bluuebunny/crossref_metadata_2025 huggingface dataset:
CHANGING ELECTRICAL CONSTANTS OF THE FUNDULUS EGG PLASMA MEMBRANE
Authors: Kao C. Y.
Published: May 2004

Electrical constants of the plasma membrane of the Fundulus egg have been measured with microelectrodes by the transient method. No consistent and significant membrane potential was measured. Membrane capacity averages 0.63 µF/cm.2 for both unactivated and activated eggs. Membrane resistance averages 3450 ohm-cm.2 in the unactivated eggs, but increases 2 to 7 times to an average of 13,290 ohm-cm.2 in the fully activated state. In a hypertonic sucrose solution, the swelling of the egg proper is accompanied by a rapid fall of membrane resistance towards that in the unactivated state. The changes of the membrane resistance are interpreted as probably caused by alterations in the effective pore size in the plasma membrane.
AN ADENOSINETRIPHOSPHATE-ACTIVATED HEMOLYTIC SYSTEM
Authors: Borek Blanche Ann , Bovarnick Max
Published: May 2004

1. Hemolyzed rabbit cells contain a factor which lyses human erythrocytes in vitro when Mg++ and certain nucleotides are supplied to the system. Of the nucleotides tested ATP is the most active, although no net loss of ATP or of labile phosphate seems to be associated with the hemolytic process.

2. The lytic factor appears to be a sulfhydryl enzyme which attacks the membrane of the human red cell, its hemolytic activity being inhibited by human stroma.

3. The system is activated by glutathione and is inhibited by heavy metals, oxidized glutathione, cysteine, ergothionine, and a number of metabolic inhibitors. Physostigmine has no effect.

4. Partial purification of the lytic factor has been achieved by fractional centrifugation.
THE ACTION OF ULTRAVIOLET RADIATION ON YEAST CATALASE
Authors: Kaplan J. Gordin , Paik Woon Ki
Published: May 2004

The effect of prolonged UV irradiation (mostly 2537 A) on the catalase activity of an aqueous yeast suspension was divisible into 4 periods. First, the period during which the cells lost their ability to form colonies, but during which no change in catalase activity was noted. Second, the period during which a considerable rise in catalase activity (Euler effect) occurred. The Euler effect was accompanied by enzyme alteration as shown by the simultaneous decrease in the activation energy of the enzyme-substrate system. However, during the initial phase of this period, as the catalase activity of the suspension began to increase, the activation energy rose to a transient level higher even than that characterizing the unaltered enzyme. Heat accelerated the rate of alteration when applied either during or after the irradiation; the activation energy for the over-all alteration reaction was 24 kcal., a value close to that recorded previously for alteration induced by chemical agents. Nevertheless, the rate-limiting step appeared to be different in the two cases. A model of these events was presented in which the primary photochemical action was on the site at which catalase is located within the cell. Third, a rather long period during which irradiation led to no diminution in the catalase activity of the maximally active suspension. This protection effect was duplicated in intro by a model crystalline catalase-KNA system, or by adding either ribonuclease digestion products of RNA or adenine to a catalase solution prior to irradiation. Evidence was adduced that the protection effect was not a simple screening, but involved some sort of interaction between the enzyme and the nitrogenous components of RNA, an interaction which must likewise occur within the cell. Alteration induced by CHCl3 did not eliminate the protection effect, but that by butanol did. The onset of photoinactivation was due to modification of protein structure, not of RNA. Fourth, the period of photoinactivation of the intracellular enzyme, which was quite similar to that of the crystalline enzyme in vitro.
THE INHIBITION OF HEMOLYSIS, AS STUDIED BY THE TECHNIQUE USED FOR INVESTIGATING PROGRESSIVE REACTIONS, AND BY A TECHNIQUE USING RADIOACTIVE HEMOLYSINS
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

Inhibition of hemolysis by plasma has been studied in systems containing saponin, digitonin, and sodium lauryl sulfate, using the methods developed for the study of the kinetics of progressive reactions. The results are that the progressive nature of the hemolytic reaction in saponin systems becomes less when the inhibitor is added, that the addition of inhibitor to digitonin systems has no effect on the final result although the velocity of the progressive reaction is reduced, and that the effect of plasma in lauryl sulfate systems is intermediate between the effects in saponin systems and digitonin systems. A simple explanation is that the lysin is very strongly fixed, to form an internal phase, to the cell surfaces in digitonin systems, less strongly in laurate systems, and still less strongly in saponin systems.

To answer the question as to whether, in a system in which some of the lysin forms as internal phase, the addition of an inhibitor results in a redistribution of the lysin between the internal phase and the bulk phase, sodium lauryl sulfate-S35 and sodium cetyl sulfate-S35 were prepared, and their distribution between the internal phase and the bulk phase was measured before and after the addition of plasma, the lysins being added to the cells either before or after the addition of the inhibitor. The results show that there is a large uptake of these lysins at the red cell surfaces when they are added first, and that the subsequent addition of plasma greatly reduces the quantity of lysin held in the internal phase. Further, if the inhibitor is added first and the lysin subsequently, the internal lysin phase is very incompletely formed.

