Chapter 3 Mitotic Synchrony in the Plasmodia of Physarum polycephalum and Mitotic Synchronization by Coalescence of Microplasmodia

Güttes, E.; Guttes, Sophie

doi:10.1016/s0091-679x(08)62085-3

Cited by 75 publications

(57 citation statements)

References 16 publications

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“…Synchronous macroplasmodia were prepared from shaken liquid cultures by a modification of the procedure of Guttes and Guttes [2] : microplasmodia were concentrated by decantation and 1 ml of the pellet was added to the middle of a cellulose nitrate membrane (Sartorius, 0.45 pm) which was then placed on a metallic grid without medium. After 3 h of starvation at 22"C, the membrane was placed on semidefined medium agar at the desired temperature.…”

Section: Preparation Of' Physarum Plasmodiamentioning

confidence: 99%

Physarum Thymidine Kinase A Step or a Peak Enzyme Depending upon Temperature of Growth

Wright

Tollon

1979

European Journal of Biochemistry

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The variations of thymidine kinase or ATP : thymidine 5'-phosphotransferase (EC 2.7.1.21) during the cell cycle of Physarum polycephalum plasmodia have been studied at two extreme physiological temperatures: 22'C and 32°C. At 22°C the enzyme activity increases near mitosis and stays constant during late S and G2 phases, exhibiting the typical pattern of a 'step enzyme'. But at 32 "C thymidine kinase activity goes through a maximum 1 h 30 min after mitosis and decreases during the subsequent phases as expected for a 'peak enzyme'. The rate of enzyme degradation andlor inactivation, measured in the presence of metabolic poisons (cycloheximide or dinitrophenol), appears to follow a simple exponential function with a half-life of approximately 3 h and 1 h at 22 "C and 32 "C respectively. The effect of growth temperature on the decrease of thymidine kinase activity can account entirely for the differences in the pattern of enzyme activity at the two extreme temperatures. Tentative calculations indicate that the rate of enzyme synthesis is nearly constant during the cell cycle except near mitosis, where it is temporarily increased. The results suggest the existence of a regulatory mechanism able to modulate the rate of synthesis of thymidine kinase during the cell cycle.

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Section: Preparation Of' Physarum Plasmodiamentioning

confidence: 99%

Physarum Thymidine Kinase A Step or a Peak Enzyme Depending upon Temperature of Growth

Wright

Tollon

1979

European Journal of Biochemistry

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“…50 ml tryptone citrate medium with haemin in an orbital shaker [8]. Macroplasmodia were established from microplasmodia in the usual way [9]. The second mitosis (M2) after fusion of microplasmodia occured 15-16 h after feeding and the third (M3) about 8 h later.…”

Section: Growth Of Physarummentioning

confidence: 99%

Fluctuations in Proline and Other Free Amino Acids during the Mitotic Cycle of the Myxomycete Physarum polycephalum

Threlfall

Thomas

1979

European Journal of Biochemistry

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1. During synchronous growth of the acellular slime mould Physarum polycephalum the free amino pool had two maxima, one of 650 units [nmol/plasmodium dry weight (mg)] at metaphase and the other of 780 units in mid G2 with minima of 550 units before and after mitosis. 2.Proline formed 20 -25 % of the total pool with aspartic acid, glutamic acid, threonine, valine, leucine, lysine and arginine making up 55 % of the pool.3. The fluctuation of proline during the mitotic cycle was quite different from that of the other amino acids and was transiently very low during telophase.A knowledge of the composition, size and intracellular distribution of pools of free amino acids is of importance in understanding the control of enzyme repression and synthesis and for the critical evaluation of pulse labeling experiments. One area where such knowledge is particularly needed is in the study of the cell cycle [l]. Distinct changes in free amino acids were found during the cell cycle of the alga Chlorella pyrenoidosa [2] whereas in the fission yeast Schizosaccharomyces pombe [3,4] and in HeLa cells [5] virtually no changes were detected.The macroplasmodium of Physarum polycephalum is a syncytium in which all the nuclei undergo a natural synchronous mitosis [6]. As a plasmodium may contain lo8 nuclei this is an ideal system for studying the biochemistry of the processes of nuclear division and growth. After nuclear division DNA synthesis begins at once, lasts for 3 h and is followed by a G2 period of about 5.5 h before the next mitosis [7]. A study by nuclear magnetic resonance (NMR) of extracts of macroplasmodia revealed a large amount of proline and temporal changes in this and in other amino acids (Dobson, Poulsen and Threlfall, unpublished). This has prompted us to investigate these changes in detail using more sensitive methods of amino acid analysis. MATERIALS AND METHODS Growth of PhysarumStrain M3C was routinely grown as microplasmodia in 500 ml indented conical flasks containing Abbreviation. NMR, nuclear magnetic resonance. Enzyme. Glutamate dehydrogenase (EC 1.4.1.2). 50 ml tryptone citrate medium with haemin in an orbital shaker [8]. Macroplasmodia were established from microplasmodia in the usual way [9]. The second mitosis (M2) after fusion of microplasmodia occured 15-16 h after feeding and the third (M3) about 8 h later. 3 h before M2 the medium was discarded and replaced by fresh. Incubation of all cultures was at 26°C in the dark. The time of metaphase and other mitotic stages was determined by phase-contrast observation of ethanol-fixed smears of small pieces of plasmodium mounted in glycerol/ethanol (111, v/v). The appearance and duration of these stages was the same as described [lo]. Extraction of Amino AcidsA whole plasmodium or 30 s in 1000 ml ice-cold 0.01 buffer pH 4.6. Excess liquid sector was washed for M sodium citrate/HCl was removed and the growing region quickly excised with a spatula to a polypropylene tube cooled in liquid nitrogen until required. The material was homogenised once for 15 s in 30 ...

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“…For morphological observation of the nuclei, ethanol-fixed smear preparations of small explants from the periphery of the plasmodia were inspected under phase contrast (12) .…”

Section: Cytological Techniques and Radioautographymentioning

confidence: 99%

REPLICATION OF NUCLEOLUS-ASSOCIATED DNA DURING "G2 PHASE" IN PHYSARUM POLYCEPHALUM

Güttes

Guttes

1969

The Journal of Cell Biology

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In the myxomycete, Physarum polycephalum, the bulk of nuclear DNA replication occurs during a period of a few hours immediately following upon mitosis . During the remainder of the intermitotic period, incorporation of thymidine-3 H continues at a low rate in the region of the nucleolus (radioautographs) . A few nuclei incorporated thymidine-3 H into the extranucleolar chromatin at a high rate at all times of the intermitotic period . These nuclei were exceptionally large and they frequently contained several small nucleoli of different sizes rather than the one, central nucleolus which is characteristic of a normal interphase nucleus .

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Chapter 3 Mitotic Synchrony in the Plasmodia of Physarum polycephalum and Mitotic Synchronization by Coalescence of Microplasmodia

Cited by 75 publications

References 16 publications

Physarum Thymidine Kinase A Step or a Peak Enzyme Depending upon Temperature of Growth

Physarum Thymidine Kinase A Step or a Peak Enzyme Depending upon Temperature of Growth

Fluctuations in Proline and Other Free Amino Acids during the Mitotic Cycle of the Myxomycete Physarum polycephalum

REPLICATION OF NUCLEOLUS-ASSOCIATED DNA DURING "G2 PHASE" IN PHYSARUM POLYCEPHALUM

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