Biomedical subjects

Z Zhao

Publications and source records attributed to Z Zhao.

At least 235 records · Page 13Linked to original sources

PubMed1997

[Improved MTT colorimetric assay for serum TNF activity].

The activity of serum tumor necrosis factor(TNF) is known to be related with the mechanism and prognosis of many diseases. The aim of this experiment was to look for an economic and reliable method for assaying the activity of serum TNF. We used the neutrophil solventor 20% SDS-50% DMF instead of the acidity solventor 0.04 mol/l acidified isopropy alcohol and established an improved 3-(4,5-dimethyl thiazoly)2,5-diphenyl-tetrazolium bromide (MTT) colorimetric assay for measuring the amount and function of living cell. We used this improved MTT colorimetric assay for measuring TNF activity of peripheral blood serum of healthy persons. It avoided the deposition of the protein in serum and medium and showed more repeatability, as compared with the conventional MTT colorimetric assay. The results showed: when the activity of target cell(TC)-L929 is > or = 95%, the density of TC is > or = 1 x 10(2)/well and the number of living cells in each well is positively correlated with the OD volume (OD570nm-OD630nm of purple formazan metabolite of MTT solution(r = 0.87, P < 0.01); when the density of TC is 5 x 10(4)/well, the level standard of TNF in each well is negatively correlated with the OD volume (OD570nm-OD630nm)r = 0.79, P < 0.01). Using this method, we measured the TNF activity of 20 healthy persons' peripheral blood serum. The mean +/- s of TNF activity is 20.95 +/- 3.2 IU/ml. This method is dependable, easy-to-do and economic, it has good repeatability within 3-12 hours.

Animals↗

PubMed1997

[Structure of rubescensin E].

Rubescensin E(I), a new diterpenoid, was isolated from the leaves of Rabdosia rubescens collcted in Jiyuan county, Henan Province On the basis of spectroscopic evidences, the structure of rubescensin E lished as ent-7 beta, 20-epoxy-7 alpha, 14 alpha-dihydroxy-6 alpha, 15 alpha-diacetoxy-16kaurene.

Diterpenes↗

PubMed1997

[Motion control system in BJ14 medical electron accelerator].

A dual computer based control mode was used in 14 Mev medical electron accelerator. The special non-linear velocity transformation method makes the positioning operation very fast and convenient. The independent driving mode of four blades are suitable to clinical uses. A multi-interlock function provides a safe environment for user's operation.

Computers↗

PubMed1997

[An observation of the percutaneous absorption of total alkaloids and terpenoid lactones of Tripterygium wilfordii].

The main ingredients of Tripterygium wilfordii are total alkaloids and terpenoid lactones. The authors studied the percutaneous absorption of these compounds on mice by means of ultravillet spectrophotometry. The results showed that these alksloids and lactones could pass through the skin of the mice. The rate of 12-hour percutaneous absorption was 13.40% for the former and 17.60% for the latter. After the application of Tripterygium wilfordii adhesive plaster to the human skin for 12 hours, the two ingredients were absorbed 17.34% and 22.13% respectively. This suggests that Tripterygium wilfordii can really be administered through the skin.

Administration, Topical↗

PubMed1997

[Isolation of coltivirus from mosquitoes in Beijing and it's biological characteristics].

Two strains (Beijing 95-70 and 95-75) of coltivirus were isolated from mosquitoes collected in Beijing during summer-autumn in 1994. The viruses caused cytopathogenic effect on C6/36 cells but not on BHK-21 and Vero cells, and were not lethal for new born mice and three week old mice. The isolates were resistant to 5'-IdU and ether, but sensitive to acid pH 3.0. There were 12 segments RNA shown by polyacrylamide gel electrophoresis (PAGE) and PAGE profile of the two isolates were similar (6-6). The PAGE profile was also similar to that of the TRT2 strain isolated in 1991, but there were at least 8 segments slightly different between the new isolates and TRT2 in band migration distance. Tissue culture cross-neutralization test showed that the new isolates were antigenically related to TRT2 strain identified as coltivirus. Growth curve of the two isolates on C6/36 cells showed that virus titer began to rise at the first day after infection and continued to increase up to 7.0 Log TCID50 per 0.1 ml and maintained a high level until the 21st day after infection. It seems that the virus may cause persistent infection on C6/36 cell.

Animals↗

PubMed1997

[Twenty-eight alphavirus strains isolated from mosquitoes and ticks captured from Hainan Island, China].

