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N Clément

Publications and source records attributed to N Clément.

11 recordsLinked to original sources
PubMed2003

Proliferation of human progenitor cells in a long-term culture system is more efficiently sustained by the addition of Flt-3 ligand or megakaryocyte growth and development factor than by Kit ligand.

INTRODUCTION: We compared the effects of the early-acting growth factors (GF), Flt-3 ligand (FL), c-Kit ligand (KL), and leukemia inhibitory factor (LIF), and the late-acting GF, granulocyte-colony stimulating factor (G-CSF) and megakaryocyte growth and development factor (MGDF), added alone in human long-term marrow culture (LTMC). MATERIALS AND METHODS: The GF were used in primary cultures of mononuclear cells (MNC) and in cocultures of CD34+ cells on murine preestablished MS-5 stromal layers. GF activity was assessed as nonadherent and adherent progenitor cell production and cobblestone area formation at week 5. RESULTS: In this system, only FL, KL, and MGDF significantly stimulated early stages of hematopoiesis, whereas only G-CSF stimulated the proliferation of mature progenitor cells within the granulo-monocyte lineage and no effect was observed with LIF. FL displayed the strongest activity, and MGDF was more efficient than KL, both in primary cultures of MNC and in cocultures of CD34+ cells. However, the stimulatory effects of these GF used alone were dependent on the presence of a stromal layer. CONCLUSION: These LTMC data emphasize the particular roles for FL and MGDF in the stimulation of primitive hematopoiesis.

Animals↗
PubMed2001

Quantitative measurements in in situ straining experiments in transmission electron microscopy.

Several examples of recent studies by in situ straining experiments in a transmission electron microscope performed in the Toulouse group (France) are presented. In particular, quantitative measurements of the features of the dislocation motion are described. These examples deal with individual or collective propagation of dislocations, which are submitted to various types of obstacle. Different metallic materials are investigated: magnesium, intermetallics, aluminium alloys and gamma phase of a superalloy.

Journal Article↗
PubMed2001

Cloning and sequencing of defective particles derived from the autonomous parvovirus minute virus of mice for the construction of vectors with minimal cis-acting sequences.

The production of wild-type-free stocks of recombinant parvovirus minute virus of mice [MVM(p)] is difficult due to the presence of homologous sequences in vector and helper genomes that cannot easily be eliminated from the overlapping coding sequences. We have therefore cloned and sequenced spontaneously occurring defective particles of MVM(p) with very small genomes to identify the minimal cis-acting sequences required for DNA amplification and virus production. One of them has lost all capsid-coding sequences but is still able to replicate in permissive cells when nonstructural proteins are provided in trans by a helper plasmid. Vectors derived from this particle produce stocks with no detectable wild-type MVM after cotransfection with new, matched, helper plasmids that present no homology downstream from the transgene.

Base Sequence↗
PubMed2001

Is gender a risk factor for adverse drug reactions? The example of drug-induced long QT syndrome.

