Water quality and diversity of the Recent ostracod fauna in lowland springs from Lombardy (northern Italy)

Sedimentary records provide important information for understanding changes in the history of eutrophication in Lake Taihu. In addition, the catchment nutrient model SWAT provides a powerful tool to examine eutrophic changes in a long-term context. Since it is difficult to evaluate impacts of natural eutrophic development and anthropogenic changes in catchment discharge and land use, simulation of past changes provides a mirror on processes and dynamics. Boundaries in the simulations are set to a pre-industrial time to evaluate natural-agricultural nutrient changes in Taihu Basin a 100 years ago. Total nitrogen (TN) and total phosphorus (TP) in the main channel flowing into the lake are simulated in four sub-basins for 200 model years. Results show that modeling can capture basic features of basin nutrient development, where mean TN concentration (0.12 mg l⁻¹) can be compared in broad scale to mean TN concentration (0.17 mg kg⁻¹) from Lake Taihu sedimentary cores dating back about 100 years. Spatial nutrient simulations suggest that the two major nutrient sources are from the southwestern sub-basin (48% TN and 68% TP of the basin total) and the northwestern sub-basin (18% TN and 17% TP). There are differences of +7.3 × 10⁴ kg TN and +2.0 × 10⁵ kg TP between total input and output values, simulating mean annual amounts of nutrient deposited into the lake. TN and TP concentration differences between input and output sub-basins become smaller in the second 100 years than the first 100 years, suggesting a 100 year period to reach a balance of net nutrients. Catchment nutrient modeling provides a basis to evaluate how nutrient production and balance responded to environmental changes over 200 years in Taihu Basin.     

Cytogenetic characterization of the Trinidad endemic, Arachnocoris trinitatus Bergroth: the first data for the tribe Arachnocorini (Heteroptera: Cimicomorpha: Nabidae)

As an extension of the ongoing cytogenetic studies of the bug family Nabidae (Heteroptera: Cimicomorpha), the first evidence for the tribe Arachnocorini (the subfamily Nabinae), with reference to the Trinidad endemic, Arachnocoris trinitatus Bergroth, is provided. This is an attempt to gain a better insight into the evolution, systematics and within-family relationships of the family Nabidae. The studies were conducted using a number of cytogenetic techniques. The male karyotype (chromosome number and size; sex chromosome system; NOR location; C-heterochromatin amount, distribution and characterization in terms of the presence of AT-rich and GC-rich DNA), and male meiosis with particular emphasis on the behavior of the sex chromosomes in metaphase II are described. Also investigated are the male and female internal reproductive organs with special reference to the number of follicles in a testis and the number of ovarioles in an ovary. A. trinitatus was found to display a number of characters differentiating it from all hitherto studied nabid species placed in the tribe Nabini of the subfamily Nabinae, and in the tribe Prostemmatini of the subfamily Prostemmatinae. Among these characters are chromosome number 2n = 12 (10 + XY), the lowest within the family, nucleolus organizer regions (NORs) situated on the autosomes rather than on the sex chromosomes as is the case in other nabid species, and testes composed of 3 follicles but not of 7 as in other nabids. All the data obtained suggest many transformations during the evolution ofA. trinitatus.     

Helicobacter pylori infection and coronary artery disease

The aim of this investigation was to determine the seroprevalence of H. pylori in patients with coronary artery disease (CAD). Patients with coronary artery disease (n = 90) and control group (n = 90) were enrolled into this randomized, multi-centre study. CAD risk factors analyzed included age, male gender, diabetes mellitus, systemic hypertension, cigarette smoking, hypercholesterolemia and socioeconomic status. The results of this study showed a higher seroprevalence of Helicobacter pylori infection in patients with CAD compared to controls (78.8% versus 58.3%, p < 0.05). However, Helicobacter pylori seropositivity was not associated with coronary artery risk factors (smoking, body mass index, diabetes mellitus, hypertension, total cholesterol and socioeconomic status) either in the whole study population or in the patients and control subjects analyzed separately (P > 0.05). Further study are needed to clarify the precise role of Helicobacter pylori infection on the development of coronary artery disease.     

