Effects of fasting and nutritional restriction on the isotopic ratios of nitrogen and carbon: a meta‐analysis

Many organisms experience fasting in their life time, and this physiological process has the potential to alter stable isotope values of organisms, and confound interpretation of food web studies. However, previous studies on the effects of fasting and starvation on stable isotopes show disparate results, and have never been quantitatively synthesized. We performed a laboratory experiment and meta‐analysis to determine how stable isotopes of δ¹⁵N and δ¹³C change with fasting, and we tested whether moderators such as taxa and tissue explain residual variation. We collected literature data from a wide variety of taxa and tissues. We surveyed over 2000 papers, and of these, 26 met our selection criteria, resulting in 51 data points for δ¹⁵N, and 43 data points for δ¹³C. We determine that fasting causes an average increase in the isotopic value of organisms of 0.5‰ for δ¹⁵N and that the only significant moderator is tissue type. We find that the overall effect size for δ¹³C is not significant, but when the significant moderator of tissue is considered, significant increases in blood and whole organisms are seen with fasting. Our results show that across tissues and taxa, the nutritional status of an organism must be considered when interpreting stable isotope data, as fasting can cause large differences in stable isotope values that would be otherwise attributed to other factors.     

Effect of temperature and arsenic on Aeromonas hydrophila growth,a modelling approach

Aeromonas hydrophila is frequently reported from arsenic affected areas. Present study was aimed to determine the effect of arsenic and temperature on growth of A. hydrophila. The bacteria were isolated from naturally infected fish from a water body in Birbhum, West-Bengal, India, which is reported to be an arsenic-free area. Arsenic concentration in natural aquatic reservoirs (e.g., pond, lake or river) varies from 0–6 mg/L. No significant change in bacterial growth was observed within this range of arsenic exposure. However, variation in temperature impacted the growth of A. hydrophila. A single dimension model was constructed using simple logistic equation. Rate parameters of the model were derived from the experimental observations. Comparison of model results and laboratory observations gives a good conformity regarding the effect of variation of arsenic concentration and temperature change on growth of this bacterium. From the analysis of this model we further get the idea that the maximum growth of A. hydrophila is supposed to be at 31.4°C in absence of arsenic, whereas at 477 mg/L arsenic concentration, the growth of the bacteria totally stops at 30°C.     

Nonstructural proteins of respiratory syncytial virus suppress premature apoptosis by an NF-kappaB-dependent, interferon-independent mechanism and facilitate virus growth

The two nonstructural (NS) proteins NS1 and NS2 of respiratory syncytial virus (RSV) are abundantly expressed in the infected cell but are not packaged in mature progeny virions. We found that both proteins were expressed early in infection, whereas the infected cells underwent apoptosis much later. Coincident with NS protein expression, a number of cellular antiapoptotic factors were expressed or activated at early stages, which included NF-kappaB and phosphorylated forms of protein kinases AKT, phosphoinositide-dependent protein kinase, and glycogen synthase kinase. Using specific short interfering RNAs (siRNAs), we achieved significant knockdown of one or both NS proteins in the infected cell, which resulted in abrogation of the antiapoptotic functions and led to early apoptosis. NS-dependent suppression of apoptosis was observed in Vero cells that are naturally devoid of type I interferons (IFN). The siRNA-based results were confirmed by the use of NS-deleted RSV mutants. Early activation of epidermal growth factor receptor (EGFR) in the RSV-infected cell did not require NS proteins. Premature apoptosis triggered by the loss of NS or by apoptosis-promoting drugs caused a severe reduction of RSV growth. Finally, recombinantly expressed NS1 and NS2, individually and together, reduced apoptosis by tumor necrosis factor alpha, suggesting an intrinsic antiapoptotic property of both. We conclude that the early-expressed nonstructural proteins of RSV boost viral replication by delaying the apoptosis of the infected cell via a novel IFN- and EGFR-independent pathway.     

