The escape response of food-deprived cod larvae (Gadus morhua L.)

The escape response of Atlantic cod larvae (Gadus morhua) 25 and 47 days post hatch (dph) - either fed or deprived of food for three days - was studied. Larval escape responses were provoked by water movement from the suction of a fixed-position pipette. Escape latency, distance, speed, burst speed, and vertical and lateral escape angles were quantified using motion tracking software designed for 3-D silhouette video recordings. Escape performance, expressed as escape distance and escape speed, improved with age. The escape angles were normally distributed and highly variable, ranging from − 170° to 170° and − 40° to 105° for lateral and vertical escape angles respectively. No food deprivation-induced effects in any of the behaviours were found, suggesting that there are no condition-related behavioural effects (size-independent effects) in escape response performance after 3 d of food deprivation. This may reflect a negligible difference in the cost/benefit equation for fed vs. food-deprived larvae in performing an escape response when under attack.     

Interaction between two retinula cell types in the anterior eye of the droneflyEristalis

Summary In the anterior region ofEristalis eye there is a type of retinula cell with the following features. The spectral sensitivity is broad and the slope of the V/log₁₀I curve increases with increasing wavelength when the response is measured to the initital peak of the receptor potential. With a change in stimulus wavelength from 452 nm to 594 nm, the optical axis moves about 1° and the plane of maximum sensitivity to polarized light changes by a definite angle. These effects can be attributed to an additional depolarizing effect on this retinula cell from a neighbouring cell of a different kind. The receptor potential waveform of the first cell type is also wavelength dependent. Measurements made to the plateau or notch following the peak reveal the same interaction but now it is an inhibition with latency 75–200 ms. A candidate cell which could cause the lateral interaction has a spectral sensitivity peak near 540 nm. If this is the correct source, the lateral interaction is in one direction because the slope of the V/log₁₀I curve of the cell with 540 nm peak is independent of wavelength and it has negligible sensitivity in the range 350–450 nm.     

Brain function in antarctic fish: frequency response analysis of central vestibular units

Summary Extracellular single-unit recordings were made from central vestibular units responding to horizontal head rotation in antarctic fish (Pagothenia borchgrevinki) at temperatures below 0 °C. The frequency of head rotation was varied between 0.05–16 Hz and the results were analysed in terms of the phase and gain of the response with respect to the stimulus. The model of the peripheral vestibular system derived by Hartmann and Klinke (1980) was fitted to the data from antarctic fish in order to obtain a quantitative comparison of vestibular function at two different temperatures. Despite the 20 °C temperature difference, and the different recording sites (primary afferents in the goldfish, and central vestibular units in the antarctic fish) vestibular function in antarctic fish is comparable to that previously reported in goldfish.     

The seasonal pattern of CO2 exchange of Festuca rubra L. in a montane meadow community in Northern Germany

Summary Completely climatized cuvettes were used to follow the CO₂ gas exchange of red fescue (Festuca rubra L.), growing on a fertilized and an unfertilized plot, during a growing season from May through October. Objective of the study was to determine the effect of environmental factors on the seasonal CO₂ gas exchange.Gas exchange rates were calculated on the basis of leaf dry weight, surface area and chlorophyll content. Photosynthetic rates differed between the fertilized and unfertilized plants when based on leaf dry weight or leaf surface area but were similar when based on chlorophyll.Multiple regression analysis was used to related photosynthetic rates to radiation, temperature, water vapor concentration difference, chlorophyll content and time. A cubic regression equation based on daily radiation alone explained 85% of the variation for the fertilized plants and 87% of the variation for the unfertilized plants.During the growing season the unfertilized plants had a continual decline in their photosynthetic rates. The fertilized plants had high photosynthetic rates in the spring and in the fall.Light response curves indicated greater photosynthetic rates at light saturation as well as in the light limited portion of the light response curve for the fertilized plants. Photosynthetic rates of the fertilized plants were generally depressed during periods of warm temperature and high light intensity in June and July.Photosynthetic rates declined at temperatures above 24°C. The decline was greater for the more mesomorphic fertilized plants. A similar response was noted to increasing water vapor difference, although it was difficult to separate from the temperature effect. Maximum photosynthetic rates were found between 14°C and 22°C, although there was considerable variation in the maximum rates.The effects of cutting (mowing) on the gas exchange were difficult to determine due to the interaction of the environmental factors.Chlorophyll content showed significant correlation with photosynthetic rates.     

