bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral Sensitivity of Larval Mosquito Ocelli
Authors: Seldin Edward B. , White Richard H. , Brown Paul K.
Published: May 2004

The spectral sensitivity of lateral ocelli in both wild-type and white-eyed larvae of the yellow fever mosquito Aedes aegypti L. (reared in darkness) was measured by means of the electroretinogram. The spectral sensitivity is maximal at about 520 nm, with a small secondary peak near 370 nm. When allowance is made for some screening and filtering by the eye tissues, the spectral sensitivity is in reasonable agreement with the absorption spectrum of ocellar rhodopsin (λmax = 515 nm).
Spectral and Polarization Sensitivity of the Dipteran Visual System
Authors: McCann Gilbert D. , Arnett David W.
Published: May 2004

Spectral and polarization sensitivity measurements were made at several levels (retina, first and third optic ganglion, cervical connective, behavior) of the dipteran visual nervous system. At all levels, it was possible to reveal contributions from the retinular cell subsystem cells 1 to 6 or the retinular cell subsystem cells 7 and 8 or both. Only retinular cells 1 to 6 were directly studied, and all possessed the same spectral sensitivity characterized by two approximately equal sensitivity peaks at 350 and 480 nm. All units of both the sustaining and on-off variety in the first optic ganglion exhibited the same spectral sensitivity as that of retinular cells 1 to 6. It was possible to demonstrate for motion detection and optomotor responses two different spectral sensitivities depending upon the spatial wavelength of the stimulus. For long spatial wavelengths, the spectral sensitivity agreed with retinular cells 1 to 6; however, the spectral sensitivity at short spatial wavelengths was characterized by a single peak at 465 nm reflecting contributions from the (7, 8) subsystem. Although the two subsystems exhibited different spectral sensitivities, the difference was small and no indication of color discrimination mechanisms was observed. Although all retinular cells 1 to 6 exhibited a preferred polarization plane, sustaining and on-off units did not. Likewise, motion detection and optomotor responses were insensitive to the polarization plane for long spatial wavelength stimuli; however, sensitivity to select polarization planes was observed for short spatial wavelengths.
THE MINIMUM CONCENTRATION OF OXYGEN FOR LUMINESCENCE BY LUMINOUS BACTERIA
Authors: Harvey E. Newton , Morrison Thomas F.
Published: May 2004

A method is described for measuring the concentration of oxygen to allow just perceptible luminescence of luminous bacteria. The value turns out to be extraordinarily low, about 0.005 mm. Hg pressure O2 or 1 part by weight oxygen dissolved in 3,700,000,000 cc. sea water.
THE RATE OF GROWTH OF THE DAIRY COW
Authors: Brody Samuel , Ragsdale Arthur C. , Turner Charles W.
Published: May 2004

It is shown that from 2 years, the age when milk secretion usually begins, to 9 years, the age of maximum body weight, the increase of milk secretion with age follows the course of growth in body weight— both can be accurately represented by the equation of a monomolecular chemical reaction having a velocity constant of approximately the same numerical value. While increase in milk secretion and increase in body weight with age follow the same course, it is shown that increasing body weight contributes only about 20 per cent to increasing milk secretion with age. The fact that milk secretion and body weight follow the same course, even though they are largely independent of each other indicates that increase in body weight is a good measure of growth of the dairy cow; this fact also shows that the increase of milk secretion with age may be used as a measure of growth. The fact that milk secretion, like body weight, follows the course of a chemical reaction, adds further support to the theory that growth is limited by a chemical reaction.
CHANGES IN THE STABILITY AND POTENTIAL OF CELL SUSPENSIONS
Authors: Eggerth Arnold H.
Published: May 2004

1. Stability and potential of Bacterium coli suspensions depend, not only on the strain of the organism and the medium in which it is suspended, but also on the previous treatment of the suspension, and the length of time it has been in the medium.

2. When treated at acid reactions, the negative charge on the bacteria is diminished; with some strains, a positive charge is acquired. Changes in stability accompany the changes in potential.

3. Washing acid-treated bacteria at neutral or slightly alkaline reactions does not restore the original potential; the zone of flocculation is moved toward the alkaline side.

4. These changes are due to two factors: the extraction of a soluble protein which combines with the surfaces of the cells, and a further irreversible change of the cell or its membrane.
STUDIES ON TOXICITY
Authors: Fulmer Ellis I. , Buchanan R. E.
Published: May 2004

With yeast subjected to the action of phenol or of phenol and alcohol the curves of survivors as measured by resistance to staining with methylene blue when plotted against time do not in general prove to be logarithmic.

It is believed that such resemblances as have been found between such curves and monomolecular reaction or logarithmic curves are superficial and fortuitous. Any method therefore of evaluating disinfecting power based upon such a concept must prove misleading.

Variations in resistance of individual cells and the distribution of such variations must be regarded as of fundamental importance in accounting for rates of death of microorganisms.
DIFFERENTIATION OF OXYHEMOGLOBINS BY MEANS OF MUTUAL SOLUBILITY TESTS
Authors: Landsteiner Karl , Heidelberger Michael
Published: May 2004

1. The rule of addition of solubilities is applicable to the differentiation of the oxyhemoglobins of not too closely related species.

