Cell-Associated and Extracellular Proteinases in Blastocrithidia culicis: Influence of Growth Conditions

The proteinase profile of Blastocrithidia culicis was analyzed, as well as how different growth conditions influenced its expression by gelatin-SDS-PAGE and the use of specific proteinase inhibitors. Multiple cell-associated proteinases with molecular masses corresponding to 33, 55, 60 kDa (cysteine proteinases) and 77, 80, 90, and 108 kDa (metalloproteinases) were detected using these methods. All the metalloproteinases identified were partitioned into the detergent phase after Triton X-114 extract, suggesting that they are membrane-bound, while all cysteine proteinases were partitioned into the aqueous phase. The proteolytic zymograms were similar when three different media were used for variable times of incubation. However, few quantitative and qualitative changes were observed. The secreted proteinase profile showed an heterogeneous pattern of enzymatic activities whose expression was dependent on time of growth and medium composition. However, the extracellular proteinase activities were abolished by 1,10-phenanthroline, suggesting that all of them are zinc-metalloproteinases. Received: 25 October 2000 / Accepted: 10 January 2001     

Effect of blending lignin biopolymer on the biodegradability of polyolefin plastics

The ability of the lignin-degrading microorganism Phanerochaete chrysosporium to attack polyethylene and polypropylene was investigated using a series of polymer blends containing 10, 20 and 30% lignin obtained from the waste product of pulp and paper industry. In the cultivation medium, lignin peroxidase and Mn(II)peroxidase activities were detected. Degradation was verified by quantitative u.v. spectrophotometric analysis of the cultivation medium and by liberation of CO₂ from the blends. Measurement of the tensile strength after 30-days cultivation showed that the mechanical properties of the polymer blends were decreased during the biodegradation process. The isolation of oligomer fractions by tetrahydrofuran (THF) extraction of biodegraded polymers and their characterization by gel permeation chromatography (GPC), u.v. and Fourier transmission infrared (FTIR) spectroscopy indicates that biotransformation of the lignin component during the cultivation process initiates partial biodegradation of the synthetic polymer matrix.     

Exogoninae (Polychaeta: Syllidae) from the Mexican Caribbean region with a key for the Gran Caribbean species]

This paper identifies the Exogoninae (Syllidae) from the Mexican Caribbean coasts and includes a key to identify all the species recorded from the Grand Caribbean Sea. The classification of the family and the composition of Exogoninae are briefly examined; the correct names of the subfamilies are Syllinae Grube, 1850, Eusyllinae Malaquin, 1893, Autolytinae Malaquin, 1893 and Exogoninae Langerhans, 1879. Exogoninae includes Anguillosyllis Day, 1963, Brania de Quatrefages, 1866, Braniella Hartman, 1963, Exogone ?rsted, 1845, Exogonella Hartman, 1961, Exogonoides Day, 1963, Parapionosyllis Fauvel, 1923, Psammosyllis Westheide, 1990, Spermosyllis Claparède, 1864, and Sphaerosyllis Claparède, 1863. Pseudexogone Augener, 1922, formerly included in the group, is not a syllid; it belongs to Pilargidae. We collected 814 specimens belonging to 3 genera, 3 subgenera and 13 species as Brania (4), Exogone (4) and Sphaerosyllis (5); five new species are described: Brania russelli n. sp, Brania uebelackerae n. sp, Brania westheidei n. sp., Exogone (Exogone) bondi n. sp. and Exogone (Parexogone) sanmartini n. sp. For each species, selected references, diagnostic features, observations on morphological variability, distribution and illustrations are provided; new species also have an english diagnosis. Most abundant species were B. uebelackerae n. sp. (295), S. taylori Perkins (169), E. (E.) dispar Webster (76), and E. (E.) bondi n sp. (72).     

