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Biomedical subjects

Y Dai

Publications and source records attributed to Y Dai.

At least 163 records · Page 9Linked to original sources
PubMed1996

Characteristic, activity and conformational studies of [A6-Ser, A11-Ser]-insulin.

Met-[A6-Ser, A11-Ser]-human proinsulin (Mut-HPI) was prepared in the same way as described previously for Met-human proinsulin (Met-HPI). After trypsin and carboxypeptidase B cleavage and DEAE-Sephadex A25 separation, Met-[A6-Ser, A11-Ser]-human insulin (Mut-HI) and Met-human insulin (Met-HI) were obtained. Their amino-acid compositions are in a good agreement with those expected. Mut-HI keeps full immuno activity, but loses almost all of its receptor binding activity with Met-HI as the control. Some physico-chemical behaviors of Mut-HI have changed to a certain extent. CD studies of mutant insulin demonstrates that the conformation of Met-HI is very similar to that of HI, while that of Mut-HI has altered slightly. The most important observation is that the binding ability of Mut-HI to the receptor has decreased abruptly. These results suggest that though the intra-A chain disulfide bond is deleted, the other two inter-chain disulfide bonds are still correctly paired, and that the intra-A chain disulfide bond is essential for insulin displaying its biological activity.

Amino Acids↗
PubMed1996

Adenovirus-mediated interferon-gamma transfer inhibits growth of transplanted HTLV-1 Tax tumors in mice.

Human T cell leukemia virus type 1 (HTLV-1) causes adult T cell leukemia (ATL), and the virus-encoded trans-activator, Tax, plays an important role in T cell transformation. In the HTLV-1 long terminal repeat (LTR)-Tax transgenic mouse model, Tax expression causes fibroblastic tumors. A tumor-derived cell line (B line) obtained from an explant of a Tax-transformed tumor, was established. This line expresses high levels of many cytokines as a consequence of Tax activation. However, the tumors are not immunogenic when transplanted into syngeneic mice. Because B line cells do not express the immunogenic cytokine interferon-gamma (IFN-gamma), a replication-defective adenoviral vector was used to deliver the IFN-gamma gene to tumor cells. The recombinant IFN-gamma adenovirus (IFN-gamma/Ad) can efficiently infect B line cells, resulting in high levels of IFN-gamma expression and secretion. Local secretion of IFN-gamma from B line cells caused both CD(4+)- and CD(8+)-positive T cell infiltration, and completely inhibited local tumor development in transplanted mice. Immunization with these cells significantly delayed tumor development after subsequent challenges of parental tumor cells. Expression of IFN-gamma in B cells also partially inhibited the highly expressed immune suppressive cytokine, transforming growth factor-beta 1 (TGF-beta 1). This system provides us with a valuable tumor immune therapy model to evaluate the effects of cytokines in induction or inhibition of specific antitumor immunity.

Adenoviruses, Human↗
PubMed1996

Accurate mass measurement of oligonucleotides using a time-lag focusing matrix-assisted laser desorption/ionization time-of-flight mass spectrometer.

A method for accurate mass measurement of oligonucleotides up to a DNA 35-mer based on matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is described. In this method, a time-lag focusing time-of-flight mass spectrometer is used to achieve high mass resolution to resolve adduct ions that often complicate the mass analysis of oligonucleotides. Mass resolutions between 1170 and 1300 (full width at half maximum) for a 17-mer, 23-mer, and 35-mer are obtained using a 1 m linear time-of-flight instrument with a total sample loading of less than 10 pmol. The effects of sample preparation, type of calibrant and matrix used on the accuracy of mass measurement, based on external calibration, are discussed. A sample preparation protocol that forms a thin film of matrix and sample crystals on a MALDI probe is described. It is shown that mass measurement error less than 100 ppm with reproducibility better than +/-60 ppm can be obtained with either proteins or DNA fragments as external calibrants. Accurate mass measurement for a mixture of DNA fragments is also illustrated.

Calibration↗
PubMed1996

Transcription of c-mos protooncogene in the pig involves both tissue-specific promoters and alternative polyadenylation sites.

