Auditory lateralization in bushcrickets: a new dichotic paradigm

Pair formation in the bushcricket Gampsocleis gratiosa is achieved through acoustic signalling by the male and phonotactic approaches of the female towards the calling song. On a walking belt in the free sound field, females tracked the position of the speaker broadcasting the male calling song with a remarkable precision, deviating by no more than 10 cm in either direction from the ideal course. Starting with stimulus angles of 6–10° the females significantly turned to the correct side, and with stimulus angles greater than 25° no incorrect turns were made. Using neurophysiological data on the directionality of the ear we calculated that with such stimulus angles the available binaural intensity difference is in the order of 1–2 dB. We developed a dichotic ear stimulation device for freely moving females with a cross-talk barrier of about 50 dB, which allowed to precisely apply small binaural intensity differences. In such a dichotic stimulation paradigm, females on average turned to the tronger stimulated side starting with a 1 dB difference between both ears. The significance of such a reliable lateralization behaviour with small interaural intensity differences for phonotactic behaviour under natural conditions is discussed.     

A new method to determine some characters of vegetation structure

The ecological importance of both horizontal and vertical denseness of vegetation is discussed. Existing methods to analyse them are reviewed and a new method is proposed. Horizontal and vertical denseness are estimated, both per layer of 10 cm and cumulative. From these data the following parameters are calculated: degree of overlap between layers, plant area index per layer, and average inclination per layer. The values thus obtained are compared with values measured directly or calculated otherwise. Some examples are given to illustrate the method.Abbreviations LAI = Leaf Area Index - GAI = Green Area Index - PAI = Plant Area Index     

Regular measurement: A new method of biophysical experiment

A system of quantized relations between the value of the parameter (quantity) measured and the range of its experimental scattering has been revealed by analyzing the results of experiments on measuring the rates of various processes. Especially long series of stereotyped measurements under stable conditions (called regular measurements) are performed for determining the squared ratio of the standard deviation to the mean value of the quantity measured (D). Regular measurements of biochemical, chemical, and physical parameters show that the D value is related to the universal dimensionless constant D ₀, whose numerical value has been determined with considerable accuracy, and this relation is described by a simple rational equation. The simplicity of the relationship between D and D ₀ may be accounted for by the quantum behavior of the macroinstrument-object system manifested in the course of regular measurement.     

A new method to determine the electrical transfer function of the human thorax

Traditional analyses have assumed that cardiac electrical activity is reflected on the surface ECG without distortion as the signal passes through the body tissues. This study aims to explore the frequency dependence of thoracic attenuation of surface-recorded intracardiac electrical activity. Twenty patients (14 men, 55 +/- 15 yr of age) undergoing electrophysiological study were enrolled. Rectangular unipolar stimuli were applied from a catheter positioned in the right ventricular apical area and another in the posteroseptal area without contact with the myocardium. An orthogonal Frank-lead surface ECG and a unipolar intracardiac electrogram near the pacing site were recorded. Frequency domain characteristics of the signal-averaged pacing impulses were analyzed. Linear regression analysis showed significant frequency-dependent attenuation in the magnitude transfer functions (R(2) = 0.84-0.89, P < 0.0001) and good linear fit for the phase transfer characteristics (R(2) = 0.98-1.0, P < 0.0001). Age, physical dimension, and respiratory characteristics had significant effects on the magnitude and phase characteristics of the transfer functions. Application of models of the low- and high-slope transfer functions to signal-averaged ECGs from 33 subjects showed differences in the attenuation of P and T waves relative to the QRS.     

A new method to determine the oxygen concentration inside the sapwood of trees

Research into the short-term fluctuations of oxygen concentrations in tree stems has been hampered by the difficulty of measuring oxygen inside tissues. A new method, which is based on fluorescence quenching of a ruthenium complex in the presence of oxygen, has been applied to measure changes of oxygen concentration in the sapwood of trees. During a field day-course oxygen increased with the radiation load and fell during the night (in Fagus orientalis from 20.3% in the afternoon to 17.5% in the morning next day). In a greenhouse experiment the sapwood oxygen concentration of Laurus nobilis could be influenced by flooding the root system. The very fast response, high resolution (better than 0.1%), easy calibration, and dependence only on oxygen and temperature make the technique well suited for measurements of oxygen concentrations in the sapwood.     

The role of pressure difference reception in the directional hearing of budgerigars (Melopsittacus undulatus)

In many birds, the middle ears are connected through an air-filled interaural pathway. Sound transmission through this pathway may improve directional hearing. However, attempts to demonstrate such a mechanism have produced conflicting results. One reason is that some species of birds develop a lower static air pressure in the middle ears when anaesthetized, which reduces eardrum vibrations. In anaesthetized budgerigars with vented interaural air spaces and presumed normal eardrum vibrations, we find that sound propagating through the interaural pathway considerably improves cues to the directional hearing. The directional cues in the received sound combined with amplitude gain and time delay of sound propagating through the interaural pathway quantitatively account for the observed dependence of eardrum vibration on direction of sound incidence. Interaural sound propagation is responsible for most of the frontal gradient of eardrum vibration (i.e. when a sound source is moved from a small contralateral angle to the same ipsilateral angle). Our study confirms that at low frequencies the interaural sound propagation may cause vibrations of the eardrum to differ much in time, thus providing a possible cue for directional hearing. The acoustically effective size of the head of our birds (diameter 28 mm) is much larger than expected from the dimensions of the skull, so apparently the feathers on the head have a considerable acoustical effect.Dedicated to Professor Franz Huber on the occasion of his 80th birthday.     

