Mitosis and the Cell Cycle in the Metamorphic Moult of the Milkweed Bug, Oncopeltus Fasciatus.: A Radioautographic Study

1968 ◽  
Vol 3 (3) ◽  
pp. 391-404
Author(s):  
P. A. LAWRENCE
Keyword(s):  
Cell Cycle ◽  
Mother Cell ◽  
Tritiated Thymidine ◽  
Cell Number ◽  
Oncopeltus Fasciatus ◽  
Simple Method ◽  
Milkweed Bug ◽  
Whole Mount ◽  
S Period ◽  
Equivalent Method

A simple method of whole-mount radioautography is devised to investigate aspects of the cell cycle during metamorphosis in the epidermis of the milkweed bug, Oncopeltus. Tritiated thymidine is used to indicate DNA synthesis. As the label only lasts in the insect for about 2 h, a wave of labelled cells passes through the different phases of the cell cycle. The S period is found to overlap with an exceptionally long prophase and there is thus no G2 period. The length of prophase (408±10 min) is estimated from a plot of the fraction of labelled prophases against time after injection of label. By an equivalent method the length of the S period is found to be 289±12 min. No labelled cells divide again until about 24 h after the previous mitosis, when some cells embark on a second mitosis. The minimum interphase (G1 period is approximately 16 h. In the area studied, the cell number more than doubles during the proliferative mitoses; and it is thus possible, but not certain, that every cell divides at least once. Fifth-stage larvae injected during the differentiative divisions (which are involved in the development of dense hairs) show that each of the three kinds of differentiative divisions has its own peculiar timing. The timing of the very first division, that of the epidermal cell which will become the hair mother cell, suggests that the cell is already different from its progenitors prior to prophase.

scholarly journals A KINETIC ANALYSIS OF MYOGENESIS IN VITRO

1972 ◽  
Vol 52 (1) ◽  
pp. 52-65 ◽  
Author(s):  
Michael C. O'Neill ◽  
Frank E. Stockdale
Keyword(s):  
Cell Cycle ◽  
Cell Fusion ◽  
Tritiated Thymidine ◽  
Culture Conditions ◽  
Complete Fusion ◽  
Low Density ◽  
A Cell ◽  
Muscle Cultures ◽  
S Period

Conditions which yielded reproducible growth kinetics with extensive, relatively synchronous differentiation are described for chick muscle cultures. The effects of cell density and medium changes on the timing of cell fusion were examined. Low-density cultures which received a change of medium at 24 hr after plating show the highest rate of cell fusion, increasing from 15 to 80% fused cells in a 10 hr period. These optimal culture conditions were employed to reexamine two questions from the earlier literature on muscle culture: (a) can cells which normally would fuse at the end of one cell cycle be forced to go through another cell cycle before fusion; and (b) how soon after its final S period can a cell complete fusion? In answer to the first question, it was found that if the medium is changed, many cells which would otherwise fuse can be made to undergo another cell cycle before fusion. In the second case, radioautographs were made from cultures incubated with tritiated thymidine for various times at the beginning of the fusion period. These show labeled nuclei in myotubes as early as 3 hr after the beginning of the incubation period. This indicates that cells can fuse as early as the beginning of the G1 period, and suggests that there is not an obligatory exit from the cell cycle or a prolonged G1 period before cell fusion and differentiation during myogenesis.

Differential mitosis and degeneration patterns in relation to the alterations in the shape of the embryonic ectoderm of early post-implantation mouse embryos

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 33-51
Author(s):  
R. E. Poelmann
Keyword(s):  
Cell Cycle ◽  
Cell Kinetics ◽  
Tritiated Thymidine ◽  
Primitive Streak ◽  
Cell Number ◽  
Mouse Embryos ◽  
Surface Ectoderm ◽  
Dividing Cells ◽  
Post Implantation ◽  
Embryonic Ectoderm

The shape of the embryonic ectoderm of early post-implantation mouse embryos changes greatly in the period of 6·2–7·3 days post coitum. The subcellular morphology of the embryonic ectoderm remains unchanged, except in the primitive-streak region. Cell kinetics differ between ectodermal regions. These differences may be related to the changes in the shape of the ectoderm. The increase in cell number in the lateral ectoderm (the prospective surface ectoderm) exceeds that in the frontal ectoderm (the future neurectoderm). This is not due to differences in the duration of the cell cycle. It can be explained, however, by the occurrence of different relative numbers of dividing and non-dividing cells. These numbers vary between the two regions. The percentage of non-dividing cells in the frontal ectoderm may reach 45, whereas in the lateral ectoderm this percentage is not higher than 15. Autoradiography in tritiated thymidine-treated embryos combined with the mitotic indices gave us all of the parameters necessary to present a model capable of clarifying the growth of the ectoderm during gastrulation, as well as the changes in the shape of the ectoderm.

