bluuebunny/crossref_metadata_2025 huggingface dataset:
THE DARK ADAPTATION OF THE HUMAN EYE
Authors: Hecht Selig
Published: May 2004

During the dark adaptation of the human eye, its visual threshold decreases to a small fraction of its original value in the light. An analysis of the quantitative data describing this adaptation shows that it follows the course of a bimolecular chemical reaction. On the basis of these findings it is suggested that visual reception in dim light is conditioned by a reversible photochemical reaction involving a photosensitive substance and its two products of decomposition. Accordingly, dark adaptation depends on the course of the "dark" reaction during which the two products of decomposition reunite to synthesize the original photosensitive substance.
THE INFLUENCE OF THE SUBSTRATE CONCENTRATION ON THE RATE OF HYDROLYSIS OF PROTEINS BY PEPSIN
Authors: Northrop John H.
Published: May 2004

1. It is pointed out that the apparent exceptions to the law of mass action found in enzyme reactions may be found in catalytic reactions in strictly homogeneous solutions.

2. These deviations in the rate of reaction from the law of mass action may be explained by the hypothesis that the active mass of the reacting substances is not directly proportional to the total concentration of substance taken.

3. In support of this suggestion it is shown that for any given concentration of pepsin the relative rate of digestion of concentrated and of dilute protein solutions is always the same. If the rate of digestion depended on the saturation of the surface of the enzyme by substrate the relative rate of digestion of concentrated protein solutions should increase more rapidly with the concentration of enzyme than that of dilute solutions. This was found not to be true, even when the enzyme could not be considered saturated in the dilute protein solutions.

4. The rate of digestion and the conductivity of egg albumin solutions of different concentration were found to be approximately proportional at the same pH. This agrees with the hypothesis first expressed by Pauli that the ionized protein is largely or entirely the form which is attacked by the enzyme.

5. The rate of digestion is diminished by a very large increase in the viscosity of the protein solution. This effect is probably a mechanical one due to the retardation of the diffusion of the enzyme.
COMPARATIVE STUDIES ON RESPIRATION
Authors: Gustafson F. G.
Published: May 2004

1. Variations in pH value between 4 and 8 produce practically no effect on the normal rate of respiration (the rate at neutrality is called normal).

2. Increasing the pH value to 8.80 causes respiration to fall to 60 per cent of the normal, after which it remains stationary for the duration of the experiment.

3. Decreasing the pH value to 2.65 causes a gradual rise and a gradual return to normal; at pH 1.10 to 1.95 the preliminary rise amounts to 20 per cent and is followed by a fall to below the normal.

4. The decrease in respiration brought about by solutions of a pH value of 1.95 or less are irreversible, while a similar decrease which occurs at pH 8.80 is reversible, the rate coming back to practically normal after the material is replaced in a neutral solution.

5. Determinations by means of Winkler's method showed an increase in the consumption of oxygen in acid solutions and a decrease in alkaline solutions.
THE KINETICS OF THE ACTION OF CATALASE EXTRACT FROM MARINE ALGÆ, WITH A NOTE ON OXIDASE
Authors: Hampton Harold Clark , Baas-Becking Lourens G. M.
Published: May 2004

Ulva tæniata contains oxidase. The existence of peroxidase is not proved.
QUANTITATIVE LAWS IN REGENERATION. II
Authors: Loeb Jacques
Published: May 2004

This paper contains the results of a reexamination of a law expressed in a previous paper; namely, that when a piece of stem inhibits the growth of shoots and roots in a leaf connected with it the dry weight of the stem increases and that this gain equals approximately the mass of shoots and roots the leaf would have produced if it had been detached from the stem. This has been confirmed and it has been shown that the gain of the stem as a rule even exceeds slightly the mass of shoots and roots the leaf would have produced if it had not been inhibited by the stem. This supports the idea that the inhibitory influence of the stem upon the formation of roots and shoots in the leaf is due to the fact that the material available and required for this process naturally flows into the stem.
PIGMENTS OF THE RETINA
Authors: Wald George
Published: May 2004

1. Visual purple from the sea robin, sea bass, and scup is almost identical spectroscopically with that from frogs. The interrelations of this pigment with vitamin A and retinene are also the same as in the frog.

2. In strong acids or at pH > 11, the visual yellow of sea robin retinas is converted irreversibly into a pH indicator, yellow in acid and almost colorless in alkaline solution. Unlike neutral visual yellow, the indicator is not removed to form either vitamin A or visual purple. In the ammoniacal retina the reversion of visual yellow itself to purple is accelerated.

3. The combined pigment epithelium and choroid layer in these fishes contain vitamin A, flavine, and an unidentified xanthophyll.
SUBSTANCES AFFECTING ADULT TISSUE IN VITRO
Authors: Simms Henry S. , Stillman Nettie P.
Published: May 2004

1. The growth of fresh adult tissue in plasma medium suggested that plasma contained a substance active in overcoming the dormancy of adult tissues.

2. Incubation of adult chicken aorta in serum (from chickens or other species) before it was planted in a plasma medium, resulted in a much shorter lag period and a faster initial growth than that of control tissue incubated in Tyrode solution (or of fresh untreated tissue). In other words, serum helped overcome the dormancy of adult tissue while Tyrode solution preserved the tissue in a dormant state. This activity of serum was shown to be due neither to its albumin or globulin nor to its lipase or other enzymes.

