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Biomedical subjects

Y L Liu

Publications and source records attributed to Y L Liu.

At least 55 records · Page 3Linked to original sources
PubMed1999

Epidemiological study of the risk factors of rampant caries in Shanghai children.

OBJECTIVE: To explore the risk factors associated with rampant caries and to provide suggestions for prevention and clinical treatment. METHODS: On the basis of a field survey, case-control study was performed to isolate variables possibly related to rampant caries in children. Data analysis was performed with individual analysis and multiple unconditional logistic regression. Four logistic models were developed. RESULTS: The risk factors of rampant caries were cariogenic foods and bottle-feeding with sugar containing bovine milk; an increased risk of caries was also associated with duration of breast-feeding. CONCLUSION: Overuse of cariogenic foods and unsuitable patterns of infant feeding were the most important risk factors associated with rampant caries.

Bottle Feeding↗
PubMed1999

[Expression of cyclin dependent kinase inhibitor p27 during proliferation in vascular smooth muscle cell].

This study was to investigate cell cycle distribution of the vascular smooth muscle cells (VSMCs) and negative regulator of cell proliferation p27 expression caused by platelet derived growth factor BB (PDGF-BB), angiotensin II (Ang II) and arginine vasopressin (AVP). Deprived of fotal calf serum for 48 h, cultured VSMCs in quiescent condition were collected at different times after stimulation of Ang II, AVP and PDGF-BB. Cell cycle distribution and p27 expression were determined with a flow cytometer. The results showed that the protein content of VSMCs was significantly increased (43.6%) by Ang II as a result of hypertrophy, but Ang II did not lead to downregulation of p27. AVP could downregulate p27 slightly. PDGF could inhibit p27 expression significantly and cause VSMCs hyperplasia. These results suggest that the progression of VSMCs through G1 to S phase might be brought out by the inhibition of p27 during proliferation.

Angiotensin II↗
PubMed1999

[The investigation of accidental swallowing of Fluoride toothpaste in young children]

OBJECTIVE:This study was to investigate the accidental swallowing of fluoride toothpastes in young children during their toothbrushing and then to discuss the security of fluoride toothpastes used by young children.METHODS:The accidental ingesting of fluoride toothpastes in 180 young children aged 3-6 years old was assayed with fluoride-specific electrode.RESULTS:Among the 180 children invited to join the test,the average amount of the ingestion of fluoride toothpastes was 0.053g.The average swallowing ratio was 26.163%.The maximums presented in the group aged 3.0 to 3.9years old were 0.082g and 30.348%;respectively.CONCLUSION:Young children swallow a quantity of toothpaste on the brush during toothbrushing inevitably.It may result in the excessive daily fluoride ingestion which includes the fluoride ingestion from toothpaste,food and surroundings.So the incidence of fluorosis will increase certainly.

Journal Article↗
PubMed1998

The effects of the beta3-adrenoceptor agonist BRL 35135 on UCP isoform mRNA expression.

The mitochondrial uncoupling protein UCP-1 uncouples respiration from ATP synthesis in brown adipose tissue (BAT) and thus energy is dissipated as heat. Recently two further isoforms have been identified which may play a similar role in other tissues. We have determined the effects of the rodent-selective beta3-adrenoceptor (beta3-AR) agonist BRL 35135, on beta3-AR and UCP mRNA levels in tissues from lean and obese (fa/fa) Zucker rats. beta3-AR mRNA levels were reduced in fa/fa white (WAT) and brown (BAT) adipose tissue relative to levels in lean littermates. BRL 35135 treatment increased expression levels of beta3-AR mRNA in both genotypes. UCP-2 and UCP-3 mRNA levels in BAT, WAT and skeletal muscle were reduced by 2-3 fold in the fa/fa rats relative to the lean rats. We confirm that BRL 35135 increases BAT UCP-1 mRNA in lean rats, and find that BAT UCP-3 mRNA was reduced 3.2 fold, with no changes in UCP-2 expression. In WAT BRL 35135 increased UCP-2 and UCP-3 expression 2-3 fold in both lean and fa/fa rats. In lean rats, skeletal muscle UCP-3 mRNA was increased 2.3 fold by BRL 35135 whereas UCP-2 was reduced by 2.2 fold. BRL 35135 had no effects on UCP-2 and UCP-3 expression in skeletal muscle of the fa/fa rats. Our results demonstrate that mechanisms regulating UCP isoform synthesis in fa/fa rats are impaired and that WAT could be involved in the thermogenic response of BRL 35135.

