Search PubMed⌕ Search

Biomedical subjects

R Liu

Publications and source records attributed to R Liu.

At least 289 records · Page 16Linked to original sources
PubMed1995

Association between coronary heart disease and the apolipoprotein A-I/C-III/A-IV complex in a Japanese population.

Several studies have reported that a variant allele (S2) of the apolipoprotein (apo) A-I/C-III/A-IV complex is associated with hyperlipoproteinemia in some populations and that the frequency of this allele is two- to fivefold higher in patients with premature coronary heart disease (CHD) than in healthy controls. In the present study in a Japanese population, we were unable to confirm the association of the S2 allele with either coronary heart disease or elevated serum apo C-III levels, as has been previously reported in Caucasians. No genotype difference was observed among the severity of coronary heart disease, as determined by the number of involved vessels (one, two and three vessel disease), compared to controls. In addition, the frequency of the S2 allele among Japanese, in both CHD (0.328) and controls (0.369), was quite different from that in many other populations.

Aged↗
PubMed1995

Simultaneous determination of copper and zinc in the hair of children by pH gradient construction in a flow-injection system.

A flow-injection method is described for the simultaneous determination of copper and zinc with a single detector using the pH gradient technique. Zincon is used as the colour reagent for the spectrophotometric determination. The linear range for the determination of zinc is 0.4-12 micrograms ml-1 and for copper is 0.1-3.0 micrograms ml-1. About 20-30 samples can be determined in one hour. The proposed method has been applied to the determination of zinc and copper in childrens' hair.

Child↗
PubMed1995

Determination of manganese in Chinese tea leaves by a catalytic kinetic spectrophotometric method.

The catalytic effect of manganese(II) on the oxidation of Rhodamine B with potassium periodate in the presence of 1,10-phenanthroline in acetic acid-sodium acetate was studied. A catalytic kinetic spectrophotometric method for determination of manganese(II) was developed. Manganese in the range 0.1-5.0 ng ml-1 can be determined, and the detection limit is 0.02 ng ml-1. Manganese in Chinese tea leaves was successfully determined.

Catalysis↗
PubMed1995

Site and menstrual cycle-dependent expression of proteins of the tumour necrosis factor (TNF) receptor family, and BCL-2 oncoprotein and phase-specific production of TNF alpha in human endometrium.

Apoptosis in human endometrial epithelium progressively increases from early to late secretory/menstrual phases and remains consistently more prominent in the basalis. It has been suggested that tumour necrosis factor (TNF) alpha secreted during the secretory/menstrual phases plays a role in induction of programmed cell death in these cells. In the present study, we characterized expression of receptors of TNF alpha, Fas antigen and BCL-2 in endometrial cells to gain insight as to whether this type of cell death in endometrium may be related to differential or preferential expression of these proteins at specific phases of the menstrual cycle. In addition, to relate production of TNF alpha to the development of apoptosis, the amount of TNF alpha released by human endometrium was measured. Immunostaining demonstrated that the TNF receptor (TNFr; p55/60)-I, TNFr-II (p75/80) as well as Fas protein were expressed in endometrial epithelium throughout the entire menstrual cycle. This expression was progressively diminished from the basalis towards the upper functionalis. In the proliferative phase, the expression of BCL-2 was prominent in the endometrial glands particularly in those residing in the basalis. This expression became weak as early as the third post-ovulatory day and remained low during the remaining phases of the menstrual cycle. The amount of TNF alpha released by endometrial fragments obtained from various phases of the menstrual cycle was determined. The amount of TNF alpha released into the culture medium by the endometrium was low in the proliferative phase. However, the amount of released TNF alpha progressively increased in the secretory phase and peaked in the menstrual phase. TNFr-I, TNFr-II, Fas, BCL-2 and TNF alpha could be identified by Western blot analysis of proteins extracted from endometrium. Therefore, endometrial epithelium by virtue of expression of receptors of TNF alpha as well as Fas protein is properly poised to respond to ligand signals that regulate apoptosis. Induction of apoptosis in endometrial epithelium and menstrual shedding may be related to loss of the protective effect of BCL-2 as well as to the amount of TNF alpha.

