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Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 811 records · Page 45Linked to original sources
PubMed1998

[The effect of PH on the growth of lactobacillus and Streptococcus mutan]

OBJECTIVE:The purpose of this study was to understand the effect of pH of culture media on the growth of lactobacillus and streptococcus mutan.METHODS: In this study the growth of two bacteria in differential pH culture media was measured by spectrophotometry. RESULTS: It was found that the growth of the bacteria was equal when the pH of the culture media was 6.2. CONCLUSION: This pH should be selected for the culture media which is used for the analysis of the cariogenicity of the two bacteria.

Journal Article↗
PubMed1998

[The measurement of growth curve and generation time of lactobacillus]

OBJECTIVE:The purpose of this test was to understand the growth pattern of lactobacillus for the research of its cariogenicity. METHODS: The growth quantity of lactobacillus which was culture in a constant condition was measured periodically by spectrophotometry and flora counting,and its growth curve and generation time were measured. RESULTS: It was found that the logarithmic phase of lactobacillus was 6-16 hours after it was cultured.And its generatin time was 54 minutes. CONCLUSIN: The growth curve of lactobacillus was in accordance with streptococcus mutan.

Journal Article↗
PubMed1998

[The influences of lanthanum,cerium and fluoride on the activity of glucosyltransferase(GTF) and adherence of oral cariogenic bacteria in vitro]

OBJECTIVE:Study of the influences of lanthanum,cerium and fluoride on the activity of flucosyltransferase(GTF) and adherence of oral cariogenic bacteria. METHODS: The influences of lanthanum,certium and fluoride on the acitivity of GTF and adherences of Steptococcus sobrinus 6715,Lactobacillus 4356 and Actinomycetes viscosus 19246 in vitro were investigated. RESULTS: Lanthanum and cerium can efficiently inhibit the acitivity of GTF than fluoride. CONCLUSION: The result was given a data that lanthanum and cerium could be used as a cariostatic agent in future.At the same time the inhibition of the bacterial adherence by these trace elements was also revealed.

Journal Article↗
PubMed1998

[A bacteriology analysis from infected root canals of human deciduous teeth]

OBJECTIVE: To provide a basis for therapy and prevention, the flora of infected root canals of human deciduous teeth was analyzed.METHODS: By immediate-enzyme method, the bacteria compositions of 22 cases with infected root canals of deciduous teeth, including 8 cases with acute periapical inflammation and 14 with chronic ones, were examined. RESULTS: Among 240 strains bactera, 200 strains were obligate anaerobes, belonging to the genera peptostreptococcus, bacteriodes, veillonella, eubacterrum, propionibacterium, actinomyces and fusobacterium. Bacteriodes and eusobacterium especially B. gingivalis and F. nucleatum have been more frequently isolated from root canals with acute periapical inflammation than that with chronic ones (P<0.05). In chronic cases, veillonella especially V. parvula, were more frequently isolated than acute inflammation. CONCLUSION: Periaplcal inflammation of deciduous teeth was mixed polymicrobial infections regardless of acute or chronic cases and anaerobic bacteria were dominated. B. gingivalis and F. nucleatum probably were related to acute periapical inflammation of deciduous teeth. The effect of V. parvula on chronic periapical innammation of deciduous teeth should not be neglected.

Journal Article↗
PubMed1998

[The influence of fluoride on the development of the osteoblast phenotype in rat calvarial osteoblasts: an in vitro study]

OBJECTIVE:The effects of low doses fluoride on the phenotypic development of rat fetal calvarial osteoblast were studied because the cellular mechanism of fluoride promotes the increasing of bone volume clinically is unclear. METHODS:The influence of fluoride on the rat first passage osteoblast were valuated by histochemistry, enzyme-histochemistry and electron microanalysis in vitro.RESULTS:The study had revealed that not only the bone tubular and the degree of mineralization, but also the activity expression of alkaline phosphatase of osteoblasts in fluoride group were better than the control group. CONCLUSION:The results suggested that low doses fluoride might not only increase the proliferation and differentiation of osteoblast precursors as well as the production and activity of alkaline phosphatase; but also favored the mineralized formation of osteoblast nodules.

