Polymeric and free sugars released by three phytoplanktonic species from a freshwater tropical eutrophic reservoir

Several studies have focused on the release of carbohydratesby phytoplankton because of the ecological significance of suchcompounds. This process increases the supply of carbon to theheterotrophic community, enhancing the phytoplankton/bacteriaassociations. In this article, we report investigations on thecarbohydrate release, both polymeric and free sugars, in axenicbatch cultures of three tropical freshwater phytoplanktonicspecies from different taxonomic positions: Cryptomonas tetrapyrenoidosa(Cryptophyceae), Staurastrum orbiculare (Zygnematophyceae) andThalassiosira sp. (Bacillariophyceae). The total carbohydraterelease rate was increased in the stationary growth phase inall the species under study. Most of the carbohydrates releasedby the three species were present in the polymeric form, althoughboth polymeric and free carbohydrates could supply carbon enoughto support bacterioplanktonic populations, according to ratesof consumption found on literature. The composition of the carbohydratesdiffered significantly from one species to another, indicatingthat carbohydrate release might be a species-specific process.We also observed that the contributions of some components frompolymeric sugars, such as fucose, rhamnose and arabinose increasedwith the advancing age of the cultures.     

Dioxycarbene complexes derived from reactions of tetrairidium carbonyl clusters with oxirane: X-ray crystal structures of and

Some novel cyclic-dioxycarbene derivatives of general formula (L = P^tBu₃, n = 1 (2), PPh₃: n = 1 (3), 2 (4)) and (L-L = PPh₂PCH₂PPh₂, n = 1 (5), norbornadiene, n = 1 (6) and 1,5-cyclooctadiene, n = 1 (7), 2 (8)) have been obtained by reaction of oxirane with the tetrairidium cluster derivatives [Ir₄(CO)₁₁(L)] and [Ir₄(CO)₁₀(L-L)] in the presence of bromide ion as catalyst. Elemental analysis, IR, and NMR spectra (¹H, ³¹P{¹H}, ¹³C{¹H}), and for compounds 2 and 5 also the X-ray crystal structures, were carried out for their characterisation. All the derivatives have 3 edge-bridging CO’s on the basal face of the iridium tetrahedron with non-CO ligands in axial and/or radial positions. For the mixed-ligand cluster compounds, two or three stereoisomers were observed in solution by ¹H, ³¹P and ¹³C NMR spectroscopies at low temperature. All these clusters are fluxional at room temperature.     

Diphenyl diselenide reverses cadmium-induced oxidative damage on mice tissues

The concept that selenium-containing molecules may be better antioxidants than classical antioxidants, has led to the design of synthetic organoselenium compounds. In the present investigation subchronic deleterious effects of cadmium-intoxication in mice and a possible protective effect of diphenyl diselenide (PhSe)2 (5 micromol/kg) were studied. Male adult Swiss albino mice (25-35 g) received CdCl2 (10 micromol/kg, subcutaneously), five times/week, for 4 weeks. A number of toxicological parameters in blood, liver, kidney, spleen and brain of mice were examined including delta-aminolevulinic acid dehydratase (delta-ALA-D) activity, lipid peroxidation and ascorbic acid content, the parameters that indicate tissue damage such as plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine and lactate dehydrogenase (LDH) were also determined. The results demonstrated that cadmium caused inhibition of delta-ALA-D activity in liver (24%), kidney (33%) and spleen (73%) and (PhSe)2 therapy was effective in restoring enzyme activity in all tissues. A reduction in ascorbic acid content was observed in kidney (11%) and spleen (10.7%) of cadmium-treated mice and (PhSe)2 was only effective in improving this reduction in kidney. An increase of lipid peroxidation induced by cadmium was noted in liver (29%) and brain (28%) tissues and (PhSe)2 therapy was effective in restoring TBARS levels in both tissues. We also observed an increase on plasma LDH (1.99-times), AST (1.93-times) and ALT (4.24-times) activities. (PhSe)2 therapy was effective in restoring AST activity at control level. (PhSe)2 did not present toxic effects when plasma parameters were evaluated. The results suggest that the administration of an antioxidant (PhSe)2, during cadmium intoxication may provide beneficial effects by reducing oxidative stress in tissues.     

