bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of inbreeding on mortality during a morbillivirus outbreak in the Mediterranean striped dolphin (Stenella coeruleoalba)
Authors: Valsecchi Elena , Amos William , Raga Juan Antonio , Podestà Michela , Sherwin William 
Published: May 2004

AbstractBetween 1990 and 1992, Mediterranean striped dolphins (Stenella coeruleoalba) suffered high mortality due to a morbillivirus epidemic. Ten highly variable microsatellite markers were used to assess the population structure of a sample of these stranded animals and to assess the genetic consequences of the epizootic on present stocks. We found little evidence of population structure within the Mediterranean, but distinct separation between this and the North Sea (Atlantic) population, the latter also showing greater genetic diversity. Using a genetic measure of inbreeding, we found that dolphins dying early in the outbreak were significantly more inbred than those dying later. Within 10 years of the end of the epidemic, the level of inbreeding among stranded dolphins had returned to its pre‐outbreak levels. However, on average all stranded animals showed elevated levels of inbreeding, suggesting that animals dying from disease may venture towards the shore more than those dying of old age. Our results imply an important role for inbreeding in the dynamics of disease spread and that, in marine mammal research, caution should be exercised when inferring demographic parameters from stranded specimens.
THE RELATION BETWEEN VISUAL ACUITY AND ILLUMINATION
Authors: Hecht Selig 
Published: May 2004

1. Visual acuity varies in a definite manner with the illumination. At low intensities visual acuity increases slowly in proportion to log I; at higher intensities it increases nearly ten times more rapidly in relation to log I; at the highest illuminations it remains constant regardless of the changes in log I.
2. These variations in visual acuity measure the variations in the resolving power of the retina. The retina is a surface composed of discrete rods and cones. Therefore its resolving power depends on the number of elements present in a unit area. The changes in visual acuity then presuppose that the number of elements in the retina is variable. This cannot be true anatomically; therefore it must be assumed functionally.
3. To explain on such a basis the variations of visual acuity, it is postulated that the thresholds of the cones and of the rods are distributed in relation to the illumination in a statistical manner similar to that of other populations. In addition the rods as a whole have thresholds lower than the cones. Then at low intensities the increase in visual acuity depends on the augmentation of the functional rod population which accompanies intensity increase; and at higher intensities the increase in visual acuity depends on the augmentation of the functional cone population. The number of cones per unit foveal area is much greater than the number of rods per unit peripheral area, which accounts for the relative rates of increase of rod and cone visual acuity with intensity. At the highest illuminations all the cones are functional and no increase in visual acuity is possible.
4. If this division into rod visual acuity and cone visual acuity is correct, a completely color-blind person should have only rod visual acuity. It is shown by a study of the data of two such individuals that this is true.
5. The rod and cone threshold distribution has been presented as a purely statistical assumption. It can be shown, however, that it is really a necessary consequence of a photochemical system which has already been used to describe other properties of vision. This system consists of a photosensitive material in reversible relation with its precursors which are its products of decomposition as well.
6. On the basis of these and other data it is shown that a minimal retinal area in the fovea, which can mediate all the steps in such functions as visual acuity, intensity discrimination, and color vision, contains about 540 cones. Certain suggestions with regard to a quantitative mechanism for color vision are then correlated with these findings, and are shown to be in harmony with accurately known phenomena in related fields of physiology.
THE GEOTROPIC REACTION OF RODLESS MICE IN LIGHT AND IN DARKNESS
Authors: Keeler Clyde E. 
Published: May 2004

"Black—short ears—kinky tail—rodless" mice, controlled by "pink eyed—dilute—brown" mice, were tested on an inclined plane in order to determine if they are photically sensitive, and, if so, to get a quantitative expression for their visual receptivity. Rodless and control animals were tested in the dark to obtain an expression for normal geotropic orientation. Light was then introduced to modify these reactions if possible. Under light, the controls failed to orient, whereas the rodless gave reactions almost identical with those in the dark.
This test has failed in this experiment to suggest sight in the rodless mouse.
PROTOPLASMIC ASYMMETRY IN NITELLA AS SHOWN BY BIOELECTRIC MEASUREMENTS
Authors: Osterhout W. J. V. , Harris E. S. 
Published: May 2004

