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J Papamatheakis

Publications and source records attributed to J Papamatheakis.

35 records · Page 2Linked to original sources
PubMed1990

Induction of class II MHC antigen expression on the murine placenta by 5-azacytidine correlates with fetal abortion.

During the gestational cycle the placental tissue does not express class II MHC antigens and whether this phenomenon is important to fetal survival has not yet been evoked. It has been reported that class II antigen expression precedes renal and cardiac graft rejection, which may also be the case in fetal abortion. In a recent report we showed that placental cells can be induced to express class II antigens in vitro and that these cells undergo different regulatory mechanisms depending on their anatomical position in the placenta. Thus, spongiotrophoblast-derived cells express these antigens after interferon-gamma treatment, whereas labyrinthine trophoblast-derived cells are induced by 5-azacytidine. In the present study we examined the effect of 5-azacytidine on class II antigen expression in the placenta and fetal abortion in vivo. We report that 5-azacytidine, when given to pregnant females before the ectoplacental cone formation, dramatically increases fetal loss, which correlates with class II antigen expression in the labyrinthine trophoblast zone. No site effects of 5-azacytidine on placental cell proliferation, splenic T and B cell responses, or reproductive capability of treated females were observed. However, after treatment with 5-azacytidine placental cells can stimulate maternal spleen cells to proliferate in a mixed cell reaction, whereas untreated controls cannot. Furthermore, the abortive effect of 5-azacytidine can be rescued in allogeneic pregnancy by anti-paternal class II monoclonal antibody injection into the animals during the 5-azacytidine treatment. These results suggest that the maintenance of the class II antigen-negative expression on the placenta is indeed necessary to avoid maternal immune attack and ensure fetal survival.

Animals↗
PubMed1990

Intracytoplasmic detection of the Tac (p55) chain of interleukin-2 receptor in pre-B leukemic cells associated with a constitutive expression of Tac mRNA.

The pre-B Reh-6 leukemic cells do not express membrane interleukin-2 (IL-2)-R alpha (Tac or p55) chain; however, their incubation with PMA induces the expression of both high and low affinity IL-2-R. Northern analysis of nonstimulated Reh-6 as well as leukemic cells from patients with acute B cell precursor lymphoblastic leukemia displayed a constitutive expression of p55 mRNA transcripts, which could be enhanced by PMA. Both actinomycin-D and cycloheximide could abrogate PMA-induced p55 membrane expression, suggesting the need for de novo mRNA and protein synthesis. The increased PMA-induced p55 mRNA accumulation was an early event (4 hr) and could be enhanced, specifically, by rIL-2 because anti-Tac moAb inhibited this rIL-2-mediated effect. Immunofluorescence and cross-linking studies using 125I-rIL-2 failed to reveal membrane-associated p55 protein on both Reh-6 and patients' leukemic cells. Conversely, immunogold staining and electron microscopy studies, revealed p55 immunoreactive molecules in the cytoplasm but not in the nucleus of all Reh-6 cells. Using a sensitive EIA, p55 molecules could be detected in cell lysates but not the culture supernatants of Reh-6 cells, suggesting that p55 was not released into the culture medium. These results indicate that constitutively expressed p55 mRNA on pre-B leukemic cells is translated into a relative immunoreactive protein that cannot be expressed on cell surface for unknown, yet, reasons.

Blotting, Northern↗
PubMed1989

Induction of class II major histocompatibility complex antigens in murine placenta by 5-azacytidine and interferon-gamma involves different cell populations.

Class II MHC antigen expression is required for recognition of an alloantigen and generation of immune response. In rodents as well as in humans primary trophoblasts do not express class II MHC antigens. In this study we focused our interest on the mechanism(s) of class II antigen suppression on murine trophoblasts. First, we examined the possibility of gene inactivation by methylation and second the possibility of lymphokine regulation of the class II genes. The first possibility was tested by treatment of placental cells with 5-azacytidine (5-AzaC), a cytidine analog which upon incorporation into the DNA inhibits further methylation, thus leading to gene activation. In order to test the second possibility we treated placental cells with interferon-gamma (IFN-gamma) or interleukin 4 (IL4) which are known to induce class II antigen expression in many systems. We showed that treatment with 5-AzaC or IFN-gamma but not IL4 significantly increased class II expression on cytokeratin-positive and vimentin-negative adherent placental cells. Following placental cell fractionation we distinguished three cell subsets with different responsiveness to 5-AzaC and IFN-gamma. The first, characterized as placental macrophages, were induced to express class II MHC antigens only after IFN-gamma treatment. The other two subsets, characterized as trophoblasts, were isolated from the labyrinthine- and spongio-trophoblast layer of the placenta and showed class II inducibility to 5-AzaC and IFN-gamma, respectively. The results show that depending on the anatomical localization of trophoblasts within the placenta, various regulatory elements control gene expression, so that the placental barrier provides fetal protection at different levels.

