Patterns of oscillation during mitosis in plasmodia ofPhysarum polycephalum

Summary The rhythmic contraction pattern in plasmodia ofPhysarum polycephalum was studied to determine whether characteristic changes occur during the synchronized nuclear division. An electrical method that measures the contraction rhythm in situ during several cell cycles was used. Biopsies of the plasmodia were taken at 17 min intervals for precise determination of the cell cycle stages and were correlated with the simultaneously measured contraction rhythm. All measurements were performed in a temperature controlled environment (27 °C) at 100% relative humidity with the plasmodia (less than 24 h old) growing on a semi-defined agar medium. A total of 14 different plasmodia have been examined, and on one occasion the plasmodium was followed through 3 subsequent mitoses. The mitotic stages were identified with aceto-orcein coloring techniques and by fluorescence methods. Except for a few cases where a mitotic asynchrony of 2–3 min was observed, the mitotic events occurred simultaneously in the nuclei within a single plasmodium. Both the occurrence of the first mitosis after inoculation and the intermitotic times were highly variable. Our study indicates that the contraction rhythm in plasmodia ofPhysarum is unperturbed during the synchronized nuclear division. However, in 5 of the 17 examined mitoses an amplitude decay was observed. We discuss possible explanations for the obtained results with emphasis on the applied techniques, interpretation of the oscillation patterns, and possible restrictions in the cell itself.     

Ca2+ oscillation in the homogenate ofPhysarum plasmodium

Summary Using aequorin luminescence, we observed a distinct oscillation in Ca²⁺ levels in the supernatant of the homogenate ofPhysarum plasmodium. Ca²⁺ oscillation continued for 10–120 minutes, with a period coinciding with that of the contraction rhythm of a plasmodium.Abbreviations EDTA Ethylenediaminetetraacetic acid - EGTA Ethyleneglycol-bis-(-aminoethylether)-N,N-tetraacetic acid - PIPES Piperazine-N,N-bis-(2-ethane sulfonic acid) - DTT Dithiothreitol The present work was supported by Grants-in Aid from the Ministry of Education, Science and Culture, Japan.     

ATP oscillation inPhysarum plasmodium

Summary Using bioluminescence of luciferin-luciferase, we showed that ATP leaked out rhythmically from a strand segment ofPhysarum plasmodium made permeable with caffeine-arsenate. With simultaneous measurement of isometric tension rhythm of the strand, it was revealed that the period and phase of oscillation in ATP leakage correspond well with those of tension production. Further, microinjection of luciferin-luciferase into the plasmodial strand indicated that the intracellular luminescence of luciferin-luciferase also oscillates with the same period and in the same phase as the tension rhythm.The free ATP concentration in a homogenate ofPhysarum plasmodium was of the order of 10 M, but if the homogenate was heated in boiling water, the intensity of luminescence suddenly increased 10–100 fold. ATP available for mechanical workin vivo is thus supposed to be at a much lower level than the total average, which was found in the range of 0.2–0.7 mM.     

Studies on contraction rhythm of the plasmodial strand IV. Site of active oscillation in an advancing plasmodium

Summary From the anterior region of an advancingPhysarum plasmodium, a slender rectangular piece of cytoplasmic gel was removed and its contractile properties were compared with those of a strand segment isolated from the network region of the same plasmodium. The anterior piece, in spite of injury caused by the surgical operation, began to contract and relax periodically without an appreciable lag stage after it had been excised. The segment of strand (vein) obtained from the network behind the advancing front showed no significant rhythm immediately after it had been isolated. Only after a lag period lasting for 10–20 minutes (stage I.Yoshimoto andKamiya 1978 a) did the strand gradually begin to oscillate under both isometric and isotonic conditions. Such behaviour of the isolated strand is interpreted as showing that the active site of the rhythmic contraction and relaxation in the advancing plasmodium is restricted to its anterior zone and the rear network structure plays no leading part in bringing about rhythmicity when it isin situ. Rhythmicity of a strand segment excised from the plasmodial network occurs only after it has been isolated as an independent system. Whether or not the strand is under tension is not important for this functional reorganization.The present work was supported in part by grants-in-aid from the Mitsubishi Foundation and the Japanese Ministry of Education, Science, and Culture.     

