bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnesium and Calcium in Isolated Cell Nuclei
Authors: Naora H. , Naora H. , Mirsky A. E. , Allfrey V. G.
Published: May 2004

The calcium and magnesium contents of thymus nuclei have been determined and the nuclear sites of attachment of these two elements have been studied. The nuclei used for these purposes were isolated in non-aqueous media and in sucrose solutions. Non-aqueous nuclei contain 0.024 per cent calcium and 0.115 per cent magnesium. Calcium and magnesium are held at different sites. The greater part of the magnesium is bound to DNA, probably to its phosphate groups. Evidence is presented that the magnesium atoms combined with the phosphate groups of DNA are also attached to mononucleotides. There is reason to believe that those DNA-phosphate groups to which magnesium is bound, less than 1/10th of the total, are metabolically active, while those to which histones are attached seem to be inactive.
The Partition of Calcium and Protein in the Blood of Oviparous Vertebrates during Estrus
Authors: Urist Marshall R. , Schjeide Arne O.
Published: May 2004

Six classes of vertebrate animals were injected with massive doses of estrogen for various periods of time necessary to produce a grossly recognizable response. Swelling of the liver, associated with hypercalcemia, hyperproteinemia, and lipemia, occurred in Teleostei, Amphibia, Reptilia, and Aves, but not in Elasmobranchii or Mammalia. Calcium that was added to the serum was bound as a calcium proteinate complex, synthesized in the liver, and liberated into the plasma. The concentration of calcium per gram was considerably higher than in other oviparous animals.

Teleostei, Amphibia, and Reptilia, produced one new component, protein-X1, having a sedimentation constant of approximately 17S, and many properties of a protein previously described in birds as X2. Calcium-binding capacity of teleostean and amphibian serum proteins was estimated at 25 to 35 mg. per gm. of the mixed proteins of the serum; reptilian serum proteins bound 55 mg. per gm.

Estrogen-treated birds clearly produced two, rather than one, new proteins, a phosphoprotein, X1, having a rate of 8.5S, and X2, a phospholipid-lipoglycoprotein, 17S. The calcium-binding capacity was approximately 50 mg. per gm. of the mixed proteins of the serums. Circumstantial evidence suggests that the plasma proteins of oviparity appeared simultaneously with the evolution of bone as a tissue and an ultimobranchial gland having parathyroid function.
The Electrophysiology of Electric Organs of Marine Electric Fishes
Authors: Bennett M. V. L. , Wurzel M. , Grundfest H.
Published: May 2004

Single electroplaques of Torpedo nobiliana have been studied with microelectrode recording. Direct evidence is presented that the only electrogenically reactive membrane of the cells is on the innervated surface and that this membrane is electrically inexcitable. Responses are not evoked by depolarizing currents applied to this membrane, but only by stimulating the innervating nerve fibers. The responses arise after a latency of 1 to 3 msec. This latency is not affected by large depolarizing or hyperpolarizing changes in membrane potential. Various properties that have been theoretically associated with electrically inexcitable responses have been also demonstrated to occur in the electroplaques. The neurally evoked response is not propagated actively in the membrane and may have different amplitudes and forms in closely adjacent regions. The maximal responses frequently are slightly larger than the recorded resting potential but the apparent small overshoot may be due to difficulty in recording the full resting potential. The responses are subject to electrochemical gradation and appear inverted in sign on applying strong outward currents across the innervated membrane. This membrane is cholinoceptive and shows marked desensitization. The membrane of the uninnervated surface has a very low resistance, a factor that aids maximum output of current during the discharge of the electric organ.
The Electrophysiology of Electric Organs of Marine Electric Fishes
Authors: Bennett M. V. L. , Grundfest H.
Published: May 2004

The electroplaques of Astroscopus y-graecum were studied in situ with microelectrode recordings. Despite the distant taxonomic relations and the different origins of the organs, their properties in the teleost and torpedine marine electric fishes are remarkably similar. Only the innervated membrane (the dorsal) is electrogenically reactive in Astroscopus, and it, too, does not respond to electrical stimuli. As in the torpedine fishes, the uninnervated membrane of the electroplaques offers a very low resistance to the discharge of the innervated membrane. Additional direct evidence for electrical inexcitability of the reactive surface was obtained by denervating one of the bilateral organs. The denervated one did not respond to strong electrical stimuli which evoked responses in the opposite, innervated organ. The denervated electroplaques had a normal resting potential and were depolarized by acetylcholine and carbamylcholine similarly to normal cells. Other properties related to electrical inexcitability were also demonstrated. A pharmacological finding of considerable theoretical significance is that desensitization occurred on depolarizing cells with acetylcholine but was absent on depolarizing them with carbamylcholine.
The Effect of Caffeine on Radiocalcium Movement in Frog Sartorius
Authors: Bianchi C. P.
Published: May 2004

