bluuebunny/crossref_metadata_2025 huggingface dataset:
THE COMPOSITION OF THE CELL SAP OF THE PLANT IN RELATION TO THE ABSORPTION OF IONS
Authors: Hoagland D. R. , Davis A. R. ,   With the Assistance of J. C. Martin.
Published: May 2004

1. Chemical examination of the cell sap of Nitella showed that the concentrations of all the principal inorganic elements, K, SO4, Ca, Mg, PO4, Cl, and Na, were very much higher than in the water in which the plants were growing.

2. Conductivity measurements and other considerations lead to the conclusion that all or nearly all of the inorganic elements present in the cell sap exist in ionic state.

3. The insoluble or combined elements found in the cell wall or protoplasm included Ca, Mg, S, Si, Fe, and Al. No potassium was present in insoluble form. Calcium was predominant.

4. The hydrogen ion concentration of healthy cells was found to be approximately constant, at pH 5.2. This value was not changed even when the outside solution varied from pH 5.0 to 9.0.

5. The penetration of NO3 ion into the cell sap from dilute solutions was definitely influenced by the hydrogen ion concentration of the solution. Penetration was much more rapid from a slightly acid solution than from an alkaline one. It is possible that the NO3 forms a combination with some constituent of the cell wall or of the protoplasm.

6. The exosmosis of chlorine from Nitella cells was found to be a delicate test for injury or altered permeability.

7. Dilute solutions of ammonium salts caused the reaction of the cell sap to increase its pH value. This change was accompanied by injury and exosmosis of chlorine.

8. Apparently the penetration of ions into the cell may take place from a solution of low concentration into a solution of higher concentration.

9. Various comparisons with higher plants are drawn, with reference to buffer systems, solubility of potassium, removal of nitrate from solution, etc.
THE EFFECT OF RADIO-ACTIVE RADIATIONS AND X-RAYS ON ENZYMES
Authors: Hussey Raymond G. , Thompson William R.
Published: May 2004

A quantitative study has been made of the radiochemical decomposition of trypsin by the radiations from radium emanation.

The following equation accounts quantitatively for the experimental results presented.

See PDF for Equation

It follows from this that the amount of trypsin decomposed by the radiations from radium emanation depends on the concentration of trypsin present and is proportional to the quantity of emanation expressed in millicuries and to the time of irradiation expressed in hours. It would seem that it is the active or undissociated trypsin that is affected.

Evidence has been found which suggests that the beta radiations produce the decomposition observed for which the above statement holds.

Qualitative evidence has been found which suggests that x-rays, gamma rays, and beta rays produce identical effects in dilute trypsin solutions.
VALENCY RULE AND ALLEGED HOFMEISTER SERIES IN THE COLLOIDAL BEHAVIOR OF PROTEINS
Authors: Loeb Jacques , Kunitz M.
Published: May 2004

It is shown by the older experiments by Loeb and by the experiments reported in this paper that the effect of salts on the membrane potentials, osmotic pressure, swelling of gelatin chloride, and that type of viscosity which is due to the swelling of protein particles, depends only on the valency but not on the chemical nature of the anion of the salt, and that the cation of the salt has no effect on these properties, if the pH of the protein solution or protein gel is not altered by the salt. The so called Hofmeister series of salt effects on these four properties are purely fictitious and due to the failure of the former authors to measure the hydrogen ion concentration of their protein solutions or gels and to compare the effects of salts at the same pH of the protein solution or the protein gel. These results confirm the older experiments of Loeb and together they furnish a further proof for the correctness of the idea that the influence of electrolytes on the four properties of proteins is determined by membrane equilibria. Such properties of proteins which do not depend on membrane equilibria, such as solubility or cohesion, may be affected not only by the valency but also by the chemical nature of the ions of a salt.
THE INACTIVATION OF TRYPSIN
Authors: Northrop John H.
Published: May 2004

1. Charcoal removes trypsin from solution. The amount removed depends on the order in which the solutions are mixed. The reaction is not reversible and is almost independent of the pH of the solution.

2. Charcoal which has been previously treated with gelatin does not remove trypsin from solution.

3. The reaction is not analogous either to the reaction between trypsin and the inhibiting substance of serum or to the reaction between solid protein and either pepsin or trypsin.
STUDIES IN PROTOPLASM POISONING
Authors: Shackell L. F.
Published: May 2004

1. After equilibrium of distribution of a phenol between water and an animal immersed in it has been once attained, the poisoning of the animal proceeds with constant velocity. The criterion of toxicity adopted in the first part of this study was the time required for initial recovery from paralysis after a given time in the phenol solution. In later work observations were made of the percentages of animals which died after stated periods in a phenol solution.

2. The numerical value of the velocity constant of poisoning for a given solution is independent of the criterion of toxicity adopted, provided that the criterion serves to measure the intensity of effect of the poison, and not merely the rate at which the poison is absorbed.

3. Recovery from paralysis produced by phenol and death from this poison has the same velocity constant. From this it may be inferred that recovery is due to a reversal of the mechanism which underlies poisoning.

