Electron microscopy of the slime moldPhysarum polycephalum

Protoplasma - Electron micrographs of fixed sections of the plasmodium of the classic protoplasmic material,Physarum polycephalum, are presented. Numerous round nuclei having well-defined membranes...     

Electron microscopy of the slime moldPhysarum polycephalum

Summary Electron micrographs of fixed sections of the plasmodium of the classic protoplasmic material,Physarum polycephalum, are presented. Numerous round nuclei having well-defined membranes and containing one to three dense nucleoli were especially prominent in the plasmodium. In the surrounding cytoplasm, many irregular membrane-limited bodies were evident, some containing tiny rod-like elements and others with inner structures resembling mitochondria. In addition, there can be seen many small dense granules plus various vacuoles and other inclusions.     

Sporulation delay by stable cAMP analogues in the slime moldPhysarum polycephalum

Summary Plasmodial cells of the slime moldPhysarum polycephalum become competent for sporulation following a prolonged period of starvation in darkness. Then sporulation can be induced by illumination. Microinjections of the stable (Sp)- and (Rp)-diastereoisomers of adenosine cyclic 3′,5′ monothionophosphate before and during a sensitive period from the start of illumination until 5 h after lead to a significant delay in the sporulation process. Both of the diastereoisomers of cyclic AMP prolong the time for sporangia to form in darkness. However, the (Sp)-diastereoisomer is more effective and causes morphological changes in plasmodia. The experimental data suggest that cyclic AMP is decisively involved in light-induced differentiation in the lower eukaryotoPhysarum polycephalum.     

Activities of DNA degrading enzymes in the slime moldPhysarum polycephalum

Crude extracts ofPhysarum polycephalum contain five DNA degrading enzyme activities. One enzyme activity degrades native DNA with a maximum activity at pH 3.2. Four others degrade heat-denatured DNA and have their maximum activity at pH's 3.4, 4.0, 7.6 and 8.5 respectively. The five DNA degrading activities react in different ways to administration of divalent cations and show different stabilities towards heat inactivation or incubation conditions.Abbreviation PIPES piperazine-N,N-bis(2-ethanesulfonic acid)     

Fragmentation of the plasmodium into equally sized pieces by low temperatures in the true slime moldPhysarum polycephalum: A new morphogenesis

Protoplasma - We found a new type of morphogenesis in the plasmodia of the true slime moldPhysarum polycephalum: The plasmodium broke temporarily into pieces with uniform size at low temperatures....     

Fine structure of plasmodial nuclei in the slime moldPhysarum polycephalum I. Comparison of diploid and haploid vegetative mitosis

Summary The same basic ultrastructural features of interphase and mitotic nuclei were found for both the haploid Colonia and the diploid wild type strains of the myxomycete,Physarum polycephalum. Differences in nuclear size and chromocenter numbers were observed, but the nucleolar cycle and the intranuclear and acentriolar type of mitosis characteristic of the plasmodial stage of the diploid is present in haploid plasmodia, ruling out any relation between ploidy level and type of mitotic figure.     

Interactions of alginates with univalent cations

Interactions of alginate with univalent cations in solution have been investigated by circular dichroism (c.d.) and rheological measurements. Poly-l-guluronate chain-segments show substantial enhancement (～ 50%) of c.d. ellipticity in the presence of excess of K⁺, with smaller changes for other univalent cations: Li⁺ < Na⁺ < K⁺ > Rb⁺ > Cs⁺ > NH₄⁺. The maximum c.d. change is attained by 0.3m, with no further increase at higher concentrations of cation. No significant dependence on polymer concentration is observed. Spectral changes for poly-d-mannuronate and heterotypic chain-sequences are much smaller. For intact alginates, the magnitude of c.d. change varies almost linearly with poly-l-guluronate content. Difference spectra (c.d. with excess of univalent counterion minus c.d. in distilled water) can be fitted accurately to two Gaussian bands at 211 and 198 nm, assigned to carboxyl n → π^* and π → π^* transitions, respectively. The perturbations induced by Li⁺, K⁺, Rb⁺, Cs⁺, and NH₄⁺ show a clear family relationship, and are mainly in the π → π^* spectral region. With Na⁺, by contrast, c.d. change is largely confined to the n → π^* transition, and is similar to that previously reported for intermolecular (“egg-box”) binding of divalent cations, consistent with results of rheological studies which indicate Na⁺-induced association of poly-l-guluronate chain-sequences. These associations are further enhanced on freezing and thawing. This combined evidence is interpreted in terms of three modes of interaction between univalent cations and alginate chains in solution: (a) ion-pair formation with carboxyl groups of mannuronate and isolated guluronate residues; (b) specific site-binding to contiguous guluronate residues; and (c) co-operative “egg-box” binding, particularly of Na⁺, between poly-l-guluronate chain-sequences.     

