Search PubMed⌕ Search

Biomedical subjects

S Alonso

Publications and source records attributed to S Alonso.

At least 19 recordsLinked to original sources
PubMed2001

Nasal vaccination using live bacterial vectors.

Live recombinant bacteria represent an attractive means to induce both mucosal and systemic immune responses against heterologous antigens. Several models have now been developed and shown to be highly efficient following intranasal immunization. In this review, we describe the two main classes of live recombinant bacteria: generally recognized as safe bacteria and attenuated strains derived from pathogenic bacteria. Among the latter, we have differentiated the bacteria, which do not usually colonize the respiratory tract from those that are especially adapted to respiratory tissues. The strategies of expression of the heterologous antigens, the invasiveness and the immunogenicity of the recombinant bacteria are discussed.

Administration, Intranasal↗
PubMed2001

Regular wave propagation out of noise in chemical active media.

A pacemaker, regularly emitting chemical waves, is created out of noise when an excitable photosensitive Belousov-Zhabotinsky medium, strictly unable to autonomously initiate autowaves, is forced with a spatiotemporal patterned random illumination. These experimental observations are also reproduced numerically by using a set of reaction-diffusion equations for an activator-inhibitor model, and further analytically interpreted in terms of genuine coupling effects arising from parametric fluctuations. Within the same framework we also address situations of noise-sustained propagation in subexcitable media.

Journal Article↗
PubMed2001

Coronavirus derived expression systems.

Both helper dependent expression systems, based on two components, and single genomes constructed by targeted recombination, or by using infectious cDNA clones, have been developed. The sequences that regulate transcription have been characterized mainly using helper dependent expression systems and it will now be possible to validate them using single genomes. The genome of coronaviruses has been engineered by modification of the infectious cDNA leading to an efficient (>20 microg ml(-1)) and stable (>20 passages) expression of the foreign gene. The possibility of engineering the tissue and species tropism to target expression to different organs and animal species, including humans, increases the potential of coronaviruses as vectors. Thus, coronaviruses are promising virus vectors for vaccine development and, possibly, for gene therapy.

Coronavirus↗
PubMed2001

The heparin-binding haemagglutinin of M. tuberculosis is required for extrapulmonary dissemination.

Tuberculosis remains the world's leading cause of death due to a single infectious agent, Mycobacterium tuberculosis, with 3 million deaths and 10 million new cases per year. The infection initiates in the lungs and can then spread rapidly to other tissues. The availability of the entire M. tuberculosis genome sequence and advances in gene disruption technologies have led to the identification of several mycobacterial determinants involved in virulence. However, no virulence factor specifically involved in the extrapulmonary dissemination of M. tuberculosis has been identified to date. Here we show that the disruption of the M. tuberculosis or Mycobacterium bovis Bacille Calmette-Guérin (BCG) hbhA gene encoding the heparin-binding haemagglutinin adhesin (HBHA) markedly affects mycobacterial interactions with epithelial cells, but not with macrophage-like cells. When nasally administered to mice, the mutant strains were severely impaired in spleen colonization, but not in lung colonization. Coating wild-type mycobacteria with anti-HBHA antibodies also impaired dissemination after intranasal infection. These results provide evidence that adhesins such as HBHA are required for extrapulmonary dissemination, and that interactions with non-phagocytic cells have an important role in the pathogenesis of tuberculosis. They also suggest that antibody responses to HBHA may add to immune protection against tuberculosis.

Animals↗
PubMed2001

Noise-induced Brownian motion of spiral waves.

We study the erratic displacement of spiral waves forced to move in a medium with random spatiotemporal excitability. Analytical work and numerical simulations are performed in relation to a kinematic scheme, assumed to describe the autowave dynamics for weakly excitable systems. Under such an approach, the Brownian character of this motion is proved and the corresponding dispersion coefficient is evaluated. This quantity shows a nontrivial dependence on the temporal and spatial correlation parameters of the external fluctuations. In particular, a resonantlike behavior is neatly evidenced in terms of the noise correlation time for the particular situation of spatially uniform fluctuations. Actually, this case turns out to be, to a large extent, exactly solvable, whereas a pair of dispersion mechanisms are discussed qualitatively and quantitatively to explain the results for the more general scenario of spatiotemporal disorder.

Journal Article↗
PubMed2001

A highly variable segment of human subterminal 16p reveals a history of population growth for modern humans outstide Africa.