4. The velocity of poisoning by phenols is nearly proportional to the square of the concentration.

5. A strictly chemical (mass law) interpretation is shown to be inadequate for the description of poisoning by phenols.

6. Certain physical factors, involved in poisoning by phenols, are discussed.

7. A precise method for obtaining the velocity constant of poisoning by a given agent is outlined.
THEORY OF REGENERATION BASED ON MASS ACTION
Authors: Loeb Jacques
Published: May 2004

1. The writer's older experiment, proving that equal masses of isolated sister leaves of Bryophyllum regenerate under equal conditions and in equal time equal masses (in dry weight) of shoots and roots, is confirmed. It is shown that in the dark this regeneration is reduced to a small fraction of that observed in light.

2. The writer's former observation is confirmed, that when a piece of stem inhibits or diminishes the regeneration in a leaf, the dry weight of the stem increases by as much or more than the weight by which the regeneration in the leaf is diminished. It is shown that this is also true when the axillary bud in the stem is removed or when the regeneration occurs in the dark.

3. These facts show that the regeneration of an isolated leaf of Bryophyllum is determined by the mass of material available or formed in the leaf during the experiment and that such a growth does not occur in a leaf connected with a normal plant for the reason that in the latter case the material available or formed in the leaf flows into the stem where it is consumed for normal growth.

4. It is shown that the sap sent out by a leaf in the descending current of a stem is capable of increasing also the rate of growth of shoots in the basal parts of the leaf when the sap has an opportunity to reach the anlagen for such shoots.

5. The fact that a defoliated piece of stem forms normally no shoots in its basal part therefore demands an explanation of the polar character of regeneration which lays no or less emphasis on the chemical difference between ascending and descending sap than does Sachs' theory of specific root- or shoot-forming substances (though such substances may in reality exist), but which uses as a basis the general mass relation as expressed in the first three statements of this summary.

6. It is suggested that the polar character of the regeneration in a stem of Bryophyllum is primarily due to the fact that the descending sap reaches normally only the root-forming tissues at the base of the stem, while the ascending sap reaches normally only the shoot-forming anlagen at the apex of the stem.

7. This suggestion is supported by the fact that when the anlagen for shoots and roots are close together as they are in the notch of a leaf, the sap of the leaf causes the growth of both roots and shoots from the same notch and the influence of the sap of the leaf on this growth increases for both roots and shoots in proportion with the mass of the leaf.
THEORY OF GEOTROPISM BASED ON MASS ACTION
Authors: Loeb Jacques
Published: May 2004

1. It is shown that the rate of geotropic curvature of a piece of stem of Bryophyllum calycinum when suspended horizontally increases with the mass of an apical leaf attached to the stem.

2. It is shown that the dry weight of the stem increases with the mass of the leaf attached and also that the degree of curvature increases with this increase in the dry weight of the stem.

3. The conclusion is drawn that geotropic curvature is in this case a function of mass action of the material sent by the leaf into the basal part of the stem.

4. The material sent by a leaf into the apical part of a stem does not lead to the same geotropic curvature.
The Action of Pitressin on Solute Permeability of the Rabbit Nephron in Vivo
Authors: Foulkes E. C.
Published: May 2004

The isotopic equilibration of urea, thiourea, and inulin between urine and plasma was determined in rabbits in the presence or absence of antidiuretic hormone (ADH). Animals were anesthetized with ethanol and permitted to reach steady state after completion of surgery. Tracer was then administered by intraarterial infusion in such a manner that a high constant specific activity in plasma was rapidly attained. Urine flow was kept independent of ADH by addition of mannitol. Urea/creatinine clearance ratios and the accumulation of urea in renal medulla and papilla also remained unaffected by ADH. Under these conditions, thiourea and inulin at all times approached equilibrium, at similar rates. In the absence of ADH, urea also equilibrated at a rate similar to that of inulin. The addition of ADH, however, significantly prolonged the delay before urinary urea reached the high constant specific activity of plasma urea. These observations are interpreted in terms of a specific effect of the hormone on the solute permeability of the nephron.
Some Relations between Changes in the Linear Electrical Properties of Striated Muscle Fibers and Changes in Ultrastructure
Authors: Freygang W. H. , Rapoport S. I. , Peachey L. D.
Published: May 2004

Some of the linear electrical properties of frog sartorius muscle have been investigated in Ringer's fluid and in a Ringer fluid made hypertonic by the addition of sucrose or NaCl. Electrical constants were determined from measurements of the phase angle of the admittance of a fiber for an applied alternating current, from measurements of the voltage induced by an inward pulse of current, and from measurements of the conduction velocity of the action potential and the time constant of its foot. The dilation of the transverse tubular system induced by the sucrose hypertonic Ringer fluid was correlated with the change in the electrical constants. From this it is concluded that a two time constant equivalent circuit for the membrane, as proposed by Falk and Fatt, is in good agreement with our results. Both the area of the membrane of the transverse tubular system, and the capacity (ce) attributed to it, increased in the sucrose hypertonic Ringer fluid. The resistance re, which is in series with ce, did not fall when the transverse tubular system was dilated and probably is not located in that system.
Oxygen Consumption Rate of Tissue Measured by a Micropolarographic Method
Authors: Takahashi G. H. , Fatt I. , Goldstick T. K.
Published: May 2004