2. The oxyhemoglobins of the horse, dog, rat, and guinea pig show differences when tested by this method. The oxyhemoglobins of the donkey and horse show a similarity which is best explained by the assumption of isomorphism.
THE NERVOUS MECHANISM OF COORDINATION IN THE CRINOID, ANTEDON ROSACEUS
Authors: Moore A. R.
Published: May 2004

1. Stimulation causes Antedon to swim by means of alternate oral bending and dorsal stroke of the arms. Two arms of a given ray move alternately so that while one is executing the aboral stroke its mate is flexing ventrally. This implies reciprocal inhibition.

2. Recriprocal inhibition between the two arms of an isolated ray can be abolished by the use of either strychnine or nicotine.

3. Coordination between the rays is referable to the conducting properties of the nervous pentagon which connects the five rays. In this system an impulse loses in effectiveness as it passes from the point of origin.

4. When Antedon is made to rest oral face down on the floor of an aquarium, oral flexion of all the rays, swimming movements, and righting result. Antedon is therefore negatively stereotropic with reference to its ventral side.

5. Excitation of the dorsal cirri results in aboral bending of all the rays. Stimulation of the cirri inhibits ventral flexion to the extent of preventing righting movements while on the other hand stimulation of the ventral surface inhibits the grasp reflex of the cirri. Thus oral and aboral sides of Antedon exhibit dynamic symmetry although structurally dissimilar.
HYDROGEN ION CONCENTRATIONS WITHIN THE ALIMENTARY TRACT OF INSECTS
Authors: Crozier W. J.
Published: May 2004

Larvæ of Psychoda and of Chironomus (diptera) maintained in solutions of appropriate indicators show that the typical acidities (pH) prevailing within the several regions of the digestive tract are: esophagus 7.1; cardiac chamber 6.2; mesenteron 7.5; the latter being functionally an intestine. The acidity of the hindgut, pH 6.4, is due to the discharge of the malphigian tubules.
THE RATE OF GROWTH OF THE DAIRY COW
Authors: Brody Samuel , Ragsdale Arthur C.
Published: May 2004

Barring fluctuations due to the cyclic phenomena, the extrauterine course of growth in linear dimensions and in weight of the dairy cow follows an exponential law having the same form as the law representing the course of monomolecular change in chemistry. This suggests the interpretation that the general course of growth is limited by a monomolecular chemical process, and that the cyclic phenomena are due to subsidiary processes in the fundamentally exponential course of growth.

The fact that growth follows or tends to follow an exponential course may be stated more simply as follows: if the unit of time is taken sufficiently large so that fluctuations due to the cyclic phenomena are balanced or eliminated, then the amount of growth made during the given unit of time at any age tends to be a constant percentage of the growth made during the preceding unit of time. Thus, the growth in height at withers made during any year is about 34 per cent of the growth made during the preceding year. Similarly the growth in weight made during any year is about 56 per cent of the growth in weight made during the preceding year. This is in accordance with expectations if it is assumed that each animal begins life with a definite endowment of limiting substance necessary for the process of growth, and that this endowment is used up at a constant rate (or percentage) of itself.
TROPISTIC REACTIONS OF CERIANTHUS MEMBRANACEUS
Authors: Moore Mary Mitchell
Published: May 2004

1. Cerianthus shows stereotropism and if fed regularly will remain indefinitely in glass tubes. The animal retains turgor only so long as the entire surface of the body is in contact with the glass.

2. Cerianthus is positively geotropic as regards the foot and body. It will work upward into a glass tube suspended at an angle of 35° as a result of stereotropism, but if the tube is raised to an angle of 45° the foot turns back and the animal reverses its position in the tube so that foot is down, head, up. Thus at an angle of 45° stereotropism and geotropism very nearly balance each other.

3. Light increases the muscle tone of Cerianthus; this results in positive phototropism. I x t = K. where I is the intensity of the light, t is exposure time, and K, a constant, = 0.46. Where reaction time is considered, I (t + k) = K, in which I is intensity of light, t is reaction time, k = 0.25, and K = 28.29. The two equations prove the operation of the Bunsen-Roscoe law.
THE KINETICS OF TRYPSIN DIGESTION
Authors: Northrop John H.
Published: May 2004

The rate of hydrolysis of edestin by trypsin at 40° and in the presence of 1 M NaCl has been studied. Under these conditions the enzyme is rapidly inactivated and the equation for the reaction may be written

See PDF for Equation

in which Et is the concentration of enzyme during the interval (T1–T2). This equation has been tested by determining the enzyme concentration at various times during the reaction and substituting these values in the above equation. The experimental results agree with this formula when the initial enzyme or edestin concentrations are varied. No anomalous results of varying substrate concentrations are apparent.

It can further be assumed as a first approximation that the enzyme is decomposing monomolecularly and the equation can then be written

See PDF for Equation

This equation is also satisfactory provided high enzyme concentrations and low edestin concentrations are used. With high concentrations of edestin and low trypsin the effects of the products of the reaction on the enzyme become too large to be neglected and the formula no longer holds.
THE ULTIMATE UNITS IN PROTEIN SOLUTIONS AND THE CHANGES WHICH ACCOMPANY THE PROCESS OF SOLUTION OF PROTEINS
Authors: Loeb Jacques , Kunitz M.
Published: May 2004

1. The experiments show that suspensions of finely divided particles of insoluble proteins incapable of swelling in acid (denatured egg albumin, casein trichloroacetate, sulfate, etc.) raise the viscosity of the suspension but little and that the influence of acid on the viscosity is negligible.

