Biomedical subjects

S Liu

Publications and source records attributed to S Liu.

At least 523 records · Page 29Linked to original sources

PubMed1999

[Subtractive cDNA cloning and analysis of murine erythroid terminal differentiation related factor].

OBJECTIVE: Cloning and identification of cDNA related to erythroid terminal differentiation factor (MEDRF). METHODS: cDNA related to erythroid terminal differentiation from the Friend virus anemia (FVA) infected splenic erythroblasts of BALB/c mice were performed by using subtractive hybridization combined with PCR technique. The splenic proerythroblasts isolated were cultured in the presence of erythropoietin for 36 hrs. Subtractive cDNA clones of differentially expressed in the 36 hrs erythroblasts (sub cDNA-36) but absent in the uncultured proerythroblasts were observed. The sub cDNA-36 was then used for construction of subtractive cDNA library using the Bluescript-SK(+) phage vector system, and differentially screened by 32P-labelled PCR generated probes. The positive clones were analyzed by nucleotide sequencing. RESULTS: The results indicated that a 472 bp cDNA fragment which contained a 309 bp reading frame from 51 to 359 coding 102 amino acids was identified and it has been accepted by GenBank as a new cDNA sequence that without comparable homology of existing sequences (accession number: AA114369). Northern blot analysis demonstrated that it was differentially expressed in the 36 hrs cultured intermediate-late stages of erythroblasts. CONCLUSIONS: The newly found cDNA, which expresses specifically in intermediate-late stages of erythroblasts, not in stages of proerythroblasts, may be a new gene related to murine erythroid terminal differentiation.

Activins↗

PubMed1999

[Construction of a pufferfish gridded cosmid library].

OBJECTIVE: Pufferfish is a newly-established model organism in human genome research, which has been demonstrated its unique advantages in comparative genomics. Construction of a genomic library of pufferfish is the prerequisite to any studies of its genome. METHODS: Genomic DNA from Fugu rubripes, a species distribute only in Japan and China seas, was used to construct a library in a novel cosmid vector, named sCOGH2, which contains an exon-trapping cassette. RESULTS: This library is composed of 57,600 clones gridded in 60,096-well cell culture plates, one clone each well. The average size of the inserts is around 35 kb. It provides 99.2% probability to find any unique DNA fragment of pufferfish in this library. The clones of this library can survive after more than 10 times freeze-thaw, also demonstrating high stability in propagation. The clones shone highly positive signals when hybridized with the pufferfish genomic DNA. CONCLUSIONS: The library accords with qualitative demands of a cosmid library.

Animals↗

PubMed1999

[Pharmacognostical studies on the roots of Euphorbia soongarica].

Morphological and microscopical characters of the roots of Euphorbia soongarica Boiss. used as one of the origins of the Chinese medicine Daji in Xinjiang Autonomous Region of China were described and illustrated with line drawings. TLC and HPLC analysis of the above drug was also undertaken. These studies provide referencial informations for clinics, quality control, development and identification of this crude drug.

Chromatography, High Pressure Liquid↗

PubMed1999

[The development and clinical application of a multipurpose neuroendoscope].

The multipurpose rigid neuroendoscope MGE-4 has been developed with the application of the self-focussing lens technology. We have been using it to examine and treat 10 neurosurgical patients who suffered from tumours, hydrocephalus, intracerebral haematomas of head injury and hypertensive cerebral haemorrhage. The short-term effect was satisfactory and there was no operative complications. It is considered that Model MGE-4 with the accessories can be used safely for the brain functional subcortical lesion or the deep-seated cystic lesions and haematomas.

Adult↗

PubMed1999

[The development of the ionization chamber and the researching of its characteristics for automatic exposure controlling in the X-ray diagnosis machine].

An ionization chamber for automatic exposure controlling used in X ray diagnosis machine was developped, and its characteristics were measured and researched. The electrodes of measuring field were made of carbon, such couldn't leave it's imaging on the film. In order to increase the ionization efficiency and decrease the thickness and electric capacity between electrodes, the chamber was constructed in multilayers. The chamber we developed can be fixed in different x ray machines convenientlly, there is a fine linearity between it's signal output and the exposures, the beam quality response is uniform and output-timing response is also good.

Air Ionization↗

PubMed1999

[Construction of adenovirus 4 vector with deletion of 78.9-86 mu fragment and express of beta-galactosidase gene].

