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Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 847 records · Page 47Linked to original sources
PubMed1990

Repair of calvarial nonunions by osteogenin, a bone-inductive protein.

Efforts were taken to determine the dose of bovine osteogenin (OG) that would induce more bone than that induced by 20 mg of rat particulate demineralized bone matrix (DBM), the amount allowed by the confines of an 8-mm rat craniotomy defect. Dose-response studies were performed for demineralized bone matrix alone and osteogenin, partially purified from bovine demineralized bone matrix, plus rat insoluble collagenous bone matrix (M). Demineralized bone matrix alone (2.5, 5.0, 10, 20, or 40 mg) or osteogenin (0.0625, 0.125, 0.250, 0.50, or 1.0 mg) plus 25 mg insoluble collagenous bone matrix was implanted into the pectoralis muscle for 3, 5, and 7 weeks. Both materials induced time- and dose-dependent formation of bone. The three highest dosages of osteogenin (plus insoluble collagenous bone matrix) induced more bone than 20 mg demineralized bone matrix and seemed to accelerate bone repair. However, when implanted into the 8-mm rat craniotomy defect for 4 weeks, 20 mg demineralized bone matrix and 0.5 mg osteogenin (plus insoluble collagenous bone matrix) induced comparable amounts of bone. These results suggest different mechanisms for bone formation in heterotopic and orthotopic sites.

Animals↗
PubMed1990

[Effects of promethazine on acupuncture analgesia].

Promethazine, one of histaminergic H1-receptor antagonist, was often used as an adjuvant drug prior to and during acupuncture anesthesia in clinics, However, its effects was not known clearly. By using potassium iontophoretic dolorimetry and stimulating unilateral "Hegu" and "Waiguan" points with electroacupuncture (EA) in 42 rabbits, we found that Promethazine could drop the pain threshold in small dosages (0.5 mg/kg, 1 mg/kg) and raise the pain threshold in relatively large dosages (2 mg/kg, 4 mg/kg). In different dosages (1 mg/kg, 2 mg/kg), promethazine could attenuate the analgesic effect of EA. It was suggested that promethazine should be used carefully in acupuncture anaesthesia.

Acupuncture Analgesia↗
PubMed1990

[Use of fluorescence polarization immunoassay and microbiological assay in the study of gentamicin pharmacokinetics in man and a comparison of the results].

Ninety serum samples of gentamicin were determined by fluorescence polarization immunoassay (FPIA) and microbiological assay (MA) and the results were compared. Liner regression analysis showed that the two methods were highly correlated with a correlation coefficient of 0.98. The mean concentration of gentamicin as determined by MA method was significantly higher than that by FPIA method. Serum concentration-time data derived from 5 patients were fitted to a one-compartment model. No significant differences in the pharmacokinetic parameters and estimated dosages were observed. The FPIA method was shown to be as correct and reliable as the MA method in estimating gentamicin pharmacokinetic parameters.

Abdomen↗
PubMed1990

[A new serotype of Shigella boydii].

Two strains which belong to the same serotype of Shigella were isolated from the bloody-pus stool of two patients (in 1986) and is reported in this paper. The results were identical both showing agglutination in low titer with serotype 8 of S. dysenteriae and serotype 4 of S. boydii when the two strains were checked well with all kinds of diagnostic antisera and vice versa, ie the antisera produced by the two strains were also checked well with sera prepared with the representative strains of all Shigella spp. No cross agglutination with O6, O7, and O150 of E. coli were found. Consequently, It appears to be a new serotype of Shigella. These two strains possess the ability of causing keratitis in guinea-pigs as well as invading epithelial cells, the DNA of both strains in agarose-electrophoresis showed a large plasmid, indicating that they are virulent strains possessing invasive ability. It was concluded that these two strains belonged to Shigella boydii as they fermented mannitol and non-related antigenically with Shigella flexneri. Since serotype 1-18 of S. boydii have been reported recently, we propose that this new serotype should be serotype 19 of Shigella boydii.

Animals↗
PubMed1990

[Determination of soluble mercury contents in Chinese traditional patent medicines for children].

Soluble mercury contents in Baochi San, Xiaoer Zhibon Ding and Xiaoer Baishou Dan have been determined using dithizone method. This method has the advantages of short digestion time, clear digestion end point, simple operation and reproducible results. The recovery rate ranges from 98.4 to 103%. The data obtained can be used as a reference for controlling soluble mercury contents in Chinese traditional patent medicines containing cinnabar.