2. The same is true for solutions of certain genuine proteins such as genuine crystalline egg albumin.

3. In contrast with these are proteins which swell in acid. It can be shown that where acid swelling of particles occurs, the viscosity is of a higher order of magnitude than where the swelling of particles is impossible and that the influence of acid on viscosity runs in these cases parallel to the influence of acid on swelling. This is shown to be the case for casein in HCl.

4. It is shown that the swelling of the powdered particles which determines the high order of viscosity varies according to the theory of membrane equilibria.

5. These results are used to ascertain with the aid of viscosity measurements whether the ultimate units of genuine protein in solutions are aggregates large enough to give rise to a Donnan equilibrium; or whether they consist of particles below this limit; and in what porportion the two kinds of units are contained in the solution.

6. It is found on the basis of viscosity measurements that when 1 gm. of isoelectric casein is dissolved in HCl so that the solution has a pH of 2.45, more than one-half of 1 gm. of casein must exist as units too small to give rise to a Donnan equilibrium, while the rest must exist in units still capable of undergoing swelling in acid.
THE MECHANISM OF VITAL STAINING WITH BASIC DYES
Authors: McCutcheon Morton , Lucre Baldwin
Published: May 2004

1. Solutions containing NH4OH and NaOH, and CO2 and HCl may be used to produce various combinations of extracellular and intracellular reactions in starfish eggs, Gonionemus, and Nitella cells.

2. Staining by basic dyes is, with a constant intracellular reaction, favored by increased extracellular alkalinity. With a constant extracellular reaction, staining is hindered by increased intracellular alkalinity.

3. These facts are in opposition to the view that staining of cells by basic dyes is chiefly governed by a combination of the dyes with cell proteins. It is more in harmony with the view that the combination is with a substance or substances of acid nature.
VALENCY RULE AND ALLEGED HOFMEISTER SERIES IN THE COLLOIDAL BEHAVIOR OF PROTEINS
Authors: Kunitz M.
Published: May 2004

A detailed study was made on the influence of salts on those physicochemical properties of sodium gelatinate which are regulated by Donnan's law of membrane equilibria; namely, osmotic pressure, membrane potentials, and swelling. It was found that the influence of salts on these properties in the case of sodium gelatinate obeys the same rules of valency as in the case of the influence of salts on gelatin chloride as discussed in a previous publication. The rules state that when a salt is added to an ionized protein, without causing a change in the hydrogen ion concentration of the protein, the general effect is a depression of the mentioned properties. The degree of depression depends not only on the concentration of the salt but on the electrical properties of the ions constituting the salt. Of the two or more oppositely charged ions of which a salt consists, only the valency of those ions which carry charges opposite to those carried by the protein ions affects the degree of depression which increases with the valency of the ions.

It was also found that the phenomenon of swelling of gelatin becomes modified by solubility of the gelatin when salts are added in concentrations higher than N/4. Emphasis is laid on the point that the valency rule holds perfectly also in relation to swelling as long as the phenomenon is pure swelling which is the case when salt solutions of concentrations lower than N/4 are added to gelatin.
THE LOCUS OF THE ACTION OF VERATRIN
Authors: Wible Charles L.
Published: May 2004

1. In Mnemiopsis veratrin shows two stages of veratrin poisoning. First, inhibition of the beats of the plates which disappears on cutting them away either singly or in small groups. Second, after half an hour mechanical stimulation excites the beat of the plates in the intact veratrinized animal. It is concluded that veratrin acts on nervous tissue and not on the substance of the swimming plates.

2. In Lumbricus, veratrin acts on the ventral nerve cord alone, and not on the muscles and peripheral nerves.

3. In Musca, veratrin first causes opisthotonos, then spasms and extreme flexion of the legs. Decapitation causes these effects to disappear hence veratrin acts on the cerebral ganglia of the fly.

4. Veratrin applied to the sciatic nerve of the frog causes, after a latent period of 20 minutes, irregular contractions of the gastrocnemius which persist for an hour or more. Veratrin is thus a neurophil alkaloid of the first class as well as second and in this way resembles tetraethyl ammonium chloride.

5. If the end of a sciatic nerve is dipped into veratrin solution, then direct stimulation of the gastrocnemius muscle results in contraction with delayed relaxation, although the muscle itself is not subject to the action of veratrin.

6. By means of preparations of the sartorius muscle of the frog it is shown that veratrin acts not on the muscle cells directly but on the nerve fibers. Hence veratrin produces the characteristic muscle curve showing delayed relaxation by its action on the nervous elements.
A NOTE ON THE SIMILARITIES BETWEEN THE CURVES OF GROWTH AND OF REGENERATION
Authors: Brody Samuel
Published: May 2004

The curves of growth and of regeneration follow the same course, and can be represented by the same exponential equation. This is taken to substantiate the theory that growth and regeneration are essentially identical processes governed by the same laws.

