bluuebunny/crossref_metadata_2025_split huggingface dataset:
TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHT
Authors: Crozier W. J. , Wolf Ernst 
Published: May 2004

For the sunfish Enneacanthus the mean value of the critical illumination for response to visual flicker at constant flash frequency (with light time = dark time) is related to temperature by the Arrhenius equation. The temperature characteristic for 1/Im is different above and below 20°C. In each range (12° to 20°; 20° to 30°) the temperature characteristic is the same for rod and cone segments of the duplex flicker response contour: 8,200 and 14,400. This makes it difficult, if not impossible, to consider that the two groups of elements are organized in a significantly different way chemically. For the presumptively rod-connected elements implicated in response to flicker, the curve is markedly discontinuous, so that the high and low temperature parts are dislocated; whereas for the cones they are not. This is entirely consistent with other (e.g., genetic) evidence pointing to their separate physical substrata.
The uncommon exhibition of a higher µ over a higher range of temperature, previously found, however, in a few cases, together with the different relations of rod and cone effects to the critical temperature, explain aspects of these data which in earlier incomplete measurements were found to be puzzling.
THE KINETICS OF PENETRATION
Authors: Jacques A. G. 
Published: May 2004

The accumulation of ammonia takes place more rapidly in light than in darkness. The accumulation appears to go on until a steady state is attained. The steady state concentration of ammonia in the sap is about twice as great in light as in darkness. Both effects are possibly due to the fact that the external pH (and hence the concentration of undissociated ammonia) outside is raised by photosynthesis.
Certain "permeability constants" have been calculated. These indicate that the rate is proportional to the concentration gradient across the protoplasm of NH4X which is formed by the interaction of NH3 or NH4OH and HX, an acid elaborated in the protoplasm. The results are interpreted to mean that HX is produced only at the sap-protoplasm interface and that on the average its concentration there is about 7 times as great as at the sea water-protoplasm interface. This ratio of HX at the two surfaces also explains why the concentration of undissociated ammonia in the steady state is about 7 times as great in the sea water as in the sap. The permeability constant P''' appears to be greater in the dark. This is possibly associated with an increase in the concentration of HX at both interfaces, the ratio at the two surfaces, however, remaining about the same.
The pH of sap has been determined by a new method which avoids the loss of gas (CO2), an important source of error. The results indicate that the pH rises during accumulation but the extent of this rise is smaller than has hitherto been supposed.
As in previous experiments, the entering ammonia displaced a practically equivalent amount of potassium from the sap and the sodium concentration remained fairly constant.
It seems probable that the pH increase is due to the entrance of small amounts of NH3 or NH4OH in excess of the potassium lost as a base.
THE ELECTRICAL IMPEDANCE OF MUSCLE DURING THE ACTION OF NARCOTICS AND OTHER AGENTS
Authors: Guttman Rita 
Published: May 2004

1. The effect of certain inorganic cations upon the electrical impedance of the sartorius muscle of the frog was investigated. While Na, K, and Mg have little effect upon the resistance of muscle, Ba and Ca cause it to fall. The use of physiologically "unbalanced" salt solution does not in itself seem to affect muscle impedance.
2. The time course of the effect upon muscle impedance of the penetration of substances into the intercellular spaces was studied by treating the muscle with sugar solutions. Half of the effect is over in three-quarters of a minute when the sugar solution is permitted to circulate past both sides of the muscle. This sets an upper limit for the time necessary for inorganic cations and organic narcotics to reach the cell surfaces. The action of inorganic cations and organic narcotics upon muscle is slow compared to the time necessary for them to reach the scene of action.
The penetration of the sugar solutions into the intercellular spaces of muscle was found to follow the well known diffusion law, the amount diffusing in being proportional to the square root of the time.
Average values of 77.7 per cent for ρ, the volume concentration of fibers; 231 ohms specific resistance for r2, the resistance of the interior of the fibers; and 71.0° for θ, the phase angle of the impedance locus, were obtained for the muscle in Ringer's solution. How these values change when the muscle is placed in various concentrations of sugar was also studied.
3. The action of a number of organic narcotics upon muscle was studied. All decrease 1000 cycle resistance if the concentration is sufficiently high. A detailed analysis of the action of the narcotic, iso-amyl carbamate, was made, and it was noted that low concentrations increase resistance while higher concentrations decrease it.
By investigating the effect of narcotics upon muscle impedance over a wide frequency range, it was found that during narcosis the resistance of the fiber membranes first increases and then decreases, and, if the drug is present in sufficiently great concentration, membrane resistance may completely disappear. Membrane capacity is only very slightly affected.
FACTORS LIMITING BACTERIAL GROWTH
Authors: Hershey A. D. 
Published: May 2004

