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S Baatout

Publications and source records attributed to S Baatout.

At least 19 recordsLinked to original sources
PubMed2001

Radiation-induced chromosome aberrations in guinea-pig growing oocytes, and their relation to follicular atresia.

The female guinea-pig has been shown to represent a good model to investigate the genetic hazard of ionizing radiation in humans. The sensitivity of the guinea-pig oocytes to radiation-induced chromosome aberrations was, therefore, studied at different stages of oocyte and follicular growth. The sensitivity of oocytes enclosed in small follicles (15 weeks before ovulation) was found to be low and comparable to that of immature oocytes present at birth. The sensitivity of growing oocytes remained low and almost constant until 3 weeks before ovulation, from which time it began to increase. The most dramatic increase of sensitivity occurred during the last week preceding ovulation: about 90% of oocytes X-irradiated with 4Gy, 2 days before ovulation showed one or more chromatid interchanges, as compared to 20% for those irradiated with the same dose 1 week earlier. A comparison of our results with those found by others in the mouse shows that considerable differences of sensitivity exist between oocytes of these two species irradiated at similar stages of development. The possible reasons for these differences are discussed.

Animals↗
PubMed1999

Molecular basis to understand polyploidy.

Polyploidy which is defined as an increase in chromosome number by an exact multiple of the haploid chromosome number is a typical characteristic of plant species but can also be found in almost all organisms from protists to humans. In the plant kingdom, since the reproduction can occur vegetatively, polyploid cells have time to settle down from the evolution point of view as a stable genetic system. So, 30 to 70% of angiosperms, including many important crop plants, are estimated to have polyploidy in their lineages. The success of polyploid species in plants has been attributed to their ability to colonise a wider range of habitats and to survive better in unstable climates compared with their diploid progenitors, presumably due to increased heterozygosity and flexibility provided by the presence of additional alleles.

Animals↗
PubMed1998

Augmentation of the number of nucleolar organizer regions in human megakaryocyte cell lines after induction of polyploidization by a microtubule inhibitor.

BACKGROUND: Megakaryocyte polyploidization is an advantageous and regulated mechanism that leads to an increase in platelet production. In megakaryocytic cell lines, polyploidization can be obtained by using colchicine, an inhibitor of the tubulin spindle. The nucleolar organizer regions (AgNORs) are parts of nucleolar DNA transcribed into ribosomal RNA and are detected by the silver-staining technique. Their number is proportional to protein synthesis. RESULTS: To estimate protein synthesis in polyploid megakaryocytes, AgNORs are measured in three cell lines with megakaryocyte properties (DAMI, HEL and K562) after a 4-day culture in the presence or absence of colchicine. The mean number of AgNORs per cell was 16+/-4 (mean+/-SEM), 24+/-3 and 14+/-3 for DAMI, HEL and K-562 cell lines respectively. The addition of colchicine (10 ng mL[-1]) significantly increased the number of AgNORs per cell (DAMI 556%, HEL 338% and K-562 300% of controls, P < 0.05 using the t-test). Moreover, the number of nucleoles per cell after the addition of colchicine was augmented significantly (DAMI 246%; HEL 237% and K-562 148% of controls, P < 0.05 using the t-test). The total protein content estimated by Bradford's method increased significantly to 226%, 215% and 304% of controls in DAMI, HEL and K562 respectively (P < 005 using the t-test). After treatment with colchicine, the endomitotic index (EI) [mean of (log2 DNA content expressed in N)-1] measured by flow cytometry (and reflecting ploidy) increased to 234%, 255% and 301%, respectively, in DAMI, HEL and K-562 cell lines (P < 0.05 using the t-test). Concomitantly, the number of AgNORs per unit of DNA increased in the DAMI and HEL cell lines (P < 0.05 using the t-test) from 48+/-8 and 39+/-5, respectively, to 79+/-11 and 61+/-10. In contrast, the number of nucleoles and the total protein content per endomitotic index were not affected by colchicine (P > 0.05 using the t-test), but the number of nucleoles per endomitotic index of DAMI cells was affected. CONCLUSION: The increase in the number of the NORs induced by an agent known to stimulate polyploidization of megakaryocytic cell lines suggests that polyploidization occurs by a proportional increase in protein synthesis per DNA unit.

Cell Count↗
PubMed1998

Induction and enhancement of normal human megakaryocyte polyploidization are concomitant with perturbation in the actin metabolism.

