bluuebunny/crossref_metadata_2025 huggingface dataset:
MICRURGICAL STUDIES IN CELL PHYSIOLOGY
Authors: Reznikoff Paul
Published: May 2004

I. Plasmalemma.

1. The order of toxicity of the salts used in these experiments on the surface membrane of a cell, taking as a criterion viability of amebæ immersed in solutions for 1 day, is HgCl2, FeCl3> AlCl3> CuCl2> PbCl2> FeCl2.

Using viability for 5 days as a criterion, the order of toxicity is PbCl2> CuCl2> HgCl2> AlCl3> FeCl3> FeCl2.

2. The rate of toxicity is in the order FeCl3> HgCl2> AlCl3> FeCl2> CuCl2> PbCl2.

3. The ability of amebæ to recover from a marked tear of the plasmalemma in the solutions of the salts occurred in the following order: AlCl3> PbCl2> FeCl2> CuCl2> FeCl3> HgCl2.

II. Internal Protoplasm.

4. The relative toxicity of the salts on the internal protoplasm, judged by the recovery of the amebæ from large injections and the range over which these salts can cause coagulation of the internal protoplasm, is in the following order: PbCl2> CuCl2> FeCl3> HgCl2> FeCl2> AlCl3.

5. AlCl3 in concentrations between M/32 and M/250 causes a marked temporary enlargement of the contractile vacuole. FeCl2, FeCl3, and CuCl3 produce a slight enlargement of the vacuole.

6. PbCl2, in concentrations used in these experiments, appears to form a different type of combination with the internal protoplasm than do the other salts.

III. Permeability.

7. Using the similarity in appearance of the internal protoplasm after injection and after immersion to indicate that the surface is permeable to a substance in which the ameba is immersed, it is concluded that AlCl3 can easily penetrate the intact plasmalemma. CuCl2 also seems to have some penetrating power. None of the other salts studied give visible internal evidence of penetrability into the ameba.

IV. Toxicity.

8. The toxic action of the chlorides of the heavy metals used in these experiments, and of aluminum, is exerted principally upon the surface of the cell and is due not only to the action of the metal cation but also to acid which is produced by hydrolysis.
HUMAN GROWTH CURVE
Authors: Davenport Charles B.
Published: May 2004

The human growth curve shows two (and only two) outstanding periods of accelerated growth—the circumnatal and the adolescent.

The circumnatal growth cycle attains great velocity, which reaches a maximum at the time of birth. The curve of this cycle is best fitted by a theoretical skew curve of Pearson's Type I. It has a theoretical range of 44 months and a standard deviation of 5.17 months. The modal velocity is 10.2 kilos per year.

The adolescent growth cycle has less maximum velocity and greater range in time than the circumnatal cycle. The best fitting theoretical curve is a normal frequency curve ranging over about 10 years with a standard deviation of about 21 months and a modal velocity of 4.5 kilos per year.

The two great growth accelerations are superimposed on a residual curve of growth which measures a substratum of growth out of which the accelerations arise. This probably extends from conception to 55 years, on the average. It is characterized by low velocity, averaging about 2 kilos per year from 2 to 12 years. It is interpreted as due to many growth operations coincident or closely blending in time.

Our curve shows no third marked period of acceleration at between the 3rd and 6th years.

The total growth in weight of the body is the sum of the weight of its constituent organs. In some cases these keep pace with the growth of the body as a whole; great accelerations of body growth are due to great accelerations in growth of the constituent organs. In other cases one of the organs of the body (like the thymus gland) may undergo a change in weight that is not in harmony with that of the body as a whole.

The development of the weight in man is the resultant of many more or less elementary growth processes. These result in two special episodes of growth and numerous smaller, blending, growth operations.

Hypotheses are suggested as to the basis of the special growth accelerations.
THE EFFECT OF ENZYME PURITY ON THE KINETICS OF TRYPTIC HYDROLYSIS
Authors: Merrill Henry Baldwin
Published: May 2004

The rates of digestion of keratose have been determined with three commercial enzymes, ranging widely in strength. It has been found that the weaker the enzyme preparation, the more nearly does the course of the hydrolysis conform to that of a reaction of the first order. This has been explained on the assumption that in solution an equilibrium exists between active enzyme, and enzyme combined with inert material. In very impure enzyme preparations, the large quantities of combined enzyme act as a reservoir for active enzyme, maintaining a constant concentration of active enzyme during the course of the digestion.
SOME PHYSICOCHEMICAL PROPERTIES OF DISSOCIATED SPONGE CELLS
Authors: Galtsoff P. S. , Pertzoff Vladimir
Published: May 2004

1. The activity of the hydrogen ion, in a system containing 0.00280 mols of NaAc, 0.520 mols of NaCl per liter, and varied amounts of HCl or NaOH has been investigated. The average value of pK' for acetic add in this system is about 4.37.

2. The effect of the addition of various amounts of HCl and NaOH to a system containing 0.00280 mols of NaAc, 0.520 mols of NaCl, and a known number of cells of either Microciona prolifera or Cliona celata was then studied. It was found that in weak acid solutions Microciona behaves as a stronger base than Cliona, the former being practically saturated with base at a pH of 7.5. Similar behavior is shown by suspensions of cells to which no acid or base was added: the cells of Cliona are more acidic than the cells of Microciona.