Characteristics of inhibition in receptive fields of the cat visual cortex

Unit responses of neurons of zone 17 in the cat striate cortex to stripes of different widths were studied. Changes in the number of spikes during different time intervals (cuts) from the beginning of the response were analyzed in relation to stimulus area. Comparison of the results with those obtained by the study of receptive fields of the lateral geniculate body showed a significant difference in the dynamics of inhibition between cortical and geniculate receptive fields. Similar results were obtained when cortical unit responses to simultaneous and consecutive appearance of two stripes in the receptive field, one in the excitatory zone and the other at the inhibitory periphery, were studied. Evidence of the longer duration of cortical inhibition also was obtained by the same technique. When both stripes were placed in the excitatory center of the field another feature of cortical inhibition was revealed: its dependence on the order of stimulus application. If the order of stimulus application coincided with the optimal direction of movement of the stripe for the given field, the unit response to the next stimulus was strongly facilitated by the action of the stimulus applied previously. Application of stimuli in the opposite order invoked inhibition. The sensitivity of inhibition to the order of stimulus application was observed in the center of the field; it diminished toward the periphery, where application of the stimuli in any order evokes inhibition of the response.Medical Academy, Sofia, Bulgaria, I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 339–346, July–August, 1977.     

Conditionality of phase resetting by inhibitors of 80 S translation inGonyaulax polyedra

Summary Gonyaulax polyedra was subjected to a cold treatment of 18 h at 10 °C leading to arrhythmicity. Subsequently, the circadian rhythm of bioluminescence was investigated at the permissive temperature of 20 °C. 1-h pulses of 10 M cycloheximide or 2 M anisomycin, when given after the temperature step-up, resulted only in a very weak resetting of the circadian oscillator, in marked contrast to the behaviour of cells kept continuously in oscillatory conditions at 20 °C. The extremely reduced sensitivity to 80 S inhibition was characteristic for the first cycle after the temperature step-up, whereas cells treated with cycloheximide in the second cycle after re-initiation of rhythmicity showed a gradual recovery of resettability, though the phase response curve was still atypical; treatment in the 3rd cycle after step-up led to a relatively normal phase response curve. The observed insensitivity in the 1st cycle was neither a consequence of insufficient drug action, nor of a transient non-oscillatory behaviour after temperature step-up. Already in the first hours after transfer to 20 °C, 80 S translation was strongly suppressed by cycloheximide, and the cells were also efficiently reset by changes of the light-dark zeitgeber. Resettability of the circadian oscillator by 80 S inhibitors is, therefore, conditional.Abbreviations Ani anisomycin - Chx cycloheximide - CT circadian time - LD light-dark cycle - LL constant light - TCA trichloroacetic acid This work was supported by the Deutsche Forschungsgemeinschaft     

Response properties of auditory activated cells in the occipital cortex of the blind mole rat: an electrophysiological study

