Biomedical subjects
Publications and source records attributed to A Pascual.
Antimicrobial susceptibility was determined in 15 epidemiologically unrelated clinical isolates of Acinetobacter genospecies 3. Moreover, the mechanisms of resistance to some beta-lactam antibiotics may be associated with the presence of a chromosomal cephalosporinase, AmpC, and the resistance to quinolones related to mutations in the gyrA and parC genes.
OBJECTIVES: Plasmid pMG252 contains the qnr locus, which is responsible for low-level resistance to quinolones by protecting the DNA gyrase. pMG252 also encodes the AmpC-type beta-lactamase (pACBL), FOX-5. The aim of this study was to determine the prevalence of qnr in strains from different geographical locations in America and Europe. METHODS: Four hundred and twenty-five (159 Klebsiella pneumoniae and 266 Escherichia coli) clinical isolates were studied. The detection of qnr was by PCR using specific primers for an internal fragment of 543 bp. RESULTS: qnr was detected in three cefoxitin-resistant K. pneumoniae strains, which also produced a pACBL. None of the E. coli isolates tested contained qnr. The three qnr-positive K. pneumoniae came from the USA, and all transferred a conjugative plasmid coding for cefoxitin resistance to E. coli J53. qnr was also transferred by the same plasmid in two out of the three strains. The sequences of amplified qnr fragments from the three strains were identical to the qnr sequence from pMG252. CONCLUSIONS: The qnr determinant is uncommon among clinical isolates of K. pneumoniae and E. coli, but its identification in three pACBL+ K. pneumoniae from the USA indicates the emergence of this quinolone resistance mechanism.
OBJECTIVES: To evaluate the penetration of ketolide cethromycin (ABT-773) into human polymorphonuclear leucocytes (PMNs) and its intracellular activity. METHODS: The uptake of radiolabelled cethromycin by PMNs was determined by a velocity gradient centrifugation technique. The activity of cethromycin against intracellular Staphylococcus aureus ATCC 25923 in PMNs was also evaluated. RESULTS: The cellular to extracellular concentration (C/E) ratio for cethromycin was >200 at an extracellular concentration of 2 mg/L. The uptake of cethromycin into PMNs was rapid and saturable. Cethromycin was slowly released from the loaded PMNs (cell associated drug>50% after 2 h of incubation). Intracellular penetration was significantly affected by the environmental temperature (C/E ratio at 4 degrees C and 37 degrees C: 13 +/- 6 and 226 +/- 31, respectively; P < 0.05), by cell viability (C/E ratio for dead and viable cells: 100 +/- 38 and 226 +/- 31, respectively; P < 0.05), by pH (C/E ratio was significantly increased at basic pH) and by the metabolic inhibitors 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone. The intracellular accumulation of cethromycin also decreased significantly when cells were activated with phorbol myristate acetate or opsonized zymosan. These data indicate that a potentially active mechanism could be involved in the uptake of cethromycin by PMNs. At high extracellular concentrations of 5 and 10 mg/L, cethromycin showed significant intracellular activity against S. aureus. CONCLUSIONS: Cethromycin achieves high intracellular concentrations within human PMNs, remaining active intracellularly.
OBJECTIVE: Wallerian degeneration in normal appearing white matter in early relapsing-remitting multiple sclerosis (RRMS), and its correlation with the number of relapses and disease duration. Background Recent pathological studies have demonstrated Wallerian degeneration in normal appearing white matter (NAWM) in multiple sclerosis (MS), in established RRMS, and in chronic MS. However, the presence of Wallerian degeneration early in the disease and its correlation with relapse and with disease duration has not been studied. METHODS: We performed proton magnetic resonance spectroscopic imaging in 21 MS patients, and 4 healthy controls, age and gender matched, aged under 45 years, with a maximum of 4 years since first bout, and an EDSS score of less than 3.0. N-acetyl-aspartate (NAA) (an index of axonal integrity) was measured in the NAWM from the pons and the cerebellar peduncles. RESULTS: We observed that the NAA levels were abnormally low in the NAWM in the early RRMS patients (p = 0.04, Student's t-test). The decrease in the NAA concentration correlated with disease duration in the two areas studied (p = 0.03 for pons and p = 0.04 for cerebellar peduncle); and with the number of previous relapses (Pearson's correlation = -0.582, p < 0.002). CONCLUSION: Wallerian degeneration measured by the NAA concentration at pons and cerebellar peduncles is present early in the disease and correlates with the number of relapses and disease duration.
