Transitions in Dictyostelium discoideum behaviour: influence of calcium and fluoride on slug phototaxis and thermotaxis

1984 ◽  
Vol 65 (1) ◽  
pp. 111-121
Author(s):  
U. Dohrmann ◽  
P.R. Fisher ◽  
M. Bruderlein ◽  
K.L. Williams
Keyword(s):  
Dictyostelium Discoideum ◽  
Temperature Gradients ◽  
Sensory Transduction ◽  
Inorganic Salts ◽  
Transition Temperatures ◽  
Temperature Dependent ◽  
High Concentrations

Phototaxis and thermotaxis by slugs of Dictyostelium discoideum show transitions that result in bimodality in phototaxis and temperature-dependent orientation up or down temperature gradients. New steps in the sensory transduction chain for these kinds of behaviour are elucidated from studies using inorganic salts (Ca2+, EGTA, KF) and several mutants. KF enhances bimodality of phototaxis, improves the accuracy of thermotaxis, and affects the transition temperatures from positive to negative thermotaxis. Changing the Ca2+ concentration has effects on both phototaxis and thermotaxis. At low Ca2+ concentrations phototaxis and thermotaxis are enhanced. In the presence of EGTA or high concentrations of Ca2+ phototaxis becomes bimodal, thermotaxis is impaired and spontaneous turning is suppressed. These results obtained by changing Ca2+ concentrations are analogous to those obtained previously with sensory transduction mutations, which coordinately affect phototaxis and thermotaxis.

Inorganic Bromide in Higher Fungi

1984 ◽  
Vol 39 (9-10) ◽  
pp. 863-866 ◽  
Author(s):  
T. Stijve
Keyword(s):  
Trace Element ◽  
Dry Weight ◽  
Mean Value ◽  
Inorganic Salts ◽  
Chromatographic Methods ◽  
The Mean ◽  
High Concentrations

Abstract A total of 138 samples of higher fungi, representing 35 species (15 belonging to the genus Amanita), were analysed for the trace element bromine using spectrophotometric and gas chromatographic methods. High concentrations of bromine, up to 100 mg/kg on dry weight, were encountered in Amanitaceae, especially in members of the subsections Phalloideae and Eu-Amanita, whereas in other fungi the mean value for this element was only 3,3 m g/kg. Some bromine-accumulating Amanitas also contained unusually high chlorine levels. Am axi­mum concentration of 3 percent on dry weight was measured in A. phalloides. It could be demonstrated that most, if not all of bromine and chlorine was present in the fungi as ionisable inorganic salts. Two organochlorine metabolites, previously reported in some mushrooms, were absent in A. phalloides and A. muscaria.

scholarly journals Effect of polyamines on the stability of brain-cortex ribosomes

1969 ◽  
Vol 114 (4) ◽  
pp. 847-854 ◽  
Author(s):  
R. K. Datta ◽  
Suchandra Sen ◽  
J. J. Ghosh
Keyword(s):  
Melting Temperature ◽  
Brain Cortex ◽  
Temperature Dependent ◽  
Enzymic Digestion ◽  
Ph Dependent ◽  
High Concentrations ◽  
The Stability ◽  
Goat Brain

1. Ribosomes isolated from the cortex tissue of goat brain contain very small amounts of spermidine and spermine. Ribosomes isolated from spermidine-treated slices have a higher spermidine content. 2. The polyamines partially prevent the temperature-dependent breakdown of ribosomes into acid-soluble nucleotides. 3. The ‘melting’ temperature of ribosomes rises slightly when the ribosomes are heated slowly in the presence of polyamines. 4. The pH-dependent breakdown of ribosomes into protein, RNA and acid-soluble nucleotide is markedly decreased by polyamines present in media in which ribosomes are suspended. 5. The breakdown of ribosomes in the presence of high concentrations of salts and EDTA is partially checked by the concurrent presence of polyamines. 6. Spermidine and spermine make ribosomes less susceptible to enzymic digestion by crystalline trypsin and ribonuclease.

