bluuebunny/crossref_metadata_2025 huggingface dataset:
Thresholds and Plateaus in the Hodgkin-Huxley Nerve Equations
Authors: Fitzhugh Richard
Published: May 2004

Phase space methods and an analog computer are used to analyze the Hodgkin-Huxley non-linear differential equations for the squid giant axon membrane. V is the membrane potential, m the Na+ activation, h the Na+ inactivation, and n the K+ activation. V and m change rapidly, relative to h and n. The (V, m) phase plane of a reduced system of equations, with h and n held constant at their resting values, has three singular points: a stable resting point, a threshold saddle point, and a stable excited point. When h and n are allowed to vary, recovery and refractoriness result from the movement with subsequent disappearance of the threshold and excited points. Multiplying the time constant of n by 100 or more, and that of h by one-third, reproduces the experimental plateau action potentials obtained with tetraethylammonium by Tasaki and Hagiwara, including the phenomena of abolition and of refractoriness of the plateau duration. The equations have, transiently, two stable states, as found in the real axon by these authors. Since the theoretical membrane conductance curves differ significantly from the experimental ones, further experimental analysis of ionic currents with tetraethylammonium is needed to decide whether the Hodgkin-Huxley model can be generalized to explain these experiments completely.
Modulation of Activity of One Neuron by Subthreshold Slow Potentials in Another in Lobster Cardiac Ganglion
Authors: Watanabe Akira , Bullock Theodore H.
Published: May 2004

A direct demonstration is given of interaction between specific neurons without impulses, via graded slow potentials electrotonically spread from one cell to another. Repetitive polarizing or depolarizing current pulses of 50 to 200 msec. and subthreshold intensity were passed through an intracellular electrode in the soma of a follower cell of the isolated ganglion. When the frequency is near the natural rhythm of impulse bursts corresponding to heart beats and arising in a pacemaker cell 5 to 10 mm. posteriorly, the bursts rapidly become synchronized with the pulses. The effect disappears upon withdrawing the intracellular electrode. Brief pulses or full spikes in the follower are not effective. Hyperpolarizing long pulses attract the burst to a fixed period after the end of the pulse, depolarizations after the beginning of the pulse. The natural rhythm promptly reappears when the pulses are stopped and occasionally breaks through during weak repetitive pulses. Current pulses in postsynaptic cells also alter the threshold of a presynaptic neuron to externally applied stimuli. Some kind of direct, low resistance pathway for electrotonic spread, discriminating against spikes because of their brevity, is inferred, providing a basis for subthreshold interaction which is specific and not by way of a field effect. Due to the sensitivity of modulation of ongoing rhythms, electrotonic currents can be effective even after decrementing over several millimeters.
The Metabolism of Serum Proteins in Neonatal Rabbits
Authors: Deichmiller Maria P. , Dixon Frank J.
Published: May 2004

1. Incorporation of S35-labeled amino acids into serum proteins has been studied in neonatal and developing rabbits. It was found that, per unit weight, neonatal rabbits synthesized only about 1/36 of the gamma globulin, 1/7 of the beta globulin, ½ of the alpha globulin, and ⅛ of the albumin that an adult synthesized. The growing rabbit developed the ability to synthesize various serum proteins at different times.

2. Plasma volumes and serum protein concentrations were determined at different times during the growth period of the rabbit. Plasma volumes were found to be 1 and ½ times larger in newborn animals than in adults, with a gradual decline to the adult level. The total serum protein concentration at birth was about 60 to 65 per cent of the adult value and gradually increased with growth as the plasma volume decreased.

3. Half-lives of homologous albumin and gamma globulin were studied. The half-life of albumin in neonates was nearly twice as long as the half-life in adults, the latter value being reached at 1 month of age. The half-life of gamma globulin in neonates was more than twice as long as the half-life in adults and reached adult values at 2 to 3 months.

4. Attempts were made to alter serum protein metabolism. Gamma globulin synthesis early in life was augmented with antigen injections.
Studies on the Nervous Regulation of the Heart Beat in Decapod Crustacea
Authors: Florey Ernst
Published: May 2004

The effect of electrical stimulation of cardioaccelerator and cardioinhibitor nerves on the mechanically recorded heart beat of crayfish was studied. Similar experiments were performed with the lobster, Homarus americanus.

Quantitative relationships between uni- and bilateral accelerator and/or inhibitor nerve stimulation and the resulting change in frequency and amplitude of the heart beat were established.

With increasing frequency of stimulation the accelerator nerves show a relative decrease in their action, while that of the inhibitor nerves increases. It appears that left and right regulator nerves have synaptic contacts at the same areas of the postsynaptic cells within the heart ganglion. Similar results are obtained whether all impulses arrive over one, or over the other, or over both accelerator (or inhibitor) nerves; the resulting acceleration or inhibition depends strictly on the number of accelerator, or inhibitor impulses arriving at the ganglion.

The ganglion cells can adapt to the inhibitor action. This is shown to be a postsynaptic phenomenon. Adaptation to accelerator stimulation is virtually absent.

Characteristic after-effects of the accelerator and inhibitor action were observed and quantitatively evaluated.

