bluuebunny/crossref_metadata_2025 huggingface dataset:
OXYGEN PROTECTION OF BACTERIOPHAGE T1 AGAINST IONIZING RADIATIONS
Authors: Bachofer C. S. , Pottinger M. Aelred
Published: May 2004

Bacteriophage T1 was suspended in distilled water and in phosphate buffer, saturated with oxygen, nitrogen, hydrogen, and carbon monoxide, and irradiated with gamma rays and x-rays. Under the same conditions phage was exposed to hydrogen peroxide.

Oxygen acted as a protective agent against both irradiation and hydrogen peroxide inactivation. As a protective agent against irradiation, oxygen was more efficient in distilled water than in buffer. The phage was much more sensitive to irradiation in the presence of hydrogen or nitrogen than in the presence of oxygen. Survivals of phage irradiated in suspensions saturated with hydrogen and with nitrogen did not differ significantly. From this it was concluded that oxygen did not protect T1 by removing atomic hydrogen from the irradiated medium, since the hydrogen-saturated medium increased the yield of atomic hydrogen but did not increase the yield of inactivated phage. It was presumed, therefore, that phage is sensitive to OH radicals and this was confirmed by irradiating phage with UV in the presence of hydrogen peroxide and comparing this survival with the survivals obtained from hydrogen peroxide alone and from UV alone. The combined effect of hydrogen peroxide and UV acting simultaneously was greater than the effect attributable to hydrogen peroxide and UV acting separately.

Evidence for sensitivity to HO2 radicals was considered, and the effect was attributed chiefly to an oxidizing action since phage sensitivity is greater at higher hydrogen ion concentrations, which favor oxidation by HO2 radicals.

Since the OH radical is a more efficient oxidizing agent than O-, the former being favored in an acid medium, the latter in an alkaline medium, and since the phage is more sensitive in the first situation than in the second, the present tests proved the importance of oxidation as the mechanism of inactivation. Since some inactivation was encountered when phage was exposed to reducing agents, independently of irradiation, it was concluded that phage is somewhat sensitive to reducing agents, but the inactivation attributable to ionizing radiations is due chiefly to oxidation, against which these reducing agents are very efficient protectors.

Under no circumstances did hydrogen peroxide protect T1, whether produced by irradiation in the medium or added beforehand to the medium to be irradiated. The first point was investigated by irradiating T1 in the presence of hydrogen and oxygen combined; this produced a higher yield of hydrogen peroxide but a lower survival of T1. In all these tests phage survival under irradiation was directly correlated with oxygen content of the medium rather than with production of hydrogen peroxide. It is proposed that the protective effect of oxygen is due to a reaction between the phage and oxygen, and this complex confers stability upon the phage.
INHIBITORY INTERACTION OF RECEPTOR UNITS IN THE EYE OF LIMULUS
Authors: Hartline H. K. , Ratliff Floyd
Published: May 2004

The inhibition that is exerted mutually among the receptor units (ommatidia) in the lateral eye of Limulus has been analyzed by recording oscillographically the discharge of nerve impulses in single optic nerve fibers. The discharges from two ommatidia were recorded simultaneously by connecting the bundles containing their optic nerve fibers to separate amplifiers and recording systems. Ommatidia were chosen that were separated by no more than a few millimeters in the eye; they were illuminated independently by separate optical systems.

The frequency of the maintained discharge of impulses from each of two ommatidia illuminated steadily is lower when both are illuminated together than when each is illuminated by itself. When only two ommatidia are illuminated, the magnitude of the inhibition of each one depends only on the degree of activity of the other; the activity of each, in turn, is the resultant of the excitation from its respective light stimulus and the inhibition exerted on it by the other.

When additional receptors are illuminated in the vicinity of an interacting pair too far from one ommatidium to affect it directly, but near enough to the second to inhibit it, the frequency of discharge of the first increases as it is partially released from the inhibition exerted on it by the second (disinhibition).

Disinhibition simulates facilitation; it is an example of indirect effects of interaction taking place over greater distances in the eye than are covered by direct inhibitory interconnections.

When only two interacting ommatidia are illuminated, the inhibition exerted on each (decrease of its frequency of discharge) is a linear function of the degree of activity (frequency of discharge) of the other. Below a certain frequency (often different for different receptors) no inhibition is exerted by a receptor. Above this threshold, the rate of increase of inhibition of one receptor with increasing frequency of discharge of the other is constant, and may be at least as high as 0.2 impulse inhibited in one receptor per impulse discharged by the other. For a given pair of interacting receptors, the inhibitory coefficients are not always the same in the two directions of action. The responses to steady illumination of two receptor units that inhibit each other mutually are described quantitatively by two simultaneous linear equations that express concisely all the features discussed above. These equations may be extended and their number supplemented to describe the responses of more than two interacting elements.
CALCIUM EQUILIBRIUM IN MUSCLE
Authors: Gilbert Daniel L. , Fenn Wallace O.
Published: May 2004

1. A study of the calcium equilibrium in isolated frog muscle has been attempted.

2. When sartorius muscles were immersed in Ca45 Ringer's solution, the surface phase took up the Ca45 in about 1 minute; the extracellular water space and connective tissue in about 30 minutes; and the intracellular space in about 300 minutes.

3. The percentages of total calcium in the whole muscle immersed in Ringer's solution was as follows: 10 per cent in the surface phase; 12 per cent in the extracellular water space; 17 per cent in the dry connective tissue; 24 per cent in the intracellular space; and 37 per cent as non-exchangeable calcium.