BACKGROUND: Megakaryocyte polyploidization results from the lack of cytoplasmic separation while the nucleus keeps dividing. METHODS: To investigate the role of actin in the megakaryocyte polyploidization, three human cell lines with megakaryocytic properties (DAMI, HEL and K562) were incubated in the presence of cytochalasin B, an inhibitor of actin polymerization. These data were then compared with normal megakaryocytes. RESULTS: Compared with control conditions, cells cultured in the presence of cytochalasin B revealed an augmentation of cell size and ploidy and an arrest of cell proliferation. The expression of platelet membrane glycoproteins Ib, IIb/IIIa, IIIa and thrombospondin and transferrin receptors was augmented after treatment with cytochalasin B. Physiologically, the role of actin in inducing polyploidization could be related to an imbalance between G- and F-actins. To test this hypothesis, we measured G-, F- and total actin in cytochalasin B-treated cells. Actin was found to be increased significantly in cytochalasin B-treated DAMI and HEL cell lines. In contrast, the G/F-actin ratio was not affected by cytochalasin B. To confirm these actin changes in physiological megakaryocytopoiesis, G- and F-actin contents were then estimated in normal megakaryocytes. The G- and F-actin contents of megakaryocytes from eight normal patients exponentially decreased from 2 to 128n, whereas the total actin content per cell kept increasing. The G/F ratio was unaffected. CONCLUSION: Polyploidization of human megakaryocytes results from either a diminution of actin synthesis or an increased actin turnover, which in turn possibly abrogates the formation of the actin cleavage furrow in telophasis.

Actins↗
PubMed1998

Analysis of megakaryocytes by flow cytometry.

A flow cytofluorometric measurement of megakaryocyte ploidy has been adapted from Tomer's method. Briefly, bone marrow is aspirated through a medium containing theophyllin, prostaglandin-E1 and other antiaggregant agents. Megakaryocytes-enriched buffy coats are recovered. Megakaryocytes are then stained for GP IIIa coupled with FITC and for DNA (propidium iodide). A Becton Dickinson FACScan flow cytometer is used for measuring the ploidy distribution of GP IIIa positive cells. The method we developed presents several advantages. Firstly, the time required is greatly decreased in comparison with other studies. Secondly, the washing steps are limited in number allowing a diminution of the cell loss. Thirdly, the method ensures a better megakaryocyte preservation. Finally, selection of megakaryocytes by ploidy and expression of GP IIIa can be made easily because of the simultaneity of the two stainings as well as by the use of a precise gating on the flow cytometer. Based on these results, we conclude that the present method provides a better means for the isolation and analysis of human normal megakaryocytes. This technique has been applied to the analysis of megakaryocyte populations from patients with abnormal platelet counts. In chronic myeloid leukemia patients, analysis of ploidy distribution shows a shift toward the low ploidy while in patients with immune thrombocytopenic purpura, polycythemia vera and essential thrombocythemia the ploidy distributions are shifted toward the high ploidy.

Adolescent↗
PubMed1998

Phorbol esters: useful tools to study megakaryocyte differentiation.

This review attempts 1) to enonciate recent observations made on the effects of phorbol esters on megakaryocyte cell lines, 2) to examine these effects taking into account megakaryocytopoiesis in vivo and 3) to demonstrate that phorbol esters stimulated megakaryocyte cell lines provide a good model to study the mechanisms governing megakaryocyte maturation.

Animals↗
PubMed1998

A historical perspective and cellular regulation of megakaryocytopoiesis.

With the recent accumulation of information about megakaryocyte biochemistry and function, our understanding of the regulatory system controlling megakaryocytopoiesis is becoming more clear. The cloning and the expression of thrombopoietin, the regulator of megakaryocytopoiesis, has been a major breakthrough. This review will discuss megakaryocyte ontogeny, cell-cell interactions between megakaryocytes and the other stromal cells and the signal transduction in megakaryocytes.

Animals↗
PubMed1997

Cytogenetic effects of X-rays in the guinea pig female germ cells. II. The maturing oocyte.

In a previous study, we showed that the guinea pig constitutes one of the best models to evaluate the genetic risk associated with an irradiation of the human female germ cells. Herewith, experiments were undertaken to evaluate the chromosomal radiosensitivity of oocytes of this species at two different stages of follicular development, separated by only 1 week. Female guinea pigs were X-irradiated on the ovaries, at either the beginning (day 3) or the middle (day 10) of the 17-day oestrous cycle. The doses delivered were 1 or 2 Gy. Meiotically competent oocytes were collected 1 week after irradiation (day 3) or immediately thereafter (day 10), and they were cultured to the metaphase of the first meiosis (MI) and examined for the presence of chromosome aberrations. Our data demonstrated a dramatic increase in the radiosensitivity of the oocyte during this short time interval: oocytes irradiated at the beginning of the oestrous cycle had a low frequency of chromosome aberrations, while those irradiated at the middle of the oestrous cycle (when growing Graafian follicles are clearly visible at the surface of the ovaries) exhibited heavy chromosome damage. However, we also found that oocytes irradiated at the middle of the oestrous cycle were eliminated from the ovaries in a few days, after their evolution to the MII stage. The stimulation of the first meiotic division by radiation required less than 24 h after doses of 1 or 2 Gy and was probably due to a rapid atresia of the large follicles containing the oocytes. On the basis of these results, it can be concluded that the radiosensitivity of the nearly mature guinea pig oocyte (1 week before ovulation) is clearly much higher than that of the corresponding stage in the mouse, both in terms of sensitivity to killing and to induction of chromosome aberrations.

Animals↗
PubMed1997

Cytogenetic effects of X-rays in the guinea pig female germ cells. I. The immature oocyte.

