The protoplasmic flow in the myxomycete plasmodium as revealed by a volumetric analysis

Summary The manner of the locomotion of the slime mold,Physarum polycephalum, was shown graphically using a double-chamber volumeter developed by the author. It enabled him to represent in undulating curves every detail of the way in which the slime mold moves on little by little by availing itself of the difference in transport-volume of the endoplasm produced at each repetition of the back and forth streaming.The curve showing the locomotion of the organism pointed out that more than 4 mm³ of protoplasm is sometimes shifted in a direction in one streaming duration. No close relationship is found between the streaming duration and the transport-volume of protoplasm. The intensity of the flow, which may be defined as the volume of protoplasm transported per unit time, can be obtained from the transport-volume curve through its graphical differentiation.     

The influence of neurohumoral transmitter substances on protoplasmic streaming in the myxomycete Physarella oblonga

The authors studied the influence of adrenaline-like substances and acetylcholine on the protoplasmic streaming in Physarella oblonga, investigating the effect on the duration of the rhythmic period. Adrenaline and noradrenaline proved to cause a shortening, whereas acetylcholine appeared to be capable of causing an extension of the period duration. The authors present and discuss critically the possibility that the adrenergic and cholinergic transmitter substances, which influence the visceral (mechano-) effectors in the higher animal organism often antagonistically, may also affect an elementary “functional” effector system responsible for protoplasmic streaming, and that in so doing they have comparable effects. The results of experiments with eserine, acetylcholine and a mixture of these two substances render it probable that an acetylcholine esterase and acetylcholine occur in the plasmodium. The mean normal value of the period duration was, calculated from 976 measurements and expressed in seconds: 284.183 ± 1.486 (S.E. of the mean). The average duration of the progressive and the regressive phase was found to be almost the same.     

Nutrient mobilization by plasmodium of myxomycete Physarum rigidum in deadwood

To assess the nutrient mobilization ability of myxomycete plasmodia in deadwood, a microcosm experiment was conducted. Alive or dead plasmodia of a common lignicolous myxomycete, Physarum rigidum, were inoculated on field-collected crushed wood powder of white-rot or brown-rot pine wood and incubated for 24 d. The activity of living plasmodia led to increased concentrations of Ca²⁺, K⁺, Mg²⁺, Na⁺, and Cl⁻, but lower PO₄^3– concentrations in the wood powder. For NO₃⁻ concentration, the effect of living plasmodia was negative in white-rotted wood but positive in brown-rotted wood. These results suggest that the plasmodium of P. rigidum has the ability to mobilize nutrients in deadwood.     

Movement of vesicles in cytoplasmic streaming in plasmodium

The moving velocities of vesicles in the cytoplasmic streaming of a slime mold were measured, in which all of the vesicles passing through a designated window were counted. Vesicles in the streaming are distributed in their moving velocities and the distribution itself varies with time. The mean velocity of vesicles and its standard deviation were found to exhibit a linear relationship, suggesting a possibility that vesicles in the cytoplasm would also be involved in force generation.     

Sedimentation velocity of myxomycete spores

Sedimentation velocities were measured for seven myxomycete species and one fungus. Values for these first measurements for Myxomycetes were fitted with the formula of Stoke’s law for the terminal velocity of small spherical bodies in air. The obtained correlation coefficient of R=0.939 indicates that sedimentation velocities of myxomycete spores follow Stoke’s law well. With spore density as a parameter, the fit estimated a mean density of 0.74 g/cm³ for air-dried spores. The importance of the stalked spore case as well as the spore diameter for dispersal abilities of Myxomycetes is discussed.     

Videomicroscopy in the study of protoplasmic streaming and cell movement

Summary Various types of cell motility have been observed and analyzed with techniques of increasing sensitivity and sophistication. Photokymography, cinemicrography and laser-Doppler spectroscopy have all made important contributions to our knowledge of cytoplasmic streaming and cell movement.Now videomicroscopy is finding applications in recording and analyzing two different kinds of images. Video intensification microscopy by image intensifiers and silicon intensified target (SIT) video cameras is used to intensify images too dim to be viewed by eye or photographed. On the other hand, video enhanced microscopy uses a less sensitive chalnicon or other vidicon camera with adjustable amplification and offset to enhance the contrast and improve the resolution of microscopes that employ instrumental compensators.Both of these videotechniques have greatly extended the usefulness of the optical microscope: image intensification to brighten dim images and video enhancement to improve the contrast and resolution so that even submicroscopic structures and events can be recorded. These video techniques can both be further extended by a frame memory, with which images can be further enhanced by computer processing. Still to be developed, however, are appropriate methods for automatic tracking of particle motions.     

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.     

Fluid-dynamical study of protoplasmic streaming in a plant cell

A mathematical model of protoplasmic streaming in a plant cell such as Nitella and Chara is studied. General rheological equations for the non-Newtonian fluid is derived theoretically, and the boundary value problem for the model is solved. The pattern of motion of cytoplasm in a living cell is obtained, and the rheological property of protoplasm is evaluated in vivo.