Simple assumptions have led to equations by which the latent period in multiplication and the bacterial numbers expected at any time during the phase of rapid growth may be predicted.
Experimental data obtained under rather diverse conditions have given satisfactory agreement with calculated values. Since the mathematical expressions contain no arbitrary constants, more than accidental significance must be attached to this agreement.
The hypotheses set forth appear completely to describe the early development of Bacterium coli and Bacterium dysenteriae in broth, without postulating differences other than size among individual cells, or cells obtained under different conditions.
REGENERATION OF VISUAL PURPLE IN SOLUTION
Authors: Chase Aurin M. , Smith Emil L. 
Published: May 2004

1. Measurements of visual purple regeneration in solution have been made by a procedure which minimized distortion of the results by other color changes so that density changes caused by the regenerating substance alone are obtained.
2. Bleaching a visual purple solution with blue and violet light causes a greater subsequent regeneration than does an equivalent bleaching with light which lacks blue and violet. This is due to a photosensitive substance which has a gradually increasing effective absorption toward the shorter wavelengths. It is uncertain whether this substance is a product of visual purple bleaching or is present in the solution before illumination.
3. The regeneration of visual purple measured at 560 mµ is maximal at about pH 6.7 and decreases markedly at more acid and more alkaline pH's.
4. The absorption spectrum of the regenerating material shows only a concentration change during the course of regeneration, but has a higher absorption at the shorter wavelengths than has visual purple before illumination.
5. Visual purple extractions made at various temperatures show no significant difference in per cent of regeneration.
6. The kinetics of regeneration is usually that of a first order process. Successive regenerations in the same solution have the same velocity constant but form smaller total amounts of regenerated substance.
7. In vivo, the frog retina shows no additional oxygen consumption while visual purple is regenerating.
INCREASE IN BACTERIOPHAGE AND GELATINASE CONCENTRATION IN CULTURES OF BACILLUS MEGATHERIUM
Authors: Northrop John H. 
Published: May 2004

1. The increase in bacteria, phage concentration, and gelatinase concentration in cultures of B. megatherium has been determined.
2. With lysogenic cultures the phage concentration, gelatinase concentration, and bacteria concentration increase logarithmically at first. The phage and gelatinase concentration then decrease while the bacteria concentration increases to a maximum.
3. The results are the same with sensitive cultures if the ratio of phage to bacteria is small. If the ratio of phage to bacteria is large phage, gelatinase, and bacteria concentration all increase at first and then decrease. The maximum rate of increase coincides approximately with the maximum rate of oxygen consumption of the culture.
4. 60–90 per cent of the phage is free from the cells.
5. The amount of phage produced is determined by the combined phage and not by the total phage.
6. Phage is produced during growth of the cells and not during lysis.
7. In a very narrow range of pH near 5.55 no increase in bacteria occurs but large increases in phage may be obtained.
CHEMICAL PACEMAKERS
Authors: Hadidian Zareh , Hoagland Hudson 
Published: May 2004

1. Iron spicules found in the brains of general paretic patients are formed from endogenous brain iron normally present in another form. This supports our earlier view that the µ value of 16,000 obtained in advanced paretics for alpha brain wave frequencies as a measure of cortical respiration comes about from the slowing of an iron catalyzed link in cortical respiration such as would result from the reduction of available cytochrome and its oxidase, thus making this step a chemical pacemaker.
2. To test the basic theory of chemical pacemakers, a study was made of the succinate-fumarate enzyme system containing succino-dehydrogenase and cytochrome-cytochrome oxidase acting sequentially.
3. The µ value for the unpoisoned system is 11,200 ± 200 calories.
4. According to theory, the addition of a critical amount of cyanide known to be a specific poison of the cytochrome-cytochrome oxidase system (and not of the dehydrogenase) should shift the µ cleanly to 16,000 calories, and it does.
5. According to theory, selenite, a specific poison for the dehydrogenase, should stop all respiration without shifting the µ. This also is found to be the case.
6. The theory also predicts that if the µ is shifted from 11,000 ± to 16,000 ± by cyanide, the subsequent addition of a critical amount of selenite should shift the µ back again to 11,000 ± calories, and this is found to occur.
7. It is concluded that approximately 11,000 calories is the energy of activation of the succino-dehydrogenase-catalyzed step and 16,000 calories is that for the cytochrome-cytochrome oxidase-catalyzed step. These two values are encountered more frequently than any others in physiological systems. It is to be recalled that a shift of µ for alpha brain wave frequencies from 11,000 to 16,000 calories occurs in the course of advancing syphilitic brain infection and is accompanied by a change in form of brain iron.
CALCULATIONS OF BIOELECTRIC POTENTIALS
Authors: Osterhout W. J. V. 
Published: May 2004

