bluuebunny/crossref_metadata_2025 huggingface dataset:
CATION TRANSPORT IN YEAST
Authors: Foulkes Ernest C.
Published: May 2004

1. The distribution of azide added to suspensions of bakers' yeast was studied under various conditions. The recovery of azide was estimated in the volume of water into which low concentrations of electrolytes can readily diffuse (anion space). Considerable azide disappeared from this anion space.

2. The incomplete recovery of azide in the anion space is due to its uptake by the cells. This uptake occurs against a concentration gradient at 0°C., and is attributed to binding of azide by cell constituents.

3. Confirmatory evidence is presented that one such constituent is the K carrier in the cell membrane. The azide inhibition of K transport is not mediated by inhibition of cytochrome oxidase in the mitochondria.

4. From the amount of combined azide and the experimentally determined dissociation constant of the K carrier-inhibitor complex, the maximum value for the concentration of this carrier is calculated as 0.1 µM/gm. yeast.

5. The addition of glucose and PO4 causes a secondary K uptake which is not azide-sensitive and is clearly distinct from the primary, azide-sensitive mechanism.

6. The existence of a separate carrier responsible for Na extrusion is reconsidered. It is concluded that present evidence does not necessitate the assumption that such a carrier is active in yeast.
THE EFFECT OF EXTERNAL CALCIUM AND MAGNESIUM DEPLETION ON SINGLE NERVE FIBERS
Authors: Adelman William J.
Published: May 2004

The three types of motor axons found in the walking legs of the lobster were shown to respond differently upon exposure to calcium-free solutions. While all fiber types became more excitable initially in calcium-free solutions, only openers became spontaneously active. Fast closers showed the least reduction in rheobase value upon calcium depletion. After 5 minutes in calcium-free solution all fibers showed a rise in rheobase value, and more rapid accommodation. A natural period for spontaneous firing of opener fibers was disclosed. Following such a spontaneous discharge, low amplitude rhythmical potentials were recorded. These small potentials had the same period as the spontaneous spikes. The role of calcium ion in the excitable process was discussed.

Magnesium ion was shown to act synergistically with calcium ion. All fiber types became spontaneously active in solutions deprived of both calcium and magnesium. Subsequent hypoexcitability was more pronounced in calcium- and magnesium-depleted solutions than it was in only calcium-depleted solutions.
THE EFFECT OF POLYPHOSPHATES AND MAGNESIUM ON THE MECHANICAL PROPERTIES OF EXTRACTED MUSCLE FIBERS
Authors: Bozler Emil
Published: May 2004

Loading of extracted muscle fibers causes a small, sudden lengthening, followed by a slower, plastic extension, which is reversed only by active contraction. Polyphosphates in the presence of Mg strongly accelerate plastic extension, but elastic changes in length remain the same as during rigor. The modulus of elasticity on the average is about 6.2 x 107 dynes per cm.2 This value is about 40 times larger than that of rubber, if compared on a water-free basis. Extension of muscle, therefore, is almost entirely due to plastic deformation.

Mg is essential for the softening action of adenosinetriphosphate (ATP) and can produce partial relaxation in the absence of a relaxation factor. After partial removal of bound Mg, ATP causes strong contraction, but only slight softening. The same condition is produced by very low concentrations of ATP in the presence of phosphocreatine. These observations show that during contraction passive mechanical properties may remain essentially like those during rigor. The constancy of elastic extensibility distinguishes contraction produced by ATP from contraction induced by non-specific agents in various fibrous structures and caused by an increase in configurational entropy.
THE ISOLATION OF MYXOMYOSIN, AN ATP-SENSITIVE PROTEIN FROM THE PLASMODIUM OF A MYXOMYCETE
Authors: Ts'o Paul O. P. , Eggman Luther , Vinograd Jerome
Published: May 2004

1. A procedure has been developed for the preparation of an active concentrate from the myxomycete, Physarum polycephalum. This concentrate responds with a lowered viscosity to the addition of small amounts of ATP. The preparation recovers in viscosity, and the process may be repeated.

2. In the most active concentrates, 75 per cent of the non-dialyzable material moves as a single boundary both in the descending limb in electrophoresis and in the ultracentrifuge. It contains about 10 per cent ribonucleic acid, which is at least in part reversibly bound to the protein.

3. The active material has been designated myxomyosin because of its origin and its similarity to actomyosin in ATP response.
SEROLOGICAL INVESTIGATIONS OF CELL ADHESION IN THE SLIME MOLDS, DICTYOSTELIUM DISCOIDEUM, DICTYOSTELIUM PURPUREUM, AND POLYSPHONDYLIUM VIOLACEUM
Authors: Gregg James H.
Published: May 2004

1. Antibodies to slime molds were produced by injecting D. discoideum and D. purpureum amebas from 48 hour cultures into rabbits.

2. Anti-D. discoideum and anti-D. purpureum sera caused agglutination of homologous amebas from 24 to 26 hour cultures, agglutination of certain heterologous amebas from 30 to 36 hour cultures, and agglutination of all heterologous amebas from 43 to 48 hour cultures.

3. The data show that new surface antigens are formed in cultures after 26 hours and it is suggested that the new antigens are concerned with cell adhesion.

