bluuebunny/crossref_metadata_2025 huggingface dataset:
The Reliability of Neurons
Authors: Bullock Theodore Holmes
Published: May 2004

The prevalent probabilistic view is virtually untestable; it remains a plausible belief. The cases usually cited can not be taken as evidence for it. Several grounds for this conclusion are developed. Three issues are distinguished in an attempt to clarify a murky debate: (a) the utility of probabilistic methods in data reduction, (b) the value of models that assume indeterminacy, and (c) the validity of the inference that the nervous system is largely indeterministic at the neuronal level. No exception is taken to the first two; the second is a private heuristic question. The third is the issue to which the assertion in the first two sentences is addressed. Of the two kinds of uncertainty, statistical mechanical (= practical unpredictability) as in a gas, and Heisenbergian indeterminancy, the first certainly exists, the second is moot at the neuronal level. It would contribute to discussion to recognize that neurons perform with a degree of reliability. Although unreliability is difficult to establish, to say nothing of measure, evidence that some neurons have a high degree of reliability, in both connections and activity is increasing greatly. An example is given from sternarchine electric fish.
Choline Permeability in Cardiac Muscle Cells of the Cat
Authors: Bosteels S. , Vleugels A. , Carmeliet E.
Published: May 2004

Permeability of the cardiac cell membrane to choline ions was estimated by measuring radioactive choline influx and efflux in cat ventricular muscle. Maximum values for choline influx in 3.5 and 137 mM choline were respectively 0.56 and 9 pmoles/cm2·sec. In 3.5 mM choline the intracellular choline concentration was raised more than five times above the extracellular concentration after 2 hr of incubation. In 137 mM choline, choline influx corresponded to the combined loss of intracellular Na and K ions. Paper chromatography of muscle extracts indicated that choline was not metabolized to any important degree. The accumulation of intracellular choline rules out the existence of an efficient active pumping mechanism. By measuring simultaneously choline and sucrose exchange, choline efflux was analyzed in an extracellular phase, followed by two intracellular phases: a rapid and a slow one. Efflux corresponding to the rapid phase was estimated at 16–45 pmoles/cm2·sec in 137 mM choline and at 1.3–3.5 pmoles/cm2·sec in 3.5 mM choline; efflux in 3.5 mM choline was proportional to the intracellular choline concentration. The absolute figures for unidirectional efflux were much larger than the net influx values. The data are compared to Na and Li exchange in heart cells. Possible mechanisms for explaining the choline behavior in heart muscle are discussed.
Actions of Some Cations on the Electrical Properties and Mechanical Threshold of Frog Sartorius Muscle Fibers
Authors: Kao C. Y. , Stanfield P. R.
Published: May 2004

With the use of a point voltage-clamp technique, the effects of Zn2+, UO22+, tetraethylammonium, and several other homologous quaternary ammonium ions on the electrical properties of the frog sartorius muscle and its mechanical threshold were studied. None of the agents separated the voltage thresholds for mechanical activation and delayed rectification. However, Zn2+, UO22+, and TEA, which are known to potentiate the twitch, caused some inhibition of the normal increase in potassium conductance during delayed rectification. Zn2+ and UO22+ also slowed the rate of development of the outward current. A strength-duration relation was studied for depolarization pulses capable of initiating contraction. With a depolarizing pulse of 2.5 msec the mechanical threshold is about -13 mv at about 20°C. UO22+, 0.5 µM, which markedly reduced the outward current produced by such a short pulse, did not raise the mechanical threshold. All findings indicate that there is no direct causal relation between delayed rectification and mechanical activation.
The Spatial Variation of Membrane Potential Near a Small Source of Current in a Spherical Cell
Authors: Eisenberg R. S. , Engel E.
Published: May 2004

A theoretical analysis is presented of the change in membrane potential produced by current supplied by a microelectrode inserted just under the membrane of a spherical cell. The results of the analysis are presented in tabular and graphic form for three wave forms of current: steady, step function, and sinusoidal. As expected from physical reasoning, we find that the membrane potential is nonuniform, that there is a steep rise in membrane potential near the current microelectrode, and that this rise is of particular importance when the membrane resistance is low, or the membrane potential is changing rapidly. The effect of this steep rise in potential on the interpretation of voltage measurements from spherical cells is discussed and practical suggestions for minimizing these effects are made: in particular, it is pointed out that if the current and voltage electrodes are separated by 60°, the change in membrane potential produced by application of current is close to that which would occur if there were no spatial variation of potential. We thus suggest that investigations of the electrical properties of spherical cells using two microelectrodes can best be made when the electrodes are separated by 60°.
Potassium Transport in Neurospora
Authors: Slayman Carolyn W. , Slayman Clifford L.
Published: May 2004

