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Biomedical subjects

R Liu

Publications and source records attributed to R Liu.

At least 253 records · Page 14Linked to original sources
PubMed1996

In vitro activation of a 60-70 kDa histone H4 protein kinase from neutrophils by limited proteolysis.

Neutrophils stimulated with the chemotactic peptide fMet-Leu-Phe (fMLP) are known to exhibit a rapid and transient activation of a histone H4 kinase that may function in a stimulatory pathway downstream of phosphatidylinositol 3-kinase. The activity of this histone kinase in unstimulated neutrophils and cells treated with 1.0 microM fMLP for 10 sec was 8.8 +/- 5 and 43 +/- 2 pmol P/min per 10(7) cells, respectively. In this paper, we report that unstimulated neutrophils contain a latent H4 kinase in the 100,000 x g soluble fraction that can be markedly activated by treatment with trypsin. The values for the untreated and trypsin treated enzyme were 5.5 +/- 1.0 and 63.6 +/- 18 pmol P/min per 10(7) cell-equivalents, respectively. This kinase was insensitive to a selective antagonist of protein kinase C (i.e., 50 microM 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7)) but completely blocked by 100 nM staurosporine. Only a single peak of activity was observed for this enzyme when the 100,000 x g supernatant fraction was fractionated on either an exclusion (KW-803) or an anion exchange column (DEAE), or during isoelectric focusing. The molecular weight of the latent kinase was 64 +/- 6 kDa and the isoelectric point was 7.6 +/- 0.1. During all fractionation procedures, the H4 kinase co-chromatographed with a trypsin-activated kinase that catalyzed the phosphorylation of a peptide which corresponds to residues 297-331 of the 47 kDa subunit of the NADPH-oxidase complex (p47-phox). The properties of the trypsin-activated H4 kinase from unstimulated neutrophils are very similar to those reported for this enzyme from fMLP-stimulated cells.

Adenosine Triphosphate↗
PubMed1996

Synthesis of long prebiotic oligomers on mineral surfaces.

Most theories of the origin of biological organization assume that polymers with lengths in the range of 30-60 monomers are needed to make a genetic system viable. But it has not proved possible to synthesize plausibly prebiotic polymers this long by condensation in aqueous solution, because hydrolysis competes with polymerization. The potential of mineral surfaces to facilitate prebiotic polymerization was pointed out long ago. Here we describe a system that models prebiotic polymerization by the oligomerization of activated monomers--both nucleotides and amino acids. We find that whereas the reactions in solution produce only short oligomers (the longest typically being a 10-mer), the presence of mineral surfaces (montmorillonite for nucleotides, illite and hydroxylapatite for amino acids) induces the formation of oligomers up to 55 monomers long. These are formed by successive 'feedings' with the monomers; polymerization takes place on the mineral surfaces in a manner akin to solid-phase synthesis of biopolymers.

Amino Acids↗
PubMed1996

Synthesis and pharmacological properties of novel 8-substituted imidazobenzodiazepines: high-affinity, selective probes for alpha 5-containing GABAA receptors.

The synthesis and pharmacological properties of imidazobenzodiazepines with both high affinity and selectivity for alpha 5-containing GABAA receptors are described. Four of these compounds (5, 6, 8, and 9) inhibited [3H]flunitrazepam binding to recombinant alpha 5 beta 2 gamma 2 GABAA receptors with IC50 values between approximately 0.4 and 5 nM. These compounds were > or = 24-75-fold more selective for recombinant receptors containing alpha 5 subunits compared to other, "diazepam-sensitive" GABAA receptors containing either alpha 1, alpha 2, or alpha 3 subunits. Imidazobenzodiazepine 9 (used as the prototypical alpha 5 selective ligand) inhibited [3H]flunitrazepam binding to hippocampal membranes with high- and low-affinity components (IC50 0.6 +/- 0.2 and 85.6 +/- 13.1 nM, respectively), representing approximately 16% and approximately 84% of the receptor pool. Inhibition of [3H]flunitrazepam binding to cerebellar membranes with imidazobenzodiazepine 9 was best fitted to a single population of sites with an IC50 of 79.8 +/- 18.3 nM. These imidazobenzodiazepines behaved as GABA negative ligands in recombinant GABAA receptors expressed in Xenopus oocytes and were convulsant in mice after parenteral administration. The relative potencies of flumazenil and zolpidem in blocking convulsions induced by 9 and DMCM, respectively, indicated that occupation of alpha 5-containing GABAA receptors substantially contributed to the convulsant properties of acetylene analog 9. These 8-substituted imidazobenzodiazepines (5, 6, 8 and 9) should prove useful in examining the physiological roles of GABAA receptors bearing an alpha 5 subunit and may also lead to the development of novel, subtype selective therapeutic agents.

