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Biomedical subjects

F Liu

Publications and source records attributed to F Liu.

At least 523 records · Page 29Linked to original sources
PubMed1996

[Two kinds of cytokine gene expression in umbilical cord blood of premature and mature neonates].

OBJECTIVE: To study the immunological function of premature and mature neonates. METHOD: By means of in situ hybridization technique, mRNA expression of interleukin-1 (IL-1) beta and IL-1r alpha in umbilical cord blood of 34 cases was analyzed. RESULTS: It showed that mRNA expression of IL-1 beta and IL-1r alpha were significantly lower in the group of preterm vaginal delivery resulting from premature rupture of membranes than that of preterm cesarean section with the indication of pregnancy induced hypertension and than that of full term delivery (P < 0.001). No significant difference was found between the latter 2 groups. CONCLUSIONS: It indicated that gene expression of IL-1 beta and IL-1r alpha probably related to the fetal maturity.

Adult↗
PubMed1996

[Superoxide dismutase encapsulated erythrocytes used in the study of cerebral ischemia-reperfusion].

The possibility of using red blood cells (RBC) as the carrier of superoxide dismutase (SOD) was studied in this paper. SOD was encapsulated into rabbit erythrocytes (RBC-SOD), and was used in the study of cerebral ischemia-reperfusion (I-R). The effect of RBC-SOD on cerebral I-R was observed. The circulation half-life (T1/2) of RBC-SOD was determined in rabbits by 51Cr radiolabel. T1/2 was 13.4 +/- 1.5 days (n = 6) for RBC, and T1/2 was 13.7 +/- 1.0 days (n = 5) for RBC-SOD. The increase of lipid peroxidation (LPO) during cerebral I-R was inhibited by RBC-SOD. The maximum concentration of nitric oxide (NO) in plasma occurred in 10 minutes following reperfusion. The concentration of nitric oxide reduced gradually as reperfusion continued in both control and SOD groups, but it remained at a relatively high level continuous during the 4.5 hours of reperfusion in RBC-SOD group. These results indicate that intact RBC-SOD could scavenge superoxide anion (O2-.) produced during cerebral I-R.

Animals↗
PubMed1996

[Research on the recombinant plasmid pDJH2 of L. interrogans serovar lai: sequencing and alignment with other known bacterial Omp sequence].

The Leptospira whole cell vaccine (LWCV) currently used in China is safe and effective, out the immunity following vaccination with two doses of the fluid medium vaccine is of low order. The duration of immunity conferred by this vaccine is rather short, six months or at most one year. Therefore, it is necessary to develop new generation vaccines against Leptospirosis for the developing world. In this paper we report the sequencing of the insert fragment of pDJH2 from genomic DNA of L. interrogans sevovar lai strain 017 and its alignment with other bacterial omp sequences. A genomic library of Leptospira interrogaans serovar lai strain 017 was constructed with the plasmid vector pUC18. A recombinant plasmid designated pJDH2 was screened from the genomic library. Inserted fragment of pDH2 is 1.9 kb by gel electrophoresis. Immunization/protection was studied in BALB/c mice model. The results showed highly significant difference between pDJH2 and pUC18 (control). Inserted fragment of pDJH2 DNA sequencing was performed by Dr Yan Zhengxin (Max-Planck-Institut for Biology. Tubingen, Germany). Insert fragment was cloned into pBluescript II KS-(stratagene) and sequenced by using AB1 (Applied Bio Systems, Model 373A). Two open reading frames of 565 and 662 nucleotides were identified. There were identifiable initiation codons, terminators, Shine-Dalgano ribosome combining site, Pribnow boxes and Sextama boxes within the 2 sequenced regions. Nucleotide sequences were analysed using Gene Work, a suit of computer program developed by Department of Biochemistry St. Jude Children's Research Hospital Memphis. U.S.A. The results of formatted alignment showed the predicted nucleotide sequence of ORF1 of the serovar lai had significant similarity with ORF2 (49.36%). L. kirschneri ompL1 (49.26%), Borrelia burgdoferi omp (48.97%), Treponema phagedenis omp (47.3%); Salmonella typhimurium ompC(46.87%), Yersinia enterocolitica ompH (46.7%), Leptospira borgpeterseni pfap (46.3%), and Serratia marcescens omp (43.3%). The close relationship of the pDJH2 ORF1 and ORF2 nucleotide sequences from Leptospira kirschneri ompL 1 is apparent. Whether the recombinant pDJH2 will prove useful for vaccine development remains to be tested.

Animals↗
PubMed1996

[Subclones of fragment DNA recombinant rpDJH2 of L. interrogans serovar lai strain 017 and it's expression of high level in E. coli].