At low extracellular pH (4–6), net uptake of potassium by Neurospora is a simple exponential process which obeys Michaelis kinetics as a function of [K]o. At high pH, however, potassium uptake becomes considerably more complex, and can be resolved into two distinct exponential components. The fast component (time constant = 1.2 min) is matched quantitatively by a rapid loss of sodium; it is attributed to ion exchange within the cell wall, since it is comparatively insensitive to low temperature and metabolic inhibitors. By contrast, the slower component (time constant = 10.9 min) is inhibited markedly at 0°C and by CN and deoxycorticosterone, and is thought to represent carrier-mediated transport of potassium across the cell membrane. This transport process exhibits sigmoid kinetics as a function of [K]o; the data can be fitted satisfactorily by two different two-site models (one involving a carrier site and a modifier site, the other an allosteric model). Either of these models could also accommodate the simple Michaelis kinetics at low pH.
The Spectral Sensitivities of Single Receptor Cells in the Lateral, Median, and Ventral Eyes of Normal and White-Eyed Limulus
Authors: Nolte John , Brown Joel E.
Published: May 2004

Spectral sensitivity curves can be distorted by screening pigments. We have determined whether this is true for Limulus polyphemus by determining, from receptor potentials recorded using intracellular microelectrodes, spectral sensitivity curves for normal animals and for white-eyed animals (which lack screening pigment). Our results show: (a) In median ocelli, the curve for UV-sensitive receptor cells peaks at 360 nm and does not depend on the presence of screening pigment, (b) The curve for ventral eye photoreceptors is identical to that for retinular cells from the lateral eyes of white-eyed animals and peaks at 520–525 nm. (c) In normal lateral eyes, when the stimulating light passes through screening pigment, the curve indicates relatively more sensitivity in the red region of the spectrum than does the curve for white-eyed animals. Therefore, the screening pigment is probably red-transmitting, (d) In median ocelli, the curve for visible-sensitive cells peaks at 525 nm and is approximately the same whether the ocelli are from normal or white-eyed animals. However, the curve is significantly broader than that for ventral eyes and for lateral eyes from white-eyed animals.
Interferons: Purification and Physicochemical Aspects
Authors: Fantes K. H.
Published: May 2004

Antiviral interferon activity in any one species can be exhibited by a variety of substances that differ in their physical and chemical properties, but the nature of these differences is not understood. Conditions that can lead to the formation of diverse types of interferons have been outlined. Reasons have been adduced why, for certain purposes, purification of interferons is desirable or even necessary, and examples have been presented to show how and to what extent this has been achieved. In spite of some very high purification factors, not a single interferon has been obtained as a pure substance. Therefore, all available knowledge of physical and chemical properties has been obtained by indirect means.
The Water and Nonelectrolyte Permeability Induced in Thin Lipid Membranes by the Polyene Antibiotics Nystatin and Amphotericin B
Authors: Holz Ronald , Finkelstein Alan
Published: May 2004

Nystatin and amphotericin B increase the permeability of thin (<100 A) lipid membranes to ions, water, and nonelectrolytes. Water and nonelectrolyte permeability increase linearly with membrane conductance (i.e., ion permeability). In the unmodified membrane, the osmotic permeability coefficient, Pf, is equal to the tagged water permeability coefficient, (Pd)w; in the nystatin- or amphotericin B-treated membrane, Pf/(Pd)w ≈ 3. The unmodified membrane is virtually impermeable to small hydrophilic solutes, such as urea, ethylene glycol, and glycerol; the nystatin- or amphotericin B-treated membrane displays a graded permeability to these solutes on the basis of size. This graded permeability is manifest both in the tracer permeabilities, Pd, and in the reflection coefficients, σ (Table I). The "cutoff" in permeability occurs with molecules about the size of glucose (Stokes-Einstein radius ≊ 4 A). We conclude that nystatin and amphotericin B create aqueous pores in thin lipid membranes; the effective radius of these pores is approximately 4 A. There is a marked similarity between the permeability of a nystatin- or amphotericin B-treated membrane to water and small hydrophilic solutes and the permeability of the human red cell membrane to these same molecules.
Comparison of In Vitro and In Vivo Labeling of Virus-Induced L-Cell Interferon
Authors: Stanček D. , Golgher R. R. , Paucker K.
Published: May 2004

Preparations of NDVuv-induced L-cell interferon were labeled in vitro with 125I and 3H gas, or in vivo through incorporation of amino acids-3H during synthesis. Prior to purification, more than 90% of the interferon titer was lost during in vitro labeling by either procedure, whereas 34% of the initial activity of in vivo-labeled material was preserved during preparatory handling. Purification by carboxymethyl-Sephadex chromatography and electrophoresis in polyacrylamide gels was about 100-fold, and electrophoretic profiles revealed close concordance between isotopes and interferon titers in all instances. Noninterferon proteins from control cells, although less extensively labeled with tritium during synthesis than proteins from interferon-producing cells and released in lesser amounts, also contained components of identical electrophoretic mobility and distribution in acrylamide gels as interferon. The highest specific activity (6 x 106 U/mg protein) but lowest cpm per interferon unit ratio (0.3) were exhibited by in vivo-labeled interferon. The advantage of better isotope incorporation through in vitro labeling techniques was largely offset by extensive losses in interferon activity.
Development of the Antiviral State in Response to Interferon
Authors: Sonnabend Joseph A. , Kerr I. M. , Martin E. M.
Published: May 2004

The development of resistance in response to interferon depends on cellular RNA synthesis and probably also on cellular protein synthesis. The evidence for these requirements is reviewed, as well as the proposal that this evidence indicates the existence of a specific response of the cell to interferon, involving the induced synthesis of an antiviral protein. Direct evidence for such an interpretation has not been obtained, and alternative explanations are discussed which do not require quantitative or qualitative differences in the RNA and protein made in cells exposed to interferon. The possible role of the ribosome in the antiviral action of interferon is also discussed.
Interferon Production by Nonviral Stimuli of Microbial Origin
Authors: Youngner Julius S.
Published: May 2004

