bluuebunny/crossref_metadata_2025_split huggingface dataset:
GEOMETRICAL ISOMERS OF RETINENE
Authors: Hubbard Ruth , Gregerman Robert I. , Wald George 
Published: May 2004

Five crystalline retinenes have been isolated, which have every appearance of being cis-trans isomers of one another. They are all-trans retinene; three apparently mono-cis isomers: neoretinenes a and b and isoretinene a; and isoretinene b, an apparently di-cis isomer.
The absorption spectra of these substances display the relations expected of cis-trans isomers. The main absorption band is displaced 5.5 to 7 mµ toward shorter wave lengths for each presumptive cis linkage. Some of the presumptive cis isomers also display a cis peak at 255 to 260 mµ. All five substances yield an identical blue product on mixing with antimony chloride. All of them are converted by light to what appears to be an identical mixture of stereoisomers. Heat isomerizes them very slowly; only neoretinene b exhibits large changes on heating at 70°C. for 3 hours. The various isomers have been extensively interconverted by gentle procedures, and all of them have been converted to all-trans retinene.
The present theory of cis-trans isomerism in carotenoids predicts the existence of four stable isomers of retinene. Instead we seem to have five—specifically three mono-cis forms where two are expected. There is no doubt that all these substances are closely related isomers of one another. The only point in question is whether they differ in part by something other than cis-trans configuration. One possibility, as yet little supported by evidence, is that isomerization between ß- and α-ionone rings may be involved. If, however, as seems more likely, all these substances are geometrical isomers of one another, some modification is needed in the present theory of configurational relationships in this class of compounds.
RELATION OF METABOLISM OF FROG SKIN TO CELLULAR INTEGRITY AND ELECTROLYTE TRANSFER
Authors: Levinsky Norman G. , Sawyer Wilbur H. 
Published: May 2004

1. The transport of sodium by frog skin and the maintenance of normal potassium levels within the cells of the skin are both dependent on metabolism and on a supply of phosphate bond energy.
2. Except for the common requirement of phosphate bond energy, the transfer mechanism for sodium and the mechanism for maintaining intracellular potassium appear to be independent.
3. The xanthines specifically inhibit the sodium transfer mechanism; at higher concentrations, they depress metabolism and cause loss of potassium from the skin.
THE MECHANISM OF THE SYNTHESIS OF ENZYMES
Authors: Koppel J. L. , Porter C. J. , Crocker Bruce F. 
Published: May 2004

1. An experimental system suitable for the study of enzyme formation has been described.
2. The formation of ß-galastosidase in E. coli B could be induced by lactose, melibiose, D-galactose and ß-methyl-D-galactoside.
3. Lactose-induced ß-galactosidase formation was found to be inhibited by D-glucose, D-mannose, D-fructose, D-arabinose, and raffinose.
4. The utilizable structural analogue, D-glucose, was found to either stimulate or inhibit ß-galactosidase formation depending upon its concentration. D-Arabinose, on the other hand, a non-utilizable structural analogue, is only capable of inhibiting, whereas succinic acid, a structurally unrelated energy source, is only capable of stimulating ß-galactosidase formation.
5. D-Arabinose inhibition of lactose-induced ß-galactosidase formation was found to be of the competitive type.
6. Some of the implications of these findings have been discussed.
CHLOROPHYLL MONOLAYERS IN CHLOROPLASTS
Authors: Wolken J. J. , Schwertz F. A. 
Published: May 2004

1. The data on the fine structure of the chloroplasts and the chlorophyll analyses, in two algal flagellates, Euglena gracilis and Poteriochromonas stipitata, are consistent with the assumption that the chlorophyll molecules are arranged in monomolecular layers at the interfaces between the lipid (dense) and the aqueous protein complex layers.
2. The cross-sectional area available to each chlorophyll molecule in the chloroplasts of Euglena and Poteriochromonas was found to be 222 x 10–16 cm2. and 246 x 10–16 cm2. By comparison, the cross-sectional area of the hydrophilic head of the chlorophyll molecule is approximately 240 x 10–16 cm2.
3. The model of the molecular network depicted in Text-fig. 1 is purely speculative. It predicts a lower limit for the number ratio of chlorophyll to other pigment molecules of about 1:1 and a weight ratio of 2:1. A loose packed structure such as that shown in Text-fig. 1 predicts a weight ratio of 4:1 to 6:1. These values bracket the large majority of experimental values found for this ratio.
The relative constancy of the number of chlorophyll molecules per chloroplast and the volume of the chloroplast indicated by the data in Table III suggest that chloroplasts probably possess a similar structural arrangement in a variety of photosynthetic microorganisms and plants.
THE ROLE OF PHOSPHOCREATINE AND ADENOSINE-TRIPHOSPHATE IN MUSCULAR CONTRACTION
Authors: Bozler Emil 
Published: May 2004

