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Biomedical subjects

Z Li

Publications and source records attributed to Z Li.

At least 469 records · Page 26Linked to original sources
PubMed2000

Structure-function analysis of a lupus anti-DNA autoantibody: central role of the heavy chain complementarity-determining region 3 Arg in binding of double- and single-stranded DNA.

To determine the contribution of the somatic point mutations and that of the complementarity-determining region (CDR)3 Arg to DNA binding, we engineered the germline V(H) and V(kappa) gene revertant and site-mutagenized the CDR3 Arg residues of the mutated and "antigen-selected" mAb 412.67. This anti-DNA autoantibody was derived from B-1 cells of a lupus patient and bore two H-CDR3 Arg, Arg105 and Arg107, encoded by N segment additions, and one kappa-CDR3 Arg, Arg97, resulting from a point mutation (Kasaian et al. 1994. J. Immunol. 152: 3137-3151; Kasaian et al. 1995. Ann. N.Y Acad. Sci. 764: 410-423). The germ-line revertant bound double-stranded (ds) DNA and single-stranded (ss) DNA as effectively as its wild-type counterpart (relative avidity: 6.4x10(-7) and 9.9x10(-9) vs. 6.7x10(-7) and 9.1 x10(-9) g/microl), raising the possibility that an antigen other than DNA was responsible for the selection of the mAb 412.67 V(H) and V(kappa) point mutations. H-CDR3 Arg105 and Arg107 were both required for dsDNA binding, but either Arg105 or Arg107 was sufficient for ssDNA binding. The central role of Arg105 and Arg107 in DNA binding reflected their solvent-exposed orientation at the apex of the H-CDR3 main loop. Consistent with its inward orientation afar from the antigen-binding surface, the kappa-CDR3 Arg97 played no role in either dsDNA or ssDNA binding.

Amino Acid Sequence↗
PubMed2000

Role of alpha-1 adrenoceptor subtypes mediating constriction of the rabbit ear thermoregulatory microvasculature.

An acute in vivo preparation of the microvasculature of the rabbit ear was used to evaluate the functional role of alpha1 (alpha1)-adrenoceptor subtypes in thermoregulatory microcirculation. The effect of alpha1-adrenoceptor subtype blockade on phenylephrine-induced vasoconstriction was assessed with the alpha1A, alpha1B, and alpha1D-adrenoceptor-selective antagonists 5-methyl-urapidil (10(-8) M), chloroethylclonidine (10(-5) M), and 8-[2-[4(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspirol[4.5]deca ne-7,9-dione dihydrochloride (BMY7378) (10(-6) M), respectively. The results demonstrated that pretreatment of the ear microvasculature with 5-methyl-urapidil or BMY7378 shifted the phenylephrine concentration-response curve rightward and significantly changed the log of the phenylephrine concentration, causing half-maximum stimulation (EC50) in arterioles (p < 0.05). BMY7378 shifted the phenylephrine concentration-response curve of the arteriovenous anastomoses about 100-fold rightward (p < 0.05). All three alpha1-adrenoceptor antagonists eliminated the vasoconstrictive effects of phenylephrine on venules. The results indicate that the ear microvasculature has a heterogenous distribution of alpha1-adrenoceptor subtypes. The alpha1A and alpha1D-adrenoceptor subtypes appear to have a greater influence on constrictive function in arterioles, whereas the alpha1D-adrenoceptor is the dominant constrictor of arteriovenous anastomoses. In general, the alpha1-adrenoceptor does not play a major vasoconstrictor role in venules. Chloroethylclonidine, an irreversible alpha1B-adrenoceptor antagonist, induced contractile responses in the ear microvasculature, probably due to its alpha2-adrenoceptor agonist effects. This study extended our understanding of the adrenergic receptor control mechanisms of a cutaneous thermoregulatory end organ characterized by two parallel perfusion circuits providing nutritional and thermoregulatory functions.

Animals↗
PubMed2000

CD34 splice variant: an attractive marker for selection of gene-modified cells.

