bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SITES FOR MECHANO-ELECTRIC CONVERSION IN A PACINIAN CORPUSCLE
Authors: Loewenstein Werner R. , Rathkamp Raquel ,   With the Assistance of I. Zamudio
Published: May 2004

The sensory nerve ending in the Pacinian corpuscle is surrounded by a non-nervous capsular structure which occupies about 99.9 per cent of the corpuscle's entire mass. After extirpation of practically all of the non-nervous structure, the sense organ's remains continue to function as a mechano-receptor, namely to produce generator and all-or-nothing potentials in response to mechanical stimuli. Compression of the first intracorpuscular node of Ranvier abolishes the production of "all-or-nothing" potentials in the corpuscle. Graded generator potentials constitute then the only response to mechanical stimulation. This reveals that the first node is the site of origin of the all-or-nothing potential and that the non-myelinated ending is incapable of producing all-or-nothing responses in response to mechanical stimulation. Compression of the entire length of non-myelinated ending suppresses the production of generator potentials. Partial compression of the ending abolishes mechano-responsiveness only of the compressed part. The intact remains of the ending continue to give generator potentials upon mechanical stimulation. This suggests that the generator potential arises at functionally independent membrane parts distributed all over the non-myelinated nerve ending. 24 to 36 hours after denervation of the corpuscle by transection of its sensory axon, no sign of electric activity is detected. Failure of mechano-reception at the nerve ending precedes that of conduction at the degenerating myelinated axon.
THE ACTION OF ALPHA CHYMOTRYPSIN UPON MIXTURES OF ESTERS AND PROTEINS AT ENZYME-SATURATING CONCENTRATIONS
Authors: Castañeda-Agulló M. , del Castillo Luz M.
Published: May 2004

The behavior of α-chymotrypsin has been studied in the simultaneous presence of two different substrates, each present in the reaction mixture at its saturation level. Mixtures of two esters were hydrolyzed at rates intermediate between the rates of hydrolysis of each ester when present alone, suggesting, in this case, competitive hydrolysis. In contrast, the rates of hydrolysis in mixtures of casein with gelatin or of either protein with an ester were equal to the sum of the rates of hydrolysis of the separate substrates, indicating in these cases independent hydrolysis. The activity of the α-chymotrypsin preparation used could not be attributed to contamination with other enzymes. Studies of the effect of soy bean inhibitor on chymotrypsin indicate that the mechanism of inhibition with protein substrates differs from that when esters are used, providing further evidence that α-chymotrypsin reacts differently with esters and proteins.

These results indicate that if chymotrypsin forms specific complexes with its substrates, it must possess at least three distinct active sites. However there is independent chemical evidence that the proteolytic and esterolytic activities of this enzyme reside in the same active center. If this is true, the experimental observations reported here cannot be explained unless it is supposed that this enzyme does not form specific Michaelis complexes with its substrates.
THE THERMAL STABILITY OF RHODOPSIN AND OPSIN
Authors: Hubbard Ruth
Published: May 2004

Rhodopsin, the red photosensitive pigment of rod vision, is composed of a specific cis isomer of retinene, neo-b (11-cis), joined as chromophore to a colorless protein, opsin. We have investigated the thermal denaturation of cattle rhodopsin and opsin in aqueous digitonin solution, and in isolated rod outer limbs. Both rhodopsin and opsin are more stable in rods than in solution. In solution as well as in rods, moreover, rhodopsin is considerably more stable than opsin. The chromophore therefore protects opsin against denaturation. This is true whether rhodopsin is extracted from dark-adapted retinas, or synthesized in vitro from neo-b retinene and opsin. Excess neo-b retinene does not protect rhodopsin against denaturation. The protection involves the specific relationship between the chromophore and opsin. Similar, though somewhat less, protection is afforded opsin by the stereoisomeric iso-a (9-cis) chromophore in isorhodopsin.

The Arrhenius activation energies (Ea) and entropies of activation (ΔS‡) are much greater for thermal denaturation of rhodopsin and isorhodopsin than of opsin. Furthermore, these values differ considerably for rhodopsins from different species —frog, squid, cattle—presumably due to species differences in the opsins.

Heat or light bleaches rhodopsin by different mechanisms, yielding different products. Light stereoisomerizes the retinene chromophore; heat denatures the opsin. Photochemical bleaching therefore yields all-trans retinene and native opsin; thermal bleaching, neo-b retinene and denatured opsin.
TUBULAR SECRETION OF CREATINE, TRIMETHYLAMINE OXIDE, AND OTHER ORGANIC BASES BY THE AGLOMERULAR KIDNEY OF LOPHIUS AMERICANUS
Authors: Forster Roy P. , Berglund Fredrik , Rennick Barbara R.
Published: May 2004

Creatine and trimethylamine oxide (TMAO) are the chief nitrogenous constituents of normal Lophius urine, and both of these organic bases characteristically have high urine/plasma concentration ratios.

Competition studies involving various organic bases indicate that creatine and TMAO are excreted independently by separate transport mechanisms.

TMAO excretion is inhibited competitively by tetraethylammonium ion (TEA) and by cyanine dye No. 863—compounds previously shown to be transferred actively by an organic base-secreting mechanism of general occurrence among vertebrates.

