RESUMEN
The interaction of DNA with monolayers of the cationic lipid dimethyldioctadecylammonium bromide, with/without 50 mol % of a neutral "helper" lipid, either dioleoylphosphatidylethanolamine or cholesterol, has been studied using specular neutron reflection, surface pressure-area isotherms, and Brewster angle microscopy. The amount of DNA bound to the lipid head groups has been comprehensively quantified in the range of 8-39 vol% of DNA with respect to the monolayer composition (monolayers composed of dimethyldioctadecylammonium bromide binding the most DNA and monolayers containing dioleoylphosphatidylethanolamine binding the least) and surface pressure (DNA binding being greatest at highest surface pressures). Surprisingly, regardless of these variables, the thickness of the DNA-containing layer remained approximately constant between 18 and 25 Å. This systematic study is the first direct quantification of the binding of DNA with two different helper-lipid-containing multicomponent monolayers, an important step toward understanding interaction parameters in more realistic models of gene delivery systems.
Asunto(s)
Colesterol/química , ADN/química , Fosfatidiletanolaminas/química , Compuestos de Amonio Cuaternario/química , Cationes , Técnicas de Transferencia de Gen , Modelos Químicos , Modelos Moleculares , Difracción de Neutrones , Propiedades de Superficie , Liposomas Unilamelares/químicaRESUMEN
Successful drug delivery via lipid-based systems has often been aided by the incorporation of 'helper lipids'. While these neutral lipids enhance the effectiveness of cationic lipid-based delivery formulations, many questions remain about the nature of their beneficial effects. The structure of monolayers of the cationic lipid dimethyldioctadecylammonium bromide (DODAB) alone, and mixed with a neutral helper lipid, either diolelyphosphatidylethanolamine or cholesterol at a 1 : 1 molar ratio was investigated at the air-water interface using a combination of surface pressure-area isotherms, Brewster angle microscopy (BAM) and specular neutron reflectivity in combination with contrast variation. BAM studies showed that while pure DODAB and DODAB with cholesterol monolayers showed fairly homogeneous surfaces, except in the regions of phase transition, monolayers of DODAB with diolelyphosphatidylethanolamine were, in contrast, inhomogeneous exhibiting irregular bean-shaped domains throughout. Neutron reflectivity data showed that while the thickness of the DODAB monolayer increased from 17 to 24 Å as it was compressed from a surface pressure of 5-40 mN m(-1), the thickness of the helper lipid-containing monolayers, over the same range of surface pressures, was relatively invariant at between 25 and 27 Å. In addition, the monolayers containing diolelyphosphatidylethanolamine were found to be more heavily hydrated than the monolayers of cationic lipid, alone or in combination with cholesterol, with hydration levels of 18 molecules of water per molecule of lipid being recorded for the diolelyphosphatidylethanolamine-containing monolayers at a surface pressure of 30 mN m(-1) compared with only six and eight molecules of water per molecule of lipid for the pure DODAB monolayer and the cholesterol-containing DODAB monolayer, respectively.
Asunto(s)
Colesterol/metabolismo , Sistemas de Liberación de Medicamentos/métodos , Lípidos de la Membrana/metabolismo , Fosfatidiletanolaminas/metabolismo , Compuestos de Amonio Cuaternario/metabolismo , Liposomas Unilamelares/metabolismo , Microscopía/métodos , Neutrones , Presión , Agua/metabolismoRESUMEN
Specular neutron reflectivity was used to study the time course and nature of the interaction of the positively charged, peripheral membrane protein cytochrome c with supported bilayers of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) containing the anionic lipid 1-palmitoyl-2-oleoyl-glycero-3-phosphatidylserine (POPS). The supported bilayers were prepared by deposition on silicon blocks of two monolayers of DOPC, the second of which contained either 10 or 20 mol % POPS at surface pressures of either 15 or 20 mN/m using a combination of Langmuir-Blodgett and Schaefer deposition techniques. Each supported bilayer was initially characterized by specular neutron reflectivity using subphases of 10 mM NaCl aqueous solutions. Regardless of POPS content and bilayer deposition pressure, the molecular architecture of the bilayers was similar. The addition of cytochrome c resulted in an almost immediate change in reflectivity, which was well modeled by assuming that an additional layer was present next to the outer leaflet of the bilayer. The thickness of this layer, which contained the volume fraction of approximately 15% protein, was approximately 30 A (consistent with the cross-section of a single cytochrome c molecule). The addition of cytochrome c to the subphase also resulted in a change in the structure of the phospholipid bilayer, suggesting some penetration of cytochrome c into the bilayer. Specular neutron reflectivity studies after careful washing with solvent showed that although most of the protein was washed off by flushing 10 mM NaCl D2O through the cell a small amount remained both within the bilayer and bound to the membrane surface.
