Electrical reactions in the cat brain during differentiation of photic stimuli]

Study of EEG responses to photic conditioned stimuli in cats has shown that the extent of brain activation depends not on the physical strength of the stimulus, but on its biological significance. The longest activation is recorded to a positive signal, even if it is the weakest flash of light. The intensity of EEG responses to negative stimuli is determined by the nearness of their physical parameters to those of the positive signal. Repeated presentation of a non-reinforced flash leads to a gradual extinction of EEG reactions. Brain activation in response to a reinforced positive signal persists unchanged even after a large number of its repetitions. The revealed properties of brain electrical reactions to stimuli of different significance accord with those previously recorded in response to acoustic stimuli. In both cases the data are in agreement with hypothesis of a central system of signal analysis, which performs the estimation of stimuli according to their biological quality.     

Effect of stimulus strength and adaptation on the thermotactic response of Dictyostelium discoideum pseudoplasmodia

The thermotactic responses of Dictyostelium discoideum strain HL50 and mutants derived from this strain have been characterized by curves of stimulus-strength vs response. With gradient midpoint temperatures of 16 and 24 °C, these curves are typical of those of a single response, i.e., the strength of the response increases with increasing stimulus strength until at some strength the response saturates. However, with a gradient midpoint temperature close to the transition from negative to positive thermotaxis, the sign of the thermotactic response depends on gradient strength. These observations support the hypothesis that the transduction pathways for positive and negative thermotaxis act concurrently and contain separable elements. An investigation of the adaptation of thermotaxis indicated that the stimulus-strength-dependence and midpoint-temperature-dependence of both thermosensory responses was altered by shifting the growth and development temperature.     

NOTE ON THE NATURE OF THE CURRENT OF INJURY IN TISSUES

Leading off from two places on the same cell (of Nitella) with 0.001 M KCl we observe that a cut produces only a temporary negative current of injury. If we lead off with 0.001 M KCl from any cell to a neighboring cell we find that when sap comes out from the cut cell and reaches the neighboring intact cell a lasting negative "current of injury" is produced. This depends on the fact that the intact cell is in contact with sap at one point and with 0.001 M KCl at the other (this applies also to tissues composed of small cells). If we employ 0.1 M KCl in place of 0.001 M the current of injury with a single cell is positive (and is more lasting when a neighboring cell is present). Divergent results obtained with tissues and single cells may be due in part to these factors.     

ON STEREOTROPISM IN TENEBRIO LARV?

Larvæ of Tenebrio while creeping show homostrophic responses, and stereotropic orientation to lateral contacts. Homostrophic orientation is inhibited by stereotropism. Both depend upon the anterior portion of the central nervous system. Stereotropic orientation due to unilateral contact, particularly at the anterior end, persists briefly after the cessation of the contact. Equal posterior bilateral contact of the body obliterates stereotropic bending. Unequal posterior bilateral contacts lead to orientation through an angle roughly proportional to the differences in contact areas. Functional symmetry in such responses is not disturbed by asymmetrical distribution of the body "hairs." The stereotropic orientation undergoes reversal of direction, central in origin, when the stimulation is sufficiently intense. Stereotropic response, leading to maintained lateral contact with a surface or to bending when the end of such a surface has been passed, is inhibited by a definite intensity of light. These findings (1) round out the demonstration that stereotropism is truly of a tropistic character, and (2) make possible the understanding of conduct in a case involving the participation of contact stimulation, phototropism, temperature, and homostrophy.     

The reflex character of stereotropism and galvanotropism in the salamander,Triturus torosus

Summary The common salamander of the Pacific coast, Triturus torosus, responds stereotropically to excitation of the dorsal and lateral surfaces of the body, head and tail. Contact stimulation of the ventral surface is without effect except when applied between the pairs of legs. It is here only that negative as well as positive stereotropic reactions are displayed, positive with weak, negative with strong stimulation. The amputated tail constitutes a preparation which reacts to contact, bending actively toward the point touched. If the skin is removed the reaction fails, or if the nerve cord of the tail be destroyed with a bristle the reaction likewise is destroyed. This proves that stereotropism in the preparation is the result of typical spinal reflexes.The constant electric current when applied to the dorsal part of the body causes characteristic muscle tension effects shown in opisthotonus and constant movement of the tail with ascending current; opisthotonus of the head with descending current. The amputated tail preparation shows undulatory movement with the ascending, quiescence with the descending current. These effects persist even after the skin has been removed, but fail when the nerve cord of the tail is destroyed. This proves that the locus of the action of the current in galvanotropism is on the cells of the nerve cord. The minimal current necessary to produce the galvanotropic reaction is 0.1 Ma. If we assume that the current is conducted equally through the tissue this means that each motor nerve cell stimulated, assuming the diameter of such a cell to be 25 , will be subject to an ionic movement to the extent of 3×10⁹ ions per second.     

