Heart tumors in children and adults: clinicopathological study of 59 patients from a surgical center.

BACKGROUND: Heart tumors are rare lesions with variegated histological types. Their clinicopathological features could be more comprehensively categorized. METHODS: This is a 19-year retrospective study of 17 infants/toddlers (<2 years of age) and 42 patients aged between 14 and 79 years (mean = 51.5) in a surgical center. RESULTS: Congenital tumors (n = 17; 29%), including rhabdomyomas (n = 9), ventricular fibromas (n = 6), and hemangiomas (n = 1), required surgery mainly because of mass effect. Familial myofibromatosis was the only embolic congenital lesion. Acquired benign tumors (n = 28; 47%) included myxomas (n = 21), fibroelastomas (n = 3), myofibroblastic inflammatory tumors (n = 2), and lipomas (n = 2). Eight (29%) were revealed by systemic embolization. These benign noncongenital tumors were all treated by complete resection, except for an incompletely resected lipoma of the mitral valve. Postoperative arrhythmia (n = 1) and pericardial effusion (n = 3) were the only complications. Primary sarcomas (n = 8; 14%) were mostly vascular tumors (five of eight), and patients with high-grade tumors had a mean survival of 15 months (n = 5). Cardiac metastases (n = 6; 10%) were from carcinomas (n = 3) or sarcomas (n = 3); apart from a necrotic metastasis, all patients died (mean survival of 6 months). CONCLUSIONS: This study shows that, regardless of patients' age, heart tumors can be classified as: (a) congenital lesions, which are spontaneously nonprogressive or regressive lesions possibly requiring surgery mainly because of mass effect; (b) acquired benign tumors, which are lesions requiring surgery often because of embolization risk; and (c) primary and secondary malignant tumors, which are lesions with globally poor prognosis but with some indications for resection.     

Molecular epidemiology of Pseudomonas aeruginosa colonization in a burn unit: persistence of a multidrug-resistant clone and a silver sulfadiazine-resistant clone

To study the epidemiology of Pseudomonas aeruginosa colonization in a 32-bed burn wound center (BWC), 321 clinical and 45 environmental P. aeruginosa isolates were collected by prospective surveillance culture over a 1-year period and analyzed by serotyping, drug susceptibility testing, and amplified fragment length polymorphism (AFLP) analysis. Among 441 patients treated at the center, 70 (16%) were colonized with P. aeruginosa, including 12 (17%) patients who were colonized on admission and 58 (83%) patients who acquired the organism during their stay. Of the 48 distinct AFLP genotypes found, 21 were found exclusively in the environment, 15 were isolated from individual patients only, and 12 were responsible for the colonization of 57 patients, of which 2 were also isolated from the environment, but secondary to patient carriage. Polyclonal P. aeruginosa colonization with strains of two to four genotypes, often with different antibiotic susceptibility patterns, was observed in 19 patients (27%). Two predominant genotypes were responsible for recurrent outbreaks and the colonization of 42 patients (60% of all colonized patients). The strain with one of those genotypes appeared to be endemic to the BWC and developed multidrug resistance (MDR) at the end of the study period, whereas the strain with the other genotype was antibiotic susceptible but resistant to silver sulfadiazine (SSD(r)). The MDR strain was found at a higher frequency in sputum samples than the SSD(r) strain, which showed a higher prevalence in burn wound samples, suggesting that anatomic habitat selection was associated with adaptive resistance to antimicrobial drugs. Repeated and thorough surveys of the hospital environment failed to detect a primary reservoir for any of those genotypes. Cross-acquisition, resulting from insufficient compliance with infection control measures, was the major route of colonization in our BWC. In addition to the AFLP pattern and serotype, analysis of the nucleotide sequences of three (lipo)protein genes (oprI, oprL, and oprD) and the pyoverdine type revealed that all predominant strains except the SSD(r) strain belonged to recently identified clonal complexes. These successful clones are widespread in nature and therefore predominate in the patient population, in whom variants accumulate drug resistance mechanisms that allow their transmission and persistence in the BWC.     

POL32, a subunit of the Saccharomyces cerevisiae DNA polymerase δ, defines a link between DNA replication and the mutagenic bypass repair pathway

Pol32 is a subunit of Saccharomyces cerevisiae DNA polymerase δ required in DNA replication and repair. To gain insight into the function of Pol32 and to determine in which repair pathway POL32 may be involved, we extended the analysis of the pol32Δ mutant with respect to UV and methylation sensitivity, UV-induced mutagenesis; and we performed an epistasis analysis of UV sensitivity by combining the pol32Δ with mutations in several genes for postreplication repair (RAD6 group), nucleotide excision repair (RAD3 group) and recombinational repair (RAD52 group). These studies showed that pol32Δ is deficient in UV-induced mutagenesis and place POL32 in the error-prone RAD6/REV3 pathway. We also found that the increase in the CAN1 spontaneous forward mutation of different rad mutators relies entirely or partially on a functional POL32 gene. Moreover, in a two-hybrid screen, we observed that Pol32 interacts with Srs2, a DNA helicase required for DNA replication and mutagenesis. Simultaneous deletion of POL32 and SRS2 dramatically decreases cellular viability at 15 °C and greatly increases cellular sensitivity to hydroxyurea at the permissive temperature. Based on these findings, we propose that POL32 defines a link between the DNA polymerase and helicase activities, and plays a role in the mutagenic bypass repair pathway. Received: 25 May 2000 / Accepted: 3 July 2000     

