Biomedical subjects

Z Yu

Publications and source records attributed to Z Yu.

At least 235 records · Page 13Linked to original sources

PubMed1997

Protein-tyrosine phosphatase SHP2 is positively linked to proteinase-activated receptor 2-mediated mitogenic pathway.

Proteinase-activated receptor-2 (PAR2), a new member of family of the G protein-coupled receptors, is activated by proteolytic cleavage of its extracellular amino terminus, a mechanism similar to that used by the thrombin receptor. It has been suggested that PAR2 has a potential role in the late phases of the acute inflammatory response and in tissue repair and/or skin-related disorders. Here we demonstrate that the agonist peptide (SLIGRL) stimulated c-fos-mediated mitogenic activation and tyrosine phosphorylation of cellular proteins. One of the tyrosine-phosphorylated proteins was identified as an Src homology-2 domain-containing protein-tyrosine phosphatase, SHP2. The stimulatory effect of the agonist peptide on early gene transcription was markedly blocked by pertussis toxin treatment whereas the induced tyrosine phosphorylation of SHP2 was completely abolished by the drug. More importantly, while expression of wild-type SHP2 enhanced the agonist-stimulatory mitogenic activity, overexpression of a catalytically inactive mutant of SHP2 strongly suppressed the stimulatory effect of the agonist peptide on both early gene transcription and DNA synthesis. These results suggest that SHP2 acts as a positive regulator linked to the PAR2-mediated mitogenic pathway coupled to a pertussis toxin-sensitive heterotrimeric G protein. Demonstration of SHP2 as a positive mediator in a G protein-coupled, receptor-mediated signaling adds to our understanding of the function of both SHP2 and PAR2 in the signaling pathway.

Animals↗

PubMed1997

Mechanism of colchicine impairment on learning and memory, and protective effect of CGP36742 in mice.

Fourteen days after hippocampal microinfusion with colchicine (COL), learning and memory ability of mice was significantly impaired, while glutamate (Glu), gamma-aminobutyric acid (GABA), Glu/GABAB and GABAB receptor levels in the cortex and/or the hippocampus were significantly changed. After treatment with a GABAB receptor antagonist, CGP36742, learning and memory impairment caused by COL could be significantly improved, and the above indices in brain regions reversed. These results suggest GABAB antagonists may have therapeutic value in the treatment of Alzheimer's disease.

Animals↗

PubMed1997

Determination of methotrexate and its metabolite 7-hydroxymethotrexate by direct injection of human plasma into a column-switching liquid chromatographic system using post-column photochemical reaction with fluorimetric detection.

A simple, sensitive and fully automated column-switching system by direct injection of plasma samples for determination of methotrexate and its metabolite 7-hydroxymethotrexate was developed. The system utilized a C8 alkyl-diol silica precolumn coupled with a LiChrospher RP-18 analytical column, followed by a photoreactor and fluorimetric detection. The photo-oxidative irradiation was accomplished at UV 254 nm in the presence of 0.1% hydrogen peroxide in the eluent. Studies showed that the fluorimetric response was influenced by the reaction time, the degree of the reactor's transparency and the choice of the working wavelengths. By optimizing the content of acetonitrile in the eluent, methotrexate can be separated from 7-hydroxymethotrexate completely. The method validation revealed quantitative recoveries (> or = 94%) with coefficients of variation < or = 4.4%. The limits of detection and quantitation for determination of methotrexate were 0.20 and 0.36 ng, respectively, corresponding to 2.0 and 3.6 ng/ml for an injection volume of 100 microliters. It was possible to enhance the sensitivity further by injecting larger plasma volumes, up to 500 microliters.

Antirheumatic Agents↗

PubMed1997

DeMonS--a new deconvolution method for estimating drug absorbed at different time intervals and/or drug disposition model parameters using a monotonic cubic spline.

