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Biomedical subjects

L Xu

Publications and source records attributed to L Xu.

At least 487 records · Page 27Linked to original sources
PubMed1998

[Synthesis and antiinflammatory activity of 2-(E)-(4-hydroxy-3-methoxybenzylidene)-5-(N-substituted aminomethyl) cyclopentanones].

In search for new antiinflammatory agents, a series of 2-(E)-(4-hydroxy-3-methoxybenzylidene)-5-(N-substituted aminomethyl) cyclopentanones was synthesized via Stork reaction, Mannich reaction and amine exchange reaction. All of the fifteen target compounds were characterized by spectral analysis and elemental analysis. Preliminary pharmacological tests showed that several target compounds exerted appreciable effect on xylene-induced ear edema in mice and that alteration of the substituents of anilines showed significant influence on antiinflammatory potency.

Animals↗
PubMed1998

[Histological studies on the roots of twelve species of Sect. Microdiscus and Sect. Adenophora of the genus Adenophora].

This paper reports the root structures of Adenophora lamarkii Fisch, A. hunanensis Nannf., A. hunanensis Nannf. subsp. huadungensis Hong, A. trachelioides Maxim., A. trachelioides Maxim. subsp. giangsuensis Hong, A. remotiflora (Sieb. et Zucc.) Miq. derived from Sect. Microdiscus of the Genus Adenophora, and A. stenanthina (Ledeb.) Kitagawa, A. stenanthina (Ledeb.) Kitagawa subsp. xifengensis P. F. Tu et Y. S. Zhou, A. liliifolioides Pax et Hoffm., A. capillaris Fisch., A. tetraphylla Fisch., A. triphylla (Thunb.) A. DC. derived from Sect. Adenophora of the Genus Adenophora. Based on the histological studies of 23 species, 5 subspecies and 2 varieties of the Genus Adenophora, a Key of histological characters is given.

Campanulaceae↗
PubMed1998

[Synthesis and antiinflammatory activity of 2-(E)-benzylidene-5-(N-substituted aminomethyl) cyclopentanones].

Nineteen kinds of 2-(E)-benzylidene-5-(N-substituted aminomethyl) cyclopentanones were synthesized via Mannich reaction or amine exchange reaction and identified spectrometrically. One compound exhibited significant antiinflammatory activity, showing obvious inhibitory effect on xylene-induced mice ear swelling, carrageenin-induced rats paw edema and increased capillary permeability induced with acetic acid in mice. Its ED50 values in these inflammatory models were calculated to be 67.8 mg.kg-1, 25.3 mg.kg-1 and 41.8 mg.kg-1 respectively, nearly equal to those of ibuprofen and aspirin.

Animals↗
PubMed1998

[Histological studies on the roots of eighteen species of sect. microdiscus of the genus Adenophora].

