bluuebunny/crossref_metadata_2025 huggingface dataset:
ELECTROKINETIC PHENOMENA
Authors: Moyer Laurence S. , Abramson Harold A.
Published: May 2004

The ratio of electroosmotic to electrophoretic mobility of certain protein-coated surfaces is very close to 1.0, even in very dilute solutions of electrolytes.
THE KINETICS OF THE REACTION WHICH TAKES PLACE BETWEEN IODOACETIC ACID AND GLYCINE
Authors: Brdička R.
Published: May 2004

1. The kinetics of the reaction which takes place between glycine and iodoacetic acid was studied by means of the polarographic method.

2. On the basis of kinetic equations, evidence was obtained that (a) The reaction proceeds in two steps in which the hydrogens of the amino group are consecutively replaced by the acetyl radicals, the velocity constants being in the ratio 2:1. (b) Only the anionic form of glycine is able to react since the velocity constants at any pH are proportional to the concentration of glycine anion. (c) The reaction is of the ionic type, showing a positive salt catalysis, which, according to Brönsted's hypothesis, involves the primary and the secondary salt effects.

3. The fact that only the glycine anion is able to react was explained as being due to the existence of an unbonded pair of electrons on the nitrogen in the NH2 group. The NH3+ group, however, in which these electrons are shared by H+, must, therefore, be inactive.
THE ADSORPTION OF EGG ALBUMIN ON COLLODION MEMBRANES
Authors: Dow Philip
Published: May 2004

An experimental study has been made of the adsorption of purified egg albumin, from aqueous solution, on collodion membranes. At protein concentrations of 4 to 7 per cent apparent saturation values were obtained which resembled closely the results obtained with gelatin, showing a maximum at pH 5.0 and lower values on either side of this region. Over large ranges of protein concentration, however, the curves for the adsorption from solutions removed in either direction from the isoelectric point exhibited a different shape from the hyperbola obtained in the neighborhood of pH 5.0. The addition of NaCl to solutions on the acid side tended to obliterate the effect of the pH difference; on the alkaline side it greatly increased the adsorption. The adsorption at 25° was about twice as great as that at 1°.

The theory of the swelling of submicroscopic particles, advanced to account for the adsorption behavior of gelatin, is not sufficient to explain the results obtained with egg albumin. It is suggested that the effect is related to alterations in the forces causing the retention of the protein on the membranes.
THE GROWTH AND RESPIRATION OF THE AVENA COLEOPTILE
Authors: Bonner James
Published: May 2004

1. Transport of the plant growth hormone into the Avena coleoptile as well as the action of the hormone on cell elongation in the coleoptile are shown to depend upon aerobic metabolism.

2. Crystalline auxine, in contrast with impure preparations, affects neither the magnitude nor the respiratory quotient of coleoptile respiration.

3. Increasing age of the coleoptile cell decreases its rate of elongation much more than its rate of respiration. HCN or phenylurethane on the other hand decrease the two processes to the same extent, in spite of the fact that only a small portion of the energy liberated by respiration can be used in the mechanical process of growth.

4. From 2 and 3 it is concluded that processes of a respiratory nature but of relatively small magnitude form one or more integral steps in the chain of reactions by which the plant growth hormone brings about cell elongation.
STUDIES ON CELL METABOLISM AND CELL DIVISION
Authors: Krahl M. E. , Clowes G. H. A.
Published: May 2004

The dihalo and trihalophenols, and phenols containing both halo and nitro substituents in the same molecule, produce, in fertilized eggs of Arbacia punctulata, a rise in rate of oxygen consumption and a reversible block to cell division. To define the conditions which affect the degree of this activity, the following factors have been varied: the arrangement of substituents in the molecule, the concentration of reagent, and the time after fertilization at which the reagent is added.

The stimulation of oxygen consumption and reversible block to cell division produced by the dihalophenols are qualitatively the same as those previously produced in fertilized Arbacia eggs by certain dinitrophenols. To yield optimum respiratory effect and maximum division block, it usually requires a higher concentration of dihalo than of the corresponding dinitrophenol. For example, with fertilized Arbacia eggs at 20°C. 2,4-dinitrophenol, in optimum concentration of 3 x 10–5 molar, raises oxygen consumption to 292 per cent of normal (4). The corresponding values for two dihalo analogues are: 2,4-dichlorophenol, 10–4 molar and 236 per cent; 2,4-dibromophenol, 6 x 10–5 molar and 282 per cent.

The halophenols differ from the nitrophenols in two interesting respects: (a) The monohalophenols produce little or no oxidative stimulation or division block in fertilized Arbacia eggs; p-nitrophenol is very active in both respects. (b) The symmetrical trihalophenols have an appreciable ability to stimulate oxygen consumption and block division; symmetrical trinitrophenol is inactive in both respects (4).

The increases in oxygen consumption produced in fertilized Arbacia eggs by 2,4-dichloro and 2,4-dinitrophenol are larger than the percentage increases given by methylene blue and o-cresol indophenol under the same experimental conditions. The dihalo and dinitrophenols produce a reversible block to the cell division of fertilized marine eggs. The oxidation-reduction indicators, in contrast to the dihalo and dinitrophenols, block cell division irreversibly and fertilized eggs of Arbacia do not recover from optimum respiratory stimulating concentrations of these oxidation-reduction dyes.

