Identification of vascular sphincters at the junction between alveolar capillaries and pulmonary venules of the mouse lung

Background: A peculiar feature of lung circulation in the lung is the pronounced variations in blood volume observed in alveolar capillaries that occur because of the changes in the conformation of the alveolar wall that are associated with the respiratory movements. This phenomenon has led to the postulate that mechanisms of postcapillary control of blood flow are to be present in the lung vessels. In the present study we searched for microanatomical evidence of vascular sphincters in the deep lung tissue of mice, namely in alveolar capillaries and pulmonary veins. Methods: We have used scanning electron microscopy (SEM) to examine two types of samples of normal lung tissue of CD-1 mice: 1) vascular corrosion casts made by vascular perfusion with Mercox® resin, and 2) routinely made gold/platinum-coated replicas of sectioned lung tissue. Results: Careful scrutiny of the vessels of the deep lung tissue led to the identification of sphincters in alveolar capillaries. These sphincters were located at the junction between capillary and pulmonary veins. They corresponded to areas to the vascular wall showing circular swellings where a radial organization was observed, since they were made up of alternating grooves and bulges. Transmission electron microscopy showed that smooth muscle cells participated in the formation of the sphincters. Conclusions: Our data reveal a new location for vascular sphincters in pulmonary vessels and, because these novel sphincters are located at the capillary-vein junction, they offer a structural setting for the existence of postcapillary control of blood flow in the pulmonary circulation of mice. © 1995 Wiley-Liss, Inc.     

Increased risk of tuberculosis with human T-lymphotropic virus-1 infection: a case-control study

OBJECTIVES: To investigate whether infection with human T-lymphotropic virus type 1 (HTLV-1) increases the risk of tuberculosis. DESIGN: A case-control study. SETTING: City of Salvador, Brazil. PARTICIPANTS: A total of 375 patients with tuberculosis (cases) and 378 individuals without tuberculosis (controls), matched by age and sex. MAIN OUTCOME MEASURE: Tuberculosis of lung or lymph node. MAIN EXPOSURE: Human HTLV-1 infection. RESULTS: The prevalence of HTLV-1 infection was 4.27% (16/375) in patients with tuberculosis and 1.32% (5/378) in controls, resulting in a crude odds ratio of 3.31 (95% CI, 1.20-9.13) and an adjusted odds ratio of 3.01 (95% CI, 1.06-8.58). CONCLUSION: HTLV-1 infection is associated with a first diagnosis of tuberculosis. This may have implications for tuberculosis control in places with high prevalence of HTLV-1.     

Solubilization and immunological identification of presynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the rat hippocampus

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been identified mostly as postsynaptic receptors mediating fast glutamatergic synaptic transmission. However, neurochemical studies based on the modulation of neurotransmitter release have suggested the existence of presynaptic AMPA receptors. We have used a recently described technique that allows a high-purity fractionation of the pre- and postsynaptic proteins of synaptic junctions to evaluate the distribution of the different AMPA receptor subunits in rat hippocampal synapses. Surprisingly, we found very high levels of GluR1- and GluR2/3-like immunoreactivity in the presynaptic fraction, but also in the postsynaptic and extrasynaptic fractions. GluR4-like immunoreactivity was much less abundant but was still detected, predominantly in the postsynaptic fraction. This methodology appears to be far more sensitive than the classical immunogold electron microscopy to determine the localization of synaptic receptors.     