The Chinese materia medica "Nanshasheng" (Radix Adenophorae) specified in Chinese Pharmacopoeia (1995) is the dried root of Adenophora tetraphylla (Thunb.) Fisch. or A. stricta Miq. (Fam. Campanulaceae). Results of an investigation on the botanical origin of the drug showed that the roots of 30 species (subspecies, varieties) of the genus Adenophora are also used in certain districts in China. Thus, it is necessary to study and compare the histological characters of these roots. In this paper, the root structure of 18 species from Sect. Microdiscus are reported, viz. Adenophora brevidiscifera Hong, A. coelestis Diels, A. stricta Miq., A. stricta Miq. var. qinglongshanica P. F. Tu et G. J. Xu, A. stricta Miq. var. nanjingensis P. F. Tu et G. J. Xu, A. stricta Miq. subsp. henanica P. F. Tu et G. J. Xu, A. stricta Miq. subsp. sessilifolia Hong, A. longipedicellata Hong, A. gmelinii (Spreng.) Fisch., A. polyantha Nakai, A. micrantha Hong, A. stenophylla Hemsl., A. potaninii Korsh., A. bockiana Diels, A. wawreana Zahlbr., A. tricuspidata (Fisch. ex Roem. et Schult.) A. DC., A. pereskiifolia (Fisch. ex Roem. et Schult.) G. Don and A. divaricata Franch. et Sav.. According to the presence, arrangement and thickening of cell walls of sclerified cork cell (SCC) in cork tissue and the rate of secondary and anomalous structures, the histological structures of Adenophora roots are classified into types A, B and C. In type A, SCC are arranged in ring shape. Type A can be further classified into subtypes A1 and A2. Only the outer and anticlinal walls of SCC are thickened in subtype A1, and all cell walls of SCC are thickened in subtype A2. In type B, SCC are arranged scatteredly, not in ring shape. In type C, there is no SCC. Type C can be classified into subtypes C1, C2 and C3. In type C1, the secondary structure occupies more than 50% of the root diameter. In type C2, the anomalous structure is more than 50% of the root diameter, and the anomalous vascular bundles are in band form. The anomalous structure occupies more than 50% of the root diameter in subtype C3, and the anomalous vascular bundles are branched.

Campanulaceae↗
PubMed1998

[A novel method for rotated images registration based on wavelet transform].

UNLABELLED: This paper presents a novel approach to image registration which addresses the problem of rotation correction. METHOD: 1. 2-DWT of medical images. 2. Maxima of wavelet coefficients (MWC) were used as feature points. 3. Starting from last level of decomposition and then iteratively for each level going up, find the best match between MWC of input image and rotated MWC of reference image. The best rotation is refined iteratively and with increasing accuracy. RESULTS: The performance of the method was compared to that of the traditional methods and found it to be superior. CONCLUSIONS: Images can be fast registrated with high accuracy and less sensitivity to noise.

Fluorescein Angiography↗
PubMed1998

[Investigation on resources and commodities of Chinese medicinal herbs of Jili].

OBJECTIVE: To make clear the current situation of application of the Chinese medicinal herbs of Jili. METHOD: The medicinal resources and commodities of the berbs in some provinces and cities in China were investigated. RESULT: The species Tribulus terrestris included in is widely distributed in China. The fruit of T. terrestris which is widely used in China as a traditional medicine is commonly called Yingjili. Being only the fruit of Atriplex entralasiatica Ruanjili is produced mainly in Shandong Province and customarily used as Fructus Tribuli in some areas of Shandong and Hebei Provinces. CONCLUSION: The current situation of medicinal application of Jili basically conforms to the requirements of . The main variety is Yingjili.

China↗
PubMed1998

[A robust method for automated retinal vascular images mosaic based on phase correlation method and mathematical morphology].

Precise mosaic techniques are essential for quantitative evaluation of retinal images to make early detection of fundus anomalies feasible. Opening of a gray-scale image by a gray-scale structuring element(SE) can generate a background image. Image mosaic was achieved by subtraction this background image from the original image and then applying a phase correlation method to find translation difference. Because of the accuracy characteristics of the phase correlation method and the speed of the FFT hardware, this new algorithm can work very fast and accurately, compared to conventional techniques. The method was also characterized by an outstanding robustness against correlated noise and disturbances, such as those encountered with nonuniform illumination. The results confirm the robustness of the chosen approach.

Algorithms↗
PubMed1998

[An experimental study on limbal stem cells autograft transplantation with cryopreservation].

