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Biomedical subjects

P Liu

Publications and source records attributed to P Liu.

At least 199 records · Page 11Linked to original sources
PubMed1998

[Influence of portal triad clamping on the intestine in pigs].

A pig model of liver ischemia and intestinal congestion was made by portal triad clamping (PTC) for 45 minutes to investigate the influence of PTC on intestine. The results were as follows: 1. The level of cathepsin D was increased significantly after PTC as compared with the value before clamping (P < 0.05); 2. The endotoxin and lactic acid were significantly increased after PTC comparing with those of pre-clamping (P < 0.05, P < 0.01) and the control group (P < 0.05, P < 0.01); 3. The intestinal mucosa had a significant damage (P < 0.05) after PTC. The results indicate that PTC can result in intestinal mucosal lesion and enterotoxin absorption. Therefore, the protection of intestinal functions is important in hepatic surgery and preoperative bowel preparation should be done.

Animals↗
PubMed1998

[Factors affecting the clinical pregnancy rate in an in vitro fertilization and embryo transfer program].

OBJECTIVE: To analyze the various factors in an in vitro fertilization and embryo transfer (IVF-ET) program which may affect the clinical pregnacy rate. METHODS: A retrospective study was done on 559 IVF-ET cycles from 1992-Nov. 1995. The indication for treatment was bilateral tubal blockage. The chi 2 analysis of single factor variants with SPSS-PC + V3.0 was used for statistics. RESULTS: The overall clinical pregnancy rate in 559 cycles was 21.6%. The cause of tubal blockage due to tuberculoses consisted of 28.4%, and 34.9% of secondary sterility had the history of artificial abortion. The changes of environment, the different causes of tubal blockage, the history of previous intrauterine pregnancy did not affect the clinical pregnancy rate. When the number of embryos transferred increased to 5, the clinical pregnancy rate was highest 32.5%. The cumulative embryo score or embryo quality was related significantly with clinical pregnancy rate. CONCLUSIONS: The number and quality of embryos transferred are important factors affecting the clinical pregnancy rate. However, measures to prevent high-order multiple pregnancy and studies on the survival potential of embryos besides their morphology should be emphasized.

Chorionic Gonadotropin↗
PubMed1998

[Development of human preantral follicles and oocytes maturation in vitro].

OBJECTIVE: To study the development of human preantral follicles and oocytes maturation by in vitro culture. METHODS: Preantral follicles obtained from follicular fluid during egg retrieval in an in vitro fertilization (IVF) program was first incubated in Ham's F10 with 15% fetal cord serum (FCS). After 28 days, the medium was supplemented with different doses of hMG, mature follicular fluid (mFF) and epidermal growth factor (EGF) by orthogonal design. Induction of final maturation was completed in the presence of human menopasual gonadotropin hMG and mFF. RESULTS: Development from preantral to antral follicles was found within 6-12 days of culture. With increasing time, the proportion of follicles with diameters of more than 300 micrograms increased at 21-28 days of culture (P < 0.005). The maximal number of oocytes extrusion and first polar body formation occurred in the presence of 1501U/L hMG, 40% (v/v) mFF and 6 micrograms/L EGF. CONCLUSIONS: Follicular fluid obtained during egg retrieval in an IVF program was found to contain many preantral follicles which could develop into antral follicles with extrusion of oocytes in culture, and the oocytes matured in vitro. However, the course of development of follicles and maturation of oocytes in vitro is quite different from that in vivo.

Cells, Cultured↗
PubMed1998

[Development of human fetal preantral follicles in vitro].

OBJECTIVE: To study oocyte maturation of human fetal preantral follicles in vitro, the effects of different factors on oocyte maturation. METHODS: Preantral follicles were obtained from fetal ovaries from termination of 20-28 weeks gestation. Factors involved in the development, maturation of fetal preantral follicles were studied in tissue and cell culture by means of Northern blot, and RT-PCR (nested). RESULTS: (1) Preantral follicles obtained from fetal ovary increased in size to more than 120 microns in diameter without antrum formation and with increasing time the preantral oocytes became mature with extrusion of 1st polar body, insulin-like growth factor 1 (IGF-1) had a more marked effect on oocyte maturation, as compared with epidermal growth factor (EGF). (2) Expression of alpha fetoprotein mRNA occurred in fetal follicles on day 5, 15, 25, 35 of culture, and became negative on day 45 of culture. (3) Medium consisted of 1. human menopasual gonadotropin (hMG), 2. follicular fluid, 3. IGF-1, 4. EGF increased the expression of bcl-2 mRNA by 17.6%, 22.4%, 47.1% and 37.5% respectively in fetal follicular cells, and down-regulated the expression of p53 mRNA by 19.8%, 22.1%, 42.6% and 31.6% respectively. CONCLUSIONS: (1) The development and maturation of fetal preantral follicles in vitro differed from those in vivo. (2) Expression of bcl-2 mRNA increased and expression of wild-type p53 mRNA decreased during follicular development and maturation.

