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K E Wohlfarth-Bottermann

Publications and source records attributed to K E Wohlfarth-Bottermann.

At least 37 records · Page 2Linked to original sources
PubMed1983

Consequences of impeding in mitochondrial function in Physarum polycephalum. II. Influence on "de novo" generation of contractile activities and responses to glucose and blue light.

The "de novo" generation of longitudinal contractile activity in endoplasmic veins is inhibited by 5 mM KCN, whereas 10 mM alpha-ketoglutarate combined with 5 mM AMP abolishes this inhibiting effect in spite of a continued presence of KCN. An analysis of the Young's modulus and studies on the morphogenesis of endoplasmic veins reveal morphological effects of an impediment of cell respiration: (1) an increased fibrillogenesis and changes in the spatial distribution of cytoplasmic actomyosin fibrils, (2) an impediment of the "de novo" generation of the plasmalemma invaginations, and (3) the appearance of a thick cortical layer of ground-plasm. These effects of KCN do not appear in the presence of alpha-ketoglutarate and AMP, and disappear by their subsequent application. Impediment of cell respiration by 5 mM KCN inhibits the tensiometrically registrable responses to glucose and blue light. Both reactions are restored in the presence of KCN by an additional application of 10 mM alpha-ketoglutarate combined with 5 mM AMP. The importance of mitochondrial function with respect to morphogenetic events and to the perception and transduction of external signals as well as to locomotory reactions of Physarum plasmodia is discussed.

Adenosine Monophosphate↗
PubMed1982

Endoplasmic veins from plasmodia of Physarum polycephalum: a new strand model defined age, structure, and behavior.

Pure endoplasm from plasmodia of Physarum polycephalum taken up into glass pipettes and subsequently extruded into water forms a long protoplasmic cylinder uniform in diameter, which is designated as an "endoplasmic vein". This new experimentally obtained model has proven advantageous for tensiometric investigation of contraction activity. During the process of aging, this model undergoes processes of 1. actin transformations, 2. cytoplasmic actomyosin fibrillogenesis and 3. development of a new plasmalemma invagination system. Within approximately 20 min the newly formed plasmalemma invaginations delimit an endoplasmic channel and shuttle streaming along the longitudinal axis appears in the artificially generated protoplasmic strands. The geometrical shape of this strand model permits unidirectional tensiometric measurements of contractile and mechanical properties of the endoplasm during the early stages of its transformation to an ectoplasmic tube. Tensiometric and morphologic observations reveal that the process of actomyosin fibrillogenesis in the early stage of development of endoplasmic veins is temporally correlated with an increase in the force output under isometric conditions of tensiometric measurement. Young's modulus, which represents mechanical properties of the model (0.8-1.4 X 10(5) dyne/cm2), is in the range of values observed in normal isolated protoplasmic strands. The advantages of the new model for the investigation of cyclic contraction behaviour are discussed.

Actins↗
PubMed1981

Cytoplasmic actomyosin fibrils after preservation with high pressure freezing.

The fine structure of the actomyosin system of Physarum polycephalum was investigated in vitrified specimens after applying a pressure of greater than 2.1 kbar and freezing rates of 500 to 5,000 degrees C/s. The frozen specimens were either freeze-substituted or freeze-fractured and compared with material processed according to conventional methods of freeze-etching preparation. Artifactual alterations, as seen in the form of destroyed areas of the cytoplasm after chemical fixation, were not observed after freeze-substitution. However, small ice crystals formed by recrystallization within most of the cytoplasmic actomyosin fibrils prevented a fine structural analysis. Such a destruction of the fibrillar fine structure was not found after freeze-etching. In replicas of deep-etched objects 10 nm-thick filaments were localized, which could be conclusively identified as F-actin. The actin filaments are located randomly in the peripheral cytoplasm forming the cell cortex. By the process of parallel aggregation, the filaments can be differentiated to fibrils. Thick myosin filaments were not observed. However, structures resembling cross bridges between single actin filaments suggest the existence of oligomeric myosin. The present investigation shows that, in addition to biomembranes, other cytoplasmic differentiations such as components of the groundplasm can be successfully demonstrated employing the deep-etching technique when the freezing methods are improved by avoiding freeze-protection pretreatments.

