bluuebunny/crossref_metadata_2025 huggingface dataset:
The Dimensions of the Extracellular Space in Sartorius Muscle
Authors: Tasker Patricia , Simon Shirley E. , Johnstone B. M. , Shankly K. H. , Shaw F. H.
Published: May 2004

A survey has been made of the amount of muscle water available to inulin, sucrose, and radioiodinated human serum albumin (RISA). The percentage spaces available to the three molecules are of the same order of magnitude, but the sucrose space > inulin space > albumin space. The kinetics of influx and efflux of RISA have been studied, and it appears that a small part of the albumin may be adsorbed in the extracellular phase. Nevertheless the albumin space would appear to give the best index of the extracellular volume.

The scatter in values found for the extracellular space by all methods is very great, ranging from 8 to 40 per cent and renders invalid the use of a mean value for the calculation of intracellular concentrations. The variation within paired muscles is less than between pairs, provided the tissue has undergone no volume change. Increase in total muscle volume when the muscle is placed in a hypotonic solution leads to a decrease in the size of the extracellular space.
The Quantum Yield of Photosynthesis in Porphyridium cruentum, and the Role of Chlorophyll a in the Photosynthesis of Red Algae
Authors: Brody Marcia , Emerson Robert
Published: May 2004

Quantum yield measurements were made with the red alga Porphyridium cruentum, cultured so as to give different proportions of chlorophyll and phycobilins. Totally absorbing suspensions were used so that there was no uncertainty in the amount of energy absorbed. These measurements have shown that chlorophyll, in this alga, has a photosynthetic efficiency as high as in other algal groups, and higher than the phycobilins—at least at wave lengths shorter than about 650 mµ. Wave lengths longer than this are beyond the range of maximum efficiency of chlorophyll. Under specified conditions of temperature and supplementary light full efficiency may be extended to longer wave lengths. The results of these measurements have made it unnecessary to suppose that in red algae chlorophyll plays a minor role while the phycobilins are the photosynthetic sensitizers of primary importance.
II. Post-Tetanic Potentiation and Depression of Generator Potential in a Single Non-Myelinated Nerve Ending
Authors: Loewenstein Werner R. , Cohen Stanley
Published: May 2004

Repetitive activity at the non-myelinated ending of Pacinian corpuscles leaves the following after-effects: (1) With certain parameters of repetitive mechanical stimulation of the ending a depression in generator potential is produced. The effect is fully reversible and has low energy requirements. The effect is a transient decrease in responsiveness of the receptor membrane which is unrelated to changes in resting membrane potential. It appears to reflect an inactivation process of the receptor membrane. Within certain limits, the depression increases as a function of strength, frequency, and train duration of repetitive stimuli. (2) With other, more critical parameters of repetitive stimulation a hyperpolarization of the ending and of the first intracorpuscular Ranvier node may be produced. This leads to respectively post-tetanic potentiation of generator potential and increase in nodal firing threshold. The balance of these after-effects determines the threshold for the production of nerve impulses by adequate (mechanical) stimulation of the sense organ. The after-effects of activity at the node can be elicited by dromic (mechanical) stimulation of the ending, as well as by antidromic (electric) stimulation of the axon; the after-effects at the ending can only be produced by dromic and not by antidromic stimulation.
The Mechanism of Dual Responsiveness in Muscle Fibers of the Grasshopper Romalea microptera
Authors: Cerf J. A. , Grundfest H. , Hoyle G. , McCann Frances V.
Published: May 2004

Dually innervated Romalea muscle fibers which respond differently to stimulation of their fast and slow axons are excited by intracellularly applied depolarizing stimuli. The responses, though spike-like in appearance, are graded in amplitude depending upon the strength of the stimuli and do not exceed about 30 mv. in height. In other respects, however, these graded responses possess properties that are characteristic of electrically excitable activity: vanishingly brief latency; refractoriness; a post-spike undershoot. They are blocked by hyperpolarizing the fiber membrane; respond repetitively to prolonged depolarization, and are subject to depolarizing inactivation. As graded activity, these responses propagate decrementally.

The fast and slow axons of the dually responsive muscle fibers initiate respectively large and small postsynaptic potentials (p.s.p.'s) in the muscle fiber. These responses possess properties that characterize electrically inexcitable depolarizing activity. They are augmented by hyperpolarization and diminished by depolarization. Their latency is independent of the membrane potential. They have no refractory period, thus being capable of summation. The fast p.s.p. evokes a considerable or maximal electrically excitable response. The combination, which resembles a spike, leads to a twitch-like contraction of the muscle fiber. The individual slow p.s.p.'s elicit no or only little electrically excitable responses, and they evoke slower smaller contractile responses. The functional aspects of dual responsiveness and the several aspects of the theoretical importance of the gradedly responsive, electrically excitable component are discussed.
The Kinetics of the Distribution and Breakdown of I131-Albumin in the Rabbit
Authors: Reeve E. B. , Roberts J. E.
Published: May 2004

Rabbit plasma albumin was labelled with I131, injected intravenously, and measurements were made of the radioactivity in plasma, urine, and feces over many days. In some experiments plasma radioactivity was fractionated into I131-albumin activity and that of labelled breakdown products. Curves of these radioactivities were compared with corresponding curves predicted by four mathematical models. Each model included a vascular and extravascular albumin compartment in transfer equilibrium, a radioactive breakdown products compartment, and an excretion compartment; but model A supposed I131-albumin catabolism to occur within the vascular system, model B within the extravascular compartment, model C within both, and model D within a separate compartment receiving albumin for catabolism from the plasma. The experimental data were reasonably well predicted by models A and C. However, model D, though data were insufficient for its complete validation, gave the best predictions and agrees with present knowledge of albumin catabolism.

