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Biomedical subjects

N Liu

Publications and source records attributed to N Liu.

At least 217 records · Page 12Linked to original sources
PubMed1995

A study on the difference of human sensation evaluation to whole-body vibration in sitting and lying postures.

The evaluation of vibration sensation is a problem which has large individual differences. In order to clarify the relationship between posture and psychological response, human sensation to whole-body vibration (from 2 to 11 Hz) in sitting and lying postures was evaluated by the semantic differential method, and the influences of posture on the evaluation were investigated by using the fuzzy measure. Furthermore, the paired t-test was used to test the significant differences in the results of evaluation between the two postures. The results were as follows: (1) Psychological responses of human beings to whole-body vibration were greatly affected by the postures. (2) Changes of the psychological responses in the lying posture were smaller than those in the sitting posture. (3) There were significant differences between sitting and lying postures in the evaluation results of physiological factor, psychological factor and synthetic evaluation (P < 0.025).

Adaptation, Psychological↗
PubMed1995

[Influence of stimulating zusanli with moxibustion of different quality and quantity on gastrointestinal motor function of reserpinized rats].

This article is focused on the observation of changes in body temperature, body weight, cholinesterase activity in blood, and gastrointestinal motility of reserpinized rats treated by stimulating Zusanli (ST 36) with moxibustion of different quality. (mugwort floss or pipe tobacco) and quantity (strong stimulation or weak stimulation). The experiment shows that better results are achieved with moxibustion not by burning tobacco; the result of strong stimulation with moxa-sticks is better than that of weak stimulation with the same material. Strong stimulation with moxa-sticks can obviously increase the activity of cholinesterase (P < 0.05), inhibit hyperactive gastrointestinal motility (P < 0.05), maintain normal body temperature (P < 0.05), and prevent body weight lossing. All these show that therapeutic results of moxibustion are closely related to the quality and quantity of moxibustion.

Animals↗
PubMed1994

Decreasing calreticulin expression lowers the Ca2+ response to bradykinin and increases sensitivity to ionomycin in NG-108-15 cells.

It has been suggested that the multifunctional protein, calreticulin, is a major calcium sequestering protein in the inositol 1,4,5-trisphosphate receptor-containing endoplasmic reticulum subcompartment. In neuroblastoma X glioma NG-108-15 cells, bradykinin can effectively stimulate the release of inositol 1,4,5-trisphosphate and cause a cytosolic calcium transient. To explore the function of calreticulin as an intracellular calcium sequestering protein, we investigated calcium dynamics in NG-108-15 cells after treatment with an antisense oligonucleotide against calreticulin, CrtAS1. Cells treated with either CrtAS1 or the corresponding sense oligonucleotide CrtPS1 were examined for their calreticulin content by Western blotting, the amplitude of their calcium transient in response to bradykinin, and their sensitivity toward the calcium ionophore, ionomycin. Treatment with CrtAS1 decreased the amount of calreticulin in comparison to CrtPS1-treated and untreated control cells. At the same time, CrtAS1-treated cells had a significantly reduced calcium response to bradykinin and were more sensitive to ionomycin-induced cell death. These data show that the level of calreticulin expression is directly related to the calcium storage capacity of the inositol 1,4,5-trisphosphate-sensitive calcium pool and indicate a direct relationship between the level of calreticulin and the protection against cytotoxic calcium overload.

Base Sequence↗
PubMed1994

ErbB-3 and ErbB-4 function as the respective low and high affinity receptors of all Neu differentiation factor/heregulin isoforms.

Neu differentiation factor (NDF or heregulin) elevates tyrosine phosphorylation of the ErbB-2 receptor tyrosine kinase, and it was, therefore, thought to function as a ligand of this receptor. However, several lines of evidence raised the possibility that the interaction between NDF and ErbB-2 involves another molecule, which belongs to the family of epidermal growth factor receptors. To address this question we constructed soluble chimeric proteins between alkaline phosphatase and the extracellular domains of ErbB-2 and either ErbB-3 or ErbB-4, two newly recognized members of the epidermal growth factor receptor family. Using the soluble proteins we found that beta isoforms of NDF specifically bind to the ErbB-3 and ErbB-4 receptors but not to the soluble ErbB-2 protein. When ectopically expressed in monkey fibroblasts, the full-length ErbB-3 and ErbB-4 receptors conferred specific binding to NDF. In these cells ErbB-3 displayed lower ligand binding affinity than ErbB-4, but like the latter receptor it preferred to bind the beta isoform over the alpha class of NDFs. These results indicate that both ErbB-3 and ErbB-4 function as physiological receptors of all NDF isoforms and suggest that a still unknown ligand of ErbB-2 exists.

