bluuebunny/crossref_metadata_2025_split huggingface dataset:
BIOELECTRIC POTENTIALS IN VALONIA
Authors: Damon E. B. 
Published: May 2004

The P.D. across the protoplasm of Valonia macrophysa has been studied while the cells were exposed to artificial solutions resembling sea water in which the concentration of KCl was varied from 0 to 0.500 mol per liter. The P.D. across the protoplasm is decreased by lowering and increased by raising the concentration of KCl in the external solution. Changes in P.D. with time when the cell is treated with KCl-rich sea water resemble those observed with cells exposed to Valonia sap.
Varying the reaction of natural sea water from pH 5 to pH 10 has no appreciable effect on the P.D. across Valonia protoplasm. Similarly, varying the pH of KCl-rich sea water within these limits does not alter the height of the first maximum in the P.D.-time curve. The subsequent behavior of the P.D., however, is considerably affected by the pH of the KCl-rich sea water. These changes in the shape of the P.D.-time curve have been interpreted as indicating that potassium enters Valonia protoplasm more rapidly from alkaline than from acidified KCl-rich sea water. This conclusion is discussed in relation to certain theories which have been proposed to explain the accumulation of KCl in Valonia sap.
The initial rise in P.D. when a Valonia cell is transferred from natural sea water to KCl-rich sea water has been correlated with the concentrations of KCl in the sea waters. It is assumed that the observed P.D. change represents a diffusion potential in the external surface layer of the protoplasm, where the relative mobilities of ions may be supposed to differ greatly from their values in water. Starting with either Planck's or Henderson's formula, an equation has been derived which expresses satisfactorily the observed relationship between P.D. change and concentration of KCl. The constants of this equation are interpreted as the relative mobilities of K+, Na+, and Cl- in the outer surface layer of the protoplasm. The apparent relative mobility of K+ has been calculated by inserting in this equation the values for the relative mobilities of Na+ (0.20) and Cl- (1.00) determined from earlier measurements of concentration effect with natural sea water. The average value for the relative mobility of K+ is found to be about 20. The relative mobility may vary considerably among different individual cells, and sometimes also in the same individual under different conditions.
Calculation of the observed P.D. changes as phase-boundary potentials proved unsatisfactory.
ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. VIII
Authors: Crozier W. J. , Pincus G. 
Published: May 2004

The upward geotropic orientation (angle θ) of adult rats (race A) has been measured as a function of slope of substratum. The relative variation of orientation angle is a declining rectilinear function of θ. The fraction of the total observable variation of performance (θ) which is controlled by the intensity of excitation (56 per cent) is identical with that found for young rats of the same strain, although the total variation is a little greater.
Injection of adrenin distorts the θ vs. α graph in a manner quite concordant with the effect obtained in young rats. With the adults the absolute magnitudes of the variations of θ, at corresponding intensities of excitation, are not affected by the action of adrenin, and, as with the young, the proportion of modifiable variation of θ is not altered. The variability of performance, considered as a function of the performance, must therefore be regarded as an organic invariant. Certain consequences of this finding are referred to.
QUANTITATIVE ASPECTS OF CUTANEOUS SENSORY ADAPTATION. I
Authors: Hoagland Hudson 
Published: May 2004

1. Adaptation of tactile receptors in the skin of the frog to excitation by an intermittent jet of air is measured and correlated with certain properties of a series of notched discs used to interrupt the air stream.
2. Adaptation in fifteen cases is found to be described by either one of two empirical formulas,
or
t = -k log f + C, for nine preparations
t = a f-b, for six preparations
where f is the per cent frequency at time t and -k and -b are constants defining the rate of adaptation.
INTERMITTENT STIMULATION BY LIGHT
Authors: Hecht Selig , Verrijp Cornelis D. 
Published: May 2004