The interpretation of the results is based on the assumption of chemical transmitter substances. It is concluded that the accelerating transmitter decays slowly while the inhibitory transmitter is inactivated relatively rapidly.
Studies on Independent Synthesis of Cytoplasmic Ribonucleic Acids in Acetabularia mediterranea
Authors: Naora Hiroto , Naora Hatsuko , Brachet Jean
Published: May 2004

1. The RNA content of anucleate and nucleate fragments of Acetabularia has been measured. It was found that there is a net synthesis of RNA in nucleate fragments. On the other hand, the RNA content of anucleate fragments did not change significantly after enucleation.

2. Anucleate fragments, however, can readily incorporate 14C-labeled adenine, orotic acid, and carbon dioxide into their cytoplasmic RNA.

3. The results of experiments on 14CO2 incorporation into the RNA of anucleate and nucleate fragments suggest that there is a mechanism for de novo synthesis of RNA in anucleate cytoplasm.

4. In Acetabularia, 81 per cent of the cytoplasmic RNA is bound to a large granule fraction, consisting mainly of chloroplasts. Even after removal of the nucleus, RNA is synthesized in this "chloroplast" fraction. The chloroplasts are thus a major site of RNA synthesis in the cytoplasm of these algae. Synthesis of "chloroplastic" RNA, in anucleate fragments, possibly occurs at the expense of the RNA present in other fractions (microsomes and supernatant).

5. 8-Azaguanine stimulates regeneration and cap formation in anucleate fragments and does not inhibit RNA synthesis in these fragments.
Na, Cl, and Water Transport by Rat Ileum in Vitro
Authors: Curran Peter F.
Published: May 2004

Interrelationships between metabolism, NaCl transport, and water transport have been studied in an in vitro preparation of rat ileum. When glucose is present in the mucosal solution, Na and Cl both appear to be actively transported from mucosa to serosa while water absorption is passive and dependent on net solute transport. Removal of glucose from the mucosal solution or treatment with dinitrophenol, monoiodoacetate, or anoxia inhibits active salt transport and as a result, water absorption is also inhibited. The dependence of water absorption on metabolism can be explained as a secondary effect due to its dependence on active salt transport. The relationship between salt and water transport has been discussed in terms of a model system.
On Dielectric Constant and Enzymatic Kinetics
Authors: Castañeda-Agulló M. , del Castillo Luz M.
Published: May 2004

The dielectric effects on trypsin and α-chymotrypsin activities have revealed that at pH 7.8 the active species of the former is the cation while that of the latter is the anion. The present study on the dielectric effects along the pH-activity curves shows that trypsin remains positive within the pH range of 5.5 to 8.5. Conversely, α-chymotrypsin is positive from pH 5.5 to 6.6, negative from 6.6 to about 8.1, and at pH 8.25 becomes positive again. The first point of inversion in charge sign shifts from 6.6 to 7.15 with the addition of 0.05 M phosphate buffer. The point of inversion does not seem to be modified significantly by changes in the substrate structure. At pH values near the point of inversion the plots of rate log vs. 100/D are broken lines formed by various straight portions, the slope of each varying progressively from a maximum positive to a maximum negative value. This suggests an effect of resonance possibly attributable to an imidazole group. As an attempt to explain the two observed points of sign inversion in α-chymotrypsin, the possibility is suggested that different enzyme configurations are disclosed by the combined action of pH and dielectric constant. On this theoretical basis, it i6s feasible that more than one isoionic point exists.
Neural Photoreception in a Lamellibranch Mollusc
Authors: Kennedy Donald
Published: May 2004

The pallial nerves of Spisula solidissima each contain a single afferent nerve fiber which responds directly to illumination of the nerve, and apparently mediates the "shadow" response of siphon retraction. These units show constant-frequency spontaneous activity in the dark; illumination abruptly inhibits this discharge, and cessation of the light stimulus then evokes a prolonged burst of impulses at high frequency (the off-response). Impulses are initiated at a point near the visceral ganglion, and propagated unidirectionally toward it. Stimulation with monochromatic light has revealed that more than one photoreceptor pigment is involved, since the discharge patterns evoked are wavelength-specific. Inhibition is relatively prominent at short wavelengths, excitation at long wavelengths. Following selective adaptation with blue light, "on" responses can be produced with red stimuli, demonstrating the unmasking of an excitatory event which takes place during illumination. The two photoreceptor pigments may be segregated in two or more cells presynaptic to the recorded unit, or,—more likely—may both be contained in the same cell. The spectral sensitivity function for inhibition shows a single maximum at 540 mµ, and is probably dependent upon a carotenoid pigment. No photoreceptor function has been demonstrated for a hemoprotein, apparently identical with cytochrome h, which occurs in high concentration in Spisula nerve.
Effect of Inhibitors on D-Xylose Permeability in Rat Diaphragm Muscle
Authors: Polleri A. , Menozzi P. , Norman D. , Hechter O.
Published: May 2004

