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Biomedical subjects

Y Dai

Publications and source records attributed to Y Dai.

At least 109 records · Page 6Linked to original sources
PubMed1999

[Mechanism of injury by active oxygen radical to hemoglobin].

The injury effects of O2-. and H2O2 on the hemoglobin were investigated. The results showed that the metal prosthetic group was injured by O2-. and H2O2, but the mechanism of O2-. and H2O2 effects was different. Through the charge neutralization O2-. destroying the static electrical interactions between prosthethic groups and amino acid residues, it thereby caused prosthetic group dropped. H2O2 had Fenton reaction with Fe2+ in prosthetic group, hence produced .OH. It can destroy the porphyrin structure at fixed point in short distance, so the prosthetic group was destroyed and non-reversible.

Hemoglobins↗
PubMed1999

[Application of molecular epidemiology in the study of occupational chemical carcinogenesis].

This paper described the concept of moleculalr epidemiology, it's differences from traditional epidemiology and what the author learned from conducting molecular epidemiology recently. 1. Molecular epidemiology is the borderline subject in combination of molecular biology with epidemiology. 2. The level of chemical carcinogen formed in vivo and the amount of combination of chemical carcinogen either in the level from vivo or in biologic effective dose of combination of chemical carcinogen with macromolecular are all related to cancer development. 3. The syndrome of chromosome aberration is an early biologic effect in cancer process and oncogen activation or suppressing gene inactivation might be necessary for malignant transformation from initiated cell. 4. Individual susceptibility could be affected by host and acquired factors. 5. Biologic bank could provide continuous observation and comparision between before and after cancer formation.

China↗
PubMed1999

Linkage between melanocytic tumor development and early burst of Ret protein expression for tolerance induction in metallothionein-I/ret transgenic mouse lines.

We examined the basis of the all or none difference in inducing melanocytic tumor development among three transgenic mouse lines (304, 192 and 242) to which the same promoter-enhancer (metallothionein-I) and oncogene (ret) were introduced. We initially demonstrated that both skin melanosis and Ret protein expression in skin, thymus and brain first became detectable before or immediately after birth in the mice of the tumor developing lines (304 and 192), whereas they became detectable a few days after birth in the mice of the non-tumor developing line (242) by Western blotting and immunohistochemical analysis. Interestingly, the Ret protein expression in skin developed rapidly after birth as a burst with peak levels on 0.5-1.5 day newborns of lines 304 and 192 and on 7.0-7.5 day-old mice of line 242. The levels of autophosphorylation of Ret kinase in skin were, however, invariable among these three transgenic mouse lines. The mice of line 242, but not those of lines 192 and 304, responded to Ret protein immunization by increased antigen-dependent lymphocyte proliferation and T-cell-mediated tumor growth suppression in vitro. Furthermore, ret-transgenic mice of line 242, but not line 304, rejected the subcutaneously transplanted tumors that had originally developed in a mouse of line 304. These results suggest that whether oncogene product-specific-tolerance is established or not to antitumor immunity may be decided by the dynamics of ret oncogene expression before and after delivery and this is the primary factor determining development or non-development of melanoma.

Animals↗
PubMed1999

One protein, two enzymes.

Two enzymes, designated, E-2 and E-2', catalyze different oxidation reactions of an aci-reductone intermediate in the methionine salvage pathway. E-2 and E-2', overproduced in Escherichia coli from the same gene, have the same protein component. E-2 and E-2' are separable on an anion exchange column or a hydrophobic column. Their distinct catalytic and chromatographic properties result from binding different metals. The apo-enzyme, obtained after metal is removed from either enzyme, is catalytically inactive. Addition of Ni2+ or Co2+ to the apo-protein yields E-2 activity. E-2' activity is obtained when Fe2+ is added. Production in intact E. coli of E-2 and E-2' depends on the availability of the corresponding metals. These observations suggest that the metal component dictates reaction specificity.

Catalytic Domain↗
PubMed1999

Detection and identification of low-mass peptides and proteins from solvent suspensions of Escherichia coli by high performance liquid chromatography fractionation and matrix-assisted laser desorption/ionization mass spectrometry.

