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Biomedical subjects

X Luo

Publications and source records attributed to X Luo.

At least 199 records · Page 11Linked to original sources
PubMed1997

[Effects of CD11/CD18 antibody on adhesive force between polymorphonuclear neutrophil and endothelial cell in response to burn serum in vitro].

UNLABELLED: Our previous studies have proved that a great number of polymorphonuclear neutrophils (PMN) adhered to endothelial lining and induced endothelial cell (EC) injury. This study was attempted to investigate the change in adhesive force between PMN and EC in response to burn patients' serum within 24 hours and effects of antibody against CD11/CD18 on PMN-EC adhesive force. Burn serum was isolated from 4 burn patients (III degrees 20%-50% TBSA) within 48 hours after burn injury. PMNs were isolated from 8 volunteers. Adhesive force between a PMN and a HUVEC was calculated by means of micropipette technique at 1 h, 3 h, 6 h, 12 h, 24 h after PMN or HUVEC incubated with burn serum or normal serum. Five individual PMN-HUVEC pairs were measured for each sample. All data were analyzed statistically using the t test. RESULTS: 1. The adhesive force between a single PMN-HUVEC pair increased sharply after PMN incubated with burn serum, which reached the maximun level at 1 h after incubation and remained at this level in the following 23 hours. However, the adhesive force was reduced by 78.5%, 72.5%, 75.2% at 1 h, 6 h, 24 h, respectively after the PMNs were pretreated with CD11/CD18 mAb; 2. The adhesive force between a single burn serum stimulated-HUVEC and PMN pair increased gradually, reached peak at 12 h and remained at this level in the following 12 hours. CONCLUSIONS: Burn serum could induce PMN-EC adhesion, with related to PMN aggregation in internal organs and EC damage after burn injury. Antibodies against CD11/CD18 could partially block PMN-EC adhesion and might reduce EC injury induced by activated PMNs.

Adolescent↗
PubMed1997

[Clinical application of modified proportional unit of middle finger to determine the depth for intra-esophageal atrial pacing to stop supraventricular tachycardia].

OBJECTIVE: To determine the location for catheter electrode of intra-esophageal atrial pacing. METHODS: The catheter load was placed at a length eleven times that of the modified proportional unit of middle finger for intra-esophageal atrial pacing to stop the supraventricular tachycardia of 21 patients. RESULTS: Ninteen of them showed remarkable effect and 2 were effective. Tachycardia of all the patients was stopped, symptoms and signs such as chest distress, palpitation relieved and the blood pressure normalized. CONCLUSION: This is an accurate localization, rapid, convenient method with remarkable effects, it is a new way in rescuing supraventricular tachycardia patients.

Adolescent↗
PubMed1997

Efficacy of systemic administration of irinotecan against neuroblastoma xenografts.

The efficacy of the topoisomerase I inhibitor 7-ethyl-10-(4-[1-piperidino]-1-piperidino)-carbonyloxy-camptotheci n (irinotecan, CPT-11) has been examined against a panel of six independently derived neuroblastoma xenografts. Intensive courses of therapy, where irinotecan was administered i.v. daily 5 days per week for two consecutive weeks [(dx5)2; defined as 1 cycle], were compared to more protracted low-dose schedules where cycles were repeated every 21 days for a total of three courses ¿abbreviated [(dx5)2]3¿. When administered (dx5)2 for a single cycle, the maximum tolerated daily dose was 40 mg/kg. Irinotecan induced a high frequency of complete regressions (CRs) in four of the six lines examined; however, most tumors achieving CR regrew during the period of observation (12 weeks). Furthermore, there was no advantage in high-dose regimens as compared to low dose (10 mg/kg) on the same schedule. Protracted schedules of administration, where three courses of therapy were given at 21-day intervals ¿[(dx5)2]3¿ i.v. were examined at 10 and 5 mg/kg/dose. Even at the lower dose level, irinotecan caused 100% CR in all tumor lines that were maintained at 12 weeks. To determine the minimum dose levels required to induce objective regressions of neuroblastoma xenografts, decreasing doses were examined using the [(dx5)2]3 i.v. schedule. At 2.5 mg/kg/dose, >90% of NB-1643, NB-1691, NB-1382.2, and NB-EB xenografts demonstrated CR, whereas at 1.25 mg/kg/dose, all six tumor lines evaluated demonstrated objective regressions (>/=50% volume reduction), with a high frequency of CRs in four tumor lines. The 10-hydroxy-7-ethyl CPT lactone single-day systemic exposure measured with the minimum dose (2.5 mg/kg) associated with complete response was 198, 257, and 228 ng.h/ml for mice bearing NB-1643, NB-1691, and NB-EB tumors, respectively. These results indicate that childhood neuroblastoma xenografts are highly sensitive to irinotecan given by parenteral administration, and that efficacy is schedule dependent.