The influence of metabolic inhibitors and low temperatures upon D-xylose transfer has been studied in rat diaphragm muscle preparations in vitro. Using intact fiber preparations, it has been confirmed that at body temperature metabolic inhibitors like DNP have an insulin-like action in that they permit D-xylose to distribute into previously unavailable intracellular aqueous regions; inhibitors, unlike insulin, disturb cation distribution in association with increased sugar penetration. Although the studies with inhibitors suggest an energy requirement for maintenance of D-xylose exclusion, the D-xylose exclusion mechanism is effectively maintained at 0° for many hours, and under these conditions, inhibitors have little or no effect on D-xylose distribution, though they do produce potassium loss. In cut muscle fiber preparations, in which insulin significantly increases the rate at which D-xylose equilibrates between cell water and external medium, DNP does not increase the rate of D-xylose entry, but does abolish the effect of insulin in this preparation. The results suggest that insulin action upon sugar permeability in muscle involves two barrier systems; some of the characteristics of these systems have been defined.
Recording of Retinal Action Potentials from Single Cells in the Insect Compound Eye
Authors: Naka Kén-Ichi
Published: May 2004

Electrical responses were recorded intracellularly from the compound eyes of a fly (Lucilia) and of several dragonflies (Copera, Agriocnemis, and Lestes). An ommatidium of the dragonflies is made up of four retinula cells and a rhabdom composed of three rhabdomeres while the Lucilia has an ommatidium of seven independent retinula cells and rhabdomeres. The intracellular responses presumably recorded from the retinula cell had the same wave form in the two groups of insects: The responses were composed of two components or phases, a transient spike-like potential and a slow one maintained during illumination. The membrane potential, in the range of -25 to -70 mv., was influenced by the level of adaptation, and it was transiently depolarized to zero by high levels of illumination.
The Inheritance of the Glucose Component of the Phage Nucleic Acids
Authors: Jesaitis Margeris A.
Published: May 2004

The wild type strains of T2 and T6 bacteriophages differ in their host range specificity, efficiency of plating on E. coli K12, and in glucose content. A study of the inheritance of these three differentiating characteristics has revealed that they are transmitted both upon serial passage of the viruses and when the two phages are crossed. It has been found, furthermore, that an extensive recombination takes place upon crossing. Four types of hybrid phages have been isolated from the progeny of crosses, which had a glucose content of one of the parental phages, and either the host range specificity or efficiency of plating or both of the other. The characteristics of each hybrid were found to be hereditarily stable. It has been concluded that the transmission of the characteristics under consideration is determined genetically and that the genes which control them are not closely linked. Since the glucose content of a phage is determined by the degree of glucosylation of its nucleic acid, the T2 and T6 phages apparently contain genes which control certain chemical properties of their nucleic acid.
Electrophysiology of the Insect Dorsal Ocellus
Authors: Ruck Philip
Published: May 2004

Large nerve fibers in the ocellar nerves of dragonflies are spontaneously active. In the absence of inhibitory influence the spontaneous activity is rhythmic. Inhibition occurs in the dark-adapted state and during illumination. Miniature inhibitory postsynaptic potentials occur in the dark-adapted state. These modulate by temporary suppression the otherwise rhythmic discharge of ocellar nerve impulses. The presence of random spontaneous receptor cell excitations is inferred from the presence of the miniature i.p.s.p.'s. Light stimulates many or all the receptor cells simultaneously, masking the random spontaneous activity of individual receptor cells. The result is a sustained hyperpolarizing i.p.s.p. and sustained inhibition of the nerve discharge. Preceding resumption of the spontaneous activity at "off" the i.p.s.p. may oscillate, overshoot the baseline as a negative after-potential, or do both. These phases of the off-effect may generate nerve impulses in an off-burst.
Ionic Permeability and Electrical Potential Differences in Necturus Kidney Cells
Authors: Whittembury Guillermo , Sugino Nobuhiro , Solomon A. K.
Published: May 2004

The cellular concentrations of Na, K, and Cl have been measured in kidney slices of the amphibian, Necturus maculosus. Permeability coefficients have been determined for Na, K, Cl, Rb, Cs, and choline, from studies both of the uptake of radioactive isotopes and the rate of cell swelling in anisotonic solutions. The results of both methods were found to agree well. Measurements were also made of electrical potential differences across the peritubular face of the kidney cells using bathing solutions in which the electrolyte composition and concentrations could be varied. The data obtained are consistent with a model cell in which the potential difference arises as a result of differences in Na permeability relative to K on the two faces of the cell. The intracellular Na concentration is considered to be regulated by a Na-K coupled pump located at the peritubular face of the cell.
Studies on the Bohr Effect of Sheep Hemoglobin
Authors: Smyth Derek G. , Battaglia Frederick C. , Meschia Giacomo
Published: May 2004

A simple method is described for the measurement of pH changes in hemoglobin solutions on oxygenation and reduction. Data are presented establishing the absence of a Bohr effect in p-chloromercuribenzoate [PCMB] treated hemoglobin.