An increasing number of nonviral materials of microbial origin has been reported to stimulate the production of interferon in cell cultures and (or) in animals. These materials include (a) gram-negative bacteria or the endotoxins prepared from their cell walls, (b) other microorganisms such as Rickettsiae, Bedsoniae, Protozoa, and (c) fungal products such as a mannan from Candida and various antibiotics which act as protein synthesis inhibitors, e.g., glutarimide antibiotics and tenuazonic acid. A summary is presented of the current state of knowledge about interferon production in animals by the most thoroughly studied nonviral substance of microbial origin, bacterial endotoxin. Further evidence is presented which clearly distinguishes the "endotoxin-type" of interferon response in animals from the response seen after the injection of virus. The data suggest that the release of preformed interferon from the tissues occurs in animals injected with endotoxin. On the other hand, interferon produced in response to the injection of virus is newly synthesized protein. While the exact chemical structure of the component of bacterial endotoxin responsible for interferon release has not yet been elucidated, it is clear that the lipid portion of the lipopolysaccharide, rather than the O-specific polysaccharide side chains or the core polysaccharide, is the active moiety.
Interferon Induction by Viruses
Authors: Lockart Royce Z.
Published: May 2004

Interferons are proteins of cellular origin capable of conferring virus resistance to vertebrate cells. Most cells do not produce interferons except in response to proper stimulation. Clearly, the stimulation of interferon production encompasses two phenomena. When stimulated, some cell systems produce their interferons by synthesizing new proteins. Other cell systems do not require the synthesis of new proteins to produce interferons, and still other cell systems may produce interferons by both means. Before much can be learned from the detailed study of the nature of the molecules which stimulate interferons, the type of phenomenon which the stimulus induces must be identified. Chick embryo tissues apparently make interferons by synthesizing new proteins. Many viruses stimulate interferon production in chick embryo tissues. Data available suggest that neither the protein nor nucleic acid moieties of the added virions act as inducing molecules. Also, double-stranded replicative form is probably not responsible. It is suggested that the inducer molecule may be cellular in nature and may be produced in response to a wide variety of insults among which are viral infections.
Evidence for a Chromatographic Model of Olfaction
Authors: Mozell Maxwell Mark
Published: May 2004

The gradient of activity produced along the olfactory mucosa by odorant stimulation was measured by the ratio (the LB/MB ratio) of the summated neural discharges recorded from two branches of the olfactory nerve, a lateral branch (LB) supplying a mucosal region near the internal naris and a medial branch (MB) supplying a region near the external naris. Twenty-four frogs "sniffed" sixteen different odorants, each odorant at four concentrations and two flow rates. Increases in concentration and flow rate produced statistically reliable increases in the ratios; the magnitude of these increases was considerably smaller than the magnitude of the statistically significant changes that could be achieved by shifting the odorants themselves. Even the small change due to concentration depended upon the odorant presented. Thus, even at the highest physiologically possible concentrations and flow rates, the general level of the activity gradient along the mucosa appeared to be determined mainly by the particular odorant used. The relative retention time of each of these 16 different odorants was measured in a gas chromatograph fitted with a Carbowax 20M column. In general, the longer the odorant's retention time the smaller its LB/MB ratio. This suggests that the different mucosal gradients of activity are established for different odorants by a chromatographic process. The data further suggest that the mucosa behaves like a polar chromatographic column.
Control of Contractility in Spirostomum by Dissociated Calcium Ions
Authors: Ettienne Earl M.
Published: May 2004

The freshwater protozoan, Spirostomum ambiguum, exhibits generalized contraction when electrically stimulated with a DC pulse. Light and electron microscopic studies show a subcortical filamentous network, believed responsible for generating contractile tension, in association with vesicles which were shown to accumulate calcium oxalate precipitates. Organisms microinjected with the calcium-sensitive, bioluminescent protein, aequorin, emit light when stimulated to contract. Analyses of cinefilm records of electrically induced contraction indicate that contraction may occur up to 25 msec after the onset of stimulation at a point when the calcium-aequorin light emission is at a peak. The evidence shows that calcium release from an interval compartment is directly associated with the onset of contraction in Spirostomum, and that the removal of calcium, through some internal sequestering mechanism, signals relaxation.
Factors in the Inactivation of Postjunctional Membrane Receptors of Frog Skeletal Muscle
Authors: Nastuk William L. , Parsons Rodney L.
Published: May 2004

Several factors which influence the rate of inactivation of muscle postjunctional membrane (PJM) receptors during the sustained application of carbamylcholine (CARB) have been studied by two methods. The rate of inactivation was increased by elevating the tonicity of the bathing medium, by increasing the CARB concentration, by raising the calcium ion concentration, and by substituting SO4= for Cl- ions in the extracellular fluid. The relative effectiveness of calcium and other divalent cations in receptor inactivation was compared. In the absence of calcium, other divalent cations such as magnesium, strontium, or manganese were not efficient substitutes for calcium. In the presence of calcium, the addition of strontium or manganese ions accelerated the rate of receptor inactivation, but the addition of magnesium (up to 12 mM) inhibited this process. The inactivation of the membrane receptors in denervated muscle fibers was found to be similar to that in innervated muscle fibers. Various factors in PJM receptor inactivation are discussed. It is suggested that PJM receptor inactivation is influenced by the binding of calcium ions to sites on the internal surface of the PJM.
Effects of Cold Periods on the Stimulus-Response System of Phycomyces
Authors: Petzuch M. , Delbrück M.
Published: May 2004