A new method for measuring the oxygen consumption rate of a sheet of homogeneous tissue is described. The method measures, by a Clark-type oxygen electrode without a membrane, the time for the tissue to consume all its dissolved oxygen. The electrode is applied to one surface of the tissue sheet and the other surface is sealed from the atmosphere by a cover slip. The consumption is calculated from an estimate of the oxygen dissolved in the tissue at the moment it is covered and the time for the oxygen tension at one surface to fall to zero. The data also yield the oxygen diffusion coefficient in the oxygen-consuming tissue.
Stimulation of the Salt Receptor of the Blowfly
Authors: Gillary Howard L.
Published: May 2004

Application of solutions of each of the alkali halides to the tip of a labellar sensillum of the blowfly elicited a repetitive neural discharge from the salt receptor. The records were qualitatively similar to those for NaCl. For each of the alkali chlorides and sodium halides, the shapes of the curves of the response of the salt receptor as a function of concentration were similar to that for NaCl. The alkali halides exhibited a regular pattern of relative stimulating effectiveness for the salt receptor. The effectiveness of the anions increased monotonically with atomic number. The effectiveness of the cations was greatest for potassium and declined as the atomic number was increased or decreased. This hierarchy for stimulating effectiveness was maintained at all tested molarities. The response to a mixture of two salts appeared to be an average of those to the single salts at concentrations equal to the total concentration of the mixture. Cross-adaptation was observed between the alkali halides. The results indicate that an explanation of stimulation of the salt receptor must apply to all the salts tested and that both the anion and the cation affect a salt's stimulating effectiveness.
Ionic Conductance Changes in Lobster Axon Membrane When Lanthanum Is Substituted for Calcium
Authors: Takata M. , Pickard W. F. , Lettvin J. Y. , Moore J. W.
Published: May 2004

The trivalent rare earth lanthanum was substituted for calcium in the sea water bathing the exterior of an "artificial node" of a lobster axon in a sucrose gap. It caused a progressive rise in threshold, and a decrease in the height of the action potential as well as in its rates of rise and fall. Prolonged application produced an excitation block. Voltage-clamp studies of the ionic currents showed that the time courses of the ionic conductance changes for both sodium and potassium were increased. Concurrently, the potentials at which the conductance increases occurred were shifted to more positive inside values for the La+++ sea water. These effects resemble changes resulting from a high external calcium concentration. Over and above this, La+++ also causes a marked reduction in the maximum amount of conductance increase following a depolarizing potential step. Membrane action potentials similar to those observed experimentally in the La+++ solution have been computed with appropriate parameter changes in the Hodgkin-Huxley equations.
Extracellular Action Potentials Recorded from the Interior of the Giant Esophageal Cell of Ascaris
Authors: del Castillo J. , Morales T.
Published: May 2004

Exploration of the cytoplasm of the giant esophageal cell of Ascaris with a recording microelectrode shows the existence of shallow spaces where the microelectrode tip becomes extracellular in spite of being in the interior of the cell. When the microelectrode penetrates into these spaces from the cytoplasm, the resting potential shifts to a different level or entirely disappears. At the same time the large intracellular spikes are replaced by small transients similar to extracellularly recorded action potentials. It is concluded that such spaces are in communication with the external solution, and separated from the cytoplasm by an electrically active membrane; i.e., able to generate action potentials. Measurement of the potential differences between the interior of the spaces and the external solution shows that although some are not polarized, many spaces have a resting potential of the same polarity as that of the cytoplasm. It is suggested that although they are of larger size these spaces may be equivalent to the tubular systems which in other muscle cells are known to be involved in the spread of excitation into the cytoplasm.
The Formation and Continuous Turnover of a Fraction of Phosphatidic Acid on Stimulation of NaCl Secretion by Acetylcholine in the Salt Gland
Authors: Hokin Mabel R. , Hokin Lowell E.
Published: May 2004

Acetylcholine, which stimulates NaCl secretion in the avian salt gland, causes the rapid formation of a fraction of phosphatidic acid, as measured by 32P incorporation, which amounts maximally to about 0.18 µmoles per g of fresh tissue. This does not appear to involve synthesis of the diglyceride moiety of phosphatidic acid, as measured by glycerol-1-14C incorporation. It presumably involves formation of phosphatidic acid by the diglyceride kinase pathway from preformed diglyceride and ATP. The specific activity of the AT32P of the tissue is not increased in the presence of acetylcholine. At time intervals after addition of acetylcholine during which a full response, measured as increased O2 uptake, may be observed, phosphatidic acid appears to be the only phosphatide which shows any increase either in total 32P radioactivity or in net specific acitvity. This responsive fraction of phosphatidic acid undergoes continuous turnover of its phosphate moiety. There is no evidence that this turnover is due to the phosphatidic acid acting as a pool of intermediate for the synthesis of other phospholipids or glycerides. The responsive fraction amounts to not more than 20% of the total phosphatidic acid of the tissue; it does not mix with the other (non-responsive) phosphatidic acid of the tissue. The observations suggest that this phosphatidic acid plays some role in the over-all secretory process.
Two Different Ionic Mechanisms Generating the Spike "Positive" Afterpotential in Molluscan Neurons
Authors: Chiarandini Dante J. , Stefani Enrique
Published: May 2004