Age-related variation in wing shape of migratory and sedentary Blackcaps Sylvia atricapilla

In many passerines, juveniles have shorter and more rounded wings than adults. Given that (1) long and pointed wings improve endurance in migratory flights, (2) shorter and rounded wings improve manoeuvrability, and (3) juvenile birds are more vulnerable to predators than adults, it has been hypothesised that ontogenetic variation in wing shape results from a greater importance of predation avoidance relative to migration performance during the first year of life. If so, wing shape should not change with age in the absence of migration-related selection for longer and more pointed wings. We test this by studying the variation with respect to age in wing length and wing pointedness of migratory and sedentary Blackcaps wintering in southern Spain. Migratory Blackcaps had longer and more pointed wings than sedentary Blackcaps. Juveniles had shorter wings than adults in migratory populations, but not in sedentary populations. The variation with age in wing pointedness was less pronounced, and was found in migratory females only. These differences between the two traits could be related to a stronger selection for pointed wings than for longer wings with increasing distance of migration, and to an increased migratoriness of females in partially migratory Blackcap populations. We hypothesise that, in migratory Blackcaps, a shorter and more rounded wing in juveniles could be selected for if the decrease in predation rate compensated for the somewhat greater costs of the first migration attempt. On the other hand, there are no costs of migration in sedentary Blackcaps, which hence maintain a similar wing shape, giving high manoeuvrability, both as juveniles and as adults.     

Genotoxicity assessment in aquatic environments under the influence of heavy metals and organic contaminants

The genotoxicity of river water and sediment including interstitial water was evaluated by microscreen phage-induction and Salmonella/microsome assays. Different processes used to fractionate the sediment sample were compared using solvents with different polarities. The results obtained for mutagenic activity using the Salmonella/microsome test were negative in the water and interstitial water samples analysed using the direct concentration method. The responses in the microscreen phage-induction assay showed the presence of genotoxic or indicative genotoxic activity for at least one water sample of each site analysed using the same concentration method. Similar results were obtained for interstitial water samples, i.e. absence of mutagenic activity in the Salmonella/microsome test and presence of genotoxic activity in the microscreen phage-induction assay. Metal contamination, as evidenced by the concentrations in stream sediments, may also help explain some of these genotoxic results. Stream sediment organic extracts showed frameshift mutagenic activity in the ether extract detected by Salmonella/microsome assay. The concentrates evaluated by microscreen phage-induction assay identified the action of organic compounds in the non-polar, medium polar and polar fractions. Thus, the microscreen phage-induction assay has proven to be a more appropriate methodology than the Salmonella/microsome test to analyse multiple pollutants in this ecosystem where both organic compounds and heavy metals are present.     

Hypothesis testing for the genetic background of quantitative traits

The testing of Bayesian point null hypotheses on variance component models have resulted in a tough assignment for which no clear and generally accepted method exists. In this work we present what we believe is a succeeding approach to such a task. It is based on a simple reparameterization of the model in terms of the total variance and the proportion of the additive genetic variance with respect to it, as well as on the explicit inclusion on the prior probability of a discrete component at origin. The reparameterization was used to bypass an arbitrariness related to the impropriety of uninformative priors onto unbounded variables while the discrete component was necessary to overcome the zero probability assigned to sets of null measure by the usual continuous variable models. The method was tested against computer simulations with appealing results.     

Genetic determination of the mitochondrial adenine nucleotide translocation system and ITS role in the eukaryotic cell

On integrating experimental data published previously, the following picture of the mitochondrial adenine nucleotide (AdN) translocation system is being presented: 1. The AdN translocation system serves not only to transport ATP synthesized within mitochondria into the cytosol but also to transport cytosolic ATP into the mitochondria when oxidative phosphorylation is not functioning. 2. The AdN translocator is coded for by nuclear genes and the mitochondrial protein synthesis is not involved in its formation. 3. The AdN translocation system must be preserved and functioning even in cells which could dispense with oxidative phosphorylation. It assures appropriate concentrations of intramitochondrial ATP. 4. The intramitochondrial ATP is required for normal replication of mitochondrial DNA. Tis supports the view that the mitochondrion is a self-replicating semi-autonomous organelle. 5. The appropriate concentration of ATP must be present in mitochondria to make possible cell growth or multiplication. This points to a direct or indirect role of mitochondria in the control of cell proliferation.     

Metabolism of benzo(a)pyrene by human lung microsomal fractions

The metabolism of benzo(a)pyrene was studied using microsomal fractions obtained from human lung derived at either resection or autopsy. The rates of metabolism and metabolite distribution were monitored using high pressure liquid chromatography and the metabolic rates were noted to be similar to those obtained using rat lung microsomes. In contrast to the rat, human lung microsomes appear to form a higher percentage of the 7,8-dihydro-7, 8-diol or 9,10-dihydro-9, 10-diol of benzo(a)pyrene as a fraction of the total metabolites. However, there was a significant variation among the human lung microsomal preparations which might reflect the clinical diagnosis and/or individual variation.