When measurements of the critical fusion frequency for white light over a large range of intensities are made with the rod-free area of the fovea, the relation between critical frequency and log I is given by a single sigmoid curve, the middle portion of which approximates a straight line whose slope is 11.0. This single relation must be a function of the foveal cones.
When the measurements are made with a retinal area placed 5° from the fovea, and therefore containing both rods and cones, the relation between critical frequency and log I shows two clearly separated sections. At the lower intensities the relation is sigmoid and reaches an upper level at about 10 cycles per second, which is maintained for 1.25 log units, and is followed by another sigmoid relationship at the higher intensities similar to the one given by the rod-free area alone.
These two parts of the data are obviously separate functions of the rods at low intensities and of the cones at high intensities. This is further borne out by similar measurements made with retinal areas 15° and 20° from the fovea where the ratio of rods to cones is anatomically greater than at 5°. The two sections of the data come out farther apart on the intensity scale, the rod portion being at lower intensities and the cone portion at higher intensities than at 5°.
The general form of the relation between critical frequency and intensity is therefore determined by the relative predominance of the cones and the rods in the retinal area used for the measurements.
THE "BOUND" WATER OF BIOLOGICAL COLLOIDS: A REPLY
Authors: Greenberg David M. , Cohn Waldo E. 
Published: May 2004

The objection by Bull to the estimation of bound water by ultrafiltration, because of an assumed adsorption of the reference substance, has been found invalid for glucose. No adsorption of glucose by the proteins, casein and gelatin, could be detected.
The estimation of the bound water of proteins from the probable surface adsorption of water by proteins leads to only a small value.
THE APPLICATION OF QUANTUM MECHANICS TO CERTAIN CASES OF HOMOGENEOUS CATALYSIS. I
Authors: Stearn Allen E. 
Published: May 2004

1. The activation energy for the hydrolytic breaking of a peptid linkage has been calculated from quantum mechanical considerations.
2. The relative catalytic effects of H+ and OH- and the mechanism of these effects have been calculated and discussed.
3. These effects are both qualitatively and semiquantitatively in agreement with experiment.
STIMULATION BY COLD IN NITELLA
Authors: Hill Samuel E. 
Published: May 2004

Sudden local chilling causes action currents to be set up in Nitella and in Chara, an effect which does not follow gradual local chilling. This may be due to a partial solidification of the non-aqueous protoplasmic surfaces which makes them susceptible to rupture by the protoplasmic streaming. This movement continues usually for several minutes after the chilling, whereas if stimulation occurs at all it occurs immediately on chilling. It is found that a chilled spot is much more sensitive to mechanical stimulation than is a spot at room temperature.
Chilling is accompanied by a rise of resistance, a lowered rate of recovery following stimulation, and usually by a falling off in the magnitude of the action curve.
CRYSTALLINE CHYMO-TRYPSIN AND CHYMO-TRYPSINOGEN
Authors: Kunitz M. , Northrop John H. 
Published: May 2004

A new crystalline protein, chymo-trypsinogen, has been isolated from acid extracts of fresh cattle pancreas. This protein is not an enzyme but is transformed by minute amounts of trypsin into an active proteolytic enzyme called chymo-trypsin. The chymo-trypsin has also been obtained in crystalline form.
The chymo-trypsinogen cannot be activated by enterokinase, pepsin, inactive trypsin, or calcium chloride. There is an extremely slow spontaneous activation upon standing in solution.
The activation of chymo-trypsinogen by trypsin follows the course of a monomolecular reaction the velocity constant of which is proportional to the trypsin concentration and independent of the chymotrypsinogen concentration. The rate of activation is a maximum at pH 7.0–8.0. Activation is accompanied by an increase of six primary amino groups per mole but no split products could be found, indicating that the activation consists in an intramolecular rearrangement. There is a slight change in optical activity but no change in molecular weight.
The physical and chemical properties of both proteins are constant through a series of fractional crystallizations.
The activity of chymo-trypsin decreases in proportion to the destruction of the native protein by pepsin digestion or denaturation by heat or acid.
Chymo-trypsin has powerful milk-clotting power but does not clot blood plasma and differs qualitatively in this respect from the crystalline trypsin previously reported. It hydrolyzes sturin, casein, gelatin, and hemoglobin more slowly than does crystalline trypsin but the hydrolysis of casein is carried much further. The hydrolysis takes place at different linkages from those attacked by trypsin. The optimum pH for the digestion of casein is about 8.0–9.0. It does not hydrolyze any of a series of dipeptides or polypeptides tested.
Several chemical and physical properties of both proteins have been determined.
ELECTRICAL FACTORS INFLUENCING THE RATE OF FILTRATION OF AQUEOUS ELECTROLYTE SOLUTIONS THROUGH CELLOPHANE MEMBRANES
Authors: White H. L. , Monaghan Betty , Urban Frank 
Published: May 2004

