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F Liu

Publications and source records attributed to F Liu.

At least 451 records · Page 25Linked to original sources
PubMed1997

Factors controlling the efficiency of cationic lipid-mediated transfection in vivo via intravenous administration.

The factors controlling the transfection efficiency of cationic lipid carrier systems following intravenous administration are poorly understood. Using N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) combined with Tween 80 as a carrier system and cDNA of luciferase or beta-galactosidase gene as a reporter, we investigated the importance of DOTMA to DNA ratio and the ratio of DOTMA to Tween 80 in the lipid formulation in determining the site and level of transgene expression following intravenous administration. The data show that all of the internal organs, including lung, liver, spleen, heart and kidneys, expressed the transgene upon systemic administration into animals with 25 micrograms of plasmid DNA when complexed with DOTMA-Tween 80 lipid formulation. The transfection efficiency was dependent on both DOTMA to DNA, and DOTMA to Tween 80 ratios. Among the organs examined, the lung appeared to be more transfectable than other organs. A better transfection activity was obtained with higher DOTMA to DNA and DOTMA to Tween 80 ratios. Time-response curve shows that gene expression was transient with a maximal level between 10 and 24 h after injection. Results from tissue distribution studies with 125I-labeled plasmid DNA and Southern analysis suggest that the transient expression is the result of the loss of transgene from the transfected cells. These results suggest that cationic lipid-based delivery systems can be efficient for gene delivery if the composition of the DNA-lipid complexes is properly controlled.

Animals↗
PubMed1997

Proximal nephron Na+/H+ exchange is regulated by alpha 1A- and alpha 1B-adrenergic receptor subtypes.

Activation of alpha 1-adrenergic receptors (alpha 1-AR) increases Na+/H+ exchange (NHE) in proximal tubule. NHE mediates the majority of active Na+ absorption in the proximal tubule. Three alpha 1-AR subtypes have been detected in kidney by molecular and binding techniques. We detected message for all three alpha 1-AR subtypes in mouse proximal tubule cells through reverse transcription-polymerase chain reaction and Northern analysis. To determine the alpha 1-AR subtypes that regulate NHE in mouse proximal tubule cells, two strategies were used: (i) antisense oligodeoxynucleotides (ODNs) to selectively inhibit expression of alpha 1A-, alpha 1B-, and alpha 1D-AR subtypes and (ii) subtype-selective alpha 1-AR antagonists. Streptolysin-O permeabilization was used to introduce antisense and sense ODNs into cells three times over 72 hr. Western blot analysis of membranes prepared from cells treated with alpha 1B-AR antisense ODN demonstrated that alpha 1B-AR protein expression was reduced by 90% at 72 hr compared with control or sense ODN treatments. Functional regulation of NHE by alpha 1-ARs was determined by alpha 1-AR agonist changes in intracellular pH (pHi) in cells grown on coverslips and loaded with 2',7'-bis(2-carboxyethyl)-5(6)carboxyfluorescein-acetoxymethyl ester. Antisense ODNs for alpha 1B-AR significantly reduced phenylephrine (PHE)-induced maximal changes in pHi by 49%. The PHE-induced changes in pHi observed in cells treated with alpha 1A-AR antisense ODNs was reduced by 42%. The selective alpha 1A-AR antagonist WB-4101 and the alpha 1B-AR antagonist spiperone reduce PHE-induced pHi increases to a comparable extent. No significant changes in pHi were observed with cells treated with alpha 1D-AR antisense ODNs or the alpha 1D-AR antagonist BMY 7378 compared with untreated cells. Combined treatment with alpha 1A- and alpha 1B-AR antisense ODNs and antagonists additively inhibits PHE-induced delta pHi by 90%. We conclude that alpha 1A and alpha 1B-AR but not alpha 1D-ARs regulate NHE in proximal tubule cells.