Serum albumin, used in place of plasma, gives essentially similar results.
PRESSURE-VOLUME RELATIONSHIP OF THE FUNDULUS EGG IN SEA WATER AND IN SUCROSE
Authors: Kao C. Y.
Published: May 2004

Upon activation, an internal hydrostatic pressure develops within the Fundulus egg, and compresses the egg proper to a reduced volume. When the perivitelline pressure is abolished by a highly hypertonic sucrose solution, the egg volume increases. As sucrose penetrates the chorion, the volume again decreases. The relation between P and V in these conditions is inverse, and approximates a rectangular hyperbola. The limiting factor causing most of the deviation is shown to be the incompressible fraction. It is concluded that the volume of the egg proper is controlled by the perivitelline pressure, and that the effect of hypertonic sucrose solution is exerted by lowering the pressure and thereby increasing membrane permeability non-specifically. It is also shown that some permanent alterations occur within the plasma membrane during activation that reduce the permeance, and thereby, increase the incompressible fraction.
THE FREEZING POINT DEPRESSION OF MAMMALIAN TISSUES IN RELATION TO THE QUESTION OF OSMOTIC ACTIVITY OF CELL FLUID
Authors: Brodsky William A. , Appelboom Johannes W. , Dennis Warren H. , Rehm Warren S. , Miley John F. , Diamond Israel
Published: May 2004

The freezing point depression of freshly excised frozen tissues, pulverized in a hydraulic press or in a mortar, is greater than that of plasma. Even at 0°C. the freezing point depression of such homogenates increases significantly with time. Dilution data indicate that such freezing point data are valid. The presence of intact cells has been shown in smears of tissues pulverized in a mortar, but not in smears of those crushed in a hydraulic press. The osmolarity of various diluent solutions affects the calculated osmotic activity of tissue homogenates presumably because of delayed diffusion between the diluent and cell fluid. With a hypertonic NaCl diluent, spuriously low values of tissue osmotic activity are found from calculations assuming instantaneous mixing between homogenates and diluents. The limitations of data from cryoscopic experiments and from tissue-swelling experiments are discussed in relation to the basic question of whether or not cell fluid is isotonic to extracellular fluid.
THE NATURE OF THE GECKO VISUAL PIGMENT
Authors: Crescitelli Frederick
Published: May 2004

Retinal extracts of the Australian gecko, Phyllurus milii (White), have revealed the presence of a photosensitive pigment, unusual for terrestrial animals, because of its absorption maximum at 524 mµ. This pigment has an absorption spectrum which is identical in form with that of other visual chromoproteins. It is not a porphyropsin, for bleaching revealed the presence, not of retinene2, but of retinene1 as a chromophore. Photolabile pigments with characteristics similar to those of the Phyllurus visual pigment were also detected in retinal extracts of six other species of nocturnal geckos.

The presence of this retinal chromoprotein adequately accounts for the unusual visual sensitivity curve described by Denton for the nocturnal gecko. This pigment may have special biological significance in terms of the unique phylogenetic position of geckos as living representatives of nocturnal animals which retain some of the characteristics of their diurnal ancestors. The occurrence of this retinene1 pigment, intermediate in spectral position between rhodopsin and iodopsin, is interpreted in support of the transmutation theory of Walls. The results and interpretation of this investigation point up the fact that, from a phylogenetic point of view, too great an emphasis on the duplicity theory may serve to detract attention from the evolutionary history of the retina and the essential unitarianism of the visual cells.
THE EFFECT OF CHANGES OF ENVIRONMENT ON THE ELECTRICAL AND IONIC PATTERN OF MUSCLE
Authors: Shaw F. H. , Simon Shirley E. , Johnstone B. M. , Holman Mollie E.
Published: May 2004

The resting and action potentials of sartorius muscles of the toad, Bufo marinus, have been measured under varying conditions of external environment. At the same time, analyses for Na+ and K+ content were carried out.

There was a slight elevation of 2 mv. when the measurements were made in phosphate-Ringer instead of in bicarbonate-Ringer. The R.P. was independent of the hydrogen ion concentration between pH 6.5 and 8.5, although at these pH's there was marked alteration in the level of Na+ and K+ in the muscle.

Alteration of the external K+ level between 0 and 50 m.eq./liter has little influence on the internal K+ concentration. When the log of the external K+ concentration is plotted against the R.P. there is not a linear relationship until the external K+ is raised above 12 m.eq./liter, at which point the cell is unexcitable. Above this value a straight line with a slope of 58 mv. per ten-fold change in concentration is obtained, but the absolute values at any point are about 35 per cent higher than those which would be given by the Nernst equation.

Alteration of the external Na+ level within a range of 45 to 650 m.eq./liter resulted in marked changes in the internal Na+ content, without, however, having any effect on the ratio Na+out/Na+in. This ratio has remained at about 3 in spite of marked fluctuations in the absolute value of the internal and external Na+ levels. When the Na+ level is lowered there is a decrease in the height of the action potential although there is no alteration in the ratio Na+out/Na+in. As the Na+ level is raised the height of the action potential is not affected even in the presence of a fivefold increase in Na+ in the Ringer.

