bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE MECHANISM OF THE INFLUENCE OF ACIDS AND ALKALIES ON THE DIGESTION OF PROTEINS BY PEPSIN OR TRYPSIN
Authors: Northrop John H. 
Published: May 2004

1. The effect of the addition of acid on the amount of ionized protein has been compared with the effect on the rate of digestion of gelatin, casein, and hemoglobin by pepsin.
2. A similar comparison has been made of the addition of alkali in the case of trypsin with gelatin, casein, hemoglobin, globin, and edestin.
3. In general, the rate of digestion may be predicted from the amount of ionized protein as determined by the titration curve or conductivity. The rate of digestion is a minimum at the isoelectric point of the protein and a maximum at that pH at which the protein is completely combined with acid or alkali to form a salt.
4. The physical properties of the protein solution have little or no effect on the rate of digestion.
MUSCLE TENSION AND REFLEXES IN THE EARTHWORM
Authors: Moore A. R. 
Published: May 2004

1. By the use of preparations of earthworm in which the cutaneous receptors have been anesthetized with a solution of M/8 MgCl2, it is shown that peristalsis can be initiated by tension alone.
2. The receptors of the tension reflex are the intermyal sensory cells of the ventral region of the body wall.
3. It is concluded that Straub obtained the tension reflex because his preparations contained the intermyal receptors; Budington was unable to observe the tension reflex in any preparation from which the intermyal receptors had been removed.
4. Intermyal receptors are the receptors of the following reaction: Passive unilateral tension of the posterior part of an earthworm induces active homolateral tension of the musculature of the anterior segments, and results in the course of progress being brought into line with the enforced orientation of the tail. This reaction is termed the homostrophic reflex.
5. The receptors for the reaction are distributed throughout the entire length of the worm, the effectors are limited to the anterior 15 to 20 segments. The impulse is conducted by the ventral nerve cord.
6. The interaction of the homostrophic reflex and tropisms is considered.
CONDUCTIVITY AS A MEASURE OF VITALITY AND DEATH
Authors: Brooks S. C. 
Published: May 2004

The conductance of Laminaria, Saccharomyces, Bacillus coli and Bacillus butyricus, Chlorella, and of red blood cells has been studied by the writer's method, and Laminaria by that of Osterhout. For the material studied it has been found that:
1. The conductance of living tissue is closely proportionate to, and determined by that of the surrounding fluid with which it is apparently in equilibrium. Changes in the conductance of the fluid are quickly followed by compensatory changes in that of the tissue.
2. A quantity is defined which is independent of the conductivity of the fluid bathing the tissues. This is called the "net conductance."
3. All the tissues studied, even when dead, offer a resistance to the passage of current greater than that of the surrounding solution. Exceptions which occur under certain conditions will be discussed in a later paper.
4. In view of the wide variety of material studied it seems admissible, in the absence of any evidence to the contrary, to suppose that these conclusions are generally applicable.
THE BEHAVIOR OF CHLORIDES IN THE CELL SAP OF NITELLA
Authors: Irwin Marian 
Published: May 2004

1. A method is given for determining the chloride content in a drop (less than 0.03 cc.) of the cell sap of Nitella.
2. Chlorides accumulate in the sap to the extent of 0.128 M; this accumulation can be followed during the growth of the cell. The chloride content does not increase when the cell is placed for 2 days in solutions (at pH 6.2) containing chlorides up to 0.128 M.
3. The exosmosis of chlorides from injured cells can be followed quantitatively. When one end of the cell is cut off a wave of injury progresses toward the other end; this is accompanied by a progressive exosmosis of chlorides.
THE REACTION OF NEREIS VIRENS TO UNILATERAL TENSION OF ITS MUSCULATURE
Authors: Moore A. R. 
Published: May 2004

1. The anterior segments of Nereis are oriented reflexly by passive unilateral tension of the posterior musculature.
2. The afferent impulses of the homostrophic reflex rise from any part of the worm and are conducted forward by way of the ventral nerve cord.
3. The efferent impulses flow out from the brain and anterior two or three ventral ganglia.
4. The homostrophic reflex may be partially or wholly masked by stereotropism.
COMPARATIVE STUDIES ON RESPIRATION
Authors: Ray George B. 
Published: May 2004