Actomyosin↗
PubMed1981

The pathway of photosensory transduction in Physarum polycephalum.

Irradiation of the plasmodia of Physarum with blue and white light results in a transient change of theie oscillatory contraction frequency. This reaction to light decreases with increasing distance from the illuminated area (Block and Wohlfarth-Bottermann, 1981). The first local appearance of light response in non-illuminated parts of the plasmodia was used to analyse the sensory pathway of the light stimulus modulating the contractile apparatus. Different experimental assays revealed that the direction of photosensory transduction is determined by the momentary direction of protoplasmic shuttle streaming. The endoplasmic flow carriers the signal responsible for photosensory transduction and light reaction to the force generating ectoplasmic tube.

Cytoplasm↗
PubMed1981

Blue light as a medium to influence oscillatory contraction frequency in Physarum.

Blue light (496 nm; threshold intensity approximately 1500 Lux) induces a transient frequency decrease of oscillatory contraction automaticity in Physarum. Many, but not all specimens react by an increase in the force amplitude of longitudinal contraction. The spectral region of 496 nm provokes a photophobic response of the plasmodia. The blue light reaction of radial and longitudinal contraction activities decreases with increasing distance from the irradiated area. The light-induced decrease in frequency can be used for experimental phase shifting, e.g., when studying the nature and the pathway of signal transmission for the spatial phase synchronization of contractile activities.

Dose-Response Relationship, Radiation↗
PubMed1981

An inexpensive "silicone photo device" for transmicroscopic registration of rhythmical movement phenomena.

A highly sensitive electronic unit (called "silicon photo probe") is described, which enables registration of cellular motion phenomena simultaneous with their light microscopic observation. Changes in light intensity caused by movements of the living object are registered by means of a silicon photo diode (silicon blue cell), which can be mounted within the binocular tube of any type of light microscope replacing one of the oculars. Its application during investigations of oscillating contraction activity in Physarum is reported. Advantages and short-comings are discussed with respect to established photometric, tensiometric and infrared registration techniques.

Cell Movement↗
PubMed1980

Influence of different freeze-fracture pretreatments on the fine structure of Physarum polycephalum. A freeze-fracture and freeze-substitution study.

The influence of different fixatives (glutaraldehyde, osmium, osmium/glutaraldehyde, and osmium/mercuric chloride) and freeze-protecting agents (glycerol and sucrose) on the fine-structural preservation of micro- and macroplasmodia of the acellular slime mold Physarum polycephalum was investigated in both freeze-substituted and freeze-fractured material. Glutaraldehyde fixation and subsequent infiltration with glycerol or sucrose caused severe destruction in the morphology of plasmodial strands and protoplasmic drops, whereas osmium- or osmium/mercuric chloride fixation prevented the formation of normal fracture planes running through the hydrophobic core of the plasma membranes. A short prefixation in a mixture of osmium/glutaraldehyde followed by postfixation in glutaraldehyde delivered the most satisfactory results in the preservation of the fine structure. For comparison, the distribution of integrated membrane particles (IMP) was analysed in freeze-fracture replicas of unfixed controls as well as glutaraldehyde- and osmium/glutaraldehyde-fixed specimens by evaluating the number of IMP per 1 micrometer 2 in two different plasmodial regions; in the peripheral plasmalemma and in the central plasmalemmal invaginations. In controls not receiving chemical pretreatment and in specimens fixed with osmium/glutaraldehyde, the central plasmalemmal invaginations showed a clearly reduced total amount of IMP (exoplasmic + protoplasmic fracture face: about 3100) as compared with the peripheral plasma membrane (about 3700). In addition both membrane systems were characterized by an asymmetrical distribution of IMP between the protoplasmic fracture face (PF) and the exoplasmic fracture face (EF): the PF:EF ratio (particle partition coefficient) in the peripheral plasma membrane is the same in controls and in osmium/glutaraldehyde-fixed specimens (2.4:1 and 2.5:1, respectively), whereas the PF:EF ratio in the central plasmalemmal invaginations is 1.5:1 in controls and 3.5:1 in fixed specimens. This shows that the membrane of the central plasmalemmal invaginations is more sensitive to chemical fixation than the peripheral plasmalemma. The results point to differences in the physiological properties and functions between the plasmalemma of the cell periphery and the plasmalemma of the invagination system.