The present experiments with halophenols are in harmony with and lend considerable support to the hypothesis (4) that nitro and similarly substituted phenols derive their biological activity from the presence and properties of the phenolic OH group, as modified by proper substitution in the phenolic benzene ring.
ON CRITICAL FREQUENCY AND CRITICAL ILLUMINATION FOR RESPONSE TO FLICKERED LIGHT
Authors: Crozier W. J. , Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

The curve of mean critical flicker frequency as a function of illumination has been determined for the reaction of the sunfish Lepomis to flicker. It exhibits expected quantitative disagreements with the curve of mean critical illumination as a function of flicker frequency in the same organism. The form of the dependence of the variation of critical frequency of flicker upon illumination can be predicted from a knowledge of the way in which variation of critical illumination depends upon flicker frequency. It is pointed out that these findings have an important bearing upon the interpretation of the data of intensity discrimination.
THE EFFECT OF HEMOLYTIC SUBSTANCES ON WHITE CELL RESPIRATION
Authors: Ponder Eric , Macleod John
Published: May 2004

Substances such as saponin, the bile salts, etc., which produce lysis of red cells also produce cytolysis of white cells from rabbit peritoneal exudates, the arbitrary criterion of their cytolytic effect being their ability to depress the O2 consumption of the leucocytes. The amount of cytolysis increases regularly as the amount of the added lysin is increased, and sufficiently large quantities of saponin, sodium taurocholate, sodium glycocholate, or sodium oleate are capable of virtually abolishing the O2 consumption altogether. At the same time, it can be shown that a lysin such as saponin is used up in combining with the white cells in much the same way as it is used up in combining with red cells, and the reduction in oxygen consumption appears to be roughly proportional to the amount so combined. The action of these lytic substances on white cells, in fact, is very similar to their action on red cells, due allowance being made for the fact that the cytolysis of the white cell is probably not an all-or-none process like hemolysis.

White cell respiration is also depressed in hypotonic solutions, the respiration being virtually linear with the tonicity.
GROWTH SUBSTANCE CURVATURES OF AVENA IN LIGHT AND DARK
Authors: Van Overbeek J.
Published: May 2004

An attempt has been made to analyze the base response, one of the light growth responses of Avena coleoptiles, by means of growth substance curvatures. The decrease in growth rate (first part of the base response) after exposure to light does not show if hetero-auxin is substituted for auxin-a (Sections 5, 6, and 10). This decreased growth after exposure very likely is due to an oxidative inactivation of auxin-a (Sections 8 and 9). Hetero-auxin can be inactivated too but in a much lesser degree than auxin-a (Section 9). The increase in growth rate following on the decreased growth (second part of the base response) is due to an increase in response of the plant to growth hormone which is independent of the type of hormone (Sections 1, 2, 7, 8, and 10). Under conditions of continuous exposure to light, however, the inactivation of the auxin-a under influence of the light is superimposed on this increased response to growth hormone. This inactivation can be eliminated from the light growth response by replacing the auxin-a by hetero-auxin. More detailed information on this subject can be found in Section 10. A review of the experiments and their results can be obtained from the scheme in Section 8.

In Section 11 it is shown that light inhibits the formation of growth hormone in the decapitated coleoptile (regeneration). Very small amounts of light (25 m.c.s.) inhibit the regeneration markedly.
INACTIVATION OF PEPSIN BY IODINE AND THE ISOLATION OF DIIODO-TYROSINE FROM IODINATED PEPSIN
Authors: Herriott Roger M.
Published: May 2004

In the presence of iodine at pH 5.0–6.0 a solution of pepsin absorbs iodine and the specific proteolytic activity of the solution decreases. The activity is less than 1 per cent of the original activity when the number of iodine atoms per mol of pepsin is 35–40.

If the pH is 4.5 or less, iodine reacts very slowly and there is a correspondingly slower loss in activity. Glycyl tyrosine reacts with iodine in a manner similar to pepsin.

Experiments were performed to determine the extent to which oxidation of pepsin by iodine occurs during iodination, and if such oxidation were responsible for the loss in enzymatic activity. Although the results were not absolutely decisive, there seems to be no appreciable oxidation taking place during iodination and no relationship between the slight oxidation and loss in peptic activity.

From a dialyzed preparation of completely iodinated pepsin which was inactive and contained 13.4 per cent bound iodine, 82 per cent of the iodine was obtained in a solution which analyzed as a solution of diiodo-tyrosine. Because of the presence of a material which contained no iodine and prevented quantitative crystallization, only 53 per cent of the iodine containing substance could be crystallized. This 53 per cent was, however, identified as diiodo-tyrosine.

The part of the titration curve which in pepsin and most proteins represents the phenolic group of tyrosine was, in the curve for iodinated pepsin, shifted toward the acid region as expected.