Amino Acid Sequence↗
PubMed1994

Brain neurons and glial cells express Neu differentiation factor/heregulin: a survival factor for astrocytes.

Neu differentiation factor (NDF, also called heregulin) was isolated from mesenchymal cells on the basis of its ability to elevate phosphorylation of ErbB proteins. Earlier in situ hybridization analysis showed that NDF was transcribed predominantly in the central nervous system during embryonic development. To gain insights into the role of NDF in brain we analyzed its distribution by immunohistochemistry and in situ hybridization. Late-gestation (day 17) rat embryos displayed high NDF immunoreactivity in both motor (e.g., putamen) and limbic (e.g., septum) regions. Lower levels of the factor were exhibited by adult brain, except for the cerebellum, where NDF expression was increased postnatally. Both neurons and glial cells were identified by immunohistochemistry as NDF-producing cells (e.g., pyramidal neurons in the cerebral cortex and glial cells in the corpus callosum). By establishment of primary cultures of rat brain cells we confirmed that NDF was expressed in neurons as well as in astrocytes. In addition, by using such primary cultures we observed that NDF treatment exerted only a limited mitogenic effect, which was accompanied by significant acceleration of astrocyte maturation. Furthermore, long-term incubation with the factor specifically protected astrocytes from apoptosis, implying that NDF functions in brain as a survival and maturation factor for astrocytes.

Animals↗
PubMed1994

Transesophageal echocardiographic assessment of left ventricular function during apnea testing for brain death.

The effects of apnea testing-induced respiratory acidosis on left ventricular function (LVF) are still controversial. The aim of the study was to assess LVF during apnea testing using transesophageal echocardiography (TEE). Twenty consecutive patients suspected of brain death, hemodynamically stable, and considered as potential organ donors were prospectively studied. A 20-min apnea test was performed after obtaining a PaCO2 > 35 mmHg and 20 min of FIO2 1 ventilation. LVF was assessed using TEE with a CFM 750 (Diasonic) connected to a 5 MHz probe. Heart rate (HR), mean arterial pressure (MAP), left ventricle end-diastolic and systolic area (LVEDA, LVESA), and LVF assessed by fractional area changes (FAC), systolic wall motion (SWM) scores, and blood gases were recorded at baseline, and after 5, 10, 15, and 20 min of apnea testing. In 19 patients, no spontaneous respiratory movement occurred during the standard 20-min period. In one patient (No. 15), the apnea test had to be stopped after 10 min because of hypoxia. HR, LVEDA, LVESA, and SWM were not significantly modified during the study. There was a progressive statistically significant decrease in MAP during apnea (from 77 +/- 10 to 63 +/- 11 mmHg), associated with a statistically significant increase in FAC at 20 min (from 48 +/- 13 to 56 +/- 8%). PaCO2 progressively rose (from 40 +/- 3 to 95 +/- 11 mmHg), associated with a decrease in pH (from 7.42 +/- 0.06 to 7.09 +/- 0.08). At the same time, PaO2 decreased slightly in all patients, but values remained well above hypoxic levels, except for one patient. Despite severe respiratory acidosis the increase in FAC suggests that apnea testing is well tolerated for brain death assessment.

Acidosis, Respiratory↗
PubMed1994

NDF/heregulin stimulates the phosphorylation of Her3/erbB3.

Her3/erbB3 has been identified as a third member of the epidermal growth factor receptor (EGFR) family [(1989) Proc. Natl. Acad. Sci. USA 86, 9193-9197; (1990) Proc. Natl. Acad. Sci. USA 87, 4905-4909]. The natural ligand for Her3 has not been identified. Although recently NDF has been proposed as a specific ligand for Her4 [(1993) Nature 366, 473-475; (1993) J. Biol. Chem. 268, 18407-18410], we report here that Her3 was phosphorylated on tyrosine not only in three breast carcinoma cell lines, MDAMB453, MDAMB468 and SKBR3, but also in Her3-transfected CHO cells in response to NDF stimulation. In further studies, cells were reacted with 125I-labeled NDF and then chemically crosslinked. Immunoprecipitation with anti-Her3 revealed a dense high Mw band, greater than 400 kDa. The results suggest that NDF may be a ligand of Her3 and induces receptor hetero-oligomerization.