Fruiting body formation of the nivicolous myxomycete Badhamia alpina in moist chamber culture

The plasmodium of Badhamia alpina thrived at lower temperatures (4 °C), and formed fruiting bodies at 8 °C. The yellow sclerotium and plasmodium were found inside a hollow, dead herbaceous stem under melting snow in Apr, and was cultured in moist chambers at 4 °C. The plasmodium did not form fruiting bodies for 6 wk at 4 °C. Sporulation was observed after the incubation temperatures rose to 8 °C. Sporulation occurred in the morning and cell cleavage at 11 a.m. The order of spore wall formation was observed by TEM for 12 h. The outer spore wall ornamentation was formed first followed by internal wall layers. Round electron transparent object was observed in the capillitium and peridium during the latter part of sporulation.     

Towards Physarum Robots: Computing and Manipulating on Water Surface

Plasmodium of Physarum polycephalum is an ideal biological substrate for implementing concurrent anu parauel computation, including combinatorial geometry and optimization on graphs. The scoping experiments on Physarum computing in conditions of minimal friction, on the water surface were performed. The laboratory and computer experimental results show that plasmodium of Physarum is capable of computing a basic spanning tree and manipulating of light-weight objects. We speculate that our results pave the pathways towards the design and implementation of amorphous biological robots.     

Flow-network adaptation in Physarum amoebae

Understanding how biological systems solve problems could aid the design of novel computational methods. Information processing in unicellular eukaryotes is of particular interest, as these organisms have survived for more than a billion years using a simple system. The large amoeboid plasmodium of Physarum is able to solve a maze and to connect multiple food locations via a smart network. This study examined how Physarum amoebae compute these solutions. The mechanism involves the adaptation of the tubular body, which appears to be similar to a network, based on cell dynamics. Our model describes how the network of tubes expands and contracts depending on the flux of protoplasmic streaming, and reproduces experimental observations of the behavior of the organism. The proposed algorithm based on Physarum is simple and powerful.     

Temperature control of male embryo viability of the aphid Megoura viciae

Summary

Early stages of gametogenesis were observed in embryos of Megoura viciae Buckton at two temperatures, 24°C and 27°C. The higher temperature is lethal for male embryos but not for female embryos. Spermatogenesis proceeds to the synizesis contraction stage at both temperatures but goes no further at 27°C. All the spermatocytes degenerate prior to undergoing metaphase I and gamete degeneration is followed by the death of the male embryos. In oogenesis, synizesis lasts for much longer and no differential viability at the two temperatures can be observed. A possible explanation, related to the different timing of meiosis in the two sexes, is proposed and discussed.     

Azadirachtin affects the circadian rhythm of locomotion in Leucophaea maderae

Abstract

Azadirachtin shortens the period length of the locomotor activity rhythm in the circadian rhythm of Leucophaea maderae and induces splitting of this rhythm in two components in about 40% of the animals. The phase relationship between the two components is 180°. Both shortening of period and splitting are more pronounced in animals possessing longer periods before the injection of azadirachtin.     

Dispersion relation in oscillatory reaction-diffusion systems with self-consistent flow in true slime mold

In the large amoeboid organism Physarum, biochemical oscillators are spatially distributed throughout the organism and their collective motion exhibits phase waves, which carry physiological signals. The basic nature of this wave behaviour is not well-understood because, to date, an important effect has been neglected, namely, the shuttle streaming of protoplasm which accompanies the biochemical rhythms. Here we study the effects of self-consistent flow on the wave behaviour of oscillatory reaction-diffusion models proposed for the Physarum plasmodium, by means of numerical simulation for the dispersion relation and weakly nonlinear analysis for derivation of the phase equation. We conclude that the flow term is able to increase the speed of phase waves (similar to elongation of wave length). We compare the theoretical consequences with real waves observed in the organism and also point out the physiological roles of these effects on control mechanisms of intracellular communication.     