Adipose Tissue↗
PubMed1998

Leptin action in intestinal cells.

The adipocyte hormone leptin activates signal transducer and activator of transcription 3 (STAT3) in the hypothalamus, mediating increased satiety and increased energy expenditure. To date, leptin-mediated activation of the STAT pathway in vivo has not been established in tissues other than hypothalamus. We now describe leptin receptor expression and in vivo signaling in discrete regions of the mouse gastrointestinal tract. Expression of the functional isoform leptin receptor (OB-Rb) is restricted to the jejunum and is readily detected by RT-PCR in isolated enterocytes from this site. Intravenous injection of leptin rapidly induced nuclear STAT5 DNA binding activity in jejunum of +/+ and obese (ob/ob) mice but had no effect in the diabetic (db/db) mouse that lacks the OB-Rb isoform. In addition, an induction of the immediate-early gene c-fos is observed in jejunum in vivo. Leptin-mediated induction of a number of immediate-early genes and activation of STAT3 and STAT5 in a human model of small intestine epithelium, CACO-2 cells, corroborate this effect. Furthermore, intravenous leptin administration caused a significant 2-fold reduction in the apolipoprotein AIV transcript levels in jejunum 90 min after a fat load. Our results suggest that the epithelium of jejunum is a direct target of leptin action, and this activity is dependent on the presence of OB-Rb. Lack of leptin or resistance to leptin action in this site may contribute to obesity and its related syndromes by directly affecting lipid handling.

Animals↗
PubMed1998

Relaxation of isolated human myometrial muscle by beta2-adrenergic receptors but not beta1-adrenergic receptors.

OBJECTIVE: Human myometrium contains both beta1-adrenergic and beta2-adrenergic receptors. This study was designed to assess the importance of each beta-adrenergic receptor subtype in relaxation of human myometrial muscle strips. STUDY DESIGN: Radioligand binding studies were used to establish the presence of each beta-adrenergic receptor subtype, whereas highly selective beta1-antagonists and beta2-antagonists were used to assess the contribution of beta-adrenergic receptor subtypes to myometrial relaxation after exposure to (-)-isoproterenol. RESULTS: Membranes prepared from myometrium contained 82% +/- 4% beta2-adrenergic receptors. After contraction produced by exposure to potassium chloride (35 mmol/L), isoproterenol produced relaxation with half maximal effect at 0.02 micromol/L and a maximal relaxation of 52% +/- 3%. Beta1-antagonist CGP-20712A had no significant effect, whereas beta2-antagonist ICI-118551 produced a characteristic rightward shift of the isoproterenol concentration-relaxation relationship. CONCLUSIONS: Although both beta1-adrenergic receptors and beta2-adrenergic receptors are present in human myometrial tissue at term, relaxation by nonselective beta-agonist isoproterenol is mediated exclusively by beta2-adrenergic receptors.

Adrenergic beta-Agonists↗
PubMed1998

Is there a synergistic effect between mixed bacterial infection in biofilm formation on biliary stents?

BACKGROUND: Biliary sludge which forms as a result of bacterial adherence and biofilm formation in the biliary system is a recognized cause of blockage of plastic stents. Bacteriological cultures of sludge have revealed a mixed infection with gram-positive and gram-negative bacteria. Animal studies have shown that prophylactic ciprofloxacin, which selectively suppress gram-negative bacteria, results in prolonged stent patency despite colonization of the stents by gram-positive bacteria. METHODS: We tested a possible synergistic effect between gram-negative and gram-positive bacteria in adherence and biofilm formation on plastic stents. Clinical isolates of Escherichia coli and Enterococcus were cultured in separate chemostats to achieve a steady growth. Adherence of the two bacteria on plastic stent surface were tested separately by perfusing infected bile with the respective bacteria through different modified Robbins devices containing 10F polyethylene stent pieces up to 4 days. In a second experiment, Enterococcus was perfused through stent pieces precolonized with E. coli for 24 hours. The stent pieces were then removed daily and analyzed by bacteriologic culture and scanning electron microscopy for bacterial adherence and biofilm formation. RESULTS: Gram-negative E. coli were more adherent than gram-positive Enterococcus. Precolonization with E. coli facilitates subsequent attachment of Enterococcus. CONCLUSIONS: We concluded that there is a synergistic effect between gram-positive and gram-negative bacteria in adherence and biofilm formation.