3. The microscopic examinations of the cells subjected to the treatment with acid or base indicate that the cells of Microciona remain alive down to pH 4.50; the cells of Cliona sustain greater acidity,— a,t pH 3.7 they exhibit no signs of cytolysis. Tests for aggregation of these cells showed that this phenomenon is greatly inhibited even by slightly acid solutions.

4. The conclusion is drawn that the concentration of cells being equal, the suspensions of cells of Microciona and Cliona differ from each other in their physicochemical properties, the comparison being made on suspensions of specified composition.
REGULATION OF THE HYDROGEN ION CONCENTRATION AND ITS RELATION TO METABOLISM AND RESPIRATION IN THE STARFISH
Authors: Irving Laurence
Published: May 2004

The normal reaction of the cœlomic fluid in Patiria miniata and Asterias ochraceus is pH 7.6, and of the cæca, 6.7, compared with sea water at 8.3, all without salt error correction. A medium at pH 6.7–7.0 is optimum for the cæca for ciliary survival and digestion of protein, and is maintained by carbon dioxide production. The optimum pH found for carbon dioxide production is a true one for the effect of hydrogen ion concentration on the tissue. It does not represent an elimination gradient for carbon dioxide.

Because the normal excised cæca maintain a definite hydrogen ion concentration and change their internal environment toward that as an optimum during life, there exists a regulatory process which is an important vital function.
AMPHOTERIC BEHAVIOR OF COMPLEX SYSTEMS
Authors: Stearn Allen E.
Published: May 2004

Conductivities of sulfanilic acid, lysin, and mixtures of the two were made over a wide pH range, the pH being adjusted by means of phosphate buffers. The actual conductivities of the sulfanilic acid, the lysin, and the mixture were calculated. The difference between the conductivity of the mixture and the sum of the conductivities of the components alone passes through a maximum at a pH theoretically calculable as the isoelectric point of the system.

Certain applications of the results are made to the explanation of the behavior of living tissues.
THE OXIDATION-REDUCTION POTENTIAL OF THE LUCIFERIN-OXYLUCIFERIN SYSTEM
Authors: Harvey E. Newton
Published: May 2004

The oxidation-reduction potential of the Cypridina luciferin-oxyluciferin system determined by a method of "bracketing" lies somewhere between that of anthraquinone 2-6-di Na sulfonate (Eo' at pH of 7.7 = –.22) which reduces luciferin, and quinhydrone (Eo' at pH of 7.7 = +.24), which oxidizes luciferin. Systems having an Eo' value between –.22 and +.24 volt neither reduce oxyluciferin nor oxidize luciferin. If the luciferin-oxyluciferin system were truly reversible considerable reduction and oxidation should occur between –.22 and +.24. The system appears to be an irreversible one, with both "apparent oxidation" and "apparent reduction potentials" in Conant's sense. Hydrosulfites, sulfides, CrCl2, TiCl3, and nascent hydrogen reduce oxyluciferin readily in absence of oxygen but without luminescence.

Luminescence only appears in water solution if luciferin is oxidized by dissolved oxygen in presence of luciferase. Rapid oxidation of luciferin by oxygen without luciferase or oxidation by K3Fe(CN)6 in presence of luciferase but without oxygen never gives luminescence.
PHOTOTROPISM IN YOUNG RATS
Authors: Crozier W. J. , Pincus G.
Published: May 2004

Before the eyelids have opened young rats are negatively heliotropic. They behave very much as does the larva of the blow-fly. The angle of orientation by lights opposed at 180° may be calculated by an equation based upon the elementary requirement of phototropism, namely that orientation is attained when the illumination of bilaterally disposed photoreceptors is equal. The precision of orientation decreases very nearly in proportion to the sum of the logarithms of the acting light intensities, due to photokinetic head movements. When the eyelids are opened, the rats move toward a darkened place in the field of vision, usually toward the shaded region immediately to one side of the lamp house. Therefore, when heliotropic, the rat is not "seeking the dark". The phototropism of these animals may be brought into conflict with their pronounced stereotropism, and the resolution of such conflicts may perhaps be utilized for the investigation of central nervous states.
THE STAGES OF THE PEPTIC HYDROLYSIS OF EGG ALBUMIN
Authors: McFarlane Jennie , Dunbar Violet E. , Borsook Henry , Wasteneys Hardolph
Published: May 2004

1. Most of the products of the peptic hydrolysis of albumin, about 85 per cent of the total N, are primary in the sense that they arise directly from the protein molecule, and undergo no further hydrolysis.

2. A slow secondary hydrolysis, involving about 15 per cent of the total N, occurs in the proteose and simpler fractions primarily split off.

3. Acid metaprotein in peptic hydrolysis arises as a result of the action of acid. It is not an essential stage in the hydrolysis of undenatured albumin.