3. The ultrafiltrate from serum was highly active in overcoming adult tissue dormancy, while the dialyzed residue was inactive. The ultrafiltrate was not species specific. It withstood 100°C. in neutral solution for 10 minutes, but not for 3 hours, and was destroyed at pH 2 and pH 12. It was active after 10 months in the ice box. It does not affect tissues in the cold.

4. Copper acetate precipitated a fraction from serum ultrafiltrate which, when freed from copper, was stimulating to the initial growth of adult aorta tissue.

5. Calcium chloride precipitated fractions from serum ultrafiltrate (and also from urine) which were stimulating.

6. Attempts to concentrate the A factor, the active agent, by vacuum evaporation and subsequent fractionation with different solvents were not satisfactory.

7. Lymph was highly stimulating and ventricular fluid slightly stimulating.

8. No growth was obtained in the absence of the A factor, but we doubt that it is alone responsible for overcoming the dormancy of adult tissue.
A METHOD FOR THE INVESTIGATION OF ELECTROSTENOLYSIS
Authors: Fetcher E. S. , Lillie R. S. , Harkins W. D.
Published: May 2004

A quantitative method for the investigation of electrostenolysis has been developed. Electrostenolysis is redefined in the light of the discovery that organic molecules are subject to it. The experimental requirements for a quantitative study are enumerated, and the apparatus and procedure described.

It is found that with ferrous and ferric ions and a cellulose acetate membrane, the potential drop across the membrane must be above about 2150 v./cm. in order to effect any oxidation and reduction. With the present apparatus and conditions the ratio of equivalents oxidized or reduced to faradays passing the membrane is low,— of the order of one to several thousand.
THE INDUCTION PERIOD IN PHOTOSYNTHESIS
Authors: Smith Emil L.
Published: May 2004

1. Measurements on the photosynthesis of Cabomba caroliniana show an induction period at low and high light intensities and CO2 concentrations.

2. The equation which describes the data for Cabomba also describes the data obtained by other investigators on different species. The phenomenon is thus shown to be similar in plants representative of three phyla.

3. A derivation of the induction period equation is made from a consideration of the cycle of light and dark processes known to occur in photosynthesis. The equation indicates that light intensity enters as the square, and that the same light reactions are involved as those which affect the stationary state rates. However, a different dark reaction appears to limit photosynthesis during the induction period.
THE ABSORPTION SPECTRUM OF VISUAL PURPLE
Authors: Chase Aurin M. , Haig Charles
Published: May 2004

The absorption spectra of visual purple solutions extracted by various means were measured with a sensitive photoelectric spectrophotometer and compared with the classical visual purple absorption spectrum.

Hardening the retinas in alum before extraction yielded visual purple solutions of much higher light transmission in the blue and violet, probably because of the removal of light-dispersing substances.

Re-extraction indicated that visual purple is more soluble in the extractive than are the other colored retinal components. However, the concentration of the extractive did not affect the color purity of the extraction but did influence the keeping power. This suggests a chemical combination between the extractive and visual purple.

The pH of the extractive affected the color purity of the resulting solution. Over the pH range from 5.5 to 10.0, the visual purple color purity was greatest at the low pH. Temperature during extraction was also effective, the color purity being greater the higher the temperature, up to 40°C.

Drying and subsequent re-dissolving of visual purple solutions extracted with digitalin freed the solution of some protein impurities and increased its keeping power. Dialysis against distilled water seemed to precipitate visual purple from solution irreversibly.

None of the treatments described improved the symmetry of the unbleached visual purple absorption spectrum sufficiently for it to resemble the classical absorption spectrum. Therefore it is very likely that the classical absorption spectrum is that of the light-sensitive group only and that the absorption spectra of our purest unbleached visual purple solutions represent the molecule as a whole.
SUCROSE INVERSION BY BAKERS' YEAST AS A FUNCTION OF TEMPERATURE
Authors: Sizer Irwin W.
Published: May 2004

Inversion of sucrose by bakers' yeast follows the same course as inversion catalyzed by yeast invertase. Rate of inversion increases exponentially with temperature; the temperature characteristic in the Arrhenius equation is 10,700 below 13–17°C., and 8,300 above that temperature. Temperature inactivation occurs above 40°C. The effects of temperature upon rate of inversion were the same using Fleischmann's yeast cake, the same yeast killed with toluene, and a pure strain (G. M. No. 21062) of bakers' yeast. The last differed from the other two only in the fact that its critical temperature was 13°C. as compared with 17°C. for the others.

The catalytic inversion is associated with enzyme activity inside the cell, not in the medium, and is independent of any vital processes inside the cell such as respiration and fermentation. Since invertase activity is the same inside the cell as it is after extraction, it appears possible to relate the temperature characteristics for physiological processes to the catalytic chemical systems which determine their rate.

At least two enzymes are capable of inverting sucrose in the yeast cell. The familiar yeast invertase (µ = 10,700) is active below 13–17°C. while a second enzyme (M = 8,300) plays the dominant role above that temperature.
DEVELOPMENT OF EYE COLORS IN DROSOPHILA: SOME PROPERTIES OF THE HORMONES CONCERNED
Authors: Tatum Edward L. , Beadle G. W.
Published: May 2004

The substance inducing the production of pigment in the eyes of vermilion brown mutants of Drosophila melanogaster has been shown to be a relatively stable chemical entity possessing true hormone-like activity.

A simple method for obtaining hormone solutions has been developed involving extraction of dried wild type Drosophila pupae with ethyl alcohol and water.