Fragment of 1.9 kb recombinant DNA of pDJH2 was linked with vectors pT7-7 and pRSETs. Then they were transformed into E. coli JM109 (DE3) respectively. Expression of subclones was achieved in E. coli JM109 (DE3) with IPTG inducement. SDS-PAGE showed that the molecular weights of products were 68kd and 23 kd respectively. The amount of production seemed to be higher than that of the outer membrane proteins of L. interrogans serovar strain 017 in nature. Immunoblotting of pDJt and pDJrB2 (both are subclones) with the specific antiserum of anti-OMP of L. interrogans serovar lai strain 017 and the experiment of initiative immuno-protection in guinea pigs showed both protein-68 kd and 23 kd might be the antigens of immuno-protection on the outer membrane of L. interrogans serovar lai strain 017.

Animals↗
PubMed1996

[A comparative study of quantification of morphological changes in intracranial and extracranial arteries between cerebral hemorrhage and infarction].

In order to compare the difference and similarity of the pathological changes in intracranial and extracranial arteries between cerebral hemorrhage (CH) and cerebral Infarction (CI), 120 autopsy cases were studied, including 42 cases of the CH, 58 cases of the CI and 20 cases of cancer as control. Medium sized intracranial arteries and their main branches, small sized intracerebral arteries, arterioles and extracranial carotid arteries (from 14 cases only) were examined with light microscopy. The ratio of lumen area to vessel area (LA-VA ratio) and the degree of narrowing of the vessels indicating the severity of arteriosclerosis were determined. Quantitative analysis was carried out with computer. The results were as follows: (1) The CH and CI patients had significantly lower mean LA-VA ratios of the medium intracranial arteries and their main branches, small intracerebral arteries and arterioles than the controls. (2) The CH patients had apparently lower LA-VA ratio of the small intracerebral arteries and arterioles than the CI patients. (3) The CI patients had significantly lower LA-VA ratio of the medium sized intracranial arteries and their main branches than the CH patients. Moreover, atherosclerotic narrowing of these vessels was also much more severe in the CI than in the CH patients. (4) Atherosclerotic narrowing of the extracranial carotid artery in the CI patients was slightly more severe than that in the CH patients. These data suggest that patients with cerebral stroke have frequently atherosclerotic lesions in the medium sized intracranial arteries and their main branches and sclerotic lesions in the small intracerebral arteries and arterioles. The principal lesion of the CH are in the small intracerebral arteries and arterioles, while those of the CI in the medium sized intracranial arteries and their main branches and sometimes in the extracranial carotid arteries.

Aged↗
PubMed1996

[Comparison of local antigen-specific IgA responses with serum IgA response after intrapulmonary antigen immunization in healthy subjects].

OBJECTIVE: To observe local lung and serum antigen-specific IgA response after local lung antigen immunization (LLI). METHODS: 11 healthy subjects were immunized with keyhole limpet hemocyanine (KLH) through bronchoscopy. 10-14 days after immunization, IgA responses were obversed in bronchoalveolar lavage fluids (BALF) and serum. RESULTS: LLI induced anti-KLH IgA response in immunized BALF and serum, and both were polymeric IgA. Anti-KLH IgA2/IgA1 ratios were greater in immunized BALF than in serum. Anti-KLH IgA activity in immunized BALF was associated with secretory component (SC), but in serum was not correlated with SC. CONCLUSIONS: LLI could induce local antigen-specific IgA production. There were markedly differences between the structure and subclass distribution of antigen-specific IgA in immunized BALF and serum.

Adjuvants, Immunologic↗
PubMed1996

[Active constituents lowering blood-lipid in beeswax].

Three compounds were isolated from the active fraction Lowering blood-lipid in the traditional Chinese beeswax (Apis cerana or A. mellifera). They were identified as dotriacontanol, triacontanol and octacosanol by chemical and spectroscopic methods.

Fatty Alcohols↗
PubMed1995

Concentration and size distribution of insulin-like growth factor-I in human normal and osteoarthritic synovial fluid and cartilage.

The concentration of free insulin-like growth Factor-I (IGF-I) and its complexes was determined in human normal and osteoarthritic synovial fluids, using ultrafiltration through 20- and 100-kDa membranes, followed by a radioimmunoassay of each fraction. In addition, freshly obtained samples of normal and osteoarthritic cartilage were incubated for several days, at both 4 and 37 degrees C. The incubation media (desorbates) were analyzed the same way as the synovial fluid samples to yield the concentration of IGF-I in cartilage in situ. Our findings are (i) Free IGF-I content is extremely low in both human serum and synovial fluid and there is no significant difference between the two; (ii) The concentration of total IGF-I in normal human synovial fluid is an order of magnitude lower than that in serum due mainly to the decrease in the concentration of the large complex; (iii) Preliminary results show that the total IGF-I in osteoarthritic synovial fluids is twice as high as in normal fluids; (iv) In normal human cartilage the levels of IGF-I in all its forms are very low and are consistent with the expected exclusion of large molecules by the extracellular matrix; (v) By contrast, in osteoarthritic cartilage, the concentrations of all forms of IGF-I are high, probably due to increased permeability of the matrix and binding; (vi) The levels of IGF-I found in normal human cartilage are more than an order of magnitude lower than those which stimulate proteoglycan synthesis in human cartilage in culture, while the IGF-I levels in osteoarthritic cartilage lie in the range in which stimulation does occur.