Various methods for calculating the rate of albumin breakdown are discussed. When calculations are based solely on the plasma radioactivity data, identical rates are predicted by models A, C, and D. When, as a valuable independent method, catabolism is calculated from plasma and excreted radioactivities, an error (ordinarily small) is incurred unless account is taken of the rate of passage of I131-albumin to the breakdown sites, and of the rate of excretion of the radioactive breakdown products.
The Catabolism of Plasma Albumin in the Rabbit
Authors: Reeve E. B. , Roberts J. E.
Published: May 2004

From I131-albumin studies and previously defined mathematical formulations, rates of breakdown were estimated for native plasma albumin in rabbits. These rates of catabolism per unit weight of animal were remarkably constant and were independent of variations in the steady state values of albumin concentration in the plasma. These results imply that, at least between animals, the breakdown of plasma albumin follows a kinetic process of approximately zero order. It seems plausible that the process operates similarly in individual animals, and hence that albumin is maintained at normal steady state levels in the healthy animal primarily by means of a regulated rate of synthesis.
The Concentration of Glucose in Mammalian Liver
Authors: Appelboom Johannes W. Th. , Brodsky William A. , Rehm Warren S.
Published: May 2004

Data on barium-zinc filtrates of liver homogenates and of boiled liver indicate that the free glucose content of liver exceeds the blood glucose level. For instance, for boiled liver, the glucose level is 10.1, compared with a blood level of 5.4 mM/kg. Method of preparation of the tissue is important for the interpretation of the final results, as has been shown in appropriate control experiments. Various methods including paper chromatography were used to show that the reducing substance in liver is glucose. The relation of the high glucose content of liver to hexokinase activity, phosphate activity, and to glucose transport between liver cell and blood is discussed.
Interactions of Calcium with Sodium and Potassium in Membrane Potentials of the Lobster Giant Axon
Authors: Adelman W. J. , Dalton J. C.
Published: May 2004

Experiments were performed on the lobster giant axon to determine the relation between intracellular spike amplitude and external calcium ion concentration. Action potential decline in low external calcium is greatly accelerated by simultaneous removal of external sodium ion. Correlation of the time course of spike decline in low calcium-low sodium solution with the time courses of spike decline in low calcium alone and in low sodium alone indicates that the effect of simultaneous removal of both ions is significantly greater than the sum of the individual effects. For a given time of treatment, spike amplitude was a function of external calcium concentration. While spike height is proportional to the log of the external calcium concentration over the range 2.5 to 50 millimolar, the proportionality constant is dependent upon the sodium concentration. Under the conditions of low external sodium (50 per cent reduction) the slope of the linear relationship between the spike height and the log of the external calcium concentration is about 5 times greater than in normal external sodium. Decreasing external calcium concentration and simultaneously increasing external potassium concentration produce a greater spike reduction than the arithmetic sum of spike reductions in low calcium alone and in high potassium alone. It is suggested that calcium interacts strongly with sodium and potassium in the spike-generating mechanism. A theoretical basis for these results is discussed.
Biochemical Studies on Amphibian Metamorphosis
Authors: Paik Woon Ki , Cohen Philip P.
Published: May 2004

Thyroxine has been shown to accelerate the synthesis of carbamyl phosphate synthetase in the liver of Rana catesbeiana. Stimulation of carbamyl phosphate synthetase synthesis by thyroxine appears to be relatively specific because of the following observations: (1) succinoxidase activity decreased during the time that carbamyl phosphate synthetase increased; (2) liver catalase responded more slowly than carbamyl phosphate synthetase to thyroxine; (3) the ratio of biochemical changes/morphological changes was greatly altered during thyroxine-induced metamorphosis. The relationships between the concentration of thyroxine and (1) temperature; (2) duration of exposure of the tadpole to thyroxine; and (3) the activity of carbamyl phosphate synthetase during the induced synthesis of carbamyl phosphate synthetase by thyroxine are discussed. Chloramphenicol and thiouracil partly counteracted the effect of thyroxine on the synthesis of carbamyl phosphate synthetase.
The Action Spectrum for Shifting the Phase of the Rhythm of Luminescence in Gonyaulax polyedra
Authors: Hastings J. Woodland , Sweeney Beatrice M.
Published: May 2004

The action spectrum for changing the phase of the rhythm of luminescence in the marine dinoflagellate Gonyaulax polyedra has been determined. Maxima in effectiveness were found at 475 and 650 mµ. The significance of these findings is discussed.
Evidences from Action Spectra for a Specific Participation of Chlorophyll b in Photosynthesis
Authors: Myers Jack , French C. S.
Published: May 2004

Rate of oxygen evolution in photosynthesis was measured as the current from a polarized platinum electrode covered by a thin layer of Chlorella. The arrangement gave a reproducibly measurable rate of photosynthesis proportional to light intensity at the low levels used and gave rapid response to changes in illumination. Two phenomena have been explored.