4. The probable role of surface antigens in the interaction of cells of different species of slime molds was discussed.
THE EFFECT UPON ACTOMYOSIN OF STOICHIOMETRIC AMOUNTS OF ADENOSINETRIPHOSPHATE REGENERATED IN A COUPLED ENZYME SYSTEM
Authors: Mommaerts W. F. H. M. , Hanson Jean
Published: May 2004

Pyruvate kinase and phosphoenolpyruvate, added to actomyosin, cause a maintenance of the response of the actomyosin to stoichiometric amounts of ATP. This steady state maintenance depends on the presence of Mg ions.
CULTURE IN VITRO OF TISSUE FROM THE SILKWORM, BOMBYX MORI L
Authors: Wyatt S. Silver
Published: May 2004

1. Ovarian tissue from Bombyx mori L. larvae about to pupate was cultured in Trager's (1935) salt solution and 10 per cent hemolymph, with indifferent results. Improvement of cultures was sought by modifying the culture medium.

2. To reduce the activity of the tyrosinase, hemolymph for culture medium was heated for 5 minutes at 60°C., and the coagulated protein removed.

3. A physiological solution was formulated containing cations and amino acids as they occur normally in silkworm hemolymph. In both hanging-drop and small tube cultures use of this medium brought about increased cell number, improved cell appearance, more rapid mitoses, and longer life of cultures.

4. To the solution formulated from analyses, tryptophan, cystine, cysteine, malate, fumarate, succinate, and α-ketoglutarate were added after testing individually, resulting in improved growth in cultures.

5. Use of a silkworm egg extract prepared 4 to 5 days after acid treatment produced an increase in cell number.

6. In small roller tube cultures, when the new medium was changed twice a week, the cells spread over the walls of the tube in 4 or 5 days (Figs. 8 and 9), rapid mitoses were observed after 2 weeks, and transparent active cells were present at 3 weeks. Subculturing was not attempted.
THE CHEMISTRY OF INSECT HEMOLYMPH
Authors: Wyatt G. R. , Loughheed T. C. , Wyatt S. S.
Published: May 2004

1. Hemolymph was collected for analysis from the silkworm, Bombyx mori, in a series of developmental stages ranging from the second molt to the late pupa. The mean pH of larval hemolymph after collection was found to be 6.45, that of pupal hemolymph, 6.57; in vivo values may be slightly lower. Total dry solids ranged from 5.4 to 10.6 per cent. Total protein ranged from 1.2 to 5.3 per cent, increasing rapidly during the fifth instar.

2. Free amino acids were separated chromatographically and estimated. Of 19 amino acids identified, amounting collectively to 823 to 1497 mg. per 100 ml., glutamine, histidine, and lysine generally occurred in greatest amount. Tryptophan was not detected, and cystine (or cysteine) was found in only one sample. The total free amino acids account for 35 to 55 per cent of the non-protein nitrogen of the plasma.

3. Free sugars, estimated semiquantitatively on chromatograms, comprise glucose, fructose, and sucrose in total amount ranging from about 5 to 40 mg. per 100 ml. Total acid-soluble, ultrafiltrable carbohydrate, estimated as glucose by the anthrone reaction, ranged from 166 to 635 mg. per 100 ml., indicating the presence of low molecular weight sugar derivatives.

4. Inorganic phosphate amounted to 5 to 15 mg. per 100 ml., and acid-soluble organic phosphate to 100 to 200 mg. per 100 ml. The latter fraction includes several substances, of which one was tentatively identified as glucose-6-phosphate and the remainder are as yet unidentified.

5. Single samples of hemolymph were also taken from larvae of the wax moth, Galleria mellonella, and the spruce sawfly, Diprion hercyniae. These contained even higher concentrations of solutes than the silkworm samples, but with a generally similar distribution. The proportions of the free amino acids were different in each species.
FURTHER OBSERVATIONS ON UPTAKE OF S35-LABELLED SULFATE BY RENAL TISSUE IN VITRO
Authors: Deyrup Ingrith J.
Published: May 2004

Additional studies have been made of the accumulation of S35 by renal cortical tissue incubated in media containing radiosulfate. This process was found to occur in several mammalian species in addition to the rat, but was not observed as a significant occurrence in three species of lower vertebrates. In the case of rat renal tissue, S35 uptake was found to be sensitive to the pH and osmolar concentration of the medium. The character of the anions present in conjunction with K+ affected it as well. Various factors known to be related to in vitro accumulative processes, as well as to renal sulfate reabsorption by the intact dog, were tested on rat kidney cortex to assess the effect on radiosulfate uptake. In general, all substances tested (amino acids, metabolic intermediates, ATP, metabolic inhibitors, competitive inhibitors for PAH accumulation in vitro) were found to lessen S35 uptake, or to be without effect upon it. The one striking exception was phlorhizin, which enhanced markedly S35 uptake in vitro, as it does sulfate reabsorption in vivo. Some implications of these findings have been discussed.
THE STABILITY OF RHODOPSIN AND OPSIN
Authors: Radding Charles M. , Wald George
Published: May 2004

The stability of cattle rhodopsin and of its protein moiety opsin toward acids and alkalies and on aging was determined by two criteria: maintenance of absorption spectrum, and capacity to regenerate after exposure to light.

On storage at 3°C. at pH near neutrality, the absorption spectrum in the visible region may remain unchanged for as long as 6 months; but the regenerability progressively declines, at very different rates in different preparations. The cause of this decline has not been determined. It may involve denaturation at sites other than the retinene-protein bond, which by the evidence of the absorption spectrum remains intact.