The application of high performance liquid chromatography (HPLC) to separate components in solvent suspension of Escherichia coli followed by off-line matrix-assisted laser desorption/ionization (MALDI) analysis of collected fractions results in the detection of over 300 peaks in the 2000-19,000 Da mass range, an order of magnitude increase in the number of components observed when compared with direct MALDI analysis of the entire solvent suspension. Mass measurements of these separated components using a time-lag focusing MALDI instrument are reported. MALDI analysis of the proteolytic digests of several collected fractions facilitates the identification of three components as specific proteins expected to be present in E. coli. The methodologies reported here should be very useful in searching for unique biomarkers for bacterial discrimination.

Bacterial Proteins↗
PubMed1999

Androgenic maintenance of the erectile response in the rat.

Ongoing studies in this laboratory have used the castrated rat, with and without testosterone replacement, to investigate how androgens maintain the erectile response. The high intracavernosal pressures during erection depend on both an increase in the rate at which blood flows into the sinuses of the corpus cavernosum and a decrease in the rate at which blood flows out (veno-occlusion). Accordingly, our studies investigated androgenic regulation of the arterioles that regulate inflow and of the intracavernosal muscle that regulates the veno-occlusive mechanism controlling outflow. The results of these studies show that castration causes a decline in the rate of inflow and that androgen replacement reverses this decline. The decline in inflow in the castrated rats is also reversed by the administration of a nitric oxide donor drug, suggesting that the androgen may regulate inflow by increasing the synthesis of nitric oxide. Testosterone also appears to regulate outflow by controlling the sensitivity of the erectile mechanisms to norepinephrine, considered to be the principle vaso-constrictor neurotransmitter in the erectile response. Taken together, the results of these studies suggest that androgens control the erectile response by altering the synthesis and action of the neurotransmitters that normally alter the state of contraction and relaxation of smooth muscle in the erectile tissue.

Androgens↗
PubMed1999

Ablation of renal tumors in a rabbit model with interstitial saline-augmented radiofrequency energy: preliminary report of a new technology.

OBJECTIVES: To evaluate the efficacy of interstitial saline radiofrequency energy for reproducibly ablating nonmalignant (control) and malignant (the VX-2 tumor) renal tissue in a rabbit model, and to determine the ability of conventional gray-scale and power sonography to image the tumor and ablative process in real time before, during, and after treatment. METHODS: The VX-2 tumor was implanted beneath the renal capsule in 18 rabbit kidneys. Twelve days after implantation, 50 W of 500-kHz radiofrequency energy was delivered into the surgically externalized renal tumor and contralateral control kidney for 30 or 45-second treatment intervals using an interstitial saline-augmented radiofrequency probe (the virtual electrode). Localization of the tumor and response to treatment were imaged with gray-scale and power Doppler ultrasonography. The effect of radiofrequency and extent of the destructive process on benign and malignant renal tissue were evaluated histologically. RESULTS: Mean tumor size was 1.3 x 0.7 cm. Both 30 and 45-second treatment intervals provided marked tissue/tumor ablation. Gross anatomic and histologic analysis showed time-dependent ablated lesions averaging 1.4+/-0.3 x 1.0+/-0.3 cm (30-second treatment) and 1.8+/-0.4 x 1.5+/-0.3 cm (45-second treatment), with clear demarcation of the surrounding parenchyma. Conventional gray-scale sonography allowed visualization of the ablative process, and power Doppler ultrasound demonstrated changes in the vascular pattern of the tumor both before and after ablation. No immediate treatment-related complications were observed. CONCLUSIONS: These preliminary studies in a rabbit model demonstrate the feasibility of using the interstitial saline-augmented electrode to ablate small renal tumors and the ability to simultaneously visualize the ablative process using real-time ultrasonography. This technology may have the potential to treat small renal tumors in a minimally invasive manner in the clinical setting.

Animals↗
PubMed1999

Cognitive behavioral therapy of minor depressive symptoms in elderly Chinese Americans: a pilot study.

