bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE PURIFICATION OF CATHEPSIN
Authors: Anson M. L. 
Published: May 2004

1. One mg. of the purified cathepsin whose preparation is described is as active as the extract of 1.3 gm. of spleen. An eightfold further purification is possible by procedures which are still being modified and so are not described in the present paper.
2. The first step of the purification consists in suspending frozen and thawed spleen in water and letting it autolyze.
3. In the second step, ammonium sulfate is added and the suspension is acidified and warmed. Much additional autolysis takes place. The cathepsin is protected from destruction by being adsorbed to the insoluble spleen material. When this insoluble material is filtered off most of the products of autolysis remain in the filtrate.
4. The cathepsin is then released from the insoluble spleen material by making the suspension slightly alkaline. Some inert protein still remains adsorbed to the insoluble spleen material.
5. More inert protein is removed by adsorption with aluminum hydroxide formed in the cathepsin solution by the addition first of aluminum chloride and then of sodium hydroxide. Preformed aluminum hydroxide is a much less effective adsorbent.
6. The purified cathepsin is precipitated from very dilute solution with tungstic acid. Tungstic acid precipitates most proteins in the native form provided the solution is not too acid.
7. Further evidence is given that cathepsin is not a proteinase of the papain type.
ACTION CURVES WITH SINGLE PEAKS IN NITELLA IN RELATION TO THE MOVEMENT OF POTASSIUM
Authors: Osterhout W. J. V. , Hill S. E. 
Published: May 2004

In Nitella the action curve has two peaks, apparently because both protoplasmic surfaces (inner and outer) are sensitive to K+.
Leaching in distilled water makes the outer surface insensitive to K+. We may therefore expect the action curve to have only one peak. This expectation is realized.
The action curve thus obtained resembles that of Chara which has an outer protoplasmic surface that is normally insensitive to K+.
The facts indicate that the movement of K+ plays an important part in determining the shape of the action curve.
EFFECTS OF GUAIACOL AND HEXYLRESORCINOL IN THE PRESENCE OF BARIUM AND CALCIUM
Authors: Osterhout W. J. V. 
Published: May 2004

Guaiacol was applied at two spots on the same cell of Nitella. At one spot it was dissolved in 0.01 M NaCl, at the other in 0.01 M CaCl2 or BaCl2. The effect was practically the same in all cases, i.e. a similar change of P.D. in a negative direction, involving a more or less complete loss of P.D. (depolarization).
When hexylresorcinol was used in place of guaiacol the result was similar. That Ca++ and Ba++ do not inhibit the effect of these organic depolarizing substances may be due to a lack of penetration of Ca++ and Ba++. The organic substances penetrate more rapidly and their effect is chiefly on the inner protoplasmic surface which is the principal seat of the P.D.
A NEW FORM OF DIFFERENTIAL MICRORESPIROMETER
Authors: Cunningham Burris , Kirk Paul L. 
Published: May 2004

1. A microrespirometer suitable for measuring oxygen uptakes from 0.1 to 10λ per hour is described.
2. The sensitivity of the instrument may be readily altered by substituting different sizes of capillary tubing.
3. By means of replaceable brass plugs the chamber volume of this instrument may be varied from 700 to less than 40λ.
4. No thermostat is required for the operation of the instrument at room temperature.
5. It may be charged at one temperature and used at a widely different one.
6. The chambers may be filled with any desired gas mixture.
7. Two solutions may be mixed during the course of an experiment.
8. The entire apparatus may be sterilized.
THE UPTAKE OF INORGANIC ELECTROLYTES BY THE CRAYFISH
Authors: Maluf N. S. Rustum 
Published: May 2004