The ionic bases of the "positive" afterpotential (ap) have been examined in the so-called DInhi neurons of the central nervous system of Cryptomphallus aspersa. In these cells EK has been determined and its value compared with the equilibrium, potential of the ap (Eap). It has been found that in half of the studied cells the EK value is very close to Eap whereas in another half, the difference (EK - Eap) is large and amounts to circa -10 mv. The effects of changes in the concentration gradients of K+, Cl-, and Na+ were assayed in both groups of cells. When the [Ki/[K]o ratio is reduced in both groups of neurons, the ap amplitude and the Eap diminished. In cells displaying a large (EK - Eap), Cl-free Ringer's solution diminished the ap amplitude and Eap, but produced no effect in the neurons with a reduced (EK - Eap). A similar effect was observed if [Cl], was increased by intracellular injection of NaCl. Changes in both [Na]o and [Na]i were ineffective. It is concluded that K+ is the only ion involved in the origin of the ap in the groups of cells with a low value for (EK - Eap). On the contrary, the ap of the neurons presenting large (EK - Eap) is produced by a simultaneous increase in the fluxes of both K+ and Cl-.
Resolution of Pump and Leak Components of Sodium and Potassium Ion Transport in Human Erythrocytes
Authors: Post R. L. , Albright C. D. , Dayani K.
Published: May 2004

Further support for the pump-leak concept was obtained. Net transport was resolved into pump and leak components with the cardiac glycoside, ouabain. The specificity of ouabain as a pump inhibitor was demonstrated by its ineffectiveness when the pump was already inhibited by lack of one of the three pump substrates, sodium ion, potassium ion, or adenosine triphosphate. In the presence of ouabain the rates of passive transport of sodium and potassium ions changed almost in proportion to changes in their extracellular concentrations when one ion was exchanged for the other. In the presence of ouabain and at the extracellular concentrations which produced zero net transport, the ratio of potassium ions to sodium ions was 1.2-fold higher inside the cells than outside. This finding was attributed to a residual pump activity of less than 2% of capacity. The permeability to potassium ions was 10% greater than the permeability to sodium ions. A test was made of the independence of pump and leak. Conditions were chosen to change the rate through each pathway separately or in combination. When both pathways were active, net transport was the sum of the rates observed when each acted separately. A ratio of three sodium ions pumped outward per two potassium ions pumped inward was confirmed.
NMR Evidence for Complexing of Na+ in Muscle, Kidney, and Brain, and by Actomyosin. The Relation of Cellular Complexing of Na+ to Water Structure and to Transport Kinetics
Authors: Cope Freeman W.
Published: May 2004

The nuclear magnetic resonance (NMR) spectrum of Na+ is suitable for qualitative and quantitative analysis of Na+ in tissues. The width of the NMR spectrum is dependent upon the environment surrounding the individual Na+ ion. NMR spectra of fresh muscle compared with spectra of the same samples after ashing show that approximately 70% of total muscle Na+ gives no detectable NMR spectrum. This is probably due to complexation of Na+ with macromolecules, which causes the NMR spectrum to be broadened beyond detection. A similar effect has been observed when Na+ interacts with ion exchange resin. NMR also indicates that about 60% of Na+ of kidney and brain is complexed. Destruction of cell structure of muscle by homogenization little alters the per cent complexing of Na+. NMR studies show that Na+ is complexed by actomyosin, which may be the molecular site of complexation of some Na+ in muscle. The same studies indicate that the solubility of Na+ in the interstitial water of actomyosin gel is markedly reduced compared with its solubility in liquid water, which suggests that the water in the gel is organized into an icelike state by the nearby actomyosin molecules. If a major fraction of intracellular Na+ exists in a complexed state, then major revisions in most theoretical treatments of equilibria, diffusion, and transport of cellular Na+ become appropriate.
Osmotic Properties of Mitochondria
Authors: Bentzel Carl J. , Solomon A. K.
Published: May 2004

The osmotic behavior of rat liver mitochondria has been studied in a sucrose medium. The mitochondria behave like a two compartment system. One compartment is permeable to sucrose and has a volume of 1.22 µl/(mg mitochondrial dry weight) in a 272 milliosmol sucrose medium; the second, inaccessible to sucrose, has a volume of 0.555 µl/mg dry weight) under the same conditions. Part of the water in the sucrose inaccessible space is apparently not free to participate in osmotic phenomena. This volume is 0.272 µl/(mg dry weight) under the same conditions. It is suggested that the osmotically inactive water corresponds to the water of hydration of the mitochondrial macromolecules. The volume of the remainder of the water in the sucrose inaccessible space depends inversely on the osmolality of the medium, as is to be expected. The volume of water in the sucrose accessible space is constant, independent of the osmolality of the medium, as is the volume of the mitochondrial framework plus the nonvolatile solutes.
The Spectral Distribution of Firefly Light. II
Authors: Biggley W. H. , Lloyd J. E. , Seliger H. H.
Published: May 2004

