Characterization of digestive carbohydrase activity in the gilthead seabream (Sparus aurata)

Six species of Phallodrilinae are reported from Hainan Island in southern China. The mesopsammic Aktedrilus yiboi sp. nov. is new to science. It is characterized by a combination of (1) small, straight, conical, strongly cuticularized penis sheaths, (2) posterior prostate glands being associated with the most ectal parts of the atria, and (3) small spermathecal ampulla. Bathydrilus ampliductus Erséus, 1997 is recorded for the first time since it was originally described from Australia's Northern Territory.     

Composting of fish offal and biosolids in northwestern Patagonia.

Composting of fish processing wastes and biosolids with wood by-products and yard trimmings was conducted during the summer of 1996 and winter of 1997 in NW Patagonia using: (i) static piles for fish offal and (ii) turning piles for biosolids. Fish offal was mixed with sawdust + wood shavings (FOC) at 3:1 ratio by weight and biosolids with wood shavings (BCw) and yard trimmings (BCt) at 1:1 ratio by volume. Samples were taken at six dates during the composting period and analyzed to determine the factors that predict compost maturity. Composting of biosolids was affected by the type of bulking agent during winter. Thermophilic temperatures > or = 55 degrees C were sustained long enough to satisfy the USEPA requirements for processes to further reduce pathogens (PFRP) in FOC and BCt, and for processes to significantly reduce pathogens (PSRP) in summer BCw, while in winter BCw temperatures were lower than those recommended for effective pathogen reduction. However, coliform fecal content in all BC treatments was less than 10 most probable number (MPN) g(-1) dry sample at the end of the process. The ratio of water soluble carbon (WSC) to total nitrogen (TN) appeared to be a more adequate index to predict compost maturity than the ratio of total organic carbon to nitrogen.     

Digestive proteases during development of larvae of red palm weevil, Rhynchophorus ferrugineus (Olivier, 1790) (Coleoptera: Curculionidae).

The evolution of digestive proteases during larval development of Rhynchophorus ferrugineus (Olivier, 1790) has been studied. A progressive increase of protease activity has been found. The optimum pH for proteolytic activity against azocasein was determined. Caseinograms revealed an active complex of alkaline proteases from the early stages of the development. From the apparent molecular masses, three groups of proteases have been found - high molecular-mass proteases, medium molecular-mass proteases, and low molecular-mass proteases. Studies using specific protease inhibitors showed the major presence of serine proteases in gut extracts. The results obtained from larvae reared on different substrates have made possible a comparative assessment of the influence of diet on the development of the digestive enzymatic system. Larvae fed on an artificial diet showed a complete pattern of digestive proteases. Data suggest that this diet seems to be suitable for future research with this insect pest.     

Down under the southeastern Pacific: marine non-indigenous species in Chile

This article presents the first compilation of marine non-indigenous species (NIS) of algae and macro-invertebrates invading Chilean waters. A total of 32 cosmopolitan and non-cosmopolitan species are reported. Among them there are six species considered as extending their southern range of distribution in connection with El Niño events. The article highlights negative and positive impacts caused by marine NIS invasions. Among the first are Codium fragile var. tomentosoide, considered as a pest in Gracilaria chilensis aquaculture facilities in northern Chile, and Ciona intestinalis, a pest in scallop aquaculture installations. Among the second are bio-engineers species, such as the ascidian Pyura praeputialis and the sea grass Heterozostera tasmanica, which have caused an increase in local biodiversity and enhancement of nursery grounds via the creation of new habitats. Further more, invaders such as the algae Mastocarpus papillosus, Porphyra linearis and P. pseudolinearis represent new exploitable resources, extracted by coastal food gatherers along the coast (M. papillosus) or potential species to develop aquaculture. Additional information is presented on the anemone Anemonia alicemartinae, which appears to be a native species (?), having shown in the past 40–50 years, a geographical southward range extension of approximately 1900 km. The number of NIS reported for Chile is compared with those published for the southwestern Atlantic, South Africa, North America (Atlantic and Pacific coasts) and New Zealand. It is suggested that probably the low number of Chilean NIS is due to the fact that the Chilean coasts are environmentally less stressed than other coasts in the world, due to the scarcity of estuaries, gulfs, enclosed bays, lagoons and low human populations. These kinds of sheltered areas have been suggested as centers for bio-invasions, due to the high rate of human-mediated transfer and increase of pollutants. Furthermore, none of NIS reported from Chile show a fast geographical expansion rate (exception of A. alicemartinae), nor invading strategies such as those described for marine NIS in other latitudes, where notorious ecological unbalances following invasions have been observed. An alternative hypothesis is that the low number of marine NIS invading Chile is underestimated, since the modern list of species generated through specific taxonomically intensive port and harbor surveys is still lacking. Fifteen species (five invertebrate and 10 fish) have been deliberately imported to Chile for aquaculture. The invertebrates appear to be controlled within aquaculture facilities and have not established naturalized populations or caused direct ecological impacts on local communities. On the contrary, several millions of salmoniforms (and rainbow trout) have escaped from farming facilities in southern Chile and established naturalized populations. Studies on ecological impacts are lacking. These escapees are also playing a role in the enhancement of artisanal and sport fishery activities.     