Previous studies have demonstrated that despite its blindness, the subterranean blind mole rat (Spalax ehrenbergi) possesses a noticeable lateral geniculate nucleus and a typical cyto-architectural occipital cortex that are reciprocally connected. These two areas, as revealed by the metabolic tracer 2-deoxyglucose, are activated by auditory stimuli. Using single unit recordings, we show that about 57% of 325 cells located within the occipital cortex of anesthetized mole rats responded to at least one of the following auditory stimuli — white noise, pure tones, clicks, and amplitude modulated tones — with the latter two being the most effective. About 85% of cells driven by either contralateral or ipsilateral stimulation also responded to binaural stimulation; about 13% responded only to binaural stimulation; and 2% were driven exclusively by contralateral stimulation. Comparing responsiveness and response strength to these three modes of stimulation revealed a contralateral predominance. Mean latency (±SD) of ipsilateral and contralateral responses were 48.5±32.6 ms and 33.5±9.4 ms, respectively. Characteristic frequencies could be divided into two distinct subgroups ranging between 80 and 125 Hz and between 2,500 and 4,400 Hz, corresponding to the most intensive spectral components of the vibratory intraspecific communication signals and airborne vocalizations.Abbreviations BMF best modulation frequency - CF characteristic frequency - 2-DG 2-deoxyglucose - dLGN dorsal lateral geniculate nucleus - IC inferior colliculus - LGN lateral geniculate nucleus - OC occipital cortex - MTF modulation transfer function - SAM sinusoidally amplitude modulation - SC superior colliculus     

A radio-telemetric study of the thermoregulation of free living water monitor lizards,Varanus S. salvator

Eight water monitor lizards, Varanus s. salvator, were captured; four individuals from an oil palm estate on the Malayan peninsula, and four from fresh water-deficient Tulai island 65 km off-shore in the South China Sea. They were fitted with a radio transmitter attached to a thermistor which was inserted into the cloaca of the animals and released. The heating rate during basking was measured as 0.117 and 0.118 °C·min^-1 while the daily cloacal temperature fluctuated between 29.5–37.3 °C. Cloacal temperature was measured on other individuals caught at random times during the day, which revealed a considerable daily and individual variation. The average cloacal temperature during activity was 30.4 °C. The peak activity appeared when body temperature was 31 °C. Thermoregulation by behavioural means included cooling in water and reducing heat loss at night by sleeping in burrows. The cooling rate for two individuals when submerged in 29 °C water was 0.308 and 0.340 °C·min^-1. There appeared to be a strong correlation between ambient temperature and cloacal temperature.Abbreviations bw body weight - T _a ambient temperature - T _a body temperature - T _c cloacal temperature - TOP Timor Oil Palm Estate - TUL Tulai Island     

Evoked potentials in the visual and association cortex of alert cats during paired uniform stimulation of the lateral geniculate body and pulvinar

Recovery curves of evoked potentials in the association and visual cortex during paired stimulation of the pulvinar in chronic experiments on alert cats were shown to be similar in character. Depression of the test response was observed only if the interval between stimuli was of the order of 10 msec, but if it was 40 msec considerable (2–4 times) facilitation of the second response was observed, mainly on account of an increase in the negative component N₁. Facilitation was less marked if the intervals were from 60 to 100 msec, and they decreased gradually to an interval of 200 msec. The recovery curve of cortical evoked potentials during paired stimulation of the lateral geniculate body differed considerably from the recovery curve during paired stimulation of the pulvinar and was characterized by a gradual increase in amplitude of the second response — from its almost total suppression with an interval of 10 msec to slight facilitation with an interval of 200 msec. If intervals of 10 to 80 msec were used, the test response was restored more slowly in the association cortex than in the visual cortex. The results are discussed from the standpoint of differences in the character of intracortical spread of excitation as a result of activation of geniculo-cortical and pulvinar-cortical pathways of conduction of information.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 497–505, July–August, 1984.     

Conduction of excitation in the cat visual system

Unit responses in area 17 of the visual cortex to stimulation of the lateral geniculate body and optic tract were studied in experiments on unanesthetized cats immobilized with D-tubocurarine. Of the neurons tested, 53.6% responded to stimulation of the lateral geniculate body. In 92% of these cells the responses were orthodromic with latent periods of between 2 and 12.5 msec. Most cells responded with latent periods of 2.0–2.5, 3.0–3.5, and 4.0–4.5 msec, corresponding to latent periods of the components of the electropositive wave of the primary response. Antidromic responses to stimulation of the lateral geniculate body were given by 8% of neurons. The difference between the latent periods of responses of the same visual cortical neurons to stimulation of the optic tract and lateral geniculate body was 0.1–1.8 msec, but for most neurons (55.8%) it was 0.5–1 msec. The histograms of response latencies of visual cortical neurons to stimulation of the above-mentioned formations were found to be similar. It is concluded that the optic radiation contains three principal groups of fibers with conduction velocities of 28.5–16.6, 11.7–8.9, and 7.4–6.0 m/sec, respectively.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 589–596, November–December, 1975.     