A common peculiarity of the curves of growth and of regeneration is that during a short period in the early stages of regeneration and of growth, the apparent observed speed of these processes seems to be relatively slow. As a result, the curve of the fitted equation cuts the time axis not at zero, the beginning of growth or regeneration, but somewhat later. Data on regeneration are cited indicating that the initial slow phase of regeneration is due to the time required for the formation of a cap of embryonic cells which serves as a basis for the more active later regeneration; in other words, to qualitative growth which cannot be expressed in terms of quantitative units. It is suggested that the apparent initial slow phase of growth of the individual from the fertilized egg is due to a similar qualitative growth. It is suggested that if the initial qualitative changes could be converted into some common unit with the subsequent quantitative changes, the apparent initial lag would disappear, and the exponential equation representing the course of these processes would then be the same as the equation used to represent the course of a monomolecular chemical reaction.

Certain implications of this reasoning are discussed in the text.
GROWTH OF MAIZE SEEDLINGS AS AFFECTED BY GLUCOKININ AND INSULIN
Authors: Eyster W. H. , Ellis M. M.
Published: May 2004

1. Solutions of glucokinin and insulin, particularly those from which the easily dialyzable substances had been removed, increased the growth of roots and tops of young maize seedlings, as shown by comparisons with untreated seedlings grown in distilled water.

2. Strong solutions of crude glucokinin or of crude insulin repressed growth.

3. Seedlings from which the tips of the primary roots had been removed just before placing the plants in the test solutions made greater gains in both top growth and root growth than seedlings with uncut roots treated with solutions of the same strength. Control experiments showed that this difference in growth was not the result of cutting the roots, and that crude glucokinin and crude insulin contained several substances some of which were more readily absorbed by the plant than others.

4. Purification of crude glucokinin and crude insulin by dialysis showed that the residue of relatively non-dialyzable substance was the growth-promoting fraction.

5. The dialysate of crude glucokinin contained at least three types of material, one of which repressed growth.

6. Ammonium sulfate, one of the possible impurities of glucokinin, repressed the growth of seedlings but did not produce the other changes in metabolism shown by seedlings treated with dialysate of onion glucokinin.

7. The endosperm of plants treated with growth-promoting solutions of purified insulin did not lose weight as rapidly as the endosperms of untreated plants, indicating that the treated plants made their greater gains in growth by more efficient utilization of the endosperm, or as a result of greater photosynthetic activity, or by a combination of these.

8. Experiments with albino seedlings suggested that the greater gain in weight made by plants treated with insulin was the result in part of increased photosynthetic activity.
PHOTOCHEMISTRY OF VISUAL PURPLE
Authors: Hecht Selig
Published: May 2004

It is shown that the velocity of bleaching of visual purple by light, under comparable conditions of concentration, volume, and surface exposed, is directly proportional to the intensity.
THE SOLUBILITY OF TYROSINE IN ACID AND IN ALKALI
Authors: Hitchcock David I.
Published: May 2004

Measurements have been made of the solubility at 25°C. of tyrosine in hydrochloric acid and in sodium hydroxide solutions varying from 0.001 to 0.05 M, and also in distilled water. The pH of the saturated solutions was measured with the hydrogen electrode. The following values for the ionization constants of tyrosine have been obtained from the measurements: kb = 1.57 x 10–12, ka1 = 7.8 x 10–10, ka2 = 8.5 x 10–11. The changes in solubility with pH can be satisfactorily explained by the use of these ionization constants.
APPLICATION OF THE DIFFUSION HYPOTHESIS TO MEMBRANE POTENTIALS
Authors: Murray Cecil D.
Published: May 2004

A system consisting of two aqueous solutions, containing equal concentrations of lactic acid, but different concentrations of Na lactate, separated by a layer of amyl alcohol has been described. This system exhibits electrical properties ranging (as the concentration of NaL is increased) from those characteristic of a simple Donnan equilibrium to those characteristic of simple diffusion.

The fact that the Donnan P.D. can be treated as a special case of a diffusion potential has been emphasized.

The experiments call attention to the effect of the thermodynamic properties of the membrane, and it is suggested that such properties as conductivities, ionic mobilities, and distribution coefficients in membranes of any sort should be investigated.

The experiments afford an interesting example of "phase reversal."
Voltage Clamp Experiments on Single Muscle Fibers of Rana pipiens
Authors: Moore L. E.
Published: May 2004

A voltage clamp for single muscle fibers has been developed. Stability of the system was achieved when an artificial node was created by enclosing a single muscle fiber in a petroleum jelly seal which served as an analogue of the myelin sheath. Typical voltage clamp records were obtained with large inward transient currents followed by a delayed rectification of the outward currents. These currents looked qualitatively similar when the transverse tubular system was destroyed. Errors in current measurement, especially those due to anomalous rectification, are discussed.
Voltage-Dependent Conductance Induced in Thin Lipid Membranes by Monazomycin
Authors: Muller Robert U. , Finkelstein Alan
Published: May 2004

