bluuebunny/crossref_metadata_2025 huggingface dataset:
Cat Heart Muscle in Vitro
Authors: Page Ernest
Published: May 2004

The "osmotic gradient" method, an intracellular microelectrode technique for determining whether an uncharged, water-soluble molecule enters cells or remains extracellular, is described. Using this method, a series of carbohydrates of graded molecular size were examined. In cat papillary muscles mannitol, molecular radius 4.0 Å, remained extracellular while arabinose, molecular radius 3.5 Å entered the cells. Measurement of the simultaneous uptake of H3-mannitol and C14-inulin showed that mannitol equilibrates with 40 per cent of total water in 1 hour, after which the mannitol space does not further increase. By contrast, inulin, molecular radius ∼15 Å, equilibrates with 24 per cent of total water in 1 hour; thereafter the inulin space continues to increase very slowly. The intracellular K concentrations are significantly higher and the intracellular Na and Cl concentrations significantly lower when mannitol rather than inulin is used to measure the extracellular space. The intracellular Cl concentration determined with Cl36 or Br82 is significantly higher than that calculated from the membrane potential assuming a passive Cl distribution. In addition, it is shown that choline enters and is probably metabolized by the cells of papillary muscle.
Adenosine Diphosphate Requirement in the Creatine Phosphate-Induced Contraction of the Glycerinated Rabbit Psoas
Authors: Cohen William D. , Schneebaum Jeanne , Hayashi Teru
Published: May 2004

Glycerinated rabbit psoas fibers were tested for their ability to contract under the influence of creatine phosphate and creatine kinase in the absence of free nucleotide. Tension development by the fibers was observed upon addition of creatine phosphate to the medium containing creatine kinase purified to the first lyophilization stage. However, when the enzyme was washed free of nucleotides by treatment with the anion exchange resin Dowex 1, no contraction occurred until free nucleotide was supplied. In all experiments, contractile activity of the psoas fibers was the criterion for determining the enzyme activity concerned. Using this criterion, creatine kinase activity native to the glycerinated fibers was also demonstrated. No evidence for direct transphosphorylation of the bound nucleotide of the fiber was found.
Changes in the Permeability of the Salivary Gland Caused by Sympathetic Stimulation and by Catecholamines
Authors: Martin K. , Burgen A. S. V.
Published: May 2004

The permeability of the submaxillary gland of cats and dogs has been tested by determining the rates at which non-electrolytes penetrate from the plasma into the saliva. Electrical stimulation of the cervical sympathetic trunk or administration of epinephrine or norepinephrine increases the permeability of the gland enabling glucose (molecular radius, MR = 3.5 Å), sucrose (MR = 4.4 Å), raffinose (MR = 5.6 Å), polyglycol 1000 (MR = 7.2 Å), and polyglycol 1540 (MR = 8.1 Å) to penetrate into the saliva from which they are otherwise excluded. Inulin (MR = 14.7 Å) does not enter the saliva under these circumstances. Analysis of the transfer rates suggests that the molecules diffuse through a pore structure permitting free diffusion for molecules with a radius less than 5.7 Å. Close intraarterial injection of C14-glucose demonstrates that at least part of this permeability is located in the duct system of the gland. Since epinephrine does not enable sucrose to enter the cells of the gland, it appears that penetration from the extracellular space into the saliva occurs by diffusion through intercellular gaps. The characteristics of the permeability allow conclusions as to the localisation and geometry of the ultrastructural change produced.
Action of the Calcium Antagonists Cocaine and Ethanol on Contraction and Potassium Efflux of Smooth Muscle
Authors: Hurwitz Leon , Battle Frank , Weiss George B.
Published: May 2004

Isolated longitudinal smooth muscle from guinea pig ileum exposed to a high potassium depolarizing medium exhibited a sustained increase in muscle tone and an increase in potassium efflux. When the concentration of calcium ion in the medium was elevated the increase in muscle tone was enhanced, but the change in potassium efflux was reduced slightly. Lowering the calcium concentration diminished the increase in muscle tone. Both cocaine and ethanol completely inhibited the sustained contraction of potassium-depolarized fibers. Addition of excess calcium ion reversed these inhibitions. Cocaine acted primarily like a competitive antagonist; and ethanol, like an indirect antagonist of calcium, ion. Under certain conditions acetylcholine potentiated the reversal by calcium ion of the drug-induced inhibitions. The two inhibitory drugs had dissimilar effects on potassium efflux from smooth muscle fibers immersed in Tyrode solution. Cocaine depressed and ethanol enhanced this membrane process. However, the increase in potassium efflux induced by acetylcholine was inhibited by ethanol. This inhibition also was reversed by increasing the concentration of calcium ion in the medium. The data suggested that calcium activates and cocaine and ethanol inhibit a cellular reaction which occurs beyond the point of membrane depolarization and is essential for smooth muscle contraction. Furthermore, calcium serves to depress membrane excitability, but appears to have a specific stimulatory role in the acetylcholine-induced increase in potassium efflux from longitudinal fibers.
Cation Transport in Escherichia coli
Authors: Schultz Stanley G. , Epstein Wolfgang , Goldstein David A.
Published: May 2004

