5-Azacytidine affects the programming of expression of the somatic nucleus of Paramecium

Development ◽  
1989 ◽  
Vol 105 (3) ◽  
pp. 559-568 ◽  
Author(s):  
F.W. Kwok ◽  
S.F. Ng
Keyword(s):  
Sexual Reproduction ◽  
Cell Lines ◽  
Compensatory Mechanism ◽  
Paramecium Tetraurelia ◽  
Growth Depression ◽  
Somatic Nucleus ◽  
Asexual Propagation ◽  
Oral Development ◽  
Asexual Cycle

This report introduces a new system in the study of programming of genomic function during development of the somatic nucleus of Paramecium tetraurelia. Previous works have established a definite, but replaceable, role of the germ nuclei (micronuclei) in oral development in the asexual cycle; their removal from the cell generates viable amicronucleate cell lines, which characteristically suffer a transient period of growth depression marked by abnormal oral development. Such cell lines gradually recover, showing that a compensatory mechanism is activated in the absence of the germ nuclei to bring the cell back to near-normal. To test the notion that the somatic nucleus (macronucleus) is involved in this compensation, cells possessing micronuclei were treated with 5-azacytidine during sexual reproduction when new somatic nuclei develop. These cells were then propagated asexually for a number of fissions in the absence of the drug, and thereafter micronuclei were removed from them. The amicronucleate cell lines generated in this manner clearly did not suffer a depression as severe as the untreated controls did in terms of growth rate and oral development, and they recovered much sooner. This supports the notion that the somatic nucleus is the physical basis of the compensatory mechanism. This study suggests that the stomatogenic sequences in question normally become repressed in the somatic nucleus developing in sexual reproduction, and that 5-azacytidine administered to the cells at this time could alter this programme which then persists during subsequent asexual propagation. The possibility that the somatic nucleus is programmed by methylation of cytosine at the 5′ position is discussed.

The rescue of oral development of defective-micronucleate conjugants of Paramecium tetraurelia by normal gametic nuclei

1988 ◽  
Vol 90 (2) ◽  
pp. 287-293
Author(s):  
M. F. CHAU ◽  
STEPHEN F. NG
Keyword(s):  
Sexual Reproduction ◽  
Cell Lines ◽  
Early Stage ◽  
Sexual Cycle ◽  
Paramecium Tetraurelia ◽  
Laser Microbeam ◽  
Nuclear Reorganization ◽  
Oral Development ◽  
Derivatives Of

The present study further analyses the importance of postmeiotic divisional derivatives of the micronucleus in the development of the oral apparatus of Paramecium during sexual reproduction. Cell lines possessing defective micronuclei generated by laser microbeam irradiation of the micronucleus were employed. They exhibited anomalies in nuclear reorganization and stomatogenesis in the sexual cycle. During autogamy, in some cells the micronuclear cycle terminated shortly after meiosis, resulting in the loss of all postmeiotic micronuclear derivatives. Stomatogenesis became arrested at an early stage of assembly of the oral membranelles, but the old oral apparatus was resorbed as usual, leading to the production of astomatous cells at the end of the sexual cycle. Conjugation of these cell lines with normal micronucleates rescued both nucleogenesis and stomatogenesis in the defective micronucleate conjugant, primarily as a result of transfer of the male gametic nucleus from the normal conjugant to the defective-micronucleate mate. These observations demonstrate the stomatogenic significance, in particular in the initiation of oral membranelle assembly, of the gametic nuclei during sexual reproduction. The present study also suggests the possibility of micronuclear activities in the early part of the sexual cycle affecting postzygotic nucleogenesis.

Cortical positioning and the fate of oral structures during the sexual process in amicronucleate homopolar tandems of Paramecium

Development ◽  
1988 ◽  
Vol 102 (3) ◽  
pp. 587-594
Author(s):  
S.F. Ng
Keyword(s):  
Sexual Reproduction ◽  
Cell Lines ◽  
Low Frequency ◽  
Positional Information ◽  
Binary Fission ◽  
Transient Growth ◽  
Paramecium Tetraurelia ◽  
Growth Depression ◽  
Sexual Process

Paramecium tetraurelia normally resorbs the pre-existing oral apparatus (and develops a new one) during sexual reproduction. Violation of this rule was found in amicronucleate cell lines. These cell lines generated chains of two cells (homopolar tandems) at a low frequency, as a result of incomplete binary fission during a transient growth depression period following emicronucleation. In autogamous chains, the proter resorbed the pre-existing oral structures, while some of the ospisthes retained them. The oral structures in the opisthes of the chains were unusually close to the opisthes' anterior end. The ectopic location of these oral structures might account for their retention, formally understood in terms of the theory of positional information. It is suggested that nongenic factors, likely involving components of the rigid cortical matrix, are involved in the fixation of positional values.