QUANTITATIVE GENETICS OF SEXUAL SELECTION IN THE FIELD CRICKET,GRYLLUS INTEGER

Major theories of sexual selection predict heritable variation in female preferences and male traits and a positive genetic correlation between preference and trait. Here we show that female Texas field crickets, Gryllus integer, have heritable genetic variation for the male calling song stimulus level that produces the greatest phonotactic response. Approximately 34% of the variation in female preferences was due to additive genetic effects. Female choosiness, that is, the strength of the female response to her most preferred stimulus relative to her average response to all stimuli, did not show significant genetic effects. The male calling song character was not related to male size or age but did show significant genetic effects. Approximately 39% of the variation in the number of pulses per trill was due to additive genetic variation. The genetic correlation estimated for the field population was 0.51 ± 0.17. The number of pulses per trill produced by males is under stabilizing sexual selection.     

Dynamics of heart rhythm in chimpanzees during the perception of the emotionally colored human voice

The performed study allowed to observe in two chimpanzees both common and individual changes of the heart rate under the action of human voice with emotionally positive or negative intonation, as well as under the action of preferred (sweet) or rejected (quinine solution) natural stimulus. The common property consists in a significant slowing down of the heart rate in response to negative vocal signal and rejected natural stimulus and in only slight change of the heart rate in response to positive signals. Individual properties comprise differences in reactions of the cardiovascular system of both animals to negative action: a greater efficiency of the vocal signal for one chimpanzee and of the direct (natural) stimulus for the second one.     

THE USE OF GLUCOSE INORGANIC SALTS MEDIA IN THE CLASSIFICATION OF THE COLI-AEROGENES BACTERIA. I. THE METHYL RED AND VOGES-PROSKAUER REACTIONS

SUMMARY: A chemically defined glucose ammonium phosphate medium gave methy red and Voges-Proskauer reactions which were superior to those in glucose peptone phosphate. Optimum condition for both tests require a starting pH of 6·8 and incubation for 3 days at 30°. The medium gave a negative correlation between the two reactions with 34 out of 35 strains that were positive to both tests in the peptone medium. The addition of glutamic acid helped to eliminate doubtful positive M. R. reactions but seemed to suppress acetylmethylcarbinol production by weakly V.-P. positive strains.     

STEREOTROPISM IN RATS AND MICE

Typical stereotropic orientation toward a lateral surface of contact is obtained in young rats and mice, and with adult mice congenitally blind. Removal of vibrissæ or tail or both does not essentially affect this response. Equal contact on both sides of the body prevents orientation toward either source of contact. Unequal contact areas on the two sides leads to orientation toward the more extensive contact. This behavior very exactly parallels the stereotropic conduct of arthropods, and thus provides a fairly complete instance of a tropism in mammals.     