Animals↗
PubMed1997

[Homology analysis of RubisCO gene of Thiobacillus versutus with extremelly acidophilic thiobacilli].

The chromosomal DNA of Thiobacillus thiooxidans and T. versutus was digested with restriction enzymes, blotted to nylon membrane by the way of Southern, and hybridized with the gene probe of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) from T. ferrooxidans. The result showed that T. thiooxidans exhibited high homology with the probe anc T. versutus was less homology with it. However T. versutus can hybridize with the gene probe of RubisCO from Rhodobacter sphaeroides, which indicated that they had high homology with each other. As RubisCO was highly reserved in the evolutionary, they should be divided into different group.

DNA, Bacterial↗
PubMed1996

DNA index of glial tumors in children. Correlation with tumor grade and prognosis.

BACKGROUND: Although DNA index (DI) has prognostic significance in a variety of pediatric malignancies, there are few data regarding its utility in central nervous system (CNS) tumors. We have previously shown that patients with hyperdiploid medulloblastoma have a significantly better survival than those whose tumors are diploid. Here, we examine the effect of DI and tumor grade on the progression free survival (PFS) of 57 patients with a variety of glial neoplasms. METHODS: DI was determined by flow cytometry on freshly obtained tumor tissue from the initial diagnostic specimens; a DI = 1.0 was defined as diploid (DIP), 1.0 < DI < 1.1 as near diploid (NDIP), and DI > 1.1 as hyperdiploid (HYP). Tumors were histologically graded according to the World Health Organization classification. RESULTS: There were 21 Grade I tumors, 20 Grade II, 8 Grade III, and 8 Grade IV. Among the 41 low grade tumors (Grade I-II), 39 were DIP or NDIP, and 2 were HYP. Among the 16 high grade tumors (Grade III-IV), 9 were DIP, 2 NDIP, and 5 HYP. The 4-year PFS of low grade tumors was 70% (standard deviation [SD] 12%) versus 8% (SD 7%) for high grade tumors. There was a significant correlation between low grade tumor histology and a DIP/NDIP DI (P = 0.015), and univariate analysis suggested improved PFS was associated with DIP/NDIP tumors (P = 0.05). However, DI did not remain a significant prognostic factor after being stratified by tumor grade (P = 0.87). CONCLUSIONS: Unlike medulloblastoma, DI is not an independent prognostic factor in pediatric glial tumors.

Adolescent↗
PubMed1996

Antiproliferative properties of the USF family of helix-loop-helix transcription factors.

USF is a family of transcription factors characterized by a highly conserved basic-helix-loop-helix-leucine zipper (bHLH-zip) DNA-binding domain. Two different USF genes, termed USF1 and USF2, are ubiquitously expressed in both humans and mice. The USF1 and USF2 proteins contain highly divergent transcriptional activation domains but share extensive homologies in the bHLH-zip region and recognize the same CACGTG DNA motifs. Although the DNA-binding and transcriptional activities of these proteins have been characterized, the biological function of USF is not well understood. Here, focus- and colony-formation assays were used to investigate the potential involvement of USF in the regulation of cellular transformation and proliferation. Both USF1 and USF2 inhibited the transformation of rat embryo fibroblasts mediated by Ras and c-Myc, a bHLH-zip transcription factor that also binds CACGTG motifs. DNA binding was required but not fully sufficient for inhibition of Myc-dependent transformation by USF, since deletion mutants containing only the DNA-binding domains of USF1 or USF2 produced partial inhibition. While the effect of USF1 was selective for Myc-dependent transformation, wild-type USF2 exerted in addition a strong inhibition of E1A-mediated transformation and a strong suppression of HeLa cell colony formation. These results suggest that members of the USF family may serve as negative regulators of cellular proliferation in two ways, one by antagonizing the transforming function of Myc, the other through a more general growth-inhibitory effect.