OBJECTIVE: To construct a human adenovirus type 4(Ad4) vector with partial deletion at E3 region (78.9-86 mu). METHODS: Ad4 DNA was extracted from purified virus cultured in WI-38 cells. The essential fragment(71.3-100 mu) covering Ad4 E3 region was cloned and partial deletion of E3 region of this clone has been performed, generating plasmid pAd4 delta KS. Furthermore, a beta-galactosidase (beta-gal) gene flanked by CMV early promoter and SV40 poly A signal was inserted into pAd4 delta KS, resulting in pAd4c beta. This plasmid was cotransfected with Ad4 DNA, Bcl I A fragments into 293 cells, producing a non-defective recombinant Ad4 virus encoding B-gal. RESULT: The results showed that the constructed recombinant virus could efficiently express the foreign gene, beta-gal. CONCLUSION: Ad4 vector with a deletion of E3 region can be explored as a live vaccine for prevention of human infectious diseases.

Adenovirus E3 Proteins↗

PubMed1999

Phase-1 studies of malariotherapy for HIV infecton.

OBJECTIVE: To determine whether malariotherapy (an old therapy for treatment of neurosyphilis) improves some clinical and laboratory parameters of HIV-positive patients without iatrogenic complications. METHODS: Total 8 asymptomatic HIV-1 positive subjects whose CD4 cell counts were over 250 x 10(6) cells/L were selected for the phase-1 studies of malariotherapy and were intravenously injected Plasmodia vivax to induce artificial malaria. Malaria was terminated with chloroquine after 10 to approximately 20 malarial fever episodes. Cell-bound CD4 levels were measured by APAAP (a solid-phase enzyme essay) and levels of neopterin (NPT), beta-2-microglobulin (B2M), soluble tumor necrosis factor receptor-2 (sTNF-RII), interleukin-2 (IL-2) and HIV P24 antigen were measured by ELISA. Patients were followed up to 24 to approximately 30 months. RESULTS: CD4 levels increased in 5, NPT decreased in 7 of 8 patients; IL-2 increased in 5 of 6 patients after malariotherapy. The total trends of B2M and sTNF-RII basically remained stable. HIV P24 antigen remained undetectable in 6, remained detectably low level in 1 and experienced increase in 1 of 8 patients after malariotherapy. No any severe complications occurred in all 8 patients. CONCLUSIONS: The results indicate that malariotherapy basically is safe for HIV infection and it seems that the therapy improves some immunological parameters of HIV patients.

Adult↗

PubMed1999

[Information system for ICP-AES in windows environment].

An information system for inductively coupled plasma atomic emission spectrometry (ICP-AES) in MS Windows environment was developed based on the previous work in the labroatory. The system contains the data of about 28 000 spectral lines and a function of ICP spectral simulation, so it would be very helpful for line selection. The system also contains the Kalman filter and factor analysis programmes written with MS Visual Basic(version 4.0), which can be used for spectral interference correction and peak position optimization. A large amount of real spectral scanning data of rare earth elements were included in the system for user's references. All these characteristics made the system more useful and practical.

English Abstract↗

PubMed1999

Mechanisms of antihyperglycemic effects of moxonidine in the obese spontaneously hypertensive Koletsky rat (SHROB).

Increased activity of the sympathetic nervous system may be a critical factor in the development of impaired insulin secretion and insulin resistance. We studied the chronic effects of sympathetic inhibition with moxonidine on glucose metabolism in the spontaneously hypertensive genetically obese rat (SHROB). This unique animal model closely resembles human syndrome X, expressing insulin resistance, genetic obesity, spontaneous hypertension, and hyperlipoproteinemia. Moxonidine, a selective imidazoline receptor agonist, was administered to lean spontaneous hypertensive rats (SHR) and SHROBs for 90 days in food at 8 mg/kg/day and significantly reduced mean blood pressure. Moxonidine treatment reduced fasting insulin levels by 71% in SHROB and lowered plasma free fatty acids by 25%. In SHR, moxonidine treatment decreased free fatty acids by 17% compared with controls. During an oral glucose tolerance test, blood glucose levels in moxonidine-treated SHROB were reduced relative to untreated controls from 60 min onwards. Insulin secretion was facilitated at 30 min (83% greater) and 60 min (67% greater) postchallenge compared with control SHROB. In skeletal muscle, moxonidine treatment increased the expression of the insulin receptor beta subunit by 19% in SHROB but was without effect in SHR. The level of insulin receptor substrate-1 (IRS-1) protein was decreased by 60% in control SHROB compared with lean SHR. Moxonidine treatment enhanced the expression and insulin-stimulated phosphorylation of IRS-1 protein in skeletal muscle in SHROB by 74 and 27%, respectively, and in SHR by 40 and 56%, respectively. Moxonidine increased the levels of expression of IRS-1 protein in liver in SHR by 275% and in SHROB by 260%. These findings indicate that chronic inhibition of sympathetic activity with moxonidine therapy can lower free fatty acids and significantly improve insulin secretion, glucose disposal, and expression of key insulin signaling intermediates in an animal model of obese hypertension.

