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Biomedical subjects

R Liu

Publications and source records attributed to R Liu.

At least 235 records · Page 13Linked to original sources
PubMed1997

Selective modulation of protein kinase A and protein kinase C activities in epidermal growth factor (EGF)-stimulated MCF-7 breast cancer cells.

In human MCF-7 breast cancer cells, both protein kinase A (PKA) and different members of the protein kinase C (PKC) family are stimulated upon binding of epidermal growth factor (EGF) to cell surface receptors. Selective stimulation of calcium-dependent PKCs with 10(-6) to 10(-9) M Thymeleatoxin significantly increased the proliferation rate of MCF-7 cells over 5 days in culture. This stimulation was blocked by the PKC antagonist Chelerythrine. In contrast, selective activation of PKA by addition of 1 mM dibutyryl cyclic AMP (dBcAMP) did not affect the proliferation rate of MCF-7 cells. Similarly, activation of the adenylate cyclase by 1 microM Forskolin and inhibition of PKA by the cyclic AMP analogue Rp-cAMPS did not modulate the proliferation rate of these cells. Activation of PKC stimulated the expression of the immediate early gene c-fos but c-myc expression was not significantly enhanced. On the other hand, PKA activation increased both c-myc and c-fos expression in MCF-7 cells. These results suggest that PKA activation and c-myc expression are not obligatory for proliferation of MCF-7 cells.

Alkaloids↗
PubMed1997

[The expression of HSP-70 gene in exocrine pancreas of the rats suffering from acute necrotizing pancreatitis].

With the acute necrotizing pancreatitis rat model induced by giving sodium taurocholate, the expression of hsp70 gene was detected in exocrine pancreas using Northern hybridization and immunohistochemistry. Nothern hybridization analysis showed that the levels of hsp70 gene expression increased and peaked at 1 h after operation, and declined to the control levels at 8-16 h. In immunohistochemistry detection, the staining for HSP70 protein enhanced significantly at 1 h, peaked at 2 h, and then decreased, persisting for 16 h or longer. The location of the large particle positive signal for HSP70 was in the apical region of the acinar cells, while very few signals for HSP70 were observed in the basal region, nucleus and acinar lumen. The results suggest that the high expression of hsp70 gene in the acinar cells may be involved in the transportation of pancrease enzymes synthesized excessively and in the prevention of early enzyme activation.

Animals↗
PubMed1997

[c-met expression in human hepatocellular cancer].

Using Northern blot method, we examined the expression of c-met in human hepatocellular cancer. Of 30 patients tested, the expression of c-met mRNA was not significantly different in HCC tissues from corresponding noncancerous parenchyma (P > 0.05). There was no significant relationship between c-met expression and grade of differentiation, stage of clinic, AFP, HBsAg (P > 0.05). Our results suggest that c-met may play different roles in the pathogenesis and metastasis of human hepatocellular carcinoma.

Adult↗
PubMed1997

[The impact of different incisions on visual acuity and corneal refractivity in cataract surgery].

OBJECTIVE: To research the impact of different incisions of cataract surgery on post-operative visual acuity and corneal refractivity. METHODS: The visual acuity and corneal refractivity in 243 eyes having undergone extracapsular cataract extraction and phacoemulsification with 5 mm tunnel incision or 7 mm frown-shaped incision were examined and compared at three post-operative periods. RESULTS: The mean increase in corneal refractivity in phacoemulsification group was significantly less (P < 0.05) and the corrected visual acuity was much better (P < 0.05) than that in conventional extracapsular cataract extraction (ECCE) group at post-operative 1/2 month, 3 months and 6 months (P < 0.05). In the phacoemuisification group, the increase of the post-operative refractivity in 7 mm frown-shaped incision group was less than that in 5 mm tunnel incision group at 1/2 month and 3 months (P < 0.05). CONCLUSION: 7 mm frown-shaped incision of phacoemulsification is the most effective method to control the post-operative corneal astigmatism in cataract surgery.

Adolescent↗
PubMed1997

[Adsorption of permanganate onto activated carbon particles].

In this paper, the adsorption behavior of permanganate onto activated carbon particles was studied as a function of pH, flow rate and the concentration of permanganate. It was found that permanganate was not adsorbed but reduced by activated carbon particles. The percent of reduction of permanganate was strongly pH-dependent. The reducing product of permanganate was mainly Mn2+ which was adsorbed onto the activated carbon particles by surface complexation.

Adsorption↗
PubMed1997

[Detection of antigen specificities of HLA-A, B loci in perennial allergic rhinitis].