scholarly journals The role of the micronucleus in stomatogenesis in sexual reproduction of Paramecium tetraurelia: laser microbeam irradiation of the micronucleus

1986 ◽  
Vol 86 (1) ◽  
pp. 287-303
Author(s):  
L.W. Tam ◽  
S.F. Ng
Keyword(s):  
Cell Lines ◽  
Critical Period ◽  
Buccal Cavity ◽  
Early Stage ◽  
Multiple Roles ◽  
Paramecium Tetraurelia ◽  
Laser Microbeam ◽  
Microbeam Irradiation ◽  
Recessive Mutations

Fifteen amicronucleate cell lines and 22 cell lines with defective micronuclei were obtained following selective laser microbeam irradiation of the micronucleus. The amicronucleate cell lines showed reduced growth rate and formed abnormal oral apparatuses in asexual reproduction, and failed to produce any oral apparatus in autogamy, in agreement with previous observations on amicronucleate cells obtained by micropipetting. The 22 cell lines with defective micronucleus exhibited various abnormalities of the oral apparatus newly formed during autogamy. These abnormalities included the arrest of membranelle assembly, reduction in the length of the buccal cavity and oral membranelles, disruption of the organization of the membranelles, quadrulation of the dorsal peniculus, and failure of addition of membranellar basal body rows. Hence the micronucleus plays multiple roles in sexual stomatogenesis, deciding early steps of oral membranelle assembly and affecting their subsequent patterning. Our results agree with the notion that the micronucleus acts during a critical period between the second meiotic division and up to the formation of the zygotic nucleus to control the early stage of oral membranelle assembly. Laser microbeam irradiation might have created recessive mutations and/or chromosomal aberrations, which were expressed during this critical period with the formation of abnormal postmeiotic nuclei.

Interspecific micronuclear transplantation in Paramecium: nucleogenesis and stomatogenesis in asexual and sexual reproduction

Development ◽  
1988 ◽  
Vol 103 (1) ◽  
pp. 179-191
Author(s):  
M.F. Chau ◽  
S.F. Ng
Keyword(s):  
Cell Division ◽  
Sexual Reproduction ◽  
Cell Lines ◽  
Essential Role ◽  
The Other ◽  
Sexual Cycle ◽  
Interspecific Incompatibility ◽  
Multicellular Development ◽  
Oral Development ◽  
Species Specific

The micronucleus of Paramecium plays an essential role in the development of the oral apparatus in both asexual and sexual cycles. The present study analyses this somatic function of the micronucleus by interspecific transplantation of the micronucleus between two species, P. jenningsi and P. tetraurelia. The two species are similar in nucleogenesis in the sexual cycle, in the dependence of stomatogenesis on the micronucleus and in the pattern of the oral ciliature. P. jenningsi, however, has a longer oral apparatus. Renucleated cell lines were derived from heterospecific transplantation (P. jenningsi amicronucleates implanted with micronuclei of P. tetraurelia), and also from homospecific transplantation (P. jenningsi). Both homo- and heterospecific transplants exhibited abnormal micronuclear propagation during cell division. In the sexual cycle, the heterospecific transplants exhibited more severe micronuclear anomalies, suggesting interspecific incompatibility. On the other hand, the stomatogenic consequences of the two types of transplants in the asexual and sexual cycles were similar. It is concluded that micronuclear functions, in the assembly and normal patterning of the oral ciliature in the sexual cycle, are not species-specific. However, the oral apparatuses developed by the homo- and heterospecific transplants were similar in length, and approaching that of normal P. jenningsi. Hence, even though the micronucleus is necessary for developing normal oral length, the oral length characteristic of a species is determined by species-specific nonmicronuclear factors. The present findings resemble heterospecific dermal-epidermal inductive interactions in multicellular development, with the micronucleus exerting a nonspecies-specific ‘intracellular inductive stimulus’ on the oral anarchic field to promote oral development.

The somatic function of the micronucleus in sexual reproduction of Paramecium tetraurelia: initiation of oral membranelle assembly

1988 ◽  
Vol 90 (1) ◽  
pp. 157-166
Author(s):  
M. F. CHAU ◽  
STEPHEN F. NG
Keyword(s):  
Sexual Reproduction ◽  
Laser Irradiation ◽  
Cell Lines ◽  
Paramecium Tetraurelia ◽  
Laser Microbeam ◽  
Microbeam Irradiation ◽  
Nuclear Reorganization

In a previous study, cell lines possessing defective micronuclei, generated by laser-microbeam irradiation, gave rise to cells lacking both oral apparatus and micronuclear derivatives after autogamy. It was concluded that astomy arose as a result of degeneration of all of the meiotic products of the micronuclei after meiotic telophase II, instead of leaving one product for subsequent nuclear reorganization. The present study consolidates this conclusion by employing 15 micronucleus-defective cell lines; these were generated by laser-irradiation of the micronucleus, treatment of the cells with cis-dichlorodiamineplatinum (II), and conjugation between diploids and amicronucleates to produce haploids. A good correlation between the presence of pregametic, gametic and zygotic nuclei and the initiation of oral membranelle assembly in stomatogenesis was demonstrated in 17 cases of autogamy. Therefore, postmeiotic micronuclear activities up to the zygotic nucleus stage, in particular in the gametic stage, are crucial for the initiation of oral membranelle assembly, while premeiotic micronuclear activities are insufficient. Micronuclear genic factors are also likely to be involved in the determination of the fate of the meiotic products.