The function of the c-mos gene has been intensively studied, but its role in the mammal is still a subject for debate. For this reason, and because the gene is regulated posttranscriptionally, further study of the gene from other mammalian species is timely. The pig c-mos gene has been cloned, and the genomic sequence is presented here. The gene has no introns and shows close similarity to human and monkey genes, with striking sequence similarities in both the 5' and 3' flanking regions. The significance of this similarity in the context of gene regulation is discussed. c-mos expression was found to be restricted to gonadal tissues in the pig. The major start sites for transcription initiation in ovary and testis were identified by primer extension and found to be distinct, as in the mouse. Within the ovary, expression is confined to oocytes. Messenger RNA is synthesized in growing oocytes, and remains stable during oocyte maturation, but begins to be degraded in electrically stimulated eggs. Unexpectedly, RNase protection assays revealed that the 3' ends of transcripts in the pig ovary are heterogeneous, and this, together with the identification of three distinct cDNA clones, shows that multiple polyadenylation sites are used. The significance of these transcripts in terms of translational control is discussed.

Alternative Splicing↗
PubMed1996

The pulmonary deposition of two aerosol preparations of nedocromil sodium delivered by MDI assessed by single photon emission computed tomography.

The pulmonary deposition and pharmacokinetics of fine and coarse radioactive aerosols of nedocromil sodium, of mass median aerodynamic diameters 16 microns and 24 microns respectively, delivered by metered dose inhaler (MDI) have been investigated. The corresponding geometric standard deviations of the particle size distributions were 5.32 and 3.93. Pulmonary deposition was assessed by both planar radionuclide scintigraphy and multi-modality three dimensional imaging using single photon emission computed tomography (SPECT) and x-ray computed tomography (CT). The three dimensional data were analysed by transformation to a hemispherical shape based on the fractional radial distance of each point in the lung from the centre to the corresponding extrapolated point on the periphery. This enabled parameters on the variation of both concentration of deposition and total amount deposited with penetration distance to be calculated. For both planar and SPECT data the central to peripheral concentration ratio (C/P ratio) was calculated. The three dimensional C/P ratio showed a median value (3.21) which was significantly higher than for the planar imaging (2.03) (p < 0.001). The parameter used to express the variation of total amount deposited was the median dose position. This showed that for both aerosols 50% of the dose was deposited at sites with a percentage central to peripheral distance of greater than 68%. There was a trend for total percentage of the fine aerosol in the lungs to be higher than for the coarse and for its deposition to be more peripheral. In addition the mean concentrations in blood were measured to be greater for the fine aerosol. However these differences were relatively small and none were individually statistically significant. The technique of combined SPECT and CT imaging was shown to be valuable in obtaining more accurate information on pulmonary distribution of inhaled aerosol deposition. The merits, limitations and potential applications of the technique are discussed.

Administration, Inhalation↗
PubMed1996

Characterization and expression of vascular endothelial growth factor (VEGF) in the ovine corpus luteum.

The corpus luteum undergoes tremendous growth, development and regression each oestrous or menstrual cycle. These changes are reflected by equally impressive growth and regression of the luteal vasculature. We have previously shown that angiogenic factors from corpora lutea are primarily heparin binding and that one of these factors is similar to vascular endothelial growth factor (VEGF). In an effort to identify this factor, and to define its role in luteal vascular development, the cDNA for the coding region of ovine VEGF was sequenced and a sensitive RNase protection assay was developed to quantitate mRNA encoding VEGF in luteal tissues from ewes in the early (days 2-4), mid- (day 8) and late (days 14-15) stages of the oestrous cycle. In addition, an N-terminal peptide was synthesized from the translated ovine cDNA sequence for VEGF and an antiserum was raised against this peptide for use in western immunoblotting procedures. Nested reverse transcriptase (RT)-PCR of RNA from ovine corpora lutea resulted in three products that correspond in size to the alternatively spliced variants of VEGF (VEGF120, VEGF164, and VEGF188) predicted from other species. The RNase protection assay revealed that the proportion of mRNA encoding VEGF was 2- to 3-fold greater on days 2-4 than on day 8 or days 14-15. Densitometric analysis of gels from the RNase protection assay showed that VEGF120 represented approximately one third of the total mRNA encoding VEGF in the corpus luteum and that this proportion did not vary with stage of the oestrous cycle. SDS-PAGE and western immunoblot analysis of a homogenate from corpora lutea showed a single 18 kDa protein. These data demonstrate that VEGF is expressed in luteal tissue throughout the ovine oestrous cycle and that expression of mRNA encoding VEGF is upregulated during the period of rapid luteal development, when luteal vascular growth is at its maximum.