Animals↗
PubMed1996

Correlated flow cytometric analysis of H-ras p21 and DNA ploidy in acute myelogenous leukemia.

The flow cytometric immunoassay was used to study the correlation between the H-ras oncogene product p21 and the DNA ploidy in 30 de novo cases of acute myelogenous leukemia (AML). The results showed that 17 cases were negative for p21 expression and 13 positive for p21. The patients with positive p21 had higher percentage of bone marrow and peripheral blasts and lower peripheral leukocyte count. The expression of p21 had no influence on the therapeutic effect. Before treatment, DNA diploidy occurred in 18 cases including 13 p21 negative ones, and DNA aneuploidy was revealed in 12 cases including 8 p21 positive ones. Patients with positive p21 or having aneuploidy in complete remission were at risk for early relapse. Our results suggest that p21 may be involved in the process of leukemogenesis and progression in AML.

DNA, Neoplasm↗
PubMed1996

Portal hypertensive vascular lesions.

The aim of present study is to assess the pathological changes of gastric coronary vein in cirrhotic patients (n = 30) by immunohistochemical and morphological observation. The damage to endothelium, hypertrophy and hyperplasia of smooth muscle and increament of ECM were found in gastric coronary vein of cirrhotic patients. The vessel wall hardened and thickened with decrease of elasticity. The results showed that the portal hypertension could accompany with portal hypertensive vascular lesions.

Adult↗
PubMed1996

Prostaglandin E1 (PGE1) reduces cardiac-derived TXA2 release in ischaemic arrest in isolated working rat heart.

To determine whether PGE1 plays a beneficial role in crystalloid cardioplegia in the isolated working rat heart, twenty isolated rat hearts were studied. The hearts were subjected to 90 min cardioplegic arrest under hypothermia (25 degrees C) and 30 min reperfusion. Prior to ischaemic arrest, the amount of TXA2 in coronary effluent, left ventricular developed pressure (LVDP), left ventricular end diastolic pressure (LVEDP), coronary flow (CF), aortic flow (AF) and cardiac output (CO) did not differ between the control and PGE1 treated rats (28 nmol/l). However, at 30 min reperfusion, the recovery of LVDP, LVEDP, CF, AF, CO and SV in hearts from PGE1 treated rats was more than in control hearts. TXA2 levels from coronary effluent were increased during reperfusion in control rats. On the other hand, PGE1 (28 nmol/l) inhibited the release of TXA2 at reperfusion. The present studies confirm that the cardiac-derived TXA2 are increased after ischaemia/reperfusion. Infusion of cardioplegia solution containing PGE1 results in the inhibition of release of cardiac-derived TXA2 and in a better preservation of cardiac function after ischaemic arrest.

Alprostadil↗
PubMed1996

Tumour necrosis factor and interferon are selectively cytostatic in vitro for hormone-dependent and hormone-independent human breast cancer cells.

Since experimental studies have shown that tumour necrosis factor-alpha (TNF-alpha) has potent anti-tumour activity that can be potentiated with cytokines, we tested the efficacy of TNF-alpha with interferon-gamma (IFN-gamma) on different human breast cancer cell lines, particularly comparing hormone-dependent and -independent phenotypes. TNF-alpha inhibited the growth of hormone-dependent human MCF-7, ZR-75-1 and T47-D breast cancer cells with a half maximal concentration of 0.25 nM. In contrast, the growth of hormone-independent cells MDA-MB-231 and HS578T was not affected by TNF-alpha alone, but a synergistic inhibition was observed when using IFN-gamma and TNF-alpha together. The mRNA for the proto-oncogene C-MYC, as an intracellular indicator of cell activation, was significantly increased in MCF-7 cells in the presence of TNF-alpha. In MDA-MB-231 cells this mRNA was increased only in the presence of both TNF-alpha and IFN-gamma, without a change in the number of surface TNF receptors. These findings indicate that TNF-alpha treatment in combination with IFN-gamma may provide a successful approach to overcome the cellular heterogeneity of advanced breast tumours.

