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Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 865 records · Page 48Linked to original sources
PubMed1995

[The establishment of ADBS data bank system for autopsy records].

The ADBS data bank system consists of PC 286 microcomputer, (or 386 and other more advanced machine) VGA color monitor, printer and ADBS V. 2.0 software. According to the international classification of diseases (ICD-9 or ICD-10, SNOMED), pathological diagnoses are coded and put into computer. This system has five functions: search, statistics, edition, print and system restore. For facilitating the operation of this system, all orders are listed as window menu. The statistic results can be shown as tables or figures and put out as disk files or prints. The system is currently an advanced computerized system of histopathological and autopsied records in Chinese.

Autopsy↗
PubMed1995

A simple method for the transformation of Agrobacterium tumefaciens by foreign DNA.

A method for successful introduction of Ti plasmid vector ( > 10 kb) into Agrobacterium tumefaciens is described. Competent A.tumefaciens cells were prepared with 50 mmol/L CaC1(2) at room temperature and introduction was done on ice followed by a 28 degrees C heat pulse. The efficiency of transformation was 10(-4)-10(-5) transformants per total recipient population or 10(6) transformants per microgram DNA. The effects of growth phase of A. tumefaciens cells, concentration of CaC1(2) solution, temperature, liquid N2, heat pulse, recovery time, and storage time of competent cells at 4 degrees C or -20 degrees C (in 15% glycerin) on transformation were studied.

Agrobacterium tumefaciens↗
PubMed1995

Studies on high salt tolerance of transgenic tobacco.

With E. coli mtlD gene (encoding mannitol 1-phosphate dehydrogenase) and gutD gene (encoding glucitol 6-phosphate dehydrogenase) cloned, plant expression vector pBIGM had been obtained by inserting mtlD and gutD genes into binary vector pBin438. Tobacco was transformed with A. tumefaciens LBA4404 containing pBIGM. Results of molecular hybridization of transformed plants indicated that mtlD and gutD genes had integrated into the genomic DNA of tobacco plants. Experiments of salt tolerance and analysis of sugar alcohols showed that the accumulation of different sugar alcohols in transgenic tobacco plants had increased salt tolerance of tobacco.

Blotting, Southern↗
PubMed1995

[The effect of intrathecal injection of neurotensin on acupuncture analgesia in rats].

The influence of intrathecal injection of Neurotensin (NT) and Anti-NT serum (ANTS) on pain threshold, and electroacupuncture (EA) analgesia in the rat was investigated. The tail-flick induced by potassium iontophoresis was used to measure the pain threshold. The increase of pain threshold was observed within 100 min, after NT injection (2 micrograms), and it was more effective than that of the ACSF injection (P < 0.01). The NT administration could also enhance the EA analgesia. On the contrary, the pain threshold was decreased in ANTS group as compared with that of ACSF control group. The ANTS administration could decreased the role of EA analgesia. Our data show that NT in spinal cord may play an important role in the EA analgesia.

Acupuncture Analgesia↗
PubMed1995

Docosahexaenoic acid ethyl ester and its ultraviolet degradation products showed DNA-breaking activity in vitro and cytotoxic effects on the HSC-4 cell line.

The DNA-breaking activity and cytotoxicity of docosahexaenoic acid ethyl ester (DHAE) and its degradation products (dDHAE) induced by ultraviolet (UV) irradiation, were demonstrated in this study. The major component of dDHAE was identified as 4-hydroxyvaleric acid ethyl ester. DHAE and dHAE solutions at a concentration of 100 mg/ml induced single-strand breaks of plasmid DNA after an incubation at 37 degrees C and pH 7.6 for 15 hours. DHAE transformed a plasmid supercoiled DNA (Form I) into an open circular relaxed form (Form II), and dDHAE completely destroyed DNA molecules. HSC-4 cells, which were derived from human prickle cell carcinoma, were cultured with various concentrations (10, 30 and 50 micrograms/ml) of DHAE and dDHAE. Both inhibited the proliferation of HSC-4 cells. The potency of their cytotoxicity was dependent on their concentration. It is noteworthy that the lethal effects of DHAE and dDHAE on HSC-4 cells were quite similar, although the DNA-breaking activity of dDHAE was much greater than that of DHAE. These results suggested that DHAE becomes more cytotoxic after undergoing oxidization and metabolism in the cell.

Antineoplastic Agents↗
PubMed1994

Conformational differences in human apolipoprotein B-100 among subspecies of low density lipoproteins (LDL). Association of altered proteolytic accessibility with decreased receptor binding of LDL subspecies from hypertriglyceridemic subjects.