TEA does not inhibit competitively the active tubular reabsorption of TMAO in Squalus with doses which markedly depress its tubular excretion in Lophius. Glycine, which inhibits creatine reabsorption in the dog, does not interfere competitively with its secretion in Lophius.
ION TRANSPORT IN NITELLOPSIS OBTUSA
Authors: MacRobbie Enid A. C. , Dainty J.
Published: May 2004

The distribution and rates of exchange of the ions sodium, potassium, and chloride in single internodal cells of the ecorticate characean, Nitellopsis obtusa, have been studied.

In tracer experiments three kinetic compartments were found, the outermost "free space" of the cell, a compartment we have called "protoplasmic non-free space", and the cell sap.

The concentrations in the vacuole were 54 mM Na+, 113 mM K+, and 206 mM Cl-. The steady state fluxes across the vacuolar membrane were 0.4 pmole Na+/cm.2 sec., 0.25 pmole K+/cm.2 sec., and 0.5 pmole Cl-/cm.2 sec.

The protoplasmic Na/K ratio is equal to that in the vacuole but protoplasmic chloride is relatively much lower. Osmotic considerations suggest a layer 4 to 6 µ thick with sodium and potassium concentrations close to those in the vacuole. The fluxes between protoplasm and external solution were of the order of 8 pmoles Na+/cm.2 sec. and 4 pmoles K+/cm.2 sec.

We suggest that the protoplasm is separated from the cell wall by an outer protoplasmic membrane at which an outward sodium transport maintains the high K/Na ratio of the cell interior, and from the vacuole by the tonoplast at which an inward chloride transport maintains the high vacuolar chloride. The tonoplast appears to be the site of the principal diffusion resistance of the cell, but the outer protoplasmic membrane probably of the main part of the potential.
THE ENTRANCE OF WATER INTO BEEF AND DOG RED CELLS
Authors: Villegas Raimundo , Barton T. C. , Solomon A. K.
Published: May 2004

The rate constants for diffusion of THO across the red cell membrane of beef and dog, and the rate of entrance of water into the erythrocytes of these species under an osmotic pressure gradient have been measured. For water entrance into the erythrocyte by diffusion the rate constants are 0.10 ± 0.02 msec.-1 (beef) and 0.14 ± 0.03 msec.-1 (dog); the permeability coefficients for water entrance under a pressure gradient of 1 osmol./cm3 are 0.28

See PDF for Equation

These values permit the calculation of an equivalent pore radius for the erythrocyte membrane of 4.1 A for beef and 7.4 A for dog. In the beef red cell the change in THO diffusion due to osmotically produced cell volume shifts has been studied. The resistance to THO diffusion increases as the cell volume increases. At the maximum volume, (1.06 times normal), THO diffusion is decreased to 0.84 times the normal rate. This change in diffusion is attributed to swelling of the cellular membrane.
THE ACTION OF ENZYMES ON RHODOPSIN
Authors: Radding Charles M. , Wald George
Published: May 2004

The effects have been examined of chymotrypsin, pepsin, trypsin, and pancreatic lipase on cattle rhodopsin in digitonin solution.

The digestion of rhodopsin by chymotrypsin was measured by the hydrolysis of peptide bonds (formol titration), changes in pH, and bleaching. The digestion proceeds in two stages: an initial rapid hydrolysis which exposes about 30 amino groups per molecule, without bleaching; superimposed on a slower hydrolysis which exposes about 50 additional amino groups, with proportionate bleaching. The chymotryptic action begins at pH about 6.0 and increases logarithmically in rate to pH 9.2.

Trypsin and pepsin also bleach rhodopsin in solution. A preparation of pancreatic lipase bleached it slightly, but no more than could be explained by contamination with proteases.

In digitonin solution each rhodopsin molecule is associated in a micelle with about 200 molecules of digitonin; yet the latter do not appear to hinder enzyme action. It is suggested that the digitonin sheath is sufficiently fluid to be penetrated on collision with an enzyme molecule; and that once together the enzyme and substrate are held together by intermolecular attractive forces, and by the "cage effect" of bombardment by surrounding solvent molecules.

The two stages of chymotryptic digestion of rhodopsin may correspond to an initial rapid fragmentation, such as has been observed with many proteinases and substrates; superimposed upon a slower digestion of the fragments. Since the first phase involves no bleaching, this may mean that rhodopsin can be broken into considerably smaller fragments without loss of optical properties.
ELECTRICAL ACTIVITY IN THE CHEMORECEPTORS OF THE BLOWFLY
Authors: Wolbarsht M. L. , Dethier V. G.
Published: May 2004

The electrical responses of the neurons associated with the various types of chemosensory hairs of the blowfly, Phormia regina Meigen, following stimulation by chemical and mechanical means have been studied. The singly innervated chemosensory hairs on the ovipositor, maxillary palpi, and antennae respond vigorously to chemical stimulation, but not to mechanical stimulation. The triply innervated chemosensory hairs on the labellum, tarsus, and wing have two neurons which respond only to chemical stimuli. The third neuron responds only to mechanical stimulation. The differential responses of the two chemosensory neurons to various chemical stimuli following the removal of the tip of the hair suggest that the structures responsible for chemoreception are located throughout the distal processes of these neurons. The response of the third neuron to mechanical stimulation is similar to the response recorded from the neuron associated with one type of tactile hair which responds to motion and not to steady deformation. Recordings have been made from the neurons associated with purely tactile hairs using the cut hair as an extension of the micropipette. The mechanosensory neuron of the wing chemosensory hair is capable of responding at the rate of at least 600 impulses per sec. and may serve to indicate changes in air flow over the wing surfaces during flight to enable the fly to correct the wing camber and attack angle.
THE PHOTOSENSITIVE RETINAL PIGMENTS OF FISHES FROM RELATIVELY TURBID COASTAL WATERS
Authors: Munz Frederick W.
Published: May 2004