DeMonS-a new numerical deconvolution method for estimating the amount of drug absorbed at different time intervals and/or drug disposition model parameters-is presented here. In DeMonS, the amount of drug absorbed at different time intervals and/or drug disposition model parameters are the unknown parameters to be calculated. The Fritsch-Butland non-decreasing cubic spline was constructed from the cumulative amount of drug absorbed-time data directly derived from the calculated amount of drug absorbed at different time intervals. The drug absorption rate, which is the derivative of this non-decreasing cubic spline, is therefore represented by a piecewise non-negative quadratic function. The drug concentrations were obtained by convoluting the drug absorption rate quadratic function with the drug disposition model function. The nonlinear optimization method with simple parameter bounds was used to estimate the optimal set of unknown parameters by minimizing the sum of squares of residuals between the observed and predicted drug concentrations. DeMonS has been applied to (i) the griseofulvin data for estimating drug absorbed at different time intervals when the drug disposition model parameters were determined separately from intravenous data, (ii) veralipride double-peak phenomenon data to estimate simultaneously the percentage of cumulative veralipride absorbed and the veralipride disposition model parameters without reference intravenous data, (iii) a comparative bioequivalence study of gastrointestinal therapeutic system (GITS) pseudoephedrine HCI (PeHCI) controlled-release oral dosage forms when the drug disposition model parameters were not available, and (iv) estimation of both drug disposition model parameters and the absorption rate of drug from Testoderm (testosterone transdermal system) in the presence of endogenous testosterone production. DeMonS was implemented using MATLAB and NAG MATLAB Toolbox, and is available for Windows 3.1.

Absorption↗

PubMed1997

Transdermal testosterone administration in hypogonadal men: comparison of pharmacokinetics at different sites of application and at the first and fifth days of application.

In this study of 13 hypogonadal men (25-69 years of age), three open-label, randomized treatments were administered to determine the pharmacokinetics of serum testosterone after application of an investigational testosterone transdermal system to the upper buttocks, upper arm, and back. Testosterone in vivo input kinetics profiles were estimated by DeMonS, a recently developed numerical deconvolution method for estimating drug absorption at different time intervals and/or drug disposition model parameters, and compared on the first and fifth days of system application. Area under the concentration-time curve from 0 to 27 hours (AUC0-27) values for testosterone after one-day applications to the upper buttocks, upper arm, and back were 9,560 ng.hr/dL, 8,651 ng.hr/dL, and 8,988 ng.hr/dL, respectively. Maximum observed concentration (Cmax) values were 482 ng/dL, 462 ng/dL, and 499 ng/dL, respectively. Serum testosterone concentrations were equivalent to each other, and Cmax values fell within the normal range. No drug accumulation was seen with repeated dosing over 5 days.

Administration, Cutaneous↗

PubMed1997

Testosterone pharmacokinetics after application of an investigational transdermal system in hypogonadal men.

This open-label, randomized, placebo lead-in, three-treatment crossover study in 19 hypogonadal men (27-82 years of age) evaluated dose proportionality of serum testosterone concentrations with application of one or two investigational transdermal testosterone systems for application to the arm or torso. Testosterone in vivo kinetics profiles were determined using DeMonS, a recently developed numerical deconvolution method that estimates drug absorption at different time intervals and/or drug disposition model parameters. After application of the investigational transdermal systems, the mean serum testosterone, dihydrotestosterone, estradiol, and free testosterone concentrations were elevated to normal levels. Treatment allowed approximation of the normal circadian pattern of endogenous testosterone secretion, and the increase in serum testosterone concentrations was proportional to the surface area of systems applied. The investigational transdermal system provided effective testosterone replacement therapy as judged by pharmacokinetic parameters.

Administration, Cutaneous↗

PubMed1997

Enhancement of immune response to naked DNA vaccine by immunization with transfected dendritic cells.

Immunization with plasmid DNA encoding various proteins promises to be a valuable vaccine approach especially if its immunogenicity could be optimized. In this study we show that the intramuscular delivery in dendritic cells (DC) of naked plasmid DNA encoding two proteins of herpes simplex virus (HSV) leads to the induction of significantly enhanced levels of resistance to viral challenge. Whereas DC transfected in vitro with DNA induced enhanced immunity, similarly transfected macrophage (M phi) populations lacked immunogenicity even though plasmid expression occurred in vitro. The enhanced immunity induced by DC-delivered DNA appeared to be associated mainly with an increased Th1 CD4+ T cell response. Our results add evidence that DC are the essential antigen-presenting cell types involved in immune responses to intramuscularly administered DNA vaccines.