There is a high prevalence of suicide among elderly Chinese, and particularly among elderly Chinese women in Mainland China with a prevalence of 19.6 per hundred thousand. Since Chinese individuals may much more highly value education, a cognitive-behavioral package originated by Ricardo Munoz, Ph.D. was adapted for Chinese American subjects. The material was videotaped in eight sessions, approximately 25 minutes in length, to be shown to community subjects who were at least 40 years and over. In addition, a videotape of muscular relaxation techniques was made. A manual written in Chinese about the content of each class, was given to each subject when he/she attended. The experimental group showed significant improvement in the scores in the Hamilton Depression Scale, including the Somatic Subscale in the Hamilton Anxiety Scale. There was no significant improvement in the control group on any of the measures. Thus the study suggests the efficacy of psychoeducational classes in reducing symptoms of depression in non-patient community elderly. Other studies are being conducted among Korean Americans and Japanese Americans in the United States, and also in the Orient among Japanese elderly.

Aged↗
PubMed1999

A role for the hepatobiliary system in IgE-mediated intestinal inflammation in the rat.

BACKGROUND: For many years the central focus of research into gastrointestinal hypersensitivity reactions has been the mast cell population of the intestinal lamina propria. Since bile is known to deliver immunological mediators to the gastrointestinal tract, the possibility arises that extra-intestinal populations of mast cells may also contribute to IgE-mediated intestinal damage. OBJECTIVES: To characterize hepatic mast cells in the rat and to investigate the role of the hepatobiliary system in a model of IgE-mediated reactivity to dietary antigen. METHODS: Wistar rats were passively sensitized with monoclonal antidinitrophenyl (DNP) IgE antibodies, and were later challenged orogastrically with DNP-HSA. Additional animals were sensitized, then bile duct-cannulated prior to antigen challenge. At various time points, liver and intestinal samples were collected for histological examination, and bile was collected and assayed for histamine and TNFalpha. RESULTS: Hepatic mast cells display a mucosal mast cell-like phenotype, and are closely associated with the vessels of the portal triads. Orogastric antigen challenge led to a rapid and significant decline (P<0.0001) in detectable mast cells as a result of anaphylactic degranulation. The median number of granulated mast cells associated with each portal triad in liver sections declined from six per portal triad to one per portal triad post-antigen challenge. After 15 min, biliary histamine concentrations rose above background levels (P<0.01). TNFalpha was also detectable in the majority (4/6) of bile samples within 15 min of challenge. Histological examination of the gastrointestinal mucosa revealed disruption to the villous epithelium ranging from oedematous changes to gross destruction. Such damage was not seen in animals in which bile had been externally drained. CONCLUSION: The data indicate that biliary products are major contributors to the gastrointestinal damage arising from IgE-mediated hypersensitivity reactions in the rat, and such hypersensitivity reactions may involve a population of mast cells which reside in the liver.

Animals↗
PubMed1999

Purification, crystallization and preliminary crystallographic studies on the N-terminal fragment of human protein disulfide isomerase.

A fragment of human protein disulfide isomerase composed of the thioredoxin-like a and b domains (ab) has been expressed in Escherichia coli as a fusion protein with glutathione-S-transferase and purified after thrombin cleavage. Two forms of ab crystal were obtained with polyethylene glycol as precipitant and different additives at pH 7.5. The space group of form I is P4(1)2(1)2 or P4(3)2(1)2, with unit-cell dimensions a = 81.5, c = 259.7 A. The space group of form II is P4(1)22 or P4(3)22, with unit-cell dimensions a = 82.7, c = 86.5 A.

Crystallization↗
PubMed1999

A novel spliced variant of the type 1 corticotropin-releasing hormone receptor with a deletion in the seventh transmembrane domain present in the human pregnant term myometrium and fetal membranes.

