bluuebunny/crossref_metadata_2025 huggingface dataset:
THE RELATIONSHIP OF HYDROGEN PEROXIDE TO THE INHIBITION OF THE GLYOXALASE ACTIVITY OF INTACT ERYTHROCYTES BY X-RADIATION
Authors: Klebanoff S. J.
Published: May 2004

The x-irradiation of a dilute suspension of erythrocytes results in a decrease in the glyoxalase activity of the cells as a result of a fall in the reduced glutathione level. The present paper deals with the possible role of H2O2 in this reaction.

The addition of intact erythrocytes to physiological saline previously irradiated with 150,000 r or 225,000 r results in a fall in the glyoxalase activity of the cells. The inhibition is prevented by the preincubation of the irradiated saline with catalase and is reversed by the addition of plasma, glucose, adenosine, and inosine to the cell suspension.

An inhibition of the glyoxalase activity is also produced by the addition of H2O2 to the suspension of erythrocytes. The inhibitory effect of H2O2 can be prevented and largely reversed by plasma, glucose, adenosine, and inosine. Methylglyoxal is also protective under these conditions.

Hydrogen peroxide formed continuously and in low concentrations by enzyme systems appears to be more effective than added H2O2 in inhibiting the glyoxalase system. The inhibition by H2O2-producing enzyme systems is minimized by the addition of catalase, plasma, glucose, methylglyoxal, and to a lesser extent, by adenosine and inosine, and is accentuated by the addition of sodium azide.

The results are discussed in relation to the role of H2O2 and catalase in the toxicity of ionizing radiations.
DISPOSITION OF INTRAPERITONEALLY INJECTED CALCIUM-45 IN SUCKLING RATS
Authors: Bronner Felix
Published: May 2004

The time course of the concentration of radiocalcium was studied in the serum, skeleton, pelt, muscles, and pooled internal organs of 10-day-old rats. Within 10 hours of injection, the specific activity of the tissue groups exceeded the specific activity of the serum and remained above it during the period studied (120 hours).

Chemical and autoradiographic analyses showed how rapidly most of the injected Ca45 found its way into the skeleton. A model was constructed with the assumption that the skeleton constitutes an essentially irreversible reservoir for the tracer in a multicompartment system in which the blood is the central or feeding compartment.

The rate of transfer of the tracer from the soft tissue compartments to the serum was calculated from the equation

See PDF for Equation

in which C = concentration in serum (expressed as a series of exponential terms)

C' = concentration in a given soft tissue

Substitution in the integrated form of this equation yielded equations which had the major properties of the empirical equations fitted to the experimental points. The relative order of transfer constants (k'–1) was: organs ≥ pelt > muscle.
THE PARTICIPATION OF PHOSPHATE IN THE FORMATION OF A "CARRIER" FOR THE TRANSPORT OF MG++ AND MN++ IONS INTO YEAST CELLS
Authors: Jennings D. H. , Hooper D. C. , Rothstein A.
Published: May 2004

During the absorption of phosphate by yeast, the cells acquire the capacity to absorb Mn++ and Mg++, a capacity which is retained even after phosphate is no longer present in the medium. Cells pretreated with phosphate and then washed, slowly lose their ability to absorb Mn++, the rate of loss depending on the temperature and on the metabolic state. The fermentation of sugars induces a very rapid loss of absorptive capacity, whereas the respiration of ethyl alcohol, lactate, or pyruvate has little effect. Inhibitor studies with sodium acetate, redox dyes, and arsenate, reveal parallel effects on Mn++ absorption, and on phosphate absorption. It is concluded that the synthesis of a carrier for the transport of Mg++ and Mn++ involves a phosphorylation step closely coupled with reactions involved in the absorption of phosphate.
SPATIAL SUMMATION OF INHIBITORY INFLUENCES IN THE EYE OF LIMULUS, AND THE MUTUAL INTERACTION OF RECEPTOR UNITS
Authors: Hartline H. K. , Ratliff Floyd
Published: May 2004

The inhibitory influences exerted mutually among the receptor units (ommatidia) of the lateral eye of Limulus are additive. If two groups of receptors are illuminated together the total inhibition they exert on a "test receptor" near them (decrease in the frequency of its nerve impulse discharge in response to light) depends on the combined inhibitory influences exerted by the two groups. If the two groups are widely separated in the eye, their total inhibitory effect on the test receptor equals the sum of the inhibitory effects they each produce separately. If they are close enough together to interact, their effect when acting together is usually less than the sum of their separate effects, since each group inhibits the activity of the other and hence reduces its inhibitory influence. However, the test receptor, or a small group illuminated with it, may interact with the two groups and affect the net inhibitory action. A variety of quantitative effects have been observed for different configurations of three such groups of receptors. The activity of a population of n interacting elements is described by a set of n simultaneous equations, linear in the frequencies of the receptor elements involved. Applied to three interacting receptors or receptor groups equations are derived that account quantitatively for the variety of effects observed in the various experimental configurations of retinal illumination used.
EFFECTS OF AZIDE AND CHLORETONE ON THE SODIUM AND POTASSIUM CONTENTS AND THE RESPIRATION OF FROG SCIATIC NERVES
Authors: Hurlbut W. P.
Published: May 2004