The Emerson effect was observed as an enhancement of photosynthesis in long wavelength red light (700 mµ) when shorter wavelengths were added. Two light beams of wavelengths 653 and 700 mµ when presented together gave a photosynthetic rate about 25 per cent higher than the sum of the rates obtained separately.

Large and reproducible transients in rate of oxygen evolution were observed accompanying change in illumination between two wavelengths adjusted in intensity to support equal steady rates of photosynthesis. The transients were found not to be specifically related to long wavelength red light.

Both enhancement and the transients have identical action spectra which are interpreted as demonstrating a specific photochemical participation of chlorophyll b.
The Interaction of Dextran with Serum Albumin, Gamma Globulin, and Fibrinogen
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

The interaction between dextran and serum albumin, gamma globulin, and fibrinogen can be studied by an electrophoretic method, which depends on obtaining electrophoretic patterns, first of each protein, then of dextran, and finally of mixtures of each protein with dextran. The areas under the electrophoretic spikes for each protein, for dextran, and for the mixtures are measured.

At pH's between 9.6 and 6.6, there is a transference of albumin to dextran when the two components are mixed, the amount of albumin lost being nearly equal to the gain in the new component, albumin plus dextran. This new species has a specific refractive index of about 0.00205 and seems to be composed of about one albumin molecule for every four dextran molecules.

The method is unsuitable for studying interaction between dextran and gamma globulin because these substances are almost immobile and do not separate into two spikes.

The method shows that a mixture of dextran and fibrinogen gives only one slowly moving spike (pH 6.6 to 8.6), the area under which is the sum of the areas under the dextran and the fibrinogen spikes taken separately. Either there is no interaction, or the new species has virtually the same refractive index increment as fibrinogen and dextran taken separately (0.0014 to 0.0015).
Growth and Division of Single Cells of Higher Plants in Vitro
Authors: Bergmann Ludwig
Published: May 2004

The cultivation of single cells of Nicotiana tabacum L. var. "Samsun" and Phaseolus vulgaris L. var. "Early Golden Cluster" on a thin agar layer in Petri dishes is described. Under these conditions about 20 per cent of the cells divided repeatedly and established tissue clones which could be isolated and maintained as growing tissue cultures. It was possible also to follow the successive divisions of isolated cells and to observe their behavior during cytogenesis under the microscope.
Effect of the Method of Leading on the Recording of the Nerve Fiber Spectrum
Authors: Gasser Herbert S.
Published: May 2004

A study has been made of the modifications of the shape of a nerve action potential dependent upon the placement of the two electrodes, always necessary for a lead. In a classic diphasic lead separation of the electrodes brings out, in addition to a separation of the phases, the appearance of a positive deflection traceable to the passage of an impulse between the electrodes. This phenomenon, called the lead separation effect (1.s.e.), must be considered as an expression of a feature of normal nerve fiber biophysics. It regularly appears and it can be analyzed with respect to the position of the sink maximum. Also it cannot be eliminated by a block at the second electrode.

The advantage of approximating the leads was shown by the absence of a 1.s.e. following spikes recorded by electronic integration of tangents, which with validity can be derived from threshold fibers. Since tangent leads are not adaptable to recording a spectrum, a block at the second electrode is required. The making of such blocks and the configuration of records obtained with them are described. Conditions for an optimal lead, but not an ideal lead, were delimited. In an optimal lead only two major elevations appear in the spectrum of a skin nerve: those known as alpha and delta. A reference to maps of fiber size analyses shows that the fibers in the delta elevation have velocities of conduction slower than they would have if following in linear sequence the fiber diameters belonging to the alpha elevation.
Resting and Action Potentials of the Squid Giant Axon in Vivo
Authors: Moore John W. , Cole Kenneth S.
Published: May 2004

Blood oxygenation and circulation were maintained in Loligo pealii for several hours by a strong flow of sea water over both gills on the open, flat mantle. Potentials were measured with a 3 M KCl-filled glass microelectrode penetrating the giant axon membrane. An hour or more after the mantle was opened, the potentials were similar to those observed in excised axons and in preparations without circulation; spike height 100 mv.; undershoot 12 mv., decaying at 6 v./sec.; resting potential 63 mv. However, the earliest (20 minute) resting potentials were up to 70 mv. and 73 mv. Occasional initial action potential measurements (40 to 50 minute) showed a decay of the undershoot that was less than one-tenth the rate observed later. This suggests that in even better preparations there would be no decay, thereby increasing the resting potential and spike height by 12 mv. With the calculated liquid junction potential of 4 mv. the absolute resting potential in the "normal" axon in vivo is estimated to be about 77 mv., which is close to the Nernst potential for the potassium ratio between squid blood and axoplasm. The differences between such a normal axon and the usual isolated axon can be accounted for by a negligible leakage conductance in the normal axon.
Liquid Junction and Membrane Potentials of the Squid Giant Axon
Authors: Cole Kenneth S. , Moore John W.
Published: May 2004

The potential differences across the squid giant axon membrane, as measured with a series of microcapillary electrodes filled with concentrations of KCl from 0.03 to 3.0 M or sea water, are consistent with a constant membrane potential and the liquid junction potentials calculated by the Henderson equation. The best value for the mobility of an organic univalent ion, such as isethionate, leads to a probably low, but not impossible, axoplasm specific resistance of 1.2 times sea water and to a liquid junction correction of 4 mv. for microelectrodes filled with 3 M KCl.

