The larval development of Petrolisthes politus (Gray, 1831) (Crustacea: Decapoda: Porcellanidae) under laboratory conditions

The complete larval development of the shallow-water Caribbean porcellanid crab, Petrolisthes politus (Gray, 1831), is described and illustrated from specimens reared in the laboratory. Petrolisthes politus hatches as a prezoea, which persist for less than 90 minutes, and then molts through two subsequent zoeal stages, which are completed in 6 to 7 and 14 to 16 days, respectively, before the megalopal stage is reached. From a total of about 2000 zoeae that were cultured, only two reached the megalopal stage. The two megalopae survived for up to 5 days but did not molt to the first crab stage. The zoeae of P. politus are compared with those of Petrolisthes rufescens (Heller, 1861), Petrolisthes lamarckii (Leach, 1820), Petrolisthes carinipes (Heller, 1861), Petrolisthes coccineus (Owen 1839) and Petrolisthes pubescens (Stimpson, 1858), which were hitherto the only species having bifid lateral spines on the telson of the first zoeal stage.     

Role of Central Metabolism in the Osmoadaptation of the Halophilic Bacterium Chromohalobacter salexigens

Bacterial osmoadaptation involves the cytoplasmic accumulation of compatible solutes to counteract extracellular osmolarity. The halophilic and highly halotolerant bacterium Chromohalobacter salexigens is able to grow up to 3 m NaCl in a minimal medium due to the de novo synthesis of ectoines. This is an osmoregulated pathway that burdens central metabolic routes by quantitatively drawing off TCA cycle intermediaries. Consequently, metabolism in C. salexigens has adapted to support this biosynthetic route. Metabolism of C. salexigens is more efficient at high salinity than at low salinity, as reflected by lower glucose consumption, lower metabolite overflow, and higher biomass yield. At low salinity, by-products (mainly gluconate, pyruvate, and acetate) accumulate extracellularly. Using [1-¹³C]-, [2-¹³C]-, [6-¹³C]-, and [U-¹³C₆]glucose as carbon sources, we were able to determine the main central metabolic pathways involved in ectoines biosynthesis from glucose. C. salexigens uses the Entner-Doudoroff pathway rather than the standard glycolytic pathway for glucose catabolism, and anaplerotic activity is high to replenish the TCA cycle with the intermediaries withdrawn for ectoines biosynthesis. Metabolic flux ratios at low and high salinity were similar, revealing a certain metabolic rigidity, probably due to its specialization to support high biosynthetic fluxes and partially explaining why metabolic yields are so highly affected by salinity. This work represents an important contribution to the elucidation of specific metabolic adaptations in compatible solute-accumulating halophilic bacteria.     

Identification of Serpin Determinants of Specificity and Selectivity for Furin Inhibition through Studies of α1PDX (α1-Protease Inhibitor Portland)-Serpin B8 and Furin Active-site Loop Chimeras

α₁-Protease inhibitor Portland (α₁PDX) is an engineered serpin family inhibitor of the proprotein convertase (PC), furin, that exhibits high specificity but limited selectivity for inhibiting furin over other PC family proteases. Here, we characterize serpin B8, a natural inhibitor of furin, together with α₁PDX-serpin B8 and furin-PC chimeras to identify determinants of serpin specificity and selectivity for furin inhibition. Replacing reactive center loop (RCL) sequences of α₁PDX with those of serpin B8 demonstrated that both the P4–P1 RXXR recognition sequence as well as the P1′–P5′ sequence are critical determinants of serpin specificity for furin. Alignments of PC catalytic domains revealed four variable active-site loops whose role in furin reactivity with serpin B8 was tested by engineering furin-PC loop chimeras. The furin(298–300) loop but not the other loops differentially affected furin reactivity with serpin B8 and α₁PDX in a manner that depended on the serpin RCL-primed sequence. Modeling of the serpin B8-furin Michaelis complex identified serpin exosites in strand 3C close to the 298–300 loop whose substitution in α₁PDX differentially affected furin reactivity depending on the furin loop and serpin RCL-primed sequences. These studies demonstrate that RCL-primed residues, strand 3C exosites, and the furin(298–300) loop are critical determinants of serpin reactivity with furin, which may be exploited in the design of specific and selective α₁PDX inhibitors of PCs.     