Animals↗
PubMed1997

Leptin inhibits glycogen synthesis in the isolated soleus muscle of obese (ob/ob) mice.

The ob gene product, leptin, causes significant and dose-dependent inhibition of basal and insulin-stimulated glycogen synthesis in isolated soleus muscle from ob/ob mice, and a smaller, non-significant inhibition in muscle from wild-type mice. Leptin had no inhibitory effect on glycogen synthesis in soleus muscle from the diabetic (db/db) mice, which lack the functional leptin receptor. The full-length leptin receptor (Ob-Rb), is expressed in soleus muscle of both ob/ob and wild-type mice, however with no detectable differences in expression level. These results suggest that hyperleptinaemia may attenuate insulin action on glucose storage in skeletal muscle.

Animals↗
PubMed1997

A c-erbB-2 promoter-specific nuclear matrix protein from human breast tumor tissues mediates NF-kappaB DNA binding activity.

The c-erbB-2 gene overexpression plays a major role in the pathogenesis of breast cancer. Binding studies detected a nuclear matrix protein (NMP) in human breast tumor tissues that recognizes a matrix attachment region (MAR) in the immediate vicinity of the c-erbB-2 gene promoter. This NMP is expressed in breast tumor tissues and cell lines along with c-erbB-2, but is not found in corresponding normal tissues. Furthermore, when NMP purified from the breast tumors by its affinity to the MAR sequence is added to nuclear extracts of breast cancer cells, it selectively stimulates the binding of the NF-kappaB transcription factor to DNA. A model is suggested in which the association of the MAR-like sequence with the nuclear matrix raises the local concentration of the specific NMP, which in turn interacts with the nuclear factor NF-kappaB to increase its local level. Such a complex could explain at a molecular level the "increase in NF-kappaB DNA binding activity" often observed in c-erbB-2- and BRCA1-positive human breast tumors. The increased NF-kappaB activity could thereby contribute to breast cancer progression.

Antigens, Nuclear↗
PubMed1997

Expression of the functional leptin receptor mRNA in pancreatic islets and direct inhibitory action of leptin on insulin secretion.

Leptin, encoded for by the mouse ob gene, regulates feeding behavior and energy metabolism. Its receptor (Ob-R) is encoded by the mouse diabetic (db) gene and is mutated in the db/db mouse so that it lacks the cytoplasmic domain. We show that the full-length leptin receptor (Ob-Rb), which is believed to transmit the leptin signal, is expressed in pancreatic islets of ob/ob and wild-type mice, as well as in hypothalamus, liver, kidney, spleen, and heart. Recombinant leptin inhibited basal insulin release in the perfused pancreas preparation from ob/ob mice but not in that from Zucker fa/fa rats. Leptin (1-100 nmol/l) also produced a dose-dependent inhibition of glucose-stimulated insulin secretion by isolated islets from ob/ob mice. In contrast, leptin at maximum effective concentration (100 nmol/l) did not inhibit glucose-stimulated insulin secretion by islets from db/db mice. These results provide evidence that a functional leptin receptor is present in pancreatic islets and suggest that leptin overproduction, particularly from abdominal adipose tissue, may modify directly both basal and glucose-stimulated insulin secretion.

Animals↗
PubMed1997

[Influence of intracerebroventricular injection of sodium nitroprusside L-arginine and NG-nitro-L-arginine on cardiovascular activity in conscious rats].

In order to study the cardiovascular effect of NO in conscious rats, sodium nitroprusside (SNP), the precursor of NO (L-Arginine, Arg-Arg) and one of the inhibitor of NOS (NG-nitro-L-arginine, NNLA) were intracerebroventricularly (icv) injected. Our experimental results indicated that, an apparent dose-dependent hypertensive effect was produced by icv administration of SNP (8, 16, 32 and 32 micrograms), a tachycardiac effect was also produced at the same time. In addition, hypertension and tachycardia were produced by icv L-arginine and the dipeptide Arg-Arg. Furthermore a hypotensive and bradycardiac effect can be produced by icv NNLA. These results suggest that there is a positive effect on cardiovascular activity due to increase of endogeneuse NO in the rat brain and a negative effect on cardiovascular activity due to decrease of endogeneuse NO in the rat brain.