Copper, nickel, and thallium uptake by the lichen Cladina rangiferina

1981 ◽  
Vol 59 (1) ◽  
pp. 91-100 ◽  
Author(s):  
M. A. S. Burton ◽  
P. LeSueur ◽  
K. J. Puckett
Keyword(s):  
Metal Uptake ◽  
Deionized Water ◽  
Metabolic Inhibitors ◽  
Temperature Dependent ◽  
Low Concentrations ◽  
Nickel Uptake ◽  
High Concentrations ◽  
Uptake Studies ◽  
Cladina Rangiferina ◽  
Very High

Metal uptake studies with Cladina rangiferina showed that the affinity for nickel was much lower than for copper or thallium. Nickel uptake was not decreased by the absence of light or oxygen or by pretreatment with metabolic inhibitors. Nickel uptake was not temperature dependent but was very dependent upon pH.Cation-exchange studies demonstrated that there was a stoichiometric exchange of Ni2+ for Sr2+, and Cu2+ for Sr2+. The exchange of Tl+ for Sr2+ was not stoichiometric, excess Tl+ was accumulated in relation to the Sr2+ released. The ratio of Sr2+:Tl+ exchange increased with increasing Tl+ availability from 1:9 (12.5 μmol Tl+ available/g of lichen) to 1:2 (500 μmol Tl+ available). Acid-treated lichen gave the expected exchange ratio of 1:2. Washing of the thalli with deionized water resulted in the continued loss of Tl+ from acid-treated and live C. rangiferina. Copper and nickel were not released in this manner.Increasing concentrations of copper and thallium produced a corresponding loss of potassium from the thallus. The potassium loss was initiated at low concentrations of copper and thallium whereas very high concentrations of manganese and nickel were required to bring about the same response.

Effect of Temperature Gradients on the Propagation of Elastoplastic Waves

1968 ◽  
Vol 35 (3) ◽  
pp. 441-448 ◽  
Author(s):  
P. H. Francis ◽  
U. S. Lindholm
Keyword(s):  
Mechanical Properties ◽  
Method Of Characteristics ◽  
Wave Attenuation ◽  
Strain Curve ◽  
Temperature Gradients ◽  
Effect Of Temperature ◽  
Plastic Wave ◽  
Temperature Dependent ◽  
Stress Strain Curve ◽  
Elastoplastic Wave

In this paper, the writers consider the problem of the propagation of an extensional elastoplastic wave through a long thin bar heated at the end to produce a continuously decreasing temperature profile. The temperature distribution is approximated as an exponential function, and the stress-strain curve is considered to be bilinear with temperature-dependent mechanical properties. The problem is formulated and solved numerically by the method of characteristics. Several graphical results are provided, and the effects of the temperature gradient and the mechanical properties are discussed in terms of plastic wave attenuation.

scholarly journals Temperature and the regulation of enzyme activity in poikilotherms. Properties of rainbow-trout fructose diphosphatase

1969 ◽  
Vol 111 (3) ◽  
pp. 287-295 ◽  
Author(s):  
H. W. Behrisch ◽  
P. W. Hochachka
Keyword(s):  
Enzyme Activity ◽  
Rainbow Trout ◽  
Temperature Adaptation ◽  
Temperature Dependent ◽  
Ph Optimum ◽  
Physiological Temperature ◽  
Low Concentrations ◽  
High Concentrations ◽  
Regulation Of Enzyme Activity ◽  
Hill Plots

1. The properties of fructose diphosphatase from the liver of rainbow trout (Salmo gairdnerii) were examined over the physiological temperature range of the organism. 2. Saturation curves for substrate (fructose 1,6-diphosphate) and a cofactor (Mg2+) are sigmoidal, and Hill plots of the results suggest a minimum of two interacting fructose 1,6-diphosphate sites and two interacting Mg2+ sites per molecule of enzyme. 3. Mn2+-saturation curves are hyperbolic, and the Ka for Mn2+, which inhibits the enzyme at high concentrations, is 50–100-fold lower than the Ka for Mg2+. 4. Fructose diphosphatase is inhibited by low concentrations of AMP; this inhibition appears to be decreased and reversed by increasing the concentrations of Mg2+ and Mn2+. Higher concentrations of AMP are required to inhibit the trout fructose diphosphatase in the presence of Mn2+. 5. The affinities of fructose diphosphatase for fructose diphosphate and Mn2+ appear to be temperature-independent, whereas the affinities for Mg2+ and AMP are highly temperature-dependent. 6. The pH optimum of the enzyme depends on the concentrations of Mg2+ and Mn2+. In addition, pH determines the Ka for Mg2+; at high pH, Ka for Mg2+ is lowered. 7. The enzyme is inhibited by Ca2+ and Zn2+, and the inhibition is competitive with respect to both cations. 8. The possible roles of these ions and AMP in the modulation of fructose diphosphatase and gluconeogenic activity are discussed in relation to temperature adaptation.