Warm and cold receptors of two sensilla on the foreleg tarsi of the tropical bont tickAmblyomma variegatum

Summary A pair of antagonistic thermal receptors has been identified in each of two long, tapering, poreless setae located distally on the foreleg tarsi of the tropicalbont tick,Amblyomma variegatum (Fig. 1). One, the cold receptor, responds to a rapiddrop in temperature (T) with a sudden rise in impulse frequency (F). The other, a warm receptor, responds to a rapidrise inT with a sudden rise inF (Figs. 2, 4). These two units are unusual for sharing their seta with two other units which are mechanosensitive. The four are distinguishable on the basis of spike amplitude and form (Fig. 3). Hence the thermal sensitivity displayed is hardly attributable to the pair of cells with tubular bodies but rather to the two extending up into the seta (for structure, see Hess and Vlimant 1982, 1983 a).As based on the first 100 ms of the response, differential sensitivity to rapidT change is –16.1± 10.4 (imp/s)/°C for cold units, 17.6 ± 9.5 (imp/s)/°C for warm (Table 1). As progressively larger segments of the spike train are employed to determineF, differential sensitivity of the warm unit drops off much more quickly than that of the cold (Table 2, Figs. 5, 6). In the cold unit resolving power (the difference in rapid temperature change discriminable with 90% probability by a pair of responses of a single unit at average sensitivity) continues to increase as the segment of the spike train determiningF is lengthened (from 0.58 °C for 100 ms segments to 0.41 °C for 1,100 ms segments). Resolving power of the warm unit, on the other hand, tends to decrease as longer segments are employed (from 0.52 °C for the first 100 ms to 0.80 °C for the first 1,100 ms). These relationships provoke the question of whether the spike trains may be evaluated in the CNS in different fashions.Abbreviations b slope of characteristic curve - F impulse frequency in impulses per second (imp/s) - n number of individuals examined - Pw partial pressure of water vapor in Torr - r correlation coefficient - s SD of responses from characteristic curve - SD standard deviation - T temperature in °C - T difference inT Refers to difference between initial and end temperature in abruptT changes     

Effects of temperature on the properties of primary auditory fibres of the spectacled caiman,Caiman crocodilus (L.)

Summary The effect of temperature on the response properties of primary auditory fibres in caiman was studied. The head temperature was varied over the range of 10–35 ° C while the body was kept at a standard temperature of 27 °C (T_s). The temperature effects observed on auditory afferents were fully reversible. Below 11 °C the neural firing ceased.The mean spontaneous firing rate increased nearly linearly with temperature. The slopes in different fibres ranged from 0.2–3.5 imp s^–1 °C^–1. A bimodal distribution of mean spontaneous firing rate was found (<20 imp s^–1 and >20 imp s^–1 at T_s) at all temperatures.The frequency-intensity response area of the primary fibres shifted uniformly with temperature. The characteristic frequency (CF) increased nearly linearly with temperature. The slopes in different fibres ranged from 3–90 Hz °C^–1. Expressed in octaves the CF-change varied in each fibre from about O.14oct °C^–1 at 15 °C to about 0.06 oct °C^–1 at 30 °C, irrespective of the fibre's CF at T_s. Thresholds were lowest near T_s. Below T_s the thresholds decreased on average by 2dB°C^–1, above T_s the thresholds rose rapidly with temperature. The sharpness of tuning (Q_10db) showed no major change in the temperature range tested.Comparison of these findings with those from other lower vertebrates and from mammals shows that only mammalian auditory afferents do not shift their CF with temperature, suggesting that a fundamental difference in mammalian and submammalian tuning mechanisms exists. This does not necessarily imply that there is a single unifying tuning mechanism for all mammals and another one for non-mammals.Abbreviations BF best frequency: frequency of maximal response at an intensity 10 dB above the CF-threshold - CF characteristic frequency - FTC frequency threshold curve, tuning curve - T _s standard temperature of 27 °C     