Animals↗

PubMed1997

Structural characterization of human hemoglobin crosslinked by bis(3,5-dibromosalicyl) fumarate using mass spectrometric techniques.

Diaspirin crosslinked hemoglobin (DCLHb) was analyzed by mass spectrometric-based techniques to identify the protein modifications effected by the crosslinking reaction with bis(3,5-dibromosalicyl) fumarate. DCLHb consists of two principal components. These components were isolated by size-exclusion chromatography and identified by measurement of their molecular weight using electrospray mass spectrometry and subsequent peptide mass mapping and mass spectrometric sequence analysis of their individual digests. Three major RP-HPLC fractions were observed from the major hemoglobin in DCLHb. Their MWs matched the MW of heme, intact hemoglobin beta-chain, and two hemoglobin alpha-chains crosslinked by a fumarate moiety, respectively. The minor HPLC peaks of DCLHb were also separated, and characterized by mass spectrometric methods. These minor components revealed additional details of the structural nature of covalent modification of DCLHb.

Amino Acid Sequence↗

PubMed1997

The use of transgenic mice to generate high affinity p53 specific cytolytic T cells.

P53 is an attractive target immunotherapy because it is overexpressed in up to one half of all malignancies, and its overexpression often correlates with a worsened prognosis. We wanted to determine the feasibility of targeting wild-type epitopes p53 on human tumor cells. HLA A2.1 transgenic mice were immunized with the immunodominant wild-type p53 peptide epitopes, p53(149-157) and p53(264-272), along with a pan-DR helper epitope peptide in incomplete Freund's adjuvant (IFA). Twelve days later, splenocytes were harvested and stimulated with syngeneic blast cells that had been acid-treated to remove endogenous peptide and p53 peptide-pulsed. The responding cells were subsequently restimulated weekly with acid washed, peptide-pulsed Jurkat cells transfected with HLA A2.1. Peptide specific activity was tested in a chromium release assay. The resulting cytotoxic T cells (CTL) were cloned by limiting dilution. Peptide specific CTL were generated against both p53(149-157) and p53(264-272. Only p53(149-157) specific CTL were able to recognize and lyse cells that overexpressed endogenous p53. CTL clones derived from the p53(149-157) cell line demonstrated high affinity and specificity for p53(149-157) when presented by HLA A2.1+ cells. The p53(149-157) specific CTL were tested for specificity against a variety of cultured human cell lines. The CTL clones only lysed cells that overexpressed p53 in the context of HLA A2.1 and did not lyse cells with normal p53 expression or cells that lacked HLA A2.1 expression. This study demonstrates the possibility of targeting tumors, which overexpress p53, and raises the possibility transferring the high affinity, p53 specific T cell receptors from the murine CTL to human T cells.

Animals↗

PubMed1997

Suppression of pentylenetetrazol-induced seizures by carnitine in mice.

When ddY mice were pretreated with L-carnitine (5, 10 or 20 mmol/kg), clonic as well as tonic seizures induced by pentylenetetrazol (PTZ) were dose-dependently suppressed. A time/response study (PTZ was injected 1, 5, 15 or 30 min after L-carnitine) showed that the anticonvulsive effects were apparent when the interval between L-carnitine and PTZ administration was 15-30 min. Saline containing 43% sucrose prolonged the latency to the first clonic seizure but was less effective than 20 mmol/kg L-carnitine and did not suppress clonic or tonic seizures. Alterations in brain energy metabolites caused by PTZ including increase of lactate and decrease of ATP and phosphocreatine were also suppressed by L-carnitine. L-carnitine was more potent than D-carnitine in prolonging the latency to the first clonic seizure and in decreasing the frequency of clonic as well as tonic seizures. The anticonvulsive effects of L-carnitine in PTZ-induced seizures may be unrelated to the transport of long-chain acyl CoA since they were not interfered with by D-carnitine.

Animals↗

PubMed1997

Relationship between static chemical and cyclic mechanical fatigue in a feldspathic porcelain.

