Aortic root to left atrium fistula: a rare complication of infective endocarditis in a native aortic valve

The image shows a pseudoaneurysm of the mitral-aortic intervalvular fibrosa and a fistula between the non-coronary sinus and the left atrium.     

Protein histidine phosphatase 1 negatively regulates CD4 T cells by inhibiting the K+ channel KCa3.1

The calcium activated K⁺ channel KCa3.1 plays an important role in T lymphocyte Ca²⁺ signaling by helping to maintain a negative membrane potential, which provides an electrochemical gradient to drive Ca²⁺ influx. We previously showed that nucleoside diphosphate kinase beta (NDPK-B), a mammalian histidine kinase, is required for KCa3.1 channel activation in human CD4 T lymphocytes. We now show that the mammalian protein histidine phosphatase (PHPT-1) directly binds and inhibits KCa3.1 by dephosphorylating histidine 358 on KCa3.1. Overexpression of wild-type, but not a phosphatase dead, PHPT-1 inhibited KCa3.1 channel activity. Decreased expression of PHPT-1 by siRNA in human CD4 T cells resulted in an increase in KCa3.1 channel activity and increased Ca²⁺ influx and proliferation after T cell receptor (TCR) activation, indicating that endogenous PHPT-1 functions to negatively regulate CD4 T cells. Our findings provide a previously unrecognized example of a mammalian histidine phosphatase negatively regulating TCR signaling and are one of the few examples of histidine phosphorylation/dephosphorylation influencing a biological process in mammals.     

Enterococcal infections in a Greek intensive care unit: a 5-y study

In this study we determined the incidence, resistance pattern, and mortality rate associated with infection caused by Enterococcus faecalis and Enterococcus faecium among patients in a multidisciplinary intensive care unit (ICU). A total of 111 patients with E. faecalis and 60 with E. faecium infections were identified during a 5-y period (1992-96). We observed an increase in the incidence of enterococcal infections (from 5.46 to 8.46 per 1000 patients-days, p = 0.0112), due mainly to the increased incidence of E. faecium (from 0.45 to 4.06 per 1000 patients-days, p = 0.002). Blood was the most common site of enterococcus isolation. E. faecium was more resistant to antibiotics than E. faecalis, but no vancomycin resistant enterococcus was isolated. Patients with E. faecium infection had a significantly higher mortality than patients with E. faecalis infection (66% vs. 41.5%, p = 0.0035 for infection from any site and 85.7 vs. 47.7%, p = 0.012 for bacteremic patients). r 4n- D I .- .- - .. . .     

The administration of cisapride as an adjuvant to PEG-electrolyte solution for colonic cleansing: a double-blind randomized study

BACKGROUND/AIMS: Traditional bowel preparation before colonoscopy involves lavage with approximately 4L of polyethylene glycol (PEG)-electrolyte solution. Only a few studies have been published evaluating the use of cisapride in routine bowel preparation. METHODOLOGY: We conducted a blinded, placebo-controlled trial with the prokinetic agent, cisapride, in addition to standard PEG-electrolyte lavage. Of 115 patients undergoing colonoscopy, 58 were randomized (double-blind) to PEG plus cisapride (10 mg per os thrice per day three days before the procedure and one 10-mg dose on the morning of the procedure) and 57 to PEG plus a placebo of identical appearance. The adequacy of the preparation was scored on a four-point grading scale for each anatomic-segment and for the overall impression. A questionnaire was also used to assess each patient's symptoms during lavage. RESULTS: The difference in the overall score between the two groups was not significant (p=0.21). The quality of bowel preparation was significantly better in transverse (p=0.001), ascending (p=0.0053), and cecum (p=0.0001) in the cisapride group than in the placebo group. The differences in symptoms scores between the two groups were not significant in nausea, abdominal cramps and bloating but there was improvement in symptom score of vomiting in cisapride group (p=0.0422). CONCLUSIONS: The administration of cisapride to patients undergoing colonic lavage may be an effective adjuvant to PEG-electrolyte solution particularly with respect to increase patient acceptability.     