Drug Combinations↗
PubMed1990

[Experimental study on anti-acute leukemia with Chinese traditional drugs].

This paper deals with the experimental study on L7212 leukemic model of mice with Chinese medicine Liushenwan, Zhijinding and Xihuangwan for the treatment. This study proved that these drugs possessed the effect of inhibiting and killing L7212 leukemic cells of the experimental leukemic mice (P less than 0.05-0.001). They affected the S stage of the cell multiplication cycle time mainly (P less than 0.01). They could relieve the infiltration of leukemic cells in the liver and spleen of L7212 mice (P less than 0.001) and obviously prolong the survival time of the mice (P less than 0.01-0.001).

Animals↗
PubMed1990

[Oral cyclosporine pharmacokinetics in renal transplantation patients].

Cyclosporine was extracted from whole blood and analyzed by HPLC. The pharmacokinetics of oral cyclosporine were studied in patients with renal transplant. They were 5 women and 3 men between the ages of 29-49 years. Cyclosporine was used for 47 days to 11 months after renal transplantation. The mean dose was 8.26 +/- 1.41 mg/kg.d (5.88-10.0 mg/kg.d), once each 12 hours. Three hundreds whole blood samples were monitored. The peak concentration (Cmax) was 664.9 +/- 87.5 ng/ml; peak time was 3.27 +/- 1.07 h; slow elimination phase t1/2 beta was 13.53 (6.13-43.3) h.

Administration, Oral↗
PubMed1989

Biological activity of hydroxylated chloroethylnitrosoureas.

1-Nitroso-1-(2-hydroxyethyl)-3-(2-chloroethyl)urea (Compound I) and 1-nitroso-1-(2-hydroxypropyl)-3-(2-chloroethyl)urea (Compound II) display significantly reduced antitumor activity compared to the corresponding isomeric derivatives 1-nitroso-1-(2-chloroethyl)-3-(2-hydroxyethyl) urea (Compound III) and 1-nitroso-1-(2-chloroethyl)-3-(2-hydroxypropyl) urea (Compound IV). Their low therapeutic activity is paralleled by low toxicity while mutagenicity and carcinogenicity are high. A comparative investigation of the genotoxicity of Compounds I and III using primary cultures of fetal hamster lung cells revealed an about 14-fold higher rate of DNA single-strand breaks following exposure (100 microM, 1 h) to Compound I as compared to Compound III. The rate of DNA interstrand cross-links, on the other hand, was 11-fold higher following Compound III as compared to Compound I. The results underline that the therapeutic activity of chloroethylnitrosoureas is mainly attributable to their cross-linking potential while induction of DNA single-strand breaks plays a decisive role for mutagenicity and carcinogenicity but appears not to be relevant for antineoplastic effectiveness.

Animals↗
PubMed1989

Effects of cigarette smoking on hemodynamics and hypoxic pulmonary vasoconstriction: role of prostaglandins and leukotrienes.

This study investigated the role of prostaglandins (PGs) and leukotrieres (LTs) in hypoxic pulmonary vasoconstriction (HPV) and in cigarette smoking-induced changes in hemodynamics and HPV in Wistar rats. Selective LTD4-LTE4 receptor antagonist LY-171883 (LY) inhibited HPV by 71.8%, while cyclooxygenase inhibitor indomethacin (IND) augmented HPV. The results indicate that LTs mediate HPV in Wistar rats. Smoking increased the level of TXB2 over control by 143.6% in plasma and 69.2% in lung tissue, concomitantly, pulmonary and systemic vascular resistance (PVR and SVR) were increased by 38.7% and 46.7%, respectively. Both LY and IND prevented the smoking-induced increase of PVR and SVR. After smoking HPV increased twofold. The increase of HPV was abolished by LY, but not by IND. Our results suggest that smoking leads to pulmonary and systemic vasoconstriction partly mediated by TXA2 and LTs; smoking also leads to an augmentation of HPV, and LTs play an important role in it.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Synthesis of functional bovine leukemia virus (BLV) p34tax protein by recombinant baculoviruses.

