Calcium (Ca) is essential for crustaceans, due to calcium carbonate (CaCO sub(3)) deposition in the new exoskeleton to harden it. The purpose of this work was to study short term Ca balance in terms ...of dietary Ca ingestion in two phylogenetically related crabs (Superfamily Grapsoidea) showing different degrees of terrestrial adaptations: Sesarma rectum Randall, 1840 and Neohelice granulata (Dana, 1851). Dietary Ca ingestion was studied using purified diets with different Ca concentrations (0, 2.2 and 6.66 % Ca), together with measurements of Ca excretion and Ca hemolymph levels. The results showed that both crabs had the same response to foods containing different levels of Ca, with both species eating more of the high Ca diet However, S. rectum consumed more per mg body mass at all Ca concentrations (6 mg.g super(-1) for S. rectum against 3 mg.g super(-1) for N. granulata). Both species excreted/egested Ca differently: S. rectum excreted Ca proportionally to ingestion, whereas N. granulata maintained constant faecal Ca output at all dietary Ca levels. Moreover, Ca hemolymph levels for crabs fed the different diets were independent of dietary Ca. In conclusion, both S. rectum and N. granulata seem to regulate the consumption of diets containing more Ca, which suggests a fine balance for Ca intake.Original Abstract: O calcio (Ca) e essencial para os crustaceos porque cristais de carbonato de calcio (CaCO sub(3)) sao depositados no novo exoesqueleto para endurece-lo. O objetivo do presente trabalho foi estudar o balanco do Ca em relacao a sua ingestao em dois caranguejos filogeneticamente relacionados (Superfamilia Grapsoidea), que apresentam diferentes graus de terrestrialidade: Sesarma rectum Randall, 1840 e Neohelice granulata (Dana, 1851). A ingestao de Ca foi estudada atraves do uso de dietas purificadas com diferentes quantidades de Ca (0, 2,2 e 6,66 % Ca), juntamente com a excrecao de Ca nas fezes e niveis de Ca na hemolinfa. Os resultados mostraram que ambos apresentam a mesma resposta em relacao aos niveis de Ca na dieta, ingerindo mais da dieta com maior quantidade de Ca. Sesarma rectum, porem, consumiu mais dieta por mg de peso para todas as concentracoes de Ca utilizadas (6 mg.g super(-1) para S. rectum contra 3 mg.g super(-1) para N. granulata). As duas especies excretaram Ca de maneira diferente: S. rectum excretou em proporcao direta a quantidade ingerida, enquanto N. granulata manteve constante a excrecao de Ca independente do Ca ingerido. Niveis de Ca na hemolinfa, por outro lado, foram iguais e independentes da quantidade de Ca ingerido para os dois caranguejos. Desse modo, tanto S. rectum como N. granulata parecem discriminar e ingerir dietas com maior quantidade de Ca, sugerindo uma regulacao fina na ingestao do Ca.
There are few intraspecific studies relating physiological parameters to body mass. This study relates scaling of ionic regulation and respiratory parameters with body mass in crayfish (Procambarus ...clarkii). These animals were chosen because of their direct development, spanning four orders of magnitude in body mass. Usually, these animals are hyperregulators and must maintain hemolymph electrolyte levels above those in the ambient freshwater. This is especially important in the postmolt, when ion imbalance can occur. Maintaining hemolymph ion levels above ambient involves active processes that are independently related to metabolic rate, ventilation, and circulation. Therefore, this study investigates relationships among size and ionic regulation, heart rate, and ventilation in crayfish, spanning a size range of 0.003–24 g. Postmolt net ion uptake of Ca, titratable base, Na, Cl, and NH4increase with body mass (positive allometry) with slopes of 0.92, 0.79, 0.90, 0.84, and 0.87, respectively. Between 72% and 97% of variation in ionic regulation was related to body mass. The slopes differed from each other for Ca and titratable base but not for Na, Cl, and NH4. For heart rate and ventilation rate, different relationships were derived for animals smaller and larger than 0.01 g (between first and third instar). Animals larger than 0.01 g show a negative allometric relationship between heart rate and body size (body mass0.15), while smaller animals show positive allometry with body size, but only 29% of variation in heart rate is explained by body size alone. For ventilation rates, the negative allometry with body size for animals larger than 0.01 g is present, but less than 15% of variation in ventilation rate is explained by size, while for smaller animals the size dependency disappears. Based on these results, predictions of physiological parameters such as ionic regulation based on body size are useful in crayfish, but estimates of respiratory parameters and body size should be used with caution.