Bacteria in an intense competition for iron: Key component of the Campylobacter jejuni iron uptake system scavenges enterobactin hydrolysis product

To acquire essential Fe(III), bacteria produce and secrete siderophores with high affinity and selectivity for Fe(III) to mediate its uptake into the cell. Here, we show that the periplasmic binding protein CeuE of Campylobacter jejuni, which was previously thought to bind the Fe(III) complex of the hexadentate siderophore enterobactin (K_d ∼ 0.4 ± 0.1 µM), preferentially binds the Fe(III) complex of the tetradentate enterobactin hydrolysis product bis(2,3-dihydroxybenzoyl-l-Ser) (H₅-bisDHBS) (K_d = 10.1 ± 3.8 nM). The protein selects Λ-configured [Fe(bisDHBS)]²⁻ from a pool of diastereomeric Fe(III)-bisDHBS species that includes complexes with metal-to-ligand ratios of 1:1 and 2:3. Cocrystal structures show that, in addition to electrostatic interactions and hydrogen bonding, [Fe(bisDHBS)]²⁻ binds through coordination of His227 and Tyr288 to the iron center. Similar binding is observed for the Fe(III) complex of the bidentate hydrolysis product 2,3-dihydroxybenzoyl-l-Ser, [Fe(monoDHBS)₂]³⁻. The mutation of His227 and Tyr288 to noncoordinating residues (H227L/Y288F) resulted in a substantial loss of affinity for [Fe(bisDHBS)]²⁻ (K_d ∼ 0.5 ± 0.2 µM). These results suggest a previously unidentified role for CeuE within the Fe(III) uptake system of C. jejuni, provide a molecular-level understanding of the underlying binding pocket adaptations, and rationalize reports on the use of enterobactin hydrolysis products by C. jejuni, Vibrio cholerae, and other bacteria with homologous periplasmic binding proteins.With the rapid rise in bacterial resistance to antibiotics, a better understanding of cooperative behavior in microbial communities is urgently needed for the development of novel approaches to controlling infections caused by resistant bacteria (1, 2). As an essential nutrient, iron is often a growth-limiting factor for beneficial, commensal, and pathogenic bacteria alike, not only due to its low solubility in water under aerobic conditions at and around neutral pH, but also because the host organism and competing microbes actively limit its availability (3, 4). Microorganisms evolved efficient Fe(III) uptake mechanisms to overcome this challenge, a common strategy being the production of siderophores, small Fe(III)-chelating molecules with high affinity and selectivity for Fe(III), with over 500 examples known to date (5). The sharing of siderophores is a recognized example for positive cooperativity that has been linked to bacterial virulence (6). The best-characterized siderophores are hexadentate ligands that form coordinatively saturated, octahedral 1:1 complexes with Fe(III) (3, 5, 7), the most studied being the triscatecholate enterobactin (H₆-ENT) produced by many enteric bacteria (8).In Escherichia coli, enterobactin is synthesized within the cell and secreted through the cell membranes to capture Fe(III) from the environment. The resulting Fe(III)-enterobactin complex [Fe(ENT)]³⁻ is recognized by the outer membrane receptor FepA and actively transported into the periplasm. In the periplasm, [Fe(ENT)]³⁻ is sequestered by the periplasmic binding protein (PBP) FepB, which transfers it to an inner membrane transporter for further transport into the cytoplasm (9). Once there, [Fe(ENT)]³⁻ is hydrolyzed by an intracellular esterase to release Fe(III) for use in the cell (8).Along with the development of structurally diverse siderophores, microorganisms adapted their associated receptor and transport proteins for the uptake of the appropriate Fe(III) complexes (9). To gain a competitive advantage, many bacteria have evolved to poach siderophores produced by other bacteria. Campylobacter jejuni, for example, does not itself produce siderophores yet possesses an uptake system that is able to use siderophores from competing species (10). Initially, it was proposed that in C. jejuni [Fe(ENT)]³⁻ is transported across the outer membrane by the receptors CfrA and CfrB (11). Once in the periplasm, [Fe(ENT)]³⁻ was proposed to bind to the PBP CeuE, the resulting complex enabling the transport of the ferric siderophore into the cytoplasm (12, 13).In addition, increasing numbers of lower-denticity siderophores are being isolated from bacterial cultures and found to coordinate Fe(III) and mediate its uptake (14–18). For example, the trilactone backbone of enterobactin makes it prone to hydrolysis, and although this lability is necessary to allow the intracellular release of Fe(III) from the siderophore, it in addition leads to its slow degradation in aqueous media (7, 19–21). Three hydrolysis products are formed: tris(2,3-dihydroxybenzoyl-l-Ser) (H₇-trisDHBS), bis(2,3-dihydroxybenzoyl-l-Ser) (H₅-bisDHBS), and 2,3-dihydroxybenzoyl-l-Ser (H₃-monoDHBS), with all three found in the growth medium of E. coli (Fig. 1). Although enterobactin, once secreted, is also available to other cells (producers or nonproducers), it can only be used once because Fe(III) release requires its hydrolysis. The enterobactin hydrolysis products, however, could be used again as secondary, lower-denticity siderophores.Open in a separate windowFig. 1.Molecular structure of enterobactin, its hydrolysis products, the siderophore mimic H₆-MECAM, and a selection of tetradentate siderophores.It has been demonstrated that the human pathogens C. jejuni (10, 22, 23) and Vibrio cholerae (24), the causes of food poisoning and cholera, respectively, can use enterobactin hydrolysis products for the uptake of Fe(III) from their environment. Both are known not to produce enterobactin.An alternative Campylobacter Fe(III) acquisition model that relies on these linear hydrolysis products was recently proposed based on the finding that Cee, the sole trilactone esterase of C. jejuni and Campylobacter coli, is located in the periplasm, i.e., these bacteria are unable to degrade enterobactin within the cytoplasm (25). The model suggests that, once the Fe(III) complex of enterobactin enters the periplasm, its ester backbone is cleaved by Cee, which is highly efficient in hydrolyzing both the Fe(III) complex and apo-enterobactin. The resulting hydrolysis products, mainly the tetradentate ligand bisDHBS⁵⁻ and the bidentate ligand monoDHBS³⁻, are then used to mediate the subsequent transport of Fe(III) into the cytoplasm.The identification of the esterase Cee and in particular the observation that bisDHBS⁵⁻ can be used independently of enterobactin (25) raise important questions about the siderophore preference of the PBP CeuE and its role in the iron uptake in C. jejuni. By using siderophore mimics, we previously demonstrated that CeuE can bind the Fe(III) complexes of both hexadentate and tetradentate catecholate ligands (26, 27). Our cocrystal structures revealed that CeuE interacts with the coordinatively saturated Fe(III) complex of the hexadentate mimic MECAM⁶⁻ through electrostatic interactions and hydrogen bonding, whereas it binds the coordinatively unsaturated complex of the tetradentate mimic 4-LICAM⁴⁻ by recruiting the side chains of two amino acid residues (His227 and Tyr288) to complete the coordination sphere of the Fe(III) center. We established that His227 and Tyr288 are conserved among a subset of related PBPs, including VctP from V. cholerae, and suggested that this subset of PBPs undergo similar structural changes to adapt to the binding of lower-denticity sidero-phores (27). The recent report that V. cholerae most efficiently uses trisDHBS⁷⁻ and bisDHBS⁵⁻ for the acquisition of Fe(III) provided a partial confirmation of this prediction (24).Here, we report that CeuE binds [Fe(bisDHBS)]²⁻ with much higher affinity than the Fe(III) complex of enterobactin, reveal the structural basis for this difference in binding strength, and examine key aspects of the relevant Fe(III) coordination chemistry in solution.     

