Biomedical subjects

X D Liu

Publications and source records attributed to X D Liu.

At least 55 records · Page 3Linked to original sources

PubMed1997

Yeast metallothionein gene expression in response to metals and oxidative stress.

Metals and oxygen are chemically linked in biological systems. Metals and oxygen play important roles in enzymatic reactions, metabolism, and signal transduction; however, metals and oxygen react to form highly toxic oxygen-derived free radical species. In this review we focus on the use of yeast cells, as unicellular eukaryotic model systems, to conduct studies aimed at understanding fundamental mechanisms for the sensation and protective responses to toxic metals and oxygen-derived radicals via the activation of yeast metallothionein gene expression.

Antioxidants↗

PubMed1996

Oxidative stress induced heat shock factor phosphorylation and HSF-dependent activation of yeast metallothionein gene transcription.

Metallothioneins (MTs) are a class of low-molecular-weight, cysteine- rich metal-binding proteins that function in metal detoxification and oxidative stress protection. We demonstrate that transcription of the Saccharomyces cerevisiae MT gene CUP1 is strongly activated by the superoxide anion generator menadione. This activation is exacerbated in a strain lacking the gene encoding Co, Zn superoxide dismutase (SOD1). CUP1 transcriptional activation by oxidative stress is dependent on a functional CUP1 promoter heat shock element (HSE) and the carboxy-terminal trans-activation domain of heat shock transcription factor (HSF). Furthermore, protection against oxidative stress conferred by CUP1 in a (sod1)delta strain requires HSF-mediated CUP1 transcription. Although in response to heat, HSF-mediated CUP1 transcription and HSF phosphorylation are transient, both CUP1 gene expression and HSF phosphorylation are sustained in response to oxidative stress. Moreover, the patterns of tryptic phosphopeptides resolved from HSF derived from cells subjected to heat shock or oxidative stress are distinct. These results demonstrate that transcription of the S. cerevisiae metallothionein gene under conditions of oxidative stress is mediated by HSF and that in response to distinct activation stimuli, HSF is differentially phosphorylated in a manner that parallels metallothionein gene transcription.

Antibodies, Fungal↗

PubMed1996

Pharmacotherapeutic effects of toki-shakuyaku-san on leukorrhagia in young women.

Toki-shakuyaku-san is a traditional Chinese herbal prescriptions that is composed of 6 herbal plants, i.e., peony root, atractylodes lancea rhizome, alisma rhizome, hoelen, cnidium rhizome and Japanese angelica root. Administration with Toki-shakuyaku-san normalized irregular menstrual cycle, healed cervical pseudo-erosion and reduced leukorrhagia in young women who had insufficient luteal function.

Adult↗

PubMed1996

[Pharmacokinetic and electocardiographic study of oral verapamil sustained-release tablet in 10 Chinese volunteers].

Both verapamil pharmacokinetics and electrocardio graphic changes in 10 Chinese volunteers were studied after po 240 mg of verapamil sustained release tablet. A one-compartment model with zero-order absorption gave a better fitting to concentration--time data with values of r2 > 0.96. The main pharmacokinetic parameters obtained were: Tmax, 5.9 +/- 1.6 h; Cmax, 118.9 +/- 37.2 micrograms.L-1; T1, 5.4 +/- 1.5 h; k0, 30.5 +/- 17.5 micrograms.L-1.h-1; T1/2, 10.8 +/- 4.9 h; MRT, 15.4 +/- 3.2 h and AUC. 1.96 +/- 0.82 mg.h.L-1. There were significant prolongations of PR intervals after dose. Relationships between PR interval changes and plasma concentrations of verapamil were better fitted to sigmoidal model, with r2 > 0.98. The corresponding pharmacodynamic parameters were estimated. EC50, 64.6 +/- 16.9 micrograms.L-1, Emax, 54 +/- 11 ms and s, 1.68 +/- 0.66.

Adult↗

PubMed1996

Diltiazem concentrations in plasma vs PR intervals on electrocardiogram in 8 men.

AIM: To develop an acute tolerant model in describing relationship between diltiazem (Dil) concentrations in plasma and PR intervals on ECG in men. METHOD: Both plasma concentrations of Dil and changes of ECG were simultaneously determined after po Dil 90 mg in 8 men. RESULTS: A two-compartmental pharmacokinetic model with first-order input gave a good fitting for the plasma concentration of Dil. Corresponding pharmacokinetic parameters were estimated: t1/2 beta, 5.9 +/- 1.0 h; MRT, 15.9 +/- 1.0 h; t0, 0.38 +/- 0.07 h; tmax, 2.7 +/- 0.4 h, and Cmax, 161 +/- 60 micrograms.L-1. The good fittings for plasma concentration-effect data were obtained with tolerant model E = S x C/(1 + T/T50). The pharmacodynamic parameters were given as follows: S, 829 +/- 293 s.g-1.L; Kt0, 0.037 +/- 0.024 h-1 and T50, 10 +/- 4 micrograms.L-1. CONCLUSION: Relationship between Dil concentrations in plasma and PR interval changes in men after po 90 mg was described using an acute tolerant model.