Effect of Interfacial Heat Transfer on Molten Tin Jet Breakup in an Oil Tank

2004 ◽  
Author(s):  
Vala Mehdi-Nejad ◽  
Javad Mostaghimi ◽  
Sanjeev Chandra
Keyword(s):  
Heat Transfer ◽  
Temperature Gradients ◽  
Temperature Dependency ◽  
Fluid Interface ◽  
Interfacial Heat Transfer ◽  
Temperature Dependent ◽  
Annular Jet ◽  
Jet Breakup ◽  
Fluid Properties ◽  
Oil Tank

This paper presents the effect of interfacial heat transfer on the breakup of an annular jet surrounded by another viscous liquid. Specifically, we consider the breakup of a molten tin jet in eicosane. One-field volume tracking is used which involves solving one set of equations for conservation of mass, momentum and energy. The original idea behind volume tracking methods has been used not only to advect mass and momentum but also energy across cell boundaries. The van Leer method is used to approximate advection temperatures across the sharp temperature gradients existing at fluid/fluid interface. To study the effect of heat transfer on the hydrodynamics of the flow, all fluid properties except density are modelled as temperature dependent. Results show a direct correlation between interfacial heat transfer and the location of the breakup. For tin, results show that the temperature dependency of viscosity is the major factor in dictating the location and time of the breakup.

scholarly journals Water temperature during winter may control striped bass recruitment during spring by affecting the development time of copepod nauplii

2019 ◽  
Vol 77 (1) ◽  
pp. 300-314 ◽  
Author(s):  
N C Millette ◽  
J J Pierson ◽  
E W North
Keyword(s):  
Chesapeake Bay ◽  
Striped Bass ◽  
Developmental Model ◽  
Temperature Dependent ◽  
Juvenile Recruitment ◽  
Patuxent River ◽  
Winter Temperatures ◽  
Recruitment Variability ◽  
High Concentrations

Abstract Striped bass (Morone saxatilis) are anadromous fish that support an important fishery along the east coast of North America. In Chesapeake Bay, strong juvenile recruitment of striped bass can occur when larvae overlap with high concentrations of their zooplankton prey, but the mechanisms fostering the temporal overlap are unknown. Here, the influence of winter temperature on the peak abundances of a key prey, Eurytemora carolleeae, was estimated with a temperature-dependent developmental model. The role of these peaks in regulating striped bass recruitment was explored in three nursery areas: upper Chesapeake Bay, Choptank River, and Patuxent River. Model results indicated that cold winters delay the timing and increase the size of peak E. carolleeae spring abundance. When the model output was used in regression relationships with striped bass juvenile recruitment and freshwater discharge, the regression models explained up to 78% of annual recruitment variability. Results suggests that cold, wet winters could increase the chance of a match between striped bass larvae and high concentrations of their prey. This mechanistic link between winter temperatures and striped bass production, acting through prey dynamics, could further understanding of fish recruitment variability and indicates that warmer winters could negatively affect some striped bass populations.

A carrier-mediated system for transport of biotin in rat intestine in vitro

1987 ◽  
Vol 252 (1) ◽  
pp. G52-G55 ◽  
Author(s):  
H. M. Said ◽  
R. Redha
Keyword(s):  
Methyl Ester ◽  
Temperature Dependent ◽  
Rat Intestine ◽  
Simple Diffusion ◽  
Low Concentrations ◽  
Structural Analogues ◽  
High Concentrations ◽  
Biotin Molecule ◽  
Energy Dependent