The errors caused by the assumptions of proportional mixing, unity activity coefficients, and a negligible internal fixed charge cannot be estimated but the results suggest that the cumulative effect of them may not be serious.
The Conjugated Plasma Proteins of the American Cockroach
Authors: Siakotos A. N.
Published: May 2004

Five protein fractions have been separated by paper electrophoresis from the plasma of the American cockroach. With the utilization of various staining procedures several of the plasma fractions were shown to be conjugated proteins. Two of these (fractions II and IV) are readily identifiable by their phospholipid, carbohydrate, and protein composition. A third conjugated protein, fraction III, is characterized by its high neutral lipid and sterol content. This lipoprotein is also sex-specific. Another fraction (I) contains neutral lipid, sterol, and protein but electrophoretically is more mobile than fraction III. Fraction V, the last and least mobile of the normally occurring proteins, possesses electrophoretic properties similar to human fibrinogen.
Magnesium Equilibrium in Muscle
Authors: Gilbert Daniel L. ,   with the technical assistance of JoAnna McGann
Published: May 2004

Isolated frog sartorii were immersed in Ringer's solution, which had a 2 mM magnesium concentration containing Mg28. The uptake of the radioactive magnesium was measured under steady state conditions. Although the biological variability was fairly large, it was observed that the uptake proceeded in three stages lasting respectively about 0.5, 30, and 300 minutes and accounting respectively for about 0.21, 0.71, and 0.67 millimole magnesium/kg. muscle. It was assumed that the first stage represents surface adsorption, the second stage represents extracellular water and connective tissue phases, and the third stage entry inside the cell. It is estimated that the maximum intracellular magnesium concentration is about 1.1 mM and that only about 0.6 millimole magnesium/liter intracellular water is exchanged per hour. The maximum energy required per hour to pump the magnesium out of the cell against the electrochemical gradient is calculated to be only 1.5 cal./kg. muscle. About 75 to 80 per cent of the magnesium in muscle is non-exchangeable and difficult to remove by diffusion. It appears from previous work that the exchangeable magnesium behaves similarly to exchangeable calcium.
Calcium and Strontium in Rat Small Intestine Their Fluxes and Their Effect on Na Flux
Authors: Dumont P. A. , Curran Peter F. , Solomon A. K.
Published: May 2004

Studies have been carried out on movements of Ca and Sr ions in rat small intestine, using the in vivo preparation developed by Curran and Solomon (5). In the concentration range of 0 to 25 mM, Sr flux appears to be passive, though restricted. Ca transport may not, however, be ascribed to passive independent movement of these ions since at higher concentrations (12.5 and 25 mM) Ca return from blood to intestinal lumen increases more than expected. An apparent diffusion coefficient of Ca and Sr ions in the membrane has been calculated and the influence of negative charges within the membrane on cation diffusion has been examined in a semiquantitative manner.

Both Ca and Sr ions exercise a drastic effect on active Na absorption from intestine and on concomitant passive water movement. From 0 to 1 mM, Ca and Sr ions cause a sharp increase in Na and water efflux from the lumen. This rising phase is interpreted in terms of combination of the divalent cation with the Na carrier system following Michaelis-Menten kinetics. At concentrations higher than 1 mM, the effect of Ca and Sr ions is reversed and Na and water absorption decreases slowly as Ca or Sr concentration is increased. This falling phase is ascribed to a non-specific Ca effect which produces a general "stiffening" of the membrane.
Chicken Intestinal Alkaline Phosphatase
Authors: Kunitz M.
Published: May 2004

Purified chicken intestinal alkaline phosphatase is active at pH 8 to 9, but becomes rapidly inactivated with change of pH to 6 or less. Also, a solution of the inactivated enzyme at pH 4.5 rapidly regains its activity at pH 8. In the range of pH 6 to 8 a solution of purified alkaline phosphatase consists of a mixture of active and inactive enzyme in equilibrium with each other. The rate of inactivation at lower pH and of reactivation at higher pH increases with increase in temperature. Also, the activity at equilibrium in the range of pH 6 to 8 increases with temperature so that a solution equilibrated at higher temperature loses part of its activity on cooling, and vice versa, a rise in temperature shifts the equilibrium toward higher activity. The kinetics of inactivation of the enzyme at lower pH and the reactivation at higher pH is that of a unimolecular reaction. The thermodynamic values for the heat and entropy of the reversible inactivation and reactivation of the enzyme are considerably lower than those observed for the reversible denaturation of proteins. The inactivated enzyme at pH 4 to 6 is rapidly reactivated on addition of Zn ions even at pH 4 to 6. However, zinc ions are unable to replace magnesium ions as cocatalysts for the enzymatic hydrolysis of organic phosphates by alkaline phosphatase.
Increase of Labeled Calcium Uptake in Heart Muscle during Potassium Lack Contracture
Authors: Thomas Lyell J.
Published: May 2004