Cells, Cultured↗
PubMed1998

Expression of splice variants of CD44 mRNA and its significance in human primary hepatocellular carcinoma.

OBJECTIVE: To investigate the relationship between the expression of splice variants of CD44 (CD44v) and the metastasis of primary hepatocellular carcinoma (PHCC) in humans. METHODS: The expression of metastasis-associated CD44v mRNA in 54 specimens of human PHCC was detected by reverse transcription and polymerase chain reaction (RT-PCR) method. RESULTS: CD44v mRNA was expressed in 50 (92.59%) of the 54 specimens of PHCC, with moderate or over expression in 42 (77.78%). Among the 42 specimens with moderate or over expression, deficient tumor capsules were found in 25 (59.52%), penetration of tumor capsule in 15 (35.71%), tumor emboli in the portal vein in 34 (80.95%), and daughter tumor nodules in 29 (69.05%). Meanwhile, 12 of the 54 specimens showed negative or weak expression of CD44v mRNA. Of them, all had tumor capsules, 1 (8.33%) had penetrated tumor capsule, 1 (8.33%) had tumor emboli in the portal vein, and 2 (16.67%) had daughter tumor nodules. CONCLUSION: CD44v may contribute to the metastatic potential of PHCC.

Carcinoma, Hepatocellular↗
PubMed1998

[Gas chromatographic determination of camphora, mentholum, isoborneol and borneol in Guanxingao].

Guanxingao is a kind of traditional Chinese rubber electuary medicine which is able to either cure or guard against coronary heart disease and angina pectoris. The contents of camphora, mentholum, isoborneol and borneol in Guanxingao are determined by gas chromatography. The purpose of the study is to detect and control the loss of the four volatile components through production and standing and to guarantee the curative effect. Chromatographic analysis was performed on a GC-4004 gas chromatograph(FID). The column was a 3 mm i.d. x 2 m stainless steel tube packed with 7% PEG-1500 on 100-110 mesh 102 non-silanized white support. The column and the FID temperatures were 115 degrees C and 180 degrees C respectively. H2 was the carrier gas, 30 mL/min. Internal standard method was used for the quantitative estimation with naphthalene as the internal standard. The linear ranges were at least within 50-450 mg/L (r = 0.9999, n = 4). The correction factors against naphthalene were 1.262-1.286 and the RSDs were 0.32%-1.5%(n = 12). The recoveries were 98.44%-101.9%. In comparison with the theoretical contents, the average loss percentages are 71.72% (camphora), 65.60% (mentholum) and 66.31% (isoborneol + borneol). The samples were pretreated by means of isothermal (35 degrees C) water-bath extraction with acetone for 6 times with four hours each.

Camphanes↗
PubMed1998

[An analysis on therapeutic effects of excimer laser photorefractive keratectomy for high myopia].

OBJECTIVE: To evaluate the therapeutic effects of 193-nm excimer laser photorefractive keratectomy for the correction of high myopia. METHODS: A Keracor 116 excimer laser and a tapered transition zone technique were used to treat high myopia. It was divided into two groups: the first group -6.00 - 9.75 D, 233 eyes; the second group -10.00 - 14.00 D, 55 eyes. The effect of the tapered transition zone on refraction stability was investigated in a 12-month follow-up study. RESULTS: At one year, of these eyes, 79.4% eyes attained visual acuity of 0.5 or better, 31.6% improved to 1.0 or better, 93.8% of the eyes improved or their best corrected visual acuity did not change, whereas 6.2% lost at least one line. Corneal haze was observed to be severe in one month, and diminished considerably at 6 and 12 months. At one year, no haze could be seen in 87.4%. 52.0% were within +/- 1.00 D and 80.9% in +/- 2.00 D. During one year, 14.9% were complicated with glaucoma because of using steroid drops. CONCLUSION: These data show that excimer PRK for treatment of high myopia is an effective and safe refractive surgery. For severe myopia, it is an effective surgery, but predictability is not satisfactory, and long term follow-up is necessary.

Adolescent↗
PubMed1998

Inhibition of nitric oxide synthase attenuates peroxynitrite generation, but augments neutrophil accumulation in hepatic ischemia-reperfusion in rats.