Amino Acid Sequence↗
PubMed1996

[Comparison between kinetics of positive inotropism of ibopamine and ouabain].

AIM: To compare the kinetics of positive inotropism between ibopamine (Ibo) and ouabain (Oua). METHODS: The isolated right papillary muscle of cat was used to assess the positive inotropic effects by cummulative concentrations of Ibo and Oua. The maximal effects was recognized as the contraction just before the appearance of spontaneous contraction. A Hill equation was developed by using lg [E/(Emax-E)] vs lg C. RESULTS: The S value of Ibo was smaller than that of Oua, causing C95/C5 (ratio of concentrations producing 95%/5% of Emax) of Ibo (264) elevenfold as large as Oua (22.9). Comparing with Oua, concentrations of Ibo initiating effects were lower, the slope was smaller, and higher concentrations were required for producing maximal effect. During drug concentration declining, the effect-concentration curve of Ibo showed a counter-hysteresis loop, more remarkable than Oua. CONCLUSION: The changes in positive inotropism of Ibo against drug concentrations were less than those of Oua.

Animals↗
PubMed1996

[Expression of metastasis suppressor gene nm23 in human hepatocellular carcinoma].

For the purpose of investigating the relationship between the metastatic potential of the tumor as well as the expression of nm23-H1 mRNA, and for determing the location of the positive sites in the cells, tumor metastasis suppressor gene nm23-H1 in human hepatocellular carcinoma (and the nonneoplastic area surrounding the tumor) was detected by in situ hybridization using digoxiginin-labeled nm23-H1 antisense complementary RNA probe. The primary results indicated (i) positive results of in situ hybridization are presence of granules or masses in the cytoplasm; (ii) the less expression of nm23-H1 mRNA, the higher metastatic rate of the human hepatocellular carcinoma (P < 0.05); (iii) expression of nm23-H1 mRNA dose not correlate with some other factors such as tumor size and the background of other liver diseases.

Carcinoma, Hepatocellular↗
PubMed1995

Cellular and humoral immune responses to adenoviral vectors containing factor IX gene: tolerization of factor IX and vector antigens allows for long-term expression.

Recombinant adenoviruses containing the canine factor IX (FIX) cDNA were directly introduced in the hind leg muscle of mice. We show that (i) in nude mice, high expression (1-5 micrograms/ml in plasma) of FIX protein can be detected for > 300 days; (ii) in contrast, expression of FIX protein was transient (7-10 days) in normal mice; (iii) CD8+ lymphocytes could be detected within 3 days in the infected muscle tissue; (iv) use of beta 2-microglobulin and immunoglobulin M heavy chain "knockout" mice showed that lack of sustained expression of FIX protein is due to cell-mediated and humoral immune responses; (v) normal mice, once infected with recombinant adenovirus, could not be reinfected efficiently for at least 30 days due to neutralizing viral antibodies; and, finally, (vi) using immunosuppressive drugs, some normal mice can be tolerized to produce and secrete FIX protein for > 5 months. We conclude that currently available adenoviral vectors have serious limitations for use for long-term gene therapy.

Adenoviridae↗
PubMed1995

Antibody response against Pseudomonas aeruginosa membrane proteins in experimentally infected sheep.