Azide (0.2 to 5.0 mM) and chloretone (2.0 to 15.0 mM) reversibly inhibited 20 to 90 per cent of the resting respiration of frog sciatic nerves, and caused a loss of potassium and a gain of sodium in this tissue. The changes in ionic contents that developed after 5 or 10 hours were roughly correlated with the degree of respiratory depression, but the time courses of these changes were different with the two reagents. In azide these changes appeared to begin immediately, while in chloretone, at concentrations between 3.0 and 5.0 mM, the ionic shifts developed after a delay of several hours. Fifteen millimolar chloretone produced immediate changes in ionic contents several times greater than those produced by anoxia. The changes in ionic distribution produced in 5 hours by anoxia, 5.0 mM azide, or 5.0 mM chloretone were at least partially reversible; those produced by 15.0 mM chloretone were irreversible. With the exception of 15.0 mM chloretone the ionic shifts produced by these reagents may be due primarily to the depression of the respiration, although there are indications that azide acts, in addition, by another pathway. Concentrations of azide or chloretone that depressed the resting rate of oxygen consumption more than 50 per cent produced a slow conduction block, while 15.0 mM chloretone blocked conduction within 15 minutes.
ENDOGENOUS PHOTOSENSITIZATION IN A CAROTENOIDLESS MUTANT OF RHODOPSEUDOMONAS SPHEROIDES
Authors: Dworkin Martin
Published: May 2004

Endogenous photosensitization in a carotenoidless mutant of Rhodopseudomonas spheroides has been studied.

When this mutant is exposed to visible light and oxygen there is a short lag period followed by exponential killing of the cells. The killing process obeys the Bunsen-Roscoe law of reciprocity and is temperature-independent.

The chlorophyll content of the cells does not affect the rate of killing until a certain low threshold has been reached.

Exposure of photosynthetically grown cells to air in the dark induces a temporary desensitization to the killing.

A certain proportion of the population is invariably resistant to the photokilling. Evidence is presented to show that the resistance of these cells is probably a result of their abnormally low chlorophyll content.

One consequence of the irradiation is the appearance of abnormally small colonies upon plating the survivors. This is interpreted in terms of a multi-hit theory.

The photosensitizing pigment itself (the intracellular bacteriochlorophyll) is destroyed. The process is zero order, temperature-dependent, and does not follow the reciprocity law.

It is suggested that the death of the cell results from a disruption of the cell membrane.
LIGHT-INDUCED EFFICIENCY AND PIGMENT ALTERATIONS IN RED ALGAE
Authors: Yocum C. S. , Blinks L. R.
Published: May 2004

The low photosynthetic efficiency of chlorophyll in freshly collected red algae, can, in the case of Porphyra perforata, P. nereocystis, and Porphyridium cruentum, be increased by growing the algae for 10 days in red or blue light. Exposure to darkness or to green light maintains the algae in their originally low efficiency with respect to chlorophyll, while retaining the high efficiency of phycobilins. Red- or blue-adapted algae are rapidly reversed by exposure to green light, the chlorophyll efficiency dropping to low values again in a few hours. This is assumed to account for the action spectrum of freshly gathered plants.

Some pigment changes were observed, but not in the direction of "chromatic adaptation;" and the carotenoid pigments were not activated, even by blue light, but remained as photosynthetically inactive shading filters. The higher red algae (Florideae) did not show activation of chlorophyll by red or blue light.
SYNAPTIC POTENTIAL IN THE MOTOR GIANT AXON OF THE CRAYFISH
Authors: Hagiwara Susumu
Published: May 2004

Some electrical properties of the synapses between central giant axons (presynaptic) and the motor giant axon (postsynaptic) of the crayfish abdominal nerve cord have been investigated. Postsynaptic potential change in response to presynaptic volleys contains two components: a spike potential and a synaptic potential of very long time course. Amplitude of the synaptic potential is graded according to the number of active presynaptic axons. Conductance increase in the synaptic membrane endures over most of the period of potential change, and it is this rather than the "electrical time constant" of the membrane that in large measure determines the form of the synaptic potential. Temporal summation of synaptic potential occurs during repetitive presynaptic stimulation, and after such stimulation the rate of decay of synaptic potential is greatly slowed.
THE CHARACTERIZATION AND LOCALIZATION OF FROG SKIN CHOLINESTERASE
Authors: Koblick Daniel C.
Published: May 2004

Frog skin cholinesterase is largely of the serum (pseudocholinesterase) type. For whole skin, the activity at 10–1 AcChCl is 4.9 µl./mg. N/hr.

Tela subcutanea isolated by dissection exhibits an activity of 65 µl./mg. N/hr. at 10–1 AcChCl. Since about one-tenth of the nitrogen of the skin is located in the tela subcutanea, it is estimated that more than 90 per cent of the enzyme is associated with this tissue layer.
THE CALCULATION OF TRANSFER RATES IN TWO COMPARTMENT SYSTEMS NOT IN DYNAMIC EQUILIBRIUM
Authors: Berger Eugene Y. , Steele J. Murray
Published: May 2004

Dynamic equilibrium in a biological system implies that the compartment under study does not change in size during the period of observation. In many biological systems there are, however, net changes with time and this report deals with the mathematical treatment necessary to calculate unequal rates of inflow and outflow.

A method is presented for the calculation of transfer rates in a two compartment system when the rates of flow between these compartments are unequal but constant. Equations were developed to calculate the amount of material transported per unit time derived from measurements of specific activity and compartment size.

