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Biomedical subjects

C Liu

Publications and source records attributed to C Liu.

At least 721 records · Page 40Linked to original sources
PubMed1994

[Role of adenosine in weak electro-acupuncture-induced depression of nociceptive response of spinal dorsal horn neurons in rats].

In this study, extracellular recordings were made from wide dynamic range (WDR) neurons in lumbar segments of the spinal cord in rats transsected at the first lumbar segment. The nociceptive discharges of WDR neurons were depressed by weak electro-acupuncture applied to "Yanglingquan"-"Xuanzhong" points. The depression was blocked by i.v. administration of adenosine receptor antagonists, theophylline and caffeine. The observations indicate that depression of the nociceptive response of the WDR neurons induced by weak EA may be mediated by adenosine within the spinal cord.

Adenosine↗
PubMed1994

[Cloning and expression of beta-glucosidase gene in Xanthomonas campestris XA5-5].

A beta-glucosidase gene from Xanthomonas campestris XA5-5 was cloned in Escherichia coli with the broad-host-range plasmid pRK404. The beta-glucosidase encoding plasmid designated pLZS1 contained a 1.1kb PstI DNA fragment deriving from XA5-5. The plasmid pLZS1 was transconjugated by filter mating into XA5-5 producing homologous clones XA5-5(pLZS1). Plasmid stability analysis revealed that pLZS1 was more stable in XA5-5 than in E. coli JM83. The level of beta-glucosidase expressed in XA5-5 (pLZS1) was much higher than in E. coli JM83 (pLZS1) using salicin as the substrate. From the results obtained, it seems that the gene product of this cloned DNA fragment has higher affinity to salicin substrate, and in some sense reduces the affinity between the enzyme and pNPG substrate in XA5-5.

Cloning, Molecular↗
PubMed1994

Cloning of polygalacturonase (PG) cDNA and inhibition effects of its antisense RNA on the expression of PG gene in transgenic tomato plants.

We have amplified a 1.5-kb PG cDNA including its complete open reading frame, using two primers specific to PG gene and PCR technique. Its fidelity and correctness were confirmed by restriction mapping and partial DNA sequencing. The PG gene was then inserted into a binary vector, pBin437, in an inverted orientation between the 35S promoter with duplicated enhancers and the Nos3' transcriptional termination sequence, and the resulting plasmid pBPG was introduced into LBA 4404. The A. tumefaciens harboring pBPG was used to transform tomato plants. Sixty kanamycin-resistant transformants were selected. PCR detection showed two-third of the transformed plants tested (30 plants) contain the exogenous PG gene. The PG activity assay and SDS-PAGE analysis of proteins from ripening fruit cell wall showed that the PG activity in transgenic tomato plants were inhibited in different extent. One of them, plant 3, gave only 7% PG activity compared with the control (100%). These results suggest that the expression of the anti-PG gene has effectively inhibited the expression of endogenous PG gene. The effect of low-level PG activity on tomato fruit ripening and storage is being investigated.

Base Sequence↗
PubMed1994

[The causes of necrosis of arteriovenous flap and its modification].

Arteriovenous flaps have been developed for more than ten years, however the cause of necrosis of the flap remains obscure. We observed the changes in the microcirculation of the flap, and it was revealed that most of capillaries were occluded in the early arterialized stage, and the capillary patency was only 10%-20%. The latter was increased to 80%-90% three days later. All these changes were due to the damage of endothelial cells by arterial blood, because of high pressure and oxygen tension, resulting if cell swelling, fissuring, exfoliation and finally thrombosis. As a consequence, the effective microcirculation volume became decreased. As venous endothelial cells required time to adapt arterial blood, and expansion of skin could increase tissue capillaries in number, the arteriovenous flap was modified by skin expansion before arterialization. This method improved the survival rate remarkably.

Animals↗
PubMed1994

[A 5-year retrospective investigation of occupation-related burns in Zhenjiang area].

UNLABELLED: During the 5 years from June 1986 to June 1991, 221 patients were admitted to our department of burn surgery because of occupation-related burns. The average age was 31.2 years, and 83.4 per cent was male. Most of the patients (79.6 per cent) were referred to our hospital within 24 h of their injury. The most common etiology was flame (33.0 per cent). The mean body surface area of all 221 cases was 17.1 per cent, with a mean full-thickness component of 8.1 per cent. COMPLICATIONS: inhalation injury 18 cases (8.1 per cent); sepsis 5 cases (2.3 per cent) confirmed by positive blood cultures at an average time of 10.2 days postburn, and the commonest organism was pseudomonas aeruginosa; pneumonia 5 cases (2.3 per cent). The mortality of these 221 cases was 1.8 per cent. The average time of stay in our hospital was 34.3 days. The total expenditure was about 740,000 Yuan. First aid on the spot and early correct treatment are stressed. It is essential to put prevention first, and the measures to lower the incidence of occupation-related burns were discussed to serve as a reference for labor protection department and occupation-related burns institute.