The present study is concerned with the measurement of the unidirectional K flux in E. coli. Methods are described by means of which a fairly dense suspension of cells may be maintained in a well defined steady-state with respect to the intracellular K concentration and the pH of the medium. The kinetics of K42 exchange under these conditions are consistent with the presence of a single intracellular K compartment with a unidirectional K flux of 1 pmol/(cm2 sec.). This rate is independent of the extracellular K concentration over the range studied. The simultaneous rate of H secretion averages 16 pmols/(cm2 sec.) indicating that in the steady-state the efflux of metabolically produced H is not linked mole for mole to K movement.
Calculation of the Albumin Catabolic Rate in the Non-Steady State
Authors: Franks J. J.
Published: May 2004

Methods which are in current use for the calculation of the albumin breakdown rate apply only to the steady state animal. In this paper a simple but more general method based on analyses of I131-albumin tracer data is presented. It utilizes easily measured plasma specific activity and excretory data and is equally applicable to the steady and non-steady states.
Electrical Inexcitability of the Frog Neuromuscular Synapse
Authors: Werman Robert
Published: May 2004

Frog muscle endplates were explored with an extracellular microelectrode. An intracellular microelectrode nearby simultaneously monitored invasion of the endplate by a spike directly evoked by a third microelectrode placed away from the endplate in the same fiber. External positivities were seen only at sites generating miniature endplate potentials. The external positivity reached a maximum prior to the internally recorded potential and was followed by a small late negativity. Small movements away from active synaptic sites resulted in positive-negative-positive potential sequences characteristic of activity and propagation. Since the external potential is a function of membrane current, the absence of negativity associated with the rising phase of the spike indicates the absence of inward current at synaptic sites. Thus, the synaptic membrane appears not to be excited by a depolarization of the magnitude of an action potential. In an Appendix it is shown that the late negativity and earlier maximum of the external potential can be accounted for by capacitative current through passive membrane.
Modes of Initiation and Propagation of Spikes in the Branching Axons of Molluscan Central Neurons
Authors: Tauc L. , Hughes G. M.
Published: May 2004

A study has been made of Aplysia nerve cells, mainly in the pleural ganglia, in which the main axon divides into at least two branches in the neighbourhood of the soma. Conduction between these branches was investigated by intracellular recordings from the soma following antidromic stimulation via the nerves containing the axonal branches. It has been shown that transmission between separate branches need not involve discharge of the soma but only of the axonal region between the soma and the origin of the branches. In some cells, the spike may fail to invade the other axonal branch, whereas transmission in the opposite direction is readily achieved. Often spikes in none of the branches are transmitted to the others, unless facilitated. Indications about the geometry of the neuron in the vicinity of the soma may be obtained from the study of the relative size of the A spikes originated in different branches. These observations, together with the presence of different sizes of A spikes, produced by orthodromic stimulation, provide evidence that spikes initiated at separate axonal "trigger zones" of Aplysia neurons may be conducted selectively to the effectors or other neurons innervated by the particular branch.
The Concentration Dependence of Sodium Efflux from Muscle
Authors: Mullins L. J. , Frumento A. S.
Published: May 2004

Frog sartorius muscles subjected to overnight loading with Na+ in K-free Ringer in the cold were subsequently labeled with Na24 and then immersed in choline Ringer and the efflux of Na24 followed for 4 hours. The initial efflux of Na+ appeared to be 17 pmole/cm2 sec.; this value was maintained for 20 minutes and was followed by an abrupt decline to about 9 pmole/cm2 sec. This latter rate was maintained for the next 20 minutes of efflux. The efflux then declined gradually with time and reached values of the order of 0.1 pmole/cm2 sec. The back addition of counts lost from muscles enabled one to calculate the relationship between efflux and [Na]i for muscle. This roughly approximates an S-shaped curve with a value at half-saturation of about 17 mmole Na per liter of fiber water. The efflux-concentration curve is closely described by assuming that 3 Na+ are transported per carrier cycle.
The Effect of Ca and Antidiuretic Hormone on Na Transport across Frog Skin
Authors: Curran Peter F. , Herrera Francisco C. , Flanigan William J.
Published: May 2004

A method has been developed for determining unidirectional Na fluxes across the two faces of the transporting cells in the frog skin. The method has been used to investigate the location of the sites at which Ca and anti-diuretic hormone act to alter the rate of active Na transport across the skin. The results have indicated that the primary effect of both agents is on the Na permeability of the outward facing membrane of the cells. Ca decreases and the hormone increases permeability of this barrier. Neither agent appears to have a direct effect on the active transport system itself assuming that it is located at the inner membrane of the cells. The rate of active Na transport is altered as a result of changes in the size of the Na pool in the cells which occur because of changes in the rate of Na entry through the outer membrane. Thus, the results indicate that the Na permeability of the outer membrane plays an important role in controlling the rate of net active Na transport across the skin.
Retardation of Division of Three Ciliates by Intermittent and Continuous Ultraviolet Radiations at Different Temperatures
Authors: Giese A. C. , McCaw B. , Cornell R.
Published: May 2004

