Maternal Larp6 controls oocyte development, chorion formation and elevation.

La-related protein 6 (Larp6) is a conserved RNA-binding protein found across eukaryotes that has been suggested to regulate collagen biogenesis, muscle development, ciliogenesis, and various aspects of cell proliferation and migration. Zebrafish have two Larp6 family genes: larp6a and larp6b Viable and fertile single and double homozygous larp6a and larp6b zygotic mutants revealed no defects in muscle structure, and were indistinguishable from heterozygous or wild-type siblings. However, larp6a mutant females produced eggs with chorions that failed to elevate fully and were fragile. Eggs from larp6b single mutant females showed minor chorion defects, but chorions from eggs laid by larp6a;larp6b double mutant females were more defective than those from larp6a single mutants. Electron microscopy revealed defective chorionogenesis during oocyte development. Despite this, maternal zygotic single and double mutants were viable and fertile. Mass spectrometry analysis provided a description of chorion protein composition and revealed significant reductions in a subset of zona pellucida and lectin-type proteins between wild-type and mutant chorions that paralleled the severity of the phenotype. We conclude that Larp6 proteins are required for normal oocyte development, chorion formation and egg activation.

Lizards possess the most complete tetrapod Hox gene repertoire despite pervasive structural changes in Hox clusters.

Hox genes are a remarkable example of conservation in animal development and their nested expression along the head-to-tail axis orchestrates embryonic patterning. Early in vertebrate history, two duplications led to the emergence of four Hox clusters (A-D) and redundancy within paralog groups has been partially accommodated with gene losses. Here we conduct an inventory of squamate Hox genes using the genomes of 10 lizard and 7 snake species. Although the HoxC1 gene has been hypothesized to be lost in the amniote ancestor, we reveal that it is retained in lizards. In contrast, all snakes lack functional HoxC1 and -D12 genes. Varying levels of degradation suggest differences in the process of gene loss between the two genes. The vertebrate HoxC1 gene is prone to gene loss and its functional domains are more variable than those of other Hox1 genes. We describe for the first time the HoxC1 expression patterns in tetrapods. HoxC1 is broadly expressed during development in the diencephalon, the neural tube, dorsal root ganglia, and limb buds in two lizard species. Our study emphasizes the value of revisiting Hox gene repertoires by densely sampling taxonomic groups and its feasibility owing to growing sequence resources in evaluating gene repertoires across taxa.

Chlorhexidine hexametaphosphate nanoparticles as a novel antimicrobial coating for dental implants.

Dental implants are an increasingly popular solution to missing teeth. Implants are prone to colonisation by pathogenic oral bacteria which can lead to inflammation, destruction of bone and ultimately implant failure. The aim of this study was to investigate the use of chlorhexidine (CHX) hexametaphosphate (HMP) nanoparticles (NPs) with a total CHX concentration equivalent to 5 mM as a coating for dental implants. The CHX HMP NPs had mean diameter 49 nm and composition was confirmed showing presence of both chlorine and phosphorus. The NPs formed micrometer-sized aggregated surface deposits on commercially pure grade II titanium substrates following immersion-coating for 30 s. When CHX HMP NP-coated titanium specimens were immersed in deionised water, sustained release of soluble CHX was observed, both in the absence and presence of a salivary pellicle, for the duration of the study (99 days) without reaching a plateau. Control specimens exposed to a solution of aqueous 25 µM CHX (equivalent to the residual aqueous CHX present with the NPs) did not exhibit CHX release. CHX HMP NP-coated surfaces exhibited antimicrobial efficacy against oral primary colonising bacterium Streptococcus gordonii within 8 h. The antimicrobial efficacy was greater in the presence of an acquired pellicle which is postulated to be due to retention of soluble CHX by the pellicle.

Molecular and Cellular Characterization of the TH Pathway in the Sea Urchin Strongylocentrotus purpuratus.

Thyroid Hormones (THs) are a class of signaling molecules produced by coupling iodine with tyrosine residues. In vertebrates, extensive data support their important role in a variety of processes such as metabolism, development and metamorphosis. On the other hand, in invertebrates, the synthesis and role of the THs have been, so far, poorly investigated, thus limiting our understanding of the function and evolution of this important animal signaling pathway. In sea urchins, for example, while several studies focused on the availability and function of external sources of iodotyrosines, preliminary evidence suggests that an endogenous TH pathway might be in place. Here, integrating available literature with an in silico analysis, various homologous genes of the vertebrate TH molecular toolkit have been identified in the sea urchin Strongylocentrotus purpuratus. They include genes involved in the synthesis (Sp-Pxdn), metabolism (Sp-Dios), transport (Sp-Ttrl, Sp-Mct7/8/10) and response (Sp-Thr, Sp-Rxr and Sp-Integrin αP) to thyroid hormones. To understand the cell type(s) involved in TH synthesis and/or response, we studied the spatial expression of the TH toolkit during urchin development. Exploiting single-cell transcriptomics data in conjunction with in situ hybridization and immunohistochemistry, we identified cell types that are potentially producing or responding to THs in the sea urchin. Finally, growing sea urchin embryos until the larva stage with and without a source of inorganic iodine, we provided evidence that iodine organification is important for larval skeleton growth.

An interproximal model to determine the erosion-protective effect of calcium silicate, sodium phosphate, fluoride formulations.

