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Biomedical subjects

X Luo

Publications and source records attributed to X Luo.

At least 109 records · Page 6Linked to original sources
PubMed1999

Two novel azadirachtin derivatives from azadirachta indica

Two novel compounds, the first 29-oxymethylene azadirachtin analogue, 29-oxymethylene-11- demethoxycarbonyl-11alpha-hydroxyazadirachtin (azadirachtin M) (1) and 22, 23-dihydro-23alpha-hydroxy-3-tigloyl-11-deoxyazadirachtinin (azadirachtin N) (2), together with known compound 11-epi-azadirachtin H were isolated from a methanolic extract of the seed kernels of Azadirachta indica. The structures of 1 and 2 were elucidated on the basis of spectral methods.

Journal Article↗
PubMed1999

LacSwitch inducible mammalian expression system in mouse Swiss 3T3 fibroblasts.

Swiss 3T3 fibroblasts were transfected with the provided plasmids of LacSwitch Inducible Mammalian Expression System (Stratagene). Stable transfectants were selected, expanded and characterised. At first, the production of CAT in these cell lines could be induced by IPTG treatment, but the inducibility was lost after a few months in culture in a reproducible manner. Further analysis revealed that the transfectants did not lose the cat gene nor the lac repressor protein. As a result, we conclude that LacSwitch Inducible Mammalian Expression System needs further modification for use in Swiss 3T3 fibroblasts.

3T3 Cells↗
PubMed1999

Synthesis and characterization of a series of novel glutamic gamma-15N-anilide dipeptides.

The preparation of a series of novel Cbz-Gln-Gly dipeptide derivatives is reported, wherein the gamma-carboxamide groups of the glutamine side chains have been modified to gamma-15N-anilides which are substituted in the para position with -NO2, -Cl, -H, -CH3, -OCH3, and -N(CH3)2. Characterization of the free anilines (p(kappa)a values and 15N NMR chemical shifts) and corresponding gamma-anilides (15N NMR chemical shifts and FTIR wavenumbers) is also reported. Correlation of these physicochemical data to Hammett substituent parameters ((sigma)para) is discussed. These novel dipeptide derivatives should prove to be generally useful for structure-function enzymology studies of gamma-glutamyl transferring enzymes.

Anilides↗
PubMed1999

Lipid A mutant Salmonella with suppressed virulence and TNFalpha induction retain tumor-targeting in vivo.

Systemically administered tumor-targeted Salmonella has been developed as an anticancer agent, although its use could be limited by the potential induction of tumor necrosis factor alpha (TNFalpha)-mediated septic shock stimulated by lipid A. Genetic modifications of tumor-targeting Salmonella that alter lipid A and increase safety must, however, retain the useful properties of this bacteria. We report here that disruption of the Salmonella msbB gene reduces TNFalpha induction and increases the LD50 of this pathogenic bacteria by 10,000-fold. Notwithstanding this enormous difference, Salmonella retains its tumor-targeting properties, exhibiting tumor accumulation ratios in excess of 1000:1 compared with normal tissues. Administration of this bacteria to mice bearing melanoma results in tumors that are less than 6% the size of tumors in untreated controls at day 18. Thus, the antitumor activity previously demonstrated using tumor-targeting Salmonella with normal lipid A is retained. Lipid modification of tumor-specific bacterial vectors provides a means for reducing septic shock and further suggests that the antitumor activity of these bacteria may be independent of TNFalpha.

Acyltransferases↗
PubMed1999

Cell-type-dependent activity of the ubiquitous transcription factor USF in cellular proliferation and transcriptional activation.

USF1 and USF2 are basic helix-loop-helix transcription factors implicated in the control of cellular proliferation. In HeLa cells, the USF proteins are transcriptionally active and their overexpression causes marked growth inhibition. In contrast, USF overexpression had essentially no effect on the proliferation of the Saos-2 osteosarcoma cell line. USF1 and USF2 also lacked transcriptional activity in Saos-2 cells when assayed by transient cotransfection with USF-dependent reporter genes. Yet, there was no difference in the expression, subcellular localization, or DNA-binding activity of the USF proteins in HeLa and Saos-2 cells. Furthermore, Gal4-USF1 and Gal4-USF2 fusion proteins activated transcription similarly in both cell lines. Mutational analysis and domain swapping experiments revealed that the small, highly conserved USF-specific region (USR) was responsible for the inactivity of USF in Saos-2 cells. In HeLa, the USR serves a dual function. It acts as an autonomous transcriptional activation domain at promoters containing an initiator element and also induces a conformational change that is required for USF activity at promoters lacking an initiator. Taken together, these results suggest a model in which the transcriptional activity of the USF proteins, and consequently their antiproliferative activity, is tightly controlled by interaction with a specialized coactivator that recognizes the conserved USR domain and, in contrast to USF, is not ubiquitous. The activity of USF is therefore context dependent, and evidence for USF DNA-binding activity in particular cells is insufficient to indicate USF function in transcriptional activation and growth control.

