The Heumann-Hotzel model for aging revisited

Since its proposition in 1995, the Heumann-Hotzel model has remained as an obscure model of biological aging. The main arguments used against it were its apparent inability to describe populations with many age intervals and its failure to prevent a population extinction when only deleterious mutations are present. We find that with a simple and minor change in the model these difficulties can be surmounted. Our numerical simulations show a plethora of interesting features: the catastrophic senescence, the Gompertz law and that postponing the reproduction increases the survival probability, as has already been experimentally confirmed for the Drosophila fly.Comment: 11 pages, 5 figures, to be published in Phys. Rev.

Sialic acid specific lectins from Episesarma tetragonum (Decapoda, Grapsidae): isolation, purification and characterization

Two sialic acid specific lectins Episesarma tetragonum agglutinin–1 and 2 were purified from the hemolymph of the Mangrove crab, Episesarma tetragonum. The major lectin was purified using CNBr-activated sepharose 4B conjugated to fetuin. N-acetyl glucosamine containing buffer was used for elution. The hemagglutination activity of purified lectin was inhibited by glycoproteins containing Siaα, 2-3Galβ, 1-4 GlcNAc linkages. On SDS-PAGE, the molecular weight of calcium dependent lectin was observed to be 70 kDa. Lectin had the maximum activity at a wide range of pH (6.5 – 9.5) and temperature (0 - 40 °C).  The physicochemical characteristics of the minor agglutinin showed that its hemagglutinating activity was calcium dependent, optimum at pH 8 – 9.5 and temperature 0 – 37 °C. The only potent inhibitor of minor lectin was bovine submaxillary mucin. An attempt was also made to purify minor lectin by affinity chromatography using bovine submaxillary mucin coupled to CNBr-activated sepharose 4B column. The lectin was eluted with elution buffer containing ethylene diamine tetra acetate. Strong inhibition of purified minor lectin by bovine submaxillary mucin and non-inhibitory action of de-O-acetylated bovine submaxillary mucin suggested that the lectin was O-acetyl sialic acid specific

Perturbations in growth trajectory due to early diet affect age-related deterioration in performance

Fluctuations in early developmental conditions can cause changes in growth trajectories that subsequently affect the adult phenotype. Here, we investigated whether compensatory growth has long-term consequences for patterns of senescence. Using three-spined sticklebacks (Gasterosteus aculeatus), we show that a brief period of dietary manipulation in early life affected skeletal growth rate not only during the manipulation itself, but also during a subsequent compensatory phase when fish caught up in size with controls. However, this growth acceleration influenced swimming endurance and its decline over the course of the breeding season, with a faster decline in fish that had undergone faster growth compensation. Similarly, accelerated growth led to a more pronounced reduction in the breeding period (as indicated by the duration of sexual ornamentation) over the following two breeding seasons, suggesting faster reproductive senescence. Parallel experiments showed a heightened effect of accelerated growth on these age-related declines in performance if the fish were under greater time stress to complete their compensation prior to the breeding season. Compensatory growth led to a reduction in median life span of 12% compared to steadily growing controls. While life span was independent of the eventual adult size attained, it was negatively correlated with the age-related decline in swimming endurance and sexual ornamentation. These results, complementary to those found when growth trajectories were altered by temperature rather than dietary manipulations, show that the costs of accelerated growth can last well beyond the time over which growth rates differ and are affected by the time available until an approaching life-history event such as reproduction

Linear Amplifier Breakdown and Concentration Properties of a Gaussian Field Given that its L2\bm{L^2}-Norm is Large

In the context of linear amplification for systems driven by the square of a Gaussian noise, we investigate the realizations of a Gaussian field in the limit where its $L^2$-norm is large. Concentration onto the eigenspace associated with the largest eigenvalue of the covariance of the field is proved. When the covariance is trace class, the concentration is in probability for the $L^2$-norm. A stronger concentration, in mean for the sup-norm, is proved for a smaller class of Gaussian fields, and an example of a field belonging to that class is given. A possible connection with Bose-Einstein condensation is briefly discussed.Comment: REVTeX file, 11 pages, 1 added paragraph in the introduction, 2 added references, minor modifications in the text and abstract, submitted to J. Stat. Phy

Wheat sample affects growth performance and the apparent metabolisable energy value for broiler chickens