1. Reasons are given for believing that the uptake of Na+, Cl-, and NaCl by the crayfish occurs through the gills.
2. A crayfish in fresh water, with a Cl concentration of about 0.2 mEq./l., can) by active Cl absorption, compensate entirely for Cl lost in the urine.
3. The carbonic anhydrase activity of the gills is markedly higher than that of other tissues of the crayfish, but the equivalent CO2 output of the crayfish is far in excess of the equivalent Cl absorption per unit time and weight and thus fails to warrant the supposition that Cl absorption is of respiratory importance.
4. The carbonic anhydrase activity of the soft integument of the lobster, before and after molting, and of the hypodermis of the hard-cuticled animal is almost identical and of the same order as that of other tissues of the lobster.
5. The concentration of the electrolytes was about 7.5 mEq./l.; i.e., considerably lower than in the blood of the crayfish. Cl- can be taken up independently of the complementary cation. Na+ can be taken up independently of the complementary anion. K+ and SO4= are not taken up at all. In pure NaCl, the Na+ and Cl- are absorbed evidently largely together. Ca++ is absorbed only in newly molted animals and in animals preparing to molt but is not absorbed by hard-cuticled animals not preparing to molt. Ca++ is taken up independently of Cl- in pure CaCl2.
6. Newly molted animals absorb Ca++ at a rate exceeding that of the absorption of other absorbable ions (Na+ and Cl-) in the same equivalent concentration.
7. A crayfish utilizes the Ca++ in fresh water in the calcification of its cuticle. Since the animal does not swallow water, the Ca++ must enter through the exterior. Reasons are given for believing that, unlike Na+ and Cl-, Ca++ is absorbed directly from the exterior by the integument and does not enter the body through the gills.
8. During molting, only about 4 per cent of the raw ash and 2.3 per cent of the organic material of the old cuticle is resorbed.
MOLECULAR WEIGHT AND ELECTROPHORESIS OF CRYSTALLINE RIBONUCLEASE
Authors: Rothen Alexandre 
Published: May 2004

Electrophoretic studies on purified crystalline ribonuclease showed the absence of any impurities differing in mobility from the bulk of material.
The isoelectric point of ribonuclease was found by electrophoresis to be at about pH 7.8.
Ultracentrifuge studies indicated fair homogeneity of ribonuclease in solution. Only one moving component has been observed.
The molecular weight of ribonuclease was found to be 12,700 from rate of sedimentation (S25 = 1.85 x 10–13 in 0.5 M (NH4)2SO4) and diffusion measurement (D = 1.36 x 10–6 in 0.5 M (NH4)2SO4), in good agreement with the average value of 13,000 found from equilibrium measurements. This low value for the molecular weight of a protein would seem to discredit the value 17,600 as representing a universal unit weight for proteins in general.
STUDIES ON PITUITARY LACTOGENIC HORMONE
Authors: Li Choh Hao , Lyons William R. , Evans Herbert M. 
Published: May 2004

The solubility of sheep pituitary lactogenic hormone in 0.302 M NaCl at pH 2.02 (solution in HCl) has been determined at room temperature. It showed a constant solubility in the presence of a considerable excess of the solid phase, an indication that the preparation contained but one component.
Beef lactogenic hormone showed a constant solubility in distilled H2O at 7–8°C in the presence of excess of the solid phase.
The salting-out effect of NaCl in acid solution of both beef and sheep hormones has been studied at room temperature. In these studies both preparations behaved as pure substances, but they exhibited differences in solubility, thus indicating a species specificity.
EFFECTS OF HEXYLRESORCINOL ON VALONIA
Authors: Osterhout W. J. V. 
Published: May 2004

The effects on Valonia of guaiacol and hexylresorcinol are similar but the latter is more effective.
Both substances lower or abolish the potassium effect; i.e., the ability of the cell to distinguish electrically between Na+ and K+.
Both substances change the order of mobilities so that vCl &gt; uNa becomes uNa &gt; vCl or uNa = vCl.
THE FLICKER RESPONSE CONTOUR FOR PHRYNOSOMA (HORNED LIZARD; CONE RETINA)
Authors: Crozier W. J. , Wolf Ernst 
Published: May 2004

The lizard Phrynosoma, with purely cone retina, provides a simplex flicker response contour (log critical flash intensity as a function of flash frequency). It is well described as a normal probability integral (F - log I).
The Phrynosoma curve differs markedly, in higher slope and in higher median intensity level, from that obtained under the same conditions for the turtle Pseudemys, also with entirely cone retina. Other comparisons having a bearing on the duplexity doctrine are discussed.
CHEMICAL PACEMAKERS
Authors: Hadidian Zareh , Hoagland Hudson 
Published: May 2004