Digitonin extracts have been prepared from the retinae of a dozen species of marine and euryhaline teleost fishes from turbid water habitats. Spectrophotometric analysis of the extracts shows that the photosensitive retinal pigments of these species have maximum absorption above 500 mµ. In nine species there are retinene1 pigments with λmax between 504 and 512 mµ. In the marine but euryhaline mullet, Mugil cephalus, there is a porphyropsin with λmax 520 mµ. A mixture of rhodopsin and porphyropsin in an extract of a marine puffer, Sphoeroides annulatus, was disclosed by partial bleaching with colored light. In addition, one other species has a 508 mµ pigment, of which the nature of the chromophore was not determined.

The habitats in which these fishes live are relatively turbid, with the water greenish or yellowish in color. The spectral transmission of such waters is probably maximal between 520 and 570 mµ. It is suggested that the fishes have become adapted to these conditions by small but significant shifts in spectral absorption of their retinal pigments. These pigments are decidedly more effective than rhodopsin in absorption of wavelengths above 500 mµ. This offers a possible interpretation of the confusing array of retinal pigments described from marine and euryhaline fishes.
EARLY AND LATE POST-TETANIC POTENTIATION, AND POST-TETANIC BLOCK IN A MONOSYNAPTIC REFLEX PATHWAY
Authors: Lloyd David P. C.
Published: May 2004

Observations have been made upon the nature of early and late post-tetanic potentiation and upon post-tetanic block of presynaptic collaterals with particular reference to behavior in circumstances of varied duration and frequency of conditioning stimulation. Early potentiation is most conspicuous following brief tetani at high frequency, late potentiation following long tetani, much lower frequencies being all that are needed. The two phenomena thus are distinguishable and separate. Dorsal root electrotonus produced by stimulations of varying duration and frequency is described, and the similarity between behavior of the D.R.IV R. electronic potential and early potentiation demonstrated. It is shown how early potentiation and post-tetanic block are due to the same process (hyperpolarization) at different intensities. The view that the agency for potentiation is associated with augmented presynaptic action due to hyperpolarization is confirmed. A diagram is constructed to indicate the probable temporal courses of early and late potentiation.
AN ADENOSINETRIPHOSPHATE-ACTIVATED HEMOLYTIC SYSTEM
Authors: Borek Blanche Ann , Miller Leo A. , Bovarnick Max
Published: May 2004

Failure to demonstrate ATP1 utilization in an ATP-activated hemolytic system had been previously reported. In the present study ATP utilization is shown to be associated with the hemolytic reaction and also with the ATP-dependent inactivation of the hemolytic factor of the system by crude, washed, human red cell stroma. Using crude stroma, relatively large ATP utilization occurs and continues, but at a decreasing rate, after inactivation of the hemolytic factor is complete. With purified stroma there is very slight uptake of ATP by the stroma in the presence of hemolytic factor and Mg++. This uptake can only be demonstrated by radioactive ATP. Both C14- and P32—labelled nucleotide were used for this purpose. In the presence of an excess of stroma the uptake seems to be dependent on the amount of hemolytic factor used. Evidence is given contraindicating the possibility that this uptake is non-specific.
A STUDY OF INOTROPIC MECHANISMS IN THE PAPILLARY MUSCLE PREPARATION
Authors: Abbott B. C. , Mommaerts W. F. H. M.
Published: May 2004

The length-tension diagram, the force-velocity relation, the characteristics of the series elasticity, and the duration of the active state have been studied on the papillary muscle preparation of the cat heart, and on other examples of cardiac muscle.

Positive inotropic changes such as the staircase phenomenon and post-extrasystolic potentiation occur without lengthening, but frequently with shortening, of the duration of the active state. They are accompanied by an increased velocity of contraction, and may be caused either by an intensification of the active state or by an alteration of the force-velocity characteristics of the contractile component.

The changes in the force-velocity relation point to an adaptation of the velocity-efficiency relation in dependence on the frequency of contraction.
ULTRAVIOLET DIFFERENCE SPECTRA OF PEPSIN
Authors: Blumenfeld Olga O. , Perlmann Gertrude E.
Published: May 2004

A shift of pH of pepsin solutions from 4.6 to 1.0 gives rise to spectral displacements in the ultraviolet. If represented as difference spectra three peaks with maxima at 2770, 2850, and 2930 Ångströms are present which can be attributed to the tyrosine and tryptophan residues in the protein. On mild autolysis of pepsin at pH 2.0 the absorbancy in the ultraviolet further decreases. Although some of these effects can be ascribed to the occurrence of hydrogen bonding between the aromatic residues and a carboxylate ion, those observed on autolysis are caused by charge effects of newly formed polar groups in the vicinity of a chromophore. No direct relation between the optical properties described here and enzymic activity of pepsin has been observed.
PROTEIN CONCENTRATION IN NORMAL MOUSE LYMPHOCYTES, THYMOCYTES, AND MOUSE AND HUMAN LEUKEMIC CELLS AS MEASURED BY INTERFERENCE MICROSCOPY
Authors: Ponder Eric , Ponder Ruth V.
Published: May 2004

The apparent protein content of a single spherical lymphocyte or a similar cell, as well as its diameter, can be measured by a modified and stabilized AO-Baker interference microscope which is either fitted with an AO half-shade eyepiece or connected to a photomultiplier.

