. against Schistosoma japonicum in China.

Paramyosin (PM), a myosin-like protein is a major antigen on Schistosoma japonicum (Sj). We reported that passive transfer of a monoclonal IgE SjE18varepsilon.1 which recognizes PM of Sj (SJPM), partially protected mice from challenge infection. In the present study, we developed an experimental model system of schistosomiasis japonica with domestic pigs in China and used it for the evaluation of vaccination with recombinant SJPM (rSJPM). Sixteen-week-old pigs were successfully infected by dermal penetration of 120 cercariae of a domestic strain of Sj (50-60% worm recovery 11 weeks after challenge). The pigs vaccinated with 400 UV attenuated cercariae showed a reduction of worm recovery (53%, p<0.001). The experimental groups were immunized intradermally with rSJPM and alum or TiterMax and were partially protected against the challenge infection (32-35% reduction).

Adjuvants, Immunologic↗

PubMed2000

Regioselective synthesis of p-nitrophenyl glycosides of beta-D-galactopyranosyl-disaccharides by transglycosylation with beta-D-galactosidases.

The beta-D-galactosidase from porcine liver induced regiospecific transglycosylation of beta-D-galactose from beta-D-Gal-OC6H4NO2-o to OH-6 of, respectively, p-nitrophenyl glycoside acceptors of Gal, GlcNAc and GalNAc to afford beta-Gal-(1-->6)-alpha-Gal-OC6H4NO2-p, beta-Gal-(1--> 6)-beta-Gal-OC6H4NO2-p, beta-Gal-(1-->6)-alpha-GalNAc-OC6H4NO2-p, beta-Gal-(1-->6)-beta-GalNAc-OC6H4NO2-p, beta-Gal-(1-->6)-alpha-GlcNAc-OC6H4NO2-p, and beta-Gal-(1-->6)-beta-GlcNAc-OC6H4NO2-p. The enzyme showed much higher transglycosylation activity for the alpha-glycoside acceptors than the corresponding beta-glycoside acceptors. The regioselectivity of the beta-D-galactosidase from Bacillus circulans ATCC 31382 greatly depended on the nature of the acceptor. When alpha-D-GalNAc-OC6H4NO2-p and alpha-D-GlcNAc-OC6H4NO2-p were used as acceptors, the enzyme showed high potency for regioselective synthesis of beta-Gal-(1-->3)-alpha-GalNAc-OC6H4NO2-p and beta-Gal-(1-->3)-alpha-GlcNAc-OC6H4NO2-p in high respective yields of 75.9 and 79.3% based on the acceptors added. However, replacement of beta-D-Gal-OC6H4NO2-p by beta-D-GalNAc-OC6H4NO2-p did change the direction of galactosylation. The enzyme formed regioselectively beta-Gal-(1-->6)-beta-Gal-OC6H4NO2-p with (beta-Gal-1-->(6-beta-Gal-1-->)n6-beta-Gal-OC6H4NO2-p, n = 1-4). No beta-(1-->3)-linked product was detected during the reaction. Use of the two readily available beta-D-galactosidases facilitates the preparation of (1-->3)- and (1-->6)-linked disaccharide glycosides of beta-D-Gal-GalNAc and beta-D-Gal-GlcNAc.

Animals↗

PubMed2000

Mice deficient in the candidate tumor suppressor gene Hic1 exhibit developmental defects of structures affected in the Miller-Dieker syndrome.

HIC1 is a candidate tumor suppressor gene which is frequently hypermethylated in human tumors, and its location within the Miller-Dieker syndrome's critical deletion region at chromosome 17p13.3 makes it a candidate gene for involvement in this gene deletion syndrome. To study the function of murine Hic1 in development, we have created Hic1 -deficient mice. These animals die perinatally and exhibit varying combinations of gross developmental defects throughout the second half of development, including acrania, exencephaly, cleft palate, limb abnormalities and omphalocele. These findings demonstrate a role for Hic1 in the development of structures affected in the Miller-Dieker syndrome, and provide functional evidence to strengthen its candidacy as a gene involved in this disorder.

