Atomic coherence and bistable lasers without inversion.
Explore the source record for details and available documents.
Journal Article↗
Biomedical subjects
X Luo
Publications and source records attributed to X Luo.
Functional domains of the transcription factor USF2: atypical nuclear localization signals and context-dependent transcriptional activation domains.
USF is a family of basic helix-loop transcriptional factors that recognizes DNA-binding sites similar to those of the Myc oncoproteins. Here, various functional domains in the mouse USF2 protein were identified and characterized. Indirect immunofluorescence studies with transiently transfected cells revealed that both the basic region and the highly conserved USF-specific region (USR) are involved in the nuclear localization of USF2. Cotransfection assays with deletion mutants containing the DNA-binding domain of either USF2 or GAL4 identified two distinct transcriptional activation domains in USF2, the USR and the exon 5-encoded region. Activity of the exon 5 activation domain was detectable in both assay systems. Within USF2, however, its potency varied with the conformation induced by the surrounding regions, especially that encoded by alternatively spliced exon 4. In contrast, the USR activated transcription only in its natural context upstream of the USF2 basic region and only with reporter constructs containing the adenovirus major late minimal promoter but not the E1b minimal promoter. However, insertion of an initiator element downstream of the TATA box rescued the activity of the USR on the E1b-driven reporters. The USR therefore represents a new type of activation domain whose function depends very strongly on the core promoter context.
Animals↗
P-glycoprotein expression at diagnosis may not be a primary mechanism of therapeutic failure in childhood rhabdomyosarcoma.
PURPOSE: To evaluate the prognostic significance of tumor cell P-glycoprotein (Pgp) expression at diagnosis in children with rhabdomyosarcoma. PATIENTS AND METHODS: A panel of three anti-Pgp monoclonal antibodies (mAb) (C219, C494, and JSB-1) that recognize different Pgp epitopes was used to measure Pgp expression in rhabdomyosarcoma specimens obtained at diagnosis from 76 patients treated at St Jude Children's Research Hospital from 1969 to 1991. Two separate experiments using different immunohistochemical methods (immune alkaline phosphatase and immunoperoxidase) were performed to evaluate Pgp expression. The immunostaining was graded using a semiquantitative scale corresponding to the percentage of tumor cells with detectable staining. The influence of Pgp expression on outcome was assessed by the Kaplan-Meier method and Cox regression analysis with stepwise selection. The relationship between Pgp expression and clinical features was assessed using the Mantel-Haenszel method. RESULTS: Pgp expression at diagnosis did not predict worse overall survival or progression-free survival when tested in either experiment with C219, C494, or JSB-1 separately. No association was shown between Pgp expression and clinical features (clinical group, primary site, or histology) or response. However, in the immune alkaline phosphatase experiment, patients whose tumors had more than 10% tumor cell staining with all three mAbs had a significantly higher rate of estimated 5-year survival (78% +/- 10%) than did all other patients (38% +/- 8%; P = .025). In this instance, Pgp expression had independent prognostic value after adjusting for clinical group. CONCLUSION: We found no strong association between Pgp expression at diagnosis and clinical features or extent of disease in pediatric rhabdomyosarcoma. Depending on the criteria used to define it, high Pgp expression at diagnosis does not predict poor outcome. Although a large prospective study is needed to provide definitive conclusions, our findings suggest that Pgp-mediated multidrug resistance may not be a primary mechanism of therapeutic failure in rhabdomyosarcoma.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
The amplification and expression of MDR1 gene in adriamycine resistant cell line of colon cancer cell HR8348.
P-glycoprotein plays an important role in highly drug resistant cells. But its high expression cannot be achieved by chemotherapy. In order to study the effect of P-glycoprotein on clinical tumors, we established a low ADM resistant colon cancer cell line HR/ADM and determined the amplification and expression of mdr-1 gene. The GLC/ADM showed a resistant pattern similar to classical MDR and the transcription of mdr-1 gene determined by RT-PCR increased. The immunocytochemical analysis showed strong positive staining with monoclonal antibody. The gene amplification of mdr-1 was clearly demonstrated by southern blot. Our results suggested that moderate expression of P-glycoprotein might be enough for a high resistant pattern.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Evaluation of irinotecan in combination with 5-fluorouracil or etoposide in xenograft models of colon adenocarcinoma and rhabdomyosarcoma.
