Effect of barnacle fouling on ship resistance and powering

Predictions of added resistances and effective powers of ships were made for varying barnacle fouling conditions. A series of towing tests were carried out using flat plates covered with artificial barnacles. The tests were designed to allow the examination of the effects of barnacle height and percent coverage on the resistance and effective power of ships. The drag coefficients and roughness function values were evaluated for the flat plates. Roughness effects of the fouling conditions on the ship frictional resistances were predicted. Added resistance diagrams were then plotted using these predictions, and powering penalties of these ships were calculated using the generated diagrams. The results indicate that the effect of barnacle size is significant, since 10% of the coverage of barnacles, which are 5mm in height, causes a similar level of added power requirements as 50% of the coverage of barnacles, which are 1.25 mm in height

Functional diversification of Argonautes in nematodes:an expanding universe

In the last decade, many diverse RNAi (RNA interference) pathways have been discovered that mediate gene silencing at epigenetic, transcriptional and post-transcriptional levels. The diversity of RNAi pathways is inherently linked to the evolution of Ago (Argonaute) proteins, the central protein component of RISCs (RNA-induced silencing complexes). An increasing number of diverse Agos have been identified in different species. The functions of most of these proteins are not yet known, but they are generally assumed to play roles in development, genome stability and/or protection against viruses. Recent research in the nematode Caenorhabditis elegans has expanded the breadth of RNAi functions to include transgenerational epigenetic memory and, possibly, environmental sensing. These functions are inherently linked to the production of secondary siRNAs (small interfering RNAs) that bind to members of a clade of WAGOs (worm-specific Agos). In the present article, we review briefly what is known about the evolution and function of Ago proteins in eukaryotes, including the expansion of WAGOs in nematodes. We postulate that the rapid evolution of WAGOs enables the exceptional functional plasticity of nematodes, including their capacity for parasitism

Mutations in XRCC4 cause primary microcephaly, short stature and increased genomic instability

DNA double-strand breaks (DSBs) are highly toxic lesions, which, if not properly repaired, can give rise to genomic instability. Non-homologous end-joining (NHEJ), a well-orchestrated, multistep process involving numerous proteins essential for cell viability, represents one major pathway to repair DSBs in mammalian cells, and mutations in different NHEJ components have been described in microcephalic syndromes associated, e.g. with short stature, facial dysmorphism and immune dysfunction. By using whole-exome sequencing, we now identified in three affected brothers of a consanguineous Turkish family a homozygous mutation, c.482G>A, in the XRCC4 gene encoding a crucial component of the NHEJ pathway. Moreover, we found one additional patient of Swiss origin carrying the compound heterozygous mutations c.25delG (p.His9Thrfs*8) and c.823C>T (p.Arg275*) in XRCC4. The clinical phenotype presented in these patients was characterized by severe microcephaly, facial dysmorphism and short stature, but they did not show a recognizable immunological phenotype. We showed that the XRCC4 c.482G>A mutation, which affects the last nucleotide of exon 4, induces defective splicing of XRCC4 pre-mRNA mainly resulting in premature protein truncation and most likely loss of XRCC4 function. Moreover, we observed on cellular level that XRCC4 deficiency leads to hypersensitivity to DSB-inducing agents and defective DSB repair, which results in increased cell death after exposure to genotoxic agents. Taken together, our data provide evidence that autosomal recessive mutations in XRCC4 induce increased genomic instability and cause a NHEJ-related syndrome defined by facial dysmorphism, primary microcephaly and short statur

De novo mutations in SMCHD1 cause Bosma arhinia microphthalmia syndrome and abrogate nasal development

Bosma arhinia microphthalmia syndrome (BAMS) is an extremely rare and striking condition characterized by complete absence of the nose with or without ocular defects. We report here that missense mutations in the epigenetic regulator SMCHD1 mapping to the extended ATPase domain of the encoded protein cause BAMS in all 14 cases studied. All mutations were de novo where parental DNA was available. Biochemical tests and in vivo assays in Xenopus laevis embryos suggest that these mutations may behave as gain-of-function alleles. This finding is in contrast to the loss-of-function mutations in SMCHD1 that have been associated with facioscapulohumeral muscular dystrophy (FSHD) type 2. Our results establish SMCHD1 as a key player in nasal development and provide biochemical insight into its enzymatic function that may be exploited for development of therapeutics for FSHD

Mutations in TOP3A Cause a Bloom Syndrome-like Disorder

Bloom syndrome, caused by biallelic mutations in BLM, is characterized by prenatal-onset growth deficiency, short stature, an erythematous photosensitive malar rash, and increased cancer predisposition. Diagnostically, a hallmark feature is the presence of increased sister chromatid exchanges (SCEs) on cytogenetic testing. Here, we describe biallelic mutations in TOP3A in ten individuals with prenatal-onset growth restriction and microcephaly. TOP3A encodes topoisomerase III alpha (TopIIIα), which binds to BLM as part of the BTRR complex, and promotes dissolution of double Holliday junctions arising during homologous recombination. We also identify a homozygous truncating variant in RMI1, which encodes another component of the BTRR complex, in two individuals with microcephalic dwarfism. The TOP3A mutations substantially reduce cellular levels of TopIIIα, and consequently subjects’ cells demonstrate elevated rates of SCE. Unresolved DNA recombination and/or replication intermediates persist into mitosis, leading to chromosome segregation defects and genome instability that most likely explain the growth restriction seen in these subjects and in Bloom syndrome. Clinical features of mitochondrial dysfunction are evident in several individuals with biallelic TOP3A mutations, consistent with the recently reported additional function of TopIIIα in mitochondrial DNA decatenation. In summary, our findings establish TOP3A mutations as an additional cause of prenatal-onset short stature with increased cytogenetic SCEs and implicate the decatenation activity of the BTRR complex in their pathogenesis

Monitoring of trace metals, biochemical composition and growth of Axillary seabream (Pagellus acarne Risso, 1827) in offshore Copper alloy net cage

The study was conducted to assess trace metal contents, biochemical composition and growth performance of axillary seabream (Pagellus acarne Risso, 1827) cultured in a copper alloy mesh cage. A total of 400 axillary seabream (initial mean weight: 176.0±14.0 g), a new candidate species for the Mediterranean aquaculture, were stocked into a high-density polyethylene frame gravity cage and fed a commercial seabream diet for a period of 6 months. At the end of the feeding trial, fish reached a final weight of 264.8±16.8 g with a weight increase of 88.8 g and a feed conversion rate of 2.51. Overall, relative growth rate, specific growth rate and feed conversion ratio were satisfactory and comparable to the pelagic fishes such as gilthead seabream or European seabass, which are presently the main fish species for the Mediterranean aquaculture industry. Trace elements in fish grown in copper alloy net cages over a 6-month period showed satisfactory results, as the metal concentrations in fish tissues such as liver, skin, muscle and gills were below the reported upper limits for human consumption, indicating that copper alloy net is an acceptable and safe material for finfish cage aquaculture. Furthermore, from the growth performance data obtained in the present study, it can be concluded that axillary seabream showed potential for cage farming, and thus is a promising new candidate for the Mediterranean aquaculture industry