1. In a previous paper it was found that 11,200 calories is obtained for the energy of activation in the oxidation of succinate to fumarate in the presence of crude beef heart extract when succino-dehydrogenase was made the limiting factor. 16,000 calories was obtained with this preparation when cytochrome-cytochrome oxidase was made the limiting factor. In the present paper activation energies of the components of this enzyme system are further studied.
2. Oxidation of p-phenylenediamine catalyzed by the extract and known not to involve the dehydrogenase component yields Arrhenius equation plots indicating a pacemaker reaction with a µ of 9,500 calories.
3. An activation energy of 17,500 calories is obtained for the oxidation of succinate to fumarate in the presence of the beef heart extract partially poisoned by pyrophosphate. Evidence is presented that this value corresponds to a link in the respiratory chain other than that of succino-dehydrogenase or cytochrome c-cytochrome oxidase.
4. Addition of a suitable amount of cresyl blue to a beef heart extract reaction mixture, completely inhibited by cyanide, restores the oxidation of succinate to normal in the presence of pure oxygen. In this system, in which the dye is substituted for the oxidase, when the enzyme extract (dehydrogenase) is made the limiting factor, a µ of 18,500 calories is obtained; when cresyl blue is made the limiting factor, the µ value is 22,000 calories.
5. Results of these experiments indicate that energies of activation are associated not with the enzyme as such, but with the particular reaction steps involving them as catalysts.
PERMEABILITY OF ERYTHROCYTES TO RADIOACTIVE POTASSIUM
Authors: Dean R. B. , Noonan T. R. , Haege L. , Fenn W. O. 
Published: May 2004

The diffusion coefficients for the exchange of potassium across the membrane of erythrocytes of humans, rats, and rabbits have been determined by the use of artificially radioactive potassium, both into and out of the erythrocytes both in vitro and in vivo.
The diffusion coefficients found in minutes–1 were 0.2 to 0.25 x 10–3 for human, 0.32 to 0.665 x 10–3 for rabbits, and 1.0 x 10–3 for rat erythrocytes. Rabbit erythrocytes appear to be more permeable in vivo.
Reasons are advanced to explain the failure of earlier workers to demonstrate appreciable exchange of potassium in erythrocytes.
STUDIES ON THE LACTASE OF ESCHERICHIA COLI
Authors: Knopfmacher H. P. , Salle A. J. 
Published: May 2004

A "lactase solution" was prepared from Escherichia coli. The mechanism of its action has been studied and changes in the rate of hydrolysis under various conditions investigated.
The hydrolysis of lactose by the enzyme approximates the course of reaction of the integrated Michaelis-Menten equation. One molecule of enzyme combines with one molecule of substrate.
E. coli lactase is readily inactivated at pH 5.0, and its optimal activity at 36°C. is reached between pH 7.0 and pH 7.5.
The optimal temperature for its action was found to be 46°C. when determinations were carried out after an incubation period of 30 minutes.
Its inactivation by heat follows the course of a first order reaction, and the critical thermal increment between the temperatures of 45°C. and 53°C. was calculated to be 56,400 calories per mol.
The enzyme is activated by potassium cyanide, sodium sulfide, and cysteine, and irreversibly inactivated by mercuric chloride, silver nitrate, and iodine.
After inactivation with copper sulfate partial reactivation is possible, while the slight inhibition brought about by hydrogen peroxide is completely reversible.
The possible structure of the active groups of E. coli lactase as compared with other enzymes has been discussed.
THE RATE OF BACTERIOPHAGE INACTIVATION BY FILTRATES OF ESCHERICHIA COLI CULTURES
Authors: Ellis Emory L. , Spizizen John 
Published: May 2004

1. The rate of inactivation of an anti-coli phage by filtrates of cultures of the homologous bacteria has been studied.
2. The inactivation rate at 37°C. is proportional to phage concentration and filtrate concentration.
3. At 0°C. the rate of phage inactivation becomes proportional to the square root of the filtrate concentration.
4. A reaction scheme to account for these observations is suggested and discussed.
5. This coli-phage is also inactivated by relatively large concentrations of soluble starch, inulin, gum arabic, and acetylated gum arabic.
6. The inactivation is markedly influenced by salt concentration, being rapid at moderate salt concentrations and slow at high or extremely low salt concentrations.
7. The inactivated phage cannot be regenerated by high salt concentrations, or by soaps.
THE CHLOROPHYLL-PROTEIN COMPOUND OF THE GREEN LEAF
Authors: Smith Emil L. 
Published: May 2004