Animals↗
PubMed1994

Properties of variant forms of human stem cell factor recombinantly expressed in Escherichia coli.

The gene for human stem cell factor (SCF) encodes a leader sequence followed by 248 amino acids (Martin et al., 1990, Cell 63, 203). Of these 248 amino acids, the first 189 correspond to an extracellular domain and the remainder correspond to a hydrophobic transmembrane domain plus a cytoplasmic domain. A naturally occurring soluble form, released by proteolytic cleavage after amino acid 165, has been described. An alternatively spliced mRNA, lacking the codons for exon 6, has also been described. Since the amino acids encoded by exon 6 include the proteolytic cleavage site, the form expressed from the alternatively spliced mRNA tends to remain membrane-bound. In the present study, we have begun to explore structure/function relationships within the extracellular domain of SCF. Forms beginning at amino acid 1 (after the leader sequence) and ranging from 127 to 189 at the C-terminus have been recombinantly expressed in Escherichia coli and purified. In addition, forms missing the amino acids encoded by exon 6, forms missing up to 10 amino acids from the N-terminus, and forms with disulfide bond alterations have been expressed and purified. The forms have been characterized structurally, as well as functionally, in quantitative cell proliferation and receptor-binding assays. The results indicate that amino acids 1-141 comprise a structural and functional core and allow conclusions about the necessity of each of the two disulfide bonds for structure and function.

Alternative Splicing↗
PubMed1994

Additive effect on gas exchange of inhaled nitric oxide and intravenous almitrine bismesylate in the adult respiratory distress syndrome.

OBJECTIVE: To assess the additive effect of inhaled nitric oxide (NO) and intravenous almitrine bismesylate (ALM) on gas exchange. DESIGN: Prospective self-controlled study. SETTING: 3 medico-surgical intensive care units. PATIENTS: 17 patients with severe hypoxemia (PaO2/FIO2 ratio: 88 +/- 30 mmHg, venous admixture: 47 +/- 7%) and elevated mean pulmonary artery pressure (MPAP: 30 +/- 5 mmHg) due to adult respiratory distress syndrome (ARDS). INTERVENTIONS: 5 conditions were studied: 1) baseline, 2) 5 to 10 ppm of NO during 30 min, 3) discontinuation of NO during 30 min, 4) ALM infusion (0.5 mg/kg) during 30 min, 5) ALM infusion (0.5 mg/kg) during 30 min in combination with 5 to 10 ppm of NO. MEASUREMENT AND RESULTS: The PaO2/FIO2 ratio rose from 88 +/- 30 to 98 +/- 37 mmHg (NS) with NO alone, and from 92 +/- 25 to 130 +/- 56 mmHg (p < 0.01) with NO + ALM (p < 0.05 vs NO alone). Seven patients were considered as "NO-responders" (rise in PaO2/FIO2 ratio of 10 mmHg or more with NO); in this subgroup the PaO2/FIO2 ratio rose from 87 +/- 30 to 128 +/- 39 mmHg (p < 0.05) with NO alone, and from 93 +/- 20 to 169 +/- 51 mmHg (p < 0.01) with NO + ALM (p < 0.05 versus NO alone). MPAP decreased from 30 +/- 5 to 26 +/- 5 mmHg (p < 0.01) with NO alone, increased slightly from 28 +/- 5 to 31 +/- 5 mmHg (NS) with ALM alone and decreased to 27 +/- 5 mmHg (p < 0.05) with NO + ALM. CONCLUSIONS: NO + ALM had additive effects on gas exchange while decreasing MPAP in patients with ARDS. The effects of NO alone were small and non significant, except in a subgroup of 7 patients in whom the combination of both therapies had the more pronounced results.

Administration, Inhalation↗
PubMed1994

Purification and characterization of the Ca2+/calmodulin-dependent protein kinase II from chicken forebrain.