Accidents, Occupational↗
PubMed1994

[Involvement of purines in analgesia produced by weak electro-acupuncture].

In the present investigation the intensity of stimulated electro-acupuncture (EA) was measured by electrophysiological collision technique. In the behavioral experiments, by applying the weak electro-acupuncture pulses (50 Hz, 1-1.5mA), not enough to activated A delta afferent fibers, to Yanglingquan and Xuanzhong points, the latency of nociceptive hind limb withdrawal reflex, but not tail-flick latency was prolonged. Administered intraperitoneally, both theophylline and caffeine, P1-purinergic (adenosine) receptor antagonists, could block the electroacupuncture-induced elevation of the nociceptive thresholds in a dose-effect related manner, whereas dipyridamole, an inhibitor of adenosine release, could shorten the after of electro-acupuncture in a dose dependent way. These results suggest that weak electro-acupuncture may induce analgesia and purines appear to be involved in this process.

Acupuncture Analgesia↗
PubMed1994

[Ribosomal DNA fingerprinting analysis of Enterobacter cloacae isolated from an outbreak of nosocomial infection].

16s and 23s ribosomal DNA (rDNA) genes were amplified form E. coli, labelled with [alpha- 32P] dATP by nick translation, and applied as conserved gene probes to detecting broad-spectrum rDNA. rDNA fingerprinting analysis of Enterobacter cloacae (E. cloacae) isolated form an outbreak of nosocomial infection and other hospital environmental sources was conducted with digestion by different restrictive endonuclease, such as Hind III, EcoRI, BamHI, Bgl I, et al. Results showed rDNA fingerprinting of E. cloacae strains isolated from 10 patients with nosocomial infection was the same as that from other sources. It suggested E. cloacae causing this outbreak was originated from one genetic clone, and its source of infection was the tubes and humidifying bottles for oxygenation. rDNA fingerprinting technique is accurate, reliable, specific and repeatable, and will plays important roles in identification and classification of bacteria, tracking the source of transmission of nosocomial infection.

Cross Infection↗
PubMed1994

Inhibition of reperfusion injury by human thioredoxin (adult T-cell leukemia-derived factor) in canine lung transplantation.

Human thioredoxin, which was previously recognized as adult T-cell leukemia-derived factor, has many physiologic activities, one of which is a radical scavenger effect. Its ability to reduce reperfusion injury was assessed in vivo in a canine lung transplantation model. In 19 dogs, left lung allotransplantation was performed after 100 minutes of warm ischemia. The function of the transplanted lung was assessed after clamping of the contralateral pulmonary artery. In the human thioredoxin group (n = 6), human thioredoxin 30 mg/kg was given to the recipients during reperfusion. In the N-acetylcysteine group (n = 5), N-acetylcysteine 150 mg/kg, known as a radical scavenger, was given in the same manner. In both groups, arterial oxygen tension was significantly higher than in the control group (n = 8). In the human thioredoxin group, peak inspiratory pressure was significantly lower than in the control group. Macroscopic and microscopic examinations showed an almost normal appearance of the lung tissues in the human thioredoxin and N-acetylcysteine groups, in contrast to the abnormal findings in the control group. Thus it would appear that human thioredoxin has a protective effect on transplanted lungs, as does N-acetylcysteine, and that its action may be a radical scavenger effect.

Animals↗
PubMed1994

[Observation on the action of extractum semen Persicae on anti-fibrosis of liver].

It was observed that Extractum Semen Persicae acted obviously on hepatic fibrosis induced by CCl4. Through promoting the degradation of collagens type I, II, IV, VI and fibronectin, ESP has proved helpful in markedly reducing the fibrous septa composed of both collagenous and reticular fibers as well as in repairing the structure of hepatic tissues.

Amygdalin↗
PubMed1994

Effects of newly developed solutions containing trehalose on twenty-hour canine lung preservation.

