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Biomedical subjects

W Yu

Publications and source records attributed to W Yu.

At least 145 records · Page 8Linked to original sources
PubMed1999

Induction of apoptosis in human breast cancer cells by tocopherols and tocotrienols.

The apoptosis-inducing properties of RRR-alpha-, beta-, gamma-, and delta-tocopherols, alpha-, gamma-, and delta-tocotrienols, RRR-alpha-tocopheryl acetate (vitamin E acetate), and RRR-alpha-tocopheryl succinate (vitamin E succinate) were investigated in estrogen-responsive MCF7 and estrogen-nonresponsive MDA-MB-435 human breast cancer cell lines in culture. Apoptosis was characterized by two criteria: 1) morphology of 4,6-diamidino-2-phenylindole-stained cells and oligonucleosomal DNA laddering. Vitamin E succinate, a known inducer of apoptosis in several cell lines, including human breast cancer cells, served as a positive control. The estrogen-responsive MCF7 cells were more susceptible than the estrogen-nonresponsive MDA-MB-435 cells, with concentrations for half-maximal response for tocotrienols (alpha, gamma, and delta) and RRR-delta-tocopherol of 14, 15, 7, and 97 micrograms/ml, respectively. The tocotrienols (alpha, gamma, and delta) and RRR-delta-tocopherol induced MDA-MB-435 cells to undergo apoptosis, with concentrations for half-maximal response of 176, 28, 13, and 145 micrograms/ml, respectively. With the exception of RRR-delta-tocopherol, the tocopherols (alpha, beta, and gamma) and the acetate derivative of RRR-alpha-tocopherol (RRR-alpha-tocopheryl acetate) were ineffective in induction of apoptosis in both cell lines when tested within the range of their solubility, i.e., 10-200 micrograms/ml. In summary, these studies demonstrate that naturally occurring tocotrienols and RRR-delta-tocopherol are effective apoptotic inducers for human breast cancer cells.

Antioxidants↗
PubMed1999

Gene transfer mediated by YKS-220 cationic particles: convenient and efficient gene delivery reagent.

A monocationic lipid, YKS-220, with a symmetrical and biodegradable structure can be used as an effective gene transfer vector in a cationic particle form (not a cationic liposome form), and is obtained by diluting an ethanol solution of YKS-220 and DOPE (1:5, molar ratio) with an aqueous medium. This preparation method is more convenient than that for cationic liposomes. YKS-220 cationic particles showed a heterogeneous large mean diameter of 4.4 microm. An obvious size change was not observed when plasmid DNA was added. The transfection activity of YKS-220 cationic particles was comparable to those of YKS-220 liposomes and DOSPA liposomes (LipofectAMINE), and even higher than that of DOGS (TRNSFECTAM). Interestingly, the YKS-220 cationic particle/DNA complexes were resistant to the neutralizing effect of serum. All of these findings indicate that YKS-220 cationic particles are a convenient and efficient gene delivery reagent.

Animals↗
PubMed1999

Acceleration and double-peak spectrum of hot electrons in relativistic laser plasmas.

A spectrum equation of hot electrons in relativistic laser plasmas is derived in which two hot-electron population peaks appear as the laser strength parameter reaches a threshold. These calculations can explain the generation of very hot electrons with several tens of MeV energy and two hot-electron population peaks observed in the recent experiments.

Journal Article↗
PubMed1999

Patterns of use of common major procedures in medical care of older adults.

OBJECTIVES: We analyzed Medicare data to determine the influence of age, mortality during the study year, and high individual Medicare costs on the frequency of hospitalization for the most common major procedures and for general medical diagnoses. METHODS: We used 1992 Medicare data to classify the most frequent diagnosis related groups (DRGs), representing one-half of all admissions, as procedural or general medical. We studied the frequency of hospitalization for the most common procedures (bowel surgery, cardiovascular procedures, hip and femur surgery) and for general medical care in the entire Medicare population, in persons aged 65 to 74, 75 to 84, and 85 or older, in those who died, and in the 5% of persons whose annual Medicare costs were the highest. RESULTS: In the entire population, common procedures accounted for 21% of the most frequent DRGs. Among those who died, the procedures were performed in only 8% of admissions. In the 5% of persons with the highest Medicare costs, 28% of admissions involved procedures. Admissions for cardiovascular procedures and for cancer chemotherapy decreased with age and were infrequent in persons 85 years and older. Hip and femur procedures increased with age and accounted for 70% of the common procedures in persons 85 years and older. CONCLUSIONS: The most common major procedures account for a minority of hospitalizations of persons more than age 65, of persons 85 and older, of those who died, and of persons with the highest Medicare expenditures. Most hospitalizations are for general medical care. Major procedures appear to be used with restraint in the very old and in persons in their last year of life.