CRH exerts its actions via activation of specific G protein-coupled receptors, which exist in two types, CRH-R1 and CRH-R2, and arise from different genes with multiple spliced variants. RT-PCR amplification of CRH receptor sequences from human myometrium and fetal membranes yielded cDNAs that encode a novel CRH-R type 1 spliced variant. This variant (CRH-R1d) is present in the human pregnant myometrium at term only, which suggests a physiologically important role at the end of human pregnancy and labor. The amino acid sequence of CRH-R1d is identical to the CRH-R1alpha receptor except that it contains an exon deletion resulting in the absence of 14 amino acids in the predicted seventh transmembrane domain. Binding studies in HEK-293 cells stably expressing the CRH-R1d or CRH-R1alpha receptors revealed that the deletion does not change the binding characteristics of the variant receptor. In contrast, studies on the G protein activation demonstrated that CRH-R1d is not well coupled to the four subtypes of G proteins (G(s), G(i), G(o), G(q)) that CRH-R1alpha can activate. These data suggest that although the deleted segment is not important for CRH binding, it plays a crucial role in CRH receptor signal transduction. Second messenger studies of the variant receptor showed that CRH and CRH-like peptides can stimulate the adenylate cyclase system, with reduced sensitivity and potency by 10-fold compared with the CRH-R1alpha. Furthermore, CRH failed to stimulate inositol trisphosphate production. Coexpression studies between the CRH-R1d or CRH-R1alpha showed that this receptor does not play a role as a dominant negative receptor for CRH.

Alternative Splicing↗
PubMed1999

Effects of "products of chicken embryo" on growth and sexual development in rats.

Products of Chicken Embryo (PCE) such as Ji-Pei-Jing is a kind of food for Chinese children prepared from chicken embryo. Female rats on 21 days were administered with aqueous solutions of Ji-Pei-Jing (1.2%, 3%, 12%, and 48%, respectively) by gavage up to their onsets of puberty. The rats in the control group were treated with distilled water. However, Ji-Pei-Jing treatment exerted some effects on sexual maturation in the immature female rats. Essentially, the effects showed a dose-response tendency with an inverted "U" shape. The age of vaginal opening for group treated with Ji-Pei-Jing was significantly earlier than that to the control. Its uterus weight/b.w. ratio also significantly increased on day 30 and at the first estrus. There were significantly increases in the adrenal weight/b.w. ratio of 30-day-old rats that were treated with 3%, 12%, and 48% Ji-Pei-Jing. The rats treated with 48% Ji-Pei-Jing had significantly lesser ovary weight/b.w. ratio on day 30, too. The rats treated with Ji-Pei-Jing could normally ovulate at the first estrus, and no significant differences were observed during estrous cycles. The effects of PCE on serum levels of E2, P, LH in 30-day-old rats and FSH in 28-day-old rats were elevated significantly by 3% Ji-Pei-Jing treatment. It appears that the effects of PCE result from interaction of contained complex physiologically active substances. Steroids, especially estradio-17 beta, possibly play a key role, and polypeptide hormones may also exert important effects.

Animals↗
PubMed1999

Development and application of a minimal-adenoviral vector system for gene therapy of hemophilia A.

To achieve efficient delivery and sustained expression of the human factor VIII cDNA in vivo, a minimal-adenoviral (mini-Ad) vector system was developed. The system is composed of a mini-Ad vector with essential cis-elements (less than 1 kb) of the viral genome, an E1-deleted ancillary Ad with packaging attenuation, and an E1-complementing production cell line. Based on this system, MiniAdFVIII was generated to deliver a 27 kb expression cassette consisting of a full-length human factor VIII cDNA flanked by human albumin promoter and genomic sequences. The MiniAdFVIII vector mediated expression of functional human factor VIII in HepG2 and 293 cells. A single-dose intravenous injection of 10(11) viral particles in hemophilic mice of MiniAdFVIII produced a sustained high-level expression of human factor VIII (at 100-800 ng/ml up to 369 days) which corrected the FVIII-deficient phenotype. Safety studies of MiniAdFVIII showed that there were no significant toxic effects in mice and dogs after single intravessel doses of up to 3 x 10(11) and 6 x 10(12) viral particles, respectively. Studies for developing the MiniAdFVIII vector with a site-specific integration mechanism and progress in the development of a human factor VIII-tolerized mouse model for pre-clinical studies of MiniAdFVIII are reported. Further pre-clinical studies and product development of MiniAdFVIII for clinical trials are also discussed.

Adenoviridae↗
PubMed1999

Aldosterone biosynthesis in extraadrenal tissues.