We asked at what point in the metabolic cascade of very low density lipoproteins (VLDL) to low density lipoproteins (LDL) the accessibility of proteolytic cleavage sites in B-100 changes, and we evaluated the effect of hypertriglyceridemia on the proteolytic accessibility, secondary structure, and receptor-binding affinity of B-100 in LDL subspecies of varying density. Limited proteolysis with Staphylococcus aureus V8 protease and cathepsin D identified the density (about 1.033 g/ml) between two LDL subspecies, designated LDL-1 and -2, as the transition point during VLDL metabolism of both normolipidemic (N-) and hypertriglyceridemic (HTG-) subjects at which accessibility to protease attack changed in three peptide regions of B-100. Hypertriglyceridemia greatly altered proteolytic accessibility of B-100 in the denser LDL subspecies. Specifically, B-100 in HTG-LDL exposed more cleavage sites than in N-LDL, including two novel sites, approximately 120 and approximately 130 kDa from the NH2 terminus in the small and dense subspecies (designated LDL-4, -4.5 or -5, d = 1.048-1.062 g/ml). Analysis of circular dichroic spectra indicated no difference in helical content between B-100 in N- and HTG-LDL but showed a greater content of beta-structure in HTG-LDL. Binding affinity for the LDL receptor of human fibroblasts decreased markedly with increasing density among HTG-LDL subspecies (by approximately 50% for LDL-4.5 or -5). We conclude that the changes in proteolytic accessibility observed between LDL-1 and -2 and in LDL-4, -4.5, or -5 indicate significant differences in local conformation of B-100 at specific peptide regions. The association of exposure of more cleavage sites, especially novel sites in the NH2-terminal regions, with greatly decreased receptor-binding affinity in LDL-4.5 or -5 suggests that altered local conformation in B-100 apart from the putative receptor-binding domain might affect interaction with the receptor.

Apolipoprotein B-100↗
PubMed1994

Characterization of the glycine transport system GLYT 1 in human placental choriocarcinoma cells (JAR).

Transport of glycine in confluent monolayer cultures of JAR human placental choriocarcinoma cells was investigated. Glycine uptake in these cells was made up of two components, one being Na(+)-dependent with no requirement for Cl- and the other being dependent on Na+ as well as Cl-. Substrate specificity studies indicated that distinct transport systems were responsible for these two components. Alanine inhibited the Na(+)-dependent glycine uptake preferentially and the Na(+)- and Cl(-)-dependent glycine uptake represented > 95% of total uptake in the presence of 5 mM alanine. Competition experiments revealed that the Na(+)- and Cl(-)-dependent transport system exhibited a very narrow substrate specificity with affinity toward only glycine and its derivatives such as sarcosine, glycine methyl ester and glycine ethyl ester. These characteristics identify the transport system as GLYT 1. This system showed high affinity for glycine, with a Michaelis-Menten constant of 15 microM. The Na+:Cl-: glycine stoichiometry appeared to be 2:1:1. Treatment of JAR cells with calmodulin antagonists resulted in the inhibition of the transport function of GLYT 1 and this inhibition was solely due to a decrease in the maximal velocity of the system with no change in the substrate affinity. It is concluded that the placental choriocarcinoma cell line JAR expresses robust activity of the glycine transporter GLYT 1 and that the activity of this transporter is under the regulation of calmodulin-dependent cellular processes.

Alanine↗
PubMed1994

A study on superoxide dismutase activity of some model compounds.

The synthesis and characteristics of a binuclear ligand N,N,N',N'-tetrakis (2'-benzimidazolyl methyl)-1,4-diethylene amino glycol ether (EGTB) and its series of coordination compounds containing copper(II), iron(III), and manganese(II) with and without exogenous bridging ligand which was imidazolate ion (Im-), bipyridine (bpy), or 1,10-phenanthroline (phen) are reported. Depending on the redox potentials by cyclic voltammetry, the coordination compounds can act as catalysts for the dismutation of superoxide radicals (O2-). The detection of the rate constant of the reaction of superoxide ion with nitroblue tetrazolium (NBT) which is inhibited by superoxide dismutase (SOD) and its model compounds of the EGTB system has been performed by a modified illumination method. The rate constants kQ of the catalytic dismutation have been obtained.

Copper↗
PubMed1994

The presence but not the sequence of the N-terminal peptide in cardiac TnC is important for function.

The most diverged region of the primary amino acid sequence between cardiac (cTnC) and fast skeletal troponin C is the N-terminal ten amino acids. We report here that major changes in the primary sequence of this region in cTnC had a minimal effect on the ability of the mutant proteins to recover maximal activity in TnC-extracted cardiac and fast skeletal muscle myofibrils. However, deletion of the N-terminal nine amino acids resulted in a 60% decrease in maximal Ca(2+)-dependent ATPase activity with only a small change in the pCa50 of activation. Deletion of the N-terminal peptide did not appear to appreciably affect the Ca(2+)-binding properties of cTnC, but it did alter the interaction with hydrophobic fluorescent probes. Thus, the presence but not the sequence, of the N-terminal extension is important for the maximal activity of cTnC. The N-terminal helix may function in a relatively non-specific manner to prevent unfavorable interactions between domains in cTnC or between cTnC and other troponin subunits.

