Control of cell size and cycle time in Schizosaccharomyces pombe

1977 ◽  
Vol 24 (1) ◽  
pp. 51-67 ◽  
Author(s):  
P.A. Fantes
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Cycle Time ◽  
Nuclear Division ◽  
Size Control ◽  
Time Lapse ◽  
Cycle Duration ◽  
Single Cycle ◽  
The Mean ◽  
Extended Cycle ◽  
Time Lapse Photomicrography

Steady-state and perturbed cells of Schizosaccharomyces pombe have been observed through several division cycles by time-lapse photomicrography. Perturbed cells were produced by the use of a conditional cell division cycle mutant in which nuclear division is reversibly blocked at high temperature. These experiments show that in both populations cell length at division and cell cycle duration are homeostatically controlled, probably by a primary size-control mechanism. Cycle time is indirectly controlled, as cells which have an extended cycle are on average larger at division, so that duaghters of such cells need to grow by a smaller amount and for a shorter period, before dividing again. In general, deviations from the mean are corrected within a single cycle, but in the case of very long cells the control breaks down because the cycle cannot be shortened by more than a quarter under the conditions used. These cells take more than one cycle to return to normal.

Patterns of extension growth of the fission yeast, Schizosaccharomyces pombe

1986 ◽  
Vol 32 (6) ◽  
pp. 528-530 ◽  
Author(s):  
H. Miyata ◽  
M. Miyata ◽  
Byron F. Johnson
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Dilution Rate ◽  
Progenitor Cells ◽  
Progenitor Cell ◽  
Chemostat Culture ◽  
Time Lapse ◽  
Extension Growth ◽  
Previous Cycle ◽  
Time Lapse Photomicrography

The growth of sausage-shaped cells of the fission yeast, Schizosaccharomyces pombe (strain NCYC 132), was followed in the second or third cycle by time-lapse photomicrography. Experimental cells were harvested from glucose-limited (0.2% glucose EMM3) chemostat culture (dilution rate, 0.125/h) and were plated onto a slide with EMM3 agar (2% glucose). By observing their extension patterns, we found some rules of extension growth. Thus, (1) all sibs with walls newly formed in the previous cycle, whose progenitor cells grew at the old end (followed Mitchison's rule), grow at the old end (also follow Mitchison's rule). (2) Sibs with old walls whose progenitor cell followed Mitchison's rule behave in one of three ways: (i) growth at the old end (follow Mitchison's rule); (ii) growth at the new end (violate Mitchison's rule); or (iii) growth at both ends (bipolar). (3) Both sibs whose progenitor grew at both ends (bipolar) always grow at the old end (follow Mitchison's rule).

Pattern of end growth of the fission yeast Schizosaccharomyces pombe

1990 ◽  
Vol 36 (6) ◽  
pp. 390-394 ◽  
Author(s):  
Hisao Miyata ◽  
Machiko Miyata ◽  
Byron F. Johnson
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Schizosaccharomyces Pombe ◽  
Key Words ◽  
Fission Yeast ◽  
Doubling Time ◽  
Time Lapse ◽  
Critical Value ◽  
Wild Type ◽  
Time Lapse Photomicrography

The patterns of end growth of individual cells of Schizosaccharomyces pombe, wild-type cells (strain 972 h−), cells exposed to 8 mM hydroxyurea, and cdc mutants (cdc11-123 and cdc2-33), were investigated by time-lapse photomicrography. It was reconfirmed that there are three patterns of end growth: cells growing at the old end, at the new end, and at both ends from the beginning of the cell cycle. Cells that initiated growth at the old (new) end increased their growth rate at the new (old) end and became constant in their growth rate at the old (new) end when cells had their growth rate higher than a critical value: 0.08, 0.09, 0.08, and 0.11 μm/min in wild-type cells, cells exposed to hydroxyurea, cdc11-123 cells, and cdc2-33 cells, respectively. The critical value is proportional to the doubling time in length. Key words: extension, growth, fission yeast.

scholarly journals A Screen for Genes Involved in the Anaphase Proteolytic Pathway Identifies tsm1+, a Novel Schizosaccharomyces pombe Gene Important for Microtubule Integrity