4. The exchange constants of isolated frog sartorius muscle to calcium has been determined. The flux of intracellular calcium in the steady state was approximately 0.8 mM/(liter hr).

5. It appears that there is a calcium pump pushing calcium out of the cell against an electrochemical gradient of about 4 cal./mM of calcium. However, since the flux is low, the maximum energy required per hour to pump calcium out of the cell against this high gradient is only about 2 cal./kg. muscle or about 1 per cent of the resting energy.
PROTEIN SYNTHESIS IN ISOLATED CELL NUCLEI
Authors: Allfrey V. G. , Mirsky A. E. , Osawa Syozo
Published: May 2004

1. Nuclei prepared from calf thymus tissue in a sucrose medium actively incorporate labelled amino acids into their proteins. This is an aerobic process which is dependent on nuclear oxidative phosphorylation.

2. Evidence is presented to show that the uptake of amino acids represents nuclear protein synthesis.

3. The deoxyribonucleic acid of the nucleus plays a role in amino acid incorporation. Protein synthesis virtually ceases when the DNA is removed from the nucleus, and uptake resumes when the DNA is restored.

4. In the essential mechanism of amino acid incorporation, the role of the DNA can be filled by denatured or partially degraded DNA, by DNAs from other tissues, and even by RNA. Purine and pyrimidine bases, monoribonucleotides, and certain dinucleotides are unable to substitute for DNA in this system.

5. When the proteins of the nucleus are fractionated and classified according to their specific activities, one finds the histones to be relatively inert. The protein fraction most closely associated with the DNA has a very high activity. A readily extractable ribonucleoprotein complex is also extremely active, and it is tempting to speculate that this may be an intermediary in nucleocytoplasmic interaction.

6. The isolated nucleus can incorporate glycine into nucleic acid purines, and orotic acid into the pyrimidines of its RNA. Orotic acid uptake into nuclear RNA requires the presence of the DNA.

7. The synthesis of ribonucleic acid can be inhibited at any time by a benzimidazole riboside (DRB) (which also retards influenza virus multiplication (11)).

8. The incorporation of amino acids into nuclear proteins seems to require a preliminary activation of the nucleus. This can be inhibited by the same benzimidazole derivative (DRB) which interferes with RNA synthesis, provided that the inhibitor is present at the outset of the incubation. DRB added 30 minutes later has no effect on nuclear protein synthesis. These results suggest that the activation of the nucleus so that it actively incorporates amino acids into its proteins requires a preliminary synthesis of ribonucleic acid.

9. Together with earlier observations (27, 28) on the incorporation of amino acids by cytoplasmic particulates, these results show that protein synthesis can occur in both nucleus and cytoplasm.
THE EQUILIBRIUM BETWEEN CYTOCHROME OXIDASE AND CARBON MONOXIDE
Authors: Wald George , Allen David W.
Published: May 2004

An evolution argument which attempted to trace the development of hemoglobins from such respiratory pigments as cytochrome oxidase presupposed that the latter possesses, in addition to its high affinity for oxygen, an approximately hyperbolic equilibrium function, and little if any Bohr effect (decline in affinity for oxygen with rise in acidity). Since cytochrome oxidase, unlike hemoglobin, is irreversibly oxidized by oxygen, the present experiments examine its combination with carbon monoxide, with which, like hemoglobin, it yields a true equilibrium. In all known hemoglobins the form of the equilibrium function and the vigor of the Bohr effect are similar with carbon monoxide and with oxygen, so that observations involving the former gas are relevant to the relations of the latter.

The equilibrium function of cytochrome oxidase with carbon monoxide—percentage saturation vs. partial pressure of CO—is slightly inflected (in the Hill equation n = 1.26; for a hyperbola, n = 1). No Bohr effect is present in the range of pH 7–8. The pressure of carbon monoxide at which half-saturation occurs (p50) is about 0.17 mm. at 10–13°C. The affinity for carbon monoxide is therefore higher than commonly supposed.

These properties are consistent with the evolution argument. They are important also for the physiological functioning of cytochrome oxidase, the nearly hyperbolic equilibrium function facilitating a high degree of saturation, and the lack of Bohr effect making this enzyme impervious to hyperacidity.

The slight inflection of the equilibrium function shows that the Fe-porphyrin units of cytochrome oxidase interact to a degree, hence that the enzyme must contain more than one such unit per molecule. It is suggested that in cytochrome oxidase two Fe-porphyrin groups may unite with one oxygen in the manner Fe++-O2-Fe++; and that the evolution of hemoglobins proceeded over a first stage in which the hemes were separated so that each combines with only one molecule of oxygen, so tending to remain reduced; to a further stage in which the separated hemes interact through the protein to facilitate one another in combining with oxygen.
THE VITAMIN A OF THE LOBSTER
Authors: Wald George , Burg Stanley P.
Published: May 2004

In many crustacea, including the lobster, the bulk of the vitamin A of the whole animal is concentrated in the eyes. Recently Fisher, Kon, and Thompson found that vitamin A extracted from the eyes of euphausiid crustacea has only about one half the biological potency of the same amount of the all-trans acetate or fish liver vitamin A.