Caffeine increases resting calcium influx approximately threefold in normally polarized and in potassium-depolarized fibers of frog sartorius muscles. It does not affect the transient rapid increase in calcium influx that occurs at the beginning of a potassium depolarization. Calcium outflux in Ringer's solution, in zero calcium Ringer's solution, and in zero calcium Ringer's solution plus 0.004 M EDTA is also markedly increased by caffeine. The increased outflux reaches a rate which is approximately the same as the increased calcium influx. One interpretation of the findings is that caffeine reduces the binding of calcium both in the membrane and in the myoplasm; this increases the "permeability" to calcium and the ionic activity of calcium in muscle. This interpretation is consistent with the view that the contractile state of muscle is dependent at least in part on the thermodynamic activity of calcium in the muscle fibers.
Factors Controlling the Production of Lysogenic Cultures of B. megatherium
Authors: Northrop John H. ,   with the technical assistance of Marie King
Published: May 2004

(1) The proportion of infected B. megatherium cells which develop lysogenic colonies depends on the number and kind of infecting virus particles and on the culture medium in which the cells are growing. (2) Cells infected with 100 or more T virus particles (from megatherium 899) in yeast extract peptone disintegrate, produce very few virus particles, and less than one lysogenic colony per 107 infected cells. Cells infected with one or a few particles produce 500 to 1000 virus particles each and about 30 lysogenic colonies per 107 infected colonies. (3) T phage obtained from lysogenic magatherium KM cultures produces many more lysogenic cells than does the original megatherium 899 virus. (4) Cells infected with megatherium 899 T virus in peptone medium and then transferred to asparagine medium give rise to 106 lysogenic colonies per 107 infected cells and this transformation will occur even after the infected cells have been in peptone for 60 to 90 minutes and are beginning to produce virus particles. (5) Continued growth of KM strain with either C or T virus from megatherium 899 for several hundred generations in the steady state apparatus results in a lysogenic strain which produces several different types of virus.
A Model Representing a Physiological Role of CO2 at the Cell Membrane
Authors: Sears D. F. , Eisenberg R. M.
Published: May 2004

A model is presented suggesting the interaction of CO2 and bicarbonate on lipids of the cell membrane. The interfacial tensions between water and oil (benzene) phases were measured using the stalagmometer and the sessile drop methods. Effects of electrolyte solutions and of CO2 on molecular arrangement at the interface were calculated. Chloride solutions against oleic acid in benzene produced little decrease in interfacial tension from that measured for pure water against the oil phase. Presence or absence of CO2 caused no change in interfacial tension of water or chloride solutions against the oil phase. Bicarbonate salts in the absence of CO2 caused marked decreases in interfacial tension from that measured for water or chloride solutions. Concomitant with this decrease in interfacial tension were an increase in hydration of the interface and changes in molecular spacings of the lipid. This hydration may be considered as reflecting a more ionic-permeable cell membrane. The addition of CO2 to the bicarbonates caused an increase in interfacial tension of the model, approaching that of the chlorides, with decreased hydration of the interface. Viewed as occurring at the cell membrane this would make the lipid more continuous and decrease the ease of ionic penetration. In this way the action of bicarbonates and CO2 at the interface suggests an explanation of the action of CO2 on the cell.
Correspondences in the Behavior of the Electroretinogram and of the Potentials Evoked at the Visual Cortex
Authors: Crescitelli Frederick , Gardner Ernest
Published: May 2004

Electrical potentials from the eye (ERG) and from the contralateral visual cortex were recorded in response to flashes of white and of colored light of various intensities and durations. The evoked potentials were found to parallel the behavior of the ERG in several significant respects. Selective changes in the ERG brought about by increasing the light intensity and by light adaptation led to parallel selective changes in the cortical responses. The dual waves (b1, b2) of the ERG were found to have counterparts in two cortical waves (c1, c2) which, in respect to changes in light intensity and to light adaptation, behaved analogously to the two retinal components. The responses evoked at high intensity showed only the diphasic c1-potential. As stimulus intensity was lowered the c1-wave decreased in magnitude and a delayed c2-component appeared. The c2-potential increased in amplitude as light intensity of the flash was further reduced. Eventually the c2-wave, too, decreased as stimulus reduction continued. There was no wave length specificity in regard to either the duplex b-waves or duplex cortical waves. Both appeared at all wave lengths from 454 mµ to 630 mµ. The two cortical waves evoked by brief flashes of colored light showed all the behavior to changes in stimulus intensity and to light adaptation that occurred with white light.
Characterization of the Resting Axolemma in the Giant Axon of the Squid
Authors: Villegas Raimundo , Barnola Flor V.
Published: May 2004

Previous electron microscope studies have shown that the Schwann cell layer is traversed by long and tortuous slit-like channels ∼60Å wide, which provide the major route of access to the axolemma surface. In the present work the restriction offered by the resting axolemma to the passage of six small non-electrolyte molecules has been determined. The radii of the probing molecules were estimated from constructed molecular models. The ability of the axolemma to discriminate between the solvent (water) and each probing molecule was expressed in terms of the reflection coefficient σ. σ was then used to calculate an effective pore size for the resting axolemma. The value of 4.25 Å found for the pore radius is in excellent agreement with the 1.5 to 8.5 Å limiting values previously calculated from our measurements of water fluxes. The presence of pores with 4.25 Å radius in the resting axolemma is compatible with restricted diffusion of Na. The present paper leads to the conclusion that the axolemma is the only continuous barrier across which the ionic gradient responsible for the normal functioning of the nerve can be maintained. The combined findings of electron microscopy, water permeability, and molecular restricted filtration indicate that in all probability the axolemma is the "excitable membrane" of the physiologists.
Graded and All-or-None Electrogenesis in Arthropod Muscle
Authors: Werman R. , Grundfest H.
Published: May 2004