Virus isolation was carried out from mosquitoes and ticks captured in nature from Hainan Island of China from 1983-1988. Twenty-eight non-dengue and non-Japanese encephalitis viral strains were isolated from different places, of which 27 strains were recovered from different species of mosquitoes and 1 strain from ticks. At the Division of Vector-Bore Viral Diseases, National Center for Infectious Diseases, Centers for Disease Control, USA, identification of virus family and virus genus on these 28 viral strains was conducted by the use of a complete set of internationally standardized antibodies against arboviruses and by means of indirect immunofluorescence. Results proved that all these 28 viral strains belonged to the Genus Alphavirus of the Family Togaviridae.

Alphavirus↗

PubMed1997

[Determination of amino acid contents in cotton-seed-cake powder].

In this work, the contents of amino acids in three kinds of cotton-seed-cake powder from domestic and abroad were determined by using Waters Automatic Amino Acid Analyzer with post-column derivatization and fluorescence detection. The operating conditions were cation exchange resin column, 250 mm x 4.6 mm i.d., gradient elution, detection wavelength lambda(ex) = 338 nm and lambda(em) = 425 nm. The results showed that contents of amino acids from both domestic cotton seed cakes were less than those from abroad.

Amino Acids↗

PubMed1997

Acanthamoebae bind to rabbit corneal epithelium in vitro.

PURPOSE: Selection of an appropriate animal model is crucial for the investigation of the pathogenesis of Acanthamoeba keratitis. To this end, it has been reported that fluorescein isothiocyanate (FITC)-labeled Acanthamoeba castellanii bind to human, pig, and hamster corneas, but not to rabbit corneas in organ culture. However, 35S-labeled A. polyphaga and A. culbertsoni have been found to bind to rabbit corneal epithelium grown in tissue culture. The purpose of the current study was to establish whether A. castellanii bind to rabbit corneal epithelium in organ culture. METHODS: Two different adhesion assays were used to determine whether 35S-labeled and FITC-labeled A. castellanii bind to epithelium of corneal buttons in vitro and, if so, whether the binding is temperature-dependent, enhanced by injury, and inhibited by specific saccharides. Ameba binding to rabbit corneal epithelium was also evaluated by scanning electron microscopy. The binding of A. castellanii to corneal epithelium of three different species (human, pig, and rabbit) was compared. RESULTS: Both 35S-labeled as well as FITC-labeled parasites were found to bind to epithelium of rabbit corneal buttons in vitro. Although the parasites bound avidly to the corneas at 25 degrees C and 35 degrees C, little binding was observed at 4 degrees C. Injury enhanced the binding. Methyl alpha-D-mannopyranoside, but not other saccharides (alpha-L-fucose and beta-galactose), inhibited binding of the parasites to the epithelium of rabbit corneas. By scanning EM, A. castellanii were found to adhere, invade, and penetrate the epithelium of rabbit corneas. Compared with rabbit corneas, ameba binding to pig, and human corneas was only 1.2 and 1.4 times higher, respectively. CONCLUSIONS: Rabbit animal model may prove useful for investigation of the molecular mechanisms that mediate adhesion of Acanthamoeba to corneal epithelium.

Acanthamoeba↗

PubMed1997

[Immunohistochemical study on myoglobin in electrocution].

We have studied the changes of myoglobin (MB) IN heart muscle cells from eight corpses died of electrocution. The changes were compared with that of the heart muscle cells died of fall. The results indicated that the immunohistochemical changes of Mb were as follows: (1) blocky separate from heart muscle cell; (2) drift away into the interval of the heart muscle. The Mb changes were small parts of an area separate from heart muscle cells in control. The authors emphasized these changes were the characteristics of oxygen deficiency of the heart by electrocution.

Adolescent↗

PubMed1997

[Employing deconvolution method for correcting scatter in radiography].

It is well known that the scattered-radiation (SR) results in degradation of the images contrast in digital X-ray radiograph. The main reason affecting radiographic image quality is the SR arising from interaction of the photons with object being radiographed and veiling glare from detector system in the II-TV chai imaging system. With the aim of improving the image quality, we employed the Gaussian function to approximate the scattered point spread function (PSF) and determined the fraction of SR, rho and the parameter, sigma experimentally on an individual system; then we built an inverse filter to process the digital chest X-ray images, which were acquired with the same system and transformed in 2-D Fourier tansform operation. The images processed were corrected by using a variable weihting factor and the resulting images are shown in this paper. The method provides a useful way for solving the problem of correction of the SR in digital X-ray images.

