Macroalgal spore dysfunction: ocean acidification delays and weakens adhesion

Early life stages of marine organisms are predicted to be vulnerable to ocean acidification. For macroalgae, reproduction and population persistence rely on spores to settle, adhere and continue the algal life cycle, yet the effect of ocean acidification on this critical life stage has been largely overlooked. We explicitly tested the biomechanical impact of reduced pH on early spore adhesion. We developed a shear flume to examine the effect of reduced pH on spore attachment time and strength in two intertidal rhodophyte macroalgae, one calcified (Corallina vancouveriensis) and one noncalcified (Polyostea robusta). Reduced pH delayed spore attachment of both species by 40%–52% and weakened attachment strength in C. vancouveriensis, causing spores to dislodge at lower flow‐induced shear forces, but had no effect on the attachment strength of P. robusta. Results are consistent with our prediction that reduced pH disrupts proper curing and gel formation of spore adhesives (anionic polysaccharides and glycoproteins) via protonation and cation displacement, although experimental verification is needed. Our results demonstrate that ocean acidification negatively, and differentially, impacts spore adhesion in two macroalgae. If results hold in field conditions, reduced ocean pH has the potential to impact macroalgal communities via spore dysfunction, regardless of the physiological tolerance of mature thalli.     

Campylobacter jejuni adenosine triphosphate phosphoribosyltransferase is an active hexamer that is allosterically controlled by the twisting of a regulatory tail

Adenosine triphosphate phosphoribosyltransferase (ATP‐PRT) catalyzes the first committed step of the histidine biosynthesis in plants and microorganisms. Here, we present the functional and structural characterization of the ATP‐PRT from the pathogenic ε‐proteobacteria Campylobacter jejuni (CjeATP‐PRT). This enzyme is a member of the long form (HisG_L) ATP‐PRT and is allosterically inhibited by histidine, which binds to a remote regulatory domain, and competitively inhibited by AMP. In the crystalline form, CjeATP‐PRT was found to adopt two distinctly different hexameric conformations, with an open homohexameric structure observed in the presence of substrate ATP, and a more compact closed form present when inhibitor histidine is bound. CjeATP‐PRT was observed to adopt only a hexameric quaternary structure in solution, contradicting previous hypotheses favoring an allosteric mechanism driven by an oligomer equilibrium. Instead, this study supports the conclusion that the ATP‐PRT long form hexamer is the active species; the tightening of this structure in response to remote histidine binding results in an inhibited enzyme.     

The placenta theory and the origin of infantile hemangioma

The pathogenesis of infantile hemangioma is unknown. In recent years, much of the focus has been placed at identifying the cell type(s) responsible for tumor initiation. New discoveries in infantile hemangioma suggest an involvement of progenitor cells in the pathogenesis of this vascular tumor. Both embryonic and extra-embryonic tissues have been postulated as potential sources for these progenitor cells. This review focuses on the placental theory, which proposes that a fetal placental progenitor is the cell type of origin for infantile hemangioma. Special emphasis will be placed on placental vasculogenesis and the presence and transit of placental progenitor cells during gestation.     

Robust filtering for stochastic genetic regulatory networks with time-varying delay

This paper addresses the robust filtering problem for a class of linear genetic regulatory networks (GRNs) with stochastic disturbances, parameter uncertainties and time delays. The parameter uncertainties are assumed to reside in a polytopic region, the stochastic disturbance is state-dependent described by a scalar Brownian motion, and the time-varying delays enter into both the translation process and the feedback regulation process. We aim to estimate the true concentrations of mRNA and protein by designing a linear filter such that, for all admissible time delays, stochastic disturbances as well as polytopic uncertainties, the augmented state estimation dynamics is exponentially mean square stable with an expected decay rate. A delay-dependent linear matrix inequality (LMI) approach is first developed to derive sufficient conditions that guarantee the exponential stability of the augmented dynamics, and then the filter gains are parameterized in terms of the solution to a set of LMIs. Note that LMIs can be easily solved by using standard software packages. A simulation example is exploited in order to illustrate the effectiveness of the proposed design procedures.     

Spaceflight has compartment- and gene-specific effects on mRNA levels for bone matrix proteins in rat femur

In the presentstudy, we evaluated the possibility that the abnormal bone matrixproduced during spaceflight may be associated with reduced expressionof bone matrix protein genes. To test this possibility, we investigatedthe effects of a 14-day spaceflight (SLS-2 experiment) on steady-statemRNA levels for glyceraldehyde-3-phosphate dehydrogenase (GAPDH),osteocalcin, osteonectin, and prepro-(1) subunit of type I collagenin the major bone compartments of rat femur. There were pronouncedsite-specific differences in the steady-state levels of expression ofthe mRNAs for the three bone matrix proteins and GAPDH in normalweight-bearing rats, and these relationships were altered afterspaceflight. Specifically, spaceflight resulted in decreases in mRNAlevels for GAPDH (decreased in proximal metaphysis), osteocalcin(decreased in proximal metaphysis), osteonectin (decreased in proximaland distal metaphysis), and collagen (decreased in proximal and distalmetaphysis) compared with ground controls. There were no changes inmRNA levels for matrix proteins or GAPDH in the shaft and distalepiphysis. These results demonstrate that spaceflight leads to site-and gene-specific decreases in mRNA levels for bone matrix proteins.These findings are consistent with the hypothesis thatspaceflight-induced decreases in bone formation are caused byconcomitant decreases in expression of genes for bone matrix proteins.