Animals↗

PubMed1998

Connexins regulate calcium signaling by controlling ATP release.

Forced expression of gap junction proteins, connexins, enables gap junction-deficient cell lines to propagate intercellular calcium waves. Here, we show that ATP secretion from the poorly coupled cell lines, C6 glioma, HeLa, and U373 glioblastoma, is potentiated 5- to 15-fold by connexin expression. ATP release required purinergic receptor-activated intracellular Ca2+ mobilization and was inhibited by Cl- channel blockers. Calcium wave propagation also was reduced by purinergic receptor antagonists and by Cl- channel blockers but insensitive to gap junction inhibitors. These observations suggest that cell-to-cell signaling associated with connexin expression results from enhanced ATP release and not, as previously believed, from an increase in intercellular coupling.

Adenosine Triphosphatases↗

PubMed1998

Nonpeptide somatostatin agonists with sst4 selectivity: synthesis and structure-activity relationships of thioureas.

Utilizing NNC 26-9100 (11) as a structural lead, a variety of nonpeptide derivatives of somatostatin were synthesized and evaluated for sst2 and sst4 receptor binding affinity. A novel thiourea scaffold was utilized to attach (1) a heteroaromatic nucleus to mimic the Trp8 residue, (2) a nonheteroaromatic nucleus to mimic Phe7, and (3) a primary amine or other basic group to mimic the Lys9 residue of somatostatin. Displacement studies were carried out using membranes from cell lines expressing ssts [BHK cells (sst4) and HEK 293 cells (sst2)] utilizing [125I]Tyr11-SRIF as the radioligand. Several thioureas (11, 38, 39, 41, and 42) and the urea 66 exhibited Ki values of less than 100 nM. The thioureas 11 (Ki = 6 nM) and 41 (Ki = 16 nM) and the urea 66 (Ki = 14 nM) are believed to be the most potent nonpeptide sst4 agonists known. Since the thiourea 11 and the urea 66 exhibit high sst4 selectivity, these novel nonpeptide derivatives may be useful tools for studying the sst4 receptor. Studies are currently in progress to evaluate the therapeutic potential of NNC 26-9100 (11) in the treatment of glaucoma.

Aminopyridines↗

PubMed1998

Structure of human methionine aminopeptidase-2 complexed with fumagillin.

The fungal metabolite fumagillin suppresses the formation of new blood vessels, and a fumagillin analog is currently in clinical trials as an anticancer agent. The molecular target of fumagillin is methionine aminopeptidase-2 (MetAP-2). A 1.8 A resolution crystal structure of free and inhibited human MetAP-2 shows a covalent bond formed between a reactive epoxide of fumagillin and histidine-231 in the active site of MetAP-2. Extensive hydrophobic and water-mediated polar interactions with other parts of fumagillin provide additional affinity. Fumagillin-based drugs inhibit MetAP-2 but not MetAP-1, and the three-dimensional structure also indicates the likely determinants of this specificity. The structural basis for fumagillin's potency and specificity forms the starting point for structure-based drug design.

Amino Acid Sequence↗

PubMed1998

Crystal structures of acutolysin A, a three-disulfide hemorrhagic zinc metalloproteinase from the snake venom of Agkistrodon acutus.