In the presence of 20 mM PC a strong contraction is produced in glycerol-extracted muscle fibers by ATP and AMP in concentrations as low as 10–6 M per liter. At low concentrations of nucleotide tension rises very slowly. This rise is interpreted as being due to absorption of nucleotide by the contractile elements. AMP gives an S-shaped tension curve, indicating that the conversion of AMP into ATP is an autocatalytic process. Tension is maintained in a contracted muscle even in PC solutions free of ATP. PC alone produces a contraction if applied within 5 minutes after ATP has been washed out from a contracting muscle. It is concluded from these results that PC is the substrate for the enzymatic activity of the contractile elements and that this activity depends on the presence of bound nucleotide which acts as an energy transfer mechanism.
PC accelerates relaxation which is caused by ATP under certain conditions. In the presence of PC even very low concentrations of ATP can produce relaxation. A strong contraction can be produced under these conditions by the addition of Ca ions. These observations support the conclusion that relaxation depends on the rephosphorylation of nucleotide bound by the contractile elements.
SYNTHESIS OF PROTEIN IN THE PANCREAS
Authors: Allfrey V. , Daly Marie M. , Mirsky A. E. 
Published: May 2004

1. The ribonucleoprotein of the microsome fraction which sediments at 40,000 R.P.M. as a pellet (and which is referred to as the pellet material) has been studied with reference to its role in protein synthesis in the pancreas.
2. In pellet material nucleic acid and protein form a definite complex as shown by its electrophoretic behavior and unchanging composition under various conditions.
3. Protein of pellet material is not especially rich in the diamino acids.
4. Evidence is brought forward indicating that the protein component of pellet material takes part in the general process of protein synthesis in the cell.
(a) The well known correlation between quantity of RNA and rate of protein synthesis in a tissue implicates the protein of the pellet material, for most of the RNA in the pancreas and other tissues is in this material.
(b) Uptake of isotopically labelled glycine by the pellet material, confirming results of previous workers, is for short periods greater than in other protein fractions.
(c) Comparing the pellet materials of pancreas, liver, and kidney—three tissues with vastly different rates of protein synthesis, in the sequence given—there is a correlation between the quantity of RNA in the pellet and the rate of protein synthesis in the tissue; a similar correlation between quantity of RNA in the pellet material and rate of N15-glycine uptake by the protein component of the pellet; and finally, the level of uptake by total protein varies with the tissue and is related to the uptake of N15-glycine by protein of the pellet.
5. In the pancreas a distinction can be made between proteins synthesized for secretion and the nucleoprotein of the pellet (not found in the secretion) which, however, takes part in the synthetic process, as shown by the fact that the N15 uptake by protein of the pellet is increased when the synthesis of digestive enzymes is stimulated by secretion.
6. The time course of N15 uptake by proteins of the pancreas indicates that pellet protein serves as precursor material in the synthesis of the secretory proteins.
7. Rate of uptake of N15-glycine by the purines of RNA of the pellet material is not correlated with uptake by the protein.
8. The uptake of C14-alanine by an in vitro system of microsomes + mitochondria is impaired by preincubation of the microsomes with ribonuclease. This is direct experimental evidence for the dependence of protein synthesis upon the presence or intactness of ribonucleic acid in the microsomes.
SOLUBLE ENZYMES OF NUCLEI ISOLATED IN SUCROSE AND NON-AQUEOUS MEDIA
Authors: Stern Herbert , Mirsky A. E. 
Published: May 2004