Amino Acid Sequence↗
PubMed1999

Biochemical pathways of caspase activation during apoptosis.

Caspase activation plays a central role in the execution of apoptosis. The key components of the biochemical pathways of caspase activation have been recently elucidated. In this review, we focus on the two most well-studied pathways of caspase activation: the cell surface death receptor pathway and the mitochondria-initiated pathway. In the cell surface death receptor pathway, activation of caspase-8 following its recruitment to the death-inducing signaling complex (DISC) is the critical event that transmits the death signal. This event is regulated at several different levels by various viral and mammalian proteins. Activated caspase-8 can activate downstream caspases by direct cleavage or indirectly by cleaving Bid and inducing cytochrome c release from the mitochondria. In the mitochondrial-initiated pathway, caspase activation is triggered by the formation of a multimeric Apaf-1/cytochrome c complex that is fully functional in recruiting and activating procaspase-9. Activated caspase-9 will then cleave and activate downstream caspases such as caspase-3, -6, and -7. This pathway is regulated at several steps, including the release of cytochrome c from the mitochondria, the binding and hydrolysis of dATP/ATP by Apaf-1, and the inhibition of caspase activation by the proteins that belong to the inhibitors of apoptosis (IAP).

Animals↗
PubMed1999

Multiple functional P2X and P2Y receptors in the luminal and basolateral membranes of pancreatic duct cells.

Purinergic receptors in the basolateral and luminal membranes of the pancreatic duct can act by a feedback mechanism to coordinate transport activity in the two membranes during ductal secretion. The goal of the present work was to identify and localize the functional P2 receptors (P2R) in the rat pancreatic duct. The lack of selective agonists and/or antagonists for any of the cloned P2R dictated the use of molecular and functional approaches to the characterization of ductal P2R. For the molecular studies, RNA was prepared from microdissected pancreatic intralobular ducts and was shown to be free of mRNA for amylase and endothelial nitric oxide synthase (markers for acinar and endothelial cells, respectively). A new procedure is described to obtain an enriched preparation of single duct cells suitable for electrophysiological studies. Localization of P2R was achieved by testing the effect of various P2R agonists on intracellular Ca(2+) concentration ([Ca(2+)](i)) of microperfused intralobular ducts. RT-PCR analysis suggested the expression of six subtypes of P2R in the pancreatic duct: three P2YR and three P2XR. Activation of Cl(-) current by various nucleotides and coupling of the receptors activated by these nucleotides to G proteins confirmed the expression of multiple P2R in duct cells. Measurement of [Ca(2+)](i) in microperfused intralobular ducts suggested the expression of P2X(1)R, P2X(4)R, probably P2X(7)R, and as yet unidentified P2YR, possibly P2Y(1)R, in the basolateral membrane. Expression of P2Y(2)R, P2Y(4)R, and P2X(7)R was found in the luminal membrane. The unprecedented expression of such a variety of P2R in one cell type, many capable of activating Cl(-) channels, suggests that these receptors may have an important role in pancreatic duct cell function.

Animals↗
PubMed1999

Effect of the 21-aminosteroid U74389G on oxygen-induced free radical production, lipid peroxidation, and inhibition of lung growth in neonatal rats.

Bronchopulmonary dysplasia is a chronic pneumopathy of preterm infants, with significant associated mortality and morbidity, for which there is no effective preventive therapy. Pulmonary O2 toxicity is thought to be a major contributor to the development of bronchopulmonary dysplasia, and antioxidant interventions hold significant promise for therapy. The relative importance of specific reactive oxygen species in the development of O2-mediated lung injury is unknown. In this study, we tested the effect of a synthetic 21-aminosteroid, U74389G, on 95% O2-induced free radical production, lipid peroxidation, and inhibition of postnatal lung growth in a neonatal rat model. Lipid peroxidation products, as measured by total 8-isoprostane and aldehydes, and hydroxyl radical formation, assessed using salicylate metabolites, in rat lungs and serum were significantly increased after exposure to 95% O2. These changes could be completely or partially attenuated by U74389G. However, U74389G did not improve the survival rate or lung wet-to-dry weight ratio. Expression of proliferating cell nuclear antigen, a marker for DNA synthesis, was examined by immunohistochemistry. Four- or 7-d-old control rat lungs had active DNA synthesis, which was inhibited by exposure to 95% O2. U74389G had a protective effect against 95% O2-mediated inhibition of DNA synthesis. Air-exposed animals treated with U74389G had a modest reduction in lung DNA synthesis, consistent with a role for hydroxyl radicals or lipid hydroperoxides as second messengers in the normal regulation of lung growth.