Animals↗
PubMed1996

Alveolar soft part sarcoma in children and adolescents: clinical features and outcome of 11 patients.

The clinical features and response to therapy of pediatric alveolar soft part sarcoma, a rare soft tissue sarcoma of uncertain histogenesis, have not been previously described in detail in the literature. We retrospectively reviewed the clinical characteristics of all patients with alveolar soft part sarcoma who were seen at our institution over a 32-year period. We found 11 patients with the diagnosis of alveolar soft part sarcoma. Their ages ranged from 2.8-16 years (median 9.8). Staging was determined using the Intergroup Rhabdomyosarcoma Study clinical grouping system and the UICC TNM system. Accordingly, there were six patients with grossly resected tumors (clinical groups I and II) and five with unresected or metastatic disease (clinical groups III and IV). Children with resected disease were more likely to have smaller noninvasive tumors. The main feature predictive of survival was tumor resectability, since chemotherapy in various combinations failed to produce significant tumor responses. Nine patients are disease-free with a median follow-up of 11.9 years. Surgical resection remains the mainstay of therapy for pediatric alveolar soft part sarcoma. Since active chemotherapy agents have not been identified, patients with unresected or metastatic disease may benefit from experimental agents. The survival rate of this cohort is superior to that seen in adults.

Adolescent↗
PubMed1996

Outcome in 43 children presenting with metastatic Ewing sarcoma: the St. Jude Children's Research Hospital experience, 1962 to 1992.

The purpose of this work was to review the St. Jude Children's Research Hospital experience of patients presenting with metastatic Ewing sarcoma over a 30-year period. Forty-three of 212 cases of Ewing sarcoma presented with metastases at diagnosis. These patients were analyzed to determine whether primary tumor site or size, metastatic site(s), or advances in therapy have had a positive impact on survival. The overall survival for our 43 patients was 35% (95% confidence intervals, 20% to 50%). Comparing patients treated prior to 1979 with those treated after 1979, the overall survival was significantly different (P = 0.0002). Comparing overall survival between pelvic and non-pelvic primaries (P = 0.24), among metastatic sites (P = 0.83), and between tumors measuring > 8 cm in diameter to tumors measuring < 8 cm in diameter (P = 0.12), no significant differences were observed. Approximately one-third of patients presenting with metastatic Ewing sarcoma may achieve long-term survival. Children with metastatic Ewing sarcoma may benefit from clinical trials which intensify the doses of doxorubicin, and the highly effective combination of ifosfamide/etoposide.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Role of irradiation in management of synovial sarcoma: St. Jude Children's Research Hospital experience.

The role of irradiation in the management of synovial sarcoma (SS) in pediatric patients is evaluated. The review covers all children seen at St. Jude Children's Research Hospital between May 1969 and December 1992 with the diagnosis of soft tissue sarcoma, of the 37 patients with the subtype SS, 16 received irradiation for the management of primary site disease. There were four IRS Group I, six Group II, four Group III, and two Group IV patients receiving irradiation. Tumor grade included seven Grade II, and nine Grade III lesions. TMN staging identified eight T1 and eight T2 lesions. Follow-up has ranged from 14 to 117 months (med = 33 months). All IRS Group I patients had documented local control. Five of six IRS Group II and 4/4 Group III patients have had documented local control at last follow-up. IRS Group IV patients had either local control tumor stabilization (n=1) or evidence of tumor regression (n=1) at autopsy. Complications following irradiation include wound dehiscence (n=1), surgery to revise a painful scar (n=1) extremity length discrepancy (n=2), and femoral head avascular necrosis (n=1). At last follow-up, 10 of 14 patients receiving curative intent irradiation remain alive. This review indicates questionable benefit to the addition of irradiation for patients with adequate surgical resection and having "good" tumor characteristics (Grade I, II; IRS Group I, TMN T1A,T1B. For lesions that have had incomplete resection or partial response to chemotherapy, there is evidence that irradiation may provide durable local control. The role of irradiation in those patients with IRS Group IV disease is at present confined to palliative roles until the time when more effective chemotherapy will mandate the decision to treat primary disease for curative measures.