From these results, it appears that the loss in proteolytic activity of pepsin, when treated with iodine under the specified conditions, is due to the reaction of the iodine with the tyrosine in pepsin.
SEROLOGICAL REACTIONS OF AZOPROTEINS DERIVED FROM AROMATIC HYDROCARBONS AND DIARYL COMPOUNDS
Authors: Jacobs John
Published: May 2004

Serological reactions of azoproteins from p-aminodiphenyl, ß-naphthylamine, ß-anthramine and some compounds containing two benzene rings (aminodiphenyl methane etc.) have been described, the last mentioned substances having been the subject of theoretical discussion on serological specificity.
CRITICAL ILLUMINATION AND CRITICAL FREQUENCY FOR RESPONSE TO FLICKERED LIGHT, IN DRAGONFLY LARVAE
Authors: Crozier W. J. , Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

Curves relating flicker frequency (F) to mean critical illumination (Im) for threshold response to flickered light, with equal durations of light and no light intervals, and relating illumination (I) to mean critical flicker frequency (Fm) for the same response, have been obtained from homogeneous data based upon the reactions of dragonfly larvae (Anax junius). These curves exhibit the properties already described in the case of the fish Lepomis. The curve for Fm lies above the curve of Im by an amount which, as a function of I, can be predicted from a knowledge either of the variation of Im or of Fm. The law of the observable connection between F and I is properly expressed as a band, not as a simple curve.

The variation of Im (and of Fm) is not due to "experimental error," but is an expression of the variable character of the organism's capacity to exhibit the reaction which is the basis of the measurements. As in other series of measurements, P.E.I is a rectilinear function of Im; P.E.F passes through a maximum as F (or I) increases. The form of P.E.F as a function of I can be predicted from the measurements of P.E.I.

It is pointed out that the equations which have been proposed for the interpretation of curves of critical flicker frequency as a function of intensity, based upon the balance of light adaptation and dark adaptation, have in fact the character of "population curves;" and that their contained constants do not have the properties requisite for the consistent application of the view that the shape of the F - I curve is governed by the steady state condition of adaptation.

These curves can, however, be understood as resulting from the achievement of a certain level of difference between the average effect of a light flash and its average after effect during the dark interval.
THE RESPIRATORY QUOTIENT OF SEEDLINGS OF LUPINUS ALBUS DURING THE EARLY STAGES OF GERMINATION
Authors: Craig F. N.
Published: May 2004

In germinating seedlings of Lupinus albus, the initial respiratory quotient was found to be unity. After a drop to 0.76 at 9 hours, the value rose to 0.90 at 12 hours, and then fell to 0.64 at 60 hours. It is improbable that the fat oxidation system is the first to become activated.
SOME REMARKS ON THE PHOTOSYNTHESIS OF GREEN PLANTS
Authors: Weiss Joseph
Published: May 2004

1. It is suggested that in the assimilation process of green plants the reduction of the CO2 takes place with the help of Fe++ ions (present in the chloroplast) under the influence of light, which is absorbed by a sensitizing chlorophyll-CO2-complex.

2. It seems that the chlorophyll has to fulfill two different functions depending on its situation in the chloroplast. The chlorophyll molecules on the surface of the lipoid phase (in contact with an aqueous phase containing Fe++) combine with CO2 to form a light absorbing chlorophyll-CO2-complex and in this way take part in the reduction of the CO2.

The light energy is also absorbed by the greater portion of the chlorophyll, which is dissolved in the interior of the lipoid phase, and eventually handed over to the chlorophyll molecules on the surface.

3. The photosynthetic unit of Emerson and Arnold may be determined by the ratio:

See PDF for Equation

so that for every chlorophyll molecule on the surface there are about 500 molecules in the interior, which provide it with the necessary quanta.
STUDIES IN BLOOD COAGULATION
Authors: Eagle Harry , Harris Tzvee N.
Published: May 2004

Crude or crystalline trypsin in proper concentration causes the blood or plasma of human beings, dogs, rabbits, guinea pigs, and horses to coagulate. It does not clot the fibrinogen directly, but reacts with prothrombin to form thrombin. Since trypsin thus has the same effect as the physiological system Ca plus platelets (or Ca plus tissue extracts), it is suggested as a tentative working hypothesis that the latter system contains a proteolytic enzyme with a specific affinity for prothrombin. Other implications of this trypsin effect with respect to the mechanism of physiological coagulation are discussed in the text (pages 557–558).

The proteolytic enzyme papain also coagulates blood. In this case the enzyme does not activate prothrombin, but acts directly on fibrinogen to form a fibrillar gel resembling fibrin. If one admits this clot to be fibrin, this constitutes strong evidence that thrombin, the physiological coagulant, is also a proteolytic enzyme with a specific action on fibrinogen.
ACTION OF ULTRAVIOLET LIGHT ON SPORES AND VEGETATIVE FORMS OF B. MEGATHERIUM SP
Authors: Herčík Ferdinand
Published: May 2004

Spores and vegetative forms of a strain of B. megatherium were irradiated by ultraviolet light of the wave lengths 2536 Å, 2803 Å, and 3132 Å. The killing rate of both bacteria and spores is exponential, in agreement with irradiation results on other bacteria. Twice as much incident energy is needed to kill the spores as the vegetative forms (50 per cent death).