The sporangiophores of Phycomyces do not exhibit phototropic responses when growth is arrested reversibly by cooling to 1°C. Unilateral UV stimuli (254 nm) applied during cold periods are stored for at least 2 hr and produce tropic responses away from the light after warm-up. During the cold period dark adaptation proceeds at a rate which decreases with the temperature.
On the Mechanisms of Sodium Ion Transport by the Irrigated Gills of Rainbow Trout (Salmo gairdneri)
Authors: Kerstetter Theodore H. , Kirschner Leonard B. , Rafuse Donald D.
Published: May 2004

Sodium uptake by rainbow trout gills has been investigated with a small-volume system enabling rapid, successive flux measurements in different solutions. Sodium influx obeys a Michaelis-Menten type relation, with a Km of 0.46 mM, and uptake proceeds unimpaired in the absence of penetrating counter-ions. This suggests a coupled cation exchange. Ammonia output is about the same as the Na+ influx when external [Na+] is 1 mM, but at higher or lower Na+ influxes, the correlation does not hold. A progressive downward shift in the pH of the irrigating medium as Na+ influx increases indicates that the exchanging cation is hydrogen. In support of this, acetazolamide, which inhibits Na+ uptake, also prevents the downward pH shift. The potential across the gill is about 10 mv, body fluids positive, in NaCl solutions up to 10 mM, and is little affected by changes in Na+ concentration below that. Finally, evidence for locating the rate-limiting step at the outer membrane of the epithelium is presented.
Photoreceptor Potentials of Opposite Polarity in the Eye of the Scallop, Pecten irradians
Authors: McReynolds John S. , Gorman A. L. F.
Published: May 2004

Intracellular recordings were obtained from single visual cells of the scallop, Pecten irradians. Two types of units are found. One type gives a graded, depolarizing response to light and the other a graded, hyperpolarizing response. The depolarizing cells are 2–3 log units more sensitive to light and have a longer latency than the hyperpolarizing type. At high light intensities the depolarizing cells are inactivated while the hyperpolarizing cells maintain their responses. When action potentials are seen they occur during illumination in depolarizing cells ("on" response) and after illumination in hyperpolarizing cells ("off" response). The evidence suggests that the depolarizing responses are from the microvilli-brearing proximal cells, and the hyperpolarizing responses from the ciliary-type distal cells of the retina, and that both responses are directly produced by light.
Further Studies of the Effect of Calcium on the Time Course of Action of Carbamylcholine at the Neuromuscular Junction
Authors: Manthey Arthur A.
Published: May 2004

The rate at which the postjunctional membrane of muscle fibers becomes desensitized to the action of carbamylcholine is increased after the muscle has been soaked in solutions containing increased concentrations of calcium. Some further aspects of this effect of calcium were investigated by measuring changes in the input resistance of single fibers of the frog sartorius during local perfusion of the neuromuscular junction with 2.73 x 10-3 M carbamylcholine in isolated muscles immersed in 165 mM potassium acetate. It was found that (a) sudden changes in the local concentration of calcium brought about by perfusing fibers with carbamylcholine solutions containing 20 mM calcium, 40 mM oxalate, or 40 mM EDTA were followed within 20 sec by marked changes in the rate of desensitization; (b) prior to 13 sec after the introduction of carbamylcholine, however, no effect on the input resistance could be detected even though the muscle had been presoaked in 10 mM calcium; (c) the ability of high concentrations of calcium to bring about rapid desensitization disappears when a lower concentration of carbamylcholine (0.137 x 10-3 M) is applied to the muscle fiber. These findings suggest that calcium present in the extracellular fluid can act directly on the postjunctional membrane to promote the desensitization process and that an increased permeability of the membrane to calcium brought about by the presence of carbamylcholine is a factor which contributes to this action.
Mechanism of Excitation of Aplysia Neurons by Carbon Dioxide
Authors: Brown A. M. , Berman P. R.
Published: May 2004

The abdominal ganglion of Aplysia californica was perfused with artificial seawater equilibrated at different PCOCO2's and pH's for 5 min or less. 5% CO2 dropped perfusate pH from 8.0 to 6.5 and produced depolarization and increased discharge rate in visceromotor neurons. Half the giant cells studied had a similar response, whereas the other half were hyperpolarized. Pacemaker neurons showed little, if any, response to such changes in pH or CO2. Membrane conductance of responsive cells was always increased. The effect of CO2 occurred even when synaptic transmission was blocked by low calcium and high magnesium, and therefore must have been a direct result of CO2 or the concomitant fall in pH. When extracellular pH was lowered to 6.5 using HCl or H2SO4 and no CO2, the same effects were observed. Also, local application of HCl or H2SO4 to the external surface of the cell soma elicited depolarization and spike discharge. When extracellular pH was held constant by continual titration, 5–50% CO2 had no effect. Intracellular pH was probably decreased at least one pH unit under these circumstances. Thus CO2 per se, decreased intracellular pH, and increased bicarbonate ion were without effect. It is concluded that CO2 acts solely through a decrease in extracellular pH.
Increased Chloride Conductance As the Proximate Cause of Hydrogen Ion Concentration Effects in Aplysia Neurons
Authors: Brown A. M. , Walker J. L. , Sutton R. B.
Published: May 2004