4. Acid metaprotein is hydrolyzed by pepsin more slowly under comparable conditions than undenatured albumin.
TEMPERATURE AND FREQUENCY OF CARDIAC CONTRACTIONS IN EMBRYOS OF LIMULUS
Authors: Crozier W. J. , Stier T. J. B.
Published: May 2004

Temperature characteristics for frequency of myogenic heart beat in Limulus embryos, before the onset of nervous control of the heart, were found to be 11,500; 16,400; 20,000; 25,500. The two first values are the best established. The different values pertain to the hearts of different individuals outwardly similar, and to the hearts of single embryos in different parts of the temperature range. These values differ from that known in connection with the control of the heart beat through the cardiac ganglion. The occurrence of critical temperatures, also, is not the same in all embryos. These facts are employed in a discussion of temperature relations in pulsating explants of chick myocardium.
GEOTROPIC CREEPING OF YOUNG RATS
Authors: Pincus G.
Published: May 2004

The rate of upward creeping in negatively geotropic rats aged 13 to 14 days is a function of the gravitational stimulus. The rate of upward movement on the creeping plane, like the angle of orientation, is directly proportional to the logarithm of the gravity component. The variability in the speed of creeping decreases in proportion to the logarithm of the gravitational effect. When weights are attached to the animals' tails the rate of upward creeping varies almost directly as the logarithm of the attached weight, and the speed of creeping is still proportional to the angle of upward orientation.
PHOSPHATE ION AS A PROMOTER CATALYST OF RESPIRATION
Authors: Lyon Charles J.
Published: May 2004

The active component of phosphate solutions, in relation to promoter action on oxidising enzymes, is the PO4''' ion. This is shown by the demonstration of a hyperbolic relationship between per cent production of CO2 (of Elodea) and pPO4, the measure of the phosphate ion potential. This is consistent with the rate of respiration as affected by changing pPO4 through change of total phosphate concentration while pH is kept constant. The equation for this relationship is

(CO2 – a) (pPO4 – b)n = K

where a, b, n, and K are constants and n = 1.

The same relationship to phosphate ion concentration, expressed by the equation

(Activity of enzyme) (pPO4)n = K,

where n and K are constants and n varies from 1 to 6 under different conditions, appears to hold for some other enzyme actions, including those of peroxidase and pancreatic lipase.
ARSENATE AS A CATALYST OF OXIDATION
Authors: Lyon Charles J.
Published: May 2004

Arsenate exerts a catalytic effect on the oxidation of pyrogallol by atmospheric oxygen, on the catalytic oxidation of pyrogallol by metallic iron, and on the presumably enzymatic production of CO2 by Elodea canadensis.
TIME RELATIONS OF GROWTH
Authors: Brody Samuel
Published: May 2004

Growth curves consist, in all cases, of two major segments. The first major segment is, in the case of higher animals and plants, made up in turn of several (probably five) shorter segments during each of which growth takes place at a constant percentage rate. The transitions between the successive stages are abrupt, the abruptness being of the order of metamorphosis in cold blooded animals.

It has been made clear in the first paper of this series that the time rate of growth following the major inflection declines at a constant percentage rate.

The junction between the two major segments occurs at puberty in animals and flowering in plants.

The two major segments are not symmetrical about the major inflection. The slope of the segment following the inflection is always less than the slope of the segment preceding the inflection. The major inflection does not occur in the center of the growth curve.

The instantaneous rate of growth at the beginning of growth is of the order of 100–200 per cent per day (i.e. the body weight is doubled in from 7 to 17 hours). It may be mentioned that 2 months after conception the rate of growth in man is only 8 per cent per day. This is contrary to all the published statements. Thus, Minot concluded that growth begins at 1000 per cent per day; Jackson concluded that in man, growth during the 1st month takes place at 57.5 million per cent per month; during the 2nd month 990 per cent per month; during the 3rd month 390 per cent per month (8 per cent per day is only 240 per cent per month). The reason for the discrepancy between the values derived, by the method adopted by the writer, and the values given in the literature is explained by Fig. 1.
THE KINETICS OF EXOSMOSIS OF WATER FROM LIVING CELLS
Authors: McCutcheon Morton , Lucke Baldwin
Published: May 2004

1. The rate of exosmosis of water was studied in unfertilized Arbacia eggs, in order to bring out possible differences between the kinetics of exosmosis and endosmosis.

2. Exosmosis, like endosmosis, is found to follow the equation

See PDF for Equation,

in which a is the total volume of water that will leave the cell before osmotic equilibrium is attained, x is the volume that has already left the cell at time t, and k is the velocity constant.

3. The velocity constants of the two processes are equal, provided the salt concentration of the medium is the same.

4. The temperature characteristic of exosmosis, as of endomosis, is high.

5. It is concluded that the kinetics of exosmosis and endosmosis of water in these cells are identical, the only difference in the processes being in the direction of the driving force of osmotic pressure.
THE ACTIVATION OF STARFISH EGGS BY ACIDS
Authors: Lillie Ralph S.
Published: May 2004

1. Comparison of the rates of activation of unfertilized starfish eggs in pure solutions of a variety of parthenogenetically effective organic acids (fatty acids, carbonic acid, benzoic and salicylic acids, chloro- and nitrobenzoic acids) shows that solutions which activate the eggs at the same rate, although widely different in molecular concentration, tend to be closely similar in CH. The dissociation constants of these acids range from 3.2 x 10–7 to 1.32 x 10–3.

