The cestode Echinococcus granulosus, the agent of hydatidosis/echinococcosis, is remarkably well adapted to its definitive host. However, the molecular mechanisms underlying the successful establishment of larval worms (protoscoleces) in the dog duodenum are unknown. With the aim of identifying molecules participating in the E. granulosus-dog cross-talk, we surveyed the transcriptomes of protoscoleces and protoscoleces treated with pepsin at pH 2. This analysis identified a multigene family of secreted monodomain Kunitz proteins associated mostly with pepsin/H(+)-treated worms, suggesting that they play a role at the onset of infection. We present the relevant molecular features of eight members of the E. granulosus Kunitz family (EgKU-1 - EgKU-8). Although diverse, the family includes three pairs of close paralogs (EgKU-1/EgKU-4; EgKU-3/EgKU-8; EgKU-6/EgKU-7), which would be the products of recent gene duplications. In addition, we describe the purification of EgKU-1 and EgKU-8 from larval worms, and provide data indicating that some members of the family (notably, EgKU-3 and EgKU-8) are secreted by protoscoleces. Detailed kinetic studies with native EgKU-1 and EgKU-8 highlighted their functional diversity. Like most monodomain Kunitz proteins, EgKU-8 behaved as a slow, tight-binding inhibitor of serine proteases, with global inhibition constants (K(I)(*)) versus trypsins in the picomolar range. In sharp contrast, EgKU-1 did not inhibit any of the assayed peptidases. Interestingly, molecular modeling revealed structural elements associated with activity in Kunitz cation-channel blockers. We propose that this family of inhibitors has the potential to act at the E. granulosus-dog interface and interfere with host physiological processes at the initial stages of infection.

Drug resistance and virulence of Mycobacterium tuberculosis are partially related to the pathogen's antioxidant systems. Peroxide detoxification in this bacterium is achieved by the heme-containing catalase peroxidase, and different two-cysteine peroxiredoxins. M. tuberculosis genome also codifies for a putative one-cysteine peroxiredoxin, alkyl hydroperoxide reductase E (MtAhpE). Its expression was previously demonstrated at a transcriptional level, and the crystallographic structure of the recombinant protein was resolved under reduced and oxidized states. Herein, we report that the conformation of MtAhpE changed depending on its single cysteine redox state, as reflected by different tryptophan fluorescence properties and changes in quaternary structure. Dynamics of fluorescence changes, complemented by competition kinetic assays, were used to perform protein functional studies. MtAhpE reduced peroxynitrite two orders of magnitude faster than hydrogen peroxide (1.9 x 107 M-1s-1 vs 8.2 x 104 M-1s-1 at pH 7.4 and 25 degrees C, respectively). The latter also caused cysteine overoxidation to sulfinic acid, but at much slower rate (40 M-1s-1). The pKa of the thiol in the reduced enzyme was 5.2, more than one unit lower than that of the sulfenic acid in the oxidized enzyme. The pH profile of hydrogen peroxide-mediated thiol and sulfenic acid oxidations indicated thiolate and sulfenate as the reacting species. The formation of sulfenic acid as well as the catalytic peroxidase activity of MtAhpE were demonstrated using the artificial reducing substrate thionitrobenzoate. Taken together our results indicate that MtAhpE is a relevant component in the antioxidant repertoire of Mycobacterium tuberculosis probably involved in peroxide, and specially peroxynitrite detoxification.

Cystathionine beta-synthase (CBS) is a homocysteine metabolizing enzyme that contains pyridoxal phosphate (PLP) and a six-coordinate heme cofactor of unknown function. CBS was inactivated by peroxynitrite, the product of nitric oxide and superoxide radicals. The IC(50) was approximately 150 muM for 5 muM ferric CBS. Stopped-flow kinetics and competition experiments showed a direct reaction with a second-order rate constant of (2.4-5.0) x 10(4) M(-1) s(-1)(pH 7.4, 37 degrees C). The radicals derived from peroxynitrite, nitrogen dioxide and carbonate radical, also inactivated CBS. Exposure to peroxynitrite did not modify bound PLP but led to nitration of Trp208, Trp43 and Tyr223 and alterations in the heme environment including loss of thiolate coordination, conversion to high spin and bleaching, with no detectable formation of oxo-ferryl compounds nor promotion of one-electron processes. This study demonstrates the susceptibility of CBS to reactive oxygen/nitrogen species, with potential relevance to hyperhomocysteinemia, a risk factor for cardiovascular diseases.

INTRODUCTION: To evaluate the impact of comprehensive geriatric assessment and management of high-risk elders in a medical short stay unit located in the emergency department of a general hospital. MATERIAL AND METHODS: We performed a descriptive, prospective study of patients admitted to the medical short stay unit for geriatric patients of the emergency department in 2006. RESULTS: A total of 749 patients were evaluated, with a mean (standard deviation) stay in the unit of 37 (16) h. The mean age was 86 (7) years; 57% were women, and 50% had moderate-severe physical impairment and dementia. Thirty-five percent lived in a nursing home. The most frequent reason for admission was exacerbation of chronic cardiopulmonary disease. Multiple geriatric syndromes were identified. The most frequent were immobility, pressure sores and behavioral disorders related to dementia. Seventy percent of the patients were discharged to home after being stabilized and were followed-up by the geriatric clinic and day hospital (39%), the home care medical team (11%), or the nursing home or primary care physician (20%). During the month after discharge, 17% were readmitted and 7.7% died, especially patients with more advanced age or functional impairment. After the unit was opened, admissions to the acute geriatric unit fell by 18.2%. CONCLUSIONS: Medical short stay units for geriatric patients in emergency departments may be useful for geriatric assessment and treatment of exacerbations of chronic diseases. These units can help to reduce the number of admissions and optimize the care provided in other ambulatory and domiciliary geriatric settings.

