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Biomedical subjects

S Merino

Publications and source records attributed to S Merino.

At least 19 recordsLinked to original sources
PubMed2006

Can the host immune system promote multiple invasions of erythrocytes in vivo? Differential effects of medication and host sex in a wild malaria-like model.

Multiple invasions (MIs) or infections, i.e. those by more than 1 parasite in the same erythrocyte, could be the result of parasite density or, alternatively, to parasite-related factors or host-related factors. According to the last possibility, to our knowledge, only 3 laboratory studies of malaria have found an increase in the occurrence of MIs when antibodies to parasite antigens were present. Therefore, we tested the possibility that MIs were influenced by the host immune status, using as model the malaria-like parasite Haemoproteus infecting blue tits (Cyanistes caeruleus). Avian hosts infected with Haemoproteus were medicated with primaquine or injected with saline solution and the density of infection and the presence of MIs counted. Medication treatment reduced significantly the density of infection by Haemoproteus in females but not in males. For females, the presence of MIs was positively associated with both the density of infection and the immunoglobulin levels on each capture, but no association was found between the treatment and the presence of MIs. For males, the density of infection but not the immunoglobulin levels was positively associated with the presence of MIs. In addition, medicated males supported more MIs than controls. Our results represent the first line of evidence in the wild for a possible role of the host immune system promoting MIs.

Animals↗
PubMed2006

New data on epizootiology and genetics of piroplasms based on sequences of small ribosomal subunit and cytochrome b genes.

As a continuation of our studies on molecular epizootiology of piroplasmosis in Spain and other countries, we present in this contribution the finding of new hosts for some piroplasms, as well as information on their 18S rRNA gene sequences. Genetic data were complemented with sequences of apocytochrome b gene (whenever possible). The following conclusions were drawn from these molecular studies: Theileria annulata is capable of infecting dogs, since it was diagnosed in a symptomatic animal. According to cytochrome b sequences, isolates from cows and dog present slight differences. The same isolates showed, however, identical sequence in the 18S rRNA gene. This exemplifies well the usefulness of the mitochondrial gene for examining infra-specific variation. Babesia bovis is an occasional parasite of equines, since it was detected in two symptomatic horses. We found evidence of genetic polymorphism occurring in the 18S rRNA gene of Spanish T. equi-like and B. ovis isolates. B. bennetti from Spanish seagull is loosely related to B. ovis, and might represent a genetically distinct branch of babesids. A partial sequence of a cytochrome b pseudogene was obtained for the first time in Babesia canis rossi from South Africa. The pseudogene is distantly related to B. bigemina cytochrome b gene. These new findings confirm the ability of some piroplasms to infect multiple hosts, as well as the existence of a relatively wide genetic polymorphisms with respect to the cytochrome b gene. On the other hand, the existence of mtDNA-like pseudogenes of possible nuclear location in piroplasms is interesting due to their possible impact on molecular phylogeny studies.

Animals↗
PubMed2006

Are multiple gametocyte infections in malarial parasites an adaptation to ensure fertility?

Multiple infections, those by more than one parasite in the same erythrocyte, may be adaptive for the malarial parasite as a means to ensure fertility. Alternatively they may simply be the consequence of a non-adaptive process forcing several parasites to compete for resources in one host cell. Avian hosts infected with Haemoproteus were medicated with primaquine or injected with saline solution and the density of infection and number, maturity and sex of mature multiple infections counted. Multiple infections depend on density of infection, and maturity is attained rarely and usually by gametocytes of the same sex. The role of multiple infections for fertility insurance is not supported by these results.

Adaptation, Physiological↗
PubMed2006

Combined protocol of cell therapy for chronic spinal cord injury. Report on the electrical and functional recovery of two patients.