In the present experiments the vitamin A of the lobster eye is found to consist almost entirely of the hindered cis isomer, neo-b, the precursor in the vertebrate retina of the visual pigments rhodopsin and iodopsin. This isomer is known to have a low biological potency in the rat, only about one quarter that of all-trans vitamin A. In the lobster eye it is virtually all extractable with petroleum ether, about 30 per cent in the form of free alcohol, about 70 per cent in the form of esters. It was identified by its absorption spectrum, as derived from measurements on crude extracts, and measured directly in purified preparations; the changes in absorption which accompany isomerization; oxidation to the corresponding retinene; and synthesis from the latter of rhodopsin.

The examination of an extract of euphausiid eyes, provided by Dr. Kon, also revealed the presence of neo-b vitamin A virtually alone. This may be the characteristic condition in the eyes of Eucarid crustacea. It is peculiar in that the neo-b isomer, being a sterically hindered form, is ordinarily expected to be represented in any equilibrium mixture of geometric isomers in very small amount. Apparently certain crustacea have ways of circumventing the difficulties implicit in producing and retaining this isomer, and store it in the eye virtually alone.
THE VITAMIN A OF A EUPHAUSIID CRUSTACEAN
Authors: Wald George , Brown Paul K.
Published: May 2004

The vitamin A of the euphausiid crustacean, Meganyctiphanes norvegica, consists almost wholly of the hindered cis isomer, neo-b (11-cis). In this animal vitamin A is concentrated almost entirely in the eyes; and its properties so closely resemble those of pure neo-b vitamin A as not in themselves to indicate that any other isomer is present. However, Fisher et al. (1955 b) have isolated a small fraction from this material which may be neo-c vitamin A (11, 13-dicis). The neo-b isomer was identified by its absolute absorption spectrum, the changes of absorption spectrum on isomerization, oxidation to neo-b retinene, and synthesis from the latter of rhodopsin. This identification is also in good accord with new, revised bioassays of Meganyctiphanes vitamin A by Plack et al. (1956).
REVERSIBLE CHANGES OF PROTEIN CONFIGURATION IN STIMULATED NERVE STRUCTURES
Authors: Ungar Georges , Aschheim Emil , Psychoyos Stacy , Romano Dominick V.
Published: May 2004

Changes in the configuration of proteins were studied by the modifications of the ultraviolet absorption of their alkaline solutions. These were expressed in terms of the ratio O.D.pH12/O.D.pH7, termed side-group ionization ratio (SGIR). This ratio showed two peaks; one at 300 to 305 mµ is known to correspond to the phenolic hydroxyl of tyrosine and another at 245 mµ seems to be caused by the ionization of the sulfhydryl group of cysteine.

The SGIR of extracts from electrically stimulated nerve structures was found to be consistently and significantly higher than that of similar extracts from resting tissues. The phenomenon was observed in isolated nerves (frog and rat sciatic) stimulated in vitro and in the cerebral cortex of cats, dogs, and rats after stimulation of their afferents. The increase in SGIR was reversible if the stimulated structures were allowed to rest.

Prolonged stimulation, in addition to causing structural changes, also caused breakdown of proteins and the appearance of proteolytic activity. The latter, studied on a synthetic substrate, could be detected even after shorter stimuli, together with configurational changes but without proteolysis.

The structural changes detected with the spectrophotometric method are closely related to reversible denaturation as produced by urea. The changes probably involve rupture of hydrogen bonds which loosens the protein molecule and perhaps changes its affinity for different ions. It is possible that such a process may play a role in the mechanism of excitation.
SENSITIVITY TO LIGHT IN THE SEA ANEMONE METRIDIUM SENILE (L.)
Authors: North Wheeler J.
Published: May 2004

1. The reaction time of the photosensitive response of Metridium was found to be composed almost entirely of a sensitization period. If a latent period exists, it is too short to be detected by the methods used and is probably less than a second in duration. The length of the reaction time, therefore, was used as a measure of the radiant energy necessary at any intensity to elicit a response.

2. The length of the reaction time was found to vary randomly by a factor of seven under constant environmental and stimulating conditions. Determination of large numbers of reaction times on several anemones, grouped according to length, gave closely similar distributions resembling Poisson distributions. It was suggested that the variability may be caused by the same factor or mechanism in each individual. An experimental scheme was presented for determining the expected error and variation in statistical quantities when groups of ten observations are used.

3. The means of groups of reaction times determined at different intensities formed a hyperbolic relationship when plotted against intensity, suggesting that the animal obeys the Bunsen-Roscoe law of reciprocity. No marked changes were noted of per cent deviation from the mean or of randomness at different intensities. Stimulation of Metridium requires roughly 5 x 109 incident quanta/cm.2 of blue-green light.

4. No temperature effect could be found on either the means, the per cent deviation from the mean, or the degree of randomness of series of about ten observations, studied over a 17°C. range. It was concluded that the variability in reaction time was not due to changes in any complex physiological state such as muscular tone.

5. A possible use of the photosensitive response is suggested and the potentialities of "integrative" photosensitivity are discussed.