Comparative bionomics of four populations of Meccus longipennis (Hemiptera: Reduviidae: Triatominae) under laboratory conditions

The values of biological parameters related to the life cycles of four populations of Meccus longipennis (Reduviidae: Triatominae) were evaluated. Cohorts of each of the four studied populations from different geographical areas of Mexico were maintained under similar laboratory conditions and then compared. The population from El Saucito de Araujo was different from the other three studied populations, which could help explain the secondary importance of M. longipennis in the state of Chihuahua. This paper also supports the proposition that biological traits are important criteria for determining relationships between populations.     

Temperature- and Salinity-Decoupled Overproduction of Hydroxyectoine by Chromohalobacter salexigens

Hydroxyectoine overproduction by the natural producer Chromohalobacter salexigens is presented in this study. Genetically engineered strains were constructed that at low salinity coexpressed, in a vector derived from a native plasmid, the ectoine (ectABC) and hydroxyectoine (ectD) genes under the control of the ectA promoter, in a temperature-independent manner. Hydroxyectoine production was further improved by increasing the copies of ectD and using a C. salexigens genetic background unable to synthesize ectoines.     

2‐(Undecyloxy)‐ethanol is a major component of the male‐produced aggregation pheromone of Monochamus sutor

The small white‐marmorated longicorn beetle, Monochamus sutor (L.) (Coleoptera: Cerambycidae), is widely distributed throughout Europe and Asia. It is a potential vector of the pine wood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, the causal agent of the devastating pine wilt disease. Volatiles were collected from both male and female beetles after maturation feeding. In analyses of these collections using gas chromatography (GC) coupled to mass spectrometry, a single male‐specific compound was detected and identified as 2‐(undecyloxy)‐ethanol. In analyses by GC coupled to electroantennography the only consistent responses from both female and male antennae were to this compound. Trapping tests were carried out in Spain, Sweden, and China. 2‐(Undecyloxy)‐ethanol was attractive to both male and female M. sutor beetles. A blend of the bark beetle pheromones ipsenol, ipsdienol, and 2‐methyl‐3‐buten‐2‐ol was also attractive to both sexes in Spain and Sweden, and further increased the attractiveness of the 2‐(undecyloxy)‐ethanol. The host plant volatiles α‐pinene, 3‐carene, and ethanol were weakly attractive, if at all, in all three countries and did not significantly increase the attractiveness of the blend of 2‐(undecyloxy)‐ethanol and bark beetle pheromones. 2‐(Undecyloxy)‐ethanol is thus proposed to be the major, if not only, component of the male‐produced aggregation pheromone of M. sutor, and its role is discussed. This compound has been reported as a pheromone of several other Monochamus species and is another example of the parsimony that seems to exist among the pheromones of many of the Cerambycidae. Traps baited with 2‐(undecyloxy)‐ethanol and bark beetle pheromones should be useful for monitoring and control of pine wilt disease, should M. sutor be proven to be a vector of the nematode.     

Spore morphology and ultrastructure of Cyathea (Cyatheaceae,Pteridophyta) species from southern South America

Spore sculpture and wall structure of eight Cyathea (Cyatheaceae) species from southern South America were studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Two layers, i.e. an inner and an outer layer, were observed in the perispore. The inner layer has two strata: the inner stratum is attached to the exospore and composed of rodlets tangentially oriented to the spore surface and randomly intermixed; the outer stratum consists of a three-dimensional network of rodlets with either free or fused distal edges forming spinules. The outer layer is thin, darkly contrasted and covers the rodlets. In most cases, the exospore has two layers and a pitted surface. In Cyathea atrovirens, the exospore surface is smooth, while in C. delgadii and C. myriotricha it is verrucate. The homogeneity of perispore features within the genus Cyathea is evident, while exospore features are heterogeneous. The exospore has different kinds of surface-structures that are of potential interest for assessing evolutionary trends within the group.     