The results do not support the conclusion that the bioelectric potentials can be calculated from the ionic ratios by means of simple physical chemical hypotheses such as the Nernst or Goldman equations.

The maintenance of the normal K+ content of the cell cannot be accounted for by a Donnan mechanism. No definite evidence has been produced to explain the mechanism of a Na+ "pump." In other words, the concept of a Na+ pump requires that there shall be a physico- or organochemical mechanism which will distinguish between Na+ and K+ (or other) ions. There is evidence that Na+ can be extruded against a concentration gradient. On the other hand the cell is able to maintain a constant ratio of external to internal Na+ even when the cell has been severely damaged by very high external Na+ levels.
EVIDENCE FOR THERMAL REACTIONS FOLLOWING EXPOSURE OF DIDINIUM TO INTERMITTENT ULTRAVIOLET RADIATIONS
Authors: Giese A. C. , Shepard D. C. , Bennett J. , Farmanfarmaian A. , Brandt C. L.
Published: May 2004

1. The nature of ultraviolet injury and its variation with the same dose given at different intensities and wave lengths have been investigated in the protozoan Didinium nasutum, using time to the fourth division as a measure of injury.

2. The injury has been found to consist of a "slowdown" of division rate, which always occurs, and a "stasis," usually at the second division after irradiation, which appears in varying degrees among more severely injured samples.

3. Injury was found to be almost independent of intensity at three wave lengths out of four studied over a wide range of intermediate and high intensities, but was found to rise sharply with lower intensity at all except the longest wave length.

4. Flashed UV of high intensity is much more effective than the same dose of continuous radiation at high intensity and shorter total time of treatment. It is also more effective than the same dose at low intensity and equal time of treatment, though only slightly so.

5. An increase of injury with rise of temperature and with increase of dark period clearly indicates that injury depends on thermochemical reactions following the absorption of UV in Didinium.

6. The most reasonable assumption is that a similar conclusion applies to other organisms as well, and that its general application may be useful in the investigation of UV effects on protoplasm.
METABOLISM OF EXCISED RAT SKIN IN HYPERTONIC MEDIA
Authors: Fuhrman Frederick A.
Published: May 2004

The rate of oxygen consumption by rat skin is inhibited similarly by hypertonic solutions of NaCl, KCl, and sucrose. The rate of anaerobic glycolysis is inhibited by hypertonic NaCl. The inhibition of QO2 by NaCl concentrations above about 2 osmols per liter is not reversible.
REFLEX DEPRESSION IN RHYTHMICALLY ACTIVE MONOSYNAPTIC REFLEX PATHWAYS
Authors: Lloyd David P. C. , Wilson Victor J.
Published: May 2004

A study has been made of the depression that occurs when a monosynaptic reflex pathway is subjected to repetitive stimulation.

Reflex depression has a dual origin. High frequency or early depression is postsynaptic in origin and results from subnormality in the motoneurons. Low frequency, late, or enduring depression is presynaptic in origin.

The conditioning volley-test volley technique and the frequency-mean monosynaptic reflex amplitude relation yield similar information concerning reflex depression. Each method has its advantages and for some purposes one or the other of the methods necessarily must be employed.

The results of a variety of experiments are consistent with the proposition that reflex depression in the monosynaptic reflex pathway originates by action in the group IA afferent fibers of muscle origin that are responsible for monosynaptic reflex transmission.

Depression is present at a frequency of 0.1 per second (6 per minute) and absent at a frequency of 0.05 per second (3 per minute). Thus it is impractical for most purposes to employ repetition rates that satisfy the requirement for designation as "single shock" stimulations.

The temporal course of enduring depression has been determined. It is identical with that for a number of other phenomena observable in monosynaptic reflex pathways, which suggests a common origin. The mechanism of low frequency or enduring depression is discussed in the light of this suggestion.
TEMPORAL SUMMATION IN RHYTHMICALLY ACTIVE MONOSYNAPTIC REFLEX PATHWAYS
Authors: Lloyd David P. C.
Published: May 2004

Monosynaptic reflex responses elicited by repetitive stimulation in the frequency range between 60 and 100 per second yield evidence of temporal summation.

The relation between stimulus interval and mean monosynaptic reflex response in the steady state at the frequencies studied is described adequately by an exponential decaying to 1/e in 4 msec.

Since the temporal course of spatial summation is described adequately by the same exponential it is concluded that the two phenomena, temporal and spatial, are expressions of the same fundamental process intrinsic to the workings of the monosynaptic reflex pathway, to wit the synaptic potential-residual facilitation mechanism of prior descriptions.

Some discussion of implications is appended.
CHEMICAL TRANSMISSION AND ADAPTATION
Authors: Florey Ernst
Published: May 2004

Acetylcholine and factor I appear to be transmitter substances of excitatory and inhibitory regulatory nerve fibers supplying the sensory neurons of stretch receptor organs of the crayfish.

Sudden application of a low concentration of acetylcholine causes the impulse frequency to jump to a peak value. But immediately the frequency falls again and gradually reaches a steady state which is not far above the previous frequency level. If the acetylcholine is now withdrawn there follows a silent period after which the frequency returns to its original level. The time course of these events is identical with that of adaptations to sudden increase or decrease of stretch.