NTP-binding properties of the blue-light receptor YtvA and effects of the E105L mutation

YtvA is a blue-light-sensing protein from Bacillus subtilis related to plant phototropins. It carries a LOV (light, oxygen and voltage) domain, binding FMN (flavin mononucleotide) as chromophore, and a STAS (sulphate transporters and antisigma-factor antagonists) domain with poorly characterized function. We have recently shown that YtvA binds triphosphate nucleotides (NTP) and highlighted a structural similarity between the STAS domain and small GTP-binding proteins. In this work we further investigated the NTP-binding properties of YtvA, employing a fluorescent derivative of GTP (GTP_TR) and mutagenesis experiments. The main results are as follows: (a) competition experiments indicate that the affinity of YtvA for GTP is much higher than that for GDP and GMP. (b) Blue-light-induced structural changes are transmitted from the LOV core to the NTP-binding cavity, establishing a possible intraprotein signal-transduction pathway. (c) A mutation in the central β-scaffold of the LOV core, E105L, impairs the light-driven spectroscopic changes of bound GTP_TR. This result is supported by circular dichroism data, in that YtvA-E105L does not show the light-induced conformational change in the turn fraction that characterizes YtvA, implying that E105 is functionally important. (d) In the structural model of the LOV-STAS complex, based on docking algorithms, the interface includes the Iβ–Hβ loop on the LOV core, as well as parts of the central β-scaffold. E105 is predicted to interact with the LOV-STAS linker region, suggested to play a role in phototropin signaling. Proceedings of the XVIII Congress of the Italian Society of Pure and Applied Biophysics (SIBPA), Palermo, Sicily, September 2006.     

Effect of mercury on selenium utilization and selenoperoxidase activity in LNCaP cells

Formation of stable complexes with protein thiols is the best-known mechanism of mercury toxicity. However, the solubility product of Hg(2+) with sulfides, although very low, is higher than that with selenides, suggesting that the fully reduced form of selenium might also be a relevant target for Hg(2+). In cells, selenide is the suggested intermediate for selenoprotein biosynthesis and selenoenzymes, in turn, contain reduced selenium as the catalytic moiety. Thus, inhibition of biological functions of selenium could be seen as a different mechanism of Hg(2+) toxicity. To address this issue, we investigated selenoperoxidase (SeGPx) activity in LNCaP cells exposed to HgCl(2). Cells growing in standard medium express a low GPx activity, which increases on addition of selenium donors such as selenite, selenomethionine, or methyl-Se-cysteine. HgCl(2) added to the medium has different effects depending on the type of Se donor. A progressive decrease of SeGPx activity is observed in cells grown in standard medium exposed to HgCl(2), while coadministration of suprastoichiometric amounts of HgCl(2) prevents the increase of SeGPx activity only when selenite, but not selenomethionine or methyl-Se-cysteine, is the selenium source. From this evidence we conclude that HgCl(2): (a) does not inhibit directly SeGPxs, as confirmed on isolated enzymes; (b) does not interfere with the intermediates of the metabolic pathway of selenoprotein synthesis; and (c) decreases the bioavailability of selenium only when ionic complexes can be formed.     

ROX1, a gene induced by rolB, is involved in procambial cell proliferation and xylem differentiation in tobacco stamen

The Agrobacterium rhizogenes oncogene rolB mimics the effects of auxin in that it increases the sensitivity of transformed cells to this hormone. Here we isolated a tobacco gene, ROX1, acting downstream of rolB. We show that plants with reduced levels of ROX1 mRNA, due to the expression of a 35S-driven ROX1-antisense construct, have flowers with stamens and pistils longer than normal because of an increased number of cells. Localized expression of rolB in anthers results in overexpression of ROX1 and reduced growth of stamens, due to a reduced number of cells. In addition, the longer stamens of antisense plants show a delayed xylem differentiation in the lateral bundles, primarily of the junction region between anther and filament, while the shorter stamens of ROX1-overexpressing plants show a precocious differentiation of xylem cells in the same tissues. Expression of ROX1 in stamens peaks at early stages of stamen growth, and ROX1 mRNA is localized mostly in anther procambial cells. The sequence of ROX1 shares a conserved element with a number of plant genes, including TED3, which is involved in xylem differentiation. These results point to a role of ROX1 in the balance between proliferation of procambial cells and xylem differentiation during stamen development.