Nuclei of calf thymus and liver and of rat liver were isolated in sucrose media and a number of their properties studied in relation to those of corresponding nuclei isolated in non-aqueous media with a view to determining their capacity to retain soluble components.
The best preparations of sucrose nuclei were obtained from calf thymus. Cytochrome oxidase measurements and DNA/N ratios were far less sensitive than microscopic examination as indicators of purity when rat liver and calf thymus nuclei were compared. No satisfactory preparation of calf liver nuclei was obtained, contamination with whole cells having been appreciable; such preparations, nevertheless, could be used to advantage in the tests undertaken.
DNA content of thymus nuclei isolated in sucrose was much the same as that of non-aqueous ones, pointing to a retention of soluble protein under aqueous conditions of isolation. That this net retention of protein was not due to the impermeability of the nuclear membrane was shown by the hydrolysis of the DNA upon addition of some crystalline DNAase to a sucrose suspension of nuclei.
A comparative study of liver and thymus nuclei isolated in aqueous and non-aqueous media with respect to the soluble enzymes glucose-6-phosphate dehydrogenase, adenosine deaminase, and nucleoside phosphorylase yielded the following results:
1. Lyophilization of sucrose-isolated nuclei and their extraction with the organic solvents used in the non-aqueous procedure did not inactivate any of the enzymes tested. In the case of thymus the reverse was true, there being a marked increase in activity of all the enzymes studied.
2. In thymus, nucleoside phosphorylase and adenosine deaminase were active to approximately the same extent in nuclei isolated by either procedure. Glucose phosphate dehydrogenase alone was more active in sucrose-isolated nuclei, pointing to the possibility of an adsorption of this enzyme.
3. In rat liver nuclei isolated in sucrose, lyophilization and treatment with organic solvents revealed only the presence of some dehydrogenase.
4. The washing out of soluble enzymes was most markedly demonstrated in the case of calf liver. Only traces of the nucleoside enzymes were found in the sucrose-isolated nuclei, and in the case of the dehydrogenase only a half of that present in the non-aqueous nucleus remained.
The main conclusions drawn were as follows:—
1. In sucrose media the nuclear membrane is ineffectual in preventing the inward or outward diffusion of protein.
2. The extent to which soluble proteins are retained by a nucleus isolated in sucrose appears to depend upon internal structural factors, such as the concentration of DNA in the nucleus.
3. With respect to determining the composition of nuclei in terms of soluble components, the sucrose isolation procedure is considered to be of indifferent merit and hence invalid for such a type of analysis.
TISSUE CULTURE STUDIES
Authors: Rosenberg Sheldon , Zitcer Elsa , Kirk Paul L. 
Published: May 2004

A fraction of the ultrafilterable portion of chick embryo extract was isolated by alcohol extraction of a lyophilized powder of the ultrafiltrate followed by ion exchange removal of many of the inert components of the alcohol extract. This fraction contained 3 per cent of the ultrafilterable nitrogen but was capable of completely restoring the growth-promoting activity of dialyzed embryo extract, when tested with chick heart fibroblasts in roller tube cultures.
The low nitrogen content, shape of the ultraviolet absorption spectrum, and presence of few free amino acids, suggest that non-dialyzable compounds serve as the chief source of nutrition for this system.
THE MECHANISM OF THE SYNTHESIS OF ENZYMES
Authors: Porter C. J. , Holmes R. , Crocker Bruce F. 
Published: May 2004

1. The pretreatment induction method of studying the formation of ß-galactosidase in E. coli B has been described.
2. It has been found that E. coli B cells have their maximum capacity to form ß-galactosidase, in response to a constant induction stimulus, when they are in the stationary phase of the growth cycle.
3. The concentration of inductor, the nature of the nitrogen source, the duration of the assimilatory phase, oxygen tension, and temperature are factors which affect, and may limit, the rate of ß-galactosidase formation.
4. When limitations imposed by these factors were removed, the time course of induced ß-galactosidase formation was strictly linear from the onset.
5. The implications of this finding were discussed and a new theory of the mechanism of enzyme formation has been proposed.
6. A very satisfactory method of synthesis of ortho-nitrophenol-α-D-galactoside has been described. This substance is a suitable chromogenic substrate for the specific determination of α-galactosidase activity.
7. Preliminary experiments using this substrate have confirmed the results of respiration studies and shown that in E. coli B α-galactosidase formation may be induced by ß- as well as by α-galactosides.
ARGON, XENON, HYDROGEN, AND THE OXYGEN CONSUMPTION AND GLYCOLYSIS OF MOUSE TISSUE SLICES
Authors: South Frank E. , Cook Sherburne F. 
Published: May 2004