Conversion of graded responsiveness of lobster muscle fibers to all-or-none activity by alkali-earth and tetraethylammonium (TEA) ions appears to be due to a combination of effects. The membrane is hyperpolarized, its resistance is increased, and its sensitivity to external K+ is diminished, all effects which indicate diminished K+ conductance. While the spikes are prolonged, the conductance is higher throughout the response than it is in the resting membrane. Repetitive activity becomes prominent. These effects indicate maintained high conductance for an ion which causes depolarization. This is normally Na+, since its presence in low concentrations potentiates the effects of Ba++, but the alkali-earth ions and TEA can also carry inward charge. Ba++, Sr++, and TEA appear to be more effective than is Ca++ in its normal role, which is probably to depress K+ conductance and Na inactivation. Thus, conversion of graded to all-or-none responsiveness appears to occur because of the relative increase of depolarizing inward ion flux and decrease of repolarizing outward flux.
The Importance of Calcium in Poststimulation Potentiation
Authors: Nayler Winifred G.
Published: May 2004

Isotonic contractions recorded both before and during poststimulation potentiation in the toad isolated ventricle (Bufo marinus) revealed that the phenomenon of poststimulation potentiation was not altered by the presence or absence of the catechol amines, or by the specific amine antagonist, DCI. Similarly the inhibitors, sodium fluoride and sodium iodoacetate, were without effect. Changes in [Ca++], [Mg++], and [Na+] affected the degree of potentiation. High [Ca++] as well as the cardiac glycosides abolished it, low [Na+] and the absence of Mg++ depressed it. It has been shown that the percentage potentiation depends to some extent upon the total number of contractions occurring during the rapid stimulation phase. The amplitude of the contractions during this stage did not influence the degree of potentiation. These results are discussed in terms of Ca++ accumulation or redistribution associated with an early phase of the membrane depolarization.
Lithium-Induced Oscillations of Potential and Resistance in Isolated Frog Skin
Authors: Finkelstein Alan
Published: May 2004

The rhythmical variations of electrical potential and DC resistance resulting from the exposure of the anatomical outside of isolated frog skin to a concentration of lithium ion greater than 20 millinormal were reinvestigated. In general, the potential and resistance changes were in phase, although in some skins, a phase shift occurred after the first few waves. The mean level of the resistance declined during the exposure to lithium, returning to its former level upon reintroduction of sodium in place of lithium. The oscillations, with a period of from 3 to 15 minutes, could last for 2 hours or more before damping out; the amplitude of the waves could be altered during this time by the passage of direct current or by the introduction of a hydrostatic pressure difference across the skin. Even after the oscillations damped out, the system remained "excitable," responding to a step of direct current or hydrostatic pressure with an oscillatory train. The nature and magnitude of the response to current and pressure were dependent upon the "polarity" of the applied perturbation. Direct observation of the skin revealed no evidence of oscillatory water movement concomitant with the electrical events.
Insulin-Induced Accumulation of D-Xylose Against an Apparent Concentration Gradient in Diaphragm Muscle, in Vivo
Authors: Eichhorn J. , Hechter O.
Published: May 2004

The effect of insulin administration upon D-xylose-1-C14 penetration into the diaphragm and gastrocnemius muscles of functionally nephrectomized normal, hypophysectomized, and adrenalectomized rats has been examined. It was found in all groups that after the administration of tracer amounts of D-xylose, this sugar enters the cell water of diaphragm to a greater extent than in gastrocnemius muscle, both in the presence and absence of exogenous insulin. Insulin increases the apparent intracellular distribution of D-xylose in both muscles in all three types of rats. After insulin administration, the intracellular concentration of D-xylose in diaphragm muscle was estimated to be about two times greater than D-xylose concentration in plasma; D-xylose accumulation was not observed in gastrocnemius muscle of insulin-treated rats. Intracellular accumulation of D-xylose occurs in diaphragm of insulin-treated rats at plasma concentrations of D-xylose ranging from 4 to 2200 µg/ml; however, a "saturation" phenomenon appears to be operative, since intracellular distribution declines as plasma D-xylose concentration is increased within this range. A decline in intracellular D-xylose distribution also occurs in gastrocnemius as plasma D-xylose is increased, suggesting that entry into this muscle as well does not exhibit the characteristics of a simple diffusion process. The significance of these in vivo observations is briefly discussed in relation to widely accepted assumptions concerning sugar permeability in muscle.
Phototropism, Adaptation, and the Light-Growth Response of Phycomyces
Authors: Castle Edward S.
Published: May 2004

Phototropic bending can be initiated without the transient changes in growth speed that characterize a light-growth response. The conditions required are a change from a symmetric to an asymmetric illumination pattern while the cell receives a constant radiant flux. Phototropism is thus basically a steady state process. It cannot be founded on differential light-growth responses as in Blaauw's theory. A possible model system for the unequal partition of growth during steady bending is discussed. The fact that light-growth responses show adaptation while phototropic bending does not follows from the different natures of the two responses.
Extracellular and Metabolic Factors Affecting the Efflux and Influx of Erythrocyte Water
Authors: Olmstead Edwin G.
Published: May 2004

