RESUMEN
The interfacial adhesion behaviour of a ZnO nanowire-Si substrate system is investigated using an in situ scanning electron microscope (SEM) mechanical peeling technique. The peel front of a nanowire advances via stick-slip events, and an equilibrium between the driving and resistant force to separation occurs immediately prior to a slip event. The interfacial adhesion energy is one order higher than that predicted theoretically by van der Waals interactions. The enhanced adhesion is primarily attributed to chemical and electrostatic interfacial interactions induced by electron irradiation. This work demonstrates that the operating environment of a nanoscale system could dramatically influence its adhesion behaviour. These findings are expected to have significant implications for interpreting the adhesion behaviour exhibited by a 1D nanostructure-substrate system when applying different testing methodologies, and for the fabrication of future NEMS devices.
RESUMEN
Theoretical models of G protein-coupled receptor (GPCR) concentration-response relationships often assume an agonist producing a single functional response via a single active state of the receptor. These models have largely been analysed assuming steady-state conditions. There is now much experimental evidence to suggest that many GPCRs can exist in multiple receptor conformations and elicit numerous functional responses, with ligands having the potential to activate different signalling pathways to varying extents-a concept referred to as biased agonism, functional selectivity or pluri-dimensional efficacy. Moreover, recent experimental results indicate a clear possibility for time-dependent bias, whereby an agonist's bias with respect to different pathways may vary dynamically. Efforts towards understanding the implications of temporal bias by characterising and quantifying ligand effects on multiple pathways will clearly be aided by extending current equilibrium binding and biased activation models to include G protein activation dynamics. Here, we present a new model of time-dependent biased agonism, based on ordinary differential equations for multiple cubic ternary complex activation models with G protein cycle dynamics. This model allows simulation and analysis of multi-pathway activation bias dynamics at a single receptor for the first time, at the level of active G protein (αGTP), towards the analysis of dynamic functional responses. The model is generally applicable to systems with NG G proteins and N* active receptor states. Numerical simulations for NG=N*=2 reveal new insights into the effects of system parameters (including cooperativities, and ligand and receptor concentrations) on bias dynamics, highlighting new phenomena including the dynamic inter-conversion of bias direction. Further, we fit this model to 'wet' experimental data for two competing G proteins (Gi and Gs) that become activated upon stimulation of the adenosine A1 receptor with adenosine derivative compounds. Finally, we show that our model can qualitatively describe the temporal dynamics of this competing G protein activation.
Asunto(s)
Algoritmos , Proteínas de Unión al GTP/metabolismo , Modelos Biológicos , Receptores Acoplados a Proteínas G/metabolismo , Animales , Humanos , Ligandos , Transducción de SeñalRESUMEN
Tidal freshwater wetlands in urban settings can be subject to elevated N concentrations, which can promote the exchange of N between the marsh, water, and atmosphere, including denitrification. We used a multitiered approach consisting of direct measurements of N fluxes and denitrification, tidal hypsometry, and N load modeling to examine N exchanges in an urban tidal freshwater wetland of the Delaware River Estuary, Philadelphia, PA. Sediment cores and aboveground biomass were collected at 20 locations across a range of elevations and plant communities in April, July, and October 2010. Nitrate was taken up by the marsh during all seasons. In the spring, the high rate of NH production from the sediment was correlated with NO uptake, suggesting dissimilatory reduction to NH as a potentially important process. Denitrification rates were greatest in July, averaging 5.5 ± 0.6 mg N m h. Adjusted for tidal inundation using a refined digital elevation model, denitrification averaged 0.08, 0.5, and 0.2 g N m mo for April, July, and October, respectively. Less than 10% of the modeled N load was estimated to have been removed in the months measured. A combination of high N load, limited marsh area that represented â¼1% of the watershed area, and conservative extrapolation of denitrification rates contributed to the low estimate of the N load attenuated.
Asunto(s)
Nitrógeno , Humedales , Monitoreo del Ambiente , Agua Dulce , Philadelphia , Estaciones del AñoRESUMEN
Cryptosporidium parvum is an opportunistic intracellular parasite that causes mild to severe diarrhoea, which can be life-threatening in an immunocompromised host. To increase our understanding of the mechanisms that play a role in host immune responses, we investigated the effects of C. parvum antigens on the phenotype of mouse and human dendritic cells (DCs). Cryptosporidium parvum antigens induced DC activation as indicated by upregulation of the maturation marker CD209, as well as by the production of the cytokines interleukin-12 p70, IL-2, IL-1beta, IL-6. In particular, significant increases in the expression of IL-12 p70 were observed from mouse DCs derived from bone marrow in response to solubilized sporozoite antigen and the recombinant cryptosporidial antigens, Cp40 and Cp23. We observed a small but significant increase in IL-18 expression following the exposure to Cp40. We found that the induction of Th1 cytokines was MyD88 dependent (MyD88 knockout mouse DCs were unresponsive). Additionally, both sporozoite preparations (solubilized and live) significantly induced IL-12 production by human monocytic dendritic cells (MoDCs). This finding indicates that solubilized as well as recombinant antigens can induce the maturation of DCs and subsequently initiate an innate immune response.
