A COMPARATIVE REVIEW OF THE USE OF DANIO RERIO (ZEBRAFISH) AS A MODEL OBJECT IN PRECLINICAL STUDIES

Danio rerio (Zebrafish) as a model object in preclinical studies have been widely used in recent years. This is facilitated by their morphological, physiological, biochemical, genetic, and embryological characteristics, as well as economic benefits and small-time costs of their breeding. The aim is to summarize the available data on the use of Danio rerio (Zebrafish) in preclinical studies. In this work a review of domestic and foreign articles on the use of Danio rerio in toxicological, pharmacological, embryological, and other research areas was carried out. Danio rerio (Zebrafish) can be used in many areas of preclinical studies of drugs. Their application in modeling novelty stress and experimental depression is especially interesting. Danio rerio are a versatile model object that allows cost-effective studies of various pharmacological drugs before they are tested on other models, particularly mammals.

The first inorganic mitogens: Cerium oxide and cerium fluoride nanoparticles stimulate planarian regeneration via neoblastic activation

We report the first experimental evidence for the mitogenic action of cerium(IV) oxide and cerium(III) fluoride nanoparticles (CONs and CFNs) on the regeneration of a whole organism - freshwater flatworms Schmidtea mediterranea (planarian). Both types of cerium-containing nanoparticles are shown to be a highly potent mitogen for planaria. Both CONs and CFNs, in micro- and nanomolar concentrations, markedly accelerate planarian blastema growth, due to the enhancement of cellular proliferation, causing an increase in the mitotic index and in the quantity of blastema cells in regenerating planaria. CONs provided maximum activity at concentrations which were two orders of magnitude lower than those for CeF₃. The valence state of cerium in cerium-containing nanoparticles plays a significant role in the planarian regeneration mechanism: CeO₂ nanoparticles containing predominantly Ce⁴⁺ species presumably scavenge wound induced reactive oxygen species and moderately activate gene expression processes, while the regenerative action of CeF₃ nanoparticles containing only Ce³⁺ species is manifested in the pronounced expression of the genes involved in cell division, differentiation and migration. This is the first report on the effect of cerium-containing nanoparticles on tissue regeneration in vivo, further revealing the mechanisms of their biological action, which enhances the possibility of their use in cellular technologies.

Ceria Nanoparticles-Decorated Microcapsules as a Smart Drug Delivery/Protective System: Protection of Encapsulated P. pyralis Luciferase

The design of novel, effective drug delivery systems is one of the most promising ways to improve the treatment of socially important diseases. This article reports on an innovative approach to the production of composite microcontainers (microcapsules) bearing advanced protective functions. Cerium oxide (CeO₂) nanoparticles were incorporated into layer-by-layer polyelectrolyte microcapsules as a protective shell for an encapsulated enzyme (luciferase of Photinus pyralis), preventing its oxidation by hydrogen peroxide, the most abundant type of reactive oxygen species (ROS). The protective effect depends on CeO₂ loading in the shell: at a low concentration, CeO₂ nanoparticles only scavenge ROS, whereas a higher content leads to a decrease in access for both ROS and the substrate to the enzyme in the core. By varying the nanoparticle concentration in the microcapsule, it is possible to control the level of core shielding, from ROS filtering to complete blocking. A comprehensive analysis of microcapsules by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, confocal laser scanning microscopy, and energy-dispersive X-ray spectroscopy techniques was carried out. Composite microcapsules decorated with CeO₂ nanoparticles and encapsulated luciferase were shown to be easily taken up by rat B-50 neuronal cells; they are nontoxic and are able to protect cells from the oxidative stress induced by hydrogen peroxide. The approach demonstrated that the active protection of microencapsulated substances by CeO₂ nanoparticles can be used in the development of new drug delivery and diagnostic systems.