CaM kinase II is known to be enriched in mammalian and avian brains. To determine the holoenzymic composition and functional characteristics of this kinase, a new approach for isolation was applied to isolate it from the chicken forebrain. Forebrains of hatched 45-d chicken were dissected, homogenized, and centrifuged. The supernatant was loaded onto a CaM-agarose affinity column and the calmodulin-binding proteins were eluted with EGTA. Selected eluates were loaded onto the antibody-agarose affinity column, which was prepared with monoclonal antibody (MAb) (6G9) to the CaM kinase II alpha subunit. Samples were subjected to SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and either silver-stained or blotted onto a nitrocellulose membrane. The protein composition and the immunoreactivity of the antibody-agarose affinity eluate fractions were analyzed with a densitometric scanner. Silver staining of gels showed that the beta subunit doublet, the beta' subunit, and a putative substrate were coeluted with the alpha subunit from the antibody affinity column although only the alpha subunit bound the 6G9 antibody. Scintillation counting showed that the autophosphorylation of the kinase was significantly reduced in the eluate from the antibody affinity column. Whereas silver staining indicated an increase in the relative amount of alpha subunit had occurred during purification, phosphorylation assays indicated an increase in the relative amount of the alpha subunit after the last purification step. A possible reason for this is discussed. The presence of beta/beta' subunits in the antibody-agarose affinity eluate indicated the existence of an alpha beta/beta' heteropolymer. The phosphorylation assay was not a good indication of the amount of purification because of the loss of enzyme activity following purification. In contrast, the immunoassay indicated a 97-fold purification from the cytosolic fraction was achieved using the method. In conclusion, the data indicate the existence of the CaM kinase II alpha beta/beta' heteropolymer in the chicken forebrain.

Animals↗
PubMed1994

Interference by complex structures of target DNA with specific PCR amplification.

It has been considered that target DNA is a forgiving component for PCR amplification. Herein we present evidence to demonstrate that secondary structure located at the end of a template may interfere with the specificity of amplification. Experiments indicate that nonspecific amplification results from a long stretch of stem and loop structures at the 3' end of prochymosin cDNA. Based on the sequence of mRNA coding for prochymosin, it is argued that the sequence responsible for the formation of the complex structure described here is most likely generated during synthesis of the second cDNA strand.

Base Sequence↗
PubMed1994

[Survey of the quality of sleep during the perioperative period. Study of factors predisposing to insomnia].

In order to assess the quality of sleep in surgical patients the amount of self-rated postoperative insomnia and its predisposing factors, we conducted a three-fold questionnaire * survey in 176 consecutive patients undergoing elective orthopaedic, vascular or abdominal surgery. The first questionnaire was completed the day preceding surgery, the second at the day of discharge and the third two weeks later. This survey concerned the patient's general status, his usual sleep profile and factors which could interfere with sleep (hypnotics, pain, environmental factors) throughout the study period. It allowed quantification of these parameters and the assessment of their time-course. Perioperative insomnia appeared to be a long-lasting phenomenon which persisted after discharge. Factor analysis and multiple regression models showed that postoperative, self-rated insomnia was multifactorial and mainly explained by the amount of postoperative pain (p = 0.035).

Adult↗
PubMed1994

[A study of 3 new ventilators for anesthesia: a series of tests].

We report the bench testing of three new anaesthesia ventilators: Flexima (Datex), SA2/RA2 and Cato (Dräger). The test circuit included a two compartment lung model, a pneumotachograph and a pressure gauge. Volume was integrated from flow signal. The tidal volume delivered by the Flexima and SA2/RA2 ventilators decreased with increasing mechanical work load contrarily to the Cato. Moreover, the tidal volume of the Flexima increased with the fresh gas flow. In spontaneous ventilation inspiratory resistance were low.

Anesthesia, Inhalation↗
PubMed1994

Responses of radiosensitive repair-proficient cell lines to restriction endonucleases.

Radiosensitive mutant mammalian cell lines fall into two categories: (1) those exhibiting a deficiency in the rejoining of dsb, e.g. Chinese hamster xrs and XR1, and murine scid cells; and (2) those exhibiting apparently normal rejoining of bulk dsb, e.g. hamster irs mutants and cells from ataxia-telangiectasia individuals. Cells of both types also show hypersensitivity to restriction endonucleases when applied by cell poration techniques. These data are reviewed, and new data are presented for Pvu II treatment of the radiosensitive dsb repair-proficient Chinese hamster VC4 mutant, which has been reported to have normal cellular and chromosomal sensitivity to restriction endonucleases and neutrons. We find that VC4 is hypersensitive to blunt-ended dsb generated by PvuII. We conclude that the enhanced sensitivity of this and other repair-proficient mutants to radiation and restriction endonucleases results from a dsb processing defect leading to abnormal conversion of dsb into chromosomal aberrations.

Animals↗
PubMed1994

Childhood and adolescent passive smoking and the risk of female lung cancer.