Using multinucleate cells of Nitella 2 or 3 inches in length it is possible to kill one end with chloroform without producing at the other any immediate alteration which can be detected by our present methods.
When a spot in external contact with sap is killed its potential difference falls approximately to zero and it is therefore possible to measure the potential difference across the protoplasm at any desired point merely by leading off from that point to the one where the protoplasm has been killed.
The results indicate that the inner and outer protoplasmic surfaces differ, for when both surfaces are in contact with the same solution (cell sap) there is an electromotive force of about 15.9 millivolts, the inner surface being positive to the outer (i.e. the positive current tends to flow from the inner surface through the electrometer to the outer surface). The situation resembles that in Valonia where the corresponding value (with Valonia sap applied to the outside) has been reported as about 14.5 millivolt (the inner surface being positive to the outer). It would seem appropriate to designate this as radial polarity.
POTENTIALLY UNLIMITED MULTIPLICATION OF YEAST WITH CONSTANT ENVIRONMENT, AND THE LIMITING OF GROWTH BY CHANGING ENVIRONMENT
Authors: Richards Oscar W. 
Published: May 2004

1. The decrease in the rate of growth of a population of yeast cells, which results in the maintenance of an equilibrium crop level, is shown to be due to substances excreted into the culture medium by the growing cells. These toxic substances tend to destroy the young buds, because the percentage of budding cells is about the same at the time of most rapid growth and at the time of the growth equilibrium.
2. Alcohol is the product which primarily causes the decline of the growth rate. For the strain of yeast used, under the particular conditions of these experiments, a concentration of alcohol of about 1 mg. per cc. is associated with the beginning of the decrease of the growth rate.
3. The increasing acidity of the medium, due to CO2, pyruvic acid, and other organic acids, is also a retarding influence. It is a secondary factor, however, as the greatest increase of the acidity of the medium occurs after pyruvic acid, probably a by-product of alcoholic fermentation, appears.
4. When the medium is maintained effectively constant, by preventing the accumulation of these toxic products, the yeast grows at a constant rate and the yeast growth is potentially unlimited. The limit of growth found in actual experiments is due only to the size of the test-tubes and to the relative efficiency of the method used in keeping the medium effectively constant. The necessity of maintaining a constant rate of growth in studies on the relations of yeasts to vitamines and other products is stressed.
TEMPERATURE CHARACTERISTICS FOR PULSATION FREQUENCY IN GONIONEMUS
Authors: Wolf Ernst 
Published: May 2004

The frequency of contraction of the bell of Gonionemus was studied in relation to temperature, with intact animals and also where different operations were made on the nervous system. A number of values of µ are found for intact animals namely 8,100±, 10,500±, 32,000± and 22,500±, with critical temperatures at 9.6°, 12.3°, and 14.0°. Four different classes of operations were used: (1) Animals where the nerve ring was cut on two opposite sides of the bell; the µ values found are 10,500± and 21,300±, with a critical temperature at 13.4°. (2) Animals with four cuts through the nerve ring gave µ = 10,600 ± and µ = 21,000, with a critical temperature at 13.1°. (3) In animals where the bell was cut in half the temperature characteristic was found to be 16,900. And finally (4) in the animals where the nerve ring was totally removed µ values of 8,100, 16,000±, and 29,000 were found, with critical temperatures at 15.0° and 9.4°.
These results are discussed from the standpoint of the theory which supposes that definite "temperature characteristics" may be associated with the functional activity of particular elements in a complex functional unit, and that these elements may be separately studied and identified by suitable experimental procedures involving the magnitudes of the respective temperature characteristics and the locations of associated critical temperatures. The swimming bell of medusæ with its marginal sense organs permits a fairly direct approach to such questions. It is found that even slight injuries to the marginal nerve ring, for example, produce specific modifications in the temperature relations which are different from those appearing when the organism is cut in half.
THE RELATION OF TIME, INTENSITY AND WAVE-LENGTH IN THE PHOTOSENSORY SYSTEM OF PHOLAS
Authors: Hecht Selig 
Published: May 2004