Antigens, Surface↗
PubMed1995

Quantitation of hepatic glucose fluxes and pathways of hepatic glycogen synthesis in conscious mice.

Mice were studied with the euglycemic hyperinsulinemic and the hyperglycemic clamp techniques after a 6-h fast: 1) euglycemic (6.7 +/- 0.2 mM) hyperinsulinemia (approximately 800 microU/ml); 2) hyperglycemic (15.3 +/- 0.4 mM) hyperinsulinemia (approximately 800 microU/ml). All mice received an infusion of [3-3H]glucose and [U-14C]lactate. Basal hepatic glucose production (HGP) averaged approximately 170 mumol.kg-1.min-1 in both groups. During euglycemic and hyperglycemic hyperinsulinemia, HGP decreased by 53% (to 76.7 +/- 11.1 mumol.kg-1.min-1; P < 0.01) and 74% (to 43.3 +/- 7.2 mumol.kg-1.min-1; P < 0.01), respectively. Hyperglycemia increased glucose cycling (by 2.1-fold; P < 0.01) and the contribution of gluconeogenesis to HGP (88 vs. 43%; P < 0.01) while decreasing that of glycogenolysis (12 vs. 57%; P < 0.01). The percentage of neosynthetized hepatic glycogen formed via the direct pathway was markedly increased during hyperglycemia (53 +/- 2% vs. 23 +/- 3%; P < 0.01): These data indicate that the assessment of hepatic glucose fluxes can be accomplished in conscious unrestrained mice and that, in the presence of hyperinsulinemia, hyperglycemia causes 1) a further inhibition of HGP mainly via inhibition of glycogenolysis and increase in hepatic glucose cycling; and 2) about a fivefold stimulation in the direct pathway of hepatic glycogen formation.

Animals↗
PubMed1995

A new case of apoA-I deficiency showing codon 8 nonsense mutation of the apoA-I gene without evidence of coronary heart disease.

We report a 39-year-old Japanese man with HDL and apoA-I deficiency as well as data from members of his family. Corneal opacity and a stomatocyte were found but not tonsillar hypertrophy, xanthomas, or splenomegaly. His serum HDL cholesterol, apoA-I, apoA-II, and LDL cholesterol levels were t mg/dL, < 3 mg/dL, 6 mg/dL, and 175 mg/dL, respectively. Plasma triglyceride, phospholipid, apoB, apoC-III, and apoE levels were all within normal limits. Lecithin:cholesterol acyltransferase activity was half of normal, while lipoprotein lipase and hepatic triglyceride lipase activities were within normal limits. ApoA-I deficiency was confirmed by combined isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by an immunoblotting method. We surveyed the apoA-I gene of the patient and five of his family members by direct sequencing after amplification by polymerase chain reaction and found a codon 8 nonsense mutation (TGG --> TAG, Trp --> stop) in exon 3 of the apoA-I gene. The results of a pedigree analysis by DNA sequencing and restricted fragment length polymorphism (Sty I) were consistent with an autosomal codominant trait. Coronary angiography was performed to evaluate coronary atherosclerosis, but no significant luminal narrowing was detected. An intracoronary ultrasound study showed mild intimal hyperplasia in segment 6. In summary, this is a case of apoA-I deficiency without evidence of coronary heart disease.

Adolescent↗
PubMed1995

Combined effects of pravastatin and probucol on high-density lipoprotein apolipoprotein A-I kinetics in cholesterol-fed rabbits.