BACKGROUND: Few studies have reported the relationship between passive smoking (PS) in early life and the risk of lung cancer. This study was done to evaluate the risk of female lung cancer from PS, especially that during childhood and adolescence. METHODS: Using household exposure to tobacco smoke as an estimate of PS, a 1:1 paired case-control study was conducted in Harbin, China. We interviewed 114 female primary lung cancer cases, aged 30-69 years, and their hospital-based controls. The controls were non-cancer patients, selected from the same hospital as the cases, and matched on age (+/- 5 years), residential area and smoking status over their lifetime. There were 59 pairs who ever smoked and 55 pairs who never smoked. Information on PS was collected by residence for each of the following periods: 0-6, 7-14, 15-22, 23-30 and 31-69 years. RESULTS: Household PS significantly increases the risk of female lung cancer for those exposed at ages 22 or younger, who have ever smoked. The risk was also increased for those non-smoking pairs when exposed under the age of 15 years. Exposure to maternal smoking at ages 14 or younger increased the risk by about 170% (odds ratio, OR 2.7, 95% confidence interval [CI]: 1.49-4.88), but not to paternal smoking (OR 1.40, 95%CI: 0.92-2.50). The risk was highest for those exposed under the age of seven (OR 3.46, 95%CI: 1.80-6.65) and was also significant at ages 7-14 (OR 3.08, 95% CI: 1.62-5.57) and 15-22 (OR 3.10, 95%CI: 1.52-6.31) years. Under the age of 23 years, the OR increased with amount of PS (P < 0.001). Of note, the OR in all five exposure periods for non-smoking pairs were similar to those for all 114 pairs studied. CONCLUSIONS: Household PS, particularly that during childhood, increases the risk of female lung cancer. The assessment of PS should be done by different periods of exposure.

Adolescent↗
PubMed1994

Measurement of the attenuation coefficient for Livermore Thoracic Phantom lungs fabricated using contemporary materials.

The University of Cincinnati has reproduced the original formulation for the Livermore Thoracic Phantom lungs using contemporary materials and has adopted the linear attenuation coefficient as the primary quality assurance parameter for evaluating the performance capabilities of these new lung phantoms. The Livermore Thoracic Phantom was originally fabricated in 1978 to intercalibrate detector systems used to measure plutonium and other low-energy, photon emitting radionuclides deposited in the respiratory tract. The linear attenuation coefficient is a critical performance indicator for these phantom lungs since the presence of any material with a high effective atomic number (where Z > or = 20) will make a significant change in the photoelectric cross section, the predominant mode of interaction for plutonium x rays. A set of test lungs was fabricated with KCl to introduce a known quantity of 40K in the phantom and to determine, by measurement and calculations, what change would be made to the attenuation coefficient at photon energies below 100 keV as a result of the modified formulation. The KCl increased the linear attenuation coefficient below 60 keV by more than a factor of two, which would produce a substantial systematic error in any subsequent calibration measurements performed with these modified phantom lungs. These results support use of the attenuation coefficient as an important performance indicator for the Livermore Thoracic Phantom lungs and also suggest that KCl not be added to the lung tissue substitute formulation as a means to incorporate 40K in the phantom for low energy calibrations.

Humans↗
PubMed1994

Structural and functional aspects of the multiplicity of Neu differentiation factors.

We used molecular cloning and functional analyses to extend the family of Neu differentiation factors (NDFs) and to explore the biochemical activity of different NDF isoforms. Exhaustive cloning revealed the existence of six distinct fibroblastic pro-NDFs, whose basic transmembrane structure includes an immunoglobulin-like motif and an epidermal growth factor (EGF)-like domain. Structural variation is confined to three domains: the C-terminal portion of the EGF-like domain (isoforms alpha and beta), the adjacent juxtamembrane stretch (isoforms 1 to 4), and the variable-length cytoplasmic domain (isoforms a, b, and c). Only certain combinations of the variable domains exist, and they display partial tissue specificity in their expression: pro-NDF-alpha 2 is the predominant form in mesenchymal cells, whereas pro-NDF-beta 1 is the major neuronal isoform. Only the transmembrane isoforms were glycosylated and secreted as biologically active 44-kDa glycoproteins, implying that the transmembrane domain functions as an internal signal peptide. Extensive glycosylation precedes proteolytic cleavage of pro-NDF but has no effect on receptor binding. By contrast, the EGF-like domain fully retains receptor binding activity when expressed separately, but its beta-type C terminus displays higher affinity than alpha-type NDFs. Likewise, structural heterogeneity of the cytoplasmic tails may determine isoform-specific rate of pro-NDF processing. Taken together, these results suggest that different NDF isoforms are generated by alternative splicing and perform distinct tissue-specific functions.

Amino Acid Sequence↗