Factor I in sufficiently low concentrations causes an immediate fall in impulse frequency (silent period) which is followed by a return to a value near the previous frequency level. Withdrawal of factor I is followed by excitation and again return of the frequency to the rate measured before the application of factor I. The time course of these phenomena is identical with that of adaptations to sudden decrease and increase of stretch.

It is suggested that adaptation may be a property not only of sensory neurons but of neurons in general and that even central neurons may be considered as receptor neurons inasmuch as they respond to chemically transmitted excitatory and inhibitory stimuli.
THE COURSE OF RESPIRATION DURING THE LIFE CYCLE OF CHLORELLA CELLS
Authors: Sorokin Constantine , Myers Jack
Published: May 2004

Endogenous and glucose respiration were studied during the life history of Chlorella pyrenoidosa. A generalized picture of the course of respiration during the life cycle is suggested. At the liberation of daughter cells from the wall of the mother cell, or soon after, the respiration rate reaches its lowest level. If the daughter cells are placed in light the respiration rate rapidly increases with time, soon reaches a maximum, and then declines slowly. Two factors are important in the initial increase—the early developmental stage of the cells and the influence of light. In autotrophically developing algae the parts played by developmental processes and by light have not been separated. Direct activation of respiratory enzymes by light, in addition to the level of respiratory substrate, cannot be excluded.

The decline of respiration rate over most of the cell history seems to have no connection with light and is probably bound to the developmental processes per se. Darkening the suspension interrupts growth and induces liberation of daughter cells, with concomitant faster decrease in respiration rate. The rate of respiration of small daughter cells decreases in darkness only slowly with time. Illumination seems necessary to bring these cells back to a high level of respiratory activity.
THE EFFECT OF ULTRAVIOLET AND WHITE LIGHT ON GROWTH RATE, LYSIS, AND PHAGE PRODUCTION OF BACILLUS MEGATHERIUM
Authors: Northrop John H. ,   With the Technical Assistance of Marie King
Published: May 2004

Cultures of megatherium 899a, growing under different conditions, were exposed to ultraviolet or white light.

1. Cultures exposed to ultraviolet light and then to white light continue to grow at the normal rate. Cultures exposed to ultraviolet light and then placed in the dark grow at the normal rate for varying lengths of time, depending on conditions, and then lyse with the liberation of from 5 to 1000 phage particles per cell, depending on the culture medium.

2. Increasing the time of exposure to ultraviolet light results in an increase in the fraction of cells which lyse in the dark. The lysis time decreases at first, remains constant over a wide range of exposure, and then increases. The lysis can be prevented by visible light after short exposure, but not after long exposures.

3. The time required for lysis is independent of the cell concentration.

4. Effect of temperature. After exposure to ultraviolet the cell concentration increases about 4 times at 20°, 30°, or 35°C., but only 1.5 to 2.0 times at 40–45°. This is due to the fact that the growth rate of the culture reaches a maximum at 38° while the lysis rate increases steadily up to 45°.

5. Terramycin decreases the growth rate and lysis rate in proportion.

6. At pH 5.1, the cultures continue to grow slowly in the dark after exposure to ultraviolet light.

7. Megatherium sensitive cells infected with T phage lyse more rapidly than ultraviolet-treated 899a, and visible light does not affect the lysis time.

The results agree with the assumption that exposure to ultraviolet results in the production of a toxic (mutagenic) substance inside the bacterial cell. This substance is inactivated by white light.
MAINTAINED ACTIVITY IN THE CAT'S RETINA IN LIGHT AND DARKNESS
Authors: Kuffler S. W. , Fitzhugh R. , Barlow H. B.
Published: May 2004

Nervous activity has been recorded from the unopened eye of decerebrate cats. Recordings were made with metal electrodes or with small micropipettes from ganglion cells or nerve fibers.

Continuous maintained discharges were seen in all ganglion cells during steady illumination of their receptive fields, as well as in complete darkness. Possible artefacts, such as electrode pressure, abnormal circulation, anesthetic, and several other factors have been excluded as the source of the maintained discharge. Visual stimuli are therefore transmitted by modulating the ever present background activity.

Discharge frequencies were measured following changes of retinal illumination. No consistent patterns of frequency change were found. The maintained discharge frequency may be permanently increased or decreased, or may remain practically unchanged by altering the steady level of illumination. In addition, there were often transient frequency changes during the first 5 to 10 minutes after changing illumination, before a final steady rate was established.

A statistical analysis of the impulse intervals of the maintained discharge showed: (a) the intervals were distributed according to the gamma distribution (Pearson's type III), (b) the first serial correlation coefficient of the intervals was between –0.10 and –0.24, with a mean value of –0.17, which is significantly different from zero, (c) the higher order serial correlation coefficients were not significantly different from zero. Thus the firing probability at any time depends on the times of occurrence of the two preceding impulses only, and in such a way as to indicate that each impulse is followed by a transient depression of excitability that outlasts the following impulse.

The possible sites at which spontaneous or maintained activity may originate in the retina are discussed.
STEPS IN THE PRODUCTION OF MOTONEURON SPIKES
Authors: Fuortes M. G. F. , Frank K. , Becker Mary C.
Published: May 2004

1. Spikes evoked in spinal motoneurons by antidromic stimulation normally present an inflection in their rising phase. A similar inflection is present in spikes evoked by direct stimulation with short pulses.