Irinotecan [7-ethyl-10-(4-[1-piperidino]-1-piperidino)-carbonyloxy-camptothec in] administered i.v. in two courses, each course consisting of administration every day for 5 days [(dx5)2] on days 1-5 and 8-12, has demonstrated significant activity against advanced human tumor xenografts derived from colon adenocarcinomas and several childhood cancers. To build on this therapy, we have evaluated the combination of irinotecan given on this schedule with 5-fluorouracil given on days 1, 7, and 14 with or without leucovorin [(dx5)3 i.v.] against colon tumors, or combined with etoposide administered (dx5)2 i.v. either 2 h before or 2 h after irinotecan for treatment of colon tumors and rhabdomyosarcomas. A combination of 5-fluorouracil at 75% and irinotecan at 50% of their respective maximum tolerated doses when administered as single agents on this schedule gave acceptable toxicity. Against colon adenocarcinoma xenografts, 5-fluorouracil did not enhance the response rate compared with that obtained with the optimum dose of irinotecan given as a single agent. Against GC3/TK- xenografts, which lack thymidine kinase and cannot salvage thymidine to circumvent the inhibition of thymidylate synthase, the addition of leucovorin to the combination increased the complete response rate from 10 to >90%, whereas the response rates for the optimal doses of irinotecan or 5-fluorouracil, as single agents, were 30 and <10%, respectively. Etoposide d x 5 i.v. for two or three courses or (d x 5)3 p.o. did not cause objective regression of any colon tumors. In contrast, three of five rhabdomyosarcoma lines demonstrated a high frequency of partial regressions or complete regressions when treated (d x 5)1 i.v. Repetitive courses [e.g., (d x 5)2 or (d x 5)3] i.v. or p.o. or by 4-h infusion d x3 i.v. were either equally effective or less effective. Irinotecan and etoposide were combined using the (d x 5)2 i.v. schedule for both drugs, in which irinotecan was given 2 h before or 2 h after the administration of etoposide. Each drug could be combined at only 38% of its respective maximum tolerated dose when administered as a single agent, indicating greater than additive toxicity. Toxicity was similar irrespective of the sequence of administration and was manifested by loss of weight (73% of the initial weight, nadir day 7), myelosuppression, and prolonged thrombocytopenia. The responses of colon carcinomas to the combination given in either sequence were similar to that achieved with irinotecan given alone at the same dose as used in the combination. Similarly, when etoposide was given before irinotecan, the responses of rhabdomyosarcomas were similar to those for irinotecan. However, in experiments in which etoposide was administered 2 h after each dose of irinotecan, there was significant antagonism of the antitumor activity of irinotecan.
Adenocarcinoma↗
[Study on major metabolites of 3H-1,2-dihydro-2-(4-methylphenylamino)-methyl-1-pyrrolizinone in rabbits].
The metabolites of a 750 mg oral dose of Z-47 [3H-1, 2-dihydro-2-(4-methylphenylamino) methyl-1-pyrrolizinone], a new anti-inflammatory and analgesic agent, in rabbit urine were separated and detected with high performance liquid chromatographic method. On basis of the chromatographic behavior of Z-47 metabolites and biotransformation pathways of drugs with partial structure of Z-47, the carboxylic derivative of Z-47 [4-(3H-1, 2-dihydro-1-pyrrolizinone-2-methylamino) benzoic acid] was proposed as a potential metabolite so that the compound was synthesized. The authentic substance was then compared with one of the metabolites by the chromatographic retention time and the ratio of their UV-absorbances at two wavelengths. The enzyme-hydrolyzed product of another metabolite was also analysed. It was consequently confirmed that the carboxylic derivative of Z-47 and its acyl beta-D-glucuronide are major metabolits of Z-47 in rabbits.
Animals↗
[Effects of 1-(2,6-dimethylphenoxy)-2-(3,4-dimethoxy phenylethylamino) propane hydrochloride on cytosolic free calcium concentration of rabbit platelets].
The effects of 1-(2, 6-dimethylphenoxy)-2- (3,4-dimethoxyphenylethylamino) propane hydrochloride (DDPH) and verapamil on cytosolic free calcium concentration of rabbit platelets were investigated. The results showed that the elevation of cytosolic free calcium concentration ([Ca2+]i) of rabbit platelets following ionophore A23187 was significantly inhibited by DDPH and verapamil. The rates of inhibition with DDPH and verapamil were 58% and 78%, respectively, with no significant difference between the two groups (P > 0.05).
Animals↗
The renin angiotensin system and the stress response.
Explore the source record for details and available documents.
Aldosterone↗
The cell-specific nuclear receptor steroidogenic factor 1 plays multiple roles in reproductive function.
