Search PubMed⌕ Search

Biomedical subjects

H Liu

Publications and source records attributed to H Liu.

At least 829 records · Page 46Linked to original sources
PubMed1997

Load assessment of the static posture and weight holding in terms of pulmonary ventilation and heart rate.

The aim of this study was to explore appropriate index for load evaluation by analyzing the changes of pulmonary ventilation (VE) and heart rate (HR) in 35 student volunteers under the condition of static posture and weight holding. Each subject was asked to perform 7 kinds of static postures and 2 kinds of weight holdings. The HR was continuously measured by a remote detecting device. VE was recorded by a ventimeter for an average of 5 min. The results showed that HR was positively correlated to VE under static activities (r = 0.89), which suggested that VE as well as HR could to some degrees reflect the static load. It was better to use VE to indicate the load of weight holdings than to use HR, which, on the other hand, was more sensible in reflection of the posture load. It is better to use relative value of both of VE and HR to reflect the static load. In addition, arm-overheaded posture increase HR more significantly than any other activities.

Adult↗
PubMed1997

The monitoring biomarker for immune function of lymphocytes in the elderly.

In this paper, we determined the number of peripheral blood lymphocytes (PBL) in the elderly and their proliferative response to PHA (Phytohemagglutinin). The data showed that the PBL number decreased with age. For the young group: 1680.0 +/- 644.7/microliters; the 60-69 years old group: 1284.0 +/- 492.3/microliters; the 70-79 years old group: 987.5 +/- 309.1/microliters, P < 0.05. The OD (optical density) value measured by MTT method for proliferative response of PBL in the elderly was 0.15 +/- 0.08, which was lower than the young group 0.18 +/- 0.05. Also, an apparent decline of soluble IL-2 receptor (sIL-2R) release from activated PBL in old people was found. The results suggested that the changes of PBL number and sIL-2R level could be considered as an indication of immune function of lymphocytes in the elderly.

Adult↗
PubMed1997

Contrast-detail detectability analysis: comparison of a digital spot mammography system and an analog screen-film mammography system.

RATIONALE AND OBJECTIVES: The authors compared the contrast-detail detectability properties of an optically coupled charge-coupled device (CCD) digital mammography system with those of a conventional analog screen-film mammography system. METHODS: A proprietary contrast-detail phantom was imaged with both systems. Twelve observers viewed analog and digital images obtained at seven different mean glandular doses. Contrast-detail-dose curves were generated on the basis of the readers' visual perceptions. Interobserver errors were also calculated. In addition, the authors applied a theoretical model for lesion detectability to calculate and compare the digital and analog mammography systems. RESULTS: The readers' contrast-detail detectability was significantly superior with the digital system in the detail and contrast ranges evaluated (P < .001). CONCLUSION: The performance of the readers paralleled the performance predicted by the theoretical model for the two imaging systems. The following features account for the superior performance of the digital mammography system: (a) higher quantum efficiency of the phosphor, (b) wider dynamic range, (c) better contrast transfer characteristics, and, most important, (d) greater photon flux at the phosphor entrance.

Contrast Sensitivity↗
PubMed1997

Refolding of soluble leukemia inhibitory factor receptor fusion protein (gp 190 sol DAF) from urea.

The insoluble inclusion bodies of soluble leukemia inhibitory factor receptor fusion protein (gp 190 sol DAF) was solubilized in 8 M urea on the unfolding transitions, and several factors on the aggregate formation were indirectly analyzed for the refolding of gp 190 sol DAF. Results indicate that the refolding yield can be considerably increased at lowering concentration of the unfolding protein, a little soluble protein with the slow refolding appears in the process of the aggregate formation and the concentration of the denaturant must be down to a minimum level for its refolding.

Glycerol↗
PubMed1997

Cyclic AMP-mediated regulation of vascular smooth muscle cell cyclic AMP phosphodiesterase activity.