This paper gives results for the apparent protein content and the diameter of normal mouse lymphocytes and thymocytes; these do not differ significantly from each other. It also gives values for the apparent protein concentration and the diameter of the lymphocytes of mice of the same strain which have developed leukemia or lymphoma; these values are significantly different from those of normal mice. Related data are given for the apparent protein content and for the diameter of normal human lymphocytes and the white cells found in myeloblastic leukemia and in stem cell leukemia in man; here the values differ significantly from those of the normal human lymphocyte. The rule seems to be that the abnormal white cells become more watery and larger as the disease advances.
IN VITRO STUDIES OF P32 UPTAKE IN MOUSE LIVER MITOCHONDRIA
Authors: Edmunds Arthur B.
Published: May 2004

Isolated mouse liver mitochondria were incubated in two types of P32-labelled sucrose-phosphate buffers. The first contained no added ATP or oxidizable substrate. The second contained added ATP. Samples were taken at specified times, up to 60 minutes, and analyses were made of the mitochondrial TCA-soluble inorganic P32 and the total mitochondrial residue P31 and P32. The results of the analyses showed that when the phosphorus inhibition index (the ratio of the amount of incubation inorganic phosphorus to the square of the amount of tyrosine in the mitochondria) was high, inorganic P32 uptake was low and vice versa. In accordance with established data, increased P32 uptake was obtained when ATP was added. ATP was found to stabilize the turnover of TCA-insoluble residue phosphorus as well as to maintain the TCA-soluble orthophosphate pool. These results support findings regarding the inhibitory and controlling effects of incubation medium phosphate in the regulation of inorganic phosphorus uptake.
EFFECTS OF CALCIUM LACK ON ACTION POTENTIAL OF MOTOR AXONS OF THE LOBSTER LIMB
Authors: Adelman W. J. , Adams J.
Published: May 2004

The effects of external calcium deprivation on certain characteristics of the action potential of the lobster motor axon have been studied. Upon exposure to calcium-free solution the spike amplitude is rapidly decreased within a few minutes and is followed by a slow linear decline. The rates of spike rise and fall are proportionally reduced more than the spike but follow similar time courses during calcium lack. Associated with these phenomena are the loss in the normal slow spike repolarization process, the development of a large and lengthy undershoot, and the appearance of a high degree of refractoriness. The mean increase in the refractory period is 525 per cent upon 10 minutes' exposure to calcium-free solution. These effects are completely reversible upon returning the axons to normal solution. These results are compared to similar effects of calcium deprivation on frog myelinated axons and squid and lobster giant axons recently observed by other workers.
X-RAY EFFECTS ON SINGLE NERVE FIBERS
Authors: Bachofer C. S. , Gautereaux M. E.
Published: May 2004

Electrophysiological responses of median and lateral giant nerve fibers of the earthworm were recorded during exposure, in vitro, to x-rays. In response to external stimulation, during x-irradiation, these nerve fibers showed initially an increase in conduction velocity, a rise in spike amplitude, a decrease in relative refractory period, and an increase in sensitivity. These responses represent an enhancement of activity, attributable to bombardment with x-rays, rarely found in other biological systems. They were followed by deterioration of activity and eventual block, representative of the lethal action of x-rays, commonly observed in other biological systems. Several properties of the enhancement of activity were noted: The time at which maximum activity of one factor occurred did not coincide with the time at which the maxima of other activities occurred; spike amplitude, for example, was observed to increase while conduction velocity had already reached its maximum and was rapidly declining. The energy supplied by bombardment with x-rays did not act synergistically during the time of the enhanced response; that is, concomitant irradiation was not necessary in order to produce the enhanced response, once the nerve had been altered by x-irradiation. Once the nerve was responding in an enhanced manner, cessation of irradiation for short periods of time had no effect on the response. The phenomenon was therefore due to an irreversible alteration of the nerve fiber itself.
ELECTROKINETIC MEMBRANE PROCESSES IN RELATION TO PROPERTIES OF EXCITABLE TISSUES
Authors: Teorell Torsten
Published: May 2004

An artificial system is studied consisting of salt solutions of different concentrations separated by a porous, "charged" membrane, through which a constant electric current is passed. Experiments on such systems demonstrate rhythmic variations of the transmembrane potential and the membrane resistance, which are concomitant with an oscillatory streaming of water solution across the membrane. The repetitive oscillations can be of a damped or undamped type dependent on the "stimulating" current density.

A qualitative discussion of the mechanism of the oscillations is given. It centers around the periodic resistance changes in the membrane, which result from a complicated interplay between the driving forces present. The importance of electro-osmotic effects is emphasized.