Adult↗

PubMed1996

[Pharmacokinetics and disposition of triptonide in rats].

Triptonide, isolated from Tripterygium wilfordii Hook., was found to show significant antiinflammatory, immunosuppression and antitumor activities. A RP-HPLC method was applied to determine the plasma concentration of triptonide at different times in rats. Concentration-time curves after i.v., 0.7, 1.4 and 2.8 mg.kg-1 of triptonide were fitted to a two-compartment open model with T1/2 alpha of 0.167-0.195 h and T1/2 beta of 4.95-6.49 h. The area under curves (AUCs) were linearly related to the dosages (gamma = 0.9894). Systematic clearances (CLs) were independent of dosages. Mean residence time (MRT) of the three doses was 3.26-5.14 h by noncompartmental (the statistical moment method) analyses. The tissue distribution of triptonide in rats appeared to be wide throughout the body. The triptonide levels were high in the lung and liver, moderate in the heart, kidney, spleen and muscle and low in the testis, intestine and brain. Data of the urine and bile excretion indicated that only a small percent of unchanged triptonide was excreted. Plasma protein binding of triptonide rate was about 75%.

Animals↗

PubMed1996

[Two-site absorption model fits to pharmacokinetic data of gemfibrozil in man].

The plasma concentration-time data of gemfibrozil in 8 male subjects were determined after an oral dose of 600 mg. Two-peak concentrations in plasma were observed. A kind of one-compartment model with two-sites of drug absorption was proposed and used to fit these data. A good agreement between observed and predicted data was found in all subjects with correlation indexes (gamma 2) > 0.99. The corresponding pharmacokinetic parameters were estimated as follows: Tmax1, 1.10 +/- 0.46 h; Tmax2, 2.60 +/- 0.73 h; Cmax1, 13.62 +/- 4.30 micrograms.ml-1; Cmax2, 17.22 +/- 3.83 micrograms.ml-1; T1, 0.06 +/- 0.06 h; T2, 1.42 +/- 0.57 h and T3, 1.79 +/- 0.60 h.

Adult↗

PubMed1994

[Familial cervical lung hernia: a report of 4 cases in a family].

In this study 4 members of three generations in one family suffered cervical lung hernia was reported. In this 4 cases, there were 2 males, and 2 females, and 3 cases found on the right side, 1 on the left side of neck. Their ages were 55, 32, 5 and 6, respectively. X-ray examinations and CT scan showed typical characteristics. Chromosome examination analysis with high resolution G band was done for 2 of them, no abnormal changes were found. From pedigree analysis we think this type of disease is an autosomal dominant hereditary disease. This familial abnormality has not been found in medical literature, and so we suggest a namelity "Familial cervical lung hernia".

Adult↗

PubMed1993

Soluble stem cell factor in human serum.

Stem cell factor (SCF) is a recently described factor active in the early stages of hematopoiesis. It can exist in membrane-bound form and in proteolytically released soluble form. The levels and nature of SCF in human serum are described. As determined by an enzyme-linked immunosorbent assay performed for 257 samples, SCF level in serum averaged 3.3 +/- 1.1 ng/mL. The serum SCF was partially purified by immunoaffinity chromatography and analyzed by glycosidase treatments in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. The results show that the SCF has N-linked and O-linked carbohydrate and corresponds to the soluble form, at or about 165 amino acids in length. The findings suggest functional importance for soluble SCF in humans.

Adult↗

PubMed1992

Preservation and visualization of molecular structure in detergent-extracted whole mounts of cultured cells.