The absorbed energy per bacterium for 50 per cent killing has been calculated on the assumption that the absorption of the vegetative cells is the same as that of colon bacilli. These results are compared with previous measurements on other bacteria.
SUBSTANCES AFFECTING ADULT TISSUE IN VITRO
Authors: Simms Henry S. , Stillman Nettie P.
Published: May 2004

Adult tissue is characterized by a lag period of several days preceding the onset of growth in vitro.

Treatment of fresh adult tissues with trypsin before planting them in culture flasks stimulated the tissues to grow sooner and more rapidly.

Best stimulation was obtained by slow digestion at low temperature. The tissues lost nitrogen during the digestion. Lowering the temperature from 22°C. to 5°C. reduced the digestion of aorta tissue much less than it reduced the digestion of casein.

Washing the tissue after trypsin treatment resulted in better stimulation.

Trypsin solutions of different degrees of purity, when diluted to equal activity toward casein, gave equal stimulation to the tissue growth. These included solutions of Northrop's crystalline trypsin and chymo-trypsin.

Papain also stimulated growth in a similar manner.

The results indicate that this stimulation of tissue growth is due entirely to proteolytic action.

Cultures of adult fibroblasts (and some tumor cultures) having reached a state of retarded growth have been treated with trypsin to digest away most of the plasma clot (used as a medium). Fresh plasma has been added to renew the clot. This treatment has resulted in an immediate renewal of growth.

Reasons are given for supposing that the cells produce an inhibitor in vitro which they deposit in the surrounding clot, and which is removed by the action of trypsin.
CHANGES OF APPARENT IONIC MOBILITIES IN PROTOPLASM
Authors: Osterhout W. J. V.
Published: May 2004

The normal P.D. across the protoplasm of Valonia macrophysa is about 10 mv. negative (inwardly directed). On adding 0.01 M guaiacol to the sea water the P.D. becomes positive and then slowly returns approximately to the normal value.

In many cases this behavior is not much affected by raising the pH and so increasing the concentration of the guaiacol ion but in other cases such an increase makes the P.D. somewhat more negative.

But if we wait until the exposure to guaiacol has lasted 5 minutes (and the P.D. has returned to its normal value) before we raise the pH, the result is very different. The cell then behaves as though it had been sensitized to the action of the guaiacol ion which appears to be far more effective than undissociated guaiacol in making the P.D. more positive. This may be due in part to the high apparent mobility of the guaiacol ion and in part to alterations which it produces in the protoplasm (such alterations increase the P.D. across the protoplasm whereas ordinary injury would be expected to lower it and the cells live on after this treatment and show no signs of injury).

This action of the guaiacol ion is in marked contrast to the behavior of other anions whose effect resembles that of Cl-.
POLARIZATION STUDIES IN COLLODION MEMBRANES AND IN SYNTHETIC PROTEIN-LIPOID MEMBRANES
Authors: Spiegel-Adolf Mona
Published: May 2004

1. Collodion membranes of high polarizability and low resistance can be obtained either by addition of certain ether-soluble substances such as phosphatides, olive oil, mastix, and gum benzoin, to the collodion or by drying collodion membranes for a limited time under pressure.

2. The permeability of membranes of different polarization has been measured by means of conductivity methods.

3. Sintered glass filter plates of Jena glass crucibles on which proteins and lipoids have been adsorbed show polarization. It could be shown that some narcotics which react with lecithin cause an increase in polarization of the protein-lipoid-glass system. Substitutions of the protein but not of the lipoid were possible, without causing a decrease in the polarizability of the membranes.
THE INFLUENCE OF LIGHT AND CARBON DIOXIDE ON PHOTOSYNTHESIS
Authors: Smith Emil L.
Published: May 2004

1. An optical system is described which furnishes an intensity of 282,000 meter candles at the bottom of a Warburg manometric vessel. With such a high intensity available it was possible to measure the rate of photosynthesis of single fronds of Cabomba caroliniana over a large range of intensities and CO2 concentrations.

2. The data obtained are described with high precision by the equation KI = p/(p2max. – p2)½ where p is the rate of photosynthesis at light intensity I, K is a constant which locates the curve on the I axis, and pmax. is the asymptotic maximum rate of photosynthesis. With CO2 concentration substituted for I, this equation describes the data of photosynthesis for Cabomba, as a function of CO2 concentration.

3. The above equation also describes the data obtained by other investigators for photosynthesis as a function of intensity, and of CO2 concentration where external diffusion rate is not the limiting factor. This shows that for different species of green plants there is a fundamental similarity in kinetic properties and therefore probably in chemical mechanism.

4. A derivation of the above equation can be made in terms of half-order photochemical and Blackman reactions, with intensity and CO2 concentration entering as the first power, or if both sides of the equation are squared, the photochemical and Blackman reactions are first order and intensity and CO2 enter as the square. The presence of fractional exponents or intensity as the square suggests a complex reaction mechanism involving more than one photochemical reaction. This is consistent with the requirement of 4 quanta for the reduction of a CO2 molecule.
THE EFFECT OF NaCl ON THE PHAGE-BACTERIUM REACTION
Authors: Scribner E. J. , Krueger A. P.
Published: May 2004

1. The presence of 0.25 M NaCl during the reaction between a staphylococcus phage and susceptible organisms results in a five to tenfold increase in the amount of phage produced.