6. Possible mechanisms to explain the variability in reaction time are discussed. In the light of evidence presented, the most likely hypothesis appears to be the uncertainty of quantum capture caused by low concentrations of photosensitive pigment. Assuming the validity of this hypothesis, evidence suggests that the anemones responded to less than 10 quanta of absorbed light. Caution, however, is recommended in accepting the hypothesis because of the indirect nature of the supporting evidence.
THE RELATIONSHIP BETWEEN SODIUM, POTASSIUM, AND CHLORIDE IN AMPHIBIAN MUSCLE
Authors: Simon Shirley E. , Shaw F. H. , Bennett Susanne , Muller Margaret
Published: May 2004

The Na,+ Cl-, and K+ content of toad plasma and the sartorius muscle has been determined. Although the Na+ and Cl- level of the muscles in the living animal varied greatly (0 to 38.0 m.eq. per kg., and 0 to 31.8 m.eq. per kg. respectively) the K+ level was subject to a smaller variation (76.5 to 136 m.eq. per kg.). There was a direct relationship between Na+ and Cl-, which was independent of the K+ level.

There is a closely related gain of Na+ and Cl- when muscle is soaked in normal Ringer. These gains are not related to the K+ loss, frequently found on soaking.

The relationship between the three ions was studied in a large series of 124 muscles in normal Ringer. As found in vivo, there was a correlation between Na+ and Cl.- This correlation was independent of K+ content, except when this was abnormally low.

Alteration of the external NaCl level produced concomitant changes in the internal levels of these ions.

Alteration of the external KCl level produced an increase in internal Cl- similar to that found with high NaCl solutions, but the amount of K+ entering the cell was approximately one-third of the external increase.

Removal of K+ from the external solution did not result in a loss of K+ from the cell, although there was an adequate amount of Cl- present to accompany it.

The results cannot be reconciled with either a Donnan concept for the accumulation of K+, or a linked carrier system.

A theory is proposed to account for the ionic differentiation within the cell. The K+ is assumed to be adsorbed onto an ordered intracellular phase. The normal metabolic functioning of the cell is necessary to maintain the specificity of the adsorption sites. There is another intracellular phase, which lacks the structural specificity for K+, and which contains Na+, Cl-, and K+ in equilibrium with the external solution. The dimensions of the free intracellular phase will vary from cell to cell, but it will be smaller in the intact animal, and will increase on soaking in normal Ringer, until it is approximately one-third of the total cellular volume. The increase in this phase may be ascribed to a decrease in the energy available to maintain the ordered phase.
ON THE MEASUREMENT OF CARBON DIOXIDE UPTAKE WITH A GLASS ELECTRODE
Authors: Rosenberg Jerome L.
Published: May 2004

1. It has been shown that the glass electrode method as previously described by the author for measurements of transient rates in photosynthesis is free of systematic errors.

2. Justification has been given for the use of the steady state-gas flow method for measuring rates of assimilation under conditions in which the solution is known not to be seriously depleted of CO2.

3. The decline of photosynthetic rates under light saturation at CO2 pressures less than several tenths per cent of an atmosphere has been shown to be a real phenomenon. It has been suggested that there may be a real discrepancy between this finding and those of some other investigators due to a difference in the previous history of the algal suspensions.
DEMONSTRATION OF TWO STABLE POTENTIAL STATES IN THE SQUID GIANT AXON UNDER TETRAETHYLAMMONIUM CHLORIDE
Authors: Tasaki Ichiji , Hagiwara Susumu
Published: May 2004

1. Intracellular injection of tetraethylammonium chloride (TEA) into a giant axon of the squid prolongs the duration of the action potential without changing the resting potential (Fig. 3). The prolongation is sometimes 100-fold or more.

2. The action potential of a giant axon treated with TEA has an initial peak followed by a plateau (Fig. 3). The membrane resistance during the plateau is practically normal (Fig. 4). Near the end of the action potential, there is an apparent increase in the membrane resistance (Fig. 5D and Fig. 6, right).

3. The phenomenon of abolition of action potentials was demonstrated in the squid giant axon treated with TEA (Fig. 7). Following an action potential abolished in its early phase, there is no refractoriness (Fig. 8).

4. By the method of voltage clamp, the voltage-current relation was investigated on normal squid axons as well as on axons treated with TEA (Figs. 9 and 10).

5. The presence of stable states of the membrane was demonstrated by clamping the membrane potential with two voltage steps (Fig. 11). Experimental evidence was presented showing that, in an "unstable" state, the membrane conductance is not uniquely determined by the membrane potential.

6. The effect of low sodium water was investigated in the axon treated with TEA (Fig. 12).

7. The similarity between the action potential of a squid axon under TEA and that of the vertebrate cardiac muscle was stressed. The experimental results were interpreted as supporting the view that there are two stable states in the membrane. Initiation and abolition of an action potential were explained as transitions between the two states.
THE METAMORPHOSIS OF VISUAL SYSTEMS IN THE SEA LAMPREY
Authors: Wald George
Published: May 2004

The life cycle of the sea lamprey, Petromyzon marinus, includes two metamorphoses. At the end of a period spent as a blind larva, buried in the mud of streams, a first metamorphosis prepares it to migrate downstream to the sea or a lake for its growth phase. Then, following a second metamorphosis, it migrates upstream as a sexually mature adult to spawn and die.

The downstream migrants have a visual system based upon rhodopsin and vitamin A1, whereas that of the upstream migrants is based upon porphyropsin and vitamin A2. The livers contain vitamin A1 at all stages.

