bluuebunny/crossref_metadata_2025 huggingface dataset:
VOLTAGE CLAMP BEHAVIOR OF IRON-NITRIC ACID SYSTEM AS COMPARED WITH THAT OF NERVE MEMBRANE
Authors: Tasaki I. , Bak A. F.
Published: May 2004

The current-voltage relation for the surface layer of an iron wire immersed in nitric acid was investigated by the voltage clamp technique. Comparing the phase of nitric acid to the axoplasm and the metallic phase to the external fluid medium for the nerve fiber, a striking analogy was found between the voltage clamp behavior of the iron-nitric acid system and that of the nerve membrane. The current voltage curve was found to consist of three parts: (a) a straight line representing the behavior of the resting (passive) membrane, (b) a straight line representing the fully excited (active) state, and (c) an intermediate zone connecting (a) and (b). It was shown that in the intermediate zone, the surface of iron consisted of a fully active patch (or patches) surrounded by a remaining resting area. The phenomenon corresponding to "repetitive firing of responses under voltage clamp" in the nerve membrane was demonstrated in the intermediate zone. The behavior of the cobalt electrode system was also investigated by the same technique. An attempt was made to interpret the phenomenon of initiation and abolition of an active potential on the basis of the thermodynamics of irreversible processes.
RESPONSES OF MOTONEURONS UNDERGOING CHROMATOLYSIS
Authors: McIntyre A. K. , Bradley K. , Brock L. G.
Published: May 2004

The delayed and asynchronous firing of chromatolytic motoneurons in response to group I afferent volleys is shown to be evoked monosynaptically, there being an abnormally long and variable delay between onset of monosynaptic action and generation of impulse discharge. Intensity of monosynaptic excitatory action is reduced, and considerable variability in the form of successively evoked postsynaptic potentials is often observed. No evidence has been found for the development of excitatory group I polysynaptic pathways.

Reduction in responsiveness of finer dendrites is indicated by the feeble "d" response evoked by an antidromic volley in a chromatolytic motor nucleus. Antidromic impulses appear to invade the cell bodies and coarse dendrites, but die out at points short of the normal extent of dendritic invasion. Vigorous firing of Renshaw cells can be elicited by antidromic volleys.

Chromatolytic motoneurons appear to maintain reasonably normal resting membrane potentials, but are more susceptible to damage than are normal cells. Action potentials are large and usually overshoot the resting potential level. Post spike potentials are similar to those of normal cells except for a less prominent, or absent, early phase of depolarisation.

In contrast with the reduced responsiveness of peripheral dendrites, there is a lowered threshold for antidromic and segmental reflex synaptic activation of the more central regions, probably the cell bodies and nearby coarse dendrites, of motoneurons undergoing chromatolysis.
EFFECTS OF EXTERNAL IONS ON MEMBRANE POTENTIALS OF A CRAYFISH GIANT AXON
Authors: Dalton John C. ,   With the Technical Assistance of David J. Houck
Published: May 2004

Transmembrane potentials in the crayfish giant axon have been investigated as a function of the concentration of normally occurring external cations. Results have been compared with data already available for the lobster and squid giant axons. The magnitude of the action potential was shown to be a linear function of the log of the external sodium concentration, as would be predicted for an ideal sodium electrode. The resting potential is an inverse function of the external potassium concentration, but behaves as an ideal potassium electrode only at the higher external concentrations of potassium. Decrease in external calcium results in a decrease in both resting potential and action potential; an increase in external calcium above normal has no effect on magnitude of transmembrane potentials. Magnesium can partially substitute for calcium in the maintenance of normal action potential magnitude, but appears to have very little effect on resting potential. All ionic effects studied are completely reversible. The results are in generally good agreement with data presently available for the lobster giant axon and for the squid giant axon.
ACTION OF INSULIN ON SUGAR PERMEABILITY IN RAT DIAPHRAGM MUSCLE
Authors: Norman David , Menozzi Piergiulio , Reid Doreen , Lester Gabriel , Hechter Oscar
Published: May 2004

Insulin action upon sugar permeability has been examined in rat diaphragm muscle prepared so that the fibers are either intact or cut. In intact preparations, sucrose and mannitol are largely excluded from the intracellular water while D-galactose, D-xylose, and L-xylose equilibrate in a small fraction of the total cell water; the availability of cell water for D-galactose, D-xylose, and L-xylose is increased by insulin. In cut preparations, in which the cell membrane is not intact, all the sugars studied penetrate into the cell, but intracellular water is not uniformly available for subsequent permeation. Sucrose distributes in a volume of about 40 to 45 per cent of the available cell water; D-xylose, D-galactose, L-xylose, and mannitol are distributed in all or most of the cell water, but these sugars diffuse at different rates. In cut preparations insulin increases the rate of equilibration of D-galactose and D-xylose without significant effect on the other sugars studied; insulin also exerts a "directive" influence on glycogen synthesis from glucose, which cannot be explained solely in terms of accelerated sugar penetration. The significance of these observations in elucidating the locus of insulin action is discussed.
I. After-Effects of Repetitive Activity in a Nerve Ending
Authors: Loewenstein Werner R. , Cohen Stanley
Published: May 2004