2. Analysis of the reaction indicates that normal kinetic relationships exist until just before lysis occurs. At this time the organisms enter the stationary phase, lysis is delayed approximately 0.7 hour as compared with control mixtures and phage continues to be produced at the usual rapid rate.

3. Apparently there are conditions under which phage can be produced in the absence of bacterial growth although previous work has uniformly emphasized growth of the bacterial substrate as the prime conditioning factor for formation of phage.
THE RELATIONSHIP BETWEEN BACTERIAL GROWTH AND PHAGE PRODUCTION
Authors: Krueger Albert P. , Fong Jacob
Published: May 2004

1. The effects of temperature and H-ion concentration on the reaction between antistaphylococcus phage and a susceptible staphylococcus have been studied.

2. The temperature optimum for phage production is in the neighborhood of 35°C. and that for bacterial growth is approximately 40°C.

3. With increasing H-ion concentrations there occur: (a) an increase in the lag phase of bacterial growth without any corresponding increase in the lag phase of phage production; (b) a diminution in the total bacterial population accumulating in the medium without any corresponding drop in the total amount of phage formed.

4. With increasing alkalinity there is no pronounced change in the curves of bacterial growth and phage formation. At pH 8.5 the lytic threshold is increased to about 1000 phage units per bacterium instead of 100–140 as is usually the case and the time of lysis is delayed.

5. By adjusting the medium to pH 6 and 28°C. bacterial growth can be completely inhibited while phage production continues at a rapid rate.

6. Apparently, the previously stressed importance of bacterial growth as the prime conditioning factor for phage formation does not hold, for under certain experimental conditions the two mechanisms can be dissociated.
AREA AND VISUAL THRESHOLD
Authors: Wald George
Published: May 2004

1. The variation of threshold with field area was measured in fields homogeneous in rod-cone composition. At 15° above the fovea, an increase in field diameter from 1° to 5° reduces the threshold sevenfold, at 25° above the fovea tenfold.

2. These changes are shown to follow qualitatively from simple statistical properties of the retinal mosaic. Analytic treatment leads to the expression, (A – nt)k I = C, in which A = area, nt = constant threshold number of elements, I = threshold intensity, and k and C are constants. This equation describes the available data accurately, and is the general form of previous empirical area-threshold formulae.
STUDIES ON ENZYMATIC HISTOCHEMISTRY
Authors: Glick David
Published: May 2004

Extraction experiments demonstrated that choline esterase could be removed from microtome sections of tissue with as great facility by 0.9 per cent NaCl as by 30 per cent glycerol.

The quantitative distribution of choline esterase through the wall of the pig stomach was studied, and it was found that the epithelial cell region possessed the greatest activity and muscle tissue the least. Pylorus was more active than fundus or cardia.

The enzyme activities found were independent of the physiological state of the normal stomach at the time the animal was killed.

Neither intramuscular injection of acetyl choline, eserine, nor atropine shortly before killing had significant influence upon the activity in any region of the stomach.

The implications of these results were discussed.
CHOLINE ESTERASE AND THE THEORY OF CHEMICAL MEDIATION OF NERVE IMPULSES
Authors: Glick David
Published: May 2004

The maximum choline esterase activity of the superior cervical ganglion of the cat was measured and found to be, on the average, equivalent to the splitting of 0.10γ of acetyl choline chloride per second per milligram of fresh tissue at a pH of 7.4 and 38°. The least possible time required for destruction of the ester liberated by one nerve impulse was calculated to be 0.015σ.

The dissociation constant of the reaction between the enzyme and acetyl choline chloride was determined, and a value of 0.001 was obtained.

From the value of the dissociation constant, the time for hydrolysis at the minimum rate was calculated to be about 8 seconds.

It was shown that a localization of enzyme and substrate within the ganglion cell would have to exist in order that enzymatic destruction of acetyl choline liberated by nerve impulses occur within the span of the refractory period.
THE KINETICS OF EXCYSTMENT IN COLPODA DUODENARIA
Authors: Brown M. G. , Taylor C. V.
Published: May 2004

1. Extensive experimental data have been collected on the time required for the excystment process of the small ciliate Colpoda duodenaria throughout a range of temperatures of 8° through 32°C. and a range of concentrations of yeast extract excystment media of 0.08 through 22.4 gm./liter.

2. The excystment process has been separated into two periods, the first inversely proportional to the concentration of the yeast extract and the second independent of its concentration.

3. The first excystment period has been found to depend on the time for diffusion through the protoplasm of a compound from the yeast extract and on the time for a chemical reaction with the extremely high energy of activation of 220,000 calories/mole.

4. The changes in viscosity with temperature for this Colpoda, inferred from diffusion rate changes, have been found to be almost the same as those found by Heilbrunn for Amoeba dubia by the direct method of centrifuging granules.