THE INFLUENCE OF THE CHEMICAL NATURE OF SOLID PARTICLES ON THEIR CATAPHORETIC P.D. IN AQUEOUS SOLUTIONS

1. The effect of eight salts, NaCl, Na₂SO₄, Na₄Fe(CN)₆, CaCl₂, LaCl₃, ThCl₄, and basic and acid fuchsin on the cataphoretic P.D. between solid particles and aqueous solutions was measured near the point of neutrality of water (pH 5.8). It was found that without the addition of electrolyte the cataphoretic P.D. between particles and water is very minute near the point of neutrality (pH 5.8), often less than 10 millivolts, if care is taken that the solutions are free from impurities. Particles which in the absence of salts have a positive charge in water near the point of neutrality (pH 5.8) are termed positive colloids and particles which have a negative charge under these conditions are termed negative colloids. 2. If care is taken that the addition of the salt does not change the hydrogen ion concentration of the solution (which in these experiments was generally pH 5.8) it can be said in general, that as long as the concentration of salts is not too high, the anions of the salt have the tendency to make the particles more negative (or less positive) and that cations have the opposite effect; and that both effects increase with the increasing valency of the ions. As soon as a maximal P.D. is reached, which varies for each salt and for each type of particles, a further addition of salt depresses the P.D. again. Aside from this general tendency the effects of salts on the P.D. are typically different for positive and negative colloids. 3. Negative colloids (collodion, mastic, Acheson''s graphite, gold, and metal proteinates) are rendered more negative by low concentrations of salts with monovalent cation (e.g. Na) the higher the valency of the anion, though the difference in the maximal P.D. is slight for the monovalent Cl and the tetravalent Fe(CN)₆ ions. Low concentrations of CaCl₂ also make negative colloids more negative but the maximal P.D. is less than for NaCl; even LaCl₃ increases the P.D. of negative particles slightly in low concentrations. ThCl₄ and basic fuchsin, however, seem to make the negative particles positive even in very low concentrations. 4. Positive colloids (ferric hydroxide, calcium oxalate, casein chloride—the latter at pH 4.0) are practically not affected by NaCl, are rendered slightly negative by high concentrations of Na₂SO₄, and are rendered more negative by Na₄Fe(CN)₆ and acid dyes. Low concentrations of CaCl₂ and LaCl₃ increase the positive charge of the particles until a maximum is reached after which the addition of more salt depresses the P.D. again. 5. It is shown that alkalies (NaOH) act on the cataphoretic P.D. of both negative and positive particles as Na₄Fe(CN)₆ does at the point of neutrality. 6. Low concentrations of HCl raise the cataphoretic P.D. of particles of collodion, mastic, graphite, and gold until a maximum is reached, after which the P.D. is depressed by a further increase in the concentration of the acid. No reversal in the sign of charge of the particle occurs in the case of collodion, while if a reversal occurs in the case of mastic, gold, and graphite, the P.D. is never more than a few millivolts. When HCl changes the chemical nature of the colloid, e.g. when HCl is added to particles of amphoteric electrolytes like sodium gelatinate, a marked reversal will occur, on account of the transformation of the metal proteinate into a protein-acid salt. 7. A real reversal in the sign of charge of positive particles occurs, however, at neutrality if Na₄Fe(CN)₆ or an acid dye is added; and in the case of negative colloids when low concentrations of basic dyes or minute traces of ThCl₄ are added. 8. Flocculation of the suspensions by salts occurs when the cataphoretic P.D. reaches a critical value which is about 14 millivolts for particles of graphite, gold, or mastic or denatured egg albumin; while for collodion particles it was about 16 millivolts. A critical P.D. of about 15 millivolts was also observed by Northrop and De Kruif for the flocculation of certain bacteria.     

The effect of different activating influences on the self stimulation reaction]

A study was made of the influence on self-stimulation of non-painful sensory stimuli of different modalities, and of intra-brain stimulations of emotionally positive and neutral points with the wiew to elucidate the specificity of certain functional relations appearing during interaction between emotionally negative and positive conditions. The data obtained attest that the influence of various excitation sites on self-stimulation reactions depends not so much on the strength of the stimuli, as on the specific neurophysiological organization of emotionally negative zones in the brain. A reciprocal enhancement of excitation of self-stimulation zones points to a certain non-specificity of positively reinforced structures.     

The Relationship between Stimulus Intensity and Oriented Phototactic Response (Topotaxis) in Chlamydomonas

Two techniques have been used to study the quantitative relationship between stimulus intensity and oriented phototactic response (topotaxis) in Chlamydomonas. The net response of a cell population was monitored photometrically and was recorded continuously against time. The responses of individual cells were observed through a microscope and their swimming tracks were recorded on film. The net response of the population is positive at low stimulus intensity and negative at high intensity. The direction of response can be reversed within two seconds by raising or lowering the intensity. The intensity-response curve for phototaxis is similar to the dose-response curve for phototropism. The net response has no distinct threshold; it increases linearly with log intensity; then it decreases and finally becomes negative. The individual-cell studies reveal that the intensity-dependent increase in net topotactic response is due primarily to an increase in the number of cells responding and in the directness of their swimming path. As stimulus intensity is raised, the swimming path becomes increasingly well-aligned with the stimulus beam, whether net response is positive throughout the intensity range tested, negative throughout that range, or changing from positive to negative. Changes in swimming rate do not contribute significantly to the intensity-dependent changes in net response. Swimming rate shows virtually no change throughout the intensity range of positive topotaxis and shows only a small increase in the negative range. However, a transient decrease in swimming rate (stop response) is often observed at the onset of stimulation. The implications of these results for the orientation mechanism are discussed.     