Repetitive mechanical stimulation causes depression of excitability in isolated Pacinian corpuscles: the mechanical threshold of the sense organ for producing nerve impulses increases progressively with time of repetitive stimulation. The effect is completely reversible; it can be elicited with repetitive stimuli of less than threshold strength. Within certain limits, the depression increases as a function of strength and frequency of the repetitive stimuli.
The Effect of the Ovarian Steroids on the Membrane Potential of Uterine Muscle
Authors: Goto M. , Csapo A.
Published: May 2004

Measurements with flexible intracellular microelectrodes show that the rabbit myometrium when insufficiently stimulated by estrogen has a low membrane potential of about 30 to 35 mv. Estrogen (endogenous or exogenous) increases this value up to 43 to 48 mv., whereas progesterone increases it still further up to 55 to 60 mv.

Between the 20th and 29th days of rabbit pregnancy the membrane potential at placental implantation sites is about 10 mv. higher than between these sites. Progesterone treatment increases the value at the interplacental sites to the level of the placental sites. The onset of labor is preceded by a drop in membrane potential at the placental sites to the level of the interplacental sites. This change results in a more or less uniform potential of 45–50 mv. along the length of the uterine horn at term.

The membrane potential of the uterus is a log function of the [K]0 at values greater than 12 mM/liter, as is the case in other excitable tissues. In Ca-free Krebs the membrane potential of the estrogen-dominated uterus drops to a low level; the progesterone-dominated myometrium exhibits only a transient and lesser decrease.

The membrane potential of the myometrial cell is influenced by endocrine regulation. The correlation between membrane potential and threshold only holds for the estrogen-dominated uterus, however, in other endocrine conditions the relationship breaks down.
The Electrophoretic Velocity of Human Red Cells, of Their Ghosts and Mechanically Produced Fragments, and of Certain Lipid Complexes
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

Ghosts prepared in CO2-saturated water from unwashed human red cells can be fragmented mechanically, but ghosts from thrice washed cells cannot. If the ghosts are prepared by freezing and thawing, this difference is not observed.

The electrophoretic velocity varies also with the way in which the ghosts are prepared. The pH-mobility dependence of washed red cells flatten off to a plateau at pH 9, and the electrophoretic velocity is zero at about pH 2. Ghosts prepared by freezing and thawing have almost the same pH-mobility dependence, but if the ghosts are prepared in CO2-saturated hyptonic saline, the mobility at pH 9.4 is 0.75 times that of washed cells. Fragments of ghosts of unwashed red cells have a smaller mobility than that of the red cells. Trypsin reduces the mobility of washed red cells and of ghosts.

Sols of lipid complexes (lecithin, cephalin, and lipositol), at varying pH's, have a mobility 1.2 times that of the washed red cell. The pH-mobility relation is otherwise similar. These complexes can be coated with dextran and trypsin.
Studies of the Origin of Bacterial Viruses
Authors: Northrop John H. ,   with the technical assistance of Marie King
Published: May 2004

Exposure of B. megatherium 899 to about 5 x 10-3 M MnCl2 for 10 minutes at 25°C. results in an increase of about ten times in the proportion of phage-producing cells, terramycin-resistant cells, streptomycin-resistant cells, and phage-resistant cells.

The proportion of phage-producing cells reaches a maximum in about 4 hours and that of the other cells is reached in about 8 hours.
The Nature of the Retinal Action Potential, and the Spectral Sensitivities of Ultraviolet and Green Receptor Systems of the Compound Eye of the Worker Honeybee
Authors: Goldsmith Timothy H.
Published: May 2004

1. The retinal action potential consists principally of a sustained negative wave which persists for as long as the stimulus. Transitory negative on-effects and off-effects may also be present, particularly at long wave lengths (green, yellow, and red) and in the light-adapted eye.

2. Only the maintained component of the potential can be elicited under CO2 anesthesia. The transient components are reversibly eliminated from the response at about the same time as the background noise of nerve and muscle spikes. It is suggested that the sustained component arises from the receptor cells, and the other components from second and higher order neurons.

3. The compound eye does not contain a homogeneous population of receptors. A green receptor system (maximum sensitivity at about 535 mµ) determines the response of the dark-adapted eye throughout most of the spectrum; during adaptation to yellow light, however, an ultraviolet receptor system is revealed, with maximum sensitivity at about 345 mµ. The anatomical bases of these receptor systems are unknown; however, they include both retinula cells and neurons in the optic ganglion.

4. There is no change in spectral sensitivity (Purkinje shift) in the first three logarithmic units above the threshold of the retinal action potential.