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BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Several families of endogenous retrovirus (ERV) exist in copious numbers in the genomes of primate species. Therefore, we undertook a systematic search for endogenous retrovirus sequences from the ...ERV-K family, comparing across both human (Homo sapiens) and chimpanzee (Pan troglodytes) genomes. Using conserved motifs of the ERV-K as query we identified and characterized 76 complete ERV-K elements, 54 in human (HERV-K), 34 of which were described previously, and 21 in the chimpanzee (CERV-K). Phylogenetic analysis using coding regions and LTRs showed the existence of two main branches. Group I was the most heterogeneous and had an average integration time of 18.3 MYBP (million years before present), using rates ranging from 1.5 to 4.0 x 10-⁹ s/s/y (substitution per site per year). Group O/N integrated around 19.4 MYBP and nested Group N integrated about 14 MYBP. We found evidence for strong positive selection on the gag, pol and env coding regions and for A/T hypermutation. Our data suggest that the endogenous elements were possibly involved in chromosomal rearrangements and retained a great deal of information from their active stage, most likely as a consequence of host interactions. This study also contributes to the annotation effort of both human and chimpanzee genomes.
The objective of this work was to link hummingbird feeding behavior with metabolic regulation and in addition to assess whether dietary composition would affect entrance into torpor. Hummingbirds ...were fed a combination of diets with contrasting amounts of protein and carbohydrate. The diets were composed of the following: 2.4 % protein (P) - 12 % sucrose (S) and 0.8 % protein (P) - 36 % sucrose (S). The main findings showed that periods of feeding on each of the diets could be distinguished as separate bouts or feeding events. Hummingbirds presented to high protein-low carbohydrate diets (2.4P-12S) ingested a larger volume of diet, fed for longer (both around 1.7x) and increased the interval between feedings compared with hummingbirds fed diets 0.8P-36S. Physiological regulation between feeding events, on the other hand, was achieved through an increase in metabolic rate for low protein-high sugar diets (0.8P-36S). This response could probably be related to high sucrose assimilation rates through the digestive system of hummingbirds, a process already known to be very efficient in these birds. Additionally, there was a steeper decrease in oxygen consumption for hummingbirds fed diets 2.4P-12S during fasting and a suggestion of a higher torpor incidence in birds fed these diets
ABSTRACT The effects of ambient pH on postmoult net fluxes of Ca, acidic/basic equivalents (H+, NH4+/OH−, HCO3−), Na and Cl−, total body Ca, haemolymph pH and electrolyte status were assessed in the ...freshwater crayfish Procambarus clarkii (Girard). Variables were monitored for 5 days postmoult in acidic (pH5.2; H2SO4) or alkaline (pH9.2; KOH) artificial tap water (ATW) and compared with those in control (pH7.4) tap water. In control ATW there was an initial net influx of Ca (+2700 μmolkg−1 h−1) and titratable basic equivalents (+5000 μmolkg−1 h−1) that declined with time. Calcium uptake accounted for 40% of total body Ca (0.49mmol g−1); haemolymph Ca concentration remained constant. Haemolymph pH was initially relatively alkalotic (7.7) but recovered within 24h. A 20% haemolymph dilution by water uptake at ecdysis necessitated uptake of Cl− and Na for the first 2–3 days postmoult (+1000 μmolkg−1 h−). In acidic ATW, Ca and basic equivalent uptake were both 60% reduced during the first 3–4 days and total body Ca was reduced by 37%. Chloride and Na uptake and haemolymph Cl− were decreased. In alkaline ATW, Ca and basic equivalent uptake were elevated by 30% for the first 2 days and haemolymph alkalosis was maintained. Sodium and Cl−balance were unaffected. Thus, ambient pH affects Ca and basic equivalent fluxes associated with postmoult calcification. Regulation of Na and Cl−levels is also impaired in acidic ATW.