Asunto(s)
Citocromos c/química , Membrana Dobles de Lípidos/química , Fosfatidilcolinas/química , Fosfatidilserinas/química , Membrana Celular/metabolismo , Citocromos c/metabolismo , Membrana Dobles de Lípidos/metabolismo , Difracción de Neutrones , Fosfatidilcolinas/metabolismo , Fosfatidilserinas/metabolismo , Unión Proteica , Silicio/química , Silicio/metabolismo , Cloruro de Sodio/química , Cloruro de Sodio/metabolismoRESUMEN
A review is presented of the major clinical features of a number of glycolipidoses including Fabry, Gaucher, Tay-Sachs, metachromatic leukodystrophy as well as CeroidLipofucinosis and Sjogren-Larsson syndrome. The possibilities offered by lipidomics for diagnosis and follow-up after enzyme replacement therapy are presented from a practical perspective. The contribution of HPLC coupled with tandem mass spectrometry has considerably simplified the detection and assay of abnormal metabolites. Corresponding internal standards consisting of weighed mixtures of the stable-isotope labeled metabolites required to calibrate and quantitate lipid components of these orphan diseases standards have yet to become commercially available. A lipidomics approach has been found to compare favorably with DNA-sequence analysis for the rapid diagnosis of pre-birth syndromes resulting from these multiple gene defects. The method also seems to be suitable for screening applications in terms of a high throughput combined with a low rate of false diagnoses based on the wide differences in metabolite concentrations found in affected patients as compared with normal subjects. The practical advantages of handling samples for lipidomic diagnoses as compared to enzyme assay are presented for application to diagnosis during pregnancy.
Asunto(s)
Terapia Enzimática , Genómica/métodos , Lipidosis/diagnóstico , Lípidos/química , Enfermedad de Fabry/diagnóstico , Enfermedad de Fabry/fisiopatología , Enfermedad de Fabry/terapia , Enfermedad de Gaucher/diagnóstico , Enfermedad de Gaucher/fisiopatología , Enfermedad de Gaucher/terapia , Humanos , Leucodistrofia Metacromática/diagnóstico , Leucodistrofia Metacromática/fisiopatología , Leucodistrofia Metacromática/terapia , Lipidosis/enzimología , Lipidosis/terapia , Lipofuscinosis Ceroideas Neuronales/diagnóstico , Lipofuscinosis Ceroideas Neuronales/fisiopatología , Lipofuscinosis Ceroideas Neuronales/terapia , Síndrome de Sjögren-Larsson/diagnóstico , Síndrome de Sjögren-Larsson/fisiopatología , Síndrome de Sjögren-Larsson/terapia , Enfermedad de Tay-Sachs/diagnóstico , Enfermedad de Tay-Sachs/fisiopatología , Enfermedad de Tay-Sachs/terapiaRESUMEN
The action of detergents in the isolation of detergent-resistant membrane fractions from rat brain is reported. Triton X-100 treatment of whole rat brain homogenate at 4 degrees C produced detergent-resistant membranes with a density of 1.07g/ml compared with Brij96 where the density of the membrane was only 1.05g/ml. The DRM fractions isolated using Triton X-100 are considerably heavier than those isolated from homogenates treated with Brij96. The major polar lipid composition of DRMs derived from Brij96 treated homogenates have a higher proportion of aminophospholipids compared with choline phospholipids than Triton X-100 derived DRMs; this may indicate that DRMs from Brij96 treated homogenates are more closely related to the parent membrane in lipid composition. Solubilization by Triton X-100 at higher temperatures resulted in the appearance of a second detergent-resistant membrane fraction distinctly lighter in density than the membrane recovered at density 1.07g/ml. Analysis of phospholipid composition of the brain homogenate during detergent treatment for up to 30min at 37 degrees C showed a decreasing proportion of sphingomyelin. Treatment of homogenates at 37 degrees C appears to activate phospholipases/sphingomyelinases that may alter the lipid content of isolated DRMs. The presence of K+/Mg2+ with Brij96 treatment results in DRM fractions with significantly thicker bilayers and of larger vesicle diameter than DRMs isolated from either Triton X-100 or Brij96 treated homogenates in the absence of cations.