Analyses of ashed muscle tissue show that the uptake of Ca45 by isolated frog heart ventricles from normal Ringer's solution containing 1 mM Ca reaches a maximum value in about 30 minutes of perfusion which is not exceeded after 3 hours of perfusion. The average amount of this labeled Ca taken up from normal Ringer's is 0.7 mM/kg. wet weight of muscle. In contrast to this, the amount of labeled Ca taken up by ventricles perfused with K-free Ringer's increases at a linear rate over a 60 minute period to twice the normal value coinciding with the gradual development of contracture and coinciding with a cellular K loss and Na gain of about 30 mM/kg. How much of the extra labeled Ca taken up from K-free Ringer's represents a net gain in cellular Ca content is not known. However, evidence has been obtained that some of this labeled Ca enters an intracellular compartment. EDTA in K-free Ringer's solution causes relaxation of ventricles in contracture and also renders the muscle fibers indiscriminately permeable. This indicates that a combination of Ca with sensitive intracellular sites is probably the cause of the K lack contracture.
Electrical Characteristics of Insect Mechanoreceptors
Authors: Wolbarsht M. L.
Published: May 2004

External direct coupled recordings from the neurons of the mechanosensory hairs of insects show nerve impulses and graded slow potentials in response to deformation of the hair. These slow potentials or receptor potentials are negative going, vary directly with the magnitude of the stimulus, and show no overshoot when returning to baseline. The impulses have an initial positive phase which varies in size directly with the amplitude of the receptor potential. The receptor potential is related to the generator potential for the impulse in that it must attain some critical level before impulses are produced, and the frequency of impulses varies directly with amplitude of the receptor potential. The receptor potential does not return to the baseline after each impulse. In some receptors static deformation of the hair will maintain the receptor potential. It appears likely that both the receptor potential and the variation in size of the impulses are caused by a change in conductance of the cell membrane at the receptor site, and that the receptor potential originates at a site which is not invaded by the propagated impulses.
Ionic Current Measurements in the Squid Giant Axon Membrane
Authors: Cole Kenneth S. , Moore John W.
Published: May 2004

The concepts, experiments, and interpretations of ionic current measurements after a step change of the squid axon membrane potential require the potential to be constant for the duration and the membrane area measured. An experimental approach to this ideal has been developed. Electrometer, operational, and control amplifiers produce the step potential between internal micropipette and external potential electrodes within 40 microseconds and a few millivolts. With an internal current electrode effective resistance of 2 ohm cm.2, the membrane potential and current may be constant within a few millivolts and 10 per cent out to near the electrode ends.

The maximum membrane current patterns of the best axons are several times larger but of the type described by Cole and analyzed by Hodgkin and Huxley when the change of potential is adequately controlled. The occasional obvious distortions are attributed to the marginal adequacy of potential control to be expected from the characteristics of the current electrodes and the axon.

Improvements are expected only to increase stability and accuracy. No reason has been found either to question the qualitative characteristics of the early measurements or to so discredit the analyses made of them.
Regulation of Cell Volume by Active Cation Transport in High and Low Potassium Sheep Red Cells
Authors: Tosteson D. C. , Hoffman J. F.
Published: May 2004

A model cell which controls its cation composition and volume by the action of a K-Na exchange pump and leaks for both ions working in parallel is presented. Equations are formulated which describe the behavior of this model in terms of three membrane parameters. From these equations and the steady state concentrations of Na, K, and Cl, values for these parameters in high potassium (HK) and low potassium (LK) sheep red cells are calculated. Kinetic experiments designed to measure the membrane parameters directly in the two types of sheep red cells are also reported. The values of the parameters obtained in these experiments agreed well with those calculated from the steady state concentrations of ions and the theoretical equations. It is concluded that both HK and LK sheep red cells control their cation composition and volume in a manner consistent with the model cell. Both have a cation pump which exchanges one sodium ion from inside the cell with one potassium ion from outside the cell but the pump is working approximately four times faster in the HK cell. The characteristics of the cation leak in the two cell types are also very different since the HK cells are relatively more leaky to sodium as compared with potassium than is the case in the LK cells. Both cell types show appreciable sodium exchange diffusion but this process is more rapid in the LK than in the HK cells.
Comparative Studies on Dark Adaptation in the Compound Eyes of Nocturnal and Diurnal Lepidoptera
Authors: Bernhard C. G. , Ottoson D.
Published: May 2004

A comparative analysis has been carried out of the time course and range of dark adaptation in the compound eyes of some common butterflies and noctuid moths (Lepidoptera). The change in sensitivity of the eye during dark adaptation was determined by measurements of the intensity of illumination necessary to elicit an electrical response of a given magnitude of the eye. It was found that the curve for dark adaptation in the diurnal species was smooth. The range of adaptive change varied in different species but usually did not cover more than 1 to 1.5 log units. In the nocturnal species the dark adaptation was found to proceed in two phases. The first phase was usually completed in less than 10 minutes and covered a range of 1 to 1.5 log units. The second phase was more prolonged and covered a range of 2 to 3 log units. In some of the experiments on nocturnal species the second phase failed to appear. Measurements of the size of the response at different intensities showed that the intensity/amplitude relationship was the same in the light-adapted eye as in the dark-adapted eye. In the nocturnal insects the response of the eye in the light-adapted condition was about 20 per cent of that in the dark-adapted eye, while in diurnal insects it was about 60 per cent.
Efflux and Influx of Erythrocyte Water
Authors: Olmstead Edwin G.
Published: May 2004

