Cellular electron tomography of the apical complex in the apicomplexan parasite Eimeria tenella shows a highly organised gateway for regulated secretion.

The apical complex of apicomplexan parasites is essential for host cell invasion and intracellular survival and as the site of regulated exocytosis from specialised secretory organelles called rhoptries and micronemes. Despite its importance, there is little data on the three-dimensional organisation and quantification of these organelles within the apical complex or how they are trafficked to this specialised region of plasma membrane for exocytosis. In coccidian apicomplexans there is an additional tubulin-containing hollow barrel structure, the conoid, which provides a structural gateway for this specialised secretion. Using a combination of cellular electron tomography and serial block face-scanning electron microscopy (SBF-SEM) we have reconstructed the entire apical end of Eimeria tenella sporozoites. We discovered that conoid fibre number varied, but there was a fixed spacing between fibres, leading to conoids of different sizes. Associated apical structures varied in size to accommodate a larger or smaller conoid diameter. However, the number of subpellicular microtubules on the apical polar ring surrounding the conoid did not vary, suggesting a control of apical complex size. We quantified the number and location of rhoptries and micronemes within cells and show a highly organised gateway for trafficking and docking of rhoptries, micronemes and vesicles within the conoid around a set of intra-conoidal microtubules. Finally, we provide ultrastructural evidence for fusion of rhoptries directly through the parasite plasma membrane early in infection and the presence of a pore in the parasitophorous vacuole membrane, providing a structural explanation for how rhoptry proteins (ROPs) may be trafficked between the parasite and the host cytoplasm

Multiscale molecular profiling of pathological bone resolves sexually dimorphic control of extracellular matrix composition

ABSTRACTCollagen assembly during development is essential for successful matrix mineralisation, which determines bone quality and mechanocompetence. However, the biochemical and structural perturbations that drive pathological skeletal collagen configuration remain unclear. Deletion of vascular endothelial growth factor (VEGF; also known as VEGFA) in bone-forming osteoblasts (OBs) induces sex-specific alterations in extracellular matrix (ECM) conformation and mineralisation coupled to vascular changes, which are augmented in males. Whether this phenotypic dimorphism arises as a result of the divergent control of ECM composition and its subsequent arrangement is unknown and is the focus of this study. Herein, we used murine osteocalcin-specific Vegf knockout (OcnVEGFKO) and performed ex vivo multiscale analysis at the tibiofibular junction of both sexes. Label-free and non-destructive polarisation-resolved second-harmonic generation (p-SHG) microscopy revealed a reduction in collagen fibre number in males following the loss of VEGF, complemented by observable defects in matrix organisation by backscattered electron scanning electron microscopy. This was accompanied by localised divergence in collagen orientation, determined by p-SHG anisotropy measurements, as a result of OcnVEGFKO. Raman spectroscopy confirmed that the effect on collagen was linked to molecular dimorphic VEGF effects on collagen-specific proline and hydroxyproline, and collagen intra-strand stability, in addition to matrix carbonation and mineralisation. Vegf deletion in male and female murine OB cultures in vitro further highlighted divergence in genes regulating local ECM structure, including Adamts2, Spp1, Mmp9 and Lama1. Our results demonstrate the utility of macromolecular imaging and spectroscopic modalities for the detection of collagen arrangement and ECM composition in pathological bone. Linking the sex-specific genetic regulators to matrix signatures could be important for treatment of dimorphic bone disorders that clinically manifest in pathological nano- and macro-level disorganisation.This article has an associated First Person interview with the first author of the paper.

Quantification of different microplastic fibres discharged from textiles in machine wash and tumble drying

Microplastic fibres released in synthetic cloth washing have been shown to be a source of microplastics into the environment. The annual emission of polyester fibres from household washing machines has earlier been estimated to be 150,000 kg in a country with a population of 5.5 × 106 (Finland). The objectives of this study were (1) to quantify the emissions of synthetic textile fibres discharged from five sequential machine washes (fibre number and length) and tumble dryings (fibre mass) and (2) to determine the collection efficiency of two commercial fibre traps. The synthetic fabrics were five types of polyester textiles, one polyamide and one polyacryl. The number of fibres released from the test fabrics in the first wash varied in the range from 1.0 × 105 to 6.3 × 106 kg−1. The fibre lengths showed that the fleece fabrics released, on average, longer fibres than the technical sports t-shirts. The mass of fibres ranged from 10 to 1700 mg/kg w/w in the first drying. Fibre emissions showed a decreasing trend both in sequential washes and dryings. The ratio of the fibre emissions in machine wash to tumble drying varied between the fabrics: the ratio was larger than one to polyester and polyamide technical t-shirts whereas it was much lower to the other tested textiles. GuppyFriend washing bag and Cora Ball trapped 39% and 10% of the polyester fibres discharged in washings, respectively.