PURPOSE: The viability of limbal stem cells with cryopreservation and the treatment effect with cryopreserved limbal autograft transplantation for ocular surface disorders (OSDs) of stem cells deficiency in rabbits. METHODS: Limbal grafts included 2 mm of peripheral cornea and 2 mm of conjunctiva and OSDs models of corneal stem cells deficiency were created in right eyes of 12 rabbits. The grafts were cryopreserved in -196 degrees C liquid nitrogen by program-controlled Bio-Freezer. The limbal autograft transplantations for ocular surface reconstruction were performed after cryopreserved 60 days and 30 days. RESULTS: The stem cells deficiency result in corneal epithelium delay healing. Seven of 12 eyes were healed post-operative 22-26 days with a mean time of 24 +/- 1 days and four eyes with recurrent erosion. The swelling and neovascularization appearing with a mean time of 5 +/- 1 days were discovered. The cryopreserved limbal autograft transplantation can increase corneal epithelial healing with a mean time of 10 +/- 2 days. It was observed that corneal stromal swelling and neovascularization were markedly decreased, and neovascularization of two eyes were disappeared. CONCLUSIONS: Cryopreservation in liquid nitrogen can preserve the viability of limbal stem cells, and provide viable limbal grafts to treat OSDs in clinical patients.

Animals↗
PubMed1998

The role of platelet-activating factor (PAF) and the efficacy of ABT-491, a highly potent and selective PAF antagonist, in experimental allergic rhinitis.

Platelet-activating factor (PAF) may be an important mediator of allergic rhinitis. In the present study we evaluated the effectiveness of a recently described PAF antagonist (ABT-491) in rat and guinea pig models of allergic rhinitis. PAF, when perfused through the nasal passages of anesthetized Brown Norway rats, provoked an acute increase, measured as dye leakage, in nasal vascular permeability evident within 15 min after exposure to PAF. ABT-491, given orally 1 hr before PAF challenge, inhibited the response in a dose-related manner (ED50 = 0.3 mg/kg). Intranasal perfusion with ovalbumin in rats sensitized to the antigen 18 to 21 days before challenge also induced an increase in vascular permeability. The antigen-induced leakage was inhibited a maximum of 74% (P < or = .001) by pretreatment with ABT-491 (3 mg/kg p.o.). An antihistamine (mepyramine, 10 mg/kg i.p.), a serotonin antagonist (methysergide) and a 5-lipoxygenase inhibitor (A-79175) also exhibited efficacy in this model (56%, 87% and 65% inhibition, respectively). Nearly complete inhibition (93%, P < or = .001) of the response was achieved by coadministration of ABT-491 and methysergide. In guinea pigs intranasal administration of PAF resulted in increased airway resistance that was inhibited in a dose-dependent manner by oral administration of ABT-491 (ED50 = 1 mg/kg). Antigen-induced nasal airway resistance, triggered by exposure of sensitized animals to aerosolized ovalbumin, was also inhibited by ABT-491 (maximum inhibition 64%, P < or = .05, 10 mg/kg p.o.). The effectiveness of the antagonist was increased to 80% protection by coadministration with either an antihistamine or a 5-lipoxygenase inhibitor, agents which were separately insignificant in blocking the response to antigen. These results suggest a therapeutic utility for ABT-491, perhaps in combination with other anti-inflammatory agents, in the treatment of allergic rhinitis.

Airway Resistance↗
PubMed1998

Quantitative nerve fiber layer measurement using scanning laser polarimetry and modulation parameters in the detection of glaucoma.

PURPOSE: To assess a new method of processing quantitative nerve fiber layer (NFL) measurement data to distinguish between eyes with glaucoma of varying severity and normal eyes, using information obtained by scanning laser polarimetry. PATIENTS AND METHODS: Scanning laser polarimetry measurements of the peripapillary NFL within a 10-pixel band located 1.8 disc diameters from and concentric with the disc margin were obtained from 36 normal eyes, 69 eyes with glaucoma, 7 eyes suspected of being glaucomatous, and 19 eyes with ocular hypertension. These values then were examined using new data processing "modulation" parameters in which the average of the nasal and temporal minimum retardation is subtracted from the retardation in the superior or inferior region of the peripapillary NFL. The ability of modulation parameters to differentiate between normal and glaucomatous eyes was compared with other parameters based either on the sum of retardation values in the superior or inferior region, or on the ratio of values in the superior or inferior region to the nasal region. RESULTS: Differences in mean polarimetric retardation between normal eyes and eyes with glaucoma were significant for all parameters, but were greatest when modulation parameters were used and were significantly greater for two modulation parameters. The range of values showed considerable overlap between all groups of eyes. Eyes with ocular hypertension had mean values intermediate between normal eyes and eyes with early glaucomatous damage. CONCLUSION: The use of new modulation parameters increases the ability of quantitative NFL measurement to distinguish between eyes with glaucoma of varying severity and normal eyes.