Drug-induced torsade de pointes is a rare life-threatening adverse drug reaction (ADR) which is strongly influenced by gender. Drugs that prolong cardiac repolarisation include antiarrhythmics, gastrokinetics, antipsychotics, antihistamines and antibacterials. Such drugs share the potential to block cardiac voltage-gated potassium channels, particularly the rapid component (I(Kr)) of the delayed rectifier potassium current (I(K)). By doing so, such drugs usually, but not always, prolong the QT interval. Even if the electrocardiographic signs are subdued, the underlying blockade of I(Kr) current may precipitate the occurrence of arrhythmia. Women are perceived to be more prone to ADRs than men. Such a propensity may result from gender-associated differences in drug exposure, in the number of drugs prescribed (polypharmacy), in drug pharmacology, as well as from possible differences in the way the adverse event is perceived. A prolonged QT interval on the electrocardiogram (time that elapses from the onset of the cardiac ventricular depolarisation to the completion of its repolarisation) is associated with the occurrence of torsade de pointes and related ventricular arrhythmias. The QT interval is influenced by heart rate, autonomic nervous system, electrolyte disturbances and above all, drugs that block potassium channels. Two-thirds of the cases of drug-induced torsade de pointes occur in women. Therefore, this adverse effect represents a perfect example of gender differences impairing women's health. Clinical and experimental studies show that female gender is associated with a longer corrected QT interval at baseline and a greater response to drugs that block I(Kr), both of which facilitate the emergence of arrhythmia. This results most likely from a specific regulation of ionic channel expression (potassium, calcium, etc) by sex steroids, even though nongenomic effects may play a role as well. Estrogens facilitate bradycardia-induced prolongation of the QT interval and the emergence of arrhythmia whereas androgens shorten the QT interval and blunt the QT response to drugs. Hence, underlying genetic defects of potassium channels that may be asymptomatic in normal conditions, may precipitate drug-induced arrhythmia in women more frequently than in men. Even in the presence of a drug that mildly blocks I(Kr) and seldom prolongs the QT interval, women are still more prone to drug-induced torsade de pointes, due to their reduced cardiac 'repolarisation reserve'. This is an important aspect of I(Kr) blockade to be aware of during the development of new drugs.

Electrocardiography↗
PubMed2001

[Apropos of 1 case of paratesticular papillary serous cystadenocarcinoma].

The occurrence within the testis or paratesticular tissue of serous tumors, similar to ovarian tumors, is rare. This article reports a primary serous paratesticular cystadenocarcinoma in a 39 year-old man. From data of the literature, we offer guidelines for diagnosis, histogenesis and treatment of this rare tumor.

Adult↗
PubMed1997

DNA ploidy by image cytometry in urothelial carcinomas. Comparison of touch imprints and paraffin-embedded biopsies from 31 patients.

OBJECTIVE: To compare DNA content measured by image cytometry from touch imprints and formalinfixed, paraffin-embedded samples in bladder carcinomas. STUDY DESIGN: Thirty-one biopsies of urothelial carcinomas were selected for a prospective study. Imprints of fresh specimens were performed. Cell suspensions were obtained from dewaxed samples by the procedure of Hedley. Sections 7 microns thick were used for carcinoma in situ and small biopsies. The DNA ploidy index was measured on Feulgen-stained slides using an image cytometer. RESULTS: From imprint analysis, seven grade 1 carcinomas (n = 9) were found to be diploid (78%). Nine grade 2 carcinomas (n = 12) exhibited aneuploidy (75%), as did all grade 3 and in situ carcinomas (n = 10). Multiploidy was demonstrated from imprints in four cases instead of the two detected from dewaxed tissue. In 27 cases (87%), G0/G1 peaks obtained from paraffin blocks showed a shift to the left. In five cases (16%), variations in the DNA index were responsible for discrepancies in the DNA ploidy evaluation between fresh imprints and dewaxed samples of the same tumors. CONCLUSION: Image cytometry on Feulgen-stained imprints of bladder biopsies is a simple and reliable procedure for assessing DNA ploidy in urothelial carcinomas, providing great sensitivity for detecting small aneuploid peaks and multiploid tumors. DNA image analysis of touch preparations is especially useful for carcinoma in situ and small biopsies unsuitable for Hedley's technique.

Aged↗
PubMedDate not supplied

Diadochokinetic rate in persons with traumatic brain injury.

This study examined diadochokinetic rate (DR) performance in a group of 28 traumatically brain injured (TBI) patients and their matched controls for 16 different articulatory positions in order to determine which articulatory positions distinguished between the two groups. Discriminant function analysis determined (p = 0.000) four variables ('ta', 'ba', 'da' and 'ch') as resulting in the successful classification of 82.2% of the subjects. This implies that this subset of variables is adequate for determining DR in this population. The test-retest reliability (ICC) was also established in a group of 12 subjects and their matched controls. The ICCs ranged from 0.12 to 0.93 for the TBI subjects with 13 of 16 variables > 0.60.

Adolescent↗