5. The relatively great effectiveness of near ultraviolet light in stimulating the positive phototaxis of the bee does not depend on excitation of the ultraviolet receptor of the ocellus.
The Basis for Prolonged Contractions in Molluscan Muscles
Authors: Johnson William H. , Twarog Betty M.
Published: May 2004

Two basically different hypotheses have been advanced to explain the behavior of molluscan muscles in cases in which relaxation of the muscle is extraordinarily prolonged. In one hypothesis, tetanic activation due to prolonged activity in an intrinsic ganglion network is postulated; in the other, changes in the mechanical properties of the muscle capable of maintaining tension generated by the contractile system are proposed. Experiments reported here were designed to test these hypotheses. Recordings were made of electrical activity in a number of circumstances in which the muscle relaxes slowly, and this activity was absent in some cases and in others was not found to correlate well with rate of relaxation. Quick release of the muscle during and after a stimulus which induced slow relaxation showed disappearance of the active state long before decay of tension. Contractile tension decreases with length below rest length whereas passive tension due to stretch following D. C. stimuli remains approximately independent of length. The latter has the same mechanical basis as prolonged relaxation following D. C. stimuli. Thus initial contractile tension and the tension remainder during prolonged relaxation appear to originate through different mechanisms. These results lead us to favor the second hypothesis above. A means by which this could be achieved in vivo is discussed.
A Study of the "Staircase" in Ventricular Muscle and Its Relationship to the Inotropic Activity of Certain Drugs
Authors: Nayler W. G.
Published: May 2004

Tension duration curves recorded during isometric contractions of toad ventricular strips were studied under a variety of conditions. Changes recorded in these curves during inotropic responses could be divided into two classes: (a) those in which the time required to reach peak tension (tp) was decreased and the twitch duration shortened. (b) those in which tp was either unaltered or increased and the twitch duration unchanged. The first class is represented by excess Ca++, strophanthin, and the "staircase" phenomenon while the second is represented by noradrenaline, "amine-like" substances liberated by tyramine, cocaine, and reserpine, and reduced K+. The results suggest that Ca++ is a common factor underlying the inotropic response recorded both during the staircase and during glycoside activity. The involvement of amines in the staircase was not demonstrated.
The Role of Calcium Ions in the Acceleration of Resting Muscle Glycolysis by Extracellular Potassium
Authors: Kaye Leon , Mommaerts W. F. H. M.
Published: May 2004

The activation of the glycolysis of resting muscle by increased extracellular potassium is dependent upon the simultaneous presence of calcium, but not of sodium ions. This regulation of metabolism by a membrane characteristic seems to act upon an early link in the glycolytic enzyme chain.
Non-Linear Current-Potential Relations in an Axon Membrane
Authors: Cole Kenneth S.
Published: May 2004

The membrane current density, Im, in the squid giant axon has been calculated from the measured external current applied to the axon, Io, by the equation

See PDF for Equation

where Vm is the membrane potential under the current electrode and r1 and r2 are the external and internal longitudinal resistances. The original derivation of this equation included in one step an assumption of a linear relation between Im and Vm. It is shown that the same equation can be obtained without this restricting assumption.
Effect of Ionic Strength on the Kinetics of Trypsin and Alpha Chymotrypsin
Authors: Castañeda-Agulló M. , del Castillo Luz M. , Whitaker J. R. , Tappel A. L.
Published: May 2004

The kinetic effects resulting from changes in the medium ionic strength on reactions involving trypsin or α-chymotrypsin are different. The reaction rate increases continuously as the ionic strength increases with α-chymotrypsin. With trypsin, the rate increases at low ionic strengths but as the ionic strength further increases a gradual inhibitory effect is observed. The effects produced by different salts of various valence types (from uni-univalent to uni-trivalent or tri-univalent) are essentially the same, and they are a function of the square root of the ionic strength. The quantitative differences among the various salts may be accounted for on the basis of individual properties of the ions, such as the size of the hydrated ion, "association," etc. The effects of salts on the enzymic reactions described herein are amenable to the same electrostatic treatment applicable to non-enzymatic reactions. By applying Brönsted's basic kinetic concepts and the Debye-Hückel law of electrolyte activity, it appears that the salt effects are mainly due to changes in the dissociation of ionizable groups. This appears to be a general method for analyzing the effect of inorganic ions on enzymic reactions.
The Duplex Nature of the Retina of the Nocturnal Gecko as Reflected in the Electroretinogram
Authors: Dodt Eberhard , Jessen Karl Heinz
Published: May 2004

The effect of light and dark adaptation on the electrical activity in two species of nocturnal gecko, Hemidactylus turcicus and Tarentola mauritanica was studied. The electroretinogram of both species changes from the scotopic type in the dark-adapted state to the photopic type after strong light adaptation. For the scotopic response fusion frequencies up to 18 flashes per sec. are obtained in both species. For the photopic response fusion frequencies up to 50 flashes per sec. are seen in Tarentola, and up to 25 flashes per sec. in Hemidactylus. Proceeding from dark to light adaptation the increment threshold (dI) is measured at different levels of adaptive illumination (I). At low levels of illumination the dI/I ratio is found to be small and at high levels of illumination to be large. No difference in the dI/I ratio is obtained for test lights of 462 and 605 mµ. During dark adaptation the change of threshold after exposure to moderate and weak lights (up to 103 times dark threshold) is rather fast. After light adaptation to strong light (106 times dark threshold) duplex dark adaptation curves are seen with a break separating a fast and a slow phase of dark adaptation. The significance of these results from a retina which possesses sense cells of only one type is discussed.
Determination of the Effective Hydrodynamic Radii of Small Molecules by Viscometry
Authors: Schultz Stanley G. , Solomon A. K.
Published: May 2004