The in vivo peak emission wavelengths of bioluminescence are reported for 15 species of American fireflies. A spectrophotometric study of the dorsal light organs of 155 specimens of the Jamaican firefly Pyrophorus plagiophthalamus showed three distinct color distributions with peak emission wavelengths at 550.1 ± 1.5 mµ, 556.8 ± 1.4 mµ, and 562.4 ± 1.0 mµ. Similar spectral measurements of 35 ventral light organs of the same insects gave peak emission wavelengths ranging from 547 through 594 mµ. This is a wider distribution than the total range of all 34 species of firefly studied to date. There was no obvious correlation between the colors of the ventral and dorsal light organs. It appears that P. plagiophthalamus is a special case in which the luciferase enzyme is not only different among members of the same species, but it may be different for the dorsal and ventral light organs in a single individual. A minimum of six different luciferase molecules for P. plagiophthalamus ventral light organs is proposed. The statistical precision in making these spectrophotometric measurements is discussed.
Nickel Substitution for Calcium in Excitation-Contraction Coupling of Skeletal Muscle
Authors: Fischman Donald A. , Swan Roy C.
Published: May 2004

In 1962 Frank (22) reported that the addition of any one of a number of divalent cations, including Ni, to a Ca-free Ringer solution prevented the rapid loss of contractility seen in the absence of external Ca. To investigate further the Ni-Ca substitution, studies were made of 45Ca and 63Ni exchange during contraction and at rest using frog striated muscle. In contrast to 45Ca, it was found that there is no increase of 63Ni uptake associated with a K contracture of the sartorius muscle. The rates of loss of 63Ni and 45Ca from resting toe muscles previously bathed in the respective radioisotopes are not significantly different. Resting and action potentials, after 1 hr in a Ringer solution with Ni replacing Ca, closely resemble these potentials in normal Ca-Ringer's solution. Studies on the syneresis of isolated myofibrils indicate that Ni cannot replace Ca in activating this reaction. It is suggested that Ca is required for at least two steps in E-C coupling: one is the spread of excitation at the sarcolemma and transverse tubular system; the second is the activation of actomyosin ATPase. Conceivably Ni can substitute for Ca in the former but not in the latter.
Evidence for Carrier-Mediated Transport of Monosaccharides in the Ehrlich Ascites Tumor Cell
Authors: Kolber Alan R. , LeFevre Paul G.
Published: May 2004

Evidence for carrier-mediated transport of monosaccharides in the Ehrlich ascites tumor cells was provided through kinetic analysis of data obtained by: (a) studying sugar uptake by dilute cell suspensions with an optical densimetric apparatus, (b) studying sugar uptake by thicker cell suspensions by means of direct chemical analytical methods using packed cell plugs, (c) observing the effects of a competitive inhibitor upon sugar uptake with the chemical analytical method, and (d) measurement of tracer uptake of a high affinity sugar in thick cell suspensions in the absence of net movement. Quantitative application of the data obtained with the above experimental procedures to theoretical model systems derived for both carrier-mediated transport and simple passive diffusion indicated that the results were consonant with predictions for the carrier-mediated transport model, but could not be explained on the basis of uncomplicated diffusion.
Relative Ion Permeabilities in the Crayfish Giant Axon Determined from Rapid External Ion Changes
Authors: Strickholm Alfred , Wallin B. Gunnar
Published: May 2004

The changes in membrane potential of isolated, single crayfish giant axons following rapid shifts in external ion concentrations have been studied. At normal resting potential the immediate change in membrane potential after a variation in external potassium concentration is quite marked compared to the effect of an equivalent chloride change. If the membrane is depolarized by a maintained potassium elevation, the immediate potential change due to a chloride variation becomes comparable to that of an equivalent potassium change. There is no appreciable effect on membrane potential when external sodium is varied, at normal or at a depolarized membrane potential. Starting from the constant field equation, expressions for the permeability ratios PCl/PK, PNa/PK, and for intracellular potassium and chloride concentrations are derived. At normal resting membrane potential, PCl/PK is 0.13 but at a membrane potential of -53 mv (external potassium level increased about five times) it is 0.85. The intracellular concentrations of potassium and chloride are estimated to be 233 and 34 mM, respectively, and it is pointed out that this is not compatible with ions distributed in a Nernst equilibrium across the membrane. It is also stressed that the information given by a plot of membrane potential vs. the logarithm of external potassium concentrations is very limited and rests upon several important assumptions.
The Mode of Transverse Spread of Contraction Initiated by Local Activation in Single Frog Muscle Fibers
Authors: Sugi Haruo , Ochi Rikuo
Published: May 2004

Isolated single frog muscle fibers were locally activated by applying negative current pulses to a pipette whose tip was in contact with the fiber surface. In contrast to the graded inward spread of contraction initiated by a moderate depolarization, the contraction in response to a strong negative current was observed to spread transversely around the whole perimeter but not through the center of the fiber. This response was elicited only with pipettes of more than 6 µ diameter. The response was still present if the sodium of the Ringer solution was replaced by choline, or the chloride was replaced by nitrate or propionate. The duration of the response appeared to be independent of the duration of stimulating current in fresh fibers, while the contraction lasted as long as the current went on in deteriorated fibers. The contraction was first initiated at the area of fiber surface covered by the pipette, and spread around the perimeter of the fiber with a velocity of 0.8–6 cm/sec. Possible mechanisms of the response are discussed in connection with the properties of the transverse tubular system, the possibility of some self-propagating process along the walls of the tubules being suggested.
Effects of External Calcium Deprivation on Single Muscle Fibers
Authors: Caputo Carlo , Gimenez Maximo
Published: May 2004