Cattle rhodopsin maintains its absorption spectrum at any pH from 3.9–9.6 for at least an hour at 25–27°C. To both sides of this pH range the pigment bleaches, the extinction falling to half in 1 hour at pH 3.3 and 10.5.

The exposure of rhodopsin to light greatly increases the vulnerability of the product (opsin) to acids and bases. Opsin rapidly loses its capacity to regenerate rhodopsin to both sides of the range of pH 5.5–7.0. Half the regenerability is lost within 45 seconds at pH 3.4 and 9.1; and within 1 hour at pH 5 and 8.
INACTIVATION OF BACTERIA BY DECAY OF INCORPORATED RADIOACTIVE PHOSPHORUS
Authors: Fuerst Clarence R. , Stent Gunther S.
Published: May 2004

Cultures of Escherichia coli will not grow in media containing very high specific activities of radiophosphorus P32, the inhibition of growth being due to the decay of assimilated P32 atoms. Experiments with a differentially labeled thymineless strain of E. coli show that the P32 disintegrations which occur in the bacterial deoxyribonucleic acid, i.e. in the nucleus, are mainly responsible for the inactivation of the cell. The kinetics with which radioactive bacterial populations are inactivated indicate that the function of several nuclei per bacterial cell must be eliminated by P32 decay before the ability to generate a colony is lost. The efficiency with which each P32 disintegration inactivates the nucleus in which it has occurred is calculated to be 0.02 (at –196°), i.e., similar in magnitude to the killing efficiency of P32 decay in bacteriophages.

P32 decay and thymine starvation cooperate in bringing about the death of individuals of the thymineless strain, from which observation it is inferred that "thymineless death" is likewise a nuclear inactivation.

The descendants of a non-radioactive bacterial culture grown for several generations in the presence of P32 and the descendants of a radioactive culture grown in the absence of P32 are inactivated by P32 decay in a manner which indicates that the phosphorus atoms of bacterial nuclei are dispersed among the progeny nuclei in their line of descendance.
THE RESPONSES OF THE PUPIL OF GEKKO GEKKO TO EXTERNAL LIGHT STIMULUS
Authors: Denton E. J.
Published: May 2004

1. The responses of the pupil of a nocturnal gecko (Gekko gekko) to external light stimulus were studied.

2. The responses of the pupil are determined by light entering the pupil and not by light acting directly on the iris.

3. The responses of the pupil are very uniform in sensitivity including spectral sensitivity for light coming in different directions to the eye.

4. The possible change in area of the pupil is more than 300-fold and probably represents an effort to shield the pure rod retina from saturating light intensities.

5. The pupil continues to contract sharply for changes in external light intensity which give retinal illuminations corresponding to 106 quanta/sec. striking a retinal rod.

6. There is a large degree of spatial summation of the response; circular external light fields subtending 5 and 140° giving the same illumination at the pupil give approximately the same pupil response.

7. The spectral sensitivity curve agrees with the absorption curve of an extracted pigment from a closely related gecko described by Crescitelli in the followig paper. It is similar to the human scotopic curve but its maximum is displaced about 20 to 30 mµ towards the red end of the spectrum. The fall in sensitivity towards the red end of the spectrum is described by the equation

See PDF for Equation
MONOSYNAPTIC REFLEX RESPONSE OF INDIVIDUAL MOTONEURONS AS A FUNCTION OF FREQUENCY
Authors: Lloyd David P. C.
Published: May 2004

An assemblage of individual motoneurons constituting a synthetic motoneuron pool has been studied from the standpoint of relating monosynaptic reflex responses to frequency of afferent stimulation.

Intensity of low frequency depression is not a simple function of transmitter potentiality.

As frequency of stimulation increases from 3 per minute to 10 per second, low frequency depression increases in magnitude. Between 10 and approximately 60 per second low frequency depression apparently diminishes and subnormality becomes a factor in causing depression. At frequencies above 60 per second temporal summation occurs, but subnormality limits the degree of response attainable by summation.

At low stimulation frequencies rhythm is determined by stimulation frequency. Interruptions of rhythmic firing depend solely upon temporal fluctuation of excitability. At high frequency of stimulation rhythm is determined by subnormality rather than inherent rhythmicity, and excitability fluctuation leads to instability of response rhythm. In short, whatever the stimulation frequency, random excitability fluctuation is the factor disrupting rhythmic response.

Monosynaptic reflex response latency is stable during high frequency stimulation as it is in low frequency stimulation provided a significant extrinsic source of random bombardment is not present. In the presence of powerful random bombardment discharge may become random with respect to monosynaptic afferent excitation provided the latter is feeble. When this occurs it does so equally at low frequency and high frequency. Thus temporal summation is not a necessary factor. There is, then, no remaining evidence to suggest that the agency for temporal summation in the monosynaptic system becomes a transmitting agency in its own right.
MONONUCLEOTIDES OF THE CELL NUCLEUS
Authors: Osawa Syozo , Allfrey V. G. , Mirsky A. E.
Published: May 2004

1. It has been demonstrated by ion exchange chromatography that the cell nucleus contains mononucleotides of adenine, guanine, cytosine, uracil, together with diphosphopyridine nucleotide, and several uridine diphosphate derivatives; the adenine nucleotides predominating in amount. Nucleotide components in the cell nucleus are in close agreement both quantitatively and qualitatively with those found in the cytoplasm.