A case-cohort design for assessing covariate effects in longitudinal studies

The case-cohort design for longitudinal data consists of a subcohort sampled at the beginning of the study that is followed repeatedly over time, and a case sample that is ascertained through the course of the study. Although some members in the subcohort may experience events over the study period, we refer to it as the "control-cohort." The case sample is a random sample of subjects not in the control-cohort, who have experienced at least one event during the study period. Different correlations among repeated observations on the same individual are accommodated by a two-level random-effects model. This design allows consistent estimation of all parameters estimable in a cohort design and is a cost-effective way to study the effects of covariates on repeated observations of relatively rare binary outcomes when exposure assessment is expensive. It is an extension of the case-cohort design (Prentice, 1986, Biometrika73, 1-11) and the bidirectional case-crossover design (Navidi, 1998, Biometrics54, 596-605). A simulation study compares the efficiency of the longitudinal case-cohort design to a full cohort analysis, and we find that in certain situations up to 90% efficiency can be obtained with half the sample size required for a full cohort analysis. A bootstrap method is presented that permits testing for intra-subject homogeneity in the presence of unidentifiable nuisance parameters in the two-level random-effects model. As an illustration we apply the design to data from an ongoing study of childhood asthma.     

Fifteen years of prothymosin alpha: contradictory past and new horizons

Prothymosin alpha (ProTalpha) is a highly acidic and small protein of only 111 amino acids with an unusual primary structure. One would expected it to play an essential role in the organism, as it has a wide distribution and is high conserved among mammals, yet its exact function remains elusive. Despite the number of effects described for ProTalpha, intracellular and extracellular, none are accepted as its physiological role. Furthermore, many other aspects of its biology still remain obscure. In this review, we discuss the structural properties, location, gene family, functions and immunomodulatory activities of and cellular receptors for ProTalpha. These topics are addressed in an attempt to reconcile opposing outlooks while emphasizing those points where scant investigations do exist. We have also re-evaluated some previous results in light of the structural properties of ProTalpha and have found that molecular mimetism could be the underlying basis. This molecular mimicry hypothesis provides a clue that must not be overlooked for a realistic appraisal of future results.     

Trichomonas vaginalis: identification of a triacylglycerol acylhydrolase

This work describes the identification of a triacylglycerol lipase named TVLip directly onto blood-LB-agar plates by hemolytic screening of a Trichomonas vaginalis cDNA expression library. Sharing significant similarity in the primary sequence with other lipases, the theoretical 3D structure of the TVLip was resolved. The structure reveals the predictive conserved characteristics of other lipases from EC3.1.1.3 group, although presenting one amino acid change in the catalytic triad Ser-His-Asp. Finally, analysis of Northern blot indicates that the expression of the TVLip gene is up-regulated by iron.     

Isolation and characterization of a cDNA encoding a serine proteinase from the root-knot nematode Meloidogyne incognita

This report describes the first serine proteinase gene isolated from the sedentary nematode Meloidogyne incognita. Using degenerate primers, a 1372bp cDNA encoding a chymotrypsin-like serine proteinase (Mi-ser1) was amplified from total RNA of adult females by RT-PCR and 5' and 3' rapid amplification of cDNA ends. The deduced amino acid sequence of Mi-ser1 encoded a putative signal peptide and a prodomain of 22 and 33 amino acids, respectively, and a mature proteinase of 341 amino acids with a predicted molecular mass of 37,680Da. Sequence identity with the top serine proteinases matches from the databases ranged from 23 to 27%, including sequences from insects, mammals, and other nematodes. Southern blot analysis suggested that Mi-ser1 is encoded by a single or few gene copies. The pattern of developmental expression analyzed by Northern blot and RT-PCR indicated that Mi-ser1 was transcribed mainly in females. The domain architecture composed of a single chymotrypsin-like catalytic domain and the detection of a putative signal peptide suggested a digestive role for Mi-ser1.