Adrenergic alpha-Agonists↗
PubMed1997

The human Myt1 kinase preferentially phosphorylates Cdc2 on threonine 14 and localizes to the endoplasmic reticulum and Golgi complex.

Entry into mitosis requires the activity of the Cdc2 kinase. Cdc2 associates with the B-type cyclins, and the Cdc2-cyclin B heterodimer is in turn regulated by phosphorylation. Phosphorylation of threonine 161 is required for the Cdc2-cyclin B complex to be catalytically active, whereas phosphorylation of threonine 14 and tyrosine 15 is inhibitory. Human kinases that catalyze the phosphorylation of threonine 161 and tyrosine 15 have been identified. Here we report the isolation of a novel human cDNA encoding a dual-specificity protein kinase (designated Myt1Hu) that preferentially phosphorylates Cdc2 on threonine 14 in a cyclin-dependent manner. Myt1Hu is 46% identical to Myt1Xe, a kinase recently characterized from Xenopus laevis. Myt1Hu localizes to the endoplasmic reticulum and Golgi complex in HeLa cells. A stretch of hydrophobic and uncharged amino acids located outside the catalytic domain of Myt1Hu is the likely membrane-targeting domain, as its deletion results in the localization of Myt1Hu primarily to the nucleus.

Amino Acid Sequence↗
PubMed1997

Permeability properties of monolayers of the human trophoblast cell line BeWo.

The BeWo cell line (b30 clone) has been examined as a potential in vitro system to study transplacental transport. At the light and electron microscope level, the cells were observed to form confluent monolayers on polycarbonate filters in approximately 5 days and morphologically resembled the typical human trophoblast. BeWo monolayers developed a modest transepithelial electrical resistance and a molecular size-dependent permeability to hydrophilic passive diffusion markers, fluorescein, and selected fluorescein-labeled dextrans. Linoleic acid permeation across BeWo monolayers was asymmetric, saturable, and inhibited by low temperature and excess competing fatty acid. Forskolin and 8-bromoadenosine 3',5'-cyclic monophosphate treatments stimulated morphological changes in BeWo cultures and enhanced the asymmetric passage of linoleic acid across the BeWo monolayers while having minimal effects on passive permeability, affirming that the differentiation state of the cells can influence membrane transporters and transmonolayer permeability. The basic permeability properties of the BeWo monolayers suggest that the cells grown on permeable supports may be examined as a convenient in vitro system to evaluate some transplacental transport mechanisms.

Amiloride↗
PubMed1997

Bioactivity of a 29-kilodalton insulin-like growth factor binding protein-3 fragment present in excess in chronic renal failure serum.

Children with chronic renal failure (CRF) have normal or high serum levels of GH, IGF-I, and IGF-II. Despite this, the serum of CRF patients has low IGF bioactivity, which may contribute to CRF growth failure. Recent studies suggest that excess IGF binding proteins (IGFBPs) in the approximately 35-kD fractions of CRF serum contribute to this low IGF bioactivity. This report characterizes a 29-kD form of IGFBP-3, IGFBP-3(29), which accumulates in the approximately 35-kD fractions of CRF serum and peritoneal dialysate. Deglycosylation and [125I]IGF ligand blot studies show that IGFBP-3(29) is a glycosylated IGFBP-3 fragment with low affinity for IGF peptides. Using an IGFBP-3 antibody column, IGFBP-3(29) was purified to homogeneity from the approximately 35-kD fractions of peritoneal dialysate from children with CRF. Compared with native IGFBP-3, pure IGFBP-3(29) has a 4-10-fold lower affinity for IGF-II and a 200-fold lower affinity for IGF-I. Consistent with the binding data, IGFBP-3(29) inhibited IGF-II-stimulated thymidine incorporation in chondrosarcoma cells, but was a less potent inhibitor than native IGFBP-3; also, native IGFBP-3 clearly inhibited IGF-I-stimulated thymidine incorporation in chondrosarcoma cells and potentiated IGF-I-stimulated aminoisobutyric acid uptake in bovine fibroblasts, but higher concentrations of IGFBP-3(29) had no effect on these IGF-I actions. Thus, the 29-kD IGFBP-3 form that accumulates in CRF serum and extravascular spaces is an IGFBP-3 fragment that may modulate IGF-II, but not IGF-I, effects on target tissues. Whether IGFBP-3(29) plays any role in the growth failure of children with CRF remains to be determined.

