scholarly journals CALCULATIONS OF BIOELECTRIC POTENTIALS

1939 ◽  
Vol 23 (1) ◽  
pp. 53-57 ◽  
Author(s):  
W. J. V. Osterhout
Keyword(s):  
Alkali Metals ◽  
Sea Water ◽  
Low Ph ◽  
Electrical Behavior ◽  
Low Concentrations ◽  
Alkaline Earths ◽  
Bioelectric Potentials

Interest in the study of Halicystis and of Valonia has been stimulated by discoveries of marked contrasts and striking similarities existing side by side. This is illustrated by new experiments with the alkali metals and alkaline earths. In Halicystis the apparent mobilities of K+, Rb+, Cs+, and Li+ (calculated by means of Henderson's equation from changes in P.D. produced by replacing sea water by a mixture of equal parts of sea water and 0.6 M of various chlorides) are as follows, uK, = 16, uRb = 16, uCs = 4.4, and uLi = 0.2; uNa is taken as 0.2. These values resemble those in Valonia except that in the latter uCs is about 0.2. No calculation is made for uNHNH4, because in these experiments even at low pH so much NH3 is present that the sign of the P.D. may reverse. This does not happen with Valonia. According to Blinks, NH4+ at pH 5 in low concentrations acts like K+. The calculation gives uMg = 1.9 which is similar to the value found for Valonia. No calculation can be made for CaCl2 since it produces protoplasmic alterations and in consequence Henderson's equation does not apply. This differs from Valonia. Evidently these plants agree closely in some aspects of electrical behavior but differ widely in others.

scholarly journals Structural complexes in the squid giant axon membrane sensitive to ionic concentrations and cardiac glycosides

1976 ◽  
Vol 69 (1) ◽  
pp. 19-28 ◽  
Author(s):  
GM Villegas ◽  
J Villegas
Keyword(s):  
Cardiac Glycosides ◽  
Sea Water ◽  
Giant Axon ◽  
Structural Features ◽  
Nerve Fibers ◽  
Axon Membrane ◽  
Ionic Concentrations ◽  
Low Concentrations ◽  
High Calcium ◽  
Active Ion Transport

Giant nerve fibers of squid Sepioteuthis sepiodea were incubated for 10 min in artificial sea water (ASW) under control conditions, in the absence of various ions, and in the presence of cardiac glycosides. The nerve fibers were fixed in OsO(4) and embedded in Epon, and structural complexes along the axolemma were studied. These complexes consist of a portion of axolemma exhibiting a three-layered substructure, an undercoating of a dense material (approximately 0.1μm in length and approximately 70-170 A in thickness), and a narrowing to disappearance of the axon-Schwann cell interspace. In the controls, the incidence of complexes per 1,000μm of axon perimeter was about 137. This number decreased to 10-25 percent when magnesium was not present in the incubating media, whatever the calcium concentration (88, 44, or 0 mM). In the presence of magnesium, the number and structural features of the complexes were preserved, though the number decreased to 65 percent when high calcium was simultaneously present. The complexes were also modified and decreased to 26-32 percent by incubating the nerves in solutions having low concentrations of sodium and potassium. The adding of 10(-5) M ouabain or strophanthoside to normal ASW incubating solution decreased them to 20-40 percent. Due to their sensitivity to changes in external ionic concentrations and to the presence of cardiac glycosides, the complexes are proposed to represent the structural correlate of specialized sites for active ion transport, although other factors may be involved.

Reactions of sand smelt to low pH sea-water

1991 ◽  
Vol 22 (2) ◽  
pp. 74-77 ◽  
Author(s):  
J.K. Davies
Keyword(s):  
Sea Water ◽  
Low Ph

The autotrophic nutrition of symbiotic marine coelenterates with special reference to hermatypic corals. I. Movement of photosynthetic products between the symbionts

1971 ◽  
Vol 178 (1050) ◽  
pp. 111-129 ◽  
Keyword(s):  
Amino Acids ◽  
Organic Nitrogen ◽  
Sea Water ◽  
Nitrogen Compounds ◽  
Organic Substances ◽  
Low Concentrations ◽  
Steady Rate ◽  
Hermatypic Corals ◽  
Photosynthetic Products ◽  
Related Compounds

When symbiotic coelenterates, especially hermatypic corals, were incubated in the light in sea water containing NaH 14 CO 3 , small quantities of fixed 14 C were released from the tissues at a steady rate over 4 h. The rate of release was greatly increased in the presence of glycerol, glucose and alanine; the additional 14 C released was in the same substance as that added to the medium. The following related compounds had little or no effect on 14 C release : ethylene glycol, sorbose, fructose, glucosamine, glycine, proline, serine and glutamic acid. Such results have been previously reported in other symbiotic systems, and the substances causing the specific release of fixed 14 C are believed to be those which move from the autotrophic to the heterotrophic symbiont. This belief is supported here by previous observations that glycerol, glucose and alanine are among the most important organic substances released by freshly isolated zooxanthellae. Ammonium chloride increased the amount of fixed 14 C released by corals into alanine media, possibly due to conversion of ammonia to amino acids by zooxanthellae. Appreciable release of 14 C fixed in the dark also occurred into alanine solutions. These results suggest possible roles of zooxanthellae in supplying organic nitrogen compounds to the host cell at night as well as during the day. The involvement of zooxanthellae in ‘recycling’ nitrogen compounds within the association may help to explain the success of corals in seas poor in nutrients. There was substantial utilization of external glycerol and glucose when supplied at either high or low concentrations. Corals may well be able to utilize some of the small amounts of organic matter dissolved in sea water in the natural environment.

