bluuebunny/crossref_metadata_2025_split huggingface dataset:
A QUANTITATIVE ELECTROCHEMICAL THEORY OF THE ELECTROLYTE PERMEABILITY OF MOSAIC MEMBRANES COMPOSED OF SELECTIVELY ANION-PERMEABLE AND SELECTIVELY CATION-PERMEABLE PARTS, AND ITS EXPERIMENTAL VERIFICATION
Authors: Neihof Rex , Sollner Karl 
Published: May 2004

The theory of the electrolyte permeability of mosaic membranes composed of ideally anion-selective and ideally cation-selective parts in juxtaposition is tested in a model which consists of an all-electrolytic cyclic arrangement of four component parts: dilute solution/anion-selective membrane/concentrated solution/cation-selective membrane/dilute solution. In this system cations move from the concentrated to the dilute solution across the cation-selective membrane and an equivalent number of anions move through the anion-selective membrane. This movement of ions corresponds to a flow of current in the system. According to the theory, the number of equivalents of electrolyte which penetrate in any given time across the membranes must be identical with the number of faradays of electricity which flow during the same period. The system is essentially a combination of two menbrane-concentration cells arranged in series in a short-circuited state without the presence of electrodes.
Experimentally the magnitude of the current was determined by measuring with probe electrodes the potential across an element of the circuit whose resistance was known and constant. The number of faradays of electricity (determined from time-current data) flowing in the system during a measured time was compared with the analytically determined number of equivalents of electrolyte which moved across the membranes during the same period. In a variety of experimental systems the two values show a 1:1 ratio with a mean deviation of ± 1.8 per cent.
PROPERTIES OF DORSAL ROOT UNMEDULLATED FIBERS ON THE TWO SIDES OF THE GANGLION
Authors: Gasser Herbert S. 
Published: May 2004

As an aid in the interpretation of the physiological properties of unmedullated nerve fibers, particularly those having their cells of origin in the dorsal root ganglia, more precise information about their morphology has been acquired through employment of the electron microscope.
The appearance of the fibers in the skin nerves is described, with special reference to the structure of their sheaths; and a notation is made about the bearing of the axon-sheath relationship on the biophysical mechanism of conduction (p. 714).
There is no basic difference between the sheath systems of the d.r.C and the s.C fibers.
Attention is called to a point of similarity between the sheaths of unmyelinated and myelinated axons (p. 715).
An assessment was made of the likelihood of interaction between the fibers. In action potentials showing temporal dispersion at several distances, the elevations appeared in their calculated positions. A model of a group of Schwann sheaths was constructed from successive electron microscope sections, showing that the lengths of the sheath branches are short in comparison with the wave lengths of the action potentials. Supported by these and other considerations, the argument is strongly in favor of the conclusion that among d.r.C fibers, as in other fibers, there is no cross-excitation between the axons.
A new analysis of the size distribution of the fibers in a sural nerve was made from electron microscope pictures; and from the measurements the action potential was constructed. The result confirmed the view, previously expressed, that the velocities of conduction in the fibers can be precisely accounted for by multiplying the diameters by a constant.
In the dorsal roots, the striking change that takes place in the appearance of the fibers and their disposition in the Schwann sheaths can be seen in Fig. 11. The axons partake of the special properties of the peripheral branches, which necessitated the creation of the subdivision of d.r.C fibers. But, their diameters are much smaller. At a set of reduced conduction velocities the configuration of the compound action potential in the nerves is repeated in the roots, with the root velocities still conforming to the size-velocity rule derived from nerve axons.
EFFECT OF BLOOD THROMBOKINASE, AS INFLUENCED BY SOY BEAN TRYPSIN INHIBITOR; ULTRACENTRIFUGATION, AND ACCESSORY FACTORS
Authors: Milstone J. H. 
Published: May 2004