The most effective point in the visible spectrum for the stimulation of Pholas is 550 mµ. On the red side, the effectiveness drops rapidly to almost zero. On the violet side, the effectiveness drops to about half, and rises again in such a way as to indicate a possible second maximum in the near ultra-violet.
On the basis of certain ideas these data are assumed to represent the properties of the absorption spectrum of the photosensitive system in Pholas. A comparison with Mya shows that the absorption spectra of the photosensitive systems in the animals are distinctly different. Nevertheless the way in which intensity and reaction time are related in the two animals are found to be identical. The conclusion is then drawn from this and from previous work, that although the fundamental properties of the photoreceptor process show an identical organization in several different animals, the materials which compose these processes are specific.
THE INFLUENCE OF pH UPON THE CONCENTRATION POTENTIALS ACROSS THE SKIN OF THE FROG
Authors: Amberson William R. , Klein Henry 
Published: May 2004

The production of concentration P.D.'s across the skin of the frog is very intimately related to the pH of the applied solutions. On the alkaline side of an isoelectric point the dilute solution is electropositive; on the acid side this solution becomes electronegative.
When the pH is suddenly lowered from a value more alkaline than this isoelectric point to one considerably more acid the change in polarity may occur within a few seconds. The effect is reversible.
When a series of unbuffered solutions at different pH values are applied reversal curves may be obtained. When the concentration gradient is .1 N-.001 N KCl the reversal points lie between pH 4.1 and 4.8.
When studied in acetate buffers this electromotive reversal is found to be closely correlated with the electrical charge upon the membrane, as determined by electroendosmosis through it. Reversal occurs between pH 4.9 and 5.2.
It is concluded that the electromotive behavior of this material is controlled by some ampholyte, or group of ampholytes, within the membrane. This ampholyte is probably a protein.
On both sides of their isoelectric point these membranes, in common with protein membranes, behave as if they retarded or prevented the movement through them of ions of the same electrical sign as they themselves bear, while permitting the movement of ions of the opposite sign. It is suggested that this correlation arises because of electrostatic effects between the charged surfaces and ions in the solution.
THE EFFECT OF CERTAIN ELECTROLYTES AND NON-ELECTROLYTES ON PERMEABILITY OF LIVING CELLS TO WATER
Authors: McCutcheon Morton , Lucke Balduin 
Published: May 2004

1. Permeability to water in unfertilized eggs of the sea urchin, Arbacia punctulata, is found to be greater in hypotonic solutions of dextrose, saccharose and glycocoll than in sea water of the same osmotic pressure.
2. The addition to dextrose solution of small amounts of CaCl2 or MgCl2 restores the permeability approximately to the value obtained in sea water.
3. This effect of CaCl2 and MgCl2 is antagonized by the further addition of NaCl or KCl.
4. It is concluded that the NaCl and KCl tend to increase the permeability of the cell to water, CaCl2 and MgCl2 to decrease it.
5. The method here employed can be used for quantitative study of salt antagonism.
THE DEATH WAVE IN NITELLA
Authors: Osterhout W. J. V. , Harris E. S. 
Published: May 2004

Experiments on cutting confirm the prediction that the current of injury will be positive when the cell is in contact with concentrated solutions and negative with dilute solutions. They support the idea that the protoplasm is made up of layers differing considerably in their properties, each having a death curve of simple and regular form, the more rapid alteration of the outer layer making the protoplasm more positive and the more rapid alteration of the inner making it more negative.
From the point where the cell is cut a wave of some sort, which we may for convenience call a death wave, passes along the cell, setting up at each point it touches a death process which has the greater speed and intensity the nearer it is to the cut.
STUDIES ON PERMEABILITY OF MEMBRANES
Authors: Weech A. A. , Michaelis L. 
Published: May 2004