The responses of central acoustic and vibratory interneurones in bushcrickets and locusts to ultrasonic stimulation

ABSTRACT. Analysis of the ultrasonic content of the calling songs of two tettigoniids, Decticus verrucivorus L. and Tettigonia cantans Fuessly, showed that the major secondary energy peaks in the ultrasonic range are only about 15–20 dB below the main audible frequency peaks. The song of the acridid, Locusta migratoria L., contains no appreciable secondary peaks at ultrasonic frequencies, Bifunctional acoustic-vibratory interneurones are present in the ventral nerve cord of all three species. They are divided into three categories, according to their response characteristics: VS (vibration and sound), S (sound) and V (vibration) neurones. All the unit-types capable of coding sound signals in the ventral cord (VS and S neurones) are sensitive to frequencies of up to 100 kHz, with one exception (S3). In tettigoniids, three of these unit-types are more sensitive at ultrasonic frequencies than they are at the audible frequencies of their conspecific songs. Among the vibratory neurones (V), one unit-type receives inhibitory inputs from ultrasonic acoustic primary receptors. The possible importance of ultrasonic perception in the natural environment is briefly discussed.     

Screening methods to determine biophysical properties of proteins in structural genomics

We have developed and tested a simple and efficient protein purification method for biophysical screening of proteins and protein fragments by nuclear magnetic resonance (NMR) and optical methods, such as circular dichroism spectroscopy. The method constitutes an extension of previously described protocols for gene expression and protein solubility screening [M. Hammarstr?m et al., (2002), Protein Science 11, 313]. Using the present purification scheme it is possible to take several target proteins, produced as fusion proteins, from cell pellet to NMR spectrum and obtain a judgment on the suitability for further structural or biophysical studies in less than 1 day. The method is independent of individual protein properties as long as the target protein can be produced in soluble form with a fusion partner. Identical procedures for cell culturing, lysis, affinity chromatography, protease cleavage, and NMR sample preparation then initially require only optimization for different fusion partner and protease combinations. The purification method can be automated, scaled up or down, and extended to a traditional purification scheme. We have tested the method on several small human proteins produced in Escherichia coli and find that the method allows for detection of structured proteins and unfolded or molten globule-like proteins.     

A new method to determine mean adult height from incomplete follow-up data

BACKGROUND/AIM: In long-term growth studies with adult height (AH) as outcome, reporting is often required while data are incomplete because some participants have not yet reached AH whereas others might be lost to follow-up. Current practice is to analyze only participants who did reach AH, which can easily give biased results. We introduce a new method into the area of growth research. METHODS: We used the data of patients from a registration database and a growth study. The new method uses growth data in time intervals. The percentage of children still growing and the mean growth at each interval are used to determine mean AH. RESULTS: With the new method, estimated mean AHs had smaller bias and standard error than with commonly used methods. The method is not hampered by a correlation between AH and age at reaching AH, unlike methods merely using patients who have reached AH. CONCLUSION: In contrast to commonly used methods, the new method provides valid results on mean AH when complete actual measurements of AH are not (yet) available, provided that drop-out, if any, is not related to (disappointing) growth. As it also uses observed data of children with incomplete follow-up, the method employs the data more effectively.     

A new simple method to determine the diffusion coefficient from Active Enzyme Centrifugation experiments

A simple and accurate procedure to determine the diffusion coefficient from Active Enzyme Centrifugation experiments is presented. Using computer-simulated concentration distributions we demonstrate that the procedure, derived by Vinograd for the conventional band sedimentation, is suitable to exploit Active Enzyme Centrifugation experiments when the Cohen's Difference Curves Method is used. This new empirical method avoids all the difficulties of the rigorous method previously proposed by Cohen et al., without any loss of accuracy. Optimal conditions are described which allow the determination of the enzyme diffusion coefficient with a 5% uncertainty. Such an easy determination of the sedimentation and diffusion coefficients by the AEC technique can provide a good and rapid estimation of the active enzyme molecular weight, either with a low amount of material or in very impure preparations.     

