bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.