OBJECTIVE: To determine whether extraadrenal tissues synthesize aldosterone in addition to vascular tissue and brain. METHODS: Ex vivo kidney perfusion was performed in normal Wistar rats, ACEI pretreated and adrenalectomized rats prior to the perfusion experiment. After equilibration for 30 minutes, 120 ml of perfusate was collected and subjected to reverse-phase HPLC and then aldosterone was measured by RIA. By RT-PCR and Southern blot the expression of aldosterone synthase gene-CYP11B2 mRNA was studied in both kidney tissue and cultured renal tubular epithelial cell, lung and liver tissues. In situ hybridization was used to identify the cell types of liver and lung expressing CYP11B2 mRNA. RESULTS: Production of aldosterone in the kidney perfusate was not changed in adrenalectomized rats although it was decreased in the group pretreated with ACEI perindopril. By RT-PCR and Southern blot the expression of CYP11B2 mRNA was demonstrated in both kidney tissue and cultured renal tubular epithelial cell. We have also identified CYP11B2 mRNA expression in liver and lung of rats. In situ hybridization showed that CYP11B2 mRNA was localized in the endoplasm of liver fat-storing cell (Ito cells) and type II alveolar cells of lung. CONCLUSIONS: These studies prove that kidney, liver and lung are able to produce aldosterone.

Aldosterone↗
PubMed1999

[Study on effect and mechanism of essential garlic oil in inhibiting monocyte-vascular endothelial cell adhesion induced by interleukin-1 alpha].

OBJECTIVE: To observe the effects of essential garlic oil (EGO) on vascular cell adhesive molecule-1 (VCAM-1) expression of endothelial cell and monocyte adhesion induced by interleukin-1 alpha (IL-1 alpha). METHODS: Human umbilical vein endothelial cells (HUVEC) were isolated by pancreatin digestion method and co-cultured with U937 monocyte and IL-1 alpha or EGO + IL-1 alpha respectively. The adhesion rate of monocyte to endothelial cell was measured and mean fluorescent intensity of immuno-stained of VCAM-1 was determined by ACAS 570. RESULTS: EGO showed significant inhibition on VCAM-1 expression induced by IL-1 alpha either in simple culture with HUVEC or in co-culture with HUVEC + U937, and could obviously down regulate the monocyte-endothelial cell adhesion under effect of IL-1 alpha. CONCLUSION: EGO has the effect of antagonizing against adhesion of monocyte and vascular endothelial cell, it may be due to the inhibition of EGO on adhesive molecular expression on endothelial cell.

Allyl Compounds↗
PubMed1999

[Plasminogen activator inhibitor-1 mRNA expression by the iris and lens epithelial cells of rabbit eye with intraocular lens implantation].

OBJECTIVE: To investigate the change of plasminogen activator inhibitor-1 (PAI-1) synthesized by the iris and the lens epithelial cells (LECs) after extracapsular cataract extraction (ECCE) with intraocular lens (IOL) implantation and the role of PAI-1 in the occurrence of fibrin reaction and the formation of posterior capsular opacification. METHODS: Eight adult rabbits were studied. In each rabbit, one eye underwent ECCE with IOL implantation and the other eye was normal without any surgical intervention. The iris tissue and the lens capsule of each two normal eyes and each two surgical eyes were excised on the postoperative 1, 7, 15 and 30 days respectively. The amount of PAI-1 mRNA expression in the specimens was detected by using reverse transcription-polymerase chain reaction (RT-PCR). The data were analyzed statistically. RESULTS: The amount of PAI-1 mRNA expresson in the iris tissue and the LECs of the surgical eyes displayed a significant increase on the first day after operation. The high expression of PAI-1 mRNA by the iris might last 15 days (P < 0.001), but it declined to the normal range on the postoperative 30 days (P = 0.87). The high level of PAI-1 mRNA expresson by the LECs in the surgical eyes had significant difference when compared with that of the normal eyes at 1, 7, 15 and 30 days postoperatively (P < 0.001). CONCLUSION: It is indicated that PAI-1 enzyme is a major cause for fibrin reaction after ECCE with IOL implantation, and may play critical roles in the development of posterior capsular opacification.

Animals↗