Water exchanges between rabbit erythrocytes and extracellular solutions equidistant from intracellular osmolarity were studied by freezing point depression techniques. Water efflux was always less than water influx and both were hypotonic to the intracellular and extracellular fluids. The magnitudes of these water exchanges were not dependent on the presence of extracellular cation. Stimulation of oxygen uptake by the addition of glucose and methylene blue increased water influx and, possibly, decreased water efflux. This could not be accounted for by accumulation of osmotically active intracellular metabolic products. O2 uptake was markedly decreased during cellular dehydration, was slightly decreased during cellular overhydration, and was maximum at the water content of erythrocytes when suspended in a medium isotonic with plasma.
Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon
Authors: Adelman William J. , Moore John W.
Published: May 2004

Voltage clamp measurements of the sodium potential have been made on the resting squid giant axon to study the effect of variations in external divalent ion concentration upon net sodium flux. From these measurements the intracellular sodium concentration and the net sodium inflow were calculated using the Nernst relation and constant activity coefficients. While an axon bathed in artificial sea water shows a slow increase in internal sodium concentration, the rate of sodium accumulation is increased about two times by reducing external calcium and magnesium concentrations to 0.1 times their normal values. The mean inward net sodium flux increases from a mean control value of 97 pmole/cm2 sec. to 186 pmole/cm2 sec. in low divalent solution. Associated with these effects of external divalent ion reduction are a marked decrease in action potential amplitude, little or no change in resting potential, and a shift along the voltage axis of the curve relating peak sodium conductance to membrane potential similar to that obtained by Frankenhaeuser and Hodgkin (1957). These results implicate divalent ions in long term (minutes to hours) sodium permeability.
Studies on Transformations of Hemophilus influenzae
Authors: Hsu Yu-Chih , Herriott Roger M.
Published: May 2004

A general method of determining the nature of the genotypes in mutants of transformable bacteria with similar phenotypes is discussed. The method is used to identify the genotypic patterns of three mutants of Hemophilus influenzae which are resistant to different levels of streptomycin. A mutant resistant to 700 µg per ml of the antibiotic was found to be made up of two unlinked, independent loci—presumably on different molecules of transforming DNA. These loci, when in separate cells, render them resistant to maximum levels of 10 and 100 µg per ml streptomycin respectively and are therefore designated as Sm10 and Sm100. When they enter the same cell they produce a resistance up to 700 µg per ml streptomycin, so the cells are noted as Sm700. This multiplicative action is more easily visualized as due to two independent processes of combating the antibiotic which enhance each other rather than two identical processes.
On The Mechanism of Spontaneous Impulse Generation in the Pacemaker of the Heart
Authors: Trautwein Wolfgang , Kassebaum Donald G.
Published: May 2004

Rhythmic activity in Purkinje fibers of sheep and in fibers of the rabbit sinus can be produced or enhanced when a constant depolarizing current is applied. When extracellular calcium is reduced successively, the required current strength is less, and eventually spontaneous beating occurs. These effects are believed due to an increase in steady-state sodium conductance. A significant hyperpolarization occurs in fibers of the rabbit sinus bathed in a sodium-free medium, suggesting an appreciable sodium conductance of the "resting" membrane. During diastole, there occurs a voltage-dependent and, to a smaller extent, time-dependent reduction in potassium conductance, and a pacemaker potential occurs as a result of a large resting sodium conductance. It is postulated that the mechanism underlying the spontaneous heart beat is a high resting sodium current in pacemaker tissue which acts as the generator of the heart beat when, after a regenerative repolarization, the decrease in potassium conductance during diastole reestablishes the condition of threshold.
Interaction of Mercury with Human Erythrocytes
Authors: Weed R. , Eber J. , Rothstein A.
Published: May 2004

The binding of mercury to red blood cells was measured in terms of Hg203 uptake and desorption. The significant features of the binding are: (a) rapid achievement of equilibrium (3 to 5 minutes); (b) release of a Hg-complexing material from the red cells themselves which distorts the binding curves at low concentrations of metal (2.5 x 10-7 to 5.0 x 10-6 M); (c) prevention of binding by cysteine, glutathione, penicillamine, and EDTA but not by imidazole or histidine; (d) binding of mercury in amounts up to 7 times the reduced glutathione concentration of the cells before combination with glutathione itself; (e) binding primarily to sulfhydryl groups of hemoglobin and to a small number of stromal sulfhydryl groups, but also to other non-sulfhydryl cellular ligands after saturation of the sulfhydryl groups. Associated with the binding is inhibition of glucose uptake, induction of loss of K+, and decrease in osmotic fragility. These effects increase over the range of concentrations (1 x 10-17 to 1 x 10-15 moles of Hg/RBC) well below those that result in saturation of the cellular binding sites; above 1 x 10-15 moles/RBC, the effects decrease as the cells become saturated.
Studies on Sulfhydryl Groups during Cell Division of Sea Urchin Egg
Authors: Sakai Hikoichi
Published: May 2004