1. Rat cultured aortic vascular smooth muscle cells (VSMC) express both cyclic GMP-inhibited cyclic AMP phosphodiesterase (PDE3) and Ro 20-1724-inhibited cyclic AMP phosphodiesterase (PDE4) activities. By utilizing either cilostamide, a PDE3-selective inhibitor, or Ro 20-1724, a PDE4-selective inhibitor, PDE3 and PDE4 activities were shown to account for 15% and 55% of total VSMC cyclic AMP phosphodiesterase (PDE) activity. 2. Treatment of VSMC with either forskolin or 8-bromo-cyclic AMP caused significant concentration- and time-dependent increases in total cellular cyclic AMP PDE activity. Using cilostamide or Ro 20-1724, we demonstrated that both PDE3 and PDE4 activities were increased following forskolin or 8-bromo-cyclic AMP treatment, with a relatively larger effect observed on PDE3 activity. The increase in cyclic AMP PDE activity induced by forskolin or 8-bromo-cyclic AMP was inhibited by actinomycin D or cycloheximide, demonstrating that new mRNA synthesis and protein synthesis were required. An analogue of forskolin which does not activate adenylyl cyclase (1,9-dideoxyforskolin) or an analogue of cyclic GMP (8-bromo-cyclic GMP) did not affect total cyclic AMP PDE activity. 3. Incubation of VSMC with 8-bromo-cyclic AMP for 16 h caused a marked rightward shift in the concentration-response curves for both isoprenaline- and forskolin-mediated activation of adenylyl cyclase. A role for up-regulated cyclic AMP PDE activity in this reduced potency is supported by our observation that cyclic AMP PDE inhibitors (IBMX, cilostamide or Ro 20-1724) partially normalized the effects of isoprenaline or forskolin in treated cells to those in untreated cells. 4. We conclude that VSMC cyclic AMP PDE activity is increased following long-term elevation of cyclic AMP and that increases in PDE3 and PDE4 activities account for more than 70% of this effect. Furthermore, we conclude that increases in cyclic AMP PDE activity contribute to the reduced potency of isoprenaline or forskolin in treated VSMC. These results have implications for long-term use of cyclic AMP PDE inhibitors as therapeutic agents.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

NO and angiotensin II effects on blood pressure and fluid homeostasis.

Angiotensin II (50 ng/5 microl) and L-NAME (250 microg/5 microl), an inhibitor of NO synthase (NOS), were administered intracerebroventricularly alone or in combination to conscious rats. Mean arterial blood pressure (MABP) increased reaching a peak within 5 min in all groups compared to controls treated with the vehicle, artificial CSF (5 microl). MABP returned to basal levels at 30 min after angiotensin II and remained stable for the following 90 min. In animals treated with L-NAME alone, after the initial pressor response, MABP declined but began to increase progressively from 30 min until the end of the experiment at 120 min. When administered with angiotensin II, however, the initial pressor response was prolonged. Angiotensin II-induced drinking was significantly attenuated by L-NAME. In control rats, inhibiting NOS elevated plasma levels of oxytocin and vasopressin but in angiotensin II-stimulated animals, only oxytocin was further elevated after L-NAME. Thus, NO formed centrally inhibits basal secretion of oxytocin and vasopressin as well as the resting blood pressure. During stimulation with angiotensin II, NO facilitates drinking, limits the pressor response and selectively inhibits oxytocin release.

Angiotensin II↗
PubMed1997

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) decreases glutamate uptake in cultured astrocytes.

