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Results for “PROTOPLASM”

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At least 181 records · Page 10Linked to original sources
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↗
PubMed1983

An extraction resistant tensile protein in the protoplasmic matrix of Physarum.

A thorough extraction of plasmodia of Physarum polycephalum by sequential treatment with 1% Triton x-100, 0.6 M KI, 4% SDS plus 7 M urea leaves behind an elastic cell ghost, which represents a cytoplasmic matrix protein arranged as a continuous network in all cell regions. The protein is present in the ectoplasm as well as in the endoplasm. The extraction-resistant ghosts reveal filaments 2-3 nm in diameter, perform a conspicuous volume condensation upon the addition of mM-concentrations of di- and trivalent cations and can be partially solubilized in 4.5 M guanidinium chloride plus 25% 2-mercaptoethanol at 70 degrees C. SDS-gel electrophoresis shows a distinct band at 43,000 daltons and a faint high molecular weight component suggesting a similarity to muscle connection.

Contractile Proteins↗
PubMed2005

"Protoplasm...is soft wax in our hands": Paul Kammerer and the art of biological transformation.

Paul Kammerer's career ended in scandal in 1926 over tampering with his evidence for "Lamarckian" evolution--the infamous midwife toad. But although Kammerer's conclusions proved false, his evidence was probably genuine. In any case his arguments were not simply for Lamarckism and against Darwinism, as the theories are understood today. If we look beyond the scandal, the Kammerer story shows us a great deal about early 20th-century biology: the range of new ideas about heredity and variation, competing theories of biological and cultural evolution and their applications in eugenics, new kinds of laboratories and professional roles for biologists, and changing standards for documenting experimental results.

Adaptation, Physiological↗
PubMed1977

Velocity distributions of the streaming protoplasm in Nitella flexilis.

Laser light is Doppler-shifted in frequency by the streaming endoplasm of living cells of Nitella flexilis. The frequency spectrum of the scattered light can be interpreted as the histogram of velocities within the organism, with the exception of the intense low-frequency portion of the spectrum. We demonstrate that the lowest-frequency component is the result of amplitude modulation of the scattered light by the array of chloroplasts in the cell. Measurement of the streaming endoplasm in a photobleached "window" region allows correction of the frequency distribution for the modulation component. The complete velocity histogram for the streaming endoplasm is calculated directly from the corrected frequency distribution. Measurements of vacuolar and endoplasmic motions show that the tonoplast, the membrane separating the vacuole and the endoplasm, seems to be flowing along with the endoplasm and vacuolar sap. Placing the cell in medium containing ATP in concentrations greater than 10(-3) M greatly increases the contribution of low velocities to the velocity histogram. Cytochalasin B at high dosages (10-50 mug/ml) does not noticably change the shape of the velocity histogram, while at low dosages (1 mug/ml) there is an increase in the contribution of low velocities to the velocity histogram. Colchicine in high concentrations (1%) has no observable effect on the velocity histogram.

Adenosine Triphosphate↗
PubMed1987

Morphometric and densitometric investigations of protoplasmic astrocytes and neurons in human hepatic encephalopathy.

Morphometric and densitometric evaluations were made of nuclei of astrocytes and nerve cells of 49 cases with chronic liver diseases and of 9 control cases. The data measured from Nissl-stained specimens of putamen were compared with clinical degrees of encephalopathy and with blood ammonia levels. The parameters measured included nuclear area and optical density of nuclei. The nuclear area of astrocytes (AAREA), on average, was found to grow significantly along with aggravation of encephalopathy, that growth being from 39 micron 2 in the control group to about 60 micron 2 in cases of severe encephalopathy. Furthermore the proportion of astrocyte nuclei with an area above 70 micron 2 (ALRG) and the proportion of the optical light area of the total nuclear area (AHOLE) rises. Mean compactness (ACEXT) and mean extinction of astrocyte nuclei (AMEXT) dropped along with growing severity of encephalopathy. Mean blood ammonia levels rose from 42 mumol/l in cases with no microscopically detectable signs of encephalopathy to about six times higher values in cases with severe encephalopathy. Optical density of astrocyte nuclei was negatively correlated and mean nuclear area positively correlated to blood ammonia levels. No characteristic morphometric and densitometric changes of nerve cell nuclei were recordable from the putamen.

Adolescent↗