This study presents a promising selection system for gene-modified cells other than human hematopoietic progenitor and endothelial cells based on transgenic expression of human CD34. Three retrovirally transduced variants of CD34 were compared, differing in the length of their cytoplasmic domains. These were the full-length transmembrane protein (flCD34), a truncated form (tCD34) that is found as a naturally occurring splice variant and has a partial deletion of the cytoplasmic domain for signal transduction, and an engineered variant which is completely deprived of its cytoplasmic tail (dCD34). All three variants allowed selection of gene-modified cells using commercially available immunoaffinity technology. However, examination by flow cytometry as well as by Southern, Northern, and Western blot revealed that dCD34, as opposed to tCD34, is not stably anchored in the membrane and thus is expressed at low levels on the surface of transduced cells. Therefore, tCD34 was chosen as the more promising candidate for a clinically applicable cell surface marker. We show that gene-modified human primary T lymphocytes expressing tCD34 can be enriched to high purity (>95%) using clinically approved immunoaffinity columns. In addition, we demonstrate the utility of tCD34 for surface marking of murine hematopoietic cells in vivo, including primary T lymphocytes detected 9 weeks after bone marrow transplantation.

Animals↗
PubMed2000

Bovine calcined bone for the repair of radial defect in a rabbit model.

In order to investigate the bovine calcined bone's ability of repairing segmental bone defect and seek a new artificial bone substitute material, the bovine calcined bone (450 degrees C, 32 h) was implanted into the 10-mm middle radial defect of rabbits with tricalcium phosphate ceramics as the control. By using the methods of histology, radiology and biomechanics their osteogenic ability were measured. It was found that the bovine calcined bone's ability of repairing bone defect was better than that of tricalcium phosphate ceramics. The histological Nilsson's scores at 3rd, 5th, 9th week after operation were significantly increased (P < 0.01). At 12th week after operation the bending strength of radius in experimental group was much higher than that of control group and turned normal. It was suggested that bovine calcined bone is an ideal artificial bone substitute material with good ability of repairing segmental bone defect and some degree of mechanical strength.

Animals↗
PubMed2000

Observation of T lymphocyte subsets in the liver of patients with advanced schistosomiasis and advanced schistosomiasis accompanied with hepatitis B.

T lymphocyte subsets in the liver were detected by Avidin-Biotin Complex (ABC) assay in 22 patients with advanced schistosomiasis (AS) and 5 cases of AS accompanied with hepatitis B. T lymphocytes in the liver of AS patients were distributed in the peripheral layer of egg granuloma or the area near eggs in non-granuloma. No infiltrative T lymphocytes were observed in area with extensive fibrosis. There was infiltration of many T cells in the portal tract, piecemeal and focal necrosis area as well as in hepatic sinus in AS patients accompanied with hepatitis B. CD8+ T cells (suppressor/cytotoxic T cells, Ts/Tc) in the liver were predominant in the two groups. In AS patients, marked hepatic fibrosis, a small number of T cell infiltration and slight hepatocellular degeneration and necrosis were observed. However, obvious hepatocellular degeneration and necrosis were seen in AS patients accompanied with hepatitis B, and 3 cases of them developed active liver cirrhosis. The results indicated immune response was weak in the liver in AS patients and Ts cells might be predominant in the subset of CD8+ T lymphocytes. Cellular immune response was relatively strong in AS patients accompanied with hepatitis B and the infiltrative CD8+ T lymphocytes might be mainly Tc cells.

Adolescent↗
PubMed2000

The Myxococcus xanthus wbgB gene encodes a glycosyltransferase homologue required for lipopolysaccharide O-antigen biosynthesis.

Myxococcus xanthus is a gram-negative soil bacterium that initiates a complex developmental program in response to starvation. A transposon insertion (Tn5-lac omega109) mutant with developmental deficiencies was isolated and characterized in this study. A strain containing this insertion mutation in an otherwise wild-type background showed delayed developmental aggregation for about 12 h and sporulated at 1-2% of the wild-type level. Tn5-lac omega109 was found to have disrupted the M. xanthus wbgB gene, which is located 2.1 kb downstream of the M. xanthus lipopolysacharide (LPS) O-antigen biosynthesis genes wzm wzt wbgA. The deduced polypeptide sequence of WbgB shares significant similarity with bacterial glycosyltransferases including M. xanthus WbgA. The wbgB::Tn5-lac omega109 mutant was found to be defective in LPS O-antigen synthesis by immunochemical analysis. Further mutational analysis indicated that the defects of the wbgB::Tn5-lac omega109 mutant were not the result of polar effects on downstream genes. Various motility assays demonstrated that the Tn5-lac omega109 mutation affected both social (S) and adventurous (A) gliding motility of M. xanthus cells. The pleiotrophic effects of wbgB mutations indicate the importance of LPS O-antigen biosynthesis for various cellular functions in M. xanthus.

Amino Acid Sequence↗
PubMed2000

In-vitro selection of Vitis vinifera 'Chardonnay' with Elsinoe ampelina culture filtrate is accompanied by fungal resistance and enhanced secretion of chitinase.