Deprivation of external calcium causes sudden potentiation of the twitch response of single muscle fibers. The potentiation was 64 ± 8%. Potentiation is simultaneous with membrane depolarization occurring after Ca++ removal. This depolarization amounted to 9 ± 2 mv. Ca++ removal also alters the action potential. 3 min after calcium withdrawal, action potential amplitude fell by 36 ± 3 mv; maximum rates of rise and fall of the spike decreased by 55 ± 5 and 63 ± 5% respectively. Changes in shape of the A. P. differ from those seen with other potentiators of the twitch response, such as Zn++. After short exposure to calcium-free media, potassium-induced contractures show potentiation of peak tension. The S-shaped curve relating potassium contracture tension to log [K]o shifts to the left after such treatment. Calcium deprivation also increased the rate of relaxation of the contractures. This effect depends on the duration of calcium deprivation, and is probably related to the effect of calcium lack on the membrane. The change in relaxation occurred immediately after calcium deprivation, and was reversed by sudden readmission of calcium. Relaxation of twitch and tetanus responses also were affected by Ca lack, but not as rapidly as potassium contractures. The results suggest that external calcium is not directly involved in the process responsible for tension development, supporting the view that this process is mediated by translocation of intracellular calcium. The relaxation process, however, appears to be rapidly affected by deprivation of external calcium.
The Discrimination between Magnesium and Manganese by Serum Proteins
Authors: Foradori A. C. , Bertinchamps Albert , Gulibon Jane M. , Cotzias George C.
Published: May 2004

Magnesium and manganese have proved physically and functionally interchangeable in many isolated biological systems investigated in vitro. This lack of discrimination contrasts sharply with the high biological specificity exhibited by intact mammals under a large variety of conditions. The dichotomy between intact animals and their isolated systems might be due at least partially to presence vs. absence of an intact circulation. Hence the capability of mammalian plasma to discriminate between the alkaline earth and the transition metal was investigated by means of equilibrium dialysis, exchange, ultrafiltration, ultracentrifugation, and zone electrophoresis. The states of the respective elements are thus contrasted as follows: (a) Magnesium is partially bound, manganese totally. (b) Magnesium is nonselectively bound by serum proteins, manganese selectively by a ß1-globulin. (c) Under conditions approaching physiological, the two metals do not interchange. This is interpreted as indicating that the plasma proteins contribute to biological specificity by discriminating between a trace metal and a macronutrient.
The Characterization of Scintillons
Authors: DeSa Richard , Hastings J. Woodland
Published: May 2004

A new type of biological particle, isolated from the marine dinoflagellate Gonyaulax polyedra, has been partially purified and characterized. When the pH is lowered, the particle emits light in vitro in a fashion closely mimicking the flash of the living cell, and it is referred to as a scintillon (flashing unit). Scintillons are obtained by breaking the cells in buffer at pH 8.2 and purifying by differential and sucrose density gradient centrifugation. The particle has a density of about 1.23 g cc-1, and activity is quantitatively correlated with the number of crystal-like birhombohedral structures. These have been found to contain guanine, but since the density of authentic guanine is about 1.73 g cc-1, the scintillon is believed to comprise additional but as yet unidentified components. The properties of the scintillon and the effects of various physical and chemical treatments are described. The reasons for believing that this particle is responsible for the flash of the intact cell are discussed.
Kinetic Analysis of the Permeability of Human Erythrocytes to NH4Cl
Authors: Hunter F. R.
Published: May 2004

A densimeter technique was used to make a kinetic analysis of the rate of swelling of human erythrocytes suspended in 1% NaCl following successive additions of NH4Cl. Two series of experiments were performed, one in the absence of and the other in the presence of 6 x 10-4 M NaHCO3. An analysis of the data using Widdas's equations gave a family of curves in each instance. When LeFevre's equation was used with a value of ø = 1.3 isotones, a straight line was obtained with both series of data. It is concluded that this system shows carrier kinetics.
Analysis of Glycerol-3H Transport in the Frog Oocyte by Extractive and Radioautographic Techniques
Authors: Horowitz Samuel B. , Fenichel I. Robert
Published: May 2004

The efflux of glycerol-3H from mature R. pipiens oocytes was studied by extractive analysis and by quantitative radioautography using techniques suitable for diffusible solutes. Extractive analysis was used to determine the total cellular concentration of tracer, and radioautography, regional intracellular concentrations, at equilibrium and as a function of efflux time, tE. The efflux was resolvable into four kinetic fractions: cytoplasmic fast and slow fractions, and nuclear fast and slow fractions. The fast fractions represent freely diffusible glycerol in the two compartments; the solvent space accessible to glycerol is unity in the nucleus (germinal vesicle), but only 0.73 in the cytoplasm. The efflux of both fast fractions from the cell is determined by the permeability of the cortical membrane, with neither the nuclear membrane nor diffusion in the cytoplasm detectably slowing the flux. The permeability at 13.6°C is 2.2 x 10-5 cm/sec. The slow fractions leave the cell at about one-tenth the rate of the fast; the interpretation is that these fractions represent glycerol bound to impermeant cellular constituents. The size of these constituents is below the radioautographic resolution; in the cytoplasm, they appear not to be the yolk platelets. The extent of binding is about fourfold greater, per milliliter of compartment water, in the cytoplasm than in the germinal vesicle.
Dynamic Processes in Soap Films
Authors: Mysels Karol J.
Published: May 2004