Journal Article↗
PubMed1998

[The effect of fluoride on bone extracellular matrix proteins expression in rat calvarial osteoblast in culture]

OBJECTIVE:The expression of various non-collagenous proteins and collagen protein on the rat fetal calvarial osteoblast cultured in low doses fluoride condition in vitro had been studied.METHODS:Our study applied the immunohistochemistry technique to detect the expression of bone sialoprotein, osteocalcin, osteopontin, alkaline phosphatase and type I collagen expressed in the bone matrix.RESULTS:They demonstrated that there were difference in the location and function of the collagenous and non-collagenous proteins in the development of bone matrix.CONCLUSION:The present results revealed that fluoride might enhance the proliferation activity of osteoblast precursors; simultaneously, fluoride might accelerate the phenotypic development of osteoblast and the expression of collagenous and non-collagenous proteins. As a result,low doses fluoride played a favorable role in the development of bone extracellular matrix.

Journal Article↗
PubMed1998

[The effects of fluoride and dexamethasone on the phenotypic development of osteoblast grown on the demineralized dental root surface]

OBJECTIVE: To investigate the effects of the phenotypic development of osteoblast growing on the periodontitis affected root surface in the condition with fluoride and dexamethasone.METHODS:Cell culture technique in vitro had been used to study the growth condition of MC3T3-E1 osteoblast line on the surf ace of cementum treated with various methods.RESULTS:The present study showed that osteoblast treated with fluoride and dexamethasone had a better cellular growth behavior.CONCLUSION: The results demonstrated that demineralization procedure by citric acid might promote the osteoblasts attachment and growth on root surface; and dexamethasone and low dose fluoride were of benefit to maintain the phenotype of osteoblast as well as promote the maturation of bone-like matrix and increase the mineralization formation.

Journal Article↗
PubMed1998

[The antibacterial efficacy to obligate anaerobes isolated from the infected root canal of deciduous teeth]

OBJECTIVE:The antibacterial efficacy of 7 kinds drugs to 4 kinds obligate anaerobes isolated from the infected canal of deciduous teeth and 4 kinds standard strains was tested.The results showed that FC,Metronidazole,Chloromycin,Cefradium have strong antibacterial effects on experimental strains,but Erythromycin and Norvancomycin Hydrochloridum were not so effective.

Journal Article↗
PubMed1998

S-Transnitrosation reactions are involved in the metabolic fate and biological actions of nitric oxide.

S-Nitrosothiols are a group of potent, bioactive compounds that form through the reaction of nitric oxide (NO) with thiols in the presence of oxygen. These compounds are naturally occurring in vivo, stabilize NO and potentiate its biological effects. S-Nitrosoglutathione is the most abundant intracellular S-nitrosothiol, and the kinetics for its formation favors de novo synthesis. In this analysis, we studied the formation of S-nitrosothiols by S-transnitrosation, or exchange of -NO for -H between sulfur atoms; we synthesized S-nitroso-glutathionyl-Sepharose 4B beads (SNO-4B) as a reagent with which to measure S-transnitrosation reactions. We detected a maximum of 1.57 +/- 0.24 pmol NO/bead (n = 5) after S-nitrosation of the beads with acidified nitrite. The stability of the S-NO bond was dependent on temperature, but not pH over the 5 to 9 range (except at pH 9 at 37 degrees ), with an estimated t1/2 of 30 hr at 22 degrees C and of approximately 2 wk at 4 degrees C. We demonstrated that SNO-4B transfers -NO to glutathione and to cysteine rapidly and in a pH-dependent manner. The initial rate of transfer of -NO from SNO-4B to glutathione at room temperature was 0.53, 3.03 and 5.14 microM/min at pH 5.0, 7.4 and 9.0, respectively (P < .05). Under the same conditions, the initial rate of -NO transfer to cysteine was 0. 72, 3.71 and 4.69 microM/min at pH 5.0, 7.4 and 9.0, respectively (P < .05). There was no appreciable S-transnitrosation between SNO-4B and bovine serum albumin. We further demonstrated that SNO-4B evokes significant vasodilator and platelet inhibitory responses in plasma-free systems and activates platelet soluble guanylyl cyclase. These data suggest a mechanism by which to explain the metabolic fate and distribution of NO among thiol pools in the vasculature, and implicate S-transnitrosation at the cell surface in NO signal transduction.

Animals↗
PubMed1998

[Detection of presymptomatic patients and heterozygotes with Wilson's disease by using haplotypes of microsatellites].