NAD(P)H oscillation in relation to the rhythmic contraction in thePhysarum plasmodium

Summary ThePhysarum plasmodium shows rhythmic contractile activities with a period of a few min. Phases of the oscillation in the plasmodium migrating unindirectionally agreed sideways throughout at the frontal part. So, time course of an intracellular chemical component was determined by analyzing small pieces cut off successively from the frontal part of the large plasmodium. Intracellular NAD(P)H concentration oscillated with the same period as the rhythmic contraction but with a different phase advancing about 1/3 of the period. UV irradiation suppressed the rhythmic contraction without affecting the rhythmic variation of NAD(P)H. Thus, the NAD(P)H oscillator works independently of the rhythmic contractile system, but seems entraining with each other.Abbreviations UV ultraviolet - NADH nicotinamide adenine dinucleotide, reduced form - NADPH nicotinamide adenine dinucleotide phosphate, reduced form - ATP adenosine 5-triphosphate - cAMP cyclic adenosine 3, 5-monophosphate - FMNH₂ flavin mononucleotide, reduced form - TCA tricarboxylic acid - BSA bovine serum albumin - DTT dithiothreitol     

Thalassomyxa australis rhythmicity II. No entrainment by light‐dark‐cycles and temperature cycles?

Abstract

The rhythmic change between an active phase and a resting phase of the plasmodial rhizopod Thalassomyxa australis sustained on the diatome Amphiprora, is not synchronized by a 12: 12 h light‐dark‐cycle. Likewise, 12: 12 h temperature cycles of 8°C difference such as 23°/15°C, 25°/17°C, 27°/19°C are not entraining this rhythm.     

The intranuclear microtubule organizing centre in the plasmodium of the myxomycete Physarum polycephalum

Physarum possesses two different microtubule cytoskeletons. In amoebae, cytoplasmic and mitotic microtubules are nucleated by a typical centrosome. In contrast, it has been reported that plasmodia have an intranuclear spindle organizing centre (SPOC) devoid of centrioles. We present genetic evidence suggesting that the SPOC located in the centrosome is very similar to the intranuclear plasmodial SPOC. The immunostaining properties of a new monoclonal antibody against Physarum centrosome has been used to compare these different MTOCs. Moreover, a dense plasmodial microtubule network was present in interphase plasmodia and absent in plasmodia undergoing mitosis. MTOCs responsible for the nucleation of the cytoplasmic microtubule network and intranuclear SPOCs were located in two different compartments of the plasmodium.     

Physical relationship between a gene and its origin of replication in Physarum polycephalum

Taking advantage of the natural synchrony of the S-phase within the plasmodium of Physarum polycephalum, we extracted highly synchronous DNA samples at precise time points in early S-phase. We then separated, by electrophoresis under denaturating conditions, the newly synthesized DNA strands of the nascent chromosomal replicons from the parental DNA template. Using the cDNA clone of the early-replicating LAV1-2 gene as a probe, we could establish by filter hybridization that the elongation rate of the replicon which encompasses this gene is constant, at a rate of 1 kb/min during the first 30 min of S-phase. The smallest replication intermediate (RI) that we have detected by probing with the LAV1-2 cDNA was 5 kb long, suggesting that the LAV1-2 gene and its origin of replication are closely associated within the chromosome. This procedure should facilitate the mapping of replication origins within the genome of Physarum.     

Evidence for an endogenous circadian rhythm of feeding in the trout (Oncorhynchus mykiss)

Abstract

The possible endogenous circadian rhythm in the feeding activity of rainbow trout (Oncorhynchus mykiss) was investigated using individual fish previously trained for self‐feeding. Under LD 12:12 conditions, the fish showed a diurnal behaviour, in many cases with a feeding rhythm with two main peaks of food demand at dawn and dusk, with an 8h interval of low feeding activity, and the actograms showed an expected 24 h rhythm. Fish kept under constant conditions (L : L, 15°±0.5°C), showed free‐running feeding activity for about 12 days. Food demands were concentrated at dawn, with a periodogram of 25.3 hour, under continuous environmental conditions. Results showed evidence for the endogenous origin of the circadian rhythm of feeding in this species.     