2. In calf thymus sucrose nuclei, nucleotide monophosphates can be phosphorylated to the energy-rich triphosphate form without participation of cytoplasmic components. As to the nature of the phosphorylation, it has been shown that there exist certain differences as well as resemblances between nuclei and mitochondria. A distinctive feature of nuclear phosphorylation is that only intranuclear monophosphates seem to be phosphorylated. The process is completely inhibited by cyanide, azide, and dinitrophenol. However, certain reagents which block oxidative phosphorylation of mitochondria, namely dicumarol, Janus green B, methylene blue, and calcium ions, have no effect on phosphorylation within the nucleus.

3. The bulk of mononucleotides is preserved within thymus nuclei after their isolation in sucrose. Nucleotides are surprisingly well retained by nuclei in a sucrose medium whether or not electrolytes are present and in buffers ranging from pH 3 to 10; under all conditions sucrose is required for retention.

4. Dilute acetate in sucrose releases nucleotides from the nucleus below pH 5.1. As to the effective pH of acetate, there is a sharp boundary between pH 5.1 and pH 5.9. At pH 5.9, and above, acetate does not remove nucleotides from the nucleus. The effects of propionate, formate, and monochloroacetate on the nuclei are the same as that of acetate.

5. When nuclei are exposed to a wide variety of conditions a close correlation is found between the retention in the nucleus of nucleotides and of potassium. This suggests that both substances are part of a common complex in the cell nucleus.

6. It has been shown that upon removal of nucleotides and potassium from calf thymus sucrose nuclei by acetate, the ability to incorporate C14-alanine into nuclear protein is greatly impaired.
INTRACELLULAR RECORDING FROM THE GIANT SYNAPSE OF THE SQUID
Authors: Bullock Theodore H. , Hagiwara Susumu
Published: May 2004

1. Recording with glass micropipette electrodes inserted close to the synaptic region, in the presynaptic and in the postsynaptic fibers of the giant synapse in the stellate ganglion of the squid, has been accomplished.

2. The forms of the spike and of the synaptic potential are very much like those reported earlier (Bullock, 1948) from macroelectrodes. The crest time and the rate of fall are labile and depend on the state of fatigue, though the time of initiation of the postsynaptic potential does not.

3. It is concluded after examination of both intra- and extracellular recordings that there is a real synaptic delay of the order of 1 or 2 milliseconds at 15–20°C.

4. There is sometimes a very small and sometimes no visible deflection in the intracellular postsynaptic record attributable to the presynaptic spike. It is concluded that transmission cannot be electrical.

5. The amplitude of the postsynaptic potential can be controlled over some range by the amplitude of the presynaptic potential.

6. Hyperpolarization of the postsynaptic membrane results in increase in amplitude of spikes up to 200 millivolts, in increase in the membrane potential level at which the spike flares up, but in no considerable change in the amplitude in postsynaptic potential.

7. The postsynaptic potential can add to the late falling phase and the undershoot of an antidromic spike in the postfiber but cannot add to the crest or early part of the falling phase. The earliest part of the antidromic spike during which the postsynaptic potential can add is probably a period of refractoriness to electrical shock by analogy with the properties of the axon.
STUDIES ON THE ELECTRICAL PROPERTIES OF A SINGLE PLANT CELL
Authors: Kishimoto Uichiro
Published: May 2004

Impedance changes of single plant cells of Nitella flexilis were studied under different environmental conditions.

With the analysis presented changes in resistance of the protoplasmic membrane and of cell sap can be studied independently and simultaneously.

Under "transcellular osmosis," the resistance of the protoplasmic membrane and of the cell sap increase at the part of the cell where water enters, while they decrease where water goes out.

Ethanol of low concentration (below 8 per cent) first decreases and later increases the resistance of the protoplasmic membrane. Concentrated ethanol (over 10 per cent), however, brings about a large decrease in resistance of the protoplasmic membrane. Its time course is not simple, but undulatory changes occur.

When ethanol is applied to one part of the cell, the resistance of the protoplasmic membrane shows a different type of change, which may be attributed to the local osmotic effect of ethanol; injury generally occurs with comparatively low concentration.

Methanol, ethanol, and propanol have almost the same effect upon the cell, while butanol is toxic at the same concentration.

When the cell dies, the resistance of the protoplasmic membrane decreases greatly, while the resistance of the cell sap increases to a level (several hundred kilo ohms or more), expected when external solution and cell sap are freely mixed with each other.
THE VISUAL SYSTEM OF THE ALLIGATOR
Authors: Wald George , Brown Paul K. , Kennedy Donald
Published: May 2004

The eye tissues and liver of the alligator contain vitamin A1 alone. The retina contains rhodopsin, typical in absorption spectrum (λmax 500 mµ); but synthesized in solution from neo-b retinene and opsin much more rapidly than are the frog, mammalian, or chicken rhodopsins previously examined. In this regard alligator rhodopsin resembles the rhodopsins and porphyropsins of fishes, all of which so far investigated are synthesized rapidly in solution. The rates of synthesis in vitro of frog and alligator rhodopsins are matched closely by the rates of rod dark adaptation in living frogs and alligators, measured electrophysiologically at the same temperature. Alligator rods dark-adapt, and alligator rhodopsin is synthesized in solution, at rates characteristically associated with cones and cone pigments in frogs, mammals, and birds.
LACTIC AND α-GLYCEROPHOSPHATE DEHYDROGENASES IN INSECTS
Authors: Zebe E. C. , McShan W. H.
Published: May 2004

Different tissues, especially muscles, from insects belonging to various groups were extracted and studied for their lactic dehydrogenase (LDH) and α-glycerophosphate dehydrogenase (GDH I) activities from the comparative point of view.