A few comparisons relating to possible electrophysiological implications are presented. In the metastable state of this membrane oscillator, "make" and "break" responses can be triggered by electric as well as by mechanical (pressure) "stimuli."
INTRACELLULAR POTASSIUM COMPARTMENTS IN NITELLA AXILLARIS
Authors: Diamond Jared M. , Solomon A. K.
Published: May 2004

Three intracellular compartments for potassium exchange have been observed in intact cells of the giant-celled alga, Nitella axillaris. These compartments have been compared with the exchange properties of isolated subcellular structures. The smallest and fastest compartment (apparent half-time, 23 seconds) appears to involve passive absorption on the cell wall. The next largest (apparent half-time, 5 hours) may represent exchange with the cytoplasmic layer through the plasma membrane, the chloroplasts being in rapid equilibrium with the surrounding cytoplasm. The largest and slowest compartment (apparent half-time, 40 days) has been identified with the central vacuole. The vacuolar membrane and the plasma membrane have similar properties with respect to K permeability. Thus, the experimental data from the whole cell can be accounted for by a structural model of the compartments. Cyanide in concentrations up to 10-3 M causes no net loss of K. The fastest compartment in Nitella and in higher plants is compared, and the ecological significance of the slow rate of potassium transport in Nitella is discussed.
SEMIPERMEABILITY OF THE NUCLEAR MEMBRANE IN THE INTACT CELL
Authors: Harding Clifford V. , Feldherr Carl
Published: May 2004

The osmotic properties of nuclei in intact cells were studied by injecting solutions into the cytoplasm of amphibian oocytes. Subsequent changes in nuclear volume were recorded photographically. The injection of solutions containing polyvinylpyrrolidone or bovine serum albumin caused changes in nuclear volume which were related to the colloid osmotic pressure of the solution injected. The concentration in which no significant nuclear volume change occurred (the isotonic range) was 1.0 to 1.5 per cent polyvinylpyrrolidone (2.0 to 3.75 x 10-4 M). 2 per cent bovine serum albumin had no significant effect on nuclear volume, whereas 4 per cent caused a significant decrease. The significance of these findings is discussed in terms of the permeability characteristics of the nuclear membrane.
PATHWAYS OF TERMINAL RESPIRATION IN MARINE INVERTEBRATES
Authors: Ghiretti F. , Ghiretti-Magaldi Anna , Tosi Luisa
Published: May 2004

The classic spectrophotometric method for identification and characterization of respiratory enzymes has been used for the study of the cytochrome system of Aplysia. Particles have been prepared from the buccal mass and the gizzard muscles. Difference spectra taken on isolated particle suspensions show the presence of a complete cytochrome system composed of five components: cytochrome a, b, c, c1, and a3. As indicated by the peaks of the sharp absorption bands of their reduced forms, they are very similar to the cytochromes of mammals and yeast. Cytochrome a3 has been identified as the terminal oxidase of Aplysia muscle by means of the spectrophotometric study of its carbon monoxide compound. Further evidence for the presence of a cytochrome system in Aplysia was obtained by assays of the catalytic activities of the isolated particles: succinic dehydrogenase, cytochrome oxidase, DPNH cytochrome c reductase. The cytochrome oxidase activity was strongly inhibited by carbon monoxide in the dark; the inhibition was totally relieved by light.

Cytochrome c has been extracted and purified from muscle tissue. Its spectrum is almost identical with that of the mammalian pigment both in the oxidized and reduced forms. From the hepatopancreas a new respiratory enzyme has been extracted which has many physical and chemical properties in common with cytochrome h from terrestrial snails.
THE ELECTROPHYSIOLOGY AND PHARMACOLOGY OF LOBSTER NEUROMUSCULAR SYNAPSES
Authors: Grundfest H. , Reuben J. P. , Rickles W. H.
Published: May 2004

Effects of drugs on resting potential, membrane resistance, and excitatory and inhibitory postsynaptic potentials (e.p.s.p.'s and i.p.s.p.'s) of lobster muscle fibers were studied using intracellular microelectrodes Acetylcholine, d-tubocurarine, strychnine, and other drugs of respectively related actions on vertebrate synapses were without effects even in 1 per cent solutions (10- w/v). Gamma-aminobutyric acid (GABA) acted powerfully and nearly maximally at 10-7 to 10-6 w/v. Membrane resistance fell two- to tenfold, the resting potential usually increasing slightly. This combination of effects, which indicates activation of inhibitory synaptic membrane, was also produced by other short chain ω-amino acids and related compounds that inactivate depolarizing axodendritic synapses of cat. The conductance change, involving increased permeability to Cl-, by its clamping action on membrane potential shortened as well as decreased individual e.p.s.p.'s.