The same dosage of ultraviolet (UV) radiation retards division of several protozoans more effectively when the light is intermittent than when it is continuous, and especially at temperatures of 25–35°C. At lower temperatures the difference between the effects of intermittent and continuous radiations is less marked. Somewhat similar results were obtained with the ciliates Paramecium caudatum, Blepharisma japonicum, and Colpidium colpoda, the disparity between intermittent and continuous light decreasing in the order given. The data are taken to indicate that thermochemical dark reactions succeed the absorption of UV radiations by the cells. In Blepharisma, besides initial delay in division, the cells stop dividing after one or two divisions, a "stasis" ensuing. Stasis is marked when the cells are irradiated at higher temperatures but is slight when they are irradiated at low temperatures, as if the temperature-sensitive reaction involved stasis (in all cases cultures are grown at 25°C). The data are related to findings in the literature.
Effect of Azide and Ca Ion on the Reversible Changes of Protein Configuration in Stimulated Nerves
Authors: Luxoro M. , Rojas E. , Wittig E.
Published: May 2004

Working with sciatic nerves from the South American frog Calyptocephalella gayi we have been able to substantiate the finding of Ungar et al., that nerve proteins undergo a reversible denaturation concomitant with a train of nerve impulses. We also showed that 0.3 mM sodium azide is capable of impairing the reversibility of those changes. Furthermore, 10 meq/liter of calcium ion applied to extracts of resting nerves induce configurational rearrangements in the proteins similar to those produced during stimulation. We also proved that nerves previously kept in low calcium Ringer's solution do not show configurational changes upon stimulation. A tentative interpretation of the results described is that the configurational changes are a consequence of the extra influx of calcium ion due to nerve impulse propagation.
Total Energy Production and Phosphocreatine Hydrolysis in the Isotonic Twitch
Authors: Carlson Francis D. , Hardy Donna J. , Wilkie Douglas R.
Published: May 2004

Using frog's sartorius muscles we have found no correlation between phosphocreatine hydrolysis and shortening under conditions (iodoacetate poisoning and anoxia) where this reaction was the only expected source of energy. Phosphocreatine hydrolysis did, however, show a constant term corresponding to the activation heat of A.V. Hill, and a linear term with work. It was concluded that shortening heat comes from some other chemical reaction, or else Hill's equation (E = A + W + ax) fails to describe correctly the energy output in a complete cycle of contraction and relaxation. To decide between these possibilities direct measurements of heat and work during a complete cycle were made. Also, experiments were performed in which heat, work, and phosphocreatine breakdown were measured simultaneously on the same muscles. The total energy output in a complete twitch could be most simply represented by a fixed "activation" heat, plus the work. There was no term corresponding to the shortening heat. Hill's equation must, therefore, be held as invalid for the complete isotonic twitch. A value of 9.8 ± 0.5 (sE) kcal/mole was obtained for the in vivo heat of hydrolysis of phosphocreatine. This quantity showed no significant dependence on load, and it is in good agreement with the value obtained from thermochemical data. It is concluded that phosphocreatine hydrolysis and its associated buffer reactions can account quantitatively for the total energy output of isometric and isotonic twitches.
Some Electrical Properties of a Nuclear Membrane Examined with a Microelectrode
Authors: Loewenstein Werner R. , Kanno Yoshinobu
Published: May 2004

Electrical potential and resistance were measured with microelectrodes in in situ and isolated nuclei of gland cells of Drosophila flavorepleta. The nucleus-cytoplasm boundary was found to be rather impermeable to ion diffusion. It presents a resistance of the order of 1 Ω cm2 and sustains a "resting" potential, the nucleoplasm being about 15 mv negative with respect to the cytoplasm. Both the resistance and potential appear to be associated with the nuclear membrane: the potential declines to zero and the resistance to a fraction of its original value, when the membrane is perforated experimentally.
Sodium Fluxes in Desheathed Frog Sciatic Nerve
Authors: Hurlbut William P.
Published: May 2004

Desheathed frog (R. pipiens) sciatic nerves were soaked in solutions that contained ouabain or NaN3, in K-free solutions, or in K- and Ca-free solutions. Then, the nerves were allowed to recover in standard Ringer's solution. At various times during the soaking periods, some nerves were analyzed for Na and K, and estimates were made of the influx and efflux of Na22. While a nerve was soaking in any one of the experimental solutions, the Na22 influx was increased, the Na content was rising, and the K content was falling by an equivalent amount. The rate coefficient for Na22 efflux was reduced by about 25 per cent by 0.05 mM ouabain and by about 50 per cent by 5 mM NaN3. Potassium-free solutions had little effect on the rate coefficient. It was concluded that the efflux of Na from frog nerve is dependent on the metabolism, but not on the external concentration of K. The equimolar exchange that is characteristic of the net movements of Na and K in frog nerve may not be due to the presence of a tightly coupled Na-K exchange pump, but may represent a constraint imposed by the requirement for electroneutrality.
Photosensitivity of the Frog Iris
Authors: Barr Lloyd , Alpern Mathew
Published: May 2004