We have sequenced a highly polymorphic subterminal noncoding region from human chromosome 16p13.3 flanking the 5' end of the hypervariable minisatellite MS205, in 100 chromosomes sampled from different African and Euroasiatic populations. Coalescence analysis indicates that the time to the most recent common ancestor (approximately 1 million years) predates the appearance of anatomically modern human forms. The root of the network describing this variability lies in Africa. African populations show a greater level of diversity and deeper branches. Most Euroasiatic variability seems to have been generated after a recent out-of-Africa range expansion. A history of population growth is the most likely scenario for the Euroasiatic populations. This pattern of nuclear variability can be reconciled with inferences based on mitochondrial DNA.

Africa↗
PubMed2001

Sorting nexin-14, a gene expressed in motoneurons trapped by an in vitro preselection method.

A gene-trap strategy was set up in embryonic stem (ES) cells with the aim of trapping genes expressed in restricted neuronal lineages. The vector used trap genes irrespective of their activity in undifferentiated totipotent ES cells. Clones were subjected individually to differentiation in a system in which ES cells differentiated into neurons. Two ES clones in which the trapped gene was expressed in ES-derived neurons were studied in detail. The corresponding cDNAs were cloned, sequenced, and analysed by in situ hybridisation on wild-type embryo sections. Both genes are expressed in the nervous system. One gene, YR-23, encodes a large intracellular protein of unknown function. The second clone, YR-14, represents a sorting nexin (SNX14) gene whose expression in vivo coincides with that of LIM-homeodomain Islet-1 in several tissues. Sorting nexins are proteins associated with the endoplasmic reticulum (ER) and may play a role in receptor trafficking. Gene trapping followed by screening based on in vitro preselection of differentiated ES recombinant clones, therefore, has the potential to identify integration events in subsets of genes before generation of mouse mutants.

Animals↗
PubMed2001

Juxtaposition of CNR protocadherins and reelin expression in the developing spinal cord.

The CNR (cadherin-related neuronal receptors) family of protocadherins is of great interest because of their potential roles as molecular tags in the formation of specific synaptic connections, and as receptors for reelin, during neuronal migration, and cell body positioning. In order to know more about potential functions of CNRs we have mapped their expression during mouse nervous system development and compared their expression with that of reelin and its intracellular effector Dab1 in several tissues. In spinal cord, CNRs and Dab1 are expressed in motoneurons, while reelin is located in adjacent cells. In the hindbrain, there is a differential expression of CNRs and Dab1 in various motor nuclei. In the retina and olfactory system, we observe CNR and reelin expression but not that of Dab1. These results provide new insights into the potential functions of CNRs and their possible integration in the reelin pathway during development.

Animals↗
PubMed2001

[Predictive factors of the mortality of digestive hemorrhage caused by esophageal varices in elderly patients].

Complications of liver cirrhosis are increasingly frequent in elderly patients due to increased life expectancy and better management of cirrhotic patients. However, the influence of this condition on the evolution of variceal bleeding has not been well established. The aim of the present study was to determine the characteristics of esophagogastric variceal bleeding in elderly patients and the possible influence of advanced age on hemorrhage-related mortality. We analyzed 321 episodes of variceal bleeding in 227 cirrhotic patients. One hundred and thirteen (35.2%) episodes occurred in patients older than 65 years. No differences were found among patients older or younger than this age in terms of bleeding characteristics or Child-Pugh score. Patients older than 65 years more frequently presented serious associated diseases, hepatocellular carcinoma and hepatic encephalopathy during the episode (52.7% vs. 14%, p < 0.001; 19.7% vs. 8.7%, p = 0.01 and 17.4% vs. 10%, p = 0.09 respectively). Although hemorrhage-related mortality was higher in elderly patients (23.2% vs. 13.5%, p = 0.04), only the Child-Pugh score, definitive hemostasis, hepatocellular carcinoma and the development of encephalopathy or bacterial infection were independent predictive factors of mortality. A considerable proportion of the patients with esophagogastric variceal bleeding were older than 65 years. Advanced age does not independently influence mortality due to variceal bleeding.

Aged↗
PubMed2001

Dynamic expression patterns of the new protocadherin families CNRs and Pcdh-gamma during mouse odontogenesis: comparison with reelin expression.