Picrotoxin in low concentration (ca. 10-7 w/v) and guanidine in higher (ca. 10-3 w/v) specifically inactivate inhibitory synapses. GABA and picrotoxin are competitive antagonists. The longer chain ω-amino acids which inactivate hyperpolarizing axodendritic synapses of cat are without effect on lobster neuromuscular synapse. However, one member of this group, carnitine (ß-OH-GABA betaine), activated the excitatory synapses, a decreased membrane resistance being associated with depolarzation. The pharmacological properties of lobster neuromuscular synapses and probably also of other crustacean inhibitory synapses appear to stand in a doubly inverted relation to axodendritic synapses of cat.
Interaction of Fibrinogen with Dextran Sulfate
Authors: Sasaki Susumu , Noguchi Hajime
Published: May 2004

Interactions of fibrinogen with dextran sulfate, dextran, and carboxymethyl cellulose were investigated by turbidity measurement, chemical analysis, and electrophoresis. Dextran sulfate and fibrinogen combined even in the physiological pH region where both of them have negative net charges, and formed a precipitate and soluble complex. Since no complex formation was observed in the case of dextran, it seems that the electrostatic force plays a part in complex formation. However, sodium carboxymethyl cellulose which carries -COO- groups did not combine with fibrinogen. Therefore, it is considered that there is a specificity for the interaction among ionized groups. Further, temperature and molecular size of dextran sulfate influenced the interaction to a large extent. It is concluded from these facts that other intermolecular binding forces should be taken into consideration in addition to the electrostatic force.
The Additivity of Contrast in the Human Eye
Authors: Alpern Mathew , David Herbert
Published: May 2004

Using the method of binocular brightness matching, simultaneous brightness contrast effects were measured on two observers. The effects of a given pattern were invariably smaller than the summation of the effects of the pattern's components. This failure of additivity was valid both for patterns with isolated components as well as for those with components exactly contiguous with one another. This failure was more pronounced the farther the inducing patterns were from the test patch. These findings are interpreted as indicating that in the human (just as in the Limulus) eye, the amount of inhibition exerted by a given region on its neighbors depends upon the inhibition exerted against it as well as its excitation state.
Muscle: A Three Phase System
Authors: Simon Shirley E. , Johnstone B. M. , Shankly K. H. , Shaw F. H.
Published: May 2004

The partition of Li+, Br-, and I- across the membrane of the sartorius muscle of the toad Bufo marinus has been investigated both at the steady state and with kinetic methods. Li+ was found to have access to an amount of muscle water similar to that of Na+. Br- and I- could be regarded as being interchangeable with cellular Cl-. None of the foreign ions caused significant losses of cellular K+.

Li+ efflux from the cell was slower in muscles which were equilibrated for long periods in Li+ than in short equilibrated muscles. Na+ efflux from Li+-treated muscles was similar in rate to normal controls, but the amount of Na+ in the slow fraction was increased by Li+.

I- efflux was extremely rapid, and it was not possible to differentiate kinetically between intra- and extracellular material.

These results have been found to be consistent with the hypothesis of a three phase system for muscle.
The Mechanical Properties of Rat Tail Tendon
Authors: Rigby Bernard J. , Hirai Nishio , Spikes John D. , Eyring Henry
Published: May 2004

The load-strain and stress-relaxation behavior of wet rat tail tendon has been examined with respect to the parameters strain, rate of straining, and temperature. It is found that this mechanical behavior is reproducible after resting the tendon for a few minutes after each extension so long as the strain does not exceed about 4 per cent. If this strain is exceeded, the tendon becomes progressively easier to extend but its length still returns to the original value after each extension. Extensions of over 35 per cent can be reached in this way. Temperature has no effect upon the mechanical behavior over the range 0–37°C. Just above this temperature, important changes take place in the mechanical properties of the tendon which may have biological significance. The application of the techniques used here to studies of connective tissue disorders is suggested. Some of the mechanical properties of tendon have been interpreted with a simple model.
Action Spectra for Two Effects of Light on Luminescence in Gonyaulax polyedra
Authors: Sweeney B. M. , Haxo F. T. , Hastings J. W.
Published: May 2004

The luminescence of the marine dinoflagellate Gonyaulax polyedra shows an endogenous diurnal rhythm. The effect of light during the phase of low luminescence capacity may be observed as an enhancement of luminescence during the subsequent bright phase. During the bright phase, however, illumination diminishes the capacity for luminescence. The action spectra for these two effects of light have been determined, and the major pigments of Gonyaulax have been examined. A consideration of the action spectrum and the pigment complement of Gonyaulax suggests that photosynthesis during the day is responsible, directly or indirectly, for the enhancement of luminescence during the following night. Photoinhibition of luminescence is in part attributable to light absorbed by the photosynthetic pigments. However, activity observed in the far red region of the spectrum beyond the absorption maximum of chlorophyll a suggests that an additional pigment, present in small amounts, may also act as sensitizer for photoinhibition.
Potassium Ions and the Inhibitory Process in the Crayfish Stretch Receptor
Authors: Edwards C. , Hagiwara S.
Published: May 2004

The effect of the absence of potassium in the bathing solution on the synaptic inhibitory potentials of the crayfish stretch receptor has been studied.

The inhibitory potentials were increased in size, i.e. became more hyperpolarizing, in the absence of potassium. Since the resting potential of the cell is increased in the absence of potassium, the alteration of the inhibitory potentials implies that the potassium conductance of the membrane is increased. While other ions, e.g. Cl-, may also be involved, it seems that the membrane potential during inhibition is mainly dominated by K+.
Studies on the Role of N-Acetylaspartic Acid in Mammalian Brain
Authors: Jacobson K. Bruce
Published: May 2004

N-Acetylaspartic acid (NAA) occurs at relatively high concentrations exclusively in the mammalian and avian brain and undergoes rapid rise in level soon after birth (Tallan, 1957).

