Studies on contraction rhythm of the plasmodial strand I. Synchronization of local rhythms

Summary A strand segment excised from a network ofPhysarum plasmodium showed no significant rhythmic activities at first, but started rhythmic contraction locally after 10–20 minutes. To express the development of local rhythms and their synchronizing process in the strand under isotonic conditions, the isolated strand was divided into several subsegments of nearly equal length with small resin particles attached as index markers. Changes in the length of each subsegment were then registered photographically every 10 seconds to obtain an overall view of local contractions. Thus we were able to find the time coordinates of individual sub-segments reaching their maximal length within the span of each corresponding wave representing contraction of the whole strand. Their standard deviation decreased with time becoming as small as 3–5 seconds or 3% of the period of the main waves after 30 minutes. Under isometric conditions, the method using index markers was useful, but we also could demonstrate the synchrony by the fact that the amplitude, period and phase of the tension waves became independent of the length of the strand. Once the contraction-relaxation cycle of each segment in the strand is synchronized, it is maintained under isotonic as well as isometric conditions.We should like to express our appreciation to Dr.Yoshio Hayashi, Professor of mathematics at Nippon University, Tokyo, for his interest in this work and his valuable suggestions. The present work was supported in part by grants-in-aid from the Mitsubishi Foundation and the Japanese Ministry of Education, Science, and Culture.     

Controlling the geometry and the coupling strength of the oscillator system in plasmodium ofPhysarum polycephalum by microfabricated structure

Summary The plasmodium of the true slime moldPhysarum polycephalum, which shows various oscillatory phenomena, can be regarded as a collective of nonlinear oscillators. Partial bodies in the plasmodium, which are assumed to be nonlinear oscillators, are mutually connected by microscale tubes named plasmodial strand. The interactions among the oscillators can be strongly affected by the geometry and the dimension of the tube network. Investigation of the collective behavior under the condition that the configuration of the network can be manipulated gives significant information on the characteristics of the plasmodium from the viewpoint of nonlinear dynamics. In this study, we have developed a new method to control the geometry and the tube dimension of the plasmodium with a microfabricated structure. It is shown that the geometry of the plasmodium can be manipulated with a microstructure which is fabricated of ultrathick photoresist resin by photolithographic processes. In order to confirm that not only the geometry but also the dimension of the tubes can be controlled with the microstructure, we observed the cross section of the patterned plasmodium with a three-dimensional internal-structure microscope. By observing the oscillatory behavior of the partial bodies of the patterned plasmodium, it was confirmed that the coupling strength between two oscillators, which corresponds to the dimension of the plasmodial strand, can be controlled by the microstructure. It is concluded that the present method is suitable for further studies of the network of Physarum plasmodium as a collective nonlinear oscillator system.     

Über den Verlauf eines schuppenorientierenden Gefälles beiGalleria mellonella

Summary Evidence for the existence of a concentration gradient in the segments ofGalleria mellonella and ofRhodnius prolixus has been reported elsewhere. InGalleria it is possible to determine the functional form of the gradient by measuring the deviation of the scales from their normal direction after the transplantation of a piece of the intersegmental integument from the anterior or the posterior margin into the segment. The calculated values indicate the force with which the scales are oriented in an axial direction. This force corresponds to the slope of the concentration gradient.Different curves are found for the forces depending on the origin of the graft (anterior or posterior margin). This seems to be the result of unequal shrinking of the grafts. The geometrical mean of the average of the forces for anterior grafts and that for posterior grafts is nearly constant all over the segment (only the parts near the segment margins could not be included in the measurement). Thus the concentration gradient declines almost linearly. Linearly declining concentrations are expected between two different but constant concentrations which may be assumed to be located in the anterior and the posterior margin of the segment.

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Ich danke Herrn Dr.Marcus für die großzügige Überlassung seiner Präparate und Herrn Dr.Schmidt-König für die hilfreiche Diskussion der statistischen Möglichkeiten dieses Falles. Die Arbeit wurde mit Unterstützung der Deutschen Forschungsgemeinschaft ausgeführt.     

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.     