The deleterious effect of the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on dopaminergic neurons of the substantia nigra is well established. In addition, increased glutamatergic drive to basal ganglia output nuclei is considered a likely contributor to the pathogenesis of Parkinson's disease. One possibility for the increased excitatory tone may be related to an impairment in glutamate uptake. As astrocytes possess efficient transport mechanisms for both MPTP and glutamate, we have examined the effect of this agent on D-aspartate uptake into these cells. Treatment of cultures with 50 microM MPTP for 24 h decreased uptake by 39%. Kinetic analysis revealed that this effect was due to a 35% decrease in Vmax with no change in the Km. Treatment with deprenyl, a monoamine oxidase B inhibitor, produced a complete reversal of MPTP-induced uptake inhibition, but was ineffective following exposure of cells to the MPTP metabolite, 1-methyl-4-phenylpyridinium (MPP+). Removal of MPTP from cultures resulted in a complete restoration of glutamate uptake after 24 h. These results show that MPTP reversibly compromises glutamate uptake in cultured astrocytes, which is dependent on the conversion of MPTP to MPP+. Such findings suggest that the glutamate transporter in astrocytes plays an important role in MPTP-induced neurotoxicity and possibly in parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1997

Characterization of a soluble IL-6 receptor alpha mutant C277D/H280I expressed in E.coli.

The pleiotropic cytokine interleukin-6(IL-6) triggers the formation of a high affinity receptor complex constituted by the ligand-binding subunit IL-6 receptor alpha (IL-6R alpha) and the signal transducer gp130. To construct the antagonist of IL-6, a DNA segment encoding the soluble human IL-6R alpha (shIL-6R alpha) mutant with two substitutions C277D/H280I was generated by overlap extension polymerase chain reaction. The DNA segment was then subcloned into vector pET-3b and expressed in E.coli at a high level. The refolded and purified recombinant protein, which was designated as DM650, exhibited an increased IL-6-binding capability by 8-fold. DM650 antagonized IL-6 perfectly, resulting in the growth-inhibition of human myeloma AF-10 cells. DNA fragmentation assay proved that the growth of AF-10 cells was inhibited through the induction of apoptosis suppressed by IL-6.

Antigens, CD↗
PubMed1997

Residues K128-Q175 of human interleukin-6 are essential for its biological activity.

Internal deletion K128-Q175 of the human interleukin-6 (hIL-6) has been generated at the cDNA level. With pBV220 as expressing vector, the recombinant pBV*-DIL-6 encoding the deletion mutant (12 kD) of hIL-6 has been constructed. The resulted recombinant plasmids were then used to transform E. coli strain HB101, and the expression in the PLPR promoter system, which is temperature-regulatable, was achieved. After purification and renaturation, the biological activity of the expressed product, designated as DM120, was measured by MTT method in an IL-6-dependent cell line 7TD1. The results show that the amino acid residues of IL-6 128 to 175 are crucial for IL-6 activity. Receptor binding assay in vitro indicates that the entire region is not involved in forming the receptor binding surface.

Gene Deletion↗
PubMed1997

Manganese superoxide dismutase expression inhibits soft agar growth in JB6 clone41 mouse epidermal cells.

Manganese superoxide dismutase (MnSOD) has been found to be depleted in a variety of tumor cells as well as in in vitro transformed cell lines, suggesting that MnSOD may function as an anticarcinogen by protecting the cell from oxidant-induced carcinogenesis. The relationship between MnSOD expression and tumor promotion was studied by transfection of a human MnSOD cDNA into the promotable mouse epidermal cell line JB6 clone41. The effect of MnSOD overexpression on the promotion-sensitive phenotype of JB6 cells was assessed by measuring growth characteristics such as growth rate and the ability to form colonies in soft agar. Compared with the parental and vector-transfected (gpt) control cells, MnSOD-overexpressing cells had a slower growth rate and their ability to form colonies in soft agar was significantly decreased in response to 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment. Since the transformation-sensitive phenotype of JB6 clone41 cells is associated with increased expression of the transcription factor AP-1, we compared c-jun and c-fos mRNA expression in MnSOD-transfected and control JB6 cells. Overexpression of MnSOD led to a significant decrease in c-jun and c-fos expression in response to treatment with TPA or the oxidant promoter superoxide. These findings indicate that the promotion-sensitive phenotype of JB6 clone41 cells can be reverted by increasing MnSOD intracellularly. A possible mechanism is that elevated MnSOD expression might change the intracellular redox state by altering the balance of reactive oxygen species. This could lead to a modulation of TPA and oxidant-induced signal transduction pathways controlling cell growth and differentiation.