Aged↗
PubMed1999

Properties of cationic liposomes composed of cationic lipid YKS-220 having an ester linkage: adequate stability, high transfection efficiency, and low cytotoxicity.

Cationic lipid N-[3-[2-(1,3-dioleoyloxy)propoxy-carbonyl]propyl]-N,N,N-trimethyla mmonium iodide (YKS-220) having a symmetrical and biodegradable structure was employed for the preparation of cationic liposomes with dioleoylphosphatidylethanolamine (DOPE). The stability, transfection activity in several cell lines and cytotoxicity of YKS-220 cationic liposomes were studied. It was found the YKS-220 cationic liposomes were very stable and their transfection activity remained even after storage at 4 degrees C for 12 months. The transfection activity of these liposomes was assayed using CHO, COS, and HepG2 cells and found to be comparable with, or better than, that of other cationic liposomes, such as N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP) liposome, N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) liposome (Lipofectin), and 2,3-dioleyloxy-N-[2-(sperminecarboxamido)ethyl]-N,N-dimethyl -1-propanaminium trifluoroacetate (DOSPA) liposome (LipofectAMINE). In addition, the cytotoxicity of YKS-220 cationic liposomes was far lower than that of other cationic liposomes.

Animals↗
PubMed1999

Shortening of endografts during deployment in endovascular AAA repair.

PURPOSE: To evaluate the incidence and extent of length changes during implantation of endovascular grafts in a prospective study of patients undergoing endovascular abdominal aortic aneurysm (AAA) repair. METHODS: Data regarding the occurrence of intraoperative technical difficulties and device complications were recorded prospectively for the Vanguard or AneuRx self-expanding, bifurcated endovascular grafts in 64 patients (56 males; mean age 75 years). Graft length was measured in the sheath system before deployment and again immediately after deployment by fluoroscopic comparison to a graduated marking catheter. RESULTS: Graft shortening > or = 15 mm was documented in 22 (56%) of 39 Vanguard cases and 11 (44%) of 25 AneuRx endografts. Additional extension grafts were required to correct endoleak caused by inadequate graft length in 9 (14%) patients, but no conversion to open repair was necessary. CONCLUSIONS: There appears to be a high incidence of intraprocedural graft shortening with 2 current designs of self-expanding endoluminal grafts.

Aged↗
PubMed1999

Effects of prenatal ethanol exposure on hypothalamic-pituitary-adrenal responses to chronic cold stress in rats.

Animals prenatally exposed to ethanol typically exhibit hypothalamic-pituitary-adrenal (HPA) hyperresponsiveness to stressors. In contrast to previous studies that have investigated effects of prenatal ethanol exposure on HPA responses to acute or intermittent stressors, our study investigated HPA responses to a chronic continuous stressor, cold stress (4 degrees C for 0, 1, or 3 days). We tested the hypothesis that prenatal ethanol exposure would result in increased plasma corticosterone (CORT) and adrenocorticotropin (ACTH) responses and increased peptide [corticotropin-releasing factor and vasopressin] mRNA levels in the paraventricular nucleus (PVN) of the hypothalamus compared to that in control animals. In addition, CORT and ACTH responses were measured after exposure to an acute stressor (i.p. isotonic saline injection), superimposed during chronic cold exposure, to examine possible sensitization of the HPA response to the acute stress. Thus, blood samples were collected at the end of each of the three periods of cold exposure, either before (0 min) or 15 min after acute stress. The subjects were adult male and female Sprague-Dawley rat offspring from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment groups. Exposure to cold stress resulted in significant body weight loss in E males at 1 day and in both males and females of all prenatal treatment groups by 3 days of cold stress. Males in all prenatal groups also exhibited significant increases in adrenal weight:body weight ratios. Cold stress alone (0 min condition) increased CORT levels in E males and overall ACTH levels in E males and females compared to controls. ACTH levels were also higher overall in E compared to control males after acute stress (15 min condition). Sensitization of the CORT response to acute stress was observed in males but not females across all prenatal treatment groups. Corticotropin-releasing factor and vasopressin mRNA levels in the PVN were not significantly affected by prenatal treatment or chronic cold stress in either males or females. In contrast, both males and females displayed increases in PVN thyrotropin-releasing hormone (TRH) mRNA levels after cold stress. These data support and extend previous work demonstrating differential effects of prenatal ethanol exposure on HPA responsiveness of male and female offspring, and suggest that E males may be more vulnerable to the effects of chronic cold stress than E females.

