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P Staquet

Publications and source records attributed to P Staquet.

At least 19 recordsLinked to original sources
PubMed1999

Pulmonary effects of short-term exposure to low levels of toluene diisocyanate in asymptomatic subjects.

Isocyanates may be involved in the development of chronic obstructive airway disease among exposed workers. A short-term exposure to toluene diisocyanate (TDI) at concentrations near the permissible levels was investigated to examine whether there was an association with changes in pulmonary function tests and in potential markers of airway injury and inflammation in bronchial lavage (BL) and bronchoalveolar lavage (BAL). Seventeen subjects without respiratory symptoms (eight smokers and nine nonsmokers) were exposed once to ambient air and once to TDI (5 parts per billion (ppb) for 6 h followed by 20 ppb for 20 min) in a randomized, single-blind sequence. Pulmonary function tests were repeatedly assessed during exposure and BAL was performed 1 h after each exposure. Biochemical studies on lavage fluids included albumin, immunoglobulins, antiproteases (alpha2-macroglobulin and alpha1-proteinase inhibitor), potential indicators of epithelial cell function (secretory component and Clara cell protein), and cytokines (tumour necrosis factor-alpha, interleukin (IL)-4, IL-5, IL-6, and IL-8). Exposure to TDI caused a modest decrease in specific airway conductance (sGaw) (p=0.053) and in maximal expiratory flow at 25% of forced vital capacity (MEF25%) (p=0.015) when compared with ambient air. Exposure to TDI resulted in a slight increase in BAL albumin level (TDI: 26.4+/-12.5 versus air: 21.8+/-8.6 microg x mL(-1), p=0.044) and in BL alpha2-macroglobulin concentration (TDI: 0.07+/-0.061 versus air: 0.05+/-0.04 microg x mL(-1), p=0.021). This study suggests that exposure to low toluene disocyanate concentrations is associated with minimal but detectable changes in airway calibre and in epithelial barrier permeability. The pulmonary effects of long-term exposure to low levels of isocyanates require further investigation.

Adult↗
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↗
PubMed1995

From health locus of control to immune control: internal locus of control has a buffering effect on natural killer cell activity decrease in major depression.

Decreased immunity in depressive as compared with control subjects has been well documented, although some depressed patients have severe alterations whereas others have milder ones or not at all. Since for equal severities of depression, there may be individual differences in the degree of perceived control over one's condition, we investigated the interaction of perceived control with immunological variations. Immune function (T and B lymphocytes, lymphocyte proliferation and natural killer cell activity (NKCA)) were evaluated in 34 adult major depressives and in 18 healthy controls. Lymphocyte proliferation did not differ between the two groups, but NKCA was significantly lower in the depressed patient group. Among the depressed subjects, those who experienced less subjective control also showed significantly lower NKCA. An internal locus of control appears to act as a buffer against the decrease in cellular immunity observed in major depression. Further studies should focus on methods of coping and on degree of perceived control rather than on diagnostic and nosographic variables alone.

Adult↗
PubMed1994

Tolerance of sequential or simultaneous administration of IL-3 and G-CSF in improving peripheral blood stem cells harvesting following multi-agent chemotherapy: a pilot study.

A pilot study was devised to assess tolerance of combined administration of interleukin-3 (IL-3) and granulocyte-colony stimulating factor (G-CSF) given after chemotherapy to mobilize peripheral blood progenitors cells (PBPC). Eight patients with advanced malignancies received 1 week courses of both IL-3 and G-CSF in one of three schedules: simultaneous 7 days administration (3 patients), sequential administration (3 patients) or partial (3 days) overlap of the two growth factors (2 patients). IL-3 (7.5 micrograms/kg/day) and G-CSF (5 micrograms/kg/day for the simultaneous schedule and 12 micrograms/kg/day for the partial overlapping and sequential schedules) were administered subcutaneously. Side-effects during cytokine administration included WHO grade I-II fever in 6 of 8 patients, flu-like symptoms (including myalgias and arthralgias) in 4 of 8, WHO grade I-II headache in 2 of 8 and WHO grade II nausea and vomiting in 1 of 8. Overall, side-effects appeared similar during combined administration of IL-3 and G-CSF to those observed during administration of IL-3 alone. No fever was observed when G-CSF was administered alone. Two leukaphereses were performed following the treatment with cytokines. Only the seven patients who received cytokines following chemotherapy were analyzed for PBPC mobilization. The median collection of CFU-GM/kg per patient in the seven analyzed patients was 1.3 x 10(5) (range 5.7 x 10(2)-3.6 x 10(5)). In two patients, a second cycle of mobilization with either granulocyte macrophage-colony stimulating factor (GM-CSF) or G-CSF was administered to allow safe engraftment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Fc alpha-receptor expression on the myelomonocytic cell line THP-1: comparison with human alveolar macrophages.