Animals↗
PubMed1997

Insulin-like growth factor-binding protein-6 levels are elevated in serum of children with chronic renal failure: a report of the Southwest Pediatric Nephrology Study Group.

Previous studies suggest that growth retardation in children with chronic renal failure (CRF) results in part from inhibition of insulin-like growth factor (IGF) action by excess serum IGF-binding proteins (IGFBPs). Excess IGFBPs in CRF serum include IGFBP-1, -2, and -3 and a diffuse approximately 24- to 28-kDa IGFBP band identified by [125I]IGF ligand blot. The present studies characterized this diffuse approximately 24- to 28-kDa band. Initial studies identified this band as IGFBP-6, because it was immunoprecipitated by antiserum raised against a synthetic peptide of human IGFBP-6 (hIGFBP-6). Additional [125I]IGF ligand blots found that the immunoprecipitated band was 1) recognized by [125I]IGF-II but not [125I]IGF-1, 2) more abundant in CRF than in normal serum, and 3) more abundant in serum from dialyzed than nondialyzed prepubertal CRF children. Using the hIGFBP-6 antiserum in a specific and sensitive RIA, we found that serum IGFBP-6 levels were 4.7 +/- 1.7 nmol/L in 10 normal prepubertal children, 21.4 +/- 6.1 nmol/L in 44 nondialyzed prepubertal CRF children, 73.5 +/- 14.4 nmol/L in 7 dialyzed prepubertal CRF children, and 94.6 +/- 26.2 nmol/L in 14 dialyzed pubertal CRF children. IGFBP-6 levels were also elevated in 71 nondialyzed European children with CRF. In nondialyzed CRF children, serum IGFBP-6 levels 1) correlated inversely with the glomerular filtration rate, 2) did not correlate with height SD score, and 3) were not altered by 12 months of daily recombinant hGH treatment. In summary, a specific antiserum and RIA were used to demonstrate elevated levels of intact IGF-II-binding IGFBP-6 in serum of CRF children. We postulate that the excess IGFBP-6 may modulate the action of IGF-II on target tissues.

Adolescent↗
PubMed1997

Site-directed mutagenesis and yeast two-hybrid studies of the insulin and insulin-like growth factor-1 receptors: the Src homology-2 domain-containing protein hGrb10 binds to the autophosphorylated tyrosine residues in the kinase domain of the insulin receptor.

To characterize the structural basis for the interaction between hGrb10 and the insulin receptor and the insulin-like growth factor-1 receptor, different mutant receptors containing a segment of deletion in either the juxtamembrane domain or in the C terminus of the receptors, or containing tyrosine-to-phenylalanine point mutations in these regions of the insulin receptor, were generated. Yeast two-hybrid and in vitro binding studies of the interaction between the mutant receptors and hGrb10 revealed that tyrosine residues in these regions are not essential for the binding of hGrb10. To further identify the binding site for hGrb10, all conserved tyrosine residues in the kinase domain of the insulin receptor were replaced with either phenylalanine or alanine by site-directed mutagenesis. Mutations of all tyrosine residues in this region, except at positions 1162/1163, did not inhibit the binding of the receptor to hGrb10. The binding of the Src homology 2 domain of hGrb10 to the receptors was significantly enhanced in the presence of an intact pleckstrin homology domain. Our findings suggest that, unlike other Src homology 2 domain-containing proteins, hGrb10 binds to the autophosphorylated tyrosine residues in the kinase domain of the insulin receptor, and the pleckstrin homology domain plays an important role in hGrb10/receptor interaction. Because the autophosphorylated tyrosine residues are critical for the autophosphorylation and kinase activity of the receptor, the binding of hGrb10 at these sites may suggest a role for the protein in the transduction or regulation of insulin receptor signaling.