Asunto(s)
Química Encefálica , Lípidos de la Membrana/aislamiento & purificación , Microdominios de Membrana/química , Animales , Colesterol/análisis , Colesterol/química , Colesterol/aislamiento & purificación , Cromatografía en Capa Delgada , Femenino , Masculino , Lípidos de la Membrana/análisis , Lípidos de la Membrana/química , Octoxinol/química , Fosfolípidos/análisis , Fosfolípidos/química , Fosfolípidos/aislamiento & purificación , Ratas , Esfingomielinas/análisis , Esfingomielinas/aislamiento & purificaciónRESUMEN
Placentae from 13 pregnant ewes infected intravenously with Chlamydophila abortus, together with placentae from nine uninfected control ewes, were examined at 14, 21 or 28 days post-inoculation (p.i.). Chlamydial inclusions were present in the trophoblast at 14 days p.i. and were widespread by 21 days p.i. Chorioallantoic lesions (oedema, arteritis and thrombosis) were severe at 28 days p.i., the changes being particularly marked in the membrane surrounding placentomes. Lymphocytes constituted only a small proportion of the cellular infiltrate in the chorioallantois; neutrophil infiltration of the chorionic surface was evident where the trophoblast layer had sloughed, whereas macrophages represented the predominant cell type in the deeper stroma. In contrast, on the maternal side of the placenta, chlamydial inclusions were sparse at all timepoints, and even at 28 days p.i., lesions were restricted to focal endometritis at the placentomal limbus and occasional foci of septal necrosis. T lymphocytes were numerous within endometrial and septal lesions, the infiltrate consistently containing more CD8(+) than CD4(+) cells. The fetal response to chlamydial invasion of the placenta was innate in character, whereas the maternal response appeared to represent an acquired, chlamydia-specific immune response.
Asunto(s)
Infecciones por Chlamydophila/veterinaria , Chlamydophila/patogenicidad , Feto/inmunología , Enfermedades Placentarias/veterinaria , Placenta/microbiología , Enfermedades de las Ovejas/microbiología , Ovinos/inmunología , Animales , Antígenos Virales/metabolismo , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/patología , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/patología , Chlamydophila/inmunología , Infecciones por Chlamydophila/inmunología , Infecciones por Chlamydophila/patología , Membrana Corioalantoides/inmunología , Membrana Corioalantoides/microbiología , Membrana Corioalantoides/patología , Femenino , Feto/microbiología , Transmisión Vertical de Enfermedad Infecciosa , Placenta/inmunología , Placenta/patología , Enfermedades Placentarias/inmunología , Enfermedades Placentarias/microbiología , Enfermedades Placentarias/patología , Embarazo , Complicaciones Infecciosas del Embarazo/inmunología , Complicaciones Infecciosas del Embarazo/microbiología , Complicaciones Infecciosas del Embarazo/patología , Complicaciones Infecciosas del Embarazo/veterinaria , ARN Mensajero/metabolismo , Ovinos/microbiología , Enfermedades de las Ovejas/inmunología , Enfermedades de las Ovejas/patologíaRESUMEN
Methicillin-resistant Staphylococcus aureus (MRSA) was isolated from five dogs with wound discharges after surgical procedures at a veterinary practice, and MRSA with similar molecular and phenotypic characteristics was isolated from the nares of one veterinary surgeon in the practice. The pulsed-field gel electrophoresis patterns of all the isolates were indistinguishable from each other and from the most common human isolates of MRSA in Ireland.
