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Biomedical subjects

R Li

Publications and source records attributed to R Li.

At least 271 records · Page 15Linked to original sources
PubMed1999

[Use of color Doppler esophageal ultrasonography for assessing hemodynamics of the lower esophageal veins before and after endoscopic esophageal variceal ligation].

Using color Doppler esophageal ultrasonography(CDEUS) with water balloon, we examined the lower esophageal veins of 24 patients with portal hypertension and esophageal varices. The results showed that CDEUS with water balloon could clearly display the lower esophageal veins and could effectively evaluate the changes of hemodynamics of the lower esophageal veins before and after endoscopic esophageal variceal ligation. The maximum blood velocity of peri-esophageal vein in the active bleeding group was higher than that in the non-active bleeding group.

Endoscopy, Digestive System↗
PubMed1999

[Chemical constituents of Saururus chinensis (Lour.) Bail].

OBJECTIVE: To search for the active chemical constituents of Saururus chinensis. METHOD: 95% ethanol extracts from the aerial part of Saururus chinensis was mixed with silica gel, and then eluted with petroleum ether, ethyl acetate and methanol. On the basis of physicochemical properties and spectroscopic analysis, structures of the compounds obtained were identified. RESULTS: Eight compounds were isolated from the ethyl acetate and methanol parts, and identified as aristolactam A II(I), daucosterol(II), hyperoside(III), isoquercitrin(IV), quercitrin(V), quercitin-3-O-beta-D-glucopyranosyl(1-->4)-alpha-L-rhamnopyranoside(VI), ellagic acid(VII) and corilagin(VIII) respectively. CONCLUSION: Compounds I, II, VI, VII and VIII were found from this plant for the first time.

Ellagic Acid↗
PubMed1999

[Effects of reperfusion on neuronal changes and macrophagic response after transient focal ischemia--reperfusion of brain in rats].

Male SD rats(n = 29) were subjected to 2 hours' middle cerebral artery occlusion and were killed at various times of reperfusion (0.5-48 hours). The histological features of neuronal changes, the macrophagic response and the relationship between them were investigated. The neurons underwent acute changes(shrinking or swollen), and the pyknotic apoptotic neurons were occasionally seen within 3 hours. The number of apoptotic neurons increased with recirculation time. The scattered red neurons and ghost cells were first found at 6 hours of reperfusion. Many apoptotic neurons, apoptotic bodies were detected in the penumbra of ischemic core at 48 hours. Lectin histochemistry with GSI-B4 was performed to observe the macrophage. The results showed the active microglia and macrophage from meninges presented at 12 hours. The macrophages from parenchyma vessels appeared at 24 hours. Reactive microglia and extrinsic macrophage aggregated into the band of macrophage which phagocytized the apoptotic neurons. The results indicate that, firstly, it is important to prevent the neuronal apoptosis and reduce the volume of infarct in stroke patients; secondly, irreversible neuronal lesions simultaneously stimulate microglial activation and the presence of extrinsic macrophages from meninges was earlier than the appearance of the macrophages from parenchyma blood-monocytes. The authors also suggest that the data on the neuronal changes over time after ischemia and reperfusion be useful reference materials for selecting the most timely medication to treat cerebral infarction.

Animals↗
PubMed1999

[Effect of transforming growth factor-beta on proliferation cycle of epiphyseal chondrocyte].

In order to investigate the effect of transforming growth factor-beta (TGF-beta) on chondrocyte proliferation cycle, we used flow-cytometry to assess the epiphyseal chondrocyte of embryonic chick femora which was cultured in free-serum media and treated with TGF-beta. The results showed that after treated with TGF-beta for 24 h, the proliferation indexes(PIs) of experimental groups(0.11 ng, 0.33 ng, 1.00 ng/ml) were lower than the PIs of the control groups, but the PI of 3.00 ng/ml group was higher than that of the control group (P < 0.001). After treated for 48 h, except the 0.11 ng/ml group, the PIs of experimental groups were lower than those of the control (P < 0.001). And after treated for 96 h, the PIs of all groups were higher than those of the control; the PI of the 0.33 ng/ml group was the highest (P < 0.001). These suggest that after treated in varied time and dosage, the effect of TGF-beta on epiphyseal chondrocyte is obvious, and TGF-beta on epiphyseal chondrocyte is obvious, and TGF-beta can inhibit chondrocyte proliferation first, and then its effect on chondrocyte can transform from inhibition into proliferation.

Animals↗
PubMed1999

[The basic model and its peculiarity of relaxation theory in chromatography].