The amount of NAA in brains of mentally abnormal human beings and of young human beings was measured. The route by which NAA is synthesized was shown to involve a direct acetylation of aspartic acid. The degradative activity of the brain toward NAA is slight. Some experiments indicate that NAA in the brain is a physiologically and metabolically active compound.
The Nature and Rates of Excretion of Radioactive Breakdown Products of I131-Albumin in the Rabbit
Authors: Zizza F. , Campbell T. J. , Reeve E. B.
Published: May 2004

When I131-albumin is given intravenously to rabbits, the radioactive breakdown products that are released into the plasma and urine can be extracted into acetone. Paper chromatography and paper electrophoresis show that about 80 per cent of these are I131-iodide and the remainder are organic I131-iodine compounds. When I131-iodide is given to rabbits taking iodide in their drinking water, the radioactivity is quantitatively excreted, without being accumulated in the tissues and without becoming attached to the plasma proteins. The rate of excretion can be defined by a first order rate process with a rate constant, a, ranging between 1 and 3day-1. The organic I131-iodine compounds liberated during the metabolism of I131-albumin can be closely matched by a mixture of the organic I131-iodine compounds liberated during the metabolism of I131-monoiodotyrosine, I131-diiodotyrosine, and the amino acids released by digestion from I131-albumin. These organic I131-iodine compounds are not accumulated in the body and their radioactivity does not become attached to the plasma proteins. Their radioactivity is excreted as fast or faster than that of I131-iodide, and, to a satisfactory approximation, the same equations describing the excretion of I131-iodide with the same constants may be used for describing the excretion of the organic I131-iodine. These results permit improved estimates of the distribution and catabolism of I131-albumin.
Experimental Study of the Independence of Diffusion and Hydrodynamic Permeability Coefficients in Collodion Membranes
Authors: Robbins Elliott , Mauro Alexander
Published: May 2004

The two parameters usually invoked when discussing transport across membranes are the "diffusion permeability coefficient" and the "hydrodynamic permeability coefficient." In this study the magnitude of these two coefficients is established experimentally for collodion membranes of differing porosities. The hydrodynamic permeability is predominant while convergence of the two permeabilities tends to obtain as the membranes become less coarse. The flux data obtained are used to calculate "average pore diameter" and the meaningfulness of these calculations is interpreted. The relationship between the two coefficients and transport across membranes as treated by the system of irreversible thermodynamics is discussed.
Apparatus for the Maintenance of Bacterial Cultures in the Steady State
Authors: Northrop John H.
Published: May 2004

(1) A more convenient method for maintaining constant turbidity in the culture cell is described. (2) An improved culture cell and cell wipers which do not cause foaming are described.
Na, Cl, and Water Transport by Rat Colon
Authors: Curran Peter F. , Schwartz Gordon F.
Published: May 2004

Segments of the colon of anesthetized rats have been perfused in vivo with isotonic NaCl solutions and isotonic mixtures of NaCl and mannitol. Unidirectional and net fluxes of Na and Cl and the net fluxes of water and mannitol have been measured. Net water transport was found to depend directly on the rate of net Na transport. There was no water absorption from these isotonic solutions in the absence of net solute transport, indicating that water transport in the colon is entirely a passive process. At all NaCl concentrations studied, the lumen was found to be electrically negative to the surface of the colon by 5 to 15 mv. Na fluxes both into and out of the lumen were linear functions of NaCl concentration in the lumen. Net Na absorption from lumen to plasma has been observed to take place against an electrochemical potential gradient indicating that Na is actively transported. This active Na transport has been interpreted in terms of a carrier model system. Cl transport has been found to be due almost entirely to passive diffusion.
Some Relations between Action Potential and Resting Potential of the Lobster Giant Axon
Authors: Dalton J. C. , Adelman W. J.
Published: May 2004

Experiments were performed to determine the quantitative relation existing between action potential and resting potential of the lobster giant axon. Resting potential changes were induced by either increasing the external potassium concentration or by reducing the external calcium concentration. For either treatment the action potential amplitude is proportional to the logarithm of the resting potential minus a constant. This constant is equivalent to the minimum resting potential at which a propagated spike is possible, and is larger for depolarization in low calcium than in high potassium. Thus the change in action potential per unit change in resting potential is greater in low external calcium than in high external potassium. Analog computer solutions to the Hodgkin-Huxley equations for squid axon membrane potentials show that, if the initial conditions are properly specified, the action potential is proportional to the logarithm of the potassium potential minus a constant. The experimental results and the analog computations suggest that reducing external calcium produces changes in the invertebrate axon that cannot be accounted for solely on the basis of alterations in the potassium potential.
The Influence of pH and Ionic Strength on the Electrokinetic Stability of the Human Erythrocyte Membrane
Authors: Heard D. H. , Seaman G. V. F.
Published: May 2004

The electrokinetic stability of washed normal human erythrocytes is discussed from the point of view of pH, ionic strength, and composition of the suspending medium. Many of the electrophoretic characteristics at low ionic strengths (sorbitol to maintain the tonicity), such as the isopotential points, are shown to arise principally from adsorption of hemolysate.

The concept of electrokinetically stable, metastable, and unstable states for the red cell at various ionic strengths is introduced in preference to the general term "cell injury." In the stable state which exists around pH 7.4 for ionic strengths >0.007, no adsorption of hemolysate occurs, in the metastable state reversible adsorption of hemolysate occurs, and in the unstable state, in which ionic strengths and pH ranges are outside the metastable range, the membrane undergoes irreversible hemolysate adsorption or more general hydrolytic degradation.