A study has been made of the relative rates at which various organic non-electrolytes diffuse through the dried collodion membrane. It was found that acetone and urea pass through the membrane many times more rapidly than glycerine and that glycerine in its turn diffuses much faster than glucose. It was also demonstrated that the rate of diffusion varies directly with the difference in concentration between the solutions on the two sides of the membrane. It was shown that the presence of glycerine on the two sides of the membrane did not appreciably affect the rate of diffusion of acetone. In a study of the changes going on during the establishment of the stationary diffusion gradient with glucose experiments were described which strongly suggested that many of the membrane channels may gradually become clogged up with glucose molecules so that the diffusion rate decreases from day to day until the stationary gradient is finally reached.
In explaining the various experimental data the conception of the collodion membrane as a sieve with pores approximating in smallness the size of individual molecules was utilized. The large differences in the diffusion rates between different substances were then referred to differences in molecular size, the relatively large molecules of glycerine and glucose being unable to pass through many of the smaller pores available for urea and acetone. From the data available it was possible to estimate that 98 per cent of the pore area distributed among holes large enough for the diffusion of acetone was unavailable for the passage of glycerine and that only 0.3 per cent of the pore area available for acetone could be utilized by glucose. In trying to correlate the ratio between the diffusion rates of two different substances with the characteristic concentration potential (Co P) given by the same membrane it was found (1) that with the acetone-glycerine ratio there is no correspondence (2) that with the acetone-glucose ratio a suggestive relation exists and (3) that with the glycerine-glucose ratio a definite correspondence can be shown, the higher ratios being obtained only with membranes giving high CO P values. A rational explanation for these facts was proposed.
DARK ADAPTATION IN AGRIOLIMAX
Authors: Crozier W. J. , Wolf Ernst 
Published: May 2004

A method is described which measures the excitation of Agriolimax by light, during the progress of light adaptation, by assuming that the orientating effect of continuous excitation is expressed as a directly proportionate tension difference in the orienting muscles of the two sides of the body. The tendency toward establishment of such a tension difference is caused to work against a similar geotropic effect at right angles to the phototropic one. This enables one to study the kinetics of light adaptation, and of dark adaptation as well. The situation in the receptors is adequately described by the paradigm
See PDF for Equation
similar to that derived by Hecht for the differential sensitivity of various forms, but with the difference that the "dark" reaction is not only "bimolecular" but also autocatalysed by the reaction product S. The progress of dark adaptation is reflected (1) in the recovery of the amplitude of the orientation and (2) in the rates of light adaptation at different levels of the recovery; each independently supports these assumptions, for which the necessary equations have been provided. These equations also account for the relative variabilities of the angles of orientation, and, more significantly, for the two quite different kinds of curves of dark adaptation which are obtained in slightly different types of tests.
STUDIES ON PERMEABILITY OF MEMBRANES
Authors: Weech A. A. , Michaelis L. 
Published: May 2004

The flat type of dried collodion membrane used by Michaelis and his associates in numerous investigations has been subjected to mensuration in order that the dimensions of these membranes may be placed on record. The membranes had a functioning area of about 30 cm., were approximately 0.1 mm. in thickness and were composed on the average of 87 per cent by volume of collodion and 13 per cent by volume of pores.
In reviewing some of the previously reported results of diffusion experiments with non-electrolytes in the light of the calculated values for the total pore area for the same membranes additional evidence was presented to show that a smaller molecule (acetone) probably utilizes a much larger percentage of the total pore area for its diffusion than is available for a larger molecule (glycerol).
By using the figures of Fricke and McClendon for the thickness of the membrane of the red blood cell some comparisons were drawn between the dried collodion membrane as a model for certain biological membranes and the red blood cell membrane. In these comparisons emphasis was placed on the exaggerated importance of small electromotive forces and very slight permeabilities when these were associated with membranes of such extreme thinness as the red blood cell membrane.
ON HEMOCHROMOGEN
Authors: Anson M. L. , Mirsky A. E. 
Published: May 2004

1. Every hemochromogen consists of the iron pyrrol complex, reduced heme, combined with some nitrogenous substance.
2. In every hemochromogen there is the equilibrium:
Hemochromogen ⇄ Reduced heme + Nitrogenous substance.
3. Cyanide can form two distinct compounds with reduced heme, one of which is the typical hemochromogen, cyan-hemochromogen.
4. Reduced heme in alkaline solution has a great affinity for cyanide.
5. Cyan-hemochromogen probably contains one cyanide group per heme.
6. The hemochromogen prepared from hemoglobin is a compound of denatured globin and reduced heme.
7. The individual molecule of denatured globin, of hypothetical molecular weight 16,700, can convert at least 10 molecules of reduced heme into hemochromogen.
8. The hemochromogen-forming capacity of globin is, under given conditions, greater than that of edestin, which in turn, is greater than that of zein.
CARBON DIOXIDE FROM THE UNSEVERED VAGUS NERVE OF THE SNAKE
Authors: Parker G. H. 
Published: May 2004