The sea lamprey therefore exhibits a metamorphosis of visual systems, like those observed earlier among amphibia. The presence of porphyropsin in this member of the most primitive living group of vertebrates, as in fishes and amphibia, supports the notion that porphyropsin may have been the primitive vertebrate visual pigment. Its association with fresh water existence throughout this range of organisms also is consistent with the view that the vertebrate stock originated in fresh water. The observation that in the life cycle of the lamprey rhodopsin precedes porphyropsin is not at variance with the idea that porphyropsin is the more primitive pigment, since this change is part of the second metamorphosis, marking the return to the original environment. The observation that in lampreys, fishes, and amphibia, porphyropsin maintains the same general association with fresh water, and rhodopsin with marine and terrestrial habit, suggests that a single genetic mechanism may govern this association throughout this wide span of organisms.
THE ACTIVE TRANSPORT OF PHOSPHATE INTO THE YEAST CELL
Authors: Goodman Joan , Rothstein Aser
Published: May 2004

Phosphate can distribute in the cell wall space, but is not bound to an appreciable extent at the cell surface in non-metabolizing yeast. During metabolism of sugars, phosphate is actively transported into the yeast cell by a mechanism specifically involving glycolysis reactions. The movement of phosphate is in the inward direction only (no appreciable efflux), and it can proceed against a concentration gradient of 100 to 1. It is dependent on external phosphate concentrations in an asymptotic relationship, but is independent of the cellular orthophosphate concentration. The pH optimum for the phosphate uptake of 6.5 is shifted to the acid side by potassium. At certain values of pH a stimulation of 700 per cent by potassium can be observed. The nature of the effects of K+ and H+ are discussed.
STUDIES OF THE CHLORIDE TRANSPORT IN THE GASTRIC MUCOSA OF THE FROG
Authors: Heinz Erich , Durbin Richard P.
Published: May 2004

The unidirectional fluxes of Cl- and Na+ across the frog gastric mucosa in vitro were investigated with radioactive isotopes, and related to the secretory and electrical properties of the normal, and metabolically inhibited, mucosa. The flux of Cl- from nutrient to secretory surface of the mucosa was observed to rise sharply with increasing acid secretion, while the corresponding flux of Na+ did not change appreciably. Lowering [NaCl] in the secretory solution caused a proportional drop in the fluxes from secretory to nutrient surface, of both Cl- and Na+. Under the same conditions, the flux of Cl- from nutrient to secretory surface fell by nearly the same amount as did the flux of Cl- in the opposite direction, while the flux of Na+ from nutrient to secretory surface remained essentially unchanged. Electrical and hydrodynamic causes for this observation could be excluded. Metabolic inhibitors, including cyanide, azide, DNP, and anaerobiosis depressed Cl- flux in both directions distinctly below the corresponding values observed with the normal, non-secreting mucosa. At the same time, a decrease in electrical potential difference and conductance was observed under inhibition. The flux of Na+ was little changed by metabolic inhibition. The relationship between fluxes and conductance of Cl- during metabolic inhibition differs markedly from that observed under normal conditions, and is consistent with the view that during metabolic inhibition most of the Cl- moving across the mucosa does so as a free ion. From the above data it is concluded that Cl- is normally transported across the mucosa in combination with a carrier, the supply of which is impaired under metabolic inhibition. According to the behavior of the Na+ flux, the passive permeability of the mucosa appeared to be little affected by the metabolic inhibition applied, but seemed to rise considerably after death of the mucosa, probably due to structural damage.
THE AMINO ACID REQUIREMENTS OF RABBIT FIBROBLASTS, STRAIN RM3-56
Authors: Haff R. F. , Swim H. E.
Published: May 2004

Strain RM3-56 of rabbit fibroblasts was found to require arginine, cystine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tryptophan, tyrosine, and valine for growth in a medium containing 2 per cent dialyzed serum as the only undefined component. The requirement for serine is less specific than that of the other 13 amino acids and it is partially replaced by glycine, or alanine, or by several combinations of so called accessory amino acids. The concentrations of essential amino acids which permit maximal proliferation range from 0.005 to 0.3 mM. Cystine, glutamine, lysine, tryptophan, tyrosine, valine are toxic at concentrations of 5 mM. The rate of proliferation of RM3-56 in a medium containing all 14 essential amino acids is increased significantly by the addition of alanine and to a lesser extent by the addition of aspartic and glutamic acids and glycine. A deficiency of cystine or glutamine results in cellular degeneration within 3 to 5 days, whereas the cells remain in good condition for 2 to 3 weeks in the absence of each of the remaining 12 essential amino acids. The results obtained with RM3-56 are compared with strains HeLa, L, and U12, whose amino acid requirements have been investigated under similar conditions.
ENTRANCE OF WATER INTO HUMAN RED CELLS UNDER AN OSMOTIC PRESSURE GRADIENT
Authors: Sidel Victor W. , Solomon A. K.
Published: May 2004

A new technique to determine the rate of water passage through the membrane of the human erythrocyte under an osmotic gradient has been developed. It utilizes a rapid mixing apparatus of the Hartridge-Roughton type which permits measurements at short intervals after the reaction has begun. This is coupled with a light-scattering device of new design which permits the determination of very small changes in volume of the cells without disturbing them. With this technique it was possible to measure the change in volume of freshly drawn human erythrocytes after about 50, 100, 155, and 215 msec. of exposure to anisotonic media. The experimental curves were compared with theoretical curves derived from accepted equations for the process and a permeability coefficient of 0.23 ± 0.03 (cm.4/osm., sec.) was obtained.
THE RATE OF EXCHANGE OF TRITIATED WATER ACROSS THE HUMAN RED CELL MEMBRANE
Authors: Paganelli C. V. , Solomon A. K.
Published: May 2004