A fall in extracellular pH increased membrane conductance of the giant cell in the abdominal ganglion of Aplysia californica. Chloride conductance was trebled whereas potassium conductance was increased by 50%. Half the giant cells were hyperpolarized (2–8 mv) and half were depolarized (3–10 mv) by lowering the pH. The hyperpolarizing response always became a depolarizing response in half-chloride solutions. When internal chloride was increased electrophoretically, the hyperpolarization was either decreased or changed to depolarization. The depolarizing response was reduced or became a hyperpolarizing response after soaking the cell in 10.0 mM chloride, artificial seawater solution for 1 hr. Depolarization was unaffected when either external sodium, calcium, or magnesium was omitted. A glass micropipette having an organic liquid chloride ion exchanger in its tip was used to measure intracellular chloride activity in 14 giant cells; 7 had values of 27.7 ± 1.8 mM (SEM) and 7 others 40.7 ± 1.5 mM. Three of the first group were hyperpolarized when pH was lowered and three of the second group were depolarized. In all six cells, these changes of membrane potential were in the direction of the chloride equilibrium potential. Intracellular potassium activity was measured by means of a potassium ion exchanger microelectrode.
Effects of Intracellular Adenosine-5'-diphosphate and Orthophosphate on the Sensitivity of Sodium Efflux from Squid Axon to External Sodium and Potassium
Authors: De Weer Paul
Published: May 2004

A study was made of sodium efflux from squid giant axon, and its sensitivity to external K and Na. When sodium efflux from untreated axons was strongly stimulated by Ko, Nao was inhibitory; when dependence on Ko was low, Nao had a stimulatory effect. Incipient CN poisoning or apyrase injection, which produces high intracellular levels of ADP1 and Pi, rendered sodium efflux less dependent on external K and more dependent on external Na. Injection of ADP, AMP, arginine, or creatine + creatine phosphokinase, all of which raise ADP levels without raising Pi levels, had the same effect as incipient CN poisoning. Pi injection had no effect on the K sensitivity of sodium efflux. Axons depleted of arginine and phosphoarginine by injection of arginase still lost their K sensitivity when the ATP:ADP ratio was lowered and regained it partially when the ratio was raised. Rough calculations show that sodium efflux is maximally Ko-dependent when the ATP:ADP ratio is about 10:1, becomes insensitive to Ko when the ratio is about 1:2, and is inhibited by Ko when the ratio is about 1:10. Deoxy-ATP mimicked ADP when injected into intact axons. Excess Mg, as well as Pi, inhibited both strophanthidin-sensitive and strophanthidin-insensitive sodium efflux. An outline is presented for a model which might explain the effects of ADP, Pi and deoxy-ATP.
Dicarboxylic Amino Acid Influx across Brush Border of Rabbit Ileum
Authors: Schultz Stanley G. , Yu-Tu Lorna , Alvarez Osvaldo O. , Curran Peter F.
Published: May 2004

Glutamate and aspartate influxes across the brush border of rabbit intestine are saturable processes that are subject to competitive inhibition and are markedly influenced by the Na concentration in the mucosal solution. Lowering the Na concentration increases the amino acid concentration needed to elicit a half-maximal influx but does not significantly affect the maximal influx. The interaction between Na and anionic amino acid influx can be described by the same kinetic model that has been applied to the influxes of neutral amino acids and lysine. Comparison of the kinetic parameters for anionic, neutral, and cationic amino acids suggests that amino acid charge influences (a) the stability of the binary (amino acid-site) complex and (b) the affinity of this binary complex for the subsequent binding of Na. A mechanistic interpretation of these interactions is proposed.
Energy Production in Cardiac Isotonic Contractions
Authors: Gibbs C. L. , Gibson W. R.
Published: May 2004

The energy output of rabbit papillary muscle is examined and it is shown that there is more energy liberated in an afterloaded isotonic contraction than in an "equivalent" isometric contraction. This statement holds true regardless of whether equivalence is based on the proposition that tension or the time integral of tension is the best index of muscle energy expenditure. Besides the external work performed there is additional heat production in isotonic contractions and this heat increases as the afterload is decreased. The additional heat is more evident when tension rather than the time integral of tension is made the determinant of energy expenditure. It is shown in single contractions that the rate of isotonic heat production, regardless of afterload size, never exceeds the heat rate recorded in an isometric contraction at the same initial length. Experiments reveal no simple linear correlation between isotonic energy output and contractile element work. Problems associated with the compartmentalization of the energy output of a contraction are discussed.
The Effects of Amino Acids on the Labellar Hair Chemosensory Cells of the Fly
Authors: Shiraishi Akio , Kuwabara Mastaro
Published: May 2004