Ultrastructure and development during meiosis and the tetrad period of sporogenesis in the leptosporangiate fern Alsophila setosa (Cyatheaceae) compared with corresponding stages in Psilotum nudum (Psilotaceae)

The pre-meiotic, meiotic and tetrad stages of development in microsporangia of Alsophila setosa were studied with particular emphasis on the early establishment of patterning in the microspore wall and the subsequent development of the sporoderm. The data obtained were compared with corresponding ontogenetic stages of Psilotum nudum. Tapetal behaviour was also examined. During the tetrad period, only one layer, a thin undulating sheet, appeared alongside the plasma membrane of the tetraspores, and this was evidently formed on a pre-patterned structure – a fibrillar layer, corresponding to a kind of primexine matrix. The early free microspores had a wavy plasma membrane with a parallel, sinusoidal, thin initial sporoderm layer. The proximal apertural fold was observed to be an extended outgrowth of this initial spore envelope. Sporoderm ontogeny during the tetrad period in Alsophila and Psilotum show some common points, but also fundamental differences, mainly in the relative timing of events: in Alsophila the end of the tetrad period is the starting point for exospore development, whereas in Psilotum the exospore is already complete at this stage. Considerable differences were also observed in the tapetum of the two species.     

Melatonin attenuates the effects of sub-acute administration of lead on kidneys in rats without altering the lead-induced reduction in nitric oxide

Exposure to lead induces oxidative stress and renal damage. Although most forms of oxidative stress are characterized by simultaneous elevation of nitrogen and oxidative species, lead-induced oxidative stress is unusual in that it is associated with a reduction in nitric oxide (NO) levels in the kidney. The role of NO in kidney injury is controversial; some studies suggest that it is associated with renal injury, whereas others show that it exerts protective effects. Concentration-dependent effects have also been proposed, linking low levels with vasodilatation and high levels with toxicity. The aim of this study was to evaluate the effects of melatonin co-exposure on the lead-induced reduction in renal NO levels. We found that sub-acute intraperitoneal administration of 10 mg/kg/day of lead for 15 days induced toxic levels of lead in the blood and caused renal toxicity (pathological and functional). Under our experimental conditions, lead induced an increase in lipid peroxidation and a decrease in NO. Melatonin co-treatment decreased lead-induced oxidative stress (peroxidation level) and toxic effects on kidneys without altering the lead-induced reduction in renal NO. These results suggest that, in our experimental model, the reduction in renal NO levels by lead exposure is not the only responsible factor for lead-induced kidney damage.     

On the use of weighting in LCA: translating decision makers’ preferences into weights via linear programming

Purpose

The main goal of any life cycle assessment (LCA) study is to identify solutions leading to environmental savings. In conventional LCA studies, practitioners select from some alternatives the one which better matches their preferences. This task is sometimes simplified by ranking these alternatives using an aggregated indicator defined by attaching weights to impacts. We address here the inverse problem. That is, given an alternative, we aim to determine the weights for which that solution becomes optimal.

Methods

We propose a method based on linear programming (LP) that determines, for a given alternative, the ranges within which the weights attached to a set of impact metrics must lie so that when a weighting combination of these impacts is optimized, the alternative can be optimal, while if the weights fall outside this range, it is guaranteed that the solution will be suboptimal. A large weight value implies that the corresponding LCA impact is given more importance, while a low value implies the converse. Furthermore, we provide a rigorous mathematical analysis on the implications of using weighting schemes in LCA, showing that this practice guides decision-making towards the adoption of some specific alternatives (those lying on the convex envelope of the resulting trade-off curve).

Results and discussion

A case study based on the design of hydrogen infrastructures is taken as a test bed to illustrate the capabilities of the approach presented. Given are a set of production and storage technologies available to produce and deliver hydrogen, a final demand, and cost and environmental data. A set of designs, each achieving a unique combination of cost and LCA impact, is considered. For each of them, we calculate the minimum and maximum weight to be given to every LCA impact so that the alternative can be optimal among all the candidate designs. Numerical results show that solutions with lower impact are selected when decision makers are willing to pay larger monetary penalties for the environmental damage caused.

Conclusions

LP can be used in LCA to translate the decision makers’ preferences into weights. This information is rather valuable, particularly when these weights represent economic penalties, as it allows screening and ranking alternatives on the basis of a common economic basis. Our framework is aimed at facilitating decision making in LCA studies and defines a general framework for comparing alternatives that show different performance in a wide variety of impact metrics.