THE ORIGIN OF THE ELECTRICAL CHARGES OF COLLOIDAL PARTICLES AND OF LIVING TISSUES

1. When a solution of a salt of gelatin or crystalline egg albumin is separated by a collodion membrane from a watery solution (free from protein) a potential difference is set up across the membrane in which the protein is positively charged in the case of protein-acid salts and in which the protein is negatively charged in the case of metal proteinates. The turning point is the isoelectric point of the protein. 2. Measurements of the pH of the (inside) protein solution and of the outside watery solution show that when equilibrium is established the value pH inside minus pH outside is positive in the case of protein-acid salts and negative in the case of metal proteinates. This is to be expected when the P.D. is caused by the establishment of a Donnan equilibrium, since in that case the pH should be lower outside than inside in the case of a protein-acid salt and should be higher outside than inside in the case of a metal proteinate. 3. At the isoelectric point where the electrical charge is zero the value of pH inside minus pH outside becomes also zero. 4. It is shown that a P.D. is established between suspended particles of powdered gelatin and the surrounding watery solution and that the sign of charge of the particles is positive when they contain gelatin-acid salts, while it is negative when the powdered particles contain metal gelatinate. At the isoelectric point the charge is zero. 5. Measurements of the pH inside the powdered particles and of the pH in the outside watery solution show that when equilibrium is established the value pH inside minus pH outside is positive when the powdered particles contain a gelatin-acid salt, while the value pH inside minus pH outside is negative when the powdered particles contain Na gelatinate. At the isoelectric point the value pH inside minus pH outside is zero. 6. The addition of neutral salts depresses the electrical charge of the powdered particles of protein-acid salts. It is shown that the addition of salts to a suspension of powdered particles of gelatin chloride also diminishes the value of pH inside minus pH outside. 7. The agreement between the values 58 (pH inside minus pH outside) and the P. D. observed by the Compton electrometer is not only qualitative but quantitative. This proves that the difference in the concentration of acid (or alkali, as the case may be) in the two phases is the only cause for the observed P.D. 8. The Donnan theory demands that the P.D. of a gelatin chloride solution should be 1½ times as great as the P.D. of a gelatin sulfate solution of the same pH and the same concentration (1 per cent) of originally isoelectric gelatin. This is found to be correct and it is also shown that the values of pH inside minus pH outside for the two solutions possess the ratio of 3:2. 9. All these measurements prove that the electrical charges of suspended particles of protein are determined exclusively by the Donnan equilibrium.     

ELECTRICAL VARIATIONS DUE TO MECHANICAL TRANSMISSION OF STIMULI

Mechanical stimulation of Nitella often produces responses resembling propagated negative variations but traveling faster and going past a killed spot. They appear to result from a mechanical disturbance traveling along the cell and stimulating each spot it touches (i.e. the stimulus itself travels). They are called mechanical variations to distinguish them from propagated negative variations. A mechanical disturbance may cause an irreversible change (death wave), but in traveling along the cell it may lose intensity and then produce only a reversible response (mechanical variation) which may eventually change to a propagated negative variation. The all or none law does not apply to incomplete mechanical variations, for the response varies with the strength of the stimulus.     

THE EVOLUTION OF MATERNAL CHARACTERS

We develop quantitative-genetic models for the evolution of multiple traits under maternal inheritance, in which traits are transmitted through non-Mendelian as well as Mendelian mechanisms, and maternal selection, in which the fitness of offspring depends on their mother's phenotype as well as their own. Maternal inheritance results in time lags in the evolutionary response to selection. These cause a population to evolve for an indefinite number of generations after selection ceases and make the rate and direction of evolution change even when the strength of selection and parameters of inheritance remain constant. The rate and direction of evolution depend on the inheritance of traits that are not under selection, unlike under classical Mendelian inheritance. The models confirm earlier findings that the response to selection can be larger or smaller than what is possible with simple Mendelian inheritance, and even in a direction opposite to what selection favors. Maternal selection, in which a mother's phenotype influences her offspring's fitness, is frequency-dependent and can cause a population to evolve maladaptively away from a fitness peak, regardless of whether traits are transmitted by Mendelian or maternal inheritance. Maternal selection differs from other forms of selection in that its force depends not only on the fitness function but also on the phenotypic resemblance of parents and offspring.     