Animals↗
PubMed1988

Molecular analysis of the mouse class II gene, E q alpha.

The structure and transcription of the mouse E q alpha gene were investigated by structural analysis of genomic clones, transient and stable cell line transformation, and spleen cell nuclear transcription studies. The transcription rate of Eq alpha is comparable to that of the Ek alpha allele. The q allele is transcribed to a normal size mRNA, but the Eq alpha mRNA level in spleen cells is 100-fold less than that of Ek alpha and is increased after cycloheximide treatment. The promoter region of the q allele can stimulate transcription of the chloramphenicol acetyl transferase gene after treatment with gamma interferon in transient expression assays. The Eq alpha gene was cloned and sequenced from -1630 nucleotide to +5200 nucleotide, and it shows 98% sequence identity with Eq alpha. A frame shift in codon 89 causes premature termination of translation, which probably accounts for its low steady state level of mRNA.

Alleles↗
PubMed1988

Isolation and characterization of cDNA clones encoding human liver glutamate dehydrogenase: evidence for a small gene family.

We have isolated a series of human liver cDNA clones encoding glutamate dehydrogenase. The cDNA-derived protein sequence specifies a single 558-amino acid long polypeptide including a cleavable signal sequence of 53 amino acids. Blotting analysis of RNA from human, monkey, and rabbit showed that glutamate dehydrogenase mRNA is present in various amounts in all tissues tested. Glutamate dehydrogenase mRNAs are of four sizes and are found in different ratios in different tissues; the predominant ones are approximately 3.5 and approximately 2.9 kilobases. Blot hybridization of human genomic DNA to nonoverlapping cDNA fragments revealed multiple bands, many of which hybridize with two or more probes in a manner inconsistent with the existence of a single GLUD gene. Moreover, two separate 36-base synthetic oligonucleotides corresponding to the coding region hybridize to multiple genomic fragments, confirming the existence of more than one GLUD-related gene in human.

Adult↗
PubMed1988

Multiple regulatory regions on the 5' side of the mouse E alpha gene.

The function of the 5'-flanking region of the mouse major histocompatibility complex gene Ed alpha has been studied by deletion analysis with the chloramphenicol acetyltransferase gene as a transient expression marker in various cell lines. This analysis reveals the presence of several control regions on the 5' side of the gene. Sequences between base pair (bp) -873 and bp -353 have a negative function in human and mouse fibroblasts but not in the mouse macrophage line WEHI-3. Additional positive and negative elements have been mapped between bp -353 and bp -38. A gamma-interferon response region has been also identified within that sequence. the 5' and 3' boundaries of the gamma-interferon response region have been located between bp -164 and bp -43. Inducible human cell lines showed the same gamma-interferon response region endpoints with the mouse cell line WEHI-3. A DNA fragment spanning the equivalent region of the mouse Ed beta gene confers gamma-interferon inducibility to the simian virus 40 and alpha-globin promoters in an orientation-independent manner. We further provide evidence that the conserved sequence motifs on the 5' side of all major histocompatibility complex class II genes are indispensable for gamma-interferon induction.

Animals↗
PubMed1985

Polymorphism in mouse and human class I H-2 and HLA genes is not the result of random independent point mutations.

Sufficient mouse H-2 and human HLA class I gene sequences have become available to make a statistical analysis of nucleotide variations within the multigene families possible. In the H-2 and HLA families, a group of four H-2K allelic sequences and three HLA-A sequences were compared with a group of four non-H-2 and three non-HLA-A sequences, respectively. Simple calculations show that nucleotide variations in each group do not occur in a random independent fashion. It is therefore possible that a number of mutations are "concerted" between the subgroups. Interestingly, these concerted mutations are clustered and distributed almost exclusively in the 5' end of H-2 and HLA genes, which is very rich in GC nucleotides, and where the dinucleotide CpG is particularly frequent. The general concept of unequal repair is proposed as the basis of a model which is supported by these observations.

Alleles↗
PubMed1981

Recurring defective variants of simian virus 40 containing monkey DNA segments.