The influence of a number of sulfhydryl inhibitors on the Bohr effect of a hemoglobin solution is reported and an interpretation based on steric factors in the protein is proposed.
Graded and All-or-None Electrogenesis in Arthropod Muscle
Authors: Werman R. , McCann F. V. , Grundfest H.
Published: May 2004

Graded electrically excited responsiveness of Romalea muscle fibers is converted to all-or-none activity by Ba++, Sr++, or Ca++, the two former being much the more effective in this action. The change occurs with as little as 7 to 10 per cent of Na+ substituted by Ba++. The spikes now produced have overshoots and may be extremely prolonged, lasting many seconds. During the spike the membrane resistance is lower than in the resting fiber, but the resting resistance and time constant are considerably increased by the alkali-earth ions. The excitability is also increased, spikes arising neurogenically from spontaneous repetitive discharges in the axon as well as myogenically from spontaneous activity in the muscle fibers. Repetitive responses frequently occur on intracellular stimulation with a brief pulse. The data indicate that the alkali-earth ions exert a complex of effects on the different action components of electrically excitable membrane. They may be described in terms of the ionic theory as follows: The resting K+ conductance is diminished. The sodium inactivation process is also diminished, and sodium activation may be increased. Together these changes can act to convert graded responsiveness to the all-or-none variety. The alkali-earth ions can also to some degree carry inward positive charge during activity, since spikes are produced when Na+ is fully replaced with the divalent ions.
In vitro Studies of the Gain and Exchange of Calcium in Frog Skeletal Muscle
Authors: Cosmos Ethel , Harris Eric J.
Published: May 2004

(1) The Ca++, Na+, and K+ contents of frog sartorius muscles were found analytically after exposure to various media including some containing labeled Ca++. (2) During storage in media with 100 to 120 mM Na+ and 1 mM Ca++ both Na+ and Ca++ are gained while K+ is lost; there is a high correlation between Na+ and Ca++ gains. (3) When Ca++ gain occurs from a solution containing labeled Ca++ there is also some exchange of the original Ca++ with the labeled Ca++. The amount exchanged is considerably less (e.g. 50 per cent) than the total amount of labeled Ca++ taken up by the tissue. (4) When the external Na+ concentration is reduced to 30 mM the amount of labeled Ca++ taken up is increased. Part of the increase is attributable to a greater net gain and part to a greater degree of exchange. (5) It is pointed out that muscles which have been loaded in vitro with labeled Ca++ will not provide a valid measure of the exchangeability of the normal Ca++ content present at the time of dissection. (6) Comparison is made between results obtained using Sr89 and Ca45 as labels for the Ca++. Little, if any, difference is perceptible.
Studies on Transformations of Hemophilus influenzae
Authors: Goodgal Sol H. , Herriott Roger M.
Published: May 2004

A procedure has been developed for obtaining Hemophilus influenzae of such competence that 1 to 10 per cent transform to any of several genetic factors by utilizing a period of aerobic growth followed by a non-aerobic period. Differences in levels of competence were not due to differences in genetic background. Competence was due to at least one factor intrinsic to the cell or site on the cell and was not transferable to non-competent cells. Competence was affected by salt concentration, pH, and temperature. Washing competent cells reduces their ability to transform, but not their capacity to bind DNA reversibly. The irreversible step could be restored with little or no accompanying growth. These facts suggest that reversible and irreversible binding represent separate biochemical steps. DNA initiates a reaction in cells leading to a loss of competence. In the absence of DNA the cells remain competent for at least an hour. Competence correlates quantitatively with predictability of multiple transformations. The observed and calculated values of multiple transformations are in closer agreement, the higher the frequency of transformation for single markers. The correction needed to bring the two figures into agreement is a measure of the fraction of non-competent cells.
The Natural Occurrence of Ethionine in Bacteria
Authors: Fisher J. F. , Mallette M. F.
Published: May 2004

Two unknown radioactive areas appeared after radioautography and two dimensional paper chromatography of culture medium in which Escherichia coli was grown. These materials were studied by paper chromatography and paper electrophoresis of several derivatives and identified as ethionine and ethionine sulfone, the latter an artifact. Chromatographic coincidence of the unknowns and their derivatives with authentic materials establishes the identification.

Ethionine was found in cellular extracts and in the growth media of Escherichia coli, Bacillus megaterium, Pseudomonas aeruginosa, and Aerobacter aerogenes but not in Scenedesmus, Saccharomyces cerevisiae, or bovine lymphosarcoma cells.

Ethionine was synthesized by resting E. coli cultures from radioactive sulfate and from radioactive methionine. Growing cells labeled ethionine within 1 minute after addition of radioactive sulfate to cultures. Levels of radioactivity in ethionine increased with time. No incorporation of this amino acid could be detected in the cellular proteins formed under the conditions of this study.
Effects of Temperature on the Generator and Action Potentials of a Sense Organ
Authors: Ishiko Nobusada , Loewenstein Werner R.
Published: May 2004

Charge transfer through the receptor membrane of the nonmyelinated ending of Pacinian corpuscles is markedly affected by temperature. The rate of rise and the amplitude of the generator potential in response to a constant mechanical stimulus increase with temperature coefficients of 2.5 and 2.0 respectively. The duration of the falling phase, presumably a purely passive component, and the rise time of the generator potential are but little affected by temperature. The following interpretation is offered: Mechanical stimulation causes the conductance of the receptor membrane to increase and ions to flow along their electrochemical gradients. An energy barrier of about 16,000 cal/mole limits the conductance change. The latter increases, thus, steeply with temperature, causing both the rate of rise and the intensity of the generator current to increase.