A logarithmic proportionality has been found to exist between the amount of hormone and the induced eye color. This relationship provides a simple method for the quantitative determination of hormone concentration in given extracts.

Larvae and pupae of D. melanogaster contain an intracellular enzyme which inactivates the hormone in the presence of molecular oxygen. The hormone is not oxidized under ordinary conditions with either molecular oxygen or hydrogen peroxide.

The hormone has been found to be an amphoteric compound with both acidic and basic groups and with a molecular weight between 400 and 600.

The solubility and precipitation reactions of the hormone suggest its amino acid-like nature. However, the instability to heat, acid, and alkali, and its rather restricted occurrence indicate a rather complex specific structure.
THE INFLUENCE OF THE MOLECULAR WEIGHT OF ANTIGEN ON THE PROPORTION OF ANTIBODY TO ANTIGEN IN PRECIPITATES
Authors: Boyd William C. , Hooker Sanford B.
Published: May 2004

A statistical examination of the available data on the ratio of antibody to antigen in specific precipitates made at or near the optimum shows a definite correlation between the ratio and the molecular weight of antigen (regression coefficient = –0.529 (±0.014)). The authors' assumption that at this point the antigen molecules are just about covered by a layer of antibody behaving as contiguous spherical ("Svedberg") units of weight 35,200 leads to predicted ratios that in general agree well with those found, though individual experimental determinations may deviate considerably.
THE CHLOROPHYLL-CARBON DIOXIDE RATIO DURING PHOTOSYNTHESIS
Authors: McAlister E. D.
Published: May 2004

Using a rapid spectrographic method of carbon dioxide measurement previously described by McAlister (1937) further studies on the time course of photosynthesis in the higher plant, wheat, variety Marquis, are herein reported. Of major importance in this work is the discovery of a pick-up of carbon dioxide in darkness immediately following a high rate of photosynthesis (see Figs. 3 and 4). This pick-up is believed to be due to the action of a carbon dioxide-combining intermediate; i.e., the "acceptor molecule" for carbon dioxide in photosynthesis. The conditions under which this phenomenon has so far been observed indicate that the intermediate is formed in relatively large quantities during the actual process of photosynthesis and not before. That the intermediate is chlorophyllous in nature is suggested by a simple stoichiometry of the order of unity that is found to exist between the number of carbon dioxide molecules taken up and the total number of chlorophyll molecules present in the plant. This is in opposition to the idea of a large photosynthetic unit of some 2000 chlorophyll molecules operating together in the reduction of 1 carbon dioxide molecule.

Further studies of the induction phase under various conditions of previous dark rest and of carbon dioxide and light limitation are herein described. Employing the simple hypothesis that the number of carbon dioxide molecules not reduced during the induction period (induction loss) gives a measure of the number of elementary photosynthetic cycles unoperative or compensated for during induction together with the experimental fact that this induction loss is of the order of the total number of chlorophyll molecules present, these latter studies also indicate, in a less direct manner, that chlorophyll participates in photosynthesis as an individual molecule and not as part of a very large multimolecular chlorophyll unit.

The fast dark reaction lasting about 1 minute (Fig. 7) required to reproduce both (a) the phenomena of induction in carbon dioxide assimilation and (b) the recovery of fluorescence of chlorophyll in leaves in darkness as observed by Franck and Wood (1936), demonstrates a close relationship between the fluorescence of chlorophyll and induction in photosynthesis.

The rate of respiration (carbon dioxide production) of the higher plant, wheat, was measured under intense illumination and in the absence of carbon dioxide (to suppress assimilation). This value was found to be identical with the dark respirational rate measured before and after the light period, indicating very positively the absence of any direct effect of light on respiration.
THE EFFECTS OF PANTOTHENIC ACID ON RESPIRATORY ACTIVITY
Authors: Pratt Ernest F. , Williams Roger J.
Published: May 2004

Experiments using the Warburg-Barcroft apparatus led to the following results and conclusions: (1) Two yeasts in three different media were strikingly stimulated in their respiration by minute amounts of pantothenic acid. (2) Nine other compounds (vitamins and other biologically important substances) were tested and found in all cases to have on the deficient G.M. yeast, lesser and in some cases no appreciable stimulative effect. Thiamin was the most effective of these compounds. Its action was shown to be different and in some ways antagonistic to that of pantothenic acid. (3) Liver extract (Lilly's Number 343) contains substances capable of speeding up respiration (and growth) to a much higher level than seems possible with known compounds. (4) Pantothenic acid was found to have a definite stimulative effect on fermentation by dialyzed maceration juice from yeast. (5) It likewise stimulated respiration of apple and potato tissue and indications of a similar effect on certain animal tissues were obtained.
PHYSICOCHEMICAL PROPERTIES OF THE PROTEOLYTIC ENZYME FROM THE LATEX OF THE MILKWEED, ASCLEPIAS SPECIOSA TORR. SOME COMPARISONS WITH OTHER PROTEASES
Authors: Winnick Theodore , Davis Alva R. , Greenberg David M.
Published: May 2004

1. The kinetics of milk clotting by asclepain, the protease of Asclepias speciosa, were investigated. At higher concentrations of enzyme, the clotting time was inversely proportional to the enzyme concentration.

2. The digestion of casein and hemoglobin in 6.6 M urea by asclepain follows the second order reaction rate. The rate was roughly second order for casein in water.

3. Evaluation of the nature of the enzyme-substrate intermediate indicates that one molecule of asclepain combines with one molecule of casein or hemoglobin in urea solution.