In order to elucidate whether there are any features of HLA haplotype in perennial allergic rhinitis and the essentials of its genetic background, the antigen specificities of HLA-A, B loci in 31 non-kindred adult cases of southern Chinese of Han nationality were detected and calculated the antigen frequency, gene frequency and relative risk value of different alleles evaluated by serological methods. The results were compared with 78 healthy adult individuals of Guizhou Han (control group) and revealed that RR (relative risk) of HLA-B27 was as high as 8.25, RR of A31 (2.68), A28 (2.57), B12 (2.57) and A33 (2.27) were also higher than the control group. It is suggested that the presence of the above mentioned antigens are positively associated with the genetic liability of the patients. The RR of A9, B60, A24, B22, B51, B15, B16, B48, B46, B7, A11 and A2 were all lower than 1 representing the genetic stability to allergic rhinitis. The antigen frequency of B27 and A9 were significantly different from that of the control group.

Adolescent↗
PubMed1997

[Color television microscope with an automatic stage].

To mount a group of stepper motors on a television microscope automates the instrument in coarse focussing and equi-spaced moving a specimen. A microprocessor 8031 application system is used to control the stepper motors. For enhancing the properties and reliability of the system, we select RIF 530, a field effect transistor for the power amplifier of the motor. Combination PC with the instrument becomes basic hardware of a universal microscopic image processing system.

Equipment Design↗
PubMed1997

[Synthesis of N-salicylidene leucine 3d metal complexes and studies on their thin-layer chromatography and ultraviolet spectrum].

The Schiff base derived from salicylaldehyde and leucine and its Mn(II), Co(II), Ni(II), Cu(II), Zn(II) complexes were synthesized. The purity of the products obtained was confirmed by elemental analysis. The results of elemental analysis and molar conductance show that coordination ratio with M(II) is 1:1 and its complexes are non-electrolyte in DMF. The thin-layer chromatography behavior of complexes was studied on silica gel G plate with ethyl acetate-methanol-acetone-water-acetic acid (4.44:3.33:2.22:0.25:0.12, V/V) as mobile phase. The results show that the Rf value of complexes increases as follows Mn<Zn<Ni<Cu<Co. The lambda(max) values of ultraviolet spectra of ligand and complexes are determined in methanol and DMSO. The lambda(max) values of complexes increase as follows: Mn(II)<Zn(II)<Ni(II)<Cu(II)<Co(II)<ligand. The Rf values and R band lambda(max) values of complexes change in the same direction as the stability constants of the complexes. This proves that the Rf values of complexes on silica gel G and R band lambda(max) values of complexes depend on coordinaton of M(II) with ligand.

Chromatography, Thin Layer↗
PubMed1997

[3H]RY 80: A high-affinity, selective ligand for gamma-aminobutyric acidA receptors containing alpha-5 subunits.

The radiochemical synthesis and pharmacological properties are described of [3H]RY 80 (ethyl-8-acetylene-5, 6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a][1, 4]benzodiazepine-3-carboxylate, [ethyl-3H]). This compound is one of a series of 8-substituted imidazobenzodiazepines that exhibits both high affinity and selectivity for gamma-aminobutyric acid (GABA)A receptors containing alpha-5 subunits. Saturable, high-affinity (Kd approximately 0.7 nM) binding of [3H]RY 80 was observed in hippocampal membranes. The maximum number (Bmax) of [3H]RY 80 binding sites was approximately 18% of that obtained with [3H]flunitrazepam, a radioligand that labels all "diazepam-sensitive" GABAA receptors. This value is consistent with previous estimates (10-20%) of the proportion of rat hippocampal GABAA receptors containing alpha-5 subunits determined by immunoprecipitation with selective antibodies and competition experiments using an alpha-5-selective ligand. In recombinant GABAA receptors composed of alpha-5 beta-3 gamma-2 subunits, the Kd of [3H]RY 80 (approximately 0.5 nM) was consistent with the value obtained in hippocampus, whereas the Bmax value was not significantly different from that obtained with [3H]flunitrazepam. The potencies of several benzodiazepine site ligands to inhibit [3H]RY 80 binding to hippocampal membranes were in agreement with the values obtained in recombinant (alpha-5 beta-3 gamma-2) GABAA receptors. [3H]RY 80 was used both in a "GABA shift" assay to correctly predict the in vivo actions of a novel, alpha-5-selective ligand and to characterize a population of GABAA receptors containing alpha-5 subunits in neonatal rat cortex. These findings demonstrate that [3H]RY 80 can be used as a radioligand to examine the properties of GABAA receptors containing alpha-5 subunits.