Construction and characterization of affibody-Fc chimeras produced in Escherichia coli

Affibody-Fc chimeras were constructed by genetic fusion between different affibody affinity proteins with prescribed specificities and an Fc fragment derived from human IgG. Using affibody ligands previously selected for binding to respiratory syncytial virus (RSV) surface protein G and Thermus aquaticus (Taq) DNA polymerase, respectively, affibody-Fc fusion proteins showing spontaneous Fc fragment-mediated homodimerization via disulfide bridges were produced in Escherichia coli and affinity purified on protein A Sepharose from bacterial periplasms at yields ranging between 1 and 6 mg/l culture. Further characterization of the chimeras using biosensor technology showed that the affibody moieties have retained high selectivities for their respective targets after fusion to the Fc fragment. Avidity effects in the target binding were observed for the affibody-Fc chimeras compared to monovalent affibody fusion proteins, indicating that both affibody moieties in the chimeras were accessible and contributed in the binding. Fusion of a head-to-tail dimeric affibody moiety to the Fc fragment resulted in tetravalent affibody constructs which showed even more pronounced avidity effects. In addition, the Fc moiety of the chimeras was demonstrated to be specifically recognized by anti-human IgG antibody enzyme conjugates. One application for this class of "artificial antibodies" was demonstrated in a western blotting experiment in which one of the anti-RSV surface protein G affibody-Fc chimeras was demonstrated to be useful for specific detection of the target protein in a complex background consisting of a total E. coli lysate. The results show that through the replacement of the Fab portion of an antibody for an alternative binding domain based on a less complicated structure, chimeric proteins compatible with bacterial production routes containing both antigen recognition domains and Fc domains can be constructed. Such "artificial antibodies" should be interesting alternatives to, for example, whole antibodies or scFv-Fc fusions as detection devices and in diagnostic or therapeutic applications.     

Mouse macrophage development in the absence of the common γ chain: defining receptor complexes responsible for IL-4 and IL-13 signaling

The common γ chain (γ_c) forms a critical component of the receptors for interleukins (IL)-2, IL-4, IL-7, IL-9, and IL-15. We analyzed γ_c-deficient mice to define a role for γ_c signaling in the development and function of the macrophage lineage. No major differences in absolute cell numbers, cell surface phenotype, or in vitro function of γ^?_c compared to γ⁺_c macrophages were observed. We therefore conclude that signaling through the γ_c chain is not essential for the differentiation of mouse macrophages. Although B and T cells require γ_c for IL-4 responses, IL-4 up-regulated major histocompatibility class II molecules and inhibited nitric oxide production from γ^?_c macrophages following stimulation with lipopolysaccharide and interferon-γ. γ^?_c macrophages could also respond to IL-13, consistent with the model of a type II IL-4 receptor α/IL-13R which can function in the absence of γ_c. Both IL-4 and IL-13 responses could be completely inhibited with the mouse IL-4 antagonist QY, suggesting that all of the observed IL-13 responses pass through the type II receptor, making it the primary signaling receptor complex for IL-13 in mouse macrophages.     

Genotypic diversity of Mycobacterium tuberculosis in the Guiana-Antilles region

This investigation dealt with 226 strains (1 isolate/patient) of Mycobacterium tuberculosis isolated in the French West Indies and French Guiana over a three-year period (1994-1996). The genotypic diversity of the isolates was investigated using various molecular markers; essentially two PCR-based rapid methods, namely spoligotyping and double-repetitive-element (DRE)-PCR, as well as three restriction fragment length polymorphism (RFLP)-based methods, namely IS6110-RFLP, DR-RFLP and PGRS-RFLP. Out of 226 isolates investigated, a total of 166 isolates were distributed in 31 spoligotype-defined clusters containing 2-31 strains, which corresponded to a rate of 73% of primary clustering. After secondary typing with DRE-PCR, IS6110-RFLP, DR-RFLP and/or PGRS-RFLP, molecular clonality was established for 73 isolates organised in 25 clusters (32% of clustered isolates). Considering one reactivation case per cluster, the rate of recent transmission was estimated to a minimal rate of 21%, however the available epidemiologic information led to the positive conclusion for only 14% of cases. The data obtained demonstrated the presence of common genotypes of M. tuberculosis among the three overseas French territories, i.e. Guadeloupe, Martinique and French Guiana. The results obtained during this retrospective study clearly indicate the importance of future prospective epidemiological investigations around the clustered cases of tuberculosis, so as to detect the persisting foci of endemic disease and characterize the chain of transmission as well as the subpopulations which are at an increased risk of contracting and/or propagating the disease. Last but not least, the present study also deals with a first phylogenetic approach of M. tuberculosis based on a comparison of the spoligotyping results obtained locally with those reported elsewhere in the world.     