Animals↗
PubMed1999

[Effects of hyperbaric oxygen therapy on the changes in serum sIL-2R and Fn in severe burn patients].

OBJECTIVE: Many reports showed that level of soluble interleukin 2 receptor (sIL-2R) in sera was obviously increased in burn patients, while plasma fibronectin (Fn) was markedly decreased, and they had close relation with the occurrence and development of burn infection. The purpose of this study was to verify the significance of hyperbaric oxygen therapy (HBOT) in the prevention and treatment of burn infections by observing its effect on the levels of serum sIL-2R and Fn in severe burn patients. METHODS: Forty two burn patients(with more than 30% body surface area or three degree more than 10%) were selected and divided into two groups at random: HBOT group(25 cases) and non-HBOT group(17 cases); forty healthy blood donors were selected as normal control. The venous blood samples were drawn from 42 patients at 1/3, 1, 2, 3, 5, 7, 10, 14, 17, 21, 28 and 35 days postburn, the levels of serum sIL-2R and Fn were measured by ELISA and rocket electrophoresis techniques respectively, meanwhile, the incidences of sepsis of two groups were compared. RESULTS: 1. In non-HBOT group: the levels of serum sIL-2R were remarkably increased, while serum Fn were markedly decreased at all periods postburn (compared with normal control: P < 0.05 or P < 0.01); 2. In HBOT group: the levels of serum sIL-2R were not obviously increased at all periods except 21 days postburn, and Fn were not decreased at all periods except 8 h postburn (compared with normal control: P > 0.05). Compared with non-HBOT group, however, the levels of serum sIL-2R were profoundly reduced, while Fn was significantly enhanced at all periods postburn(P < 0.05 or P < 0.01), and the incidence of sepsis was obviously lowered (P < 0.05). CONCLUSION: HBOT can significantly reduce the level of serum sIL-2R but enhance Fn in severe burn patients, so it may have a positive effect on the prevention and treatment of burn infections.

Adolescent↗
PubMed1999

Immunological characteristics of natural resistance in Microtus fortis to infection with Schistosoma japonicum.

OBJECTIVE: To explore the immunological characteristics of natural resistance to Schistosoma japonicum infection in Microtus fortis (MF) living in the Dongting Lake area. METHODS: Passive transfer of sera from uninfected laboratory bred MF (BMF) to albinao mice (AM) was performed to observe the acquired protection. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunoblotting (ELIB) methods were used to recognize 4 different life-cycle stage antigens of S. japonicum by sera from wild MF (WMF), BMF, BMF13 and BMF19. Tests were also performed on in vitro killing effect of sera and/or lymphocytes from BMF and WMF to schistosomulae; quantitative determination of C3 and C4 by immunoturbidometry, and interleukin-4 (IL-4) and antibodies to the 4 stage antigens in sera from WMF, BMF and infected BMF by ELISA. RESULTS: Compared with the control group, stool eggs per gram (EPG) of AM in the test group was significantly reduced by 81.54%, miracidium hatching rate, by 50.67%, liver egg counts, by 72.07%, the diameter of hepatic egg granuloma, by 70.39 microns. Western blotting probed with the 4 MF sera all revealed 7 specific bands for SSA, 3 for AWA and SEA, but none for CA antigens. The sera and/or lymphocytes from WMF and BMF gave obvious killing effects on schistosomulae with an adjusted death rate of 64.12%-78.83%. The levels of "natural antibodies" produced by MF to S. japonicum were in the following order: anti-SSA > anti-AWA > anti-SEA > anti-CA, all of which increased significantly after the infection. Serum levels of C3, C4 and IL-4 in uninfected BMF were significantly higher than those in AM. After infection, levels of C3 and C4 were further increased respectively by 72.83% and 295.49% in the 4th week and IL-4 by 303.83% in the 9th day. CONCLUSIONS: Immunological characteristics of innate resistance in M. fortis to S. japonicum infection were existed with no significant difference between WMF and BMF.

Animals↗
PubMed1999

[Development of partially sintered alumina block for dental CAD/CAM and mechanical properties testing].

