Culture of postimplantation mouse embryos.
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Animals↗
Biomedical subjects
P Martin
Publications and source records attributed to P Martin.
Fast control of DNA replication in response to hypoxia and to inhibited protein synthesis in CCRF-CEM and HeLa cells.
In order to elucidate whether data about the fast regulation of DNA replication in dependence on oxygen supply and on a functioning protein synthesis, previously elaborated with Ehrlich ascites cells, are valid for human cells too, we repeated key experiments with CCRF-CEM and HeLa cells. The most important techniques employed were DNA fibre autoradiography and alkaline sedimentation analyses of growing (pulse-labeled) daughter strand DNA. It was found that CCRF-CEM and HeLa cells responded to transient hypoxia and to transient inhibition of protein synthesis in an almost identical fashion. Scheduled replicon initiations were reversibly suppressed and the progress rates of replication forks, which were already active before the respective inhibitory conditions were established, were reversibly slowed down. The inclusion of the fork progress rate in the response differs from Ehrlich ascites cells, which respond only by suppressing initiation. Further circumstances of the fast oxygen dependent response, concerning the behaviour of ribonucleotide reductase and of the dNTP pools, revealed no significant differences among the three cell lines. The striking identity of the response of each of the cell lines to hypoxia and to inhibited protein synthesis prompts the suspicion that converging fast regulatory pathways act on the cellular replication machinery. The phenomena as such seem to be rather widespread among mammalian cells.
Autoradiography↗
[Therapeutic strategy in stage I seminomas: which lymph node areas are to be irradiated?].
OBJECTIVES: Our aims were to describe the results of adjuvant irradiation given to the paraaortic lymph nodes without pelvic irradiation in patients treated for stage 1 seminoma. MATERIALS AND METHODS: From 1990 to 1997, thirteen patients with stage I testis seminoma have been treated with external beam irradiation to the paraaortic lymph nodes (volume treated: from D10-D11 to L5-S1). The stage was: pT1 in 10 patients, pT2 in 2, pT3 in 1. Median follow-up was 35 months (range: 13-90). RESULTS: Twelve of 13 patients are alive without recurrence. One patient with previous orchidopexy treated for seminoma of the right testis relapsed to the external iliac lymph area. No grade 3-4 adverse event of radiation in the SOMA LENT scale were observed. CONCLUSION: Despite the short number of patients in this series, these results had an impact on our routine practice. External beam irradiation given to the paraaortic lymph nodes is considered the standard adjuvant procedure in our institution.
Adult↗
[Specifics of a dual action: toward new and more effective antidepressants?].
Depression raises numerous questions that are pathophysiological, diagnostic and epidemiological as well as therapeutic. Amongst those questions, antidepressant drugs and their action mechanism(s) remain the subject of many studies in all fields, with a view to enhanced management of patients suffering from mood disorders. Numerous hypotheses both neurobiological and pharmacological have been advanced with respect to the neurochemical mechanisms involved in depressive disease and the neurobiological impact of antidepressants. In addition to the aminergic hypotheses which are currently the best supported, numerous arguments tend to show the value of taking into account the overall function of the brain and no longer only considering a single neuronal system. In this context, the value of a dual specific action on the main two central aminergic systems, the noradrenergic and serotoninergic systems, has now emerged.
Acetylcholine↗
Expression of the microphthalmia-associated basic helix-loop-helix leucine zipper transcription factor Mi in avian neuroretina cells induces a pigmented phenotype.
The microphthalmia gene (mi) appears to be required for pigment cell development, based on its mutation in mi mice. The mi gene encodes a basic helix-loop-helix leucine zipper transcription factor (Mi) with tissue-restricted expression. To investigate the role of mi in cell proliferation and pigmentation, we transfected neuroretina (NR) cells with a recombinant virus expressing the murine mi cDNA. The virus induced the proliferation of chicken NR cells in response to fibroblast growth factor 2, which enabled them to form colonies in soft agar. In contrast to control cultures, transfected chicken NR cells or quail NR cells became rapidly pigmented and strongly expressed the QNR-71 mRNA encoding a melanosomal protein. These results demonstrate that Mi not only acts as pigmentation inducer but is also able to modulate the response of cells to growth factors.
Amino Acid Sequence↗
Hepatitis E virus in end-stage renal disease.
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Comorbidity↗
Plasma estradiol-17beta levels and gonadosomatic index in tench (Tinca tinca L.) reared in natural and controlled conditions.