Proembryogenic masses of grapevine (Vitis vinifera L.) 'Chardonnay' (clone 02Ch) were exposed to the culture filtrate of Elsinoe ampelina (deBary) Shear, the causal agent of anthracnose disease. After four or five cycles of recurrent in-vitro selection with medium containing 40% fungal culture filtrate, putative resistant lines RC1 and RC2 respectively, were established. The selected lines inhibited the growth of E. ampelina and Fusarium oxysporium (Schlecht.) (isolated from watermelon) in a dual-culture assay and reduced the growth of mycelium on a conditioned-medium test, thus suggesting the involvement of extracellular compounds in resistance. Sodium dodecyl sulfate-polyacrylamide (SDS-PAGE) gel electrophoresis of extracellular proteins from spent suspension-culture medium showed enhanced secretion of new proteins by selected lines. A 36-kDa protein was immunodetected by a chitinase antiserum. This chitinase continued to express constitutively in differentiated somatic embryos and also in the intercellular fluids of plants regenerated from the selected lines. Somatic embryos from selected lines grew uninhibitedly in a medium containing 40% fungal culture filtrate, whereas non-selected (control) somatic embryos became necrotic and died within a few days. Plants regenerated from selected lines exhibited resistance to infection by E. ampelina in both greenhouse tests and detached leaf bioassays. Results suggest that embryogenic cells can be selected for resistance following in-vitro selection, resulting in resistant plants. Whether or not resistant cells pre-existed in the original embryogenic culture or were induced by the selection pressure could not be determined.

Ascomycota↗
PubMed2000

The relationship between apoptosis and splenocyte depletion in rats following ethanol treatment.

Splenocyte depletion observed in chronic ethanol-treated rats (ETRs) was studied in relation to apoptosis. The rats were fed with ethanol in a Liber-DeCarli liquid diet (36% of total calories as ethanol) for 7 weeks. Spleens of ETRs and control rats were examined by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method, immunohistochemistry using anti-rat p53 and RM4 (specific for macrophages) monoclonal antibodies, and transmission electron microscopy (TEM). The splenic white pulp in ETRs decreased in size and showed a moth-eaten appearance because of the severe depletion of splenocytes. Most TUNEL-positive cells aggregated into clusters or nests and were not isolated in the white pulp of ETRs. The site of RM4 immunoreactivity was consistent with that of clusters of TUNEL-positive cells. The p53 immunoreactivity was observed in apoptotic splenocytes that were isolated or phagocytosed by macrophages. TEM study revealed the increase in tingible body macrophages phagocytosing apoptotic splenocytes in their cytoplasm in ETRs. Chronic ethanol intake certainly induces apoptosis in splenic white pulps, and tingible body macrophages act as both sentinels and scavengers of apoptotic splenocytes expressing p53.

Animals↗
PubMed2000

Hepatic microsomal and peroxisomal docosahexaenoate biosynthesis during piglet development.

The roles of peroxisomes and microsomes on the biosynthetic pathway for docosahexaenoic acid (DHA) from alpha-linolenic acid (ALA) were investigated. Microsomes and peroxisomes were prepared from livers of fetal and neonatal piglets by a combination of differential and gradient layer centrifugation. Microsomes, peroxisomes, and combined cell fractions were incubated with [13C-U]18:3n-3. The [M] and [M + 18] isotopomers of the fatty acids in the long-chain polyunsaturated fatty acid (LCPUFA) n-3 pathway were detected by gas chromatography-mass spectrometry. The quantity of each fatty acid was determined by gas chromatography, and synthesis of each fatty acid was calculated for a 30-min period. Synthesis of DHA was not detected in combined fetal liver fractions. The data suggest that DHA in the fetus is probably supplied from maternal sources through the placenta. In either singly incubated microsomal or peroxisomal preparations from neonatal livers, no DHA synthesis was detected. After combination of the microsomal and peroxisomal fractions, DHA synthesis was evident and increased rapidly between birth and 2 wk of age. This is the first demonstration of the entire biosynthetic LCPUFA n-3 pathway in subcellular organelles starting from isotopically labeled ALA to the final product, DHA, with all the intermediates present and isotopically labeled. The primary importance of the data is that it unequivocally demonstrates that peroxisomes are required for biosynthesis of DHA from ALA.

Animals↗
PubMed2000

Distribution of serum apolipoproteins A-I and B and lipoprotein(a) in European elderly. The SENECA study.