2. In the case of each of the fourteen acids showing parthenogenetic action the rate of activation (within the favorable range of concentration) proved nearly proportional to the concentration of acid. The estimated CH of solutions exhibiting an optimum action with exposures of 10 minutes (at 20°) lay typically between 1.1 x 10–4 M and 2.1 x 10–4 M (pH = 3.7–3.96), and in most cases between 1.6 x 10–4 M and 2.1 x 10–4 M (pH = 3.7–3.8). Formic acid (CH = 4.2 x 10–4 M) and o-chlorobenzoic acid (CH = 3.5 x 10–4 M) are exceptions; o-nitrobenzoic acid is ineffective, apparently because of slow penetration.

3. Activation is not dependent on the penetration of H ions into the egg from without, as is shown by the effects following the addition of its Na salt to the solution of the activating acid (acetic, benzoic, salicylic). The rate of activation is increased by such addition, to a degree indicating that the parthenogenetically effective component of the external solution is the undissociated free acid. Apparently the undissociated molecules alone penetrate the egg freely. It is assumed that, having penetrated, they dissociate in the interior of the egg, furnishing there the H ions which effect activation.

4. Attention is drawn to certain parallels between the physiological conditions controlling activation in the starfish egg and in the vertebrate respiratory center.
A RELATIONSHIP BETWEEN CIRCUMFERENCE AND WEIGHT IN TREES AND ITS BEARING ON BRANCHING ANGLES
Authors: Murray Cecil D.
Published: May 2004

Observation reveals a linear relationship between the logarithm of the circumference of a tree, branch, or leaf stem, and the logarithm of the weight of the tree, branch, or leaf. The bearing of this on the angles of branching in trees is discussed.
MICRURGICAL STUDIES IN CELL PHYSIOLOGY
Authors: Chambers Robert , Pollack Herbert
Published: May 2004

I. Cytoplasm.

1. The normal cytoplasmic pH, colorimetrically determined, of the starfish eggs in the unfertilized, fertilized, and first and second cleavage stages is 6.7 ± 0.1.

2. Cytolysis lowers the pH to a value 5.5 ± 0.1.

3. The cytolyzed material in time assumes the pH of its environing sea water.

4. The acid due to mechanical injury can also be detected in the environment of the egg.

5. Injury to the cytoplasm unaccompanied by visible disintegration causes an increase in acidity which is quickly neutralized.

II. Germinal Vesicle.

6. The intranuclear pH, colorimetrically determined, of the immature Asterias egg is 7.5 ± 0.1.

7. Injury to the nucleus does not change its pH.

8. The spherical nuclear remnant which persists after injury gradually assumes the pH of its environment.

III. Plasmalemma.

9. A dye to which the cell is normally impermeable can penetrate through a tear in the surface from an environment more acid than normal. This may be due to a difference in the formation of the plasmalemma in a normal and an acid medium.
GEOTROPISM OF AGRIOLIMAX
Authors: Wolf Ernst
Published: May 2004

On an inclined glass plate the slug Agriolimax orients and creeps upward or downward. The angle of orientation on the plane (θ) is proportional to the logarithm of the component of gravity in the creeping plane. The coefficient of variability of the measured values of (θ) decreases linearly as the logarithm at the gravity component in the creeping plane increases. The cosine of the angle of orientation decreases almost directly in proportion to the sine of the angle of inclination of the creeping plane to the horizontal, as previously found for young rats (Crozier and Pincus). But a more satisfactory formulation for the present case shows that the sine of the angle of orientation (θ) decreases in direct proportion to the increase of the reciprocal of the sine of the angle of inclination of the creeping plane. This formulation is derived from the theory that the geotropic orientation is limited by the threshold difference between the pull of the body mass on the mutually inclined longitudinal muscles at the anterior end of the slug.
THE KINETICS OF DARK ADAPTATION
Authors: Hecht Selig
Published: May 2004

1. Data are presented for the dark adaptation of four species of animals. They show that during dark adaptation the reaction time of an animal to light of constant intensity decreases at first rapidly, then slowly, until it reaches a constant minimum.

2. On the assumption that at all stages of adaptation a given response to light involves a constant photochemical effect, it is possible to describe the progress of dark adaptation by the equation of a bimolecular reaction. This supposes, therefore, that dark adaptation represents the accumulation within the sense cells of a photosensitive material formed by the chemical combination of two other substances.

3. The chemical nature of the process is further borne out by the fact that the speed of dark adaptation is affected by the temperature. The velocity constant of the bimolecular process describing dark adaptation bears in Mya a relation to the temperature such that the Arrhenius equation expresses it with considerable exactness when µ = 17,400.

4. A chemical mechanism is suggested which can account not only for the data of dark adaptation here presented, but for many other properties of the photosensory process which have already been investigated in these animals. This assumes the existence of a coupled photochemical reaction of which the secondary, "dark" reaction is catalyzed by the products of the primary photochemical reaction proper. This primary photochemical reaction itself is reversible in that its main products combine to form again the photosensitive material, whose concentration controls the behavior of the system during dark adaptation.
STUDIES ON ENZYME ACTION
Authors: Noyes Helen Miller , Lorberblatt I. , Falk K. George
Published: May 2004

The ester-hydrolyzing actions of trout extracts at different hydrogen ion concentrations were studied. It was pointed out that the behavior was similar to that found with various tissue and tumor materials and that similar relations hold.