2. In either case the inflection becomes less prominent if the motoneuron membrane is depolarized and more prominent when it is hyperpolarized. Both antidromic and direct spikes may fall from the level of the inflection thus evoking a "small spike" only if sufficient hyperpolarization is applied. Similar events occur when antidromic or direct spikes are evoked in the aftermath of a preceding spike.

3. Spikes evoked by direct stimuli applied shortly after firing of a "small spike" may also become partially blocked at a critical stimulus interval. At shorter intervals, however, spike size again increases and no inflection can be detected in the rising phase.

4. When a weak direct stimulus evokes a small spike only, a stronger stimulus may evoke a full spike. Curves of the strength of the stimuli required for eliciting small or full spikes have been constructed in a number of conditions.

5. To explain the results it is assumed that threshold of the major portions of the soma membrane is higher than the threshold of the axon, the transition occurring over a finite area near the axon hillock. Following antidromic or direct stimulation, soma excitation is then initiated in the region of the axon hillock. Spread of activity towards the soma occurs at first slowly and with low safety factor. At this stage block may be easily evoked. Safety factor for propagation increases rapidly as the growing impulse involves larger and larger areas of the soma membrane so that, once the critical areas are excited, activation of the remaining portions of the soma membrane will suddenly occur.
STAPHYLOCOCCAL VIROLYSIN, A PHAGE-INDUCED LYSIN
Authors: Ralston D. J. , Lieberman Miriam , Baer B. , Krueger A. P.
Published: May 2004

Virolysin is a lysin which appears in Staphylococcus aureus K1 cells infected with phage P14; together with phage, virolysin is released from phage-infected cells at the time of lysis. Autolysin is a lysin formed by uninfected cells of the K1 strain; autolysin is released from uninfected cells by autolysis.

They show the following similarities: Both agents act within the genus Micrococcus. They lyse cells only after the cell has been subjected to a damaging or "sensitizing" treatment, such as heat, bacteriophage, acetone, or ultraviolet irradiation. The course of lysis of heated cells by both lysins has been found to proceed in a similar manner. A constant percentage of cells is lysed, independent of the concentration of lysin; the residual cells remain resistant to either lysin. Lysis proceeds logarithmically with time, and the velocity constants K are proportional to the lysin concentration. K increases with increasing temperature.

Both lysins are unaffected by antiserum to the phage. They are inhibited alike by a number of chemicals, including known enzyme inhibitors. Both agents are destroyed by proteolytic enzymes and are precipitated by 40 per cent saturation with (NH4)2SO4. Both lysins are very thermolabile.

The two lysins differ with respect to their pH optimum, antigenic relationship and specificity for Micrococcus lysodeikticus.

These results suggest that (1) both lysins have many properties associated with enzymes, (2) the lysis of heated cells, which they produce, has some of the characteristics of a chemical reaction, (3) the lysin from the phage-infected cell is clearly different from the lysin of the uninfected cell.
THE CHEMISTRY OF INSECT HEMOLYMPH
Authors: Wyatt G. R. , Kalf G. F.
Published: May 2004

α,α-Trehalose, a sugar previously regarded as a product characteristic of certain lower plants, has been identified as a major blood sugar of insects. Trehalose has been isolated in pure form from the blood of pupae of the silk moth, Telea polyphemus, and has been recognized chromatographically in all the insects examined, which comprise 10 species belonging to 5 different orders. Trehalose has been determined quantitatively with anthrone after either chromatographic separation or chemical degradation of other sugars. In larvae and pupae of 4 species of Lepidoptera it ranges from 0.2 to 1.5 gm. per 100 ml. of blood and makes up over 90 per cent of the blood sugar; in larvae of a sawfly, about 80 per cent of the blood sugar is trehalose. In Bombyx mori and Platysamia cecropia, the pupal blood trehalose level is about half that in the mature larva, suggesting utilization of trehalose for glycogen synthesis during pupation. Small amounts of glucose and apparent glycogen are also present in the plasma of these insects. In Bombyx larval plasma there is also 0.04 to 0.12 gm. per 100 ml. of glucose-6-phosphate and smaller amounts of an apparent ketose phosphate.
THE PROPORTION OF MUTANTS IN BACTERIAL CULTURES
Authors: Northrop John H. , Kunitz M.
Published: May 2004

The proportion of mutants in a growing culture of organisms will depend upon (a) the rate at which the wild cells produce them (with or without growth), (b) the back mutation rate, and (c) the growth rates of the wild and mutant cells. If the mutation rate without growth and the back mutation rate are neglected, the growth of a mutant is expressed by

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and the ratio of the mutant to wild by

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in which λ = mutation frequency rate constant, "mutation rate," A = growth rate constant of wild cells W, B = growth rate constant of mutant cells M. If the term [B – (1 – 2λ)A] is positive, the proportion of mutants increases continuously. If it is negative, the proportion of mutants reaches a constant value

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If mutation is assumed to occur without growth at the rate C, then the corresponding equations are (11), (12), and (14).