Asunto(s)
Enfermedades de los Perros/microbiología , Resistencia a la Meticilina , Infecciones Estafilocócicas/veterinaria , Staphylococcus aureus/aislamiento & purificación , Infección de la Herida Quirúrgica/veterinaria , Animales , Perros , Electroforesis en Gel de Campo Pulsado/veterinaria , Irlanda , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/clasificación , Staphylococcus aureus/efectos de los fármacos , Infección de la Herida Quirúrgica/microbiologíaRESUMEN
Twin bearing mature ewes (n=40) were treated with exogenous progesterone (100mg daily in oil) or vehicle (oil control) from Day 143 of gestation until lambing to investigate the effects on gestation length, foetal survival and colostrum yield and composition. Compared to control ewes, progesterone treated ewes had increased (P<0.05) serum progesterone concentrations (by 4.3 ng/ml) before lambing and in the first day post-partum (by 10 ng/ml). Progesterone treatment increased gestation length (150.4+/-0.6 days versus 147.8+/-0.6 days, P<0.05) and colostrum yield at 1h after lambing (P<0.05) but the colostrum had a lower concentration of IgG (P=0.02). In the first 24h after lambing, total colostrum and IgG yields were not different between groups. Four (20%) of the progesterone treated ewes produced either one or two dead lambs, while one ewe died on day 155 without initiating the birth process. We conclude that the daily administration of 100mg progesterone resulted in extended gestation length and reduced lamb survival but did not lower colostrum yield.
Asunto(s)
Calostro/fisiología , Feto/fisiología , Edad Gestacional , Progesterona/administración & dosificación , Ovinos/fisiología , Animales , Femenino , Feto/efectos de los fármacos , Embarazo , Progesterona/sangreRESUMEN
Reports of methicillin-resistant Staphylococcus aureus (MRSA) in animals have become more frequent in recent years. This paper documents the recovery of MRSA from animals with respiratory, urinary tract or wound infection and from animals subjected to surgical procedures following treatment in one veterinary hospital and 16 private veterinary clinics in different geographical locations throughout Ireland. MRSA was recovered from 25 animals comprising 14 dogs, eight horses, one cat, one rabbit and a seal, and also from 10 attendant veterinary personnel. Clinical susceptibility testing suggested that the 35 isolates fell into two different groups. One group of isolates (Group 1) was resistant to one or more of the following classes of antimicrobials: macrolides, lincosamines, tetracyclines and/or fluoroquinolones. The second group (Group 2) was resistant to macrolides, aminoglycosides, tetracyclines and trimethoprim/sulphamethoxazole and variably resistant to fluoroquinolones, lincosamines and rifampicin. One isolate in Group 2 was susceptible to trimethoprim. Epidemiological typing by antibiogram-resistogram (AR) typing, biotyping and by chromosomal DNA restriction fragment length polymorphism analysis using SmaI digestion followed by pulsed field gel electrophoresis (PFGE), confirmed these two major clusters. PFGE analysis showed that most isolates from non-equine animals were indistinguishable from each other and from the isolates from personnel caring for these animals. MRSA was isolated from eight horses which attended six different veterinary practices before referral to an equine veterinary hospital. Isolates from the eight horses and from their attendant personnel had PFGE patterns that were indistinguishable and were unlike the patterns obtained from the other isolates. Comparison of PFGE patterns of isolates from veterinary sources with patterns from MRSA recovered in human hospitals showed that the most frequently occurring pattern of MRSA from non-equine animals was indistinguishable from the predominant pattern obtained from the most prevalent MRSA strain in the human population in Ireland. However, the patterns of the isolates from horses were unlike any patterns previously reported in Irish studies of human isolates. This study shows that transmission of two strains of MRSA is occurring in veterinary practices in Ireland and that one strain may have arisen from human hospitals. The source of the second strain remains to be determined.