Glycerol solutions extracted somewhat larger amounts of active enzyme material from trout than did water and sodium chloride solutions, although the differences were not large. Evidence was presented for the existence of a so called "coenzyme."
STUDIES ON THE AMOUNT OF LIGHT EMITTED BY MIXTURES OF CYPRIDINA LUCIFERIN AND LUCIFERASE
Authors: Stevens Kenneth P.
Published: May 2004

1. A photometric method was devised for measuring the intensities of light emitted per cc. of hiciferin solution and calculating the amount of light emitted per gm. of dried Cypridina powder. A total of 128 runs was made and the data are incorporated in this report.

2. The maximum amount of light emitted from 1 gm. of powder under the experimental conditions was 0.655 lumens. Different samples of powder vary greatly in amount of light production.

3. When the concentration of substrate is doubled, nearly twice as much light is emitted, or an average ratio 2C/C of 1.86. Calculations of total light emissions per gm. of powder at different concentrations indicate that slightly more light is produced from the smaller concentrations. The maximum amount of light was produced by the solutions made with neutral sea water and averaged 0.445 lumens. The least light was obtained from solutions in distilled water saturated with hydrogen. The technique allows too rapid spontaneous oxidation prior to the saturation with hydrogen. The maximum amount of light from such experiments was only 0.077 lumens. Acid sea water solutions subsequently neutralized gave an average maximum of 0.386 lumens per gm. of powder per second.

4. When the concentration of enzyme is doubled, approximately the same amount of light is produced by both concentrations, although the stronger concentrations are slightly less effective than weaker ones. This undoubtedly is due to the colloidal nature of the enzyme and is a function of surface rather than of mass. In dilute solutions greater dispersion probably allows for greater adsorption to the surface of the enzyme. The average maximum amount of light produced in the series of enzyme experiments is of the magnitude 0.56 lumens per gm. of powder.
THE KINETICS OF OSMOSIS
Authors: Northrop John H.
Published: May 2004

It is shown that by combining the osmotic pressure and rate of diffusion laws an equation can be derived for the kinetics of osmosis.

The equation has been found to agree with experiments on the rate of osmosis for egg albumin and gelatin solutions with collodion membranes.
THE SWELLING OF ISOELECTRIC GELATIN IN WATER
Authors: Northrop John H. , Kunitz M.
Published: May 2004

It has been assumed that gelatin consists of a network of an insoluble material enclosing a solution of a more soluble material.

The swelling of gelatin is therefore primarily an osmotic phenomena in that the water tends to diffuse in owing to the osmotic pressure of the soluble material. This osmotic pressure is opposed by the elasticity of the insoluble constituent, and equilibrium results when these two pressures are equal.

The rate of the entrance of water should then obey Poiseuille's law, provided the variable terms are expressed as functions of the volume. Equations have been derived in this way which agree quite well with the experimental curves and which predict the proper relation between the size and shape of the block and the rate of swelling. They lead to a value for the rate of flow of water through gelatin which has been checked by direct measurement.

The mechanism assumed predicts that at a higher temperature and under conditions such that the water has to pass through collodion before reaching the gelatin, the experiment should follow the same course as that of osmosis discussed previously. This was also found to be the case.

The slow secondary increase in swelling is ascribed to fatigue of the elastic properties of the gelatin. The rate of this secondary swelling should therefore be independent of the size of the block, in contrast to the rate of primary swelling which is inversely proportional to the size. It can further be shown that this secondary swelling should be proportional to the square root of the time, and also that with large blocks at higher temperatures the entire swelling should be of this secondary type. These predictions have also been found to be true.
UDDER SIZE IN RELATION TO MILK SECRETION
Authors: Gowen John W. , Tobey Elmer R.
Published: May 2004

The results herein presented furnish exact critical evidence for the conclusion that the most of the milk is present as such in the udder of dairy cattle at the time of milking. The amount of milk which may be secreted during milking cannot, on the basis of these results, be over 20 per cent of the milk yield of the cow.

The results show clearly that the size of the udder measures closely the amount of milk which the cow is able to secrete.

The results indicate that about 1/5 of a pound of secreting tissue is necessary for the secretion of a pound of milk during a period of 15 hours. The weight of the udder during the period that the cow is dry appears to be between 6 and 8 pounds.
THE EFFECT OF TEMPERATURE UPON SOME OF THE PROPERTIES OF CASEIN
Authors: Pertzoff Vladimir
Published: May 2004

1. The investigations dealing with the properties of casein as an acid were reviewed.

2. The solubility of uncombined casein in water was measured at 5°C. and found to be 0.70±0.1 mg. of N per 100 gm. of water.

3. Robertson's solubility measurements of casein in bases at various temperatures were recalculated and found to agree well with more recent measurements.

4. By combining the observations of several investigators, as well as the author's measurements of the solubility of casein, in base, at various temperatures, the following conclusions were reached:

(a) The solubility of casein in base is affected by the temperature in a discontinuous manner.

(b) There exist two ranges of temperature, one, extending from about 21° to 37°C. and the other from about 60° to 85°C. where the solubility of casein in base is practically independent of temperature.

(c) From 37° to 60° the equivalent combining weight of casein rises from the value 2100 to about 3700 gm.