Effects of TiO2, ZrO2 and Al2O3 dopants on the compressive strength of tricalcium phosphate

Tricalcium phosphate (TCP) powders synthesised using the Ca(NO3)2 and Ca(OH)2 routes were doped with TiO2, ZrO2 and Al2O3 in order to increase their compressive strength. An ultimate compressive strength (UCS) of 255 +/- 6 MPa was achieved for approximately 10 vol% TiO2 doping compared to 30 +/- 3 MPa for an un-doped control processed and tested in the same manner. Higher levels of TiO2 doping resulted in smaller increases in UCS with 30 and 50 vol% achieving 213 +/- 9 and 178 +/- 15 MPa, respectively. Very small amounts of Al2O3 doping (< 0.5 vol%) also resulted in a stronger materials. However, under the processing conditions employed, higher levels of Al2O3 and ZrO2 doping resulted in no beneficial effect on the UCS. Polyvinyl alcohol (PVA) was used as binding agent to facilitate processing. As expected, higher levels of PVA were associated with smaller increases in UCS. Powders synthesised using the Ca(OH)2 route had smaller particle size and resulted in larger increases in UCS compared to the Ca(NO3)2-synthesised powders. Although some powders contained alpha and beta-TCP phases, no other calcium phosphate, CaO, CaTiO3 or CaZrO3 phases were detected. In conclusion, a significant increase in the UCS of TCP was achieved by doping with approximately 10 vol% TiO2 which is expected to have little or no effect on the bioactivity or bioresorbability of the material.

A locus that influences susceptibility to 1, 2-dimethylhydrazine-induced colon tumors maps to the distal end of mouse chromosome 3

While inheritance of mutated alleles of highly penetrant tumor suppressor genes such as retinoblastoma or p53 predisposes individuals to a greatly increased risk of developing cancer, epidemiological data indicate that the majority of sporadic tumors in humans result from interactions of environmental and host genetic factors. The host genetic factors are poorly penetrant tumor susceptibility genes that determine the likelihood that a cancer will arise from carcinogen exposure. The majority of colon tumors in humans are sporadic in nature. 1,2-dimethylhydrazine (DMH)-induced colon tumors in mice provide a useful animal model to identify genes that influence susceptibility to carcinogen-induced colon tumors in humans. A genome-wide scan of genetic crosses of relatively sensitive C57BL/6J with relatively resistant CBA mice treated with DMH revealed a linkage of DMH susceptibility with the distal end of mouse chromosome 3, suggesting that one or more tumor susceptibility genes may map to this region.

Congenital cataracts facial dysmorphism neuropathy syndrome, a novel complex genetic disease in Balkan Gypsies: clinical and electrophysiological observations

During a study of hereditary motor and sensory neuropathy-Lom in Bulgaria, a previously unrecognized neurological disorder was encountered, mainly in Wallachian Gypsies, who represent a relatively recent genetic isolate. The disorder has been termed the congenital cataracts facial dysmorphism neuropathy (CCFDN) syndrome to emphasize its salient features. Fifty individuals from 19 extended pedigrees were identified and examined clinically and electrophysiologically. At least 1 patient from each family was admitted to the hospital in Sofia for full investigation. Pedigree analysis indicates autosomal recessive inheritance. The disorder is recognized in infancy by the presence of congenital cataracts and microcorneas. A predominantly motor neuropathy beginning in the lower limbs and later affecting the upper limbs develops during childhood and leads to severe disability by the third decade. Associated neurological features are a moderate nonprogressive cognitive deficit in most affected individuals together with pyramidal signs and mild chorea in some. Accompanying nonneurological features include short stature, characteristic facial dysmorphism, and hypogonadotrophic hypogonadism. Nerve conduction studies suggest a hypomyelinating/demyelinating neuropathy, confirmed by nerve biopsy. The CCFDN syndrome is thus a pleomorphic autosomal recessive disorder displaying a combination of neurological and nonneurological features.

Comparative analysis of radiometric and autoradiographic methods in the investigation of DNA synthetic activity of tumor cells in vitro

DNA synthesis in cell cultures of Ehrlich ascites carcinoma (EAC) was studied by means of autoradiography and liquid scintillation radiometry. The following parameters were compared for estimation of DNA synthesis: a) total radioactivity of incorporated [H-3]thymidine registered by a liquid scintillation counter, b) labeling index (LI) reflecting the relative number of cells which synthesize DNA, and c) mean grain count (MGC) indicating average intensity of DNA synthesis in the S-phase of the cell cycle. Kinetics of total radioactivity of incorporated [H-3]thymidine was determined to correlate better with LI. Changes in DNA synthesis in vitro were shown to be monitored with a higher level of significance by the radiometric technique, but autoradiography was more sensitive in some cases. Priority and informative value of the two methods were discussed. Autoradiography and liquid scintillation radiometry were concluded to be mutually complementary for investigation of DNA synthesis in tumor cells in vitro. Combination of the two methods was recommended for investigation of influence of cell proliferation inhibitors on DNA synthesis.