1. Crystallized soy bean trypsin inhibitor, at a concentration of 100 µg./ml., suppressed the production of thrombin from a mixture of prothrombin and blood thrombokinase. The experiment was performed in the presence of 0.011 M oxalate, in order to minimize the possibility of participation by accessory factors which require ionic calcium. The results are in accord with the view that thrombokinase is a trypsin-like enzyme.
2. When a solution of blood thrombokinase was centrifuged at 85,000 g for 120 minutes, almost all the activity remained in the supernate. This supernate activated the supernate from a prothrombin solution which had been similarly centrifuged. The activation of prothrombin by thrombokinase can proceed in the absence of material completely sedimentable in 120 minutes at 85,000 g.
3. An "accelerator" reagent was prepared by treating bovine serum with barium carbonate, and then passing the serum through a column of diatomaceous earth. This "accelerator" was used together with prothrombin, blood thrombokinase, Howell's cephalin, and calcium chloride to compose a five-reagent thrombin-producing system. In this system, no thrombin was produced without thrombokinase. On the other hand, thrombin was produced from prothrombin and thrombokinase, even when all the other reagents were omitted. When calcium was omitted, thrombokinase was able to function; but cephalin and the "accelerator" reagent were ineffective.
4. Quantitative tests indicated that the "accelerator" reagent exerted an effect distinct from those of thrombokinase and cephalin. However, it is not certain whether the "accelerator" reagent functioned as an accessory factor, as a potential source of more thrombokinase, or both. In the experiments reported, thrombokinase was primary to, or necessary for, the effect of "accelerator."
5. The effectiveness of thrombokinase was multiplied a hundred times or more, when complemented by calcium, cephalin, and "accelerator" reagent. Ionic calcium was a necessary component of this complementing system. This may help to explain why removal of calcium ions keeps blood fluid, even though thrombokinase, by itself, is little influenced either by calcium ions or by oxalate.
MONOSYNAPTIC REFLEX RESPONSES OF INDIVIDUAL MOTONEURONS
Authors: Lloyd David P. C. , McIntyre A. K. 
Published: May 2004

Individual motoneuron responses to a variety of afferent inputs have been examined. At a given input some motoneurons respond to every trial, some to no trial, and some respond to a certain percentage of trials that is characteristic for the motoneuron at that input. The performance of a motoneuron is expressed by means of a firing index that relates the number of responses to the number of trials.
In a representative assemblage of individual motoneurons some 20 to 30 per cent display intermediate firing indices. This number, comprising an "intermediate zone" remains fairly constant at different levels of input although the individuals within it may be entirely different at two different levels of input.
Frequency distribution of individuals with respect to firing indices is U-shaped.
Intermediacy of firing indices depends upon temporal fluctuation of excitability which, in the first approximation, is normal.
The individual motoneurons are approximately equally frequently distributed with respect to transmitter potentiality of their monosynaptic reflex afferent connections.
The distribution of motoneurons with respect to transmitter potentiality of their monosynaptic reflex connections is considered representative of a natural pool in that the sum of their individual post-tetanic response behaviors accurately reproduces the course of post-tetanic potentiation in a natural pool.
SILICON METABOLISM IN DIATOMS
Authors: Lewin Joyce C. 
Published: May 2004

1. Evidence is presented that silicon uptake in the diatom Navicula pelliculosa is linked with aerobic respiration.
2. Cyanide, fluoride, iodoacetate, arsenite, azide, and fluoroacetate, at concentrations inhibitory to respiration, were also inhibitory to silicon uptake.
3. 2,4-Dinitrophenol (1 to 2 x 10–5 M) stimulated respiration by 100 per cent, but almost completely inhibited silicon uptake.
4. The respiratory quotient of non-Si-deficient cells decreased from 0.93 to 0.75 after 4 days of starvation in darkness. Glucose (1 per cent) raised the respiratory quotient of such starved cells to 1.05.
5. Silicate (20 mg. Si/liter) stimulated respiration of unstarved Si-deficient cells by about 40 per cent. The effect of silicate on the respiration of Si-deficient cells which had been starved in darkness for 4 days was less marked.
6. The respiratory quotient of Si-deficient cells decreased from 0.8–0.9 to 0.3 after 4 days of starvation in darkness. The addition of silicate to starved cells raised the quotient to 0.5. This represented a 25 per cent stimulation of oxygen uptake concomitant with a 90 per cent stimulation of carbon dioxide evolution.
7. Glucose (1 per cent) caused an increase of respiratory quotient in starved cells from 0.3 to 0.7–0.8. The addition of silicate had no effect on the R.Q. during the oxidation of exogenous glucose.
8. Substrates (glucose, fructose, galactose, lactate, succinate, citrate, glycerol), which caused a stimulation of respiration in starved cells, also stimulated silicon uptake by those cells. However, the stimulation of silicon uptake (50 to 100 per cent) was not proportional to the respiratory stimulation by these substrates (30 to 300 per cent).
MICROANATOMY OF THE ABDOMINAL STRETCH RECEPTORS OF THE CRAYFISH (ASTACUS FLUVIATILIS L.)
Authors: Florey Elisabeth , Florey Ernst 
Published: May 2004