1. Chloroform in low concentration (0.25 per cent) causes an increase in the rate of production of CO2 in Ulva; this is followed by a decrease. In higher concentration (0.5 per cent) only a decrease is observed.
2. Assuming that the normal oxidation depends on the action of peroxide and peroxidase, experiments were made by placing Ulva in 1.0 per cent H2O2 and in Fe2(SO4)3 (which acts like a peroxidase). The former diminishes the rate, the latter increases and subsequently decreases it.
3. When Ulva is killed in such a manner as to destroy the oxidizing enzymes, no CO2 is produced unless H2O2 and Fe2(SO4)3 are present. If to this mixture chloroform is added, the effect depends on the concentration of the iron. If the concentration is low there is an increase in the production of CO2 followed by a decrease. If the concentration is high the rate appears to decrease from the start.
HOMOSTROPHIC REFLEX AND STEREOTROPISM IN DIPLOPODS
Authors: Crozier W. J. , Moore A. R. 
Published: May 2004

1. With suitable arthropods, such as the diplopods, it can be shown that body orientation following passive unilateral tension involves the homostrophic reflex. The phenomenon is exhibited when the animal is quiescent and during forward locomotion, but nothing of the sort appears in backward locomotion.
2. Receptors for the homostrophic reflex are in the body wall and are distributed throughout the length of the animal.
3. The effector nerves take their origin from the ganglia of the head alone.
4. The diplopods are stereotropic, the head turning toward the side in contact with a solid surface only as long as some part of the body maintains contact. Under suitable conditions stereotropism may mask the homostrophic reflex.
5. When a diplopod is in contact with two lateral surfaces of equal extent the path upon emergence is a straight one, conforming to the law of the parallelogram of forces.
COMPARATIVE STUDIES ON RESPIRATION
Authors: Ray George B. 
Published: May 2004

1. Organic acids when treated with H2O2 and Fe2(SO4)3 produce CO2 at a rate that can be measured by the indicator method.
2. In the case of acids containing a double bond, the rate of production of CO2 can be varied by the addition of an anesthetic. The changes in the rate of production of CO2 under the influence of a typical anesthetic, such as chloroform, show a striking resemblance to the reaction of the organism.
THE COMPOSITION OF THE CELL SAP OF THE PLANT IN RELATION TO THE ABSORPTION OF IONS
Authors: Hoagland D. R. , Davis A. R. ,   With the Assistance of J. C. Martin.
Published: May 2004

1. Chemical examination of the cell sap of Nitella showed that the concentrations of all the principal inorganic elements, K, SO4, Ca, Mg, PO4, Cl, and Na, were very much higher than in the water in which the plants were growing.
2. Conductivity measurements and other considerations lead to the conclusion that all or nearly all of the inorganic elements present in the cell sap exist in ionic state.
3. The insoluble or combined elements found in the cell wall or protoplasm included Ca, Mg, S, Si, Fe, and Al. No potassium was present in insoluble form. Calcium was predominant.
4. The hydrogen ion concentration of healthy cells was found to be approximately constant, at pH 5.2. This value was not changed even when the outside solution varied from pH 5.0 to 9.0.
5. The penetration of NO3 ion into the cell sap from dilute solutions was definitely influenced by the hydrogen ion concentration of the solution. Penetration was much more rapid from a slightly acid solution than from an alkaline one. It is possible that the NO3 forms a combination with some constituent of the cell wall or of the protoplasm.
6. The exosmosis of chlorine from Nitella cells was found to be a delicate test for injury or altered permeability.
7. Dilute solutions of ammonium salts caused the reaction of the cell sap to increase its pH value. This change was accompanied by injury and exosmosis of chlorine.
8. Apparently the penetration of ions into the cell may take place from a solution of low concentration into a solution of higher concentration.
9. Various comparisons with higher plants are drawn, with reference to buffer systems, solubility of potassium, removal of nitrate from solution, etc.
THE EFFECT OF RADIO-ACTIVE RADIATIONS AND X-RAYS ON ENZYMES
Authors: Hussey Raymond G. , Thompson William R. 
Published: May 2004