Asunto(s)
Antibacterianos/farmacología , Enfermedades de los Gatos/microbiología , Enfermedades de los Perros/microbiología , Resistencia a la Meticilina/genética , Enfermedades Profesionales/microbiología , Infecciones Estafilocócicas/veterinaria , Staphylococcus aureus/aislamiento & purificación , Técnicos de Animales , Animales , Antibacterianos/uso terapéutico , Enfermedades de los Gatos/tratamiento farmacológico , Enfermedades de los Gatos/epidemiología , Gatos , ADN Bacteriano/química , ADN Bacteriano/genética , Enfermedades de los Perros/tratamiento farmacológico , Enfermedades de los Perros/epidemiología , Perros , Electroforesis en Gel de Campo Pulsado/veterinaria , Humanos , Irlanda/epidemiología , Pruebas de Sensibilidad Microbiana/veterinaria , Exposición Profesional , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/genética , VeterinariosRESUMEN
The long-range and molecular orders and dynamics in codispersions of egg sphingomyelin-cholesterol have been investigated by synchrotron x-ray diffraction and electron spin resonance using phosphatidylcholine spin-labeled at several positions on the sn-2 chain. Mixtures containing 0, 17, 33, 41, 50 mol% cholesterol exhibited a single phase by x-ray diffraction methods. The temperature dependence of the d-spacing between 20 and 50 degrees C is attenuated with increasing proportions of cholesterol, becoming invariant for cholesterol contents of 41 and 50 mol% on completion of the liquid-ordered phase. Electron spin resonance revealed two sites for 17 and 33 mol% cholesterol. One site is highly ordered and the other is less ordered than the fluid phase of pure sphingomyelin as shown by the molecular and the intramolecular order parameters reflecting the segmental motions of the probe. The two-sites exchange rate indicates a mean lifetime of the sites of approximately 0.1 micros during which the lipid displacement is approximately 1 nm. The short lifetime of the sites probed by ESR and the single phase detected by x-ray diffraction support in this binary mixture, the building up of the Lo phase by a progressive accumulation of randomly distributed sphingomyelin-cholesterol condensed complexes rather than by diffusional exchange between extended domains.
Asunto(s)
Colesterol/química , Lípidos de la Membrana/química , Esfingomielinas/química , Fenómenos Biofísicos , Biofisica , Espectroscopía de Resonancia por Spin del Electrón , Técnicas In Vitro , Modelos Moleculares , Sincrotrones , Difracción de Rayos XRESUMEN
Vitamin E acts as an antioxidant and stabilizer of membranes. Other functions of vitamin E unrelated to its effects on membranes are emerging. Vitamin E partitions into the lipid bilayer matrix of membranes. It orients perpendicularly to the plane of the membrane with the hydroxyl group pointing to the lipid-water interface. The vitamin is not randomly distributed in the plane of the membrane but tends to form clusters. These clusters appear to be composed of vitamin E and phosphatidylcholine in a stoichiometry of about one vitamin E per 10 phospholipid molecules. Vitamin E partitions into domains of phosphatidylcholine in model membranes formed from mixtures of phosphatidylcholine and phosphatidylethanolamine irrespective of whether the phosphatidylcholine is in the fluid or gel phase. The creation of domains enriched in vitamin E in membranes is not consistent with an antioxidant function and effects on membrane structure and stability indicate other roles of the vitamin.
Asunto(s)
Membrana Celular/metabolismo , alfa-Tocoferol/metabolismo , Membrana Celular/química , Membrana Celular/ultraestructura , Fosfolípidos/química , Fosfolípidos/metabolismo , Temperatura , alfa-Tocoferol/químicaRESUMEN
A survey of the prevalence of Salmonella species infection was conducted on 59 Irish farrow-to-finish pig herds. Faecal samples were collected from the pens of first-stage weaners (growing pigs approximately three to 10 weeks of age), second-stage weaners (approximately 10 to 17 weeks of age) and fatteners, and from the dry sow and farrowing sow houses. The prevalence of infection was estimated to within 5 per cent with a 95 per cent confidence interval. Thirty of the 59 herds were infected, 12 with Salmonella Typhimurium only, eight with Salmonella Derby only and seven with both S Typhimurium and S Derby; serotypes London, Livingstone and Infantis were each isolated from a single herd. Farms in Ireland are assigned to one of three infection categories on the basis of the antibody levels in samples of meat juice taken at slaughter. When a herd was classified as either positive or negative on the basis of the isolation of Salmonella from at least one faecal sample there was no association between the herd's category as determined by meat juice serology and the probability of the isolation of Salmonella from the faecal samples. However, there were differences in prevalence between pigs at different stages of production in herds of different categories. Farrowing sow houses in moderately infected (category 2) herds had significantly lower infection rates (P < or = 0.05) than other herd categories and other stages of production. Pigs from first-stage weaner pens in slightly infected (category 1) herds were more likely to be infected with Salmonella than pigs at any other stage of production or category of herd.