Today's electron microscopes have a resolution sufficient to resolve supramolecular structures. However, the methods used to prepare biological samples for electron microscopy often limit our ability to achieve the resolution that is theoretically possible. We use whole mounts of detergent-extracted cells grown on Formvar-coated gold grids as a model system to evaluate various steps in the preparation of biological samples for high resolution scanning electron microscopy (SEM). Factors that are important in determining the structure and composition of detergent-extracted cells include the nature of the detergent and the composition of the extraction vehicle. Chelation of calcium is extremely important to stabilize and preserve the cytoskeletal filaments. We have also demonstrated both morphologically and by gel electrophoresis that treatment of cells with bifunctional protein crosslinkers before or during extraction with detergent can significantly enhance the preservation of both proteins and supramolecular structures. The methods used to dry samples are a major determinant of the quality of structural preservation. For cytoskeletons freeze-drying (FD) is superior to critical point-drying (CPD), one reason being that CPD samples have to be dehydrated, thereby causing more shrinkage as compared to FD samples. The high pressures to which samples are exposed during CPD may also cause increased shrinkage, and water contamination during CPD causes severe structural damage. We have obtained the best structural preservation of detergent-extracted and fixed cells by manually plunging them into liquid propane and drying over night in a freeze-dryer. The factor that most limits achievement of high resolution in SEM is the metal coat, which has to be very thin, uniform, and free of grain in order not to hide structures or to create artifactual ones. We have found that sputter-coating with 1-3 nm of tungsten (W) or niobium (Nb) gives extremely fine-grained films as well as satisfactory emission of secondary electrons. These samples can also be examined at high resolution by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The best preservation and visualization of supramolecular structures have been obtained using cryosputtering, in which the samples are freeze-dried and then sputter-coated within the freeze-dryer while still frozen.

Animals↗

PubMed1992

Prediction of N-acetylprocainamide disposition kinetics in rat by combination of gamma variate and physiological pharmacokinetic model.

Clearances and tissue/blood drug concentration ratios of N-acetylprocainamide (NAPA) in rats were determined. The clearances of NAPA in rat blood, liver, and kidney were 13.1, 4.88, and 8.24 ml.kg-1.min-1, respectively. Disposition kinetics of NAPA in rats was predicted with combination of gamma variate and physiological pharmacokinetic model. Equation for estimating the concentration of NAPA in rat blood following iv NAPA 40 mg.kg-1 was C = 55.06t(-0.220) exp(-0.00713t). Using r2 value as a criterion, we found a good agreement between predicted and observed concentrations in blood, lung, small intestine, heart, brain, and skin.

Acecainide↗

PubMed1991

Host associations and seasonal abundance of immature Ixodes persulcatus (Acari: Ixodidae) in a Lyme-disease-endemic area in China.

Ticks of nine small mammal species were studied in an area of endemic Lyme disease in Hailin County, Heilongjiang Province, from 1 May to 10 October 1986. The bulk (93%) total small mammal captures were Apodemus speciosus (45%), Clethrionomys rufocanus (31%), A. agrarius (11%) and Eutamias sibiricus; (5%): these host species accounted for 97% of the 162 ticks collected. Ixodes persulcatus Schulze were most abundant on E. sibiricus (0.64 larvae and 0.08 nymphs/squirrel), and less abundant on A. agrarius (1.16 larvae/mouse), A. speciosus (0.38 larvae/mouse) and C. rufocanus (0.37 larvae and nymphs/vole). The seasonal abundance pattern of larval I. persulcatus on four small mammal species appears as a bimodal peak (June and September), but nymphal I. persulcatus has a monomodal peak during spring. The prevalence of immature I. persulcatus on four small mammal species may play an important role in the epidemiology of Lyme disease in Hailin County.

Animals↗

PubMed1991

[Simultaneous predictions of disposition kinetics of procainamide and its metabolite N-acetylprocainamide in rat by a physiological pharmacokinetic model].

Disposition kinetics of procainamide (PA) and its metabolite N-acetylprocainamide (NAPA) in rats was simulataneously predicted by a physiological pharmacokinetic model. The parameters, such as clearances in kidney and liver and tissue/blood concentration ratios, which were needed for simulations, were determined. The estimated clearances of PA in rat blood, kidney and liver were 47. 28, 13. 56 and and 33. 71 ml.kg-1.min-1, respectively. Tissue/blood drug concentration ratios were obtained after iv administration according to Gallo's method and demonstrated that heart, liver, kidney, muscle and small intestine have greater affinity for PA than do blood components. The concentrations of PA and NAPA in rat tissues following iv administration of PA.HCl 75 mg/kg were predicted and compared with observed values. The results showed that a good agreement between predictions and observed data was found in most of rat tissues. Concentrations of PA and NAPA in plasma of man, based on scaling-up of kinetics of PA and NAPA from rat to man, was also simulated.

Acecainide↗

PubMed1990

Epidemiological and aetiological evidence for transmission of Lyme disease by adult Ixodes persulcatus in an endemic area in China.

Involvement of adult Ixodes persulcatus ticks in the transmission of Lyme disease in Hailin County, Heilongjiang Province, China, is reported. In 1986 from April through August adult I. persulcatus was the dominant tick in this endemic area with an infection rate of 43% for the Lyme disease spirochaete, Borrelia burgdorferi. The incidence of Lyme disease cases presenting the symptom of erythema chronicum migrans (ECM) within this area was correlated with the seasonal abundance of adult I. persulcatus and the number of people bitten by ticks. The frequency of ECM formation in all age groups varied and was associated with the frequency of tick bites. In addition, a strain of B. burgdorferi was isolated from a pool of six female I. persulcatus collected from this area. We demonstrate that the seasonal abundance of adult I. persulcatus and its frequent attachment to humans result in the spring and summer transmission of Lyme disease in this endemic area. The role of immature I. persulcatus in Lyme disease transmission is apparently minimal.