The cytochrome P450 steroid hydroxylases exhibit tissue-specific and developmentally regulated gene expression. Recent studies showed that the orphan nuclear receptor steroidogenic factor 1 (SF-1) plays a key role in their gene regulation. In mouse embryos, SF-1 expression began at the inception of adrenal and gonadal development, suggesting that SF-1 plays a key role in the steroidogenic cell differentiation. SF-1 was also expressed in the developing pituitary gland and diencephalon, which raised the possibility that it also has additional roles in endocrine development. To examine the role of SF-1 in intact mice, we disrupted the gene encoding SF-1 by homologous recombination in embryonic stem cells; this approach ultimately permitted us to generate SF-1 knockout mice in which the gene encoding SF-1 was inactivated. These studies revealed essential roles of SF-1 in endocrine development that included adrenal and gonadal development, expression of several markers of pituitary gonadotropes, and formation of the ventromedial hypothalamic (VMH) nucleus. These results indicate that SF-1 acts at multiple levels of the reproductive axis to maintain reproductive competence.
Adrenal Glands↗
Cloning and characterization of three Aspergillus niger promoters.
An Aspergillus niger (An) genomic library was constructed using the promoter-trap vector, pLX2A, which contains a hygromycin B (Hy) phosphotransferase-encoding gene (hph) for selection of DNA fragments with promoter activity. This library was transformed in Escherichia coli and 80,000 colonies were obtained, 94% of which contained inserts. Transformations of plasmid DNA from the library into An resulted in 53 Hy-resistant (HyR) colonies. Southern blot analysis of 21 transformants confirmed the integration of hph into the An genome. Using the sib selection procedure, three functional promoters, PX6, PX18 and PX21, were identified from this library. Both DNA strands of all three fragments were sequenced and their sequences showed no significant homology to those in the database. Comparison of the sequences of all known promoters from An suggested that C+T-rich stretches are probably important for promoter structures. The promoter activity was analysed further using beta-galactosidase (beta Gal) as a quantitative marker. The results suggest that while PX21 is a much stronger promoter than the known alpha-amylase promoter of A. oryzae, PX6 promotes only weak expression of beta Gal.
Aspergillus niger↗
On the possibility of coherently stimulated recombination and cosmological structure generation: recombination instability.
Possible instabilities during cosmological recombination may produce an epoch of nonlinear density growth and fractal-like structural patterns out to the horizon scale at that epoch (approximately 200 Mpc today). With this motivation, we examine the consequences of the change in effective radiative recombination reaction rate coefficients produced by intense stimulated emission. The proton-electron recombination is considered as a natural laser, leading to the formation of spatially nonuniform distributions of neutral matter earlier than the recombination epoch.
Journal Article↗
On the possibility of coherently stimulated recombination and cosmological structure generation: cosmological consequences.
Given a specific physical mechanism for instabilities during cosmological recombination discussed in an earlier paper, we examine the nonlinear growth of density structures to form fractal-like structural patterns out to the horizon scale at that epoch (approximately 200 Mpc today). A model for such fractal patterns is presented. Such effects could explain observed large-scale structure patterns and the formation of objects at high z, while keeping microwave background anisotropies at the observed minimal levels. We also discuss possible microwave background implications of such a transition and note a potentially observable spectral signature at lambda approximately 0.18 mm as well as a weak line near the peak in the microwave background.
Journal Article↗
mRNA expression of two transmembrane protein tyrosine phosphatases is modulated by growth factors and growth arrest in 3T3 fibroblasts.
Changes in mRNA expression are physiological regulatory mechanisms and frequently deliver important information regarding functions of corresponding gene products. We investigated changes of abundantly expressed mRNAs of two transmembrane protein tyrosine phosphatases, LRP (leukocyte common antigen-related phosphatase) and mRPTP-sigma. The LRP mRNA expression was modulated by platelet derived growth factor (PDGF) treatment and seems to be regulated by PDGF receptor kinase. The expression of mRPTP-sigma mRNA was low in actively cycling cells, like those in the exponential phase of growth or those treated with different growth factors. In cells whose growth was arrested by contact inhibition at high cell density or by serum starvation at low cell density mRPTP-sigma mRNA level increased. The possible implications of these mRNA expression patterns are discussed.
3T3 Cells↗
A phase I study of sulofenur in refractory pediatric malignant solid tumors.
The diarylsulfonylureas have shown promise in xenograft models of childhood cancer. Sulofenur has been evaluated in phase I and II trials in adults with a variety of solid tumors, but the toxicity and maximum tolerated dose of sulofenur in children and adolescents have not been determined. In a phase I study, sulofenur was administered to 13 patients with refractory pediatric malignant solid tumors. Daily dosages of 640, 800, and 960 mg/M2 in two divided oral doses were given for 5 consecutive days each week for 3 weeks. The primary and dose-limiting toxicity was methemoglobinemia, which occurred at all dose levels and required transfusions of packed red blood cells, administration of methylene blue, or both. Anemia and, less frequently, leukopenia and thrombocytopenia were also observed. A maximum tolerated daily dosage was not defined, as methemoglobinemia was noted with each dosage level. There were no measurable tumor responses. The toxicity of this agent makes it unattractive for further investigation in pediatric patients.