5. The second excystment period is shown to be controlled by reactions whose apparent activation energies are 44,000 calories/mole below 15°C. and 18,000 calories/mole above 15°C.; above 25°C. this period is independent of temperature.

6. The distribution of the log excystment times of individual organisms about the mean log excystment time is found to be independent of temperature except in the range where the reaction with highest activation energy takes a significant length of time, and to increase rapidly with decreasing temperatures in this range.
ON RHODOPSIN IN SOLUTION
Authors: Wald George
Published: May 2004

1. The properties of rhodopsin in solution have been examined in preparations from marine fishes, frogs, and mammals.

2. The bleaching of neutral rhodopsin in solution includes a photic and at least three thermal ("dark") processes. Thermal reactions account for approximately half the total fall in extinction at 500 mµ.

3. Bleaching has been investigated at various pH's from 3.9 to about 11. With increase in pH the velocity of the thermal components increases rapidly. Though the spectrum of rhodopsin itself is scarcely affected by change in pH, the spectra of all product-mixtures following irradiation are highly pH-labile.

4. The spectrum of pure rhodopsin—or of the rhodopsin chromophore—is fixed within narrow limits. The extinction at 400 mµ lies between 0.20 to 0.32 of that at the maximum.

5. Within the limitations of available data, the spectrum of pure rhodopsin corresponds in form and position with the spectral sensitivity of human rod vision, computed at the retinal surface.

6. The nature of bleaching of rhodopsin in solution, its kinetics, and its significance in the retinal cycle are discussed.
INTENSITY DISCRIMINATION IN THE HUMAN EYE
Authors: Hecht Selig , Peskin James C. , Patt Marjorie
Published: May 2004

1. A new apparatus is described for measuring visual intensity discrimination over a large range of intensities, with white light and with selected portions of the spectrum. With it measurements were made of the intensity ΔI which is just perceptible when it is added for a short time to a portion of a field of intensity I to which the eye has been adapted.

2. For white and for all colors the fraction ΔI/I decreases as I increases and reaches an asymptotic minimum value at high values of I. In addition, with white light the relation between ΔI/I and I shows two sections, one at low intensities and the other at high intensities, the two being separated by an abrupt transition. These findings are contrary to the generally accepted measurements of Koenig and Brodhun; however, they confirm the recent work of Steinhardt, as well as the older work of Blanchard and of Aubert. The abrupt transition is in keeping with the Duplicity theory which attributes the two sections to the functions of the rods and cones respectively.

3. Measurements with five parts of the spectrum amplify these relationships in terms of the different spectral sensibilities of the rods and cones. With extreme red light the relation of ΔI/I to I shows only a high intensity section corresponding to cone function, while with other colors the low intensity rod section appears and increases in extent as the light used moves toward the violet end of the spectrum.

4. Like most of the previously published data from various sources, the present numerical data are all described with precision by the theory which supposes that intensity discrimination is determined by the initial photochemical and chemical events in the rods and cones.
THE KINETICS OF PENETRATION
Authors: Jacques A. G.
Published: May 2004

When Valonia cells are impaled on capillaries, it is in some ways equivalent to removing the comparatively inelastic cellulose wall. Under these conditions sap can migrate into a free space and it is found that on the average the rate of increase of volume of the sap is 15 times what it is in intact cells kept under comparable conditions.

The rate of increase of volume is a little faster during the first few hours of the experiment, but it soon becomes approximately linear and remains so as long as the experiment is continued.

The slightly faster rate at first may mean that the osmotic pressure of the sap is approaching that of the sea water (in the intact cell the sap osmotic pressure is always slightly above that of the sea water). This might result from a more rapid entrance of water than of electrolyte, as would be expected when the restriction of the cellulose wall was removed.

During the linear part of the curve the osmotic concentration and the composition of the sap suffer no change, so that entrance of electrolyte must be 15 times as fast in the impaled cells as it is in the intact cells.

The explanation which best accords with the facts is that in the intact cell the entrance of electrolyte tends to increase the osmotic pressure. As a consequence the protoplasm is partially dehydrated temporarily and it cannot take up more water until the cellulose wall grows so that it can enclose more volume. The dehydration of the protoplasm may have the effect of making the non-aqueous protoplasm less permeable to electrolytes by reducing the diffusion and partition coefficients on which the rate of entrance depends. In this way the cell is protected against great fluctuations in the osmotic concentration of the sap.
THE PARTIAL REACTIVATION OF FORMOLIZED TOBACCO MOSAIC VIRUS PROTEIN
Authors: Ross A. Frank , Stanley W. M.
Published: May 2004

A marked reactivation of tobacco mosaic virus protein that has been partially or completely inactivated by formaldehyde was obtained by dialysis at pH 3. The activity of partially inactivated virus proteins was generally increased about 10-fold by the reactivation process. It was also found possible to reactivate completely inactive preparations to an appreciable extent. It was shown that the inactivation and the subsequent reactivation cannot be explained by the toxicity of the formaldehyde or of the formolized protein or by aggregation.