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If (B + C – A) is negative and t = ∞,

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If C << A,

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ION AND WATER FLUXES IN THE ILEUM OF RATS
Authors: Curran Peter F. , Solomon A. K.
Published: May 2004

Studies have been carried out on the movement of salt and water across the small intestine of the rat. Segments of the ileum of anesthetized rats have been perfused in vivo with unbuffered NaCl solutions or isotonic solutions of NaCl and mannitol. Kinetic analysis of movements of Na24 and Cl36 has permitted determination of the efflux and influx of Na and Cl. Net water absorption has been measured using hemoglobin as a reference substance.

Water was found to move freely in response to gradients of osmotic pressure. Net water flux from isotonic solutions with varying NaCl concentration was directly dependent on net solute flux. The amount of water absorbed was equivalent to the amount required to maintain the absorbed solute at isotonic concentration. These results have been interpreted as indicating that water movement is a passive process depending on gradients of water activity and on the rate of absorption of solute.

The effluxes of Na and Cl are linear functions of concentration in the lumen, but both ions are actively transported by the ileum according to the criterion of Ussing (Acta Physiol. Scand., 1949, 19, 43). The electrical potential difference between the lumen and plasma has been interpreted as a diffusion potential slightly modified by the excess of active Cl flux over active Na flux.

The physical properties of the epithelial membrane indicate that it is equivalent to a membrane having negatively charged uniform right circular pores of 36 Å radius occupying 0.001 per cent of the surface area.
XANTHINE OXIDASE ACTIVITY IN REGENERATING LIVER
Authors: Feigelson Muriel , Feigelson Philip , Gross Paul R.
Published: May 2004

The xanthine oxidase activity of mouse regenerating liver has been shown to be elevated during the period of rapid liver growth and proliferation. This increase is evident when the enzyme activity is expressed per unit wet tissue weight, per unit nitrogen, or per cell. The adrenal cortex probably plays only a minor role in implementing this phenomenon. Further augmentation of the xanthine oxidase level of regenerating liver is not induced by the administration of large quantities of the substrate, xanthine, to the animal.
γ-BUTYROBETAINE AS A SPECIFIC ANTAGONIST FOR CARNITINE IN THE DEVELOPMENT OF THE EARLY CHICK EMBRYO
Authors: Ito Toshio , Fraenkel G.
Published: May 2004

The effect of γ-butyrobetaine alone and with the addition of carnitine on the development of the early excised chick embryo has been studied. γ-Butyrobetaine in appropriate amounts exerts an inhibitory effect which can be relieved or annulled by the inclusion of appropriate amounts of carnitine. This has been interpreted as a metabolite-antimetabolite relationship, in which the normal metabolite, carnitine, is antagonized by the structurally closely related γ-butyrobetaine, and is regarded as evidence of an important role of carnitine in the metabolism of the developing chick embryo.
THE EFFECT OF TEMPERATURE, POTASSIUM, AND SODIUM ON THE CONDUCTANCE CHANGE ACCOMPANYING THE ACTION POTENTIAL IN THE SQUID GIANT AXON
Authors: Amatniek E. , Freygang W. , Grundfest H. , Kiebel G. , Shanes A.
Published: May 2004

Conductance changes associated with the response of the squid giant axon have been studied at two temperature ranges (26–27°C.; 9–10°C.) and with modified concentrations of sodium and potassium in the medium. The phase of "initial after-conductance," during which the membrane resistance increases above the resting value, is smaller at the lower temperature. At both temperature ranges it is diminished by doubling K+ in the medium and enhanced by removal of K+. Halving the Na+ of the medium also enhances this phase when K+ is absent, but not otherwise. The time course of the conductance changes alters in form with changes of the external medium. These changes indicate independent changes in the complex of ionic events associated with the response. The experiments therefore confirm the reality of the phase of increased membrane resistance. The magnitude of this change appears to be considerable and requires a transient decrease in the mobility and/or concentration of ions in the membrane. The possible cause of this decrease is discussed.
The action of air ions on bacteria
Authors: Krueger A. P. , Smith R. F. , Go Ing Gan
Published: May 2004

Techniques have been devised for studying quantitatively the effects of air ions on microorganisms suspended in small drops. In smog-contaminated atmospheres moderate concentrations of positive and negative air ions exerted a protective effect on staphylococci by delaying the drop in pH customarily observed and by diminishing the rate of evaporation. In clean air higher concentrations of positive and negative air ions accelerated the rate of death of staphylococci apparently by direct action on the cells and by increasing the rate of evaporation.

Air ion action in these experiments did not involve cell agglutination or direct radiation from the radioactive isotopes employed.
SIMULTANEOUS HYDROLYSES OF ESTERS AND PROTEINS AT SATURATION LEVELS
Authors: Castañeda-Agulló M. , Del Castillo Luz M.
Published: May 2004

A direct titration method for the determination of proteolytic activity is discussed. This involves the potentiometric measurement of the volume of 0.08 N NaOH required to maintain a constant pH (8.0) during the time of the hydrolysis. It is a sensitive method which presents several advantages; viz., it measures simultaneously protease and esterase activity, it follows the hydrolysis very closely and from the first stages; the titration is continuous and on the same sample. This method determines a constant fraction of the groups titratable by formol titration. The ratio formol: direct titration is represented by a factor "f" which is presumed to be distinct for each protein-enzyme system.