The effective hydrodynamic radii of small uncharged molecules in dilute aqueous solution were determined using Einstein's classical theory of viscosity. The radii thus obtained are those of a hypothetical sphere whose hydrodynamic behavior is the same as that of the solute molecule plus that water of hydration which is too firmly bound to partake in the viscous shearing process. The results obtained compare favorably with radii determined from molecular models constructed in accordance with atomic dimensions compiled by Pauling. Although the application of the Einstein theory to molecules whose size is comparable to that of water represents a considerable extrapolation, the results suggest that this deviation from the assumptions of the theory, in the case of the molecules studied, is of second order importance.

Employing the viscometric radii, we have formulated an empirical correction of the Stokes-Einstein diffusion equation. This correction is similar in form to those previously proposed by Cunningham (22) and Millikan (21) and is of particular significance when the solute molecule is comparable in size to the discontinuities of the surrounding medium. The molecular radii of a number of small organic molecules obtained by means of the corrected Stokes-Einstein equation do not differ significantly from the radii obtained from molecular models of these compounds.
Tropic Responses of Phycomyces Sporangiophores to Gravitational and Centrifugal Stimuli
Authors: Dennison David S.
Published: May 2004

A low-speed centrifuge was used to study the tropic responses of Phycomyces sporangiophores in darkness to the stimulus of combined gravitational and centrifugal forces. If this stimulus is constant the response is a relatively slow tropic reaction, which persists for up to 12 hours. The response is accelerated by increasing the magnitude of the gravitational-centrifugal force. A wholly different tropic response, the transient response, is elicited by an abrupt change in the gravitational-centrifugal stimulus. The transient response has a duration of only about 6 min. but is characterized by a high bending speed (about 5°/min.). An analysis of the distribution of the transient response along the growing zone shows that the active phase of the response has a distribution similar to that of the light sensitivity for the light-growth and phototropic responses. Experiments in which sporangiophores are centrifuged in an inert dense fluid indicate that the sensory mechanism of the transient response is closely related to the physical deformation of the growing zone caused by the action of the gravitational-centrifugal force on the sporangiophore as a whole. However, the response to a steady gravitational-centrifugal force is most likely not connected with this deformation, but is probably triggered by the shifting of regions or particles of differing density relative to one another inside the cell.
Interplay between the Reactions to Light and to Gravity in Phycomyces
Authors: Varjú D. , Edgar Lois , Delbrück M.
Published: May 2004

Sporangiophores of Phycomyces do not grow directly towards a horizontal beam of light, but equilibrate at an angle of about 30° above the horizontal. After describing several related observations, this paper suggests that the dioptric properties of an obliquely illuminated cylindrical lens, illustrated by a dummy cell, as well as a negative geotropic response, play major roles in determining the direction of growth. The shift of the equilibrium direction of growth towards the vertical, or a purely geotropic response, over a tenfold range of very low intensities (around 106 quanta/cm2 sec., or 10-13watt/cm2) has been studied, and an action spectrum made, measuring the quantum fluxes producing a standard intermediate equilibrium direction of growth at different wavelengths. This may differ from the action spectra at higher intensities in lacking conspicuous maxima from 370 to 490 mµ. However, in the ultraviolet it parallels the other spectra, although without showing the much higher quantum efficiency of ultraviolet relative to visible light previously noted. Possible interpretations are discussed.
Calcium Flux and Contractility in Guinea Pig Atria
Authors: Winegrad Saul , Shanes Abraham M.
Published: May 2004

The calcium in guinea pig atria can be divided into three components by kinetic studies with Ca45: (a) a rapidly exchangeable fraction with a half-time of 4.5 minutes; (b) a slowly exchangeable fraction with a half-time of 86 (or 168) minutes; and (c) an inexchangeable fraction. In Krebs-Henseleit solution containing 2.5 mM calcium, the calcium content of the tissue at rest remains constant, the flux being about 0.02 µµmol/cm2-second. An increase or a decrease in extracellular calcium concentration by 1.25 mM causes a proportionate change in influx. A large increase in Ca45 entry, equivalent to as much as 0.55 µµ/mol/cm2 accompanies a contraction. When the strength of contraction is varied by stimulating at different frequencies or in solutions containing calcium at different concentrations, the increment of Ca45 uptake per beat changes proportionally with the strength of the beat. Total atrial calcium is not increased by stimulation; however, the increase in outflux of Ca45 during contraction that this constant tissue calcium implies could not be demonstrated under the experimental conditions employed. The observations are discussed in the light of the possible role of calcium transfer in excitation-contraction coupling.
Movement of Sodium Across the Mucosal Surface of the Isolated Toad Bladder and its Modification by Vasopressin
Authors: Frazier Howard S. , Dempsey Eleanor F. , Leaf Alexander
Published: May 2004