The effects of xenon, argon, and hydrogen on the aerobic and anaerobic metabolism of mouse liver, brain, and sarcoma slices have been investigated. Xenon was found to alter the rates of metabolism of these tissues in a manner almost identical with helium. The gas increased the rate of oxygen consumption in all three tissues and significantly depressed that of anaerobic glycolysis in brain and liver. The depression of glycolysis in sarcoma was less pronounced and not highly significant.
Although both the magnitude and statistical significance of the effects observed with argon were much smaller, there was a seeming adherence to the general pattern established by xenon and helium. Hydrogen while remaining essentially ineffective insofar as oxygen uptake was concerned, depressed glycolysis in both liver and brain slices but did not significantly affect sarcoma slices.
The following points are stressed in the Discussion: (1) the magnitude and direction of effects exerted by helium, argon, xenon, hydrogen, and nitrogen do not conform with the relative values of molecular weight, density, and solubility of these gases; (2) the effect of these gases on tissue metabolism does not necessarily parallel that exerted upon the whole organism.
INVESTIGATIONS ON THE MITOCHONDRIA OF THE HOUSEFLY, MUSCA DOMESTICA L
Authors: Sacktor Bertram 
Published: May 2004

It has been found that mitochondria isolated from the flight muscle of the housefly, Musca domestica, are capable of effecting oxidative phosphorylation. A systematic investigation of the factors which regulate this coupling was undertaken. It was found:
1. The molarity of the isolation medium had considerable influence on the morphology of the mitochondria. These physical alterations were associated with changes in oxidation, phosphorylation, and ATPase activity.
2. In addition to an optimum isolation medium, the normal morphology of the mitochondria needed to be further stabilized by serum albumin.
3. A "latent" ATPase activity in insect mitochondria was demonstrated. An inverse relationship was found between oxidative phosphorylation and ATPase activity.
4. Oxygen consumption and the uptake of phosphate were linear with respect to time.
5. A respiratory substrate was necessary for phosphorylation and for maintenance of spatially organized mitochondria.
6. No differences in oxygen uptake were found in the presence or absence of inorganic phosphate.
7. Magnesium was required for optimal oxidative phosphorylation. Calcium and manganese inhibited both respiration and phosphorylation.
8. The addition of cytochrome c had no effect on either oxygen or phosphate uptake.
9. ATP, ADP, or AMP were capable of participating in oxidative phosphorylation, but the glucose-hexokinase trapping system was necessary.
10. Fluoride inhibited the phosphorylation of AMP, but increased P/O when ATP was used. This stimulation was not due to the inhibition of ATPase.
11. Neither arginine nor creatine was phosphorylated.
12. The addition of other isolated fractions of flight muscle to the mitochondrial system had no appreciable effect on respiration or phosphorylation.
THE MOLECULAR WEIGHT OF RHODOPSIN AND THE NATURE OF THE RHODOPSIN-DIGITONIN COMPLEX
Authors: Hubbard Ruth 
Published: May 2004

The sedimentation behavior of aqueous solutions of digitonin and of cattle rhodopsin in digitonin has been examined in the ultracentrifuge. In confirmation of earlier work, digitonin was found to sediment as a micelle (D-1) with an s20 of about 6.35 Svedberg units, and containing at least 60 molecules. The rhodopsin solutions sediment as a stoichiometric complex of rhodopsin with digitonin (RD-1) with an s20 of about 9.77 Svedberg units. The s20 of the RD-1 micelle is constant between pH 6.3 and 9.6, and in the presence of excess digitonin.
RD-1 travels as a single boundary also in the electrophoresis apparatus at pH 8.5, and on filter paper at pH 8.0. The molecular weight of the RD-1 micelle lies between 260,000 and 290,000. Of this, only about 40,000 gm. are due to rhodopsin; the rest is digitonin (180 to 200 moles).
Comparison of the relative concentrations of RD-1 and retinene in solutions of rhodopsin-digitonin shows that RD-1 contains only one retinene equivalent. It can therefore contain only one molecule of rhodopsin with a molecular weight of about 40,000. Cattle rhodopsin therefore contains only one chromophore consisting of a single molecule of retinene. It is likely that frog rhodopsin has a similar molecular weight and also contains only one chromophore per molecule.
The molar extinction coefficient of rhodopsin is therefore identical with the extinction coefficient per mole of retinene (40,600 cm.2 per mole) and the E(1 per cent, 1 cm., 500 mµ) has a value of about 10.
Rhodopsin constitutes about 14 per cent of the dry weight, and 3.7 per cent of the wet weight of cattle outer limbs. This corresponds to about 4.2 x 106 molecules of rhodopsin per outer limb. The rhodopsin content of frog outer limbs is considerably higher: about 35 per cent of the dry weight, and 10 per cent of the wet weight, corresponding to about 2.1 x 109 molecules per outer limb. Thus the frog outer limb contains about five hundred times as much rhodopsin as the cattle outer limb. But the relative volumes of these structures are such that the ratio of concentrations is only about 2.5 to 1 on a weight basis. Rhodopsin accounts for at least one-fifth of the total protein of the cattle outer limb; for the frog, this value must be higher. The extinction (K500) along its axis is about 0.037 cm.2 for the cattle outer limb, and about 0.50 cm.2 for the frog outer limb.
EVIDENCE FOR THE PRESENCE OF SEPARATE MECHANISMS REGULATING POTASSIUM AND SODIUM DISTRIBUTION IN ULVA LACTUCA
Authors: Scott George T. , Hayward Hugh R. 
Published: May 2004