Glioblastoma invasion and NMDA receptors: A novel prospect

2019 ◽  
Vol 106 (3) ◽  
pp. 250-260 ◽  
Author(s):  
DN Nandakumar ◽  
P Ramaswamy ◽  
C Prasad ◽  
D Srinivas ◽  
K Goswami
Keyword(s):  
Glutamate Receptors ◽  
Cell Lines ◽  
Intracellular Signaling ◽  
Transcript Level ◽  
Glioblastoma Cells ◽  
Invasion And Migration ◽  
Matrigel Invasion ◽  
Nmdar Activation ◽  
And Migration

Purpose Glioblastoma cells create glutamate-rich tumor microenvironment, which initiates activation of ion channels and modulates downstream intracellular signaling. N-methyl-D-aspartate receptors (NMDARs; a type of glutamate receptors) have a high affinity for glutamate. The role of NMDAR activation on invasion of glioblastoma cells and the crosstalk with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is yet to be explored. Main methods LN18, U251MG, and patient-derived glioblastoma cells were stimulated with NMDA to activate NMDAR glutamate receptors. The role of NMDAR activation on invasion and migration and its crosstalk with AMPAR were evaluated. Invasion and migration of glioblastoma cells were investigated by in vitro trans-well Matrigel invasion and trans-well migration assays, respectively. Expression of NMDARs and AMPARs at transcript level was evaluated by quantitative real-time polymerase chain reaction. Results We determined that NMDA stimulation leads to enhanced invasion in LN18, U251MG, and patient-derived glioblastoma cells, whereas inhibition of NMDAR using MK-801, a non-competitive antagonist of the NMDAR, significantly decreased the invasive capacity. Concordant with these findings, migration was significantly augmented by NMDAR in both cell lines. Furthermore, NMDA stimulation upregulated the expression of GluN2 and GluA1 subunits at the transcript level. Conclusions This study demonstrated the previously unexplored role of NMDAR in invasion of glioblastoma cells. Furthermore, the expression of the GluN2 subunit of NMDAR and the differential overexpression of the GluA1 subunit of AMPAR in both cell lines provide a plausible rationale of crosstalk between these calcium-permeable subunits in the glutamate-rich microenvironment of glioblastoma.

Stew in its Own Juice: Protein Homeostasis Machinery Inhibition Reduces Cell Viability in Multiple Myeloma Cell Lines

2019 ◽  
Vol 19 (2) ◽  
pp. 112-119 ◽  
Author(s):  
Mariana B. de Oliveira ◽  
Luiz F.G. Sanson ◽  
Angela I.P. Eugenio ◽  
Rebecca S.S. Barbosa-Dantas ◽  
Gisele W.B. Colleoni
Keyword(s):  
Multiple Myeloma ◽  
Cell Death ◽  
Cell Viability ◽  
Cell Lines ◽  
Treatment Options ◽  
Compensatory Mechanism ◽  
Protein Homeostasis ◽  
Protein Response ◽  
Rpmi 8226

Introduction:Multiple myeloma (MM) cells accumulate in the bone marrow and produce enormous quantities of immunoglobulins, causing endoplasmatic reticulum stress and activation of protein handling machinery, such as heat shock protein response, autophagy and unfolded protein response (UPR).Methods:We evaluated cell lines viability after treatment with bortezomib (B) in combination with HSP70 (VER-15508) and autophagy (SBI-0206965) or UPR (STF- 083010) inhibitors.Results:For RPMI-8226, after 72 hours of treatment with B+VER+STF or B+VER+SBI, we observed 15% of viable cells, but treatment with B alone was better (90% of cell death). For U266, treatment with B+VER+STF or with B+VER+SBI for 72 hours resulted in 20% of cell viability and both treatments were better than treatment with B alone (40% of cell death). After both triplet combinations, RPMI-8226 and U266 presented the overexpression of XBP-1 UPR protein, suggesting that it is acting as a compensatory mechanism, in an attempt of the cell to handle the otherwise lethal large amount of immunoglobulin overload.Conclusion:Our in vitro results provide additional evidence that combinations of protein homeostasis inhibitors might be explored as treatment options for MM.

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