Biomedical subjects

K E Wohlfarth-Bottermann

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

At least 55 records · Page 3Linked to original sources

PubMed1979

Oscillatory contraction activity in Physarum.

The plasmodia of Physarum polycephalum show different oscillatory phenomena (time period approximately 1.3 min) in their contraction behaviour and their protoplasmic flow. The force generating system for these phenomena is cytoplasmic actomyosin. The biochemical nature and location(s) of the oscillator(s), i.e. the clock governing these phenomena are unknown. The following locations are discussed as possible sites of the oscillator: (1) cytoplasmic actomyosin, (2) the energy supply system, (3) inner Ca2+ stores, and (4) the plasmalemma, which must be involved at least in modulating the force generated by the contractile machinery during a chemotactic response. The following oscillatory phenomena were used to assess the effects of externally and internally applied substances (e.g. calcium antagonistic drugs, caffeine, D2O) on oscillating force output: (1) persistance of longitudinal contractile activity of veins (for external application of test substances), (2) persistance of radial activity of veins (for internal application of the test substances), (3) de novo generation of contractile activity in protoplasmic drops (external application). The data seem to exclude rhythmical Ca2+, Na+ or K+ transport across the plasmalemma as a triggering function for the oscillation. Contractile activity seems to represent a spontaneous, endogeneous oscillation which can be modulated via the plasmalemma during chemotaxis.

Actomyosin↗

PubMed1979

Plasmalemma invaginations, contraction and locomotion in normal and caffeine-treated protoplasmic drops of Physarum.

The de novo formation of plasmalemma invaginations and vacuoles of light microscopic dimension in protoplasmic drops at different age-stages was studied quantitatively by applying morphometric methods and marker techniques. The study includes: i) the normal morphogenetic development to a drop age of 1 hour, ii) the influence of caffeine treatment, and iii) the effects of removal of this drug. In untreated drops, formation of invaginations and vacuoles is accomplished within 10 to 15 min. By application of 5 mM caffeine, the formation of plasmalemma invaginations is inhibited for 20 to 30 min. The onset of oscillating contraction activity is delayed, but not hindered by the drug. Drug removal 20 min after drop generation leads to an immediate initiation of plasmalemma infolding. Although caffeine does not hinder initiation of normal contraction activity, the locomotory ability of the drop is blocked if the drug is not removed from the drop and the substrate. Thus, caffeine uncouples motive force generation from locomotion in all plasmodial stages of Physarum. The cellular sites of drug action are discussed.

Amoeba↗

PubMed1978

Oscillating contractions in protoplasmic strands of Physarum: infared reflexion as a non-invasive registration technique.

An inexpensive electronic device employing a miniaturised infrared reflection detector is described which enables the automatic registration of intrinsic radial contraction activities of protoplasmic strands of Physarum growing on their original substrate. Advantages and shortcoming of the new registration technique are discussed in relation to recent tensiometric techniques applied to protoplasmic strands for analysing the contraction physiology of cytoplasmic actomyosins, the force generating substrate of the contraction automaticity in the Physarum system.

Cytoplasm↗

PubMed1978

[Spatio-temporal analysis of contraction dependent surface movements in Physarum polycephalum (author's transl)].

Plasmodial veins of Physarum polycephalum were investigated by combining cinematographical and tensiometrical methods. Veins remaining on their original growing substrate show characteristic surface movements resulting from an intrinsic contraction automaticity. Radial and longitudinal components of surface movements were registered simultaneously. Both contraction activities show identical frequencies, in contrast to results derived from experiments with isolated veins. There is only one genuine frequency and therefore one has not necessarily to suppose the existence of a cooperation of two oscillating systems underlying the rhythmic contraction phenomena. The results are discussed in respect to the basis of the contraction phenomena: the cytoplasmic actomyosin fibrils of Physarum and their function in motive force generation for protoplasmic streaming.

Actomyosin↗

PubMed1978

Spatio-temporal relationships between protoplasmic streaming and contraction activities in plasmodial veins of Physarum polycephalum.

Plasmodial veins of Physarum polycephalum were investigated by combining cinematographical, morphological, and tensiometrical techniques. Translucent and nontranslucent (thicker) strands remaining in their original position on filter paper were analyzed in respect to their radial contraction cycles and the resulting streaming activity of the endoplasm. A new technique for measuring the flow intensity by a microbalance method allowed testing of the influence of radial contraction on actual streaming processes within a strand. Stationary ectoplasm and flowing endoplasm are involved in a mutual transformation process: thereia an exchange of ectoplasm and endoplasm in the form of protoplasmic streamlets crossing the borderline between the endoplasmic stream and the ectoplasmic tube. Radial contraction cycles show the same time periodicity as the endoplasmic shuttle streaming. Relationships between radial contractions, streaming rates of endoplasm and streamlets between ectoplasm and endoplasm were analyzed. The participation of the ectoplasmic walls in motive force generation and their function in control of streaming throughput is discussed.

Cytoplasm↗

PubMed1978

Reaction of the contractile apparatus in Physarum to injected Ca++, ATP, ADP and 5'AMP.