Kinetic studies, using this method, revealed that the rates of hydrolysis of mixtures casein-gelatin on one hand, casein-BAEE or gelatin-BAEE on the other, are always larger than those of the corresponding isolated substrates. In many cases the resulting rates are equal or nearly equal to the sum of the individual rates, even though the mentioned rates have been determined within the saturation zones for every substrate.

The former observations are inconsistent with the theory of the formation of an intermediary enzyme-substrate compound, unless it is assumed that the enzyme has a specific active group for each substrate.
AN ANALYSIS OF EXTRACELLULAR POTENTIALS FROM SINGLE NEURONS IN THE LATERAL GENICULATE NUCLEUS OF THE CAT
Authors: Freygang W. H.
Published: May 2004

The lateral geniculate nucleus of the cat was explored with micropipettes having submicroscopic tips. The only reliably recorded intracellular activity was from axons. Following orthodromic stimulation, the potentials recorded by the extracellular electrodes registered the net flow of current across the soma-dendritic membrane of the principal cell bodies. The current has three phases of flow away from the soma-dendritic membrane followed by a flow of current toward this membrane. The first component is ascribed to synaptic activity. Subsequent components are ascribed to the activity of the initial segment of the axon and a limited area of high threshold membrane on the soma. The evidence is interpreted as suggesting that most of the soma-dendritic membrane is excited synaptically to produce a postsynaptic potential, but is not excited electrically and does not produce a propagating spike.
A ZONE PHENOMENON AND A PROGRESSIVE REACTION OCCURRING WITH A RADIOACTIVE HEMOLYSIN, SODIUM ERUCATE-I131
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

Sodium erucate reacts progressively (i.e., once the reaction is started in a time which is so short that the lysin is in contact with the red cells for 30 seconds, it cannot be stopped even by being diluted 10-fold) with human red cells at pH 7. At the same time, systems containing the lysin and human red cells show a zone phenomenon, lysis occurring most readily in a certain concentration of lysin but more slowly in larger or smaller concentrations. Sodium erucate-I131 can be used to investigate both the zone phenomenon and the progressive character of the reaction. As regards the former, large concentrations of the lysin react relatively poorly with the red cell surfaces and the resistance of the red cells is relatively high. This may be due to the presence of an admixed inhibitor or to the development of an inhibitory state. The lysin is taken up and fixed by material in the red cell surface, so that the "internal phase" of lysin attached to the cell surfaces is so firmly fixed that a 10-fold dilution has no effect on it. It follows that lysis in these systems is progressive, as it is found to be.
THE DISTRIBUTION OF INORGANIC PHOSPHATE IN AMPHIBIAN MUSCLE
Authors: Briner G. P. , Simon Shirley E. , Shaw F. H.
Published: May 2004

The Na+, K+, and inorganic phosphate levels of the plasma and sartorius muscle of the toad Bufo marinus were determined.

Soaking in normal Ringer brought about the usual cation shifts, but did not alter the level of inorganic phosphate in the cell.

Increases in the external phosphate level brought about an increase in the internal phosphate, but the apparent phosphate space of muscle is somewhat smaller than the apparent Cl- space.

Phosphate spaces were compared with inulin spaces and were found to be significantly greater.

Alteration of the H+ concentration of the high phosphate Ringer did not alter the partition of phosphate across the cell membrane.

These results have been found to be consistent with the theory of a three compartment system for muscle, wherein the tissue is assumed to consist of an extracellular phase, and two intracellular phases. The inorganic phosphate of the cell is assumed to be adsorbed onto the "ordered phase," and increments in organic phosphate found on raising the external level are assumed to take place in the "free intracellular phase."
GENERATOR PROCESSES OF REPETITIVE ACTIVITY IN A PACINIAN CORPUSCLE
Authors: Loewenstein Werner R.
Published: May 2004

Response patterns resulting from repetitive mechanical stimulation of the corpuscle depend on (1) the time course of recovery of the generator potential, on (2) the recovery of critical firing height, and on (3) the stimulus strength/generator potential function. By either augmenting stimulus frequency at constant strength, or by reducing strength at constant frequency, a sequence of propagated potentials is turned into a pattern of alternating regenerative and generator responses. In such a pattern an extra impulse can be set up whenever an extra stimulus produces a generator potential of enough amplitude to reach the firing height of the corresponding period. The new requirements of firing height introduced by the refractory trail of the extra impulse determine resetting of periodicity and appearance of a "compensatory pause." The decay time of the single generator potential is independent of stimulus duration. This is interpreted as a factor determining receptor adaptation. Upon repetitive stimulation at intervals above ½ decay time of the single generator potential, a compound generator potential is built up which shows no spontaneous decline. However, in spite of being considerably greater than the firing height for single impulses, the constant level of depolarization of the compound generator potential is unable to produce propagated potentials. A hypothesis is brought forward which considers the generator potential to arise from membrane units with fluctuating excitability scattered over the non-myelinated nerve ending.
EARLY POST-TETANIC POTENTIATION AND LOW FREQUENCY DEPRESSION OF SOME GROUP I REFLEX ACTIONS
Authors: Wilson Victor J.
Published: May 2004