Acutolysin A alias AaHI, a 22 kDa hemorrhagic toxin isolated from the snake venom of Agkistrodon acutus, is a member of the adamalysin subfamily of the metzincin family and is a snake venom zinc metalloproteinase possessing only one catalytic domain. Acutolysin A was found to have a high-activity and a low-activity under weakly alkaline and acidic conditions, respectively. With the adamalysin II structure as the initial trial-and-error model, the crystal structures were solved to the final crystallographic R-factors of 0. 168 and 0.171, against the diffraction data of crystals grown under pH 5.0 and pH 7.5 conditions to 1.9 A and 1.95 A resolution, respectively. One zinc ion, binding in the active-site, one structural calcium ion and some water molecules were localized in both of the structures. The catalytic zinc ion is coordinated in a tetrahedral manner with one catalytic water molecule anchoring to an intermediate glutamic acid residue (Glu143) and three imidazole Nepsilon2 atoms of His142, His146 and His152 in the highly conserved sequence H142E143XXH146XXGXXH152. There are two new disulfide bridges (Cys157-Cys181 and Cys159-Cys164) in acutolysin A in addition to the highly conserved disulfide bridge Cys117-Cys197. The calcium ion occurs on the molecular surface. The superposition showed that there was no significant conformational changes between the two structures except for a few slight changes of some flexible residue side-chains on the molecular surface, terminal residues and the active-site cleft. The average contact distance between the catalytic water molecule and oxygen atoms of the Glu143 carboxylate group in the weakly alkaline structure was also found to be closer than that in the weakly acidic structure. By comparing the available structural information of the members of the adamalysin subfamily, it seems that, when lowering the pH value, the polarization capability of the Glu143 carboxylate group to the catalytic water molecule become weaker, which might be the structural reason why the snake venom metalloproteinases are inactive or have a low activity under acidic conditions.

Acids↗

PubMed1998

Synthesis and characterization of heteroarotinoids demonstrate structure specificity relationships.

Heteroarotinoids are synthetic retinoids derived from trans-retinoic acid and the arotinoid structures and include a heteroatom in a five- or six-membered cyclic ring. This is the first systematic study of influences of the heteroatom, ring size, number of aryl groups, and terminal side chain on retinoid receptor specificity. Two new heteroarotinoids were synthesized and characterized. Although all heteroarotinoids activated RAR receptors, two dominant associations between structure and specificity were identified across all compounds. The six-membered ring conferred increased RARbeta specificity over the five-membered ring. The sulfur atom conferred greater specificity for RARgamma than the oxygen atom. RARalpha specificity was attenuated by a combination of influences from the heteroatom and aryl groups. In summary, the heteroatom and cyclic ring size exerted dominant effects, while the number of aryl rings and terminal side chain had attenuating effects on retinoid receptor specificity of heteroarotinoids.

Animals↗

PubMed1998

Cloning and functional characterization of the 5'-flanking region of human methionine adenosyltransferase 2A gene.

Methionine adenosyltransferase (MAT) is a critical cellular enzyme which catalyzes the formation of S-adenosylmethionine, the principal methyl donor. In mammals, two different genes, MAT1A and MAT2A, encode for liver-specific and non-liver-specific MAT, respectively. We have cloned and characterized a 1.4-kb 5'-flanking region of the human MAT2A (GenBank Accession No. AF039088). Two major transcriptional start sites were identified by primer extension and S1 nuclease protection analysis; one was within 10 nucleotides downstream and the other was located at 158 nucleotides upstream from the consensus TATA box, respectively. The promoter is highly GC rich (75%) in the first 300 base pairs and contains several Sp-1 binding sites, a C/EBP, a HSF2, a STATx, a c-Myb, several v-Myb, and numerous GATA consensus binding sites. The human MAT2A promoter was able to efficiently drive luciferase expression in both Jurkat and 293 cells, but sequential deletion analysis of the promoter revealed that different regions of the promoter are important for cell-specific MAT2A expression.

Base Sequence↗

PubMed1998

[Detection of minimal residual disease in acute lymphoblastic leukemia using PCR-molecule hybridization of RNA transcripts].

OBJECTIVE: To detect acute lymphoblastic leukemia's(ALL's) minimal residual disease(MRD) rapidly and effectively. METHODS: In this assay, the gamma T-cell receptor gene rearrangements serve as marker genes. The gene rearrangements are amplified from the diagnostic specimens using a consensus V segment primer and a consensus J segment primer to which the promoter T7 RNA polymerase has been appended. The PCR product from this amplification is transcribed into a radiolabeled RNA probe. The opposite DNA strand is transcribed into test RNA from the PCR product of different staged specimens. The test RNA is hybridized with the probe, and later the digestion with RNase A, Polyacrylamide gel electrophoresis and autoradiography are in progress. RESULTS: According to the mechanism, the perfectly matched RNA duplex can prevent the digestion of RNase A, and the presence of the leukemia cells in the test specimen can be determined. Logarithmical dilution experiments with DNA of a cell line from ALL have shown that this assay's sensitivity is at the 10(-5) level. Minimal residual disease was successfully detected in a case of ALL during its complete remission stage. But if the probe and test RNA are not from the same individual, the results of this kind of cross hybridization are negative. CONCLUSION: The above results suggest that this assay can become an effective measure in the detection of ALL-MRD clinically.

