Long duration of mitosis and consequences for the cell cycle concept, as seen in the isthmal cells of the mouse pyloric antrum. II. Duration of mitotic phases and cycle stages, and their relation to one another

The kinetics of isthmal cells in mouse antrum were examined in three ways: the duration of cell cycle and DNA-synthesizing (S) stage was measured by the 'fraction of labelled mitoses' method; the duration of interphase and mitotic phases was determined from how frequently they occurred; and mice were killed at various intervals after an intravenous injection of 3H-thymidine to time the acquisition of label by the various phases of mitosis. The duration of the isthmal cell cycle was found to be 13.8 hr and that of the DNA-synthesizing (S) stage, 5.8 h. Estimates for the duration of the G1 and G2 stages were 6.8 and 1.0 hr, respectively. From the frequency of mitotic phases, defined as indicated in the preceding article (El-Alfy & Leblond, 1987) and corrected for the probability of their occurrence, it was estimated that prophase lasted 4.8 hr; metaphase, 0.2 hr; anaphase, 0.06 hr and telophase, 3.3 hr, while the interphase lasted 5.4 hr. In accordance with this, the duration of the whole mitotic process was 8.4 hr. Ten minutes after an intravenous injection of 3H-thymidine, 38% of labelled isthmal cells were in interphase and 62% in early or mid prophase, while cells in late prophase and other mitotic phases were unlabelled. After 60 min, label was in late prophase, after 120 min, in mid telophase and after 180 min, in late telophase. We conclude that there is overlap between some mitotic phases and cycle stages. Thus, while nuclei are at interphase during the early third of S, they are in prophase during the late two-thirds as well as during G2. Also, nuclei are in telophase during the early half of G1 but at interphase during the late half. Differences in nuclear diameter show that subdivision of both S and G1 into early and late periods is practical.     

Long duration of mitosis and consequences for the cell cycle concept, as seen in the isthmal cells of the mouse pyloric antrum. I. Identification of early and late steps of mitosis

Abstract. In this series of two articles, the duration of mitosis and that of the cell cycle were examined in a group of proliferating cells located in the mouse pyloric antrum and known as isthmal cells. However, before measuring the duration of mitosis, as described in the second article, it is necessary to identify the early and late steps of the mitotic process. This is attempted in the present article, in which the four phases of mitosis and the interphase are described in semithin (0.5 μ m thick) Epon serial sections stained with hemalun. The frequency of these phases is then estimated.
The beginning of prophase is indicated by the appearance in the nucleus of numerous 0.2-0.3 μ m thick basophilic threads. The threads gradually increase in thickness to become the typical chromosomes (about 0.7- μ m thick) observed at the end of prophase. Metaphase and anaphase show no remarkable features. At telophase, chromosomes separate from one another, gradually acquire pale segments along their length eventually to look like rows of alternating dark and light patches, and finally vanish.
When prophases and telophases are defined in this manner, the enumeration of isthmal cells yields a high proportion of prophases (28%) and telophases (31%), but a low proportion of metaphases (1%) and anaphases (0.3%). Forty per cent of the cells are in interphase.     

Long duration of mitosis and consequences for the cell cycle concept, as seen in the isthmal cells of the mouse pyloric antrum. I. Identification of early and late steps of mitosis

In this series of two articles, the duration of mitosis and that of the cell cycle were examined in a group of proliferating cells located in the mouse pyloric antrum and known as isthmal cells. However, before measuring the duration of mitosis, as described in the second article, it is necessary to identify the early and late steps of the mitotic process. This is attempted in the present article, in which the four phases of mitosis and the interphase are described in semithin (0.5 micron thick) Epon serial sections stained with hemalun. The frequency of these phases is then estimated. The beginning of prophase is indicated by the appearance in the nucleus of numerous 0.2-0.3 micron thick basophilic threads. The threads gradually increase in thickness to become the typical chromosomes (about 0.7-micron thick) observed at the end of prophase. Metaphase and anaphase show no remarkable features. At telophase, chromosomes separate from one another, gradually acquire pale segments along their length eventually to look like rows of alternating dark and light patches, and finally vanish. When prophases and telophases are defined in this manner, the enumeration of isthmal cells yields a high proportion of prophases (28%) and telophases (31%), but a low proportion of metaphases (1%) and anaphases (0.3%). Forty per cent of the cells are in interphase.     