Adrenocorticotropic Hormone↗
PubMed1999

Morphologic findings in explanted Hancock II porcine bioprostheses.

BACKGROUND AND AIM OF THE STUDY: Heart valve substitutes have been in use for over 30 years. Bioprosthetic heart valves have many advantages, but unfortunately suffer tissue degeneration and calcification. Many approaches, such as antimineralization treatment to prevent or delay these changes, have been tried. We present the morphologic findings from a series of Hancock II (antimineralization-treated) porcine bioprostheses. METHODS: Forty-five Hancock II porcine valve bioprostheses (16 mitral, 29 aortic) surgically explanted between March 1991 and December 1995 at the Toronto Hospital were analyzed for morphologic findings and causes of failure. The prostheses were implanted in 36 adults (mean age 55+/-14.7 years, range: 27 to 75 years) and had been in place between one month and 11 years (mean 5.1+/-3.3 years). RESULTS: Structural valve deterioration (SVD) characterized by tissue degeneration, calcification, cusp tears and increased stiffness, was the single most significant finding and cause of failure, affecting 56% of valves. Some degree of calcification was seen in 55% of prostheses, with severe calcification (grade 3 or 4) in 18%. Aortic bioprostheses showed more severe and earlier calcification than mitral ones (p = 0.03). Compared with the standard Hancock valve, the low incidence of significant calcification suggests a beneficial protective effect of antimineralization treatment. Severe pannus (grade 3 or 4) was seen in 60% of these prostheses. The pattern of pannus growth differs between mitral and aortic sites; mitral prostheses showed pannus on the flow and non-flow surfaces, often associated with cusp tears, mitral regurgitation and mitral leaflet preservation. A similar degree of pannus on aortic prostheses was invariably present on the flow surface and extended onto the valve cusps, leading to changes in the orifice which may cause clinical aortic stenosis. Infective endocarditis was seen in 15 prostheses (five mitral, 10 aortic) from 11 patients, and comprised the second most important cause of prosthesis failure. The risk of recurrent endocarditis was particularly high in patients who had infective endocarditis before valve replacement, even at five and six years post implantation. CONCLUSIONS: SVD is the major finding in explanted Hancock II bioprostheses and is associated with cusp tears and calcification. The incidence of tissue calcification appears lower at the mitral site. These findings suggest that the antimineralization treatment had some beneficial effect. Pannus associated with prosthesis dysfunction at the mitral sites is a prominent finding and on the non-flow surface may be related to the native mitral valve-conserving procedure.

Adult↗
PubMed1999

Glucocorticoid fast feedback is not altered in rats prenatally exposed to ethanol.

