Long‐term tree fern dynamics linked to disturbance and shade tolerance

Question: Do New Zealand tree ferns have recognizable shade tolerance niches? Location: Lowland temperate rain forest of New Zealand (41°20′S, 174°58′E). Methods: Growth, death and recruitment of five tree fern species were estimated from a 38‐year record of stem heights, collected within a 2.25‐ha block of forest, and electron transport rates (ETR) of photosystem II of fronds were measured. Results: Two species of Cyathea were comparatively common (603 and 351 stems in total) and two were comparatively rare (155 and 17 stems in total) on the site. The common species had lower rates of growth, recruitment and mortality than the rare species, had skewed age distributions typical of shade‐tolerant species and were probably recruited soon after a catastrophic earthquake in 1855. The two rare species were failing to recruit under closed forests; their age distributions indicated that all had regenerated long after the earthquake. ETR were higher for faster‐growing than for the shade‐tolerant species. A tree fern that regenerates vegetatively from aerial buds, Dicksonia squarrosa, was common on the site (361 stems in total). Its age distribution suggested it was relatively shade tolerant, but its mortality and recruitment rates were much higher than those of the two shade‐tolerating Cyathea species, suggesting that this multi‐stemmed species functions differently from the monopodial Cyathea species. Conclusions: New Zealand Cyathea tree ferns occupy distinct niches along a shade tolerance spectrum and their relative abundances are strongly influenced by disturbance history. The study provides evidence that tree fern species differ strongly in their responses to canopy disturbance and are not ecologically equivalent.     

Interaction of a Partially Disordered Antisigma Factor with Its Partner,the Signaling Domain of the TonB-Dependent Transporter HasR

Bacteria use diverse signaling pathways to control gene expression in response to external stimuli. In Gram-negative bacteria, the binding of a nutrient is sensed by an outer membrane transporter. This signal is then transmitted to an antisigma factor and subsequently to the cytoplasm where an ECF sigma factor induces expression of genes related to the acquisition of this nutrient. The molecular interactions involved in this transmembrane signaling are poorly understood and structural data on this family of antisigma factor are rare. Here, we present the first structural study of the periplasmic domain of an antisigma factor and its interaction with the transporter. The study concerns the signaling in the heme acquisition system (Has) of Serratia marcescens. Our data support unprecedented partially disordered periplasmic domain of an anti-sigma factor HasS in contact with a membrane-mimicking environment. We solved the 3D structure of the signaling domain of HasR transporter and identified the residues at the HasS−HasR interface. Their conservation in several bacteria suggests wider significance of the proposed model for the understanding of bacterial transmembrane signaling.     

Metabolic Profiling of Alternative NAD Biosynthetic Routes in Mouse Tissues

NAD plays essential redox and non-redox roles in cell biology. In mammals, its de novo and recycling biosynthetic pathways encompass two independent branches, the “amidated” and “deamidated” routes. Here we focused on the indispensable enzymes gating these two routes, i.e. nicotinamide mononucleotide adenylyltransferase (NMNAT), which in mammals comprises three distinct isozymes, and NAD synthetase (NADS). First, we measured the in vitro activity of the enzymes, and the levels of all their substrates and products in a number of tissues from the C57BL/6 mouse. Second, from these data, we derived in vivo estimates of enzymes''rates and quantitative contributions to NAD homeostasis. The NMNAT activity, mainly represented by nuclear NMNAT1, appears to be high and nonrate-limiting in all examined tissues, except in blood. The NADS activity, however, appears rate-limiting in lung and skeletal muscle, where its undetectable levels parallel a relative accumulation of the enzyme''s substrate NaAD (nicotinic acid adenine dinucleotide). In all tissues, the amidated NAD route was predominant, displaying highest rates in liver and kidney, and lowest in blood. In contrast, the minor deamidated route showed higher relative proportions in blood and small intestine, and higher absolute values in liver and small intestine. Such results provide the first comprehensive picture of the balance of the two alternative NAD biosynthetic routes in different mammalian tissues under physiological conditions. This fills a gap in the current knowledge of NAD biosynthesis, and provides a crucial information for the study of NAD metabolism and its role in disease.     