Inactivation was accompanied by a decrease in amino groups as indicated by Van Slyke gasometric determinations and by colorimetric estimations using ninhydrin. Inactivation also causes a decrease in the number of groups that react with Folin's reagent at pH 7.7. The latter are probably the indole nuclei of tryptophane, for it was demonstrated that tryptophane, glycyltryptophane, and indole propionic acid react with formaldehyde in a similar manner, while tyrosine and glycyltyrosine do not. Evidence that reactivation is accompanied by an increase in amino nitrogen and in groups that react with Folin's reagent was obtained by colorimetric estimation.

The demonstration that the addition of formaldehyde to the virus protein results in a simultaneous decrease of activity, of amino groups, and of groups that react with Folin's phenol reagent, and that under conditions favorable for the removal of formaldehyde the virus activity is regained and the number of such groups increases, indicates that certain of these groups play at least a partial role in the structure necessary for virus activity. These changes can best be interpreted on the basis of known chemical reactions and are considered as evidence that virus activity is a specific property of the protein.
ON THE DISTRIBUTION OF VITAMINS A1 AND A2
Authors: Wald George
Published: May 2004

The distribution of vitamins A1 and A2 has been determined in the eye tissues and livers of a number of fishes. The vitamins were differentiated by means of the antimony chloride reaction, which yields with A1 a band at 615–620 mµ and with A2 a band at about 696 mµ. In the retina the presence of vitamin A1 is diagnostic of the operation of a rhodopsin, and vitamin A2 of a porphyropsin cycle.

The eye tissues of all permanently marine fishes examined, except the tautog, contain vitamin A1 alone. Those of all permanently freshwater fishes possess only vitamin A2. Those of all euryhaline (potentially migratory) fishes, except possibly the alewife, contain mixtures of both vitamins A, and always predominantly that one which ordinarily is associated with the environment in which the fish is spawned.

These correlations extend in part to the liver oils, but most livers contain mixtures of both vitamins A, and occasionally in proportions the reverse of those in the eye tissues.

The vitamin A configuration does not depend upon environmental circumstances, but is determined genetically. The transfer from vitamin A1 to A2 metabolism appears associated phylogenetically with migration of marine teleosts into fresh water.
THE KINETICS OF PENETRATION
Authors: Jacques A. G.
Published: May 2004

The exit of accumulated ammonia from the sap of Valonia macrophysa, Kütz., into normal (nearly ammonia-free) sea water, has been studied in light (alternation of daylight and darkness) and in darkness. Exit is always preceded by an induction period lasting 1 or more days. This is longer in darkness. After exit starts the rate is greater in light than in darkness.

The pH of the sap drops off soon after the cells are exposed to normal sea water even before any definite decrease in the ammonia concentration of the sap has occurred. This suggests that the decrease in the pH is due to the loss of a very small amount of NH3 or NH4OH without a corresponding gain of sodium as a base.

In most cases sodium replaced the ammonia lost during exit, but there is some evidence that potassium may also replace ammonia.

To account for the induction period it is suggested that other species than NH4X are concerned in the transport of ammonia, for example urea or amino acids.
TEMPERATURE ACTIVATION OF THE UREASE-UREA SYSTEM USING CRUDE AND CRYSTALLINE UREASE
Authors: Sizer Irwin W.
Published: May 2004

1. The hydrolysis of urea catalyzed by jack bean meal has been followed by determining colorimetrically after Nesslerization the ammonia nitrogen, and volumetrically the carbon dioxide liberated at successive intervals during the reaction. During the early part of hydrolysis the rate of ammonia or carbon dioxide liberation is constant for all the urease solutions which were used.

2. When log rate of NH3 or CO2 formation was plotted against 1/T, the points fell along a straight line, the slope of which corresponded to an activation energy of either 8,700 or 11,700 calories per gram mol. Frequently urease, when dissolved in sulfite solution, was characterized by an activation energy of 11,700 below and 8,700 above the critical temperature of about 23°C. At high temperatures the plotted points fell off from the curve due to temperature inactivation.

3. Essentially the same results on temperature activation were obtained with crude jack bean meal, Arlco urease, crystalline urease not recrystallized, and crystalline urease once recrystallized. The temperature characteristic which was obtained depended in part upon the composition of the medium. When dissolved in water, or aqueous solutions of glycerine, KCN, Na2S2O2, cystine, Na2SO4, and K4Fe(CN)6, the temperature characteristic or µ of urease is 8,700. On the other hand, when urease is dissolved in solutions of K3Fe(CN)6 or H2O2 the µ value is 11,700. When dissolved in a solution containing Na2SO3 and NaHSO3 the µ value may be either 8,700 or 11,700 over the whole temperature range, or 11,700 below and 8,700 above 23°C.

4. When crystalline urease is dissolved in varying mixtures of K4Fe(CN)6 and K3Fe(CN)6, the temperature characteristic depends upon the oxidation-reduction potential of the digest. When Eh is greater than +0.46 volt µ = 11,700, when less than +0.42 volt µ = 8,700, when between +0.42 – +0.46 µ = 11,700 below and 8,700 above the critical temperature.