Studies have been made on the isolated urinary bladder of the toad, Bufo marinus, in an attempt to evaluate gradients of chemical activity across the mucosal surfaces of the epithelial cells which would serve to maintain a net movement of sodium from the mucosal medium into the cells. The likelihood of such chemical gradients has been established by the demonstration of lower contents of sodium within the tissue, expressed as microequivalents per gram of tissue water, than of concentrations of sodium in the mucosal medium at all levels of the latter examined. The transepithelial transport of sodium and the sodium content of the tissue were found to increase rapidly with rise in concentration of sodium in the mucosal medium up to values of 30 to 60 meq per liter. Further increase in concentration of the medium above this value failed to induce further stimulation of sodium transport or increase in the sodium content of the tissue. Vasopressin increased the rate of transport of sodium at every concentration of sodium in the mucosal medium without altering this relationship. Although entry of sodium across the mucosal surface of the epithelial cells may be passive it is not by free diffusion but involves some considerable interaction with the mucosal surface of the bladder and constitutes the major determinant of the rate of transepithelial transport of sodium. Vasopressin acts to enhance this initial step in the transport of sodium.
Some Researches on Histones
Authors: Butler J. A. V.
Published: May 2004

The histone extracted from calf thymus glands is a complex system of proteins, which can be fractionated by chromatography on carboxymethyl cellulose columns into three principal fractions (1) very lysine-rich, (2) moderately lysine-rich, (3) arginine-rich. When examined by starch gel chromatography each of these gives more than one band. Methods have been devised for further separation of the components in some cases. The components show characteristic differences in end groups and certain amino acids as well as in their basic character. Histones extracted from various rat tissues can be separated into similar fractions, of which the amino acid analyses are similar to those derived from calf thymus, within the experimental error. To this extent, no species or tissue specificity of the fractionated histones was observed. Although all the histone fractions contain approximately one basic amino acid to three non-basic amino acids their structure is not regular, as Phillips has shown that in certain fractions the number of non-basic groups between two basic groups may vary from 0 to seven or more. The possible functions of histones are discussed.
The Significance of the Variable Solvent and Specific Property Solubility Tests in Protein Chemistry
Authors: Taylor Dermot B.
Published: May 2004

An attempt has been made to review briefly the present status of the application of solubility measurements to the field of protein chemistry and in particular the quantitative significance of the measurable parameters obtained from the variable solvent solubility test has been evaluated.
Air Ions and Physiological Function
Authors: Krueger Albert Paul
Published: May 2004

Although gaseous ions possess no obvious physical properties which would predict a capability to influence living cells or tissues they can be shown to produce functional changes. The physiological effects so far demonstrated are limited in extent. In the mammalian trachea air ion action appears to depend upon the release of bound 5-hydroxytryptamine by CO2+ and upon O--induced acceleration of its metabolic destruction.
Transcellular Diffusion of Non-Electrolytes across the Renal Tubular Epithelium
Authors: Peña José Carlos , Malvin Richard L.
Published: May 2004

The stop flow technique was used to investigate the permeability characteristics of the dog nephron to various C14-labeled non-electrolytes. 12 minutes after clamping the ureter, creatinine, PAH, and C14 compound were injected intravenously. 2 minutes later, urine samples were collected. Urea and glycerol were able to enter the tubular urine along the entire nephron at rates which were commensurate with their molecular weights. No significant movement of larger molecules (D-arabinose, D-glucose, and mannitol) could be detected. However, after administration of twenty units of pitressin, D-arabinose was able to diffuse across the distal and proximal tubular epithelium.
Specific Binding of Rubidium in Chlorella
Authors: Cohen Dan
Published: May 2004

Specific binding sites for potassium, which may be components of the carriers for active transport for K in Chlorella, were characterized by their capacity to bind rubidium. A dense suspension was allowed to take up Rb86 from a low concentration of Rb86 and a high concentration of ions which saturate non-specific sites. The amount bound was derived from the increase in the external concentration of Rb86 following addition of excess potassium. The sites were heterogeneous. The average affinity of Rb and various other ions for the sites was determined by plotting the degree of displacement of Rb86 against log molar concentration of the individual ions. Interpolation gave the concentration for 50 per cent displacement of Rb, which is inversely related to affinity. The order of affinity was not changed when the cells were frozen, or boiled either in water or in 70 per cent ethanol. The affinity is maximal for ions with a crystalline radius of 1.3 to 1.5 A and a high polarizability, and is not related to the hydrated radius or valency. It is suggested that binding groups in a site are rigidly arranged, the irregular space between them being 2.6 to 3.0 A across, so that affinity is high for ions of this diameter and high polarizability.
Site of Origin and Propagation of Spike in the Giant Neuron of Aplysia
Authors: Tauc L.
Published: May 2004