The plasma estradiol-17beta levels (E2-17beta) and gonadosomatic index (GSI) of female tench (Tinca tinca L.) reared outdoors and indoors were studied from December 1996 to April 1997. Water temperature and daylight were gradually increased (from 10 to 25 degrees C and from 9 to 16 hours per day, respectively) in the indoor group. Animals reared in natural conditions had similar plasma levels throughout the experiment but animals under controlled conditions experienced an increase in these levels in March in relation to previous months (4.81+/-0.73 ng/ml in March vs. 0.29+/-0.03 ng/ml and 0.99+/-0.31 ng/ml in January and February, respectively; P < 0.05) and in relation to animals reared outdoors (4.81+/-0.73 ng/ml vs. 0.47+/-0.19 ng/ml, respectively; P < 0.05). In April, a sharp decrease in estradiol-17beta in these animals was observed, probably associated with the end of vitellogenesis. GSI increased in both groups through the experiment and indoor animals showed greater values in March vs outdoor fishes (7.57+/-2.18 vs. 4.05+/-0.63; P < 0.05). No significant correlation was found between E2-17beta and GSI, (r = 0.35). It is concluded that manipulation of the photoperiod and temperature can modify gonadal development in tench, and this is similar to the situation in other Teleostei species. This research is the first step towards achieving, out of season, spawning in tench.
Animals↗
Hepatitis C infection in patients undergoing liver retransplantation.
BACKGROUND: There is concern that repeat orthotopic liver transplantation in patients with hepatitis C virus (HCV) infection may be associated with poor long-term survival. The specific aims of the current analysis were to determine (1) the prevalence of HCV infection in a large cohort of patients undergoing retransplantation, (2) define the impact of HCV infection on patient survival, and (3) determine the predictors of outcome of HCV-positive patients undergoing retransplantation for graft failure not caused by primary nonfunction. METHODS: We analyzed the United Network of Organ Sharing (UNOS) registry data of 1539 adults undergoing orthotopic liver retransplantation between January 1990 and February 1996; 357 patients (23%) were HCV-positive. RESULTS: The prevalence of HCV infection increased significantly from 6.5% in 1990 to 38.4% in 1995 (P<0.0001). Comparing the HCV-positive versus HCV-negative groups, there were no significant differences with regards to age, time to retransplantation, biochemical parameters immediately preceding retransplantation, UNOS registry status mix, or cause of graft failure (% with primary nonfunction). However, Kaplan-Meier analysis demonstrated significantly diminished survival in the HCV-positive group (P=0.0038, log-rank test; relative risk, 1.36; 95% confidence interval: 1.07-1.71). Multivariate logistic regression analysis of the subgroup of HCV-positive patients undergoing retransplantation for graft failure not caused by primary nonfunction identified preoperative serum bilirubin and serum creatinine as significant predictors of outcome. Seven of 207 (3.4%) patients undergoing retransplantation died of recurrent HCV in their second allografts. CONCLUSION: The prevalence of HCV infection in patients undergoing retransplantation appears to have significantly increased since 1990. HCV infection is an independent risk factor for death after retransplantation. However, acceptable results are attainable in highly selected patients, i.e., those patients without severe hyperbilirubinemia and renal failure, and retransplantation remains the only viable option for patients whose allografts fail because of recurrent disease.
Adolescent↗
Ocular toxicity from ethambutol: a review of four cases and recommended precautions.
AIMS: To document the clinical and demographic features of cases of ethambutol ocular toxicity, to review the literature on this subject and to critically review current guidelines for ethambutol administration. METHODS: Cases of ocular toxicity from ethambutol were sought retrospectively at Green Lane and Wellington Hospitals between 1992 and 1995. The records of cases identified were examined. RESULTS: Four subjects with tuberculosis developed ocular toxicity 2 1/2, 7 1/2, 8 and 12 months after starting ethambutol. Normal visual acuity returned in three cases; one patient has severe, permanent visual impairment. Language difficulties were present in three subjects. CONCLUSIONS: Impaired communication was potentially very important in this series. Special care is needed in educating patients about ethambutol. We propose additional recommendations: 1. the usual daily dose of ethambutol should be 15 mg/kg/day, not 25 mg/kg/day; using 25 mg/kg/day (or lesser doses in the presence of renal impairment) should prompt regular formal ophthalmological evaluation (e.g. monthly) in cases with comprehension or communication difficulties; 3. both ethambutol and isoniazid should be stopped immediately if severe optic neuritis occurs. Isoniazid should be stopped if less severe optic neuritis does not improve within six weeks after stopping ethambutol.
Adult↗
Minimal criteria for placement of adults on the liver transplant waiting list: a report of a national conference organized by the American Society of Transplant Physicians and the American Association for the Study of Liver Diseases.
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Adult↗
Generation of a genetic polymorphism in clonal populations of the bacterium Streptomyces ambofaciens: characterization of different mutator states.