Genetics ◽  
1998 ◽  
Vol 149 (3) ◽  
pp. 1251-1264
Author(s):  
Ekaterina L Grishchuk ◽  
James L Howe ◽  
J Richard McIntosh
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Nuclear Division ◽  
Mitotic Division ◽  
Temperature Sensitive ◽  
Permissive Temperature ◽  
Anaphase Promoting Complex ◽  
Chloromethyl Ketone ◽  
Proteolytic Pathway ◽  
Functional Involvement ◽  
Spindle Elongation

Abstract The growth of several mitotic mutants of Schizosaccharomyces pombe, including nuc2-663, is inhibited by the protease inhibitor N-Tosyl-L-Phenylalanine Chloromethyl Ketone (TPCK). Because nuc2+ encodes a presumptive component of the Anaphase Promoting Complex, which is required for the ubiquitin-dependent proteolysis of certain proteins during exit from mitosis, we have used sensitivity to TPCK as a criterion by which to search for novel S. pombe mutants defective in the anaphase-promoting pathway. In a genetic screen for temperature-sensitive mitotic mutants that were also sensitive to TPCK at a permissive temperature, we isolated three tsm (TPCK-sensitive mitotic) strains. Two of these are alleles of cut1+, but tsm1-512 maps to a novel genetic location. The tsm1-512 mutation leads to delayed nuclear division at restrictive temperatures, apparently as a result of an impaired ability to form a metaphase spindle. After shift of early G2 cells to 36°, tsm1-512 arrests transiently in the second mitotic division and then exits mitosis, as judged by spindle elongation and septation. The chromosomes, however, often fail to segregate properly. Genetic interactions between tsm1-512 and components of the anaphase proteolytic pathway suggest a functional involvement of the Tsm1 protein in this pathway.

Motion of Active Fluids: Diffusion Dynamics of Cyanobacteria

2016 ◽  
Author(s):  
Thomas Vourc’h ◽  
Julien Léopoldès ◽  
Annick Méjean ◽  
Hassan Peerhossaini
Keyword(s):  
Time Lapse ◽  
Global Behavior ◽  
Diffusion Dynamics ◽  
Mean Squared Displacement ◽  
Terrestrial Environments ◽  
The Mean ◽  
Micro Organisms ◽  
Synechocystis Sp ◽  
Time Lapse Video ◽  
Pcc 6803

Cyanobacteria are photosynthetic micro-organisms colonizing all aquatic and terrestrial environments. The motility of such living micro-organisms should make their diffusion distinct from typical Brownian motion. This diffusion can be investigated in terms of global behavior (Fickian or not) and in terms of displacement probabilities, which provide more detail about the motility process. Using cyanobacterium Synechocystis sp. PCC 6803 as the model micro-organism, we carry out time-lapse video microscopy to track and analyze the bacteria’s trajectories, from which we compute the mean-squared displacement (MSD) and the distribution function of displacement probabilities. We find that the motility of Synechocystis sp. PCC 6803 is intermittent: high-motility “run” phases are separated by low-motility “tumble” phases corresponding to trapped states. However, this intermittent motility leads to a Fickian diffusive behavior, as shown by the evolution of the MSD with time.

scholarly journals A comparison of two methods for predicting changes in the distribution of gene frequency when selection is applied repeatedly to a finite population

1969 ◽  
Vol 13 (2) ◽  
pp. 117-126 ◽  
Author(s):  
Derek J. Pike
Keyword(s):  
Iterative Procedure ◽  
Gene Frequency ◽  
Finite Population ◽  
Transition Matrices ◽  
Single Cycle ◽  
Gene Frequencies ◽  
Mean And Variance ◽  
The Mean ◽  
The One ◽  
Selection Of

Robertson (1960) used probability transition matrices to estimate changes in gene frequency when sampling and selection are applied to a finite population. Curnow & Baker (1968) used Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population to develop an iterative procedure for studying the effects of repeated cycles of selection and regeneration. To do this they assumed a beta distribution for the unfixed gene frequencies at each generation.These two methods are discussed and a result used in Kojima's paper is proved. A number of sets of calculations are carried out using both methods and the results are compared to assess the accuracy of Curnow & Baker's method in relation to Robertson's approach.It is found that the one real fault in the Curnow-Baker method is its tendency to fix too high a proportion of the genes, particularly when the initial gene frequency is near to a fixation point. This fault is largely overcome when more individuals are selected. For selection of eight or more individuals the Curnow-Baker method is very accurate and appreciably faster than the transition matrix method.