Characterisation of columnar neurons and visual signal processing in the medulla of the locust optic lobe by system identification techniques

We describe visual responses of seventeen physiological classes of columnar neuron from the retina, lamina and medulla of the locust (Locusta migratoria) optic lobe. Many of these neurons were anatomically identified by neurobiotin injection. Characterisation of neuronal responses was made by moving and flash stimuli, and by two system identification techniques: 1. The first-order spatiotemporal kernel was estimated from response to a spatiotemporal white-noise stimulus; 2. A set of kernels to second order was derived by the maximal-length shift register (M-sequence) technique, describing the system response to a two-channel centre-surround stimulus. Most cells have small receptive fields, usually with a centre diameter of about 1.5°, which is similar to that of a single receptor in the compound eye. Linear response components show varying spatial and temporal tuning, although lateral inhibition is generally fairly weak. Second-order nonlinearities often have a simple form consistent with a static nonlinear transformation of the input from the large monopolar cells of the lamina followed by further linear filtering.Abbreviations LMC large monopolar cell - LVF long visual fibre - RF receptive field - SMC small monopolar cell - SVF short visual fibre     

The use of automated tubidimetric data for the construction of kinetic models

Summary An automated tubidimetric instrument (Bioscreen) was used to observe the growth response ofListeria monocytogenes to combinations of temperature (15–30°C), hydrogen-ion (0.1–21.9 m) (equivalent pH 4.66–7.0) and NaCl concentration (0.5–9.5% w/v). Compared to traditional plate count techniques, the technique allowed many more data points to be captured and replicates to be used, with less expenditure of effort. Optical density curves were filtered (smoothed) to minimize the effect of signal noise and the mean signal from uninoculated wells was subtracted to minimize the effect of signal draft. A novel procedure for fitting growth curves to optical density data has been developed. The procedure involves the use of the logistic function and a calibration equation for fitting, in a single step, in the dimension of optical density. This approach allowed the four parameters of the logistic equation to be derived at each set of experimental conditions. A quadratic response surface was then fitted to the curve parameters using temperature, NaCl and hydrogen-ion concentration as three independent variables. Predicted time to 1000-fold increase in cell numbers compared well to predictions from predictive microbial growth equations generated in other laboratories using traditional plate counting. We propose that this technique should be further evaluated as a method for generating data for modeling the kinetics of microbial growth.Mention of brand or firm names does not constitute an endorsement by the US Department of Agriculture over others of a similar nature not mentioned.     

On-off units in the first optic chiasm of the blowfly II. Spatial properties

We recorded from the spiking on-off unit in the first optic chiasm (between lamina and medulla) in the blowfly Calliphora vicina, and investigated its spatial properties. The receptive field extends over (11.4±0.9)° horizontally and (8.7±0.6)° vertically, i.e. about 7 by 5 interommatidial angles. The line spread function of the on-off unit — calculated from its response to moving sinusoidal gratings — has a half-width of (2.3±0.2)°. This half-width is slightly broader than that of the photoreceptor. Lateral inhibition occurs when two different areas of the receptive field are stimulated simultaneously. Fast temporal adaptation (i.e. adaptation to trains of short light pulses) takes place independently in different areas of the receptive field.     