OBJECTIVE: It is a new way to fabricate all ceramic crowns by combining dental CAD/CAM with glass infiltration technology. METHODS: A partially alumina sintered block made of a high purity, fine alumina powder was shaped by isostastic pressure and sintered at 1,400 degrees C. Its mechanical properties were tested and microstructure was observed by SEM. RESULTS: The Vicker's hardness, three-point bending strength, fracture toughness of partially sintered alumina block were 1.65 MPa, 210 MPa, 1.90 MPam1/2 respectively. Micrographs of SEM indicated that partially sintered alumina contained the structure of continuous three-dimensional open pores through the neck growth and surface diffusion of the interparticles. CONCLUSION: The partially sintered alumina block that developed in this way may be used to mill for CAD/CAM and fabricate the shrinkage-free all ceramic crown.

Aluminum Oxide↗
PubMed1999

[Studies on apoptosis of human lung adenocarcinoma cells induced by oltipraz].

OBJECTIVE: To study whether oltipraz can induce apoptosis of human lung adenocarcinoma (GLC-82) cells and its possible mechanism. METHODS: Light microscopy, DNA electrophoresis, flow cytometry and video time-lapse monitoring were used to observe apoptosis of GLC-82 induced by oltipraz. RESULTS: GLC-82 cells treated with oltipraz underwent the arrest of cell mitosis at metaphase, higher percentage of G(2)/M and peak of apoptosis were found, and cell body shrunk, nuclear chromosome condensed or fragmented and nuclear DNA fragment displayed "laden" bands in apoptic cells. Apoptosis of GLC-82 induced by oltipraz was more obvious at a concentration of 120 microg/ml. CONCLUSION: Oltipraz could induce apoptosis of GLC-82 at certain concentrations, which associated closely with the arrest of mitotic cycle.

Adenocarcinoma↗
PubMed1999

[Pathomorphological and amyloid beta-protein immunohistochemical findings in autopsied brains of Alzheimer's disease].

OBJECTIVE: To study the incidence and neuropathological features of Alzheimer's disease in Chinese and the significance of silver and amyloid beta-protein staining for the pathological diagnosis of Alzheimer's disease. METHODS: Among 445 autopsy cases above 60 years in age (including 60) collected from 1982-1998 in the Department of Pathology, Beijing Hospital, totally 29 cases were diagnosed as Alzheimer's disease pathologically (6.5%), accompanying with a history of mental deterioration and the histological changes in certain areas of the brain fulfilling the Khachaturian or Mirra criteria. Tissue blocks were taken from 6 standard regions of the brains for Bodian, Bielschowsky and amyloid beta-protein immunostaining. Senile plaques and neurofibrillary tangles were quantified. RESULTS: Four main types of senile plaques were noticed and the result by amyloid beta-protein immunostaining was considered more sensitive than that of the silver impregnation staining. The former one enabled to demonstrate all the 4 types of senile plaques, while silver impregnation staining could only demonstrate clearly the primitive and neuritic plaques, but not the small diffuse and burn-out plaques. The senile plaques were noticed to be focused in the hippocampus, superior temporal gyrus and middle frontal gyrus while the neurofibrillary tangles, were mainly obtained in the hippocampus, temporal cortex and amygdaloid. Cerebral amyloid angiopathy was found in 25 out of 29 Alzheimer's disease cases. CONCLUSIONS: Alzheimer's disease may be the main cause of dementia among the elders in Chinese and immunostaining for amyloid beta-protein pretreated with formic acid may set a high value on the pathological diagnosis of Alzheimer's disease.

Aged↗
PubMed1999

[Studies on the preparation and characters of anti-AFB1 antibody from the yolk of laying hens].

AFB1O-BSA conjugates were injected into four laying hens (A, B, C and D). The yolk anti-AFB1 antibodies A,C and D produced were obviously increased after 90 days of the first injection, and reached the peak after 135 days, and started dropping after 165 days. The indirect ELISA titer of yolk antibodies A,C and D were 1:8000, 1:6000 and 1:6000 respectively. The specificity of the antibody A was good, but a cross-reaction with AFB2, AFG1, AFG2, with an exception of AFM1, was found. The sensitivities of AFB1, AFB2, AFG1 and AFG2 were 6, 25, 125 and 2495 micrograms/L respectively.

Aflatoxin B1↗
PubMed1999

[Changes of left ventricular diastolic function in hypertensive patients with left atrial enlargement].

In order to find out the relationship between the left atrial enlargement and left ventricular diastolic function in hypertension, radionuclide ventriculography was performed in 45 hypertensive patients with normal left ventricular mass index(LVMI), including 23 with normal left atrium(Group I), 22 with left atrial enlargement(Group II), and 28 matched subjects as control(Group III). The results showed that the left ventricular diastolic function in Group I was normal, but abnormal in Group II. It is considered that left atrial enlargement and left ventricular diastolic dysfunction are the early signs of the hypertensive heart disease.

Adult↗