The membrane of the adjacent Ranvier node behaves in a distinctly different manner. The amplitude of the nodal action potential is little changed over a wide range of temperature, while the durations of its rising and falling phases increase markedly. The electrical threshold of the nodal membrane is rather constant between 40 and 12°C. Below 12°C the threshold rises, and the mechanically elicited generator current fails to meet the threshold requirements of the first node. Cold block of nerve impulse initiation then ensues, although the receptor membrane still continues to produce generator potentials in response to mechanical stimulation.
Electronic Measurement of the Intracellular Concentration and Net Flux of Sodium in the Squid Axon
Authors: Moore John W. , Adelman William J.
Published: May 2004

A unique, rapid, and non-destructive determination of the intracellular sodium concentration of a squid axon may be provided by the "voltage clamp" technique, in which the potential across the axon membrane is under electronic control. The potential at which the early component of ionic current reverses following a membrane potential step was used as an index of the intracellular sodium concentration. Several types of experiments were used to test the applicability of this method for measurement of intracellular sodium and its net flux. The concentration was found to increase from 38 mM for a fresh axon to 50 mM in about an hour. From this change, the net flux for a fresh resting axon was estimated to be 40 pmoles/cm2 sec. Rapid stimulation of an unclamped axon produced a marked increase in the rate of sodium accumulation. Rapid pulsing of the membrane in a voltage clamp to potentials more positive than the sodium potential moved sodium out fast enough to produce a definite decrease in internal concentration. The agreement between the results with this method and those with more direct methods is quite satisfactory. An attractive feature of this method of intracellular sodium determination is that the physiological function of the axon is maintained and other measurements may be made concurrently.
Studies on Transformations of Hemophilus influenzae
Authors: Goodgal Sol H.
Published: May 2004

Unlinked transformations were demonstrated to occur by varying the multiplicity of DNA molecules taken up by competent cells. The number of doubles was directly proportional to the product of the frequency of singles for varying concentrations of cells. The kinetics of transformation to doubles and the effect of DNA concentration on double transformations were consistent with the concept that the cell must take up two molecules of DNA in order to be doubly transformed. Linked markers, on the other hand, were a constant fraction of the single transformation for variations in DNA or cell concentration, or time. The kinetics of transformation of linked markers was the same as for the kinetics of single transforming factors. It was, therefore, concluded that linked transformations involve interaction between the cell and a molecule of DNA carrying both markers. The frequency of transformation was found to be the same from resistance to sensitivity as from sensitivity to resistance for the markers streptomycin (S) and cathomycin (C). Purified DNAs, in general, show lower levels of linkage than crude DNA preparations, and for some crude preparations all the S markers were linked to C, suggesting that some dispersion, at least, was a result of DNA preparation. The inactivation of linked markers by heat, ultraviolet, and DNAase was studied.
Impulse Propagation at the Septal and Commissural Junctions of Crayfish Lateral Giant Axons
Authors: Watanabe A. , Grundfest H.
Published: May 2004

Transmission across the septal junctions of the segmented giant axons of crayfish is accounted for quantitatively by a simple equivalent circuit. The septal membranes are passive, resistive components and transmission is ephaptic, by the electrotonic spread of the action current of the pre-septal spike. The electrotonic spread appears as a septal potential, considerably smaller than the pre-septal spike, but usually still large enough to initiate a new spike in the post-septal segments. The septal membranes do not exhibit rectification, at least over a range of ± 25 mv polarization and this accounts for their capacity for bidirectional transmission. The commissural branches, which are put forth by each lateral axon, make functional connections between the two axons. Transmission across these junctions can also be bidirectional and is probably also ephaptic. Under various conditions, the ladder-like network of cross-connections formed by the commissural junctions can give rise to circus propagation of impulses from one axon to the other. This can give rise to reverberatory activity of both axons at frequencies as high as 400/sec.
Effects of Insulin on the Permeability of D- and L-Xylose and D- and L-Arabinose in Rat Diaphragm Muscle
Authors: Carlin H. , Hechter O.
Published: May 2004

The permeability characteristics of D- and L-xylose and D- and L-arabinose have been compared in isolated intact rat diaphragm muscle preparations, in the absence and presence of exogenous insulin. In the absence of added insulin, these pentoses distribute in less than a third of the total cell water. In the presence of added insulin, intracellular distribution of all these pentoses is increased. L-Xylose and D-arabinose distribute in 50 per cent of the intracellular water, whereas D-xylose and L-arabinose distribute in 80 per cent of the cell water. A significant lag period was observed before the insulin effect upon the penetration of L-xylose and D-arabinose was evident whereas the effect upon D-xylose and L-arabinose was rapid. The lag period with L-xylose could be abolished by pretreating the tissues with insulin for 1 hour, but such pretreatment had little effect on D-xylose. These results indicate that insulin has a biphasic effect upon the monosaccharide exclusion system in diaphragm muscle. In dinitrophenol-treated tissues, in which all permeability processes are irreversibly damaged and in which sucrose and pentoses penetrate into most of the cell water, the entry rate of pentoses and sucrose is initially similar but subsequently D-xylose and L-arabinose penetrate more rapidly than their corresponding optical isomers.
Activation of the Feeding Reflex in Hydra littoralis
Authors: Lenhoff Howard M.
Published: May 2004

