scholarly journals Cytolytic T lymphocyte function is independent of growth phase and position in the mitotic cycle

1981 ◽  
Vol 154 (2) ◽  
pp. 575-580 ◽  
Author(s):  
RP Sekaly ◽  
HR MacDonald ◽  
P Zaech ◽  
AL Glasebrook ◽  
J-C Cerottini
Keyword(s):  
Cell Cycle ◽  
Growth Phase ◽  
Mitotic Cycle ◽  
Mitotic Cell ◽  
Lytic Activity ◽  
Lymphocyte Function ◽  
Significant Difference ◽  
Cytolytic T Lymphocyte ◽  
Release Assay ◽  
Phase Regulation

We have investigated mitotic cell cycle and growth phase regulation of homogeneous cytolytic T lymphocytes (CTL). Two independently derived CTL clones were stained with the DNA-binding dye Hoechst 33342, sorted in a fluorescence-activated cell sorter according to their position in the cell cycle, and then assayed for specific lytic activity using a short-term (30 min) (51)Cr release assay. Results show that lytic activity remained unchanged throughout the cell cycle. Furthermore, there was no significant difference in the lytic activity of CTL clones growing exponentially or arrested in a plateau phase. These results demonstrate that T cell-mediated cytolysis is independent of growth phase and position in the cell cycle.

scholarly journals A Meiosis-Specific Cyclin Regulated by Splicing Is Required for Proper Progression through Meiosis

2005 ◽  
Vol 25 (15) ◽  
pp. 6330-6337 ◽  
Author(s):  
Jordi Malapeira ◽  
Alberto Moldón ◽  
Elena Hidalgo ◽  
Gerald R. Smith ◽  
Paul Nurse ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Chromosome Segregation ◽  
Mitotic Cycle ◽  
Mitotic Cell ◽  
S Phase ◽  
Mitotic Cell Cycle ◽  
Meiotic Cell ◽  
Cyclin Dependent Kinases ◽  
Negative Factor

ABSTRACT The meiotic cell cycle is modified from the mitotic cell cycle by having a premeiotic S phase which leads to high levels of recombination, a reductional pattern of chromosome segregation at the first division, and a second division with no intervening DNA synthesis. Cyclin-dependent kinases are essential for progression through the meiotic cell cycle, as for the mitotic cycle. Here we show that a fission yeast cyclin, Rem1, is present only during meiosis. Cells lacking Rem1 have impaired meiotic recombination, and Rem1 is required for premeiotic DNA synthesis when Cig2 is not present. rem1 expression is regulated at the level of both transcription and splicing, with Mei4 as a positive and Cig2 a negative factor of rem1 splicing. This regulation ensures the timely appearance of the different cyclins during meiosis, which is required for the proper progression through the meiotic cell cycle. We propose that the meiosis-specific B-type cyclin Rem1 has a central role in bringing about progression through meiosis.

scholarly journals Reprogramming the Cell Cycle for Endoreduplication in Rodent Trophoblast Cells

1998 ◽  
Vol 9 (4) ◽  
pp. 795-807 ◽  
Author(s):  
Alasdair MacAuley ◽  
James C. Cross ◽  
Zena Werb
Keyword(s):  
Cell Cycle ◽  
Cell Differentiation ◽  
Giant Cell ◽  
Mitotic Cycle ◽  
Mitotic Cell ◽  
Giant Cells ◽  
Cyclin B ◽  
Helix Loop Helix ◽  
Trophoblast Giant Cells ◽  
Cycle Regulation

Differentiation of trophoblast giant cells in the rodent placenta is accompanied by exit from the mitotic cell cycle and onset of endoreduplication. Commitment to giant cell differentiation is under developmental control, involving down-regulation of Id1and Id2, concomitant with up-regulation of the basic helix-loop-helix factor Hxt and acquisition of increased adhesiveness. Endoreduplication disrupts the alternation of DNA synthesis and mitosis that maintains euploid DNA content during proliferation. To determine how the mammalian endocycle is regulated, we examined the expression of the cyclins and cyclin-dependent kinases during the transition from replication to endoreduplication in the Rcho-1 rat choriocarcinoma cell line. We cultured these cells under conditions that gave relatively synchronous endoreduplication. This allowed us to study the events that occur during the transition from the mitotic cycle to the first endocycle. With giant cell differentiation, the cells switched cyclin D isoform expression from D3 to D1 and altered several checkpoint functions, acquiring a relative insensitivity to DNA-damaging agents and a coincident serum independence. The initiation of S phase during endocycles appeared to involve cycles of synthesis of cyclins E and A, and termination of S was associated with abrupt loss of cyclin A and E. Both cyclins were absent from gap phase cells, suggesting that their degradation may be necessary to allow reinitiation of the endocycle. The arrest of the mitotic cycle at the onset of endoreduplication was associated with a failure to assemble cyclin B/p34cdk1complexes during the first endocycle. In subsequent endocycles, cyclin B expression was suppressed. Together these data suggest several points at which cell cycle regulation could be targeted to shift cells from a mitotic to an endoreduplicative cycle.

