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Biomedical subjects

X Luo

Publications and source records attributed to X Luo.

At least 181 records · Page 10Linked to original sources
PubMed1997

Purification of the simian virus 40 (SV40) T antigen DNA-binding domain and characterization of its interactions with the SV40 origin.

To better define protein-DNA interactions at a eukaryotic origin, the domain of simian virus 40 (SV40) large T antigen that specifically interacts with the SV40 origin has been purified and its binding to DNA has been characterized. Evidence is presented that the affinity of the purified T antigen DNA-binding domain for the SV40 origin is comparable to that of the full-length T antigen. Furthermore, stable binding of the T antigen DNA-binding domain to the SV40 origin requires pairs of pentanucleotide recognition sites separated by approximately one turn of a DNA double helix and positioned in a head-to-head orientation. Although two pairs of pentanucleotides are present in the SV40 origin, footprinting and band shift experiments indicate that binding is limited to dimer formation on a single pair of pentanucleotides. Finally, it is demonstrated that the T antigen DNA-binding domain interacts poorly with single-stranded DNA.

Antigens, Polyomavirus Transforming↗
PubMed1997

Use of chest computed tomography in the staging of pediatric Wilms' tumor: interobserver variability and prognostic significance.

PURPOSE: To determine the specificity and prognostic significance of computed tomography (CT) of the chest in pediatric Wilms' tumor. PATIENTS AND METHODS: Patients treated for newly diagnosed Wilms' tumor at St Jude Children's Research Hospital between December 1978 and July 1995 were included in the study if an initial chest radiograph and CT were available and if pulmonary involvement (determined by chest radiographs) was absent. For the 202 patients studied, radiographs and CT scans were reviewed blindly and independently by three experienced radiologists for the presence of pulmonary nodules. Outcome variables consisted of intraobserver variability (in a subsample of 40 cases) and concordance between ratings on radiographs and CT scans (both by McNemar's test), interrater variability (by logistic regression), and the cumulative incidence of pulmonary relapse for patients with and without positive CT scans, by reviewer. RESULTS: As expected, ratings of pulmonary involvement on radiographs were discordant with CT ratings. There was marked variability among reviewers in CT ratings (P = .0001). Of 202 CT scans, 78 were read as positive by at least one reviewer, 41 were rated positive by only one reviewer, 18 by two reviewers, and 19 by all three. Intrarater variability on repeat reviews was not significant. Patients with nodules identified on CT had a significantly higher pulmonary relapse rate when analyzed separately by reviewer. However, for the 14 patients who had pulmonary relapse, CT scans were rated positive by all three reviewers in only five cases and as negative by all three in another five cases. CONCLUSION: The variability in interpretation of chest CT scans in patients with Wilms' tumor limits the predictive utility of these studies. Optimal, standardized techniques and central review are essential if chest CT is to be used for staging in cooperative studies.

Adolescent↗
PubMed1997

[Respiratory monitoring and high frequence jet ventilation (HFJV) in the treatment of severe chest injuries].

Twenty-eight patients with severe chest injuries were classified into 3 groups: fractures of rib, hemopneumothorax and lung injured. Their respiratory rate (RR), SpO2 and blood gas were analysed. The results showed that SpO2 and PaO2 in lung-injured group were the lowest and RR was the highest in the 3 groups. After HFJV, there was a significant rise in PaO2 and SpO2 (P < 0.05) and a gradual recovery of respiratory and pulse rates in lung-injured group. The results suggest that respiratory monitoring is important for patients with chest injuries and HFJV may be used as an effective ventilation method for treating patients with severe chest injuries.

Adult↗
PubMed1997

[Molecular mechanism of mutagenesis induced by aflatoxin B1 using a shuttle vector pSP189/mammalian cell system].

AFB1 is one of the most potent carcinogenic mycotoxins, naturally occurred in foods. We applied a new SV40-based shuttle vector pSP189 and African Green kidney cells (VeroE6 cell line), which constitute shuttle vector/mammalian cell system to detect mutagenesis induced by AFB1 and to study the effects of AFB1 on the mutation site, type and sequence specificity of DNA molecular level through sequence analysis of pSP189 target gene SupF TRNA. The results indicated that through various time treatment of AFB1 and rat liver microsome, the mutants were obtained by transformation of E. Coli MBM 7070 with progeny of pSP189 generated during replication in veroE6 cells, which increased gradually with the lapse of time, and this experiment showed a significant dose-response relationship. Most detected mutants were point mutations evidenced by agarose gel electrophoresis analysis. The results of direct sequencing SupF TRNA of 53 independent mutants showed that most mutations (about 84.9%) were single base substitutions, among which 95.2% of base substitutions happened on the site of G:C base pair, the predominant mutation was G:C-->T:A transversion, accounting for 53.3%, followed by G:C-->A:T transition, accounting for 35.6%. AFB1-induced mutations did not distributed randomly, and had mutation hot spots and sequence specificity, which contained 5 base pair sequence 5'-NNTTC-3'. The mutations on the SupF shuttle vector were consistent with the results from studies of oncogene tumor suppressor genes and DNA adduct.