A simple and accurate quantitative assay of the glutathione-activated feeding reflex in Hydra is described. The results show: (a) There are a limited number of receptor-effector systems, probably localized in the area immediately around the mouth and on the tentacles. (b) Concentrations of glutathione greater than 5 x 10-6 M activate all these systems; 10-5 M glutathione elicits a half-maximum response. (c) Glutathione must be constantly present at the receptor site in order for a response to occur. (d) The response stops in the presence of excess glutathione because of some change within the Hydra, and not as a result of any alteration to the glutathione. The present state of knowledge concerning the mechanism by which glutathione combines with and activates the glutathione receptor to elicit the feeding reflex is summarized.
The "Apparent Molecular Weight" of Myelin Forms Prepared from Normal Red Cells and Some of Its Variations
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

Some of the properties of myelin forms prepared by freezing, thawing, and homogenization of ghosts of human red cells are described, among these being the "apparent molecular weight" as found by light scattering, the effect of repeated freezing and thawing on the "apparent molecular weight," the quantity of fatty acids split off at various temperatures of freezing, the effect of the anticoagulant used, and the remarkable constancy in the "apparent molecular weight" met with when myelin forms are prepared from the ghosts of the red cells of normal people. Taken together, these observations lead to the description of a "standard technique" for the preparations of myelin forms; this technique can later be extended to the myelin forms obtained from animals other than man and also to those obtained from abnormal red cells.
Alkaline Phosphatase Content and the Effects of Prednisolone on Mammalian Cells in Culture
Authors: Cox Rody P. , MacLeod Colin M.
Published: May 2004

The alkaline phosphatase content of different tissue culture cell lines has been shown to vary from no detectable activity to high enzyme concentration. Within the epithelial lines studied alkaline phosphatase is either constitutive or inducible. Two epithelial cell strains in which alkaline phosphatase was "absent" could be induced to develop significant amounts of the enzyme when grown in the presence of Δ1-hydrocortisone. Phosphate did not repress enzyme induction by prednisolone. Under conditions of deadaptation the induced enzyme was diluted by cell multiplication. The mouse fibroblastic L line and several human fibroblastic lines did not contain alkaline phosphatase when grown under the conditions described nor could they be induced to produce the enzyme when cultivated in medium with prednisolone.

Δ1-Hydrocortisone has other characteristic effects on established mammalian cell cultures which vary among cell lines. Human epithelial lines show reduction in cell multiplication with increase in mitotic index. The cytoplasm is increased and cell volume is nearly doubled. Mouse fibroblasts show a similar reduction in cell multiplication with a decrease in mitotic index. There is no increase in cell cytoplasm. Human fibroblast strains show no inhibition of multiplication or alteration in total cell protein when grown in medium containing prednisolone.

Antisera prepared against "negative" prednisolone-inducible human cell lines and against a positive human line inhibited alkaline phosphatase activity to an equal degree.
The Coefficient of Thermal Conductivity of Blood and of Various Tissues
Authors: Ponder Eric
Published: May 2004

A method for measuring K, the coefficient of thermal conductivity, for a variety of dog tissues is described. The values of K for muscle and liver are larger than that for water, the value of K for lung is smaller than that for water and the values of K for brain, plasma, and blood are about the same as that of water. The values found for K are given in a table.
Are Animal Tumor Viruses Always Virus-Like?
Authors: Shope Richard E.
Published: May 2004

Three tumors initiated by well characterized viruses, but in which virus is not detectable by ordinary virological techniques, are discussed. The question of the possible state of the virus within these seemingly non-infectious tumors is considered, largely from the standpoint of findings with the rabbit papilloma virus. This agent in its natural host, the cottontail rabbit, is infective, can be seen as virus bodies with the electron microscope, and can be visualized with fluorescent antibody only in the upper keratinizing cells of individual papillomas. At the growing bases of such papillomas, where neoplasia is in active progress, no infective virus is demonstrable and viral bodies cannot be visualized by either the electron microscope or fluorescent antibody. A hypothesis is presented that rabbit papilloma virus exists in cottontail papillomas in two forms—one, the complete mature virus, composed of nucleic acid and protein, and the other, immature virus, composed of naked viral nucleic acid without its protein coating. The function of the mature papilloma virus is to initiate tumor formation,—that of the immature virus, to maintain neoplasia. In the non-infective domestic rabbit papilloma, the viral nucleic acid and protein fail to combine to form mature infective virus and, as in the cottontail papilloma, neoplasia is maintained by the activity of the viral nucleic acid alone.
Purification of B. megatherium Phage G and Evidence for a Muralytic Enzyme as an Integral Part of the Phage
Authors: Murphy James S. , Philipson Lennart
Published: May 2004