Esclerosis sistémica sin esclerodermia en pacientes mexicanos. Serie de casos

Systemic sclerosis sine scleroderma (ssSSc) is a form of systemic sclerosis that is characterized by Raynaud's phenomenon (RP), visceral involvement without thickening of skin and anticentromere antibodies (ACA). We studied 10 ssSsc patients with a prevalence of 2%. The clinical signs were: RP 9/10, esophageal manifestations 8/10, pulmonary arterial hypertension 4/10, interstitial lung disease 4/10, cardiac signs 3/10 and ACA 8/10.

Serological profile of Helicobacter pylori infection in the population of San Luis (Argentina)

We performed a seroepidemiological study of anti-Helicobacter pylori IgG by a commercial enzyme immunoassay kit (Meridian Diagnostics, USA) in 509 serum samples from 314 randomly selected asymptomatic subjects from among the population, and grouped into children (n = 124), adolescents (n = 74) and adults (n = 116), and in 195 serum samples from subjects presenting clinical gastric symptoms, grouped into children (n = 38) and adults (n = 157). The cut-off value was redefined and set at OD450 = 0.050. The percentage of seropositive individuals was not significantly different between the two groups of adults studied (75.9% and 80.2%, respectively) (p < 0.05), suggesting a high degree of contact with the microorganism in this region.     

Phospholipase A2 group IIA expression in gastric adenocarcinoma is associated with prolonged survival and less frequent metastasis

We analyzed gene expression patterns in human gastric cancers by using cDNA microarrays representing approximately equal 30,300 genes. Expression of PLA2G2A, a gene previously implicated as a modifier of the Apc(Min/+) (multiple intestinal neoplasia 1) mutant phenotype in the mouse, was significantly correlated with patient survival. We confirmed this observation in an independent set of patient samples by using quantitative RT-PCR. Beyond its potential diagnostic and prognostic significance, this result suggests the intriguing possibility that the activity of PLA2G2A may suppress progression or metastasis of human gastric cancer.