Germinal center B cells regulate their capability to present antigen by modulation of HLA-DO

Peptide acquisition by MHC class II molecules is catalyzed by HLA-DM (DM). In B cells, HLA-DO (DO) inhibits or modifies the peptide exchange activity of DM. We show here that DO protein levels are modulated during B cell differentiation. Remarkably, germinal center (GC) B cells, which have low levels of DO relative to naive and memory B cells, are shown to have enhanced antigen presentation capabilities. DM protein levels also were somewhat reduced in GC B cells; however, the ratio of DM to DO in GC B cells was substantially increased, resulting in more free DM in GC B cells. We conclude that modulation of DM and DO in distinct stages of B cell differentiation represents a mechanism by which B cells regulate their capacity to function as antigen-presenting cells. Efficient antigen presentation in GC B cells would promote GC B cell-T cell interactions that are essential for B cells to survive positive selection in the GC.     

Effect of nitric oxide on megakaryocyte growth induced by thrombopoietin

The present study investigated the effect of nitric oxide (NO) on megakaryocyte (Mk) proliferation induced by thrombopoietin (TPO). Low-density mononuclear cells (MNCs) and CD34+ cells from human bone marrow (BM) were cultured in liquid medium in the presence of sodium nitroprusside (SNP) or (Z)-1-[2-(aminoethyl)-N-(2-ammonioethyl) amino] diazen-1-ium-1, 2-diolate (DETA/NO) and then stimulated with TPO. Mk number decreased in both NO donors, as identified by flow cytometry 11 to 13 days after TPO stimulation. Nitrite, cyanide, or the carrier molecule DETA failed to reproduce the inhibition caused by NO donors. When CD34+ cells were treated with DETA/NO, the inhibition of Mk growth was even more pronounced than that in MNCs. Failure of the guanosine 3',5'-cyclic monophosphate (cGMP) analog 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) to inhibit Mk proliferation suggests that cGMP is not involved in Mk suppression mediated by NO. On the other hand, DNA analysis by flow cytometry showed that apoptosis of CD34+ cells and Mks seemed to be at least one of the mechanisms associated with the cytotoxic DETA/NO effect. Stimulation of MNCs or CD34+ cells with tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) increased endogenous NO levels and suppressed Mk growth. Treatment with NO synthesis inhibitors such as L -N(G)-monomethyl arginine (L -NMMA) or L -N(G)-nitroarginine methyl ester hydrochloride (L -NAME) partially reversed Mk growth inhibition induced by TNF-alpha and IFN-gamma, although increased NO levels returned to normal values. The results presented here strongly indicate that NO regulates the growth of Mks induced by TPO by a direct effect on both progenitors and mature Mks.     

Apparatus for ultrasound tissue characterization of excised specimens

Apparatus is described for measurement of sound speed and ultrasound attenuation coefficients by the substitution technique in the frequency range 3 to 8 MHz. Phase-cancellation artifacts leading to overestimation of attenuation coefficients are avoided by use of an acoustoelectric transducer. Specimens confined by polystyrene windows can be interrogated by focused ultrasound beams at selected locations spaced on a grid of 3 x 3 mm voxels. Pulse time of flight is measured with an accuracy of 30 ns, yielding sound speeds accurate to +/- 6.7 m/s, for samples 10 mm thick. Uncertainties in measured insertion losses range from 0.1 dB in low-loss (10 dB) specimens to 0.5 dB in high-loss (25 dB) specimens.     

Real time PCR method for simultaneous detection, quantitation and differentiation of capripoxviruses

The genus Capripoxvirus (CaPV) comprises three members namely, sheep poxvirus (SPPV), goat poxvirus (GTPV) and lumpy skin disease virus (LSDV) affecting sheep, goats and cattle, respectively. CaPV infections produce similar symptoms in sheep and goats, and the three viruses cannot be distinguished serologically. Since there are conflicting opinions regarding the host specificity of CaPVs, particularly for goatpox and sheeppox viruses, the development of rapid genotyping tools will facilitate more accurate disease diagnosis and surveillance for better management of capripox outbreaks.This paper describes a species-specific, real time polymerase chain reaction (PCR), based on unique molecular markers that were found in the G-protein-coupled chemokine receptor (GPCR) gene sequences of CaPVs, that uses dual hybridization probes for their simultaneous detection, quantitation and genotyping.The assay can differentiate between CaPV strains based on differences in the melting point temperature (Tm) obtained after fluorescence melting curve analysis (FMCA). It is highly sensitive and presents low intra- and inter-run variation.This real time PCR assay will make a significant contribution to CaPV diagnosis and to the better understanding of the epidemiology of CaPVs by enabling rapid genotyping and gene-based classification of viral strains and unequivocal identification of isolates.     

A 7-year national survey on bacterial resistance in bronchoalveolar lavage from patients hospitalized in Argentina

The purpose of this study is to undertake a nationwide survey on bacterial resistance in bronchoalveolar lavage (BAL) from patients hospitalized in Argentina. A 2-month point prevalence study was conducted twice yearly (April-May and October-November) from 1997 to 2003 by 36 Argentinean centers. Antimicrobial susceptibility data of the potential pathogens recovered from the BAL (samples containing <1% of squamous epithelial cells and bacterial counts >or=10(4) CFU/mL) of inpatients (i.e., >or=48-h hospital length of stay) with suspected hospital-acquired pneumonia (HAP) were collected on a computerized system (SIR) described previously. The survey was split into 2 periods for comparison purposes, 1997 to 2000 and 2001 to 2003. A total of 752 organisms were included. Staphylococcus aureus was the most frequent species, followed by Acinetobacter spp. and Pseudomonas aeruginosa. In both periods, more than a half of the Klebsiella pneumoniae strains displayed a phenotype of extended-spectrum beta-lactamase producer. A doubling of imipenem-resistant Acinetobacter frequency was shown from the 1st period to the 2nd one (25-48%). More than two-thirds of the S. aureus strains proved to be methicillin resistant in both periods, and a pronounced decrease of resistance rates to trimethoprim/sulfamethoxazole and rifampin was shown in the 2nd period. The present study shows the worrisome increasing bacterial resistance in BAL samples to most available antimicrobial options for treating patients with suspected HAP. Variations over time support the need for systematic tailored surveillance and compel us to establish a rational usage of antimicrobial agents in our country.     

Home gardens and the energy and nutrient intakes of women and preschoolers in rural Puerto Rico

The study investigated how the increased availability of self‐grown foods was related to the adequacy of the energy and nutrient intake of rural women and preschoolers in Puerto Rico. The 109 women included in the study were found to be most seriously deficient in iron and calcium, and tended to suffer from obesity. The 50 preschoolers demonstrated no serious chronic/acute undernutrition or growth retardation, and were most seriously deficient in iron and vitamin C. Results indicated that per capita food expenditures did not decrease with increased availability of self‐grown foods. Home gardens had the effect of increasing the total food supply of the household during certain seasons. Preschoolers appeared to benefit nutritionally more from horticultural production than adult women. With the exception of iron intake, more adequate energy and nutrient intakes of preschoolers were associated with the availability of different self‐grown foods. This was only true for the vitamin A intake of the women.