The purpose of this study is to describe sex and geographic differences in apolipoproteins (apo) A-I and B and lipoprotein(a) [Lp(a)] concentrations in elderly Europeans. Subjects were 2164 elderly participants of the SENECA study from different regions of Europe. Sera for apo A-I, apo B, and Lp(a) measurement were available for 1703 individuals. In men, mean values ranged from 1.38 to 1.79 g/l for apo A-I, 1.03-1.36 g/l for apo B, and 0.26-0.67 g/l for Lp(a). In women, mean values ranged from 1.54 to 1.98, 1.20-1.51, and 0.26-0.68 g/l for apo A-I, apo B, and Lp(a), respectively. A comparison of northern (Norway, Denmark, Netherlands), middle (France, Switzerland), and southern (Portugal, Spain, Italy, Greece) communities showed a less atherogenic profile in the south, including lower LDL cholesterol, apo B, TC/HDL cholesterol ratio, and apoB/apo A-I ratio. Men, but not women, also had significantly higher HDL cholesterol and apo A-I concentrations in the South. Paradoxically, Lp(a) concentrations were generally high among all elderly and were significantly higher in the southern communities. These data show that the elderly in Europe are very heterogeneous with respect to plasma lipoproteins, including apo A-I, apo B, and Lp(a).

Aged↗
PubMed2000

Dietary cholesterol increases the susceptibility of low density lipoprotein to oxidative modification.

Evidence suggests that oxidative modification of low density lipoprotein (LDL) occurs in vivo, increasing the atherogenecity of the particle. A total of 13 subjects (age range 46-78 years) with an LDL cholesterol concentration >3.36 mmol/l consumed each of four diets for 32-day periods. The diets contained 30% energy as fat of which 2/3 was either corn oil or beef tallow with and without 115 mg/4.2 MJ of supplemental cholesterol in the form of cooked egg yolk. The susceptibility of LDL to oxidation was assessed during a challenge with hemin and hydrogen peroxide, and results are expressed as lag time to oxidation in minutes. Addition of moderate amounts of cholesterol to either the corn oil or beef tallow enriched diet resulted in increased susceptibility of LDL to oxidation (decreased lag time): 69+/-22 min versus 96+/-24 min in the corn oil diet with versus without supplemental cholesterol, respectively, P = 0.006; 82+/-20 min versus 96+/-26 min in the beef tallow diet with versus without supplemental cholesterol, respectively, P = 0.025. A stepwise equation indicated that as plasma oleic acid concentrations increased and/or linoleic acid concentrations decreased, lag time increased (decreased susceptibility to oxidation), whereas as dietary cholesterol concentrations increased, lag time decreased (increased susceptibility to oxidation). In conclusion, these data suggest that addition of a moderate amount of dietary cholesterol to a reduced fat diet rich in polyunsaturated or saturated fatty acids increased the in vitro susceptibility of LDL to oxidation.

Aged↗
PubMed2000

Antagonistic effect of pseudoginsenoside-F11 on the behavioral actions of morphine in mice.

The antagonistic effect of pseudoginoside-F11 (PF(11)) on the various actions of morphine was studied in mice. The results demonstrated that PF(11), at the doses of 4 and 8 mg/kg, PO, significantly inhibited morphine (10 mg/kg, SC)-induced memory impairment in the Morris water maze test. PF(11), at 4 mg/kg, PO, did not influence conditioned place preference per se, yet markedly blocked the conditioned place preference to morphine. PF(11), at the doses of 4 and 8 mg/kg, PO, also significantly antagonized morphine (5 mg/kg, SC)-induced analgesia tested by tail pinch method. PF(11), at 4 mg/kg, PO, did not influence locomotor activity per se, yet inhibited the development of the reverse tolerance, as shown by the increase in locomotor activity, to morphine. At the doses of 4 and 8 mg/kg, PO, PF(11) significantly antagonized the development of analgesia tolerance to morphine in the tail pinch test. Thus, the above results demonstrate for the first time that PF(11) can antagonize some actions of morphine. However, the mechanism of action of PF(11) merits further evaluation.

Analgesia↗
PubMed2000

Laboratory and field studies of an antigen capture ELISA for bluetongue virus.