scholarly journals Clonal heterogeneity in the requirement for T3, T4, and T8 molecules in human cytolytic T lymphocyte function.

1984 ◽  
Vol 159 (3) ◽  
pp. 921-934 ◽  
Author(s):  
A Moretta ◽  
G Pantaleo ◽  
M C Mingari ◽  
L Moretta ◽  
J C Cerottini
Keyword(s):  
Mixed Lymphocyte Culture ◽  
Lymphocyte Culture ◽  
Cytolytic Activity ◽  
Lytic Activity ◽  
Target Cells ◽  
Lymphocyte Function ◽  
Clonal Heterogeneity ◽  
Surface Molecules ◽  
Cytolytic T Lymphocyte ◽  
Susceptible Clone

In an attempt to define the requirement of T8, T4, and T3 surface molecules in functional interactions occurring between human cytolytic T lymphocytes (CTL) and specific target cells, we have analyzed a large number of CTL clones derived from primary mixed lymphocyte culture (MLC) T cell populations for their susceptibility to inhibition by monoclonal antibodies (mAb) directed against these surface antigens. In most experiments, MLC T cells were stained with B9.4 (anti-T8) or OKT4 (anti-T4) mAb, separated into positive and negative cells using a fluorescence-activated cell sorter (FACS) and cloned under limiting conditions. While the lytic activity of the majority of T8+ CTL clones was inhibited by B9.4 mAb, approximately 15% of these clones were unaffected even in the presence of excess antibody. Flow cytofluorometric analysis of T8 antigen in individual clones did not show any correlation between the amount of T8 antigen expressed, the magnitude of cytolytic activity and the susceptibility (or lack thereof) to inhibition by B9.4 mAb. Of the 16 T4+ CTL clones analyzed, 7 were resistant to inhibition by OKT4 mAb even at doses 10-fold higher than that sufficient for complete inhibition of susceptible clones. Again, no correlation was found between the amount of T4 antigen expressed and the susceptibility to inhibition by the corresponding antibody. The same sets of T8+ and T4+ CTL clones were also analyzed for their susceptibility to inhibition by OKT3 mAb. Although all of the clones expressed the T3 surface antigen, only 15/23 T8+ clones and 9/14 T4+ clones were inhibited by anti-T3 mAb. To further document this clonal heterogeneity, we selected two T3+ T4- T8+ CTL clones that had no concomitant NK-like activity. One clone was resistant to inhibition by OKT3 mAb, whereas the other was highly susceptible. Incubation with OKT3 mAb resulted in modulation of the T3 molecules in both clones. Following modulation, however, the cytolytic activity of the resistant clones was unaffected, whereas the lytic activity of the susceptible clone was abrogated. These results thus indicate extensive clonal heterogeneity in the requirement for T3, T4, and T8 molecules in CTL function. Moreover, it appears that T3 molecules are not always physically and functionally linked to CTL receptor structures.

The Drosophila gene morula inhibits mitotic functions in the endo cell cycle and the mitotic cell cycle

Development ◽  
1997 ◽  
Vol 124 (18) ◽  
pp. 3543-3553 ◽  
Author(s):  
B.H. Reed ◽  
T.L. Orr-Weaver
Keyword(s):  
Cell Cycle ◽  
Mitotic Cycle ◽  
Mitotic Cell ◽  
Cyclin B ◽  
Dual Function ◽  
Nurse Cells ◽  
M Cell ◽  
Ring Gland ◽  
Dividing Cells ◽  
A Cell