Temperature effects on energy metabolism in banded and unbanded morphs of the snail Cepaea hortensis Müll

Summary Energy metabolism (oxygen consumption) in acclimated juvenile yellow banded and unbanded Cepaea hortensis Müll. was measured at 5°, 10°, 15°, 20°, and 25°C with Englemann respirometers. Metabolic rates were also measured after abrupt temperature changes from 5° to 20° and from 25° to 10°C.Energy metabolism in the two morphs was significantly different at 5° and 20°C. The metabolism/temperature curve in the banded morph was relatively flat with reduced regulating power at 20°C. The yellow unbanded form had a lower metabolism at 5°C, but between 15° and 25°C the curve was flat and indicated good regulating ability. A sudden decrease in experimental temperature gave significant response in both morphs. The effect of abrupt temperature increase was significant only in unbanded snails. Banded and unbanded snails thus displayed different adaptation strategies.Differential heating because of different pigmentation is discussed. The increase in metabolic rate with increased temperature was highest in the yellow unbanded morph. The effects were small and probably overridden by the influences of acclimation and behavior.The use of energetic parameters in ecological genetics is considered. It is suggested that the cohort producing most progeny with lowest energetic cost per energy unit of offspring is the better adapted to the local environment.     

Thermal Inactivation of Salmonella Serotypes in Red Meat as Affected by Fat Content

Survival curves of a cocktail of eight serotypes of Salmonella in ground beef and pork meat of different levels of fat (4% to 28%), at temperatures that ranged from 58°C to 65°C, were examined. Asymptotic D-values (D-values for large times) and initial D-values (D-values for small times, near zero) were estimated by identifying regions where the survival curves were linear, and performing linear regressions on data within the identified regions. The initial lag D-values increase with increasing fat levels for both beef and pork. The relationship of the asymptotic D-values with fat levels and temperature is complex, and definitive conclusions could not be made. It appears that, for ground beef, asymptotic D-values increase with increasing fat levels, but this was not the case for ground pork. The shapes of the survival curves were concave, convex, and sigmoidal, and depended upon the temperature, where for the lower temperatures studied (58°C and 60°C) the curves exhibited tailing. The Gompertz function was found to provide a good fit to the data over the range of temperatures and fat levels studied. These results, particularly for beef, suggest the importance of determining the shape of the survival curves (concave, convex or sigmoidal) when estimating times needed to obtain an adequate margin of safety for thermal processes of red meat.     

Polarized-light sensitivity in rainbow trout (Oncorhynchus mykiss): characterization from multi-unit responses in the optic nerve

Integrated spike activity of axons from the optic nerve was measured in an investigation of the e-vector sensitive mechanism underlying the ability of rainbow trout (Oncorhynchus mykiss) for orientation in downwelling, linearly-polarized light. In anaesthetized, immobilized fish, one eye was exposed to incremental light flashes which were superimposed over closely controlled background conditions. Under scotopic and various photopic conditions, intensity/response curves were generated from the on-response of the optic nerve. Relative sensitivity curves were then obtained as a function of e-vector direction for the 5 kinds of receptor cells in this trout's retina: rods, ultraviolet cones (UV), short wavelength cones (S), medium wavelength cones (M), and long wavelength cones (L).Under scotopic conditions, no sensitivity to e-vector was apparent: thus, rods do not mediate polarization sensitivity. Under photopic conditions, parr weighing 8–10 g exhibited e-vector sensitivity in two orthogonal channels. A UV stimulus (380 nm) on a white background evoked a three-peaked response (0°, 90°, and 180°) to the e-vector orientations presented in 30° increments between 0° and 180°. In contrast, when the background was illuminated with appropriate short and long wavelength cut-off filters, M-and L-cones showed maximum responses only to the horizontal (90°) plane whether they were stimulated at their -absorption band or their -absorption band in the near UV. Isolated UV-cones gave maximum responses to the vertical (0° and 180°) e-vector, thus corresponding to a second channel. The blue sensitive, S-cones, did not show evidence of polarization sensitivity. As well, no evidence of the polarization sensitivity was observed under UV isolating background conditions in larger individuals, 50–78 g smolts, although the other cone mechanisms responded as in smaller individuals.