The effects of amino acids on the labellar hair chemosensory cells were examined with two kinds of flies (the fleshfly, Boettcherisca peregrina, and the blowfly, Phormia regina). As a result of this examination, the effects of amino acids were divided into four main classes. Amino acids in class 1 did not stimulate any chemoreceptor cell. Amino acids in class 2 inhibited nonspecifically the discharges from three kinds of chemosensory cells. Amino acids in class 3 stimulated the salt receptor cell. Amino acids in class 4 stimulated the sugar receptor cell. A possibility that a fourth neuron in the labellar hair chemosensory cell might be a protein or an amino acid receptor cell was eliminated.
Peripheral Interactions among Single Papilla Inputs to Gustatory Nerve Fibers
Authors: Miller Inglis J.
Published: May 2004

Recordings were made from single fibers of the rat chorda tympani nerve while the peripheral receptor fields were mapped using a stimulator developed to stimulate single fungiform papillae which in the rat contain a solitary taste bud. The results indicate that several fungiform papillae may supply input to a single fiber, and the most sensitive papilla of these provided, on the average, about one-half of the response of that fiber to stimulation of the entire tongue. The magnitude of the response to each concentration of stimulus and the shape of the concentration-response curves differ among papillae innervated by the same fiber. If one of the papillae supplying input to the fiber was stimulated individually with NaCl solution, application of this stimulus to the tongue surface surrounding the isolated papilla resulted in enhancement of the fiber response. If the papilla was stimulated with NaCl and potassium benzoate solution was applied to the surround, a depression of the response occurred. The excitatory input of the cationic stimuli and the depressing influence of the anionic stimuli interacted to determine the resultant steady-state impulse frequency of the single afferent fiber. A hypothetical model involving the summation of generator currents along the unmyelinated terminals of the single afferent neuron is presented as a speculative explanation of the integration of inputs from several receptors innervated by the same single fiber.
Molecular Weight Distribution of Proteins Synthesized in Single, Identified Neurons of Aplysia
Authors: Wilson David L.
Published: May 2004

Parietovisceral ganglia from Aplysia californica were incubated in medium containing leucine-3H. Single, identified nerve cell somas were isolated from the ganglia, and their proteins extracted and separated by electrophoresis on 5% SDS-polyacrylamide gels. The distribution of total or newly synthesized proteins from the single neurons was determined by staining or slicing and liquid scintillation counting of the gels. Experiments showed that: (a) a number of proteins were being synthesized in abundance in the nerve cells; (b) different, identified neurons showed reproducibly different labeling patterns in the gels; (c) cells R2 and R15, which showed different distributions of radioactivity in the gels, had similar staining patterns; and (d) there was significant incorporation into material of high (>75,000) molecular weight in most of the cells.
The Avoidance Response in Phycomyces
Authors: Johnson Daniel Leon , Gamow R. Igor
Published: May 2004

Phycomyces sporangiophores grow away from stationary objects, a phenomenon known as the avoidance response. Evidence is presented suggesting that a growth-stimulating gas is emitted from the sporangiophore and is then swept to the leeward side by air currents resulting in higher gas concentration on that side. The presence of a stationary barrier decreases the passive movement of the gas away from the leeward side. It is proposed that an increase of this gas on one side causes that side to grow faster. Indirect evidence suggests that the gas is water vapor.
Regulatory Mechanisms of the Calcium Transport System of Fragmented Rabbit Sarcoplasmic Reticulum
Authors: Weber A.
Published: May 2004

The outflux of calcium from vesicles of sarcoplasmic reticulum is controlled by the concentration of ionized calcium in the medium. In a calcium-free medium calcium outflux is at a minimum provided ATP and Mg are present. If they are removed calcium outflux becomes rapid and has a rate constant similar to that of outflux during steady-state 40Ca-45Ca exchange with saturating calcium concentrations in the medium. In order to maintain the low permeability state of the membrane only the presence but not the continued hydrolysis of ATP is necessary.
Hemoglobin Charge Dependence on Hemoglobin Concentration in Vitro
Authors: Gary-Bobo C. M. , Solomon A. K.
Published: May 2004

Studies have been made of the dependence of the charge of the hemoglobin molecule on hemoglobin concentration in the concentration range between 3 and 11 mmolal. The charge has been determined by measuring the distribution of 42K between a hemoglobin solution in a cellophane bag and an external solution. The pH was 6.6, the K concentration was 10 mM, and the temperature was 4°C. The charge decreased along a sigmoid curve from a value of +3 in the most dilute solutions to a value of +0.5 in the most concentrated solutions. The results were in excellent agreement with earlier studies of Gary-Bobo and Solomon in which Cl distribution was measured between human red cells and external solutions and thus give added support to the conclusion that the apparent anomalous osmotic behavior of human red cells may be attributed to concentration-dependent changes in the hemoglobin net charge. The present findings also support the view that the water in the red cell is solvent water for K and Cl and differs in no quantitatively important respect from bulk water in free solution.
Membrane Currents in Mammalian Ventricular Heart Muscle Fibers Using a Voltage-Clamp Technique
Authors: Giebisch Gerhard , Weidmann Silvio
Published: May 2004