BACKGROUND: This is a preliminary report on successful results obtained during treatment of two patients with chronic spinal cord injury. The therapeutic approach was based on the generation of controlled inflammatory activity at the injury site that induced a microenvironment for the subsequent administration of autologous, BM-driven transdifferentiated neural stem cells (NSC). METHODS: BM mesenchymal stem cells (MSC) were cocultured with the patient's autoimmune T (AT) cells to be transdifferentiated into NSC. Forty-eight hours prior to NSC implant, patients received an i.v. infusion of 5 x 10(8) to 1 x 10(9) AT cells. NSC were infused via a feeding artery of the lesion site. Safety evaluations were performed everyday, from the day of the first infusion until 96 h after the second infusion. After treatment, patients started a Vojta and Bobath neurorehabilitation program. RESULTS: At present two patients have been treated. Patient 1 was a 19-year-old man who presented paraplegia at the eight thoracic vertebra (T8) with his sensitive level corresponding to his sixth thoracic metamere (T6). He received two AT-NSC treatments and neurorehabilitation for 6 months. At present his motor level corresponds to his first sacral metamere (S1) and his sensitive level to the fourth sacral metamere (S4). Patient 2 was a 21-year-old woman who had a lesion that extended from her third to her fifth cervical vertebrae (C3-C5). Prior to her first therapeutic cycle she had severe quadriplegia and her sensitive level corresponded to her second cervical metamere (C2). After 3 months of treatment her motor and sensitive levels reached her first and second thoracic metameres (T1-T2). No adverse events were detected in either patient. DISCUSSION: The preliminary results lead us to think that this minimally invasive approach, which has minor adverse events, is effective for the repair of chronic spinal cord lesions.

Adult↗
PubMed2005

Identification and characterization of putative virulence genes and gene clusters in Aeromonas hydrophila PPD134/91.

Aeromonas hydrophila is a gram-negative opportunistic pathogen of animals and humans. The pathogenesis of A. hydrophila is multifactorial. Genomic subtraction and markers of genomic islands (GIs) were used to identify putative virulence genes in A. hydrophila PPD134/91. Two rounds of genomic subtraction led to the identification of 22 unique DNA fragments encoding 19 putative virulence factors and seven new open reading frames, which are commonly present in the eight virulence strains examined. In addition, four GIs were found, including O-antigen, capsule, phage-associated, and type III secretion system (TTSS) gene clusters. These putative virulence genes and gene clusters were positioned on a physical map of A. hydrophila PPD134/91 to determine their genetic organization in this bacterium. Further in vivo study of insertion and deletion mutants showed that the TTSS may be one of the important virulence factors in A. hydrophila pathogenesis. Furthermore, deletions of multiple virulence factors such as S-layer, serine protease, and metalloprotease also increased the 50% lethal dose to the same level as the TTSS mutation (about 1 log) in a blue gourami infection model. This observation sheds light on the multifactorial and concerted nature of pathogenicity in A. hydrophila. The large number of putative virulence genes identified in this study will form the basis for further investigation of this emerging pathogen and help to develop effective vaccines, diagnostics, and novel therapeutics.

Aeromonas hydrophila↗
PubMed2004

A type III secretion system is required for Aeromonas hydrophila AH-1 pathogenesis.

Aeromonas hydrophila is a gram-negative opportunistic pathogen in fish and humans. Many bacterial pathogens of animals and plants have been shown to inject anti-host virulence determinants into the hosts via a type III secretion system (TTSS). Degenerate primers based on lcrD family genes that are present in every known TTSS allowed us to locate the TTSS gene cluster in A. hydrophila AH-1. A series of genome walking steps helped in the identification of 25 open reading frames that encode proteins homologous to those in TTSSs in other bacteria. PCR-based analysis showed the presence of lcrD homologs (ascV) in all of the 33 strains of A. hydrophila isolated from various sources. Insertional inactivation of two of the TTSS genes (aopB and aopD) led to decreased cytotoxicity in carp epithelial cells, increased phagocytosis, and reduced virulence in blue gourami. These results show that a TTSS is required for A. hydrophila pathogenesis. This is the first report of sequencing and characterization of TTSS gene clusters from A. hydrophila. The TTSS identified here may help in developing suitable vaccines as well as in further understanding of the pathogenesis of A. hydrophila.