A quantitative study has been made of the radiochemical decomposition of trypsin by the radiations from radium emanation.
The following equation accounts quantitatively for the experimental results presented.
See PDF for Equation
It follows from this that the amount of trypsin decomposed by the radiations from radium emanation depends on the concentration of trypsin present and is proportional to the quantity of emanation expressed in millicuries and to the time of irradiation expressed in hours. It would seem that it is the active or undissociated trypsin that is affected.
Evidence has been found which suggests that the beta radiations produce the decomposition observed for which the above statement holds.
Qualitative evidence has been found which suggests that x-rays, gamma rays, and beta rays produce identical effects in dilute trypsin solutions.
THE INACTIVATION OF TRYPSIN
Authors: Northrop John H. 
Published: May 2004

1. Charcoal removes trypsin from solution. The amount removed depends on the order in which the solutions are mixed. The reaction is not reversible and is almost independent of the pH of the solution.
2. Charcoal which has been previously treated with gelatin does not remove trypsin from solution.
3. The reaction is not analogous either to the reaction between trypsin and the inhibiting substance of serum or to the reaction between solid protein and either pepsin or trypsin.
STUDIES IN PROTOPLASM POISONING
Authors: Shackell L. F. 
Published: May 2004

1. After equilibrium of distribution of a phenol between water and an animal immersed in it has been once attained, the poisoning of the animal proceeds with constant velocity. The criterion of toxicity adopted in the first part of this study was the time required for initial recovery from paralysis after a given time in the phenol solution. In later work observations were made of the percentages of animals which died after stated periods in a phenol solution.
2. The numerical value of the velocity constant of poisoning for a given solution is independent of the criterion of toxicity adopted, provided that the criterion serves to measure the intensity of effect of the poison, and not merely the rate at which the poison is absorbed.
3. Recovery from paralysis produced by phenol and death from this poison has the same velocity constant. From this it may be inferred that recovery is due to a reversal of the mechanism which underlies poisoning.
4. The velocity of poisoning by phenols is nearly proportional to the square of the concentration.
5. A strictly chemical (mass law) interpretation is shown to be inadequate for the description of poisoning by phenols.
6. Certain physical factors, involved in poisoning by phenols, are discussed.
7. A precise method for obtaining the velocity constant of poisoning by a given agent is outlined.
THEORY OF REGENERATION BASED ON MASS ACTION
Authors: Loeb Jacques 
Published: May 2004

1. The writer's older experiment, proving that equal masses of isolated sister leaves of Bryophyllum regenerate under equal conditions and in equal time equal masses (in dry weight) of shoots and roots, is confirmed. It is shown that in the dark this regeneration is reduced to a small fraction of that observed in light.
2. The writer's former observation is confirmed, that when a piece of stem inhibits or diminishes the regeneration in a leaf, the dry weight of the stem increases by as much or more than the weight by which the regeneration in the leaf is diminished. It is shown that this is also true when the axillary bud in the stem is removed or when the regeneration occurs in the dark.
3. These facts show that the regeneration of an isolated leaf of Bryophyllum is determined by the mass of material available or formed in the leaf during the experiment and that such a growth does not occur in a leaf connected with a normal plant for the reason that in the latter case the material available or formed in the leaf flows into the stem where it is consumed for normal growth.
4. It is shown that the sap sent out by a leaf in the descending current of a stem is capable of increasing also the rate of growth of shoots in the basal parts of the leaf when the sap has an opportunity to reach the anlagen for such shoots.
5. The fact that a defoliated piece of stem forms normally no shoots in its basal part therefore demands an explanation of the polar character of regeneration which lays no or less emphasis on the chemical difference between ascending and descending sap than does Sachs' theory of specific root- or shoot-forming substances (though such substances may in reality exist), but which uses as a basis the general mass relation as expressed in the first three statements of this summary.
6. It is suggested that the polar character of the regeneration in a stem of Bryophyllum is primarily due to the fact that the descending sap reaches normally only the root-forming tissues at the base of the stem, while the ascending sap reaches normally only the shoot-forming anlagen at the apex of the stem.
7. This suggestion is supported by the fact that when the anlagen for shoots and roots are close together as they are in the notch of a leaf, the sap of the leaf causes the growth of both roots and shoots from the same notch and the influence of the sap of the leaf on this growth increases for both roots and shoots in proportion with the mass of the leaf.
THEORY OF GEOTROPISM BASED ON MASS ACTION
Authors: Loeb Jacques 
Published: May 2004