Design Optimization of Autoswitch Hydrogen Absorption and Desorption Device Using Metal Hydrides

2017 ◽  
Vol 15 (6) ◽  
Author(s):  
Ceng He ◽  
Yuqi Wang ◽  
Jing Song ◽  
Shanshan Li ◽  
Fusheng Yang ◽  
...  
Keyword(s):  
Metal Hydride ◽  
Cycle Time ◽  
Single Cycle ◽  
Desorption Process ◽  
Operation Conditions ◽  
Time Simulation ◽  
Structure Improvement ◽  
New Type ◽  
Simulation Results ◽  
Desorption Cycle

Abstract Metal hydride is an influential and promising material for hydrogen utilization. Researchers have carried out a large number of studies on hydrogen storage apparatus, and developed a few new devices for its promotion. Unfortunately, for most metal hydride reactors, the hydrogenation and dehydrogenation are two independent processes owing to the different required conditions, which could cause many inconveniences and safety problems to the H2 absorption & desorption cycle with high frequency and intensity. Hence we proposed a new type of autoswitch H2 absorption & desorption device based on the structure improvement, which consists of rotation disc, fixed disc and the reactor. The numerical simulation for H2 absorption/desorption using LaNi5 was accomplished, and the optimizations on both structure and operation conditions were achieved within a certain period of cycle time. Simulation results show when the single cycle time is set to 1600 s, the absorption temperature has to be lower than 45 °C (3 MPa) and pressure higher than 1.28 MPa (20 °C), and the desorption temperature should be higher than 41 °C (0.1 MPa) and pressure lower than 0.48 MPa (80 °C) under the same cycle time. Meanwhile, the effects of reaction finish time, operating temperature and H2 pressure during absorption/desorption process was investigated and simulation data were also fitted to develop the structural optimization. Under the hydrogenation/dehydrogenation conditions of 3 MPa (20 °C)/0.1 MPa (80 °C), the simulation results indicate the optimal initial reacted fraction and total cycle time are 0.07 and 1287 s, respectively. Moreover, both structures of autoswitch device with 4 and 6 openings have been optimized to satisfy the requirement of each stage. The autoswitch H2 absorption & desorption device can realize the automatic switch between hydrogenation and dehydrogenation orderly and controllably, which would provide convenience for the occasions with this demand and show its remarkable value during popularization and application.

Conidium ontogeny in hyphomycetes. The meristem arthrospores of Wallemia sebi

1973 ◽  
Vol 51 (9) ◽  
pp. 1669-1671 ◽  
Author(s):  
M. H. Hashmi ◽  
G. Morgan-Jones
Keyword(s):  
Time Lapse ◽  
Unique Type ◽  
Nuclear Distribution ◽  
Wallemia Sebi ◽  
Time Lapse Photomicrography

Conidium ontogeny in Wallemia sebi (Fr.) v. Arx is analyzed and illustrated by time-lapse photomicrography. The nuclear configurations occurring during conidiogenesis are described and subsequent nuclear distribution reported. The conidia are considered to be meristem arthrospores of a unique type.

Toward An MRI-Based Method to Measure Non-Uniform Cartilage Deformation: An MRI-Cyclic Loading Apparatus System and Steady-State Cyclic Displacement of Articular Cartilage Under Compressive Loading

2003 ◽  
Vol 125 (2) ◽  
pp. 180-188 ◽  
Author(s):  
C. P. Neu ◽  
M. L. Hull
Keyword(s):  
Steady State ◽  
Articular Cartilage ◽  
Pneumatic Cylinder ◽  
Cycle Duration ◽  
Steady State Response ◽  
Time Duration ◽  
Bovine Articular Cartilage ◽  
State Response ◽  
The Mean ◽  
Phantom Material