The absorption of quanta by rhodopsin leads to the contraction of frog iris muscle. The contractions reach a maximum after about 8 sec. in the light. When the light is turned off the irises relax exponentially with a half-time of about 6 sec. Membrane polarization is not necessary for the response but calcium movement and membrane permeability changes probably are. The response is not mediated by acetylcholine or epinephrine. The curves of log It vs. log t for constant response amplitude bend progressively upward away from a unit slope line at short times as larger response criteria are used because (a) light influences tension development over longer times and (b) the higher intensity, shorter duration flashes are less effective.
The Influence of Sodium-Free Solutions on the Membrane Potential of Frog Muscle Fibers
Authors: Mullins L. J. , Noda K.
Published: May 2004

The membrane potential of frog sartorius muscle fibers in a Cl- and Na-free Ringer's solution when sucrose replaces NaCl is about the same as that in normal Ringer's solution. The K+ efflux is also about the same in the two solutions but muscles lose K and PO4 in sucrose Ringer's solutions. The membrane potential in sucrose Ringer's solution is equal to that given by the Nernst equation for a K+ electrode, when corrections are made for the activity coefficients for K+ inside and outside the fiber. For a muscle in normal Ringer's solution, the measured membrane potential is within a few millivolts of EK. This finding is incompatible with a 1:1 coupled Na-K pump. It is consistent with either no coupling of Na efflux to K influx, or a coupling ratio of 3 or greater.
Osmotic Behavior of Oat Coleoptile Tissue in Relation to Growth
Authors: Ray Peter M. , Ruesink Albert W.
Published: May 2004

Efforts were made to estimate the water potential difference that is required, between rapidly growing oat coleoptile cylinders and dilute medium, to support the rate of water uptake involved in elongation, (a) by the traditional method of determining the concentration of mannitol in which the tissue neither gains nor loses water, and (b) by measuring the rates of osmotic exchanges induced by treating the tissue with different hypotonic mannitol concentrations. Both methods indicated large water potential differences (3 to 10 atm), in some cases approaching the osmotic pressure of the cells. However, indication was obtained that the rates of osmotic exchanges induced by mannitol solutions, and presumably also the equilibrium response sought in (a), are governed by the rate of diffusional exchange of mannitol with the free space rather than by the permeability of the tissue to water. Osmotic swelling of the tissue measured by immersing it in water after its turgor pressure had been reduced by evaporation, was at least two to four times more rapid than when mannitol was involved. The permeability to water estimated by the evaporation-immersion method indicated that rapidly elongating cylinders have water potentials between -0.8 and -2.5 atm, or between 10 and 25 per cent of their osmotic pressure.
Changes in Electrical Conductance of Rhodopsin on Photolysis
Authors: Hara Reiko
Published: May 2004

The change in electrical conductance of rhodopsin solutions was studied with flash-photolysis techniques. The whole pattern of the conductance change on illumination consists of three different processes: (I) the initial decrease, (II) the increase, and (III) the slow decrease, which are in decreasing order of reaction rate. The processes I, II, and III can be most distinctly recognized on flash illumination of acid, slightly acid, and alkaline rhodopsins, respectively. On the other hand, the bleaching of rhodopsin also shows at least three successive phases of different rates, but none of them corresponds in reaction rate to any of the processes of the conductance change. The conductance change may be related to conformational changes of opsin following photoisomerization of retinene, being due to hydrogen or hydroxyl ions and some other inorganic electrolytes. The amount of the change, especially the initial decrease, is proportional to the amount of rhodopsin bleached, even when the photochemical back reaction towards rhodopsin and isorhodopsin occurs in the chromophore depending on the intensity of illumination. Of the three processes, the slow decrease is most severely affected by aging, but the initial decrease and increase are slightly affected. These two processes promptly caused by illumination are connected closely to the conformational changes during the conversion of rhodopsin to metarhodopsin, and perhaps to the initial stage of excitation of rod cells.
The Dependence of the Photopupil Response on Flash Duration and Intensity
Authors: Alpern Mathew , McCready Donald W. , Barr Lloyd
Published: May 2004

The changes in pupil size were recorded by infrared pupillographic methods in response to light flashes of different durations and intensities for a 13 degree 34 minute centrally fixated circular field. For such stimuli, the threshold intensities for (rod) vision and for the pupil response were found to be about the same. The response amplitudes were related to the logarithm of the flash energy, the reciprocity law remaining valid up to about one-half second. The curve relating flash energy and pupil response was clearly divisible into two parts commensurate with the duplex character of the human retina. A similar dichotomy appears in curves relating response amplitude to response latency. Since the pupil response is determined by total flash energy, intense long flashes produce larger pupil responses than shorter (and perceptually brighter) ones of the same intensity.
Nitrous Acid Reactivation of Ultraviolet-Irradiated Transforming DNA from Hemophilus influenzae
Authors: Cabrera-Juárez Emiliano
Published: May 2004

Partial recovery of ultraviolet-damaged denatured or native transforming DNA from Hemophilus influenzae, has been obtained by exposing the irradiated DNA in the denatured form to nitrous acid. Some factors that affect this recovery are described. An erythromycin marker (E20) was not reactivated. The UV damage reactivable by nitrous acid is different from that repaired by the photoreactivating enzyme from bakers' yeast. The pretreatment with nitrous acid affords a slight protection for denatured C25 DNA and Sm250 DNA against ultraviolet irradiation, but this pretreatment sensitized the E20 DNA to this irradiation.
Independence of the Endovestibular Potential in Homeotherms
Authors: Schmidt Robert S.
Published: May 2004

