Heterochronic development of lateral plates in the three-spined stickleback induced by thyroid hormone level alterations

The three-spined stickleback Gasterosteus aculeatus is an important model for studying microevolution and parallel adaptation to freshwater environments. Marine and freshwater forms differ markedly in their phenotype, especially in the number of lateral plates, which are serially repeated elements of the exoskeleton. In fishes, thyroid hormones are involved in adaptation to salinity, as well as the developmental regulation of serially repeated elements. To study how thyroid hormones influence lateral plate development, we manipulated levels of triiodothyronine and thiourea during early ontogeny in a marine and freshwater population with complete and low plate phenotypes, respectively. The development of lateral plates along the body and keel was heterochronic among experimental groups. Fish with a low dosage of exogenous triiodothyronine and those treated with thiourea exhibited retarded development of bony plates compared to both control fish and those treated with higher a triiodothyronine dosage. Several triiodothyronine-treated individuals of the marine form expressed the partial lateral plate phenotype. Some individuals with delayed development of lateral plates manifested 1-2 extra bony plates located above the main row of lateral plates.Peer reviewe

Meristic characters of <i>Gasterosteus aculeatus</i>.

<p>A–number of anal fin rays, C–caudal fin rays, D–dorsal fin rays, P–pectoral fin rays (clipped fin shown), LP–total number of lateral plates, GR–number of gill rakers on the lower and upper branches of the first branchial arch, Vt–number of total vertebrae, Va–abdominal vertebrae, and Vc–caudal vertebrae.</p

Heterochronic development of lateral plates in the three-spined stickleback induced by thyroid hormone level alterations - Fig 4

<p>(A) Heterochronies in development (appearance) of lateral (left y-axis, four upper lines) and keel plate (right y-axis, four lower lines) in different experimental groups of the MF fish. Development of keel plates is given until forming a single continuous row with anterior plates. Plotted values are treatment-specific means. (B) Differences in degree of development of the lateral plates in MF cross at 42 dpf. Representative specimens of three sizes (largest, intermediate, and smallest) are shown from each experimental group.</p

Mean (±SEM; range) values of meristic traits in different experimental groups separately for FF and MF fish.

<p>Mean (±SEM; range) values of meristic traits in different experimental groups separately for FF and MF fish.</p

Four of the TH-0.5 treated individuals (101 dpf) of the MF with the partial lateral plate phenotype.

<p>Ellipses delineate areas with no lateral plates.</p

Additional two small bony plates (arrows).

<p>Additional plates are located above the main row of lateral plates, behind the head as exemplified from a TH-0.5 fish of marine form (fully plated phenotype, right side), age 101 dpf, TL = 34.7 mm (alizarin red S stained). Scale bar = 1 mm.</p

T₃ concentrations in the three-spined stickleback.

<p>(A) Plasma T₃ concentrations of wild caught three-spined sticklebacks. (B) Whole-body T₃ concentrations in laboratory-raised three-spined sticklebacks (61 dpf). Middle point is median, box and whisker are quartiles and range respectively. Samples are combined and each contains between 4 and 13 individuals; the sample size for each group is indicated above the bar. Different lowercase letters above the bars indicate significant differences between forms (p < 0.05, Mann-Whitney U-test for wild fish) or between experimental groups (p < 0.05, Kruskal-Wallis test with Dunn’s <i>post hoc</i> test for laboratory-raised fish). Differences between groups were tested independently within each panel and each cross.</p

Heterochronic development of lateral plates in the three-spined stickleback induced by thyroid hormone level alterations - Fig 2

<p>(A) Alizarin red stained control fish of the freshwater (FF, 130 dpf age) and marine (MF, 101 dpf) forms. (B) Sites of sampling of parental fish at the White Sea basin. Maps were obtained from <a href="http://www.sasgis.org/" target="_blank">http://www.sasgis.org</a>.</p

High antiviral effect of TiO2·PL–DNA nanocomposites targeted to conservative regions of (−)RNA and (+)RNA of influenza A virus in cell culture

Background: The development of new antiviral drugs based on nucleic acids is under scrutiny. An important problem in this aspect is to find the most vulnerable conservative regions in the viral genome as targets for the action of these agents. Another challenge is the development of an efficient system for their delivery into cells. To solve this problem, we proposed a TiO2·PL–DNA nanocomposite consisting of titanium dioxide nanoparticles and polylysine (PL)-containing oligonucleotides.Results: The TiO2·PL–DNA nanocomposites bearing the DNA fragments targeted to different conservative regions of (−)RNA and (+)RNA of segment 5 of influenza A virus (IAV) were studied for their antiviral activity in MDCK cells infected with the H1N1, H5N1, and H3N2 virus subtypes. Within the negative strand of each of the studied strains, the efficiency of DNA fragments increased in the direction of its 3’-end. Thus, the DNA fragment aimed at the 3’-noncoding region of (−)RNA was the most efficient and inhibited the reproduction of different IAV subtypes by 3–4 orders of magnitude. Although to a lesser extent, the DNA fragments targeted at the AUG region of (+)RNA and the corresponding region of (−)RNA were also active. For all studied viral subtypes, the nanocomposites bearing the DNA fragments targeted to (−)RNA appeared to be more efficient than those containing fragments aimed at the corresponding (+)RNA regions.Conclusion: The proposed TiO2·PL–DNA nanocomposites can be successfully used for highly efficient and site-specific inhibition of influenza A virus of different subtypes. Some patterns of localization of the most vulnerable regions in IAV segment 5 for the action of DNA-based drugs were found. The (−)RNA strand of IAV segment 5 appeared to be more sensitive as compared to (+)RNA