In all cases assays of flight muscle extracts showed extremely low values of LDH activity whereas the GDH activities were surprisingly high. The activities in leg muscles were generally lower. In some insects, however, a very active LDH was found; in these cases the GDH activity seemed to be decreased.

GDH I was rather active in the fat bodies.

The presence of particulate glycerophosphate dehydrogenase (GDH II) was also demonstrated in insect muscles.

These results were interpreted as indicating a system by which there is accomplished immediate and direct breakdown of metabolites to supply large amounts of energy during flight and other activities without the accumulation of intermediate substances.
THE EFFECTS OF HYDROSTATIC PRESSURE UPON THE NORMAL AND NARCOTIZED NERVE FIBER
Authors: Spyropoulos Constantine S.
Published: May 2004

The properties of the giant axon of the squid Loligo pealii were studied at different hydrostatic pressures from 14.7 to 16,000 psi. At 4000 psi the resting potential, the membrane resistance, membrane capacity, the conduction velocity, the amplitude of the action potential, and the maximal change in the membrane impedance during activity were only slightly affected. At the same pressure the duration of the falling phase of the action potential was increased by about 40 to 60 per cent and the duration of the rising phase by about 20 to 35 per cent. The duration of the membrane impedance change during activity was increased by 50 to 100 per cent at 4000 psi. At pressures even slightly above atmospheric the threshold membrane current was appreciably reduced. At about 3000 to 7000 psi the fiber fired spontaneously. At pressures considerably above 5000 psi the membrane resistance decreased to about one-half to one-third the original value. The narcotizing effect upon the nerve fiber of 3 to 7 per cent ethanol was partly or almost completely opposed by low temperatures or high pressures.
THE CONTRIBUTIONS OF NORMAL AND ANOMALOUS OSMOSIS TO THE OSMOTIC EFFECTS ARISING ACROSS CHARGED MEMBRANES WITH SOLUTIONS OF ELECTROLYTES
Authors: Grim Eugene , Sollner Karl
Published: May 2004

The osmotic effect arising across a porous membrane separating the solution of an electrolyte from water (or a more dilute solution) is ordinarily due to both normal osmosis, as it occurs also with non-electrolytes, and to "anomalous" osmosis. It is shown that the normal osmotic component cannot be measured quantitatively by the conventional comparison with a non-electrolytic reference solute. Anomalous osmosis does not occur with electroneutral membranes. Accordingly, with membranes which can be charged and discharged reversibly (without changes in geometrical structure), such as many proteinized membranes, the osmotic effects caused by an electrolyte can be measured both when only normal osmosis arises (with the membrane in the electroneutral state) and when normal as well as anomalous osmosis occurs (with the membrane in a charged state). The difference between these two effects is the true anomalous osmosis. Data are presented on the osmotic effects across an oxyhemoglobin membrane in the uncharged state at pH 6.75 and in two charged states, positive at pH 4.0 and negative at pH 10.0, with solutions of a variety of electrolytes using a concentration ratio of 2:1 over a wide range of concentrations. The rates of the movement of liquid across the membrane against an inconsequentially small hydrostatic head are recorded instead of, as conventional, the physiologically less significant pressure rises after a standard time.
THE STATISTICAL DETECTION OF THRESHOLD SIGNALS IN THE RETINA
Authors: Fitzhugh Richard
Published: May 2004

1. Photographic records of impulses from single ganglion cells in the cat's retina were made while the retina was stimulated by flashes occurring once a second. Ten flashes at each of several intensities near threshold were used.

2. For the purpose of statistical analysis, the number of impulses (x) falling within a critical period following each flash was used as an index of the response. Histograms of x were plotted and used to calculate rates of transfer of information by the ganglion cell for the case of an ideal experiment, the yes-no choice, in which flashes of intensity I and blanks are to be distinguished.

3. The information rate increased (a) with increasing stimulus intensity and (b) with the number of identical flashes or blanks presented successively in a block. The intensity chosen as threshold by the experimenter, who observed the impulses visually and aurally, corresponded to an average information rate for single flashes of 0.7 bit/flash, compared to the maximum possible rate of 1 bit/flash. A threshold intensity giving 0.4 or more bit/flash, if presented in blocks of six identical flashes, corresponded to 0.95 or more bit/block, or near certainty. Thus the calculation of information rates using the index x provides an estimate of threshold at least as sensitive as those obtained during an experiment, which were made only after observing the responses to five to ten flashes of the same intensity.