5. By comparing the values of base bound by 1 gm. of casein at the two temperature ranges with a constant, the value of base necessary to saturate the same amount of casein, it was found that the latter value is a common multiple of the former values, indicating the stoichiometric nature of the effect of temperature.
Potassium channel types in arterial chemoreceptor cells and their selective modulation by oxygen.
Authors: Ganfornina M D , López-Barneo J
Published: May 2004

Single K+ channel currents were recorded in excised membrane patches from dispersed chemoreceptor cells of the rabbit carotid body under conditions that abolish current flow through Na+ and Ca2+ channels. We have found three classes of voltage-gated K+ channels that differ in their single-channel conductance (gamma), dependence on internal Ca2+ (Ca2+i), and sensitivity to changes in O2 tension (PO2). Ca(2+)-activated K+ channels (KCa channels) with gamma approximately 210 pS in symmetrical K+ solutions were observed when [Ca2+]i was greater than 0.1 microM. Small conductance channels with gamma = 16 pS were not affected by [Ca2+]i and they exhibited slow activation and inactivation time courses. In these two channel types open probability (P(open)) was unaffected when exposed to normoxic (PO2 = 140 mmHg) or hypoxic (PO2 approximately 5-10 mmHg) external solutions. A third channel type (referred to as KO2 channel), having an intermediate gamma(approximately 40 pS), was the most frequently recorded. KO2 channels are steeply voltage dependent and not affected by [Ca2+]i, they inactivate almost completely in less than 500 ms, and their P(open) reversibly decreases upon exposure to low PO2. The effect of low PO2 is voltage dependent, being more pronounced at moderately depolarized voltages. At 0 mV, for example, P(open) diminishes to approximately 40% of the control value. The time course of ensemble current averages of KO2 channels is remarkably similar to that of the O2-sensitive K+ current. In addition, ensemble average and macroscopic K+ currents are affected similarly by low PO2. These observations strongly suggest that KO2 channels are the main contributors to the macroscopic K+ current of glomus cells. The reversible inhibition of KO2 channel activity by low PO2 does not desensitize and is not related to the presence of F-, ATP, and GTP-gamma-S at the internal face of the membrane. These results indicate that KO2 channels confer upon glomus cells their unique chemoreceptor properties and that the O2-K+ channel interaction occurs either directly or through an O2 sensor intrinsic to the plasma membrane closely associated with the channel molecule.
pH regulation in adult rat carotid body glomus cells. Importance of extracellular pH, sodium, and potassium.
Authors: Wilding T J , Cheng B , Roos A
Published: May 2004

The course of intracellular pH (pHi) was followed in superfused (36 degrees C) single glomus (type I) cells of the freshly dissociated adult rat carotid body. The cells had been loaded with the pH-sensitive fluorescent dye 2',7'-(2-carboxyethyl)-5 (and -6)-carboxyfluorescein. The high K(+)-nigericin method was used for calibration. The pHi of the glomus cell at pHo 7.40, without CO2, was 7.23 +/- 0.02 (n = 70); in 5% CO2/25 mM HCO3-, pHi was 7.18 +/- 0.08 (n = 9). The pHi was very sensitive to changes in pHo. Without CO2, delta pHi/delta pHo was 0.85 (pHo 6.20-8.00; 32 cells), while in CO2/HCO3- this ratio was 0.82 irrespective of whether pHo (6.80-7.40; 14 cells) was changed at constant PCO2 or at constant [HCO3-]o. The great pHi sensitivity of the glomus cell to pHo is matched only by that of the human red cell. An active Na+/H+ exchanger (apparent Km = 58 +/- 6 mM) is present in glomus cells: Na+ removal or addition of the amiloride derivative 5-(N,N-hexamethylene)-amiloride induced pHi to fall by as much as 0.9. The membrane of these cells also contains a K+/H+ exchanger. Raising [K+]o from 4.7 to 25, 50, or 140 mM reversibly raised pHi by 0.2, 0.3, and 0.6, respectively. Rb+ had no effect, but in corresponding concentrations of Tl+ alkalinization was much faster than in K+. Reducing [K+]o to 1.5 mM lowered pHi by 0.1. These pHi changes were shown not to be due to changes in membrane voltage, and were even more striking in the absence of Na+. Intrinsic buffering power (amount of strong base required to produce, in the nominal absence of CO2, a small pHi rise) increased from 3 to approximately 21 mM as pHi was lowered, but remained nearly unchanged below pHi 6.60. The fitted expression assumed the presence of one "equivalent" intracellular buffer (pK 6.41, 41 mM). The exceptional pHi sensitivity to pHo suggests that the pHi of the glomus cell is a link in the chemoreceptor's response to external acidity.
Grayanotoxin-I-modified eel electroplax sodium channels. Correlation with batrachotoxin and veratridine modifications.
Authors: Duch D S , Hernandez A , Levinson S R , Urban B W
Published: May 2004