The flow method of reaction rate measurement has been adapted to the determination of the rate of diffusion of water into the human red cell. In seven experiments the half-time for diffusion exchange has been found to be 4.2 ± 1.1 msec., which is equivalent to a diffusion flow of 8.6 x 10–9 ml. H2O/(sec., red cell). This figure has been compared with the rate of water entrance under an osmotic pressure gradient, and has been found to be smaller by a factor of 2.5. The difference between these two rates of water entrance has been interpreted as indicating the presence of water-filled channels in the membrane. An estimate of the equivalent radius of these channels (on the assumption of uniform right cylindrical pores) leads to a value of 3.5 Å, which is viewed as an operational description of the resistance offered by the membrane to the passage of water.
INPUT-OUTPUT RELATION IN A FLEXOR REFLEX
Authors: Lloyd David P. C.
Published: May 2004

Observations have been made upon a typical flexor reflex with the aim of disclosing the changes in amount, latency, and temporal configuration of reflex discharge that take place as afferent input is varied from zero to maximal for the band of cutaneous myelinated afferent fibers that extends upward from approximately 6 µ in diameter (group II fibers). Reflex threshold is reached at 6 to 12 per cent maximal afferent input. From threshold to maximal input the relation between input and amount of output is essentially linear, latency on the average decreases, the shorter central paths in general gain preference, but the known minimum pathway, one of three neurons, does not transmit unless aided by convergent activity. Flexor reflex discharge may occur in several bursts suggesting the existence of closed chain connections in the internuncial pools of the spinal cord. At any given input there is, in successively elicited reflexes, little correlation between latency and amount of discharge, at first sight a surprising result for each variable can be taken as a measure of excitability status of the motoneuron population. However, latency of discharge indicates excitability at the beginning of the reflex event whereas amount of discharge is an expression of excitability over the entire period of discharge. Given a constantly and rapidly fluctuating excitability absence of correlation between these variables would be an anticipated result.
LYSIS FROM WITHOUT OF S. AUREUS K1 BY THE COMBINED ACTION OF PHAGE AND VIROLYSIN
Authors: Ralston Doris J. , Baer Beatrice S. , Lieberman Miriam , Krueger Albert P.
Published: May 2004

Lysis from without (LFW) occurs in two steps: (1) sensitization of cells by phage, which renders the cells susceptible to (2) destruction of an essential cell structure by an extracellular lytic enzyme. Virolysin, from phage-infected cells, was used in these studies. Normal cell autolysin is also effective.

Evidence is presented that:

1. Neither phage nor lysin alone causes LFW.

2. Sensitization requires phage adsorption.

3. It can be caused by non-infectious particles. This establishes a new biological activity of the particle.

4. Heat, U.V., detergents, penicillin, and other damaging agents also sensitize cells.

5. Sensitization involves a non-lethal, reversible reaction.

6. Sensitization by phage prevents virus synthesis. Following adsorption, a cell can undergo sensitization or infection but not simultaneously. When only a few particles are adsorbed, infection can occur; when sufficient particles are adsorbed, sensitization takes place.

7. Quantitative aspects of LFW are described. Lysis proceeds logarithmically. The lysis end-point depends upon the phage concentration but is independent of the enzyme concentration.
PHOTOREACTIVATION IN VITRO OF ULTRAVIOLET INACTIVATED HEMOPHILUS INFLUENZAE TRANSFORMING FACTOR
Authors: Rupert Claud S. , Goodgal Sol H. , Herriott Roger M.
Published: May 2004

Hemophilus influenzae—transforming DNA, which has been inactivated by ultra-violet radiation, is reactivated by visible light in the presence of a cell-free extract of Escherichia coli B.

The time rate of reactivation is increased by increasing the E. coli extract concentration, the temperature, and the intensity of illumination.

Only DNA containing an ultraviolet-damaged genetic marker exhibits increased transforming activity after treatment with the photoreactivating system.

The reactivating capacity of the extract remains in the top supernatant after centrifugation at 110,000 x g for 1 hour and is not present in the pellet. This capacity is destroyed by heating to 90°C. for 1 minute.

The active system of the E. coli extract is separable into dialyzable, heat-stable and non-dialyzable, heat-labile fractions. The dialyzable fraction contains at least one component which limits the maximum degree of recovery attained.
THE RHODOPSIN SYSTEM OF THE SQUID
Authors: Hubbard Ruth , St. George Robert C. C.
Published: May 2004

Squid rhodopsin (λmax 493 mµ)—like vertebrate rhodopsins—contains a retinene chromophore linked to a protein, opsin. Light transforms rhodopsin to lumi- and metarhodopsin. However, whereas vertebrate metarhodopsin at physiological temperatures decomposes into retinene and opsin, squid metarhodopsin is stable.

Light also converts squid metarhodopsin to rhodopsin. Rhodopsin is therefore regenerated from metarhodopsin in the light. Irradiation of rhodopsin or metarhodopsin produces a steady state by promoting the reactions,

See PDF for Equation

Squid rhodopsin contains neo-b (11-cis) retinene; metarhodopsin all-trans retinene. The interconversion of rhodopsin and metarhodopsin involves only the stereoisomerization of their chromophores.

