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Biomedical subjects

N Li

Publications and source records attributed to N Li.

At least 181 records · Page 10Linked to original sources
PubMed2000

Polymorphisms in IgG Fc receptor IIB regulatory regions associated with autoimmune susceptibility.

Autoimmune diseases involve multiple genes. While functions of these genes are largely unknown, some may be related to an intrinsic hyperresponsiveness of B cells. B-cell responses are controlled by signaling thresholds through the B-cell antigen receptor (BCR) complex. The B1 isoform of type II IgG Fc receptors (FcgammaRIIB1) is exclusively expressed on B cells and serves as a negative regulator for inhibiting BCR-elicited activation. Thus, its allelic variants associated with functional deficits could be examined for possible associations with susceptibility to autoimmune diseases. We found that there are three types of polymorphisms in the reported FcgammaRIIB transcription regulatory regions in mouse strains. Compared to normal healthy mouse strains (group III), autoimmune disease-prone strains (group I) share three deletion sites: two in the promoter region and one in the third intron. Strains (group II) that per se are not autoimmune-prone, but have potentials to accelerate autoimmune diseases share two deletion sites in the third intron: one identical to that in group I and the other unique to group II. These polymorphisms correlated well with extents of down-regulation of FcgammaRIIB1 expression in germinal-center B cells upon stimulation with antigens and up-regulation of IgG antibody responses. Our data imply that these FcgammaRIIB polymorphisms are selected evolutionarily for natural defense against pathogens, and that such polymorphisms may, in turn, form the basis of one aspect of autoimmune susceptibility.

Animals↗
PubMed2000

Transcobalamin II and its cell surface receptor.

Transcobalamin II (TC II), a nonglycoprotein secretory protein of molecular mass 43 kDa, and its plasma membrane receptor (TC II-R), a heavily glycosylated protein with a monomeric molecular mass of 62 kDa, are essential components of plasma cobalamin (Cbl; vitamin B12) transport to all cells. Evidence from studies over the past 10 years has provided some important information on their structure, regulation of expression, and function. Some of the specific findings include (a) identification of the structural relationship of the ligand TC II with other members of the Cbl-binding family of proteins, intrinsic factor (IF) and haptocorrin (HC), (b) regulation of TC II gene expression, (c) molecular basis for human TC II deficiency in patients with a lack of plasma TC II, (d) membrane expression, interactions, and dimerization of TC II-R, and (e) targeting and function of TC II-R in polarized epithelial cells. It is hoped that some of the recent findings presented in this review will provide new insights into the structure and function of these two fascinating proteins and stimulate future research in this area.

Amino Acid Sequence↗
PubMed2000

Scanning tunneling microscopy nanofabrication of electronic industry compatible thermal Si oxide

We report here a nanofabrication result on a 2.7 nm thermal oxide layer using the low-energy e-beam/scanning tunneling microscope (STM) technique in conjunction with thermal annealing, in which line windows with average width of 50 nm can be formed. Comparing to the low-energy e-beam processing on thin layers of native Si oxide, this nanofabrication shows a uniform etching of the electronic industry compatible Si oxide, with which nanoscale trenches can be formed. In addition to demonstrating further the nanofabrication capability of this technique on the thermal oxide, the results present critical evidence to our previous discussions on the mechanism of the low-energy e-beam/STM nanofabrication.

Journal Article↗
PubMed2000

Effect of nitric oxide on calcium-induced calcium release in coronary arterial smooth muscle.

The present study was designed to determine whether nitric oxide (NO)-induced reduction of [Ca(2+)](i) is associated with Ca(2+)-induced Ca(2+) release (CICR) in coronary arterial smooth muscle cells (CASMCs). Caffeine was used as a CICR activator to induce Ca(2+) release in these cells. The effects of NO donor, sodium nitroprusside (SNP), on caffeine-induced Ca(2+) release were examined in freshly dissociated bovine CASMCs using single cell fluorescence microscopic spectrometry. The effects of NO donor on caffeine-induced coronary vasoconstriction were examined by isometric tension recordings. Caffeine, a CICR or ryanodine receptor (RYR) activator, produced a rapid Ca(2+) release with a 330 nM increase in [Ca(2+)](i). Pretreatment of the CASMCs with SNP, CICR inhibitor tetracaine or RYR blocker ryanodine markedly decreased caffeine-induced Ca(2+) release. Addition of caffeine to the Ca(2+)-free bath solution produced a transient coronary vasoconstriction. SNP, tetracaine and ryanodine, but not guanylyl cyclase inhibitor, ODQ, significantly attenuated caffeine-induced vasoconstriction. These results suggest that CICR is functioning in CASMCs and participates in the vasoconstriction in response to caffeine-induced Ca(2+) release and that inhibition of CICR is of importance in mediating the vasodilator response of coronary arteries to NO.