Retinoic acid (RA) is a potent regulator of morphogenesis, growth and cell differentiation. Incubation with RA causes arrest of proliferation and neurite extension in SH-SY5Y cells, a neuroblastoma cell line of human origin. In these cells, RA regulates the expression of the beta-amyloid precursor protein. The retinoid increases the levels of intracellular and secreted forms of APP (amyloid precursor protein), APP-mRNA levels and the activity of the APP promoter in transient transfection studies. These responses require long periods of exposition to the ligand, thus suggesting a nondirect effect of the RA receptors on the APP gene. Also in these cells, RA induces the expression of TrkB, the tyrosine kinase receptor for brain-derived neurotrophic factor (BDNF), and 4 days of pretreatment with retinoic acid confers BDNF responsiveness to the APP promoter.
The aim of this study was to evaluate the WIDER I system for susceptibility testing of Haemophilus influenzae and Streptococcus pneumoniae. MICs of 12 antimicrobials against 42 H. influenzae and 58 S. pneumoniae strains were determined using 1W MIC panels and compared with those obtained by microdilution. Overall essential agreements were >99%. Very major errors were not detected. Major errors occurred with ampicillin (1.7% H. influenzae). Minor errors were 2.3% (amoxicillin-clavulanate, cefuroxime, chloramphenicol), 7.1% (ampicillin) and 16.7% (clarithromycin) for H. influenzae, and 1.7% (chloramphenicol, erythromycin, meropenem), 3.4% (amoxicillin-clavulanate, cefuroxime, tetracycline) and 8.6% (levofloxacin) for S. pneumoniae. The WIDER I system is a reliable method for susceptibility testing of H. influenzae and S. pneumoniae.
We describe an atypical presentation of bacteremia caused by N. meningitidis serogroup X. By multilocus sequence typing the isolate was characterized to the sequence type 2139, which is not related with the clonal complex recently isolated in Africa. Since 1984, only six cases of serogroup X N. meningitidis infections have been diagnosed in Spain. Nevertheless, after the application of the conjugated vaccine, attention should be paid to the emergence of infections caused by unusual serogroups of N. meningitidis.
The activity of azithromycin against 225 clinical strains of Acinetobacter baumannii isolated consecutively from 26 Spanish hospitals in November 2000 was studied. The MICs of azithromycin were determined by microdilution, according to the NCCLS guidelines. The bactericidal activity of azithromycin against 15 clonally unrelated A. baumannii strains with different antimicrobial susceptibility patterns was tested using the subculture method. The killing-curves method was also performed against five strains with different susceptibility to azithromycin. The MIC(50) and MIC(90) of azithromycin were 32 and 64 mg/l, respectively. Moderate bactericidal activity was observed in 14 out of the 15 strains evaluated by the subculture method (MBCs from 1 to 4 dilution steps higher than the MICs) and by the killing-curve method. For three strains the number of CFU/ml was reduced 1 to 1.4 log by concentrations of azithromycin equivalent to 1 and 4 times their MICs. lt is concluded that azithromycin has moderate bactericidal activity against the strains of A. baumannii evaluated.
In the last decade, two main strategies have been employed in the prevention of catheter-related infections: the creation of anti-adhesive biomaterials using physicochemical methods, and the incorporation of antimicrobial or antiseptic agents into current polymer biomaterials. There has been limited success with the first approach. Intravascular catheters and cuffs with an antimicrobial coating have been developed in recent years. Nevertheless, preventive strategies should avoid the use of therapeutic antibiotics. Exposure to antimicrobial agents could favor the development of resistance or the expression of genes responsible for biofilm formation. The use of these catheters should be restricted to situations where the rate of infection is high despite adherence to other strategies that do not incorporate antimicrobial agents. Better knowledge of the pathogenesis of catheter-related infections will facilitate the design of new devices that avoid the use of antimicrobial agents and decrease the risk of associated bloodstream infections. This could include the use of 'biospecific polymers' coated with anti-adhesive molecules or the use of agents which might block the expression of genes controlling biofilm formation for the most prevalent pathogens.
OBJECTIVE: To study if there are different patterns of clinical activity--measured by the annual exacerbation rate (AER)--among relapsing-remitting multiple sderosis (RRMS), "early" secondary multiple sclerosis (SPMS) and "late" SPMS. METHODS: A prospective 5-year follow-up study in 80 MS patients has been carried out, calculating the AER and the mean expanded disability status scale (EDSS) change rate (MCR). RESULTS: A significant difference on the AER, among RRMS, early SPMS and late SPMS, has been found. CONCLUSIONS: The SPMS has a high clinical inflammatory activity before and during its transformation from a RRMS.
The mushroom bodies, substructures of the Drosophila brain, are involved in olfactory learning and short-term memory, but their role in long-term memory is unknown. Here we show that the alpha-lobes-absent (ala) mutant lacks either the two vertical lobes of the mushroom body or two of the three median lobes which contain branches of vertical lobe neurons. This unique phenotype allows analysis of mushroom body function. Long-term memory required the presence of the vertical lobes but not the median lobes. Short-term memory was normal in flies without either vertical lobes or the two median lobes studied.