Amino Acid Sequence↗
PubMed1997

Assemblases and coupling proteins in thick filament assembly.

Thick filaments are stable assemblies of myosin that are characteristic of specific muscle types from both vertebrates and invertebrates. In general, their structure and assembly require remarkably precise determination of lengths and diameters, structural differentiation and nonequivalence of myosins, a high degree of inelasticity and rigidity, and dynamic regulation of assembly and disassembly in response to both extracellular and intracellular signals. Directed assembly of myosin in which additional proteins function in key roles, therefore, is more likely to be significant than the simple self assembly of myosin into thick filaments. The nematode Caenorhabditis elegans permits a wide spectrum of biochemical, genetic, molecular and structural approaches to be applied to the experimental testing of this hypothesis. Biochemical analysis of C. elegans thick filaments reveals that paramyosin, a homologue of the myosin rod that is the unique product of a single genetic locus, exists as two populations which differ by post-translational modification. The major paramyosin species interacts with the two genetically specified myosin heavy chain isoforms. The minor paramyosin species is organized within the cores of the thick filaments, where it is associated stoichiometrically with three recently identified proteins P20, P28 and P30. These proteins have now been characterized molecularly and contain unique, novel amino acid sequences. Structural analysis of the core shows that seven paramyosin subfilaments are crosslinked by additional internal proteins into a highly rigid tubule. P20, P28 and P30 are proposed to couple the paramyosin subfilaments together into the core tubule during filament assembly. Mutants that affect paramyosin assembly are being characterized for alterations in the core proteins. A fourth protein has been identified recently as the product of the unc-45 gene. Computational analysis of this gene's DNA suggests that the predicted protein may exhibit protein phosphatase and chaperone activities. Genetic analysis shows that three classes of specific unc-45 mutant proteins differentially interact with the two myosins during thick filament assembly. The unc-45 protein is proposed to be a myosin assemblase, a protein catalyst of thick filament assembly.

Actin Cytoskeleton↗
PubMed1997

[Changes in arterial blood pressure and hypothalamic neural activity in response to caloric stimulation in guinea pigs].

We investigated the effects of caloric stimulation on arterial blood pressure (AP) and neural activity in the hypothalamic paraventricular nucleus (PVN) in anesthetized guinea pigs. Hot water stimulation of the labyrinth produced a decrease in AP in 56 of 73 cases tested, and AP decrease followed by increase in 12 cases. In the cases where AP initially decreased and then increased, 92% of PVN neurons responded as excitatory or inhibitory to caloric stimulation. When the AP change was a decrease alone, the responsive rate of the PVN neurons was 63%, and no change in PVN neural activity was seen in the group which showed no AP change after caloric stimulation. The ratio of the PVN neurons showing inhibition in the group that showed AP decrease-increase sequence was significantly higher than that in the group showing AP decrease alone. AP changes following caloric stimulation were greatly reduced after electric destruction of the anterior and middle parts of the hypothalamus. This indicates that the activation of the hypothalamic neurons by the vestibular input is important to produce the vestibulovasomotor response and its pattern. When the same amount of stimulus was applied periodically to the labyrinth, the AP increment component was increased with time. It is suggested that the pattern of AP changes is greatly influenced by level of consciousness. It is suggested that the basal activity level of the autonomic nervous system, and the variety and magnitude of the vestibular stimuli should be synthetically evaluated when the autonomic nerve function test is applied to patients suffering dizziness.

Animals↗
PubMed1997

[Proliferative activities, oncoprotein expression and their significance in human gliomas].