Squid metarhodopsin is a pH indicator, red (λmax 500 mµ) near neutrality, yellow (λmax 380 mµ) in alkaline solution. The two forms—acid and alkaline metarhodopsin—are interconverted according to the equation,

Alkaline metarhodopsin + H+ ⇌acid metarhodopsin,

with pK 7.7. In both forms, retinene is attached to opsin at the same site as in rhodopsin. However, metarhodopsin decomposes more readily than rhodopsin into retinene and opsin.

The opsins apparently fit the shape of the neo-b chromophore. When light isomerizes the chromophore to the all-trans configuration, squid opsin accepts the all-trans chromophore, while vertebrate opsins do not and hence release all-trans retinene.

Light triggers vision by affecting directly the shape of the retinene chromophore. This changes its relationship with opsin, so initiating a train of chemical reactions.
EFFECTS OF EXTERNAL IONS ON MEMBRANE POTENTIALS OF A LOBSTER GIANT AXON
Authors: Dalton John C.
Published: May 2004

The effects of varying external concentrations of normally occurring cations on membrane potentials in the lobster giant axon have been studied and compared with data presently available from the squid giant axon. A decrease in the external concentration of sodium ions causes a reversible reduction in the amplitude of the action potential and its rate of rise. No effect on the resting potential was detected. The changes are of the same order of magnitude, but greater than would be predicted for an ideal sodium electrode. Increase in external potassium causes a decrease in resting potential, and a decrease in potassium causes an increase in potential. The data so obtained are similar to those which have been reported for the squid giant axon, and cannot be exactly fitted to the Goldman constant field equation. Lowering external calcium below 25 mM causes a reduction in resting and action potentials, and the occasional occurrence of repetitive activity. The decrease in action potential is not solely attributable to a decrease in resting potential. Increase of external calcium from 25 to 50 mM causes no change in transmembrane potentials. Variations of external magnesium concentration between zero and 50 mM had no measurable effect on membrane potentials. These studies on membrane potentials do not indicate a clear choice between the use of sea water and Cole's perfusion solution as the better external medium for studies on lobster nerve.
POTASSIUM AND SODIUM MOVEMENTS IN THE EHRLICH MOUSE ASCITES TUMOR CELL
Authors: Hempling H. G.
Published: May 2004

Studies have been conducted on the movements of sodium and potassium into and out of the Ehrlich ascites tumor cell. Under steady state conditions, at 22°C., in the absence of an exogenous source of glucose, the cell flux for both potassium and sodium averaged 0.8 µM107 cells/hr, or 3.0 pM/cm.2/sec. The cell can accumulate potassium and extrude sodium against electrochemical gradients for both ions. It is possible under the experimental conditions reported to separate the transport systems for these two ions. Thus, it has been shown that under conditions of low temperature with a diminished metabolism, net fluxes for the two ions are different. Also, following periods of 24 hours at 2°C., an exogenous source of glucose enhances the accumulation of potassium sevenfold while sodium extrusion is uninfluenced by the presence of glucose. Similarly potassium exchange rates are temperature-dependent, with Q10 values as high as 5, while exchange rates for sodium are temperature-insensitive, with Q10 values of 1.2 to 1.6. Glycolysis has been eliminated as an energy source for the transport processes since these processes go on in the absence of an exogenous source of glucose. It is estimated that a maximum of 0.3 per cent of the energy derived from the total oxidative metabolism of glucose would be required to support independent transport of potassium and sodium.
THE ACTIVE TRANSPORT OF Mg++ AND Mn++ INTO THE YEAST CELL
Authors: Rothstein A. , Hayes A. , Jennings D. , Hooper D.
Published: May 2004

Certain bivalent cations, particularly Mg++ and Mn++, can be absorbed by yeast cells, provided that glucose is available, and that phosphate is also absorbed. The cation absorption is stimulated by potassium in low concentrations, but inhibited by higher concentrations. From the time course studies, it is apparent that the absorption rather than the presence of phosphate and the potassium is the important factor. Competition studies with pairs of cations indicate that binding on the surface of the cell is not a prerequisite to absorption. The absorption mechanism if highly selective for Mg++ and Mn++, as compared to Ca++, Sr++, and UO2++, whereas the binding affinity is greatest for UO2++, with little discrimination between Mg++, Ca++, Mn++, and Sr++. In contrast to the surface-bound cations which are completely exchangeable, the absorbed cations are not exchangeable. It is concluded that Mg++ and Mn++ are actively transported into the cell by a mechanism involving a phosphate and a protein constituent.
THE POSTSPIKE POSITIVITY OF UNMEDULLATED FIBERS OF DORSAL ROOT ORIGIN
Authors: Gasser Herbert S.
Published: May 2004

The positivity following the spike in the action potential of unmedullated nerve fibers of dorsal root origin (d.r.C) has been shown to be homologous with the first positive potential (P1) of other varieties of nerve fibers. Thus it is only through the large size of the positivity that this group of nerve fibers is set apart from other groups. New findings accentuate and make more explicit the difference of d.r.C fiber behavior from that of the sympathetic unmedullated fibers.

Support of the conclusion is derived from re-examination of the A fibers as well as from observations on the d.r.C fibers.

Increase in size of the P1's in a tetanus of the d.r.C fibers can occur if the frequency is high enough; and it does not occur in an A fiber tetanus if the frequency is low enough. Frequency is also critical in the obtainment of increasing P1's in a tetanus of sympathetic C fibers.