Elevated levels of DNA-protein crosslinks and micronuclei in peripheral lymphocytes of tannery workers exposed to trivalent chromium

DNA-protein crosslinks (DPC) are a promising biomarker of exposure to hexavalent chromium, a known human carcinogen. Although trivalent chromium is considered to have much lower toxicity, the risk involved in chronic exposure is uncertain. DPC may be a useful tool in clarifying this risk, by signaling an exposure of body tissues to biologically active forms of chromium. DPC quantification was carried out in lymphocytes of a group of tannery workers exposed to trivalent chromium, a small group of manual metal arc stainless steel welders exposed to hexavalent chromium and a control group. This biomarker was compared with the frequency of micronuclei in cytokinesis blocked peripheral lymphocytes as a biomarker of cytogenetic lesions and total plasma and urine chromium levels as an index of exposure. The results indicate a significant increase in the formation of DPC in tannery workers compared with controls (0.88 +/- 0.19 versus 0.57 +/- 0.21%, P < 0.001, Mann-Whitney test) and an even higher level of DPC in welders (2.22 +/- 1.12%, P = 0.03). Tanners showed a significant increase in micronucleated cells compared with controls (6.35 +/- 2.94 versus 3.58 +/- 1.69 per thousand, P < 0.01), whereas in welders this increase was not significant (5.40 +/- 1.67 per thousand ). Urinary chromium was increased in both groups, with a greater increase observed in tanners compared with controls (2.63 +/- 1.62 versus 0.70 +/- 0.38 microg/g creatinine, P < 0.001) than in welders (1.90 +/- 0.37 microg/g creatinine, P < 0.005). Plasma chromium was also increased in both groups (tanners 2.43 +/- 2.11 microg/l, P < 0.001, welders 1.55 +/- 0.67 microg/l, P < 0.005 versus controls 0.41 +/- 0.11 microg/l). In summary, chronic occupational exposure to trivalent chromium can lead to a detectable increase in lymphocyte DNA damage which correlates with a significant exposure of the cells to the metal.     

Intrasplenic immunization with infected hepatocytes: a mouse model for studying protective immunity against malaria pre-erythrocytic stage.

Malaria liver forms are the target of antibody or T-cell-mediated immune mechanisms induced by previous or subsequent developmental stages of the parasite. The potential for vaccine development of antigens expressed exclusively in the liver stages has not been fully explored partly because of the lack of an experimental animal model. Here we show that protective immunity against sporozoite-induced infection with Plasmodium yoelii and P. berghei can be obtained by intrasplenic injection of a small number of liver stages of the parasites. The serum of the protected animals did not contain antibodies against sporozoites, liver or blood stage malaria parasites. Protective immunity was abolished by depletion of either CD4+ or CD8+ T cells from the vaccinated mice before challenge.     

Gene deletions in spinal muscular atrophy.

Two candidate genes (NAIP and SMN) have recently been reported for childhood onset spinal muscular atrophy (SMA). Although affected subjects show deletions of these genes, these deletions can lead to either a very mild or a severe phenotype. We have analysed a large number of clinically well defined patients, carriers, and normal controls to assess the frequency and extent of deletions encompassing both of these genes. A genotype analysis indicates that more extensive deletions are seen in the severe form of SMA than in the milder forms. In addition, 1 center dot 9% of phenotypically normal carriers are deleted for the NAIP gene; no carriers were deleted for the SMN gene. Our data suggest that deletions in both of these genes, using the currently available assays, are associated with both a severe and very mild phenotype.     

DNA sequences encoding CD4+ and CD8+ T-cell epitopes are important for efficient protective immunity induced by DNA vaccination with a Trypanosoma cruzi gene

Immunization of BALB/c mice with a plasmid containing the gene for Trypanosoma cruzi trans-sialidase (TS) induced antibodies that inhibited TS enzymatic activity, CD4+ Th1 and CD8+ Tc1 cells, and protective immunity against infection. We used this model to obtain basic information on the requirement of CD4 or CD8 or B-cell epitopes for an effective DNA-induced immunity against T. cruzi infection. For that purpose, mice were immunized with plasmids containing DNA sequences encoding (i) the entire TS protein, (ii) the TS enzymatic domain, (iii) the TS CD4+ T-cell epitopes, (iv) the TS CD8+ T-cell epitope, or (v) TS CD4+ and CD8+ T-cell epitopes. Plasmids expressing the entire TS or its enzymatic domain elicited similar levels of TS-inhibitory antibodies, gamma interferon (IFN-gamma)-producing T cells, and protective immunity against infection. Although the plasmid expressing TS CD4 epitopes was immunogenic, its protective efficacy against experimental infection was limited. The plasmid expressing the CD8 epitope was poorly immunogenic and provided little protective immunity. The reason for the limited priming of CD8+ T cells was due to a requirement for CD4+ T cells. To circumvent this problem, a plasmid expressing both CD4+ and CD8+ T-cell epitopes was produced. This plasmid generated levels of IFN-gamma-producing T cells and protective immunity comparable to that of the plasmid expressing the entire catalytic domain of TS. Our observations suggest that plasmids expressing epitopes recognized by CD4+ and CD8+ T cells may have a better protective potential against infection with T. cruzi.     