scholarly journals Ano1 as a regulator of proliferation

2011 ◽  
Vol 301 (6) ◽  
pp. G1044-G1051 ◽  
Author(s):  
Jennifer E. Stanich ◽  
Simon J. Gibbons ◽  
Seth T. Eisenman ◽  
Michael R. Bardsley ◽  
Jason R. Rock ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Slow Wave ◽  
Interstitial Cells Of Cajal ◽  
Primary Cultures ◽  
Channel Blockers ◽  
Proliferating Cells ◽  
Stromal Tumors ◽  
Whole Mount ◽  
Cells Of Cajal ◽  
Regular Medium

Ano1 is a recently discovered Ca2+-activated Cl− channel expressed on interstitial cells of Cajal (ICC) that has been implicated in slow-wave activity in the gut. However, Ano1 is expressed on all classes of ICC, even those that do not contribute to generation of the slow wave, suggesting that Ano1 may have an alternate function in these cells. Ano1 is also highly expressed in gastrointestinal stromal tumors. Mice lacking Ano1 had fewer proliferating ICC in whole mount preparations and in culture, raising the possibility that Ano1 is involved in proliferation. Cl− channel blockers decreased proliferation in cells expressing Ano1, including primary cultures of ICC and in the pancreatic cancer-derived cell line, CFPAC-1. Cl− channel blockers had a reduced effect on Ano1(−/−) cultures, confirming that the blockers are acting on Ano1. Ki67 immunoreactivity, 5-ethynyl-2′-deoxyuridine incorporation, and cell-cycle analysis of cells grown in low-Cl− media showed fewer proliferating cells than in cultures grown in regular medium. We confirmed that mice lacking Ano1 had less phosphorylated retinoblastoma protein compared with controls. These data led us to conclude that Ano1 regulates proliferation at the G1/S transition of the cell cycle and may play a role in tumorigenesis.

Studies on the pteridines in the milkweed bug, Oncopeltus fasciatus (Dallas)

1966 ◽  
Vol 12 (11) ◽  
pp. 1411-1421 ◽  
Author(s):  
Hugh S. Forrest ◽  
Michael Menaker ◽  
Jennifer Alexander
Keyword(s):  
Oncopeltus Fasciatus ◽  
Milkweed Bug

An Ultrastructural and Radio-Autographic Study of the Evolution of the Interphase Nucleus in Plant Meristematic Cells (Allium Porrum)

1974 ◽  
Vol 14 (2) ◽  
pp. 263-287
Author(s):  
J. G. LAFONTAINE ◽  
A. LORD
Keyword(s):  
Interphase Nucleus ◽  
Structural Changes ◽  
Tritiated Thymidine ◽  
Light And Electron Microscopy ◽  
Allium Porrum ◽  
Meristematic Cells ◽  
Fibrillar Material ◽  
Nuclear Structures ◽  
S Period ◽  
Dense Chromatin

Radioautography under both light and electron microscopy was exploited to investigate the structural changes of the chromatin reticulum which characterizes the interphase nucleus of a number of plants. Allium porrum meristematic plant cells were used for this purpose. In this species, the telophase chromosomes uncoil into dense strands which, during the G1 period, gradually give rise to a coarse reticulum. There then follows an extensive unravelling of portions of these strands, and high-resolution radioautography reveals that labelling with tritiated thymidine predominantly occurs over zones of the nucleus consisting of diffuse fine fibrillar material. As the S-period progresses, a chromatin reticulum reappears throughout the nuclear cavity, the tortuous strands being approximately 0.25 µm in diameter. Most of the radioautographic grains still remain over the light nucleoplasmic areas but a number of these are now located on the outermost portion of the dense chromatin profiles. By the end of the S-period, the chromatin strands are slightly thicker (ca. 0.3 µm) and form a looser reticulum. Labelling has decreased noticeably in nuclei of that period, the radioautographic grains being grouped into clusters resting over more or less spherical regions of the chromatin reticulum. Judging from their localization at the surface of the nucleolus or close to the nuclear envelope, these structures correspond to chromocentres. The additional interesting finding that such nuclear structures appear much less compactly organized strongly suggests that chromocentres undergo important conformational modifications during duplication of their DNA.

scholarly journals CHANGES IN THE DNA SYNTHESIS PATTERN OF PARAMECIUM WITH INCREASED CLONAL AGE AND INTERFISSION TIME

1974 ◽  
Vol 61 (3) ◽  
pp. 591-598 ◽  
Author(s):  
Joan Smith-Sonneborn ◽  
Michael Klass
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Unicellular Organism ◽  
Time Intervals ◽  
Synchronized Cells ◽  
Different Ages ◽  
Self Fertilization ◽  
Autoradiographic Analysis ◽  
S Period ◽  
First Time

The clonal age in paramecia refers to the total number of vegetative divisions a clone has undergone since its origin at autogamy (self-fertilization). As clonal age increases, the interfission time usually increases. The DNA synthesis pattern of cells of different ages was compared by autoradiographic analysis of the DNA synthesis of synchronized cells at various time intervals during the cell cycle (from one division to the next). The study showed that the G1 period (the lag in DNA synthesis post division) was constant, irrespective of interfission time or clonal age; but the duration of the DNA synthesis period increased with increased interfission time or clonal age. Therefore, we have shown for the first time that the G1 period is fixed, and the S period is increased in a eukaryotic unicellular organism as a function of interfission time and clonal age.

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