The role of nitric oxide (NO) and peroxynitrite in the process of neutrophil adhesion and infiltration was investigated in a model of hepatic ischemia-reperfusion. Male Fischer rats were subjected to 30 min of hepatic no-flow ischemia followed by 4 h of reperfusion (I/R). I/R induced liver injury as evidenced by a 13.7-fold increase in plasma alanine aminotransferase activity. Induction of liver injury was associated with an increase in neutrophil accumulation in ischemic lobes of livers [215 +/- 27 polymorphonuclear neutrophil leukocytes/50 high-power field (HPF), P < .05 compared with sham control] and 8-fold augmentation of inducible NO synthase (NOS) activity. However, NO levels in the liver decreased; this decrease may be caused by peroxynitrite formation by the reaction of NO with superoxide. Sections of ischemic lobes of the liver tissue of I/R animals exhibited marked immunoreactivity with anti-nitrotyrosine antibody, which indicates the presence of nitrotyrosine. Administration of Nw-nitro-L-arginine methyl ester (10 mg/kg i.v. before reperfusion) attenuated total and inducible NOS activity in both ischemic and nonischemic lobes of liver, and reduced NO levels in plasma and liver. However, NOS inhibition aggravated liver injury as alanine aminotransferase increased by 61% compared with rats subjected to reperfusion injury. Neutrophil accumulation was enhanced in ischemic (436 +/- 48/50 HPF, P < .05 compared with I/R animal) and nonischemic lobes of livers (34 +/- 3.2/50 HPF, P < .05 compared with sham control). NOS inhibition also attenuated immunohistochemically detected nitrotyrosine formation, but increased superoxide production in the liver. The NO-dependent regulation of neutrophil accumulation in the liver may be linked closely to P-selectin and intracellular adhesion molecule-1 expression because inhibition of NOS resulted in significant increases in gene expression of these two adhesion molecules (determined by reverse transcription-polymerase chain reaction analysis). These results suggest that NO is important in attenuating neutrophil accumulation and liver damage in ischemia-reperfusion injury. Inhibition of NOS activity reduces peroxynitrite formation but aggravates liver injury and increases neutrophil accumulation, which suggests that the anti-inflammatory function of NO is more important than the cytotoxic potential of peroxynitrite in acute inflammation.

Alanine Transaminase↗
PubMed1998

Comparative study on 4 EIA kits for screening antibody to hepatitis C virus in pooled sera.

Four enzyme immunoassay (EIA) test kits, 1 Canadian product and 3 Chinese products, were used in the comparative study. Each pool consisted of 5 sera, and the 5 single sera were tested as controls. The tests were carried out according to the instructions, keeping the same dilution of each serum in single and pool samples. It was found that with the Canadian kit, the positive and negative results of pooled sera had no difference from that of the controls (P > 0.10). In the case of Chinese Yali and Kehua kits, the positive results of pooled sera showed no difference from the controls (P > 0.10), but the optical density (OD) of negative pools were increased (P < 0.01), though quite distant from the cut-off values. In the case of Changzheng kit, the OD of positive pools were significantly lower than those of the controls (P < 0.05), and weak positive samples missed the detection. However this problem could be overcome by blocking the microwells beforehand. Our experiment demonstrate that not all EIA test kits are suitable for screening pools for antibody to hepatitis C virus, and that it is important to assess the sensitivity of the EIA kit to be used for this purpose.

Antibodies, Viral↗
PubMed1998

Clinical and pathophysiological effects of active and passive smoking on the cardiovascular system.

Both passive and active cigarette smoking increase the risk of cardiovascular disease, the leading cause of death in Western industrialized nations. The prevalence of smoking as a major cardiovascular risk factor has been well characterized over the past 30 years. The two demographic groups of particular concern are women and the young. The relationship between active tobacco smoking and increased risk of coronary artery disease (stable and unstable angina, acute myocardial infarction or sudden death), cerebrovascular disease (cerebral infarction, and cerebral and subarachnoid hemorrhage), peripheral arterial disease (large and small vessel) and aortic aneurysm has been well established in numerous longitudinal and cross-sectional epidemiological and basic science studies. More recently, passive smoking has been shown to represent an important risk factor for coronary artery disease. Smoking can elicit both acute and chronic cardiac and vascular events due to the multiplicity of mechanisms involved: hematological, neurohormonal, metabolic, hemodynamic, molecular genetic and biochemical pathways. Smoking cessation can result in both the inhibition of progression and the regression of pathophysiological changes, improving morbidity and mortality among chronic smokers. The incidence of coronary artery and cerebrovascular diseases in former smokers decreases by 50% two to three years following cessation, but a small long term excess risk persists. Smoking as a cardiovascular risk factor and the clinical cardiovascular features associated with active and passive smoking are discussed, and a pathophysiological framework to explain the association between cigarette smoking and cardiovascular disease is provided.