Values have been calculated for apparent mobilities and partition coefficients in the outer non-aqueous layer of the protoplasm of Nitella. Among the alkali metals (with the exception of cesium) the order of mobilities resembles that in water and the partition coefficients (except for cesium) follow the rule of Shedlovsky and Uhlig, according to which the partition coefficient increases with the ionic radius.
Taking the mobility of the chloride ion as unity, we obtain the following: lithium 2.04, sodium 2.33, potassium 8.76, rubidium 8.76, cesium 1.72, ammonium 4.05, ½ magnesium 20.7, and ½ calcium 7.52.
After exposure to guaiacol these values become: lithium 5.83, sodium 7.30, potassium 8.76, rubidium 8,76, cesium 3.38, ammonium 4.91, ½ magnesium 20.7, and ½ calcium 14.46.
The partition coefficients of the chlorides are as follows, when that of potassium chloride is taken as unity: lithium 0.0133, sodium 0.0263, rubidium 1.0, cesium 0.0152, ammonium 0.0182, magnesium 0.0017, and calcium 0.02.
These are raised by guaiacol to the following: lithium 0.149, sodium 0.426, rubidium 1.0, cesium 0.82, ammonium 0.935, magnesium 0.0263, and calcium 0.323 (that of potassium is not changed).
The effect of guaiacol on the mobilities of the sodium and potassium ions resembles that seen in Halicystis but differs from that found in Valonia where guaiacol increases the mobility of the sodium ion but decreases that of the potassium ion.
PERFORMANCE OF THE HEPP MICRO-OSMOMETER
Authors: Peters Erich , Saslow George 
Published: May 2004

Estimation of the molecular weight of horse serum albumin from the osmotic pressure of solutions containing 0.713 to 5.12 gm. per 100 cc. shows that the Hepp osmometer yields the same values as the standard simple osmometer of Adair.
Accuracy and precision of the instrument decrease noticeably at concentrations of albumin less than 0.7 gm. per 100 cc.
A determination in duplicate can be carried out with this instrument in less than 2 hours.
The instrument is easily operated.
STUDIES CONCERNING THE NATURE OF THE SECRETORY ACTIVITY OF THE ISOLATED RINGER-PERFUSED FROG LIVER
Authors: Hober Rudolf , Moore Elinor 
Published: May 2004

The ability of the isolated Ringer-perfused frog liver, to concentrate dyestuffs in its secretion several hundred times, can be abolished entirely and reversibly by replacing in the Ringer solution about 1/8 of the NaCl by the isosmotic amount of a surface-inactive non-electrolyte (disaccharide, hexose, pentose, polyhydric alcohol, amino acid, acid amide) or electrolyte (salts of lower fatty acids, hydroxyl carboxylic, and dicarboxylic acids). This effect is not dependent upon changes in the perfusion rate.
The opposite effect, promotion of secretory activity, can be brought about by polar-non-polar electrolytes (salts of higher fatty acids, bile acids, and other aromatic carboxylic acids, aromatic sulfonic acids) and surface-active non-electrolytes (anesthetics, alkaloids, digitonin). However, reversibility of this effect cannot be regularly observed, since cytolysis is frequently the end result.
Suitable concentrations of inhibitory and promoting substances, simultaneously applied, counteract each other.
Inhibitory and promoting substances, in general, exhibit opposite effects upon the dispersion of colloids (starch, lecithin, gelatin).
The correlation between the physicochemical and the physiological action of the organic compounds is discussed.
ON THE PERMEABILITY OF THE STOMACH MUCOSA FOR ACIDS AND SOME OTHER SUBSTANCES
Authors: Teorell Torsten 
Published: May 2004