The form and time sequence of spikes generated by orthodromic, antidromic, and direct stimulation and during spontaneous activity have been studied with intracellular electrodes simultaneously introduced in the soma and in different parts of the axon of the giant nerve cell of Aplysia. Evidence was obtained that under normal conditions of excitability, the spike originates at some distance from the soma in an axonal region with a higher excitability surpassing that of the surrounding membranes. Between the trigger zone and the soma is situated a region of transitional excitability where the conduction of the spike towards the soma may be blocked at a functionally determined and variable locus. The cell body is electrically excitable, but has the highest threshold of all parts of the neuron. The inactivation or even the removal of the cell body does not suppress synaptic transmission.
The Effects of Mechanical Stimulation on Some Electrical Properties of Axons
Authors: Julian Fred J. , Goldman David E.
Published: May 2004

Rapid, short duration mechanical compression of lobster giant axons by a crystal-driven stylus produces a depolarization and an increase in membrane conductance which develop immediately with compression but take several seconds to recover. The conductance increase occurs even when the depolarization is prevented electrically. If sodium is removed from the external medium or if procaine is added to it, compression produces almost no depolarization. Small bundles of myelinated frog fibers are depolarized by rapid compression but recover very rapidly (milliseconds); "off" responses are occasionally seen. The results are discussed in terms of the mechanoelectric transducer behavior of an axon membrane.
Electrical Interaction of Paired Ganglion Cells in the Leech
Authors: Eckert Roger
Published: May 2004

The two paired giant ganglion cells (PGC's) found in each ganglion of the leech central nervous system fire synchronously in response to certain sensory input. Polarizing current passed into either of these cells is seen to displace the membrane potentials of both cells, the voltage attenuation between the two somata ranging from 2 to 5 times. This attenuation factor remains unchanged when the direction of the polarizing current is reversed, and remains about the same when the other cell of the pair is directly polarized. When one of the PGC's is partially depolarized with outward current, a repetitive train of impulses is generated. Each spike is followed by a spike in the other cell. Occasionally, a small subspike potential is seen in place of a follower spike. This potential appears to differ in shape and time course from synaptic potentials elicited by afferent input to these cells, and appears rather to be an electrotonic potential derived from the prejunctional impulse in the stimulated PGC. It is proposed that transmission between these cells is electrical, being accomplished by a flow of local circuit current across a non-rectifying junction or connection to the spike-initiating region of the other PGC.
On the Mechanism of the Relaxing Effect of Fragmented Sarcoplasmic Reticulum
Authors: Weber Annemarie , Herz Ruth , Reiss Ingrid
Published: May 2004

The vesicles of fragmented sarcoplasmic reticulum, i.e. the physiological relaxing factor, remove most of the exchangeable Ca bound to actomyosin and myofibrils. The extent to which they remove Ca and the extent to which they inhibit myofibrillar activity are closely correlated. Previous work has shown that those in vitro reactions of actomyosin with ATP which are equivalent to its contraction, i.e. superprecipitation and a high ATPase activity, require the formation of a Ca-actomyosin complex, and that actomyosin after the removal of most of its bound Ca is inhibited by physiological concentrations of ATP. The evidence now suggests that the factor achieves its relaxing effect through the dissociation of the Ca-actomyosin complex and that it has no other direct influence on the biological activity of actomyosin. Experiments, showing that under similar conditions the vesicles of the factor are capable of reducing the concentration of ionized Ca in the surrounding medium to about 0.02 µM and less, suggest that the factor competes successfully with actomyosin for the available Ca through its mechanism of Ca accumulation.
Spectrophotometric Studies on Intact Muscle
Authors: Jöbsis Frans F.
Published: May 2004

The concentrations of the components of the respiratory chain were determined in a variety of intact skeletal muscles by a method of spectrophotometric observation of the transmitted light. In the case of the toad sartorius, these measurements were checked against isolated mitochondrial suspensions prepared from toad skeletal muscles. The relative concentrations of the respiratory components were found to be in reasonable agreement with those of various mitochondrial preparations of mammalian tissues and of the ones from toad skeletal muscle. The rather low cytochrome b and pyridine nucleotide levels in the anoxic minus oxygenated difference spectra were shown to be caused to a certain degree by a partial reduction during the resting steady state. Upon treatment with a strong, reducing agent or after long anoxia some absorption bands appeared with maxima at 591, 562 to 564, and 432 to 434 mµ both in the intact and in the mitochondrial fractions of muscle tissue; they do not appear to be associated with the respiratory chain.
Spectrophotometric Studies on Intact Muscle
Authors: Jöbsis Frans F.
Published: May 2004