     

Roles of an endogenous serum lectin in the immune protection of blue gourami, Trichogaster trichopterus (Pallus) against Aeromonas hydrophila

The serum of blue gourami, Trichogaster trichopterus (Pallus), contains a calcium-dependent, N-acetyl-galactosamine-binding lectin (BGL) which efficiently activates and enhances the non-specific immune response of fish towards a virulent strain of Aeromonas hydrophila. In the in vitro studies, a lectin concentration range of 0.05-1.0 ng ml(-1) was found to significantly promote phagocytic uptake of the bacteria by macrophages. This effect was further augmented when purified lectin was combined with laminarin (beta-1,3-D-glucan). Supernatants obtained from these lectin-stimulated macrophage cultures also exhibited significant bacteria-killing activities. In addition, complement from naive fish serum, in the presence of purified BGL, was able to kill A. hydrophila. Finally, challenge experiments demonstrated that BGL could confer effective immune protection to naive blue gourami against an Aeromonas infection.     

Monitoring toxicity associated with parenteral sodium stibogluconate in the day-case management of returned travellers with New World cutaneous leishmaniasi

Background

Patients with New World cutaneous leishmaniasis (NWCL) caused by Leishmania Viannia are treated with parenteral sodium stibogluconate (SbV) to reduce the risk of development of mucocutanous leishmaniasis. Our centre manages patients with NWCL on an outpatient-basis. This study was conducted to assess the safety and efficacy of this approach.

Methodology

We reviewed records of 67 consecutive NWCL patients, aged 17–61 years, treated as day-cases with 20 mg/kg/day SbV for up to 28 days at our UK centre. Data had been collected in a standardised format at the time of treatment using a care-record tool. Patients reported adverse-effects daily using a structured questionnaire. Blood tests and electrocardiograms were performed twice weekly to monitor for toxicity.

Principal Findings

Parenteral SbV treatment was associated with an early, significant suppression of mean lymphocyte and platelet counts. By day four of treatment, lymphocytes reduced by 0.53×10⁹/L (CI 0.29×10⁹/L to 0.76×10⁹/L, p<0.001), and platelets by 31,000/µL (CI 16,000/µL to 46,000/µL, p<0.001). SbV was further associated with significant elevation of serum alanine transaminase concentrations, with a mean peak rise of 107 iu/L by day 13 (CI 52 iu/L to 161 iu/L, p<0.001). These disturbances were temporary and did not result in adverse clinical events. Patient-described symptoms were cumulative and at three weeks of treatment, 59.6% of patients experienced myalgia and 29.8% malaise. Treatment adherence and clinical outcomes were comparable to inpatient treatment studies. A total of 1407 individual doses of SbV resulted in only 26 nights'' hospital admission, a saving of 1381 bed-days compared to inpatient treatment.

Conclusions/Significance

In specialist centres, NWCL patients aged below 65 years and without co-morbidities can be safely and effectively treated without hospital admission. This reduces the cost of treatment, and is much preferred by patients. Twice weekly blood and electrocardiographic monitoring may be surplus to requirement in clinically well, low-risk patients.     

Competing phytoplankton undermines allelopathy of a bloom-forming dinoflagellate

Biotic interactions in the plankton can be both complex and dynamic. Competition among phytoplankton is often chemically mediated, but no studies have considered whether allelopathic compounds are modified by biotic interactions. Here, we show that compounds exuded during Karenia brevis blooms were allelopathic to the cosmopolitan diatom Skeletonema costatum, but that bloom allelopathy varied dramatically among collections and years. We investigated several possible causes of this variability and found that neither bloom density nor concentrations of water-borne brevetoxins correlated with allelopathic potency. However, when we directly tested whether the presence of competing phytoplankton influenced bloom allelopathy, we found that S. costatum reduced the growth-inhibiting effects of bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Additional laboratory experiments indicated that inducible changes to K. brevis allelopathy were restricted to two diatoms among five sensitive phytoplankton species, whereas five other species were constitutively resistant to K. brevis allelopathy. Our results suggest that competitors differ in their responses to phytoplankton allelopathy, with S. costatum exhibiting a previously undescribed method of resistance that may influence community structure and alter bloom dynamics.