OBJECTIVES: Previous work has shown the effectiveness of a newly developed interproximal model to differentiate between the amount of remineralization caused by toothpastes used with or without a dual-phase gel treatment system containing calcium silicate, sodium phosphate salts and fluoride to repair acid-softened enamel. The aim of this study was to utilize the same interproximal model to identify how effective calcium silicate phosphate toothpastes are at reducing surface softening in the early stages of erosion. The model was also used to identify the effect of increasing the frequency of acid exposure on the reduction in surface hardness. METHODS: Human enamel specimens were prepared and mounted in an interproximal face-to-face arrangement and exposed to a cycling regime of whole human saliva, treatment, artificial saliva and 1% citric acid pH 3.75. Specimens were measured by surface microhardness at baseline and after three and seven days. The frequency of acid exposure was increased from 2 to 4 cycles a day for the second part of the study. RESULTS: The results showed that specimens treated with the calcium silicate phosphate toothpastes softened less than those treated with control fluoridated or non-fluoride toothpastes at each time point and following an increase in the frequency of acid exposure. SIGNIFICANCE: This work has demonstrated how an interproximal model can also be successfully used to determine differences in the erosion protection of various treatments as well as determining how they perform when the frequency of acid exposure is increased.

Neuropeptidergic Systems in Pluteus Larvae of the Sea Urchin Strongylocentrotus purpuratus: Neurochemical Complexity in a "Simple" Nervous System.

The nervous system of the free-living planktonic larvae of sea urchins is relatively "simple," but sufficiently complex to enable sensing of the environment and control of swimming and feeding behaviors. At the pluteus stage of development, the nervous system comprises a central ganglion of serotonergic neurons located in the apical organ and sensory and motor neurons associated with the ciliary band and the gut. Neuropeptides are key mediators of neuronal signaling in nervous systems but currently little is known about neuropeptidergic systems in sea urchin larvae. Analysis of the genome sequence of the sea urchin Strongylocentrotus purpuratus has enabled the identification of 38 genes encoding neuropeptide precursors (NP) in this species. Here we characterize for the first time the expression of nine of these NP genes in S. purpuratus larvae, providing a basis for a functional understanding of the neurochemical organization of the larval nervous system. In order to accomplish this we used single and double in situ hybridization, coupled with immunohistochemistry, to investigate NP gene expression in comparison with known markers (e.g., the neurotransmitter serotonin). Several sub-populations of cells that express one or more NP genes were identified, which are located in the apica organ, at the base of the arms, around the mouth, in the ciliary band and in the mid- and fore-gut. Furthermore, high levels of cell proliferation were observed in neurogenic territories, consistent with an increase in the number of neuropeptidergic cells at late larval stages. This study has revealed that the sea urchin larval nervous system is far more complex at a neurochemical level than was previously known. Our NP gene expression map provides the basis for future work, aimed at understanding the role of diverse neuropeptides in control of various aspects of embryonic and larval behavior.

Functionalization of ethylene vinyl acetate with antimicrobial chlorhexidine hexametaphosphate nanoparticles.

Ethylene vinyl acetate (EVA) is in widespread use as a polymeric biomaterial with diverse applications such as intravitreal devices, catheters, artificial organs, and mouthguards. Many biomaterials are inherently prone to bacterial colonization, as the human body is host to a vast array of microbes. This can lead to infection at the biomaterial's site of implantation or application. In this study, EVA was coated with chlorhexidine (CHX) hexametaphosphate (HMP) nanoparticles (NPs) precipitated using two different reagent concentrations: CHX-HMP-5 (5 mM CHX and HMP) and CHX-HMP-0.5 (0.5 mM CHX and HMP). Data gathered using dynamic light scattering, transmission electron microscopy, and atomic force microscopy indicated that the NPs were polydisperse, ~40-80 nm in diameter, and aggregated in solution to form clusters of ~140-200 nm and some much larger aggregates of 4-5 µM. CHX-HMP-5 formed large deposits on the polymer surface discernible using scanning electron microscopy, whereas CHX-HMP-0.5 did not. Soluble CHX was released by CHX-HMP-5 NP-coated surfaces over the experimental period of 56 days. CHX-HMP-5 NPs prevented growth of methicillin-resistant Staphylococcus aureus when applied to the polymer surfaces, and also inhibited or prevented growth of Pseudomonas aeruginosa with greater efficacy when the NP suspension was not rinsed from the polymer surface, providing a greater NP coverage. This approach may provide a useful means to treat medical devices fabricated from EVA to render them resistant to colonization by pathogenic microorganisms.

Synthesis, characterization, and efficacy of antimicrobial chlorhexidine hexametaphosphate nanoparticles for applications in biomedical materials and consumer products.

Chlorhexidine (CHX) is an antimicrobial agent that is efficacious against gram-negative and -positive bacteria and yeasts. Its mechanism of action is based on cell membrane disruption and, as such, it does not promote the development of bacterial resistance, which is associated with the widespread use of antibiotics. In this manuscript, we report the development of novel antimicrobial nanoparticles (NPs) based on a hexametaphosphate salt of CHX. These are synthesized by instantaneous reaction between equimolar aqueous solutions of CHX digluconate and sodium hexametaphosphate, under room temperature and pressure. The reaction results in a stable colloid composed of highly negatively charged NPs (-50 mV), of size 20-160 nm. The NPs adhere rapidly to specimens of glass, titanium, and an elastomeric wound dressing, in a dose-dependent manner. The functionalized materials exhibit a gradual leaching of soluble CHX over a period of at least 50 days. The NP colloid is efficacious against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa in both planktonic and biofilm conditions. These NPs may find application in a range of biomedical and consumer materials.