4. Inhibition by the reaction products was deduced from the fact that the digestion velocity of hemoglobin in urea solution varied with the asclepain concentration in agreement with the Schütz-Borissov rule.
TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHT
Authors: Crozier W. J. , Wolf Ernst
Published: May 2004

For the turtle Pseudemys scripta the temperature characteristics for excitability of the response to visual flicker are found to be independent of flash frequency F, flash intensity I, and proportion of light time in the flash cycle. The maximum F to which the flicker response contour (F vs. log I) rises, and the abscissa of its inflection, are rectilinear functions of the percentage light-time in the flash cycle, but µ for 1/Iat any flash frequency is the same with different values of the percentage light-time (10 to 90 per cent).

These facts, together with the properties of the variation of the critical intensity, objectively demonstrate the essentially simple or unitary character of the controlling events in the mechanism governing the excitability. They also provide a means of further illustrating a procedure whereby certain statistical factors in the performance of a population of units may be analytically separated from excitability properties common to all of the individual units. In particular, it is of general significance that it can be seen how it is possible for biologically exhibited frequencies or rates of performance to provide simple and physically significant relations to temperature, despite the fact that this performance may involve, almost inevitably does involve, the integrated actions of many individual units.
THE EFFECT OF OXIDANTS AND REDUCTANTS UPON THE BIOELECTRIC POTENTIAL OF NITELLA
Authors: Blinks L. R. , Pickett M. J.
Published: May 2004

Nitella cells were exposed to various oxidants and reductants, to determine their effect upon the bioelectric potential. These included five systems, with an Eh range from +0.454 v. to –0.288 v., a total range of 0.742 v.

When proper regard was given to buffering against acidity changes, and concentration changes of Na or K ions in the oxidized and reduced forms, no significant effect upon the bioelectric potential was found:

1. When an oxidant or reductant (K ferri- or ferrocyanide) was applied instead of an equivalent normality of an "indifferent" salt (KCl).

2. In changing from a given oxidant to its corresponding reductant (ferri- to ferrocyanide; oxidized to leuco-dye, etc.).

3. When a mixture of 2 dyes, (indophenol with positive E'0, and safranin with negative E'0) was oxidized and reduced, to give better poising at the extremes.

It is conduded that the outer surface of this cell is not influenced by the state of oxidation or reduction of the systems employed; at least it does not respond with a manifest change of bioelectric potential to changes in oxidation-reduction intensity of the medium.

The cells continued to show, however, at all times their usual response to concentration changes of KCl, NaCl, etc., and to electrical stimulation.
FRACTIONATION OF PEPSIN
Authors: Herriott Roger M. , Desreux V. , Northrop John H.
Published: May 2004

1. Solubility curves of crude pepsin preparations indicate the presence of more than one protein.

2. One of these proteins has been isolated and crystallized and found to have constant activity and constant solubility in several solvents.

3. The solubility measurements are complicated by the unstable nature of the protein and the fact that in certain solvents the solubility of the protein is markedly affected by the presence of non-protein nitrogen decomposition products while in others this is not the case.

4. A more insoluble protein has been prepared of lower solubility and lower activity, as measured by hemoglobin digestion. The activity, as measured by the digestion of other proteins, is about the same as the more soluble fraction. This insoluble fraction does not have constant solubility.

5. Mixtures of the insoluble and the soluble fractions give preparations having rounded solubility curves typical of solid solutions and resembling very closely those of the original preparation.

6. A small amount of pepsinogen and pepsin from pepsinogen has been separated which has nearly twice the enzymatic activity on hemoglobin as does the most active pepsin previously isolated.
ELECTROPHORETIC STUDIES ON HUMAN RED BLOOD CELLS
Authors: Furchgott Robert F. , Ponder Eric
Published: May 2004

1. The electrophoretic mobility of unhemolyzed human red cells has been determined as a function of ionic strength at approximately constant pH in isotonic mixtures of glucose solution and saline-phosphate buffer solution.

2. Above an ionic strength of about 0.02 the cells behave as particles with a smooth surface of large radius of curvature. Below an ionic strength of about 0.02, changes of the surface occur, probably involving a decrease of charge density and perhaps connected with injury of the surface.

3. The mobility as a function of pH at an ionic strength of 0.172 has been determined for human red cells, for the lipid extract of the cells, and for the stroma protein of the cells. The isoelectric points of cells, lipid, and protein have been found to be about 1.7, 2.6, and 4.7 respectively.

4. The pH-mobility data lead to the conclusion that a red cell surface is composed largely of lipid and dominated by strong acid groups, possibly the phosphoric acid groups of cephalin molecules.
TRANSVERSE IMPEDANCE OF THE SQUID GIANT AXON DURING CURRENT FLOW
Authors: Cole Kenneth S. , Baker Richard F.
Published: May 2004

The change in the transverse impedance of the squid giant axon caused by direct current flow has been measured at frequencies from 1 kc. per second to 500 kc. per second. The impedance change is equivalent to an increase of membrane conductance at the cathode to a maximum value approximately the same as that obtained during activity and a decrease at the anode to a minimum not far from zero. There is no evidence of appreciable membrane capacity change in either case. It then follows that the membrane has the electrical characteristics of a rectifier. Interpreting the membrane conductance as a measure of ion permeability, this permeability is increased at the cathode and decreased at the anode.
MEMBRANE POTENTIAL OF THE SQUID GIANT AXON DURING CURRENT FLOW
Authors: Cole Kenneth S. , Curtis Howard J.
Published: May 2004

The squid giant axon was placed in a shallow narrow trough and current was sent in at two electrodes in opposite sides of the trough and out at a third electrode several centimeters away. The potential difference across the membrane was measured between an inside fine capillary electrode with its tip in the axoplasm between the pair of polarizing electrodes, and an outside capillary electrode with its tip flush with the surface of one polarizing electrode.