The bovine leukemia virus (BLV) p34tax (also called tat, p34, XLOR gene product) is a 34-kDa polypeptide encoded in the 3'-terminal region of the virus. This protein is responsible for positive transcriptional trans-activation of promoter elements located within the BLV long-terminal repeat. We introduced the protein-coding region of BLV p34tax into the genome of the baculovirus Autographa californica nuclear polyhedrosis virus. After infection of the insect Spodoptera frugiperda (SF9) cell line, this recombinant strain of baculovirus produced approximately 100 to 150 mg of p34tax per 2 X 10(9) cells. This protein, when introduced into mammalian fibroblasts by using a cell-to-cell fusion technique, functionally trans-activated the BLV long-terminal repeat. Analysis of 32P-labeled proteins of SF9 cells expressing BLV tax by two-dimensional gel electrophoresis indicated that the BLV p34tax was phosphorylated.

Animals↗
PubMed1989

Structural and functional characterization of mutants of the bovine leukemia virus transactivator protein p34.

Mutants of the bovine leukemia virus (BLV) transactivator protein (tat, tax, p34, the XLOR gene product) were constructed by site-directed deletions, in-phase linker insertions, or fragment replacements (swapping) among BLV variants. The mutant constructs were transfected into cos cells and transiently expressed. Western blot analysis using a mixture of monoclonal antibodies to wild-type p34 revealed the presence of mutated XLOR gene products in all the mutants tested. The transactivating activity of 11 tax mutants containing site-directed deletions and in-phase linker insertions was completely abolished. Only the swapping mutant tested, a hybrid between two BLV variants, transactivated LTR-directed gene expression at wild-type levels. These data illustrate the narrow range of structural variations that allow full activity of the BLV tax product and suggest that the present molecular structure of the transactivator protein results from heavy evolutionary constraints.

Blotting, Western↗
PubMed1989

Determination of intracellular reduced glutathione and glutathione related enzyme activities in cisplatin-sensitive and resistant experimental ovarian carcinoma cell lines.

The level of GSH in ovarian carcinoma cells which were sensitive and resistant to cisplatin was serially determined following tumor removal from the animals, in addition, activities of GSH-reductase and GSH-S-transferase were assessed. The GSH level in the resistant line (O-342/DDP) was almost twice as high as that in its sensitive counterpart (O-342), when determined immediately following removal of the tumor (1.55 +/- 0.47 vs. 0.81 +/- 0.32 nmol/10(6) cells). Culturing the cells resulted in a decrease of GSH levels in both cell lines during the first 4 h. Thereafter, GSH levels in both cell lines increased up to 24 h. At this time the GSH level was higher in O-342 than in O-342/DDP. GSH-reductase activity in O-342/DDP cells was significantly higher than in O-342 cells when the enzyme was determined immediately after tumor removal; at the same time there was no difference in activity of GSH-S-transferase between two cell lines. After 24 h in culture, no significant difference between O-342 and O-342/DDP cells could be observed in the activity of the two enzymes.

Animals↗
PubMed1989

Superconducting properties of copper oxide high-temperature superconductors.

The equations for the magnon pairing theory of high-temperature copper-oxide-based superconductors are solved and used to calculate several properties, leading to results for specific heat and critical magnetic fields consistent with experimental results. In addition, the theory suggests an explanation of why there are two sets of transition temperatures (T(c) approximately 90 K and T(c) approximately 55 K) for the Y(1)Ba(2)Cu(3)O(6+x) class of superconductors. It also provides an explanation of why La(2-x)Sr(x)CuO(4) is a superconductor for only a small range of x (and suggests an experiment to independently test the theory). These results provide support for the magnon pairing theory of high-temperature superconductors. On the basis of the theory, some suggestions are made for improving these materials.

Journal Article↗
PubMed1989

Long-term effects of progestin and RU 486 on prolactin production and synthesis in human endometrial stromal cells.

Previous studies have shown that the production of prolactin (PRL) is increased in human endometrial stromal cells cultured with medroxyprogesterone acetate (MPA) for 3-5 days. In the present study, we have investigated the effect of prolonged treatment of progestin and anti-progestin, RU 486, on the production and synthesis of PRL. Stromal cells were isolated from human endometrium obtained from non-pregnant women and cultured for 20-30 days in medium RPMI 1640 with 2% fetal calf serum or supplemented with MPA, RU 486, alone or in sequence. The PRL content in medium was measured by radioimmunoassay. The production rate was estimated from the PRL content in medium accumulated in 24 h. The PRL production rate was progressively increased in stromal cells continuously treated with MPA for 30 days (greater than 100-fold over the control value, i.e. 0-0.01 microgram/0.1 mg cell DNA/day). RU 486 alone had no effect on the production of PRL. However, the production of PRL was increased by MPA in stromal cells pretreated with RU 486 indicating that the effect of RU 486 is reversible. When stromal cells were treated with MPA and RU 486 sequentially, RU 486 stimulated the PRL production (approximately 2-fold over the MPA-treated cells) for 2-3 days and then reduced to basal levels over a 5-day period. The stimulatory and inhibitory effects of RU 486 on PRL production in stromal cells pretreated with progestin was also observed in the rate of synthesis of PRL estimated by incubating the stromal cells with [35S]methionine and immuno-isolating the [35S]PRL with anti-PRL.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Endothelium-dependent relaxation and hyperpolarization of canine coronary artery smooth muscles in relation to the electrogenic Na-K pump.