Algorithms↗

PubMed1996

Genomic analysis of a new mammalian distal-less gene: Dlx7.

We have cloned a new Dlx gene (Dlx7) from human and mouse that may represent the mammalian orthologue of the newt gene NvHBox-5. The homeodomains of these genes are highly similar to all other vertebrate Dlx genes, and regions of similarity also exist between mammalian Dlx7 and a subset of vertebrate Dlx genes downstream of the homeodomain. The sequence divergence between human and mouse Dlx7 in these regions is greater than that predicted from comparisons of other vertebrate Dlx genes, however, and there is little sequence similarity upstream of the homeodomain both between these two genes and with other Dlx genes. We present evidence for alternative splicing of mouse Dlx7 upstream of the homeodomain that may account for some of this divergence. We have mapped human DLX7 distal to the 5' end of the HOXB cluster at an estimated distance of between 1 and 2 Mb by FISH. Both the human and the mouse Dlx7 are shown to be closely linked to Dlx3 in a convergently transcribed orientation. These mapping results support the possibility that vertebrate distal-less genes have been duplicated in concert with the Hox clusters.

Amino Acid Sequence↗

PubMed1996

Chromatographic measurement of drug-protein interaction: determination of HIV protease inhibitor-serum albumin association.

A chromatographic method for evaluation of the serum protein binding of a large number of non-peptide human immunodeficiency virus (HIV) protease inhibitors in short analysis time and automated fashion was developed. The method utilizes a size exclusion HPLC column. Bovine or human serum albumin is added to the mobile-phase running buffer. Qualitatively, a shift to shorter drug retention time in the presence of protein in the mobile phase is indicative of binding interaction of the drug and protein. The extent of binding of the drug to the protein is quantitated by comparison of the shift in retention time in the presence of protein to the retention time of the drug in the same buffer in the absence of protein (i.e., the drug's "intrinsic" retention time on the column). Binding measurements were carried out a 37 degrees C with a temperature-controlled autosampler and column oven. Results were compared with those obtained by ultrafiltration. The method yields thermodynamically valid binding measurements and is capable of directly detecting differences in the protein binding of individual stereoisomers present in mixtures (either enantiomers or diastereomers) without prior purification of the individual stereoisomers. The method measures overall binding to albumin and is not binding-site specific. Because of this, quantitative comparison of the extent of albumin binding of drugs which bind to the same site, different sites, or nonspecifically (i.e., not at discrete sites) is possible.

Animals↗

PubMed1996

Numerous members of the Sox family of HMG box-containing genes are expressed in developing mouse teeth.

We used RT-PCR to detect the expression in mouse molar and incisor tooth germs of 14 of the 19 known members of the Sox family of HMG box-containing transcription factors. These sequences fell into all 6 of the main subdivisions of the Sox family. In general, the relative transcript abundance of the different Sox genes is similar between molar and incisor tooth germs, although 3 low-abundance transcripts were found in only a single tooth type. The expression of Sox genes during tooth development has not been reported previously and further experiments will be required to determine their role in this process.

Animals↗

PubMed1996

Interaction of phosphorylated FcepsilonRIgamma immunoglobulin receptor tyrosine activation motif-based peptides with dual and single SH2 domains of p72syk. Assessment of binding parameters and real time binding kinetics.

To examine the characteristics of the interaction of the FcepsilonRIgamma ITAM with the SH2 domains of p72(syk), the binding of an 125I-labeled dual phosphorylated FcepsilonRIgamma ITAM-based peptide to the p72(syk) SH2 domains was monitored utilizing a novel scintillation proximity based assay. The Kd for this interaction, determined from the saturation binding isotherm, was 1.4 nM. This high affinity binding was reflected in the rapid rate of association for the peptide binding to the SH2 domains. Competition studies utilizing a soluble C-terminal SH2 domain knockout and N-terminal SH2 domain knockouts revealed that both domains contribute cooperatively to the high affinity binding. Unlabeled dual phosphorylated peptide competed with the 125I-labeled peptide for binding to the dual p72(syk) SH2 domains with an IC50 value of 4.8 nM. Monophosphorylated 24-mer FcepsilonRIgamma ITAM peptides, and phosphotyrosine also competed for binding, but with substantially higher IC50 values. This, and other data discussed, suggest that high affinity binding requires both tyrosine residues to be phosphorylated and that the preferred binding orientation of the ITAM is such that the N-terminal phosphotyrosine occupies the C-terminal SH2 domain and the C-terminal phosphotyrosine occupies the N-terminal SH2 domain.