According to the basic idea of relaxation theory in chemical dynamics and the moving character of the sample molecules in a chromatographic column, a new transfer model was established. It was supposed that solute molecules were in equilibrium between the stationary phase and mobile phase, and transferred in the mobile phase by a way of jumping. The generating function was used to investigate the non-continuous dynamic transfer differential equations, and the basic profile of solute's distribution in the column is gained [formula: see text] Based on this equation, the effect of transfer coefficient on the profile had been explained. The results show that relaxation time is an important factor which is related to the capacity factor and diffusion coefficient, and the number of jumping is a similar parameter to the plate number. The digital calculation method was used to study the influence of different physical parameters on the profile. The continuous form of the profile was also compared with the one from other methods.

English Abstract↗
PubMed1999

[The identification of 5 new serotypes of Bacillus thuringiensis from soil in China].

Five new strains of Bacillus thuringiensis(Bt) from soil in China were classified. 5 new H-serotypes: H42, H43, H56, H60 and H62 were identified. There were some distinction in the morphology, biochemical reaction and toxicity against species of insect. Five new Bt subspecies were identified as follows: Strain YGd22-03 Bacillus thuringiensis subsp. jinghongiensis, H42; Strain KK31-01 Bacillus thuringiensis subsp. guiyangiensis, H43; Strain SCg04-02 B. thuringiensis subsp. rongseni, H56; Strain NXP15-04 B. thuringiensis subsp. pingluonsis, H60; Strain HZ39-04 B. thuringiensis subsp. zhaodongensis, H62.

Animals↗
PubMed1999

[New coleopterancidai strains of Bacillus thuringiensis and production of coleopterancide].

Two coleopterancidal strains of Bacillus thuringiensis, YM-03 and SHQ11-10, were isolated from soil in China. H-Serotype of YM-03 was H8a8b, and H-Serotype of SHQ11-10 has not been identified. Both of them produced flat bipyramid-like crystals which consisted of 68-70 kD and 65 kD protein respectively. Bioassay indicated that these two Bt strains were very active on the larva of Leptinotarsa decemlineata and Plagioder aversicolora. They grew prosperously in fermentation. Powder of YM-03 product was high effect against colorado potato beetle in the field experiment.

Animals↗
PubMed1999

[Chemical composition of essential oil from leaves of litsea cubeba and its antifungal activities].

The 24 chemical constituents of the essential oil extracted from the leaves of Litsea cubeba have been identified by means of GC-MS technique. Among which, alpha-cis-ocimene(25.11%), 3,7-dimethyl-1,6-octadien-3-ol(16.85%) and n-transnerolidol (13.89%) were the principal components. In vitro this oil had a manifest antifungal activities with MIC between 0.03-0.4 microliter/ml for utilized pathogenic fungi and 1.0-2.0 microliters/ml for moulds.

Acyclic Monoterpenes↗
PubMed1999

[Experimental study on pharmacological action of fukean tablet on gastrointestinal tract].

The pharmacological effects of FuKean Tablet(FKT) on gastrointestinal tract were studied. The results showed FKT cured the diarrhea induced by rhubarb or senna, prominently reduced the quantity of feces and delayed the time of excreting charcoal powder in the diarrhea induced by rhubarb or senna model NIH mice; FKT inhibited intestinal propelling-movement in diarrhea induced by senna mmodel NIH mice. FKT inhibited the automatic contraction and Ach induced spasmodic contraction of isolated rabbit intestine(decreased the frequency and intensity of contraction). The above results revealed that the pharmacological base of curing the urgent disease in gastrointestinal tract may be curing the diarrhea, inhibiting intestinal propelling-movement and inhibiting the contraction of intestine.

Animals↗
PubMed1999

[Detection of Epstein-Barr virus gene in nasopharyngeal carcinoma with neck lymphatic metastasis].

OBJECTIVE: To investigate the presence of Epstein-Barr virus(EBV) gene in neck lymphatic metastasis of nasopharyngeal carcinoma. METHODS: Fifty patients' masses in the neck were punctured and the fluids were analyzed with PCR for EBV DNA. RESULTS: Twenty seven cases showed EBV DNA positive among thirty cases of nasopharyngeal carcinoma with neck lymphatic metastasis, and the positive rate was 90%. One case was EBV DNA positive in seven cases of malignant lymphoma and the positive rate was 14.3%. One case was EBV DNA positive in eight tumor patients without NPC metastasis and the positive rate was 12.5%. Five cases with nasopharyngeal inflammation and neck lymphatic node proliferation were demonstrated to be EBV DNA negative. CONCLUSION: This technique is rapid, sensitive and specific, which is valuable clinically, especially for the diagnosis in patients with cryptic nasopharyngeal carcinoma and with neck metastasis but lack of clear original focus.

Adolescent↗
PubMed1999

The radiation-induced S-phase checkpoint is independent of CDKN1A.