Agrobacterium radiobacter K84 is a commercial agent used worldwide to control crown gall disease caused by pathogenic isolates of A. tumefaciens. More than 2,000 transposon insertion derivatives of strain K84 were screened by a standardized greenhouse bioassay to identify mutants defective in biocontrol. Three mutants affected in biocontrol properties were identified. All three mutants displayed normal levels of attachment to tomato seed and root colonization. One of these mutants, M19-164, exhibited partial biocontrol and did not produce detectable levels of agrocin 84. In this mutant, the transposon is located in the agn locus of pAgK84, which codes for agrocin 84 biosynthesis. The second mutant, M19-158, also exhibited partial biocontrol and produced reduced amounts of agrocin 84 as a result of a mutation in a chromosomal gene of unknown function. The third mutant, M9-22, failed to biocontrol, was impaired in both growth in minimal medium and siderophore production, and failed to produce detectable levels of agrocin 84. The chromosomal gene ahcY, which encodes S-adenosyl-l-homocysteine hydrolase, was disrupted in this mutant. Expression of a functional copy of ahcY in M9-22 restored all of the altered phenotypes. The fact that all identified biocontrol mutants exhibited a partial or total defect in production of agrocin 84 indicates that this antibiotic is required for optimum biocontrol. This study also identified two chromosomally encoded genes required for agrocin 84 production. That a mutation in ahcY abolishes biocontrol suggests that the intracellular ratio of S-adenosyl-l-methionine to S-adenosyl-l-homocysteine is an important factor for agrocin 84 biosynthesis. Finally, we demonstrate that the ahcY gene in strain K84 is also required for optimal growth as well as for antibiotic production and biocontrol of crown gall disease.

The single thiol of human serum albumin (HSA-SH) is the predominant plasma thiol. Both circulating albumin and pharmaceutical preparations are heterogeneous regarding the thiol redox status, as revealed by anion-exchange-hydrophobic interaction chromatography. Sulfenic acid (HSA-SOH) is an intermediate in HSA-SH oxidation processes that was detected through different techniques including mass spectrometry. Recently, quantitative data led to the determination of rate constants. The preferred fate of HSA-SOH is the formation of mixed disulfides. Alternatively, HSA-SOH can be further oxidized to sulfinic and sulfonic acids. Oxidized forms increase under disease conditions, underscoring the importance of HSA-SH as a plasma scavenger of intravascular oxidants. We here provide a critical review of the oxidation of HSA-SH in the context of the intravascular compartment, with emphasis in the methodological approaches of mass spectrometry and chromatography for the analysis of albumin thiol redox states.

BACKGROUND: Honduras has the highest concentration of HIV and AIDS cases in Central America, with an estimated adult HIV prevalence of 1.5%. Prevalence is higher among certain ethnic groups such as the Garífuna with a reported HIV prevalence of 8%. METHODS: A biological and behavioral survey was conducted on a stratified random sample of the Garífuna population in Honduras, using computer-assisted interviews. Blood was tested for HIV, herpes simplex type 2 (HSV-2), and syphilis; urine was tested for Chlamydia trachomatis, Neisseria gonorrhoea, Trichomonas vaginalis, and Mycoplasma genitalum. RESULTS: We enrolled a total of 817 participants, 41% female and 51% male. Estimated prevalences and 95% confidence intervals (CI) were: HIV, 4.5%(95% CI: 3.0 to 6.6), HSV-2, 51.1%(95% CI: 46.7 to 55.6), and syphilis seropositivity, 2.4%(95% CI: 1.4 to 4.0). Sexually transmitted infections in urine were: chlamydia, 6.8%(95% CI: 4.7 to 9.7), gonorrhea, 1.1%(95% CI: 0.4 to 2.9), trichomoniasis, 10.5%(95% CI: 8.1 to 13.6), and Mycoplasma genitalium, 7.1%(95% CI: 5.1 to 9.9). Consistent condom use was low with stable (10.6%) and casual (41.4%) partners. In multivariate analysis, HIV was associated with rural residence. HSV-2 was associated with female sex, older age, and syphilis seropositivity. CONCLUSIONS: We found a moderate prevalence of HIV and a high prevalence of HSV-2 among the Garífunas. HSV-2 may increase the vulnerability of these populations to HIV in the future. Intervention strategies should emphasize sexually transmitted infection control and condom promotion, specifically targeting the Garífuna population.

Human serum albumin (HSA) is the most abundant protein in the intravascular compartment. It possesses a single thiol, Cys34, which constitutes ~80% of the total thiols in plasma. This thiol is able to scavenge plasma oxidants. A central intermediate in this potential antioxidant activity of human serum albumin is sulfenic acid (HSA-SOH). Work from our laboratories has demonstrated the formation of a relatively stable sulfenic acid in albumin through complementary spectrophotometric and mass spectrometric approaches. Recently, we have been able to obtain quantitative data that allowed us to measure the rate constants of sulfenic acid reactions with molecules of analytical and biological interest. Kinetic considerations led us to conclude that the most likely fate for sulfenic acid formed in the plasma environment is the reaction with low molecular weight thiols to form mixed disulfides, a reversible modification that is actually observed in ~25% of circulating albumin. Another possible fate for sulfenic acid is further oxidation to sulfinic and sulfonic acids. These irreversible modifications are also detected in the circulation. Oxidized forms of albumin are increased in different pathophysiological conditions and sulfenic acid lies in a mechanistic junction, relating oxidizing species to final thiol oxidation products.