5. It is suggested that in reducing or in indifferent solutions the configuration of the urease molecule (as determined especially by SH groups present) is such that the activation energy is 8,700 calories. In oxidizing solutions the urease molecule has been so altered (perhaps by the oxidation of the SH groups) as to be partly inactivated and now has an activation energy of 11,700. Such changes in the urease molecule are reversible (unless oxidation has proceeded too far) and are accompanied by a corresponding change in the activation energy.
THE KINETICS OF PENETRATION
Authors: Jacques A. G.
Published: May 2004

The rate of entrance of water into impaled cells of Halicystis Osterhoutii, Blinks and Blinks, has been determined directly by measurements of the rise of sap in a capillary for dilute sea waters (containing between 90 and 30 per cent sea water).

The velocity constant remains reasonably constant down to 50 per cent sea water but it decreases markedly in lower concentrations.
THE KINETICS OF PENETRATION
Authors: Jacques A. G.
Published: May 2004

When cells of Halicystis are impaled on a capillary so that space is provided into which the sap can migrate, the rate of entrance of water and of electrolyte is increased about 10-fold. In impaled Valonia cells the rate is increased about 15-fold.

After a relatively rapid non-linear rate of increase of sap volume immediately after impalement (which may possibly represent the partial dissipation of the difference of the osmotic energy between intact and impaled cells) the volume increases at a linear rate, apparently indefinitely.

Since the halide concentration of the sap at the end of the experiment is (within the limits of natural variation) the same as in the intact cell, we conclude that electrolyte also enters the sap about 10 times as fast as in the intact cell.

As in the case of Valonia we conclude that there is a mechanism whereby in the intact cell the osmotic concentration of the sap is prevented from greatly exceeding that of the sea water. This may be associated with the state of hydration of the non-aqueous protoplasmic surfaces.
THE PORPHYROPSIN VISUAL SYSTEM
Authors: Wald George
Published: May 2004

1. In the rods of fresh-water and some anadromous fishes, rhodopsin is replaced by the purple photolabile pigment porphyropsin. This participates in a retinal cycle identical in form with that of rhodopsin, but in which new carotenoids replace retinene and vitamin A.

2. Porphyropsin possesses a broad absorption maximum at 522 ± 2 mµ, and perhaps a minimum at about 430 mµ. The vitamin A-analogue, vitamin A2, possesses a maximum in chloroform at 355 mµ and yields with antimony trichloride a deep blue color due to a band at 696 mµ. The retinene-analogue, retinene2, absorbs maximally in chloroform at 405 mµ and possesses an antimony chloride maximum at 706 mµ.

3. Its non-diffusibility through a semi-permeable membrane, salting-out properties, and sensitivity to chemical denaturants and to heat, characterize porphyropsin as a conjugated carotenoid-protein.

4. The porphyropsin cycle may be formulated: porphyropsin

See PDF for Structure.

retinene2-protein (2)→ vitamin A2-protein (3)→ porphyropsin. Isolation of the retina cuts this cycle at (3); denaturation procedures or extraction of porphyropsin into aqueous solution eliminate in addition (1) and (2).

5. The primary difference between the rhodopsin and porphyropsin systems appears to be the possession by the latter of an added ethylenic group in the polyene chain.
THEORY AND MEASUREMENT OF VISUAL MECHANISMS
Authors: Crozier W. J. , Holway A. H.
Published: May 2004

Measurements of ΔI as a function of retinal area illuminated have been obtained at various levels of standard intensity I1, using "white" light and light of three modal wave-lengths (λ465, 525, 680), for monocular stimulation and for simultaneous excitation of the two eyes ("binocular"), using several methods of varying (rectangular) area and retinal location, with control of exposure time.

For data homogeneous with respect to method of presentation,

log ΔIm = -Z log A + C,

where ΔI = Ĩ2 – I1, A is area illuminated, and C is a terminal constant (= log ΔIm for A = 1 unit) depending on the units in which ΔI and A are expressed, and upon I1.

The equation is readily deduced on dimensional grounds, without reference to specific theories of the nature of ΔI or of retinal area in terms of its excitable units. Z is independent of the units of I and A. Experimentally it is found to be the same for monocular and binocular excitations, as is to be expected. Also as is expected it is not independent of λ, and it is markedly influenced by the scheme according to which A is varied; it depends directly upon the rate at which potentially excitable elements are added when A is made to increase.

For simultaneous excitation of the two eyes (when of very nearly equivalent excitability), ΔĪB is less than for stimulation of either eye alone, at all levels of I1, A, λ. The mean ratio (ΔĪL + ΔĪR)/2 to ΔIB was 1.38. For white light, doubling A on one retina reduces ΔIm in the ratio 1.21, or a little less than for binocular presentation under the same conditions. These facts are consistent with the view that the properties of ΔI are quantitatively determined by events central to the retina.

The measure σ1ΔI of organic variation in discrimination of intensities and ΔIm are found to be in simple proportion, independent of I1, A, λ (and exposure time). Variability (σ1ΔI) is not a function of the mode of presentation, save that it may be slightly higher when both retinas are excited, and its magnitude (for a given level of ΔIm) is independent of the law according to which the adjustable intensity I2 is instrumentally controlled.
CALCULATIONS OF BIOELECTRIC POTENTIALS
Authors: Osterhout W. J. V.
Published: May 2004

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.