Trehalose is a nonreducing disaccharide that stabilizes the cell membrane under various stressful conditions. A previous study demonstrated that trehalose was effective in 12-hour canine lung preservation. We have developed new preservation solutions containing trehalose: an extracellular type ET-Kyoto solution (Na 100 mmol/L, K 44 mmol/L) and an intracellular type IT-Kyoto solution (Na 20 mmol/L, K 130 mmol/L). The composition of these solutions is identical except for the electrolyte content. We examined their efficacy in 20-hour lung preservation. Canine lungs were flushed with ET-Kyoto (group A, n = 6), with IT-Kyoto and prostaglandin E1 (25 micrograms/kg) (group B, n = 6), or with Euro-Collins solution and prostaglandin E1 (25 micrograms/kg) (group C, n = 7), and stored for 20 hours at 4 degrees C. Left lung transplantation was performed and evaluated for up to 130 minutes. The flush time was similar in the three groups. Arterial oxygen tensions (inspired oxygen fraction = 0.5) in group A were uniformly excellent (303.3 +/- 7.0 mm Hg 70 minutes after reperfusion and 303.0 +/- 19.6 mm Hg 130 minutes after reperfusion) and significantly higher than in group B (202.6 +/- 32.0 mm Hg, p < 0.05, and 197.8 +/- 44.0 mm Hg, p = 0.054, respectively) or group C (185.9 +/- 23.0 mm Hg, p < 0.01, and 155.7 +/- 36.3 mm Hg, p < 0.05, respectively). Peak inspiratory pressure in group A was significantly lower than in groups B and C (p < 0.05). Wet/dry weight ratio in group A was significantly lower than in groups B (p < 0.05) and C (p < 0.01). Histologic and scanning electron microscopic examinations showed better preservation in group A than in groups B and C. We conclude that ET-Kyoto is superior to IT-Kyoto and to Euro-Collins solution for 20-hour lung preservation.

Animals↗
PubMed1994

[Enlarged and prolongated cochlear microphonics and its clinical significance].

Bilateral cochlear microphonics (CM) were evoked by tone burst simultaneously. A speaker was put in head-foot axis 2m from the mid-point of a given line connecting the bilateral external meatus. Seven normal persons and 106 cases of unilateral sensory hearing loss and recruitment were examined. When recruitment was present, CM at corresponding frequencies were enlarged and prolongated. In 62 cases CM delayed slowly, while other 27 cases quickly. In addition to 2 cases of bilateral Ménière disease with sensory hearing loss and recruitment, CM were enlarged and prolongated at some frequencies in left ears and at other frequencies in right ears in accordance with predominant recruitment. Meanwhile CM of the opposite normal ear decreased obviously. CM could not be evoked from profound and totally deaf ears.

Acoustic Stimulation↗
PubMed1994

Nerve growth factor increases nicotinic ACh receptor gene expression and current density in wild-type and protein kinase A-deficient PC12 cells.

Although neuronal nicotinic ACh receptors (nAChR) play a key role in synaptic transmission and information transfer in the nervous system, little is known about the molecular mechanisms that govern the expression of the multiple subunits that form the receptors and determine their functional properties. Using electrophysiological and molecular biological approaches, we have investigated the NGF-mediated regulation of nAChR expression in rat pheochromocytoma (PC12) cells and protein kinase A (PKA)-deficient PC12 cells. We report that NGF treatment increases steady state levels of mRNA encoding the alpha 3, alpha 5, alpha 7, beta 2, and beta 4 subunits, increases the occurrence of ACh-induced single-channel activity in excised patches, and increases ACh-induced macroscopic current density, all by mechanisms independent of PKA activity.

Animals↗
PubMed1994

Characterization of the antiviral effects of 2' carbodeoxyguanosine in ducks chronically infected with duck hepatitis B virus.

This study was carried out to evaluate benefits and limitations of long-term therapy of hepatitis B virus infections with a nucleoside analog inhibitor of virus replication. The model we used was the domestic duck chronically infected with duck hepatitis B virus by in ovo infection. 2' Carbodeoxyguanosine was used as an inhibitor of viral DNA synthesis. In all animals examined there was a reduction in virus production during therapy. A dose of 2' carbodeoxyguanosine of 10 micrograms/kg every other day reduced the number of infected hepatocytes from greater than 95% to 25% to 50% in less than 3 mo, whereas a 10-fold higher dose produced a decline to less than 10%. Histological evaluation revealed mild to moderate liver injury in ducks receiving the higher dose of 2' carbodeoxyguanosine, suggesting that disappearance of infected hepatocytes may have been accelerated by a toxic effect of the drug. Drug treatment did not completely eliminate duck hepatitis B virus from any duck, and replication was restored in all hepatocytes within a few weeks to several months after antiviral therapy was terminated. Our results suggest that elimination of a chronic infection with a single inhibitor of replication may be difficult in a host that lacks an antiviral immune response capable of eliminating at least a portion of the infected hepatocytes and of ultimately producing antibodies capable of neutralizing residual virus.