Rabbit erythrocytes were washed in buffered NaCl solutions isotonic with rabbit serum (Δt -0.558°C.) and suspended in buffered NaCl solutions of tonicity equidistant from intracellular tonicity (Δt = -0.558°C. ± 0.112°C.) of varying pH and incubated at varying temperatures. After incubation, the freezing point depression (Δt) was measured on the supernatant. Change in the Δt measured change in the water content of the extracellular solutions—water being withdrawn by erythrocytes (WI) from the hypotonic solutions and added (WE) to the hypertonic solutions. WE was always less than WI and was inversely proportional to the pH in the range 6.5–8.0. WE was significantly increased by lowering the temperature of the cell suspension to 4°C. WI was increased by raising or lowering the pH or raising the temperature of the cell suspension. WE x WI ≠ k. WE and WI were affected differently by changes in pH and temperature. It was concluded that WE and WE were probably under different physicochemical control.
The Uptake of Divalent Manganese Ion by Mature Normal Human Red Blood Cells
Authors: Weed Robert I. , Rothstein Aser
Published: May 2004

At physiological pH and concentrations of Mn++ in excess of 5 x 10-4 M, study of the Mn++ ion movement into human red cells is complicated by physicochemical alterations of the ion itself. At concentrations below 5 x 10x4 M, the rate of uptake bears a linear relationship to the Mn++ concentration. The permeability constant for inward movement of Mn++ is 2.87 ± 0.13 (S.E.) x 10-9 cm./sec. The rate is not influenced by the addition of metabolic substrates such as glucose or adenosine or the metabolic inhibitors iodoacetate or fluoride. Co++, Ca++, and Mg++ do not appear to compete with Mn++ for entry, but at high concentrations relative to Mn++, they reduce the rate of entry. Ca++ is far more effective than Co++ or Mg++ in this regard. The permeability constant for outward Mn++ movement is 1.38 ± 0.21 (S.E.) x 10-9 cm./sec., about half of that for entry. This slower rate of outward movement is consistent with the finding that 40 to 60 per cent of the Mn++ taken up by the red cells is non-ultrafilterable. Less than 5 to 10 per cent of the Mn++ appears to be bound to the stroma. It is concluded that entry and exit of Mn++ is a process of passive diffusion involving no carriers, transport, or metabolic linkage.
Cat Heart Muscle in Vitro
Authors: Page Ernest , Solomon A. K.
Published: May 2004

Methods have been developed for the simultaneous determination of total water, inulin space, and K and Na content in muscles of 0.5 to 10 mg. wet weight. These methods have been used to define steady state conditions with respect to intracellular K concentration in papillary muscles from cat hearts perfused and contracting isometrically at 27–28°C. and at 37–38°C. Cell volumes and intracellular ionic concentrations have been followed as a function of the external K concentration and compared with values predicted on the basis of electroneutrality and osmotic equilibrium.
Permeability of the Ehrlich Ascites Tumor Cell to Water
Authors: Hempling H. G.
Published: May 2004

The osmotic permeability coefficient for water has been measured for the Ehrlich mouse ascites tumor cell. Measurements were made of the rate of cell shrinkage in hyperosmotic solutions of NaCI, a functionally impermeable solute. During the first 9 months of weekly serial transplantation the mean was 6.4 µ3/µ3/atm. ± 0.8 (S.E.). By the end of the 2nd year the permeability coefficient was much lower and averaged 1.6 ± 0.09. There were no significant differences in the volume of the tumor cells which could explain the discrepancy on the basis of a change in the volume to surface area ratio. Studies of the effect of temperature were done and Eyring's theory of absolute reaction rates was applied to the data. The apparent energy of activation was 9.6 kcal./mol and ΔS‡ was 39.1 entropy units. The thermodynamic data are twice as high as data reported by Wang for self-diffusion and viscous properties of water. Two alternate explanations have been advanced based on the pore hypothesis of membrane permeability. One explains the thermodynamic data from a change in the A'/Δx available for water movement; the other assumes A'/Δx constant and bases the results on the interaction of water dipoles with each other and the membrane.
Studies on the Hemolytic Properties of Protamine
Authors: Becker Frederick F.
Published: May 2004

The basic protein protamine causes a rapid hemolysis when incubated with the red blood cells of many mammalian species. The age of the cells does not affect the process. Neutralization of the active side groups of the protamine molecule with formalinization demonstrates that a specific degree of charge is necessary for hemolysis, as more than 30 per cent of the guanidine groups must remain unreacted to maintain activity. Unlike the hemolysis induced by the synthetic polypeptides polylysine and polyhomoarginine, protamine hemolysis is temperature-dependent.

Whole lipoprotein material derived from red blood cell membranes inhibits protamine hemolysis to a greater extent than do the membranes themselves, serum, serum protein fractions, or cholesterol. The phosphatide and protein moieties derived from the membranes are quite avid in inhibiting protamine hemolysis. A probable explanation is that intracellular aggregation of these structural elements may cause changes in electrostatic charge and surface tension which result in increased permeability.