1. Aqueous extracts of spinach and Aspidistra leaves yield highly opalescent preparations which are not in true solution. Such extracts differ markedly from colloidal chlorophyll in their spectrum and fluorescence. The differences between the green leaf pigment and chlorophyll in organic solvents are shown to be due to combination of chlorophyll with protein in the leaf.
2. The effect of some agents on extracts of the chlorophyll-protein compound has been investigated. Both strong acid and alkali modify the absorption spectrum, acid converting the compound to the phaeophytin derivative and alkali saponifying the esterified groups of chlorophyll. Even weakly acid solutions (pH 4.5) denature the protein. Heating denatures the protein and modifies the absorption spectrum and fluorescence as earlier described for the intact leaf. The protein is denatured by drying. Low concentrations of alcohol or acetone precipitate and denature the protein; higher concentrations cause dissociation liberating the pigments.
3. Detergents such as digitonin, bile salts, and sodium desoxycholate clarify the leaf extracts but denature the protein changing the spectrum and other properties.
4. Inhibiting agents of photosynthesis are without effect on the absorption spectrum of the chlorophyll-protein compound.
5. The red absorption band of chlorophyll possesses the same extinction value in organic solvents such as ether or petroleum ether, and in aqueous leaf extracts clarified by digitonin although the band positions are different. Using previously determined values of the extinction coefficients of purified chlorophylls a and b, the chlorophyll content of the leaf extracts may be estimated spectrophotometrically.
6. It was found that the average chlorophyll content of the purified chloroplasts was 7.86 per cent. The protein content was 46.5 per cent yielding an average value of 16.1 parts per 100 parts of protein. This corresponds to a chlorophyll content of three molecules of chlorophyll a and one of chlorophyll bfor the Svedberg unit of 17,500. It is suggested that this may represent a definite combining ratio of a and b in the protein molecule.
SOME EFFECTS OF IODINE AND OTHER REAGENTS ON THE STRUCTURE AND ACTIVITY OF TOBACCO MOSAIC VIRUS
Authors: Anson M. L. , Stanley W. M. 
Published: May 2004

1. Denatured tobacco mosaic virus has a number of SH groups corresponding to its total sulfur content of 0.2 per cent. The SH groups were estimated by titration with ferricyanide, tetrathionate, and p-chloromercuribenzoate in guanidine hydrochloride solution and by reduction of the uric acid reagent in urea solution.
2. The SH groups of tobacco mosaic virus or their precursors can be abolished by reaction of the native form of the virus with iodine.
3. Tobacco mosaic virus whose SH groups have been oxidized beyond the S-S stage by iodine but whose tyrosine groups have not been converted into di-iodotyrosine groups still retains its normal biological activity as shown by the number of lesions it causes on Nicotiana glutinosa plants and by the characteristic disease produced in Turkish tobacco plants.
4. The inoculation of Turkish tobacco plants with active virus whose SH groups have been abolished by iodine results in the production of virus with the normal number of SH groups.
5. If enough iodine is added to tobacco mosaic virus or if the iodine reaction is carried out at a sufficiently high temperature, then the tyrosine groups are converted into di-iodotyrosine groups and the virus is inactivated.
6. Tobacco mosaic virus can be almost completely inactivated by iodoacetamide under conditions under which iodoacetamide reacts with few if any of the protein's SH groups.
7. Tobacco mosaic virus is not inactivated by dilute p-chloromercuribenzoate.
THE COURSE OF ROD DARK ADAPTATION AS INFLUENCED BY THE INTENSITY AND DURATION OF PRE-ADAPTATION TO LIGHT
Authors: Haig Charles 
Published: May 2004

An increase in the degree of light adaptation causes a decrease in the slope of the subsequent rod dark adaptation function and a displacement of the function to the right on the time axis.
Over a wide range, these changes occur to the same extent whether the increase in the degree of light adaptation is produced by raising the intensity or by prolonging the exposure. Within these limits, the Bunsen-Roscoe reciprocity law applies to the intensity and duration of pre-exposure.
Over a still wider range, dark adaptation has the same course following brief exposure to a bright light as it has following prolonged exposure to a dim light, provided the degree of light adaptation is the same in both instances (as indicated by identical initial dark adaptation thresholds).
LONGITUDINAL IMPEDANCE OF THE SQUID GIANT AXON
Authors: Cole Kenneth S. , Baker Richard F. 
Published: May 2004