The problems of (1) sampling from the pool and (2) the effects of analytical errors on the estimation of rate have been evaluated. An example has been presented in which the derived equations have been applied to a study of the simultaneous passage of sodium into and out of a permanently isolated loop of bowel.
THE FREEZING POINT DEPRESSION OF MAMMALIAN TISSUES AFTER SUDDEN HEATING IN BOILING DISTILLED WATER
Authors: Appelboom Johannes W. Th. , Brodsky William A. , Tuttle William S. , Diamond Israel
Published: May 2004

The calculated freezing point depression of freshly excised boiled mammalian tissue is approximately the same as that of plasma. The boiling procedure was chosen to eliminate the influence of metabolism on the level of the freezing point depression. Problems created by the boiling, such as equilibrium between tissue and diluent, change in activity coefficient by dilution, and loss of CO2 content, are discussed.

A frozen crushed tissue homogenate is hypertonic to plasma. Boiling and dilution of such hypertonic homogenate exposed to room temperature for 5 to 15 minutes did not produce significant or unexplicable decreases in its osmotic activity. Moreover, freezing and crushing of a boiled diluted tissue did not produce any increase of the isoosmotic level of freezing point depression.

It is possible to explain these data either with the hypothesis of hypertonic cell fluid or with that of isotonic cell fluid. In the case of an assumed isotonic cell fluid, data can be explained with one assumption, experimentally backed. In the case of an assumed hypertonic theory data can be explained only with the help of at least three ad hoc postulates. The data support the validity of the classical concept which holds that cell fluid is isotonic to extracellular fluid.
THE SPECTRAL SENSITIVITIES OF THE DORSAL OCELLI OF COCKROACHES AND HONEYBEES
Authors: Goldsmith Timothy H. , Ruck Philip R.
Published: May 2004

The spectral sensitivities of the dorsal ocelli of cockroaches (Periplaneta americana, Blaberus craniifer) and worker honeybees (Apis mellifera) have been measured by electrophysiological methods. The relative numbers of quanta necessary to produce a constant size electrical response in the ocellus were measured at various wave lengths between 302 and 623 mµ.

The wave form of the electrical response (ERG) of the dark-adapted roach ocellus depends on the intensity but not the wave length of the stimulating light. The roach ocellus appears to possess a single photoreceptor type, maximally sensitive about 500 mµ.

The ERG's of bee ocelli are qualitatively different in the ultraviolet and visible regions of the spectrum. The bee ocellus has two types of photoreceptor, maximally sensitive at 490 mµ and at about 335 to 340 mµ.

The spectral absorption of the ocellar cornea of Blaberus craniifer was measured. There is no significant absorption between 350 and 700 mµ.
EFFECTS OF POTASSIUM, SODIUM, AND AZIDE ON THE IONIC MOVEMENTS THAT ACCOMPANY ACTIVITY IN FROG NERVES
Authors: Asano Tomoaki , Hurlbut W. P.
Published: May 2004

Stimulation of intact or desheathed frog sciatic nerves produced an increase in the sodium content and a decrease in the potassium content of this tissue. In desheathed preparations the magnitudes of the changes in ionic contents decreased as the concentration of the potassium in the bathing solution was increased, while changing the external sodium concentration produced small effects on the ionic shifts. During tetanization, the rate of decline of the compound action potential also decreased as the external potassium concentration increased. Eliminating the activity respiration with 0.2 mM azide did not greatly modify the changes in sodium and potassium distribution that accompanied activity in either intact or desheathed nerves.
STUDIES ON THE ORIGIN OF BACTERIAL VIRUSES
Authors: Northrop John H. ,   With the Technical Assistance of Marie King
Published: May 2004

I. The Incidence of Phage-Producing Cells in Various B. megatherium Cultures

Analyses of small samples containing a few cells each show that lysogenic B. megatherium produces phage particles in groups of from 10 to 1000 depending on the megatherium strain and the culture medium.

These groups probably correspond to the number of particles produced by a single cell. The proportion of such phage-producing cells varies from <1 x 10-10 to about 1 x 10-2 depending on the megatherium strain and the culture medium.

If a culture produces two types of phage, the different types usually appear in separate samples. If mixed samples occur, the number of such samples is about what would be expected for the probability that two separate groups would appear in one sample. This result indicates that the appearance of a distinct phage type is the result of a change in the bacterial cell rather than a change in a phage particle, since in the latter case a mixture of the two types would result.

II. The Effect of Ultraviolet Light on the Incidence of Phage-Producing and of Terramycin-Resistant Cells in Various B. megatherium Cultures

Low intensity of ultraviolet light increases the proportion of both phage-producing cells and of terramycin-resistant mutants. The increase in phage-producing cells is greater than the increase in terramycin-resistant cells.

High intensities of ultraviolet light cause practically all the cells of some B. megatherium strains to produce phage. The number of terramycin-resistant mutants cannot be determined under these conditions.

The effect of ultraviolet light varies, depending on the megatherium strain and the culture medium.

III. The Effect of Hydrogen Peroxide on the Incidence of Phage-Producing and of Terramycin-Resistant Cells in Various B. megatherium Cultures

Low concentrations of hydrogen peroxide increase the number of phage-producing cells and of terramycin-resistant cells, concomitantly, from two to five times.

High concentrations of hydrogen peroxide cause almost all the cells of some strains of megatherium to produce phage.