Degradation of bacterial lipopolysaccharide by the slime mould Physarum polycephalum.

A strain of the acellular slime mould Physarum polycephalum degraded lipopolysaccharides (LPS) from a variety of bacteria. The anticomplementary (AC) activity of LPS was greatly reduced, as was the content of lauric, myristic, and palmitic acids, and the ability to sensitize erythrocytes to agglutination by antibody. These results indicate that Physarum has enzymes which reduce the lipid A moiety of LPS. In contrast, 2-keto-3-deoxy-D-manno-actanoic acid (KDO), immunodominant sugars, and beta-hydroxymyristic acid were scarcely affected. Both supernates and plasmodial extracts of Physarum had LPS-degradative activity and were able to attack both purified LPS and LPS in killed bacteria.     

Effect of sugars on salt reception in true slime mold Physarum polycephalum. Physicochemical interpretation of interaction between salt and sugar receptions

Interaction between salt and sugar receptions in plasmodium of Physarum polycephalum was studied by using double-chamber method. Effect of sugars on salt reception was evaluated by measuring membrane potential and the motive force of tactic movement of the slime mold, where salt concentration in one compartment was increased successively with a fixed sugar concentration. Results are summarized as follows: (1) The presence of D-glucose, D-mannose, D-maltose, or sucrose in medium led to increase of the threshold concentration Cth, for salts (chlorides and nitrates of Li, Na, K), whereas D-ribose decreased the threshold for salt reception. D-galactose showed no appreciable effect on Cth of every salt species examined. No change in Cth for salt reception was observed until concentration of sugars exceeded their respective thresholds. (2) Double logarithmic plots of Cth for salts against sugar concentration followed different straight lines for different cations, whose slopes being closely correlated with the effects of lyotropic number of anions in the absence of sugars. (3) Plots of log Cth against the reciprocal of the absolute temperature, 1/T, gave linear relations, and the slopes of the straight line became small with increase of sugar concentration above their respective thresholds. Experimental results obtained here suggest that the structure of water at the interface of cell membrane plays an indispensable role in the interaction between salt and sugar receptions.     

Immunocytochemistry of the acellular slime mold Physarum polycephalum

Abstract. The polygonal arrangement of actomyosin fibrils in different stages of the acellular slime mold Physarum polycephalum is correlated with morphogenetic processes at the cell surface. Light and electron microscopic investigations on both endoplasmic drops and thin-spread small plasmodia demonstrate that the differentiation of a polygonal pattern depends on a transient deficiency of plasma membrane invaginations.
Glycerol-extracted specimens show condensation and drastic spatial changes in the organization of the polygonal net after addition of ATP, thus indicating contractile properties of this system. Observations with the polarizing microscope reveal rhythmic changes in fibrillar birefringence intensity corresponding to the protoplasmic streaming activity, i.e., birefringence increases during contraction and decreases during relaxation. Cell fusion experiments, local irradiation with blue light (450 nm), and chemical treatment by impeding the mitochondria1 function with DNP (2,4-di-nitrophenol) demonstrate morphological as well as physiological interdependences of the actomyosin system, the motive force generation, and the expression of a locomotor polarity in plasmodia of Physarum polycephalum.     

Identification of mRNA in the slime mold Physarum polycephalum.