Decrease in the size of the P1's in the course of a tetanus is attributable to development of the negative after-potential (N a-p). In rested d.r.C fibers the N a-p is latent. But it appears during a tetanus, develops in size, and after the tetanus leads to a long lasting and clearly defined second positive potential.

Absence of a supernormal period during the N a-p of the d.r.C fibers is accounted for.

An analysis is made of the apparent increase in size of the spike elevations during a tetanus, for the two subgroups of the C fibers.

The difference between the after-potentials of A fibers and of sympathetic C fibers is correlated with the shapes of the curves of cathodal electrotonus of these fibers.
ACTIVE SODIUM TRANSPORT BY THE ISOLATED TOAD BLADDER
Authors: Leaf Alexander , Anderson John , Page Lot B.
Published: May 2004

Studies were made of the active ion transport by the isolated urinary bladder of the European toad, Bufo bufo, and the large American toad, Bufo marinus. The urinary bladder of the toad is a thin membrane consisting of a single layer of mucosal cells supported on a small amount of connective tissue.

The bladder exhibits a characteristic transmembrane potential with the serosal surface electrically positive to the mucosal surface. Active sodium transport was demonstrated by the isolated bladder under both aerobic and anaerobic conditions. Aerobically the mean net sodium flux across the bladder wall measured with radioactive isotopes, Na24 and Na22, just equalled the simultaneous short-circuit current in 42 periods each of 1 hour's duration. The electrical phenomenon exhibited by the isolated membrane was thus quantitatively accounted for solely by active transport of sodium. Anaerobically the mean net sodium flux was found to be slightly less than the short-circuit current in 21 periods of observation. The cause of this discrepancy is not known.

The short-circuit current of the isolated toad bladder was regularly stimulated with pure oxytocin and vasopressin when applied to the serosal surface under aerobic and anaerobic conditions. Adrenaline failed to stimulate the short-circuit current of the toad bladder.
THE EFFECT OF X-RADIATION ON THE GLUTATHIONE METABOLISM OF INTACT ERYTHROCYTES IN VITRO
Authors: Klebanoff S. J.
Published: May 2004

The x-irradiation of intact washed erythrocytes results in an inhibition of the glyoxalase activity of the cells chiefly as a result of a decrease in the reduced glutathione level. The percentage inhibition is markedly increased by an increase in the dilution of the cells in physiological saline suggesting that the effect of radiation is indirect, via the production in the aqueous medium of free radicals, H2O2, etc. This is supported by the decrease in the inhibition produced by lowering the oxygen tension or by the addition of catalase. The inhibition of glyoxalase activity is also decreased by the addition of methylglyoxal, plasma, adenosine, inosine, glucose, and a number of other sugars to the erythrocyte suspension prior to radiation. Furthermore, some reactivation of the glyoxalase system results from the addition of plasma, glucose, adenosine, and inosine following radiation. These results are discussed in relation to the role of SH compounds, particularly glutathione, in the toxicity of ionizing radiations.
THE REFRACTORY STATE OF THE GENERATOR AND PROPAGATED POTENTIALS IN A PACINIAN CORPUSCLE
Authors: Loewenstein Werner R. , Altamirano-Orrego Rafael
Published: May 2004

A propagated potential produced in the Pacinian corpuscle in response to mechanical stimuli leaves a refractory state of 7 to 10 msec. duration. The refractory state is presumably produced at the first intracorpuscular node of Ranvier. The recovery of receptor excitability for producing an all-or-none response to mechanical stimulation follows the same time course as that of the electrically excited axon. Upon progressive reduction of stimulus interval (mechanical), the propagated potential falls progressively to 75 per cent of its resting magnitude and becomes finally blocked within the corpuscle. A non-propagated all-or-none potential, presumably corresponding to activity of the first node, is then detected. The critical firing level for all-or-none potentials increases progressively during the relative refractory period of the all-or-none potential, as the stimulus interval is shortened. Thus generator potentials up to 85 per cent of a propagated potential can be produced in absence of all-or-none activity. Generator potentials show: gradual over-all increase in amplitude and rate of rise as a function of stimulus strength; constant latency; and spontaneous fluctuations in amplitude. A generator potential leaves a refractory state (presumably at the non-myelinated ending) so that the amplitude of a second generator response which falls on its refractory trail is directly related to the time elapsed after the first generator response and inversely to its amplitude. The generator potential develops independently of any refractory state left by a preceding all-or-none potential.
THE PROLONGED GROWTH AND SURVIVAL OF OVARIAN TISSUE OF THE PROMETHEA MOTH (CALLOSAMIA PROMETHEA) IN VITRO
Authors: Grace T. D. C.
Published: May 2004

1. The ovarian tissues from diapausing pupae of the promethea moth (Callosamia promethea) have survived and grown for 186 days under in vitro conditions. There was continual cell migration and multiplication for a period of 53 days, followed by a period of 47 days during which no cells migrated from the tissues. Between the 100th and 105th days after setting up the cultures, cell migration was resumed, and by the 111th day 250 cells were present in the medium. A few cell divisions were observed between the 126th and 136th days. After the tissues were subcultured on the 140th day, the explant culture continued to survive, but the cell culture died 3 days later.

2. The tissues were subcultured a total of 6 times during the 186 days. By the introduction of a piece of live tissue into the cell cultures, the growth and survival of the cells were increased from 8 days to about 20 days.

3. It is possible that the tissues had become adapted to the medium during their long survival, as the cells which migrated from them after 100 days showed considerably longer survival than those in earlier cultures.