Adenosine Triphosphatases↗
PubMed1994

Luffin-S--a small novel ribosome-inactivating protein from Luffa cylindrica. Characterization and mechanism studies.

We purified and characterized a novel RIP (ribosome inactivating protein), Luffin-S from the seeds of Luffa cylindrica. Different from Luffin-A and B, which are RNA N-glycosidases with molecular weights of 27 and 28 kDa, respectively, Luffin-S has an M.W. of only approx. 10 kDa, much smaller than any other RIPs so far investigated. Its abundant resources, toxicity similar to TCS in a cell-free protein synthesis system and unique mechanism as phosphodiesterase, like alpha-sarcin, promisingly make it a potential toxic moiety of immunotoxin.

Amino Acids↗
PubMed1994

Localization and regulation of low affinity nerve growth factor receptor expression in the rat olfactory system during development and regeneration.

Nerve growth factor (NGF), a classic neurotrophic factor, promotes neuronal survival, maintenance, regeneration and differentiation in the peripheral nervous system and parts of the central nervous system. NGF activity is mediated by cell surface bound receptors including the low affinity NGF receptor (LNGFr) which is expressed by some peripheral and central neurons and is present on peripheral nerve Schwann cells during development and regeneration. The olfactory system is a useful model for the study of the role of LNGFr in neuronal development and regeneration. The growth of olfactory axons into the brain begins in the embryo and continues through the first few postnatal weeks. In mature animals there is persistent turnover and generation of olfactory receptor neurons (ORNs) and continuous growth of new axons into the olfactory bulb. These new axons grow along the preexisting olfactory pathway. In the mature olfactory system, LNGFr has been observed in the glomerular layer of the olfactory bulb, the target of ORNs. However, neither the cellular localization nor the developmental expression of LNGFr has been characterized. Here, we tested the hypothesis that LNGFr expression is developmentally regulated in the olfactory nerve and is reinduced following injury to the mature olfactory nerve. LNGFr-immunoreactivity (IR) was first observed in the olfactory mucosa at embryonic day (E)13 and in the olfactory nerve at E14. LNGFr-IR increased in the nerve during embryonic development, began to decrease at around postnatal day (P)5 and was scarcely detectable in normal adults. The staining pattern suggests that LNGFr is located on the olfactory nerve Schwann cells. Streaks of LNGFr-IR were present in the adult olfactory nerve. We reasoned that these streaks might represent transient reexpression of LNGFr associated with normal olfactory neuron turnover and replacement. Consistent with this hypothesis, LNGFr was robustly reexpressed in the adult olfactory nerve following lesion of the olfactory epithelium. Starting late in development (E21) and in the adult, LNGFr-IR was also observed on fibers in deep layers of the olfactory bulb. LNGFr-IR was also observed in neurons of the nucleus of the diagonal band (NDB) in the basal forebrain. NDB is the sole source of cholinergic afferents of the olfactory bulb. Thus, we tested the hypothesis that LNGFr in the deep layers of the olfactory bulb is located on NDB axons by making lesions of NDB. Following the lesion, LNGFr-IR disappeared in the deep layers of the olfactory bulb but remained in the glomerular layer.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase↗
PubMed1994

A radiometric assay for Ras-processing peptidase using an enzymatically radiolabeled peptide.

A simple and sensitive radiometric assay for the peptidase involved in the post-translational processing of p21ras proteins at the carboxy-terminal Cys-aliphatic-aliphatic--any amino acid (CAAX) motif is described. An isoprenylated tetrapeptide substrate, N-acetyl-S-[3H]farnesyl-Cys-Val-Ile-Ser-OH (22-27 Ci/mmol), was synthesized from N-acetyl-Cys-Val-Ile-Ser-OH and commercial [3H]farnesyl pyrophosphate via farnesyltransferase. The isoprenylated tetrapeptide was then used at a concentration (0.3 microM) well below Km (6 microM) in assays with a microsomal preparation of Ras-processing peptidase from bovine liver. Under assay conditions, the peptidase reaction followed first order kinetics with respect to the substrate, allowing the IC50 values for alternative substrates and inhibitors to approximate Km and Ki values, respectively. In a further simplification, substrate and N-acetyl-S-[3H]farnesyl-Cys-OH product were separated by thin-layer chromatography on silica gel plates using chloroform:acetic acid:methanol:acetone (60:5:10:20, v/v) as solvents. The assay does not require costly, specialized equipment and provides easy means for screening potential substrates and inhibitors of Ras-processing peptidase.