When present in micromolar amounts on one side of phospholipid bilayer membranes, monazomycin (a positively charged, polyene-like antibiotic) induces dramatic voltage-dependent conductance effects. Voltage clamp records are very similar in shape to those obtained from the potassium conductance system of the squid axon. The steady-state conductance is proportional to the 5th power of the monazomycin concentration and increases exponentially with positive voltage (monazomycin side positive); there is an e-fold change in conductance per 4–6 mv. The major current-carrying ions are univalent cations. For a lipid having no net charge, steady-state conductance increases linearly with KCl (or NaCl) concentration and is unaffected by Ca++ or Mg++. The current-voltage characteristic which is normally monotonic in symmetrical salt solutions is converted by a salt gradient to one with a negative slope-conductance region, although the conductance-voltage characteristic is unaffected. A membrane treated with both monazomycin and the polyene antibiotic nystatin (which alone creates anion-selective channels) displays bistability in the presence of a salt gradient. Thus monazomycin and nystatin channels can exist in parallel. We believe that many monazomycin monomers (within the membrane) cooperate to form a multimolecular conductance channel; the voltage control of conductance arises from the electric field driving monazomycin molecules at the membrane surface into the membrane and thus affecting the number of channels that are formed.
The Role of Oxidized Nicotinamide Adenine Dinucleotide in Fluoride Inhibition of Active Sodium Transport in Human Erythrocytes
Authors: Millman Marshall S. , Omachi Akira
Published: May 2004

The rate coefficient for 22Na release from previously labeled human erythrocytes was determined in the presence of 0.1–10 mM sodium fluoride (F). The oxidized nicotinamide adenine dinucleotide (NAD+) level at the end of 2 hr of incubation in tris(hydroxymethyl)aminomethane (Tris)-Ringer medium was also measured. Both parameters decreased proportionately as F concentration was raised. Both F-induced changes were immediate and were reversed by 10 mM pyruvate. The decrease in NAD+ concentration following enolase inhibition by F is attributed to a diminished rate of formation in the reaction catalyzed by lactic dehydrogenase (LDH) with undiminished continued utilization in the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase (GAPDH). It is postulated that the NAD+ lowering limited the GAPDH step, resulting in proportionate decreases in the rates of phosphoglycerate kinase (PGK) and Na,K-dependent adenosine triphosphatase (Na,K-ATPase), a reaction sequence thought to link glycolysis with active Na extrusion. Adding pyruvate with F increased NAD+ production at the LDH step, thus reactivating GAPDH, PGK, and Na,K-ATPase and leading to the observed restoration of 22Na release. The results suggest, therefore, that F inhibits active Na transport in intact human erythrocytes indirectly through a lowering of NAD+, although, direct inhibition of the Na,K-ATPase by F may possibly occur simultaneously.
Alanine Efflux across the Serosal Border of Turtle Intestine
Authors: Hajjar J.J. , Khuri R.N. , Curran Peter F.
Published: May 2004

The exit of alanine across the serosal border of the epithelial cells of turtle intestine was measured by direct and indirect techniques. A decrease or an increase in cell Na did not affect the amino acid flux from cell to serosal solution. Cells loaded with Na and alanine did not exhibit any extrusion of alanine when their serosal membranes were exposed to an Na-free medium containing alanine. However, substantial amino acid extrusion was observed across the mucosal cell border under similar conditions. Although alanine flux across the serosal membrane appeared to be Na-independent, it showed a tendency toward saturation as cellular alanine concentration was elevated. The results are consistent with the postulate that the serosal and mucosal membranes of intestinal cells are asymmetrical with respect to amino acid transport mechanisms. The serosal membrane appears to have an Na-independent carrier-mediated mechanism responsible for alanine transport while transport across the mucosal border involves an Na-dependent process.
The Structure of Mytilus Smooth Muscle and the Electrical Constants of the Resting Muscle
Authors: Twarog Betty M. , Dewey Maynard M. , Hidaka Tohoru
Published: May 2004

The individual muscle fibers of the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. are uninucleate, 1.2–1.8 mm in length, 5 µm in diameter, and organized into bundles 100–200 µm in diameter, surrounded by connective tissue. Some bundles run the length of the whole muscle. Adjacent muscle cell membranes are interconnected by nexuses at frequent intervals. Specialized attachments exist between muscle fibers and connective tissue. Electrical constants of the resting muscle membrane were measured with intracellular recording electrodes and both extracellular and intracellular current-passing electrodes. With an intracellular current-passing electrode, the time constant τ, was 4.3 ± 1.5 ms. With current delivered via an extracellular electrode τ was 68.3 ± 15 ms. The space constant, λ, was 1.8 mm ± 0.4. The membrane input resistance, Reff, ranged from 23 to 51 MΩ. The observations that values of τ depend on the method of passing current, and that the value of λ is large relative to fiber length and diameter are considered evidence that the individual muscle fibers are electrically interconnected within bundles in a three-dimensional network. Estimations are made of the membrane resistance, Rm, to compare the values to fast and slow striated muscle fibers and mammalian smooth muscles. The implications of this study in reinterpreting previous mechanical and electrical studies are discussed.
Impedance of Membrane and Myoplasm during the Action Potential of Frog Muscle
Authors: Freygang W. H. , Gunn R.
Published: May 2004