An improved bluetongue antigen capture ELISA (BTACE) technique was evaluated for its ability to detect the full range of 24 bluetongue (BLU) serotypes. The BTACE detected all 24 serotypes in cell culture fluids, including eight serotypes where the representative strains originated from both Australia and also from the South African reference collection. The amount of infectious virus required to obtain a positive BTACE result varied between 100-1000 TCID50. This was approximately 10-fold more sensitive than the antigen capture test described previously (Hosseini, M., Hawkes, R.A., Kirkland, P.D., Dixon, R., 1998. J. Virol. Methods 75, 39-46.). The BTACE method was compared with conventional passage in cell culture to detect the presence of virus in the tissues of embryonated chicken eggs (ECEs) which had been inoculated intravenously with the blood of sheep and cattle infected experimentally with the eight Australian serotypes of BLU (1, 3, 9, 15, 16, 20, 21, and 23). The BTACE method was at least as sensitive as the conventional cell culture detecting virus in ECEs, obviating the need for prolonged cell culture passage to detect the virus. A comparison of the amount of antigen detected in different embryo tissues indicated that liver homogenates gave the highest positive to negative ratios in the BTACE and were selected as the specimen of choice. In studies of sheep infected with all 24 South African reference BLU serotypes this new BTACE was able to detect viraemia with all serotypes. Finally, the BTACE was validated in surveillance programs for BLU in both New South Wales, Australia and in Yunnan Province, People's Republic of China. Blood samples from sentinel cattle were inoculated into ECEs. Homogenised ECE livers were tested by BTACE and those positive were passaged subsequently in cell culture for virus isolation and identification. This protocol led to the efficient isolation of field isolates of many serotypes. The high sensitivity and broad reactivity of the method indicates that it should be valuable for BLU diagnosis and surveillance programs.

Animals↗
PubMed2000

Comparing the urea reduction ratio and the urea product as outcome-based measures of hemodialysis dose.

The urea reduction ratio (URR) and normalized treatment ratio (Kt/V) are related quantities that have become accepted measures of hemodialysis dose. Recent studies, however, have suggested that they combine two elements, both favorably associated with clinical outcome, as a single ratio. These elements, Kt and V, may offset each other, producing a complex quantity that does not reflect a true relationship between dialysis exposure and clinical outcome. This project explored and compared the associations of the URR and the ¿urea clearance x time¿ product (Kt) with mortality in a large sample of hemodialysis patients (37,108 patients) during 1998. Survival analyses using conventional techniques were the primary analytic tools. The relationship between URR and survival was U-shaped or J-shaped, with greater relative mortality at both extremes of the URR distribution than at its middle. Thus, identifying a threshold for adequate dialysis was not possible unless one considers also a threshold for overdialysis. Conversely, the association between Kt and outcome was much simpler, reflecting progressive improvement over the range of Kt evaluated here. These analyses suggest that such measures as URR and Kt/V are compound and complex, and that a simpler, more direct, measure, such as the Kt, should be considered to describe hemodialysis dose.

Body Mass Index↗
PubMed2000

A subnanogram API LC/MS/MS quantitation method for depsipeptide FR901228 and its preclinical pharmacokinetics.

A highly sensitive and specific atmospheric pressure ionization (API) liquid chromatographic-tandem mass spectrometric (LC/MS/MS) method for the quantitation of depsipeptide FR901228 (NSC-630176, FR), a naturally occurring antitumor agent, was developed and validated. FR was extracted from human or rat plasma along with the internal standard, t-Boc-Met-Leu-Phe (BMLP) with ethyl acetate. Components in the extract were separated on a 5-microm C8 Spherisorb 50 x 4.6 mm i.d. column by isocratic elution with methanol/acetonitrile/12 mM ammonium acetate (60:10:30, v/v/v). The liquid flow was passed through a presource splitter and 5% of the eluate was introduced into the API source. The components were analyzed in the multiple-reaction monitoring (MRM) mode to enhance specificity. Linear calibration curves were obtained in the range of 0.1-100.0 ng/ml with 0.5 ml human plasma and 0.5-100.0 ng/ml with 0.1 ml rat plasma. The limit of quantitation (LOQ) was 0.1 ng/ml using 0.5 ml human plasma and 0.5 ng/ml using 0.1 ml rat plasma. The overall within-day precision was below 12% in human plasma and below 7% in rat plasma; and the between-day precision was below 10.2% in human plasma and 7.2% in rat plasma. The accuracy at low, medium and high levels ranged from 99.3 to 111.7% in human plasma and 96.2-107.3% in rat plasma. The high sensitivity permitted pharmacokinetic study of FR in the rat at a single i.v. dose as low as 1 mg/kg. At this dose, plasma FR levels declined biexponentially with a mean terminal t(1/2) of 187.7 min (n = 6) and were detectable up to 24 h. After an oral dose at 5 mg/kg, plasma FR levels were highly erratic and yielded a mean bioavailability of 1.6% (n = 6). At a higher oral dose of 50 mg/kg, a mean bioavailability of 10.6% was obtained, both being estimated by a non-crossover method.

Administration, Oral↗