Shedded sheep inoculated epicutaneously with P. aeruginosa and then wetted experimentally by a sprinkler system, rapidly develop a green bacterial stain. This was associated with an outpouring of serious exudates onto the skin surface in the fleecerot lesion site. Histopathological analysis of dermatitic lesions revealed an infiltration of polymorphonuclear leucocytes into the dermis and the formation of a mosaic of microabscesses beneath the sloughed sheets of cornified epithelium. P. aeruginosa if present, was always localized as aggregates at the leading front of the seropurulent exudate and was never observed to invade the dermis. Animals that had been inoculated with P. aeruginosa but kept dry, showed no signs of dermatitis or serological reactivity against the inoculated bacterium. In contrast, sheep that had been inoculated and wetted, reacted serologically against P. aeruginosa whole cells in an enzyme-linked immunosorbent assay (ELISA). Eleven of 18 sheep were considered to be high-antibody responders and registered an ELISA ratio > 2.5 at one or more time points over the duration of the experiment (14 weeks). Analysis of ELISA reactivity of fleecerot sheep against fractionated cell envelope proteins of P. aeruginosa showed a preferential antibody response to outer (OMP) rather than inner (IMP) membrane proteins. Immunoblots revealed strong antibody activity against 2 major OMPs-Opr F and Opr H with apparent molecular masses of 39 and 21 kDa respectively. OMPs prepared from sarkosyl-resistant outer membrane vesicles were electrophoretically identical to OMPs prepared by a more rapid and efficient organic phase partitioning procedure (Chin and Dai, 1990). Although two other OMPs-Opr E (44 kDa) and Opr G (25 kDa) were seen in Coomassie blue-stained SDS-PAGE gels of P. aeruginosa OMPs, they were not reactive with sera from fleecerot affected sheep. It is likely that sheep with high levels of circulating serum antibody against major outer membrane proteins of P. aeruginosa may, in the event of a fleecerot episode, exude such antibodies onto the skin surface. This could provide a strategy for the control of ovine fleecerot by vaccination if highly conserved outer membrane proteins of P. aeruginosa were found to be protective.

Animals↗
PubMed1995

Oncogene-linked in situ immunotherapy of pre-B lymphoma arising in E mu/ret transgenic mice.

We attempted to induce anti-tumour immunity for rejecting pre-B lymphoma derived from E mu/ret transgenic mice (TGM). We established pre-B-lymphoma cell lines of C57BL/6 x Balb/c background (H-2b/d) into which H-2k alloantigen and C3H background were introduced (retL1-6 and retL6-6), and we inoculated BCF1 mice with these immunising tumour cells. After these tumours were rejected by alloantigen (H-2k/C3H background)-specific effector cells, the mice were challenged with the pre-B-lymphoma cell line derived from the original E mu/ret TGM (ret0-2). All non-immunised control mice died within 80 days, whereas half the immunised mice survived for over 300 days. The immunity was also effective against primary pre-B-lymphoma cells from E mu/ret TGM and the ret-driven melanoma cell line (MEL-ret), but not against the pre-B-lymphoma cell line from E mu/myc TGM. This immunity was at least in part mediated by cell-mediated cytotoxicity that was specific to the ret oncogene product or ret-regulated antigen. Next we immunised E mu/ret TGM by inoculating them with retL6-6 cells once every 2 weeks beginning at the age of 1 month. Interestingly, this immunisation enabled the TGM to survive longer than the non-immunised control group (P < 0.05). Moreover, 2 of 11 transgenic mice receiving such immunisation were free from both macroscopic and microscopic tumours at the time when all of the 12 non-immunised control TGM had died from their tumour. This provides a new model for oncogene-linked immunotherapy research.

Animals↗
PubMed1995

Respiratory rate and signs in roentgenographically confirmed pneumonia among children in China.

A clinical study was conducted in three Chinese community hospitals to investigate the reliability of respiratory rate and various clinical signs in the diagnosis of pneumonia among 54 children less than 5 years of age. Anteroposterior chest film was used as the diagnostic standard. The cutoff criterion for rapid breathing was 50 breaths/minute for infants ages 2 to 11 months and 40/minute in children 1 to 5 years old. Rapid breathing was a better predictor of pneumonia than rales (positive predictive values of 74.5 and 66.9%). Nasal flaring, chest indrawing, stridor and cyanosis of the tongue had predictive values of > 86%, but these clinical signs were observed in only a small proportion of patients. We recommend that village health workers use rapid breathing for diagnosis of pneumonia, rather than auscultation which is difficult and has proved unreliable. Sensitivity, specificity and positive and negative predictive values are presented for seven signs and symptoms of pneumonia.