Animals↗
PubMed1993

Myo-inositol 1,3,4,5-tetrakisphosphate can independently mobilise intracellular calcium, via the inositol 1,4,5-trisphosphate receptor: studies with myo-inositol 1,4,5-trisphosphate-3-phosphorothioate and myo-inositol hexakisphosphate.

Myo-inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] acts as a full agonist for Ca2+ release in saponin-permeabilised SH-SY5Y neuroblastoma cells. Studies were conducted in the presence of myo-inositol hexakisphosphate (InsP6, 10 microM), to inhibit the Ins(1,3,4,5)P(4)-3-phosphatase catalysed back conversion of Ins(1,3,4,5)P4 to Ins(1,4,5)P3. HPLC analysis confirmed that Ins(1,3,4,5)P4 releases the entire content of Ins(1,4,5)P3-sensitive intracellular Ca2+ stores, independent of 3-phosphatase activity. Further we utilised racemic myo-inositol 1,4,5-trisphosphate-3-phosphorothioate [DL-Ins(1,3,4,5)P(4)-3S], a novel intrinsically Ins(1,3,4,5)P(4)-3-phosphatase resistant Ins(1,3,4,5)P4 analogue. DL-Ins(1,3,4,5)P(4)-3S specifically displaced [3H]Ins(1,4,5)P3 from bovine adrenal cortex Ins(1,4,5)P3 binding sites (IC50 = 889 nM, compared to Ins(1,4,5)P3, IC50 = 4.4 nM and Ins(1,3,4,5)P4, IC50 = 152 nM). DL-Ins(1,3,4,5)P(4)-3S was a full agonist for Ca2+ release (EC50 = 4.7 microM), being 90- and 2-fold less potent than Ins(1,4,5)P3 and Ins(1,3,4,5)P4 (with InsP6), respectively. DL-Ins(1,3,4,5)P(4)-3S will be an important tool for identification of potentially exclusive Ins(1,3,4,5)P4 second messenger functions, since its resistance to 3-phosphatase action precludes the inconvenient artefact of steady state Ins(1,4,5)P3 generation.

Animals↗
PubMed1993

Site-directed alanine mutagenesis of Phe33, Arg35, and Arg42-Ser43-Lys44 in the human gonadotropin alpha-subunit.

Residues Phe33 and Arg35, individually, and a composite mutation of residues Arg42, Ser43, and Lys44 were changed to alanine in the human glycoprotein hormone common alpha-subunit using site-directed mutagenesis. These specific residues are highly conserved across species and have by chemical modification and synthetic peptide approaches been implicated in the binding of human chorionic gonadotropin (hCG) to leutinizing hormone (LH) receptor. In the present study we tested the hypothesis that specific alpha-subunit amino acid residues which stabilize the hormone receptor interaction for hCG have the same function in human follicle-stimulating hormone (hFSH). Wild type or mutant alpha-subunit cDNAs were coexpressed with wild type hFSH or hCG beta cDNA in sialylation defective Chinese hamster ovary cells. Recombinant hormones were tested in a radioligand receptor competition assay, using rat testis membranes as a source of FSH and LH receptors. Mutant hFSH heterodimers F33A-FSH, R35A-FSH, Arg42-Ser43-Lys44/Ala42-Ala43-Ala44- FSH all displaced 125I-hFSH in a similar fashion, indicating that these residues are not important for binding of hFSH to the rat FSH receptor. On the other hand, F33A-CG evidenced a 5-fold decrease in binding, while R35A-CG had over a 100-fold decrease in binding to the rat LH receptor when compared to the wild type recombinant hCG. These data demonstrate that a receptor-binding site on the common alpha-subunit which is very important for hCG binding to LH receptor is not important for the binding of hFSH to FSH receptor. Our interpretation of these findings is that there are fundamental structural differences in the receptor interface contacts of the common alpha-subunit, which stabilize receptor binding among members of the glycoprotein hormone family.

Amino Acid Sequence↗