The transient imbalance of a Wheatstone bridge was used to estimate the changes in both membrane and myoplasmic impedance that occurred as an action potential propagated over a 1 mm length of a frog muscle fiber. It was also used to estimate the changes in the membrane impedance alone. Alterations in myoplasmic impedance that might have been predicted were not found.
The Myofilament Lattice: Studies on Isolated Fibers
Authors: April Ernest W. , Brandt Philip W.
Published: May 2004

The effect of ionic strength on the generation of tension and upon the interfilament spacing in living intact and skinned single striated muscle fibers from the walking leg of crayfish (Orconectes) were determined by isometric contraction studies correlated with low-angle X-ray diffraction. Sarcomere lengths were determined by light diffraction. Tensions were induced in intact fibers by caffeine in the bathing medium and by ionophoretic microinjection of calcium. Tensions were induced in skinned fibers by a buffered calcium-EGTA solution. The interfilament spacing of intact and skinned fibers over the range of ionic strengths investigated were determined by X-ray diffraction and correlated with the physiological data. It is demonstrated that the ionic strength affects the tension-generating capacity of the muscle as it affects the chemo-mechanical transform of excitation-contraction coupling. It is further demonstrated that interfilament spacing changes encountered during shortening and with variation in the osmotic strength have no effect upon the tension-generating capacity of muscle.
Potassium Channels in Myelinated Nerve
Authors: Hille Bertil
Published: May 2004

The permeability of K channels to various cations is studied in myelinated nerve. Ionic currents under voltage clamp are measured in Ringer solution containing tetrodotoxin and a high concentration of the test ion. Reversal potentials for current in K channels are determined and used with the Goldman-Hodgkin-Katz equation to calculate relative permeabilities. The ratios PTl:PK:PRb:PNHNH4 are 2.3:1.00:0.92:0.13. No other ions are found to be measurably permeant including Li+, Na+, Cs+, methylamine, guanidine, hydrazine, or hydroxylamine. The ratio PNa/PK is less than 0.01. Potassium conductance is depressed at pH values below 5.0. Leakage conductance is higher in K, Rb, Cs, NH4, and Tl Ringer than in Na Ringer, but the selectivity sequence probably is not the same as for K channels. The hypothesis is offered that the narrowest part of the K channel is a circle of oxygen atoms about 3 Å in diameter with low electrostatic field strength.
Early Receptor Potential Evidence for the Existence of Two Thermally Stable States in the Barnacle Visual Pigment
Authors: Minke B. , Hochstein S. , Hillman P.
Published: May 2004

The early receptor potential (ERP) in the barnacle photoreceptor is shown by intracellular recording to exhibit a strong dependence on the color of the stimulus and of the preceding adaptation. The adaptation effects appear to be stable for at least 3 h in the dark. Most strikingly, the ERP is positive after red adaptation and mainly negative after blue adaptation. The simplest hypothesis which accounts for these observations is that two thermally stable pigment states with different absorption spectra contribute to the ERP. All ERP responses appear to be consistent with the sums of different ratios of the ERP's of the two pure states. The relative populations of the two states are shown to vary reciprocally, suggesting that the two are states of the same closed pigment cycle. Both states have approximately Dartnall nomogram-shaped absorption spectra, one peaked near 495 nm, and the other near 532 nm.
Dog Red Blood Cells
Authors: Parker John C.
Published: May 2004

Dog red blood cells (RBC) lack a ouabain-sensitive sodium pump, and yet they are capable of volume regulation in vivo. The present study was designed to find in vitro conditions under which dog RBC could transport sodium outward, against an electrochemical gradient. Cells were first loaded with sodium chloride and water by preincubation in hypertonic saline. They were then incubated at 37°C in media containing physiologic concentrations of sodium, potassium, chloride, bicarbonate, glucose, and calcium. The cells returned to a normal salt and water content in 16–20 h. Without calcium in the medium the cells continued slowly to accumulate sodium. Removal of glucose caused rapid swelling and lysis, whether or not calcium was present. The net efflux of sodium showed a close relationship to medium calcium over a concentration range from 0 to 5 mM. Extrusion of salt and water was also demonstrated in fresh RBC (no hypertonic preincubation) when calcium levels in the media were sufficiently raised. The ion and water movements in these experiments were not influenced by ouabain or by removal of extracellular potassium. Magnesium could not substitute for calcium. It is concluded that dog RBC have an energy-dependent mechanism for extruding sodium chloride which requires external calcium and is quite distinct from the sodium-potassium exchange pump.
Anion Conductance of Frog Muscle Membranes: One Channel, Two Kinds of pH Dependence
Authors: Woodbury J. W. , Miles P. R.
Published: May 2004

Anion conductance and permeability sequences were obtained for frog skeletal muscle membranes from the changes in characteristic resistance and transmembrane potential after the replacement of one anion by another in the bathing solution. Permeability and conductance sequences are the same. The conductance sequence at pH = 7.4 is Cl- Br- > NO3- > I- > trichloroacetate ≥ benzoate > valerate > butyrate > proprionate > formate > acetate ≥ lactate > benzenesulfonate ≥ isethionate > methylsulfonate > glutamate ≥ cysteate. The anions are divided into two classes: (a) Chloride-like anions (Cl- through trichloroacetate) have membrane conductances that decrease as pH decreases. The last six members of the complete sequence are also chloride like. (b) Benzoate-like anions (benzoate through acetate) have conductances that increase as pH decreases. At pH = 6.7 zinc ions block Cl- and benzoate conductances with inhibitory dissociation constants of 0.12 and 0.16 mM, respectively. Chloride-like and benzoate-like anions probably use the same channels. The minimum size of the channel aperture is estimated as 5.5 x 6.5 Å from the dimensions of the largest permeating anions. A simple model of the channel qualitatively explains chloride-like and benzoate-like conductance sequences and their dependence on pH.
Functional Organization of the Cardiac Ganglion of the Lobster, Homarus americanus
Authors: Mayeri Earl
Published: May 2004