Transport of biotin was examined in rat intestine using the everted sac technique. Transport of 0.1 microM biotin was linear with time for at least 30 min of incubation and occurred at a rate of 3.7 pmol X g initial tissue wet wt-1 X min-1. Transport of biotin was higher in the jejunum than the ileum and was minimum in the colon (85 +/- 6, 36 +/- 6, and 2.8 +/- 0.6 pmol X g initial tissue wet wt-1 X 25 min-1, respectively). In the jejunum, transport of biotin was saturable at low concentrations (Kt = 3.73, microM, Vmax = 3.11 nmol X g initial tissue wet wt-1 X 25 min-1) but linear at higher concentrations (greater than 10 microM). The transport of low concentrations of biotin was inhibited by structural analogues (desthiobiotin, biotin methyl ester, diaminobiotin, and biocytin), Na+ dependent, energy dependent, temperature dependent, and proceeded against a concentration gradient in the serosal compartment. No metabolic alteration occurs to the biotin molecule during transport. This study demonstrates that biotin transport in rat intestine occurs by a carrier-mediated process at low concentrations and by simple diffusion at high concentrations. Furthermore, the carrier-mediated process is Na+, energy, and temperature dependent.

scholarly journals Dynamics of Rising Bubbles in a Quiescent Slag Bath with Varying Thermo-Physical Properties

2020 ◽  
Vol 51 (6) ◽  
pp. 2843-2861
Author(s):  
D. Obiso ◽  
D. H. Schwitalla ◽  
I. Korobeinikov ◽  
B. Meyer ◽  
M. Reuter ◽  
...  
Keyword(s):  
Physical Properties ◽  
Bubble Dynamics ◽  
Fluid Dynamic ◽  
Temperature Gradients ◽  
Slag Bath ◽  
Bubble Motion ◽  
Temperature Dependent ◽  
Slag Properties ◽  
Temperature Dependent Properties ◽  
Thermo Physical Properties

AbstractThe motion of bubbles in a liquid slag bath with temperature gradients is investigated by means of 3D fluid dynamic computations. The goal of the work is to describe the dynamics of the rising bubbles, taking into account the temperature dependency of the thermo-physical properties of the slag. Attention is paid to the modeling approach used for the slag properties and how this affects the simulation of the bubble motion. In particular, the usage of constant values is compared to the usage of temperature-dependent data, taken from models available in the literature and from in-house experimental measurements. Although the present study focuses on temperature gradients, the consideration of varying thermo-physical properties is greatly relevant for the fluid dynamic modeling of reactive slag baths, since the same effect is given by heterogeneous species and solid fraction distributions. CFD is applied to evaluate the bubble dynamics in terms of the rising path, terminal bubble shape, and velocity, the gas–liquid interface area, and the appearance of break-up phenomena. It is shown that the presence of a thermal gradient strongly acts on the gas–liquid interaction when the temperature-dependent properties are considered. Furthermore, the use of literature models and experimental data produces different results, demonstrating the importance of correctly modeling the slag’s thermo-physical properties.

Haemolytic Properties of Cereal 5-n-Alk(en)ylresorcinols

1984 ◽  
Vol 39 (11-12) ◽  
pp. 1132-1136 ◽  
Author(s):  
Arkadiusz Kozubek
Keyword(s):  
Free Energy ◽  
Blood Cell ◽  
Erythrocyte Membrane ◽  
Red Blood Cell ◽  
Haemolytic Activity ◽  
Transition Temperatures ◽  
Temperature Dependent ◽  
Strong Affinity ◽  
Erythrocyte Lysis ◽  
Derivatives Of

Abstract The haemolytic activity of 5-n-alk(en)ylresorcinols is temperature dependent and correlated to their transition temperatures. The values of the parameters describing the 5-n-alk(en)yl-resorcinol-induced red blood cell lysis indicate strong affinity of the compounds to the membrane and their high lytic capacity. The affinity of the compounds for the membrane decrease with the increasing quantity of the molecules incorporated into the erythrocyte membrane and is much higher for saturated resorcinols than unsaturated ones. The amount of 5-n-alk(en)ylresorcinol molecules bound to the membrane at a hundred percent lysis is about eighty times and eleven times (for alkyl and alkenyl derivatives respectively) higher than at zero percent lysis. Estimated free energy of erythrocyte lysis was similar for alkyl and alkenyl derivatives of resorcinol provided the preparation of the resorcinolic suspensions above their transition temperatures.

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