Association of miR-208b polymorphism with meat quality traits and texture parameters in pigs

Previous studies have shown that single nucleotide polymorphism (SNP) (rs328743478) located downstream of pre-miR-208b in MYH7 gene is correlated with fibre number composition and drip loss in pigs. Because fibre characteristics are linked to meat quality, the aim of this study was to analyse the relationships between rs328743478 polymorphism and meat quality and texture parameters. The study utilised 578 pigs belonging to Polish Landrace, Polish Large White, Puławska, Pietrain, Duroc, and Hampshire breeds. Association study was performed for the first three breeds separately and for all six breeds joined together. Obtained results showed a significant influence (P ≤ 0.05) of miR-208b genotypes on water holding capacity (WHC) in the whole population and individual breeds and on intramuscular fat content (IMF) and luminosity in the whole population as well as in Landrace and Puławska breeds, respectively. By analysing texture parameters, we found association (P ≤ 0.05 or P ≤ 0.01) between rs328743478 polymorphism and toughness, firmness, and chewiness measured in m. semimembranosus and m. longissimus lumborum. The highest values of these traits in m. semimembranosus were noticed for AA genotype, however in m. longissimus lumborum for GG in the whole population and some individual breeds. It was found that miR-208b genotypes were also associated with cohesiveness (P ≤ 0.01), springiness, and hardness (P ≤ 0.05) but obtained results were not consistent among breeds and the whole population. The obtained results confirm that miR-208b polymorphism is associated with some economically important traits in pigs.

Myotome adaptability confers developmental robustness to somitic myogenesis in response to fibre number alteration

Summary StatementHomeostatic interactions between muscle stem cells and fibres during myogenesis ensure the correct muscle size is formed independent of fibre number in zebrafishAbstractBalancing the number of stem cells and their progeny is crucial for tissue development and repair. Here we examine how muscle stem/precursor cell (MPC) numbers are tightly regulated during zebrafish somitic muscle development. MPCs expressing Pax7 are initially located in the dermomyotome (DM) external cell layer, adopt a highly stereotypical distribution and thereafter a proportion of MPCs migrate into the myotome. Regional variations in the proliferation and terminal differentiation of MPCs contribute to growth of the myotome. To probe the robustness of spatiotemporal regulation of MPCs, we compared the behaviour of wild type (wt) MPCs with those in mutant zebrafish that lack the muscle regulatory factor Myod. Myodfh261 mutants form one third fewer multinucleate fast muscle fibres than wt and show a significant expansion of the Pax7+ MPC population in the DM. Subsequently, myodfh261 mutant fibres generate more cytoplasm per nucleus, leading to recovery of muscle bulk. In addition, relative to wt siblings, there is an increased number of MPCs in myodfh261 mutants and these migrate prematurely into the myotome, differentiate and contribute to the hypertrophy of existing fibres. Thus, homeostatic reduction of the excess MPCs returns their number to normal levels, but fibre numbers remain low. The GSK3 antagonist BIO prevents MPC migration into the deep myotome, suggesting that canonical Wnt pathway activation maintains the DM in zebrafish, as in amniotes. BIO does not, however, block recovery of the myodfh261 mutant myotome, indicating that homeostasis acts on fibre intrinsic growth to maintain muscle bulk. The findings suggest the existence of a critical window for early fast fibre formation followed by a period in which homeostatic mechanisms regulate myotome growth by controlling fibre size.

EVALUATION OF THE LATVIAN FLAX GENETIC RESOURCES AND PERSPECTIVE OF THEIR UTILISATION

Flax (Linum usitatissimum L.) is one of the oldest fibre and oil crop in Europe, including Latvia. In the middle of the last century growing areas of this crop was reduced dramatically. Nowadays flax attracted a great interest again as a fibre and oil processor, as well as a crop for diversification of agriculture and, in the same time, as a crop for producing high quality fibre for industry, high quantity oil for biofuel and high quality oil for feeding, food, and pharmacy (source of α-linolenic acid, linoleic acid and vitamins). We evaluated all available flax accessions of the Latvian origin and number of their hybrid lines. Agronomically important qualitative and quantitative traits, such as total plant height, technical plant height, number of seed vessels, logging resistance, vegetation period, yield of straws and seeds, 1000 seeds weight, bast fibre, number of seeds in a seed vessel, oil content and rust resistance gene L alleles L2 and L9 were recorded. Results of the field trials of two last years were summarized. Local accessions are useful as a source for breeding to adaptation of flax varieties to the local Latvian conditions. With use of molecular methods flax rust resistance allele L2 and L9 were found in eleven accessions.

Effect of Piglet Birth Weight on Carcass Muscle and Fat Content and Pork Quality – A Review

Piglet birth weight is determined by the maternal environment, intrauterine crowding, and nutrition, which influence embryonic and fetal survival and, as a result, fertility. The internal environment regulates prenatal myogenesis and muscle fibre number nutritionally and hormonally. The growth and metabolic differentiation of muscle fibres take place during the postnatal period. The effect of intrauterine undernutrition on myogenesis and on fetal growth and development (IUGR) is reflected in the low piglet birth weight and its high within-litter variation. Slaughter traits are determined by many factors, including genetic (breed), environmental (nutrition) and preslaughter handling. Slaughter traits and the physico-chemical and sensory characteristics of meat are dependent on prenatal myogenesis and neonatal weight. Optimized body weight of newborn piglets is conducive to improving quantitative traits (meatiness, fatness) and qualitative traits. However, slaughter traits are also influenced by many other differentiating factors, which is reflected in research results. Muscle fibres become metabolically differentiated during postnatal development, and one of the factors of large variation in pig meat quality traits is variation in the proportions of different fibre types in mature muscle. Considering the divergent opinions among scientists about the effect of prenatal myogenesis and piglet birth weight on slaughter value and pork quality, as well as the existence of areas that have received little investigation, it is justified to continue research in this area.