OBJECTIVE: To develop a rapid, exact and effective technique of gene diagnosis for the early diagnosis of patients with wilson's disease(WD) and detection of WD heterozygotes. METHODS: Five microsatellite (or short tandem repeat, STR) loci at D13S301, D13S316, D13S296, AFM238vc3 and AFM184xc5 were amplified by polymerase chain reaction(PCR). D13S301 was a locus within WD gene, the others were in the flank of WD gene. After detection of amplified fragment length polymorphism of the five STR loci with denaturing polyacrylamide gel electrophoresis(AFLP-PAGE), the STR haplotypes analyses were performed on 120 members in 23 WD families. RESULTS: The five STR loci had high polymorphism information content(PIC). PICs of D13S301, D13S316, D13S296, AFM084xc5 and AFM238vc3 were 0.89, 0.93, 0.91, 0.91 and 0.94 respectively. The STR haplotypes analyses confirmed that the two patients previously diagnosed doubtfully were WD patients definitely. Among 31 sibs without any clinical symptoms, 4 were diagnosed as presymptomatic patients, 8 as WD heterozygotes, 17 as normal homozygotes and 2 as doubtful presymptomatic patients. CONCLUSION: Haplotypes analysis of the five STR loci can provide high genetic information. It provides a new important technique in gene diagnosis of WD.

Adult↗
PubMed1998

Characterization of an A/T-rich family of sequences from channel catfish (Ictalurus punctatus).

A family of highly repetitive DNA sequences referred to as Xba elements was identified and characterized from the channel catfish (Ictalurus punctatus) genome. The Xba elements represent about 5% to 6% of the total genomic DNA of the channel catfish. The Xba elements are distributed specifically in the channel catfish and blue catfish (I. furcatus), but not in closely related species such as white catfish (Ameiurus catus) and flathead catfish (Pylodictus olivaris). These Xba elements are arranged as head-to-tail tandem repeats. Seven sequences were sequenced. They are A/T-rich (over 65%). Each sequence contains four copies of the ATTA repeat and eight copies of (A)3-6 GT/TG motifs whose function is not known. Each unit of the repeats is 325 bp from the Kansas strain, and 321 pb from the Auburn and Stuttgart strains of channel catfish. The Xba elements are conserved in length within a specific strain, and highly conserved in sequence identity. Sequence identity is more conserved among copies isolated from the same strain than from different strains. The sequence length polymorphism among strains may be useful for identification of strains by polymerase chain reaction analysis. Many features of these elements could make them potentially important for development of homologous recombination expression vectors and position-independent expression vectors.

Adenine↗
PubMed1998

[Abnormalities of electrocardiographic P wave morphology and the relationship to electrophysiological parameters of the atrium in patients with idiopathic paroxysmal atrial fibrillation].

In 39 patients with idiopathic paroxysmal atrial fibrillation (PAF group), the incidence of the abnormal P wave morphology (prolonged P wave and mitral P in lead II and increased P terminal force in lead V1: PTF V1) was examined, and the relationships to the electrophysiologic findings of the atrial muscle were investigated. The control group consisted of 42 patients with various cardiac arrhythmias other than sick sinus syndrome. P wave duration was significantly longer in the PAF group than in the control group (112 +/- 12 vs 98 +/- 10 msec, p < 0.0001). PTF V1 was greater in the PAF group than in the control group (0.051 +/- 0.018 vs 0.028 +/- 0.010 msec, p < 0.0001). P mitrale occurred in only 5 patients (12%) in the control group as compared to 25 patients in the PAF group (64%, p < 0.0001). The longest duration of the right atrial electrograms was longer in the PAF group than in the control group (101 +/- 17 vs 85 +/- 10 msec, p < 0.0001), as was the maximal number of the fragmented deflections (8.0 +/- 2.5 vs 5.8 +/- 1.4, p < 0.0001). Repetitive atrial firing zone and also fragmented atrial activity zone were longer in the PAF group than in the control group (34 +/- 24 vs 12 +/- 19 msec, p < 0.02 and 47 +/- 27 vs 24 +/- 19 msec, p < 0.001, respectively). Interatrial conduction delay zone was longer in the PAF group than in the control group (55 +/- 25 vs 38 +/- 18 msec, p < 0.001). P wave duration and PTF V1 had significant and/or borderline correlations with the longest duration of the right atrial electrocardiograms (r = 0.75, p < 0.0001 and r = 0.68, p < 0.0001, respectively), and the maximal number of its fragmented defections (r = 0.50, p < 0.002 and r = 0.40, p < 0.05, respectively). Furthermore, P wave duration had a correlation with the repetitive atrial firing zone (r = 0.55, p < 0.01). Prolonged P wave duration and increased PTF V1 are electrocardiographic indicators for the coexistence of electrophysiologic abnormalities in patients with idiopathic paroxysmal atrial fibrillation.