1. It is shown that the rate of geotropic curvature of a piece of stem of Bryophyllum calycinum when suspended horizontally increases with the mass of an apical leaf attached to the stem.
2. It is shown that the dry weight of the stem increases with the mass of the leaf attached and also that the degree of curvature increases with this increase in the dry weight of the stem.
3. The conclusion is drawn that geotropic curvature is in this case a function of mass action of the material sent by the leaf into the basal part of the stem.
4. The material sent by a leaf into the apical part of a stem does not lead to the same geotropic curvature.
CHANGES IN THE STABILITY AND POTENTIAL OF CELL SUSPENSIONS
Authors: Eggerth Arnold H. 
Published: May 2004

1. Stability and potential of Bacterium coli suspensions depend, not only on the strain of the organism and the medium in which it is suspended, but also on the previous treatment of the suspension, and the length of time it has been in the medium.
2. When treated at acid reactions, the negative charge on the bacteria is diminished; with some strains, a positive charge is acquired. Changes in stability accompany the changes in potential.
3. Washing acid-treated bacteria at neutral or slightly alkaline reactions does not restore the original potential; the zone of flocculation is moved toward the alkaline side.
4. These changes are due to two factors: the extraction of a soluble protein which combines with the surfaces of the cells, and a further irreversible change of the cell or its membrane.
STUDIES ON TOXICITY
Authors: Fulmer Ellis I. , Buchanan R. E. 
Published: May 2004

With yeast subjected to the action of phenol or of phenol and alcohol the curves of survivors as measured by resistance to staining with methylene blue when plotted against time do not in general prove to be logarithmic.
It is believed that such resemblances as have been found between such curves and monomolecular reaction or logarithmic curves are superficial and fortuitous. Any method therefore of evaluating disinfecting power based upon such a concept must prove misleading.
Variations in resistance of individual cells and the distribution of such variations must be regarded as of fundamental importance in accounting for rates of death of microorganisms.
DIFFERENTIATION OF OXYHEMOGLOBINS BY MEANS OF MUTUAL SOLUBILITY TESTS
Authors: Landsteiner Karl , Heidelberger Michael 
Published: May 2004

1. The rule of addition of solubilities is applicable to the differentiation of the oxyhemoglobins of not too closely related species.
2. The oxyhemoglobins of the horse, dog, rat, and guinea pig show differences when tested by this method. The oxyhemoglobins of the donkey and horse show a similarity which is best explained by the assumption of isomorphism.
THE NERVOUS MECHANISM OF COORDINATION IN THE CRINOID, ANTEDON ROSACEUS
Authors: Moore A. R. 
Published: May 2004

1. Stimulation causes Antedon to swim by means of alternate oral bending and dorsal stroke of the arms. Two arms of a given ray move alternately so that while one is executing the aboral stroke its mate is flexing ventrally. This implies reciprocal inhibition.
2. Recriprocal inhibition between the two arms of an isolated ray can be abolished by the use of either strychnine or nicotine.
3. Coordination between the rays is referable to the conducting properties of the nervous pentagon which connects the five rays. In this system an impulse loses in effectiveness as it passes from the point of origin.
4. When Antedon is made to rest oral face down on the floor of an aquarium, oral flexion of all the rays, swimming movements, and righting result. Antedon is therefore negatively stereotropic with reference to its ventral side.
5. Excitation of the dorsal cirri results in aboral bending of all the rays. Stimulation of the cirri inhibits ventral flexion to the extent of preventing righting movements while on the other hand stimulation of the ventral surface inhibits the grasp reflex of the cirri. Thus oral and aboral sides of Antedon exhibit dynamic symmetry although structurally dissimilar.
THE RATE OF GROWTH OF THE DAIRY COW
Authors: Brody Samuel , Ragsdale Arthur C. 
Published: May 2004