To probe the structure-function relationships of voltage-dependent sodium channels, we have been examining the mechanisms of channel modification by batrachotoxin (BTX), veratridine (VTD), and grayanotoxin-I (GTX), investigating the unifying mechanisms that underlie the diverse modifications of this class of neurotoxins. In this paper, highly purified sodium channel polypeptides from the electric organ of the electric eel were incorporated into planar lipid bilayers in the presence of GTX for comparison with our previous studies of BTX (Recio-Pinto, E., D. S. Duch, S. R. Levinson, and B. W. Urban. 1987. J. Gen. Physiol. 90:375-395) and VTD (Duch, D. S., E. Recio-Pinto, C. Frenkel, S. R. Levinson, and B. W. Urban. 1989. J. Gen. Physiol. 94:813-831) modifications. GTX-modified channels had a single channel conductance of 16 pS. An additional large GTX-modified open state (40-55 pS) was found which occurred in bursts correlated with channel openings and closings. Two voltage-dependent processes controlling the open time of these modified channels were characterized: (a) a concentration-dependent removal of inactivation analogous to VTD-modified channels, and (b) activation gating similar to BTX-modified channels, but occurring at more hyperpolarized potentials. The voltage dependence of removal of inactivation correlated with parallel voltage-dependent changes in the estimated K1/2 of VTD and GTX modifications. Ranking either the single channel conductances or the depolarization required for 50% activation, the same sequence is obtained: unmodified > BTX > GTX > VTD. The efficacy of the toxins as activators follows the same ranking (Catterall, W. A. 1977. J. Biol. Chem. 252:8669-8676).
Proton currents through amiloride-sensitive Na channels in hamster taste cells. Role in acid transduction.
Authors: Gilbertson T A , Avenet P , Kinnamon S C , Roper S D
Published: May 2004

The activity of taste cells maintained in the intact hamster tongue was monitored in response to acid stimulation by recording action currents from taste receptor cells with an extracellular "macro" patch pipette: a glass pipette was pressed over the taste pore of fungiform papillae and perfused with citric acid, hydrochloric acid, or NaCl. Because this technique restricted stimulus application to the small surface area of the apical membranes of the taste cells, many nonspecific, and potentially detrimental, effects of acid stimulation could be avoided. Acid stimulation reliably elicited fast transient currents (action currents of average amplitude, 9 pA) which were consistently smaller than those elicited by NaCl (29 pA). The frequency of action currents elicited by acid stimuli increased in a dose-dependent manner with decreasing pH from a threshold of about pH 5.0. Acid-elicited responses were independent of K+, Na+, Cl-, or Ca2+ at physiological (salivary) concentrations, and were unaffected by anthracene-9-carboxylic acid, tetraethylammonium bromide, diisothiocyanate-stilbene-2,2'-disulfonic acid, vanadate, or Cd2+. In contrast, amiloride (< or = 30 microM) fully and reversibly suppressed acid-evoked action currents. At submaximal amiloride concentrations, the frequency and amplitude of the action currents were reduced, indicating a reduction of the taste cell apical conductance concomitant with a decrease in cell excitation. Exposure to low pH elicited, in addition to transient currents, an amiloride-sensitive sustained d.c. current. This current is apparently carried by protons instead of Na+ through amiloride-sensitive channels. When citric acid was applied while the taste bud was stimulated by NaCl, the action currents became smaller and the response resembled that produced by acid alone. Because of the strong interdependence of the acid and salt (NaCl) responses when both stimuli are applied simultaneously, and because of the similarity in the concentration dependence of amiloride block, we conclude that amiloride-sensitive Na+ channels on hamster taste receptor cells are permeable to protons and may play a role in acid (sour) taste.
Interactions between divalent cations and the gating machinery of cyclic GMP-activated channels in salamander retinal rods.
Authors: Karpen J W , Brown R L , Stryer L , Baylor D A
Published: May 2004

The effects of divalent cations on the gating of the cGMP-activated channel, and the effects of gating on the movement of divalent cations in and out of the channel's pore were studied by recording macroscopic currents in excised membrane patches from salamander retinal rods. The fractional block of cGMP-activated Na+ currents by internal and external Mg2+ as well as internal Ca2+ was nearly independent of cGMP concentration. This indicates that Mg2+ and Ca2+ bind with similar affinity to open and closed states of the channel. In contrast, the efficiency of block by internal Cd2+ or Zn2+ increased in proportion to the fraction of open channels, indicating that these ions preferentially occupy open channels. The kinetics of block by internal Ni2+, which competes with Mg2+ but blocks more slowly, were found to be unaffected by the fraction of channels open. External Ni2+, however, blocked and unblocked much more rapidly when channels were mostly open. This suggests that within the pore a gate is located between the binding site(s) for ions and the extracellular mouth of the channel. Micromolar concentrations of the transition metal divalent cations Ni2+, Cd2+, Zn2+, and Mn2+ applied to the cytoplasmic surface of a patch potentiated the response to subsaturating concentrations of cGMP without affecting the maximum current induced by saturating cGMP. The concentration of cGMP that opened half the channels was often lowered by a factor of three or more. Potentiation persisted after the experimental chamber was washed with divalent-free solution and fresh cGMP was applied, indicating that it does not result from an interaction between divalent cations and cGMP in solution; 1 mM EDTA or isotonic MgCl2 reversed potentiation. Voltage-jump experiments suggest that potentiation results from an increase in the rate of cGMP binding. Lowering the ionic strength of the bathing solution enhanced potentiation, suggesting that it involves electrostatic interactions. The strong electrostatic effect on cGMP binding and absence of effect on ion permeation through open channels implies that the cGMP binding sites on the channel are well separated from the permeation pathway.
Ca(2+)-blockable, poorly selective cation channels in the apical membrane of amphibian epithelia. Tetracaine blocks the UO2(2+)-insensitive pathway.
Authors: Desmedt L , Simaels J , Van Driessche W
Published: May 2004