IV. Calculation of the Incidence of Phage-Producing Cells

The time rate of the appearance of phage particles in normal cultures, or in cultures treated with ultraviolet light or hydrogen peroxide, may be calculated by the same equations which predict the occurrence of terramycin-resistant mutants in B. megatherium cultures.

These equations predict that the number of mutants will increase more or less in proportion to the concentration of mutagenic agent, so long as the mutation rate remains very small compared to the growth rate. As the mutation rate approaches the growth rate, there will be a very rapid increase in the proportion of mutants. This explains the striking effect of higher concentrations of mutagenic agents.

In order to calculate the results after exposure to strong ultraviolet light or hydrogen peroxide, it is necessary to assume that the change from normal to phage-producing cell occurs without cell division.
EFFECTS OF EXTERNAL CURRENTS ON DURATION AND AMPLITUDE OF NORMAL AND PROLONGED ACTION POTENTIALS FROM SINGLE NODES OF RANVIER
Authors: Mueller Paul
Published: May 2004

Duration and amplitude of normal and prolonged action potentials from single nodes of Ranvier vary as functions of potential changes induced by currents from an external source. The quantitative relations between externally applied potential and the resulting potential generated within the system are analyzed in order to obtain information about the kinetics of the electromotance,—potential,—and chemical changes taking place during excitation. The following preliminary conclusions are drawn:

A depolarizing and a repolarizing process (positive and negative electromotance) increase and decrease with the potential. For a sudden potential displacement the negative electromotance reaches its new value at a faster rate than the positive electromotance. Since the individual values of the two electromotances depend on the potential and since they both generate a potential which is proportional to the difference of their absolute values, the values of either electromotance are determined by this difference as well as by any externally induced potential change.
ON THE KINETICS OF POTENTIAL, ELECTROMOTANCE, AND CHEMICAL CHANGE IN THE EXCITABLE SYSTEM OF NERVE
Authors: Mueller Paul
Published: May 2004

The kinetics of interaction between potential, chemical equilibrium, and electromotance in the excitable system of nerve are analyzed. The theoretical system has the following properties:

It gives rise to two electromotances each of which depends directly on a chemical equilibrium. The equilibria are determined by the potential across the system.

After a sudden potential shift the equilibria reach their new value with an exponential time course, the time constant of which is determined by the rate constants of the two reactions. The rate constants are different due to different activation energies.

The two electromotances give rise to potentials of opposite sign. The total potential produced by the system is equal to the sum of the two potentials. The two equilibria are thus determined by any externally applied potential as well as by the sum of the internally produced potentials. The dependence of the equilibria on the potential is calculated from first principles.

The equations which describe this system are solved by an analogue computer, which gives instantaneous solutions of the total internal potential as a function of time and any voltage applied from an external source. Comparison between recorded and computed action potentials shows excellent agreement under all experimental conditions.

The electromotances might originate from a Ca++—Na+—K+ exchange at fixed negative sites in the Schwann cell.
ACTION OF MEPROBAMATE ON SPINAL MONOSYNAPTIC REFLEXES AND ON INHIBITORY PATHWAYS
Authors: Wilson Victor J.
Published: May 2004

Meprobamate was administered intravenously to spinal cats, in cumulative doses of 30 to 40 mg./kg. each. Initial doses may have a variable action on monosynaptic reflexes. At times some reflexes are depressed, while others are enhanced or unaffected. When dose levels of 100 mg./kg. or higher are reached, monosynaptic reflexes, both flexor and extensor, are depressed. Monosynaptic reflexes can be strongly depressed by meprobamate, their input-output relations often remaining unchanged. In such cases there is thus no change in the spatial summation requirements of those motoneurons remaining in the excitable zone. Inhibitory pathways, both direct and disynaptic, are highly resistant to the action of meprobamate. The drug does not distinguish between the direct and disynaptic pathways. It is suggested that meprobamate acts as a general depressant of excitatory synaptic transmission.
OSCILLATORY BEHAVIOR OF THE SQUID AXON MEMBRANE POTENTIAL
Authors: Sjodin R. A. , Mullins L. J.
Published: May 2004

Squid axons impaled with a microelectrode have been treated with concentrations of xylene and benzene such that there is no change in threshold or resting potential at 20°C., while the spike height declines about 10 mv. A decrease in ambient temperature results in large, reversible, increases in threshold. While neither low temperature nor the added blocking agent induces repetitive firing from a single stimulus, the two treatments when combined do yield repetitive responses which commence at a sharply defined temperature. The alteration in the membrane responsible for the effects observed can be described by saying that there has been a large increase in the inductance of the equivalent electric circuit, and the temperature coefficient of the apparent membrane inductance has a Q10 = 5.
THE EFFECTS OF AIR IONS ON THE LIVING MAMMALIAN TRACHEA
Authors: Krueger Albert P. , Smith Richard F.
Published: May 2004

Studies on the effects of air ions on the functional efficiency of the extirpated tracheal strip have been extended to the trachea of the living rabbit, rat, and mouse. Animals exposed to high mobility (+) air ions administered via a tracheotomy aperture displayed: (a) Decreased ciliary activity. (b) Decline in mucus flow rate, sometimes reversed by prolonged exposure to (+) ions; a frequent drop in the volume of mucous secretion. (c) Contraction of the membranous posterior tracheal wall. (d) Increased vulnerability to trauma of cilia and mucosal blood vessels.