Barring fluctuations due to the cyclic phenomena, the extrauterine course of growth in linear dimensions and in weight of the dairy cow follows an exponential law having the same form as the law representing the course of monomolecular change in chemistry. This suggests the interpretation that the general course of growth is limited by a monomolecular chemical process, and that the cyclic phenomena are due to subsidiary processes in the fundamentally exponential course of growth.
The fact that growth follows or tends to follow an exponential course may be stated more simply as follows: if the unit of time is taken sufficiently large so that fluctuations due to the cyclic phenomena are balanced or eliminated, then the amount of growth made during the given unit of time at any age tends to be a constant percentage of the growth made during the preceding unit of time. Thus, the growth in height at withers made during any year is about 34 per cent of the growth made during the preceding year. Similarly the growth in weight made during any year is about 56 per cent of the growth in weight made during the preceding year. This is in accordance with expectations if it is assumed that each animal begins life with a definite endowment of limiting substance necessary for the process of growth, and that this endowment is used up at a constant rate (or percentage) of itself.
TROPISTIC REACTIONS OF CERIANTHUS MEMBRANACEUS
Authors: Moore Mary Mitchell 
Published: May 2004

1. Cerianthus shows stereotropism and if fed regularly will remain indefinitely in glass tubes. The animal retains turgor only so long as the entire surface of the body is in contact with the glass.
2. Cerianthus is positively geotropic as regards the foot and body. It will work upward into a glass tube suspended at an angle of 35° as a result of stereotropism, but if the tube is raised to an angle of 45° the foot turns back and the animal reverses its position in the tube so that foot is down, head, up. Thus at an angle of 45° stereotropism and geotropism very nearly balance each other.
3. Light increases the muscle tone of Cerianthus; this results in positive phototropism. I x t = K. where I is the intensity of the light, t is exposure time, and K, a constant, = 0.46. Where reaction time is considered, I (t + k) = K, in which I is intensity of light, t is reaction time, k = 0.25, and K = 28.29. The two equations prove the operation of the Bunsen-Roscoe law.
THE KINETICS OF TRYPSIN DIGESTION
Authors: Northrop John H. 
Published: May 2004

The rate of hydrolysis of edestin by trypsin at 40° and in the presence of 1 M NaCl has been studied. Under these conditions the enzyme is rapidly inactivated and the equation for the reaction may be written
See PDF for Equation
in which Et is the concentration of enzyme during the interval (T1–T2). This equation has been tested by determining the enzyme concentration at various times during the reaction and substituting these values in the above equation. The experimental results agree with this formula when the initial enzyme or edestin concentrations are varied. No anomalous results of varying substrate concentrations are apparent.
It can further be assumed as a first approximation that the enzyme is decomposing monomolecularly and the equation can then be written
See PDF for Equation
This equation is also satisfactory provided high enzyme concentrations and low edestin concentrations are used. With high concentrations of edestin and low trypsin the effects of the products of the reaction on the enzyme become too large to be neglected and the formula no longer holds.
THE ULTIMATE UNITS IN PROTEIN SOLUTIONS AND THE CHANGES WHICH ACCOMPANY THE PROCESS OF SOLUTION OF PROTEINS
Authors: Loeb Jacques , Kunitz M. 
Published: May 2004

1. The experiments show that suspensions of finely divided particles of insoluble proteins incapable of swelling in acid (denatured egg albumin, casein trichloroacetate, sulfate, etc.) raise the viscosity of the suspension but little and that the influence of acid on the viscosity is negligible.
2. The same is true for solutions of certain genuine proteins such as genuine crystalline egg albumin.
3. In contrast with these are proteins which swell in acid. It can be shown that where acid swelling of particles occurs, the viscosity is of a higher order of magnitude than where the swelling of particles is impossible and that the influence of acid on viscosity runs in these cases parallel to the influence of acid on swelling. This is shown to be the case for casein in HCl.
4. It is shown that the swelling of the powdered particles which determines the high order of viscosity varies according to the theory of membrane equilibria.
5. These results are used to ascertain with the aid of viscosity measurements whether the ultimate units of genuine protein in solutions are aggregates large enough to give rise to a Donnan equilibrium; or whether they consist of particles below this limit; and in what porportion the two kinds of units are contained in the solution.
6. It is found on the basis of viscosity measurements that when 1 gm. of isoelectric casein is dissolved in HCl so that the solution has a pH of 2.45, more than one-half of 1 gm. of casein must exist as units too small to give rise to a Donnan equilibrium, while the rest must exist in units still capable of undergoing swelling in acid.