Evolution of MHC-G in humans and primates based on three new 3'UT polymorphisms

MHC-G is a class Ib (non-classical) major histocompatibility complex (MHC) whose functional and evolutionary characteristics are still under scrutiny. The study of noncoding sequences in the MHC genes may provide important phylogenetic information. In this work we have sequenced the MHC-G exon 8, which encodes for the 3'UT region, in different species of primates. It has been shown that: (1) a previously described 14 base pair (bp) deletion polymorphism is human-specific and the HLA-G alleles may be classified according to its absence or presence; (2) another newly described 3 bp deletion/insertion polymorphism is also human-specific; and (3) another newly described 51 bp deletion polymorphism is common to Pongidae and humans, but is not found in other primates belonging to the Cercopithecinae family. A hypothesis on the evolutionary pathway of this gene is put forward in the light of these findings.     

Activity of aphids associated with lettuce and broccoli in Spain and their efficiency as vectors of Lettuce mosaic virus

This research sought to identify the aphid virus vector species associated with lettuce and broccoli crops in Spain, and to determine their population dynamics and ability to transmit Lettuce mosaic virus (LMV). Green tile traps and Moericke yellow water-pan traps were used to monitor aphid flights during the spring and autumn growing seasons of 2001. Aphid species feeding on lettuce were counted weekly. The transmission efficiencies of LMV were determined for the aphid species caught most frequently. The Moericke traps generally caught more aphid species than the tile trap, but the latter was the most suitable to estimate flight activity of species involved in virus spread. Spring aphid catches indicated that the main aphid species landing on lettuce in the regions of Madrid and Murcia was Hyperomyzus lactucae, but Brachycaudus helichrysi was also abundant in both regions. In broccoli in the Navarra region, the most abundant species in spring were Aphis fabae, B. helichrysi and H. lactucae. In autumn-sown crops, the main species landing on lettuce in the Madrid region were Hyadaphis coriandri and Aphis spiraecola. In Murcia, A. spiraecola and Myzus persicae were the most abundant, while in Navarra, Therioaphis trifolii, and various Aphis spp. were the most numerous landing on broccoli. The main aphid species colonising lettuce was Nasonovia ribisnigri, but other less abundant colonising species were Aulacorthum solani and Macrosiphum euphorbiae. The most efficient vectors of LMV were M. persicae, Aphis gossypii and M. euphorbiae, while A. fabae and H. lactucae transmitted with low efficiency, and Rhopalosiphum padi and N. ribisnigri did not transmit. Occurrence of LMV epidemics in central Spain in relation to aphid flights and the role of weeds as virus reservoirs is discussed.     

Selection ofCandida glabrata strains with reduced susceptibility to azoles in four liver transplant patients with invasive candidiasis

The cases of four liver transplant recipients who developed invasive candidiasis (2 cholangitis, 1 perihepatic abscess, 1 candidemia) due to azole-resistantCandida glabrata are reported. Three patients were receiving azolic compounds (2 itraconazole, 1 fluconazole) when the infection was diagnosed. All four patients received fluconazole as intestinal decontamination during the first three weeks post transplantation. The infections occurred two months after transplantation in all patients, and in one patientCandida infection was the direct cause of death. Infection of the biliary tree was the origin of candidiasis in three patients; the fourth patient developed neutropenic-related candidemia. Fluconazole MICs exceeded 16 g/ml in all cases; itraconazole MICs were 16, 2, 1, and 2 g/ml, respectively. The potential role ofCandida species other thanalbicans in these patients after administration of azole agents is discussed.     

Renal dysfunction after chronic blockade of nitric oxide synthesis

The effects of the chronic inhibition of nitric oxide (NO) on renal hemodynamics and tubular function were studied in rats treated for 8 weeks with the NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME; 40 mg/kg/day). In addition, the effect of L-NAME administration on vasoactive systems (renin-angiotensin system, aldosterone, catecholamines, endothelin, and thromboxane A(2)) was evaluated. Chronic inhibition of NO significantly elevated blood pressure, reduced glomerular filtration rate and renal blood flow, blunted the pressure-diuresis-natriuresis response, and increased protein urine excretion. All these changes were associated with blunted nitrite production in response to acetylcholine in glomeruli. No changes were observed in the plasma levels of either renin activity, aldosterone, or endothelin in L-NAME-treated rats. Similarly, no differences were observed in the urinary excretion of thromboxane B(2) between both group of animals. By contrast, plasma concentrations of both epinephrine and norepinephrine were elevated in rats treated with L-NAME. In summary, the results show that chronic blockade of NO produced not only alterations in renal function, but also renal damage, suggesting an important renoprotective role of NO. An activation of sympathoadrenal system could participate in these renal alterations.     