Aflatoxin B1↗
PubMed1997

[A monoclonal antibody-based indirect competitive inhibition enzyme-linked immunosorbent assay for detecting tetrodotoxin in puffer fish].

The homogenized tissue samples of puffer fish were extracted with boiling 0.1% acetic acid solution for 2 times, then the combined filtrate was defatted with ether ethyl for 2 times and the water phase were diluted with 0.05 mol/L PBS for ELISA determination (adjusted pH to 6.5-7.0). The results showed that the minimum detecable concentration of tetrodotoxin was 1.0 x 10(-3) mg/L (0.1 ng/assay), and the standard curve was linear between 1.0 x 10(-2) and 1.0 mg/L. The recovery rates from tetrodotoxin spiked samples of this method were 73.8%-117.4%. The accuracy of ELISA was compared with the traditional mouse bioassay system. The results showed no significant differences between the two methods (for paired-t test, P > 0.2), and significant correlations in tetrodotoxin concentration were obtained (r = 0.916).

Animals↗
PubMed1997

[Cell culture of human lamina cribrosa in vitro].

OBJECTIVE: To investigate the physiology and pathology of the biosynthesis of extracellular matrix (ECM) by lamina cribrosa cells (LCC) and to establish a model of cultured LCC. METHODS: The LCC of 10 human dead fetal eyes were cultured with enzyme digestion procedures in vitro. The cultured cells were identified by immunohistochemistry assays and electron microscopy. RESULTS: The cultured cells were flat, polygonal in shape, and their cytoplasm contained abundant perinuclear granules. The nuclei were relatively transparent and nucleoli were clear, there were basement membrane-like material and ECM surrounding the cell membrane. The immunofluorescent staining was positive for collagen type I, III, IV, fibronectin and laminin, negative for glial fibrillar acid protein and factor-VIII. The characteristics mentioned above were coincident with the morphology of LCC. This cell line has been cultured to its fourth generation. CONCLUSION: We have successfully cultured a cell line of LCC, and it may be utilized in the study of pathogenesis of glaucoma.

Cells, Cultured↗
PubMed1997

[Effects of CD11/CD18 on adhesion between endothelial cell and PMN and its expression in early stage postburn].

This study was to investigate the expressions of CD11a/CD18 and CD11b/CD18 on burn patient's polymorphonuclear neutrophil (PMN) in early postburn stage and effects of CD11/CD18 mAb on PMN-EC adhesion and endothelial cell (EC) damage induced by PMN. Adhesive rate between PMN and EC, the filtration coefficient (kf) and monolayer volume flux (Jv) were determined after incubating burn patient's PMN with human umbilical vein endothelial cell (HUVEC) for 24 hours. CD11a/CD18 monoclonal antibodies (mAb) and CD11b/CD18 mAb were used to pretreat burn patient's PMNs in order to demonstrate the role of CD11/CD18 in PMN-EC adhesion and EC damage. Expressions of CD11a/CD18 and CD11b/CD18 were determined by flow cytometry 1, 3, 5, 7 d postburn. The results indicated that expressions of CD11a/CD18 and CD11b/CD18 on burn patient's PMNs increased quickly, reaching the peak on day 1 postburn and remained in high level till 7 days postburn. The values of Kf and Jv were increased markedly after burn patient's PMNs was incubated with HUVECs, which were cultured on micropore filter membrane. When burn patient's PMNs were pretreated with CD11a/CD18 mAb and CD11b/CD18 mAb, PMN-HUVEC adhesive rate was inhibited by 70%-80% and the values of Jv and kf were decreased significantly. It suggested that there were increased expressions of CD11a/CD18 and CD11b/CD18 on PMNs after burn injury. Burn patient's PMNs could damage EC and increased EC monolayer permeability (kf, Jv). CD11/CD18 mAb inhibited PMN-EC adhesion and attenuated EC damage induced by PMNs.

Adolescent↗
PubMed1997

[Fully length MDR1 cDNA transfer conferring resistance to adriamycine on sensitive cells GLC].