Animals↗
PubMed1997

Regulated expression system for GD3 synthase cDNA and induction of differentiation in Neuro2a cells.

It was reported recently by our group that the transfection of GD3 synthase cDNA into Neuro2a cells, a neuroblastoma cell line, caused cell differentiation with neurite sprouting (Kojima et al., 1994; J. Biol. Chem., 269, 30451-30456). To further explore this phenomenon in detail, we applied tetracycline-regulated system to control the expression of GD3 synthase cDNA in Neuro2a cells. Under this system, the process of Neuro2a cell differentiation was rather slow, about 3 weeks of cell culturing in the absence of tetracycline was required for most cells to extend the neurite-like structures. The RNase protection assay indicated that the mRNA of GD3 synthase gene was first detected between 4 h and 8 h after the gene was activated and kept at approximately the same level through the process. Furthermore, time-course analysis of total ganglioside expressions has shown that GD3 and GT1b gangliosides appeared on the cell surface early in the process and reached the maximum level around day 6. We also found that the amounts of GD3 and GT1b on the cell surface started to decrease after day 6 and returned gradually to the basal values after 3 weeks. On the other hand, GQ1b and GD1b were started to be synthesized at early stage and the amounts were continuously to increase through the whole Neuro2a morphological change process. In addition, time-course analysis by flow cytometry method for GD3 and GQ1b suggested that the conversions of simple gangliosides to more complex gangliosides may be required to induce the Neuro2a differentiation. Our results indicated that the combination of cDNA transfection and regulated gene expression is a powerful tool to study the function of glycolipids and should have a general application to the glycobiology field.

Animals↗
PubMed1997

Applications in in ovo technology.

By mid-August 1995, 55% of broiler embryos in North America were vaccinated for Marek's disease using the INOVOJECT system, with 201 INOVOJECT machines placed with 16 of the top 25 poultry producers, providing the industry with the capacity to inject in excess of 400 million eggs per month or about 5 billion eggs per annum. In ovo administration of a bursal disease antibody-infectious bursal disease virus (BDA-IBDV) complexed vaccine to specific-pathogen-free (SPF) embryos was safer and more potent than conventional IBDV vaccine alone because it delayed the appearance of bursal lesions, produced no early mortality, produced higher geometric mean antibody titers against IBDV, and generated protective immunity against challenge. In ovo administration of a BDA-IBDV complexed vaccine to broiler embryos generated antibody titers against IBDV sooner than conventional virus vaccinates, and generated protective immunity against challenge Direct DNA injection of plasmid DNA encoding beta-galactosidase into breast muscle in ovo and posthatch was an effective means to achieve both gene transfer and expression, with potential for the development of gene vaccines using plasmids encoding protective antigens from poultry pathogens. In ovo administration of 800 U chicken myelomonocytic growth factor (cMGF), a chicken hematopoietic cytokine for cells of the monocytic-granulocytic lineages, significantly reduced mortality associated with Escherichia coli exposure within the hatcher when compared to PBS controls (6.1 vs 12.4, P < or = 0.05), but not when compared to a yeast expression control. A procedure was developed enabling injection prior to the onset of incubation without compromising embryo viability. This in ovo injection process has opened up the window of embryo development during incubation for intervention, as illustrated by the 100% male phenotype produced in chicks hatching from eggs injected with aromatase inhibitor prior to incubation. These data illustrate some of the in ovo applications presently in use by the poultry industry, and under development or in research at EMBREX.

Animals↗
PubMed1997

Maize streak virus coat protein binds single- and double-stranded DNA in vitro.