Some relations between the two main types of thin liquid films, the water-in-air "soap" films and the invert oil-in-water "lipid" films, are outlined, and several dynamic aspects of film behavior are illustrated and briefly reviewed with reference to more complete treatments. These dynamic processes are important in both types of films, but are easier to study in soap films. The topics include the difference between rigid and mobile films and their interconversion; the origin and measurement of film elasticity; the effect of rate of formation upon film thickness, and the evidence against the existence of thick rigid water layers at the surface; and the kinetics of drainage and the role played in it by viscous flow, marginal regeneration, and intermolecular forces.
Black Lipid Membranes at Bifaces
Authors: Ti Tien H.
Published: May 2004

Black lipid membranes (BLM) less than 90 A thick have been shown to be the most realistic approach to biological membrane models. This paper describes the formation characteristics, optical properties, and thermodynamics of BLM at water/oil/water bifaces. In particular, the nature of the Plateau-Gibbs border which supports the black membrane is analyzed in some detail. The formation of BLM at the biface involves a spontaneous reduction of the free energy of the system. As long as the integrity of the membrane is maintained, the limiting structure of the BLM represents the lowest free energy configuration.
Monolayer and Interfacial Permeation
Authors: Blank Martin
Published: May 2004

Transport across physical-chemical interfaces is considered in connection with three particular problems of biological interfaces: the structure and properties of cell membranes, the properties of the lung surfactant, and the effects of ionic currents across excitable membranes. With regard to cell membranes, studies of monolayer permeation suggest that permselectivity on the basis of size is a property of bilayer structure and probably gives rise to the observed dependence of the permeability on partition coefficients. The permeabilities of lipid and protein monolayers are consistent with the bimolecular leaflet (BML) model of the membrane and not with mosaic models. Experiments with the lung surfactant indicate that, in addition to its surface tension-lowering properties, it is unusual in its ability to form a strong two-dimensional network, which probably contributes to alveolar stability. Finally, the results of studies of interfacial ionic transference suggest a new way of accounting for the ionic fluxes in excitable membranes during an action potential without assuming ion-selective pores or carriers. In the suggested mechanism, it is possible to account for the change in ionic selectivity and the proper phasing of the fluxes, as well as other aspects of excitation in natural membranes.
Photosynthetic Units
Authors: Schmid Georg H. , Gaffron Hans
Published: May 2004

Leaf tissues of aurea mutants of tobacco and Lespedeza have been shown to have higher photosynthetic capacity per molecule of chlorophyll, a higher saturation intensity, a simpler lamellar structure, and the same quantum yield as their dark green parents. Here we report on the values of photosynthetic units for both types of plants and some algae. The unit has been assumed to be about as uniform and steady in the plant world as the quantum efficiency. The number on which all theoretical discussions have been based so far is 2400 per O2 evolved or CO2 reduced. With dark green plants and algae our determinations of units by means of 40 µsec flashes superimposed on a steady rate of background photosynthesis at 900 ergs cm-2 sec-1 of red light yielded mostly numbers between 2000 and 2700. However, the photosynthetic unit turned out to be very variable, even in these objects. In aurea mutants the unit was distinctly smaller, averaging 600 chl/CO2. By choosing the right combination of colors for flash and background light, units as low as 300 chl/CO2 or 40 chl/e- could be measured consistently. We found five well-defined groups of units composed of multiples of its smallest member. These new findings are discussed in terms of structural entities that double or divide under the influence of far-red light.
The Electrical Activity of Embryonic Chick Heart Cells Isolated in Tissue Culture Singly or in Interconnected Cell Sheets
Authors: DeHaan Robert L. , Gottlieb Sheldon H.
Published: May 2004

Embryonic chick heart cells were cultured on a plastic surface in sparse sheets of 2–50 cells mutually in contact, or isolated as single cells. Conditions are described which permitted conjoint cells to be impaled with recording microelectrodes with 75 % success, and isolated single cells with 8 % success. It is proposed that cells in electrical contact with neighbors are protected from irreversible damage by the penetrating electrode, by a flow of ions or other substances from connected cells across low-impedance intercellular junctions. Action potentials recorded from conjoint and isolated single cells were similar in form and amplitude. The height or shape of the action potential thus appears not to depend upon spatial relationships of one cell to another. As the external potassium concentration was increased from 1.3 mM to 6 mM, cells became hyperpolarized while the afterhyperpolarization was reduced. At higher potassium levels, the afterhyperpolarization disappeared, the slope of the slow diastolic depolarization decreased, and resting potential fell along a linear curve with a slope of 61 mv per 10-fold increase in potassium. In pacemaker cells the diastolic depolarization consists of two phases: (a) recovery from the afterpotential of the previous action potential and (b) the pacemaker potential. These phases are separated by a point of inflection, and represent manifestations of different mechanisms. Evidence is presented that it is the point of inflection (PBA) rather than the point of maximal diastolic potential, that should be taken as the resting potential.
Anesthetic Gases and Water Structure
Authors: Berger Eugene Y. , Pecikyan F. Rene , Kanzaki Grace
Published: May 2004