The combined effects of pravastatin and probucol on high- density lipoprotein (HDL) apolipoprotein (apo) A-I kinetics in cholesterol (Ch)-fed rabbits were investigated. Japanese White rabbits were treated with 0.15% pravastatin and 0.5% Ch (group 1) or 0.15% pravastatin plus 1% probucol and 0.5% Ch (group 2) for 2 months. After treatment, the serum total cholesterol levels in groups 1 and 2 had significantly (p < 0.01) increased (37.4 +/- 6.7 mg/dl vs 117.1 +/- 46.4 mg/dl, and 31.4 +/- 4.9 mg/dl vs 143.0 +/- 84.5 mg /dl, respectively). The serum HDL-cholesterol levels in both groups decreased (18.2 +/- 2.8 mg/dl, vs 16.2 +/- 3.7 mg/dl p < 0.01 for group 1; 18.2 +/- 1.9 mg/dl vs 15.5 +/- 4.5 mg/dl, ns for group 2). Apo A-I kinetics were assessed by injecting (125)I-labeled HDL intravenously into both groups of rabbits, and taking blood samples periodically for 6 days. Kinetic parameters calculated from apo A-I specific radioactivity decay curves showed that the apo A-I fractional catabolic rates in rabbits fed pravastatin and Ch (group 1) were significantly less than those in rabbits fed pravastatin plus probucol and Ch (group 2) (0.546 +/- 0.017 /day vs 0.730 +/- 0.126 /day, p < 0.05), while the synthetic rate of apo A-I was lower in group 2 than in group 1 (14.76 +/- 1.71 mg/kg per day vs 11.21 +/- 2.38 mg/kg per day, respectively, p < 0.01). These data indicate that pravastatin and probucol have different effects on HDL-apo A-I kinetics in a diet which includes cholesterol.

Animals↗
PubMed1995

[Physicochemical properties of a beta-glucan from Sclerotinia sclerotiorum].

Sclerotan (SSG) was an extracellular polysaccharide from Sclerotinia sclerotiorum by submerged fermentation. It had potential immunomodulating and antitumor activity. The SSG was a glucan composed of beta-linked D-glucoses. It was hard to dissolve in water under normal condition, but its aqueous solution had fine rheological properties. Its intrinsic viscosity [eta] hardly changed with ionic strenth. Change of its [eta] value was not remarkable between pH 1.88-12.36. Nevertheless, when the pH came to 13.32, the [eta] value decreased rapidly due to change of molecules conformation. Effect of temperature < or = 90 degrees C and heat treatment on apparent viscosity of SSG solution was minor.

Adjuvants, Immunologic↗
PubMed1995

[Sensitivity of Plasmodium falciparum to seven antimalarials in China-Laos border].

The sensitivity of P. falciparum to chloroquine (CHL), piperaquine (PIP), artesunate (ATS), dihydroartemisinine (DAT), artemether (ATM), arteether (ATE) and pyronaridine (PRN) were assayed by in vitro microtechnique in China-Laos border in 1992. The resistance rates of isolates from the south of Yunnan of China in the border were 97.0%, 96.4%, 12.5%, 16.0%, 6.3% and 34.5%, respectively; ID50 were 119.0, 320.0, 7.2, 5.4, 295.0, 74.4 and 31.9 nmol/L, ID95 were 625.0, 2426.0, 42.2, 36.6, 767.0, 371.1 and 325.2 nmol/L. The resistance rates of isolates from the north border of Laos were in order 9/10, 8/10, 1/5 to CHL, PIP, PRN, ID50 were 114.0, 166.9, 16.4 nmol/L, ID95 were 570.0, 631.1 and 107.7 nmol/L. All the isolates from Laos were sensitive to ATS, DAT, ATM and ATE. ID50 were 5.0, 4.4, 91.6 and 56.7 nmol/L, ID95 were 23.4, 11.1, 3276.1 and 223.9 nmol/L, respectively. The results indicate that P. falciparum in the border was highly resistant to CHL and PIP, while most of the isolates were susceptible to the other 5 of the above-mentioned drugs. A comparison between the isolates from China and Laos showed that there was no significant difference in resistance degree to CHL but the sensitivity of isolates from China to other 6 drugs was lower than those from Laos.

Animals↗
PubMed1994

The transcription factor YY1 binds to negative regulatory elements in the human cytomegalovirus major immediate early enhancer/promoter and mediates repression in non-permissive cells.