Adult↗
PubMed1998

Correlation of peripapillary nerve fiber layer thickness by scanning laser polarimetry with visual field defects in patients with glaucoma.

PURPOSE: To assess the correlation between the results of peripapillary scanning laser polarimetry of the retinal nerve fiber layer (NFL) and automated visual field testing in patients with open-angle glaucoma. METHODS: Visual fields from 42 patients with varying stages of glaucoma were scored using Collaborative Initial Glaucoma Treatment Study (CIGTS) criteria. Mean deviation, pattern standard deviation, and CIGTS total and hemifield visual field scores were correlated with peripapillary NFL thickness measured by scanning laser polarimetry using summed, ratio-based, and modulation parameters. RESULTS: Mean deviation and CIGTS total and upper hemifield score were significantly correlated with NFL retardation values using summed, ratio-based, or modulation parameters. The CIGTS lower hemifield score was significantly correlated with modulation parameter values only. Correlation of CIGTS scores was significantly stronger with modulation parameters than with summed parameters (total and lower hemifield scores) and ratio-based parameters (lower hemifield only) by the Hotelling t test. CONCLUSION: Relative NFL thickness measured by scanning laser polarimetry correlates well with visual field defects seen on Humphrey perimetry of patients with open-angle glaucoma. Modulation parameters, in which the superior and inferior peak NFL thickness (as measured by scanning laser polarimetry) are adjusted for the patient's average minimum NFL thickness in the nasal and temporal quadrants, provided stronger correlation than summed parameters and ratio-based parameters.

Adult↗
PubMed1997

Primary human hepatocytes as a tool for the evaluation of structure-activity relationship in cytochrome P450 induction potential of xenobiotics: evaluation of rifampin, rifapentine and rifabutin.

In our laboratory, primary human hepatocytes are being investigated as an in vitro experimental system for the evaluation of pharmacokinetic drug-drug interactions. Our study here represents the first reported study that directly compares the cytochrome P450 isozyme 3A (CYP3A) induction potential of three antimicrobials derived from rifamycin B, namely, rifampin, rifapentine and rifabutin. Two endpoints of CYP3A activity, testosterone 6 beta-hydroxylation and midazolam 1-hydroxylation have been used. Results obtained with hepatocytes from four different human donors show consistently that rifampin and rifapentine are potent inducers of CYP3A, while a significantly lower induction potential is observed for rifabutin. The relative induction potency of the three antimicrobials (rifampin > rifapentine >> rifabutin) is consistent with the available human in vivo data. For CYP1A measured as ethoxyresorufin O-deethylase activity, CYP2C8/9 measured as tolbutamide 4-hydroxylation activity, CYP2D6 measured as dextromethorphan O-demethylation, and AZT glucuronidation, there is either no effect or, where induction is found to be statistically significant in these other endpoints, the maximum induction values are consistently < 100% of the control. Our results suggest that CYP3A is the major CYP induced by these rifamycin B derivatives. These studies illustrate the application of human hepatocytes in the evaluation of the structure-activity relationships in CYP induction for this class of chemicals and as an in vitro screen for drug-drug interaction potential via CYP induction.

Antibiotics, Antitubercular↗
PubMed1997

Strain-specific expression of spliced MMTV RNAs containing the superantigen gene.