It is deduced from the equivalent binding of CNS, I, Cl, and F, the pH mobility relationships, and the conformation of the ionic strength data in the stable state to a Langmuir adsorption isotherm, that the membrane of the human erythrocyte behaves as a macropolyanion whose properties are modified by gegen ion association and in some instances by hemolysate adsorption.

The experimental results are insufficient to establish conclusively the nature of the ionogenic groupings present in the membrane interphase.
Activity Patterns of Interneurons in the Caudal Ganglion of the Crayfish
Authors: Kennedy Donald , Preston James B.
Published: May 2004

Responses of ascending interneurons from the caudal ganglion of crayfish have been recorded from single units isolated by dissection from the ventral nerve cord; in addition, post-synaptic activity within the ganglionic neuropile has been studied with intracellular micropipettes. The following classes of interneurons have been found: (1) Large fibers which responded to tactile stimuli with single spikes or phasic bursts. These units usually showed broad receptive fields; and spontaneous activity, when present, showed transitory depressions following responses to natural stimuli. (2) A group of fibers, including many small ones, which responded to proprioceptive stimuli with tonic discharges of varying adaptation rate. (3) Interneurons which showed responses both to tactile stimuli and to activation of the sixth ganglion photoreceptor; and (4) units with constant frequency discharges which were unmodifiable by any of the above afferent inputs.

Intracellular recording of post-synaptic activity has shown (1) that widely graded excitatory post-synaptic potentials occur; (2) that multiple firing from single synaptic potentials is usual; (3) that the post-synaptic responses to phasic natural stimuli and to electrical stimulation of ganglionic roots are similar.

The existence of widely graded post-synaptic potentials and of extensive receptive fields suggests a high degree of convergence from primary afferents to interneurons. The activation of such post-synaptic units involves integrative synaptic transfer, without 1:1 correspondence between pre- and post-fiber activity.
Electrical Impedance Changes of the Cat's Foot Pad in Relation to Sweat Secretion and Reabsorption
Authors: Lloyd David P. C.
Published: May 2004

Impedance across the cat's foot pad, the glands being at rest, has a high quite constant value in a given preparation. Stimulation of the sudomotor nerves causes a decrease to a low constant value. After cessation of stimulation impedance returns slowly over a course that is linear with respect to the logarithm of time. The resistive and capacitative components vary with each other. Sweat reabsorption during recovery progresses linearly with respect to time. Hence impedance varies as the logarithm of reabsorption, and therefore as the mean level of sweat columns in the ducts. This relation can be accommodated by supposing that the sweat duct epithelium resembles a core conductor. An electrical model constructed on this principle is shown to behave as does the foot pad. During stimulation at a fixed frequency impedance change varies as the logarithm of duration showing that the amount of sweat produced per impulse at a given frequency is a constant. With frequency of a fixed number of stimuli varied the impedance change varies with it in a manner consistent with the view that the amount of sweat produced per impulse is a constant regardless of frequency.
Physical-Chemical Studies of Proteins of Squid Nerve Axoplasm, with Special Reference to the Axon Fibrous Protein
Authors: Davison Peter F. , Taylor Edwin W.
Published: May 2004

The proteins in the axoplasm of the squid, Dosidicus gigas, have been resolved electrophoretically into a major fraction including the fibrous protein, and possibly its structural subunits, and a minor fraction including at least two proteins with low sedimentation coefficients. A partially reversible change in the structure of the fibrous protein occurs under the action of 0.4 M salt or high pH. These experiments have been interpreted to indicate that in the intact fiber one, or a few, protofibrils are arranged helically or longitudinally along the fiber axis, and linked by electrostatic bonds. On the dissociation of these bonds the separated protofibrils assume a less extended form and sediment more rapidly than the intact fibers. Some material with a lower sedimentation rate is also released on the dissociation. This fraction may comprise smaller chain fragments. The volume fraction and the approximate refractive index of the fibers have been calculated.
The Use of DFP32 as a Red Cell Tag with and without Simultaneous Tagging with Chromium51 in Certain Animals in the Presence or Absence of Random Destruction
Authors: Eadie G. S. , Smith Wirt W. , Brown Ivan W.
Published: May 2004

DFP32, used to label erythrocytes in vitro, combines with cell constituents in two stages, the first almost immediate and involving tributyrinase inactivation, the second slower (more than 40 minutes) involving cholinesterase inactivation. Raising the DFP concentration increases the amount irreversibly bound, but increases even more the immediate post-transfusion elution, and DFP is unsuited for investigating erythrocyte viability of stored samples. In vivo tagging by intramuscular injection is satisfactory and normal survival curves are linear since the sample tagged has normal age distribution of cells in absence of random destruction. Here DFP32 curves are easier to interpret than Cr51 curves. In sheep, chromium elution occurs at two different rates producing a rapid initial drop followed by a slower one of about 3 per cent daily.

Random destruction alters cell age distribution. New equations are derived for cases in which this is constant both with and without chromium elution; they were applied satisfactorily to dog and sheep blood. Analysis of such curves is difficult; approximate values for random destruction rates can be obtained though not potential life spans. Chromium curves can be analyzed only with the help of DFP32 or similar curves, and yield little additional information. DFP32 and chromium can be used simultaneously to provide controls.