Measurement of ultrasound velocity in yolk and blastula of fish embryo in vivo

An acoustic microscopy method for measuring the velocity of ultrasound in the yolk and blastula of bony fish embryos at early stages of development was proposed. The yolk and blastula were approximated as a sphere and a spherical dome, respectively, consisting of a homogeneous liquid. A theoretical model of ultrasonic wave propagation through a spherical liquid drop located on a solid substrate was developed in the ray approximation. The dependence of the wave propagation time on the speed of sound in the drop, its diameter, and the position of the focus of the ultrasonic transducer has been determined. It was shown that the velocity in the drop can be found by solving the inverse problem by minimizing the discrepancy between the experimental and model spatial distributions of the propagation time, assuming that the velocity in the immersion liquid and the radius of the drop are known. The velocities in the yolk and blastula of the loach (Misgurnus fossilis) embryo at the stage of development of the middle blastula were measured in vivo using a pulsed scanning acoustic microscope operating at a central frequency of 50 MHz. The yolk and blastula radii were determined from ultrasound images of the embryo. Acoustic microscopy measurements conducted with four embryos provide velocities of the acoustic longitudinal wave in the yolk and blastula. They were measured to be 1581 ± 5 m/s and 1525 ± 4 m/s when the temperature of the liquid in the water tank was kept at 22 ± 2 °C.

Blood Vessel Imaging at Pre-Larval Stages of Zebrafish Embryonic Development

The zebrafish (Danio rerio) is an increasingly popular animal model biological system. In cardiovascular research, it has been used to model specific cardiac phenomena as well as to identify novel therapies for human cardiovascular disease. While the zebrafish cardiovascular system functioning is well examined at larval stages, the mechanisms by which vessel activity is initiated remain a subject of intense investigation. In this research, we report on an in vivo stain-free blood vessel imaging technique at pre-larval stages of zebrafish embryonic development. We have developed the algorithm for the enhancement, alignment and spatiotemporal analysis of bright-field microscopy images of zebrafish embryos. It enables the detection, mapping and quantitative characterization of cardiac activity across the whole specimen. To validate the proposed approach, we have analyzed multiple data cubes, calculated vessel images and evaluated blood flow velocity and heart rate dynamics in the absence of any anesthesia. This non-invasive technique may shed light on the mechanism of vessel activity initiation and stabilization as well as the cardiovascular system’s susceptibility to environmental stressors at early developmental stages.

Imaging photoplethysmography and videocapillaroscopy enable noninvasive study of zebrafish cardiovascular system functioning

We report on the noninvasive method for in vivo study of fish's cardiovascular system, that is, the heart and the structure of vessels that carry blood throughout the body. The proposed approach is based on combined photoplethysmographic and videocapillaroscopic microscopic imaging and enables noncontact two-dimensional mapping of blood volume changes. We demonstrate that the obtained data allows precise measurements of heartbeat, blood flow velocity and other important parameters (see Videos S1 and S2). To validate the developed image processing technique, we have carried out multiple experiments on zebrafish-a well-proven informative model organism widely used to understand cardiac development. The proposed approach may be effective for the study of cardiovascular system formation and functioning as well as the impact of various influencing factors on them.

[Dynamics of the Incubation Medium Redox Potential during Early Development Stages of Misgurnus fossilis Loach]

The analysis of kinetic curve of redox potential changes (ORP) of aqueous medium in the process of loach embryo population development at 17°C was conducted. The system of critical points defining periodization of the major stages of embryo development was identified on the ORP curve in the time interval up to τ(0) using novel methods for processing of nonlinear signals. It was shown that τ(0) was a natural periodization parameter of main morphological changes in an embryo known in the developmental biology.

[Statistical and frequency-amplitude characteristics of ultra-weak emissions of loach eggs and embryos under normal conditions and on their optic interactions. II. Changes in characteristics of ultra-weak emissions upon optic interaction of groups of embryos of different ages. ]

We compared the characteristics of ultraweak emissions from groups of loach embryos of different ages in the presence or absence of optic interaction. The percentage of zero values of emission gradually increased during the first hour of optic interaction. The number and height of rare big pulses estimated by the value of kurtosis increased in parallel. In addition, the correlation between the Fourier spectra of optically interacting samples decreased at a higher rate than in the absence of optical contact. Just after the 1-hour optic interaction was terminated, the number of high pulses decreased in a younger interacting group and increased in the older one and the farther away the partner groups were in developmental stages, the more pronounced these differences were. Measurements of the Fourier spectra after long-term (12-22-hour) optic interactions have shown that an "exchange" of autocorrelation characteristics of the spectra took place among the samples: the sums of autocorrelation coefficients were inverted in the vast majority of cases, often with an "overshoot" or, at least, were smoothed over with reference to the control samples. We conclude that the previously described effects of optic interactions between groups of loach embryos of different ages could be due to changes in the frequency spectra of their ultraweak emissions.