Molecular drift of the bride of sevenless (boss) gene in Drosophila

DNA sequences were determined for three to five alleles of the bride-of- sevenless (boss) gene in each of four species of Drosophila. The product of boss is a transmembrane receptor for a ligand coded by the sevenless gene that triggers differentiation of the R7 photoreceptor cell in the compound eye. Population parameters affecting the rate and pattern of molecular evolution of boss were estimated from the multinomial configurations of nucleotide polymorphisms of synonymous codons. The time of divergence between D. melanogaster and D. simulans was estimated as approximately 1 Myr, that between D. teissieri and D. yakuba as approximately 0.75 Myr, and that between the two pairs of sibling species as approximately 2 Myr. (The boss genes themselves have estimated divergence times approximately 50% greater than the species divergence times.) The effective size of the species was estimated as approximately 5 x 10(6), and the average mutation rate was estimated as 1-2 x 10(-9)/nucleotide/generation. The ratio of amino acid polymorphisms within species to fixed differences between species suggests that approximately 25% of all possible single-step amino acid replacements in the boss gene product may be selectively neutral or nearly neutral. The data also imply that random genetic drift has been responsible for virtually all of the observed differences in the portion of the boss gene analyzed among the four species.      

Simple Sequence Repeats and Mucoid Conversion: Biased mucA Mutagenesis in Mismatch Repair-Deficient Pseudomonas aeruginosa

In Pseudomonas aeruginosa, conversion to the mucoid phenotype marks the onset of an irreversible state of the infection in Cystic Fibrosis (CF) patients. The main pathway for mucoid conversion is mutagenesis of the mucA gene, frequently due to −1 bp deletions in a simple sequence repeat (SSR) of 5 Gs (G⁵-SSR₄₂₆). We have recently observed that this mucA mutation is particularly accentuated in Mismatch Repair System (MRS)-deficient cells grown in vitro. Interestingly, previous reports have shown a high prevalence of hypermutable MRS-deficient strains occurring naturally in CF chronic lung infections. Here, we used mucA as a forward mutation model to systematically evaluate the role of G⁵-SSR₄₂₆ in conversion to mucoidy in a MRS-deficient background, with this being the first analysis combining SSR-dependent localized hypermutability and the acquisition of a particular virulence/persistence trait in P. aeruginosa. In this study, mucA alleles were engineered with different contents of G:C SSRs, and tested for their effect on the mucoid conversion frequency and mucA mutational spectra in a mutS-deficient strain of P. aeruginosa. Importantly, deletion of G⁵-SSR₄₂₆ severely reduced the emergence frequency of mucoid variants, with no preferential site of mutagenesis within mucA. Moreover, although mutagenesis in mucA was not totally removed, this was no longer the main pathway for mucoid conversion, suggesting that G⁵-SSR₄₂₆ biased mutations towards mucA. Mutagenesis in mucA was restored by the addition of a new SSR (C⁶-SSR₄₃₁), and even synergistically increased when G⁵-SSR₄₂₆ and C⁶-SSR₄₃₁ were present simultaneously, with the mucA mutations being restricted to −1 bp deletions within any of both G:C SSRs. These results confirm a critical role for G⁵-SSR₄₂₆ enhancing the mutagenic process of mucA in MRS-deficient cells, and shed light on another mechanism, the SSR- localized hypermutability, contributing to mucoid conversion in P. aeruginosa.     