Amino Acid Sequence↗

PubMed1996

The evolution of the vertebrate Dlx gene family.

The vertebrate Dlx gene family consists of homeobox-containing transcription factors distributed in pairs on the same chromosomes as the Hox genes. To investigate the evolutionary history of Dlx genes, we have cloned five new zebrafish family members and have provided additional sequence information for two mouse genes. Phylogenetic analyses of Dlx gene sequences considered in the context of their chromosomal arrangements suggest that an initial tandem duplication produced a linked pair of Dlx genes after the divergence of chordates and arthropods but prior to the divergence of tunicates and vertebrates. This pair of Dlx genes was then duplicated in the chromosomal events that led to the four clusters of Hox genes characteristic of bony fish and tetrapods. It is possible that a pair of Dlx genes linked to the Hoxc cluster has been lost from mammals. We were unable to distinguish between independent duplication and retention of the ancestral state of bony vertebrates to explain the presence of a greater number of Dlx genes in zebrafish than mammals. Determination of the linkage relationship of these additional zebrafish Dlx genes to Hox clusters should help resolve this issue.

Animals↗

PubMed1996

Activation of mitogen-activated protein (MAP) kinase pathway by pervanadate, a potent inhibitor of tyrosine phosphatases.

Rapid tyrosine phosphorylation of key cellular proteins is a crucial event in signal transduction. The regulatory role of protein-tyrosine phosphatases (PTPs) in this process was explored by studying the effects of a powerful PTP inhibitor, pervanadate, on the activation of the mitogen-activated protein (MAP) kinase cascade. Treatment of HeLa cells with pervanadate resulted in a marked inhibition of PTP activity, accompanied by a drastic increase in tyrosine phosphorylation of cellular proteins. The increased tyrosine phosphorylation coincided with the activation of the MAP kinase cascade as indicated by enzymatic activity assays of MEK (MAP kinase/ERK-kinase) and MAP kinase and gel mobility shift analyses of Raf-1 and MAP kinase. The activation was sustained but reversible. Upon removal of pervanadate, both tyrosine phosphorylation and MAP kinase activation declined to basal levels. Therefore, inhibition of PTP activity is sufficient per se to initiate a complete MAP kinase activation program.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed1996

Effects of deletion of the carboxyl-terminal domain of ApoA-I or of its substitution with helices of ApoA-II on in vitro and in vivo lipoprotein association.

In the present study, the lipoprotein association of apoA-I, an apoA-I (DeltaAla190-Gln243) deletion mutant and an apoA-I (Asp1-Leu189)/apoA-II (Ser12-Gln77) chimera were compared. At equilibrium, 80% of the 125I-labeled apolipoproteins associated with lipoproteins in rabbit or human plasma but with very different distribution profiles. High density lipoprotein (HDL)2,3-associated fractions were 0.60 for apoA-I, 0.30 for the chimera, and 0.15 for the deletion mutant, and corresponding very high density lipoprotein-associated fractions were 0.20, 0.50, and 0.65. Clearance curves after intravenous bolus injection of 125I-labeled apolipoproteins (3 microg/kg) in normolipemic rabbits could be adequately fitted with a sum of three exponential terms, yielding overall plasma clearance rates of 0.028 +/- 0.0012 ml.min-1 for apoA-I (mean +/- S.E.; n = 6), 0.10 +/- 0.008 ml.min-1 for the chimera (p < 0.001 versus apoA-I) and 0.38 +/- 0.022 ml.min-1 for the deletion mutant (p < 0.001 versus apoA-I and versus the chimera). Fractions that were initially cleared with a t1/2 of 3 min, most probably representing free apolipoproteins, were 0.30 +/- 0.04, 0.50 +/- 0.06 (p = 0.02 versus apoA-I), and 0.64 +/- 0.07 (p = 0.002 versus apoA-I), respectively. At 20 min after the bolus, the fractions of injected material associated with HDL2,3 were 0.55 +/- 0.06, 0.25 +/- 0.03 (p = 0.001 versus apoA-I), and 0.09 +/- 0.01 (p < 0.001 versus apoA-I and versus the chimera), respectively, whereas the fractions associated with very high density lipoprotein were 0. 15 +/- 0.006, 0.25 +/- 0.03 (p = 0.008 versus apoA-I), and 0.27 +/- 0.03 (p = 0.003 versus apoA-I), respectively. The ability of the different apolipoproteins to bind to HDL3 particles and displace apoA-I in vitro were compared. The molar ratios at which 50% of 125I-labeled apoA-I was displaced from the surface of HDL3 particles were 1:1 for apoA-I, 3:1 for the chimera and 12:1 for the deletion mutant, indicating 3- and 12-fold reductions of the affinities for HDL3 of the chimera and the deletion mutant, respectively. These data suggest that the carboxyl-terminal pair of helices of apoA-I are involved in the initial rapid binding of apoA-I to the lipid surface of HDL. Although the lipid affinity of apoA-II is higher than that of apoA-I, substitution of the carboxyl-terminal helices of apoA-I with those of apoA-II only partially restores its lipoprotein association. Thus, this substitution may affect cooperative interactions with the middle amphipathic helices of apoA-I that are critical for its specific distribution over the different HDL species.