Rho-kinase inhibition improves vasodilator responsiveness during hyperinsulinemia in the metabolic syndrome

In patients with the metabolic syndrome (MetS), the facilitatory effect of insulin on forearm vasodilator responsiveness to different stimuli is impaired. Whether the RhoA/Rho kinase (ROCK) pathway is involved in this abnormality is unknown. We tested the hypotheses that, in MetS patients, ROCK inhibition with fasudil restores insulin-stimulated vasodilator reactivity and that oxidative stress plays a role in this mechanism. Endothelium-dependent and -independent forearm blood flow responses to acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were assessed in MetS patients (n = 8) and healthy controls (n = 5) before and after the addition of fasudil (200 μg/min) to an intra-arterial infusion of insulin (0.1 mU/kg/min). In MetS patients (n = 5), fasudil was also infused without hyperinsulinemia. The possible involvement of oxidative stress in the effect of fasudil during hyperinsulinemia was investigated in MetS patients (n = 5) by infusing vitamin C (25 mg/min). In MetS patients, compared with saline, fasudil enhanced endothelium-dependent and -independent vasodilator responses during insulin infusion (P < 0.001 and P = 0.008, respectively), but not in the absence of hyperinsulinemia (P = 0.25 and P = 0.13, respectively). By contrast, fasudil did not affect vasoreactivity to ACh and SNP during hyperinsulinemia in controls (P = 0.11 and P = 0.56, respectively). In MetS patients, fasudil added to insulin and vitamin C did not further enhance vasodilation to ACh and SNP (P = 0.15 and P = 0.43, respectively). In the forearm circulation of patients with the MetS, ROCK inhibition by fasudil improves endothelium-dependent and -independent vasodilator responsiveness during hyperinsulinemia; increased oxidative stress seems to be involved in the pathophysiology of this phenomenon.     

Alterations in Phosphorylation of Hepatocyte Ribosomal Protein S6 Control Plasmodium Liver Stage Infection

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Human Parechovirus Genotypes -10, -13 and -15 in Pakistani Children with Acute Dehydrating Gastroenteritis

Human parechoviruses are known to cause asymptomatic to severe clinical illness predominantly respiratory and gastroenetric infections. Despite their global prevalence, epidemiological studies have not been performed in Pakistan. In this study, we retrospectively analyzed 110 fecal specimen and found 26 (24%) positive for viral RNA with HPeV-10 (n = 3, 23%), HPeV-13 (n = 4, 31%) and HPeV-15 (n = 6, 46%) genotypes. Clinical features of patients with different HPeV genotypes were compared. All HPeV positive children were aged ≤4 years (mean 13.92 months). The male-to-female ratio was 1: 1.17 (46.2 vs 53.8%) with significant association (p = .031) to HPeV infectivity. HPeV-10 and -13 were found during summer while HPeV-15 was only detected during late winter season. Disease symptoms were more severe in children infected with HPeV-10 and -13 as compared to HPeV-15. Fever and vomiting were observed in 100% cases of HPeV-10 and -13 while only 17% patients of HPeV-15 had these complaints. Phylogenetic analyses showed that HPeV-10, -13 and -15 strains found in this study have 9–13%, 16.8% and 21.8% nucleotide divergence respectively from the prototype strains and were clustered to distinct genetic lineages. This is the first report of HPeV-15 infection in humans although first identified in rhesus macaques. The arginine-glycine-aspartic acid (RGD) motif present at the C-terminal of VP1 responsible for the viral attachment to cellular integrins was not found in all of these strains. In conclusion, these findings enhance our knowledge related to the epidemiology and genetic diversity of the HPeV in Pakistan and support the need for continued laboratory based surveillance programs especially in infants and neonatal clinical settings. Further, the parechovirus pathogenesis, cross-species transmission and disease reservoirs must be ascertained to adopt better prevention measures.     