Interleukin-7-engineered mesenchymal cells: in vitro effects on naive T-cell population.

T-cell homeostasis is regulated by several molecules; among these, interleukin (IL)-7 plays an essential role in the survival and homeostatic proliferation of peripheral naive T cells. In a previous study, we investigated whether human mesenchymal stromal cells (MSCs) could be engineered with the IL-7 gene to produce functional level of this cytokine. In the present study, we analyzed the impact of different quantities of IL-7 produced by MSCs on the survival and proliferation of a negative immunoselected naive (CD3(+)/CD45RA(+)) T-cell population. Co-cultivation of peripheral naive T cells with MSCs producing low (16 pg/mL) or high (1000 pg/mL) IL-7 levels or in the presence of exogenous IL-7 (0.01 ng/mL and 100 ng/mL) maintained the CD3(+)/CD45RA(+) naive T-cell phenotype. Chemokine receptor CCR7(+) expression was also maintained among this T-cell population. Naive T-cell molecular characteristics were maintained as assessed by the Vbeta spectratyping complexity score, which showed the maintenance of a broad T-cell repertoire. No Th1 or Th2 differentiation was observed, as assessed by interferon-gamma or IL-4 accumulation. In contrast, only MSCs producing high amounts of IL-7 caused increased activation (CD25 31.2% +/- 12% vs 10% +/- 3.5%; P < .05), proliferation (CD71 17.8+/-7% vs 9.3%+/-3, P < .05), apoptosis (assessed by annexin V: 18.6% +/- 5% vs 14.9% +/- 2.6%; P > .05), and the phase S cell cycle (15% vs 6.9%, P > .05). Exogenous IL-7 exhibited no significant effect. In conclusion, we demonstrated that IL-7 produced by MSCs has a dose-independent effect on naive T-cell survival while exerting a dose-dependent effect on activation/proliferation. Due to the continuous production of IL-7 by engineered cells, our system is more efficacious than exogenous IL-7.     

Myocardial oxygen extraction and oxygen-hemoglobin equilibrium curve during moderate exercise

Summary Conditions of oxygen extraction by the myocardium have been studied in 12 subjects (44±9 years old) with pure mitral stenosis without clinical, metabolic or electrical sign of coronary insufficiency.Oxygen-hemoglobin equilibrium curves (OHEC) have been determined on arterial, mixed venous and coronary sinus blood, at rest and during a moderate (60 W, 10 min) exercise performed on a bicycle ergometer in supine position. Physiological values, at rest and during exercise, of the following functional parameters of the OHEC were determined in the in-vivo conditions of pH and P_CO2P₅₀, n_Hill, DS max = maximal value of OHEC slope (DS=S_O2/P_O2), P_{DS max}, S_{DS max}. The concentration of plasma electrolytes capable to modify one of these parameters was controlled in each blood sample.In coronary sinus blood, P₅₀ rises from 27.5±1.7 to 28.9±1.6 Torr during exercise (p<0.01). At rest, Hill's n in myocardial venous blood (2.67±0.09) is significantly higher than in arterial blood (2.61±0.08, p<0.01). A decrease in DS max (2.67±0.20 to 2.53±0.12%. Torr^–1; p<0.01) and an increase in P_{DS max} (20.9±1.9 to 22.6±2.1 Torr, p<0.01) are observed. At rest, the myocardial venous point (PcsO₂, ScsO₂) is not significantly distinct from the maximal slope point (P_{DS max}, S_{DS max}). After 1 min of exercise, a small gap appears which becomes significant at the end of the exercise (P_{DS max}-PcsO₂=0.2 Torr at rest, 2.7 Torr after exercise; S_{DS max}-ScsO₂=4.1% at rest, 7.9% after exercise). DS value at the myocardial venous point is only 2% at rest and 6% after exercise, lower than its maximal value.The gap between venous point and DS max point could constitute an error signal in the regulation loop of the coronary circulation. The existence of a physiological receptor, sensitive to instant variations in myocardial tissue P_O2 and able to maintain venous point near DS max point could be considered.     

Bacteremia caused by a metronidazole-resistant Prevotella sp. strain

Metronidazole resistance among Prevotella spp. is rare. We report here the first case of bacteremia due to a high-level metronidazole-resistant Prevotella sp. responsible for treatment failure.