OBJECTIVES: The goal of this study was to determine if static chemical and cyclic mechanical fatigue are independent, or if they interact to produce greater than additive strength loss in a feldspathic porcelain. METHODS: A blunt indentation technique was used to investigate the response of a feldspathic dental porcelain to cyclic mechanical fatigue and static chemical fatigue. All specimens were fabricated in a dry inert environment and then mechanically fatigued by cyclic loading and strength-tested in dry inert nitrogenous, ambient or wet environments. A series of experiments were performed to evaluate the effects of chemical and mechanical fatigue, and their interaction on strength loss; to determine the effects of, and interaction between, the factors of cyclic fatigue environment and strength test environment on strength; to ascertain if the type of environment during strength testing influenced specimen strength; and to distinguish between chemical damage caused by exposure to moisture alone and stress corrosion damage resulting from the strength testing environment, using a pair of two-way analysis of variance, a single one-way analysis of variance and a t-test (p < 0.05). RESULTS: These experiments indicated that both static chemical fatigue and cyclic mechanical fatigue significantly reduced specimen strength, but they did not interact to produce greater than summative effects. It was also learned that chemical fatigue was not detected on initial exposure to moisture and that it occurred to a small extent during mechanical fatigue cycling, and primarily occurred during strength testing through a stress-corrosion phenomenon. Micrographs visually evaluated the effects of mechanical and chemical fatigue on surface contact damage. SIGNIFICANCE: As both static chemical and cyclic mechanical fatigue influenced porcelain strength, they should both be considered in future evaluations. However, because they largely acted independently, they can be studied separately.

Aluminum Silicates↗

PubMed1997

Alkylation of a catalytic aspartate group of the SIV protease by an epoxide inhibitor.

Specific irreversible inhibition of the SIV protease by FMOC-protected piperidine epoxide 1 involves alkylation of the protein. Tryptic digestion of the alkylated protein and mass spectrometric analysis of the peptides identify an active site aspartic acid (Asp-25) as the single residue that is alkylated. Computer modeling of 1 bound in the crystal structure of the SIV protease using DOCK 3.5 indicates that 1 has appropriate access to the active site. It is able to align in an orientation that allows a proton to be transferred to the epoxide from one of the catalytic aspartic acid groups in conjunction with nucleophilic attack on the epoxide of the carboxylate moiety of the second catalytic aspartic acid residue. Hydrophobic interactions are not optimal for this process due, in part, to the rigidity of the inhibitor ring system and the planar conformation of the amide. The combination of modeling with protein alkylation can provide insights into structural modifications of the inhibitor that may lead to improved inhibitory activity.

Alkylation↗

PubMed1997

A low molecular weight substance purified from human placenta inhibits cAMP-dependent protein kinase and activates protein kinase C.

We have purified from human placenta a low molecular mass substance that inhibits cAMP-dependent protein kinase and activates protein kinase C. This protein kinase regulator was purified in three steps: (1) homogenizing placentas in chloroform/methanol and extracting the regulator into water; (2) eluting a strong anion exchange high performance liquid chromatography (HPLC) column with a quaternary gradient; and (3) eluting a reversed-phase HPLC column with a binary gradient. The regulator was found to be highly purified by HPLC, thin-layer chromatography (TLC) and laser desorption ionization mass spectrometry with a molecular mass of 703 Daltons by the latter procedure. The physical and biochemical properties of this protein kinase regulator suggest that it is a phospholipid but it did not co-elute by HPLC or by TLC with any of the known phospholipid activators of protein kinase C.

Biological Factors↗

PubMed1997

Association of influenza virus NP and M1 proteins with cellular cytoskeletal elements in influenza virus-infected cells.