Bundles of sheep ventricular fibers were voltage-clamped utilizing a modified sucrose gap technique and intracellular voltage control. An action potential was fired off in the usual way, and the clamp circuit was switched on at preselected times during activity. Clamping the membrane back to its resting potential during the early part of an action potential resulted in a surge of inward current. The initial amplitude of this current surge decreased as the clamp was switched on progressively later during the action potential. Inward current decreasing as a function of time was also recorded if the membrane potential was clamped beyond the presumed K equilibrium potential (to -130 mv). Clamping the membrane to the inside positive range (+40 mv to +60 mv) at different times of an action potential resulted in a step of outward current which was not time-dependent. The results suggest that normal repolarization of sheep ventricle depends on a time-dependent decrease of inward current (Na, Ca) rather than on a time-dependent increase of outward current (K).
The Kinetics of Sodium Transport in the Toad Bladder
Authors: Finn Arthur L.
Published: May 2004

In the accompanying paper, a compartmental model for the toad bladder sodium transport system was developed. In the present paper, the model is tested by determining the effects of antidiuretic hormone on the pools and fluxes. It is shown that this hormone affects only that sodium pool previously designated as the transport pool, and that the effects are on two separate sites. In the first place, the hormone stimulates entry at the mucosal side of the transport compartment, and by this means brings about an increase in the amount of sodium contained in the compartment. Second, the hormone has a distinct stimulatory effect on the rate coefficient for efflux across the serosal boundary, the pump rate coefficient. Evidence is presented that under control conditions, the pump rate coefficient is a decreasing function of the pool size, a characteristic feature of a saturating system. Therefore, the effect of vasopressin in increasing both the pool size and the pump rate coefficient must be construed as a direct effect on the pump, and not one which is secondary to the increase in the pool size. Furthermore, it is shown that the effect of the hormone on the sodium pump is not dependent on the presence of sodium in the serosal medium.
The Spectral Sensitivity of Single Units in the Nucleus Rotundus of Pigeon, Columba livia
Authors: Granda A. M. , Yazulla S.
Published: May 2004

Responses to diffuse monochromatic light were recorded from single units in the diencephalon of pigeon. Units were both excited and inhibited by light stimulation. Intensity-response functions based on latency measures to the first spike after stimulation were used to generate action spectra. One class of spectral sensitivity functions presumably from rods, showed peak sensitivities near 500 nm: these functions were unaffected by changing criterion values used to generate the functions. A second class of cone functions showed multiple peak sensitivities at 540 nm and 600–620 nm. These units shifted their peak sensitivities with a change in criterion values. Unit response types tended to be localized differentially in the nucleus rotundus. Excitatory units were located in the dorsal half of the nucleus, while inhibitory units were located in the ventral half, with a few exceptions. An attempt was made to integrate the present findings with previous behavioral, electrophysiological, photochemical, and anatomical data in the pigeon.
Fluctuations of the Impulse Rate in Limulus Eccentric Cells
Authors: Shapley Robert
Published: May 2004

Fluctuations in the discharge of impulses were studied in eccentric cells of the compound eye of the horseshoe crab, Limulus polyphemus. A theory is presented which accounts for the variability in the response of the eccentric cell to light. The main idea of this theory is that the source of randomness in the impulse rate is "noise" in the generator potential. Another essential aspect of the theory is that the process which transforms the generator potential "noise" into the impulse rate fluctuations may be treated as a linear filter. These ideas lead directly to Fourier analysis of the fluctuations. Experimental verification of theoretical predictions was obtained by calculation of the variance spectrum of the impulse rate. The variance spectrum of the impulse rate is shown to be the filtered variance spectrum of the generator potential.
The Kinetics of Ouabain Inhibition and the Partition of Rubidium Influx in Human Red Blood Cells
Authors: Beauge L. A. , Adragna Norma
Published: May 2004

In the development of ouabain inhibition of rubidium influx in human red blood cells a time lag can be detected which is a function of at least three variables: the concentrations of external sodium, rubidium, and ouabain. The inhibition is antagonized by rubidium and favored by sodium. Similar considerations could be applied to the binding of ouabain to membrane sites. The total influx of rubidium as a function of external rubidium concentration can be separated into two components: (a) a linear uptake not affected by external sodium or ouabain and not requiring an energy supply, and (b) a saturable component. The latter component, on the basis of the different effects of the aforementioned factors, can be divided into three fractions. The first is ouabain-sensitive, inhibited by external sodium at low rubidium, and requires an energy supply; this represents about 70–80% of the total uptake and is related to the active sodium extrusion mechanism. The second is ouabain-insensitive, activated by external sodium over the entire range of rubidium concentrations studied, and dependent on internal ATP; this represents about 15% of the total influx; it could be coupled to an active sodium extrusion or belong to a rubidium-potassium exchange. The third, which can be called residual influx, is ouabain-insensitive, unaffected by external sodium, and independent of internal ATP; this represents about 10–20% of the total influx.
The Effect of 2,4,6-Trinitro-m-Cresol on Cation and Anion Transport in Sheep Red Blood Cells
Authors: Gunn Robert B. , Tosteson Daniel C.
Published: May 2004