Maize streak virus (MSV) coat protein (CP) is required for virus movement within the plant. Deletion or mutation of MSV CP does not prevent virus replication in single cells or protoplasts but leads to a loss of infectivity in the inoculated plant. The mechanism by which MSV CP mediates the transfer of MSV DNA from cell to cell and through the vascular bundle is still unknown. Towards understanding the role of MSV CP in virus movement, the interaction of the CP with viral DNA was investigated using the 'south-western' assay. Wild-type and truncated MSV CPs were expressed in E. coli and the expressed CPs were used to investigate interactions with single-stranded (ss) and double-stranded (ds) DNA. The results showed that MSV CP bound ss and ds viral and plasmid DNA in a sequence non-specific manner. The binding domain was mapped to within the 104 N-terminal amino acids of the MSV CP. We propose that the binding of CP to MSV DNA is involved in viral DNA nuclear transport as well as encapsidation and thus may have a role in intra- and inter-cellular movement as well as systemic infection.

Animals↗
PubMed1997

Surrogate and physician understanding of patients' preferences for living permanently in a nursing home.

OBJECTIVE: To evaluate patients' willingness to live permanently in a nursing home and surrogate and physician understanding of that preference. DESIGN: Evaluation of cross-sectional interview data from a cohort study. SETTING: Five academic medical centers. PARTICIPANTS: Seriously ill hospitalized adults enrolled in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT). MEASUREMENTS: Patients' willingness to live permanently in a nursing home was measured on a 5-point scale ranging from "very willing" to "rather die." Ordinal logistic regression was used to identify patient demographic and clinical characteristics associated with this preference. Surrogate and physician perceptions of patient preferences were compared with patients' responses, and factors associated independently with surrogate and physician understanding of patient preference were identified. RESULTS: Of 9105 patients, 3262 (36%) provided responses to the study question: 7% were "very willing" to live permanently in a nursing home, 19% "somewhat willing," 11% "somewhat unwilling," 26% "very unwilling," and 30% would "rather die." Older age was associated independently with less willingness to live permanently in a nursing home (odds ratio [OR] = .90 per decade; 95% confidence interval [CI]: 0.85, 0.96). Patients with more education (OR = 1.03 per year; 95% CI: 1.00, 1.05) and more disabilities (OR = 1.05 per disability; 95% CI: 1.01, 1.09), and black patients (OR = 1.46 compared with white patients; 95% CI: 1.20, 1.76) were more willing to live in a nursing home. Surrogates understood 61% of patients' nursing home preferences but identified only 35% of patients who were willing to live permanently in a nursing home. Physicians identified 18% of patients willing to live permanently in a nursing home. CONCLUSION: Patient attitudes about living permanently in a nursing home can be elicited, cannot be reliably predicted from demographic and clinical variables, and are frequently misunderstood by surrogates and physicians. Elicitation of patient preferences regarding permanent nursing home placement should be explored before patients become unable to participate in decision making in order to enhance the concordance of patient preference with the way they spend the end of their lives.

Aged↗
PubMed1997

Incorporation of functional human immunodeficiency virus type 1 integrase into virions independent of the Gag-Pol precursor protein.