Cell Membrane↗
PubMed1979

Induction of a plasmodial stage of Physarum without plasmalemma invaginations.

Experimentally generated protoplasmic drops of Physarum show time-dependent differentiation processes, i.e. regeneration of plasmalemma, actomyosin fibrillogenesis and regeneration of the plasmalemma invagination system. According to Hatano (1970), caffeine treatment of drops results in a pinching off process of small translucent droplets in which specific effects of Ca++ on protoplasmic streaming phenomena were demonstrated. The light and electron microscopic investigation of the original drop reveal that the time-dependent differentiation processes, e.g. actomyosin fibrillogenesis, are not inhibited by caffeine. However, caffeine hinders the regeneration of the plasmalemma invaginations in the original drop (up to a drop age of 30--40 min). The experimental advantage of this stage of Physarum with full vitality, but without plasmalemma invaginations is discussed.

Caffeine↗
PubMed1979

Effects of caffeine and D2O on persistence and de novo generation of intrinsic oscillatory contraction automaticity in Physarum.

The present investigation was performed in an attempt to contribute to answering the question whether the plasmalemma of the plasmodial stage of Physarum represents the site of a trigger mechanism for the oscillating contraction activity of cytoplasmic actomyosin. The effects of the following substances on persistence of tensiometrically measured longitudinal and radial activities of Physarum veins and on de novo generation of activities in experimentally generated drops were studied: caffeine, theophylline, acetylcholinium chloride, procaine, physostigminium salicylate, iso-ompa, nifedipin, sodium nitroprusside, potassium thiocyanate, D2O; as well as the effects of ions such as La+++ and high outer concentrations of Na+ and K+. Some of the substances were applied simultaneously for comparison externally (by bathing solutions) and internally (by injection). The experimental data speak against the existence of electrogenic rhythmical Ca++, Na+ or K+ pumps across the plasmalemma which could have a triggering function for the oscillation. The contraction activities of the cytoplasmic actomyosin seem to represent a spontaneous endogeneous oscillation which can be modulated via the plasmalemma during chemotaxis.

Biological Transport, Active↗
PubMed1979

Evidence for actin transformation during the contraction-relaxation cycle of cytoplasmic actomyosin: cycle blockade by phalloidin injection.

1) The injection of a mushroom drug, Phalloidin (750 microgram -1 mg/ml), into the endoplasmic channel of Physarum veins induces an irreversible blockade of the intrinsic contraction-relaxation automaticity of the ectoplasmic tube wall, as measured by tensiometrical methods. 2) The morphological responses to Phalloidin injection include an increase and condensation of cytoplasmic actomyosin sheets bordering the plasmalemma invaginations within the ectoplasmic tube and a more pronounced dense layer of "groundplasm" in the cell cortex. This is in accordance with experiments with other cells as well as with Physarum. 3) The addition of marker particles to the injection solution revealed that the injected substances can be brought into direct contact with the contractile substrate, before newly formed membranes separate off the injection fluid. 4) Since Phalloidin irreversibly transforms oligomeric actin into a filamentous "Phalloidin-actin complex" and because this transformation does not hinder the actin in activating myosin ATPase, it is concluded that the contraction-relaxation cycle of cytoplasmic actomyosin in Physarum involves actin transformations. If these transformations are hindered, e.g. by Phalloidin, one stage and thereby the whole cycle is sustained which results in a blockade of the intrinsic contraction automaticity. 5) The functional importance of actin transformations in the congraction physiology of cytoplasmic actomyosins and cell motility phenomena is discussed.

Actins↗
PubMed1979

Plasmalemma invaginations of Physarum dependent on the nutritional content of the plasmodial environment.

Quantitative estimates of plasmalemma invaginations in plasmodial veins of Physarum polycephalum were made under different conditions of nutrition. Pronounced differences were observed dependent on the nutritional content of the substrate. There was a decided increase in the number of plasmalemma invaginations in plasmodial veins grown on substrates containing absorbable food substances compared to veins migrating on non-nutrient substrates. This observation supports the proposition that the nutritional content, rather than the physical properties, of the substrate is the decisive factor for the formation of plasmalemma invaginations. The invaginations are believed to be concerned with the uptake of non-particulate food substances.

Biometry↗