L-glutamine (Gln) sensitizes tumor cells to tumor necrosis factor (TNF)-alpha-induced cytotoxicity. The type and mechanism of cell death induced by TNF-alpha was studied in Ehrlich ascites tumor (EAT)-bearing mice fed a Gln-enriched diet (GED; where 30% of the total dietary nitrogen was from Gln). A high rate of Gln oxidation promotes a selective depletion of mitochondrial glutathione (mtGSH) content to approximately 58% of the level found in tumor mitochondria of mice fed a nutritionally complete elemental diet (standard diet, SD). The mechanism of mtGSH depletion involves a glutamate-induced inhibition of GSH transport from the cytosol into mitochondria. The increase in reactive oxygen intermediates (ROIs) production induced by TNF-alpha further depletes mtGSH to approximately 35% of control values, which associates with a decrease in the mitochondrial transmembrane potential (MMP), and elicits mitochondrial membrane permeabilization and release of cytochrome c. Mitochondrial membrane permeabilization was also found in intact tumor cells cultured with a Gln-enriched medium under conditions of buthionine sulfoximine (BSO)-induced selective GSH synthesis inhibition. Enforced expression of the bcl-2 gene in tumor cells could not avoid the glutamine- and TNF-alpha-induced cell death under conditions of mtGSH depletion. However, addition of GSH ester, which delivers free intracellular GSH and increases mtGSH levels, preserved cell viability. These findings show that glutamine oxidation and TNF-alpha, by causing a change in the glutathione redox status within tumor mitochondria, activates the molecular mechanism of apoptotic cell death.
A broad range of benzophenone hydrazone derivatives was prepared and tested against selected chewing insect pests, allowing the analysis of structure-activity relationships. Good activity was found only when the aromatic rings were substituted at the 4-positions with an halogen atom and a triflate or perhaloalkoxy group. In contrast, a number of substituents on the hydrazone part led to active compounds, the best results being achieved with acyl-type substituents. The excellent laboratory and greenhouse activity of the best representatives was confirmed in semi-field trials against Spodoptera littoralis.
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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.
The beta-amyloid protein, component of the senile plaques found in Alzheimer brains is proteolytically derived from the beta-amyloid precursor protein (APP), a larger membrane-associated protein that is expressed in both neural and non-neural cells. Overexpression of APP might be one of the mechanisms that more directly contributes to the development of Alzheimer's disease. The APP gene expression is regulated by a number of cellular mediators including nerve growth factor (NGF) and other ligands of tyrosine kinase receptors. We have previously described that NGF increases APP mRNA levels in PC12 cells. However, the molecular mechanisms and the precise signalling pathways that mediate its regulation are not yet well understood. In the present study we present evidence that NGF, and to a lesser extent fibroblast growth factor and epidermal growth factor, stimulate APP promoter activity in PC12 cells. This induction is mediated by DNA sequences located between the nucleotides - 307 and - 15, and involves activation of the Ras-MAP kinase signalling pathway. In contrast, we have also found that NGF-induced secretion of soluble fragments of APP into the culture medium is mediated by a Ras independent mechanism.
The beta-amyloid peptide, the major component of Alzheimer-associated plaques, derives from a larger beta-amyloid precursor protein (APP), that is expressed in both neural and non-neural cells. Overexpression of APP actively contributes to the development of senile plaques and is considered a risk factor for the disease. APP expression is regulated by a variety of cellular mediators, among them ligands of tyrosine kinase receptors. In this study, we present evidence that brain-derived neurotrophic factor (BDNF) modulates, in a dose- and time-dependent fashion, APP promoter activity in SH-SY5Y neuroblastoma cells transiently expressing the receptor TrkB. The APP promoter contains two potential AP-1 sites, and we examined whether or not protein kinase C (PKC) and the AP-1 sites of the promoter mediate the BDNF-induced stimulation of APP. Stimulation of APP promoter activity by BDNF was not affected by the PKC inhibitor bisindolylmaleimide, or by dominant negative mutants of the AP-1 components Fos and Jun, which, however, blocked the response to phorbol esters. These results suggest that activation of the APP promoter by BDNF is largely independent of PKC and AP-1. In contrast, activated Ras increased APP promoter activity in SH-SY5Y cells, and a dominant negative mutant of Ras abolished BDNF-mediated promoter stimulation. Taken together, our results suggest a mechanism that involves activation of the Ras/MAP kinase signaling pathway, and phosphorylation of as yet unidentified effectors which in turn can activate response elements within the APP promoter.
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