The endolymphatic potential was recorded from various vestibular parts of the labyrinth from which the cochlea (in the case of guinea pigs) or the cochlea, lagena, and sacculus (in the case of pigeons) had been removed. This endovestibular potential of the isolated vestibule declined during anoxia and recovered after anoxia in the same manner as the endovestibular potential of the intact labyrinth. Its non-anoxic level was the same as in the intact labyrinth; i.e., +5 to +8 mv in the pigeon and +2 to +5 mv in the guinea pig. It is, therefore, concluded that the endovestibular potential is independent of the cochlea, stria vascularis, and endocochlear potential.
Changes in the Membrane Permeability of Frog's Sartorius Muscle Fibers in Ca-Free EDTA Solution
Authors: Kimizuka H. , Koketsu K.
Published: May 2004

The changes in the membrane permeability to sodium, potassium, and chloride ions as well as the changes in the intracellular concentration of these ions were studied on frog sartorius muscles in Ca-free EDTA solution. It was found that the rate constants for potassium and chloride efflux became almost constant within 10 minutes in the absence of external calcium ions, that for potassium increasing to 1.5 to 2 times normal and that for chloride decreasing about one-half. The sodium influx in Ca-free EDTA solution, between 30 and 40 minutes, was about 4 times that in Ringer's solution. The intracellular sodium and potassium contents did not change appreciably but the intracellular chloride content had increased to about 4 times normal after 40 minutes. By applying the constant field theory to these results, it was concluded that (a) PCl did not change appreciably whereas PK decreased to a level that, in the interval between 10 and 40 minutes, was about one-half normal, (b) PNa increased until between 30 and 40 minutes it was about 8 times normal. The low value of the membrane potential between 30 and 40 minutes was explained in terms of the changes in the membrane permeability and the intracellular ion concentrations. The mechanism for membrane depolarization in this solution was briefly discussed.
Ion Transport in Isolated Rabbit Ileum
Authors: Schultz Stanley G. , Zalusky Ralph
Published: May 2004

The transmural potential difference, short-circuit current, and Na fluxes have been investigated in an in vitro preparation of isolated rabbit ileum. When the tissue is perfused with a physiological buffer, the serosal surface is electrically positive with respect to the mucosal surface and the initial potential difference in the presence of glucose averages 9 mv. Unidirectional and net Na fluxes have been determined under a variety of conditions, and in each instance, most if not all of the simultaneously measured short-circuit current could be attributed to the active transport of Na from mucosa to serosa. Active Na transport is dependent upon the presence of intact aerobic metabolic pathways and is inhibited by low concentrations of ouabain in the serosal medium. A method is described for determining whether a unidirectional ionic flux is the result of passive diffusion alone, in the presence of active transport of that ion in the opposite direction. Using this method we have demonstrated that the serosa-to-mucosa flux of Na may be attributed to passive diffusion with no evidence for the presence of carrier-mediated exchange diffusion or the influence of solvent-drag.
Contracture Coupling of Slow Striated Muscle in Non-Ionic Solutions and Replacement of Calcium, Sodium, and Potassium
Authors: Irwin Richard L. , Hein Manfred M.
Published: May 2004

The development of contracture related to changes of ionic environment (ionic contracture coupling) has been studied in the slowly responding fibers of frog skeletal muscle. When deprived of external ions for 30 minutes by use of solutions of sucrose, mannitol, or glucose, the slow skeletal muscle fibers, but not the fast, develop pronounced and easily reversible contractures. Partial replacement of the non-ionic substance with calcium or sodium reduces the development of the contractures but replacement by potassium does not. The concentration of calcium necessary to prevent contracture induced by a non-ionic solution is greater than that needed to maintain relaxation in ionic solutions. To suppress the non-ionic-induced contractures to the same extent as does calcium requires several fold higher concentrations of sodium. Two types of ionic contracture coupling occur in slow type striated muscle fibers: (a) a calcium deprivation type which develops maximally at full physiological concentration of external sodium, shows a flow rate dependency for the calcium-depriving fluid, and is lessened when the sodium concentration is decreased by replacement with sucrose; (b) a sodium deprivation type which occurs maximally without external sodium, is lessened by increasing the sodium concentration, and has no flow rate dependency for ion deprivation. Both types of contracture are largely prevented by the presence of sufficient calcium. There thus seem to be calcium- and sodium-linked processes at work in the ionic contracture coupling of slow striated muscle.
An Estimate of Reflection Coefficients for Rabbit Heart Capillaries
Authors: Vargas Fernando , Johnson John A.
Published: May 2004

Isolated perfused rabbit hearts have been used to determine the reflection coefficients, σ, of the heart capillaries to certain lipoid-insoluble substances. This was done by initially perfusing the heart with a Ringer solution containing no test molecule and then suddenly switching to a solution which differed from the original only by containing a small amount of test substance. This produced a loss of weight of the heart which was continuously recorded as a function of time. Taking the "zero" time rate of weight change and using an equation given by Kedem and Katchalsky reflection coefficients for urea, sucrose, raffinose, and inulin were obtained. These turned out to be 0.1, 0.3, 0.38, and 0.69 respectively. Using the approach of Durbin and Solomon equivalent pore radii were estimated to be about 35 Angstroms.
Electrical Properties of Hypothalamic Neuroendocrine Cells
Authors: Kandel E. R.
Published: May 2004

