bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE NON-CORRELATION OF BIOELECTRIC POTENTIALS WITH IONIC GRADIENTS
Authors: Shaw F. H. , Simon Shirley E. , Johnstone B. M. 
Published: May 2004

The sartorius muscles of 320 toads have been analyzed for Na+ and K+. There is a wide variation in the Na+ content which when calculated intracellularly varied from 0 m.eq./kg. to 58 m.eq./kg. In particular it was found that the distribution of internal Na+ in the intact animal was such that only 17 per cent of the muscles should give from the Nernst equation the observed overshoot of 37 mv.
In contrast to this wide variation the K+ content is comparatively constant, the range being 71 to 112 m.eq./kg. The mean observed resting potential of 87 mv. agreed well with the potential calculated from the mean intracellular K+ by the Nernst equation.
Analyses of plasma show that the Na+ content is constant at 130 m.eq./liter, and the K+ is 3.0 m.eq./liter.
The resting and action potentials of 77 muscles have been recorded and then the muscles have been analyzed. The results have shown that there is no correlation between the level of intracellular Na+ and the overshoot. Furthermore the apparent correlation between the average K+ content and the average resting potential has been shown to be fortuitous, when the correlation in individual muscles is considered.
When a muscle is soaked in Ringer solution for several hours there is a gain of Na+ and a loss of K+. These shifts should result in changes in the respective potentials, but such changes were not found.
The above findings have been discussed in the light of the present theories that the resting potential and the action potential are directly related to the ionic ratio across the membrane. Our results very definitely do not support the theory that the overshoot is related to the Na+ gradient, and this also applies with respect to the K+ gradient and the resting potential.
CHANGES IN MEMBRANE CHARACTERISTICS OF HEART MUSCLE DURING INHIBITION
Authors: Trautwein W. , Kuffler S. W. , Edwards C. 
Published: May 2004

Membrane characteristics were studied in isolated muscle strands from auricles of frogs using the "square pulse" technique. Changes in the time course and spatial spread of subthreshold electrotonic potentials were measured. If acetylcholine is applied in concentrations which cause slowing or stoppage of the heart beat, the following changes are produced: (a) the length constant (λ) of the membrane is reduced, (b) the time constant is shortened. The effects are reversible and increase with acetylcholine concentration. The membrane changes caused by acetylcholine dimmish with time.
It is concluded that during acetylcholine inhibition, as well as during vagal inhibition, the conductance of the muscle membrane is increased. Appreciable changes in the resting membrane potential need not accompany inhibition.
SOME PERMEABILITY PROPERTIES OF ISOLATED RAT LIVER CELL MITOCHONDRIA
Authors: Jackson Kenneth L. , Pace Nello 
Published: May 2004

The rates of penetration of various solutes into isolated rat liver mitochondria have been studied.
Sodium, potassium, and sucrose were observed to enter the mitochondria until an equilibrium concentration was reached. The diffusion of these solutes, after the first few minutes, followed the predicted diffusion curve for solutes entering a particle with a rate-limiting membrane and instantaneous mixing in the interior. Reasons for deviations from the predicted equation during the first few minutes of diffusion are suggested.
The data show that at pH 7.4 sodium and potassium enter more rapidly than sucrose. I131-labelled albumin was found to enter very slowly, if at all. Increasing the pH from 7.4 reduced the rate at which sodium ion penetrated the mitochondria. The rate of diffusion of sucrose into mitochondria was considerably slower than diffusion of sucrose into a sphere of water of the same size.
Sodium ion was not found to be concentrated in vitro against an external concentration gradient as has been reported by other investigators.
It is concluded that the rate of diffusion of solutes between the external medium and the interior of mitochondria is probably restricted and controlled by a mitochondrial membrane exhibiting passive permeability characteristics.
STUDIES OF FLUID EXCHANGES BETWEEN RAT LIVER SLICES AND SIMPLE MEDIA
Authors: Itoh Shinji , Schwartz Irving L. 
Published: May 2004

1. The exchange of fluid between slices of rat liver and solutions of monosaccharides, disaccharides, and sodium chloride has been studied in relation to the temperature of incubation. The point of apparent isotonicity (P.A.I.) of the tissue was defined as the concentration of the solution in which the slices neither gained nor lost weight after immersion for a period of 10 minutes.
2. In solutions of glucose, the P.A.I. of the slices was significantly lower at 4°C. than at 20°C. but similar at 20°C. and 37°C. Upon immersion for 15 to 60 minutes in 0.66 molar glucose the slices always swelled more at 37°C. than at 20°C. In solutions of sucrose change in the temperature of incubation was without effect on the hydration of the tissues.
3. In solutions of sodium chloride, the P.A.I. and the content of water, chloride, and sodium plus potassium were lower at 37°C. than at 20°C.
4. These findings emphasize the role of translocation of solute in providing an osmotic gradient for the movement of water between the tissue slices and the media.
THE EXCITABLE PROPERTIES OF THREE TYPES OF MOTOR AXONS
Authors: Adelman William J. 
Published: May 2004

1. Three anatomically different types of lobster motor axons have been shown to possess different excitabilities under identical conditions.
2. The type, openers, which fired the longest trains of repetitive responses also had the lowest rheobase values, the longest utilization times, and the least accommodation.
3. A relationship between the time course of the local potential and the time course of the excitatory state has been disclosed.
4. The characterization of the excitatory state by simple two factor equations has been discussed and found to be only approximate since both the excitatory state and the local response tend to be somewhat oscillatory.
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.
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.