The Purification Of B. megatherium G phage is described and it is shown that DEAE cellulose chromatography combined with conventional methods gave a phage preparation which was at least 95 per cent pure, and contained 2.16 µg nitrogen/1011 infective particles. The phage particle weight in molecular weight units was 91 x 106. The small amount of contaminating material appeared to represent phage "ghosts." An essentially 1:1 ratio of particles to infective units was found when data from electron microscopic counts or data from chemical analysis were related to phage infectivity. Comparison, by several methods, of the G phage and coliphage T2 shows that T2 is 2.6 times larger than G phage. The specific activity of the muralytic component obtained by disintegration of phage preparations with urea was unchanged by the purification indicating that the phage-"bound" muralytic activity is an integral part of the phage structure.
Seromucoid Fraction Patterns of Individuals with Pneumonia or Leukemia
Authors: Price W. H. , Matanowski G. , Prewer A. , Rector L.
Published: May 2004

Chromatographic separations on DEAE cellulose have been carried out on the seromucoid fraction from forty-one normal individuals and twenty-three patients horpitalized with unilateral pneumococcal pneumonia. During the acute stages of their illness, all twenty-three patients showed a very marked difference in their seromucoid pattern as contrasted to the control group, both groups being comparable in age, sex, and race. As the patients recovered, their seromucoid patterns returned to that of the control group. Three patients with bilateral pneumococcal pneumonia showed seromucoid patterns similar to those of the twenty-three patients with unilateral pneumococcal pneumonia. Five individuals with viral pneumonia showed a seromucoid pattern similar to those observed in patients with pneumococcal pneumonia. The data suggested that the seromucoid pattern observed in pneumonia depended upon the stage of the disease of the patient, different patterns being observed during the acute, convalescent, and complete recovery stages. Each stage showed a characteristic pattern. The seromucoid pattern of seven patients with acute leukemia differed from that of the control groups and also differed from that observed in patients with pneumonia. Five individuals with chronic lymphocytic leukemia showed seromucoid patterns which could not be distinguished from those of the control group in spite of the fact that all showed clinical signs of disease at the time the blood sample was drawn for fractionation.
On Dielectric Constant and Enzymatic Kinetics
Authors: Castañeda-Agulló M. , del Castillo Luz M.
Published: May 2004

A study was made on the effect of glycine on systems involving trypsin and BAEE1 or TSAME on the one hand, or α-chymotrypsin with any of the substrates BAEE, TEE, or PEE, on the other. In all cases there was a linear relationship between the rate logarithm and the reciprocal of the dielectric constant of the glycine solution. The slopes were positive in the reactions of trypsin. In those catalyzed by α-chymotrypsin, the slopes were positive at pH 6.5 or lower, and negative at pH 7.5. However, the effects of glycine differ quantitatively from those of urea or other solvents. The presence of salt modifies somewhat the glycine effects. A low ionic strength increases the effect of glycine on trypsin, but if the inhibition caused by the ionic strength is relatively strong, the addition of glycine partially neutralizes the salt effect. Addition of salt to systems containing α-chymotrypsin always resulted in a diminished effect of glycine. An attempt is made to interpret the anomalies of glycine effects on the basis of its dipolar ion structure.
Early Experiments in the Quest of an Active Center in Chymotrypsin
Authors: Balls A. K.
Published: May 2004

It is now quite proper to speak of an "active site" or "center" in (or on) a number of hydrolytic enzymes, chymotrypsin in particular. Such sites have been clearly demonstrated and in some cases they have even been investigated in detail. We are almost persuaded that they are the actual loci of enzyme activity in nature. Whatever we think of them, we do know that they are "some peculiar arrangement of amino acids" (2 a).
Amino Acids as Gustatory Stimuli in the Rat
Authors: Halpern Bruce P. , Bernard Rudy A. , Kare Morley R.
Published: May 2004

Neural activity in intact chorda tympani nerve of rats was studied with an electronic summator. Neural activity increased when amino acid solutions 0.01 M or above passed over the tongue. Response magnitude, at concentrations close to solubility limits for the amino acids tested, was: DL-methionine < DL-tryptophan < DL-valine < DL-alanine < glycine < 0.1 M NaCl. Maximum response magnitudes to 1 M D-, and 1.2 M DL-alanine, and 1.5 M glycine developed in 1 to 3 minutes. Following such stimulation, a 63 per cent reduction in response to 0.1 M NaCl occurred 60 minutes after the first stimulation (medians). The depression was still present 20 hours later. Responses to glycine and alanine were not depressed. Amino acids vs. water preferences were investigated. With ascending concentration sequences, rats selected low concentration DL- and L-alanine and glycine; accepted D-, L-, and DL-tryptophan and low concentration DL-methionine; and rejected high concentration glycine, DL-alanine, and DL-methionine. Descending sequences showed depressed and delayed selection of glycine and DL-alanine, and DL-methionine and D- and L-tryptophan rejection. Both groups rejected DL-valine. It is concluded that glycine and alanine receptor effects differ from those of NaCl, but that all three compounds may affect a common receptor site. Prior exposure to amino acids may modify subsequent neural and/or behavioral responses.
Photoenzymatic Repair of Ultraviolet Damage in DNA
Authors: Rupert Claud S.
Published: May 2004