Animals↗
PubMed2000

A whole-blood flow cytometric assay for leukocyte CD11b expression using fluorescence signal triggering.

A flow cytometric assay for measurements of leukocyte CD11b expression in whole blood has been developed and evaluated. The method is based on triggering of the flow cytometer by a fluorescent pan leukocyte marker, RPE-CD45. This enabled flow cytometric analysis in whole blood, and avoidance of in vitro artefacts related to cell purification and hemolysis. Our methodological evaluation suggested the following routine procedure: sampling with sodium citrate as the anticoagulant, sample incubation at 22 degrees C, and mild sample fixation with 0.5% formaldehyde saline. The latter provided good sample stability during 24 h. Moreover, the assay provided good assay reproducibility, low labelling antibody consumption, and minimal sample manipulation (< 30 min) and acquisition time demands. The assay seems to reflect the CD11b expression of circulating leukocytes, and is also suitable for studies of agonist stimulated CD11b expression in leukocyte subpopulations in vitro. When full CD11b responsiveness to agonist stimulation is desired, samples should be incubated at 37 degrees C, but this also elevated CD11b expression in unstimulated samples. The present whole-blood technique is thus suitable for analyses of CD11b expression for both research and clinical routine laboratory use. The assay can easily be modified for measurements of other leukocyte antigens by use of other specific fluorescent antibodies.

Adenosine Diphosphate↗
PubMed2000

Analysis of CD44 isoform v10 expression and its prognostic value in renal cell carcinoma.

OBJECTIVE: To examine the expression of CD44 isoform v10 (CD44v10) in patients with renal cell carcinoma (RCC), analyse its role in RCC and its relationship with conventional clinical-histopathological experience. Materials and methods Sixty-four RCC specimens and five metastatic specimens were analysed immunohistochemically using a CD44v10 specific antibody. The expression of CD44v10 was compared with the histological grade and clinical or pathological stage of the tumours. RESULTS: Of the 64 primary tumour specimens, 22 (34%) expressed CD44v10 protein; all of these positive specimens were clear-cell and mixed-cell RCC. Staining was also positive in four of five metastatic specimens and negative in all four cases of granular cell carcinoma. CD44v10 expression was significantly correlated with the histological grade (P<0.0001), clinical stage (P = 0.0050) and pathological stage (P = 0.0143) of the tumours. The prognosis for patients with clear-cell RCC who were CD44v10-positive was worse than for patients who were CD44v10-negative (P<0.0001). In subgroups with different tumour stage (< or =pT2 or > or =pT3), the prognosis for patients with positive CD44v10 expression was also worse than for those with no expression (P<0.05). CONCLUSION: The expression of CD44v10 correlated significantly with histological grade, clinical and pathological stage, and with survival in patients with clear-cell RCC. CD44v10 protein may play a role in the progression of clear-cell and mixed-cell RCC, and thus the analysis of CD44v10 expression may provide useful prognostic information.

Adult↗
PubMed2000

Regulation of hepatic vitamin A storage in a rat model of controlled vitamin A status during aging.

It is currently unknown whether the capacity of the liver to esterify and store vitamin A (VA) changes as a function of long-term VA intake or age. The objective of this study was to investigate whether age and/or VA status are factors for the hepatic expression of cellular retinol-binding protein (CRBP), the esterification of retinol by lecithin:retinol acyltransferase (LRAT) and the accumulation of VA and lipids in liver. Two factors, VA intake and age, were studied in a 3x3 design. Diets denoted as VA-marginal, control and supplemented contained 0.35, 4 and 25 mg retinol equivalents/kg diet, respectively; male Lewis rats were fed these diets from weaning until the ages of 2-3 mo (young), 8-10 mo (middle-aged) and 18-20 mo (old) (n = 6/group. Liver CRBP mRNA differed (two-way ANOVA) with dietary VA (P<0.0001) and age (P<0.05). Hepatic LRAT activity increased with dietary VA (P<0.0001). Age was not a factor (P = 0.47) although there was an interaction of age and dietary VA (P<0.0001). Hepatic LRAT activity was correlated (r = 0.633, P<0.0001) with plasma retinol at physiologic concentrations. In VA-supplemented rats of all ages, the plasma molar ratio of total retinol:retinol-binding protein (RBP) exceeded 1, and liver VA and total lipid concentrations were elevated. However, tests of liver function had previously been shown to be within normal values. Thus, the capacity of the liver for retinol esterification by LRAT was not diminished by age or the accumulation of VA and other lipids. We conclude the following: 1) hepatic LRAT activity is regulated across a broad, physiologic range of dietary VA; 2) LRAT activity is regulated throughout life; and 3) the capacity for hepatic VA storage is high throughout life.