Breast Neoplasms↗
PubMed1996

Polymorphism of the apolipoprotein A-IV gene and its significance in lipid metabolism and coronary heart disease in a Japanese population.

Apolipoprotein A-IV (apo A-IV) is involved in the metabolism of both triglycerides and high-density lipoproteins (HDLs). Apo A-IV has been suggested as participating in several stages of reverse cholesterol transport. Uncertainty about the exact biochemical function of apo A-IV has made the use of genetic apo A-IV polymorphism (variants) attractive in evaluating its physiological role. To date, although some reports indicate that DNA polymorphisms at this locus play an important role in the metabolism of lipids and lipoproteins in western (Caucasian) populations, no similar comprehensive analysis has been performed in a distinct Japanese population. Using DNA sequencing and a restriction fragment length polymorphism (RFLP) study with polymerase chain reaction (PCR), the following allele frequencies were established: (a) codon -8 (G-->A, non-synonymous) allele 2 = 0 (n = 105); (b) codon 9 (A-->G, synonymous) allele 2 = 0.388 (n = 152); (c) codon 347 (A-->T, non-synonymous) allele 2 = 0 (n = 900); (d) codon 360 (T-->G, non-synonymous) allele 2 = 0 (n = 800); (e) VNTR exon 3 [(CTGT)3 and (CTGT)4] (CTGT)3 = 0.262 (n = 105); and (f) MspI (newly detected polymorphic site) polymorphism (C C/T GG) within intron 2, allele 2 = 0.096 (n = 193). The frequencies of these polymorphisms, except for that of the newly identified MspI site, are completely different from those reported in western populations. Among the 900 subjects examined, we found one ACT (Thr) to ACG (Thr) synonymous mutation at codon 347, which does not change the primary structure of apo A-IV. The apo A-IV allele frequency in patients (166 men and 56 women) with angiographically proven coronary heart disease (CHD) was also studied [codon 9 allele 2 = 0.329 (n = 217); VNTR exon 3 (CTGT)3 = 0.262 (n = 84); MspI within intron 2, allele 2 = 0.092 (n = 222)]. Furthermore, we evaluated serum lipid and lipoprotein levels quantitatively in control subjects and Japanese CHD patients. These polymorphisms did not show any consistent and significant association with lipid and lipoprotein parameters. In addition, no gender-specific effects of apo A-IV polymorphisms on lipid parameters adjusted for confounding factors were observed in either CHD patients or control subjects. Our results indicate that the apo A-IV gene is not a major determinant of the risk for CHD in Japanese.

Adult↗
PubMed1996

Pretreatment with tetramethylpyrazine increases the release of PGI2 and decreases TXA2 release in isolated rat heart.

We investigated the release of PGI2 and TXA2 by measuring their stable metabolites of 6-keto-PGF1a and TXB2 in the perfusate in the isolated rat heart after pretreatment with tetramethylpyrazine (TMP). Pretreatment with TMP (12 mg/kg, i.p.) 7 days before preparation produced a significant elevation of 6-keto-PGF1a from 2.30 +/- 0.65 ng/min/g of untreated controls to 3.8 +/- 0.77 ng/mir/g (p < 0.05). Pretreatment with TMP also decreased TXB2 release (p < 0.05 versus control).

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Choline deficiency induces apoptosis in SV40-immortalized CWSV-1 rat hepatocytes in culture.

Immortalized CWSV-1 rat hepatocytes, in which p53 protein is inactivated by SV40 large T antigen, had increased numbers of cells with strand breaks in genomic DNA (terminal dUTP end labeling) when grown in 0 Micron choline (67-73% of cells) than when grown in 70 Micron choline (2-3% of cells). Internucleosomal fragmentation of DNA (DNA ladders) was detected in cells grown with 5 Micron and 0 Micron choline for 72h. Cells treated with 0 or 5 Micron choline for 72h detached from the substrate in high numbers (58% of choline deficient cells vs. 1.4% of choline sufficient cells detached) exhibited a high incidence of apoptosis (apoptotic bodies were seen in 55-75% of cells; 67-73% had DNA strand breaks), and an absence of mitosis and proliferating cell nuclear antigen (PCNA) expression. Cells undergoing DNA fragmentation had functioning mitochondria. At 24h, cells grown in 0 or 5 Micron choline synthesize DNA more rapidly than those grown in 70 Micron choline. By 72h, the cells grown in 0 or 5 Micron choline were forming DNA much more slowly than control cells (assessed by thymidine incorporation, PCNA expression, and mitotic index). Western blot analysis showed that p53 in the nucleus of cells was detected in direct association with SV40 T-antigen, and was therefore likely to be inactive. We conclude that choline deficiency kills CWSV-1 hepatocytes in culture by inducing apoptosis via what may be a p53-independent process, and that this process begins in viable cells before they detach from the culture dish.