Geometric morphometrics of carapace of Macrobrachium australe (Crustacea: Palaemonidae) from Reunion Island

Zimmermann, G., Bosc, P., Valade, P., Cornette, R., Améziane, N. and Debat, V. 2011. Geometric morphometrics of carapace of Macrobrachium australe (Crustacea: Palaemonidae) from Reunion Island. —Acta Zoologica (Stockholm) 93 : 492–500. We investigated the structure of carapace shape variation in six populations of Macrobrachium australe Guérin‐Méneville 1838 (Crustacea: Decapoda: Palaemonidae) from Reunion Island (Indian Ocean) freshwaters. The morphometric analysis revealed the occurrence of two morphotypes corresponding to two different types of habitats. Individuals living in lotic habitats present a thick carapace armed with a short, robust and straight rostrum, while individuals from lentic habitats have a slender carapace armed with a thin long rostrum orientated upward. This difference suggests an adaptation to lotic disturbances and is tentatively interpreted as adaptive phenotypic plasticity. In such amphidromous organisms regressing to freshwaters after a marine larval phase, selection for physiological and developmental flexibility might facilitate further adaptation and allows the colonisation of a wide panel of environmentally different and sometimes geographically distant insular streams.     

Kinetic and analytical study of the photo-induced degradation of monuron by nitrates and nitrites under irradiation or in the dark

The photo-induced transformation of monuron (3-(4-chlorophenyl)-1,1 dimethylurea) was investigated in an aqueous solution containing nitrates and nitrites at 310 nm and 365 nm, respectively. In both NO(3)(-) and NO(2)(-) conditions, the degradation of monuron followed pseudo-first order kinetics. The intermediate products were identified by GC-MS, and the nitration, hydroxylation and coupling reactions were determined. In addition, the oxidation of the N-terminus group, the substitution of chlorine by ˙OH and the nitration by ˙NO(2) radical onto the phenyl ring were observed. The photo-induced transformation of monuron was studied under variable conditions of pH, inducer concentration, substrate concentration, humic acids, oxygen content and salts used as hydroxyl radical scavengers. The photodegradation rates were strongly influenced by all the above parameters. The degradation of monuron was also studied in the dark and in the presence of NO(2)(-) as well as in an aqueous solution with the addition of hydrogen peroxide.     

New protein clustering of breast cancer tissue proteomics using actin content as a cellularity indicator

In the present study, we report the comparative proteome profiles of proteins solubilized from 37 breast cancer surgical tissues, normalized for the actin content. Blood-derived proteins were excluded from the analysis. Among the tumor-derived protein spots, a large proportion (39%) was found present in all patients. These included several glycolytic enzymes, detox and heat shock proteins, members of annexin and S100 protein families, cathepsin D, and two "rare" proteins, DDAH2 involved in the angiogenesis control, and the oncogene PARK7. Other proteins, such as psoriasin, galectin1, cofilin, peroredoxins, SH3L1, and others, showed sporadic presence and high expression level, which suggests their possible role for patient stratification.     

Electrocommunication behaviour and non invasively-measured androgen changes following induced seasonal breeding in the weakly electric fish, Apteronotus leptorhynchus

Androgens are known to be involved in reproductive behaviours including courtship and aggression. According to the Challenge Hypothesis, androgen activity upregulates male reproductive behaviour seasonally and also modulates short term adaptation of these behaviours in response to social context. In the weakly electric fish, Apteronotus leptorhynchus, 11-ketotestosterone (11-KT) has been previously implicated in the regulation of electrocommunication behaviours that are believed to have roles in both aggression and courtship. Changes in male 11-KT levels were quantified using a non-invasive measurement technique alongside changes in electrocommunication behaviour following environmental cues that simulated the onset of the breeding season. Males showed an increase in mean electric organ discharge frequency (EODf), which is consistent with earlier results showing a female preference for high EODf. A subset of males with high initial EODfs showed increases in both 11-KT and EODf, which provides support for an EODf-based dominance hierarchy in this species. Males housed in social conditions and exposed to breeding conditioning also showed higher overall electric organ discharge frequencies and 11-KT compared to males housed in isolation. Evidence is presented that another type of electrocommunication signal previously implicated in courtship may also serve as an inter-male signal of submission. Our results are consistent with earlier observations that electrocommunication signals produced during inter-male aggression serve in deterring attacks, and their pattern of production further suggested the formation of a dominance hierarchy.