Abnormalities, Multiple↗

PubMed2000

[Effects of local vibration on the levels of plasma endothelin and nitric oxide in rabbits].

In order to explore the effects of local vibration on plasma endothelin(ET) and nitric oxide (NO) and the relations with vibration-induced vascular impairment(VVI), plasma ET and NO levels of rabbits were measured after exposure to different vibration power and different exposure period. The results showed an increasing tendency in plasma ET levels, and a decreasing tendency in plasma NO levels in experiment groups, while lasting vibration exposure and enhancing vibration power. It suggested that local vibration could result in the increasing of plasma ET level and decreasing of plasma NO level, which might be one of the mechanisms of vibration-induced vascular impairment.

Animals↗

PubMed2000

Immunological effects of BCG as an adjuvant in autologous tumor vaccines.

The role of Bacillus Colmette-Guérin (BCG) as an adjuvant in autologous tumor vaccines was examined. In nine patients with renal cell cancer, irradiated tumor cells alone (wild-type, WT) or with BCG were inoculated intradermally into contralateral thighs. Seven to 10 days later, the draining vaccine-primed lymph nodes (WT-VPLN and BCG-VPLN) were excised. BCG increased the number of harvested VPLN cells by 10-fold (mean +/- SE = 61.8 +/- 20.6/x10(-7)/patient). BCG-VPLN had significantly greater percentages of CD3(+) and CD4(+) T cells compared to WT-VPLN. Both groups of VPLN cells were activated in vitro with anti-CD3 or anti-CD3/CD28 mAbs followed by expansion in IL-2. Anti-CD3/CD28 activation resulted in greater expansion of CD4(+) T cells compared to anti-CD3. After activation, VPLN cells were stimulated with irradiated autologous tumor targets and cytokines (IFN-gamma, GM-CSF, IL-10) released into the supernatants were measured 24 h later. Anti-CD3/CD28-activated BCG-VPLN cells were found to have a greater release of IFN-gamma compared with that of WT-VPLN cells, which was not observed significantly with IL-10 or GM-CSF. BCG resulted in increased VPLN cell yield as well as enhanced type 1 (IFN-gamma release) immune responses of VPLN cells to autologous tumor without upregulating type 2 (IL-10 release) responses. Anti-CD3/CD28 was superior to anti-CD3 activation in this cellular response.

Adjuvants, Immunologic↗

PubMed2000

Correlative expression of glutathione S-transferase-pi and multidrug resistance associated protein in bladder transitional cell carcinoma.

In order to elucidate the mechanisms of multidrug resistance (MDR) in bladder cancer, the expression of glutathione S-transferase-pi (GST-pi) and multidrug resistance associated protein (MRP) in tissue samples resected from 44 patients and 6 normal bladder mucosa as control was detected by using immunohistochemical method, and the results were analyzed by computer-assisted image analyzing system (IAS) to achieve semi-quantitative data. In addition, correlation between the expression of both factors was studied. The results showed that the positive expression rate of GST-pi and MRP in bladder cancer was 72.7% (32/44) and 68.2% (30/44) respectively, significantly higher than those in normal bladder mucosa, being 16.7% and 33.3% respectively. The rate of GST-pi positive staining was increased correspondingly with tumor grade and stage elevated, being higher in recurrent tumors treated by chemotherapy, but not significantly (P > 0.05). There was no significant differences between the expression of MRP and tumors' behaviors and clinical characters. However, the results demonstrated that the correlation between the expression of both resistant factors was very evident (r = 0.695, P < 0.0025). It was suggested that the activation of GST-pi and MRP might occur during malignant transformation of normal mucosa, but tumors' differentiation and progression could not be the unique factors that influenced both overexpression. Chemotherapy might be another important reason. The correlation of both indicated that there was a common mechanism regulating their expression probably, which made them play a pivotal role in chemotherapy drug resistance of bladder cancers.