Surface functions during mitosis. II. Quantitation of pinocytosis and kinetic characterization of the mitotic cycle with a new fluorescence technique

The profound depression of fluid pinocytosis observed in mitotic cells (Berlin, R. D., et al. 1978. Cell. 15:327--341) is documented by quantitative microspectrofluorimetry of fluorescein-labeled dextran uptake in single cells. In J774.2 macrophages, fluid pinocytosis is reduced 30-fold during mitosis. The depression develops within 30 s of entry into prophase and recovers with equal rapidity upon emergence from telophase into G1. This characteristic pattern of fluid pinocytosis forms the basis of a new method for detailed kinetic analysis of the duration of mitosis and its phases. The analysis is applied to the J774.2 macrophage cell line but should be generally applicable to other lines. Effects of ouabain and colchicine on the length of mitosis and its phases are evaluated, revealing a selective prolongation of metaphase by ouabain and suggesting a role for microtubules in the transition from G2 into mitosis.     

Dynamic histology of the antral epithelium in the mouse stomach: II. Ultrastructure and renewal of isthmal cells

The isthmus of typical mucous units of the pyloric antrum was investigated in 3- to 4-month-old CD1 mice using light and electron microscopy as well as 3H-thymidine radioautography. On the average, the isthmus measured 25 microns in length and was composed of 36 isthmal cells and two enteroendocrine cells. Isthmal cells generally displayed features found in embryonic cells, such as many free ribosomes, scant organelles, and a large reticulated nucleolus, and were, therefore, at an immature stage of development. Isthmal cells could be devoid of secretory granules ("granule-free cells," 2%) or contain a few small, spherical, PA-Schiff-positive, mucous granules in their apex. The granules in some of the cells had a variegated appearance and a diameter averaging 235 nm ("mottled granule cells," 39%); in other cells, the granules had a large diameter, 278 nm, with a pale background and a dense core ("core granule cells," 28%); while in still others they were homogeneously dark and measured 264 nm ("dense granule cells," 12%). Finally, some cells included a mixture of core and dense granules ("mixed granule cells," 14%). One hour after a single injection of 3H-thymidine, 37% of the isthmal cells were labeled. Each of the five isthmal cell types could acquire label and, therefore, divide. After one or more days of continuous 3H-thymidine infusion, all isthmal cells were labeled. Their turnover time was estimated to be 16.1 hr (t1/2 = 11.2 hr). The isthmus is thus composed of several cell types which are turning over rapidly. While all are relatively immature, the various types are thought to represent different developmental stages in the life history of an isthmal cell. A model devised on this basis proposes that the granule-free cells are stem cells, from which mottled granule cells are derived. These in turn evolve into either the dense granule cells of the upper isthmus or the core granule cells of the lower isthmus, or into the mixed granule cells (which are believed to develop eventually into dense granule cells or core granule cells). Maintenance of a steady state requires that the rapid production of isthmal cells be associated with rapid emigration; the dense granule cells presumably going to the pit and the core granule cells to the gland. The turnover of isthmal cells is accordingly described as following a "bidirectional pattern" of renewal.     

Comparative study of the level of mitotic activity and duration of mitosis over a 24 hour period in mouse tumors and normal tissue]

Circadian rhythm of cell division in the forestomack epithelium proved to be largely similar to that in the transplantable (continuous) carcinoma of the forestomack; the duration of mitosis in these tissues changed in the course of 24-hours. The mean 24-hour mitotic activity in the tumour was double that in the forestomack contrary to this, colchamine (colcemide) accumulated in the course of the 24-hours 121.1% mitoses in the forestomack and 83.8% mitoses in the carcinoma. A greater number of mitoses in the tumour with the usual count is attributed to the fact that the mean 24-hour duration of mitosis of the remen carcinoma was 2.7 greater than in the epithelium of the forestomack.     

Renewal time, proliferative pool and duration of the mitotic cycle of the epithelial cells of the common bile duct]

Using cholchicine and H3-thymidine the following parameters of the mitotic cycle (in hours) were calculated: T=56.6; tm=0.9; tg2=1.2; ts=6; tg1=48.5 The proliferative pool was 7.5% and the time of epithelium renewal--754.5 hours. The common bile duct epithelium should be referred to the tissue systems with slow renewal.     

Dependence of the duration of one mitotic cycle during synchronous cleavage divisions (tau o) on the temperature in 4 Rana species and the limits of the optimal temperatures for their reproduction and early development

The dependence of the duration of one mitotic cycle during synchronous cleavage divisions (tau o) on temperature was studied in Rana temporaria, R. arvalis, R. lessonae, R. ridibunda and the corresponding curves were plotted in both linear and semilogarithmic scale. The curves can be used to characterize the relative duration of development, as well as to estimate the limits of optimal temperatures and to reveal the temperature-temporal regularities of development in these species.