We recently demonstrated that, in response to radiation, replication is down-regulated at the level of individual origins throughout S phase of the cell cycle. Since several in vitro studies demonstrate that CDKN1A (formerly known as p21) down-regulates replication by inhibiting PCNA, and since CDKN1A can retard progression of cells through S phase in vivo, the question arises whether CDKN1A is involved in the S-phase damage-sensing pathway. In the present study we analyzed the effect of ionizing radiation on CDKN1A+/+ and CDKN1A-/- cells derived from the HCT 116 cell line. Neither progression of cells through S phase nor survival after exposure to ionizing radiation is influenced by CDKN1A status in either synchronous or asynchronous cells. These results establish that CDKN1A is not necessary for the acute S-phase damage-sensing pathway that functions to prevent firing of replication origins during S phase.

Cells, Cultured↗
PubMed1998

Dual function of Cyk2, a cdc15/PSTPIP family protein, in regulating actomyosin ring dynamics and septin distribution.

We previously showed that the budding yeast Saccharomyces cerevisiae assembles an actomyosin-based ring that undergoes a contraction-like size change during cytokinesis. To learn more about the biochemical composition and activity of this ring, we have characterized the in vivo distribution and function of Cyk2p, a budding yeast protein that exhibits significant sequence similarity to the cdc15/PSTPIP family of cleavage furrow proteins. Video microscopy of cells expressing green fluorescent protein (GFP)-tagged Cyk2p revealed that Cyk2p forms a double ring that coincides with the septins through most of the cell cycle. During cytokinesis, however, the Cyk2 double ring merges with the actomyosin ring and exhibits a contraction-like size change that is dependent on Myo1p. The septin double ring, in contrast, does not undergo the contraction-like size change but the separation between the two rings increases during cytokinesis. These observations suggest that the septin-containing ring is dynamically distinct from the actomyosin ring and that Cyk2p transits between the two types of structures. Gene disruption of CYK2 does not affect the assembly of the actomyosin ring but results in rapid disassembly of the ring during the contraction phase, leading to incomplete cytokinesis, suggesting that Cyk2p has an important function in modulating the stability of the actomyosin ring during contraction. Overexpression of Cyk2p also blocks cytokinesis, most likely due to a loss of the septins from the bud neck, indicating that Cyk2p may also play a role in regulating the localization of the septins.

Actomyosin↗
PubMed1998

Cloning and characterization of GEF-H1, a microtubule-associated guanine nucleotide exchange factor for Rac and Rho GTPases.

The Rho-related small GTPases are critical elements involved in regulation of signal transduction cascades from extracellular stimuli to cell nucleus and cytoskeleton. The Dbl-like guanine nucleotide exchange factors (GEF) have been implicated in direct activation of these GTPases. Here we have identified a new member of the Dbl family, GEF-H1, by screening a human HeLa cell cDNA library. GEF-H1 encodes a 100-kDa protein containing the conserved structural array of a Dbl homology domain in tandem with a pleckstrin homology domain and is most closely related to the lfc oncogene, but additionally it contains a unique coiled-coil domain at the carboxyl terminus. Biochemical analysis reveals that GEF-H1 is capable of stimulating guanine nucleotide exchange of Rac and Rho but is inactive toward Cdc42, TC10, or Ras. Moreover, GEF-H1 binds to Rac and Rho proteins in both the GDP- and guanosine 5'-3-O-(thio)triphosphate-bound states without detectable affinity for Cdc42 or Ras. Immunofluorescence reveals that GEF-H1 colocalizes with microtubules through the carboxyl-terminal coiled-coil domain. Overexpression of GEF-H1 in COS-7 cells results in induction of membrane ruffles. These results suggest that GEF-H1 may have a direct role in activation of Rac and/or Rho and in bringing the activated GTPase to specific target sites such as microtubules.

3T3 Cells↗
PubMed1998

Two functional states of the CD11b A-domain: correlations with key features of two Mn2+-complexed crystal structures.

In the presence of bound Mn2+, the three- dimensional structure of the ligand-binding A-domain from the integrin CR3 (CD11b/CD18) is shown to exist in the "open" conformation previously described only for a crystalline Mg2+ complex. The open conformation is distinguished from the "closed" form by the solvent exposure of F302, a direct T209-Mn2+ bond, and the presence of a glutamate side chain in the MIDAS site. Approximately 10% of wild-type CD11b A-domain is present in an "active" state (binds to activation-dependent ligands, e.g., iC3b and the mAb 7E3). In the isolated domain and in the holoreceptor, the percentage of the active form can be quantitatively increased or abolished in F302W and T209A mutants, respectively. The iC3b-binding site is located on the MIDAS face and includes conformationally sensitive residues that undergo significant shifts in the open versus closed structures. We suggest that stabilization of the open structure is independent of the nature of the metal ligand and that the open conformation may represent the physiologically active form.

Amino Acid Substitution↗