Interaction of phenylisothiocyanates with the mitochondrial phosphate carrier. I. Covalent modification and inhibition of phosphate transport

The effects of phenylisothiocyanate (PITC) and of the polar analogue p-sulfophenylisothiocyanate (p-sulfoPITC) on the phosphate carrier of bovine heart mitochondria have been investigated. Incubation of mitochondria with the two phenylisothiocyanates leads to inhibition of the phosphate carrier protein. The inhibition of phosphate transport by PITC is unaffected by the addition of dithioerythritol (DTE) or by variation of the pH. The inhibition by p-sulfoPITC is in part removed by DTE; the remaining inactivation of the phosphate carrier, which can be attributed to the reaction with NH₂ groups, is temperature and pH-dependent. Inhibition of phosphate transport by both p-sulfoPITC and PITC depends on the time of incubation and the concentration of the inhibitor. Preincubation with mersalyl protects the carrier protein against the inactivation by p-sulfoPITC but not against PITC. Other SH reagents tested do not show any protective effect. It can thus be concluded that two types of lysine residues are essential for the activity of the phosphate carrier. Lysine(s) of the former type are located at the surface of the membrane and are topologically related to the functional SH groups of the protein. Lysine residue(s) of the latter type are buried in the hydrophobic phase of the membrane.     

Periplasmic Cu,Zn superoxide dismutase and cytoplasmic Dps concur in protecting Salmonella enterica serovar Typhimurium from extracellular reactive oxygen species

Several bacteria possess periplasmic Cu,Zn superoxide dismutases which can confer protection from extracellular reactive oxygen species. Thus, deletion of the sodC1 gene reduces Salmonella enterica serovar Typhimurium ability to colonize the spleens of wild type mice, but enhances virulence in p47phox mutant mice. To look into the role of periplamic Cu,Zn superoxide dismutase and into possible additive effects of the ferritin-like Dps protein involved in hydrogen peroxide detoxification, we have analyzed bacterial survival in response to extracellular sources of superoxide and/or hydrogen peroxide. Exposure to extracellular superoxide of Salmonella Typhimurium mutant strains lacking the sodC1 and sodC2 genes and/or the dps gene does not cause direct killing of bacteria, indicating that extracellular superoxide is poorly bactericidal. In contrast, all mutant strains display a sharp hydrogen peroxide-dependent loss of viability, the dps,sodC1,sodC2 mutant being less resistant than the dps or the sodC1,sodC2 mutants. These findings suggest that the role of Cu,Zn superoxide dismutase in bacteria is to remove rapidly superoxide from the periplasm to prevent its reaction with other reactive molecules. Moreover, the nearly additive effect of the sodC and dps mutations suggests that localization of antioxidant enzymes in different cellular compartments is required for bacterial resistance to extracytoplasmic oxidative attack.     

International retrospective cohort study of neural tube defects in relation to folic acid recommendations: are the recommendations working?

Objectives To evaluate the effectiveness of policies and recommendations on folic acid aimed at reducing the occurrence of neural tube defects.Design Retrospective cohort study of births monitored by birth defect registries.Setting 13 birth defects registries monitoring rates of neural tube defects from 1988 to 1998 in Norway, Finland, Northern Netherlands, England and Wales, Ireland, France (Paris, Strasbourg, and Central East), Hungary, Italy (Emilia Romagna and Campania), Portugal, and Israel. Cases of neural tube defects were ascertained among liveborn infants, stillbirths, and pregnancy terminations (where legal). Policies and recommendations were ascertained by interview and literature review.Main outcome measures Incidences and trends in rates of neural tube defects before and after 1992 (the year of the first recommendations) and before and after the year of local recommendations (when applicable).Results The issuing of recommendations on folic acid was followed by no detectable improvement in the trends of incidence of neural tube defects.Conclusions Recommendations alone did not seem to influence trends in neural tube defects up to six years after the confirmation of the effectiveness of folic acid in clinical trials. New cases of neural tube defects preventable by folic acid continue to accumulate. A reasonable strategy would be to quickly integrate food fortification with fuller implementation of recommendations on supplements.     

Author Index (2003)

Authors Index

Author Index (2003)     

Graded deletion and virus-induced activation of autoreactive CD4+ T cells

We have examined factors governing the negative selection of autoreactive CD4(+) T cells in transgenic mice expressing low (HA12 mice) vs. high (HA104 mice) amounts of the influenza virus hemagglutinin (HA). When mated with TS1 mice that express a transgenic TCR specific for the I-Ed-restricted determinant site 1 (S1) of HA, thymocytes expressing high levels of the clonotypic TCR were deleted in both HA-transgenic lineages. However, through allelic inclusion, thymocytes with lower levels of the clonotypic TCR evaded deletion in TS1 x HA12 and TS1 x HA104 mice to graded degrees. Moreover, in both lineages, peripheral CD4(+) T cells could be activated by the S1 peptide in vitro, and by influenza virus in vivo. These findings indicate that allelic inclusion can allow autoreactive CD4(+) thymocytes to evade thymic deletion to varying extents reflecting variation in the expression of the self peptide, and can provide a basis for the activation of autoreactive peripheral T cells by viruses bearing homologues of self peptides ("molecular mimicry").     