Adolescent↗
PubMed1996

Response of pediatric malignant solid tumors following ifosfamide or ifosfamide/carboplatin/etoposide: a single hospital experience.

One hundred thirty-eight pediatric patients have received treatment for malignant solid tumors with ifosfamide with mesna, and 71 have received a combination with ifosfamide/carboplatin/etoposide (ICE). Responses were obtained in many types of pediatric tumors, yet comparison of responses was not possible because of inadequate numbers of tumors of differing histiotypes. Comparison of results between patients with all tumors treated with ifosfamide or ICE indicated that there was a higher response rate for patients treated with ICE, with an estimated odds ratio of 2.74 (95% C.I. 1.45-5.179). Excluding patients without prior chemotherapy and radiotherapy, the odds ratio for 2.801 (95% C.I. 1.45-5.4) suggests a similar result. There remain no guarantees that the more costly treatment with ICE, which requires cytokine support, will offer therapeutic benefits against resistant solid tumors.

Antineoplastic Agents, Alkylating↗
PubMed1996

In vitro study of the metabolic effects of D-amino acids.

While the L-configuration of amino acids predominates in all known living systems, D-enantiomers of amino acids have been detected with highly sensitive chromatographic techniques in human physiological fluids. In the present study, the survival of Chinese hamster ovary cells (CHO) and HeLa cells was inhibited by exposure to high concentrations of some D- or L-amino acids. Inhibition of colony formation, though, was not necessarily observed to be chiral-dependent. Some L-amino acids (LAAs) were found to be toxic while other D-amino acids (DAAs) were innocuous in both cultures. This is contradictory to the previous observations that DAAs were generally considered to be harmful. Frequently it was implied, although not experimentally proven, that the LAAs were not toxic. One of the metabolites produced by oxidative deamination of D- or LAAs is hydrogen peroxide (H2O2), a reactive oxygen species (ROS) that is decomposed by catalase. Increased intracellular H2O2 can result in peroxidation of lipids. We measured catalase activity and the lipid peroxide levels (LPO) after incubating cells in either D- or LAAs. The amino acids (AAs) that were found to inhibit colony formation were found to be associated with higher levels of catalase activity and LPO. Therefore, we hypothesize that enhanced ROS generation may be, in part, responsible for the observed toxicity of some amino acids.

Amino Acids↗
PubMed1996

Evaluation of Bacillus thuringiensis and Bacillus sphaericus Strains from Chinese Soils Toxic to Mosquito Larvae

During our research to isolate and screen microbial agents, eight Bacillus thuringiensis isolates and five Bacillus sphaericus isolates were shown to have high toxicity to mosquito larvae. Comparing the LC50 values, four B. sphaericus isolates with LC50 values ranging from 0.50 to 1.47 ng/ml were about two to six times more toxic than strain 1593 (LC50 3.00 ng/ml) against larvae of Culex quinquefasciatus. Four B. thuringiensis isolates (LC50 values ranging from 3.80 to 7.54 ng/ml) and four B. sphaericus isolates with LC50 of 17.0 to 43.7 ng/ml were more toxic to Aedes aegypti than strain 1897 (LC50 8.46 ng/ml) and strain 1593 (LC50 67.3 ng/ml). As to Anopheles hyrcanus, the LC50 values of three B. sphaericus isolates ranging from 3.63 to 5.73 ng/ml were three to five times smaller than that of strain 1593 (LC50 16.1 ng/ml). Two B. sphaericus isolates showed high toxicity against mosquito larvae in the three genera Culex, Aedes, and Anopheles.

Journal Article↗
PubMed1996

HCN, a triple-resonance NMR technique for selective observation of histidine and tryptophan side chains in 13C/15N-labeled proteins.