Evaluation of the impact of shielding materials in radiation protection in transgenic animals

We are using a plasmid-based transgenic mouse mutation model system to evaluate the effectiveness of aluminum or low-density polyethylene (LDPE) shielding after 250 MeV/u protons or 1 GeV/u iron ion irradiation. Transgenic mice, with multiple copies of the plasmid pUR288 lacZ transgene integrated into the genome of every cell of the animal, were either irradiated or sham-treated. Multiple endpoints, including early cytogenetic damage in erythrocytes at 48 h after exposure, chromosome aberrations in bone marrow lymphocytes, and lacZ mutant frequencies (MF) in brain and spleen tissues were measured in the same animals. The frequency of total circulating reticulocytes (fRET) dropped precipitously at 48 h after 2 Gy of proton irradiation. The average level of micronucleated reticulocytes (fMN–RET) was fivefold higher in the irradiated samples relative to the controls at the same time point. There was an increase in total chromosome aberrations in bone marrow lymphocytes at 8 weeks after proton irradiation but this increase was not statistically significant relative to the controls. Evaluation of the lacZ MF in the brain and spleen tissues showed that proton irradiation induced a twofold increase in MF in each tissue. Similar samples were collected from animals that were shielded from the proton beam by aluminum. Compared to the unshielded treatment group, we noted no difference in fRET, fMN–RET, chromosome aberrations in lymphocytes and lacZ MF in brain and spleen tissues obtained from these animals. In a separate study, animals were exposed to high-energy iron ions with or without 10 or 15 cm LDPE. Using the same approach, we noted a precipitous drop in fRET, and an elevation in fMN–RET within 48 h after 1 Gy of iron ions. Total chromosome aberrations in bone marrow lymphocytes were slightly elevated but not significant at 8 weeks after iron ion exposure. Shielding animals with 10 or 15 cm of polyethylene appeared to have no effect on the level of RET, MN–RET or chromosome aberrations in these animals. LacZ MF in brain and spleen tissues increased 1.5–2-fold above control levels after 1 Gy iron ions at 8 weeks after treatment. On the other hand, MF in tissues harvested from shielded animals appeared to be lower than their unshielded litermates, suggesting the polyethylene shielding was effective in reducing the iron-induced genomic damage in tissues. Although shielding may be effective, in some cases, in reducing the physical dose of particle radiation, our cytogenetic results showed that the biological impact of the particle beam remain unchanged. On the other hand, reduction in transgene MF in tissues from LDPE-shielded animals but not in the aluminum-shielded animals strongly suggests that careful consideration of the biological endpoints used is necessary in the evaluation of the efficacy of the selected shielding material.     

Phosphorus availability to rice (Oriza sativa L.)-wheat (Triticum estivum L.) in a Vertisol after eight years of inorganic and organic fertilizer additions

Integrated use of inorganic fertilizer N and well decomposed cattle manure (CM) or 30-35 days old Parthenium (Parthenium hysterophorus L.), a weed grown off site as green manure (GM) under repeated applications of fertilizer P and urea N for eight years in a rice (Oriza sativa L.)-wheat (Triticum estivum L.) sequence was studied on transformation of fertilizer P applied to soil at the National Research Center for Weed Science, Jabalpur, India. Based on the results, it appeared that, repeated applications of 52 kg super-phosphate P resulted in a marked increase in Olsen P linearly with time. Conjunctive use of urea fertilizer N with organic manure resulted in a larger increase in Olsen P in the Vertisol. Studies further revealed that the greater accumulation of fertilizer P applied in excess to crop removal occurred in inorganic P in the plots receiving only fertilizer N. However, plots receiving fertilizer N along with organic manures led to P accumulation predominantly in organic forms. The study suggests that these two pools of P acted as a sink when fertilizer P was applied in excess to crop removal and are bio-chemically active. The Olsen P status after 8 cycles of rice-wheat crops revealed that the average amount of fertilizer P required after adjusting for crop uptake to increase Olsen P by 1 mg kg(-1) soil was 7.2 kg Pha(-1) in the plots receiving only fertilizer N. Whereas, application of 5t FYM or 6t GM reduced it to 4.6 kg Pha(-1). The plots receiving manure always maintained a greater concentration of Olsen P. The application of CM or GM with fertilizer N enriched short-term inorganic P as well as long-term organic P fertility. After eight years, larger concentrations of organic P in the subsurface layer (16-30 cm), compared to initial values, indicates downward movement of P in organic forms.     