Animals↗

PubMed1996

Wheat bran and psyllium diets: effects on N-methylnitrosourea-induced mammary tumorigenesis in F344 rats.

BACKGROUND: Experimental and epidemiologic evidence suggests that increased dietary fiber is associated with decreased breast cancer risk. Little is known about the role played by different types of fiber and, particularly, mixtures of soluble and insoluble fibers similar to those consumed by human populations in reducing breast cancer risk. High intake of fiber may suppress bacterial hydrolysis of biliary estrogen conjugates to free (absorbable) estrogens in the colon and thus may decrease the availability of circulating estrogens necessary for the development and growth of breast cancers. PURPOSE: The purpose of this study was to evaluate the effect of wheat bran (an insoluble fiber) and psyllium (a soluble fiber) alone and in combination on overall estrogen status, on fecal bacterial beta-D-glucuronidase (a key diet-responsive estrogen-deconjugating enzyme) activity, and on the induction of mammary tumors in rats treated with N-methylnitrosourea (MNU). METHODS: One hundred fifty virgin female F344 rats were fed the NIH-07 diet from 28 days of age until 50 days of age; they were then given a single dose (40 mg/kg of body weight) of MNU by tail vein injection. Three days later, they were randomly assigned to one of five experimental dietary groups (30 animals per group). Soft, white wheat bran (45% dietary fiber content) and psyllium (80% dietary fiber content) were added to a modified (high-fat) American Institute of Nutrition (AIN)-76A diet at the following percents, respectively: 12% + 0% (group 1), 8% + 2% (group 2), 6% + 3% (group 3), 4% + 4% (group 4), and 0% + 6% (group 5). Blood, urine, and feces were collected and analyzed by radioimmunoassay techniques for estrogens. Cecal contents were analyzed for bacterial beta-D-glucuronidase activity. After 19 weeks on the experimental diets, the rats were killed, and mammary tumors were counted and classified by histologic type. Cumulative tumor incidence was evaluated by the Kaplan-Meier life-table method and the logrank test. Tumor number was evaluated by the chi-squared test of association, and tumor multiplicity was evaluated by the Mantel-Haenszel chi-squared test. All statistical tests were two-tailed. RESULTS: As the level of psyllium relative to that of wheat bran increased, the total tumor number and multiplicity of mammary adenocarcinomas in rats decreased as a statistically significant linear trend across groups 1-5 (P < .05). Compared with the group given wheat bran alone, the group given the 1:1 (wheat bran:psyllium) combination had maximum protection against mammary tumorigenesis, while the groups given the 4:1 or 2:1 (wheat bran:psyllium) combination or psyllium alone had intermediate protection. No statistically significant differences in circulating estrogens or urinary estrogen excretion patterns were observed among the five experimental groups. Fecal estrogen excretion, however, decreased with increasing levels of psyllium (P < .01), and cecal beta-D-glucuronidase activity exhibited a decreasing trend with respect to the increasing psyllium content of the diet across groups 1-5 (P < .01). CONCLUSIONS: The addition of a 4%:4% mixture of an insoluble (wheat bran) fiber and a soluble (psyllium) fiber to a high-fat diet provided the maximum tumor-inhibiting effects in this mammary tumor model. Although increasing levels of dietary psyllium were associated with decreased cecal bacterial beta-D-glucuronidase activity, these changes were not reflected in decreased circulating levels of tumor-promoting estrogens. Therefore, the mechanism(s) by which mixtures of soluble and insoluble dietary fibers protect against mammary tumorigenesis remains to be clarified.

Animals↗