Animals↗
PubMed1997

[Isoflavones from Glycyrrhiza eurycarpa].

A new isoflavone, named eurycarpin A and a new natural product isoflavone named eurycarpin B have been isolated from the roots of Glycyrrhiza eurycarpa P. C. Li. Their structures were determined to be 7,2',4'-trihydroxy-3'-(3,3-dimethylallyl) isoflavone(I) and 7,2'-dihydroxy-6",6"-dimethylpyrano-(2",3":4',3') isoflavone(II) on the basis of spectroscopic analysis (UV, EI-MS, 1HNMR, 13CNMR, NOE difference and HMBC). In addition, three known isoflavones, licoisoflavone A, calycosin and formononetin, were obtained for the first time from this plant.

Drugs, Chinese Herbal↗
PubMed1997

[The clinical effects of tea polyphenol varnish on caries prevention]

The aim of the present research is observing the effects of tea polyphenol varnish on caries prevention.107 children were in treated group,their first deciduous molars and deciduous incisors were treated by tea polyphenol varnish twice each.Other 110 children in control group did not receive any treatment.Two doctors examined their dental caries and recorded dmft and dmfs befoe treated and one year after treatment.The results indicate that the new caries incidence of the first deciduous molars and deciduous incisors in treatment group decreased 66% than that in control group.The results show that the new caries incidence of other untreated teethin treated group is lower significantly than that in control group.The effects of tea polyphenol varnish on preventing caries were more significant in deciduous molar than in deciduous incisor.The results also indicate that the effect of varnish is stronger in occlusal surface,and less in medial and distal surfaces of teeth.

Journal Article↗
PubMed1996

A nuclear matrix-specific factor that binds a specific segment of the negative regulatory element (NRE) of HIV-1 LTR and inhibits NF-kappa(B) activity.

The negative regulatory element (NRE) of human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR) is a defined region that has been reported to downregulate LTR-directed HIV gene expression. However, information on the precise role of this region in regulating HIV gone transcription is lacking. We have investigated the possibility that these NRE sequences regulate HIV transcription by a mechanism mediated through a nuclear matrix-specific DNA-protein interaction. We find a nuclear matrix attachment region (MAR) present within the NRE of the HIV-1 LTR that recognizes a sequence-specific DNA-binding protein present in the nuclear matrix of HIV infected cells. Moreover, we also show that the purified DNA-binding nuclear matrix protein (NMP) specifically represses the DNA-binding activity of NF-kappaB. It is likely that the MAR and MAR-enriched specific DNA-binding NMP are brought into juxtaposition by the non-chromatin scaffolding of the nucleus, thus influencing NF-kappaB (and other nuclear proteins) DNA-binding activity through protein-protein and protein-DNA interactions. Our date suggest that one possible role of the NRE could be to act as a matrix attachment site in the nuclear matrix, thus, allowing interaction with a sequence-specific trans-acting factor. The negative effect on NF-kappaB activity due to this MAR-NMP-specific interaction provides a mechanism by which the NRE downregulates HIV gene expression.

Antigens, Nuclear↗
PubMed1996

PLC gamma 1 Src homology domain induces mitogenesis in quiescent NIH 3T3 fibroblasts.

Previously, we demonstrated that microinjection of phosphoinositide-specific phospholipase C gamma 1 (PLC gamma 1) and lipase-defective mutants of PLC gamma 1 induced G(0) growth arrested NIH 3T3 fibroblasts to enter S phase of the cell cycle. These experiments suggested that regions other than the catalytic domain of PLC gamma 1 may be responsible for inducing mitogenesis. To test other regions of PLC gamma 1 for DNA synthesis inducing activity, cDNA fragments encoding Src homology (SH) and pleckstrin homology (PH) domains were subcloned into the bacterial expression plasmid pGEX-2TK, and the GST fusion proteins were purified. The complete PLC gamma l SH domain peptide was found to induce DNA synthesis after microinjection into growth arrested fibroblasts. Peptides containing a single SH3 domain or two SH2 domains induced a partial response that was restored to full activity if they were co-injected. The PH domain peptide did not induce DNA synthesis. Thus, both SH3 and SH2 activity combine to give maximum DNA synthesis induction, demonstrating that non-catalytic structural domains of PLC gamma 1 have pronounced effects on mitogenic signaling pathways.

3T3 Cells↗