External recording and stimulation, techniques were used to determine which neurons and interactions are essential for production of the periodic burst discharge in the lobster cardiac ganglion. Burst activity can be modulated by brief single shocks applied to the four small cells, but not by similar stimulation of the five large cells, suggesting that normally one or more small cells primarily determine burst rate and duration. Repetitive electrical stimulation of large cells initiates spike activity in small cells, probably via excitatory synaptic and/or electrotonic connections which may normally act to prolong bursts and decrease burst rate. Transection of the ganglion can result in burst activity in small cells in the partial or complete absence of large cell spike activity, but large cells isolated from small cell excitatory synaptic input by transection or by application of dinitrophenol do not burst. Generally, transections which decrease excitatory feedback to small cells are accompanied by an increase in burst rate, but mean spike frequency over an entire burst cycle stabilizes at the original level within 10–30 min for various groups of cells whose spike-initiating sites are still intact. These and previous results suggest that the system is two layered: one or more small cells generate the burst pattern and impose it on the large cells which are the system's motorneurons.
K Permeability of Nitella clavata in the Depolarized State
Authors: Kitasato Hiroshi
Published: May 2004

Membrane current responses to sudden potential changes were recorded in solutions of various [K]o on 52 internodal cells of Nitella clavata. The membrane current after sudden depolarization had a component sensitive to [K]o which increased with time from 0.3 to 2.0 s and remained steady thereafter. This late current became zero at values of E and [K]o which suggests that the current was nearly all carried by K+. The potassium conductivity represented by this current increased with depolarization, with a half-maximum value at about -70 mV, and saturation at about -30 to -20 mV. The potassium conductance also increased with increasing [K]o, but less rapidly than predicted for constant potassium permeability. This failure of the conductance to increase with [K]o was relatively the same at all membrane potentials and may be explained by a model with a finite number of channels. No attempt was made to model the dependence of gK on time after depolarization or on membrane potential. However, the finding that the membrane potential did not affect the way in which the permeability depended on [K]o suggests that the membrane potential change does not affect the affinity of the sites, and that the increase in gK with time after depolarization is brought about by an increase in the number of channels with such sites.
Interaction of External K, Na, and Cardioactive Steroids with the Na-K Pump of the Human Red Blood Cell
Authors: Sachs John R.
Published: May 2004

The interaction of extracellular Na (Nao), K (Ko), and strophanthidin with the Na-K pump of the human red blood cell has been investigated. Inhibition by submaximal concentrations of strophanthidin rapidly reaches a level which does not increase further over a relatively long period of time. Under these circumstances, it is possible to apply a steady-state kinetic analysis to the interaction of Nao, Ko, and strophanthidin with the pump. In Na-free solutions, strophanthidin increases the apparent K1/2 of the pump for Ko, but does not change the form of the relation between the reciprocal of the active K influx (iMKP–1) and the reciprocal of [Ko] ([Ko]–1); the relation both in the presence and absence of strophanthidin is adequately described by a straight line. In solutions containing Na, strophanthidin changes the form of the curve describing the relation between iMKP–1 vs. [Ko]–1; the curve becomes more parabolic in solutions containing strophanthidin. The rate of ouabain binding to K-free cells has also been measured; in the absence of K, the rate of binding is unaffected by Nao. The data are considered in terms of a simple kinetic model.

The findings can be explained if it is supposed that at low external K the form of the pump combined with one Nao is more likely to combine with strophanthidin than is the uncombined form of the pump. The uncombined form of the pump is more likely to combine with K even at very low Ko than with strophanthidin.
Chemical Characterization and Pronase Susceptibility of the Na:K Pump-Associated Phosphoprotein of Human Red Blood Cells
Authors: Knauf Philip A. , Proverbio Fulgencio , Hoffman Joseph F.
Published: May 2004

The phosphoproteins formed by incubation of red cell ghosts with [γ-32P]ATP in the presence of Mg and Na + Mg have been characterized by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The 32P-labeled phosphoprotein was seen as a single peak confined to the region of the diffuse 90,000 dalton polypeptide band; labeling with Na + Mg considerably increased the quantity of 32P-phosphoprotein contained in this band relative to labeling with Mg alone. Treatment of intact cells with Pronase known to partially hydrolyze the glycoproteins and the 90,000 daltons polypeptide did not change either the amount or the position of the 32P-phosphoprotein present in the gels. The molecular weight of the 32P-phosphoprotein is estimated to be 103,000. Pronase treatment of intact cells also did not significantly alter any of the transport parameters of the membrane such as the K pump flux, ouabain binding, or Na,K-ATPase. In contrast, treatment of ghosts with Pronase not only resulted in drastic alteration of the transport parameters but also inhibited the formation of the phosphoprotein under all conditions. Thus, while the Na:K pump is not intrinsically resistant to Pronase, those elements of the pump which are susceptible are not accessible from the outside of the cell. Further, SDS-polyacrylamide gel electrophoresis after Pronase treatment of intact cells results in a substantial increase in the purification of the phosphoprotein relative to that which was previously possible in ghosts.
Ionic Strength and the Contraction Kinetics of Skinned Muscle Fibers
Authors: Thames Marc D. , Teichholz Louis E. , Podolsky Richard J.
Published: May 2004