In the endo cell cycle, rounds of DNA replication occur in the absence of mitosis, giving rise to polyploid or polytene cells. We show that the Drosophila morula gene is essential to maintain the absence of mitosis during the endo cycle. During oogenesis in wild-type Drosophila, nurse cells become polyploid and do not contain cyclin B protein. Nurse cells in female-sterile alleles of morula begin to become polyploid but revert to a mitotic-like state, condensing the chromosomes and forming spindles. In strong, larval lethal alleles of morula, the polytene ring gland cells also inappropriately regress into mitosis and form spindles. In addition to its role in the endo cycle, morula function is necessary for dividing cells to exit mitosis. Embryonic S-M cycles and the archetypal (G1-S-G2-M) cell cycle are both arrested in metaphase in different morula mutants. These phenotypes suggest that morula acts to block mitosis-promoting activity in both the endo cycle and at the metaphase/anaphase transition of the mitotic cycle. Consistent with this, we found cyclin B protein to be inappropriately present in morula mutant nurse cells. Thus morula serves a dual function as a cell cycle regulator that promotes exit from mitosis and maintains the absence of mitosis during the endo cycle, possibly by activating the cyclin destruction machinery.

Notch-Delta signaling induces a transition from mitotic cell cycle to endocycle inDrosophilafollicle cells

Development ◽  
2001 ◽  
Vol 128 (23) ◽  
pp. 4737-4746 ◽  
Author(s):  
Wu-Min Deng ◽  
Cassandra Althauser ◽  
Hannele Ruohola-Baker
Keyword(s):  
Cell Cycle ◽  
Mitotic Cycle ◽  
Notch Pathway ◽  
Follicle Cell ◽  
Delta Function ◽  
Mitotic Cell ◽  
Follicle Cells ◽  
Transcriptional Level ◽  
M Cell ◽  
Normal Transition

In many developmental processes, polyploid cells are generated by a variation of the normal cell cycle called the endocycle in which cells increase their genomic content without dividing. How the transition from the normal mitotic cycle to endocycle is regulated is poorly understood. We show that the transition from mitotic cycle to endocycle in the Drosophila follicle cell epithelium is regulated by the Notch pathway. Loss of Notch function in follicle cells or its ligand Delta function in the underlying germline disrupts the normal transition of the follicle cells from mitotic cycle to endocycle, mitotic cycling continues, leading to overproliferation of these cells. The regulation is at the transcriptional level, as Su(H), a downstream transcription factor in the pathway, is also required cell autonomously in follicle cells for proper transitioning to the endocycle. One target of Notch and Su(H) is likely to be the G2/M cell cycle regulator String, a phosphatase that activates Cdc2 by dephosphorylation. String is normally repressed in the follicle cells just before the endocycle transition, but is expressed when Notch is inactivated. Analysis of the activity of String enhancer elements in follicle cells reveals the presence of an element that promotes expression of String until just before the onset of polyploidy in wild-type follicle cells but well beyond this stage in Notch mutant follicle cells. This suggests that it may be the target of the endocycle promoting activity of the Notch pathway. A second element that is insensitive to Notch regulation promotes String expression earlier in follicle cell development, which explains why Notch, while active at both stages, represses String only at the mitotic cycle-endocycle transition.

Immunocytochemical studies on the behavior of RuBisCO and LHCP II during the cell cycle of synchronized Euglena gracilis

1990 ◽  
Vol 48 (3) ◽  
pp. 662-663
Author(s):  
Tetsuaki Osafune ◽  
Shuji Sumida ◽  
Tomoko Ehara ◽  
Eiji Hase ◽  
Jerome A. Schiff
Keyword(s):  
Cell Cycle ◽  
Immunoelectron Microscopy ◽  
Growth Phase ◽  
Euglena Gracilis ◽  
Dark Period ◽  
Light Period ◽  
Carboxylase Activity ◽  
Immunocytochemical Studies ◽  
Lhcp Ii

Changes in the morphology of pyrenoid and the distribution of RuBisCO in the chloroplast of Euglena gracilis were followed by immunoelectron microscopy during the cell cycle in a light (14 h)- dark (10 h) synchronized culture under photoautotrophic conditions. The imrnunoreactive proteins wereconcentrated in the pyrenoid, and less densely distributed in the stroma during the light period (growth phase, Fig. 1-2), but the pyrenoid disappeared during the dark period (division phase), and RuBisCO was dispersed throughout the stroma. Toward the end of the division phase, the pyrenoid began to form in the center of the stroma, and RuBisCO is again concentrated in that pyrenoid region. From a comparison of photosynthetic CO2-fixation with the total carboxylase activity of RuBisCO extracted from Euglena cells in the growth phase, it is suggested that the carboxylase in the pyrenoid functions in CO2-fixation in photosynthesis.

scholarly journals The Short Life Span of Saccharomyces cerevisiae sgs1 and srs2 Mutants Is a Composite of Normal Aging Processes and Mitotic Arrest Due to Defective Recombination