Retroviral integrase (IN) is expressed and incorporated into virions as part of the Gag-Pol polyprotein precursor. IN catalyzes integration of the proviral DNA into host cell chromosomes during the early stages of the virus life cycle, and as a component of Gag-Pol, it is involved in virion morphogenesis during late stages. It is unknown whether the scheme, conserved among retroviruses, for expressing and incorporating IN as a component of the Gag-Pol precursor protein is necessary for its function in the infected cell after viral entry. We have developed human immunodeficiency virus (HIV) virion-associated accessory proteins (Vpr and Vpx) as vehicles to deliver both foreign and viral proteins into the virus particle by their expression in trans as heterologous fusion proteins (X. Wu, et al., J. Virol. 69:3389-3398, 1995; X. Wu, et al., J. Virol. 70:3378-3384, 1996; X. Wu, et al., EMBO J. 16:5113-5122, 1977). To analyze IN function independent of its expression as a part of Gag-Pol, we expressed and incorporated IN into HIV type 1 (HIV-1) virions in trans as a fusion partner of Vpr (Vpr-IN). Our results demonstrate that the Vpr-IN fusion protein is efficiently incorporated into virions and then processed by the viral protease to liberate the IN protein. Virus derived from IN-minus provirus is noninfectious. However, this defect is overcome by trans complementation with the Vpr-IN fusion protein. Moreover, complemented virions are able to replicate through a complete cycle of infection, including formation of the provirus (integration). These results show, for the first time, that full IN function can be provided in trans, independent of its expression and incorporation into virions as a component of Gag-Pol. This finding also indicates that the IN domain of Gag-Pol is not required for the formation of infectious virions when IN is provided in trans. The ability to incorporate functional IN into retroviral particles in trans will provide unique opportunities to explore the function of this critical enzyme in a biologically relevant context, i.e., in infected cells as part of the nucleoprotein/preintegration complex.

Cell Line↗
PubMed1997

In vivo sequence variability of human immunodeficiency virus type 1 envelope gp120: association of V2 extension with slow disease progression.

According to the rate of depletion of CD4 cell counts, we grouped 12 cases of human immunodeficiency virus type 1 (HIV-1) infection as 6 rapid (21.0 to 33.8 cells per microl per month) and 6 slow (0.9 to 7.9 cells per microl per month) progressors and determined the individual viral quasispecies patterns by sequencing the genome region encoding the V1, V2, and V3 loops of envelope protein. Although the quasispecies structures varied widely from one individual to another, a strong correlation was observed between a low rate of disease progression and a high degree of genetic diversity of HIV-1. Furthermore, the V2 loop extension was observed specifically in individuals with slow or no disease progression, whereas basic amino acid substitutions in V3 characteristic of a viral phenotype shift from non-syncytium inducing to syncytium inducing were observed in patients with advanced stages of disease regardless of their rate of disease progression. Studies with recombinant viruses suggested that elongation of V2 potentially restricts the capacity of HIV-1 to replicate in macrophages. Thus, our results suggest the association of distinct sequence features of both V3 and V2 with particular patterns of disease progression. Elongation of the V2 loop may be a good predictor of slow disease progression, while basic substitutions of V3 without elongation of V2 are characteristic of rapid progression.

Amino Acid Sequence↗
PubMed1997

Tyrosine kinase inhibitor, genistein, inhibits macroscopic L-type calcium current in rat portal vein smooth muscle cells.

The effect of genistein, a specific tyrosine kinase inhibitor, was tested on the slow (L-type) Ca2+ current (ICa(L)) of vascular smooth muscle cells from freshly isolated rat portal vein, using whole-cell voltage clamp. To isolate ICa(L), the pipette contained high Cs+ and the bath contained 140 mM tetraethylammonium (TEA) to block K+ currents. Bath application of genistein decreased ICa(L) in a concentration-dependent manner within 3-6 min. The concentration for half-maximal inhibition (IC50) was 54.9 microM (at a holding potential of -40 mV). At a concentration of 300 microM, genistein produced nearly complete inhibition of ICa(L). The inhibitory effect of genistein was not reversed after washout for up to 5 min. The potential for half-inhibition (V1/2) of the steady-state inactivation curve for ICa(L) was shifted to the left by genistein (10.6 mV at 50 microM), suggesting that genistein exerts a voltage-dependent block. Superfusion with daidzein, an inactive analog of genistein, had no inhibitory effect on ICa(L) at concentrations as high as 300 microM. These results may suggest that the L-type Ca2+ channels in vascular smooth muscle cells are possibly modulated by endogenous tyrosine kinase activity. That is, tonic phosphorylation by tyrosine kinases maintains the Ca2+ channels in an available state for activation by depolarization. Thus, the vascular tone may be controlled by tyrosine kinase activity.

Animals↗