Cardiovascular Diseases↗
PubMed1998

Thirteen years of manipulating the mouse genome: a personal history.

In 1974, Dr. Ralph Brinster published a paper describing the consequences of injecting embryonal carcinoma cells, the predecessors of embryonic stem cells, into mouse blastocysts. Despite their early promise, embryonal carcinoma cells would not efficiently populate the germ line of mice. A decade later Elizabeth Robertson and I described the efficient generation of germline chimaeras from cultured embryonic stem cells and shortly afterwards the genetic manipulation of the mouse germline using ES cells. Our demonstration of the potency of Embryonic Stem cells gave birth to a new era in manipulative mouse genetics, one in which endogenous genes can now be mutated at will using gene targeting of retroviral mutagenesis. This review focuses on the development and testing of concepts and techniques during the thirteen years after we knew germline modification of endogenous genes in the mouse would be possible. This period is one in which more and more sophisticated tools for manipulating the mouse germline were developed and implemented. In this review I have taken the rare opportunity to reveal some of my thought processes, frustrations, successes and failures as we moved through this exciting period of rapid technological change. As I look forward to the next thirteen years, I feel that this will be an equally exciting period for manipulative genetics as we struggle to formulate concepts and design experiments that enable us to understand gene function in an era when the sequence of all genes will be known.

Animals↗
PubMed1997

Platelet-derived growth factor activates mitogen-activated protein kinase in isolated caveolae.

The ability of a peptide hormone to affect many different intracellular targets is thought to be possible because of the modular organization of signal transducing molecules in the cell. Evidence for the presence of signaling modules in metazoan cells, however, is incomplete. Herein we show, with morphology and cell fractionation, that all the components of a mitogen-activated protein kinase pathway are concentrated in caveolae of unstimulated human fibroblasts. Addition of platelet-derived growth factor to either the intact cell or caveolae isolated from these cells stimulates tyrosine phosphorylation and activates mitogen-activated protein kinases in caveolae. The molecular machinery for kinase activation, therefore, is preorganized at the cell surface of quiescent cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

Activating mutations in the N- and K-ras oncogenes differentially affect the growth properties of the IL-6-dependent myeloma cell line ANBL6.

Although the underlying genetic defect in multiple myeloma is unknown, activating mutations in the N- and K-ras oncogenes are common. Recent studies have suggested that ras mutations are associated with disease progression. We have introduced an activated N-ras12, N-ras61, or K-ras12 cDNA into the interleukin 6 (IL-6)-dependent multiple myeloma cell line ANBL6 to determine the effect of N- and K-ras on the growth/death properties of ANBL6. All three transduced cell populations demonstrate a growth advantage over the parent ANBL6 when propagated on normal human bone marrow stromal cells. In the absence of bone marrow stromal cells, augmentation of growth was observed in all three mutant ras-expressing populations at optimal and suboptimal concentrations of IL-6. Furthermore, in the absence of IL-6, all mutant ras populations demonstrated an augmentation in DNA synthesis when compared to the parent ANBL6. However, growth of the K-ras12 population in the absence of IL-6 was significantly inhibited when compared to the mutant N-ras populations. This could be explained by the observation that in the absence of IL-6, N-ras12 and N-ras61 suppress apoptosis, whereas K-ras12 does not. We also found that mutant ras expression could result in early protection from glucocorticoid-induced apoptosis similar to that observed by the addition of IL-6. However, the combination of mutant ras and IL-6 could completely block the glucocorticoid induction of apoptosis in long-term cultures. These data suggest that mutations in different ras family members may have similar or distinct effects on myeloma tumor growth and death and may alter the response to glucocorticoid treatment.

Apoptosis↗
PubMed1997

Binding of the ubiquitous cellular transcription factors Sp1 and Sp3 to the ZI domains in the Epstein-Barr virus lytic switch BZLF1 gene promoter.