Recent magnetic resonance imaging (MRI) techniques have shown potential for measuring non-uniform deformations throughout the volume (i.e. three-dimensional (3D) deformations) in small orthopedic tissues such as articular cartilage. However, to analyze cartilage deformation using MRI techniques, a system is required which can construct images from multiple acquisitions of MRI signals from the cartilage in both the undeformed and deformed states. The objectives of the work reported in this article were to 1) design an apparatus that could apply highly repeatable cyclic compressive loads of 400 N and operate in the bore of an MRI scanner, 2) demonstrate that the apparatus and MRI scanner can be successfully integrated to observe 3D deformations in a phantom material, 3) use the apparatus to determine the load cycle necessary to achieve a steady-state deformation response in normal bovine articular cartilage samples using a flat-surfaced and nonporous indentor in unconfined compression. Composed of electronic and pneumatic components, the apparatus regulated pressure to a double-acting pneumatic cylinder so that (1) load-controlled compression cycles were applied to cartilage samples immersed in a saline bath, (2) loading and recovery periods within a cycle varied in time duration, and (3) load magnitude varied so that the stress applied to cartilage samples was within typical physiological ranges. In addition the apparatus allowed gating for MR image acquisition, and operation within the bore of an MRI scanner without creating image artifacts. The apparatus demonstrated high repeatability in load application with a standard deviation of 1.8% of the mean 400 N load applied. When the apparatus was integrated with an MRI scanner programmed with appropriate pulse sequences, images of a phantom material in both the undeformed and deformed states were constructed by assembling data acquired through multiple signal acquisitions. Additionally, the number of cycles to reach a steady-state response in normal bovine articular cartilage was 49 for a total cycle duration of 5 seconds, but decreased to 33 and 27 for increasing total cycle durations of 10 and 15 seconds, respectively. Once the steady-state response was achieved, 95% of all displacements were within ±7.42μm of the mean displacement, indicating that the displacement response to the cyclic loads was highly repeatable. With this performance, the MRI-loading apparatus system meets the requirements to create images of articular cartilage from which 3D deformation can be determined.

Nuclear DNA content and minimum generation time in herbaceous plants

1972 ◽  
Vol 181 (1063) ◽  
pp. 109-135 ◽  
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Cycle Time ◽  
Generation Time ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Annual Species ◽  
Cell Cycle Time ◽  
Developmental Processes ◽  
The Mean

Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.

scholarly journals Numerical Climatic Analysis of Soybean Development in Sowing Dates in Humid Subtropical Climate

2021 ◽  
Author(s):  
Mateus Possebon Bortoluzzi ◽  
Arno Bernardo Heldwein ◽  
Roberto Trentin ◽  
Ivan Carlos Maldaner ◽  
Jocélia Rosa da Silva ◽  
...  
Keyword(s):  
Meteorological Data ◽  
Sowing Date ◽  
Cycle Duration ◽  
Subtropical Climate ◽  
Climate Conditions ◽  
Development Cycle ◽  
Sowing Dates ◽  
Climatological Station ◽  
The Mean ◽  
Santa Maria

Abstract The objective of this study was to determine the mean duration and the interannual variability of phenological subperiods and total soybean development cycle for 11 sowing dates in the humid subtropical climate conditions of the state of Rio Grande do Sul. Daily meteorological data were used from 1971 to 2017 obtained from the Pelotas agroclimatological station and from 1968 to 2017 from the main climatological station of Santa Maria. The soybean development simulation was performed considering three sets of cultivars of relative maturity groups between 5.9-6.8, 6.9-7.3 and 7.4-8.0, with intervals between the sowing dates of approximately 10 days, comprising September, 21 to December, 31. The data of phenological subperiods duration and total development cycle were subjected to the exploratory analysis BoxPlot, analysis of variance and mean comparison by the Scott-Knott test, with 5% of probability. The development cycle duration is greater in Pelotas than in Santa Maria. There was a decrease in soybean cycle duration from the first to the last sowing date for both locations. The R1-R5 subperiod duration is decreasing from October to December due to photoperiod reduction.

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