1. The methods employed in these and preceding (25–27) studies were shown to allow analysis of true cellular sodium and potassium concentrations.
2. The rate of reaccumulation of potassium by potassium-deficient cells is independent of the presence or absence of sodium in the external medium.
3. Phenylurethane (10–3 M), a photosynthetic and metabolic inhibitor, causes a marked progressive loss of potassium and gain of sodium, both of which changes are completely reversible on transferring the samples to running sea water.
4. Iodoacetate, while not effective in causing potassium and sodium shifts in the light, effects a loss of potassium and a gain of sodium in the light in the presence of phenylurethane.
5. Arsenate (5 x 10–3 M) completely protects Ulva against the potassium loss usually observed with iodoacetate in the dark while it affords no protection against the sodium influx under the same conditions. Arsenate given after 18 to 20 hours in iodoacetate gives significant protection against potassium loss in the dark, and allows a slight net reaccumulation of potassium in the light. Arsenate in the dark after iodoacetate affords no protection against the sodium uptake caused by iodoacetate in the dark, while in the light under the same conditions sodium is rapidly secreted to the control level within a few hours. This resecretion of sodium is thought to be primarily an effect of light, the presence of arsenate being incidental.
6. The "decoupling agent" 4,6-dinitro-o-cresol causes a marked progressive increase in cellular sodium and a drop in cellular potassium, though the kinetics of these two movements are distinctly different from each other.
7. Pyruvate (50 mg. per cent) given with iodoacetate (2 x 10–3 M) for 5 hours in the dark completely prevents the sodium increase caused by iodoacetate, while affording less protection against the potassium loss. Phosphoglycerate, on the other hand, offers more protection against potassium loss, and essentially none against the sodium gain.
8. ATP added in small amounts at short intervals to samples maintained in 10–3 M iodoacetate in the dark affords significant protection against the potassium loss observed in iodoacetate. Cellular sodium is somewhat higher in the ATP-iodoacetate samples than in the iodoacetate samples.
9. In the discussion of the data presented two major points are emphasized: (1) the close correlation between cellular metabolism and normal cation control; (2) two mechanisms must be operative in cation regulation in this organism: one for moving potassium inwards and the other for transporting sodium outwards. These mechanisms are independent of each other.
THE COMPOUND ORIGIN OF POTENTIAL IN A STIMULATED DORSAL ROOT
Authors: Eisenman George , Rudin Donald O. 
Published: May 2004

The electrotonic potential appearing in a stimulated dorsal root is found to be the resultant of two independent systems of current of different origin.
One component, labelled DRα, is non-occluding.
The other component, labelled DRß, occludes strongly and has the characteristics of the potential which appears in a neighboring unstimulated rootlet (DRIV-V).
Because DRα does not occlude, its origin is assigned to the primary afferent neuron. The result of a general examination of its origin leads to the additional conclusion that it must arise from a physiological spatial gradient in the post-spike recovery cycle of membrane potential along the afferent neuron.
The specific locus of this gradient within the primary neuron is the subject of the succeeding paper (16).
A THEORY OF TASTE STIMULATION
Authors: Beidler Lloyd M. 
Published: May 2004

The treatment in this paper of available quantitative data on the response of taste receptors to sodium salt stimulation clearly indicates that the ions of the chemical stimulus are loosely bound to some substance of the taste receptor. This can be thought of as an initial reaction which ultimately leads to stimulation of the receptor and an eventual depolarization of the associated sensory neuron. The speed of the total reaction suggests that the receptor substance is located on or near the surface of the receptor.
The recently proposed (7) enzymatic reactions for chemoreceptors do not appear plausible for sodium salt stimulation of the taste receptors of the rat.