Alkynes↗
PubMed1997

[A comparative chromosome map between human and Hylobates hoolock built by chromosome painting].

We established chromosomal homologies between all human chromosomes except Y and those of Hylobates hoolock by chromosome painting (chromosome in situ suppression hybridization with human chromosome-specific DNA libraries). Human chromosomes 9,13,15,18,21,22,X libraries hybridized to single G-banding H. hoolock chromosomal region, other human DNA libraries showed at least two homologous segments in H. hoolock chromosomes. 59 segments homologous to one of 22 human autosomes were detected in 18 H. hoolock autosomes. There were at least 39 translocations. Thus an uniquivocally high degree of synteny between human and H. hoolock was confirmed. This will finally allow H. hoolock to be integrated into the overall picture of chromosomal evolution in Hylobatids.

Animals↗
PubMed1997

Changes of ultrasonography and two serum biochemical indices for hepatic fibrosis in schistosomiasis japonica patients one year after praziquantel treatment.

OBJECTIVE: To observe the changes of abdominal sonography and 2 biochemical indicators for hepatic fibrosis before and after treatment with praziquantel in schistosomiasis japonica patients. METHODS: Fifty-five persons infected with Schistosoma japonicum and treated with praziquantel were examined with ultrasonography and serum hyaluronic acid (HA) and type III procollagen (PC III) before and 1 year after treatment, and their data were compared with those in 55 normal controls. RESULTS: With comparison of the data before praziquantel treatment, the length of the left liver lobe and the spleen in 55 patients all decreased (P < 0.01) 1 year after treatment. No significant change was seen in interior diameter (d) of the portal vein, while a decrease in the ratio of the exterior diameter (D) and interior diameter of the second branch of the portal vein was very significant (P < 0.01). Compared with the data in normal control, significantly higher levels in the thickness of the left lobe, the maximum oblique diameter of the right lobe, the length of the spleen, spleen index, the interior diameter of the portal vein and D/d ratio were seen in the patients both before and after treatment. The abnormal rate of the 2 serum parameters for hepatic fibrosis decreased significantly after treatment. CONCLUSIONS: Parameters of hepatic fibrosis either by ultrasonography or by the 2 biochemical tests showed a significant improvement in 55 patients 1 year after treatment, although some of the indices did not yet return to normal levels.

Adolescent↗
PubMed1997

[The role of urokinase-type plasminogen activator in the pathogenesis of pemphigus].

OBJECTIVE: To investigate the changes of urokinase-type plasmino-gen activator (u-PA) in the process of acantholysis in pemphigus and observe the influence of purified urokinase on the cultured skin explant. METHODS: The expression of urokinase antigen on the pemphigus organ model was revealed by immunohistochemical method; PA activity was assayed in the acantholysis model; the influence of urokinase on the epidermis was observed by adding purified urokinase into the cultured skin explant. RESULTS: PA activity was elevated in the acantholysis model at 24 hour and was continuing its increase at 48 and 72 hours. The expression of urokinase was high in the epidermis of pemphigus organ model; purified urokinase could induce acantholysis like changes. CONCLUSION: Pemphigus antibody induces acantholysis through activating keratinocytes. The latter secretes an elevated u-PA, which locates on the membrane of the epidermal cells producing a limited pro-teolysis which damages the cohesion of epidermal cells.

Acantholysis↗
PubMed1997

[A study on the infiltration of macrophages and lymphocytes in interrenal tissues in patients with acute renal tubulointerstitial disease].

Renal tissues of 14 patients with acute renal tubulointerstitial disease were studied by using immunohistochemical method. Cells infiltrated in interrenal tissue were observed. The results show that the causes which result in acute renal tubulointerstitial disease are different; the renal tubular and interstitial damages are reversible or irreversible; the major inflammatory cells infiltrated in interrenal tissues are CD68 and CD45ro positive cells. The results suggest that the macrophages and T lymphocytes infiltrated in interrenal tissues play an important role in the progress of acute renal tubulointerstital disease.

Acute Disease↗
PubMed1996

Site-directed fluorescence labeling of P-glycoprotein on cysteine residues in the nucleotide binding domains.