Using a differential extraction procedure which had previously been shown to yield one nucleic acid fraction enriched in cytoplasmic RNA and another enriched in nuclear RNA, we have been able to isolate two polyadenylated RNA populations from microplasmodia of Physarum polycephalum. The poly(A)-containing RNA from the cytoplasmic-enriched fraction accounts for approximately 1.2% of the cytoplasmic nucleic acid, has a number-average nucleotide size of 1339+/- 39 nucleotides, and has been shown, in a protein-synthesizing system in vitro, to be capable of directing the synthesis of peptides which have also been shown to be synthesized in vivo by microplasmodia. The poly(A)-containing RNA from the nuclear-enriched fraction has a number-average nucleotide size of 1533 +/- 104 nucleotides and represents a mixture of cytoplasmic and nuclear adenylated RNA molecules. Based upon these observations, we have identified the polyadenylated RNA isolated from the fraction enriched in cytoplasmic nuclei acid as Physarum poly(A)-containing messenger RNA.     

Induction of mitochondrial migration in the slime mold Physarum polycephalum

Mitochondrial migration in a microplasmodium of Physarum polycephalumwas studied by litgh and electron microscopy. The mitochondriawere dispersed evenly in the microplasmodium of Physarum polycephalumin shaken cultures but when the microplasmodia were left unshakenin a liquid culture for more than 3 hr, the mitochondria migratedtoward the peripheral area and came into contact with an semi-electrontransparent layer beneath the cell membrane. Once the peripherallocalization of mitochondria was established in unshaken culture,subsequent reversal to the shaken cultures induced a reversion.These results suggest that mitochondrial migration is reversiblyindicated by culture condition. (Received June 19, 1978; )     

The interaction of sodium alginate with univalent cations

The M/G ratio, dyad and triad frequencies in the sodium alginate chain, were determined from ¹³C-nmr spectra. The interactions of sodium alginate in solution with the univalent cations K⁺ ion and Na⁺ ion have been investigated by viscometry and membrane osmometry. The dependencies of intrinsic viscosity, Huggins constant, and second virial coefficient on ionic strength were observed, and the maximums in reduced viscosity were obtained in low KCl and NaCl concentrations, respectively. These show that the electroviscous effects play an important role in polyelectrolyte solution, and the effect of the Na⁺ ion on aqueous solution of sodium alginate is greater than the K⁺ ion. The experimental observations are interpreted in terms of ion-pair formation with carboxyl groups of mannuronate and isolated guluronate residues and cooperation “egg-box” binding between polyguluronate chain sequence. The difference of interaction between univalent cations and alginate chains in solution is attributed to the ability of their binding with the polyion, which depends on the properties of ions itself. © 1998 John Wiley & Sons, Inc. Biopoly 46: 395–402, 1998     

The uptake and metabolism of uridine by the slime mould Physarum polycephalum.

1. Uridine is taken up by microplasmodia of Physarum polycephalum via a saturatable transport system with an apparent Km of 29 muM. An intracellular concentration significantly higher than that in the growth medium is attained, suggesting that the uptake is an active process. Both deoxyribonucleosides and ribonucleosides are competitive inhibitors of the uptake of uridine. 2. In contrast, the rate of entry of uridine into surface plasmodia is a linear function of the concentration of the nucleoside in the growth medium, and the uptake is not inhibited by other nucleosides. 3. As well as serving as a source of pyrimidine nucleotides for the synthesis of nucleic acids, uridine is also catabolised by P. polycephalum. Uracil accumulates in the growth medium and there is also significant conversion of C-2 of the pyrimidine ring to CO2. The proportion of uridine subject to catabolism in surface plasmodia is less than that observed for microplasmodia.     

Unusual polyamines in slime molds Physarum polycephalum and Dictyostelium discoideum

We analyzed the cellular contents of not only major polyamines but also minor polyamines in slime molds Physarum polycephalum and Dictyostelium discoideum. The presence of putrescine and spermidine in either plasmodia or myxamoebae of these molds as major polyamines was confirmed. In addition to these polyamines, appreciable amounts of 1,3-diaminopropane were detected in P. polycephalum and D. discoideum. Cadaverine and sym-homospermidine were detected in P. polycephalum even when the slime mold was cultured in a chemically defined growth medium. Spermine was not detected when these molds were grown in synthetic media. Other "unusual" polyamines such as norspermidine, norspermine, thermospermine, aminopropylcadaverine, and canavalmine were not detected in either mold.