The hemolytic and antitumor cell properties of protamine could not be segregated from its animal toxicity. Despite formalinization to a degree which eliminated the former, the compound remained quite toxic to mice and rabbits.
The Secretion of Oxygen into the Swim-bladder of Fish
Authors: Wittenberg Jonathan B.
Published: May 2004

Fish were maintained in sea water equilibrated with a gas mixture containing a non-equilibrium mixture of the three molecular species of oxygen, O18-O18 (mass 36), O18-O16 (mass 34), and O16-O16 (mass 32). Analyses in the mass spectrometer, of the gases secreted into the swim-bladder showed that no change in the relative abundance of these three molecular species had occurred during the secretory process and that therefore no exchange of atoms between oxygen molecules had occurred. Scission of the oxygen-oxygen bond probably does not occur during the transport process.

It is concluded that the active transport of oxygen into the swim-bladder by the gas gland is a transport of molecular oxygen.
Retardation of Regeneration and Division of Blepharisma by Ultraviolet Radiation and Its Photoreversal
Authors: Giese Arthur C. , Lusignan Molly
Published: May 2004

Regeneration of Blepharisma undulans variety japonicus from which the hypostome has been removed is retarded by dosages of 3000 to 4600 ergs/mm.2 at wavelength 2654A most strongly when the fragment is exposed soon after cutting. Dosages greater than 4600 ergs/mm.2 prevent regeneration. Regeneration is also retarded strongly when the Blepharisma are cut soon after irradiation. Starvation retards regeneration and potentiates the effect of ultraviolet radiations. Division after regeneration of Blepharisma is also retarded by ultraviolet radiations about equally, regardless of when the Blepharisma are cut indicating a more lasting effect of the radiations upon the cells. Blepharisma cut after irradiation usually recover from the effects of the radiations sooner than uncut individuals given the same dosage. Retardation of division by ultraviolet radiation is subject to photoreversal by visible light, especially in a nitrogen atmosphere, provided the ultraviolet dose is not excessive. Visible light alone if prolonged, retards regeneration or may even kill the cut fragments of Blepharisma.
Measurements of Electrical Potential Differences on Single Nephrons of the Perfused Necturus Kidney
Authors: Giebisch Gerhard
Published: May 2004

Stable electrical potential differences can be measured by means of conventional glass microelectrodes across the cell membrane of renal tubule cells and across the epithelial wall of single tubules in the doubly perfused kidney of Necturus. These measurements have been carried out with amphibian Ringer's solution, and with solutions of altered ionic composition. The proximal tubule cell has been found to be electrically asymmetrical inasmuch as a smaller potential difference is maintained across the luminal cell membrane than across the peritubular cell boundary. The tubule lumen is always electrically negative with respect to the peritubular extracellular medium. Observations on the effectiveness of potassium ions in depolarizing single tubule cells indicate that the transmembrane potential is essentially an inverse function of the logarithm of the external potassium concentration. The behavior of the peritubular transmembrane potential resembles more closely an ideal potassium electrode than that of the luminal transmembrane potential. From these results, and the effects of various ionic substitutions on the electrical profile of the renal tubular epithelium, a thesis concerning the origin of the observed potential differences is presented. A sodium extrusion mechanism is considered to be located at the peritubular cell boundary, and reasons are given for the hypothesis that the electrical asymmetry across the proximal renal tubule cell could arise as a consequence of differences in the relative sodium and potassium permeability at the luminal and peritubular cell boundaries.
Electrical Potential Difference Measurements in Perfused Single Proximal Tubules of Necturus Kidney
Authors: Whittembury Guillermo , Windhager Erich E.
Published: May 2004

Transtubular and peritubular face electrical potential differences (P.D.) of the proximal tubules of the kidney of the amphibian Necturus maculosus have been measured in situ. These measurements have been carried out both under normal conditions, when the tubular fluid originates in the glomerular filtrate, and under conditions when the composition of the tubular fluid has been altered using the stopped flow microperfusion technique. Under normal conditions the transtubular potential difference is 20 mv. (lumen-negative) and the P.D. across the peritubular face is 74 mv. (cell-negative). The P.D. across the luminal face is thus 54 mv. (cell-negative). This electrical asymmetry is not influenced by replacing the normal tubular fluid by NaCl, NaCl + mannitol, or by alteration in the intraluminal pH from 7 to 4. On the other hand, replacement of Na by K or choline and the addition of small amounts of DNP to the perfusate diminish this asymmetry.
The Electrophysiology of Electric Organs of Marine Electric Fishes
Authors: Bennett M. V. L. , Grundfest H.
Published: May 2004

Studies on the electric organs of Narcine brasiliensis and particularly of the responses of the electroplaques of the accessory organ confirm and amplify data obtained on the electroplaques of Torpedo nobiliana. Only the innervated surface is electrogenically reactive and the uninnervated surface has a low resistance, as in Torpedo electroplaques. However, in the accessory organ of Narcine the innervated surface is the dorsal, rather than the ventral, and it has a different pattern of innervation. The responses of single cells of the accessory organ exhibit marked facilitation on repetitive stimulation. The facilitated responses, like the individual responses of Torpedo and of the main organ of Narcine, are electrochemically graded on changing the membrane potential with applied currents, and are inverted in sign when outward currents through the innervated face are very strong.
Chromatographic Separation, and Characteristics of Nucleic Acids from HeLa Cells
Authors: Philipson Lennart
Published: May 2004