4. The index x has statistical properties similar to those of the "index of neural activity" used by Tanner and Swets (1954) in their statistical model of human vision, and represents a possible physical interpretation of their index. However, x gave values (0.5 to 1.5) of the parameter called the slope which were consistently smaller than their values (2.1 to 3.1).
A MODEL OF GROWTH AND GROWTH CONTROL IN MATHEMATICAL TERMS
Authors: Weiss Paul , Kavanau J. Lee
Published: May 2004

A practicable model of the growth process, which gives better definition to the problem of growth and growth regulation and greater precision to related experimental work than do earlier models, is developed on the basis of the following assumptions: "Growth" is the net balance of mass produced and retained over mass destroyed and otherwise lost, implying continual metabolic degradation and replacement. Terminal size represents stationary equilibrium between incremental and decremental components. The mass of an organic system consists of two functionally different components,—generative and differentiated. Generative mass increases by the catalytic action of key compounds ("templates") characteristic of each cell type. Each cell also produces specific freely diffusible compounds antagonistic to these templates ("antitemplates"). Growth regulation occurs automatically by a negative "feedback" in which increasing numbers of antitemplates progressively block the corresponding templates.

Differential equations expressing these interrelationships are formulated, integrated, and the solutions evaluated for the case of chick growth. These specific solutions lead to descriptions of the normal growth of a biological system which are in good agreement with known facts, and to predictions of the course of automatic growth regulations after experimental or pathological disturbances which reproduce adequately biological observations in this domain.
THE PROPORTION OF TERRAMYCIN-RESISTANT MUTANTS IN B. MEGATHERIUM CULTURES
Authors: Northrop John H. ,   With the Technical Assistance of Marie King
Published: May 2004

The number of terramycin-resistant mutants in Bacillus megatherium cultures, their mutation rate, and the growth rate of the wild and mutant cells have been determined under various conditions. These values are in agreement with the following equations (Northrop and Kunitz, 1957):—

See PDF for Equation

λ = mutation rate, A = growth rate constant of wild cells,

B = growth rate constant of mutants,

See PDF for Equation

equilibrium. The value of the mutation rate as determined from equation (6) agrees with that found by the null fraction method.
DIFFUSION AND PERMEATION OF CATIONS IN HUMAN AND DOG ERYTHROCYTES
Authors: Harris E. J. , Prankerd T. A. J.
Published: May 2004

The kinetics of movement of tracer Na into human and dog red cells have been studied. The time courses of these processes and of K transfer were compared with the theoretical time course for saturation of a flat sheet having a resistive surface. The theoretical and the experimental curves when plotted against t½ have a considerable portion which is linear; on the basis of this resemblance the results are interpreted in terms of a permeability constant and an internal diffusion constant. It is supposed that selective adsorption acts to bring about concentration of K in the human cell and that the bulk of the Na of that cell is present in a thin outer region, while the K is in the interior. The action of strophanthin is to remove the usual limit to the Na capacity of the cell and it is proposed that the Na region increases in thickness at the expense of the K region. Omission of K from the medium has a similar result. Na uptake into poisoned cells measured either with tracer or as a net gain has a linear dependence upon t½ after a delay. The permeability of the dog cell to Na is reduced when K is added to the medium; this may be due to the formation of an outer K-rich region which imposes a resistance to Na movement.
FACTORS INFLUENCING THE UPTAKE AND LOSS OF RADIOSULFATE BY RAT RENAL CORTICAL TISSUE IN VITRO
Authors: Deyrup Ingrith J.
Published: May 2004

Rat kidney cortical slices, during incubation in vitro, lose previously accumulated radiosulfur when exposed to conditions (e.g. addition to the medium of metabolic inhibitors) which normally depress the uptake of S35. The extent of this loss is not affected significantly by the presence of phlorhizin, an agent which enhances markedly radiosulfate accumulation. On the other hand, when tissues are chilled to 1°C., loss is slight or negligible even in the presence of metabolic inhibitors. These data, and observations on the effect of pre-incubation of kidney slices in S35-free media before the addition of radiosulfate, have been interpreted as evidence that S35 accumulation in vitro may be resolved into at least two processes, namely (a) entrance of the isotope-labelled anion into the cells, by diffusion and/or active transport, and (b) complexing of S35 (in ionic or other form) with an intracellular component. The postulated complex is stabilized, perhaps through inactivation of a specific enzyme, by chilling the tissue to 1°C. Possible relationships are discussed among the observations noted above, sulfur metabolism in general, and aspects of the known in vivo transport mechanism for sulfate ion; i.e., renal tubular reabsorption.
STUDIES ON STREPTOCOCCUS PYOGENES
Authors: Slade Hutton D.
Published: May 2004

Electron microscopic observations of Streptococcus pyogenes (strain S43, type 6) treated with trypsin and cetyltrimethylammonium bromide (Cetab) are presented. The concentration of trypsin necessary to remove the M protein antigen was shown to bring about a partial digestion of the cells. The cell protoplasm and protoplasmic membrane were affected. No microscopic changes appeared in the cell wall. Cetab did not alter the appearance of the cells.

Both trypsin and detergent altered the permeability of the cell so that citrulline and carbamylphosphate were metabolized. Cells exhibiting enzyme activity on these substrates after Cetab treatment were characterized by the release of lysine, glutamic acid, nucleic acid, and other cellular material.

Enzymes responsible for the metabolism of arginine, citrulline, and carbamylphosphate were shown to reside in the cell protoplasm. Cells which had lost their viability after Cetab treatment still possessed the ability to utilize the latter substrates. Under similar conditions the metabolism of glucose did not occur.