Adolescent↗
Pharmacokinetics and pharmacodynamics of 21-day continuous oral etoposide in pediatric patients with solid tumors.
PURPOSE: The objectives of this study were to determine etoposide pharmacokinetics during continuous low-dose oral administration to children with solid tumors and to evaluate the relationships between parameters of etoposide systemic exposure and toxicity. PATIENTS AND METHODS: In this phase I study, children were administered oral etoposide (25 to 75 mg/m2/day) for 21 days as a diluted solution of the intravenous preparation, divided into three equal daily doses. Plasma pharmacokinetics were studied on day 1 of therapy in 18 children and again on day 21 in 14 of these children. Etoposide plasma concentration-time data were fitted to a first-order absorption, two-compartment model with use of bayesian estimation. Pharmacokinetic parameter estimates from day 1 were used to estimate steady-state etoposide systemic exposure in all children. Stepwise multivariate regression was used in an exploratory manner to determine patient, laboratory, or pharmacokinetic predictors of toxicity. RESULTS: Although there was substantial intrapatient variability, there was no difference in the area under the concentration-time curve [AUC(0-8hr)] measured at day 21 compared with the steady-state AUC(0-8hr) estimated from day 1 pharmacokinetic parameters (p = 0.64). Degree of neutropenia was best predicted by the estimated duration that steady-state plasma etoposide concentrations were maintained above 1 microgram/ml (t > 1 microgram/ml) rather than peak plasma concentrations, AUC(0-8hr), dosage, or other patient characteristics. Assuming a bioavailability of the oral solution of approximately 50%, the median etoposide systemic clearance was 21.4 ml/min/m2, a value similar to clearance estimates after intravenous etoposide in pediatric populations. CONCLUSION: We conclude that a parameter reflective of etoposide systemic exposure (t > 1 microgram/ml) correlates more strongly with neutropenia than does dosage or other patient characteristics.
Administration, Oral↗
Infants with metastatic neuroblastoma have improved survival with resection of the primary tumor.
Although infants (age less than 1 year) with neuroblastoma have a favorable overall prognosis, metastatic disease is associated with poorer treatment outcome. To assess the role of surgery in these patients, the authors reviewed survival data for 151 infants treated for neuroblastoma, focusing on patient and tumor characteristics, biological markers, and surgical management among the 99 patients with metastatic disease. Patients were divided into early (1961 to 1978) and contemporary (1979 to 1993) treatment eras. Potential prognostic factors were statistically tested to determine their significance in affecting survival. Five-year survival by Pediatric Oncology Group stage was: A, 100% (+/- 0%); B, 94% (+/- 6%); DS, 77% (+/- 9%); C, 73% (+/- 9%); and D, 61% (+/- 8%). Survival for infants with metastatic disease (stages C, D, and DS) was affected significantly by treatment era (P = .0001). Analyses restricted to patients treated during the contemporary era showed prognostic significance for DNA index (P = .02), N-myc copy number (P = .007), serum lactate dehydrogenase level (P = .001), and extent of resection (P = .01). A > or = 95% resection of the primary tumor was found to be associated with improved survival. Significantly more surgical complications were associated with resections performed at the time of diagnosis (P = .007), and delaying surgery until after several courses of chemotherapy did not decrease survival. In conclusion, multiple factors affect the outcome of treatment for infants with metastatic neuroblastoma, and whenever feasible, a > or = 95% resection of the primary tumor should be performed in this patient subgroup.
Biomarkers↗
A cell-specific nuclear receptor regulates the steroid hydroxylases.
Recent studies of the gene regulation of the cytochrome P450 steroid hydroxylases have established a key role for an orphan nuclear receptor, designated steroidogenic factor 1 (SF-1). SF-1 binds to shared promoter elements upstream of the steroid hydroxylases to mediate their coordinate expression in steroidogenic cells. Analyses of SF-1 expression during mouse embryonic development showed that SF-1 is expressed from the earliest stages of organogenesis of the steroidogenic tissues, suggesting an intimate link between SF-1 and steroidogenic cell differentiation. Finally, in gene disruption experiments, the gene encoding SF-1 was shown to be essential for development of the adrenal glands and gonads. These results establish the essential role of this orphan nuclear receptor in the development and function of the primary steroidogenic tissues.
Adrenal Glands↗