The initial transient was roughly exponential at the anode make and damped oscillatory at the sub-threshold cathode make with the action potential arising from the first maximum when threshold was reached.

The constant change of membrane potential, after the initial transient, was measured as a function of the total polarizing current and from these data the membrane potential is obtained as a function of the membrane current density. The absolute value of the resting membrane resistance approached at low polarizing currents is about 23 ohm cm.2. This low value is considered to be a result of the puncture of the axon. The membrane was found to be an excellent rectifier with a ratio of about one hundred between the high resistance at the anode and the low resistance at the cathode for the current range investigated.

On the assumption that the membrane conductance is a measure of its ion permeability, these experiments show an increase of ion permeability under a cathode and a decrease under an anode.
ELECTRIC POTENTIAL AND ACTIVITY OF CHOLINE ESTERASE IN THE ELECTRIC ORGAN OF ELECTROPHORUS ELECTRICUS (LINNAEUS)
Authors: Nachmansohn D. , Coates C. W. , Cox R. T.
Published: May 2004

1. If the concentration of choline esterase is determined at different sections from the head to the caudal end of the electric organ of Electrophorus electricus (Linneaus) S-like curves are obtained. These curves are essentially the same as those which show the number of electric discs per centimeter and the E.M.F. per centimeter.

2. In the organ of Hunter the concentration of the enzyme does not differ from that in the adjacent parts in the main organ. This again coincides with the observations on the number of plates per centimeter in this organ.

3. The concentration of the enzyme was determined in different parts of the brain and the spinal cord and compared with that in a gold fish. The concentrations here are of the same order, but in the spinal cord of the eel the concentration is even lower than in the gold fish. As the cell bodies of the nerves innervating the electric organ in the spinal cord, these results do not lend support to the assumption of a special concentration of the enzyme in these nerves.

4. In the muscles adjacent to the electric organ an enzyme concentration has been found which is of the order of that in the electric tissue itself and much higher than in ordinary striated muscles.

5. The suitability of the organ for the preparation of enzyme solutions has been investigated and compared with that of the organ of Torpedo.
THEORY AND MEASUREMENT OF VISUAL MECHANISMS
Authors: Crozier W. J. , Wolf Ernst
Published: May 2004

The several parameters of the flicker response contour (F – log I) are considered as a function of wave-length composition (white, blue, and red) and light-time fraction, for an extra-foveal region (monocular, temporal retina). These data are compared with those secured for the same image area centrally fixated at the fovea. The systematic changes in the parameters are shown to be in rational relation to other relevant excitability data. Since for two retinal regions the primary contours are quite different, the systematic nature of the behavior of the parameters in the two cases is a real test of the power of the analysis proposed. Theoretical interpretation is required to deal with the properties of sets of performance contours under systematically varied conditions, and cannot rely simply on the comparison of (for example) two contours under the same arbitrary conditions at two retinal locations. In particular it is emphasized that a qualitative separation must be made of the two factors of (a) number of units and (b) the frequencies of their actions, before the wave-length problem can be dealt with effectively.
REVIVAL OF MAMMALIAN SPERM AFTER IMMERSION IN LIQUID NITROGEN
Authors: Hoagland Hudson , Pincus Gregory
Published: May 2004

1. A wide variety of procedures was used to test the motility of mammalian sperm after plunging them into liquid nitrogen at –195°C. and later rapidly warming them to 35°C. by plunging them into a suitable balanced and isotonic medium.

2. Using seminal fluid sperm from the same human donor, maximal numbers of motile sperm survived vitrification when the samples were (a) very fresh, (b) untreated with plasmolysing solutions, (c) plunged into the refrigerant in the form of a foam. The maximum yield of motile human sperm recoverable from the liquid nitrogen was 50 per cent. Since in this sample only 75 per cent of the sperm were alive before immersion, 67 per cent of the living sperm survived vitrification.

3. Experiments with sperm from 31 rabbits were made with a variety of conditions of pretreatment to obtain maximal yields of recoverable, motile sperm after vitrification by liquid nitrogen. (a) A consistent recoverable yield of about 0.5 per cent was obtained when the untreated suspension of sperm was smeared on cellophane and partially dried in air before immersing in liquid nitrogen. (b) On a few out of many occasions plasmolysis for several minutes with hypertonic Ringer solution gave a recoverable yield of 0.1 per cent as did (c) pretreatment with hypertonic Ringer and butyric acid.
THE REVERSIBLE INACTIVATION OF TOBACCO MOSAIC VIRUS BY CRYSTALLINE RIBONUCLEASE
Authors: Loring Hubert S.
Published: May 2004

The reversible inactivation of tobacco mosaic virus by crystalline ribonuclease is reported. Studies on the effect of time of standing on the amount of inactivation, and on the effect of dilution and repeated high speed centrifugation on the recovery of virus activity, and the preparation of an insoluble virus-enzyme complex show that the inactivation is brought about at least in part by a combination between virus and enzyme. The significance of the fact that ribonuclease has no detectable effect on the virus nucleic acid when the latter is in combination with protein in the form of virus is discussed with respect to the structure of the virus.
THE ACTION OF SULFONAMIDES ON THE RESPIRATION OF BACTERIA AND YEAST
Authors: Sevag M. G. , Shelburne M. , Mudd Stuart
Published: May 2004

The inhibiting effects of sulfonamide drugs and their derivatives on the anaerobic decarboxylation of pyruvic acid by Staphylococcus aureus, Escherichia coli, baker's and brewer's yeast, and a carboxylase preparation from brewer's yeast have been investigated. These drugs are: sulfanilamide, sulfapyridine, sulfadiazine, sulfamethyldiazine, sulfathiazole, sulfamethylthiazole, sulfanilamido-5-ethyl-4-thiazolone, 2-aminopyrimidine, 2-aminothiazole, and 2-aminopyridine.