Normal cells were shown to possess the ability to fluoresce in the presence of a dye. The intensity of the fluorescence was reduced by trypsin treatment.
UPHILL TRANSPORT INDUCED BY COUNTERFLOW
Authors: Rosenberg Thomas , Wilbrandt W.
Published: May 2004

1. In a membrane transport system containing a mobile carrier with affinities for two substrates a concentration gradient with respect to one of the substrates under certain conditions is able to induce an "uphill" transport (against the concentration gradient) of the other.

2. In a kinetic treatment quantitative conditions for such a "flow-induced uphill transport" and some of its characteristics are derived.

3. Experimentally the uphill transport of labelled glucose induced by a concentration gradient for mannose or unlabelled glucose is demonstrated in the human red cell.

4. It is shown that the flow-induced uphill transport is a feature characteristic for mobile carrier systems only and is not to be expected in systems in which the substrate is bound to a fixed membrane component ("adsorption membrane"), although such a system may yield identical transport kinetics. Also with respect to Ussing's flux ratio the two systems are different, the adsorption membrane meeting Ussing's criterion, the carrier membrane not.

5. It is concluded that the transport system in the human red cells must contain a mobile carrier, identical for glucose and mannose.
THE PROTEIN COATS OR "GHOSTS" OF COLI PHAGE T2
Authors: Herriott Roger M. , Barlow James L.
Published: May 2004

Phage coats or ghosts, composed entirely of protein, appear to be responsible for protecting the phage nucleic acid from degradation by factors in the surrounding medium; attachment of the virus to its susceptible host; and delivering the nucleic acid to the interior of the cell. In addition, the ghosts have a number of biological actions which resemble similar actions of the parent phage. Thus, they both "kill" cells, inhibit pentosenucleic acid formation, interfere with subsequent infection by other virus particles, block adaptive enzyme formation, induce or trigger lysis of the host, and cause a leakage of phosphorus-containing fragments from the cell. Results to date fail to demonstrate a direct involvement of the ghosts in the passage of genetic information to the progeny. Several of the above changes induced in the host cell following attachment of ghosts could be derived from an alteration in but a single metabolic reaction. The stoichiometry of the ghost-bacterial cell interaction is different from that of the parent phage. Experiments to distinguish between a variable response of the host cell to reaction at different sites and a state of heterogeneity in the ghost preparations suggest the former but they are not decisive.
ELECTROOSMOSIS IN NITELLA
Authors: Blinks L. R. , Airth R. L.
Published: May 2004

The role of electroosmosis was studied directly in Nitella. The cells were mounted in a water-tight barrier between two chambers containing reversible electrodes for the application of potentials, and fitted with calibrated capillaries to measure water movement.

No water movement was found when small existing bioelectric potentials were short-circuited through an external connection, nor when external potentials up to 1 or 2 volts were applied (producing currents up to 5 µa).

Higher potentials (up to 10 volts) caused small movements of water, toward the negative pole. Larger and often irreversible water movements were produced by potentials up to 20 volts—sometimes persisting after current flow.

A variety of evidence suggests that the effects are caused by injury at the cathodal end of the cell, allowing water to be attracted osmotically at the intact end and forced out at the injured end (transosmosis). This injury is reversible under small applied potentials, irreversible after large ones (100 to 200 times the natural bioelectric values).

Such water flows persist in low salt concentrations (up to 0.09 M NaCl) but almost completely vanish in isotonic (0.26 M) mannitol. This confirms the osmotic, rather than the electroosmotic nature of the water movement. It is estimated that electroosmosis cannot account for more than 1 per cent of the water movement (or turgor) in Nitella cells. The dead cellulose walls display a small electroosmotic water flow at very high current densities (under 20 volts applied potential).
BLUE LIGHT AND THE REGENERATION OF HUMAN RHODOPSIN IN SITU
Authors: Rushton W. A. H.
Published: May 2004

Hubbard has found that the photoisomerization of retinene was important for the regeneration of rhodopsin in vitro, and the object of the present investigation was to find whether this was also true for regeneration in the living human eye.

In the Appendix is described a device which permits the rhodopsin density to be measured by analysing the light reflected from the fundus oculi in an ophthalmoscopic arrangement, the measurement taking about 5 seconds. Now if a blue and a yellow light viewed scotopically are adjusted in intensity so as to appear identical, they must bleach rhodopsin equally, but the blue will be more than 10 times as effective in isomerizing retinene. Therefore if retinene isomerization is important for rhodopsin regeneration, blue light should cause a more rapid regeneration after bleaching, and during bleaching the equilibrium level attained should be less profound. But, as the figures show, the course of bleaching and regeneration is identical for the matched yellow or blue bleaching lights, therefore isomerization of retinene is not important for rhodopsin regeneration in the living human eye.
ENZYMIC DEPHOSPHORYLATION OF PEPSIN AND PEPSINOGEN
Authors: Perlmann Gertrude E.
Published: May 2004

It has been shown by the work presented in this paper that it is possible to dephosphorylate enzymically pepsin and pepsinogen with a variety of phosphatases. With the aid of a phosphodiesterase and the prostate phosphatase it has been established that the phosphorus in the two proteins is present as a diester and connects two sites of the peptide chain in a cyclic configuration. Removal of the phosphorus does not affect the proteolytic activity against hemoglobin or the synthetic substrate acetyl-L-phenylalanyl diiodotryosine, nor the pepsinogen pepsin transformation. However, an increase of the autodigestion of pepsin is observed.
TRANSMISSION IN SQUID GIANT SYNAPSES
Authors: Bryant S. H.
Published: May 2004

Synaptic transmission was studied in giant synapses of the stellate ganglion of the squid. When bathed in air-saturated sea water, the synapses deteriorate in 10 to 20 min.; if the sea water is saturated with 100 per cent oxygen, they function steadily for up to 12 hours. Optimal results probably require a medium with lower magnesium and higher calcium than the sea water used.

