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M Jotterand-Bellomo

Publications and source records attributed to M Jotterand-Bellomo.

At least 19 recordsLinked to original sources
PubMed1991

[Unusual initial manifestation in a case of refractory anemia with excess of blasts].

In 1987, a 50-year-old patient presented with isolated thrombocytopenia (27,000/mm3) which proved to be refractory to steroid medication and high i.v. doses of immunoglobulin. Two years later he developed macrocytic anemia. Chromosomal analysis confirmed the diagnosis of myelodysplastic syndrome (MDS), refractory anemia type with blast excess. Cytogenetically, three cellular populations were observed: one normal (75% of metaphases) and two abnormal, clone A (2%) 46,XY, del(5q), del(11q), and clone B (23%) 46,XY, del(5q), del(11q) plus 2 other anomalies. Evolution was characterized by worsening of the bicytopenia with marked hypoplasia of the megakaryocytic and erythroid series while the percentage of blasts remained stable. Concerning the chromosomal markers, the normal population disappeared and clone A became predominant (clone A 97%, clone B 3%). This case shows that isolated thrombocytopenia can be the sole initial manifestation of MDS. We discuss the possibility that "refractory thrombocytopenia" constitutes a diagnostic category like refractory anemia or refractory anemia with ring sideroblasts. The proliferative advantage of clone A or the disadvantage of clone B may be due to the occurrence of new, cytogenetically non-detectable mutations.

Anemia, Refractory, with Excess of Blasts↗
PubMed1990

Inducible and constitutive MHC class II gene expression. Distinct tissue-specific genetic controls.

B cells express MHC class II Ag in a constitutive fashion, whereas macrophages can do so only after induction by a variety of exogenous stimuli. In this study we describe interspecies somatic cell hybrids between the human B cell Raji and the murine macrophage cell P388 D1. This murine cell line does not express detectable levels of class II mRNA. Phenotypic, molecular, and karyotype analysis of a series of hybrids showed that murine macrophage class II genes can be expressed in a constitutive fashion under the control of the human B cell genome. This event is the consequence of de novo accumulation of class II specific mRNA and thus probably reflects activation of transcription. In certain cases the amount of murine class II Ag expressed on the surface of the hybrid cell was significantly higher than the one observed in the parental macrophage cells after induction with IFN-gamma and was not further modified by treatment with the murine lymphokine. Reversion from a murine class II-positive to class II-negative cell surface phenotype in the hybrids correlated with reduced expression of human markers and more important with segregation of human chromosomes. Interestingly, in this case certain hybrids still expressed detectable levels of murine class II mRNA and increased levels of murine invariant chain mRNA when compared with parental P388 D1 murine macrophage cells. These results indicate that constitutive class II gene expression behaves as a dominant trait in B cell x macrophage somatic cell hybrids. Possible mechanisms responsible of the different control of class II gene expression during cell type differentiation are discussed.

Animals↗
PubMed1990

A new case of myelodysplastic syndrome with 6p rearrangement.

Bone marrow cells from a patient with refractory anemia with ringed sideroblasts were studied cytogenetically. All metaphases analyzed revealed an abnormal karyotype with complex defects. The most prominent defect consisted of a rearrangement of the short arm of chromosome 6. Until now, 6p rearrangements have been preferentially observed in myelodysplastic patients with a history of previous exposure to toxic products such as alkylating agents or environmental factors of occupational origin. Although our patient was not exposed to alkylating agents, for about 20 years he has regularly consumed important quantities of analgesics, tranquilizers, and nonsteroidal antiinflammatory drugs. The eventual relationship between sideroblastic anemia and drug abuse, as well as the existence of chromosome sites preferentially rearranged in the bone marrow cells of myelodysplastic patients, are discussed.

Adult↗
PubMed1990

Cytogenetic analysis of 54 cases of myelodysplastic syndrome.