The neutrophil-activating Dps protein of Helicobacter pylori, HP-NAP, adopts a mechanism different from Escherichia coli Dps to bind and condense DNA

The Helicobacter pylori neutrophil-activating protein (HP-NAP), a member of the Dps family, is a fundamental virulence factor involved in H.pylori-associated disease. Dps proteins protect bacterial DNA from oxidizing radicals generated by the Fenton reaction and also from various other damaging agents. DNA protection has a chemical component based on the highly conserved ferroxidase activity of Dps proteins, and a physical one based on the capacity of those Dps proteins that contain a positively charged N-terminus to bind and condense DNA. HP-NAP does not possess a positively charged N-terminus but, unlike the other members of the family, is characterized by a positively charged protein surface. To establish whether this distinctive property could be exploited to bind DNA, gel shift, fluorescence quenching and atomic force microscopy (AFM) experiments were performed over the pH range 6.5–8.5. HP-NAP does not self-aggregate in contrast to Escherichia coli Dps, but is able to bind and even condense DNA at slightly acid pH values. The DNA condensation capacity acts in concert with the ferritin-like activity and could be used to advantage by H.pylori to survive during host-infection and other stress challenges. A model for DNA binding/condensation is proposed that accounts for all the experimental observations.     

Web-Based Surveillance of Public Information Needs for Informing Preconception Interventions

Background

The risk of adverse pregnancy outcomes can be minimized through the adoption of healthy lifestyles before pregnancy by women of childbearing age. Initiatives for promotion of preconception health may be difficult to implement. Internet can be used to build tailored health interventions through identification of the public''s information needs. To this aim, we developed a semi-automatic web-based system for monitoring Google searches, web pages and activity on social networks, regarding preconception health.

Methods

Based on the American College of Obstetricians and Gynecologists guidelines and on the actual search behaviors of Italian Internet users, we defined a set of keywords targeting preconception care topics. Using these keywords, we analyzed the usage of Google search engine and identified web pages containing preconception care recommendations. We also monitored how the selected web pages were shared on social networks. We analyzed discrepancies between searched and published information and the sharing pattern of the topics.

Results

We identified 1,807 Google search queries which generated a total of 1,995,030 searches during the study period. Less than 10% of the reviewed pages contained preconception care information and in 42.8% information was consistent with ACOG guidelines. Facebook was the most used social network for sharing. Nutrition, Chronic Diseases and Infectious Diseases were the most published and searched topics. Regarding Genetic Risk and Folic Acid, a high search volume was not associated to a high web page production, while Medication pages were more frequently published than searched. Vaccinations elicited high sharing although web page production was low; this effect was quite variable in time.

Conclusion

Our study represent a resource to prioritize communication on specific topics on the web, to address misconceptions, and to tailor interventions to specific populations.     

Isoindolone derivatives, a new class of 5-HT2C antagonists: synthesis and biological evaluation

Two independent approaches resulted in the identification of a series of isoindolone derivatives as potent and selective 5-HT2C antagonists. From a Medicinal Chemistry perspective this template was considered interesting as it allowed the incorporation of the carbon-carbon double bond of an earlier dihydropyrrolone series in an aromatic system within a comparatively simple and compact motif. Additionally an in silico screening approach of the corporate database using a 5-HT2C pharmacophore model resulted in the identification of a related structure containing this template. The strategy used to optimise potency at the target receptor and to improve the pharmacokinetic profile is described, resulting in molecules combining high potency with good selectivity and oral bioavailability.     

Phenological stages of natural species and their use as climate indicators

 The objectives of this paper are to: (1) present 10 years of phenological data for nine natural species growing in a Mediterranean-type climate, (2) present threshold temperatures that were derived for the computation of cumulative degree-days (CDD), and (3) evaluate the sensitivity of the nine natural species to weather variability. The study was conducted at the Phenological Research Garden of Oristano, Sardinia, Italy, during the period 1986–96. The observations were made on five typical Mediterranean species and four species that are typical of higher latitudes. The mean annual pattern of phenological events and the CDD from 1 January are given for each development stage. Temperature thresholds were evaluated by comparing the standard deviation about the mean number of days in the development period for each species. A good relationship between timing of phenophase occurrence and temperature was observed for the Mediterranean species, which were little affected by variations in rainfall. Phenological development of the non-native species was affected by springtime rainfall. Accepted: 28 October 1998