The aim of this study was to examine chemical composition, quality characteristics, apparent metabolisable energy (AME) and nutrient utilisation of wheat samples currently available to the UK poultry industry and their effect on broiler growth performance. Seventeen current UK wheat samples were used to formulate 17 diets, all of which included 670 g/kg of each wheat sample and 330 g/kg of a balancer feed. Eight hundred (800), day old male Ross 308 broilers were allocated randomly to 160 raised floor pens. Each diet was replicated eight times, fed ad libitum from 0 to 21d age in a randomised complete block design. Excreta were quantitatively collected during the last three days for AME determination. The content of protein, ash and gross energy (GE) ranged from 97 to 143 g/kg DM, 12.8 to 19.6 g/kg DM and 17.81 to 18.24 MJ/kg DM, respectively. The amount of starch and total non-starch polysaccharides (NSP) ranged from 671 to 728 and 80.1 to 98.2 g/kg DM, respectively. The quality characteristics of wheat samples were in the expected range. There were differences (P<0.05) in AME and AMEn of wheat samples. The AME of the wheat had a maximum range of 1.13 MJ/kg DM between samples. Dry matter retention (DMR) and fat digestibility (FD) were significantly different (P<0.05) between wheat samples. The daily feed intake (FI) and weight gain (WG) of broilers fed two wheat samples were significantly (P<0.05) lower as compared to other samples and their low FI and WG were not related to their chemical composition and quality characteristics. The ash content of wheat samples was negatively associated with AMEn (r = − 0.489, P<0.05). The coefficient of FD was positively related to AMEn (r = 0.552, P<0.05). Chemical composition and quality characteristics of the wheat did not relate (P>0.05) to FI and WG of broilers. There was no relationship between growth performance of broilers and AMEn of the wheat samples

Genetic partitioning of interleukin-6 signalling in mice dissociates Stat3 from Smad3-mediated lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal disease that is unresponsive to current therapies and characterized by excessive collagen deposition and subsequent fibrosis. While inflammatory cytokines, including interleukin (IL)-6, are elevated in IPF, the molecular mechanisms that underlie this disease are incompletely understood, although the development of fibrosis is believed to depend on canonical transforming growth factor (TGF)-β signalling. We examined bleomycin-induced inflammation and fibrosis in mice carrying a mutation in the shared IL-6 family receptor gp130. Using genetic complementation, we directly correlate the extent of IL-6-mediated, excessive Stat3 activity with inflammatory infiltrates in the lung and the severity of fibrosis in corresponding gp130757F mice. The extent of fibrosis was attenuated in B lymphocyte-deficient gp130757F;µMT−/− compound mutant mice, but fibrosis still occurred in their Smad3−/− counterparts consistent with the capacity of excessive Stat3 activity to induce collagen 1α1 gene transcription independently of canonical TGF-β/Smad3 signalling. These findings are of therapeutic relevance, since we confirmed abundant STAT3 activation in fibrotic lungs from IPF patients and showed that genetic reduction of Stat3 protected mice from bleomycin-induced lung fibrosis

Spin in relativistic quantum theory

We discuss the role of spin in Poincar\'e invariant formulations of quantum mechanics.Comment: 54 page

Evaluating use cases for human challenge trials in accelerating SARS-CoV-2 vaccine development

Human challenge trials (HCTs) have been proposed as a means to accelerate SARS-CoV-2 vaccine development. We identify and discuss three potential use cases of HCTs in the current pandemic: evaluating efficacy, converging on correlates of protection, and improving understanding of pathogenesis and the human immune response. We outline the limitations of HCTs and find that HCTs are likely to be most useful for vaccine candidates currently in preclinical stages of development. We conclude that, while currently limited in their application, there are scenarios in which HCTs would be extremely beneficial. Therefore, the option of conducting HCTs to accelerate SARS-CoV-2 vaccine development should be preserved. As HCTs require many months of preparation, we recommend an immediate effort to (1) establish guidelines for HCTs for COVID-19; (2) take the first steps toward HCTs, including preparing challenge virus and making preliminary logistical arrangements; and (3) commit to periodically re-evaluating the utility of HCTs

Effect of age on the relationship between metabolizable energy and digestible energy for broiler chickens

A total of 960 male Ross 308 chicks (day-old) were used to investigate the effect of age on the relationship between metabolizable energy (ME) and digestible energy (DE) for broiler chickens. Bird growth variables, nitrogen retention (NR), nitrogen digestibility (ND), as well as the relative weight of liver, pancreas, and the gastrointestinal tract were determined. Practical diets that compared 2 cereals (corn and wheat) and exogenous xylanase (0 or 16,000 BXU/kg) were evaluated at 5 ages (7, 14, 21, 28, and 35 D) in a 2 × 2 × 5 factorial arrangement of treatments with 8 replicates per treatment and started with 30 birds per replicate. A randomized block ANOVA analysis of repeated measures was performed, and a 2 × 2 × 5 factorial structure was used to investigate the 2 dietary treatment factors (cereal type and the presence of xylanase) within the 5 bird ages (7, 14, 21, 28, and 35 D), and their interactions. Apparent metabolizable energy (AME) increased linearly from 7 until 28 D of age, but (P 0.05) from 14 to 35 D of age. The AME: DE ratio was lowest (P 0.05) differences thereafter. Cereal type and xylanase supplementation did not (P > 0.05) change the ME: DE ratio. The results indicate that determining ME before 14 D of age may give absolute values that are lower than would be obtained with older birds. ME values that are determined on older broiler chickens may overestimate the energy availability of practical feeds used in broiler starter feeds