2,4,6-Trinitro-3-methyl-phenol (trinitrocresol, H+TNC-) was found to inhibit anion and stimulate cation movements across the membranes of both high potassium (HK) and low potassium (LK) sheep red blood cells. The concentration of TNC- required to inhibit SO4- and Cl- efflux (10-5-10-3 M) was less than that required to increase Na+ and K+ leakage (10-3-10-2 M). Both the inhibition of anion and stimulation of cation permeation were reversed if TNC- was washed from the red cells. The cation leak caused by TNC- was much greater at 0° and 37°C than at room temperature (23°C). In sheep red cells, TNC- was found to be about 20 times more effective than salicylate and about 40 times more effective than thiocyanate in increasing cation leak. TNC- also inhibited the ouabain-sensitive potassium influx.
Nonelectrolyte Permeability, Sodium Influx, Electrical Potentials, and Axolemma Ultrastructure in Squid Axons of Various Diameters
Authors: Villegas Raimundo , Villegas Gloria M. , DiPolo Reinaldo , Villegas Jorge
Published: May 2004

The penetration of 14C-labeled ethylene glycol, erythritol, mannitol, and sucrose was measured in giant axons of various diameters isolated from the hindmost stellar nerves of Doryteuthis plei squid. Axon diameter depends mainly on the age of the squid. The influx of 22Na, some electrical properties, and the ultrastructure of the axolemma were also studied. The results confirm our previous observation that in medium sized axons of D. plei stimulation causes an increase in the permeability to the penetration of erythritol, mannitol, and sucrose. They also demonstrate that the magnitude of the increase in the penetration of these probing molecules diminishes progressively as the axon diameter increases. The diminution in permeability may be due to a reduction in size of the pathways used by nonelectrolytes to enter the axon. No effect of stimulation on the ethylene glycol permeability is observed. The sodium influx and electrical properties are independent of axon size. The ultrastructural study shows that the axolemma thickness increases with axon diameter. The present experiments indicate that the nonelectrolyte permeability of stimulated axons depends on nerve fiber properties related to axon diameter and on the size of the hydrophilic nonelectrolyte probe.
The Mechanism of the Calorigenic Action of Thyroid Hormone
Authors: Ismail-Beigi Faramarz , Edelman Isidore S.
Published: May 2004

In an earlier study, we proposed that thyroid hormone stimulation of energy utilization by the Na+ pump mediates the calorigenic response. In this study, the effects of triiodothyronine (T3) on total oxygen consumption (QOO2), the ouabain-sensitive oxygen consumption [QOO2(t)], and NaK-ATPase in liver, kidney, and cerebrum were measured. In liver, ∼90% of the increase in QOO2 produced by T3 in either thyroidectomized or euthyroid rats was attributable to the increase in QOO2(t). In kidney, the increase in QOO2(t) accounted for 29% of the increase in QOO2 in thyroidectomized and 46% of the increase in QOO2 in euthyroid rats. There was no demonstrable effect of T3 in euthyroid rats on QOO2 or QOO2(t) of cerebral slices. The effects of T3 on NaK-ATPase activity in homogenates were as follows: In liver +81% from euthyroid rats and +54% from hypothyroid rats. In kidney, +21% from euthyroid rats and +69% from hypothyroid rats. T3 in euthyroid rats produced no significant changes in NaK-ATPase or Mg-ATPase activity of cerebral homogenates. Liver plasma membrane fractions showed a 69% increase in NaK-ATPase and no significant changes in either Mg-ATPase or 5'-nucleotidase activities after T3 injection. These results indicate that thyroid hormones stimulate NaK-ATPase activity differentially. This effect may account, at least in part, for the calorigenic effects of these hormones.
Electrophysiological Studies of the Smooth Muscle Cell Membrane of the Rabbit Common Carotid Artery
Authors: Mekata F.
Published: May 2004

The electrical responses of the smooth muscle cells of the rabbit common carotid artery to extracellular stimulation were studied in isotonic and hypertonic solution (1.7 times normal tonicity) with microelectrodes. No spontaneous electrical or mechanical activity was recorded when the tissue was in either isotonic or hypertonic solution. The voltage-current relation of smooth muscle cells in the common carotid artery showed marked rectification in both isotonic and hypertonic solutions. In isotonic and hypertonic solutions mean values for membrane potentials were -44.5 and -51.5 mv, for space constants 1.13 and 1.21 mm, and for time constants 212.2 and 238.2 msec, respectively. Addition of 34.3 mM TEA to the solutions caused spontaneous action potentials in the common carotid artery. The action potentials recorded simultaneously from two microelectrodes showed good synchronization. It was concluded that there is electrical transmission between cells of this artery.
Two Fast Transient Current Components during Voltage Clamp on Snail Neurons
Authors: Neher Erwin
Published: May 2004

Voltage clamp currents from medium sized ganglion cells of Helix pomatia have a fast transient outward current component in addition to the usually observed inward and outward currents. This component is inactivated at normal resting potential. The current, which is carried by K+ ions, may surpass leakage currents by a factor of 100 after inactivation has been removed by hyperpolarizing conditioning pulses. Its kinetics are similar to those of the inward current, except that it has a longer time constant of inactivation. It has a threshold close to resting potential. This additional component is also present in giant cells, where however, it is less prominent. Pacemaker activity is controlled by this current. It was found that inward currents have a slow inactivating process in addition to a fast, Hodgkin-Huxley type inactivation. The time constants of the slow process are similar to those of slow outward current inactivation.