Goldfish hypothalamic neuroendocrine cells have been investigated with intracellular recordings. The cells showed resting potentials of 50 mv and action potentials up to 117 mv followed by a long lasting and prominent diphasic hyperpolarizing afterpotential. The action potential occurred in two steps indicating sequential invasion. "Total" neuron (input) resistance was measured to be 3.3 x 107 Ω and total neuron time constant was 42 msec. Orthodromic volleys, produced by olfactory tract stimulation, generated graded excitatory postsynaptic potentials. These neuroendocrine cells seem, therefore, to have electrical membrane properties that are similar to those of other central neurons. Antidromic volleys (pituitary stimulation) produced inhibitory post-synaptic potentials whose latency was only slightly longer than that of the antidromic spike indicating the presence of recurrent collaterals. This finding suggests that the concept of the neuroendocrine cell as a neuron whose axon forms contacts only on blood vessels and not on other neurons or effector cells is too restrictive. Perfusion of the gills with dilute (0.3 per cent) sea water produced an inhibition of spontaneous activity. This inhibition is discussed in relation to recent work which demonstrates that goldfish hypothalamic hormones facilitate Na+ influx across the gill membrane.
The Effect of Aconitine on the Giant Axon of the Squid
Authors: Herzog W. H. , Feibel R. M. , Bryant S. H.
Published: May 2004

In the giant axon of Loligo pealii, "aconitine potent" Merck added to the bath (10-7 to 1.25 x 10-6 gm/ml) (a) had no effect on resting membrane potential, membrane resistance and rectification, membrane response to subthreshold currents, critical depolarization, or action potential, but (b) on repetitive stimulation produced oscillations of membrane potential after the spike, depolarization, and decrease of membrane resistance. The effect sums with successive action potentials; it increases with concentration of aconitine, time of exposure, and frequency of stimulation. When the oscillations are large enough and the membrane potential is 51.6 ± SD 1.5 mv a burst of self-sustained activity begins; it usually lasts 20 to 70 sec. and at its end the membrane potential is 41.5 ± SD 1.9 mv. Repolarization occurs with a time constant of 2.5 to 11.1 min. Substitution of choline for external sodium after a burst hyperpolarizes the membrane to -70 mv, and return to normal external sodium depolarizes again beyond the resting membrane potential. The effect of aconitine on the membrane is attributed to an increase of sodium and potassium or chloride conductances following the action potential.
Anion Requirements for Gastric Acid Secretion
Authors: Durbin Richard P.
Published: May 2004

The rate of hydrochloric acid production by isolated, bullfrog gastric mucosae depends critically on the supply of chloride ion to the serosal surface. Secretion of acid is negligible if chloride is completely replaced by glucuronate and gluconate ion. The experimental evidence indicates that the rate of acid secretion may be regarded as a reaction velocity, depending on chloride concentration in a manner closely resembling Michaelis-Menten kinetics. Bromide and iodide ions substitute, in varying degree, for chloride as substrate. A familiar inhibitor of gastric acid production, thiocyanate ion, appears to act by competition with chloride in a reaction leading to the formation of acid. This reaction is included in a hypothetical reaction cycle, generalized from the redox model for gastric acid production. Under certain conditions, the model predicts a dependence of secretion rate on chloride supply of the Michaelis-Menten type, as was observed.
Membrane Resistance of Human Red Cells
Authors: Johnson S. L. , Woodbury J. W.
Published: May 2004

A method has been devised to measure the specific membrane resistance of single human red cells. The cells were sucked into a 3 to 5 micron diameter pore in the end of a glass tube. By passing a small current through the cells, the total cell resistance was measured. The dimensions of the cell were measured optically and the specific membrane resistance was then calculated. Leakage of current between the cell and the walls of the pore was minimized by filling this region with isotonic sucrose. The measured specific membrane resistance values of four human red cells were 6.3, 6.32, 10.0, and 19.7 ohm-cm2.
Water Permeability of the Fetal Erythrocyte
Authors: Barton T. C. , Brown D. A. J.
Published: May 2004

The rate constant for the diffusion of tritiated water across the fetal erythrocyte membrane has been measured as 0.056 ± SD 0.013 msec.-1 The equivalent pore radius calculated by the method of Paganelli and Solomon for the fetal erythrocyte is 3.9 A. The effect of a normal distribution of channel sizes within the erythrocyte membrane is discussed and the theoretical effect of variation of the distribution on the diffusion to bulk flow ratio is evaluated. Since membrane channels of 4 A characterize a variety of membranes, it is suggested that permeability differences may be associated with slight variations in the statistical distribution of the channel sizes within the membrane. The limits of ±0.5 A standard deviation that qualitative experiments place on the expected variability of channel size will not account for the lower rate of water diffusion in the fetal cell.
Estimation of the Life Span of Red Blood Cells
Authors: Carter Melvin W. , Matrone Gennard , Mendenhall W.
Published: May 2004