Induction of the Epstein-Barr virus lytic cycle in latently infected B cells requires the expression of the immediate-early lytic gene BZLF1. We have previously identified several cis-elements within the BZLF1 promoter that are required for induction by known inducers of the lytic cycle [E. Flemington and S. H. Speck (1990)J. Virol. 64, 1217-1226]. These include four elements termed the ZI domains (ZIA, ZIB, ZIC, and ZID) that share extensive homology and that have recently been shown to bind several cellular transcription factors [A. M. Borras, J. L. Strominger, and S. H. Speck (1996) J. Virol. 70, 3894-3901]. Here Sp1 and Sp3 are identified as the cellular factors present in crude B cell nuclear extract preparations that bind to the ZIC domain. In addition, three of the four complexes observed in electrophoretic mobility shift analyses employing probes containing either the ZIA or the ZID domains also represent Sp1 or Sp3 binding. Binding of Sp1 and Sp3 to the ZI domains was shown to be significantly weaker than binding of these factors to a consensus Sp1 site. A heterologous promoter construct containing three repeats of a consensus Sp1 site, cloned upstream of a single copy of the ZII (CREB/ AP1) element from the BZLF1 promoter linked to the beta-globin TATA box, exhibited phorbol ester inducibility. The latter observation was consistent with the functional behavior exhibited by a heterologous promoter construct containing multiple copies of the ZIC domain liked to the ZII element. However, the basal activity of the heterologous promoter construct driven by the consensus Sp1 sites was ca. 10-fold higher than that of the heterologous reporter construct containing multimerized ZIC sites. Thus, the low affinity of Sp1 binding to the ZI domains may contribute to the low-level basal activity of the BZLF1 promoter.

Binding Sites↗
PubMed1997

Cyclosporin A-sensitive induction of the Epstein-Barr virus lytic switch is mediated via a novel pathway involving a MEF2 family member.

Induction of the Epstein-Barr virus (EBV) lytic cycle by crosslinking surface immunoglobulin is inhibited by the immunosuppressants cyclosporin A (CsA) and FK506. This correlates with the ability of CsA to inhibit Ca2+-dependent transcription of the lytic cycle switch gene BZLF1. It is shown here that CsA sensitivity maps to three sites (ZIA, ZIB and ZID) that bind the serum response factor-related protein MEF2D. A synthetic promoter containing multiple copies of a MEF2D site from Zp, in conjunction with a CREB/AP-1 site (ZII) from Zp, exhibits CsA-sensitive inducibility. Furthermore, the Zp MEF2D sites were functionally interchangeable with MEF2 sites derived from heterologous promoters. While no evidence of a NFAT family member binding to either the MEF2 or CREB/AP-1 sites was obtained, it could be demonstrated that CsA-sensitive induction of Zp was mediated by calcineurin and NFATc2 in synergy with either phorbol ester or especially with the EBV-induced Ca2+/calmodulin-dependent kinase type IV/Gr. These studies identify Zp as prototypic of a novel class of CsA-sensitive and NFAT-dependent promoters defined by the presence of MEF2 sites.

Binding Sites↗
PubMed1997

Parallel involvement of perirhinal and lateral entorhinal cortex in the polysynaptic activation of hippocampus by olfactory inputs.

It has previously been shown that olfactory input to the hippocampus (HPC) is mediated polysynaptically via the lateral entorhinal cortex (LEC), the site of origin of the lateral perforant pathway (LPP). Because previous anatomical studies have shown that olfactory projections also terminate in perirhinal cortex and that this latter region projects directly to the hippocampus, we investigated the role of perirhinal cortex (PRC) in the mediation of the olfactory-hippocampal potential in the rat. Single-pulse stimulation of the lateral olfactory tract (LOT) resulted in a long onset latency (12-20 ms) evoked response in the dentate gyrus of the ipsilateral hippocampal formation. LOT-HPC potentials were rapidly and completely abolished following the microinfusion of procaine into the LPP, suggesting that they are ultimately mediated via this pathway. In support of this finding, current source density analysis indicated that the LOT-HPC response was generated by a current sink at the outer molecular layer of both dorsal and ventral blades of the dentate gurus. Electrolytic and ibotenic acid lesions of PRC produced a significant decrease in the amplitude of LOT-HPC potentials when testing was conducted 4-7 days postlesion. Lesions of LEC produced similar effects and combined lesions of LEC and PRC resulted in an almost complete eradication of the potential, suggesting that parallel entorhinal-hippocampal and perirhinal-hippocampal pathways are involved. These data suggest, therefore, that a portion of the olfactory input to the hippocampus is mediated via polysynaptic connections routed through perirhinal cortex. Because recent research has suggested that PRC plays an important role within the temporal lobe memory system, this connectivity may be important for olfactory memory processes.

Amygdala↗