Fifty-four patients with myelodysplastic syndrome (MDS) (35 men and 19 women aged 34-92 years) were studied cytogenetically. Bone marrow cell culture and chromosome preparation were performed according to four different protocols used in parallel: methotrexate (MTX)-synchronized or thymidine (TdR)-unsynchronized techniques, and presence or absence of 5637 conditioned medium (CM). Some patients responded better to MTX; others had better results with TdR exposure only. Use of 5637 CM generally improved quantity and quality of metaphases. A cytogenetic result was obtained in 53 cases. 60% of the patients had a chromosome abnormality. Percentage of abnormality varied from one French-American-British (FAB) subtype to the other: 62% in refractory anemia with ringed sideroblasts (RARS, 8/13), 50% in refractory anemia (RA, 6/12), 60% in refractory anemia with excess of blasts (RAEB, 3/5), 77% in refractory anemia with excess of blasts in transformation (RAEB-T, 7/9), and 57% in chronic myelomonocytic leukemia (CMMoL, 8/14). Chromosome defects were subdivided into three categories: single, two, and complex defects. The most frequent chromosome abnormalities, either single or one of two or complex defects were del(5q) or monosomy 5 (13 cases), trisomy or rearrangement of chromosome 8 (eight cases), total or partial monosomy or rearrangement of chromosome 7 (eight cases), Y loss (seven cases), and del(20q) (two cases). With the exception of del(5q) in macrocytic RA, this study confirms the absence of chromosome defects specific to each FAB category of MDS. Recurrent defects in MDS are relatively limited, however, in terms of chromosomes involved and type of abnormality. Consequently, these defects, mostly of deleted type, are assumed to play a specific role in the genesis of myelodysplasia.

Adult↗
PubMed1989

Loss of interleukin 2 dependence in cloned interleukin 2-dependent rat T lymphocyte x BW5147 hybridomas is not associated with segregation of a specific pair of rat chromosomes.

A fusion between the mouse AKR thymoma BW5147 and a culture of homogeneously OX8+ (CD8) rat T lymphoblasts yield interleukin (IL) 2-dependent T cell hybridomas when selected in HAT medium supplemented with IL 2-containing supernatants of concanvalin A-activated cells and dexamethasone. IL 2-independent variants can be selected from cloned IL2-dependent hybrids in the absence of conditioned medium. Karyotype analysis was used to test a previously proposed hypothesis according to which IL2-independent variants arise through loss of a specific cytotoxic T lymphocyte (rat) chromosome carrying a gene responsible for IL2 dependence. Comparison of karyotypes of several independently derived hybrids with those of their IL 2-independent variants showed that the hybrids contain at least one homologue of all rat chromosomes, and that no pair of rat chromosomes is consistently absent in the IL 2-independent variants.

Animals↗
PubMed1989

Constitutional karyotype in retinoblastoma. Case report and review of literature.

High resolution karyotype was performed in 13 retinoblastoma patients. A mosaic pattern for del(13)(q14.1;q14.3) was found in a girl with sporadic bilateral retinoblastoma and midface dysmorphism. In addition, 162 cases of 13q aberrations were reviewed, including 140 retinoblastoma patients and 22 non-penetrance 13q14 deletions. Some epidemiological and genetic involvements are discussed.

Carboxylesterase↗
PubMed1988

[Chromosomes of the Cuming rat, Phloeomys cumingi Waterhouse, 1839 (Mammalia: Rodentia)].

The chromosome formula of Phloeomys cumingi is described for the first time. The diploid number is 40 in both sexes, the fundamental number is 60. The 38 autosomes are divided into 5 pairs of submetacentrics, 4 pairs of metacentrics, 6 pairs of large acrocentrics and 4 pairs of small acrocentrics. The sex chromosomes are large and rich in C-positive heterochromatin. The comparative analysis of the chromosomes of Phloeomys with those of Mus musculus and Rattus norvegicus puts forward numerous analogies between these 3 species. According to the comparison of the chromosomes of Phloeomys with the ancestral karyotype of the Cricetidae, eleven chromosome pairs at least have conserved their original G-banding pattern. Although chromosome data reveal a close relationship between Phloeomys and Muridae, they do not exclude the possible belonging of this species to a separate family, that of Phloeomyidae.

Animals↗
PubMed1988

Active suppression of major histocompatibility complex class II gene expression during differentiation from B cells to plasma cells.