Spatio-temporal organization of intracellular ATP content and oscillation patterns in response to blue light byPhysarum polycephalum

Summary Phototactic responses in a giant amoeboid cell ofPhysarum plasmodium were studied both by analyzing intracellular ATP content and by applying image processing for recording oscillatory changes in thickness with use of a microcomputer. The ATP content fluctuated and deviated from the initial level upon exposure to light with varying wavelength from 400 to 600 nm. The maximum decrease in the integrated value dt with T=9 minutes occurred at the wavelength 450 nm. The ATP in a migrating plasmodium distributed twice as high in the front as in the rear. This polar pattern became unstable, and a new wavy pattern appeared by stimulating a local frontal part with blue light. In a concentrically extending plasmodium, peripheral and inside regions oscillated in opposite phase to each other. When part of this organism was exposed to light, stimulated and unslimulated regions began to oscillate in opposite phase, and phase waves propagated inward the stimulated region. And the protoplasm there became thinner, the strongest avoidance reaction occurring to 450 nm light as in ATP response. Phototactic behavior inPhysarum is discussed in terms of bifurcation in spatio-temporal organization appearing in a self-organizing system.     

Life Cycle and Temperature Requirements of Seven Herbaceous Species

Abstract

A series of observations were made on the life cycle, phenology, and germination capacity of Galantbus nivalis L., Corydalis cava Schw. et Krt., Anemone nemorosa L., Symphytum tuberosum L., Allium ursinum L., Aegopodium podagraria L., and Campanula rapunculoides L. The studies were conducted in field, in the Arboretum of the Botanical Garden of Padua, in experimental field chambers, and in growth cabinets maintained at temperature of 4°, 15° and 25°C. The various stages of life cycle of plants require different optimal thermoperiods. High temperature induce dormancy in A. nemorosa and S. tuberosum, while in G. nivalis and A. ursinum the rest period at the end of the vegetative cycle, is not broken by temperature treatments. A. podagraria and C. rapunculoides respond with a different morphogenesis to different temperatures. Temperature change (in the controlled conditions from one constant temperature to another) induced subsequent stage development. Vernalization is essential for all the species under study. However the minimum temperature for vernalization and the duration of exposure at this temperature varies in different species.

The life cycle observed of the various species may be considered as examples of different types of adaptation to a same environment.     

On the distribution of four species of agama (Agamidae) in Turkey

Abstract

The distribution of the Hardun, Agama stellio, the Caucasian Agama, Agama caucasia, the Syrian Agama, Agama ruderata, and Phrynocephalus helioscopus, in Turkey is presented with dot maps A. stellio and A. caucasia are sharply separated both horizontally and vertically. The area of A. stellio is defined by the March isotherm of 8°C and the July and August isotherms of 24°C. A. ruderata occurs in the large steppe areas of Inner and South-east Anatolia, but not in those of Eastern Anatolia.     

Inhibitory ca2+-control of movement of beads coated withphysarum myosin along actin-cables inChara internodal cells

Summary The actin-activated ATPase activityPhysarum myosin was shown to be inhibited of M levels of Ca²⁺. To determine if Ca²⁺ regulates ATP-dependent movement ofPhysarum myosin on actin, latex beads coated withPhysarum myosin were introduced intoChara cells by intracellular perfusion. In perfusion solution containing EGTA, the beads moved along the parallel arrays ofChara actin filaments at a rate of 1.0–1.8 m/sec; however, in perfusion solution containing Ca²⁺, the rate reduced to 0.0–0.7 m/sec. The movement of beads coated with scallop myosin, whose actin-activated ATPase activity is activated by Ca²⁺, was observed only in the perfusion solution containing Ca²⁺, indicating that myosin is responsible for the inhibitory effect of Ca²⁺ onPhysarum myosin movement. The involvement of this myosin-linked regulation in the inhibitory effect of Ca²⁺ on the cytoplasmic streaming observed inChara internodal cell andPhysarum plasmodium was discussed.Abbreviations ATP adenosine 5-triphosphate - DTT dithiothreitol - EDTA ethylenediaminetetraacetic acid - EGTA ethyleneglycolbis(-aminoethylether) N,N,N,N-tetraacetic acid - PIPES piperazine-N,N-bis(2-ethanesulfonic acid)