Acyltransferases↗
PubMed2000

A rapid method for determining the G+C content of bacterial chromosomes by monitoring fluorescence intensity during DNA denaturation in a capillary tube.

A simple and rapid method to determine the G+C content of bacterial chromosomal DNA was developed. It involves determination of Tm by a Light Cycler and calculation of the G+C content by an empirical formula relating Tm to G+C content. Instead of a conventional thermal denaturation method, which monitors the increase of absorbance at 260 nm, thermal denaturation was monitored by the decrease of fluorescence intensity in the presence of SYBR Green 1. In this method, the apparent Tm of DNA was influenced by the concentration of SYBR Green 1, DNA and salt. In addition, when the G+C content was calculated from a linear equation [(mol% G+Cx = mol% G+Cr+1.99(Tmx-Tmr), where x is the unknown organism and y is the reference organism], an error value was introduced among strains with extremely low or high G+C content. Based upon five standards (G+C contents in the range 33-66 mol%), a suitable equation was formulated for the capillary method: mol% G+Cx = mol% G+Cr+1.4652(Tmx-Tmr)+0.0063(Tmx2-Tmr2). To determine the Tm of organisms within this range of G+C contents, Escherichia coli ATCC 11775T was used as a DNA standard and fixed concentrations of SYBR Green 1, sodium citrate and DNA were used. The data from 37 bacterial strains indicated that this equation behaved well. Because it is rapid and simple, it may prove useful for bacterial identification.

Bacteria↗
PubMed2000

Characterization, crystallization and preliminary X--ray diffraction analysis of acutohaemolysin, a haemolytic toxin from Agkistrodon acutus venom.

Acutohaemolysin, a phospholipase A(2) (PLA(2)) from the venom of the snake Agkistrodon acutus, has been isolated and purified to homogeneity by anion-exchange chromatography on a DEAE-Sepharose column followed by cation-exchange chromatography on a CM-Sepharose column. It is an alkaline protein with an isoelectric point of 10.5 and is comprised of a single polypeptide chain of 13 938 Da. Its N-terminal amino-acid sequence shows very high similarity to Lys49-type PLA(2) proteins from other snake venoms. Although its PLA(2) enzymatic activity is very low, acutohaemolysin has a strong indirect haemolytic activity and anticoagulant activity. Acutohaemolysin crystals with a diffraction limit of 1.60 A were obtained by the hanging-drop vapour-diffusion method. The crystals belong to the space group C2, with unit-cell parameters a = 45.30, b = 59.55, c = 46.13 A, beta = 117.69 degrees. The asymmetric unit contains one molecule.

Agkistrodon↗
PubMed2000

Platelet-leukocyte cross talk in whole blood.

Thrombosis and inflammation involve complex platelet-leukocyte interaction, the details of which are not fully elucidated. Therefore, we investigated cross talk between platelets and leukocytes in whole blood, under the following physiological conditions: at 37 degrees C, with normal calcium concentrations, and with shear force. Platelet P-selectin and leukocyte CD11b expression were used to monitor platelet and leukocyte activation, respectively, and platelet-leukocyte aggregation (PLA) was analyzed. The leukocyte-specific agonist N:-formyl-methionyl-leucyl-phenylalanine (10(-6) mol/L) increased P-selectin-positive platelets from 2.5+/-0. 1% to 5.1+/-0.6% (P:<0.05). The increase was inhibited by either the platelet-activating factor (PAF) antagonist SR27417, the superoxide anion scavenger superoxide dismutase, the 5-lipoxygenase inhibitor Zileuton, or the 5-lipoxygenase-activating protein inhibitor MK-886, suggesting the involvement of PAF, superoxide anion, and 5-lipoxygenase products in leukocyte-induced platelet activation. The platelet-specific agonist collagen (1 microg/mL) increased leukocyte CD11b expression from 2.94+/-0.52 to 3.81+/-0.58 (P:<0. 05); this was not inhibited by the thromboxane A(2) receptor antagonist ICI 192.605 or the PAF antagonist SR27417. Platelet P-selectin expression induced by N:-formyl-methionyl-leucyl-phenylalanine and leukocyte CD11b expression induced by collagen could be suppressed by glycoprotein IIb/IIIa blockade or P-selectin blockade. This study documents platelet-leukocyte cross talk under conditions that mimic a physiological state and suggests that this involves multiple mediators and mechanisms. Furthermore, new evidence of integrin and selectin involvement in intracellular and intercellular signaling during platelet-leukocyte cross talk is provided.

Adult↗
PubMed2000

Hypopigmented mycosis fungoides: case reports and literature review.