Child↗

PubMed1998

Inactivation of voltage-gated cardiac K+ channels.

Inactivation is the process by which an open channel enters a stable nonconducting conformation after a depolarizing change in membrane potential. Inactivation is a widespread property of many different types of voltage-gated ion channels. Recent advances in the molecular biology of K+ channels have elucidated two mechanistically distinct types of inactivation, N-type and C-type. N-type inactivation involves occlusion of the intracellular mouth of the pore through binding of a short segment of residues at the extreme N-terminal. In contrast to this "tethered ball" mechanism of N-type inactivation, C-type inactivation involves movement of conserved core domain residues that result in closure of the external mouth of the pore. Although C-type inactivation can show rapid kinetics that approach those observed for N-type inactivation, it is often thought of as a slowly developing and slowly recovering process. Current models of C-type inactivation also suggest that this process involves a relatively localized change in conformation of residues near the external mouth of the permeation pathway. The rate of C-type inactivation and recovery can be strongly influenced by other factors, such as N-type inactivation, drug binding, and changes in [K+]o. These interactions make C-type inactivation an important biophysical process in determining such physiologically important properties as refractoriness and drug binding. C-type inactivation is currently viewed as arising from small-scale rearrangements at the external mouth of the pore. This review will examine the multiplicity of interactions of C-type inactivation with N-terminal-mediated inactivation and drug binding that suggest that our current view of C-type inactivation is incomplete. This review will suggest that C-type inactivation must involve larger-scale movements of transmembrane-spanning domains and that such movements contribute to the diversity of kinetic properties observed for C-type inactivation.

Allosteric Regulation↗

PubMed1998

A peptide sequence of heparin/heparan sulfate (HP/HS)-interacting protein supports selective, high affinity binding of HP/HS and cell attachment.

We previously have identified a novel cell surface heparan sulfate/heparin (HS/HP)-interacting protein (HIP) found in human uterine epithelia and a variety of other human epithelial and endothelial cells and cell lines (Liu, S., Smith, S. E., Julian, J., Rohde, L. H., Karin, N. J., and Carson, D. D. (1996) J. Biol. Chem. 271, 11817-11823; Rohde, L. H., Julian, J., Babaknia, A., and Carson, D. D. (1996) J. Biol. Chem. 271, 11824-11830). The amino acid sequence predicted for HIP revealed a potential HS/HP-binding motif. In the present studies, a synthetic peptide corresponding to this putative HS/HP-binding motif, HIP peptide, was synthesized and examined with regard to its HS/HP binding and cell attachment promoting activity. Results using solid phase binding assays demonstrate that HIP peptide binds HS/HP with high selectivity and has high affinity for bulk HP (50% saturation congruent with 300 nM) and even higher affinity for a subset of polysaccharides found in commercial [3H]HP (half-saturation congruent with 10 nM). Moreover, HIP peptide binds subsets of cell and extracellular matrix-associated HS and dermatan sulfate expressed by RL95 cells, a human uterine adenocarcinoma cell line. HIP peptide also binds a similar fraction of HS as well as dermatan sulfate expressed by JAR cells, a human choriocarcinoma cell line. In contrast to binding of cell- or extracellular matrix-associated HS, HIP peptide does not bind secreted or released forms of HS or DS from either RL95 or JAR cells to a significant extent. HS species that bind to HIP peptide are generally larger, have a higher negative charge density, and have a larger proportion of di- and trisulfated disaccharide units than HS species that do not bind to HIP peptide, demonstrating structural differences among these polysaccharides. This same peptide supports HS-dependent JAR cell attachment. Collectively, these data demonstrate that a linear peptide sequence found within HIP can account, at least in part, for the HS/HP binding and cell adhesion promoting activities of this protein.

Amino Acid Sequence↗