A KCl-soluble protein fraction can be extracted from the water-insoluble residue of the homogenate of sea urchin eggs which contains three major components separable by ultracentrifugation. When the extract is stirred in acetone or distilled water, a fibrous precipitate appears which has a strong birefringence positive in the direction of the long axis. When the fraction is squirted through a slender tubing, it precipitates in the form of a thread. The thread model contracts vigorously under the action of di-, tri-, and tetravalent metal ions; the contraction can be reversed by EDTA. The contraction and the elongation of the thread model can be repeated many times. The thread model contracts also in the presence of dehydroascorbic acid, cystine, oxidized glutathione, or other oxidizing agents, and this contraction is reversed by reducing agents such as cysteine or ascorbic acid. When —SH groups of the thread model are blocked by various —SH reagents, the contraction by metal ions is inhibited to some extent. As mechanisms of the contraction, electrostatic forces between metal ions and negative charges of the thread model are essential for metal ion-induced contraction and oxidation of —SH groups of the thread model for the contraction by oxidizing reagents.
Studies on Sulfhydryl Groups during Cell Division of Sea Urchin Egg
Authors: Sakai Hikoichi
Published: May 2004

The contractility of the thread model prepared from the KCl-soluble proteins of the egg and in vivo factors for the contraction are investigated in Hemicentrotus, Anthocidaris, and Pseudocentrotus eggs.

The contractility of the thread model induced by metal ions or cystine changes during development in the characteristic pattern of high at the metaphase and low at the monaster and the interkinetic stages. The change in contractility is paralleled by the change in the —SH content of the protein.

The water-soluble fraction of the eggs has activity in causing contraction of the thread model. This activity changes during development in the same way as the contractility itself. The contraction of the thread induced by the water-soluble fractions is accompanied by a decrease in the —SH content of the thread. The activity of the water-soluble fraction in inducing the contraction is proportional to its ability to decrease the number of —SH groups. On boiling, the activity is largely destroyed. The activity is due to two components, one being non-dialyzable and the other dialyzable. Separately each component has little effect, but when mixed, the activity of the original sample is completely restored.
The Metabolism of Serum Proteins in the Hen and Chick and Secretion of Serum Proteins by the Ovary of the Hen
Authors: Patterson R. , Youngner J. S. , Weigle W. O. , Dixon F. J.
Published: May 2004

In the chicken, serum gamma globulin (CGG) is preferentially transferred by the follicular epithelium of the ovary to the developing ova. The concentration of gamma globulin in the yolk of the unfertilized egg is many times the concentration of chicken serum albumin (CSA). This transfer occurs largely during the 4 to 5 days preceding ovulation when the growth of the ovum is most rapid. Thus, in the chicken, the follicular epithelium of the ovary serves the same purpose in the passive immunization of offspring as does the acinar epithelium of the udder in ungulates and the extraembryonic membranes in rabbits and man.

The amount of gamma globulin synthesis by the chick is low during the first 2 weeks of life and is associated with low levels of serum gamma globulin. By the end of the 1st month of life, the level of serum gamma globulin increases, presumably reflecting an increased rate of synthesis.

In the adult hens the half-life of I131-labeled CSA is 66 hours and that of I131-labeled CGG, 35 hours, while in the newly hatched chick for I131-labeled CSA it is 42 hours and for I131-labeled CGG, 72 hours. Thus, this species shows a gamma globulin sparing in the first days of life, as do most mammalian species.
Variations in the Lactic Dehydrogenase of Vertebrate Erythrocytes
Authors: Vesell Elliot S. , Bearn Alexander G.
Published: May 2004

Erythrocytes from representatives of the 5 classes of vertebrates revealed a marked species variation in the number of LDH isozymes, in the distribution of the total LDH activity among these isozymes, and in their electrophoretic mobilities. Starch gel electrophoresis of hemolysates followed by direct histochemical demonstration of LDH activity with nitro blue tetrazolium as dye and phenazine methosulfate as electron transporter showed that closely related species exhibited similar LDH patterns. The rhesus monkey had LDH isozymes of similar pattern to those of human hemolysate but slightly slower in electrophoretic mobility. The goat and sheep each had 1 band of LDH activity in their erythrocytes of identical electrophoretic mobility, whereas the single band in steer hemolysate migrated slightly faster. The 5 bands of chicken hemolysate were quite similar in pattern to the 5 bands of duck hemolysate but migrated slightly faster and exhibited a different distribution of the total LDH activity. The 2 species of snake each had 1 band of LDH activity with identical mobility. Staining occurred with the levorotatory form of the substrate and not with the dextrorotatory form. Examination of more than 380 human hemolysates failed to reveal any differences among individuals in the main LDH bands. The genetic basis for the species differences in erythrocyte lactic dehydrogenases is discussed.
Thrombokinase of the Blood as Trypsin-Like Enzyme
Authors: Milstone J. H.
Published: May 2004