Aeromonas hydrophila↗
PubMed2001

Synthesis, characterization, and optical response of dipolar and non-dipolar poly(phenylenevinylene) dendrimers.

New dipolar and non-dipolar poly(phenylenevinylene) dendrimers bearing electron-donating and electron-withdrawing groups have been efficiently synthesized using Heck and Horner-Wadsworth-Emmons reactions. The photoluminescence of these systems may be tuned in the blue zone by choosing the appropriate peripheral groups. Despite the meta-substitution pattern, large Stokes shifts can be observed when pi-donor and pi-acceptor groups are connected by a m-phenylenevinylene system.

Journal Article↗
PubMed2001

Synthesis and characterization of linear, hyperbranched, and dendrimer-like polymers constituted of the same repeating unit.

The synthesis of a linear polymer that includes both P=N and P=S double bonds, and P-O and P-C single bonds is reported by using two different paths that involve deprotection reactions and the Staudinger reaction. The preparation of hyperbranched polymers made up of OC6H4P(Ph)2=N-P=S repeating units is also described. Five generations of dendrimers originating from the same building blocks were prepared. The characterisation of all these phosphorus-based macromolecular architectures (solution behaviour, size exclusion chromatography, intrinsic viscosity, thermal behaviour) revealed marked differences in their respective behaviour.

Journal Article↗
PubMed2001

Determination of the partition coefficients of a homologous series of ciprofloxacin: influence of the N-4 piperazinyl alkylation on the antimicrobial activity.

Partitioning of a fluoroquinolone antibiotic, ciprofloxacin, and its N-piperazinyl alkyl derivatives, between octanol or Escherichia coli lipid membrane extract and aqueous buffer pH 7.4, was studied. The experimental partition coefficients (Pexp) were corrected at this pH using an expression that includes the microconstant values of each compound. The relationship between the corrected partition coefficients expressed as logP (thermodynamic partition coefficient) and the diffusion through the lipid bilayers ('hydrophobic pathway') of entry has been considered here. In this work, we have explored the possibility of using our model to provide physicochemical evidences to support such a via. The correlation between logP values and antibacterial activities (expressed as minimal inhibitory concentration (MIC) values) of the homologous series of antibiotics against different bacteria were studied. A parabolic behaviour was observed which evidenced that the only increase in lipophilicity does not result in an enhanced antimicrobial activity for the homologous family studied.

Alkylation↗
PubMed2001

The cell division genes (ftsE and X) of Aeromonas hydrophila and their relationship with opsonophagocytosis.

A transposon mutant from Aeromonas hydrophila AH-3 was obtained which was highly resistant to opsonophagocytosis. The mutation was identified in the ftsE gene and we characterised the operon ftsY, E and X from this bacterium. These genes, as in enteric bacteria, are neighbours to rpoH. The A. hydrophilia ftsE and X genes were fully able to complement Escherichia coli ftsE mutants, and also complement the opsonophagocytosis-resistant phenotype of the A. hydrophila mutant strain. This phenotype seems to be related to the filamentous phenotype at 37 degrees C exhibited by the A. hydrophila ftsE mutant.

ATP-Binding Cassette Transporters↗
PubMed2001

The MgtE Mg2+ transport protein is involved in Aeromonas hydrophila adherence.

Aeromonas hydrophila AH-3 strains carrying mutations in mgtE, which encodes a Mg2+ and Co2+ transport system, showed a 50% reduction of in vitro adherence to HEp-2 cells, a reduction in swarming in semisolid swarming agar, and decrease in biofilm formation of over 60% in comparison to the wild-type strain. The cloned A. hydrophila mgtE expressed from a plasmid complements a Salmonella typhimurium strain deleted for all Mg2+ transporters both phenotypically and by measurement of 57Co2+ uptake. Likewise, plasmid-borne mgtE was able to complement the changes observed in A. hydrophila mgtE mutants. We suggest that MgtE and thus Mg2+ and possibly Co2+ have a role in A. hydrophila related to their swarming ability and related consequences such as adherence and biofilm formation.