New microsatellite multiplex PCR for Candida albicans strain typing reveals microevolutionary changes

Five new microsatellite loci were described and characterized for use as molecular markers for the identification and genetic differentiation of Candida albicans strains. Following the typing of 72 unrelated clinical isolates, the analysis revealed that they were all polymorphic, presenting from 5 to 30 alleles and 8 to 46 different genotypes. The discriminatory power obtained by combining the information generated by three microsatellites used in a multiplex PCR amplification strategy was 0.99, the highest ever reported. The multiplex PCR was later used to test a total of 114 C. albicans strains, including multiple isolates from the same patient collected from different body locations and along episodes of vulvovaginal infections. Three different scenarios for strain relatedness were identified: (i) different isolates that were revealed to be the same strain, (ii) isolates that were the same strain but that apparently underwent a process of microevolution, and (iii) isolates that corresponded to different strains. Analysis of the microevolutionary changes between isolates from recurrent infections indicated that the genotype alterations observed could be the result of events that lead to the loss of heterozygosity (LOH). In one case of recurrent infection, LOH was observed at the CAI locus, and this could have been related to exposure to fluconazole, since such strains were exposed to this antifungal during treatment. The analysis of microsatellites by a multiplex PCR strategy was found to be a highly efficient tool for the rapid and accurate differentiation of C. albicans strains and adequate for the identification of fine microevolutionary events that could be related to strain microevolution in response to environmental stress conditions.     

Identification of N-acetylneuraminic acid and its 9-O-acetylated derivative on the cell surface of Cryptococcus neoformans: influence on fungal phagocytosis.

Sialic acids from sialoglycoconjugates present at the cell surface of Cryptococcus neoformans yeast forms were analyzed by high-performance thin-layer chromatography, binding of influenza A and C virus strains, enzymatic treatment, and flow cytofluorimetry with fluorescein isothiocyanate-labeled lectins. C. neoformans yeast forms grown in a chemically defined medium contain N-acetylneuraminic acid and its 9-O-acetylated derivative. A density of 3 x 10(6) residues of sialic acid per cell was found in C. neoformans. Sialic acids in cryptococcal cells are glycosidically linked to galactopyranosyl units as inferred from the increased reactivity of neuraminidase-treated yeasts with peanut agglutinin. N-Acetylneuraminic acids are alpha-2,6 and alpha-2,3 linked, as indicated by using virus strains M1/5 and M1/5 HS8, respectively, as agglutination probes. The alpha-2,6 linkage markedly predominated. These findings were essentially confirmed by the interaction of cryptococcal cells with the lectins Sambucus nigra agglutinin and Maackia amurensis agglutinin. We also investigated whether the sialyl residues present in C. neoformans are involved in the fungal interaction with a cationic solid-phase substrate and with mouse resident macrophages. Adhesion of yeast cells to poly-L-lysine was mediated, in part, by sialic acid residues, since the number of adherent cells was markedly reduced after treatment with bacterial neuraminidase. The enzymatic removal of sialic acids also made C. neoformans yeast cells more susceptible to endocytosis by macrophages. The results show that sialic acids are components of the cryptococcal cell surface that contribute to its negative charge and protect yeast forms against phagocytosis.