Genome‐based estimates of fungal rDNA copy number variation across phylogenetic scales and ecological lifestyles

Ribosomal DNA (rDNA) copy number variation (CNV) has major physiological implications for all organisms, but how it varies for fungi, an ecologically ubiquitous and important group of microorganisms, has yet to be systemically investigated. Here, we examine rDNA CNV using an in silico read depth approach for 91 fungal taxa with sequenced genomes and assess copy number conservation across phylogenetic scales and ecological lifestyles. rDNA copy number varied considerably across fungi, ranging from an estimated 14 to 1,442 copies (mean = 113, median = 82), and copy number similarity was inversely correlated with phylogenetic distance. No correlations were found between rDNA CNV and fungal trophic mode, ecological guild or genome size. Taken together, these results show that like other microorganisms, fungi exhibit substantial variation in rDNA copy number, which is linked to their phylogeny in a scale‐dependent manner.     

On the use of oxygenic photosynthesis for the sustainable production of commodity chemicals

A sustainable society will have to largely refrain from the use of fossil carbon deposits. In such a regime, renewable electricity can be harvested as a primary source of energy. However, as for the synthesis of carbon‐based materials from bulk chemicals, an alternative is required. A sustainable approach towards this is the synthesis of commodity chemicals from CO₂, water and sunlight. Multiple paths to achieve this have been designed and tested in the domains of chemistry and biology. In the latter, the use of both chemotrophic and phototrophic organisms has been advocated. ‘Direct conversion’ of CO₂ and H₂O, catalyzed by an oxyphototroph, has excellent prospects to become the most economically competitive of these transformations, because of the relative ease of scale‐up of this process. Significantly, for a wide range of energy and commodity products, a proof of principle via engineering of the corresponding production organism has been provided. In the optimization of a cyanobacterial production organism, a wide range of aspects has to be addressed. Of these, here we will put our focus on: (1) optimizing the (carbon) flux to the desired product; (2) increasing the genetic stability of the producing organism and (3) maximizing its energy conversion efficiency. Significant advances have been made on all these three aspects during the past 2 years and these will be discussed: (1) increasing the carbon partitioning to >50%; (2) aligning product formation with the growth of the cells and (3) expanding the photosynthetically active radiation region for oxygenic photosynthesis.     

Expression and purification of the recombinant SALT lectin from rice (Oryza sativa L.)

The SALT protein is a 14.5 kDa mannose-binding lectin, originally described as preferentially expressed in rice plant roots in response to NaCl stress. Recombinant SALT lectin was produced in Escherichia coli from a cDNA clone encoding protein. After isopropyl-beta-d-thiogalactopyranoside induction, the expression level achieved was 23% of the soluble protein. The recombinant agglutinin was purified by a single-step process by dialyses against a high concentrated salt solution. After purification, hemagglutination assays of rabbit erythrocytes revealed that the recombinant SALT protein is a potent agglutinin (0.078 microg ml(-1) minimal concentration). The purified recombinant lectin was also used for comparative estimation of native protein amounts in protein extracts from rice plants by Western blot assay.     

Antipyretic effect of arginine vasotocin in toads

Arginine vasotocin (AVT) is a nonmammalian analog of the mammalian hormone arginine vasopressin (AVP). These peptides are known for their antidiuretic and pressor effects. More recently, AVP has been recognized as an important antipyretic molecule in mammals. However, no information exists about the role of AVT in febrile ectotherms. We tested the hypothesis that AVT is an antipyretic molecule in the toad Bufo paracnemis. Toads equipped with a temperature probe were placed in a thermal gradient, and preferred body temperature was recorded continuously. A behavioral fever was observed after lipopolysaccharide (LPS) was injected systemically (200 microg/kg). Systemically injected AVT (300 pmol/kg) alone caused no significant change in body temperature, but abolished LPS-induced fever. Moreover, a smaller dose of AVT (10 pmol/kg), which did not affect LPS-induced fever when injected peripherally, abolished fever when injected intracerebroventricularly. We therefore conclude that AVT plays an antipyretic role in the central nervous system, by means of behavior, in an ectotherm, a fact consistent with the notion that AVT/AVP elicits antipyresis by reducing the thermoregulatory set point.     