The mechanisms by which electrokinetic factors might influence the filtration rate of aqueous electrolyte solutions through membranes are discussed. The filtration rate of a thorium chloride solution in which the membrane is isoelectric is compared with those of other solutions. The maximum filtration rate is found at the isoelectric concentration, the rate falling as the electrokinetic potential increases.
The results demonstrate an inverse relation between the electrokinetic potential and the filtration rate but do not permit the evaluation with any great exactitude of the respective rôles played by the two proposed mechanisms, namely, a stream potential-electroosmotic back-transport and a variation in effective pore diameter due to an orientation of water dipoles determined by electrical factors.
Evidence is presented that Lepeschkin's membrane resistance is an artifact.
THE CHROMATOPHORAL NEUROHUMORS OF THE DOGFISH
Authors: Parker G. H. 
Published: May 2004

1. The common dogfish, Mustelus canis, as is well known, exhibits two temporary extremes of tint, one dark, the other light. The dark phase is induced by a secretion from the pituitary gland which is carried in the blood, hence a substance soluble in water (a hydroneurohumor). The light phase is under the control of nerves and cannot be excited by blood from a light fish.
2. When an olive oil or ether extract is made from the fins of a light dogfish and this extract is injected into a dark fish, large light spots may appear in from 1 to 2 days and persist for several days. These light spots, which may be called secondary spots, are not to be confused with certain small and very temporary light spots, the primary spots, which occur soon after the injection and which are believed to be purely operative in origin.
3. The secondary light spots are not due to the death of the integumentary tissue, for, after their formation, they can be made to disappear by the action of obstetrical pituitrin and will subsequently reappear.
4. They are produced by some substance extracted from the light fins by ether or by olive oil. They are not produced by sea water, ether, or olive oil alone.
5. The extracted substance, which can resist dry heat up to at least 110°C., owes its limited range of action in the dogfish to its inability to dissolve in water. It is soluble in oil (a liponeurohumor).
6. This liponeurohumor is believed to emanate from the nerve terminals concerned with the concentration of melanophore pigment and to spread through the fatty components of the integumentary cells.
THE RESISTANCE OF DROSOPHILA TO ALCOHOL
Authors: Crozier W. J. , Pincus G. , Zahl P. A. 
Published: May 2004

The mean time-to-death (t) of imaginal Drosophila of an inbred line in alcohol vapor of constant partial pressure (P) is a declining rectilinear function of P for each age. The time-to-death depends upon the diffusion into the fly of an amount of alcohol sufficient to kill. It does not depend upon any measurable property of a reaction between the substance of the fly and the alcohol which produces death. The relation between t and P is independent of temperature, but the invasion coefficient S = Δt/ΔP declines with age and differs for the two sexes. The first derivative of S with respect to age exhibits sharp discontinuities. The internal alcohol required to kill declines with age, varying with S. The relative variation of t, σt/t, is directly proportional to the resistance to diffusive penetration of alcohol R, where R = 1/S.
The vapor pressure of alcohol estimated to kill instantaneously shows periodic fluctuations with age; these are precisely correlated with changes in the slope of S as a function of age.
Periodic fluctuations of invasibility by alcohol, and of the lethal dose, are interpreted as due to the incidence of suppressed moults. It is shown that in the accumulation of deaths as a function of time (age) in a genetically uniform population of Drosophila of one sex, similar fluctuations are apparent in the rate. The statistical smoothing of such data is not legitimate.
ELECTRIC IMPEDANCE OF ASTERIAS EGGS
Authors: Cole Kenneth S. , Cole Robert H. 
Published: May 2004