Thrombokinase of the blood, while resembling enterokinase in its role of activator, is more closely analogous to trypsin in its intrinsic origin. It probably arises from a plasma precursor; but it is different from plasmin (fibrinolysin). Like trypsin, thrombokinase can activate prothrombin without the aid of other factors; however, it is potentiated by platelets plus calcium. Unlike certain tissue "thromboplastins," it does not sediment appreciably in 2 hours at 85,000 g. Like trypsin, it hydrolyzes p-toluenesulfonylarginine methyl ester (TAMe). Chromatography on DEAE-cellulose separated thrombin from thrombokinase. The TAMe esterase associated with the thrombokinase fractions was largely suppressed by soybean trypsin inhibitor, while that associated with the thrombin fractions was not. Highly purified thrombokinase was used as starting material; and thrombokinase was eluted in the last major protein band. Under these conditions stepwise elution was as effective as gradient in leading to further purification. The product of 199 liters of bovine plasma was chromatographed in 1 day; and the specific activity was comparable to that attained previously by repeated electrophoretic fractionations. The assembled data suggest that the thrombokinase protein may be approaching homogeneity.
Bacteriolytic Enzymes from Streptomycetes
Authors: Welsch Maurice
Published: May 2004

A study of the bacteriolytic properties of streptomycetes has progressively uncovered the production by these microorganisms of a large number of different enzymes acting upon various bacterial constituents, especially on some of them located in the cell wall. Although the mechanism of the bacteriolysis is far from being completely elucidated at present, it can, however, be stated that, in two instances at least, it can be regarded as an osmotic explosion following upon the destruction of the structure responsible for the rigidity of the cell wall.
Uber Phosphorylierung im Licht
Authors: Warburg Otto
Published: May 2004

Während bisher der Zusammenhang zwischen Dehydrierung und Phosphorylierung im Licht nur für die stöchiometrischen Chinonreactionen bewiesen worden war, ist nunmehr auch für die katalytischen Chinonreactionen, die aeroben wie die anaeroben, gezeigt worden, dass die Dehydrierung die Phosphorylierung bewirkt. Eine andere Phosphorylierung, als die Phosphorylierung durch Dehydrierung gibt es in den grünen Grana nicht. Natürlich entsteht nunmehr die Frage, welche Substanz das Substrat von Dehydrierung und Phosphorylierung ist. Da die Grana keine Dunkelatmung haben und deshalb im Dunkeln nicht phosphorylieren können, auch nicht nach Zusatz von Chinon, so muss das gesuchte Substrat im Licht entstehen; und da der Photolyt der Granareactionen eine Kohlensäureverbindung ist, so muss das gesuchte Substrat eine im Licht entstehende Kohlenstoffverbindung sein. Wegen der Gärungen und dem einzigen bisher bekannten chemischen Mechanismus der Phosphorylierung durch Dehydrierung (4) denkt man an Triosephosphat. Aber chemisch ist jeder Aldehyd möglich.
Pepsinogen and Pepsin
Authors: Herriott Roger M.
Published: May 2004

Evidence relating to the structure and properties of swine pepsinogen and pepsin has been reviewed and used to suggest a tentative two dimensional picture of the skeleton of these two proteins. When pepsinogen, a folded single peptide chain, is converted to pepsin, there is a profound change in the physical and chemical properties of the protein. In an as yet unknown manner, except that it is initiated by a peptic cleavage of the protein chain, a single enzymic site is formed. This site is made up, quite probably, of the secondary carboxyl group of glutamic acid or of aspartic acid and a tyrosine phenol group in close proximity so that they can form hydrogen or hydrophobic bonds with the substrate in some unique manner that permits hydrolysis to occur at an accelerated rate.
The Effect of Calcium on Sodium Transport by Frog Skin
Authors: Curran Peter F. , Gill John R.
Published: May 2004

Calcium added to the solution bathing the outside of isolated frog skin caused a reversible decrease in net sodium transport across the skin. At constant sodium concentration, the inhibition of transport increased with increasing calcium concentration, but approached a limiting value. This maximum degree of inhibition was found to depend on sodium concentration; sodium transport could be inhibited by 60 per cent at 96 mM sodium, but by only 18 per cent at 19 mM sodium. The relative effectiveness of a given calcium concentration was also greater the higher the sodium concentration. The unidirectional flux of chloride across the short-circuited skin was decreased by calcium to approximately the same degree as active sodium transport. The results have been interpreted in terms of a relatively non-specific decrease in permeability of the outward facing membrane of the transporting cells. The resulting decrease in sodium permeability apparently causes a decrease in active sodium transport by reducing the availability of sodium to the transporting system.
Accumulation of Sulfate by Mitochondria of Rat Kidney Cortex
Authors: Winters Robert W. , Delluva Adelaide M. , Deyrup Ingrith J. , Davies Robert E.
Published: May 2004

Twice washed mitochondria from rat kidney cortex can accumulate sulfate ions from low (10-7 M) ambient concentrations to create virtual gradients of several hundred to one. This sulfate is subsequently released. The activation energy for the uptake is 12,000 calories per mole; for release it is about 30,000 calories per mole. Variations in the sulfate concentration of the medium show that there is a straight line Freundlich adsorption isotherm over a million-fold range of concentration of sulfate in the medium. There are 9 x 104 sites at 10-5 M and 9 x 105 sites at 10-3 M sulfate per average single mitochondrion. Preincubation at 30°C rapidly destroys the ability to accumulate sulfate. Partial protection occurs if oxidative phosphorylation is proceeding during the preincubation. The concentration of the endogenous inorganic sulfate of twice washed mitochondria is 4.2 x 10-4 moles per liter of mitochondrial pellet water; 99.85 per cent of this endogenous sulfate is inexchangeable with external sulfate in vitro. It is all exchangeable in vivo. The pH optimum for accumulation of radiosulfate from dilute external sulfate concentrations is 5.5. These observations show that there is a delicate and specific mechanism in mitochondria from kidney cortex which accumulates sulfate. The chemical nature of the accumulated sulfate is unknown.
Bioluminescence of Marine Dinoflagellates
Authors: Seliger H. H. , Fastie W. G. , Taylor W. R. , McElroy W. D.
Published: May 2004