After replacement of endoplasm by artificial media, the ectoplasmic tube of the plasmodial veins survives and contraction automaticity continues. Motive force generation for plasmodial locomotion is widely independent of the presence of endoplasm, i.e. force generation is located within the ectoplasmic tube. The replacement of endoplasm offers the possibility to study the effects of physiologically active substances upon the contraction activity of cytoplasmic actomyosin under in vivo conditions. Using different methods for measuring the force output as indicator of the effects of injected substances, the influences of free Ca++-ions and different nucleotides were studied. The injection of Ca++ buffers revealed that force output of the veins increased with ascending Ca++ concentrations between 2 x 10(-7) and 10(-6) M. Half maximal response was found to lie in the range of 4 x 10(-7) M, the saturation value at 6 x 10(-7) M Ca++. The injection of adenosine nucleotides induced optimal contraction responses at 0.2 mM ATP, 0.5 mM ADP and 2.5 mM 5'AMP, respectively. The contraction response induced by 0.2 mM ATP depends strongly on the concentration of the available Ca++. From a threshold concentration of 2 x 10(-7) M Ca++, force output increased up to 10(-5) M Ca++. In presence of 0.2 mM ATP, the value for half maximal contraction response to Ca++ was 10(-6) M Ca++. It is concluded that 0.2 mM ATP and 2 to 4 x 10(-7) M Ca++, are the conditions, under which the cytoplasmic actomyosin system of Physarum performs its function in vivo. The implication of the results and the possibilites of the new method for further investigations of the contraction physiology of Physarum as a model system for cytoplasmic actomyosin are discussed.

Actomyosin↗

PubMed1977

Oscillating contractions in protoplasmic strands of Physarum: effects of external Ca++-depletion and Ca++-antagonistic drugs on intrinsic contraction automaticity.

1. The minimal requirement of external Ca-concentration for continuance of contraction activity lies in the range of 10(-4) M. 2. As in mammalian smooth muscle, the Ca antagonistic drugs verapamil and D 600 (5.10(-4) M) suppress the minute-rhythms. The action of the drugs is inhibited by 5mM Ca, La or Mn. De novo generation of contraction automaticity is not inhibited by external Ca depletion or by Ca antagonists. 3. It is concluded that rhythmical Ca fluxes across the cortical plasmalemma are not a precondition for triggering continuance or de novo generation of contraction automaticity.

Calcium↗

PubMed1977

Oscillating contractions in protoplasmic strands of Physarum: simultaneous tensiometry of longitudinal and radial rhythms, periodicity analysis and temperature dependence.

1. The construction of a 'twin-tension transducer' allows the simultaneous measurement of the same or different contraction rhythms at any selected sites of living plasmodia of Physarum polycephalum. This method has been used to analyse the relation of longitudinal and radial contraction activity within migrating plasmodia and plasmodial veins, under isometric as well as under isotonic conditions of measurement. 2. A periodicity analysis of the oscillating contraction rhythms revealed average period values for the longitudinal contraction cycle of 2-1 min and for the radial contraction cycle of 1-3 min at a temperature of 22 degrees C. 3. The periods of longitudinal contraction depend on the environment of the strands. The mean value under submerged conditions was 2-9 min. 4. The temperature dependences for both longitudinal and radial contraction cycles were determined to provide reliable values for the normal reaction range of the contractile system (cytoplasmic actomyosin). The values for radial contraction activity are 2-0 min at 16 degrees C, 1-5 min at 20 degrees C, and 1-2 min at 24 degrees C. The range between 16 degrees and 24 degrees C can be regarded as physiological. 5. The possibility is discussed that only one 'genuine' contraction frequency of cytoplasmic actomyosin exists in Physarum.

Cytoplasm↗

PubMed1976

Transformation of cytoplasmic actin. Importance for the organization of the contractile gel reticulum and the contraction--relasation cycle of cytoplasmic actomyosin.

(1) Within the low viscous flowing endoplasm of Physarum polycephalum a considerable amount of actin is in the non-filamentous state. This can be demonstrated by applying poly-L-lysin to surface spreads of native protoplasm. (2) It has been shown that in protoplasmic drops the endoplasm-ectoplasm transformation is accompanied by an actin polymerization from the non-filamentous state to F-actin. (3) The actual state of the labile G-F-actin equilibrium determines the varying consistency (viscosity) of the cytoplasm. (4) Increasing viscosity can be interpreted as being brought about by a) shifting of the G-F-actin equilibrium to the filamentous side, and (b) increased myosin-mediated binding sites between actin filaments. (5) Polymerization and depolymerization processes are involved in the rhythmically occurring contraction-relaxation cycle of cytoplasmic actomyosin in Physarum. (6) Cytoplasmic actin and myosin represent the architectural proteins of the contractile gel reticulum in eukaryotic cells. (7) The importance of the regulation of actin polymerization as a basic control mechanism of the eukaryotic cell is discussed.

Actins↗

PubMed1976

Cytoplasmic actomyosin fibrils in tissue culture cells: direct proof of contractility by visualization of ATP-induced contraction in fibrils isolated by laser micro-beam dissection.

A special cell line derived from a rat mammary adenocarcinoma (RMCD cells) displays a distinct pattern of actomyosin fibrils (AM fibrils) visible with phase contrast, Nomarski interference and polarized light optics. It was shown that the cytoplasmic AM fibrils are arranged as bundles of highly parallel F-actin filaments. The chimical nature of the filaments was identified by incubation with heavy meromyosin from rabbit skeletal muscle. These cytoplasmic actomyosin fibrils actively contract under isotonic conditions. This was shown by contraction experiments under polarized light optics, by cinematographic analysis and by direct proof of the contractility of AM fibrils isolated by laser micro-dissection. Thus, cytoplasmic AM fibrils can be assumed to represent structures essential for motive force generation in contraction processes in non-muscle cells.

Actomyosin↗

PubMed1974