A new non-orthogonal decomposition method to determine effective torques for three-dimensional joint rotation

This paper describes a new non-orthogonal decomposition method to determine effective torques for three-dimensional (3D) joint rotation. A rotation about a joint coordinate axis (e.g. shoulder internal/external rotation) cannot be explained only by the torque about the joint coordinate axis because the joint coordinate axes usually deviate from the principal axes of inertia of the entire kinematic chain distal to the joint. Instead of decomposing torques into three orthogonal joint coordinate axes, our new method decomposes torques into three "non-orthogonal effective axes" that are determined in such a way that a torque about each effective axis produces a joint rotation only about one of the joint coordinate axes. To demonstrate the validity of this new method, a simple internal/external rotation of the upper arm with the elbow flexed at 90 degrees was analyzed by both orthogonal and non-orthogonal decomposition methods. The results showed that only the non-orthogonal decomposition method could explain the cause-effect mechanism whereby three angular accelerations at the shoulder joint are produced by the gravity torque, resultant joint torque, and interaction torque. The proposed method would be helpful for biomechanics and motor control researchers to investigate the manner in which the central nervous system coordinates the gravity torque, resultant joint torque, and interaction torque to control 3D joint rotations.     

A new method to determine optimum temperature and activation energies for enzymatic reactions

A new method for determination of the optimum temperature and activation energies based on an idea of the average rate of enzymatic reaction has been developed. A mathematical model describing the effect of temperature on a dimensionless activity for enzyme deactivation following the first-order kinetics has been derived. The necessary condition for existence of the function extreme of the optimal temperature has been applied in the model. The developed method has been verified using the experimental data for inulinase from Kluyveromyces marxianus.     

A new method to determine sex and gonad size in live fishes by using ultrasonography

A method to determine, non-invasively, sex and gonad size employing ultrasonography and using Atlantic salmon, Salmo salar Linnaeus, as an example, is described. Although gonads of immature males may be difficult to discern, gonads of females are always visible and hence sexing is possible by deduction. Gonad diameter can be estimated by ultrasonography; the correlation coefficients between ultrasonographic and ruler-derived measurements were 0.926 for females and 0.754 for males. The appearance of ultrasonographic images of the gonads during sexual maturation are described. The results are discussed and suggestions made to improve the quality of images and reliability of measurements.     

A rapid method to determine the mammalian cell cycle

A method was developed for determining the duration of the mammalian cell cycle and each of its major phases, mitosis, G1, DNA synthetic period, and G2. Mitotic time was determined by assessment of the mitotic index at intervals after cells collected in mitosis and stored at 4 °C were reincubated at 37 °C. The duration of the three remaining phases was derived from a graphic representation of the uptake of ³H-thymidine by a synchronous population of cells grown directly in scintillation vials. The scintillation counting method for determination of these parameters is advantageous over methods using autoradiography in that the investigator's bias in scoring cells is eliminated. Complex mathematical interpretations are unnecessary, and the data obtained from the scintillation counter are readily processed. Results from scintillation counting and autoradiographic methods are shown to be comparable.     

Sensory basis for sound intensity discrimination in the bushcricket Requena verticalis (Tettigoniidae, Orthoptera)

The ability of the female bushcricket, Requena verticalis, to discriminate between two conspecific sound signals that differed in sound pressure level (SPL) was tested in a two-choice paradigm. Significant discrimination was achieved with a 2-dB difference. The property of each pair of receptors to establish binaural discharge differences was investigated in electrophysiological experiments. The threshold to the conspecific signal varies for each fibre from about 40 to 90 dB SPL, allowing for a range fractionation of the hearing organ. Each pair of receptors establishes significant binaural discharge differences only within a restricted intensity range about 10 dB above threshold. Based on a model of the intensity response function of a receptor the total discharge of the 22 receptors in both ears was calculated with monaural and binaural stimulation. The profile of receptors exhibiting significant discharge differences changes with increasing SPL, from the most sensitive fibres with a characteristic frequency between 12 kHz and 35 kHz at low SPLs to the least sensitive fibres at very low and high characteristic frequencies at medium to high SPLs. The discharge difference with an intensity difference of 2 dB is rather small (4% of the total receptor activity) and limited only to a few pairs of receptors. Accepted: 8 November 1997     

A new method to determine the aw range in which immobilized lipases display optimum activity in organic media

Summary We describe a qualitative method to predict the pre-equilibration a_w, system value in which, covalent immobilized lipase B from Candida antarctica to sepharose and silica, displayed best synthetic activity. The methodology is based in the analysis of the water adsorption isotherms of the biocatalyst in air and in the organic solvent. The biocatalyst is active at pre-equilibration a_w values higher than the divergence point between both isotherms. In addition, native and immobilized lipase display highest activity if the biocatalyst is pre-equilibrated at a_w=P point. For preparative purposes, the validity of the method was proved in the esterification of racemic 2-(4-isobutyl phenyl) propionic acid with 1-propanol in isooctane at long reaction time.     

A theoretical experimental method to determine the locus of desensitization

Consider a ligand-gated channel with n agonist binding sites which can undergo desensitization. We present a theoretical experimental procedure for pinpointing the principal receptor state from which there is a transition to the desensitized state. The method is based on the observation that the dependence of the slope of the time constant of desensitization vs agonist concentration, at low concentrations, represents the state from which desensitization occurs. In those receptors where desensitization occurs from the open state (or the one immediately preceding it), the method also enables us to determine the number of binding sites.