We have investigated the association of the influenza virus matrix (M1) and nucleoprotein (NP) with the host cell cytoskeletal elements in influenza virus-infected MDCK and MDBK cells. At 6.5 h postinfection, the newly synthesized M1 was Triton X-100 (TX-100) extractable but became resistant to TX-100 extraction during the chase with a t1/2 of 20 min. NP, on the other hand, acquired TX-100 resistance immediately after synthesis. Significant fractions of both M1 and NP remained resistant to differential detergent (Triton X-114, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate [CHAPS], octylglucoside) extraction, suggesting that M1 and NP were interacting with the cytoskeletal elements. However, the high-molecular-weight form of the viral transmembrane protein hemagglutinin (HA), which had undergone complex glycosylation, also became resistant to TX-100 extraction but was sensitive to octylglucoside detergent extraction, indicating that HA, unlike M1 or NP, was interacting with TX-100-insoluble lipids and not with cytoskeletal elements. Morphological analysis with cytoskeletal disrupting agents demonstrated that M1 and NP were associated with microfilaments in virus-infected cells. However, M1, expressed alone in MDCK or HeLa cells from cloned cDNA or coexpressed with NP, did not become resistant to TX-100 extraction even after a long chase. NP, on the other hand, became TX-100 insoluble as in the virus-infected cells. M1 also did not acquire TX-100 insolubility in ts 56 (a temperature-sensitive mutant with a defect in NP protein)-infected cells at the nonpermissive temperature. Furthermore, early in the infectious cycle in WSN-infected cells, M1 acquired TX-100 resistance very slowly after a long chase and did not acquire TX-100 resistance at all when chased in the presence of cycloheximide. On the other hand, late in the infectious cycle, M1 acquired TX-100 resistance when chased in either the presence or absence of cycloheximide. Taken together, these results demonstrate that M1 and NP interact with host microfilaments in virus-infected cells and that M1 requires other viral proteins or subviral components (possibly viral ribonucleoprotein) for interaction with host cytoskeletal components. The implication of these results for viral morphogenesis is discussed.

Animals↗

PubMed1997

[Effects of hypoxia and taurine on vasoconstriction peptides from cultured bovine pulmonary arterial endothelial cells].

OBJECTIVE: To study roles of endothein-1 (ET-1), angiotensin-II (AT-II) and endogenous digitalis-like factor (EDF) from cultured bovine pulmonary arterial endothelial cells (PAEC) in the pathogenesis of hypoxic pulmonary hypertension, and to evaluate whether Taurine is capable of protecting tissue cells from injury. METHODS: Culture of bovine pulmonary arterial endothelial cells and dot blot hybridization. RESULTS: PAEC cultured under hypoxia resulted in an increase in ET-1 mRNA expression. PAEC cultured under hypoxia induced increase in ET-1, AT-II and EDF release. By adding taurine to the culture medium, ET-1 mRNA express was inhibited. ET-1, AT-II and EDF release were inhibited. CONCLUSIONS: Expression of ET-1 mRNA and release of ET-1, AT-II and EDF from PAEC increased under hypoxia. Taurine can inhibit the hypoxia-induced expression of ET-1 mRNA of PAEC and reduce the release of ET-1, AT-II and EDF from PAEC.

Angiotensin II↗

PubMed1997

[Meningo-cerebral arteriovenous malformations].

22 patients with meningo-cerebral arteriovenous malformations, we treated in our hospital between 1990 and 1995. Clinical manifestations included headache, nausea, seizure, intracranial hemorrhage, and progressive hemispheric neurologic deficits. The niduses were extensive and had dual feeding from internal and external carotid arteries. All patients underwent endovascular treatment and 4 surgical operations. The curative effect was satisfactory. The clinical and angiographic characteristics were discussed.

Adolescent↗

PubMed1997

[Hodgkin's disease with concurrent infection of toxoplasmosis].

Hodgkin's disease (HD) is a specific type of malignant lymphoma characteristic of local and general lymphadenectasis. Aquired toxoplasmosis (AT) is one kind of lymphoadenopathy without fever and fatigue. When the two diseases coexist, clinical and pathological misdiagnosis may be made. This is the first male case of toxoplasmosis and Hodgkin's disease in China, diagnosed by surgical removal of the major part of the cervical and supraclavicular masses, detection of blood anti-toxoplasma gondii antibody, PCR analysis of toxoplasma gondii DNA, and pathological, ultrastructural and immunohistochemical studies of the tumour tissues. The patient treated by radiation and chemotherapy was abated.

Adult↗

PubMed1997

[Thin split thickness skin grafting double taken from avulsed skin in treatment for skin avulsion in children].

In order to utilize avulsed skin to cover skin defects, a new skin grafting technique, thin split thickness skin grafting double taken from avulsed skin, was used in 23 cases of severe skin avulsion. The skin grafts in profound layer were observed histologically. The results showed no difference between skin grafts in superficial layer and ones in profound layer, but the latter needed longer time to heal. Using this technique, we can obtain skin graft in double amount from avulsed skin.

Adolescent↗