Of eighteen compounds known to affect other synapses (Table I), none had stimulatory effects when applied to the preparation, but ten produced synaptic depression in concentrations of 10–3 gm. per ml. or higher. The only exception was procaine, which blocked at 6 x 10–5 gm. per ml.

Intracellular recording with microelectrodes near the synapse showed that the block was associated with a slower rise of the excitatory post-synaptic potential, without a change in the depolarization required to initiate the spike. Procaine was exceptional in also increasing the depolarization at which the spike occurred.
THE PROPERTIES AND THE ENZYMATIC DEGRADATION OF DESOXYRIBONUCLEOPROTEIN FROM LIVER CELL NUCLEI
Authors: Monty Kenneth J. , Dounce Alexander L.
Published: May 2004

The isolation and properties of a desoxyribonucleoprotein of the rat liver cell nucleus are described. This material consists of DNA (desoxyribonucleic acid) bound to the residual chromosomal protein by what appear to be covalent linkages. Lipide is present, but can be removed by extraction in lipide solvents prior to isolation of the nucleoprotein, without much change in the physical properties of the latter. The nucleoprotein in question forms elastic, recoilable gels in molar saline at pH 7.0 or in water at pH 8.0 to 10.0 or even higher, which are similar to those that can be obtained from whole nuclei.

The effects of x-rays, heat, and enzymes on the nucleoprotein are discussed, and the composition of the protein component is investigated. The latter contains an "occult" protein that can be liberated by heating in 0.1 N HCl.

A study of the enzymatic degradation of the desoxyribonucleoprotein has been made, with the aim of attempting the isolation of small polynucleotide fragments attached to amino acids or short peptides that might be useful in characterizing the mode of attachment of the desoxyribonucleic acid to the protein in the desoxyribonucleoprotein. Evidence is presented indicating that such products can be isolated through the use of electrophoresis on paper.
A PROGRESSIVE REACTION OCCURRING WITH A RADIOACTIVE HEMOLYSIN, SODIUM OLEATE-I131
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

Sodium oleate reacts progressively with human red cells at pH 7. By progressive is meant a reaction which is not adequately described as reversible or irreversible; such reactions cannot be stopped once they are under way, and are probably associated with a more or less stable "internal" lysin phase at the cell surfaces. The uptake of the lysin and the effect of dilution on the uptake can be studied by converting sodium oleate into the radioactive form, sodium oleate-I131. The uptake is a parabolic function of the lysin initially present in the system, and the effect of a tenfold dilution of systems in which red cells have remained in contact with the lysin for 2 minutes is to reduce the lysin taken up at the cell surfaces twofold. The lysin rapidly forms a relatively stable layer at the cell interfaces, and this layer is little affected by the dilution of the system as a whole.
PROPAGATED REPOLARIZATION IN HEART MUSCLE
Authors: Cranefield Paul F. , Hoffman Brian F.
Published: May 2004

The effect of current flow on the transmembrane action potential of single fibers of ventricular muscle has been examined. Pulses of repolarizing current applied during the plateau of the action potential displace membrane potential much more than do pulses of depolarizing current. The application of sufficiently strong pulses of repolarizing current initiates sustained repolarization which persists after the end of the pulse. This sustained repolarization appears to propagate throughout the length of the fiber. Demonstration of propagated repolarization is made difficult by appearance of break excitation at the end of the repolarizing pulse. The thresholds for sustained repolarization and break excitation are separated by reducing the concentration of Ca++ in the environment of the fiber. In fibers in such an environment it is easier to demonstrate apparently propagated repolarization and also, by further increase of the strength of the repolarizing current, to demonstrate graded break excitation.
A STATISTICAL ANALYZER FOR OPTIC NERVE MESSAGES
Authors: Fitzhugh Richard
Published: May 2004

A statistical mathematical model of the discharge in a single optic nerve fiber is proposed, based on a discharge with intervals between impulses distributed independently according to a gamma distribution ("gamma discharge"). A light stimulus distorts the time axis of this discharge according to a "frequency function" which is characteristic of the stimulus.

A linear filter is described which calculates the likelihood of a certain stimulus when the nerve fiber message is fed into it. This filter forms the basis of theoretical nerve message analyzers for three visual experiments: (a) The detection of the occurrence of a flash of light of known intensity and time of occurrence, (b) the detection of the time of occurrence of a flash of known intensity, and (c) The estimation of the intensity of a flash occurring at a known time.

Possible neural mechanisms in the brain for analyzing optic nerve messages, based on the above mathematical models, are suggested. Changes of excitability or discharge frequency correspond to the output of the likelihood filter. Any such mechanism must be sufficiently plastic to have a response matched to each expected stimuus for most efficient vision near threshold.