Constitutive expression of major histocompatibility complex class II genes is acquired very early in B-cell ontogeny and is maintained up to the B-cell blast stage. Terminal differentiation in plasma cells is, however, accompanied by a loss of class II gene expression. In B cells this gene system is under the control of several loci encoding transacting factors with activator function, one of which, the aIr-1 gene product, operates across species barriers. In this report human class II gene expression is shown to be extinguished in somatic cell hybrids between the human class II-positive B-cell line Raji and the mouse class II-negative plasmacytoma cell line P3-U1. Since all murine chromosomes are retained in these hybrids and no preferential segregation of a specific human chromosome is observed, the results are compatible with the presence of suppressor factors of mouse origin, operating across species barriers and inhibiting class II gene expression. Suppression seems to act at the level of transcription or accumulation of class II-specific mRNA, since no human, and very few murine, class II transcripts are detectable in the hybrids.

Animals↗
PubMed1988

Cytogenetic analysis of 570 first trimester chorionic villi samplings: technique and results.

In this report we present our experience based on 570 chorionic villi samplings performed by the transcervical method at 8 to 12 weeks gestation. Cytogenetic results were obtained for 551 samples, hence a failure rate of 3.33%. The previously described technique was modified by prolonging the incubation period to 48 hours. The total number of abnormalities was 26, which represents 4.71% of our sample. Of 24 chromosomal abnormalities, 21 were unbalanced and 3 were balanced of parental origin. Five discordant cases are thoroughly discussed.

Chorionic Villi↗
PubMed1987

Distinct mechanisms regulate MHC class II gene expression in B cells and macrophages.

In a previous series of studies, we had shown that the constitutive Ia expression in an immunoselected Ia-human B cell variant, RJ 2.2.5, could be restored by somatic cell hybridization with mouse B cells. These experiments allowed us to show the existence of a transacting activator factor(s) operating across species barriers and encoded by the aIr-1 locus located on mouse chromosome 16. The aim of the present study was to investigate whether the B cell constitutive Ia expression and the inducible Ia expression, as seen in macrophages treated with IFN-gamma, are controlled by similar intracellular factors. To this purpose, we constructed an interspecies somatic cell hybrid between the human Ia-RJ 2.2.5 B cells and the mouse Ia-P388 D1 macrophage cells. These murine cells transiently express Ia antigens when incubated with IFN-gamma. Our results show that RJ 2.2.5 X P388 D1 cell hybrids do not express either human or mouse class II gene products. Treatment with human recombinant IFN-gamma did not modify the MHC phenotype of either the hybrid cells or the human parental cells. On the other hand, treatment of the hybrid cells with murine recombinant IFN-gamma resulted in de novo expression of mouse Ia mRNA and corresponding cell surface antigens without, however, reinduction of the human class II-positive phenotype. Furthermore, treatment with the mouse lymphokine significantly increased the levels of human HLA class I mRNA and corresponding cell surface antigens in the hybrid cells, further reinforcing the notion of the existence of non-species-specific secondary mediators generated after receptor-ligand interaction in the IFN-gamma system. Together, these results indicate that in macrophages, the intracellular events taking place after binding of IFN-gamma with its own receptor and leading to the expression of a class II-positive phenotype do not operate via an activation of the aIr-1 locus and/or its products. Thus, at least in our experimental system, we can firmly establish a first, relevant distinction between constitutive and inducible class II gene expression. This difference, dictated by the specific differentiation program of each cell type, may be relevant for the understanding of the function of class II gene products.

Animals↗
PubMed1986

aIr-1, a newly found locus on mouse chromosome 16 encoding a trans-acting activator factor for MHC class II gene expression.

RJ 2.2.5 is a human B cell line that has lost the capacity to express MHC class II genes. The human class II-positive phenotype is restored in somatic cell hybrids between RJ 2.2.5 and mouse spleen cells. By karyotype and molecular studies of an informative family of hybrids we have now shown that the reexpression of human class II gene products, as well as the maintenance of the mouse class II-positive phenotype, correlates with the presence of mouse chromosome 16. Thus, the existence on this mouse chromosome of a newly found locus, designated by us aIr-1, that determines a trans-acting activator function for class II gene expression, is established. Possible implications of this finding are discussed.

Animals↗