The sulfathiazole ring appears to exercise decidedly greater specific inhibiting effect on the carboxylases of Staph. aureus and E. coli. The inhibiting effect on yeast carboxylase is non-differentiable among all the substances tried, except sulfamethyldiazine which is completely ineffective on the carboxylases of the organisms studied.

The specific inhibitory effect of sulfathiazole on the carboxylases of Staph. aureus and E. coli in comparison to sulfanilamide, sulfapyridine, and sulfadiazine is in harmony with in vivo and in vitro experimental results of other investigators.

The results of the present investigation appear to support the hypothesis (1) that sulfonamides exert their bacteriostatic action through chemical affinity for the carrier proteins of certain respiratory enzymes of the bacterial cell, and that this affinity may in part be related to structural similarity between components of the drugs and the corresponding respiratory coenzymes.
CYANIDE-SENSITIVE BACTERIAL RESPIRATORY SYSTEMS DIFFERENT FROM THE USUAL CYTOCHROME-CYTOCHROME OXIDASE SYSTEM
Authors: Sevag M. G. , Shelburne M.
Published: May 2004

Aerobic respiration of Streptococcus pyogenes and pneumococcus Type 1 are strongly inhibited by KCN, NaN3, and Na2S. The anaerobic glycolysis of glucose by pneumococcus is also inhibited by KCN and NaN3.

Streptococcus pyogenes, E. coli, pneumococcus Type 1, B. subtilis, B. proteus, and Staphylococcus aureus did not catalyze the oxygen uptake by p-phenylenediamine in the presence of added cytochrome c or in its absence. Yeast cells, B. subtilis, and B. pyocyaneus oxidized p-phenylenediamine to a dark purple meriquinoid substance in contrast to the other bacteria mentioned above.

Streptococcus pyogenes in contrast to pneumococcus Type 1 catalyzed the oxygen uptake by cysteine. Neither of these bacteria catalyzed the oxygen uptake by tyrosine, adrenaline, pyrocatechin, xanthine, and hypoxanthine.

Streptococcus pyogenes, pneumococcus Type 1, and E. coli, boiled and not boiled, gave positive peroxidative tests with benzidine showing the presence of hematin compounds.

The results discussed in the light of the interpretations offered by Keilin and Harpley show that Streptococcus pyogenes and pneumococcus Type 1 contain cyanide-sensitive respiratory systems which are different from the cytochrome c-cytochrome oxidase system.
ON THE CALCULATION OF "TURNOVER TIME" AND "TURNOVER RATE" FROM EXPERIMENTS INVOLVING THE USE OF LABELING AGENTS
Authors: Zilversmit D. B. , Entenman C. , Fishler M. C.
Published: May 2004

1. A new method for the determination of an immediate precursor of a substance occurring in the animal body is presented.

2. Calculations on the quantitative determination of the rate of turnover of a substance and their application to experiments involving the use of labeling agents are given. These calculations take into account loss of the isotopic substance by way of breakdown or transport.
THE EFFECT OF TEMPERATURE ON THE RATE OF HYDROLYSIS OF TRIGLYCERIDES BY PANCREATIC LIPASE
Authors: Schwartz Boris
Published: May 2004

1. The temperature characteristics for the hydrolysis of various concentrations of tributyrin, trivalerin, tricaproin, triheptylin, and tricaprylin have been determined.

2. The µ values for the hydrolysis of all concentrations of tributyrin by pancreatic lipase, except the most dilute, were found to be constant within the experimental error, 8,500 ± 1,000.

3. The temperature characteristics for the hydrolysis of trivalerin, tricaproin, triheptylin, and tricaprylin varied from approximately 8,500 ± 1,000 for the high concentrations to 12,400, 20,000, 22,400, and 23,700 respectively for the most dilute concentration of each.

4. An interpretation of these results was presented.
THE QUANTITATIVE EFFECT OF X-RAYS ON ASCORBIC ACID IN SIMPLE SOLUTION AND IN MIXTURES OF NATURALLY OCCURRING COMPOUNDS
Authors: Anderson Rubert S. , Harrison Bernice
Published: May 2004

Data on the x-ray induced reaction of ascorbic acid in simple inorganic solution, in solutions containing serum albumin, in plasma, and in muscle have been presented. The reaction occurred in the presence of serum albumin and in human plasma but was relatively small in excised rat muscle.
THE QUANTUM YIELD OF OXYGEN PRODUCTION BY CHLOROPLASTS SUSPENDED IN SOLUTIONS CONTAINING FERRIC OXALATE
Authors: French C. S. , Rabideau G. S.
Published: May 2004

1. The quantum yield of oxygen liberation by spinach and Tradescantia chloroplasts suspended in solutions containing ferric oxalate and potassium ferricyanide varied from 0.013 to 0.080.