Aeromonas hydrophila↗
PubMed2001

Does clutch size evolve in response to parasites and immunocompetence?

Parasites have been argued to influence clutch size evolution, but past work and theory has largely focused on within-species optimization solutions rather than clearly addressing among-species variation. The effects of parasites on clutch size variation among species can be complex, however, because different parasites can induce age-specific differences in mortality that can cause clutch size to evolve in different directions. We provide a conceptual argument that differences in immunocompetence among species should integrate differences in overall levels of parasite-induced mortality to which a species is exposed. We test this assumption and show that mortality caused by parasites is positively correlated with immunocompetence measured by cell-mediated measures. Under life history theory, clutch size should increase with increased adult mortality and decrease with increased juvenile mortality. Using immunocompetence as a general assay of parasite-induced mortality, we tested these predictions by using data for 25 species. We found that clutch size increased strongly with adult immunocompetence. In contrast, clutch size decreased weakly with increased juvenile immunocompetence. But, immunocompetence of juveniles may be constrained by selection on adults, and, when we controlled for adult immunocompetence, clutch size decreased with juvenile immunocompetence. Thus, immunocompetence seems to reflect evolutionary differences in parasite virulence experienced by species, and differences in age-specific parasite virulence appears to exert opposite selection on clutch size evolution.

Animals↗
PubMed2001

Physiological and haematological consequences of a novel parasite on the red-rumped swallow Hirundo daurica.

Parasite virulence has been hypothesised to increase with the degree of host sociality because highly social hosts have a greater probability of encountering horizontal transmission of parasites and experiencing infections with multiple strains of the same parasites than do solitary hosts. As compared with the defences of closely related social host species, we predicted that solitary hosts should have relatively weak defences against parasites, thus being relatively more affected when parasitised by a novel parasite. We tested this prediction by either experimentally infesting 12 nests of the solitarily nesting red-rumped swallow Hirundo daurica with 50 individuals of the generalist martin bug Oeciacus hirundinis or by fumigation of nine nests. Nestlings 13 days old from the parasite addition group experienced increased mortality, attained lower body mass and tended to have shorter tarsi compared to nestlings from fumigated nests. Surprisingly, nestlings from the parasite addition group had higher packed cell volume (cellular fraction of blood) and lower levels of heat shock proteins (HSP60) than nestlings from the fumigation group. A measure of immunocompetence was not significantly affected by treatment, but its magnitude was positively related to packed cell volume and negatively related to level of HSP60. Solitary hosts like the red-rumped swallow have weak immune responses and low levels of heat shock proteins when infested with ectoparasites while highly social hosts have strong immune responses and high levels of heat shock proteins when infested. These findings partially support the hypothesis that potential host species with weak defences are more susceptible to infection and the deleterious effects of evolving parasites than potential hosts with strong defences.

Animals↗
PubMed2001

Unusual changing CT and MR appearance of an epithelial intracranial cyst.

INTRODUCTION: Epithelial cysts are infrequent intracranial lesions and may content cilia and mucosecretant cells that may be responsible for the protein concentration within the contents and the variable radiological appearance on CT and MRI. METHODS AND PATIENTS: We present a case of an extraaxial epithelial cyst with changing CT and MR characteristics. RESULTS: The appearance of our cyst on CT or MRI changed with size and morphology. When CT studies showed an hypodense cyst, the lesion was large but when an hyperdense mass was present, the lesion was smaller. In the later situation MRI showed hyperintensity on T1-weighted images and hypointensity on T2-weighted images and the protein concentration of the cystic contents was high. CONCLUSIONS: We believe that a relatively high protein concentration in our cyst was the major factor for the high attenuation on CT and the hyperintensity or hypointensity on T1- and T2-weighted images, respectively. We believe than these atypical imaging findings were caused by changes in the protein concentration within the cyst.