1. The vagus nerve of the gopher-snake, Drymarchon corais couperi (Holbrook), discharges carbon dioxide at an average rate of 0.00234 mgm. of gas per gram of nerve per minute. The extremes were 0.0032 mgm. and 0.0017 mgm.
2. These rates were maintained as well when the nerve was separated from its central and its peripheral connections as when these connections were intact showing that the resting metabolism of nerve is a local operation and is not immediately dependent upon distant connections.
3. These observations also point to the conclusion that the passage of normal impulses over a nerve call for an increase of activity that is unobservable by the method employed and that must be small in amount compared with that produced by artificial stimulation.
CHEMICAL ANTAGONISM OF IONS
Authors: Simms Henry S. 
Published: May 2004

1.25 per cent gelatin solutions containing enough NaOH to bring them to pH 7.367 (or KOH to pH 7.203) were made up with various concentrations of NaCl, KCl and MgCl2, alone and in mixtures, up to molar ionic strength. The effects of these salts on the pH were observed.
MgCl2 and NaCl alone lower the pH of the Na gelatinate or the K gelatinate, in all amounts of these salts.
KCl first lowers the pH (up to 0.01 M K+), then raises the pH.
Mixtures of NaCl and KCl (up to 0.09 M of the salt whose concentration is varied) raise the pH; then (up to 0.125 M Na+ or K+) lower the pH; and finally (above 0.125 M) behave like KCl alone.
Mixtures of MgCl2 and NaCl raise the pH up to 0.10 M Na+, and lower it up to 0.15 M Na+ regardless of the amount of MgCl2. Higher concentrations of NaCl have little effect, but the pH in this range of NaCl concentration is lowered with increase of MgCl2.
Mixtures of MgCl2 and KCl behave as above described (for MgCl2 and NaCl) and the addition of NaCl plus KCl to gelatin containing MgCl2 produces essentially the same effect as the addition of either alone, except that the first two breaks in this curve come at 0.07 M and 0.08 M [Na+ + K+] and there is a third break at 0.12 M.
In this pH range the free groups of the dicarboxylic acids and of lysine are essentially all ionized and the prearginine and histidine groups are essentially all non-ionized. The arginine group is about 84 per cent ionized. Hence we are studying a solution with two ionic species in equilibrium, one with the arginine group ionized, and one with it non-ionized.
It is shown that the effect of each salt alone depends upon the effect of the cation on the activity of these two species due to combination. The anomalous effects of cation mixtures may be qualitatively accounted for if one or both of these species fail to combine with the cations in a mixture in proportion to the relative combination in solutions of each cation alone.
Special precautions were taken to ensure accuracy in the pH measurements. The mother solutions gave identical readings to 0.001 pH and the readings with salts were discarded when not reproducible to 0.003 pH. All doubtful data were discarded.
CHEMICAL AND PHYSICAL CHANGES IN GELATIN SOLUTIONS DURING HYDROLYSIS
Authors: Northrop John H. 
Published: May 2004

1. The change in viscosity and the corresponding increase in the carboxyl groups, as determined by the formol titration, has been determined in gelatin solutions during the progress of hydrolysis by pepsin.
2. Very marked changes in viscosity are found to result from very slight chemical changes. If the viscosity is increased by the addition of acid a greater change in viscosity (volume of solute) is caused by the same percentage change in the number of carboxyl groups. The percentage change in the volume of solute, caused by the same percentage increase in the number of carboxyl groups, is independent of the concentration of gelatin.
3. These results are in agreement with the idea that the high viscosity of gelatin solutions is due to the presence of swollen micells, since a slight chemical hydrolysis may be sufficient to rupture a micella and so cause a very large change in viscosity.