Pauling and Miller have independently proposed that the presence of an anesthetic gas in tissue induces a cage-like arrangement of hydrogen-bonded water molecules. The theories recognize that most gas-hydrate crystals would not form at the temperature and pressure that exist during anesthesia and propose that other components of tissue such as protein should have a stabilizing effect. Measurements of the behavior of water, rather than the anesthetic agent, would provide alternative information about the likelihood of hydrate crystal formation and this information could be such as to be applicable to body temperature and to pressures used for anesthesia. If the number of hydrogen-bonded water molecules in tissue is increased, then the movement of an average water molecule should be hindered. Movement of water through the tissue may be measured by tagging it with tritium and the anesthetic gas should then slow the movement of tritiated water through the tissue. The flux of tritiated water through rat cecum is indeed slowed when the cecum is exposed to the anesthetic gas, xenon, which can participate biochemically only by virtue of its van der Waals interaction. The decrement in water flux is in reasonable agreement with what could be expected theoretically from calculations based on the activation energy for the self-diffusion of water and the degree of hypothermia necessary to produce narcosis.
Further Studies on the Roles of Sodium and Potassium in the Generation of the Electro-Olfactogram
Authors: Takagi S. F. , Kitamura H. , Imai K. , Takeuchi H.
Published: May 2004

In the negative EOG-generating process a cation which can substitute for Na+ was sought among the monovalent ions, Li+, Rb+, Cs+, NH4+, and TEA+, the divalent ions, Mg++, Ca++, Sr++, Ba++, Zn++, Cd++, Mn++, Co++, and Ni++, and the trivalent ions, Al+++ and Fe+++. In Ringer solutions in which Na+ was replaced by one of these cations the negative EOG's decreased in amplitude and could not maintain the original amplitudes. In K+-Ringer solution in which Na+ was replaced by K+, the negative EOG's reversed their polarity. Recovery of these reversed potentials was examined in modified Ringer solutions in which Na+ was replaced by one of the above cations. Complete recovery was found only in the normal Ringer solution. Thus, it was clarified that Na+ plays an irreplaceable role in the generation of the negative EOG's. The sieve hypothesis which was valid for the positive EOG-generating membrane or IPSP was not found applicable in any form to the negative EOG-generating membrane. The reversal of the negative EOG's found in K+- , Rb+- , and Ba++-Ringer solutions was attributed to the exit of the internal K+. It is, however, not known whether or not Cl- permeability increases in these Na+-free solutions and contributes to the generation of the reversed EOG's.
Electrophysiological Organization of the Eye of Aplysia
Authors: Jacklet Jon W.
Published: May 2004

The eye of Aplysia californica was studied by electrophysiological and histological methods. It has a central spheroidal lens which is surrounded by a retina composed of several thousand receptor cells which are replete with clear vesicles, pigmented support cells, neurons which contain secretory granules, and glial cells. The thin optic nerve that connects the eye to the cerebral ganglion gives a simple "on" response of synchronized action potentials. Tonic activity occurs in the optic nerve in the dark and is dependent on previous dark adaptation. Micropipette recordings indicate that the ERG is positive (relative to a bathelectrode) on the outer surface of the eye and negative in the region of the distal segments of the receptors. Intracellular recordings show that receptor cells have resting potentials of 40–50 mv and respond to illumination with graded potentials of up to 55 mv. Dark-adapted receptors exhibit discrete bumps on the graded response to brief light flashes. Other elements in the retina that do not give large graded responses fall into two classes. One class responds to illumination with action potentials that are in synchrony with the extracellularly recorded compound optic nerve potentials. The other class is tonically active and is depolarized or hyperpolarized and inhibited upon illumination. It is apparent that complex excitatory and lateral inhibitory interactions occur among the elements of the retina.
Kinetic Analyses of Calcium Movements in HeLa Cell Cultures
Authors: Borle André B.
Published: May 2004

Calcium influx was studied in monolayers of HeLa cells to determine the number of exchangeable and nonexchangeable pools and the rate constant of the different fluxes. Of the two exchangeable pools, one has a very fast rate of exchange with a half-time of 1.54 min, a compartment size of 1.06 mµmoles/mg cell protein, and an exchange rate of 474 µµmoles/(mg protein\·min). This compartment is likely to be extracellular and could represent calcium exchange between the extracellular fluids and surface binding sites of the cell membrane. The second exchangeable pool has a half-time of exchange of 31 min, a compartment size of 2.69 mµmoles/mg cell protein (0.224 millimole calcium/kg cell water), and a flux rate of 0.0546 µµmole cm-2 sec-1. This compartment can be considered to be the intracellular pool of exchangeable calcium. An unexchangeable intracellular pool of calcium of 3.05 mµmoles/mg cell protein was detected implying that only 45% of the intracellular calcium is exchangeable. In addition, a large extracellular pool of calcium has been found to be unexchangeable, probably a part of the cell glycocalix. Finally, dinitrophenol 10-3 M does not affect the slow component of the calcium uptake curve which brings new evidence that calcium entry into the cell is not a metabolically dependent process.