Electro-osmotic and biopotential measurements on phloem strands of Nymphoides

Summary Electroosmotic measurements on the excised vascular strand from the petiole of the water plant Nymphoides peltatum have been carried out, and the Onsager coefficients obtained. About 120 water moleculer per ion are carried electroosmotically when the strand is in 10^-4 M KCl, about 30 in 10^-1 M KCl. Potential measurements made on an intact and functioning petiole are discussed in the light of the pressure-flow and electroosmotic theories of translocation.This work has been made possible for one of us (D. S. Fensom) through the assistance of the National Research Council of Canada and a special grant from the Marjorie Young Bell Fund of Mount Allison University.     

Single calcium-dependent cation channels in mouse pancreatic acinar cells

Summary The Ca²⁺-activated nonselective cation channel in mouse pancreatic acini has been studied with the help of patch-clamp single-channel current recording in both the cell-attached conformation and in excised inside-out membrane patches. In intact resting mouse pancreatic acinar cells no unitary activity was observed. Adding saponin to the bath solution to disrupt the plasma membrane (apart from the isolated patch membrane from which current recording was made) evoked unitary inward current steps when the free ionized Ca²⁺ concentration in the bath ([Ca²⁺] _i ) was 5×10^–8 m or above. When an electrically isolated patch membrane was excised and the internal aspects of the plasma membrane were exposed to the bath solution, channel activation could be obtained when [Ca²⁺] _i was 10^–7 m or above. However, with the passage of time the total inward current declined and about 1 min after excision no unitary current steps could be observed. At this stage Ca²⁺ in micromolar concentration was needed to open the channels and several hundred micromoles of Ca²⁺ per liter were required for maximal channel activation. Our results indicate that the Ca²⁺-activated nonselective cation channel is more sensitive to internal Ca²⁺ than hitherto understood and that it may therefore play a role under physiological conditions in intact cells.     

A polarized light and electron microscopic study of the birefringent fibrils inPhysarum plasmodia

Summary The birefringent fibrils in thin-spread plasmodium ofPhysarum polycephalum have been investigated with both polarizing and electron microscopes. The birefringent fibrils were classified into three groups by polarized light microscopy. The first type of fibril is observed in the advancing frontal region as a mutual orthogonal array. The birefringence changes rhythmically in accordance with the shuttle streaming. The second type of birefringent fibril is located in the strand region and runs parallel or somewhat oblique to the strand axis. The third type is observed in the strand region always perpendicular to the streaming axis. Electron microscopy confirmed that all these fibrils are composed of microfilaments, which range in densities in the cross view of the fibril from 1.2 to 1.7 × 10³/m² (1.5 × 10³/(xm² on the average).     

A spontaneous derivative of abnormal chromosome 10 in maize

Summary A new type of abnormal chromosome 10 has been found among maize plants grown from seeds sent by Dr. Y. C. Ting of Harvard University. This chromosome deviates in its morphology from the orthodox abnormal chromosome 10 described by Rhoades (1952) and from the one described by Ting (1958b). It produces a low degree of neo-centric activity.Cytological observations of plants heterozygous for the new abnormal chromosome 10 and either an orthodox abnormal chromosome 10 or a normal one, have suggested that the new type was derived from an orthodox abnormal 10 through spontaneous breakage and loss of an important piece of its long arm. The delection involved the distal part of the long arm of orthodox abnormal chromosome 10, proximally limited by the third most distal dissimilar and prominent chromomere. This corresponds approximately to the extra segment at the end of orthodox abnormal chromosome 10 which remains unpaired in heterozygotes with the normal 10. It bears a large heterochromatic knob. The missing piece is a part of the larger fraction of the long arm of orthodox abnormal chromosome 10 that remains unaffected by crossingover in a heteromorphic bivalent having a normal chromosome 10 (telo-segment). The telo-segment has its proximal limit at the left of the most proximal of the 3 dissimilar chromomeres, probably between the R and Sr ₂ loci. It has been proposed that a factor or factors responsible for neo-centric activity are located in the portion of the telosegment between its proximal limit and the third most distal dissimilar chromomere (3 dissimilar chromomere region).Since the telo-segment of the orthodox abnormal 10 also bears a large knob in its distal half, it has been suggested that this segment has a dual role in neo-centric activity. The factor or factors located in the proximal piece of the telo-segment would stimulate over-abundance of fiber-forming substance, whereas local production of chromosomal fibers would depend ultimately on the knob's activity.If the large knob is absent, its role in neo-centric activity would be transferred to the next smaller and distally located hetero-chromatic mass, such as the knob-like body near the end of the new abnormal 10 which results from the fusion of the two most proximal prominent chromomeres of the telo-segment.This work has been partly done in the United States, under an I.C.A. — National Academy of Sciences fellowship.     