1. Solutions approximately isotonic with blood of strong and weak acids, several salts, glucose, and glycine were introduced in the resting stomachs of cats. The concentration and volume changes were recorded.
2. It was found that the stomach mucosa was permeable to the majority of the ions tested. There was also a permeability in the opposite direction from the blood (mucosa) to the stomach content, particularly of alkali chlorides. Poorly permeable substances were glucose, glycine, and sodium iodate. Pure weak acids such as acetic acid penetrated very rapidly.
3. The electrolyte concentration changes in the stomach content (or gastric juice) are pictured as an exchange diffusion; for instance, the hydrogen ions of an acid are exchanged against alkali ions of the mucosa or blood.
4. It is pointed out that the concept of the mucosa as an ion permeable membrane could be used as the foundation of a "diffusion theory," which can explain the acidity and chloride variations of the gastric juice without postulating neutralizing or diluting secretions.
A DIFFERENTIAL VOLUMETER FOR MICRO-RESPIRATION MEASUREMENTS
Authors: Thimann Kenneth V. , Commoner Barry 
Published: May 2004

A modified micro-respirometer employing the differential volumeter principle, and mechanical accessories for the same, are described.
The apparatus enables addition of solutions to be made to the biological material during the experiment. It is of a high sensitivity, a drop movement of 1.0 mm. indicating a volume change of about 0.06 c.mm. It may be used with very small amounts of biological material, provides for convenience in manipulation) and allows readings to be made at 1 minute intervals.
Typical results on plant tissue and protozoa are given.
ELECTROPHORESIS OF PEPSIN
Authors: Herriott Roger M. , Desreux Victor , Northrop John H. 
Published: May 2004

1. A number of pepsin solutions containing several protein components have been studied by the electrophoresis method. All samples show a homogeneous boundary moving to the anode at pH 4.4.
2. The activity of this material may be higher than that of the original solution on the basis of total nitrogen but is the same as that of the original solution on the basis of protein nitrogen.
3. There is no separation of the various protein components under these conditions.
4. The apparent isoelectric point at pH 2.7, previously obtained by the collodion particle method is due to the presence of decomposition products. Pure crystalline pepsin, free from decomposition products, is always negatively charged.
TIME-TEMPERATURE RELATIONS IN THE INCUBATION OF THE WHITEFISH, COREGONUS CLUPEAFORMIS (MITCHILL)
Authors: Price John W. 
Published: May 2004

1. Whitefish eggs incubated in aerated lake water at controlled tempera tures of 0°, 0.5°, 2°, 4°, 6°, 8°, 10°, and 12°C., failed to hatch at either 0° or 12°C. 0.6 per cent hatched alive at 10°C., 72.67 per cent hatched alive at 0.5°C., and an intermediate proportion hatched at intermediate temperatures.
2. The percentage of abnormal embryos which developed to the hatching stage varied directly with temperature between 4° and 12°, all embryos being abnormal at 12°C.; but none were abnormal at either 0.5°, or 2°C. Normal development predominated from 0.5 to 6°C. The highest proportion of embryos to hatch alive was 72.67 per cent at 0.5°C., which is, hence, the optimum temperature.
3. Total incubation time ranged from 29.6 days at 10°C. to 141 days at 0.5°C.
4. The time (T) required to attain any given stage of development is expressed in equations
See PDF for Equation
where temperature, t, is a negative exponent of the constant, A, whose value differs above or below 6°C., a critical temperature. Values of A above 6° fluctuate about 1.13; those of A below 6° fluctuate about 1.19 as a mean.
5. Applying Arrhenius' equation µ values for the total incubation period are 27,500 below 6° and 27,100 above it.
6. The relative magnitude of A values of the exponential equation and µ values of Arrhenius' equation show corresponding changes from one developmental period to another.
7. When plotted, thermal increments show cyclic variations, with maxima during periods of cleavage and of organogenesis. These may indicate the interaction of two separate sets of embryonic processes, which give a maximal response to temperature differences during these two separate periods.
8. Above 6°, µ values during the hatching process are distinct from those of developmental stages and are regarded as being due to the action of hatching enzymes.
BIOELECTRIC POTENTIALS IN HALICYSTIS
Authors: Blinks L. R. 
Published: May 2004