Auscultation↗
PubMed1995

MDM-2 protein expression in nasopharyngeal carcinomas. Comparative study with p53 protein expression.

Aims-To investigate the immunohistochemical expression of MDM-2 protein in comparison with that of p53 protein in nasopharyngeal carcinomas.Methods-Formalin fixed, paraffin wax embedded tissue from 59 cases of nasopharyngeal carcinoma was stained by immunohistochemistry for MDM-2 and p53 proteins.Results-The tumours were divided histologically into seven cases of keratinising nasopharyngeal carcinoma (KNPC), 14 cases of non-keratinising nasopharyngeal carcinoma (NKNPC), and 38 cases of undifferentiated nasopharyngeal carcinoma (UNPC). MDM-2 nuclear expression was observed in 0/7 KNPC, 1/14 NKNPC, and 11/38 UNPC. p53 nuclear expression was observed in 1/7 KNPC, 2/14 NKNPC, and 15/38 UNPC. Parallel MDM-2 and p53 expression was found in 12 cases (11 UNPC and one NKNPC). Discordant MDM-2-/p53 + expression was found in six cases (four UNPC, one NKNPC, and one KNPC), and absence of expression of both proteins in the remaining 41 cases.Conclusions-Expression of MDM-2 and p53 proteins may be associated with the level of tumour cell differentiation in nasopharyngeal carcinoma. Simultaneous expression of MDM-2/p53 in a proportion of UNPC suggests that MDM-2 protein may be responsible for stabilisation of p53 protein in these cases, in view of the previous demonstration of the p53 gene in germ line configuration. This could be important in the pathogenesis of these cases, since MDM-2 may deregulate the p53 dependent growth suppressive pathway. Discordant MDM-2-/p53 + expression in a few cases of nasopharyngeal carcinoma may reflect stabilisation of p53 protein by other proteins, or p53 mutations unable to activate MDM-2.

Journal Article↗
PubMed1995

An investigation of the relationship between color choice and depression measured by the Beck Depression Inventory.

The relationship between self-reported depression and color preference was investigated. It was proposed that a cognitive schema would be activated affecting negatively that part of the environment selected for cognitive preference. When requested to select a series of preferred colors, the 72 undergraduates scoring above 10 on the Beck Depression Inventory tended to choose black or brown. It is believed that internal schema represented in 3 questions may be reflected in color choice(s).

Black or African American↗
PubMed1995

[Correlated multiple parameters in pleural effusion with pathology of pleurae for differential diagnosis of tuberculous and carcinomatous pleuritis].

The level of ADA, LZM, leukocyte count, lymphocyte in tuberculous effusion is higher than that of carcinomatous effusion (P < 0.05). All results showed that the change of multiple parameters is related to the pathological manifestation of pleurae. The false positive or negative result was influenced by pathological appearance and bloody character of pleural effusion. Using the ADA, LZM cut off value at 35U and 30mg, respectively, and pleural/serum ADA ratio > 1.4, LZM > 1.1, a sensitivity and specificity of 100 percent were achieved.

Adenosine Deaminase↗
PubMed1995

[Effects of coconut juice on the formation of hyperlipidemia and atherosclerosis].

Eight-week old male quails were fed with high-fat fodder supplemented by 20 milliliters of coconut juice daily for each one for 12 weeks. Results showed coconut juice could increase their serum high density lipoprotein cholesterol levels by 46.2% and reduce their index of atherosclerosis by 41.1% and liver total cholesterol levels by 26.3% in quails, all with a P-value of less than 0.01, as compared in those with high-fat fodder only. Coconut juice could inhibit the formation of atherosclerosis in animals obviously. Coconut juice, as a kind of natural and nutritious drink with an action of keeping-fit, can play certain roles in preventing from hyperlipidemia and atherosclerosis with a dose used in animal experiments.

Animals↗