Reproductive ecology of the blue crab, Callinectes danae Smith, 1869 in the Conceição Lagoon system, Santa Catarina Isle, Brazil

Abundance of ovigerous females, size of the first gonadal maturation and the possible migration, route of the blue crab Callinectes danae from the Concei??o Lagoon system, Santa Catarina Isle, Brazil, are described. This lagoon is connected with the coastal area through a canal. A total of 1,124 crabs was caught during a 19 month sampling period. The reproduction and recruitment of juveniles occurred all year-round, with two peaks of abundance (February and September), correlated with the presence of ovigerous females (June and January). The mean carapace width at which the crabs attained gonadal maturity for the first time was 9.4 cm in males and 8.4 cm in females. The Concei??o Lagoon is a growth, reproduction, and spawning area for the species. However, egg eclosion occurs outside the lagoon following migration of ovigerous females to the open sea. After hatching the eggs, some females return to the lagoon, but males stay there for most of their life cycle.     

Effect of modification of histidine residues on organization of the pigment--protein complexes of chromatium minutissimum

The effect of diethyl pyrocarbonate on chromatophores and isolated pigment--protein complexes of Chromatium minutissimum was studied. It is shown that modification of histidine residues results in the destruction of the core antenna LHI (B880) and in a spectral shift from 850 to 830 nm in the peripheral antenna LHII (B800-850). In the purple sulfur bacterium Chromatium minutissimum the pigment--protein complexes B800-B850 (peripheral antenna, LHII) and B880 (core antenna, LHI) collect and transmit the absorbed light energy to the reaction centers. The composition of pigments and proteins as well as primary structure of the majority of polypeptides in both types of complexes from various photosynthetic bacteria have been determined.     

Effect of nitric oxide synthase inhibition on hypercapnia-induced hypothermia and hyperventilation

Hypercapnia elicits hypothermia in a numberof vertebrates, but the mechanisms involved are not well understood. Inthe present study, we assessed the participation of the nitric oxide(NO) pathway in hypercapnia-induced hypothermia and hyperventilation bymeans of NO synthase inhibition by usingN-nitro-L-arginine(L-NNA). Measurements ofventilation, body temperature, and oxygen consumption were performed inawake unrestrained rats before and afterL-NNA injection(intraperitoneally) and L-NNA injection followed by hypercapnia (5%CO₂). Control animals received saline injections. L-NNA alteredthe breathing pattern during the control situation but not duringhypercapnia. A significant (P < 0.05) drop in body temperature was measured after bothL-NNA (40 mg/kg) and 5%inspired CO₂, with a drop inoxygen consumption in the first situation but not in the second.Hypercapnia had no effect onL-NNA-induced hypothermia. Theventilatory response to hypercapnia was not changed byL-NNA, even thoughL-NNA caused a drop in bodytemperature. The present data indicate that the two responses elicitedby hypercapnia, i.e., hyperventilation and hypothermia, do not share NOas a common mediator. However, theL-arginine-NO pathwayparticipates, although in an unrelated way, in respiratory function andthermoregulation.

     

Synthesis and biodistribution studies of carbohydrate derivatives radiolabeled with technetium-99m

Three carbohydrate derivatives, MAG₃-Gl, MAG₃-Ga, MAG₃-NG, were synthesized and radiolabeled in high yields. These substances were injected in health Swiss mice and their biodistribution were evaluated. Among them, ^99mTc-MAG₃-Ga displayed higher accumulation in hepatic tissue, due to the presence of specific receptors in the liver for this carbohydrate. Thus, the use of ^99mTc-MAG₃-Ga to assess hepatic function can be considered.     

Bayesian analysis for nonlinear regression model under skewed errors,with application in growth curves

We have considered a Bayesian approach for the nonlinear regression model by replacing the normal distribution on the error term by some skewed distributions, which account for both skewness and heavy tails or skewness alone. The type of data considered in this paper concerns repeated measurements taken in time on a set of individuals. Such multiple observations on the same individual generally produce serially correlated outcomes. Thus, additionally, our model does allow for a correlation between observations made from the same individual. We have illustrated the procedure using a data set to study the growth curves of a clinic measurement of a group of pregnant women from an obstetrics clinic in Santiago, Chile. Parameter estimation and prediction were carried out using appropriate posterior simulation schemes based in Markov Chain Monte Carlo methods. Besides the deviance information criterion (DIC) and the conditional predictive ordinate (CPO), we suggest the use of proper scoring rules based on the posterior predictive distribution for comparing models. For our data set, all these criteria chose the skew‐t model as the best model for the errors. These DIC and CPO criteria are also validated, for the model proposed here, through a simulation study. As a conclusion of this study, the DIC criterion is not trustful for this kind of complex model.