The Ehrlich ascites carcinoma (EAC) contains 300-500 Da inhibitor(s) suppressing DNA synthesis in cultured EAC cells and EAC cell division in tumor-bearing mice

A protein preparation obtained from the Ehrlich ascites carcinoma (EAC) by acetone precipitation, water extraction and subsequent two-step alcohol fractionation reduced significantly EAC cell proliferation in vivo and in vitro. The preparation was found to contain a low molecular-weight growth-inhibitory activity, suppressing both DNA synthesis in cultured EAC cells and EAC cell division in tumor-bearing mice. The approximate molecular weight of this inhibitory component(s) is about 300-500 Da, corresponding to oligopeptide molecule(s).

Immune responses in male mice with aggressive and submissive behavior patterns: strain differences

Immune responses in two strains of male mice with aggressive and submissive behavior patterns was studied. In aggressive CBA males immunized on the 10th day of agonistic confrontations with submissive partners, greater numbers of plaque-forming cells (PFC) and rosette-forming cells (RFC) were noted compared to control mice. Unlike the CBA strain, both PFC and RFC levels in aggressive C57BL males did not increase, but both PFC and RFC numbers decreased in submissive animals.

Regulation of the expression of the sex-specific isoforms of cytochrome P-450 in rat liver

The hepatic metabolism of steroid hormones and of xenobiotics frequently depends on the expression of the sex-specific isoforms of cytochrome P-450 and on differences in sex hormones. Following biochemical, immunological and molecular biological investigations, it was shown that in adult rat liver there exist at least four male-specific and one female-specific isoforms of cytochrome P-450. The designation of these sex-specific genes is IIC11, IIIA2, IIC13 and IIA2 in males, and IIC12 in females. The irreversible programming of the expression of these isoforms of cytochrome P-450 in adulthood occurs during the perinatal period of life, and is named enzyme imprinting. One of the main factors that regulates the expression of the sex-specific isoforms of cytochrome P-450 is the level of androgens in the blood. Castration of adult rats decreased the level of the male isoforms of cytochrome P-450 and the activity of the monooxygenase enzyme system that remained higher than in intact females. The mechanism of enzyme imprinting can be explained as follows: neonatal androgens program the secretion of hypothalamic hormones, somatostatin and growth-hormone-releasing factor. These factors determine the type of growth hormone secretion in adult rats, and this controls the type of sex-specific isoforms of cytochrome P-450 expressed in adulthood. Metabolic regulation similar to that outlined above was shown to occur for several metabolism-dependent chemical carcinogens. Such a pathway may explain the different sensitivity displayed by male and female rats to treatment with these carcinogenic agents. One possible way of modulating the expression of some isoforms of cytochrome P-450 in adult rats is by treating neonates with specific xenobiotics that change the constitutive expression of neonatal androgens. It appears that this enzyme imprinting plays an important role in determining the individual sensitivity to the carcinogenic effects of chemicals.

Changes in ECG, plasma and myocardial lipids in experimental myocardial hypertrophy in rats

ECG, systolic blood pressure (BP), the ratio (R) of grams of myocardial mass/100 g of body mass, total lipids, cholesterol, triglycerides and phospholipids in blood plasma and the left ventricular myocardium, as well as the plasma free fatty acids, were investigated in 58 male Wistar rats 3, 30 and 180 days after operation, in a model of myocardial hypertrophy (MH) induced by experimental coarctation hypertension, after the method of Selye. An attempt was made to correlate some functional and metabolic indices which characterize the development of this type of MH. On a background of progressively rising BP and parallel increasing R, ECG changes were recorded. They were typical of the respective stage of arterial hypertension and MH and expressed mostly in a shifting of the electrical axis of the heart to the left and in essential repolarization disturbances. The most significant changes in the studied lipid fractions were found 30 days after the induction of hypertension. The pathological changes manifested on the 180th day are discussed in relation to age, the stage of hypertension and especially in relation to the developing hypoxic and ischaemic myocardial damage.