Ultrastructure of the plasmodial slime moldPerichaena vermicularis

Summary Mature plasmodia ofPerichaena vermicularis require a light period to induce sporulation. In this paper the ultrastructure and acid phosphatase localization of the mature plasmodium ofPerichaena vermicularis are investigated. Acid phosphatase is localized in vacuoles containing remnants of bacteria and cell organelles. Morphological and histochemical evidence support the interpretation that these vacuoles constitute two types of lysosomes called respectively heterophagic and autophagic vacuoles.Coated vesicles which apparently originate from smooth endoplasmic reticulum are dispersed throughout the plasmodium and frequently associated with lysosomes. Several dumbbellshaped mitochondria are observed in the plasmodium at the onset of fruiting but not during later stages of plasmodiocarp development. Cytoplasmic microtubules are identified inPerichaena vermicularis. Some of these are closely associated with microfilaments.This work was supported by National Science Foundation grants (GB-5884 and GB-8537) to Dr.Ian K.Ross, NSF grant (GB 12371) to Dr.James Cronshaw, and an NSF Traineeship (GZ 445 and 796) to I.Charvat.This constitutes a portion of a thesis presented to the Regents of the University of California by the first author in partial fulfillment of the requirements for the Ph. D. degree.     

Phosphate requirements of the nitrifying bacteria

The influence of the phosphate concentration on the specific growth rate and the duration of lag has been studied inNitrobacter winogradskyi andNitrosomonas europaea.The optimum phosphate concentration range for the specific growth rate was 10 to 30mm forNitrobacter and 10 to 100mm forNitrosomonas. In this range the lag was least. Depletion of the cell-P does not affect the relation between specific growth rate and phosphate concentration while the lag seems to increase as cell-P depletion proceeds.     

Effect of cobalt and nickel on growth and carboxymethyl cellulase activity ofCellulomonas spp

ACellulomonas spp isolated from soil produced carboxymethyl cellulase (CMCase) and xylanase enzymes. Cobalt (0.1mm) and nickel (0.1mm) decreased the growth rate ofCellulomonas spp. These metal ions activated CMCase activity but not xylanase activity; cobalt being the greater stimulatory ion than nickel. A predominant long lag phase was observed in adapted cells when compared with the non-adapted cells. However, the growth level of control cells was never obtained by the adapted cells.     

Pseudoeurotium globosum n. sp., a new ascomycete from Indian soils

Summary The namePseudoeurotium globosum Rai andTewari n. sp. has been given to a fungus isolated from soil collected from the banks of a stream in village Harchandpur, District Rae Bareli, (U.P.) India. This form is distinguished from any other described so far in this genus, in having multisporous asci with large globose ascospores. P.globosum n. sp. inhabits a specialised habitat, and this along with the fact that it was isolated only byWarcup's Soil-plate Method, makes it an ecologically interesting form.     

Production of seedlings from ovules excised at the zygote stage in Lilium spp.

The present study was undertaken to establish a culture system for ovules excised at the zygote stage in Lilium spp. Ovules of Lilium × `Connecticut King' and L. × `Enchantment' were excised together with placental tissue 3, 5, and 10 days after pollination (DAP) and cultured on B5 medium and half-strength B5 medium containing sucrose at different concentrations. In vitro embryo development in ovules cultured at 3 DAP was influenced by the basal media and the sucrose concentration. The half-strength B5 medium with 9% sucrose was the best condition, but only a few ovules isolated from placental tissue developed into seedlings. Application of embryo culture, in which embryos were excised from ovules after 14 weeks of ovule-with-plancetal-tissue culture, greatly improved the production of seedlings. The present study indicates that a two-step culture procedure, ovule-with-placental-tissue culture and embryo culture, make it possible to produce seedlings from ovules just after fertilization.     