Human lung cancer leads the mortality of cancers and the chemotherapy is often uneffective because of drug resistance. In order to study the role of mdr-1 gene in resistant lung cancer, the fully length mdr-1 cDNA was transferred into a sensitive lung cancer cell line GLC. The mdr-1 cDNA was constructed in a retroviral vector, pDORneo. The transfection of recombinant plasmid was carried out by lipofectin. Supernatant containing infective viruses derived from a G418 resistant clone of package cell PA317 was used to infect GLC cell which is sensitive to chemotherapeutic agents. After G418 and adriamycine selections, three P-glycoprotein positive clones were isolated and the integration of mdr-1 cDNA was demonstrated by PCR of genomic DNA. The relative resistance of 3 clones to adriamycine as and elevated by 5.4, 6.0 respectively 7.8 times compared with the untransfected cell and the transcription of mdr-1 gene in these transfected cells as obviously enhanced by in situ hybridization. This results suggest that the mdr-1 gene plays a role in increasing drug resistance of human lung cancer.

Adenocarcinoma↗
PubMed1997

[Limb salvage and amputation in osteosarcoma: report of 31 cases].

Three different types of operation were performed in 31 osteosarcoma patients, and some cases received chemotherapy. It revealed, wide resection of tumor supplemented with chemotherapy improved the survival and limb salvage rate enormously. Chemotherapy and wide resection were all absolutely essential. The life of prosthesis was long and most patients were satisfied with it. Chemotherapy and limb salvage can enhance the survival and life quality in patients with osteosarcoma.

Adolescent↗
PubMed1997

[Chemical constituents of fructus Amomi].

Seven compounds have been isolated from Fructus Amomi. They were identified as bornyl acetate, camphor, borneol, beta-sitosterol, vanillic acid, stearic acid and palmitic acid. The vanillic acid was found in this medicine for the first time. Fifty-seven components were identified from the volatile oil of Fructus Amomi on the basis of GC-MS analysis. Eight components in the volatile oil over 1% in content are bornyl acetate, camphor, borneol, limonene, camphene, myrecene, carene-3 and alpha-terpeneol.

Drugs, Chinese Herbal↗
PubMed1997

[The effect of the mold temperature on the mechanical properties and reaction layer structure of the titanium castings].

Titanium is very reactive at the high temperature, easily oxidized, and reacts with investment components. The mold temperature is an important factor on the quality of the titanium castings. The paper investigated the effect of the mold temperature on the mechanical properties and reaction layer structure of the titanium castings with the tensile test and modern surface analysis technique. The results indicated that the tensile strength and yield strength of titanium castings increased but elongation rate decreased, and the hardness layer become thicker when the mold temperature raised. The hardness layer of titanium castings was 50 microns for the room temperature mold, 125 microns for the 850 degrees C mold. SX-macro electric probe analysis indicated the spreading depth of Zr, Al elements on the surface of titanium castings was not increased when the mold temperature raised, but, the spreading depth of Si element became deeper on the surface of titanium casting, Si layer was about 30 microns for the room temperature mold, 40 microns for the 250 degrees C mold, 50 microns for the 450 degrees C mold, 70 microns for the 650 degrees C mold, 90 microns for the 850 degrees C mold. So, it is necessary to consider the effect of the mold temperature on the qualities of titanium castings when titanium castings for prosthodontics were made in clinic.

Dental Casting Technique↗
PubMed1997

[The influence of teeth positions to lower complete denture retention and health of supporting tissues].

Three kinds of three dimension finite element models of edentulous mandibile and the complete denture were established to investigate the influence of artificial teeth positions to denture retention and the supporting tissue. Ten myodynamic and traditional complete dentures were constructed to compare the difference of artificial teeth positions to alveolar ridge. The results indicated: 1. The stress was not obvious different in mandible when teeth were placed over the crest of the ridge or moved lingually or buccally to the ridge in 3 mm; 2. Under occlusion force, it was beneficial for the lower supporting tissue with artificial molars being placed over the slope of mandible and beneficial for denture retention with molars teeth being placed on the crest of ridge buccally; 3. With the effects of oral muscles, the teeth on the crest of ridge buccally or lingually in 3 mm in molar and premolar regions were respectively available; 4. There were obvious difference in arch width of artificial teeth arrangement between traditional and myodynamic complete dentures, the arch was wider in myodynamic complete denture than that of traditional complete denture at molar region.

Denture Retention↗
PubMed1997

[Fabrication and use of two kinds of overdenture attachments].

The authors introduced the fabrication of stud attachment and bar attachment used to increase the stability and retention of overdenture. During two years' periods, the results of the clinical practice indicated: the retention of overdenture was increased and patients' masticator function was improved when attachments were used, and then the fabrications of two kinds of attachments were simple and value of attachments is cheap. The technique was popularized and used easily.

Denture Precision Attachment↗
PubMed1997

[Effect of stud attachment post design on dentin stress distribution].