Portable light-baffled underwater photometers have been designed for the measurement of dinoflagellate bioluminescence by day and night. Maximal light emission is obtained by mechanical stimulation in a defined volume. The pump which stimulates the dinoflagellates also constantly replenishes the sample volume so that continuous measurements are possible. Evidence for both diurnal variation and vertical migration is presented. Using luminous bacteria for calibration a single dinoflagellate has been found to emit of the order of 1010 light quanta per flash. The technique suggests that large scale mapping of bioluminescence is feasible.
The Active Transport of Sodium by Ghosts of Human Red Blood Cells
Authors: Hoffman Joseph F.
Published: May 2004

The outflux of Na24 from prelabeled ghosts was measured under various conditions. Prelabeling was accomplished by hypotonic hemolysis of intact human cells in the presence of tracer Na24. The resultant ghosts when subsequently washed were found to retain 10 to 20 per cent of the initial Na24. Separate experiments indicated that this trapped amount resides in only a portion of ghosts comprising the total population. The characteristics of the outflux of this residual Na24 indicated that the ghost system closely resembles intact red cells. The outflux of Na from ghosts could be divided into three components: active and passive transport and exchange diffusion. The active transport system, necessarily driven by metabolism, required the presence of K in the extracellular phase and was blocked by strophanthidin. The concentration dependence of the Na pump flux on the external K and internal Na appeared the same in ghosts as in intact cells. Certain other features of this ghost system are also discussed.
Permeability of the Isolated Toad Bladder to Solutes and Its Modification by Vasopressin
Authors: Leaf Alexander , Hays Richard M.
Published: May 2004

Measurements have been made of the permeability of the isolated urinary bladder of the toad to a number of small solute molecules, in the presence and absence of vasopressin. Vasopressin has a strikingly specific effect on increasing permeability of the bladder to a group of small, uncharged amides and alcohols while penetration by other small molecules and ions is unaffected. The movement of urea is passive, as indicated by equal flux rates in the two directions. The reflection coefficients for chloride and thiourea indicate a high degree of impermeability of the bladder to these solutes even in the presence of large net movements of water. The low concentration of thiourea in the tissue water when this compound is added to the mucosal bathing medium indicates that the major permeability barrier to thiourea is at the mucosal surface of the bladder. The findings can be accounted for by a double permeability barrier consisting of a fine selective diffusion barrier and a porous barrier in series. The former would constitute the permeability barrier to most small solutes while the latter would be the rate-limiting barrier for water and the amides. It would be the porous barrier which is affected by vasopressin. Reasons are presented which require both barriers to be contained in or near the plasma membrane at the mucosal surface of the bladder.
The State of Water in the Isolated Toad Bladder in the Presence and Absence of Vasopressin
Authors: Hays Richard M. , Leaf Alexander
Published: May 2004

An attempt has been made to assess the validity of applying the frictional and viscous coefficients of bulk water to the movement of water and solutes through the urinary bladder of the toad. The temperature dependence of diffusion of THO, C14-urea, C14-thiourea, and net water transfer across the bladder was determined in the presence and absence of vasopressin. The activation energy for diffusion of THO was 9.8 kcal per mole in the absence of vasopressin and 4.1 kcal per mole with the hormone present. Activation energies simultaneously determined following vasopressin for diffusion and net transfers of water were similar, and in the same range as known activation energies for diffusion and viscous flow in water. Urea had activation energies for diffusion of 4.1 and 3.9 kcal per mole in the absence and presence of vasopressin, respectively. Thiourea had a high activation energy for diffusion of 6.3 kcal per mole, which was unchanged, 6.6 kcal per mole, following hormone. These findings suggest that in its rate-limiting permeability barrier, water is present in a structured state, offering a high resistance to penetration by water. Vasopressin enlarges the aqueous channels so that the core of water they contain possesses the physical properties of ordinary bulk water. Urea penetrates the tissue via these aqueous channels while thiourea is limited by some other permeability barrier.
The Electroretinogram of a Diurnal Gecko
Authors: Arden G. B. , Tansley Katharine
Published: May 2004