Microanatomical studies on the abdominal stretch receptor organs of the crayfish Astacus fluviatilis L. have been carried out in order to establish a basis for the physiological work that has been, and is being carried out on stretch receptors of various species of crayfish.
Important differences have been found between these organs and those previously described by Alexandrowicz for the lobsters Homarus vulgaris and Palinurus vulgaris.
With the aid of silver-impregnated preparations the relationship of sensory endings and muscle fibers has been shown as well as the pattern of the efferent innervation. The physiological significance of the histological findings has been discussed.
THE PARALLELISM BETWEEN THE ACTION POTENTIAL, ACTION CURRENT, AND MEMBRANE RESISTANCE AT A NODE OF RANVIER
Authors: Tasaki I. , Freygang W. H. 
Published: May 2004

1. Simultaneous measurements of action potential and resistance and of action current and impedance change have been made at a single node of Ranvier.
2. There is a parallelism between action potential, action current, and resistance change measured at a node of Ranvier.
3. Some implications of these results have been discussed in relation to the corresponding data obtained from the squid giant axon.
INITIATION AND ABOLITION OF THE ACTION POTENTIAL OF A SINGLE NODE OF RANVIER
Authors: Tasaki I. 
Published: May 2004

1. Using single node preparations of the bull frog or the toad, observations were made on the variation of the voltage across the nodal membrane under various experimental conditions.
2. The time constant of the variation in the membrane voltage caused by a long subthreshold rectangular pulse was of the order of 0.1 msec.
3. The action potential was initiated when the potential inside the node was raised stimulating pulses above a threshold level of approximately 15 mv. for a node in normal Ringer; it was greater in a relatively refractory node and in a partially narcotized node.
4. The variation of the membrane voltage caused by long stimulating pulses of subrheobasic strengths was in general proportional to the strength of the applied pulse. A non-linear behavior of the membrane voltage was observed with barely subthreshold stimulating pulses.
5. The early portion of the action potential of a node was not modified by a direct current which was strong enough to produce measurable potential changes (IR drops) across the resting membrane.
6. A strong pulse of inward current applied to the node during activity abolished the portion of the action potential following the pulse in all-or-none manner.
7. There was no refractory period after a response abolished in its early phase. Following a response abolished later, the recovery in the spike height started from the level of the action potential at the time of abolition.
8. Initiation and abolition of action potentials at a single node are interpreted as "transitions" between the two "equilibrium potential levels" at the node.
THE NATURE OF THE LAMPREY VISUAL PIGMENT
Authors: Crescitelli Frederick 
Published: May 2004

From the retina of the land-locked population of the sea lamprey, Petromyzon marinus, a photolabile pigment was extracted which was identified spectrophotometrically as a member of the rhodopsin group of pigments. Using the absorption spectrum of a relatively pure solution and analysis by means of difference spectra, the peak of this pigment was placed at about 497 mµ. The method of selective bleaching by light of different wave lengths revealed no significant amounts of any other pigment in the extracts. A similar pigment was also detected in retinal extracts of the Pacific Coast lamprey, Entospenus tridentatus.
These results are significant for two reasons: (a) the lamprey is shown to be an example of an animal which spawns in fresh water but which is characterized by the presence of rhodopsin, rather than porphyropsin, in the retina; (b) the primitive phylogenetic position of the lamprey suggests that rhodopsin was the visual pigment of the original vertebrates.
WATER FLOW THROUGH FROG GASTRIC MUCOSA
Authors: Durbin Richard P. , Frank Heddy , Solomon A. K. 
Published: May 2004

