No abstract

An antibody reacting with the plasma membrane of working myocardial cells, skeletal muscle fibres, and endothelial cells (EVI antibody) has been described in the sera of patients with Chagas' disease. In the present study of rat isolated atrial preparations beating in ddifferent media, direct immunofluorescence and ultrastructural immunohistochemical procedures indicate that the antibody can interact with the living tissue, becoming fixed to the plasma membranes. Transmission electronmicroscopy studies also showed the presence of sarcolemmal alterations. These observations suggest a possible pathogenic effect of the EVI antibody. The presence of EVI-positive sera in the beating medium leads to a significant increase in the frequency of contractions; no significant effects of EVI-positive sera in contractile force were seen. The increase in frequency could be prevented by previous treatment with a b-adrenergic blocking agent (MJ-1999), but not by an x-blocker (phentolamine) or by an anti-histamine compound (cyproheptadine). The changes described were observed only in those atrial preparations which were beating in media containing EVI-positive sera. In those atria beating in control media (KR,KR plus normal human serum, KR plus EVI-negative chagasic serum), neither immunological nor morphological or functional changes wersence of EVI-positive chagasic serum diminished atrial stimulation after added norepinephrine. These results suggest the possibility that the EVI antibody may act as a b-adrenergic agonist at the cell plasma membrane level. Such an effect might account for some of the clinical features of chronic Chagas' heart disease.

No abstract

L-Ergothioneine (ET), the 2-thioimidazole derivative of trimethylhistidine, is biosynthesized by select fungi and bacteria, notably Mycobacterium tuberculosis, and functions as a scavenger of reactive oxygen species. The extent to which ET broadly functions in bacterial cells unable to synthesize it is unknown. Here we show that spd_1642-1643 in Streptococcus pneumoniae, a Gram-positive respiratory pathogen, encodes an ET uptake ATP-binding cassette (ABC) transporter, designated EgtU. The solute binding domain (SBD) of EgtU, EgtUC, binds ET with high affinity and exquisite specificity in a cleft between the two subdomains, with cation-π interactions engaging the betaine moiety and a network of water molecules that surround the thioimidazole ring. EgtU is highly conserved among known quaternary amine compound-specific transporters and widely distributed in Firmicutes, including the human pathogens Listeria monocytogenes, as BilEB, Enterococcus faecalis and Staphylococcus aureus. ET increases the chemical diversity of the low molecular weight thiol pool in Gram-positive human pathogens and may contribute to antioxidant defenses in the infected host.

SUMMARYTwenty-four out of 25 patients with Chagas' heart disease have circulating immunoglobulins which react by indirect immunofluorescence technique with endocardium, interstitium and blood vessels of the heart. With skeletal muscle the reaction was observed in interstitium and vascular structures, but with other organs it was limited to vascular structures. This endocardial-vascularinterstitial factor (EVI) fixed complement. Some evidence indicated that this reaction could be obtained using the serum and tissues from the same patient: for instance, in one positive case a right atrium biopsy was performed. When this substrate was used for indirect immunofluorescence, employing the patient's own serum, positive results were obtained. Specificity is not related to AB blood group systems, or to Forssman or Wassermann antigens. The reacting factor was effectively absorbed from sera with organ homogenates, and with guinea pig red blood cells although it was independent of heterophil antibodies. In almost all cases studied, the EVI factor of the serum, when absorbed with epimastigotes of T.cruzi, results in a negative reaction, suggesting that the genesis of the reacting gamma globulin is related to antigens of T.cruzi.The EVI factor was also observed in 19 of 47 asymptomatic controls from an endemic area with positive serology for T.cruzi and in 3 of 27 with negative serology. These 3 cases had anti-T.cruzi antibodies in titers just below those considered of clinical value. The EVI factor was not observed in 119 normal individuals and 286 patients with selected cardiovascular diseases or another pathology from a nonendemic area. These findings and those mentioned above were statistically significant (P < 0.001). These results indicate the possibility of a more accurate diagnosis of chagasic myocardiopathy based on the study of the EVI factor, because in an individual case the diagnosis of chronic chagasic cardiopathy can be considered with a low probability in the absence of this factor.

An antibody reacting with endocardium, vascular structures and interstitium of striated muscle (EVI antibody), by the indirect immunofluorescence technique, was recently described in Chagas' disease. In the present report the identification of tissue structures responsible for the EVI reaction was studied by means of ultrastructural immunochemical methods. Positive reactions were observed in the plasma membrane of the heart and skeletal muscle fibers and endothelial cells of blood vessels.Absorption of positive sera with T. cruzi abolished both patterns observed by electron microscopic methods. These results are in agreement with observations performed with the indirect immunofluorescence technique. Additional Indexing Words:American Trypanosomiasis Sarcolemmal antigens Endothelial cell antigensImmunity and the hear Parasitic diseases of the heart THE PRESENCE OF a circulating antibody reacting with endocardium, vascular structures, and interstitium of striated muscle (EVI antibody) has recently been described using immunofluorescence techniques and has been reported to be present in 95% of patients with Chagas' heart disease and in 45% of asymptomatic individuals infected with Trypanosoma cruzi.' This antibody seems to have a high clinical specificity.' Absorption experiments suggest that the EVI antigenic system is present in mammals' tissues and in T. cruzi.' In the original communication' the precise localization of the tissue struc-

In this work, the antifouling activity of five alkaloids, isolated from trees of the Atlantic rainforest, was studied. The tested alkaloids were olivacine (1), uleine (2) and N‐methyltetrahydroellipticine (3) from Aspidosperma australe (‘yellow guatambú’) and the furoquinoline alkaloids kokusaginine (4) and flindersiamine (5) from Balfourodendron riedelianum (‘white guatambú’). All these compounds can be isolated from their natural sources in high yields in a sustainable way. The five compounds were subjected to laboratory tests (attachment test of the mussel Mytilus edulis platensis) and field trials, by incorporation into soluble matrix paints, and 45 days of exposure of the painted panels in the sea. The results show that compound 3 is a very potent antifoulant, and that compounds 4 and 5 are also very active, while compounds 1 and 2 did not show any significant antifouling activity. These results open the way for the development of environmentally friendly antifouling agents, based on abundant and easy‐to‐purify compounds that can be obtained in a sustainable way.

The different niches through which bacteria move during their life cycle require a fast response to the many environmental queues they encounter. The sensing of these stimuli and their correct response is driven primarily by transcriptional regulators. This kind of protein is involved in sensing a wide array of chemical species, a process that ultimately leads to the regulation of gene transcription. The allosteric-coupling mechanism of sensing and regulation is a central aspect of biological systems and has become an important field of research during the last decades. In this review, we summarize the state-of-the-art techniques applied to unravel these complex mechanisms. We introduce a roadmap that may serve for experimental design, depending on the answers we seek and the initial information we have about the system of study. We also provide information on databases containing available structural information on each family of transcriptional regulators. Finally, we discuss the recent results of research about the allosteric mechanisms of sensing and regulation involving many transcriptional regulators of interest, highlighting multipronged strategies and novel experimental techniques. The aim of the experiments discussed here was to provide a better understanding at a molecular level of how bacteria adapt to the different environmental threats they face.