OBJECTIVE: To explore the relationship between the proliferative activities, oncoprotein expression, cell differentiation and prognosis of gliomas. METHODS: Immunohistochemistry and image analysis were used to study the expression of proliferating cell nuclear antigen (PCNA) and several oncoproteins both qualitatively and quantitatively in 124 brain gliomas. RESULTS: It was found that the intensities of PCNA reaction were significantly related to both the grade and prognosis of gliomas. Overexpression of c-erbB-2 protein was slightly stronger in well than in poorly-differenciated gliomas. Moreover, the reactions in patients who survived over 5 years were stronger than in those under 5 years. EGF (40.0%), EGFR (91.4%) and p21ras (53.3%) expression levels were related to neigher the grading nor prognosis of this tumor. The positive ratios of the three antibodies to p53 protein were higher in grades II-IV than in grade I gliomas. The intensity of p53 reaction was correlated to that of PCNA. CONCLUSION: It is suggested that the aberration of c-erbB-2, p21ras, EGF and EGFR might be the early events in the initiation and progression of gliomas, whereas p53 is involved in all stages of these tumors. PCNA could reflect the degree of malignancy to a certain extent.

Brain Neoplasms↗
PubMed1997

[Effect of hypoxia on maximal myocardial blood flow in right ventricle].

In order to study the changes of coronary reserve capacity, the effects of hypoxia on hemodynamics and maximal myocardial blood flow in right ventricle were observed. Rats wre divided into 3 groups:normoxic group (control), acute hypoxic group and chronic hypoxic group. Maxmimal myocardial blood flow in the right ventricle was measured with 99 m Tc radiolabelled from RBC during adenosine infusion. The results showed that cardiac output, PaO2 and oxygen delivery were decreased during acute hypoxia, but myocardial blood flow in right ventricle was increased, as compared with the control group. There were no significant change of maximal myocardial blood flow in the right ventricle in acute hypoxic rats. Hematocrit and blood viscosity at different shear rate and RV weight index were augmented, whereas oxygen delivery and myocardial blood flow became normal during chronic hypoxia. Maximal blood flow in RV was significantly decreased whereas arterial wall thickness and collagen in arterial adventitia were increased in chronic hypoxic rats. The above results suggest that the decreased coronary reserve might beresulted from the increasedblood viscosity, arterial wall thickness and collagen in arterial adventitia and right ventricular hypertrophy.

Animals↗
PubMed1997

[The diagnosis and surgical treatment in rectal endometriosis].

From Jun 1975 to Mar 1995, 26 cases of endometriosis in the rectum (RE) were admitted. Local resection was performed in 16 and Dixon's operation in 10. The result showed 21 cases were symptomatically cured and 5 with remission. 2 cases were reoperated because of recurrence in 5 years after the first operation and cured. RE is difficult in distiguishing from rectal cancer. It is characterized by tenesmus, bursting pain, hematochezia in young and middle aged women during periods. The diagnosis can be made by tipycal history and vaginal examination, rectal examination, barium enema, proctoscopy and so on. The indications of operation include severe clinic symptoms and failed conservative therapy. Wedge resection was suitable in cases with small lession in rectum, while large, deep seated lessions in lower rectum were treated with Dixon's operation in order to prevent recurrence.

Adult↗
PubMed1997

[Influence of preoperative on gastric cancer tissues and cells].

We studied how gastric cancer tissues and cells changed as a result of preoperative chemotherapy. 82 patients with gastric cancer in TNM I-IV stage underwent preoperative selective vascular chemotherapy with routine quantity of FAM. Histological analysis of their postoperative specimens revealed the following results. (1) Cancer tissues necrosed in 56.1% patients. These necroses, due to the chemotherapy, were located around vascular vessels. (2) Cancer cells were found to change with karyopyknosis, karyorrhexis, coagulation and necrosis of cytoplasm. There were invasion of lymphocytes, inflammation edema, and fibroelastosis around cancer cells as well. Changes were also observed in vessels with proliferous intima and thrombus. Most of these changes were grade 2. This paper summarises that preoperative vascular chemotherapy can bring about evident histological and cell changes in different types of gastric cancer. This kind of chemotherapy is recommended as one of integrative treatments to gastric cancer.