A modified method for fitting the model of Shemin and Rittenberg to study the life span of red cells is described. In this modification the assumption that incorporation of tag is complete before any cells die is relaxed. A recursion formula useful for fitting the model on the digital computer is given. Good results were obtained with data from the sheep, rat, cat, rabbit, and the dog, whereas in several of these cases the method of Shemin and Rittenberg was not satisfactory. By varying critical parameters of the model a continuum of curves is possible. Curves which formerly were explained on the basis of random death can be obtained without this assumption. Limitations and implications of the method are discussed.
Effect of Current on Transmembrane Potentials in Cultured Chick Heart Cells
Authors: Sperelakis Nick , Lehmkuhl D.
Published: May 2004

By means of a DC bridge circuit one microelectrode was used for simultaneously passing current and recording transmembrane potentials. In some cells, depolarization increased the frequency of discharge whereas hyperpolarization decreased the frequency; the frequency/current relation was sigmoid. In other cells, polarizing currents were without effect upon frequency. The change in action potential magnitude was in proportion to the degree of polarization. From control values of about 5 mv/sec., the slope of the pacemaker potential increased to 60 mv/sec. upon depolarization and diminished to zero upon hyperpolarization. In many cells a transient hyperpolarization was produced on the cessation of depolarizing currents. The voltage/current relationship was linear and had a slope of about 13 MΩ. With an AC bridge circuit, the cell capacitance averaged 800 pf and the time constant, 9.6 msec. Rm was estimated to be 480 Ω-cm2 and Cm, 20 µf/cm2. The magnitudes of some prepotentials were affected by polarizing currents, which suggests that the prepotentials represent postsynaptic potentials.
The After-Potential that Follows Trains of Impulses in Frog Muscle Fibers
Authors: Freygang W. H. , Goldstein D. A. , Hellam D. C.
Published: May 2004

Intracellular recordings of the negative after-potential that follows a train of impulses in frog muscle are described. It is postulated that the cause of this after-potential is an accumulation of potassium, during the train, in an intermediary space that is located between the major portion of the sarcoplasm and the external fluid. The decline of the after-potential is then produced by the exchange of potassium from the intermediary space with sodium from the external fluid.
Water Transfer and Cell Structure in Isolated Crayfish Muscle Fibers
Authors: Reuben John P. , Girardier Lucien , Grundfest Harry
Published: May 2004

Changes in volume of crayfish single muscle fibers in response to changes in ionic or electrical conditions have been studied in conjunction with electrophysiological measurements and electron microscopic examinations. The occurrence of at least three mechanisms of water movements is revealed, two being processes which are superimposed on the normal osmotic water movement that results from a change in the concentration of solute in the medium. Differences between the time courses of the changes in volume and potential on changing Ki/Ko indicate that water may be distributed unequally for a time within compartments of the fiber. Electron micrographs reveal a selective accumulation of water at the periphery of the fiber under certain conditions. A correlation of H2O transfer with a change in membrane potential is apparent in crayfish muscle fibers and is probably due to electroosmotic effects. Electrokinetic water movements are produced whenever the membrane potential is changed to a considerable degree by changing the level of K and/or Cl in the medium, or by applying currents with an intracellular microelectrode. Depolarizations cause shrinkage. Hyperpolarizations or repolarizations cause swelling. The volume changes are independent of the occurrence or absence of swelling in the anion-permselective transverse tubular system. They indicate that the fiber membrane along the surface is heterogeneous, not only with respect to the signs of its fixed charge sites, but also with respect to the sizes and relative permselectivities of these charged channels.
Sodium Movement across Single Perfused Proximal Tubules of Rat Kidneys
Authors: Giebisch Gerhard , Klose Ruth M. , Malnic Gerhard , Sullivan W. James , Windhager Erich E.
Published: May 2004

Using perfusion techniques in single proximal tubule segments of rat kidney, the relationship between net sodium movement and active transport of ions, as measured by the short-circuit method, has been studied. In addition, the role of the colloid-osmotic pressure gradient in proximal transtubular fluid and sodium movement has been considered. Furthermore, the limiting concentration gradient against which sodium movement can occur and the relationship between intratubular sodium concentration and fluid transfer have been investigated. Comparison of the short-circuit current with the reabsorptive movement of sodium ions indicates that this process is largely, perhaps exclusively, active in nature. No measurable contribution of the normally existing colloid-osmotic pressure gradient to transtubular water movement was detected. On the other hand, fluid movement across the proximal tubular epithelium is dependent upon the transtubular sodium gradient and is abolished when a mean concentration difference of 50 mEq/liter is exceeded.
The Mechanism of Sodium and Chloride Uptake by the Gills of a Fresh-Water Fish, Carassius auratus
Authors: Maetz J. , García Romeu F.
Published: May 2004