Asunto(s)
Salmonelosis Animal/epidemiología , Salmonella/clasificación , Animales , Animales Lactantes , Heces/microbiología , Femenino , Irlanda/epidemiología , Masculino , Prevalencia , Salmonella/aislamiento & purificación , Salmonelosis Animal/etiología , Salmonelosis Animal/microbiología , Serotipificación/veterinaria , PorcinosRESUMEN
Myeloperoxidase (MPO)-catalyzed one-electron oxidation of endogenous phenolic constituents (e.g., antioxidants, hydroxylated metabolites) and exogenous compounds (e.g., drugs, environmental chemicals) generates free radical intermediates: phenoxyl radicals. Reduction of these intermediates by endogenous reductants, i.e. recycling, may enhance their antioxidant potential and/or prevent their potential cytotoxic and genotoxic effects. The goal of this work was to determine whether generation and recycling of MPO-catalyzed phenoxyl radicals of a vitamin E homologue, 2,2,5,7,8-pentamethyl-6-hydroxychromane (PMC), by physiologically relevant intracellular reductants such as ascorbate/lipoate could be demonstrated in intact MPO-rich human leukemia HL-60 cells. A model system was developed to show that MPO/H(2)O(2)-catalyzed PMC phenoxyl radicals (PMC*) could be recycled by ascorbate or ascorbate/dihydrolipoic acid (DHLA) to regenerate the parent compound. Absorbance measurements demonstrated that ascorbate prevents net oxidation of PMC by recycling the phenoxyl radical back to the parent compound. The presence of DHLA in the reaction mixture containing ascorbate extended the recycling reaction through regeneration of ascorbate. DHLA alone was unable to prevent PMC oxidation. These conclusions were confirmed by direct detection of PMC* and ascorbate radicals formed during the time course of the reactions by EPR spectroscopy. Based on results in the model system, PMC* and ascorbate radicals were identified by EPR spectroscopy in ascorbate-loaded HL-60 cells after addition of H(2)O(2) and the inhibitor of catalase, 3-aminotriazole (3-AT). The time course of PMC* and ascorbate radicals was found to follow the same reaction sequence as during their recycling in the model system. Recycling of PMC by ascorbate was also confirmed by HPLC assays in HL-60 cells. Pre-loading of HL-60 cells with lipoic acid regenerated ascorbate and thus increased the efficiency of ascorbate in recycling PMC*. Lipoic acid had no effect on PMC oxidation in the absence of ascorbate. Thus PMC phenoxyl radical does not directly oxidize thiols but can be recycled by dihydrolipoate in the presence of ascorbate. The role of phenoxyl radical recycling in maintaining antioxidant defense and protecting against cytotoxic and genotoxic phenolics is discussed.
Asunto(s)
Ácido Ascórbico/metabolismo , Cromanos/metabolismo , Radicales Libres/metabolismo , Peroxidasa/metabolismo , Ácido Tióctico/análogos & derivados , Ácido Tióctico/metabolismo , Antioxidantes/metabolismo , Supervivencia Celular , Cromatografía Líquida de Alta Presión , Espectroscopía de Resonancia por Spin del Electrón , Células HL-60 , Humanos , Peróxido de Hidrógeno/farmacología , Oxidación-Reducción , Fenoles/metabolismo , Espectrofotometría , Ciclo del Sustrato/efectos de los fármacosRESUMEN
Fifteen greyhounds with tonsillar enlargement were subjected to detailed investigation. Affected greyhounds exhibited coughing, poor racing performance and tonsillar lymphoid hyperplasia over a period of months. Each of the 15 affected animals had evidence of respiratory tract disease. Twelve had non-specific respiratory tract disease, two had pneumonia and one had pulmonary infiltration with eosinophils (PIE). Histopathological examination of the tonsils from affected dogs revealed that greyhounds with tonsillar enlargement are more likely to have tonsillar lymphoid hyperplasia than tonsillitis. As a result, lymphoid hyperplasia would be a suitable term to describe this tonsillar condition. Respiratory tract diseases, rather than tonsillar hyperplasia, was the more likely cause of the poor racing performance of affected dogs. The aetiological relationship, if any, between respiratory disease and tonsillar enlargement is unclear from this study and requires further investigation.