Immunoglobulin A (IgA) and alveolar macrophages are two important components of the immune system in the respiratory tract. Fc alpha-receptors (Fc alpha R) are present on neutrophils, eosinophils and a series of human mononuclear phagocytes, including monocytes, alveolar macrophages and leukaemia cell lines (U-937). In the present study, using idiotypes and anti-idiotypic antibodies, we report that THP-1 cells, a myelomonocytic cell line, constitutively express Fc alpha R and that all IgA preparations used bind the receptor. Of the stimuli used (phorbol myristate acetate, retinoic acid, calcitriol), only calcitriol can induce differentiation of THP-1 cells, as assessed by CD14 expression. The expression of Fc alpha R appears to be independent of cell differentiation, since calcitriol pretreatment has no effect on IgA-binding. Finally, My43, a monoclonal antibody recognizing the Fc alpha R on U-937 cells, does not bind to THP-1 cells or to human alveolar macrophages. In addition, preincubation of THP-1 cells or human alveolar macrophages with My43 does not diminish IgA-binding to these cells. Ribonucleic acid (RNA) encoding the Fc alpha R isolated from U-937 is expressed, although possibly at a lower level, in alveolar macrophages and THP-1 cells. In conclusion, Fc alpha R are constitutively expressed on THP-1 cells and share some characteristics with the Fc alpha R described in human alveolar macrophages. THP-1 cells, therefore, may represent a reasonable model for further investigation of the interaction of immunoglobulin A and tissue macrophages.

Base Sequence↗
PubMed1993

Blunted rise in intracellular calcium in CD4+ T cells in response to mitogen following autologous bone marrow transplantation.

Following autologous bone marrow transplantation (ABMT), both impaired T cell activation and defective production of the principal T cell growth factor, interleukin-2 (IL-2), has been observed. These processes are dependent on a rise of intracellular calcium ([Ca2+]i), a step which follows binding of T cell receptor (TCR) and transduction of signal via the generation of cytoplasmic second messengers. In order to better understand the nature of defective cellular immunity in ABMT, in the present study we investigated the rise of [Ca2+]i in T cells of recipients of ABMT. By concomitant labelling lymphocytes with anti-CD4 antibody and addition of fluo-3 as fluorescent calcium indicator, we have selected for the T cell subset which is the principal source of IL-2. Short-term (less than 1 year post-transplantation) recipients of ABMT show a statistically significant blunted rise in [Ca2+]i in response to concanavalin A as compared to normal controls not accounted for solely by a decreased percentage of CD4+ cells in these patients. The [Ca2+]i response of CD4+ cells from long-term (greater than 1 year post-transplant) recipients was lower than that of the normal group although not to a statistically significant level. These findings suggest that following ABMT is a defect in the early stages of T cell activation involving either T cell receptor binding or early signal transduction ultimately resulting in depressed transcription of IL-2 mRNA. These defects are analogous to findings in both allogeneic transplantation where factors of histoincompatibility and graft-versus-host disease (GVHD) come into play, as well as in the defective T cell activation of the normal ageing process.

Adolescent↗
PubMed1992

Effects of escalating doses of recombinant human interleukin-2 in correcting functional T-cell defects following autologous bone marrow transplantation for lymphomas and solid tumors.