In female mammals, the immature oocyte is the germ cell most at risk, from the genetic point of view. We have previously shown that ovaries of newborn guinea pigs contain a great majority of immature oocytes and small numbers of maturing oocytes. At this time, all immature oocytes are in a typical diplotene stage, comparable to that of the human resting oocyte. Furthermore, the LD50 of the guinea pig oocytes is about 4 Gy, like that of human oocytes. Consequently, performing genetic studies on guinea pig oocytes irradiated just after birth constitutes a very useful approach to predict the mutational response of the human resting oocyte. Female guinea pigs were X-irradiated with 1 or 2 Gy within 24 h of birth, and their meiotically competent oocytes were collected and cultured to the metaphase I stage, 1 year after treatment, ensuring that all oocytes were at the immature stage at the time of irradiation. The proportion of oocytes that showed chromosome aberrations (breaks, fragments or interchanges) was only 1-2% Gy(-1). Although not definitive, these results provide support for a low risk in women from an exposure of the immature oocyte to low doses of radiation.

Animals↗
PubMed1996

Interleukin-6 and megakaryocytopoiesis: an update.

Interleukin-6 is a pleiotropic cytokine which shows a wide variety of biologic functions on various tissues and cells. Indeed. IL-6 acts not only B cells but also on T cells, hepatocytes, hematopoietic progenitor cells, megakaryocytes, etc. In this review, I have attempted to summarize the new data concerning the effect of IL-6 on megakaryocytes and platelets.

Anemia↗
PubMed1996

The importance of cytoskeleton proteins in megakaryocyte spreading and platelet formation.

The release of platelets into the circulation is preceded by considerable morphologic change of the parent megakaryocyte. The cell extends cytoplasmic processes into the venous sinusoids, which develop constrictions at intervals, revealing putative platelets. The pattern of cytoskeletal distribution changes during the spread of megakaryocytes in vitro. In this review, an attempt was made to summarize the data of the literature concerning the changes in the cytoskeletal pattern of megakaryocytes during their spreading and platelet formation.

Animals↗
PubMed1996

Staining of the nucleolar organizer regions: relevance in hematology.

There is growing interest in staining for the nucleolar organizer regions to detect nucleolar organizer region-associated proteins. In some cases, this technique facilitates the study of hematological disorders and allows us to distinguish between certain pathologies. Furthermore, it can provide information about cell proliferation, activity and malignancy. This paper attempts to give the recent advances in the use of the staining of nucleolar organizer regions and its clinical relevance in hematology.

Animals↗
PubMed1995

Thrombopoietic effects and toxicity of interleukin-6 in patients with ovarian cancer before and after chemotherapy: a multicentric placebo-controlled, randomized phase Ib study.

Recombinant human interleukin-6 (IL-6) has previously been shown to increase platelet counts in normal and sublethally irradiated mice, dogs, and primates. To assess its tolerance and efficacy in clinical use, we performed a randomized phase Ib study in patients with ovarian carcinoma. IL-6 was administered during an initial 7-day cycle before any chemotherapy. Beginning 7 days later, six cycles of chemotherapy containing carboplatin were administered every 3 weeks. During chemotherapy cycles 2 to 6, IL-6 was administered from day 4 through day 17 at escalating dose levels from 0.5 to 10 micrograms/kg/d. At each level, three patients received IL-6 and one patient received a placebo. During the prechemotherapy cycle of IL-6, a dose-dependent increase in platelet count was observed from day 12 to 15 and was maximal on day 15 (r = .77; P < .01). The median ploidy of bone marrow megakaryocytes shifted from 16 N to 32 N after 7 days of the initial prechemotherapy IL-6 administration. Dose-dependent increases in C-reactive protein (CRP) and fibrinogen levels were observed on day 8 (P < .0001 for both). A significant decrease in hemoglobin level occured rapidly after initiation of IL-6 therapy and was maximal on day 8 (P < .001). When given after chemotherapy, IL-6 accelerated platelet recovery after chemotherapy cycles 2 to 6. Postponements of scheduled chemotherapy due to thrombocytopenia were less frequent in patients treated with IL-6. No difference in either neutrophils or peripheral blood progenitor assays was observed during or after IL-6 treatment. Toxicity of IL-6 appeared mild and was not dose-limiting up to 10 micrograms/kg/d. Systemic symptoms such as fever, headache, and myalgia were the main side effects and were easily relieved by acetaminophen administration. No biologic toxicity was observed. The data indicate that IL-6 is a well-tolerated cytokine and capable of accelerating platelet recovery in patients receiving chemotherapy.

Acute-Phase Proteins↗
PubMedDate not supplied

Thrombopoietin. A review.

The regulator of platelet count is believed to be thrombopoietin (mpl ligand). It is thought to act on the megakaryocytic lineage affecting the proliferation of committed cells, the maturation of megakaryocytes and the blood platelet levels by activation of its receptor (the c-mpl). Recently, it has been purified and sequenced. Thrombopoietin offers potential applications for treatment of thrombocytopenia.

Animals↗