Similar treatment with (-) air ions reversed (+) ion effects on ciliary activity, mucus flow, contraction of the tracheal smooth muscle. Continued (-) ion treatment raised the ciliary rate (invariably) and the mucus flow rate (often) above their initial levels.

(+) Air ions administered to unoperated resting mice and rats increased the respiratory rate; (-) ions reversed this effect.

Long exposure of unoperated ambulatory mice to (+) air ions produced: (a) Decreased ciliary activity. (b) No clear cut effect on mucus flow. (c) Contraction of the posterior tracheal wall. (d) Increased vulnerability of the mucosa to trauma. (-) Air ions increased ciliary activity but had no clear-cut effect on the mucus flow rate.
PHYSIOLOGICAL CHARACTERISTICS OF HUMAN RED BLOOD CELL GHOSTS
Authors: Hoffman Joseph F.
Published: May 2004

The properties of ghosts prepared by hypotonic hemolysis at various ratios of cells (C) to hemolyzing solution (H) have been studied. At all ratios, hemoglobin (Hb) was found to be distributed equally between the ghost and supernatant compartments. Techniques employing Fe59—labelled Hb showed that during hemolysis all of the Hb is exchangeable and that following hemolysis the ghost is impermeable to Hb.

Ghosts containing defined fractions of their original Hb were prepared by appropriately altering the ratio C/H. When washed and suspended in 0.17 M NaCl—PO4—buffered media, the ghosts returned to their initial volume, recovered normal shape, and behaved as osmometers. The rate of rehemolysis of these reconstituted ghosts was observed to be proportional to the concentration of Hb in the ghosts. The rate of rehemolysis was accelerated by the addition of n-butyl alcohol (BA). For a given concentration of BA, temperature, and Hb content the rate of rehemolysis was minimal around the isoelectric point of Hb. Rehemolysis by BA was inhibited by the addition of sucrose to the medium. K influx and outflux were measured and found to be increased by the addition of BA and not influenced by the presence of sucrose. These results on the rehemolytic characteristics of ghosts are consistent with and support the colloid-osmotic theory of hemolysis.
DELAYED LIGHT ACTION SPECTRA OF SEVERAL ALGAE IN VISIBLE AND ULTRAVIOLET LIGHT
Authors: McLeod G. C.
Published: May 2004

Action spectra for delayed light production by several algae were determined from 250 to 750 mµ incident light.

In the visible portion of the spectrum the action spectra resemble those reported by previous workers for photosynthesis and light emission. Blue-green algae had a maximum at 620 mµ, red algae at 550 mµ, whereas green and brown algae have action spectra corresponding to chlorophyll and carotenoid absorption.

In the ultraviolet portion of the spectrum delayed light is emitted by algae down to 250 mµ incident light.

The action spectra of the different algae are not alike in the ultraviolet portion of the spectrum.

This indicates that pigments other than chlorophyll must be sensitizing or shielding the algae in the ultraviolet region.
COMPARATIVE STUDIES OF THREE METHODS FOR MEASURING PEPSIN ACTIVITY
Authors: Loken Merle K. , Terrill Kathleen D. , Marvin James F. , Mosser Donn G.
Published: May 2004

Comparison has been made of a simple method originated by Absolon and modified in our laboratories for assay of proteolytic activity using RISA (radioactive iodinated serum albumin—Abbott Laboratories), with the commonly used photometric methods of Anson and Kunitz. In this method, pepsin was incubated with an albumin substrate containing RISA, followed by precipitation of the undigested substrate with trichloroacetic acid and measurement of radioactive digestion products in the supernatant fluid.

The I131—albumin bond was shown in the present studies to be altered only by the proteolytic activity, and not by the incubation procedures at various values of pH. Any free iodine present originally in the RISA was removed by a single passage through a resin column (amberlite IRA-400-C1).

Pepsin was shown to be most stable in solution at a pH of 5.5. Activity of pepsin was shown to be maximal when it was incubated with albumin at a pH of 2.5. Pepsin activity was shown to be altered in the presence of various electrolytes. Pepsin activity measured by the RISA and Anson methods as a function of concentration or of time of incubation indicated that these two methods are in good agreement and are equally sensitive. Consistently smaller standard errors were obtained by the RISA method of pepsin assay than were obtained with either of the other methods.
STUDIES ON THE ORIGIN OF BACTERIAL VIRUSES
Authors: Northrop John H. ,   With the Technical Assistance of Marie King
Published: May 2004

The growth rates, the mutation frequency rate constants of the terramycin-resistant cells, the burst size of the phage-producing cells, and the ratio of phage to cells all have a temperature coefficient of about 2 from 20 to 35° (µ = 9 x 103 calories), with a maximum at 40°.

The mutation frequency rate constant (or time rate constant) of the phage-producing cells increases from 20 to 45° with a temperature coefficient of about 3 (µ = 2 to 3 x 104 cal.).

The change in the values for the growth rate, mutation rate, and cell volume occurs in less than 1 hour, after the temperature is changed. The value for the burst size of phage-producing cells changes for 3 to 4 hours.