The transmission of milk-borne or exogenous mouse mammary tumor virus (MMTV) requires infection of B cells in the gut-associated lymphoid tissue and expression of the superantigen (Sag) protein at the B-cell surface. Presentation of Sag at the B-cell surface is required for the transmission of MMTV to T cells and subsequent infection of the target mammary gland tissue. Because several different promoters have been reported for MMTV sag mRNA expression, we investigated whether the detection of spliced sag RNAs was dependent upon the cell type infected or the particular MMTV strain examined. In this study, we detected expression of spliced sag RNA from the standard promoter and from an internal U3 promoter in B-cell lines expressing endogenous Mtv-6 by RT-PCR, although expression from the standard promoter appeared to be at least 10-fold higher than that observed from the internal U3 promoter. Sag RNA originating from exogenous C3H MMTV was not observed from either of the U3 promoters in any cell type examined. However, spliced mRNAs containing the exogenous C3H MMTV, endogenous Mtv-8, or endogenous Mtv-17 sag genes could be detected from a previously described promoter in the envelope coding region regardless of the cell type infected. Because sag-specific RNAs can be initiated independently of the LTR promoters, there may be selection for independent control of MMTV sag and structural gene expression.

Amino Acid Sequence↗
PubMed1997

Electrophore mass tag dideoxy DNA sequencing.

Toward a goal of dideoxy sequencing DNA utilizing electrophore labels, we prepared four electrophore-labeled DNA oligonucleotide primers. Each primer has a different electrophore and DNA sequence but a common glycol keto (alpha,beta-dihydroxyketo) release group. Cleavage of this latter group by either periodate oxidation or a thermal retroaldol reaction releases the electrophores for detection by mass spectrometry. Successful sequencing data with these primers was obtained by capillary electrophoresis on an ABI Model 310 after fluorescence dideoxy terminator cycle sequencing reactions were conducted. In a separate experiment, it was demonstrated that a cocktail of the four electrophore DNA primers could be detected as a dried sample spot by CO2 laser desorption/capillary collection/gas chromatography electron capture mass spectrometry. These results establish some feasibility for our long-term goal of high-speed multiplex electrophore mass tag dideoxy DNA sequencing. Ultimately we plan to use a higher number of electrophore mass tags and to rely on direct detection of the desorbed electrophores by electron capture time-of-flight mass spectrometry.

Chromatography, High Pressure Liquid↗
PubMed1997

Nitric oxide-mediated apoptosis of K-1735 melanoma cells is associated with downregulation of Bcl-2.

Recent studies have shown that the treatment of nonmetastatic K-1735 murine melanoma cells with cytokines induces the production of nitric oxide (NO) and hence cell death. The purpose of this study was to determine the mechanism of this cytokine-induced NO-mediated apoptosis. Incubation of nonmetastatic K-1735 cells with interleukin-1 alpha (IL-1alpha) and interferon-gamma (IFN-gamma) induced high NO production, Bcl-2 downregulation, and apoptotic cell death. In contrast, incubation of metastatic K-1735 cells with IL-1alpha and IFN-gamma did not induce significant production of NO, downregulation of Bcl-2, or cell death. The exposure to exogenous NO derived from the NO donors, sodium nitroprusside (SNP), or GEA5024 produced a dose-dependent apoptotic cell death in both the metastatic and nonmetastatic K-1735 cells, which was associated with downregulation of Bcl-2 at the mRNA level and, to a lesser extent, at the protein level. Nonmetastatic and metastatic K-1735 cells transfected with the Bcl-2 gene were more resistant to apoptosis mediated by both endogenous and exogenous NO. Subsequent to intravenous injection, the tumor cells transfected with the Bcl-2 gene had an increased survival rate in the lungs of nude mice and produced a higher number of experimental lung metastases. These data suggest that NO-induced apoptosis in K-1735 melanoma cells is associated with downregulation of Bcl-2.

Animals↗