The transport of water through biological membranes can be attributed to several causes. Gradients of chemical activity caused by the application of hydrostatic pressure or differences in solute concentration across the membrane may produce a net water flow, called passive transport (1). In the absence of such gradients a net flow may also occur which is defined as active transport, and is presumed to arise from metabolic processes occurring in the membrane. Pappenhehner, Renkin, and Borrero (2) and Koefoed-Johnsen and Ussing (3) have independently shown that passive flows can be interpreted to give a model of the membrane in terms of pore structure.
In the present study two types of experiments have been performed on passive water transport across the isolated gastric mucosa of the frog. First, the unidirectional diffusion flow of water in either direction has been measured using tritiated water as a tracer. Second, an osmotic gradient has been applied across the membrane and a passive net flow has been measured. At the same time an active net flow in the same direction as HC1 secretion has also been observed.
In addition to the water transport studies, separate measurements have been made of the restriction offered by the membrane to diffusion of various sized molecules. The combined results of these experiments are interpreted in terms of a polydisperse population of pores in the membrane.
PROTEIN SYNTHESIS IN THE PERFUSED RAT LIVER
Authors: Jensen David , Tarver Harold 
Published: May 2004

1. When the rat livers are perfused under the conditions of these experiments with rat blood diluted with saline, the livers remain capable of removing colloidal chromic phosphate normally for 4 hours or more; that is, the reticuloendothelial system continues to function normally.
2. Good rates of bile flow continue, generally for 4 hours.
3. The livers incorporate radioactivity from the amino acids methionine, lysine, and histidine at rapid rates for 1 or 2 hours. Thereafter the rates fall.
4. The specific activity of the free lysine and histidine in the perfusate falls rapidly during the experiments (to 25 or 35 per cent of its original value at 10 minutes).
5. The fall in rate of incorporation of radioactivity is attributable to the fall in amino acid specific activity.
6. Addition of a complete amino acid mixture to the perfusate does not appear to have any stimulatory effect on incorporation of radioactivity from labelled amino acids.
7. With lysine, on the assumption that incorporation is due to new protein formation, there is a rate of synthesis equivalent to 230 mg. of plasma protein per 100 gm. of rat per day. This result is in agreement with turnover data obtained from rats in vivo.
8. The results emphasize once again the importance of precursor specific activity in the interpretation of metabolic experiments with labelled amino acids.
CATION TRANSPORT IN YEAST
Authors: Foulkes Ernest C. 
Published: May 2004

1. The distribution of azide added to suspensions of bakers' yeast was studied under various conditions. The recovery of azide was estimated in the volume of water into which low concentrations of electrolytes can readily diffuse (anion space). Considerable azide disappeared from this anion space.
2. The incomplete recovery of azide in the anion space is due to its uptake by the cells. This uptake occurs against a concentration gradient at 0°C., and is attributed to binding of azide by cell constituents.
3. Confirmatory evidence is presented that one such constituent is the K carrier in the cell membrane. The azide inhibition of K transport is not mediated by inhibition of cytochrome oxidase in the mitochondria.
4. From the amount of combined azide and the experimentally determined dissociation constant of the K carrier-inhibitor complex, the maximum value for the concentration of this carrier is calculated as 0.1 µM/gm. yeast.
5. The addition of glucose and PO4 causes a secondary K uptake which is not azide-sensitive and is clearly distinct from the primary, azide-sensitive mechanism.
6. The existence of a separate carrier responsible for Na extrusion is reconsidered. It is concluded that present evidence does not necessitate the assumption that such a carrier is active in yeast.
THE EFFECT OF EXTERNAL CALCIUM AND MAGNESIUM DEPLETION ON SINGLE NERVE FIBERS
Authors: Adelman William J. 
Published: May 2004

The three types of motor axons found in the walking legs of the lobster were shown to respond differently upon exposure to calcium-free solutions. While all fiber types became more excitable initially in calcium-free solutions, only openers became spontaneously active. Fast closers showed the least reduction in rheobase value upon calcium depletion. After 5 minutes in calcium-free solution all fibers showed a rise in rheobase value, and more rapid accommodation. A natural period for spontaneous firing of opener fibers was disclosed. Following such a spontaneous discharge, low amplitude rhythmical potentials were recorded. These small potentials had the same period as the spontaneous spikes. The role of calcium ion in the excitable process was discussed.
Magnesium ion was shown to act synergistically with calcium ion. All fiber types became spontaneously active in solutions deprived of both calcium and magnesium. Subsequent hypoexcitability was more pronounced in calcium- and magnesium-depleted solutions than it was in only calcium-depleted solutions.
THE EFFECT OF POLYPHOSPHATES AND MAGNESIUM ON THE MECHANICAL PROPERTIES OF EXTRACTED MUSCLE FIBERS
Authors: Bozler Emil 
Published: May 2004