In Streptomyces ambofaciens, colony pigmentation is an unstable character. Very unstable mutants selected from twelve wild type (WT) subclones of S. ambofaciens ATCC23877 were investigated. This research showed that the polymorphism in colony pigmentation had distinct features. The first aspect is the coexistence of four types of colonies: pigmented colonies (Pig+), pigment-defective colonies (Pigcol-), pigmented colonies harboring pigment-defective sectors (Pigsec+) or pigment-defective papillae (Pigpap+). The second feature was revealed by the study on Pigpap+ colonies. We showed that WT progeny after 14 days of growth consisted almost totally of Pigpap+ colonies. Pigpap+ colonies were also found to be genetically different from each other. Characterization of twelve colonies presenting more than 20 papillae (Hyperpap colonies) led to the isolation of twelve mutator strains which produced at high frequency Pigcol- and Hyperpap colonies. Each exhibited a specific mutator phenotype and were distinct from each other. Such strains constituted a part of the polymorphism observed in each of the WT progeny and also generated a high variability. Finally, we showed that pigment-defective papillae were mutants and constituted a new form of genetic instability.
Chromosomes, Bacterial↗
Targeting the PML/RAR alpha translocation product triggers apoptosis in promyelocytic leukemia cells.
The t(15;17) rearrangement found in acute promyelocytic leukemia (APL) yields a fusion transcript, PML/RAR alpha. PML/RAR alpha expression is linked to leukemogenesis and to clinical sensitivity to all-trans retinoic acid (RA). Paradoxically, RA treatment causes transient complete remissions in most t(15;17) APL cases. The precise roles of PML/RAR alpha in triggering leukemia or in causing a maturation block are not yet known. This study explores directly these PML/RAR alpha functions in the growth and differentiation of APL cells using a hammerhead ribozyme to target PML/RAR alpha mRNA in the NB4 APL cell line. When the PML/RAR alpha cleaving but not the non-catalytic control ribozyme is introduced into the NB4 APL cell line, PML/RAR alpha protein expression is reduced. This catalysis signals growth suppression, cytotoxicity, and apoptosis without overcoming the maturation block found in these leukemic cells. These biologic effects depend on the selective pressure used to express the ribozyme from an episomal vector. Introduction of a non-catalytic, control ribozyme into NB4 cells caused no observed phenotype due to anti-sense activities. Expression of the catalytic or non-catalytic ribozymes in control cells lacking PML/RAR alpha mRNA yielded no apparent growth or differentiation effects. Thus, use of a hammerhead ribozyme that targets PML/RAR alpha expression in APL cells reveals the anti-apoptotic function of this translocation product and demonstrates that PML/RAR alpha cleavage is insufficient to overcome the differentiation block observed in these leukemic cells. Taken together, these findings indicate that persistent PML/RAR alpha expression is required to maintain basal leukemic cell growth and point to the therapeutic potential of targeting PML/RAR alpha in APL.
Apoptosis↗
Templates for design of inhibitors for serine proteases: application of the program DOCK to the discovery of novel inhibitors for thrombin.
The program DOCK was used to search for novel inhibitors for alpha-thrombin. Four among the top twelve best scoring compounds from the Cambridge Structural Data Base inhibited this enzyme, and three of them inhibited alpha-thrombin in a competitive mode. These molecules are expected to serve as general templates for structural elaboration in targeting diverse serine proteases for selective inhibition.
Binding Sites↗
Systemic PCP treatment elevates brain extracellular 5-HT: a microdialysis study in awake rats.
THE NMDA receptor antagonist phencyclidine (PCP) has low micromolar affinity for the 5-HT reuptake site, but it is uncertain whether PCP blocks 5-HT reuptake when given systemically to rats in behaviourally stimulating doses. We here report for the first time that systemically administered PCP (5 mg/kg, s.c.) increases extracellular 5-HT levels in the rat medial prefrontal cortex (to 322%) and dorsal hippocampus (to 233%). Increases were found also when citalopram (1 microM) was included in the perfusion medium (to 184 and 180%, respectively). Extracellular 5-HIAA concentrations increased during both conditions, and extracellular GABA decreased in the dorsal hippocampus. It is concluded that systemic PCP treatment elevates extracellular 5-HT levels, probably through mechanisms other than a blockade of 5-HT reuptake.
Animals↗
Comparison of the properties of polymeric and C8 based materials for solid phase extraction.