Prolonged growth of megatherium 899 at 48 to 50° results in the production of C + S phage, in place of T. Returning the culture to 25° results in the production of small T phage.
ELECTRICAL ACTIVITY IN THE CHEMORECEPTORS OF THE BLOWFLY
Authors: Wolbarsht M. L.
Published: May 2004

An analysis of the various parts of the electrical responses to the chemical and electrical stimulation of a single labellar chemosensory hair of the blowfly, Phormia regina, indicates that the recording conditions for the spike potentials approximate the intracellular recordings made in other types of sense cells. The large positive resting potential probably arises from the basement membrane of the hypodermal cells and neurilemma rather than from the neurons at the base of the chemosensory hair. The responses to polarizing currents passed through single chemosensory hairs support this analysis. The behavioral responses to similar polarizing currents are shown to result from the action of the current on the neurons at the bases of the adjacent chemosensory hairs. The reported neural interaction of the two chemosensory neurons associated with the chemosensory hair is probably due to the physical-chemical attributes of the stimulating solution rather than to any real neural interaction. Observations on the latency of the initial nerve impulse in response to chemical stimulation indicate that the chemosensory neurons are normally free from spontaneous spike activity.
THE AMINO ACID COMPOSITION OF CRYSTALLINE PEPSIN
Authors: Blumenfeld Olga O. , Perlmann Gertrude E.
Published: May 2004

The amino acid composition of twice recrystallized pepsin (Worthington Biochemical Corporation) has been determined chromatographically on columns of Amberlite IR 120 resin. The results of the analyses obtained on four different preparations indicate a close agreement in their amino acid composition. Pepsin is unique in that it has a great predominance of acidic amino acids over basic ones. Moreover, all the preparations contain a small and constant amount of hydroxyproline, corresponding to about 0.1 residue per molecule.
THE EFFECT OF ULTRAVIOLET LIGHT ON THE SODIUM AND POTASSIUM COMPOSITION OF RESTING YEAST CELLS
Authors: Sanders Raymond T. , Giese Arthur C.
Published: May 2004

The Na+ and K+ content of non-metabolizing yeast cells was determined before and after monochromatic ultraviolet (UV) irradiation. UV facilitated the uptake of Na+ into and the loss of K+ from the cells (net ion flux); the effect is greatest for the shortest wavelength employed (239 mµ) and is partly dependent upon the presence of oxygen. The UV effect on net ion flux persists for at least 90 minutes during which tests were made and it occurs following dosages which are without measurable effect on colony formation. The UV effect on net ion flux is decreased by acidity and promoted by alkalinity. Addition of calcium ions in sufficient amount prevents the usual net ion flux changes observed in irradiated yeast. Increase in concentration gradient between the inside and the outside of the cell increases the net ion flux of irradiated yeast, Na+ uptake leading K+ loss in all cases. UV appears to act by disorganizing the constituents of the cell surface, permitting K+ to leave the cell in exchange for Na+. At low intensities of UV this ionic exchange approaches equivalence, but at higher intensities more Na+ is taken up than K+ is lost. Some evidence suggests that the Na+ in excess over that exchanged for K+ is adsorbed to charged groups produced by the photochemical effect of UV on the cell surface.
PREPARATION OF THROMBOKINASE FROM BOVINE PLASMA
Authors: Milstone J. H.
Published: May 2004

Thrombokinase is prepared from bovine plasma by a procedure involving: treatment with diatomaceous silica, adsorption on barium sulfate, flowing elution with two successive phosphate buffers, ammonium sulfate fractionation, "spontaneous" activation in concentrated solution, and isoelectric precipitation. The yield of nitrogen is 0.002 per cent, corresponding to 1.2 mg. protein per liter of plasma.

When diluted back to the volume of parent plasma, and complemented by calcium plus cephalin, the product causes appreciable activation of prothrombin in 1 minute. Thus, the quantity of thrombokinase obtainable is compatible with a physiologic role. In the more complex system used for routine assay, thrombokinase can be supplied by crude plasma at a dilution of 1/500. In parallel tests, the product appears to be more active than its parent plasma, although it contains only 0.002 per cent of the nitrogen. However, the thrombokinase of the product has been activated, whereas the thrombokinase of the plasma is probably in an inactive precursor state.

When diluted back to the volume of parent plasma, to a concentration of 0.2 microgram nitrogen per ml., thrombokinase can slowly activate prothrombin in the presence of oxalate, and without the addition of accessory factors. Activation of prothrombin in the presence of oxalate is faster with higher concentrations of thrombokinase.
PHOTOREACTIONS IN PHYCOMYCES
Authors: Cohen R. , Delbrück M.
Published: May 2004

Sporangiophores of Phycomyces in stage IV b have been stimulated by parallel light in test areas 0.2 mm. wide.

The growth responses to large stimuli are very large, owing probably to light scattered within the specimen. For medium stimuli the sensitive zone coincides with the growth response zone obtained previously and excludes the region of maximum stretch.

Sustained stimulations were used to elicit tropic responses. The bends formed travel away from the sporangium at a speed equal to the growth speed. Thus they remain very close to the stimulus when this is held at a constant level relative to ground but separate from it for stimuli programmed differently.