Oligomeric forms of the membrane-bound acetylcholine receptor disclosed upon extraction of the M(r) 43,000 nonreceptor peptide

Oligomeric forms of the acetylcholine receptor are directly visualized by electron microscopy in receptor-rich membranes from torpedo marmorata. The receptor structures are quantitatively correlated with the molecular species so far identified only after detergent solubilization, and further related to the polypeptide composition of the membranes and changes thereof. The structural identification is made possibly by the increased fragility of the membranes after extraction of nonreceptor peptides and their subsequent disruption upon drying onto hydrophilic carbon supports. Receptor particles in native membranes depleted of nonreceptor peptides appear as single units of 7-8 nm, and double and multiple aggregates thereof. Particle doublets having a main-axis diameter of 19 +/- 3 nm predominate in these membranes. Linear aggregates of particles similar to those observed in rotary replicas of quick-frozen fresh electrolytes (Heuser, J.E. and S. R. Salpeter. 1979, J. Cell Biol. 82: 150-173) are also present in the alkaline-extracted membranes. Chemical modifications of the thiol groups shift the distribution of structural species. Dithiothreitol reduction, which renders almost exclusively the 9S, monomeric receptor form, results in the observation of the 7-8 nm particle in isolated form. The proportion of doublets increases in membranes alkylated with N-ethylmaleimide. Treatment with 5,5’-dithiobis-(nitrobenzoic acid) increases the proportion of higher oligomeric species, and particle aggregates (n=oligo) predominate. The nonreceptor v-peptide (doublet of M(r) 43,000) appears to play a role in the receptor monomer-polymer equilibria. Receptor protein and v-peptide co-aggregate upon reduction and reoxidation of native membranes. In membranes protected ab initio with N- ethylmaleimide, only the receptor appears to self-aggregate. The v-peptide cannot be extracted from these alkylated membranes, though it is easily released from normal, subsequently alkylated or reduced membranes. A stabilization of the dimeric species by the nonreceptor v-peptide is suggested by these experiments. Monospecific antibodies against the v-peptide are used in conjunction with rhodamine- labeled anti-bodies in an indirect immunoflourescence assay to map the vectorial exposure of the v-peptide. When intact membranes, v-peptide depleted and “holey” native membranes (treated with 0.3 percent saponin) are compared, maximal labeling is obtained with the latter type of membranes, suggesting a predominantly cytoplasmic exposure of the antigenic determinants of the v-peptide in the membrane. The influence of the v-peptide in the thiol-dependent interconversions of the receptor protein and the putative topography of the peptide are analyzed in the light of the present results.     

Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene

We have analyzed the conserved regions of the gene coding for the circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria parasite. The closest evolutionary relative of P. falciparum, the agent of malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is consistent with the hypothesis that P. falciparum is an ancient human parasite, associated with humans since the divergence of the hominids from their closest hominoid relatives. Three other human Plasmodium species are each genetically indistinguishable from species parasitic to nonhuman primates; that is, for the DNA sequences included in our analysis, the differences between species are not greater than the differences between strains of the human species. The human P. malariae is indistinguishable from P. brasilianum, and P. vivax is indistinguishable from P. simium; P. brasilianum and P. simium are parasitic to New World monkeys. The human P. vivax-like is indistinguishable from P. simiovale, a parasite of Old World macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are evolutionarily recent human parasites, the first two at least acquired only within the last several thousand years, and perhaps within the last few hundred years, after the expansion of human populations in South America following the European colonizations. We estimate the rate of evolution of the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year. The divergence between the P. falciparum and P. reichenowi lineages is accordingly dated 8.9 Myr ago. The divergence between the three lineages leading to the human parasites is very ancient, about 100 Myr old between P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between P. falciparum and the other two.      

Characterization of the TRBP domain required for Dicer interaction and function in RNA interference

Background  

Dicer, Ago2 and TRBP are the minimum components of the human RNA-induced silencing complex (RISC). While Dicer and Ago2 are RNases, TRBP is the double-stranded RNA binding protein (dsRBP) that loads small interfering RNA into the RISC. TRBP binds directly to Dicer through its C-terminal domain.