P-Glycoprotein is a member of the ABC superfamily of membrane transporters, and functions as an ATP-driven active efflux pump for natural products and chemotherapeutic drugs. Overexpression of P-glycoprotein is a major cause of multidrug resistance in human cancers. Sulfhydryl modification agents are known to inactivate both P-glycoprotein ATPase activity and transport function. In the present study, P-glycoprotein purified from CHRB30 cells was covalently labeled at two conserved Cys residues, one within each of the nucleotide binding domains, using 2-(4-maleimidoanilino)naphthalene-6-sulfonic acid (MIANS). MIANS modification inactivated P-glycoprotein ATPase function, in a concentration-dependent fashion. Increasing concentrations of ATP blocked MIANS labeling with an IC50 of 0.37 mM (similar to the KM for ATP hydrolysis), which suggests that the label is located close to the site of ATP binding within the nucleotide binding domain. A blue shift in the fluorescence spectrum of MIANS bound to P-glycoprotein indicated that the labeled Cys residues are situated in a nonpolar environment. MIANS-labeled P-glycoprotein was still able to bind ATP, as demonstrated by quenching of the fluorescence, with a Kd of 0.46 mM. Addition of a variety of drugs and chemosensitizers to MIANS-labeled P-glycoprotein led to substantial quenching of the probe fluorescence within the nucleotide binding domains. Dissociation constants for drug binding measured by fluorescence quenching were in the range of 0.77 microM for vinblastine to 158 microM for colchicine. Quenching by ATP and drugs was independent and additive, suggesting that each produces a defined change in the protein. The rate of MIANS labeling of Pgp was reduced in the presence of drugs and chemosensitizers, implying that a long-range conformational change arises from drug binding which alters the accessibility of the nucleotide binding domains to MIANS. These results suggest that there is conformational communication between the drug binding site(s) of P-glycoprotein and the ATPase catalytic sites within the nucleotide binding domains.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Homozygous defect in HIV-1 coreceptor accounts for resistance of some multiply-exposed individuals to HIV-1 infection.

Rare individuals have been multiply exposed to HIV-1 but remain uninfected. The CD4+ T-cells of two of these individuals, designated EU2 and EU3, are highly resistant in vitro to the entry of primary macrophagetropic virus but are readily infectable with transformed T-cell line adapted viruses. We report here on the genetic basis of this resistance. We found that EU2 and EU3 have a homozygous defect in CKR-5, the gene encoding the recently described coreceptor for primary HIV-1 isolates. These individuals appear to have inherited a defective CKR-5 allele that contains an internal 32 base pair deletion. The encoded protein is severely truncated and cannot be detected at the cell surface. Surprisingly, this defect has no obvious phenotype in the affected individuals. Thus, a CKR-5 allele present in the human population appears to protect homozygous individuals from sexual transmission of HIV-1. Heterozygous individuals are quite common (approximately 20%) in some populations. These findings indicate the importance of CKR-5 in HIV-1 transmission and suggest that targeting the HIV-1-CKR-5 interaction may provide a means of preventing or slowing disease progression.

Alleles↗
PubMed1996

Molecular dissection of a protein SopB essential for Escherichia coli F plasmid partition.

Biochemical and genetic experiments were carried out to deduce the structural and functional domains of SopB protein involved in the equipartition of F plasmid. The protein is dimeric. Proteolytic and chemical footprinting studies support earlier genetic analyses that the binding of SopB to specific sites within the F plasmid sopC locus involves mainly the C-terminal region. In vivo, the expression of a high level of SopB protein is known to repress sopC-linked genes. This silencing activity is shown to be unaffected by the deletion of 35 N-terminal residues, but abolished when 71 or more were removed from the N terminus. An excess of SopB protein does not extend its in vitro binding outside sopC, implicating participation of a host factor(s) in SopB-mediated gene silencing. A data base search identified a number of SopB homologues, including both chromosomally encoded bacterial proteins and phage- and plasmid-encoded proteins known to be involved in partition. Sequence homology is limited to the N-terminal half, suggesting that the N-terminal regions of these proteins are conserved to interact with a conserved cellular structure(s), whereas the C-terminal regions have diverged to bind different nucleotide sequences.

Amino Acid Sequence↗
PubMed1996

Identification of a major co-receptor for primary isolates of HIV-1.

Entry of HIV-1 into target cells requires cell-surface CD4 and additional host cell cofactors. A cofactor required for infection with virus adapted for growth in transformed T-cell lines was recently identified and named fusin. However, fusin does not promote entry of macrophage-tropic viruses, which are believed to be the key pathogenic strains in vivo. The principal cofactor for entry mediated by the envelope glycoproteins of primary macrophage-tropic strains of HIV-1 is CC-CKR-5, a receptor for the beta-chemokines RANTES, MIP-1alpha and MIP-1beta.

3T3 Cells↗