Using the electroretinogram as the criterion of retinal activity the flicker fusion frequency, course of dark adaptation, and spectral sensitivity of the pure cone retina of the diurnal gecko, Phelsuma inunguis, were investigated. Both the curve relating flicker fusion frequency to stimulus intensity and that relating the amplitude of the flicker response to stimulus intensity showed a break as the intensity was increased. The dark adaptation curve was that typical of cone retinae; there was no break, adaptation was relatively rapid, and there was a total increase of sensitivity of only about 3 log units. The spectral sensitivity curve showed two maxima, a major one at about 560 mµ and another at about 460 mµ. Chromatic adaptation with red and blue lights demonstrated the presence of two independent mechanisms. Although red adaptation could not have had a direct effect on the pigment responsible for the "blue" mechanism the sensitivity of this mechanism was depressed by red adaptation. The possible relationships of the two mechanisms are discussed.
Interpretation of the Repetitive Firing of Nerve Cells
Authors: Fuortes M. G. F. , Mantegazzini Francoise
Published: May 2004

Eccentric cells of Limulus respond with repetitive firing to sustained depolarizing currents. Following stimulation with a step of current, latency is shorter than first interval and later intervals increase progressively. A shock of intensity twice threshold can evoke firing 25 msec. after an impulse. But in the same cell, a current step twice rheobase evokes a second impulse more than 50 msec. after the first, and current intensity must be raised to over five times rheobase to obtain a first interval of about 25 msec. Repetitive firing was evoked by means of trains of shocks. With stimuli of moderate intensity, firing was evoked by only some of the shocks and intervals between successive impulses increased with time. This is ascribed to accumulation of refractoriness with successive impulses. Higher frequencies of firing are obtained with shocks of intensity n x threshold than with constant currents of intensity n x rheobase. It is concluded that prolonged currents depress the processes leading to excitation and that (in the cells studied) repetitive firing is controlled both by the after-effects of firing (refractoriness) and by the depressant effects of sustained stimuli (accommodation). Development of subthreshold "graded activity" is an important process leading to excitation of eccentric cells, but is not the principal factor determining frequency of firing in response to constant currents.
Membrane Potentials of the Lobster Giant Axon Obtained by Use of the Sucrose-Gap Technique
Authors: Julian Fred J. , Moore John W. , Goldman David E.
Published: May 2004

A method similar to the sucrose-gap technique introduced be Stäpfli is described for measuring membrane potential and current in singly lobster giant axons (diameter about 100 micra). The isotonic sucrose solution used to perfuse the gaps raises the external leakage resistance so that the recorded potential is only about 5 per cent less than the actual membrane potential. However, the resting potential of an axon in the sucrose-gap arrangement is increased 20 to 60 mv over that recorded by a conventional micropipette electrode when the entire axon is bathed in sea water. A complete explanation for this effect has not been discovered. The relation between resting potential and external potassium and sodium ion concentrations shows that potassium carries most of the current in a depolarized axon in the sucrose-gap arrangement, but that near the resting potential other ions make significant contributions. Lowering the external chloride concentration decreases the resting potential. Varying the concentration of the sucrose solution has little effect. A study of the impedance changes associated with the action potential shows that the membrane resistance decreases to a minimum at the peak of the spike and returns to near its initial value before repolarization is complete (a normal lobster giant axon action potential does not have an undershoot). Action potentials recorded simultaneously by the sucrose-gap technique and by micropipette electrodes are practically superposable.
Inhibition of the Tyrosinase Oxidation of One Substrate by Another
Authors: Mayberry J. M. , Mallette M. F.
Published: May 2004

The catalytic oxidation of catechol by crude preparations of mushroom tyrosinase was studied by a method yielding data on initial reaction velocities. Graphical analysis of the results suggests that an excess of catechol inhibits its own oxidation by a competitive process, thus accounting for the observed optimum in the substrate concentration. However, added phenol, though itself a substrate, inhibits the enzymatic oxidation of catechol by a process that is neither competitive nor non-competitive, but a mixture of the two types. Mechanisms of this inhibition of the enzyme by a second substrate are discussed in exploring the problem of substrate-substrate inhibition.
The Pattern of Activation in the Sartorius Muscle of the Frog
Authors: Close R.
Published: May 2004

The development of isometric twitch tension has been compared with the redevelopment of isometric tension in the fully active frog sartorius muscle following release. At 0°C the rate of rise of isometric twitch tension is the same as that for the muscle in the fully active state at the same tension but not until about 40 msec. after the stimulus and then only for a few milliseconds. The rates of rise of tension in the twitch and in the redevelopment of tension in the fully active muscle appear to be nearly the same at low tensions. Substitution of nitrate for chloride in the Ringer's solution bathing the muscle retards the development of tension during the early part of the contraction phase of the twitch and the effect reaches a maximum within 3 minutes after changing the solutions. These observations have been discussed in connection with some possible patterns of activation and the hypothesis has been advanced that the rate of activation of a sarcomere is determined mainly by the rate at which the transverse component of the link between excitation and contraction is propagated inwards from the periphery to the center of the fiber. This hypothesis has been discussed in relation to others concerning the nature of excitation-contraction coupling.
Cat Heart Muscle in Vitro
Authors: Page Ernest
Published: May 2004

The steady state transmembrane resting potential difference (Vm) has been measured in quiescent papillary muscles. Vm was determined as a function of the external K concentration in Cl and SO4 solutions and compared with the K equilibrium potential. Other measurements were made after replacement of external Na by choline, K by Rb and Cs, and Cl by SO4, CH3SO4, and NO3. Effects on Vm of albumin, temperature, and variation in internal K concentration are described.