Biophotonic patterns of optical interactions between fish eggs and embryos

The optical (non-substantial) interactions between various biological samples have been evident in a number of cases mainly by the effects on their functional activity and developmental patterns. However, the mechanisms of these interactions have remained obscure. Effect of optical interaction has been observed on the intensity and Fourier patterns of biophoton emission of fish embryos. We demonstrate that: (1) the short-term optical interactions are accompanied by a gradual decrease of a total emission intensity of the interacting batches; (2) this effect is spread laterally to that part of a batch which does not have any direct optical contacts with its partner; and (3) the long-term optical contacts lead to a mutual exchange of spectral characteristics of interacting batches in which the total spectral density values are reversed (often with an overshoot). The reversal rate depends upon the developmental distance between the optical partners and the initial differences of their spectral characteristics. The results are discussed in terms of a sub-radiance and Le Chatelier principle.

[Statistical and frequency-amplitude characteristics of ultra weak emissions of the loach eggs and embryos under the normal conditions and during their optic interactions. I. Characteristics of ultra weak emission in normal development and the optic role of egg envelope]

Ultraweak emissions of groups comprising several dozens of unfertilized and fertilized loach eggs, embryos, larvae, and their egg envelopes were measured on a photomultiplier tube. The envelopes absorbed the light from external sources but readily gave it back in the absence of embryos. We carried out statistical and frequency-amplitude analyses of ultraweak emissions and studied the autocorrelation structure of their frequency spectra. The frequencies of signals with different intensity underwent regular changes during development. Cascades of short-term (< or = 1 ms) flashes timed (during cleavage) to furrowing were a characteristic element of ultraweak emission. The Fourier spectra of developing embryos had pronounced frequency-amplitude peaks and higher, than in unfertilized eggs and inanimate samples, mutual correlation during successive time intervals. Stage-specific translational symmetry of the frequency spectra of ultraweak emissions was demonstrated, which suggests the presence in groups of embryos of a coordinated system of harmonic oscillators. The latter underwent regular changes during development. The measurement of ultraweak emissions represents a unique non-invasive method of analysis of these oscillators.

[Distant wave interaction in the early embryogenesis of the loach Misgurnus fossilis L]

Groups of loach (Misgurnus fossilis L.) embryos of different ages were kept in different quartz cuvettes for 20-24 h so that only optic contact between the groups was possible. Subsequent observations showed that parameters of their development deviated from those in the control groups. Wave-mediated biocorrection proved to have both positive and negative effects, depending on the developmental stages of the interacting groups. Changes in spectral characteristics and polarization of biological radiation affected the results of the experiments. Various developmental abnormalities caused by distant wave-mediated interactions of embryos and specific to each combination of developmental stages and conditions of optic communication are described.

[Effect of lutropins on oocyte maturation and ovulation in various carp-like fishes in vitro and in vivo]

The study of biological effect of LH and iso-LH isolated from the hypophyses of higher vertebrates on two zoons of carp-like lower vertebrates, has shown that both preparations injected in vivo induce maturation of female loaches, while in the carp, iso-LH stimulates fish maturation and LH single and/or repeated doses (2-3 injections) do not provoke female maturation. Both preparations in vitro stimulate the maturation process and the loach oocyte ovulation, but the character of this effect is dissimilar. LH exerts a high stimulating effect on the loach oocyte maturation and a low one on ovulation. Iso-LH possesses a more complicated biologic effect, depending on its concentration in the medium. Within the limits of 0.01 to 0.2 mg/ml concentrations stimulation of 50% oocyte ovulation is observed (80% ovulating normally), while within 0.5 to 4-5 mg/ml concentrations a more pronounced ability to stimulate the maturation process, but almost the same capability as in the first concentration limits to stimulate the ovulation process, is seen. A comparison of the biological effects of both preparations on the carp oocytes in vitro has shown LH to possess marked maturation-stimulating activity and almost complete absence of ovulation-stimulating action, while iso-LH to be less active as a maturation process stimulant, but to exert a high stimulating effect on ovulation process of mature oocytes.

[Sex differences in the gonadotropins of the Black Sea plaice Scophthalmus maeoticus]

No quantitative differences in the effect of acetone-dried pituitaries from male and female plaice upon loach-recipients (Misgurnus fossilis) have been found in testing the activity of the glands on plaice-recipients. This fact suggests the existence of qualitative differences between gonadotropins from plaice males and females. This conclusion was supported in the experiments on the effect of purified gonadotropic fractions, isolated separately from male and female hypophyses, on maturation of the loach. Three gonadotropic fractions obtained by preparative disc-electrophoresis in polyacrylamide gel, differ in their biological activity and electrophoretic mobility. The activity of gonadotropic fractions in males is higher, than in females; electrophoretic mobility of two fractions is also higher in males, whereas the third fraction does not exhibit sexual differences.

[The effect of pituitary injections on the isoenzyme composition of non-specific esterases in the tissues of the silver carp, Hypophthalmichthys molitrix]

Polyacrylamide gel electrophoresis reveals differences in the isoenzymic spectra of non-specific esterases from various tissues of H. molitrix. Hypophyseal injections result in changes of the isoenzymic spectra of all the tissues studied. The pattern of changes depends on the tissue examined. Some of the isoenzymes are resistant to hypophyseal injections, whereas the other ones undergo changes which depend on the dose of the hormone.