Group I reflex functions, namely monosynaptic reflex transmission, facilitation of synergists, and direct and disynaptic inhibition, show early post-tetanic potentiation following conditioning with a brief, high frequency, tetanus. Of these reflex functions, monosynaptic transmission always shows low frequency depression. Direct inhibitory pathways, and therefore inhibitory junctions, are insensitive to low frequency depression. The fact that direct inhibition can be potentiated shows it to be sufficiently labile that a decrease in efficacy at inhibitory junctions during repetitive activity should be revealed. Disynaptic inhibition often shows low frequency depression. As it is likely that inhibitory junctions in the direct and disynaptic pathways are similar, the low frequency depression of disynaptic inhibition is probably due to the properties of the excitatory relay between afferent fibers and interneurons in that pathway. Facilitation between synergists is often more depressed when the conditioning and testing volleys are nearly simultaneous than when they are separated by 1 to 1.5 msec. This result indicates that an early and rapid phase of action, responsible for homonymous and heteronymous transmission, is more sensitive to low frequency depression than is residual facilitation. In general, reflex transmission is more sensitive than are other aspects of action by group I fibers to events concurrent with and following repetitive activation.
THE PROTEIN COATS OR "GHOSTS" OF COLIPHAGE T2
Authors: Lehman I. R. , Herriott Roger M.
Published: May 2004

Assimilation of oxygen, inorganic phosphate, and ammonia nitrogen by normal T2 phage and T2 ghost-infected E. coli B was studied. The rate of oxygen and phosphorus uptake by ghost-infected bacteria is similar to that of normal and phage-infected cells. The R.Q. in glucose-salts medium remains approximately 1. Assimilation of ammonia nitrogen by ghost-infected bacteria is maintained at a rate approximately 80 per cent of normal.

The inorganic phosphate which is assimilated was found to be incorporated into TCA-soluble compounds which were rapidly released into the medium. Within 5 minutes after absorption of the ghosts there was a loss from the cell of TCA-soluble constituents including organic phosphorus and compounds which absorb at 260 mµ. No corresponding breakdown of nucleic acid present in the cell prior to infection could be detected. The incorporation of inorganic phosphate into organic linkages in the ghost-infected cell and its release into the medium were found to proceed at a rate approaching that of the incorporation of inorganic phosphorus into the nucleic acid of normal cells. The net increase in 260 mµ absorbing compounds appeared to be inhibited.
THE EFFECT OF ILLUMINATION ON THE ELECTRICAL CONDUCTANCE OF RHODOPSIN SOLUTIONS
Authors: Hara Tomiyuki
Published: May 2004

An apparatus was constructed in order to record continuously and simultaneously changes in extinction and electrical conductance of rhodopsin solutions. With this apparatus, changes in electrical conductance on exposing rhodopsin to light were investigated. On illumination solutions of rhodopsin revealed a conductance change so long as they preserved their photosensitivity. The conductance change begins almost immediately upon illumination and is almost proportional to the amount of rhodopsin decomposed, continuing until rhodopsin is converted to indicator yellow. Near pH 7 the conductance is apt to increase slightly, while it decreases considerably outside the range of pH 6–9, being accompanied by a pH change towards neutrality. The conductance change is regarded as an essential property of rhodopsin, because it occurs in aqueous suspension as well as in digitonin solution; it may be caused by hydrogen or hydroxyl ions and some other conductive substances. It is also noteworthy that the petroleum ether-soluble component of the rod outer segments—presumably the lipide—tends to increase the conductance change. In suspensions of rod outer segments and retinal homogenates, the conductance increases on illumination irrespective of pH: this may be due to secondary reactions following the photic reaction of rhodopsin. We shall discuss the significance of the conductance change in relation to the initiation of visual excitation.
RHYTHMICITY IN THE PROTOPLASMIC STREAMING OF A SLIME MOLD, PHYSARUM POLYCEPHALUM
Authors: Kishimoto Uichiro
Published: May 2004

The electric potential difference (1 to 15 mv.) between two loci of the slime mold connected with a strand of protoplasm changes rhythmically with the same period (60 to 180 seconds) as that of the back and forth protoplasmic streaming along the strand. Generally some phase difference is observed between them. Periods of the electric potential rhythm show a Gaussian distribution. Amplitudes give a somewhat different distribution curve. Wave forms are not always simple harmonic ones, but are distorted more or less. However, auto-correlation analysis proves that there is a dominant rhythm of a nearly constant period which coincides with the mean period of the Gaussian distribution curve. Calculations made on an assumption that the electric potential rhythm is the result of many elementary rhythms (i.e., same periodicity, arbitrary phase angles) distributed throughout the plasmodium, give a satisfactory coincidence with the observed distribution for the amplitude. The predominance of a rhythm of a nearly constant periodicity suggests the existence of well organized interactions among components of a contractile protein network, the rhythmic deformation of which is supposed to be responsible for the protoplasmic streaming and for the electric potential rhythm.