The kinetics of the mitochondrial respiratory chain of intact muscle and the concomitant changes of the intercellular pH were investigated. Addition of lactate and pyruvate under resting conditions produces reductions of DPN and cytochrome b, and, occasionally, of cytochrome c and flavoprotein. Succinate gives similar but smaller changes. In recently excised muscles moderate contractile activity produces a reduction of cytochrome c and oxidations of DPNH, cytochrome b, and sometimes of the flavoproteins. Tetanic contractions and larger numbers of twitches produce reductions of DPN and of cytochromes b and c. In sartorii of the tropical toad, stored for approximately 2 days at 0–3°C, contractile activity always gives rise to long lasting oxidations of DPNH and cytochrome b. Addition of pyruvate or lactate shortens these oxidation cycles with a concomitant reduction of cytochrome c. These responses to contractions agree with those of mitochondria isolated from leg muscles of the toad upon the addition of ADP. Apparently the mitochondria in resting, excised muscles are not supplied with an excess of substrate. Measurements on the intercellular pH showed that even limited activity ( < 5 twitches) initiates glycolysis. The primary control of respiration resides, nevertheless, in the ADP concentration, rather than in the levels of substrate or inorganic phosphate. The results are quantitatively consistent with the view that ATP is the primary energy donor for muscular contraction.
Studies of the Origin of Bacterial Viruses
Authors: Northrop John H. ,   with the technical assistance of Marie King
Published: May 2004

The mutagens, urethane, ethyl urethane, hydrogen peroxide, desoxycholate, versene, maleic hydrazide, butadiene dioxide, and triethylene melamine, all increase the proportion of virus-producing cells and streptomycin-resistant cells in B. megatherium 20δ cultures to about the same extent. Acriflavine has no effect on the proportion of either type of cell. Triethylene melamine appears to cause mutations to occur without cell division.
Intraspecies and Interspecies Transformation Reactions in Pneumococcus and Streptococcus
Authors: Krauss Marjorie R. , MacLeod Colin M.
Published: May 2004

The efficiency of transformation of pneumococcus and a strain of viridans streptococcus (strain D) to streptomycin resistance is influenced by the species in which the mutation to resistance occurred, as well as by the species in which the mutated gene has been replicated. Pneumococcus and streptococcus strain D transform in higher frequency with DNA that has been replicated in bacteria of the same species than with DNA from the heterologous species. However, the difference between the frequencies of interspecific and intraspecific transformation is much greater with pneumococcus as receptor than with streptococcus. In addition pneumococcus transforms in higher frequency with wholly homologous (pneumococcal) DNA than with DNA from pneumococci that have replicated the streptococcal Smr gene. Pneumococcus is transformed in lower frequency by wholly heterologous (streptococcal) DNA than by DNA from streptococci that have replicated the pneumococcal Smr gene. Streptococcus behaves similarly in that wholly homologous (streptococcal) DNA transforms it more efficiently than when the transforming fragment contains a pneumococcal moiety. Streptococcus is transformed in the same or lower frequency by wholly heterologous (pneumococcal) DNA than by DNA from pneumococci that have replicated the streptococcal Smr gene. When erythromycin resistance was used as genetic marker instead of streptomycin resistance, similar results were found.
On the Mechanism of Some Temperature Effects on Drosophila
Authors: Milkman Roger
Published: May 2004

The results of detailed kinetic studies on temperature adaptation and on crossvein deformation in Drosophila melanogaster pupae are presented. A scheme which unifies most of these effects is offered, suggesting that the basic events are a series of changes in the tertiary structure of a protein. Implications of the findings and the scheme are discussed with particular respect to temperature adaptation and to development.
The Reversion of Catalase during Growth of Yeast in Anaerobiosis
Authors: Kaplan J. Gordin
Published: May 2004

Growth of originally aerobic bakers' yeast under conditions of anaerobiosis caused a decrease in the total specific catalatic activity (patent plus cryptic) of one-half per generation. It is concluded that reversion of catalase was a dilution, rather than a destruction, of the intracellular enzyme. However, the specific patent (whole cell) catalase activity remained constant for one or more generations, and then declined at a considerably slower rate than did the total activity. Thus the cryptic factor diminished progressively during anaerobic growth; after seven or eight generations virtually all the catalase was patent; i.e., the cryptic factor (the ratio of total enzyme to patent enzyme) was approximately unity. At this point, the basal level of enzyme was attained, and thereafter maintained by a basal synthesis, which produced only the patent, heat-stable, variety. Aerobic growth caused a significant, but much smaller, decline of both total catalase activity and of the cryptic factor. The data suggested that during reversion, the cryptic, heat-labile catalase became progressively converted to the patent, heat-resistant form. A model of these events is presented.
Evidence for Anion-Permselective Membrane in Crayfish Muscle Fibers and Its Possible Role in Excitation-Contraction Coupling
Authors: Girardier Lucien , Reuben John P. , Brandt Philip W. , Grundfest Harry
Published: May 2004