The alternating current resistance and capacity of suspensions of unfertilized eggs of Asterias forbesi have been measured at frequencies from one thousand to sixteen million cycles per second.
The plasma membrane of the egg has a static capacity of 1.10µf/cm.2 which is practically independent of frequency. The suspensions show a capacity dependent on frequency at low frequencies which may be attributable to surface conductance.
The specific resistance of the cytoplasm is between 136 and 225 ohm cm. (4 to 7 times sea water), indicating a relatively high concentration of non-electrolytes.
At frequencies above one million cycles there is definite evidence of another element of which the nucleus is presumably a part.
ADAPTATION OF CUTANEOUS TACTILE RECEPTORS
Authors: Rubin Morton A. 
Published: May 2004

The potassium content of the skin of Rana pipiens is found to be 132 m.g. per cent. This is roughly of the order of magnitude of the content of potassium in nerve.
Analyses were also made of the skin for Na, Ca, Mg, Cl, S, and P.
SUBSTANCES AFFECTING ADULT TISSUE IN VITRO
Authors: Simms Henry S. , Stillman Nettie P. 
Published: May 2004

Digestion of adult tissue with trypsin has been shown to stimulate its initial growth in vitro. This stimulation appeared to result from the removal of an inhibitory material from the tissue due to the proteolytic action of the trypsin.
This paper shows that the fluid after the digestion contains material which inhibits the initial growth of adult chicken aorta tissue.
This tissue inhibitor has been obtained from chicken, dog, and sheep aortas. It is partly precipitated by an equal volume of alcohol, and is more completely precipitated by the further addition of CaCl2 (plus a little NaOH). The inhibitor is destroyed at 100°C. but usually withstands 58°C. for 20 minutes. Moderate tryptic digestion renders it soluble without destroying it. It sometimes withstands dialysis, but at other times is lost.
Its physical and chemical properties, as far as we know them, coincide with those of lactenin (a bacteriostatic substance in milk). Lactenin was found to inhibit adult tissue growth; but the tissue inhibitor failed to restrain bacterial growth.
This tissue inhibitor is believed to play a rôle in limiting the growth of tissue in the adult animal.
DARK ADAPTATION IN DINEUTES
Authors: Clark Leonard B. 
Published: May 2004

The level of dark adaptation of the whirligig beetle can be measured in terms of the threshold intensity calling forth a response.
The course of dark adaptation was determined at levels of light adaptation of 6.5, 91.6, and 6100 foot-candles. All data can be fitted by the same curve. This indicates that dark adaptation follows parts of the same course irrespective of the level of light adaptation. The intensity of the adapting light determines the level at which dark adaptation will begin.
The relation between log aI0 (instantaneous threshold) and log of adapting light intensity is linear over the range studied.
EFFECTS OF POTASSIUM ON THE POTENTIAL OF HALICYSTIS
Authors: Osterhout W. J. V. 
Published: May 2004

Sea water in which sodium has been replaced by potassium produces about the same degree of negativity in Halicystis and in Valonia.
With increasing dilution of this sea water up to 1 ÷ 16 the degree of negativity steadily falls off in Halicystis. This differs from the situation in Valonia where Damon finds that with increasing dilution the negativity passes through a minimum after which increasing dilution produces increasing negativity. But conditions in the two organisms differ so greatly that a comparison is of rather doubtful significance.
THE ACCUMULATION OF ELECTROLYTES
Authors: Jacques A. G. 
Published: May 2004