Four independently and newly isolated defective variants of simian virus 40 have been characterized. All four are very similar, if not identical, to two previously and independently isolated variants (Wakamiya et al., J. Biol. Chem. 254:3584-3591, 1979; J. Papamatheakis, E. Kuff, E. Winocour, and M. F. Singer, J. Biol. Chem. 255:8919-8927, 1980). The documented similarities include restriction endonuclease maps and the presence of the same monkey DNA segments covalently linked to simian virus 40 DNA sequences. Each of the newly described variants was first detected upon serial passaging of wild-type simian virus 40 at a high multiplicity of infection at 33 degrees C as recently described (M. F. Singer and R. E. Thayer, J. Virol. 35:141-149, 1980). A variety of experiments support the idea that the various isolates were independent and do not reflect inadvertent cross-contamination. Two of the new isolates arose during passage of wild-type strain 777 virus in BSC-1 cells, one during passage of strain 776 in BSC-1 cells, and one during passage of strain 776 in primary African green monkey kidney cells. The two variants obtained after passage of strain 776 were shown to contain a particular recognition site for restriction endonuclease MboII within their simian virus 40 DNA segments, as do the two previous isolates. This site is not present in wild-type strain 776 DNA but is shown here to be present in wild-type strain 777 DNA. The surprising recurrence of closely related variants and particularly the unexpected presence of the endo R.MboII site in variants derived from passaging strain 776 suggest that these variants may arise by mechanisms other than recombination between the initial infecting viral genome and the host DNA.

Animals↗
PubMedDate not supplied

Chromosomal mapping of two members of the human glutamate dehydrogenase (GLUD) gene family to chromosomes 10q22.3-q23 and Xq22-q23.

Glutamate dehydrogenase (GLUD) is an important mitochondrial enzyme that participates in neuronal transmission by catalyzing the deamination of L-glutamate, which serves as a potent excitatory neurotransmitter. The direct involvement of GLUD in the pathogenesis of certain human neurodegenerative disorders has been suggested recently. To investigate its possible role in the induction and progression of these disorders, we have initiated studies focusing on the chromosomal organization of the several members of the GLUD family and their functional status. In the present study using a panel of human x rodent somatic cell hybrids and in situ hybridization to metaphase chromosomes, we documented that the members of the GLUD gene family are dispersed in the human genome. The functional GLUD1 gene was mapped to chromosome 10q22.3-q23, and an intronless processed gene (GLUDP1) to chromosome Xq22-q23, while the truncated intron-containing GLUD pseudogene GLUDP2 was also assigned on chromosome 10, but not closely linked to the GLUD1 gene. These results provide novel information concerning the chromosomal organization of the human GLUD gene family.

Animals↗
PubMedDate not supplied

Mouse genes coding for the major class I transplantation antigens: a mosaic structure might be related to the antigenic polymorphism.

The recent isolation, by recombinant DNA techniques, of cloned probes for mouse and human class I major transplantation antigens has initiated the molecular analysis of the corresponding genes. Mouse genes belong to a relatively large multigene family, whose members share extensive structural homologies. Sequence analyses suggest that some genes could have a mosaic structure. This feature might help us to understand one of the distinctive traits of these antigens: their large antigenic polymorphism.

Animals↗
PubMedDate not supplied

One and two-level regulation patterns affecting NF-kappa B mRNA and nuclear NF-kappa B activity after treatment with TNF-alpha, IFN-gamma and IL-4.

The transactivating nuclear factor NF-kappa B is believed to be important in the pathophysiology of many cellular systems and mainly during HIV infection. kappa B activation has also been implicated in the process of differentiation as a cell progresses to a more mature and functional stage. As induction of differentiation equals growth retardation we undertook this study in order to establish the role of NF-kappa B in cell growth and maturity. Thus we employed the well described HL-60 cellular system that expresses constitutively basal amounts of NF-kappa B and is susceptible to NF-kappa B induction by various biological or chemical agents. We also used known inducers of differentiation like TNF-alpha, IFN-gamma and IL-4 that interact via their corresponding surface receptors found on HL-60 cells. We first studied by Northern analysis the possible correlation between c-myc and NF-kappa B precursor (p105) mRNA. We witnessed that all three cytokines were able to confer proliferative senescence and down-regulate concomitantly c-myc and NF-kappa B mRNA levels, events chronologically in accord with induction of differentiation as assessed by the induction of HLA-DR surface antigens. It is known that TNF-alpha is capable of inducing nuclear kappa B activity in HL-60 as the cells progress to a more mature stage. Therefore we examined whether the other two cytokines could do the same during the time they lead the cells to a differentiated phenotype. If this was the case, nuclear activation of NF-kappa B should be obtained by the same factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