Brain Diseases↗
PubMed2001

Channeling agent and drug release from a central core matrix tablet.

A new oral dosage form for controlled and complete release of drug after a predetermined lag time is described. The system, designed to exploit the relatively constant small intestine transit time, consists of a drug-containing core coated with a polymeric matrix formed by a channeling agent (NaCl, mannitol, and Emdex) and an inert polymer (Eudragit RS100). The lag time was found to be dependent on type and particle size of the channeling substances used. Also, rheological properties of the binary mixtures (channeling substance--polymer) can affect the lag time periods. On the other hand, the release kinetics were found to be influenced significantly by excipient type and particle size. Results obtained from in vitro dissolution testing demonstrated that this device potentially could be used to deliver drugs orally for up to once-a-day dosing at controllable rates.

Administration, Oral↗
PubMed2001

Role of flm locus in mesophilic Aeromonas species adherence.

The adherence mechanism of Aeromonas caviae Sch3N to HEp-2 cells was initially investigated through four mini-Tn5 mutants that showed a 10-fold decrease in adherence. These mutants lost motility, flagella, and their lipopolysaccharide (LPS) O antigen (O-Ag). Three genes, flmB-neuA-flmD, were found to be interrupted by the transposon insertions; additionally, two other genes, one lying upstream (flmA) and one downstream (neuB), were found to be clustered in the same operon. While the flmA and flmB genes were present in all mesophilic Aeromonas spp. (A. hydrophila, A. caviae, A. veronii bv. veronii, and A. veronii bv. sobria) tested, this was not the case for the neuA-flmD-neuB genes. Construction and characterization of flmB insertion mutants in five other mesophilic Aeromonas strains revealed the loss of motility, flagella, and adherence but did not alter the LPS composition of these strains. Taking the above findings into consideration, we conclude (i) that flagella and possibly the LPS O-Ag are involved in the adherence of the mesophilic Aeromonas to human epithelial cells; (ii) flmA and flmB are genes widely distributed in the mesophilic Aeromonas and are involved in flagella assembly, and thus adherence; and (iii) in A. caviae Sch3N the flmA and flmB genes are found in a putative operon together with neuA, flmD, and neuB and are involved in LPS O-Ag biosynthesis and probably have a role in flagellum assembly.

Aeromonas↗
PubMed2001

Genetic characterization of the Klebsiella pneumoniae waa gene cluster, involved in core lipopolysaccharide biosynthesis.

A recombinant cosmid containing genes involved in Klebsiella pneumoniae C3 core lipopolysaccharide biosynthesis was identified by its ability to confer bacteriocin 28b resistance to Escherichia coli K-12. The recombinant cosmid contains 12 genes, the whole waa gene cluster, flanked by kbl and coaD genes, as was found in E. coli K-12. PCR amplification analysis showed that this cluster is conserved in representative K. pneumoniae strains. Partial nucleotide sequence determination showed that the same genes and gene order are found in K. pneumoniae subsp. ozaenae, for which the core chemical structure is known. Complementation analysis of known waa mutants from E. coli K-12 and/or Salmonella enterica led to the identification of genes involved in biosynthesis of the inner core backbone that are shared by these three members of the Enterobacteriaceae. K. pneumoniae orf10 mutants showed a two-log-fold reduction in a mice virulence assay and a strong decrease in capsule amount. Analysis of a constructed K. pneumoniae waaE deletion mutant suggests that the WaaE protein is involved in the transfer of the branch beta-D-Glc to the O-4 position of L-glycero-D-manno-heptose I, a feature shared by K. pneumoniae, Proteus mirabilis, and Yersinia enterocolitica.

Animals↗