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1531-1542 ◽  
Author(s):  
Mitch McVey ◽  
Matt Kaeberlein ◽  
Heidi A Tissenbaum ◽  
Leonard Guarente
Keyword(s):  
Cell Cycle ◽  
Life Span ◽  
Mitotic Cell ◽  
Dna Helicase ◽  
Premature Aging ◽  
Growth Defect ◽  
Short Life Span ◽  
Single Strand Annealing ◽  
Late Generation ◽  
Strand Annealing

Abstract Evidence from many organisms indicates that the conserved RecQ helicases function in the maintenance of genomic stability. Mutation of SGS1 and WRN, which encode RecQ homologues in budding yeast and humans, respectively, results in phenotypes characteristic of premature aging. Mutation of SRS2, another DNA helicase, causes synthetic slow growth in an sgs1 background. In this work, we demonstrate that srs2 mutants have a shortened life span similar to sgs1 mutants. Further dissection of the sgs1 and srs2 survival curves reveals two distinct phenomena. A majority of sgs1 and srs2 cells stops dividing stochastically as large-budded cells. This mitotic cell cycle arrest is age independent and requires the RAD9-dependent DNA damage checkpoint. Late-generation sgs1 and srs2 cells senesce due to apparent premature aging, most likely involving the accumulation of extrachromosomal rDNA circles. Double sgs1 srs2 mutants are viable but have a high stochastic rate of terminal G2/M arrest. This arrest can be suppressed by mutations in RAD51, RAD52, and RAD57, suggesting that the cell cycle defect in sgs1 srs2 mutants results from inappropriate homologous recombination. Finally, mutation of RAD1 or RAD50 exacerbates the growth defect of sgs1 srs2 cells, indicating that sgs1 srs2 mutants may utilize single-strand annealing as an alternative repair pathway.

Ethylisopropylamiloride-sensitive pH control mechanisms modulate vascular smooth muscle cell growth

1991 ◽  
Vol 260 (3) ◽  
pp. C581-C588 ◽  
Author(s):  
A. Bobik ◽  
A. Grooms ◽  
P. J. Little ◽  
E. J. Cragoe ◽  
S. Grinpukel
Keyword(s):  
Cell Cycle ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Mitotic Cell ◽  
Ph Control ◽  
S Phase ◽  
Control Mechanisms ◽  
Aortic Smooth Muscle ◽  
Exchange Activity

The reported effects of alterations in Na-H exchange activity on mitogenesis are variable and appear dependent on the cell type examined. We examined the effects of reductions in ethylisopropylamiloride (EIPA)-sensitive pH-regulating mechanisms including Na-H exchange and alterations in intracellular pH (pHi) on the growth characteristics of rat aortic smooth muscle cells (RASM) cultured in serum-containing bicarbonate-buffered medium. Exposure of RASM replicating in bicarbonate-containing medium to the Na-H exchange inhibitors EIPA, dimethylamiloride (DMA), or amiloride (A) attenuated their replication rate. The order of potency of the inhibitors (EIPA greater than DMA much greater than A) was similar to their documented effects on Na-H exchange activity and to their order of potency for inhibiting recovery from CO2-induced acidosis in these cells. Reductions in pHi induced by lowering extracellular pH also attenuated the incorporation of [3H]-thymidine into DNA, while increases in pHi were associated with an acceleration in the rate of incorporation of [3H]thymidine into DNA. The effects of the Na-H exchange inhibitors on RASM replication were due to a reduction in the ability of the smooth muscle cells to enter the S phase of the mitotic cell cycle. This appeared predominantly the consequence of effects late within the G1 phase of the cell cycle. Concentrations of EIPA that markedly reduced the ability of RASM to enter S phase and to replicate also attenuated the increase in protein synthesis occurring 6-8 h after exposure to serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Paclitaxel inhibits osteoclast formation and bone resorption via influencing mitotic cell cycle arrest and RANKL-induced activation of NF-κB and ERK

2012 ◽  
Vol 113 (3) ◽  
pp. 946-955 ◽  
Author(s):  
Estabelle S. M. Ang ◽  
Nathan J. Pavlos ◽  
Shek Man Chim ◽  
Hao Tian Feng ◽  
Robin M. Scaife ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bone Resorption ◽  
Cell Cycle Arrest ◽  
Mitotic Cell ◽  
Osteoclast Formation ◽  
Mitotic Cell Cycle ◽  
Cycle Arrest
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