Crayfish develop directly from 0.003 g hatchlings to 100 g adults providing an ideal species in which to study intraspecific allometries. Most size relationships are based on interspecific data. The ...allometric relation for mass specific O sub(2) uptake had an exponent of -0.21. The present study addressed the allometry of net postmolt ion fluxes in Procambarus clarkii) (0.03 -23.8 g). Double logarithmic plots of initial (first 24 h postmolt) mass specific flux rate versus mass yielded exponents of -0.20 for titratable based and Cl uptake. Ammonia output had an exponent of -0.16 and Na and Ca uptake had exponents of -0.11. The mass coefficient (intercept at 1 g mass in mu mol/kg/h) was calculated as 3962 and 2242 for titratable base and Ca uptake respectively and around 600 for Na and Cl uptake and ammonia excretion. Analysis of the time-course of calcification revealed that calcification was 50% complete within 1 day in small crayfish (0.06 g) whereas medium (1.99 g) and large animals (14.9 g) required 3 and 5 days respectively.
Lithium disilicates are commercially important and among the most widely studied and well-characterized glass-ceramics, but their toughening mechanism – and those of most glass-ceramics – is still ...unknown. In this work, stoichiometric lithium disilicate glasses were used as a model system and crystallized using carefully designed and controlled two-stage heat treatments to give different crystallized volume fractions while maintaining a constant grain size of approximately 12μm. This original procedure allowed us to separately control the effects of these two microstructural parameters on the mechanical properties of the glass-ceramic. The hardness, elastic modulus, four-point bending strength, indentation fracture toughness and double-torsion fracture toughness were measured for samples with different crystallized volume fractions, ranging from the parent glass to fully crystallized samples. We found that the bending strength increases rapidly with crystallization at crystal volume fractions below 10% and reaches a value 2.5 times greater than that of the original glass. For a fully crystallized sample, the fracture toughness increases almost fivefold, from 0.75 to 3.5MPa.m1/2. Laser confocal microscopy was used to reveal the topography of the fracture surfaces. Three mechanisms that contribute to toughening – crack deflection, crack bowing and trapping, and crack bridging – were evaluated. A model incorporating the elastic modulus, crystal fracture toughness and crystallized volume fraction was proposed and successfully tested to explain the increased fracture toughness with crystallized volume fraction for the full range of crystallization in LS2 glass-ceramics.
Zika virus (ZIKV) is a flavivirus that is responsible for the current epidemic in Brazil and the Americas. ZIKV has been causally associated with fetal microcephaly, intrauterine growth restriction, ...and other birth defects in both humans and mice. The rapid development of a safe and effective ZIKV vaccine is a global health priority, but very little is currently known about ZIKV immunology and mechanisms of immune protection. Here we show that a single immunization with a plasmid DNA vaccine or a purified inactivated virus vaccine provides complete protection in susceptible mice against challenge with a strain of ZIKV involved in the outbreak in northeast Brazil. This ZIKV strain has recently been shown to cross the placenta and to induce fetal microcephaly and other congenital malformations in mice. We produced DNA vaccines expressing ZIKV pre-membrane and envelope (prM-Env), as well as a series of deletion mutants. The prM-Env DNA vaccine, but not the deletion mutants, afforded complete protection against ZIKV, as measured by absence of detectable viraemia following challenge, and protective efficacy correlated with Env-specific antibody titers. Adoptive transfer of purified IgG from vaccinated mice conferred passive protection, and depletion of CD4 and CD8 T lymphocytes in vaccinated mice did not abrogate this protection. These data demonstrate that protection against ZIKV challenge can be achieved by single-shot subunit and inactivated virus vaccines in mice and that Env-specific antibody titers represent key immunologic correlates of protection. Our findings suggest that the development of a ZIKV vaccine for humans is likely to be achievable.
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