Longitudinal alternating current impedance measurements have been made on the squid giant axon over the frequency range from 30 cycles per second to 200 kc. per second. Large sea water electrodes were used and the inter-electrode length was immersed in oil. The impedance at high frequency was approximately as predicted theoretically on the basis of the poorly conducting dielectric characteristics of the membrane previously determined. For the large majority of the axons, the impedance reached a maximum at a low frequency and the reactance then vanished at a frequency between 150 and 300 cycles per second. Below this frequency, the reactance was inductive, reaching a maximum and then approaching zero as the frequency was decreased.
The inductive reactance is a property of the axon and requires that it contain an inductive structure. The variation of the impedance with interpolar distance indicates that the inductance is in the membrane. The impedance characteristics of the membrane as calculated from the measured longitudinal impedance of the axon may be expressed by an equivalent membrane circuit containing inductance, capacity, and resistance. For a square centimeter of membrane the capacity of 1 µf with dielectric loss is shunted by the series combination of a resistance of 400 ohms and an inductance of one-fifth henry.
THEORY AND MEASUREMENT OF VISUAL MECHANISMS
Authors: Crozier W. J. , Wolf Ernst 
Published: May 2004

For spectral regions associated with violet, blue, green, and red the relation between mean critical flash intensity Im for visual flicker and the flash frequency F is modified as already found with white light when the light time fraction tL in the flash cycle is changed. For a square image 6.13° on a side, foveally fixated, the "rod" and "cone" contributions to the duplex contour are analyzed in the way already used for white. It is pointed out that several customary qualitative criteria for cone functioning do not necessarily give concordant results. The analysis shows that the three parameters of the probability summations giving the "rod" and "cone" curves are changed independently as a function of wave-length composition of the light, and of the light time fraction.
The correlation of these changes, and of those found in the associated variability functions, can be understood in terms of differences in (1) the numbers of neural units potentially excitable and (2) in the numbers of elements of neural effect obtained from them. In a multivariate situation of this kind it is necessary to compare intensities of luminous flux required to activate half the total population of potentially available elements when this total size is held constant for the different conditions. The results of this comparison, for the filtered lights used, are discussed in relation to certain aspects of excitation vs. wave-length. The problem is a general one, arising where the effects produced as a function of a particular variable are concerned. In the distinction between (1) units excited and (2) the actions they produce may be found the clue for the curious fact that with certain wave-lengths the critical intensities are lower than for white. The extension of the observations to other parts of the retina may be expected to further this analysis.
THE ACTIVITY OF PERIPHERALLY STORED NEUROHUMORS IN CATFISHES
Authors: Parker G. H. 
Published: May 2004

1. Adrenalin when mixed with olive oil 1:100 and injected subcutaneously into a catfish will produce a marked pale spot and a general blanching of the whole fish. The general blanching will disappear in about a day. The pale spot may last 3 to 4 weeks.
2. Injections of adrenalin in oil 1:1000 to 1:10,000,000 cause the formation of only pale spots in catfishes. Adrenalin in oil 1:100,000,000 has no effect on the fish's color.
3. Acetylcholine, though ordinarily more powerful than adrenalin, when mixed with oil is effective only in high concentrations 1:20 to 1:100. It then produces clusters of moderately dark spots.
4. The pale spot on a catfish due to adrenalin in oil may be temporarily obliterated by intermedin. It will return of itself, and this process may be repeated a number of times. The same is true of the dark spots produced by acetylcholine in oil when subjected to adrenalin. These observations indicate the subcutaneous storage of both adrenalin and acetylcholine in oil.
5. In the natural color changes in catfishes the nervous neurohumors, probably also adrenalin and acetylcholine, appear both to be stored in the fish's lipoids and to serve thus as a means of lenghthening the times of initial color responses till these stores of neurohumors are exhausted.
THE INFLUENCE OF PROTEINS ON THE REACTIVATION OF YEAST INVERTASE
Authors: Wagreich Harry , Schwartz Lawrence I. , Kamin Henry 
Published: May 2004

1. Acid-inactivated yeast invertase could not be regenerated in the presence of the proteolytic enzymes trypsin, pepsin, and chymotrypsin.
2. Certain foreign proteins of non-enzymatic nature partially inhibited the reactivation of acid-inactivated invertase.
3. Certain proteins as gelatin, lacto-globulin, and carbohydrate-free horse crystalbumin did not prevent the reactivation of invertase at all.
4. Highly purified reactivated invertase was shown to exhibit an effect typical of original native invertase; that is, acceleration of its activity in presence of foreign protein at pH 3.0.
5. Native invertase was not digested by trypsin and chymotrypsin.
6. The addition of trypsin and chymotrypsin to reactivating invertase did not affect the invertase which had already reverted to the active form, but prevented further reactivation of inactive invertase.