The shape design of attachment post is crucial factors influencing post retention and stress distribution to the dentin. By means of CAD and FEA, the present study investigated the effects of the shape designs of attachment posts on the stress distribution in dentin. The results indicated that the taper post had wedging effects on the dentin and produced higher Von Misses stress than that of parallel side post and the Von Misses stress value of the dentin was about 1.1 times. The maximum Von Misses stress value that the design of the thread post produced was about 1.06 times the stress of the nonthread post did. However, the effects of post design on the dentin were minor compared with the bite force directions. In the same post design, the maximum Von Misses stress in dentin with 45 degree oblique force was about 2.1 times with vertical force. Therefore, reducing oblique force is the main method to prevent root fracture in clinic.

Computer-Aided Design↗
PubMed1997

[Pharmacological study of cholagogic capsule].

Cholagogic capsule is mainly composed of Fiuctus Cardui, Mariae, Oleum Menthae Piperilae, Radix Currmae, olia taraxaci, Oleum Hyperici. It is shown that Cholagogic Capsule increase the rat's bile secretion significantly, but bile component is not influenced effectively, the retention jaundice models of which are created by ANIT isn't influenced effectively. It can reduce the mouse pinna swelling caused by dimethythenzene and depress the metatarsal swelling induced by carragenin, the antiinflammatory effect keeps for more than 4 h. It inhibits the contraction of gallbladder smooth musele of Guinea Pig caused by Ach. The results show that cholagogic Capsule increase bile secretion, antispasmodic and antiinflammatory effect. It is suggested the therapeutic effects of Cholagogic Capsule in sand-like calcul and acute chronic cholecystitis are related to the above pharmaological effects.

Animals↗
PubMed1997

Steroidogenic factor 1 plays multiple roles in endocrine development and function.

The nuclear hormone receptor family comprises a group of structurally related transcriptional regulators that mediate the actions of diverse ligands, including steroid hormones, thyroid hormone, vitamin D, and retinoids. The nuclear receptor family also contains members for which activating ligands have not been identified-the orphan nuclear receptors. One of these orphan nuclear receptors, steroidogenic factor 1 (SF-1), has emerged as an essential regulator of steroidogenic cell function within the adrenal cortex and gonads; SF-1 also plays important roles in reproduction at all three levels of the hypothalamic-pituitary-gonadal axis. First identified as a tissue-specific regulator of the transcription of the cytochrome P450 steroid hydroxylases, considerably broader roles for SF-1 were revealed by genetic studies in mice lacking SF-1 due to targeted gene disruption. These SF-1-knockout mice had agenesis of their adrenal glands and gonads, male-to-female sex reversal of their internal and external genitalia, impaired gonadotrope function, and agenesis of the ventromedial hypothalamic nucleus. These studies delineated essential roles of SF-1 in regulating endocrine differentiation and function at multiple levels. Despite these insights into roles of SF-1, the precise mechanisms by which SF-1 exerts its multiple effects remain to be determined. This review highlights experiments that have established SF-1 as a pivotal determinant of endocrine differentiation and function and identifies areas in which additional studies are needed to expand our understanding of SF-1 action.

Animals↗
PubMed1997

Effects of dobutamine, epinephrine and norepinephrine on the hemodynamics of dogs during hemorrhagic shock.

BACKGROUND: The present study examined how effective epinephrine (EPI), norepinephrine (NOR) and dobutamine (DOB) were for resuscitating dogs subjected to hemorrhagic shock (HS). METHODS: Dogs (n = 42) were randomly assigned to seven test groups: EPI, NOR and DOB infusion with and without HS, and HS dogs with no catecholamine. Following baseline measurements, the dogs were bled to a mean arterial blood pressure of 40 mmHg. After 3 h, the shed blood was reinfused. EPI and NOR (0.1, 0.4 and 1.6 micrograms/kg/min) and DOB (2.5, 5.0 and 10.0 micrograms/kg/min) were given and the dog allowed to stabilize for 30 min. Hemodynamic and blood gas data were obtained at 6 time points (control, shock, resuscitation and after catecholamine infusion). RESULTS: There was no significant difference in myocardial performance (dP/dt) between the respective shocked and unshocked groups after blood resuscitation. In dogs without catecholamine infusion, CO and SvO2 continued to decline whereas SVR increased. DOB (2.5 to 10.0 micrograms/kg/min) with and without shock improved CO, LV dP/dt, SVR and SvO2. EPI did not further improve CO or SvO2 at infusion rates above 0.1 microgram/kg/min (with and without shock). NOR did not improve SvO2 at any infusion rate (with and without shock) and did not improve CO until the infusion rate was at 0.4 microgram/kg/min (without shock). CONCLUSIONS: This study advocates the use of both volume replacement therapy and DOB for resuscitation of HS dogs.

Animals↗