Human ribosomal protein L13a is dispensable for canonical ribosome function but indispensable for efficient rRNA methylation

Previously, we demonstrated that treatment of monocytic cells with IFN-gamma causes release of ribosomal protein L13a from the 60S ribosome and subsequent translational silencing of Ceruloplasmin (Cp) mRNA. Here, evidence using cultured cells demonstrates that Cp mRNA silencing is dependent on L13a and that L13a-deficient ribosomes are competent for global translational activity. Human monocytic U937 cells were stably transfected with two different shRNA sequences for L13a and clonally selected for more than 98% abrogation of total L13a expression. Metabolic labeling of these cells showed rescue of Cp translation from the IFN-gamma mediated translational silencing activity. Depletion of L13a caused significant reduction of methylation of ribosomal RNA and of cap-independent translation mediated by Internal Ribosome Entry Site (IRES) elements derived from p27, p53, and SNAT2 mRNAs. However, no significant differences in the ribosomal RNA processing, polysome formation, global translational activity, translational fidelity, and cell proliferation were observed between L13a-deficient and wild-type control cells. These results support the notion that ribosome can serve as a depot for releasable translation-regulatory factors unrelated to its basal polypeptide synthetic function. Unlike mammalian cells, the L13a homolog in yeast is indispensable for growth. Thus, L13a may have evolved from an essential ribosomal protein in lower eukaryotes to having a role as a dispensable extra-ribosomal function in higher eukaryotes.     

Roles of the negatively charged N-terminal extension of Saccharomyces cerevisiae ribosomal protein S5 revealed by characterization of a yeast strain containing human ribosomal protein S5

Ribosomal protein (rp) S5 belongs to a family of ribosomal proteins that includes bacterial rpS7. rpS5 forms part of the exit (E) site on the 40S ribosomal subunit and is essential for yeast viability. Human rpS5 is 67% identical and 79% similar to Saccharomyces cerevisiae rpS5 but lacks a negatively charged (pI approximately 3.27) 21 amino acid long N-terminal extension that is present in fungi. Here we report that replacement of yeast rpS5 with its human homolog yielded a viable yeast strain with a 20%-25% decrease in growth rate. This replacement also resulted in a moderate increase in the heavy polyribosomal components in the mutant strain, suggesting either translation elongation or termination defects, and in a reduction in the polyribosomal association of the elongation factors eEF3 and eEF1A. In addition, the mutant strain was characterized by moderate increases in +1 and -1 programmed frameshifting and hyperaccurate recognition of the UAA stop codon. The activities of the cricket paralysis virus (CrPV) IRES and two mammalian cellular IRESs (CAT-1 and SNAT-2) were also increased in the mutant strain. Consistently, the rpS5 replacement led to enhanced direct interaction between the CrPV IRES and the mutant yeast ribosomes. Taken together, these data indicate that rpS5 plays an important role in maintaining the accuracy of translation in eukaryotes and suggest that the negatively charged N-terminal extension of yeast rpS5 might affect the ribosomal recruitment of specific mRNAs.     

Pathogenic Potential,Genetic Diversity,and Population Structure of Escherichia coli Strains Isolated from a Forest-Dominated Watershed (Comox Lake) in British Columbia,Canada

Escherichia coli isolates (n = 658) obtained from drinking water intakes of Comox Lake (2011 to 2013) were screened for the following virulence genes (VGs): stx₁ and stx₂ (Shiga toxin-producing E. coli [STEC]), eae and the adherence factor (EAF) gene (enteropathogenic E. coli [EPEC]), heat-stable (ST) enterotoxin (variants STh and STp) and heat-labile enterotoxin (LT) genes (enterotoxigenic E. coli [ETEC]), and ipaH (enteroinvasive E. coli [EIEC]). The only genes detected were eae and stx₂, which were carried by 37.69% (n = 248) of the isolates. Only eae was harbored by 26.74% (n = 176) of the isolates, representing potential atypical EPEC strains, while only stx₂ was detected in 10.33% (n = 68) of the isolates, indicating potential STEC strains. Moreover, four isolates were positive for both the stx₂ and eae genes, representing potential EHEC strains. The prevalence of VGs (eae or stx₂) was significantly (P < 0.0001) higher in the fall season, and multiple genes (eae plus stx₂) were detected only in fall. Repetitive element palindromic PCR (rep-PCR) fingerprint analysis of 658 E. coli isolates identified 335 unique fingerprints, with an overall Shannon diversity (H′) index of 3.653. Diversity varied among seasons over the years, with relatively higher diversity during fall. Multivariate analysis of variance (MANOVA) revealed that the majority of the fingerprints showed a tendency to cluster according to year, season, and month. Taken together, the results indicated that the diversity and population structure of E. coli fluctuate on a temporal scale, reflecting the presence of diverse host sources and their behavior over time in the watershed. Furthermore, the occurrence of potentially pathogenic E. coli strains in the drinking water intakes highlights the risk to human health associated with direct and indirect consumption of untreated surface water.