Experiments on Valonia were carried out as follows:
Stage I.—Cells in dim light accumulated 0.08 M ammonia (NH3 + NH4OH + NH4+) from sea water containing 0.0025 M ammonia (but the concentration of undissociated ammonia appeared to remain less inside than outside). Potassium came out.
Stage II.—Cells in dim light in nearly ammonia-free normal sea water lost ammonia which was replaced by sodium entering from the sea water. Potassium in the sap remained practically constant.
Stage III.—The cells were placed in stronger light where the loss of ammonia continued and potassium entered. Sodium entered more rapidly than in Stage II.
Stage IV.—Cells transferred to sea water containing 0.0025 M ammonia again accumulated ammonia up to 0.1345 M.
The results in general harmonize with the view that the direction of movement of a base M through the protoplasm depends on the difference of the activity products (M)o(OH)o and (M)i(OH)i where the subscripts o and i refer to sea water and sap respectively.
On this basis, if the entrance of ammonia raised the internal concentration of OH sufficiently in Stage I potassium should come out in Stage I, as actually happened. The behavior of sodium is in doubt.
If the internal pH in Stage II were sufficiently high sodium should enter but not potassium. This was actually found.
In Stage III, if we suppose that the effect of stronger light is to increase the external pH (by photosynthesis) more than the internal pH (as found by Crozier) we can understand why potassium entered, because such an increase in pH could readily make the external value of (K) (OH) greater than the internal. This would also explain why sodium entered more rapidly than in Stage II.
When ammonia is coming out of the cell, sodium and potassium may enter more rapidly than usual without raising the internal concentration of halide above a certain critical value at which entrance appears to be checked.
LIMITING FACTORS IN PHOTOSYNTHESIS: LIGHT AND CARBON DIOXIDE
Authors: Smith Emil L. 
Published: May 2004

1. Extensive measurements have been obtained (a) relating photosynthesis and light intensity for a large range of CO2 concentrations and (b) relating photosynthesis and CO2 at different light intensities. From these families of curves, the limiting factor relationship can be secured for any value of the photosynthesis rate.
2. In terms of previous work an equation has been derived for describing these relations between the intensity and CO2 concentration necessary to produce a definite amount of photosynthesis. This equation furnishes an exact description for all the data, except those for low rates of photosynthesis where a slightly different equation is required. The nature of the two equations suggests that a simple first order reaction determines the velocity of the light process at low photosynthesis rates, but that at high rates the mechanism is complicated by another factor.
KINETICS OF THE FORMATION OF PEPSIN FROM SWINE PEPSINOGEN AND IDENTIFICATION OF AN INTERMEDIATE COMPOUND
Authors: Herriott Roger M. 
Published: May 2004

A study of the kinetics of the transformation of swine pepsinogen into pepsin under a variety of conditions has been made. The results show that the transformation as a whole is essentially autocatalytic in nature under all conditions.
Evidence is presented to show the existence of a compound intermediate between pepsinogen and pepsin. This compound was found to be a reversibly dissociable complex of pepsin and a low molecular weight inhibitor.
Some of the general properties of the intermediate compound and of the inhibitor have been examined.
THE VISIBILITY OF SINGLE LINES AT VARIOUS ILLUMINATIONS AND THE RETINAL BASIS OF VISUAL RESOLUTION
Authors: Hecht Selig , Mintz Esther U. 
Published: May 2004

The visual resolution of a single opaque line against an evenly illuminated background has been studied over a large range of background brightness. It was found that the visual angle occupied by the thickness of the line when it is just resolved varies from about 10 minutes at the lowest illuminations to 0.5 second at the highest illuminations, a range of 1200 to 1.
The relation between background brightness and just resolvable visual angle shows two sections similar to those found in other visual functions; the data at low light intensities represent rod vision while those at the higher intensities represent cone vision. With violet light instead of white the two sections become even more clearly defined and separated.
The retinal image produced by the finest perceptible line at the highest brightness is not a sharp narrow shadow, but a thin broad shadow whose density distribution is described in terms of diffraction optics. The line of foveal cones occupying the center of this shadow suffers a decrease in the light intensity by very nearly 1 per cent in comparison either with the general retinal illumination or with that on the row of cones to either side of the central row. Since this percentage difference is near the limit of intensity discrimination by the retina, its retinal recognition is probably the limiting factor in the visual resolution of the line.
The resolution of a line at any light intensity may also be limited by the just recognizable intensity difference, because this percentage difference varies with the prevailing light intensity. As evidence for this it is found that the just resolvable visual angle varies with the light intensity in the same way that the power of intensity discrimination of the eye varies with light intensity.
It is possible that visual resolution of test objects like hooks and broken circles is determined by the recognition of intensity differences in their diffracted images, since the way in which their resolution varies with the light intensity is similar to the relation between intensity discrimination and light intensity.