The existence of a protoplasmic structure, the "inner wall," with the following properties is postulated: it is attached to the lower, non-growing part of the sporangiophore and grows by addition above the sensitive zone. It neither stretches nor twists in the sensitive zone. It is the seat of the light receptors and gives growth and tropic responses. The cell wall follows its bends by elastic stretch.
PHENOTYPIC EXPRESSION OF A GENETIC PROPERTY INTRODUCED BY DEOXYRIBONUCLEATE
Authors: Fox Maurice S.
Published: May 2004

The time course of the appearance of cells showing a new phenotype, following treatment with a specific DNA, has been analyzed. A plot as a function of time of the number of cells showing the new property closely resembles the summation under a normal distribution curve. Describing the appearance of the new phenotype in these terms permits the definition of two parameters, the mean time, and the standard deviation of the distribution curve. This distribution is not affected either by the DNA concentration with which the transformable population has been treated, or by the streptomycin concentration with which the transformed population has been challenged. Interruptions of the expression process, by cooling to 20° or 0°C., serve only to displace the expression curves, without changing their shape, while small reductions in temperature change both the mean time of expression and the standard deviation of the distribution curve. On the basis of these observations a number of hypotheses have been examined concerning the mechanism whereby transforming DNA manifests a phenotypic alteration in the transformed cells. It can be concluded that there exist at least two stages in the process of expression. The completion of the first stage, causing the randomization, occurs with a mean time of about 60 minutes, and a terminal step, that of the transition of phenotype, occurs in less than 3 minutes.
EXTRACELLULAR POTENTIALS FROM SINGLE SPINAL MOTONEURONS
Authors: Freygang W. H. , Frank K.
Published: May 2004

Extracellular action potentials found close to the surface of motoneurons are related to the intracellular spikes. Evidence is cited to support the assumption that the extracellular spikes have the same time course as the membrane current at the site of recording. Simultaneously recorded intracellular and extracellular spikes are compared. Intracellular spikes are transformed, by means of a circuit which is equivalent to the extracellular recording situation, into transients that are like those appearing extracellularly. Evidence is given that the recordings are from the cell bodies of motoneurons. The results show that the membrane at the extracellular recording site does not produce a spike since the time course of the extracellular potentials is determined by the passive properties of the membrane.
SPREAD OF DIRECTLY EVOKED RESPONSES IN THE CAT'S CEREBRAL CORTEX
Authors: Brooks V. B. , Enger P. S.
Published: May 2004

A study has been made of the electrical responses to direct stimulation of the exposed cerebral cortex of cats that had been immobilized with neuromuscular blocking drugs, and whose muscle and skin wounds had been locally anesthetized. The characteristics and spread of the first and second surface-negative responses are described. It was found that the first surface-negative response to weak stimuli decays linearly to zero at 3 to 6 mm. from the point of stimulation. Intermediate stimuli cause farther and non-linear spread: responses are re-initiated, or reinforced, at 6 to 10 mm.; and supramaximal stimulation produces reinforcement both at 5 and at 10 mm. The conduction velocity of these responses is uniform for linear spread (0.7 to 2.0 m./sec.), but reinforced responses occur 1 to 3 msec. earlier than would be expected for simple conduction. The phenomenon of re-initiation, or reinforcement, depends upon the excitatory state of the brain; circulation and previous stimulation are important factors. Connections outside the gyrus matter only in so far as they provide other sources of general excitation. It is concluded that two types of transmission: slow and fast, can lead to generation of similar surface-negative responses. The suggestion is made that the slowly conducted surface-negative potentials are due to direct or to synaptic excitation of pyramidal cells; while the responses with shortened latency are initiated synaptically on other pyramidal cells after fast conduction at about 10 m./sec. in tangential fibres.
ACTIVE STATE OF MUSCLE IN IODOACETATE RIGOR
Authors: Mauriello George E. , Sandow Alexander
Published: May 2004

Frog sartorius muscles, equilibrated to 2 x 10-4 M iodoacetic acid-Ringer's solution and activated by a series of twitches or a long tetanus, perform a rigor response consisting in general of a contractile change which plateaus and is then automatically reversed. Isotonic rigor shortening obeys a force-velocity relation which, with certain differences in value of the constants, accords with Hill's equation for this relation. Changes in rigidity during either isotonic or isometric rigor response show that the capacity of the rigor muscle to bear a load increases more abruptly than the corresponding onset of the ordinarily recorded response, briefly plateaus, and then decays. A quick release of about 1 mm. applied at any instant of isometric rigor output causes the tension to drop instantaneously to zero and then redevelop, the rate of redevelopment varying as does the intensity of the load-bearing capacity. These results demonstrate that rigor mechanical responses result from interaction of a passive, undamped series elastic component, and a contractile component with active state properties like those of normal contraction. Adenosinetriphosphate is known to break down in association with development of the rigor active state. This is discussed in relation to the apparent absence of ATP splitting in normal activation of the contractile component.
PHOTODYNAMIC RESPONSE IN BACTERIA
Authors: Baugh C. L. , Clark J. B.
Published: May 2004

The photodynamic lethal response of Gram negative bacteria was found to be a one event phenomenon as previously reported. However, the kinetics of the lethal response in Gram-positive microorganisms was found to be more complex. The survivor response of the latter was dividable into at least two distinct parts, each of which could be influenced by various environmental and genetic factors. Some correlation was found between sensitivity or resistance to x-ray and ultraviolet radiations and sensitivity or resistance to photodynamic action.
A CONTINUOUS FLOW METHOD FOR THE DETERMINATION OF GLUCOSE UPTAKE BY EXCISED RAT DIAPHRAGM
Authors: Williams G. R.
Published: May 2004