Protocadherins are transmembrane glycoproteins belonging to the cadherin superfamily of molecules, which are involved in many biological processes such as cell adhesion, cytoskeletal organization and morphogenesis. Protocadherins generally exhibit only moderate adhesive activity and are highly expressed in the nervous system. Here, we report on the expression pattern of two novel families of protocadherins (CNRs and Pcdh-gamma) during rodent teeth development. Furthermore, we compare their expression with that of reelin, which is the potential ligand of CNRs. Throughout odontogenesis, CNRs, Pcdh-gamma and reelin show dynamic spatiotemporal expression patterns, which relate to both morphogenesis and cell differentiation events.

Animals↗
PubMed2001

Randomized controlled trial of aspiration needle versus automated biopsy device for transjugular liver biopsy.

PURPOSE: The efficacy and safety of transjugular liver biopsy used to obtain liver specimens in patients with coagulation disorders have been widely proven. However, histopathologic examination is not always possible because of fragmented samples provided by the aspiration technique. Recently, an automated device with a Tru-Cut-type needle was designed. In this randomized controlled trial, the use of this new device is compared with the traditional method in terms of efficacy and safety. METHOD: Fifty-six patients were included in the study; 28 were randomized to undergo the aspiration technique and 28 were randomized to undergo the automated biopsy technique. RESULTS: Correct positioning of the device was achieved in 93% of patients undergoing the aspiration technique and 96% of patients undergoing the automated biopsy technique (P = NS). Mean duration of the procedure and total number of passes were significantly higher in the aspiration needle group than in the automated device group (22.6 min +/- 12.6 vs 15.5 min +/- 9.4; P = .03, and 3.3 min +/- 1.9 vs 1.5 min +/- 0.63; P < .001, respectively). The number of portal tracts was significantly higher in the automated device group (4.7 +/- 2.5 vs. 2.7 +/- 3.4; P < .05). Adequate specimens for histopathologic evaluation were obtained in 26 patients in the automated device group and 24 patients in the aspiration needle group (92.8% vs 85.7%; P = NS), but a definite histopathologic diagnosis was more frequently obtained with the automated biopsy device (68% vs 43%; P = .05). No significant differences were observed in complication rates (7.14% vs. 10.7%; P = NS). CONCLUSION: The automated biopsy device for transjugular liver biopsy is more effective than an aspiration needle in obtaining good samples for a definite histologic diagnosis.

Adult↗
PubMed2001

Role of ADP-ribosyltransferase activity of pertussis toxin in toxin-adhesin redundancy with filamentous hemagglutinin during Bordetella pertussis infection.

Pertussis toxin (PT) and filamentous hemagglutinin (FHA) are two major virulence factors of Bordetella pertussis. FHA is the main adhesin, whereas PT is a toxin with an A-B structure, in which the A protomer expresses ADP-ribosyltransferase activity and the B moiety is responsible for binding to the target cells. Here, we show redundancy of FHA and PT during infection. Whereas PT-deficient and FHA-deficient mutants colonized the mouse respiratory tract nearly as efficiently as did the isogenic parent strain, a mutant deficient for both factors colonized substantially less well. This was not due to redundant functions of PT and FHA as adhesins, since in vitro studies of epithelial cells and macrophages indicated that FHA, but not PT, acts as an adhesin. An FHA-deficient B. pertussis strain producing enzymatically inactive PT colonized as poorly as did the FHA-deficient, PT-deficient strain, indicating that the ADP-ribosyltransferase activity of PT is required for redundancy with FHA. Only strains producing active PT induced a local transient release of tumor necrosis factor alpha (TNF-alpha), suggesting that the pharmacological effects of PT are the basis of the redundancy with FHA, through the release of TNF-alpha. This may lead to damage of the pulmonary epithelium, allowing the bacteria to colonize even in the absence of FHA.

Adhesins, Bacterial↗
PubMed2001

Production of Neisseria meningitidis transferrin-binding protein B by recombinant Bordetella pertussis.