Anomalous uptake ofd-ribose byRhodotorula gracilis

d-Ribose was found to enter the cells ofRhodotorula gracilis by a mechanism resembling simple diffusion (proportionality between rate and concentration, no effect of inhibitors, of temperature, of other sugars) at concentrations from 0.001 to 10mm. With a lag of about 1 hour,d-ribose was oxidized and, with a lag of about 20 hours, it could serve as a growth substrate. The transport step appears to be rate-limiting for the subsequent metabolic processes. The oxidation was stimulated byd-xylose but unaffected byd-glucose. Dedicated to Academician Ivan Málek on the occasion of his 60th birthday     

The cell structure of the reticulopodial amoeba <Emphasis Type="Italic">Filoreta marina</Emphasis> Bass et Cavalier-Smith (Cercozoa)

The cell structure of a reticulopodial amoeba, Filoreta marina Bass et Cavalier-Smith, is described. The cell is covered by a unitary membrane; glycostyles are absent. The life cycle comprises the uninucleate stage, multinucleate plasmodium, and spherical uninucleate cysts. The microtubules inside pseudopodia and the flagella are absent. The vesicular nuclei, endoplasmic reticulum, and Golgi apparatus are of a typical structure. The plasmodium produces a branched network of narrow anastomosing (reticulopodia) and wide pseudopodia. Thin unbranched micropseudopodia have also been observed. Oval mitochondria with a size of 0.3 × 0.6 μm contain the tubular cristae. A bidirectional motion of the cytoplasm inside the reticulopodia has been detected. Extrusomes (extrusive organelles) have not been found. The contractile vacuole is absent. F. marina feeds on bacteria. A similarity of this amoeba to other filose and reticulopodial amoebas is discussed.     

Variety of mitochondrial shapes,sizes, and volumes inChlamydomonas reinhardii

Summary Mitochondria in cells ofChlamydomonas reinhardii, which at an intermediate stage of the vegetative cell cycle have been submitted to gametogenesis under dark and cold conditions, remain more or less unchanged with and without the addition of chloramphenicol. They exist in various number, shapes, and sizes and can be branched or unbranched as well as small or large. Giant mitochondria can be fused to a mitochondrial network, which, in contrast to the previously reported network (Grobe andArnold 1975), lies predominantly in the center of the cell. Mitochondrial volumes were revealed by means of morphometrical analyses from serial sections of four entire cells.     

Cytologie comparée deMus (Leggada) Minutoides minutoides Smith D'afrique du Sud et d'une forme voisine de l'Angola

In the pigmy-mouse,Mus (Leggada) minutoides minutoides A. Smith, 1834 from South-Africa, the author (1964) has described a chromosome complement of 18. The 16 autosomes are metacentric. TheX is big and metacentric, theY short and acrocentric. Owing to the fact that, at the first metaphase, both sex-chromosomes are united through a true chiasma, it was supposed that theY was primitively of the translocated type (TR), like theX, and that an intercalary deletion had destroyed the main part of the autosomic segment of theY, leaving only a small telomeric piece necessary for the formation of a chiasma. This hypothesis is confirmed by the analysis of pigmy-mice from Angola which morphologically are very like but not identical to the South-African form. The single chromosomic difference is the shape of theY which is big and submetacentric, also of theTR type.     

Information processing for the organization of chemotactic behavior ofPhysarum polycephalum studied by micro-thermography

Summary The spatial and temporal pattern of oscillating temperatures on the cell surface of a plasmodial strand ofPhysarum polycephalum was measured with a sensitive thermal image camera. The longitudinal tension of the strand was studied simultaneously. In the absence of chemical stimulation, the phases of the temperature oscillation observed at various portions of the strand were entrained with almost coincidental phase. The temperature and tension oscillation were synchronized, although the phase difference between them was occasionally changed. With local chemical stimulation, the phase of the temperature oscillation advanced in the portion to which the plasmodium would be induced to migrate. The phases between temperature and tension oscillations then became constant. The mechanism by which the plasmodium processes local information of chemical stimulus to global information for the migration is discussed.     

On the morphology and life-history of a form of gloeocapsa showing some new stages

Summary A new variety of Gloeocapsa, G. crepidinum Thuret var. ghazipurensis n. var., has been isolated from enrichment cultures of paddy field soils of Ghazipur, Uttar Pradesh, India. The alga has been studied in detail. The form is especially interesting since it showed certain growth-stages recorded in G. alpina Naeg.The authors are thankful to Rev. Dr. H. Santapau for rendering the Latin diagnosis of the new variety.