Animals↗
PubMed1996

Dot-immunogold filtration assay as a screening test for syphilis.

A dot-immunogold filtration assay (DIGFA) for the rapid detection of reaginic antibody in the serum of syphilitic patients was developed. The assay was simple, rapid, and reproducible. The test completion time was 2 min, and the assay required no equipment. The positive dot was very obvious, and the results could easily be determined with the naked eye. A total of 350 serum samples were examined by DIGFA, the rapid plasma reagin test, and the fluorescent treponemal antibody-absorption test. The levels of agreement between DIGFA and the rapid reagin test and between DIGFA and the fluorescent treponemal antibody-absorption test were 100 and 98%, respectively. The results of clinical application indicated that DIGFA could be used as a routine screening test for syphilis.

Antibodies, Bacterial↗
PubMed1996

Serine proteinase inhibitors influence the stability of tropoelastin mRNA in neonatal rat lung fibroblast cultures.

Elastin, an elastic extracellular structural protein, is a polymer comprised of soluble tropoelastin (TE) monomers that are joined by covalent cross-links and become insoluble. In cultured vascular smooth muscle cells, the steady-state level of TE mRNA is influenced by soluble elastin moieties in the culture medium, either TE or its fragmentation products. We have hypothesized that an enzyme-mediated proteolytic event may modulate the quantities of TE and its fragmentation products in the culture medium of mesenchymal cells, and thereby indirectly regulate the steady-state level of TE mRNA. Neonatal rat lung fibroblasts were cultured in the presence or absence of the serine proteinase inhibitor, aprotinin, and the quantities of soluble elastin and TE mRNA were analyzed. Exposures to aprotinin lasting up to 12 h increased the soluble elastin content of the culture medium. The increase in the soluble elastin content did not reflect an increase in TE mRNA, which diminished after exposures for 12 h or longer. The decrease in TE mRNA resulted from a decrease in its half-life, rather than a decrease in the rate of TE gene transcription. Aprotinin did not reduce TE mRNA in plasminogen-depleted cultures, but the effect of aprotinin was evident when purified plasminogen was added back to the cultures. Therefore, a serine proteinase, possibly plasmin, may participate in a feedback mechanism and modulate the quantity of TE in lung fibroblast cultures. This mechanism may help ensure that intracellular TE synthesis occurs in tandem with extracellular elastin deposition and cross-linking.

Animals↗
PubMed1996

A translational fidelity mutation in the universally conserved sarcin/ricin domain of 25S yeast ribosomal RNA.

Recent evidence suggests that ribosomal RNAs have functional roles in translation. We describe here a new ribosomal RNA mutation that causes translational suppression and antibiotic resistance in eukaryotic cells. Using random mutagenesis of the cloned ribosomal RNA gene and in vivo selection, we isolated a C --> U mutation in the universally conserved sarcin/ricin domain in Saccharomyces cerevisiae 25S ribosomal RNA. This mutation changes the putative CG pair, which closes the GAGA tetraloop in the sarcin/ricin domain, into a weaker UG pair without eliminating ribosomal sensitivity to ricin. We show that suppression of several UGA, UAG, and frameshift mutations is evident when a portion of the cellular ribosomal RNA contains the C --> U mutation. Cells that contain essentially all mutant ribosomal RNA grow only 10% slower than the wild-type, but show increased suppression as well as resistance to paramomycin, G418, and hygromycin, and sensitivity to cycloheximide. Our results provide genetic evidence for the participation of the sarcin/ricin loop in maintaining translational accuracy and are discussed in terms of a hypothesis that this ribosomal RNA region normally undergoes a conformational change during translation.