As previously reported, ultraviolet-inactivated bacterial transforming DNA can be restored to activity by an enzyme-like agent from bakers' yeast which requires light for its activity. Kinetics of this reaction, in the presence and absence of inhibitors, are found consistent with the Michaelis-Menten reaction scheme, with the sites of ultraviolet damage on the DNA serving as substrate and the repaired structure as product. Kinetic studies with different light intensities suggest that the necessary illumination causes photolysis of the enzyme-substrate complex with concurrent repair of the DNA. Competitive inhibition of irradiated transforming DNA repair, which occurs when irradiated non-transforming DNA is present in the same reaction mixture, permits ultraviolet damage (of the kind capable of being photoreactivated) to be detected in any type of DNA.
Photoenzymatic Repair of Ultraviolet Damage in DNA
Authors: Rupert Claud S.
Published: May 2004

The photoenzyme from bakers' yeast which repairs ultraviolet-inactivated transforming DNA is mechanically bound to ultraviolet-irradiated DNA in the dark, but not to unirradiated DNA. In the bound condition it is stabilized against inactivation by heat and heavy metals. Both the mechanical binding and stabilization are eliminated by illumination. These observations are consistent with the reaction scheme suggested by kinetic studies, in which the enzyme combines with the ultraviolet lesions in DNA and the complex absorbs light, producing repair and subsequent liberation of the enzyme. The approximately exponential decrease of heat stabilization during illumination gives the first order rate constant for the light-dependent step at the corresponding light intensity. This quantity in turn sets limits on the possible magnitude of the molar absorption coefficient of the enzyme-substrate complex and on the quantum yield of the process.
Phototropic Curvature in Phycomyces
Authors: Castle Edward S.
Published: May 2004

The distribution of curvature and of bending speed along the cell's growing region are studied during steady state phototropic bending. At the start, elemental bending speed parallels the known axial distribution of growth rate. Hence regional phototropic sensitivity is initially determined by the local growth rate, and unilateral visible light acts proportionally at all levels of the growth zone. In the later course of bending, the bending speed distribution shifts downward instead of progressing upward in step with the cell's elongation. Furthermore, during phototropic inversion reversed bending begins high in the growth zone and progresses downward while normal bending continues below. These spatial and temporal changes in the distribution of differential growth are considered to be due to a fixed rate of supply of material used in growth that is transported from lower regions of the cell and asymmetrically distributed within the growth zone.
Activation of Deoxyribonucleases by Divalent Cations
Authors: Desreux V. , Hacha R. , Fredericq E.
Published: May 2004

The activation of DNase I by Mg, Mn, Co, Ni, Fe, Cd, Zn, Ba, Sr, Ca, and Cu ions has been studied by several methods, at different pH and salt concentrations. Mg, Mn, and Co are the best activators for initial stages of degradation. A synergistic effect is shown only by the pair Mg-Ca. Optimal pH of action is always situated at 6.5. DNase II is activated to about the same degree by alkaline earths and Mn ions. Cd and Cu are strong inhibitors. Optimal pH is always 4.6. By titration of liberated secondary phosphate groups, two stages in the hydrolysis of DNA by DNase I are evidenced: a rapid phase activated most by Mg and a slow phase activated by Ca. Some possible mechanisms of action of both enzymes are outlined and the general influence of metal ions is discussed.
Ionic Relations of Nitella translucens
Authors: MacRobbie Enid A. C.
Published: May 2004

The ionic state of single internodal cells of a fresh water characean, Nitella translucens, has been studied. In mature cells the vacuolar concentrations were 78 mM K, 60 mM Na, and 151 mM Cl, compared with concentrations of 0.1 mM K, 1.0 mM Na, and 1.3 mM Cl in the bathing medium. The results suggest an active influx of potassium and an active efflux of sodium at the plasmalemma, and an active influx of chloride, probably at the tonoplast. The cation transport is inhibited by ouabain, and is more efficient in young cells; the chloride transport is insensitive to ouabain, and unaffected by age. Thus the two systems appear to be independent. It is suggested that the active fluxes are 0.5 to 0.6 µµmoles K/cm2 sec. inwards, and 0.45 µµmoles Na/cm2 sec. outwards. The passive influxes, 0.3 µµmoles K/cm2 sec. and 0.55 µµmoles Na/cm2sec., give a value for the relative permeabilities of the plasmalemma, PNa/PK, of 0.18. The absolute magnitudes of the permeabilities, compared with those derived from resistance measurements, suggest that potassium ions interact strongly in the membrane. The cation fluxes at the tonoplast are much higher than those at the plasmalemma. The active influx of chloride is 0.85 µµmoles/cm2 sec. in light, but only 0.052 µµmoles/cm2 sec. in the dark. The potassium influx is also reduced in the dark. Thus the energy for both active transport processes is closely geared to light-dependent metabolism, rather than to respiration.
Studies on the Effects of Gaseous Ions on Plant Growth
Authors: Krueger Albert P. , Beckett J. C. , Andriese Paul C. , Kotaka Sadao ,   with the technical assistance of Eddie J. Reed.
Published: May 2004

Air pollutants seriously interfere with the maintenance of unipolar ionized atmospheres required in experimenting with the biological effects of gaseous ions. The construction and operation of an air purification unit designed to reduce air pollution to tolerable levels are described; it has functioned satisfactorily in conducting experiments with plants and animals.