The application of the phenol-duponol method to extraction of nucleic acids from HeLa cells is described. Chromatography of the phenol extract on an esterified bovine serum albumin column with a salt gradient of sodium chloride gives separation of soluble RNA, DNA, and two different high molecular RNA fractions. Ultracentrifugation of the DNA eluted from the column gives a sedimentation coefficient (s20o,w) of 38, which agrees with ultracentrifugation data on the phenol extract. The eluted RNA appears polydisperse at low ionic strength, but at high ionic strength and after alcohol precipitation two fractions with the sedimentation coefficients of 16 and 25 to 29, respectively, were obtained.
The Influence of Exogenous Steroids on the Growth of Aspergillus niger and Torula utilis
Authors: Jefferson W. E. , Sisco Gladys
Published: May 2004

The yield of Aspergillus niger mycelium from a synthetic medium can be increased by the addition of microgram quantities of cholesterol, ergosterol, cholestanol, 7-dehydrocholesterol, stigmasterol, sitosterol, pregnenolone, and the vitamins D. The stimulation is not due to degradation to the acetate level. It is obtained only in highly aerated cultures. The rate of growth of Torula utilis was not increased.

Both organisms were inhibited by desoxycorticosterone, testosterone, androstenedione, cortisone acetate, progesterone, and diethylstilbestrol. T. utilis was also inhibited by estradiol.

A small decrease in progesterone inhibition of T. utilis was obtained by adding ergosterol, cholesterol, or pregnenolone.

Of the compounds which have been adequately tested the order of stimulatory activity for A. niger is: ergosterol > cholesterol > stigmasterol > 7-dehydrocholesterol > cholestanol > pregnenolone. Progesterone was inhibitory at low concentrations but stimulatory at higher ones, while 17-hydroxyprogesterone was neither inhibitory nor stimulatory. Desoxycorticosterone and testosterone were inhibitory at all concentrations. Complete inhibition of the growth of the fungus was not obtained with any of the steroids.

It is concluded that A. niger has a metabolic requirement for a steroid with a hydroxy group on carbon 3, a double bond in the 5–6 position, and a side chain similar to that in ergosterol or cholesterol and that this material is growth-limiting in the early stages of the cultures described.
The Effect of Variations in the Intra- and Extracellular Ion Concentrations upon the Electrical Activity of Normal and Dystrophic Mouse Skeletal Muscle
Authors: Mclennan H.
Published: May 2004

The resting and action potentials of the m. gastrocnemii of normal and dystrophic mice have been measured in vitro, under various conditions of the ionic environment. The observed effects are consistent with the view that, when equilibrium is established between internal and external ionic concentrations, the resting potential is determined very largely, and perhaps entirely, by the gradient of K ions. Action potentials are associated with a greatly increased Na conductance in this as in other excitable tissues. No differences in electrical activity between normal and dystrophic muscle cells could be established.
Impedance of a Small Electrically Isolated Area of the Muscle Cell Surface
Authors: Strickholm A.
Published: May 2004

A method has been developed permitting measurement of membrane impedance and current, as a function of transmembrane potential, at small, electrically isolated regions of the muscle cell surface without microelectrode impalement. The frequency dependence of the muscle cell membrane capacity found earlier by other methods has been confirmed. The average capacity is 3.5 µf/cm2 with a phase angle of 71° at 5 kilocycles. The internal phase angle of the complex impedance plot of whole muscle probably does not result from a distribution of fiber diameters and membrane capacities, since it also appears in the present experiments where measurements are confined to a small region of a single fiber.
The Spectral Sensitivity of Crayfish and Lobster Vision
Authors: Kennedy Donald , Bruno Merle S.
Published: May 2004

(1) The spectral sensitivity function for the compound eye of the crayfish has been determined by recording the retinal action potentials elicited by monochromatic stimuli. Its peak lies at approximately 570 mµ. (2) Similar measurements made on lobster eyes yield functions with maxima in the region of 520 to 525 mµ, which agree well with the absorption spectrum of lobster rhodopsin if minor allowances are made for distortion by known screening pigments. (3) The crayfish sensitivity function, since it is unaffected by selective monochromatic light adaptation, must be determined by a single photosensitive pigment. The absorption maximum of this pigment may be inferred with reasonable accuracy from the sensitivity data. (4) The visual pigment of the crayfish thus has its maximum absorption displaced by 50 to 60 mµ towards the red end of the spectrum from that of the lobster and other marine crustacea. This shift parallels that found in both rod and cone pigments between fresh water and marine vertebrates. In the crayfish, however, an altered protein is responsible for the shift and not a new carotenoid chromophore as in the vertebrates. (5) The existence of this situation in a new group of animals (with photoreceptors which have been evolved independently from those of vertebrates) strengthens the view that there may be strong selection for long wavelength visual sensitivity in fresh water.