2. It was concluded that the nature of this oxygen liberation reaction is not fundamentally different from the formation of oxygen in normal photosynthesis, with respect to its light efficiency.
METABOLISM OF TISSUE CULTURES
Authors: Cohn Waldo E. , Brues Austin M.
Published: May 2004

By using radioactive isotopes in tissue cultures, the rate of permeation of substances into cells can be measured independently of concurrent metabolic reactions of these substances. Techniques of obtaining and analyzing data are described. Examples are given using radioactive potassium and phosphorus.

Using cultures of chick embryo muscle, turnover time for cell potassium is 6 hours, and for cell inorganic phosphate is 7 hours in the examples cited. Permeability rates, based on estimates of the cell surface involved and expressed as millimoles per cm.2 per hour, are of the order of magnitude of 10–6 for potassium and of 10–7 for phosphate.
THE TEMPERATURE COEFFICIENT OF THE UREA DENATURATION OF EGG ALBUMIN
Authors: Clark Janet Howell
Published: May 2004

Evidence is brought forward to show that at concentrations of urea high enough to split the egg albumin molecule the solubility changes produced by urea are profoundly modified. The degree of precipitation after dialysis is the net result of two changes produced by the urea: the first, normally spoken of as denaturation, which makes the protein insoluble in dilute solution and the second, a splitting of the molecule which makes it soluble. These two reactions may proceed independently and simultaneously or the second reaction may follow the first, taking place in the denatured molecule only. In view of the decrease in the opalescence with time, the latter process is more probable.

Both of these reactions have positive temperature coefficients, but as the concentration of urea increases the second reaction is more affected by increase in temperature than the first, and consequently the resulting opalescence decreases rather than increases with temperature. This accounts for and explains reports of negative temperature coefficients of denaturation, when denaturation is measured by the amount of insoluble material found on dilution.

The occurrence of these two reactions, one leading to an increase and the other to a decrease in the amount of insoluble protein, should be taken into account when denaturation changes in egg albumin with urea are studied.
THE EFFECTS OF OXYGEN, CARBON DIOXIDE, AND PRESSURE ON GROWTH IN CHILOMONAS PARAMECIUM AND TETRAHYMENA GELEII FURGASON
Authors: Pace D. M. , Ireland R. L.
Published: May 2004

1. The effects of O2, CO2, and pressure were studied in two very different species of protozoa, a flagellate, Chilomonas paramecium, grown in acetate-ammonium solution and a ciliate, Tetrahymena geleii, grown in 2 per cent proteose-peptone solution.

2. Chilomonas and Tetrahymena live and reproduce in solutions exposed to a wide range of O2 concentrations, but Chilomonas is killed at high O2 tensions in which Tetrahymena grows best. The optimum O2 concentration for Chilomonas is about 75 mm. pressure but it lives and reproduces in O2 tensions as low as 0.5 mm. while Tetrahymena fails to grow in concentrations below 10 mm. O2 pressure.

3. With a constant O2 tension of 50 mm. pressure, it was found that there is no significant variation in growth in Chilomonas between 50 mm. and 740 mm. total pressure. In Tetrahymena, however, under the same conditions, an optimum total pressure was found at about 500 mm. and growth is comparatively poor at 50 mm. total pressure.

4. Tetrahymena does not live very long in CO2 tensions over 122 mm., although Chilomonas grows as well at 400 mm. CO2 as in air at atmospheric pressure (0.2 mm. CO2). Tetrahymena grows best in an environment minus CO2, but the optimum for Chilomonas is 100 mm. CO2 at which pressure an average of 668,600 ± 30,000 organisms per ml. was produced (temperature, 25 ± 1° C.).

5. Chilomonads grown in high CO2 concentrations (e.g., 122 mm.) produce larger starch granules and more starch than those grown in ordinary air at atmospheric pressure.

6. In solutions exposed to 75 mm. O2 tension (optimum) and 122 mm. CO2 plus 540 mm. N2 pressure, chilomonads contain very little, if any, fat. This phenomenon seems to be due to the action of CO2 on the mechanisms concerned with fat production.

7. In Tetrahymena exposed to pure O2, there is very little fat compared to those grown in atmospheric air. This may be due to the greater oxidation of fat in the higher O2 concentrations.

8. Further evidence is presented in support of the contention that Chilomonas utilizes CO2 in the production of starch.
ON THE NATURE OF FORCES OPERATING IN BLOOD CLOTTING
Authors: Mommaerts W. F. H. M.
Published: May 2004

The results of the study of the inhibiting effect of neutral salts upon the clotting tendency of fibrinogen by thrombin may be summarised as follows:

Salts like NaCl and KCl inhibit only weakly.

Salts of the same cation (K•) with monovalent anions of different ionic radius are the more active the larger the anion (Cl',Br',I').

Salts of the same cation with anions of different valency are the more active the higher the charge of the anion (1–1 <1–2 <1–3 <1–4).

Salts with the same anion with cations of different valency show stronger inhibition in the case of cations of higher charge (K•,Na• < Mg••, Ca••, Sr••, Ba••).

Salts with the same anion and cations of the same charge, but of different radius, are the more active the larger the cation (but with an inversion between Mg•• and Ca•• in the series of the alkali earths, which is not infrequent in biocolloids).