Expansion and clonal deletion of peripheral T cells induced by bacterial superantigen is independent of the interleukin-2 pathway

Injection of the bacterial superantigen Staphylococcus aureus enterotoxin B (SEB) into mice provokes a rapid expansion and subsequent contraction of the pool of SEB-reactive T cells bearing T cell receptor (TcR) V_β8 gene products. Given that interleukin 2 (IL-2) stimulates proliferation, abolishes anergy, and counteracts apoptotic cell death in T cells in vitro, we tested whether the IL-2 synthesis inhibitor cyclosporin A (CsA) or a vaccinia virus recombinant releasing high amounts of human IL-2 modulate SEB responses in vivo. Surprisingly, neither IL-2 nor CsA were able to change the in vivo kinetics and magnitude of SEB-induced expansion, unresponsiveness to SEB, and peripheral clonal deletion of T cells expressing products of the SEB-reactive TcR V_β8 gene family. In accord with these in vivo observations, IL-2 is incapable of reversing “anergy” and apoptotic cell death of V_β8⁺ SEB-reactive T cells isolated from SEB-primed mice in vitro. Accordingly, upon SEB injection V_β8⁺ T cells expand rapidly, without expressing IL-2 receptor (IL-2R)α chains in vivo, although SEB induces IL-2R α in vitro. Altogether, these results indicate that the IL-2/IL-2R-mediated pathway is not involved in T cell repertoire modulation by bacterial superantigens. Moreover, the data suggest that unresponsiveness of V_β8⁺ T cells from SEB-primed mice is not a reversible process, but involves an unreversible commitment to programmed cell death. Absence or presence of IL-2 responsiveness could be a hallmark to distinguish truly reversible anergy and peripheral clonal deletion.     

Phorbol esters and CAMP differentially regulate the expression of CD4 and CD8 in human thymocytes

Background  

Intrathymic development and selection of the T lymphocyte repertoire is restricted by the interactions of the T cell antigen receptor and CD4 or CD8 co-receptors with self major histocompatibility complex molecules. Positive or negative selection depends on a tight regulatory control of CD4 and CD8 expression. Determining the intracellular signals that differentially regulate the expression of CD4 and CD8 is important to understand the mechanisms that are implicated in selection of single positive CD4⁺CD8^- or CD4^-CD8⁺.     

Rapid detection of cucumber vein yellowing virus by tissue-print hybridisation with digoxigenin-labelled cDNA probes

Hybridisation of tissue prints with nonradioactive cDNA probes was developed to detect cucumber vein yellowing virus (CVYV) in cucurbit plants. Results showed irregular distribution of the virus within cucumber, zucchini or melon plants without defined tropism for a specific tissue. Therefore, reliable diagnosis of CVYV requires analysis of tissue prints from at least five different plant sites. This detection procedure allows rapid analysis of large numbers of plants and it can be useful for epidemiological studies of CVYV and to control virus spread via eradication of early foci.     

Immunoglobulin isotype in the murine response to polysaccharide antigens

Murine antisera specific for the α (1→3) and α (1→6)-linked glucosyl determinants of dextran, as well as for meningococcal polysaccharide group C, have been examined for the distribution of their immunoglobulin classes and subclasses. Whereas the thymus-independent anti-α (1→3) dextran response in BALB/c mice was found to be IgM > IgG₃ > IgA, thus corresponding to previously published work, neither the α (1→6) response in its thymus-dependent or-independent form, nor the response to purified meningococcal polysaccharide, corresponded to this pattern. No preference for any of the IgG subclasses appeared for these antigens when given as thymus-independent carbohydrates. On the other hand, thymus-dependent forms of α (1→6) dextran showed an IgG₁ > IgG₃ > IgG₂ pattern.     

Karyotyping chromosomes by electron microscopy. Condensation-inhibition of G bands in human and Chinese hamster chromosomes by a BrdU-Hoechst 33258 treatment

A BrdU-Hoechst 33258 treatment of living cells, which selectively induced condensation-inhibition of G-band chromatin in human and Chinese hamster chromosomes, is presented. As a consequence mitotic chromosomes showed high resolution R-banding patterns when examined by light and electron microscopy. Besides each whole chromosome identification, this procedure also permitted the electron microscopic study of specific structures, such as satellites, secondary constrictions, telomeres, centromeres, as well as G and R bands, some of them not visible by light microscopy. We have also observed that the chromatin of G and R bands behave as blocks of chromatin condensation and that G-band chromatin develops condensation along G₂. Under the BrdU-Hoechst 33258 treatment, chromatin fibers seem to invert their spontaneous pattern of condensation within the chromosomes.     

Immunohistochemical characterization of fibroblast subpopulations in normal peritoneal tissue and in peritoneal dialysis-induced fibrosis

Peritoneal fibrosis is one of the most common morphological changes observed in continuous ambulatory peritoneal dialysis (CAPD) patients. Both resident fibroblasts and new fibroblast-like cells derived from the mesothelium by epithelial-to-mesenchymal transition are the main cells involved fibrogenesis. In order to establish markers of peritoneal impairment and pathogenic clues to explain the fibrogenic process, we conducted an immunohistochemical study focused on peritoneal fibroblasts. Parietal peritoneal biopsies were collected from four patient groups: normal controls (n=15), non-CAPD uremic patients (n=17), uremic patients on CAPD (n=27) and non-renal patients with inguinal hernia (n=12). To study myofibroblastic conversion of mesothelial cells, -smooth muscle actin (SMA), desmin, cytokeratins and E-cadherin were analyzed. The expression of CD34 by fibroblasts was also analyzed. Fibroblasts from controls and non-CAPD uremic patients showed expression of CD34, but no myofibroblastic or mesothelial markers. The opposite pattern was present during CAPD-related fibrosis. Expression of cytokeratins and E-cadherin by fibroblast-like cells and -SMA by mesothelial and stromal cells supports that mesothelial-to-myofibroblast transition occurs during CAPD. Loss of CD34 expression correlated with the degree of peritoneal fibrosis. The immunophenotype of fibroblasts varies during the progression of fibrosis. Myofibroblasts seem to derive from both activation of resident fibroblasts and local conversion of mesothelial cells.Manuel López-Cabrera and Rafael Selgas contributed equally to the article.