High-dose chemotherapy followed by autologous bone marrow transplantation (ABMT) in the treatment of malignancies is often associated with immune deficiency following transplantation, possibly contributing to tumor relapse or fatal infection. Interleukin 2 (IL-2), which enhances major histocompatibility complex (MHC)-unrestricted cytotoxicity in vitro, can be applied in vivo as immunotherapy to reduce these potential complications. Recombinant human IL-2 (rIL-2) was administered by continuous i.v. infusion for four courses in 19 patients following ABMT for lymphomas and solid tumors. The patients were assigned to five groups of escalating doses of rIL-2 ranging from 3 to 30 x 10(6) IU/m2/day. The immunological effects and toxicity were monitored. After a transient reduction of lymphocytes in the peripheral blood, a significant lymphocytosis was observed during the rIL-2 infusion with an augmentation of CD2+, CD25+, and CD8(+)-Ia+ T cells and a dose-related increase of CD56+ lymphocytes. Natural killer (NK) activity appeared enhanced in patients treated with as little as 6 x 10(6) IU/m2/day. No statistically significant increase in lymphokine-activated killer (LAK) activity was seen after rIL-2, when compared to LAK activity following ABMT prior to rIL-2 administration. Administration of exogenous rIL-2 to patients who have undergone ablative chemotherapy and ABMT has a role in restoring defective T-cell function. Further trials defining those patients most likely to benefit from rIL-2 integrated with ablative chemotherapy and ABMT are now warranted.

Adult↗
PubMed1989

Surface IgA and Fc-alpha receptors on human alveolar macrophages from normal subjects and from patients with sarcoidosis.

Human alveolar macrophages (AM) obtained by bronchoalveolar lavage (BAL) were found to bear cytophilic IgA and Fc alpha-receptors (Fc alpha R) on their surface. The cytophilic IgA belongs to the IgA1 subclass, but unoccupied receptors can be saturated with either IgA1 or IgA2 molecules. Although both polymeric and monomeric forms could attach, binding was about 5-fold greater for the polymers. Both cytophilic IgA and Fc alpha R are sensitive to trypsin and disappear after 18 h of AM culture. An increase in cytophilic IgA was observed on AM from untreated patients with pulmonary sarcoidosis, but not on AM from steroid-treated patients. A significant correlation was found between IgA levels in BAL and the percentage of AM with cytophilic IgA in normal subjects and in steroid-treated sarcoid patients. However, no such relationship was seen among untreated patients. These data suggest that multiple factors may modulate AM surface receptors for IgA. Inflammatory events occurring in the lungs could alter receptor expression and perhaps be of significance in the immunophysiopathology of certain pulmonary diseases.

Binding, Competitive↗
PubMed1988

Antiproteases are increased in bronchoalveolar lavage in interstitial lung disease.

The present study evaluates different cellular and soluble components in the bronchoalveolar lavage (BAL) from patients with interstitial lung disease. We observed an increased T4/T8 lymphocyte ratio in BAL but not in blood from 24 patients with active pulmonary sarcoidosis compared to sixteen normal individuals and to eleven patients with inactive pulmonary sarcoidosis. Seven patients with hypersensitivity pneumonitis had a normal T4/T8 ratio. In the active sarcoidosis and hypersensitivity pneumonitis groups, alpha 1-Protease Inhibitor (alpha 1 PI) in BAL is significantly higher than in the normal group and a significant correlation between the two antiproteases (alpha 2-macroglobulin and alpha 1 PI) is observed. These data demonstrate that antiprotease levels (alpha 1 PI and alpha 2 M) are increased in the lower respiratory tract of patients with interstitial lung disease and that among cellular and soluble components of BAL, alpha 2 M represents a sensitive marker of the alveolitis.

Alveolitis, Extrinsic Allergic↗
PubMedDate not supplied

Interaction between protein kinase C and actin in megakaryocyte polyploidization.