Adolescent↗

PubMed1990

[Effect of Chinese medicinal herbs on sperm membrane of infertile male].

The authors carried on the quantitative analysis of fluorescence polarization degree and fluorescent intensity on wheat germ agglutinin (WGA) receptor in sperm membrane surface and protein macromolecule 1-Anilinonaph thalene-8-suphonic acid salt (1,8-ANS) of sperm membrane to the patients with infertility and adult male with normal fertility, with the method of ultraviolet microspectrofluorometer (SMP, type: 05, made in West Germany). The results were as follows: the patient's WGA receptor in sperm membrane surface was decreased (P less than 0.001), and the 1, 8-ANS of fluorescent intensity in hydrophobic area of protein macromolecule of sperm membrane was increased (P less than 0.05). After the treatment of Shenjing Zhongzitang, WGA receptor was increased obviously and 1, 8-ANS of fluorescent intensity was changed to be almost normal. It showed that the Chinese medicinal herbs mentioned above have certain influence upon the constitution of WGA receptor and protein macromolecule of sperm membrane.

Anilino Naphthalenesulfonates↗

PubMed1989

[Spectrophotometric determination of complex formation constants of naproxen with caffeine, nicotinamide and salicylic acid in aqueous solution].

The interaction between water insoluble drug naproxen with caffeine, nicotinamide and salicylic acid in aqueous solutions were determined by spectrophotometry. Naproxen was found to form 1:1 molecular complex with these substances. The complex formation constants were determined by spectrophotometry at room temperature. The thermodynamic functions associated with complexation of naproxen-drugs were also evaluated. It may be concluded that the complex formation may be attributed to hydrogen bonding since enthalpy changes were shown to be a few KJ.mol-1.

Caffeine↗

PubMed1989

Problems associated with the preparation of whole mounts of cytoskeletons for high resolution electron microscopy.

The resolution currently available in both transmission and scanning electron microscopes is theoretically adequate to visualize the organization of the cytoskeleton at the supramolecular and macromolecular levels. However, achieving this resolution in practice requires that the methods used to prepare the specimens both preserve the structures of interest and render them visible for observation in the microscope without obscuring or altering them. In this paper we discuss our own and others efforts to develop methods to overcome several problems associated with preparing whole mounts of cytoskeletons for observation by electron microscopy. These problems include: controlling the degree to which cellular components are extracted; the effects of osmium tetroxide on the cytoskeleton; controlling and recognizing shrinkage and drying artifacts; the choice of a method of visualization; deposition of grain-free ultrathin films of metal; and interpreting the results. The standard procedure which we currently use consists of the following steps: growing cells on carbon-stabilized Formvar-coated gold electron microscope grids; extracting in 0.5% Triton X-100 detergent in a microtubule stabilizing buffer; postfixing in 2.5% glutaraldehyde in stabilizing buffer; freeze-drying; magnetron sputter-coating with 1.5 nm of tungsten; and observation by TEM, SEM, or STEM. Cytoskeletons prepared in this manner contain over 100 polypeptides and are composed of a complex three dimensional meshwork of clean, uniform filaments, the smallest of which are 7 nm in diameter. A structure resembling the microtrabecular lattice is present only if the cells are prefixed with a relatively long bifunctional protein crosslinking reagent prior to extraction with detergent.

Animals↗

PubMed1988

Clinical manifestations and epidemiological characteristics of Lyme disease in Hailin county, Heilongjiang Province, China.

Clinical manifestations and epidemiological characteristics of Lyme disease in Hailin county, Heilongjiang Province, China have been reported. The clinical picture of erythema chronicum migrans (ECM) is variable. ECM in the form of annular erythematous patch is uncommon. It is an extensive and indurated lesion. In some instances, a vesicle or necrosis appears in the center of the lesion. Secondary erythema may present in some patients. The neurologic abnormalities consist of meningitis, facial palsy, and polyneuritis. Cardiac abnormalities are rare. In addition, there were cases with lymphadenosis benigna cutis (LABC), which had heretofore only been reported in Europe. The attack rate of ECM is 8.4%. There was a significant sex difference, and most cases occurred in May and June. All patients had a history of tick bite. The prevalence rates of neurologic abnormalities and arthritis were 4.6% and 6.6%, respectively. Three strains of spirochete that are closely related to Borrelia burgdorferi were isolated from Ixodes persulcatus ticks and facial palsy patients. From the above results it is concluded that a focus of Lyme disease exists in this region.

Animals↗