Asunto(s)
Enfermedades de los Perros/patología , Perros , Tonsila Palatina/patología , Infecciones del Sistema Respiratorio/patología , Infecciones del Sistema Respiratorio/veterinaria , Animales , Enfermedades de los Perros/microbiología , Tonsila Palatina/microbiología , Infecciones del Sistema Respiratorio/complicaciones , Infecciones del Sistema Respiratorio/diagnóstico , DeportesRESUMEN
The nature of dark matter remains mysterious, with luminous material accounting for at most approximately 25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). The presence of the dark matter would be revealed by gravitational lensing of the light from an LMC star as the foreground dark matter moves across the line of sight. The duration of the lensing event is the key observable parameter, but gives non-unique solutions when attempting to estimate the mass, distance and transverse velocity of the lens. The survey results to date indicate that between 8 and 50 per cent of the baryonic mass of the Galactic halo is in the form of MACHOs (ref. 3), but removing the degeneracy by identifying a lensing object would tighten the constraints on the mass in MACHOs. Here we report a direct image of a microlens, revealing it to be a nearby low-mass star in the disk of the Milky Way. This is consistent with the expected frequency of nearby stars acting as lenses, and demonstrates a direct determination of a lens mass from a microlensing event. Complete solutions such as this for halo microlensing events will probe directly the nature of the MACHOs.
RESUMEN
The aim of this study was to compare the prevalence of Salmonella serotypes at two different sites on pig carcasses from herds classified as high-risk or low-risk and to elucidate the relationship between carcass contamination levels and serological status. Caecal samples and carcass surface swabs were cultured for Salmonella from a total of 210 pigs from low risk herds (< 19% of pigs in herd Salmonella seropositive) and 209 pigs from high risk herds (> 32% of pigs in herd Salmonella seropositive) in three abattoirs. Meat juice samples were collected for analysis by ELISA. The prevalence of Salmonella in the caecal contents of "low-risk" pigs was 10%, which was significantly lower than the 19% prevalence in "high-risk" pigs (p < 0.01). The corresponding figures for skin samples collected immediately post-evisceration were 2% and 12%. The predominant Salmonella serotype in the caecal contents of both the low-risk and high-risk pigs was Salmonella Typhimurium. Salmonella Kentucky and Salmonella Derby were the most frequent isolates from the carcass surface swabs of low- and high-risk pigs respectively. There was a positive association between seropositivity of pigs from high-risk herds and caecal carriage (p < 0.05). Results showed that herd categorisation based on serological results was useful in predicting Salmonella isolation rates from caecal samples and surface swabs of slaughtered pigs.
Asunto(s)
Carne/microbiología , Salmonelosis Animal/microbiología , Salmonella/clasificación , Enfermedades de los Porcinos/microbiología , Mataderos , Animales , Ciego/microbiología , Heces/microbiología , Modelos Logísticos , Prevalencia , Factores de Riesgo , Salmonella/aislamiento & purificación , Salmonelosis Animal/epidemiología , Estudios Seroepidemiológicos , Serotipificación , Piel/microbiología , Porcinos , Enfermedades de los Porcinos/epidemiologíaRESUMEN
To characterize oxidative stress in phospholipids of normal human epidermal keratinocytes we metabolically labeled their membrane phospholipids with a natural oxidation-sensitive fluorescent fatty acid, cis-parinaric acid, and exposed the cells to two different sources of oxidants--a lipid-soluble azo-initiator of peroxyl radicals, 2,2'-azobis(2,4-dimethyl-valeronitrile), AMVN, and a superoxide generator, xanthine oxidase/xanthine. We demonstrated that both oxidants induced pronounced oxidation of four major classes of cis-parinaric acid-labeled phospholipids-phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol-in normal human epidermal keratinocytes that was not detectable as any significant change of their phospholipid composition. Vitamin E was effective in protecting the cells against phospholipid peroxidation. Since viability of normal human epidermal keratinocytes was not changed either by labeling or exposure to oxidants the labeling protocol and oxidative stress employed are compatible with the quantitative analysis of phospholipid peroxidation in viable cells.