Animals exposed in utero to ethanol exhibit hormonal hyperresponsiveness to stressors in adulthood. One possible mechanism for this hyperresponsiveness is a deficit in negative feedback regulation of the hypothalamic-pituitary-adrenal axis. The present study tested the hypothesis that a deficit in the fast feedback time domain may play a role in the hormonal hyperresponsiveness in ethanol-exposed rats. Sprague-Dawley offspring from prenatal ethanol (E), pair-fed (PF), and ad lib-fed control (C) groups were tested in two experiments. Experiment 1 used a swim stress paradigm and tested animals at the trough of the corticosterone (CORT) circadian rhythm. Experiment 2 used ether stress and tested animals at the peak of the circadian rhythm. Animals were injected subcutaneously with CORT or saline and were immediately subjected to either a 5-min swim stress or a 1-min ether stress. Half the animals were terminated immediately after stress (5-min postinjection), and the rest were terminated 25 min later. Plasma levels of CORT and ACTH were assayed to determine whether E animals differed from control animals in showing a CORT-induced blunting of the ACTH response to the stressor, indicating alterations in fast feedback regulation. Injection of CORT significantly blunted the ACTH response to swim stress (experiment 1) in E, PF, and C females and males, compared with their saline-injected counterparts. There were no significant differences among groups. Similarly, CORT-injected males in E, PF, and C groups all exhibited a significantly blunted ACTH response to ether stress (experiment 2). CORT-injected C females also exhibited a significantly blunted ACTH response to ether stress, whereas E females showed an obvious CORT decrease that approached significance. However, PF females showed a clear deficit in fast feedback regulation. Together, these data suggest that: (1) CORT injection can serve as a fast feedback signal that can blunt the ACTH response to a stressor; and (2) prenatal ethanol exposure does not produce a deficit in hypothalamic-pituitary-adrenal feedback regulation in the fast feedback time domain.

Adrenal Cortex Hormones↗
PubMed1999

[Investigation on the adhesive properties of different cycle hepatoma cells].

OBJECTIVE: To study the adhesive forces of HTC cells on different concentration of artificial basement membrane (collagen IV coated)and synchronous G1&S phase HTC cells on a certain concentration of artificial basement membrane. METHODS: The adhesive forces of HTC cells were investigated by micropipette aspiration technique. The synchronous G1 and S phase cells were achieved through thymine-2-desoryriboside and cochicine sequential blockage method and double thymine-2-desoryriboside blockage method respectively. RESULTS: HTC cells with 72.10% of G1 phase and 98.94% of S phase were achieved through thymine-2-desoryriboside and cochicine sequential blockage method and double thymine-2-desoryriboside blockage method respectively. The adhesive force of HTC cells on artificial basement membrane was in direct proportion to the concentration of collagen IV. G1 phase HTC cells had higher adhesive forces than S phase cells. CONCLUSION: These studies suggested that the increase of basement membrane might be conducive to the chemotactic motion and adhesion of tumor cells; G1 phase cells were more capable of adhering to and getting through basement membrane than S phase cells, and reflected the differences of receptors between G1 phase cells and S phase cells.

Animals↗
PubMed1999

High level expression of the deleted and mutated urokinase-scFv fusion gene in Escherichia coli.

The fusion gene of a specific anti-human fibrinogen D-dimer scFv and low molecular weight single chain urokinase (scu-PA-32K) was restricted, spliced, and digested with exonuclease Bal31 to obtain a series of deletion mutants. Study of their expressions in E.coli revealed that the key sequence which reduced its expression level resided in the fragment from 841 to 851 bp, in which a tandem of AGG codons (encoding arginine, rarely used in E.coli) existed. By means of PCR mediated site-directed mutagenesis, we altered these two AGG codons to CGT codons, which could be more efficiently translated in E.coli, and the expression level turned out to be about 30% of the total bacterial proteins while that of the natural gene was only 2%-3%.

Base Sequence↗
PubMed1999

[Progress of speeding up measles control strategies in Anhui].

OBJECTIVE: To speed up measles control program. METHODS: Catching-up immunization campaigns on measles have been conducted among the children aged 1-6 years in three prefectures of Anhui by the end of 1997 and the measles surveillance system was established at the beginning of 1998. IgM antibody of measles and rubella was tested with ELISA and IgG antibody was examined with HI test. RESULTS: The positive rate of measles antibody among children was 100%, GMT increased from 1:18.97 to 1:43.45 after the campaigns. Measles cases in the three districts from January to June 1998 had a 87.71% decrease, comparing with the same period of 1997 with measles outbreak avoided. There were 105(58.01%) cases of measles with positive IgM and 32(17.68%) cases of rubella with positive IgM out of 181 testees having fever and rash illnesses. CONCLUSION: Results indicated the programs as catching-up immunization campaigns on measles and keeping high level of MV immunization, establishing measles surveillance system with improvement of its sensibility together with rubella control program all seemed to be important strategies in speeding up the positive outcome of measles control.