The extraction properties of two polymeric solid phase extraction materials, styryldivinyl benzene (SDB) and 'Oasis' have been compared with those of a base deactivated C8 bonded silica gel using a range of acidic and basic test analytes. In the case of the two polymer phases good extraction of all the test compounds from aqueous buffer was obtained over the pH range 2-10. On the C8 material, efficient extraction of the most polar acidic analyte, anisic acid, was only obtained between pH 2 and 6. The use of methanol water mixtures, or methanol water mixtures modified with either trifluoroacetic acid (TFA) or triethylamine (TEA) as eluents was investigated for the recovery of the analytes following extraction. The use of TFA or TEA as ionic modifiers strongly influenced the efficiency of the elution step. The effect of a plasma matrix on extraction efficiency was also investigated, with the result depending upon the analyte. An approach to assessing the performance of the three phases has been developed based on the percentages of methanol in the eluent resulting in the recovery of 50% of the analyte, and in determining the difference between eluents giving recoveries of 10 and 90%.
Chemistry Techniques, Analytical↗
Targeting of PML/RARalpha is lethal to retinoic acid-resistant promyelocytic leukemia cells.
Acute promyelocytic leukemia (APL) cells, containing the t(15;17) rearrangement, express the fusion protein, PML/RARalpha. Clinically, patients respond to all-trans retinoic acid (ATRA) through complete remissions associated with myeloid maturation of leukemic cells. This clinical ATRA response of APL is linked to PML/RARalpha expression. Unfortunately, these remissions are transient and relapsed APL is often ATRA-resistant. The role PML/RARalpha plays in the growth and maturation of these APL cells with acquired ATRA resistance has not been fully explored. This study uses an ATRA-resistant NB4 cell line (NB4-R1) to investigate the contribution of PML/RARalpha expression to ATRA resistance. Targeting of PML/RARalpha in NB4-R1 cells was undertaken using two approaches: homologous recombination and hammerhead ribozyme-mediated cleavage. Reducing PML/RARalpha protein in NB4-R1 cells rendered these cells more sensitive to ATRA. These cells were growth-inhibited in ATRA, apoptosis was induced, and there was no apparent signaling of differentiation. Sequence analysis identified a mutation in the ligand binding domain (LBD) of the RARalpha portion of PML/RARalpha. Results show that these retinoid-resistant NB4 cells require persistent PML/RARalpha expression for leukemic cell growth. Taken together, these findings can account for why these cells do not respond to ATRA and how reduction of PML/RARalpha abrogates the antiapoptotic effect it confers to these leukemic cells.
Antineoplastic Agents↗
Enterohaemorrhagic Escherichia coli in Ngoïla (Cameroon) during an outbreak of bloody diarrhoea.
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Adolescent↗
Structure-activity relationships for triphenylethylene antiestrogens on hepatic phase-I and phase-II enzyme expression.
To better understand the mechanism(s) by which tamoxifen induces rat hepatic CYPIIB2 and suppresses GSTA1, structure-activity studies were performed. Compounds employed in these studies included: tamoxifen, fixed-ring tamoxifen, ethylated fixed-ring tamoxifen, pyrrolidino-tamoxifen, 4-iodotamoxifen, idoxifene, and toremifene. With respect to GSTA1 suppression, tamoxifen, fixed-ring tamoxifen, 4-iodotamoxifen, idoxifene, and toremifene were all potent suppressors of GSTA1, while ethylated fixed-ring tamoxifen and pyrrolidino-tamoxifen were completely without activity. The results suggest that the aminoethoxy side chain plays a crucial role in GSTA1 suppression, and that 4-iodination may potentiate this activity. With respect to induction of CYPIIB2, tamoxifen, fixed-ring tamoxifen, and ethylated fixed-ring tamoxifen were inducers of this enzyme, while toremifene and 4-iodotamoxifen were inactive, suggesting that the aminoethoxy side chain is not a structural determinant of CYPIIB2 induction. Because ethylated fixed-ring tamoxifen, toremifene, and 4-iodotamoxifen had differential activities in the two assays, we conclude that CYPIIB2 induction and GSTA1 suppression by triphenylethylenes are the result of two separate and distinct mechanistic pathways. Structure-activity relationships for GSTA1 suppression and CYPIIB2 induction were compared with previously published relationships for triphenylethylene: 1) estrogen receptor relative binding affinity; 2) calmodulin antagonism; 3) antiuterotrophic activity; and 4) antagonism of MCF-7 cell growth. No clear correlation was observed between the effects on CYPIIB2 and these other four activities, suggesting no relationship between the mechanisms responsible for these effects. Similarly, no precise correlation was observed between GSTA1 suppression and these other activities, although rough similarities were observed for relative binding affinity and antiuterotrophic activity. This suggests that the mechanisms responsible for CYPIIB2 induction and GSTA1 suppression are not related to the mechanisms of action for these other documented activities, and may represent different mechanistic pathways.
Animals↗