1 In the smooth muscle cells of canine coronary artery, acetylcholine (ACh) produced a transient, endothelium-dependent hyperpolarization of the membrane. A similar hyperpolarization was also elicited by exposure to Krebs solution after incubation of the artery in K-free solution for 30 min. 2 A hyperpolarization of reproducible amplitude was generated when ACh was applied at intervals greater than 30 min. Repetitive application of ACh at 15 min intervals caused a successive reduction in the amplitude of hyperpolarization. 3 The reduction in the amplitude of relaxation during five successive applications of ACh at 15 min intervals was less than 10% of the first relaxation. 4 The ACh-induced hyperpolarization was blocked by atropine but not by ouabain, whereas the K-free induced hyperpolarization was blocked by ouabain. In low Na (Li-substituted) solution, ACh still induced a hyperpolarization but the K-free induced hyperpolarization was absent. 5 In coronary artery precontracted by high-K solution, ACh produced an endothelium-dependent relaxation, without membrane hyperpolarization. The associated relaxation was resistant to ouabain but sensitive to atropine. 6 It is concluded that in the canine coronary artery, the electrogenic Na-K pump does not contribute to the endothelium-dependent hyperpolarization or relaxation. The results are consistent with the release of two different inhibitory factors from the vascular endothelium.

Acetylcholine↗
PubMed1989

Some electrical properties of the endothelium-dependent hyperpolarization recorded from rat arterial smooth muscle cells.

1. Electrical responses produced by acetylcholine (ACh) and histamine were recorded from smooth muscle cells of the intralobular small pulmonary artery (SPA), main pulmonary artery (MPA) and thoracic aorta of rats. 2. In MPA and SPA, ACh and histamine produced a transient hyperpolarization of the membrane, and the potential decayed exponentially with a time constant of 2-3 min. In aorta, ACh produced a sustained and histamine produced a transient hyperpolarization. 3. The ACh- and histamine-induced hyperpolarizations were blocked by atropine and mepyramine, respectively, or by removing the endothelial cells. 4. The amplitude of the hyperpolarization was increased in low [K+]o solutions and decreased in high [K+]o solutions. The ionic conductance of the membrane was increased during the hyperpolarization, suggesting an involvement of the increased potassium conductance. 5. A reproducible amplitude of hyperpolarization was generated when ACh or histamine was applied at intervals of over 10 or 30 min, respectively. 6. In aorta, after the transient hyperpolarization had ceased during continued application of histamine, ACh again produced a hyperpolarization, i.e. the transient nature of the hyperpolarization was not due to desensitization of the receptor upon which the hyperpolarizing substance acted, assuming histamine and ACh release the same hyperpolarizing substance. 7. ACh and histamine relaxed the tissues from SPA, MPA and aorta during the noradrenaline (NA)- or high [K+]o solution-induced contraction, in a concentration-dependent manner, only when the endothelial cells were intact. Both ACh and histamine were potent relaxants in MPA and aorta, but showed weak relaxing actions in SPA. 8. In aorta, ACh and histamine produced a sustained relaxation for up to 10 min, and Methylene Blue diminished and altered it to a transient relaxation (for histamine) or an initial large, followed by a small sustained (for ACh), relaxation. 9. In the presence of NA and NA plus Methylene Blue, ACh and histamine also produced a hyperpolarization similar to that seen in the control. 10. It is concluded that in arteries of the rat, ACh and histamine release a hyperpolarizing substance from the endothelial cells. This substance may be different from the endothelium-derived relaxing factor (EDRF), and is released mainly transiently. The hyperpolarization is generated by an increase in potassium conductance of the membrane, and this has some contribution to the endothelium-dependent relaxation.

Acetylcholine↗