Under certain conditions only, isolated crayfish skeletal muscle fibers change in appearance, becoming grainy, darkening, and seemingly losing their striations. These changes result from development of large vesicles on both sides of the Z-line. The longitudinal sarcoplasmic reticulum remains unaffected. The vesicles are due to swelling of a transverse tubular system (TTS) which is presumably homologous with the T-system tubules of other muscle fibers. The vesiculations occur during efflux of water or on reducing external K or Cl, but only when KCl can leave the fiber. They never result from osmotic, ionic, or electrical changes when KCl cannot leave. Inward currents, applied through a KCl-filled intracellular cathode, also cause the vesiculations. These are not produced when the cathode is filled with K-propionate, nor by outward or longitudinal currents. Thus the transverse tubules swell only when Cl leaves the cell. Accordingly, their membrane is largely or exclusively anion-permselective. These findings also indicate that the TTS forms part of a current loop, connecting with the exterior of the fiber probably through radial tubules (RT) possessing membrane of low conductivity. Thus, part of the current flowing inward across the sarcolemma during activity can return to the exterior through the membrane of the TTS. The structure and properties of the latter offer the possibility for an efficient electrical mechanism to initiate excitation-contraction coupling.
The Origin of the Short-Circuit Current in the Isolated Skin of the South American Frog Leptodactylus ocellatus
Authors: Zadunaisky José A. , Candia Oscar A. , Chiarandini Dante J.
Published: May 2004

In isolated skins of Leptodactylus ocellatus the short-circuit current is smaller than the sodium net flux and this difference disappears when the skins are bathed in solutions in which the chloride ions have been replaced by sulfate or methylsulfate ions. There is a net movement of chloride ions from outside to inside of the skins in the short-circuit condition with chloride Ringer's solutions bathing the skins. The addition of ouabain to the inside solution markedly reduced not only sodium net flux but also the chloride net influx found. Copper ions added to the outside solutions produced a rise in short-circuit current, as well as the known increase in potential difference. In sodium-free Ringer's (sodium replaced by choline) the orientation of the potential difference across the skins was reversed, the inside being negative instead of positive. The results are interpreted as direct or indirect indications of the presence of a net transfer of chloride ions from outside to inside of these frog skins.
The Frictional Coefficients of the Flows of Non-Electrolytes Through Artificial Membranes
Authors: Ginzburg B. Z. , Katchalsky A.
Published: May 2004

The phenomenological permeation coefficients were determined for two artificial cellulose membranes of known thickness and water content. Transport of non-electrolytes was studied with tagged water, urea, glucose, and sucrose. The effect of the unstirred layers on the experimental determination of the coefficients is discussed. Frictional coefficients between membrane matrix and solutes, and between solvent and solutes in the membrane are calculated. It was shown that the geometrical tortuosity does not correspond to a physical tortuosity.
Probability of Occurrence of Discrete Potential Waves in the Eye of Limulus
Authors: Fuortes M. G. F. , Yeandle S.
Published: May 2004

Discrete potential waves can be recorded from cells in the eye of Limulus both in darkness and in dim illumination. With constant illumination the frequency of these waves is linearly related to light intensity and the distribution of intervals between waves follows an exponential function. The latency of waves evoked by short flashes of light is usually long and variable and the number of waves evoked by a flash varies randomly, obeying approximately a Poisson distribution. The results of experiments with flashes of light have been compared with the predictions derived from the hypotheses that one, two, or three quanta of light are required for production of one wave. The agreement of the data with the theory can be considered acceptable for the "one quantum" hypothesis, is less satisfactory for the "two quanta" hypothesis, and is very poor for the "three quanta" hypothesis.
Effects of D2O and Osmotic Gradients on Potential and Resistance of the Isolated Frog Skin
Authors: Lindley Barry D. , Hoshiko T. , Leb D. E.
Published: May 2004

Exposure of the outside surface of isolated frog skin (R. pipiens and R. catesbeiana) to sulfate solution made up with D2O decreased skin potential and resistance. Exposure of the inside surface to D2O solution decreased the potential slightly but increased the resistance. The changes were linearly related to the D2O concentration. Since D2O acts like a hyperosmotic solution, the skin potential and resistance were studied upon exposure to solution made hyperosmotic by addition of sucrose, mannitol, acetamide, urea, thiourea, Na2SO4, or K2SO4. Skin potential and resistance decreased when the outside solution was made hyperosmotic. The changes depended upon the concentration and the nature of the solute. Thiourea and urea solutions were the most effective. Treatment of the inside surface gave relatively small decreases in potential; the resistance either increased or remained unchanged. These effects appeared to depend upon the direction of the osmotic gradient across the skin rather than upon the value of the osmolarity compared to normal body fluids. Experiments with a series of six polyhydric alcohols from methanol to mannitol and the polysaccharides, sucrose and raffinose, showed adonitol with 5 carbons to decrease the potential the most. Smaller and larger compounds of this set gave lesser effects. As yet no consistent explanation of the effects is forthcoming, but their demonstration calls for caution in the indiscriminate use of solutes such as mannitol or sucrose "to make up the osmolality" and in the neglect of urea because "it penetrates freely."
Rhythmical Variations Accompanying Gustatory Stimulation Observed by Means of Localization Phenomena
Authors: von Békésy Georg
Published: May 2004

When two taste stimuli are presented, one to each side of the tongue, with a time delay of up to 1 msec., the taste sensation seems to move across the tongue. This phenomenon which is similar to directional hearing, can be used to show periodic fluctuations in sensation magnitude as well as other aspects of sensation. When the apparatus was refined to present taste stimuli, it was possible to observe rhythmic changes in the perception of taste. An analogy is demonstrated between hearing and taste sensation, even to some quantitative values.