Adult↗
PubMed1995

The insulin receptor substrate-1-related 4PS substrate but not the interleukin-2R gamma chain is involved in interleukin-13-mediated signal transduction.

Interleukin-13 (IL-13) induced a potent mitogenic response in IL-3-dependent TF-1 cells and DNA synthesis to a lesser extent in MO7E and FDC-P1 cells. IL-13 stimulation of these lines, like IL-4 and insulin-like growth factor-1 (IGF-1), resulted in tyrosine phosphorylation of a 170-kD substrate. The tyrosine-phosphorylated 170-kD substrate strongly associated with the 85-kD subunit of phosphoinositol-3 (PI-3) kinase and with Grb-2. Anti-4PS serum readily detected the 170-kD substrate in lysates from both TF-1 and FDC-P1 cells stimulated with IL-13 or IL-4. These data provide evidence that IL-13 induces tyrosine phosphorylation of the 4PS substrate, providing an essential interface between the IL-13 receptor and signaling molecules containing SH2 domains. IL-13 and IL-4 stimulation of murine L cell fibroblasts, which endogenously express the IL-4 receptor (IL-4R alpha) and lack expression of the IL-2 receptor gamma subunit (IL-2R gamma), resulted in tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1)/4PS. Enhanced tyrosine phosphorylation of IRS-1/4PS was observed in response to IL-4, but not IL-13 treatment of L cells transfected with the IL-2R gamma chain. These results indicate that IL-13 does not use the IL-2R gamma subunit in its receptor complex and that expression of IL-2R gamma enhances, but is not absolutely required for mediating IL-4-induced tyrosine phosphorylation of IRS-1/4PS.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Molecular and functional characterization of a partial cDNA encoding a novel chicken brain melatonin receptor.

An approach based on homology probing was used to clone a partial cDNA encoding a novel melatonin (ML) receptor (MLR) from chicken (Gallus domesticus) brain. Based on available deduced amino-acid sequence, the chicken MLR (cMLR) displayed greater sequence homology to the frog (Xenopus) MLR than cloned human/mammalian receptors, with overall identities of 73% and 66%, respectively. In order to gain functional expression, a chimeric frog/chicken (flc)MLR was constructed in which the 5' end of the cMLR, including the N-terminus, TM1 and part of the first intracellular loop was substituted by fMLR sequence. [125I]Iodo-ML bound with high affinity (Kd of approximately 35 pM) to COS-7 cells transiently expressing the flcMLR in a saturable and guanine nucleotide-sensitive manner with the following rank order of potency: 2-iodo-ML > ML > 6-Cl-ML > S20750 > 6-OH-ML > S20642 > S20753 > N-acetyl-5HT >> 5-HT. Estimated Ki values for these compounds at the flcMLR correlated well to those obtained in native chicken brain membranes. In line with the observed structural similarity to the fMLR, the flcMLR exhibited affinities for ML, 6-Cl-ML and 6-OH-ML approximately 10-fold lower than mammalian receptors. Functionally, opposing interactions between ML and dopamine receptor signal transduction pathways were observed with ML potently inhibiting dopamine D1A-receptor-mediated cAMP accumulation in cells (HEK-293) transiently co-expressing these receptors. cMLR mRNAs were found expressed in chicken brain and kidney with trace levels observed in the lung. The availability of cloned vertebrate MLRs distinct at both the amino acid and pharmacological level from their mammalian counterparts may now allow for the identification of those amino-acid residues and structural motifs that regulate ML-binding specificity and affinity.

Adenylyl Cyclase Inhibitors↗
PubMed1995

Grb-IR: a SH2-domain-containing protein that binds to the insulin receptor and inhibits its function.

To identify potential signaling molecules involved in mediating insulin-induced biological responses, a yeast two-hybrid screen was performed with the cytoplasmic domain of the human insulin receptor (IR) as bait to trap high-affinity interacting proteins encoded by human liver or HeLa cDNA libraries. A SH2-domain-containing protein was identified that binds with high affinity in vitro to the autophosphorylated IR. The mRNA for this protein was found by Northern blot analyses to be highest in skeletal muscle and was also detected in fat by PCR. To study the role of this protein in insulin signaling, a full-length cDNA encoding this protein (called Grb-IR) was isolated and stably expressed in Chinese hamster ovary cells overexpressing the human IR. Insulin treatment of these cells resulted in the in situ formation of a complex of the IR and the 60-kDa Grb-IR. Although almost 75% of the Grb-IR protein was bound to the IR, it was only weakly tyrosine-phosphorylated. The formation of this complex appeared to inhibit the insulin-induced increase in tyrosine phosphorylation of two endogenous substrates, a 60-kDa GTPase-activating-protein-associated protein and, to a lesser extent, IR substrate 1. The subsequent association of this latter protein with phosphatidylinositol 3-kinase also appeared to be inhibited. These findings raise the possibility that Grb-IR is a SH2-domain-containing protein that directly complexes with the IR and serves to inhibit signaling or redirect the IR signaling pathway.