We have previously shown that repression of human cytomegalovirus (HCMV) major immediate early (IE) gene expression in non-permissive human teratocarcinoma (T2) cells is associated with a number of nuclear factors which bind to the imperfect dyad symmetry located in the modulator region upstream of the major IE enhancer as well as to the 21 bp repeat elements within the enhancer. Differentiation of T2 cells with retinoic acid (RA) results in a decrease in binding of some of these nuclear factors to these sites and deletion of these specific binding sites from major IE promoter/reporter constructs results in increased IE promoter activity in normally non-permissive cells. In this study, we demonstrate that the transcription factor YY1, which can negatively regulate the adeno-associated virus P5 promoter, directly binds to both the imperfect dyad symmetry and the 21 bp repeat elements in the HCMV major IE promoter/regulatory region and mediates repression of HCMV IE gene expression. This strongly suggests that YY1 plays an important role in regulating HCMV expression in non-permissive cells.

Antigens, Viral↗
PubMed1994

Plasma HDL levels are regulated by the catabolic rate of large particles of lipoprotein containing apo-A-I.

Lp-A-I was isolated by immunoaffinity chromatography and then separated into two fractions of large and small Lp-A-I particles by conventional ultracentrifugation with a cut-off density of 1.125 g/ml. The large and small particle-rich fractions were then radiolabeled with [125I]-Na and [131I]-Na, respectively. Both of the labeled lipoproteins were injected (20 microCi, i.v.) simultaneously into normolipidemic rabbits. The FCR of the large Lp-A-I particles was much less than that of the small Lp-A-I particles (0.801 +/- 0.026/day vs. 2.227 +/- 0.067/day, P < 0.0001). These data indicate that the two particles have distinctly different metabolic pathways and that the lower FCR of larger Lp-A-I particles can effectively raise plasma HDL levels.

Animals↗
PubMed1994

Differential signal transduction of epidermal-growth-factor receptors in hormone-dependent and hormone-independent human breast cancer cells.

In breast cancer, hormone dependency is inversely correlated with the number of surface epidermal-growth-factor (EGF) receptors on the tumor cells. In vitro, EGF stimulated only hormone-dependent immortalized human breast cancer cells to grow with an increased rate whereas hormone-independent cells were not affected by EGF. The number of EGF surface receptors is about 5-10-times smaller on hormone-dependent cells than on hormone-independent cells. Two cell lines representing the two cell types were used to demonstrate the signal-transduction capabilities of the EGF receptors. The two cell lines were the hormone-dependent MCF-7 cells and the hormone-independent MDA-MB-231 cells. Incubation at 37 degrees C for 15 min with 10(-8) M EGF increased the surface EGF-receptor density substantially on MCF-7 cells (50%) and reduced the number of these receptors on MDA-MB-231 cells to about 65% of the control. Both cell lines internalized a fluorescein-isothiocyanate-labeled EGF with similar kinetics. EGF triggered tyrosine phosphorylation of several targets in isolated MCF-7 cell membranes. One of these targets was shown by immunoprecipitation to be the EGF receptor. In MDA-MB-231 cell membranes, the EGF receptor was demonstrated to be the main target for tyrosine phosphorylation. The mRNA expression of the immediate early proto-oncogene c-fos was stimulated by EGF only in MCF-7 cells. In contrast, the mRNA of the EGF receptors was stimulated by EGF in both cell lines. These results demonstrate that, although EGF-binding sites are present on both cell lines, their signal-transduction capacity and activities are substantially different and resulted in a divergent response of the two cell types to EGF.

Blotting, Northern↗
PubMed1994

In vitro conversion of recombinant human proapolipoprotein A-I to apolipoprotein A-I.

We recently investigated the in vivo conversion of recombinant human proapolipoprotein A-I (rh-Met-proapo A-I) from E. coli to apolipoprotein (apo) A-I in rabbits. In vitro incubation of rh-Met-proapo A-I with rabbit serum produced mature apo A-I3 isoproteins, as determined by the immunoblotting method. However, at the time we were unable to chemically confirm a newly produced protein band which appeared at the position of human apo A-I3. Since then, we have confirmed the amino acid sequence of the protein using a membrane protein sequence technique, and have concluded that it corresponds to human apo A-I3.

Amino Acid Sequence↗