The addition of ammonium ions to the external medium results in an inhibition of the sodium influx and net uptake in Carassius auratus, while intraperitoneal injection of ammonium produces the opposite effect. The simultaneous chloride balance is not significantly affected by these treatments. The addition of bicarbonate ions to the external medium results in a reduction of the influx and net flux of chloride, while injection of bicarbonate produces the opposite effect. The simultaneous sodium balance is not significantly altered. The effects of the external additions are reversible after elimination of the excess ammonium or bicarbonate ions by rinsing. Inhibition of carbonic anhydrase in the gill by injection of acetazoleamide produces a simultaneous inhibition of both sodium and chloride exchanges. These results confirm the hypothesis of an exchange of sodium for ammonium, and of bicarbonate for chloride across the gill. A tentative schematic representation of the ionic absorption mechanisms in the branchial cell of the fresh-water teleosts is given. Similarities with other biological membranes and especially with the renal tubule are pointed out.
Transport of Salt and Water in Rabbit and Guinea Pig Gall Bladder
Authors: Diamond Jared M.
Published: May 2004

A simple and reproducible method has been developed for following fluid transport by an in vitro preparation of mammalian gall bladder, based upon weighing the organ at 5 minute intervals. Both guinea pig and rabbit gall bladders transport NaCl and water in isotonic proportions from lumen to serosa. In the rabbit bicarbonate stimulates transport, but there is no need for exogenous glucose. The transport rate is not affected by removal of potassium from the bathing solutions. Albumin causes a transient weight loss from the gall bladder wall, apparently by making the serosal smooth muscle fibers contract. Active NaCl transport can carry water against osmotic gradients of up to two atmospheres. Under passive conditions water may also move against its activity gradient in the presence of a permeating solute. The significance of water movement against osmotic gradients during active solute transport is discussed.
The Accumulation of Calcium Ions by Sarcotubular Vesicles
Authors: Carsten Mary E. , Mommaerts W. F. H. M.
Published: May 2004

The accumulation of Ca++ by microsomal (sarcotubular) preparations of rabbit skeletal muscle in the presence of oxalate, and the concurrent splitting of nucleoside triphosphate, displayed moderate nucleotide specificity in the sequence ATP > GTP, CTP, ITP > UTP > (ADP) > ATetraP for the former, ATP > (ADP) > ITP > GTP > CTP > UTP > ATetraP for the latter process. The "calcium pump" was weakly inhibited by caffeine, and was inhibited together with the ATPase by pyridoxalphosphate. Carnosine had no effect as such nor in the presence of pyridoxalphosphate except at high concentration; thiourea and p-chloromercuribenzoate were inhibiting while iodoacetate was inactive. Ca++ accumulation and ATPase were inhibited by atabrine (not tested on ATPase), dinitrophenol, and amytal. High concentrations of oligomycin and rutamycin inhibited Ca++ uptake while slightly stimulating ATPase. Antimycin A stimulated the Ca++ uptake. These results are discussed in the light of their possible relation to partial reactions in oxidative phosphorylation. The Ca++ uptake and relaxing factor activities did not behave identically throughout. This is in part ascribed to changes in reactivity of actomyosin in the relaxation test, in part to the participation of relaxing substances other than the calcium pump.
Effect of Ethanol on the Sodium and Potassium Conductances of the Squid Axon Membrane
Authors: Moore John W. , Ulbricht Werner , Takata Mitsuru
Published: May 2004

The effects of ethanol on squid giant axons were studied by means of the sucrose-gap technique. The membrane action potential height is moderately reduced and the duration sometimes shortened by ethanol in sea water. Voltage clamp experiments showed that ethanol in sea water reduced the maximum membrane conductances for sodium (g'Na) and potassium (g'K). In experiments with multiple application of ethyl alcohol to the same spot of membrane, a reduction of g'Na to 82 per cent and of g'K to 80 per cent of their value in sea water was brought about by 3 per cent ethanol (by volume) while 6 per cent caused a decrease of g'Na to 59 per cent and of g'K to 69 per cent. Ethanol has no significant effect on the steady-state inactivation of gNa (as a function of conditioning membrane potential) or on such kinetic parameters as τh or the time course of turning on gi gNa and gK. It is concluded that ethanol mainly reduces gNa and gK in the Hodgkin-Huxley terminology.
The Effect of Electrotonus on the Olfactory Epithelium
Authors: Higashino Shoji , Takagi Sadayuki F.
Published: May 2004

The effect of electrotonus on the slow potential of the olfactory epithelium of the frog was studied. The "on"-slow potential induced by a general odor like amyl acetate increased its magnitude in accordance with increase of anodal current, while it decreased its magnitude with increase of cathodal current. Similar relations were also found in the case of the vapors of organic solvents like ethyl ether of low concentrations. Conversely, the on-slow potential induced by the vapors of organic solvents of high concentration decreased its magnitude in accordance with the increase of anodal current, while it increased its magnitude with the increase of cathodal current. The "off"-slow potential induced by the vapors of organic solvents of high concentration showed a potential change under the action of electrotonic currents which is similar to the change of the on-slow potential induced by general odors. It was concluded that there are two receptive processes in the olfactory cell. One is an ordinary excitatory process which produces an electronegative slow potential in response to general odors. The other is a process of a different kind which is activated only by the vapor of an organic solvent of high concentration and which shows an entirely opposite reaction from that generally found in excitable tissues when an electrotonic current is applied.