scholarly journals Bacteriocins: molecules of fundamental impact on the microbial ecology and potential food biopreservatives

2005 ◽  
Vol 48 (4) ◽  
pp. 559-566 ◽  
Author(s):  
Evandro Leite de Souza ◽  
Clemilson Antonio da Silva ◽  
Cristina Paiva de Sousa
Keyword(s):  
Proteolytic Enzymes ◽  
Antimicrobial Property ◽  
Low Ph ◽  
Microbial Cell ◽  
Gram Negative Bacteria ◽  
Microbial Survival ◽  
Low Concentrations ◽  
Genetic Mechanisms ◽  
Potential Food ◽  
Heat Low

Bacteriocins are proteic molecules synthesized for various lineages of Gram-positive and Gram-negative bacteria when exposed to stressful conditions. Bacteriocins have been characterized as molecules of high antimicrobial property even at low concentrations, provoking the microbial survival inhibition by antibiosis. These substances have their synthesis mediated for genetic mechanisms and develop their lethal action on the microbial cell by multiples mechanisms that can act of isolated or concomitant way culminating with microbial cell killing. This molecules class presents characteristic of stability to heat, low pH, refrigeration and freezing, and resistance to weak organics solvents, salts and enzymes. On the other hand, they are very sensitive to proteolytic enzymes action. Bacteriocins could appear as potential agents to be applied in food conservation systems in order to provide microbiologically stable foods.

scholarly journals The alkaline earth halide spectra and their origin

1928 ◽  
Vol 118 (779) ◽  
pp. 120-137 ◽  
Keyword(s):  
Calcium Chloride ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Careful Study ◽  
Background Spectrum ◽  
Continuous Background ◽  
Alkaline Earths ◽  
The Subject ◽  
Band Spectra ◽  
Halogen Salts

It has been known since the early days of spectroscopy that there is a group of band spectra associated with the halogen salts of the alkaline earths. Probably the first distinction between the oxide and chloride bands of these elements was made by Lecoq de Boisbaudran when he observed relative intensity fluctuations between two band systems on introducing hydrochloric acid vapour into a flame charged with calcium chloride. The system intensified by the acid vapour he attributed to the chloride. The other halides were also found to yield characteristic spectra. Since their discovery they have been the subject of only one publication of any real note. Olmsted made a careful study of these spectra as they are found under flame excitation, and his catalogue of bands contains the only reliable data concerning these spectra which is available. An exception must be made of the fluoride spectra, which have been closely studied by Dufour, Datta, and others. The origin of the present investigation of these bands was the discovery that it is possible to observe them, very conveniently, in absorption against a continuous background spectrum. In the course of attempts to find band spectra of the alkaline earth metals (corresponding to those of the alkali metals) a pair of bands at about λ 6200 was observed in the absorption spectrum of a column of calcium vapour at temperatures of 900°C. and upwards. On measurement, these bands, which are reproduced in Plate 2, figs. 1, 2 and 5, were found to coincide with two prominent calcium chloride bands. Ordinary commercial calcium had been used for the experiments, and on analysis approximately 0·05 per cent, of chloride was found in it. It seemed evident that the development of the bands was due to this impurity in the metal, and the matter was clinched by adding a trace of bromide to the metal before heating, when the calcium bromide bands in the red also appeared prominently in absorption.

THE INFLUENCE OF CATION RADIUS AND SALT CONCENTRATION IN THE SALTING OUT OF ETHYL ETHER FROM AQUEOUS NITRATE SOLUTIONS AT 25°C.

1951 ◽  
Vol 29 (7) ◽  
pp. 563-574
Author(s):  
H. G. Heal
Keyword(s):  
Aqueous Solutions ◽  
Ethyl Ether ◽  
Salt Concentration ◽  
Alkali Metals ◽  
Infinite Dilution ◽  
Salting Out ◽  
Debye Theory ◽  
Cation Radius ◽  
Alkaline Earths ◽  
Nitrate Solutions

The solubility of ethyl ether in aqueous solutions of the nitrates of the alkali metals, the alkaline earths and magnesium, and ammonium, tetramethyl, tetraethyl, and tetra-n-propyl ammonium has been measured with high precision. The salting out at infinite dilution of salt, estimated by extrapolation from data for salt concentrations below 0.1 molal, conforms in a general way to the Debye theory, with some discrepancies. Data for high salt concentrations are also given.

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