Adult↗

PubMed2000

Selective electrodes for silver based on polymeric membranes containing cali.

Silver ion-selective electrodes were prepared with polymeric membranes based on two calix[4]arene derivatives functionalized by two hydroxy and two benzothiazolylthioethoxy groups. The electrodes all gave a good Nernstian response of 58mV decade(-1) for silver in the activity range 5 x 10(-6)-10(-1) M, the limits of detection reached 10(-5.8) M and exhibited high selectivity towards alkali, alkaline earth and some transition metal ions. The electrode was used as indicator electrode in titrations of Ag+ with Cl- ion.

Journal Article↗

PubMed2000

Cephalometric comparisons between Chinese and Caucasian patients with obstructive sleep apnea.

The purpose of this study was to compare two groups of adult men from different ethnic backgrounds and with obstructive sleep apnea; they were selected by matching age, gender, skeletal pattern, body mass index, and respiratory disturbance index. Pretreatment cephalometric radiographs and overnight polysomnograms of 30 Chinese and 43 Caucasian patients with Class II, Division 1 malocclusions were analyzed to investigate if there were craniofacial and upper airway structural differences between the two ethnic groups. The Chinese group, when compared with the group of Caucasian patients, revealed more severe underlying craniofacial skeletal discrepancies with significantly smaller maxilla and mandibles, more severe mandibular retrognathism, proclined lower incisors, increased total and upper facial heights, and steeper and shorter anterior cranial bases. However, no significant differences were found between the two groups in posterior facial height, ratio of upper to lower anterior facial height, and the position of hyoid bone, maxilla, and upper incisors. With regard to soft tissue and upper airway measurements, there were no significant ethnic differences in tongue and soft palate size, vertical length of oropharynx, and anteroposterior dimensions of the upper airway at most of the levels except for a larger super-posterior airway space, a larger nasopharynx and oropharynx cross-sectional area, and a smaller tongue height in the Chinese group. We conclude that there are a number of craniofacial and upper airway structures that differ between the two ethnic groups that may be relevant to the treatment of obstructive sleep apnea in various ethnic groups.

Asian People↗

PubMed2000

Effects of zinc on creatine kinase: activity changes, conformational changes, and aggregation.

The effects of zinc on creatine kinase (CK) are very distinctive compared with other bivalent metal ions. Zinc up to 0.1 mM induced increases in CK activity, accompanied by significant hydrophobic surface exposure and increase in alpha-helix content of CK. Zinc over 0.1 mM denatured and inactived CK. In the presence of 0.1 mM zinc, the CK activity was very close to that of the native CK, but its conformation changed greatly. The kinetic courses of CK inactivation and conformational change in the presence of 1 mM zinc were measured to determine apparent rate constants of inactivation and conformational change. Zinc over 0.05 mM induced CK aggregation at 37 degrees C, and the aggregation was dependent on zinc concentration, CK concentration, and temperature. The inactivation and aggregation can be reversed by EDTA. An explanation for CK aggregation induced by zinc is proposed, as well as a mechanism for CK abnormality in Alzheimer's disease.

Alzheimer Disease↗

PubMed2000

Cytogenetic studies of Hynobiidae (Urodela) XVI. Comparative C-banded karyotype analysis of Pseudohynobius flavomaculatus (Fei et Ye), Ranodon shihi (Liu) and Batrachuperus pinchonii (David).

Initial analysis of Pseudohynobius flavomaculatus chromosomes determined the chromosome number of this species to be 2n = 52. A re-examination of Ranodon shihi chromosomes detected 2n = 66 chromosomes, in contrast with a previous finding of 2n = 64. The C-banding patterns of these two species and that of Batrachuperus pinchonii were compared with each other. Regions of homoeology in the C-banding pattern among these three species represented 33.51-48.30% of the total length of their chromosomes. We also detected two types of chromosome rearrangement in hynobiid species based on the results of the present and previous cytogenetic studies.

Animals↗