THE USE OF THE MALE CALIFORNIA TOAD IN THE DIAGNOSIS OF PREGNANCY

The California male toad, readily available in most areas of the state, and for many other reasons a better subject for test purposes than the frog, was used in 237 tests to determine the presence or absence of pregnancy in humans. Human urine was injected into the toads, and the cloacal discharge then was examined for the presence of sperm. There were only two false reactions in the series—both false negative. In subsequent tests in both these cases, the result was positive.     

Temperature Effect on the Photo-Accumulation and Phobic Response of Volvox aureus*

SYNOPSIS. The effect of temperature on photoaccumulation and photophobic response of Volvox aureus were studied. The algae exhibited positive photoaccumulation at room temperature and negative at low temperature. When stimulated with light of intermediate intensiy (～ 5 × 10³ lux), the phobic response of the algae consisted of a decrease in the frequency or the cessation of flagellar movement in the anterior cells. At room temperature, an increase in light intensity elicited the phobic response, whereas at low temperature a decrease in light intensity was the effective stimulus. The phobic response lasted only a few seconds. The positive and negative photoaccumulations of the algae could be explained by the brief cessation of flagellar movement in the anterior cells, elicited by an increase of stimulus light at room temperature or a decrease of stimulus at low temperature.     

MEMBRANE EQUILIBRIA AND THE ELECTRIC CHARGE OF RED BLOOD CELLS

It has been shown, within the probable limit of error of the methods of measurement employed, that the Donnan equilibrium determines the distribution of H and Cl ions between the cell and the surrounding fluid. This equilibrium is a consequence of the impermeability of the cell membrane to the inorganic cations of the cell. The mechanism responsible for this equilibrium is suggested as that concerned in the secretion of HCl by the cells of the gastric mucosa. If the salt concentration of the medium is low there may result from the Donnan equilibrium a thermodynamic P.D. of considerable magnitude. In the presence of low concentrations of electrolytes, this P.D. is to be regarded as positive in sign at reactions of the medium at which the cataphoretic charge of the cell is negative in sign. The explanation of this discrepancy in sign of charge may lie in the existence at an outer phase-boundary of a second Donnan equilibrium the nature of which is determined by the ionization of the protein of the cell membrane.     

Peripheral and central nervous responses evoked by small water movements in a cephalopod

Potentials were recorded from the epidermal head lines and from the CNS of young cuttlefish, Sepia officinalis, in response to weak water movements. 1. Within the test range 0.5-400 Hz a sinusoidal water movement elicits up to 4 components of response if the electrode is placed on a headline: (i) a positive phasic ON response; (ii) a tonic frequency-following microphonic response; (iii) a slow negative OFF response; and (iv) compound nerve impulses. 2. The amplitude of both the ON wave and the microphonic potential depends on stimulus frequency, stimulus amplitude and stimulus rise time. Frequencies around 100 Hz and short rise times are most effective in eliciting strong potentials. The minimal threshold was 0.06 microns peak-to-peak water displacement at 100 Hz (18.8 microns/s as velocity). 3. Change of direction of tangential sphere movement (parallel vs. across the head lines) has only a small effect on the microphonic and the summed nerve potentials. 4. Frequency and/or amplitude modulations of a carrier stimulus elicit responses at the onset and offset of the modulation and marked changes in the tonic microphonic response. 5. Evoked potentials can be recorded from the brain while stimulating the epidermal lines with weak water movements. The brain potentials differ in several aspects from the potentials of the head lines and show little or no onset or offset wave at the transitions of a frequency and amplitude modulation.     

Influence of stimulation of the ocular muscles on the formation of visual responses of the lateral geniculate nucleus of the cat

In acute experiments on anesthetized cats it was shown that a single stimulation of the ocular muscles leads to unambiguous changes in the formation of the negative and positive components of the evoked response of the lateral geniculate nucleus to the presentation of a light stimulus. It was established that the nature of the muscular influences on the formation of these components of the evoked response of the lateral geniculate nucleus depends on the interval between conditioning muscular and test light stimuli.A. I. Karaev Institute of Physiology, Academy of Sciences of the Azerbaidzhan Republic, Baku. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 451–455, July–August, 1991.