Megakaryocytes undergo a peculiar and irreversible program by which they become polyploid through repeated cycles of DNA synthesis without concomitant cell division. In order to study the possible concomitant role of protein kinase C and actin in megakaryocyte polyploidization, three cell lines (DAMI, HEL and K562), expressing some properties of the megakaryocytic lineage and known to differentiate into the megakaryocytic pathway in the presence of phorbol esters, were cultivated in the presence of phorbol myristate acetate alone (PMA, 5 x 10(-9) M, activator of protein kinase C, PKC) or concomitantly with cytochalasin B (2 micrograms/ml, inhibitor of actin polymerization). We have previously shown that DAMI, HEL and K562 cells in which actin polymerization was inhibited by cytochalasin B, acquired megakaryocytic properties in the way that they became polyploid, acquired a megakaryocytic phenotype and arrested proliferation (4). After four days of culture in the presence of PMA and cytochalasin B, the number of polyploid cells (estimated by flow cytometry) increased in comparison with control or PMA-treated cells. However, it was lower than in cytochalasin B-treated cells. Indeed, control cells predominantly diploid (2N) became polyploid with the appearance of 8N, 16N and 32N cells after addition of PMA, cytochalasin B or PMA + cytochalasin B. The endomitotic index (EI, as described in 5) which corresponds to the mean of (¿log2 DNA content expressed in N¿-1) was 0.5 +/- 0.1, 0.7 +/- 0.1 and 0.3 +/- 0.1 in control DAMI, HEL and K562 cells, respectively. The EI increased to 0.9 +/- 0.2; 1.0 +/- 0.2 and 0.4 + 0.1 in cells treated with PMA and to 1.6 +/- 0.3; 1.4 +/- 0, and 0.9 +/- 0.2 when PMA was added concomitantly to cytochalasin B. Total DNA estimated from the cell content and the percentage of cells present at each ploidy stage did not change in cytochalasin B-treated cells in comparison to control conditions. However, treatment of DAMI, HEL and K562 cells with PMA alone or concomitantly with cytochalasin B revealed that the total DNA content significantly decreased in these conditions. At last, treatment of the three cell lines with PMA alone or concomitantly with cytochalasin B for 4 days caused a complete inhibition of proliferation. In conclusion, the concomitant addition of PMA and cytochalasin B to the three cell lines lead to an augmentation of cell ploidy and to a cessation of proliferation. However, we did not observe any synergistic effect of the two compounds. The possible interaction between actin and protein kinase C is discussed in the paper.

Actins↗
PubMedDate not supplied

Protein content and number of nucleolar organizer regions are enhanced during phorbol ester-induced differentiation of cultured human megakaryocytic cells.

In order to investigate the protein synthesis in megakaryocyte polyploidization, phorbol myristate acetate (PMA, 5 x 10(-9) M), a differentiation marker known to induce megakaryocyte polyploidization, was added to human megakaryocytic cell lines (DAMI, HEL and K562) and the expression of platelet/megakaryocytic integrins, the numbers of nucleolar organizer regions (AgNORs) and the total protein content were estimated. Following exposure of PMA, the expression of the platelet membrane glycoprotein GPIIIa and thrombospondin and transferrin receptors was augmented in the three cell lines. The number of AgNORs shifted from 16.4 +/- 4.3, 24.4 +/- 2.5 and 13.6 +/- 3.1 for unstimulated cells to 20.0 +/- 5.3, 38.7 +/- 7.9 and 16.8 +/- 2.3 for PMA-treated DAMI, HEL and K562 cells, respectively. Furthermore, after treatment with PMA, the numbers of AgNORs clusters or nucleoles increased significantly to 179%, 238% and 154% of controls in DAMI, HEL and K562 cell lines, respectively. Finally, addition of PMA culture for four days, significantly increased the protein contents to 153%, 171% and 254% of controls for DAMI, HEL and K562 cell lines, respectively (p < 0.05 by t-test). In conclusion, the increase in the total protein content and in the number of AgNORs by PMA, suggests that PMA-induced-megakaryocyte polyploidization occurs by enhanced protein production.

Cell Differentiation↗
PubMedDate not supplied

The G and F contents in megakaryocyte cell lines after stimulation with phorbol myristate acetate.