Asunto(s)
Antioxidantes/farmacología , Queratinocitos/metabolismo , Peroxidación de Lípido/fisiología , Oxidantes/farmacología , Estrés Oxidativo/fisiología , Fosfolípidos/metabolismo , Piel/metabolismo , Adulto , Compuestos Azo/farmacología , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Células Cultivadas/efectos de los fármacos , Células Cultivadas/metabolismo , Cromatografía Líquida de Alta Presión , Relación Dosis-Respuesta a Droga , Ácidos Grasos Insaturados/farmacocinética , Colorantes Fluorescentes/farmacocinética , Humanos , Queratinocitos/efectos de los fármacos , Peroxidación de Lípido/efectos de los fármacos , Nitrilos/farmacología , Estrés Oxidativo/efectos de los fármacos , Piel/efectos de los fármacos , Piel/fisiopatología , Vitamina E/farmacología , Xantina Oxidasa/farmacologíaRESUMEN
The phase behavior of mixed lipid dispersions representing the inner leaflet of the cell membrane has been characterized by X-ray diffraction. Aqueous dispersions of phosphatidylethanolamine:phosphatidylserine (4:1 mole/mole) have a heterogeneous structure comprising an inverted hexagonal phase H(II) and a lamellar phase. Both phases coexist in the temperature range 20-45 degrees C. The fluid-to-gel mid-transition temperature of the lamellar phase assigned to phosphatidylserine is decreased from 27 to 24 degrees C in the presence of calcium. Addition of sphingomyelin to phosphatidylethanolamine/phosphatidylserine prevents phase separation of the hexagonal H(II) phase of phosphatidylethanolamine but the ternary mixture phase separates into two lamellar phases of periodcity 6.2 and 5.6 nm, respectively. The 6.2-nm periodicity is assigned to the gel phase enriched in sphingomyelin of molecular species comprising predominantly long saturated hydrocarbon chains because it undergoes a gel-to-fluid phase transition above 40 degrees C. The coexisting fluid phase we assign to phosphatidylethanolamine and phosphatidylserine and low melting point molecular species of sphingomyelin which suppresses the tendency of phosphatidylethanolamine to phase-separate into hexagonal H(II) structure. There is evidence for considerable hysteresis in the separation of lamellar fluid and gel phases during cooling. The addition of cholesterol prevents phase separation of the gel phase of high melting point sphingomyelin in mixtures with phosphatidylserine and phosphatidylethanolamine. In the quaternary mixture the lamellar fluid phase, however, is phase separated into two lamellar phases of periodicities of 6.3 and 5.6 nm (20 degrees C), respectively. The lamellar phase of periodicity 5.6 nm is assigned to a phase enriched in aminoglycerophospholipids and the periodicity 6.3 nm to a liquid-ordered phase formed from cholesterol and high melting point molecular species of sphingomyelin characterized previously by ESR. Substituting 7-dehydrocholesterol for cholesterol did not result in evidence for lamellar phase separation in the mixture within the temperature range 20-40 degrees C. The specificity of cholesterol in creation of liquid-ordered lamellar phase is inferred.
Asunto(s)
Membrana Celular/química , Colesterol/química , Microdominios de Membrana/química , Esfingomielinas/química , Animales , Fosfatidiletanolaminas/química , Fosfatidilserinas/química , Temperatura , Difracción de Rayos XRESUMEN
Phase behavior of distearoylphosphatidylethanolamine dispersed in excess glycerol has been examined by differential scanning calorimetry. Transformation from lamellar-gel to lamellar crystalline phase was found to take place at temperatures near 74.9 degrees C upon cooling and near 76.3 degrees C during heating scans. The transition can also be observed under isothermal conditions at temperature in this range. The kinetics of the transformation from lamellar-gel to lamellar-crystal phase was analyzed by the well-known Avrami equation. The apparent Avrami exponents were found to be approximately 1.6. The effective dimensionality of the growth pattern can then be set as 1, after taking into account the contribution of nucleation at the examination temperatures. The activation energy of the phase transition was estimated as approximately 255 kJ mol(-1). The data are discussed in terms of development of successful cryoprotective strategies using glycerol.