HCN, a new 3D NMR technique for stepwise coherence transfer from 1H to 13C to 15N and reverse through direct spin couplings 1JCH and 1JCN, is presented as a method for detection and assignment of histidine and tryptophan side-chain 1H, 13C, and 15N resonances in uniformly 13C/15N-labeled proteins. Product-operator calculations of cross-peak volumes vs adjustable delay tau 3 were employed for determination of optimal tau 3. For the phosphatidylinositol 3-kinase (PI3K SH3 domain, MW = 9.6 kD) at pH 6, H(C)N, the 1H/15N projection, produced observable cross peaks within 20 min. and was completely selective for the single tryptophan and single histidine. The 3D HCN experiment yielded well-defined cross peaks in 20 h for the 13C/15N-labeled origin-specific DNA binding domain from simian virus 40 T-antigen (T-ag-OBD131-259, MW = 15.4 kD) at pH 5.5. Resonances from all six histidines in T-ag-OBD were observed, and 11 of the 12 1H and 13C chemical shifts and 10 of the 12 15N chemical shifts were determined. The 13C dimension proved essential in assignment of the multiply overlapping 1H and 15N resonances. From the spectra recorded at a single pH, three of the imidazoles were essentially neutral and the other three were partially protonated (22-37%). HCN yielded strong cross peaks after 18 h on a 2.0 mM sample of phenylmethanesulfonyl fluoride (PMSF)-inhibited alpha-lytic protease (MW = 19.8 kD) at pH 4.4. No spectra have been obtained, however, of native or boronic acid-inhibited alpha-lytic protease after 18 h at various temperatures ranging from 5 to 55 degrees C, probably due to efficient relaxation of active-site imidazole 1H and/or 15N nuclei.

1-Phosphatidylinositol 4-Kinase↗
PubMed1996

The roles of steroidogenic factor-1 in reproductive function.

The cytochrome P450 steroid hydroxylases are expressed in a tissue-specific and developmentally regulated manner, and the orphan nuclear receptor steroidogenic factor 1 (SF-1) participates in both aspects of regulated expression. SF-1 is expressed in mouse embryos from the inception of adrenal and gonadal development, suggesting that SF-1 plays important roles in their differentiation. SF-1 is also expressed in the embryonic pituitary gland and ventral diencephalon, suggesting additional roles within the hypothalamic-pituitary-steroidogenic organ axis. To examine the roles of SF-1 in vivo, we used targeted gene disruption to "knock out" the mouse gene encoding SF-1. Analyses of these knockout mice established roles of SF-1 at levels of endocrine development that include adrenal and gonadal differentiation, pituitary gonadotrope function, and formation of the ventromedial hypothalamic nucleus. These results indicate that SF-1 plays multiple roles in endocrine development that are essential for reproduction.

Adrenal Glands↗
PubMed1996

Solution structure of the origin DNA-binding domain of SV40 T-antigen.

The structure of the domain from simian virus 40 (SV40) large T-antigen that binds to the SV40 origin of DNA replication (T-ag-OBD131-260) has been determined by nuclear magnetic resonance spectroscopy. The overall fold, consisting of a central five-stranded antiparallel beta-sheet flanked by two alpha-helices on one side and one alpha-helix and one 3(10)-helix on the other, is a new one. Previous mutational analyses have identified two elements, termed A (approximately 152-155) and B2 (203-207), as essential for origin-specific recognition. These elements form two closely juxtaposed loops that define a continuous surface on the protein. The addition of a duplex oligonucleotide containing the origin recognition pentanucleotide GAGGC induces chemical shift changes and slows amide proton exchange in resonances from this region, indicating that this surface directly contacts the DNA.

Amino Acid Sequence↗
PubMed1996

Genetic polymorphisms of debrisoquine and S-mephenytoin oxidation metabolism in Chinese populations: a meta-analysis.

Chinese data on the polymorphic metabolism of debrisoquine, metoprolol, codeine and mephenytoin were collected and re-analysed using a meta-analysis method. There were no significant differences in the incidences of poor metabolizer (PM) between the separate series of debrisoquine, metoprolol and codeine, which are the three probe drugs reflecting the same enzyme polymorphism. PMs were detected at low frequencies for debrisoquine (1.20%; 95% confidence interval, CI: 0.67-1.98%), metoprolol (0.72%; CI: 0.29-1.49%) and codeine (0.48%, CI: 0.01-2.68%). The overall estimate of PM was 0.95% (CI: 0.60-1.42%) based on the 2427 determinations of all three probe drugs. The overall mean of PM of mephenytoin was 14.32% (12.26-16.38%) in the 1117 subjects. In summary, the present meta-analysis determined the accurate incidences of the genetic deficiency of S-mephenytoin 4'-hydroxylase (cytochrome P450 2C19) and debrisoquine hydroxylase (cytochrome P450 2D6) in Chinese populations.

China↗