Adult↗
PubMed1997

Regulated human erythropoietin receptor expression in mouse brain.

Erythropoietin (Epo) is known for its role in erythropoiesis and acts by binding to its receptor (EpoR) on the surface of erythroid progenitors. EpoR activity follows the site of hematopoiesis from the embryonic yolk sac to the fetal liver and then the adult spleen and bone marrow. Expression of EpoR has also been observed in selected cells of non-hematopoietic origin, such as the embryonic mouse brain during mid-gestation, at levels comparable to adult bone marrow. EpoR transcripts in brain decrease during development falling by birth to less than 1-3% of the level in hematopoietic tissue. We have now recapitulated this pattern of expression using a human EpoR transgene consisting of an 80-kb human EpoR genomic fragment. The highest level of expression was observed in the embryonic yolk sac and fetal liver, analogous to the endogenous gene, in addition to expression in adult spleen and bone marrow. Although activity of this transgene in brain is initially lower than the endogenous gene, it does exhibit the down-regulation observed for the endogenous gene in adult brain. The expression pattern of hybrid transgenes of an hEpoR promoter fused to beta-galactosidase in 9. 5-day embryos suggested that the hEpoR promoter region between -1778 and -150 bp 5' of the transcription start site is necessary to direct EpoR expression in the neural tube. EpoR expression in the neural tube may be the origin of the EpoR transcripts detected in brain during development. These data demonstrate that both the mouse and human EpoR genes contain regulatory elements to direct significant levels of expression in a developmentally controlled manner in brain and suggest that in addition to its function during erythropoiesis, EpoR may play a role in the development of selected non-hematopoietic tissue.

Animals↗
PubMed1997

Genetic interactions of conserved regions in the DEAD-box protein Prp28p.

The yeast PRP28 g ene has been implicated in nuclear precursor messenger RNA (pre-mRNA) splicing, a two-step reaction involved in a multitude of RNA structural alterations. Prp28p, the gene product of PRP28 , is a member of the evolutionarily conserved DEAD-box proteins (DBPs). Members of DBPs are involved in a variety of RNA-related biochemical processes, presumably by their putative RNA helicase activities. Prp28p has been speculated to play a role in melting the duplex between U4 and U6 small nuclear RNAs (snRNAs), leading to the formation of an active spliceosome. To study the function of Prp28p and its interactions with other components of the splicing machinery, we have isolated and characterized a large number of prp28 conditional mutants. Strikingly, many of these prp28 mutations are localized in the highly conserved motifs found in all the DBPs. Intragenic reversion analysis suggests that regions of motifs II, III and V, as well as of motifs I and IV, in Prp28p are likely to be in close proximity to each other. Our results thus provide the first hint of the local structural arrangement for Prp28p, and perhaps for other DBPs as well.

DEAD-box RNA Helicases↗
PubMed1997

A unique transcription factor for the A alpha fibrinogen gene is related to the mitochondrial single-stranded DNA binding protein P16.

Although stimulation of hepatic cells with interleukin-6 induces the expression of fibrinogen, the molecular basis for this regulation remains largely uncharacterized. A recent examination of the A alpha fibrinogen gene promoter identified a protein, termed the A alpha-core protein, that bound constitutively to the IL-6 response element [Liu, Z. & Fuller, G. M. (1995) J. Biol. Chem. 270, 7580-7586]. This current study provides further characterization of this regulatory protein. The data presented show the following: (i) The A alpha-core protein has a similar molecular weight and identical N-terminal sequence to that of the mitochondrial single-stranded DNA binding protein P16. (ii) The A alpha-core protein and P16 have similar characteristics in terms of DNA binding preference and antigenic properties. (iii) Overexpression of P16 gene in the hepatoma cell lines Hep G2 and Hep 3B enhances the IL-6-induced expression of A alpha fibrinogen. These results demonstrate that the A alpha-core protein is closely related to P16 and involved in the IL-6-regulated transcription of A alpha fibrinogen.

Amino Acids↗