Loading of extracted muscle fibers causes a small, sudden lengthening, followed by a slower, plastic extension, which is reversed only by active contraction. Polyphosphates in the presence of Mg strongly accelerate plastic extension, but elastic changes in length remain the same as during rigor. The modulus of elasticity on the average is about 6.2 x 107 dynes per cm.2 This value is about 40 times larger than that of rubber, if compared on a water-free basis. Extension of muscle, therefore, is almost entirely due to plastic deformation.
Mg is essential for the softening action of adenosinetriphosphate (ATP) and can produce partial relaxation in the absence of a relaxation factor. After partial removal of bound Mg, ATP causes strong contraction, but only slight softening. The same condition is produced by very low concentrations of ATP in the presence of phosphocreatine. These observations show that during contraction passive mechanical properties may remain essentially like those during rigor. The constancy of elastic extensibility distinguishes contraction produced by ATP from contraction induced by non-specific agents in various fibrous structures and caused by an increase in configurational entropy.
THE ISOLATION OF MYXOMYOSIN, AN ATP-SENSITIVE PROTEIN FROM THE PLASMODIUM OF A MYXOMYCETE
Authors: Ts'o Paul O. P. , Eggman Luther , Vinograd Jerome 
Published: May 2004

1. A procedure has been developed for the preparation of an active concentrate from the myxomycete, Physarum polycephalum. This concentrate responds with a lowered viscosity to the addition of small amounts of ATP. The preparation recovers in viscosity, and the process may be repeated.
2. In the most active concentrates, 75 per cent of the non-dialyzable material moves as a single boundary both in the descending limb in electrophoresis and in the ultracentrifuge. It contains about 10 per cent ribonucleic acid, which is at least in part reversibly bound to the protein.
3. The active material has been designated myxomyosin because of its origin and its similarity to actomyosin in ATP response.
SEROLOGICAL INVESTIGATIONS OF CELL ADHESION IN THE SLIME MOLDS, DICTYOSTELIUM DISCOIDEUM, DICTYOSTELIUM PURPUREUM, AND POLYSPHONDYLIUM VIOLACEUM
Authors: Gregg James H. 
Published: May 2004

1. Antibodies to slime molds were produced by injecting D. discoideum and D. purpureum amebas from 48 hour cultures into rabbits.
2. Anti-D. discoideum and anti-D. purpureum sera caused agglutination of homologous amebas from 24 to 26 hour cultures, agglutination of certain heterologous amebas from 30 to 36 hour cultures, and agglutination of all heterologous amebas from 43 to 48 hour cultures.
3. The data show that new surface antigens are formed in cultures after 26 hours and it is suggested that the new antigens are concerned with cell adhesion.
4. The probable role of surface antigens in the interaction of cells of different species of slime molds was discussed.
CULTURE IN VITRO OF TISSUE FROM THE SILKWORM, BOMBYX MORI L
Authors: Wyatt S. Silver 
Published: May 2004

1. Ovarian tissue from Bombyx mori L. larvae about to pupate was cultured in Trager's (1935) salt solution and 10 per cent hemolymph, with indifferent results. Improvement of cultures was sought by modifying the culture medium.
2. To reduce the activity of the tyrosinase, hemolymph for culture medium was heated for 5 minutes at 60°C., and the coagulated protein removed.
3. A physiological solution was formulated containing cations and amino acids as they occur normally in silkworm hemolymph. In both hanging-drop and small tube cultures use of this medium brought about increased cell number, improved cell appearance, more rapid mitoses, and longer life of cultures.
4. To the solution formulated from analyses, tryptophan, cystine, cysteine, malate, fumarate, succinate, and α-ketoglutarate were added after testing individually, resulting in improved growth in cultures.
5. Use of a silkworm egg extract prepared 4 to 5 days after acid treatment produced an increase in cell number.
6. In small roller tube cultures, when the new medium was changed twice a week, the cells spread over the walls of the tube in 4 or 5 days (Figs. 8 and 9), rapid mitoses were observed after 2 weeks, and transparent active cells were present at 3 weeks. Subculturing was not attempted.