Child↗
PubMed1999

The role of plasminogen activator receptor in cancer invasion and dormancy.

Urokinase plasminogen activator receptor (uPAR) has been identified some 15 years ago and the anticipation was that its presence on the cell surface will provide a focus for anchoring uPA and possibly protect the enzyme from native inhibitors. The studies of the last decade have shown that uPA localized to the surface of cells by uPAR is indeed an important factor in the process of cancer cell invasion and metastasis. We developed a chick embryo model in which we showed that uPAR is crucial in invasion of stroma and in intravasation (breaching of the blood vessels walls). More recently and unexpectedly, uPAR--a protein anchored in the outer leaf-let of the plasma membrane, has been shown to initiate signal transduction events and affect cell migration. We have shown that uPAR co-associates with fibronectin binding integrin, alpha 5 beta 1, activates them and that this interaction leads to a greatly increased level of active ERK. When the association between uPAR and integrin or integrin and fibronectin are interrupted either by reduction of surface uPAR expression, or by other means, human carcinoma cells enter a state of protracted dormancy. We show that very high levels of active ERK are required to keep cancer cells proliferating in vivo.

Animals↗
PubMed1999

Interaction between gene p53 and oncogene mdm2 in human glandular lung cancer cell line GLC-82.

OBJECTIVE: To study the interaction between oncogene mdm2 and wp53 in human glandular lung cancer cell line GLC-82. METHODS: By lipofectamine-mediated DNA transfection, wp53 and mdm2 were transfected separately or co-transfected into GLC-82 cells via retrovival vector pDOR-neo, a carrier of wp53 and mdm2. RESULTS: The growth of GLC-82 cells was blocked and their DNA synthesis inhibited by wp53, its colony-forming rate in soft agar culture and the tumorigenicity in nude mice declined and mdm2 antagonized the function of wp53. CONCLUSION: After the recombinant vector pDOR-mdm2 was transfected into GLC-82 cells containing wp53, mdm2 partially deprives wp53 of its function of inhibiting the growth of GLC-82 cells.

Adenocarcinoma↗
PubMed1999

[Clinical analysis of 90 cases with endobronchial tuberculosis].

OBJECTIVE: To explore the clinical features and early definite diagnosis of endobronchial tuberculosis(EBTB). METHODS: Clinical symptoms, chest X-ray/CT manifestations and fiberoptic bronchoscopic findings of 90 cases with EBTB were analyzed. RESULTS: Main symptoms were as follows: cough in 75 cases, fever in 27, haemoptysis in 24, pleural pain in 18, dyspnea in 11, weight loss in 7, etc. Signs of airway obstruction were rare, localized wheezing was found only in 2 cases. 7 cases in chest X-ray were normal, and only 2 cases in CT were indicative of EBTB. Bronchoscopic results showed exudative lesions in 38% of the cases, granulomatous lesions in 9%, cicatricial lesions in 26%, ulcerative lesions in 17%, and normal-like demonstrations in 11%. Positive results were found in 8 out of 50 by sputum acid-fast staining, 73 out of 86 by bronchoscopic brushing smears, and 17 out of 56 by bronchial biopsies. CONCLUSIONS: The clinical features of EBTB are non-specific, and EBTB can not be excluded only by normal chest X-ray findings. In contrast to CT, bronchoscopy plays an important role in definite diagnosis of the disease. When patients with slight fever of unknown origin or respiratory symptoms do not respond to general treatment, EBTB should be suspected and early fibereoptic bronchoscopy be performed. Fiberoptic bronchoscopic brushing examination for acid-fast bacillus and bronchial biopsy are beneficial to rapid and definite diagnosis of EBTB.

Adolescent↗
PubMed1999

[Application of supercritical fluid extraction (SFE) on environmental analysis].

In this paper, publications from 1993 are classified according to the type of matrix from which the environmental analytes are extracted. Although the most applications of SFE are used for the solid, some analysts have concerned with aqueous and gaseous media. Various aspects of investigation of environmental potential carcinogen, such as, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, pesticides, phenols and other hazardous and toxic pollutants in environmental samples have been reviewed with 55 references. The coupled techniques of SFE have also been introduced in this paper.

Air Pollutants↗