Amino Acid Sequence↗
PubMed1994

GM-CSF promotes proliferation of human fetal and adult microglia in primary cultures.

Proliferation of microglia/macrophages is a common finding in many central nervous system diseases. To identify mitogenic signals for human microglia, we examined primary cultures of human fetal and adult microglia after stimulation with cytokines, colony stimulating factors (CSFs), or LPS, using proliferating cell nuclear antigen (PCNA) expression as an index of cell proliferation. The results showed that both M-CSF and GM-CSF induced microglial proliferation in fetal and adult human cultures, but that GM-CSF provided a much stronger stimulus. At 96 h post-stimulation, the mean PCNA labeling index was 2.4 for M-CSF and 13.3 for GM-CSF in fetal microglia; in adult microglia, the PCNA labeling index was 4.7 for M-CSF and 9.0 for GM-CSF. The effect of GM-CSF on fetal microglia was dose dependent and synergistic with M-CSF. LPS abolished the basal level of PCNA labeling in adult microglia, but in fetal microglia, caused a slight increase in PCNA labeling (1.9) at 96 h and consistently enhanced microglial cell survival and differentiation into highly branched cells. The production of GM-CSF in purified human fetal astrocyte and microglial cultures was examined after stimulation with LPS, TNF-alpha, or IL-1 beta. Unlike M-CSF, neither cell type produced GM-CSF in unstimulated cultures; however, when stimulated with IL-1 beta, astrocytes expressed GM-CSF mRNA and protein, which accumulated in the culture through 72 h. In microglia, LPS was the only effective inducing agent. An immunocytochemical study performed to identify in vivo sources of GM-CSF revealed selective labeling of reactive astrocytes in active lesions of multiple sclerosis and senile plaques of Alzheimer's disease. Our data demonstrate that both fetal and adult human microglia are capable of proliferation in response to CSFs, GM-CSF being the more effective stimulus.

Aged↗
PubMed1994

Expression of desiccation-induced and lipoxygenase genes during the transition from the maturation to the germination phases in soybean somatic embryos.

Transitions between developmental programs during plant embryogenesis are usually characterized by differential gene expression. Soybean (Glycine max (L.) Merr.) somatic embryos from embryogenic suspension cultures germinate poorly on a germination medium even after being grown on medium containing abscisic acid until developmental changes are induced by desiccation. The objectives of this study were to investigate: (i) the relationship between water loss and germination of somatic embryos, (ii) changes in desiccation-induced polypeptides, and (iii) the expression of maturation- and germination-associated genes during the transition from maturation to germination of soybean somatic embryos. The results revealed that partial drying of somatic embryos at 76% relative humidity for 96 h resulted in more than 90% germination. Germination frequency was correlated with the percent fresh weight loss of the somatic embryos. Polypeptides induced by desiccation were classified into three groups based on the tissues in which they were expressed and the inducing agents to which they responded. Desiccation-induced polypeptides decreased or became undetectable upon inhibition. The expression of a maturation-associated gene, Mat1, was induced in both cotyledons and hypocotyl/radicle tissues of somatic embryos after 72 h desiccation. The transcript for this gene increased in concert with water loss from the embryos. During maturation of somatic embryos, the expression of embryonic lipoxygenase genes was turned on. Desiccation alone did not directly induce expression of germination-associated lipoxygenase genes SC514 and LOXB2 in somatic embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1994

Alterations in plasma total and high density lipoprotein cholesterol levels in hyperlipidemic rats fed diets with varied content of selenium and vitamin E.

The effect of dietary selenium and vitamin E on plasma total (TC) and high density lipoprotein cholesterol (HDLC) was evaluated in 54 Sprague Dawley rats fed cholesterol/cholic acid enriched diets. Diets 1, 2, and 3 had no added selenium (low Se) and 0 (low), 60 (adequate), and 600 (high) mg/kg dL alpha tocopheryl acetate added respectively. Sodium selenite at 0.2 mg/kg (adequate Se) was added to diets 4, 5, and 6 and at 4.0 mg/kg (toxic Se) to diet 7, 8, and 9 with the same pattern of vitamin E added to the diet as described above. TC and HDLC were measured using the Kodak Ectachem system. Rats in the low and adequate Se groups fed high vitamin E had lower TC values than rats fed lower vitamin E levels but differences were not significant. In the toxic Se groups, rats fed high vitamin E had significantly (p < 0.05) higher plasma TC values than did lower Vitamin E groups. Rats on the high vitamin E diets with low or adequate Se had significantly (p < 0.05) higher mean plasma HDLC values when compared to rats fed low or adequate vitamin E diets. HDLC values for animals on Se toxic diets were significantly (p < 0.05) lower in rats fed a low vitamin E diet. In rats fed Se deficient and adequate diets, a high vitamin E intake resulted in a decrease in TC and an increase in HDLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