A technique is described for the determination of the rate of uptake of glucose by the excised rat diaphragm preparation at intervals as short as 20 seconds. The rate is estimated from the fall in glucose concentration which occurs when a suitable medium flows over the muscle at constant rate. When insulin is added to the perfusion fluid, the rate of glucose uptake rises to a value about 50 per cent higher than that established before the introduction of insulin. Under the conditions described the change in uptake rate requires about 10 to 12 minutes to reach completion, being three-quarters complete in about 7 minutes. Although the major part of this delay must be ascribed to the time required for the washing out of insulin-free medium from the apparatus, and for the diffusion of insulin into the interstitial space, it is suggested that some of the delay may be due to processes occurring between the arrival of insulin at the fibre surface and the exertion of its characteristic effect on glucose uptake, although neither the time-course nor the nature of this induction phase is established.
ENZYME BIOSYNTHESIS IN ESCHERICHIA COLI
Authors: Weinbaum George , Mallette M. F.
Published: May 2004

Escherichia coli B synthesized ß-galactosidase and an enzyme system for D-xylose when exposed to lactose and xylose respectively in nitrogen-free media. The amount of ß-galactosidase formed in the absence of external nitrogen depended upon the nature of the medium in which the cells had originally been grown. Half as much of this enzyme was synthesized without exogenous nitrogen by cells taken from a nitrogen-rich medium as was formed by cells under favorable conditions with an external supply of nitrogen. Escherichia coli B contained a pool of nitrogen compounds soluble in 80 per cent ethanol and made up of several ninhydrin-positive components. One of these was identified chromatographically as glycine using an authentic radioactive sample. Another substance behaved like serine on the chromatograms. The internal pool of amino acids and peptides was large enough to account for the ß-galactosidase synthesized by cells exposed to lactose in a medium free of nitrogen. Some degree of interaction of the syntheses of the ß-galactosidase and xylose enzyme systems was observed in nitrogen-free media. This interaction produced a greater effect on the formation of ß-galactosidase and was attributed to a limiting factor(s) in the internal nitrogenous pool or to a limiting intermediate in enzyme synthesis.
THE INHIBITORY EFFECT OF STROPHANTHIDIN ON SECRETION BY THE ISOLATED GASTRIC MUCOSA
Authors: Cooperstein I. L.
Published: May 2004

The unidirectional fluxes of Na+ and Cl- were measured across the isolated gastric mucosa of the bullfrog (R. catesbiana). The addition of strophanthidin, a cardiac aglycone, resulted in marked reductions of the spontaneous potential and short-circuit current. Associated with these changes, the isolated gastric mucosa ceased secreting chloride and hydrogen ion. Although the active component of chloride transfer was inhibited, the exchange diffusion component seemed to increase. No significant changes in membrane conductance or sodium flux were noted.

Possible mechanisms of strophanthidin inhibition were discussed in view of its effect on chloride transport across the gastric mucosa and on sodium and potassium transfer in other tissues. It was concluded that the cardiac glycosides may not be specific inhibitors of sodium and potassium transport. This non-specific inhibition suggests that active chloride transport is affected by strophanthidin directly and/or anion secretion is dependent upon normal functioning of cation transport systems in the tissue.
THE RESPONSES OF LIMULUS OPTIC NERVE FIBERS TO PATTERNS OF ILLUMINATION ON THE RECEPTOR MOSAIC
Authors: Ratliff Floyd , Hartline H. K.
Published: May 2004

The inhibition that is exerted mutually among receptor units (ommatidia) of the compound eye of Limulus is less for units widely separated than for those close together. This diminution of inhibition with distance is the resultant of two factors: (1) the threshold of inhibitory action increases with increasing distance between the units involved; and (2) the coefficient of inhibitory action decreases with increasing distance.

The discharge of nerve impulses from ommatidia at various distances from one another may be described quantitatively by a set of simultaneous linear equations which express the excitatory effects of the illumination on each ommatidium and the inhibitory interactions between each ommatidium and its neighbors. The values of the thresholds and coefficients of inhibitory action, which appear as parameters in these equations, must be determined empirically: their dependence on distance is somewhat irregular and cannot yet be expressed in an exact general law. Nevertheless the diminution of inhibitory influences with distance is sufficiently uniform that patterns of neural response generated by various patterns of illumination on the receptor mosaic can be predicted qualitatively. Such predictions have been verified experimentally for two simple patterns of illumination: an abrupt step in intensity, and a simple gradient between two levels of intensity (the so-called Mach pattern). In each case, transitions in the pattern of illumination are accentuated in the corresponding pattern of neural response.
Electrical Characteristics and Activation Potential of Bufo Eggs
Authors: Maéno Takashi
Published: May 2004

Electrical characteristics and their changes during activation were studied with the microelectrodes on the oocytes and eggs of the toad, Bufo vulgaris formosus Boulenger.

In young oocytes, the membrane characteristics had some similarities to those of nerve and muscle, except for a relatively large resistance of 25 KΩcm.2 and an absence of the action potential in the former. After maturation, however, the membrane characteristics became entirely different from those of oocytes and other excitable tissues. In the mature eggs the membrane resistance was measured to be as high as 200 KΩcm.2, and no specific permeability of the membrane to potassium ions was observable.

A slow monophasic change in the membrane potential was recorded in every activation produced by mechanical stimulation, and termed "activation potential." In fresh water, its amplitude was as large as 80 to 90 mv. with an overshoot of about 50 mv. The activation potential might be comparable to the action potential of nerve and muscle, but was fundamentally different in ionic mechanism from the latter, since the former was caused by a marked increase in permeability to chloride ions.