Anti-Bacterial Agents↗
PubMed1996

Short-term effects of a high-sucrose diet on plasma lipid, lipoprotein cholesterol, tissue lipoprotein lipase and hepatic triglyceride lipase in rats.

Short-term (2 weeks) effects of a high-sucrose diet on plasma lipids, lipoproteins, tissue lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities were investigated in rats. Three days of sucrose feeding significantly increased plasma TG (42 +/- 3 mg/dl vs. 56 +/- 2 mg/dl, p = 0.032), while TC increased significantly after 10 days of the diet (50 +/- 2 mg/dl vs. 62 +/- 2 mg/dl, p = 0.0001). HDL-C increased significantly after 3 days of sucrose feeding (36.2 +/- 0.9 mg/dl vs. 42.4 +/- 2.7 mg/dl, p = 0.011). Although LDL-C tended to decrease on days 3, 7 and 10, these changes were not significant. The plasma glucose level did not change during the study. Increased LPL activity in adipose tissue and decreased enzyme activities in skeletal and heart muscles were observed. Adipose tissue LPL returned to the baseline value after 14 days of the diet treatment, while LPL in skeletal and heart muscles remained at the decreased level. HTGL and HTGL/total liver lipase activities were significantly increased after 14 days of the diet. The different responses of lipase activities in various tissues may help to regulate serum lipid and lipoprotein levels in sucrose-fed rats.

Adipose Tissue↗
PubMed1996

Analysis of a new polymorphism in the human apolipoprotein A-I gene: association with serum lipoprotein levels and coronary heart disease.

Systematic sequencing of the coding and exon flanking regions of the apolipoprotein (apo) A-I gene has identified a new polymorphic Msp I site (C C/T-GG). This polymorphism is situated between the transcriptional starting site and the signal peptide start coding site (intron 1), so may influence the efficiency of surrounding splicing, thereby interfering with the expression of the apo A-I gene product, or serve as a linkage marker with a hitherto unidentified mutation defect responsible for hyperlipidemia and/or premature coronary heart disease. However, there was no significant difference in the allele frequencies between control and coronary heart disease subjects in a Japanese population. The -78 G-->A promoter polymorphism of apo A-I, previously reported in Western populations, has also been analyzed. The results show that neither mutation is likely to be the etiology for predisposition to a change of high-density lipoprotein cholesterol and/or variation in lipid and lipoprotein levels, or for the occurrence of coronary heart disease in Japanese populations.

Aged↗
PubMed1996

[Phylogenetic relationships among six species of Macaca inferred from ribosomal DNA variations].

Restriction maps of ribosomal DNA repeating units of six species of Macaca (M. mulatta, M. facsicularis, M. arctoides, M. assamensis, M. thibetana, M. nemestrina) and two outgroup species, Rhinopithecus bieti and Hylobates leucogenys, were constructed with 15 restriction endonucleases and 28S, 18S rDNA probes cloned from human, M. arctoides shares a common restriction map with M. assamensis. Phylogenetic tree derived from the neighbor-joining was somewhat different that derived from the maximum likelihood methods using the NEIGHBOR and RESTML program in PHYLIP version 3.5c. However, the consensus of our phylogenetic trees supports the viewpoint that M. facsicularis and M. mulatta were maybe diverged first in the genus Macaca. Further studies using DNA sequencing method are required to resolve the phylogeny of the genus Macaca.

Animals↗
PubMed1996

[A time-course observation of influence of pemphigus autoantibody upon desomosome].

OBJECTIVE: To observe the time-course changes of desmosome and its dg2/3 component in the process of acantholysis. METHOD: After setting up a pemphigus organ model and an acantholysis model by purified pemphigus autoantibody, the desmosome structures at light and electromicroscopic levels and desmoglycoprotein dg2/3 immunohistochemical stains were observed at different culture times. RESULTS: In pemphigus organ model and acantholysis model, pemphigus autoantibody only induced the increase of the intercellular space at 24 hour. Even at 48 hour, only a few desmosomes were damaged. But by 72 hour, the structures of desmosomes almost completely disappeared, and the cell membrane flattened. Immunohistochemical stains showed that there was an internalization of desmoglycoprotein dg2/3 at 48 and 72 hour during the process of acantholysis. CONCLUSION: Our results suggested that the influence of pemphigus autoantibody on desmosomes appears at a relative later stage, but the damage of desmosomes is a pivotal step to acantholysis.

Autoantibodies↗