We examined the effect of the local anesthetic tetracaine on the Ca(2+)-blockable, poorly selective cation channels in the isolated skin of Rana temporaria and the urinary bladder of Bufo marinus using noise analysis and microelectrode impalements. Experiments with frog skin demonstrated that mucosal concentrations of the compound up to 100 microM did not affect the Na+ current through type S channels (slowly fluctuating, UO2(2+)-blockable channels) and the associated noise. On the other hand, 20 microM mucosal tetracaine already suffices to inhibit approximately 50% of the current carried by Cs+ and Na+ through channel type F (fast fluctuating, UO2(2+)-insensitive channel) and So of the associated Lorentzian component. With 100 microM of the inhibitor the current and So values were reduced by at least 70-80%. The time course of the response to serosal tetracaine was markedly slower and the effects on the current and So were smaller. Possible effects on the basolateral K+ conductance were excluded on the basis of the lack of response of transepithelial K+ movements to 100 microM tetracaine. UO2(2+) and tetracaine together blocked the poorly selective cation pathways almost completely. Moreover, both agents retain their inhibitory effect in the presence of the other. In toad urinary bladder, the Ca(2+)-blockable channel is also tetracaine blockable. The concentration required for half-maximal inhibition is approximately 100 microM in SO4(2-) and approximately 20 microM in Cl-. The data with tetracaine complement those obtained with UO2(2+) and support the idea that the Ca(2+)-blockable current proceeds through two distinct classes of cation channels. Using tetracaine and UO2(2+) as channel-specific compounds, we demonstrated with microelectrode measurements that both channel types are located in the granulosum cells.
Charge movement by the Na/K pump in Xenopus oocytes.
Authors: Rakowski R F
Published: May 2004

Pre-steady-state transient currents (1986. Nakao, M., and D. C. Gadsby. Nature [Lond.]. 323:628-630) mediated by the Na/K pump were measured under conditions for Na/Na exchange (K-free solution) in voltage-clamped Xenopus oocytes. Signal-averaged (eight times) current records obtained in response to voltage clamp steps over the range -160 to +60 mV after the addition of 100 microM dihydroouabain (DHO) or removal of external Na (control) were subtracted from test records obtained before the solution change. A slow component of DHO- or Na-sensitive difference current was consistently observed and its properties were analyzed. The quantity of charge moved was well described as a Boltzmann function of membrane potential with an apparent valence of 1.0. The relaxation rate of the current was fit by the sum of an exponentially voltage-dependent reverse rate coefficient plus a voltage-independent forward rate constant. The quantity of charge moved at the on and off of each voltage pulse was approximately equal except at extreme negative values of membrane potential where the on charge tended to be less than the off. The midpoint voltage of the charge distribution function (Vq) was shifted by -24.8 +/- 1.7 mV by changing the external [Na] in the test condition from 90 to 45 mM and by +14.7 +/- 1.7 mV by changing the test [Na] from 90 to 120 mM. A pseudo three-state model of charge translocation is discussed in which Na+ is bound and occluded at the internal face of the enzyme and is released into an external-facing high field access channel (ion well). The model predicts a shift of the charge distribution function to more hyperpolarized potentials as extracellular [Na] is lowered; however, several features of the data are not predicted by the model.
Depolarization-activated potentiation of the T fiber synapse in the blue crab.
Authors: Lin J W , Llinas R
Published: May 2004

The blue crab T fiber synapse, associated with the stretch receptor of the swimming leg, has a nonspiking presynaptic element that mediates tonic transmission. This synapse was isolated and a voltage clamp circuit was used to control the membrane potential at the release sites. The dependence of transmitter release on extracellular calcium, [Ca]o, was studied over a range of 2.5-40 mM. A power relationship of 2.7 was obtained between excitatory postsynaptic potential (EPSP) rate of rise and [Ca]o. Brief presynaptic depolarizing steps, 5-10 ms, presented at 0.5 Hz activated EPSP's of constant amplitude. Inserting a 300-ms pulse (conditioning pulse) between these test pulses potentiated the subsequent test EPSPs. This depolarization-activated potentiation (DAP) lasted for 10-20 s and decayed with a single exponential time course. The decay time course remained invariant with test pulse frequencies ranging from 0.11 to 1.1 Hz. The magnitude and decay time course of DAP were independent of the test pulse amplitudes. The magnitude of DAP was a function of conditioning pulse amplitudes. Large conditioning pulses activated large potentiations, whereas the decay time constants were not changed. The DAP is a Ca-dependent process. When the amplitude of conditioning pulses approached the Ca equilibrium potential, the magnitude of potentiation decreased. Repeated application of conditioning pulses, at 2-s intervals, did not produce additional potentiation beyond the level activated by the first conditioning pulse. Comparison of the conditioning EPSP waveforms activated repetitively indicated that potentiation lasted transiently, 100 ms, during a prolonged release. Possible mechanisms of the potentiation are discussed in light of these new findings.