These results show that the clotting of fibrinogen with thrombin is, at least partly, caused by a coacervation process, due to electrostatic attraction between positive and negative groups. Its nature and localisation will be dealt with in the next paper of this series.
ON THE NATURE OF FORCES OPERATING IN BLOOD CLOTTING
Authors: Mommaerts W. F. H. M.
Published: May 2004

It is found that clotting of fibrinogen by thrombin does not occur on the acid side of the isoelectric point of the fibrinogen. At such pH values, however, a primary reaction between thrombin and fibrinogen takes place, leading to the formation of profibrin, a compound of thrombin and fibrinogen.

At pH values at which clotting is possible, fibrinogen is negatively, thrombin positively charged, whereas profibrin has a pattern of positive and negative charges.

The primary reaction, the formation of profibrin by combination of thrombin and fibrinogen, is inhibited by urea but not by neutral salts. The combination of thrombin with fibrinogen most probably takes place by hydrogen bonds.

The second reaction, the polymerisation of profibrin to fibrin, is inhibited by neutral salts in the same way as complex or autocomplex coacervates. It is caused therefore by electrostatic attraction between the positive and the negative charges of the profibrin.
POTASSIUM ACCUMULATION IN THE PROXIMAL CONVOLUTED TUBULES OF THE FROG'S KIDNEY
Authors: Conway E. J. , Fitzgerald O. , Macdougald T. C.
Published: May 2004

1. In a manner similar to that of the sartorius muscle, the isolated kidney of the frog can accumulate K against a gradient to upwards of three times its normal concentration.

2. The K-accumulating region is identified as the proximal tubule, which in the isolated tissue immersed over 24 hours in the cold (2–3°C.) amounts to about 90 per cent of the nephron minus the glomerulus. In the fresh tissue it constitutes about 70 per cent.

The cells of the proximal tubule are impermeable to Na, but freely permeable to K and Cl.

3. The distal tubule in the isolated kidney does not accumulate K over the external concentration. The cells are permeable to Na which they actively extrude. This extrusion of Na goes parallel with a loss of osmotically associated water amounting to about 15 per cent of the weight of the fresh kidney, but varying somewhat with the conditions.

4. The accumulation of K in the proximal tubules is in accordance with the equations established for the sartorius muscle, and, as theoretically expected, there is no volume increase (but rather a small decrease) with the large accumulations, when the external Na concentration is maintained throughout.

5. With K accumulation in isotonic mixtures large volume changes occur as K is progressively substituted for Na. Over the range of external K concentration of 10 to 100 mM per litre the weight of the whole kidney changes to 2.5 times and the water of the cells of the proximal tubules increases to over four times. Up to an external K value of 90 mM per litre the mean weight of the kidney shows a linear relation when plotted against the reciprocal of the Na concentration plus the small glucose and Ca concentration. This relation is interpreted theoretically.

6. The effect of cyanide in the isotonic mixtures is to prevent the contraction of the distal tubules and to cause swelling of the same. It does not affect the volume, volume changes, or differential permeability of the proximal tubule. At the same time the membranes of the proximal tubule cells lose their characteristic permeability at a lower level of distension in the presence of cyanide.

7. The mean Na ratio for the kidney after 24 hours' immersion in the cold is 0.26 ± 0.014 (giving standard deviation of mean). The ratio is defined as

See PDF for Equation.

For the fresh kidney the mean ratio is 0.39 ± 0.006.

8. The mean inulin ratio (28 observed in the cold) is 0.23 ± 0.012 and the same value for 10 observed at room temperature. At room temperature—2 hour immersion—the ratio is increased by cyanide to a mean of 0.32 ± 0.028, but only a slight increase is caused by cyanide in the cold.

9. The mean hemoglobin ratio after 24 hours' immersion in the cold is 0.17 ± 0.004 and is unaffected by cyanide.
CULTURE CONDITIONS AND THE DEVELOPMENT OF THE PHOTOSYNTHETIC MECHANISM
Authors: Myers Jack ,   With the Technical Assistance of Frank Ervin and Mary Lou Murray
Published: May 2004

1. Chlorella pyrenoidosa has been grown in a continuous-culture apparatus under various light intensities provided by incandescent lamps, other conditions of culture being maintained constant. Light intensity curves for cells immersed in the No. 11 Warburg buffer and in Knop's solution + 4.4 per cent CO2 at a saturating light intensity were determined as characteristics of the photosynthetic mechanism. These characteristics were referred to the centrifuged cell volume as an index of quantity of cellular material.

2. Cells grown at intensities in the range of about 35 f.-c. develop a capacity for a high rate of photosynthesis (c.mm. O2/hour/c.mm. cells). At culture intensities above or below this range the cells produced have a lower capacity for photosynthesis. A similar effect is observed for rate of photosynthesis per unit dry weight or rate per unit cell nitrogen.

3. The rate of photosynthesis per cell or rate per unit chlorophyll shows no maximum at any light intensity of culture but increases continuously throughout the range of light intensities studied.

4. Maximum rate of growth is attained at a light intensity of about 100 f.-c. The hypothesis is advanced that at culture intensities above that needed to give maximum rate of growth (100 f.-c.) a mechanism is developed which opposes the photosynthetic process and removes the photosynthetic products.

5. The low capacity for photosynthesis shown by cells grown at culture intensities below 35 f.-c. finds no immediate explanation.

6. The shape of the light intensity curve is markedly affected by the light intensity at which the cells have been cultured. Cells grown at lower intensities give light intensity curves approaching the Blackman type with a short transitional region between light limitation and light saturation.