Neisseria meningitidis serogroup B infections are among the major causes of fulminant septicemia and meningitis, especially severe in young children, and no broad vaccine is available yet. Because of poor immunogenicity of the serogroup B capsule, many efforts are now devoted to the identification of protective protein antigens. Among those are PorA and, more recently, transferrin-binding protein B (TbpB). In this study, TbpB of N. meningitidis was genetically fused to the N-terminal domain of the Bordetella pertussis filamentous hemagglutinin (FHA), and the fha-tbpB hybrid gene was expressed in B. pertussis either as a plasmid-borne gene or as a single copy inserted into the chromosome. The hybrid protein was efficiently secreted by the recombinant strains, despite its large size, and was recognized by both anti-FHA and anti-TbpB antibodies. A single intranasal administration of recombinant virulent or pertussis-toxin-deficient, attenuated B. pertussis to mice resulted in the production of antigen-specific systemic immunoglobulin G (IgG), as well as local IgG and IgA. The anti-TbpB serum antibodies were of the IgG1, IgG2a, and IgG2b isotypes and were found to express complement-mediated bactericidal activity against N. meningitidis. These observations indicate that recombinant B. pertussis may be a promising vector for the development of a mucosal vaccine against serogroup B meningococci.

Adhesins, Bacterial↗
PubMed2001

External-pH-dependent expression of the maltose regulon and ompF gene in Escherichia coli is affected by the level of glycerol kinase, encoded by glpK.

The expression of the maltose system in Escherichia coli is regulated at both transcriptional and translational levels by the pH of the growth medium (pHo). With glycerol as the carbon source, transcription of malT, encoding the transcriptional activator of the maltose regulon, is weaker in acidic medium than in alkaline medium. malT transcription became high, regardless of the pHo, when glycerol-3-phosphate or succinate was used as the carbon source. Conversely, malT expression was low, regardless of the pHo, when maltose was used as the carbon source. The increase in malT transcription, associated with the pHo, requires the presence of glycerol in the growth medium and the expression of the glycerol kinase (GlpK). Changes in the level of glpK transcription had a great effect on malT transcription. Indeed, a glpFKX promoter-down mutation has been isolated, and in the presence of this mutation, malT expression was increased. When glpK was expressed from a high-copy-number plasmid, the glpK-dependent reduced expression of the maltose system became effective regardless of the pHo. Analysis of this repression showed that a malTp1 malTp10 promoter, which is independent of the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex, was no longer repressed by glpFKX amplification. Thus, GlpK-dependent repression of the maltose system requires the cAMP-CRP complex. We propose that the pHo may affect a complex interplay between GlpK, the phosphotransferase-mediated uptake of glucose, and the adenylate cyclase.

ATP-Binding Cassette Transporters↗
PubMed2001

Rigid multilamellar bilayer cooperativity is modified by non covalently linked neuraminic-5-acid: a spectrophotometric determination.

By means of recording a simple serie of merocyanine 540 spectra, we present a method to calculate the value proportional to co-operative unit size of membranes (n). Our calculations, applied to different liposomal samples processed in the presence or absence of sugars, in high or low ionic strength showed two main results. First, that any temperature cycling in high ionic strength of rigid DPPC bilayers will modify the membrane cooperativity. Second, the presence of polysaccharide Neu-5-ac in solution will always produce a strong drop in co-operativity of a rigid membrane of DPPC, whenever the negative charge is fully exposed. This last result indicates a differential ability of charged Neu-5-ac to disrupt a rigid membrane structure, even in the absence of a covalent linkage and--remarkably-in fully hydrated media.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Integrated analysis of sequence evolution and population history using hypervariable compound haplotypes.

We have examined compound haplotypes from a highly informative region of human chromosome 16, in which information from the rapid evolution of a highly unstable minisatellite is integrated with data on the longer-term evolution of this segment from 10 flanking substitutional polymorphisms. Combined with sequence data from non-human primates, analysis of relationships between these compound haplotypes allows the reconstruction of a rooted network of the evolutionary pathways between them. Most relationships can be explained via simple substitutional mutations, although the origins of some haplotypes involve recurrent events at a hotspot for substitutional mutation and/or gene conversion. For compound haplotypes including the minisatellite array, the network found in a range of world-wide populations constitutes a highly informative data set for the analysis of population history (437 different compound haplotypes were discriminated among 658 studied). Since the mutation rates and processes of the minisatellite array are known from direct studies, ages for individual lineages have been estimated using associated minisatellite diversity. These analyses suggest that the higher information content and sampling depth of these compound haplotypes may allow more precise calibration of lineage ages than is possible using coalescent analysis of DNA sequence. Using this method we have dated the oldest Eurasian lineage as 52,000-66,000 years and the oldest European specific lineage as 37,600-56,200 years.

Africa↗