Adenocarcinoma↗
PubMed1997

[The role of CDDP on cytotoxicity of TILs obtained from colorectal tumors].

The effects of intravenous injection of cisplatin (CDDP) and the incubated with CDDP in vitro on the epitopes and cytotoxicity of TIL obtained from eight colorectal tumor patients were detected respectively by flow cytometer. There was a significant increase in CD3+/CD8+ subset in TIL in patients receiving intravenous injection of CDDP. And the cytotoxicity of these TILs increased significantly. The cytotoxities were positively correlated with the amount of CD3+/CD8+ subset in TIL. Raji cells incubated with CDDP in vitro showed increased susceptibility to TIL induced lysis.

Antineoplastic Agents↗
PubMed1997

[Perioperative plasma amino acid spectrum analysis in portal hypertensive cirrhotic patients undergoing portacaval H-graft shunt].

Perioperative plasma amino acid spectrum (PAAS) was analysed in 10 portal hypertensive patients (PH) receiving portacaval H-graft shunt (D = 8 mm) and 10 gastroenteropathic patients (GE) without hepatic disease. In both groups, arterial, peripheral and hepatic venous blood was drawn for analysis immediately pre- and post-operation on the table, postoperative day 1 and 3, respectively. It was found that amino acid concentration decreased in both groups but in PH group it was changed significantly. The preoperative branched chain amino acid (BCAA)/aromatic amino acid (AAA) ratio was less than 2 in the PH group and larger than 3 in the GE group after operation. The ratio did not change significantly in both groups after operation. In the PH group, the pre- and post-operative BCAA and AAA level in hepatic vein was higher than in other sites. The immediately BCAA and AAA levels were lower than preoperative levels. Among the changes the postoperative decrease of VAL and LEU was significant. Both BCAA and AAA reached preoperative level at postoperative day3. The results reveal that small diameter portacaval shunt has no significant influence on PAAS. The temporary decrease of amino acid levels postoperatively may be related to the stress of operation and liver impairement.

Adult↗
PubMed1997

[Study on optimal conditions for the determination of glucose by measurement of oxygen consumption rate].

We studied optimal conditions for the determination of oxygen consumption rate (OCR). The assay, with a working range up to 35 mmol/L, had an intra-assay coefficient of variation of 0.7%-3.52%, and the inter-assay coefficient of variation was 4.86%. In spiking experiments, the recovery range was 98.9%-101%. The assay was compared with CX3 (Beckman Co.). A linear regression analysis yielded a slope of 1.05, an inercept of 3.82 and a correlation coefficient of 0.999. The serum of turbidity above +2 had a negative interference on the assay (> 3.4%). The obvious interference of hemolysis, icterus and vitamin C to the assay were not observed.

Blood Glucose↗
PubMed1997

[Application of preoperative angiography in diagnosis of gastric cancer].

To improve preoperative diagnosis of gastric cancer, we applied DSA in clinical diagnosis. 36 patients with gastric cancer were observed. Preoperative DSA and postoperative pathological analysis revealed the following results. With DSA, the accuracy of diagnosis of invasion depth of gastric cancer reached 72.2%. We summarised the criteria for diagnosis of gastric cancer. If subsidiary anastomotic channels narrow or obliterate in DSA, the case may be early cancer. If parietal branches narrow or obliterate in DSA, the cancer may invade the muscle of the stomach. If arcade of this lesser curvature narrows in DSA, the cancer may invade the serosa of the stomach. If the roots of main vascular vessels, such as the left gastric artery, and vascular vessels of other organs narrow or obliterate in DSA, the cancer may directly invade other organs as well. Two-thirds of gastric cancer could be identified through DSA with their shapes and characteristics. The varied shapes of vascular vessels caused by invasion of gastric cancer could reveal growing mode of the cancer.

Adult↗