The influence of KCl concentration on the contraction kinetics of skinned frog muscle fibers at 5–7°C was studied at various calcium levels. The magnitude of the calcium-activated force decreased continuously as the KCl concentration of the bathing solution was increased from 0 to 280 mM. The shortening velocity at a given relative load was unaffected by the level of calcium activation at 140 mM KCl, as has been previously reported by Podolsky and Teichholz (1970. J. Physiol. [Lond.]. 211: 19), and was independent of ionic strength when the KCl concentration was increased from 140 to 280 mM. In contrast, the shortening velocity decreased as the KCl concentration was reduced below 140 mM; the decrease in velocity was enhanced when the fibers were only partially activated. In the low KCl range, the resting tension of the fibers increased after the first contraction cycle. The results suggest that in fibers activated at low ionic strength some of the cross bridges that are formed are abnormal in the sense that they retard shortening and persist in relaxing solution.
Longitudinal Impedance of Skinned Frog Muscle Fibers
Authors: Mobley Bert A. , Leung J. , Eisenberg R. S.
Published: May 2004

Longitudinal impedance of skinned muscle fibers was measured with extracellular electrodes and an oil gap method in which a central longitudinal section of fiber is insulated by oil while the ends of the fiber are bathed in conducting pools of relaxing solution. Intact single fibers were isolated from frog semitendinosus muscle and the sarcolemma removed either by mechanical or chemical methods. Stray capacitance across the oil gap was measured after each experiment and its admittance subtracted from the admittance of the fiber and oil gap. Effects of impedance at the ends of the fiber were eliminated by measuring the impedance with two lengths of fiber in the oil gap and subtracting the impedance at the shorter length from that at the longer length. Longitudinal impedance so determined for mechanically and chemically skinned fibers exhibited zero phase shift from 1 to 10,000 Hz, i.e., the longitudinal impedance of skinned fibers is purely resistive. If we assume that our skinned fibers are a model of the sarcoplasm of muscle, we conclude that the equivalent circuit of the sarcoplasm is a resistor.
Light-Induced Changes in Photoreceptor Membrane Resistance and Potential in Gecko Retinas
Authors: Pinto L. H. , Pak W. L.
Published: May 2004

The time-course of the light-induced changes in membrane voltage and resistance were measured for single photoreceptors in the retina of Gekko gekko. In the surgically isolated retina, small stimuli directed toward the impaled receptor produced a membrane hyperpolarization the time-course of which was identical to that of the increase in membrane resistance. In the eyecup preparation nearly identical time-courses were evoked only after perfusion of the vitreous surface with solution having high (Mg++). Disparate time-courses were obtained in (a) the isolated retina when large or displaced stimuli were used, and (b) the eyecup preparation when it was treated normally (see Pinto and Pak. 1974. J. Gen. Physiol. 64:49) and when it was exposed to aspartate ions or hypoxia. These results are consistent with the hypothesis that the receptor potential (elicited in the impaled receptor as a result of quanta only it captures) is generated by a single ionic process that decreases membrane conductance. These measurements provide a means to distinguish the receptor potential from interactions. From direct measurements of membrane time constant and total resistance in darkness, total membrane capacitance was calculated. The mean capacitance was 7.1 x 10-5 µF. This high value is consistent with anatomical observations of membrane infoldings at the base of gecko photoreceptors.
Associative Training of Hermissenda
Authors: Alkon Daniel L.
Published: May 2004

Reflex behavior of Hermissenda in response to visual and rotational stimuli is described. It is shown that repeated association of light with rotation modifies the subsequent responses of the animals to light. This modification does not occur after the same period of light or rotation alone. The effect of the associative training is strongly dependent on the amount of daily light with which the animals are maintained.
Short Circuiting of the Ocular Oxygen Concentrating Mechanism in the Teleost Salmo gairdneri Using Carbonic Anhydrase Inhibitors
Authors: Fairbanks Michael B. , Hoffert J. Russell , Fromm Paul O.
Published: May 2004

Ocular oxygen concentration by the process of counter current multiplication in rainbow trout (Salmo gairdneri) was rapidly suppressed after intraperitoneal injections of the carbonic anhydrase inhibitor CL-11,366. The rapidity with which this drug acted suggested a short circuiting of the choroidal rete mirabile. A comparison was made between the time after injection of inhibitor at which oxygen concentrating ability was lost to the time after injection of inhibitor at which its presence in red blood cells, choroidal rete, pseudobranch, and retinal tissue was first noted. A scheme for the possible role of carbonic anhydrase from each of these tissues in the process of ocular oxygen concentration is given.