Megakaryocyte polyploidization responds to platelet demand and results from the lack of cytoplasmic separation while the nucleus keeps dividing. In order to investigate the role of actin in the megakaryocyte polyploidization, phorbol myristate acetate (PMA, 5 x 10(-9) M), a differentiation marker known to induce megakaryocyte polyploidization, was added to human megakaryocytic cell lines (DAMI and HEL) and G, F and total actins were estimated by DNase I inhibition. After four days of culture in the presence of PMA, G actin contents in pg per 10(6) cells were 13.0 pg +/- 2.8 and 1.0 pg +/- 0.1 for unstimulated DAMI and HEL cells. F actin contents per 10(6) cells were 5.8 pg +/- 1.5 and 0.1 pg +/- 0.0 for DAMI and HEL cells. Addition of PMA for four days to culture significantly increased G actin contents (235% and 268% of controls) and F actin contents (234% and 394%), for DAMI and HEL cell lines, respectively (p < 0.05 by t-test). In contrast, G/F actin ratio was not affected (p < 0.05 by t-test) by PMA. DAMI cells from each ploidy classes were then sorted on an ELITE Coulter and assayed for actin content. While total actin, G actin and F actin per cell increased in polyploid cells cultured with PMA, there was a reduction in G, F and total actin contents per diploid equivalent when cells became polyploid. In conclusion, megakaryocyte polyploidization of these cell lines is not related to an unbalance between G and F actins but would be rather due at least partly to a defect in total actin production that could lead to a prevention of the formation of the constriction ring in telophase.

Actins↗
PubMedDate not supplied

Human megakaryocyte polyploidization is associated with a decrease in GPIIIA expression.

Megakaryocytes are platelet forming cells and are characterized by polyploidization, a phenomenon by which nuclear division occurs without corresponding cytoplasmic separation. Among the markers allowing to identify megakaryocytes, glycoprotein (GP) IIIa with GPIb and GPIIb are the most important. Using GPIIIa as a marker to recognize megakaryocytes in the bone marrow, we have estimated GPIIIa expression by flow cytometry in megakaryocyte populations from normal individuals and from patients with chronic myelogenous leukemia, immune thrombocytopenic purpura or polycythemia vera. We showed that the expression of GPIIIa is decreasing during megakaryocyte polyploidization in normal and pathological situations.

Antigens, CD↗
PubMedDate not supplied

Inhibition of actin polymerization by cytochalasin B induces polyploidization and increases the number of nucleolar organizer regions in human megakaryocyte cell lines.

Megakaryocyte polyploidization is an advantageous and regulated mechanism which leads to an increase in platelet production. In megakaryocyte cell lines, polyploidization can be obtained by using cytochalasin B, an inhibitor of the actin polymerization. The Nucleolar Organizer Regions (AgNORs) are parts of nucleolar DNA transcribed into ribosomal RNA. They are detected by silver staining technique and their number is proportional to protein synthesis. In order to estimate protein synthesis in polyploidizing megakaryocytes, AgNORs were measured in three cell lines with megakaryocyte properties (DAMI, HEL and K562) after a 4-day culture in the presence or absence of cytochalasin B, an inhibitor of the actin polymerization. The mean number of AgNORs per cell was 16.4 +/- 4.3 (m +/- SEM); 24.4 +/- 2.5 and 13.6 +/- 3.1 for DAMI, HEL and K-562 cell lines, respectively. The addition of cytochalasin B (2 micrograms/ml) increased significantly the number of AgNORs per cell (DAMI: 437%, HEL: 384% and K-562: 345% of controls, p < 0.05 by t-test). Moreover, the numbers of nucleoles per cell after addition of cytochalasin B were augmented significantly (DAMI: 258%, HEL: 271% and K-562: 264% of controls, p < 0.05 by t-test). The total protein content estimated by Bradford's method increased significantly to 938%, 326% and 388% of controls in DAMI, HEL and K562, respectively (p < 0.05 by t-test) in cells where actin was inhibited by cytochalasin B. In the presence of cytochalasin B, the endomitotic index (EI) [mean of (log2 DNA content expressed in N) 1] measured by flow cytometry increased to 368%, 207% and 538%, for DAMI, HEL and K-562 cell lines, respectively (p < 0.05 by t-test) after treatment with cytochalasin B. In contrast, the number of AgNORs per unit of DNA (EI) and the total protein content per unit of DNA did not change for DAMI, HEL and K-562 cell lines (p < 0.05 by t-test) after treatment with cytochalasin B. In conclusion, the increase in the number of the Nucleolar Organizer Regions by an agent known to stimulate polyploidization of megakaryocytic cell lines suggests that polyploidization occurs by enhanced protein production proportionally to DNA synthesis.

Actins↗