Adipose Tissue↗
PubMed1995

Identification of a 95-kDa WEE1-like tyrosine kinase in HeLa cells.

Human WEE1 (WEE1Hu) was cloned on the basis of its ability to rescue wee1+ mutants in fission yeast [Igarashi, M., Nagata, A., Jinno, S., Suto, K. & Okayama, H. (1991) Nature (London) 353, 80-83]. Biochemical studies carried out in vitro with recombinant protein demonstrated that WEE1Hu encodes a tyrosine kinase of approximately 49 kDa that phosphorylates p34cdc2 on Tyr-15 [Parker, L. L. & Piwnica-Worms, H. (1992) Science 257, 1955-1957]. To study the regulation of WEE1Hu in human cells, two polyclonal antibodies to bacterially produced p49WEE1Hu were generated. In addition, a peptide antibody generated against amino acids 361-388 of p49WEE1Hu was also used. Unexpectantly, these antibodies recognized a protein with an apparent molecular mass of 95 kDa in HeLa cells, rather than one of 49 kDa. Immunoprecipitates of p95 phosphorylated p34cdc2 on Tyr-15, indicating that p95 is functionally related to p49WEEIHu, and mapping studies demonstrated that p95 is structurally related to p49WEE1Hu. In addition, the substrate specificity of p95 was more similar to that of fission yeast p107wee1 than to that of human p49WEE1. Finally, the kinase activity of p95 toward p34cdc2/cyclin B was severely impaired during mitosis. Taken together, these results indicate that the original WEE1Hu clone isolated in genetic screens encodes only the catalytic domain of human WEE1 and that the authentic human WEE1 protein has an apparent molecular mass of approximately 95 kDa.

Antibody Specificity↗
PubMed1995

Activation of protein kinase C alpha inhibits signaling by members of the insulin receptor family.

Stimulation of the activity of protein kinase C by pretreatment of cells with phorbol esters was tested for its ability to inhibit signaling by four members of the insulin receptor family, including the human insulin and insulin-like growth factor-I receptors, the human insulin receptor-related receptor, and the Drosophila insulin receptor. Activation of overexpressed protein kinase C alpha resulted in a subsequent inhibition of the ligand-stimulated increase in antiphosphotyrosine-precipitable phosphatidylinositol 3-kinase mediated by the kinase domains of all four receptors. This inhibition varied from 97% for the insulin receptor-related receptor to 65% for the Drosophila insulin receptor. In addition, the activation of protein kinase C alpha inhibited the in situ ligand-stimulated increase in tyrosine phosphorylation of the GTPase-activating protein-associated p60 protein as well as Shc mediated by these receptors. The mechanism for this inhibition was further studied in the case of the insulin-like growth factor-I receptor. Although the in situ phosphorylation of insulin-receptor substrate-1 and p60 by this receptor was inhibited by prior stimulation of protein kinase C alpha, the in vitro tyrosine phosphorylation of these two substrates by this receptor was not decreased by prior stimulation of the protein kinase C alpha in the cells that served as a source of the substrates. Finally, the insulin-like growth factor-I-stimulated increase in cell proliferation was found to be inhibited by prior activation of protein kinase C alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Relationship of 13C NMR chemical shift tensors to diffraction structures.

13C chemical shift tensor measurements on single crystals provide a powerful method to study changes in the electron environment of nuclei with changes in molecular structure. Thus, diffraction structures are critical to an understanding of chemical shift tensors. This work explores the general reliability of using structural data to predict components of the symmetrical chemical shift tensor. Imprecision in the hydrogen positions introduces considerable scatter in the simulated 13C shift tensors, and optimized C-H bond distances in methyl-beta-D-glucopyranoside used with the X-ray positions of the heavier C and O atoms greatly improve the simulated chemical shifts. Acenaphthene, with two crystallographically different molecules per unit cell, offers an excellent example for comparing and contrasting structural differences in the two molecules. A recently improved X-ray structure of naphthalene obtained at low temperature provides chemical shift simulations which are comparable to those from neutron diffraction methods and appear to reflect breaks in the D2h symmetry measured in the NMR chemical shift tensors. These data illustrate the close relationship between NMR and diffraction structures.

Carbohydrate Conformation↗