The effects of light upon the potential difference across the protoplasm of impaled Halicystis cells are described. These effects are very slight upon the normal P.D., increasing it 3 or 4 per cent, or at most 10 per cent, with a characteristic cusped time course, and a corresponding decrease on darkening.
Light effects become much greater when the P.D. has been decreased by low O2 content of the sea water; light restores the P.D. in much the same time course as aeration, and doubtless acts by the photosynthetic production of O2. There are in both cases anomalous cusps which decrease the P.D. before it rises. Short light exposures may give only this anomaly. Over part of the potential range the light effects are dependent upon intensity.
Increased CO2 content of the sea water likewise depresses the P.D. in the dark, and light overcomes this depression if it is not carried too far. Recovery is probably due to photosynthetic consumption of CO2, unless there is too much present. Again there are anomalous cusps during the first moments of illumination, and these may be the only effect if the P.D. is too low.
The presence of ammonium salts in the sea water markedly sensitizes the cells to light. Subthreshold NH4 concentrations in the dark become effective in the light, and the P.D. reverses to a negative sign on illumination, recovering again in the dark. This is due to increase of pH outside the cell as CO2 is photosynthetically reduced, with increase of undissociated NH3 which penetrates the cell.
Anomalous cusps which first carry the P.D. in the opposite direction to the later drift are very marked in the presence of ammonia, and may represent an increased acidity which precedes the alkaline drift of photosynthesis. This acid gush seems to be primarily within the protoplasm, persisting when the sea water is buffered. Glass electrode measurements also indicate anomalies in the pH drift.
There are contrary cusps on darkening which suggest temporarily increased alkalinity.
Even more complex time courses are given by combining low O2 and NH4 exposures with light; these may have three or more cusps, with reversal, recovery, and new reversal.
The ultimate cause of the light effects is to be found in an alteration of the surface properties by the treatments, which is overcome (low O2, high CO2), or aided (NH4) by light. This alteration causes the surface to lose much of its ionic discrimination, and increases its electrical resistance. Tests with various anion substitutions indicate this, with recovery of normal response in the light.
A theory of the P.D. in Halicystis is proposed, based on low mobility of the organic anions of the protoplasm, with differences in the two surfaces with respect to these, and the more mobile Na and K. ions.
EFFECTS OF HEXYLRESORCINOL ON NITELLA
Authors: Osterhout W. J. V. 
Published: May 2004

In some ways the effects of hexylresorcinol on Nitella resemble those of guaiacol but in others they differ.
Both substances depress the P.D. reversibly and both decrease the potassium effect.
Hexylresorcinol decreases the apparent mobility of Na+ and of K+. Guaiacol increases that of Na+ but not of K+.
The action of hexylresorcinol is more striking than that of guaiacol since 0.0003 M of the former is as effective as 0.03 M of the latter in depressing the P.D.
It is evident that organic substances can change the behavior of inorganic ions in a variety of ways.
THE RELATION BETWEEN FOVEAL VISUAL ACUITY AND ILLUMINATION UNDER REDUCED OXYGEN TENSION
Authors: McFarland R. A. , Halperin M. H. 
Published: May 2004

1. The foveal visual acuity of eleven subjects was studied in relation to illumination under normal atmospheric conditions and at simulated altitudes of 10,000 feet (14.3 per cent O2) and 18,000 feet (10.3 per cent O2). A mask was used to administer the desired mixtures of oxygen and nitrogen. At the end of each experiment, measurements were made while inhaling 100 per cent oxygen from a cylinder. A red filter (No. 70 Wratten) was used so as to study only the behavior of the cones of the retina.
2. The logarithm of illumination was plotted horizontally (abscissa) and the logarithm of visual acuity vertically (ordinate). The reduced oxygen tensions resulted in a shift of the curve to the right, along the intensity axis, the extent of the change being 0.24 of a log unit at 14.3 per cent O2 and 0.47 of a log unit at 10.3 per cent O2. These effects were completely counteracted within a few minutes by inhaling oxygen.
3. As a consequence of the shape of the curve, such a shift to the right resulted in a relatively large decrease of visual acuity at low illuminations. At increasing light intensities anoxia produced less and less change, until at very high illuminations the decrease was negligible. Thus with 10.34 per cent O2 the visual acuity at 0.144 photons decreased an average of 0.344 of a log unit, to 45 per cent of its normal value. At 1320 photons, however, it decreased only 0.026 of a log unit, to 94 per cent of its normal value for that intensity.