BACKGROUND: Hypopigmented mycosis fungoides is a rare variant of mycosis fungoides (MF) that usually has a predilection for young individuals with dark complexion. OBJECTIVE: The aim is to describe new cases of hypopigmented MF with confirmed T-cell receptor gene rearrangement analysis. METHODS: This article includes case reports and a literature review. RESULTS: Three out of four hypopigmented MF patients had a positive TCR gene rearrangement. A fifth patient is reported who had hypopigmented mycosis fungoides and classical Pautrier microabscesses, for whom no TCR gene rearrangement analysis was performed. CONCLUSION: Although hypopigmented MF has a predilection for dark-complexioned populations, it can also affect Caucasian patients. In challenging cases, polymerase chain reaction can be a useful method for detecting early cases of hypopigmented MF.

Adult↗
PubMed2000

A clinical study of yi zhi capsules in prevention of vascular dementia.

The raised score in the revised Hasegawa dementia scales (HDS) demonstrated that the effect of Yi Zhi Capsules (YZC) in treating loss of intellectual function after cerebrovascular diseases was significantly better than that of the western drug Piracetam [symbol: see text] (P < 0.01). The morbidity of vascular dementia was much lower in the treatment group than that of the control group (P < 0.05) after a one-year follow-up; and the blood lipid level and some indexes in rheological examinations were also improved significantly (P < 0.05, or < 0.01). The data indicate that YZC is a relatively good preparation for prevention of vascular dementia.

Aged↗
PubMed2000

Multi-cellular activation in vivo by endotoxin in humans--limited protection by adenosine infusion.

The influence of adenosine infusion (40 microg/kg/min for 4 h) on inflammatory and hemostatic parameters was investigated in healthy males without (n = 10) or with (n = 11) intravenous endotoxin injection (4 ng/kg). Without endotoxin, adenosine elevated circulating leukocytes and circulating platelet-leukocyte aggregates. Endotoxin activated platelets and leukocytes in vivo. Platelet activation was seen as slightly increased platelet P-selectin expression, decreased platelet counts, and elevated plasma soluble P-selectin (from 39.6 +/- 3.4 to 68.9 +/- 6.6 ng/ml, P<0.01). Leukocyte activation was evidenced by increased CD1 lb expression (from MFI of 0.54 +/- 0.02 to 2.21 +/- 0.17; P<0.01) and plasma elastase levels (from 25.3 +/- 2.5 to 169.3 +/- 22.5 ng/ml: P <0.01). Endotoxin also enhanced platelet and leukocyte responsiveness to in vitro stimulation. Endotoxin induced von Willebrand factor secretion (from 92 +/- 8 units to 265 +/- 19 units at 4 h; P <0.001) and enhanced thrombin generation in vivo. Endotoxin induced leukocytosis and thus increased circulating platelet-leukocyte, mainly platelet-neutrophil, aggregates. Adenosine caused slight attenuation of platelet reactivity to agonist stimulation, enhanced the endotoxin-induced leukocytosis, and detained more platelet-leukocyte aggregates in circulation, but did not attenuate endotoxin-induced neutrophil elastase secretion, von Willebrand factor secretion, or thrombin generation. Thus, endotoxemia induces multi-cellular activation in vivo. Adenosine inhibits leukocyte adhesion and extravasation, and mildly attenuates platelet responsiveness and soluble P-selectin release. Adenosine has the potential of becoming a therapeutic antiinflammatory drug, but an optimal treatment strategy needs to be developed.

Adenosine↗
PubMed2000

[Research on constructing phylogenetics trees of ruminants basing on the database of milk protein gene sequences].

Primers designed according to the sequences of four milk protein genes of cow Bos taurus (alpha-lactoalbumin, beta-lactoglobin, beta- and kappa-casein) were used to amplify the full length gene of alpha-lactalbumin in yak Bos grunniens (2999 bp), water buffalo Bubalus arnee bubalis (278 bp), partial sequence of this gene in red deer cervus elaphs xanthopygus (1582 bp), 5' and 3' flanking region of beta-lactoglobin gene (2167 bp and 1096 bp in length respectively), 5'-flanking region and exon VIII to exon IX of beta-casein gene (987 bp and 1096 bp in length respectively), exonIV of kappa-casein gene (780 bp). All the amplified DNA fragments were cloned and the Nt sequences were determined. Phylogenetic tree containing 20 species (or subspecies) of ruminantia suborder was constructed according to the partial sequence of kappa-casein gene exon IV (363 bp in length), which shows good monophyly of the Bovidae. And trees constructed according to other milk protein genes indicate that all the milk protein genes have good features for drawing phylogenetics tree at least among species belonging to different subfamilies.

Animals↗