Asunto(s)
Antígenos de Protozoos/inmunología , Cryptosporidium parvum/inmunología , Citocinas/metabolismo , Células Dendríticas/inmunología , Células TH1/inmunología , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Moléculas de Adhesión Celular/análisis , Células Cultivadas , Células Dendríticas/química , Femenino , Humanos , Lectinas Tipo C/análisis , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Factor 88 de Diferenciación Mieloide/deficiencia , Factor 88 de Diferenciación Mieloide/metabolismo , Receptores de Superficie Celular/análisisRESUMEN
We investigated whether variations in gene expression of enzymes associated with anaerobic resistance of laboratory-derived strains of Trichomonas vaginalis could be detected in a group of 28 clinical isolates with variations in metronidazole sensitivity. We compared isolates by real-time PCR because this method allows for highly sensitive quantification of mRNA and for evaluation of several genes simultaneously. We found that PFOR gene A mRNA levels were highly correlated with PFOR gene B levels, as well as the D subunit of malic enzyme and ferrodoxin. Ferrodoxin mRNA expression was also significantly correlated with that of malic enzyme and hydrogenase. However, when we evaluated relationships between these enzymes and resistance to metronidazole, we found no significant correlations between aerobic or anaerobic in vitro sensitivity to drug and mRNA levels of any of the enzymes tested. Similarly, using a Student's t-test, no significant differences in enzyme mRNA levels were observed between isolates separated by metronidazole resistance or susceptibility. The lack of correlation between gene expression and resistance or susceptibility could be the result of differences in expression at the protein level or because other biochemical pathways or genes are involved in the resistance observed in clinical settings.
Asunto(s)
Antiprotozoarios/farmacología , Resistencia a Medicamentos/genética , Metronidazol/farmacología , Vaginitis por Trichomonas/tratamiento farmacológico , Trichomonas vaginalis/genética , Animales , Células Cultivadas , Cartilla de ADN/química , Femenino , Expresión Génica/genética , Genes de ARNr/genética , Humanos , Hidrogenasas/genética , Reacción en Cadena de la Polimerasa/métodos , Piruvato-Sintasa/genética , ARN Mensajero/análisis , Estadística como Asunto , Trichomonas vaginalis/efectos de los fármacos , Trichomonas vaginalis/aislamiento & purificaciónRESUMEN
Studies of cellular immune responses to Cryptosporidium parvum have been limited in part by lack of suitable animal models. IL-12p40(-/-)mice are susceptible to initial infection with C. parvum but recover within 2 weeks, rendering the animals resistant to reinfection. Because the host responses that determine duration and severity of primary infection are not yet understood, we studied the cellular immune response to primary infection with C. parvum in IL-12p40(-/-)mice and also explored possible mechanisms for this response. Female IL-12p40(-/-)mice were inoculated with 10,000 oocysts. Uninfected age-matched mice served as controls. At different time intervals following exposure to oocysts, mice were sacrificed and their intestine, spleen, and mesenteric lymph node tissues were harvested. Cellular immune responses to C. parvum were characterized. Infection of IL-12p40(-/-)mice induced changes in the gene expression of the cytokines IFN-gamma, IL-4, IL-15, IL-18, TNF-alpha and TGF-beta during primary infection. There was also a significant increase in total numbers of lymphocytes and CD19/CD62L-expressing cells in mesenteric lymph nodes. These MLN cells exhibited increased antigen-specific proliferation and cytokine production (IL-6 and IFN-gamma) levels when stimulated in vitro. These observations delineate the cellular immune responses during acute C. parvum infection of the IL-12p40(-/-)mouse model.
Asunto(s)
Criptosporidiosis/inmunología , Cryptosporidium parvum/inmunología , Citocinas/genética , Perfilación de la Expresión Génica , Inmunidad Mucosa , Interleucina-12/genética , Subunidades de Proteína/genética , Animales , Criptosporidiosis/patología , Citocinas/biosíntesis , Modelos Animales de Enfermedad , Femenino , Inmunidad Celular , Subunidad p40 de la Interleucina-12 , Intestinos/inmunología , Intestinos/patología , Ganglios Linfáticos/inmunología , Ganglios Linfáticos/patología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Bazo/inmunología , Bazo/patologíaRESUMEN
DNA sequences from orthologous loci can provide universal characters for taxonomic identification. Molecular taxonomy is of particular value for groups in which distinctive morphological features are difficult to observe or compare. To assist in species identification for the little known family Ziphiidae (beaked whales), we compiled a reference database of mitochondrial DNA (mtDNA) control region (437 bp) and cytochrome b (384 bp) sequences for all 21 described species in this group. This mtDNA database is complemented by a nuclear database of actin intron sequences (925 bp) for 17 of the 21 species. All reference sequences were derived from specimens validated by diagnostic skeletal material or other documentation, and included four holotypes. Phylogenetic analyses of mtDNA sequences confirmed the genetic distinctiveness of all beaked whale species currently recognized. Both mitochondrial loci were well suited for species identification, with reference sequences for all known ziphiids forming robust species-specific clades in phylogenetic reconstructions. The majority of species were also distinguished by nuclear alleles. Phylogenetic comparison of sequence data from "test" specimens to these reference databases resulted in three major taxonomic discoveries involving animals previously misclassified from morphology. Based on our experience with this family and the order Cetacea as a whole, we suggest that a molecular taxonomy should consider the following components: comprehensiveness, validation, locus sensitivity, genetic distinctiveness and exclusivity, concordance, and universal accessibility and curation.
Asunto(s)
Ballenas/clasificación , Actinas/genética , Animales , Citocromos b/genética , ADN Mitocondrial , Bases de Datos Genéticas , Evolución Molecular , Variación Genética , Mitocondrias/genética , Filogenia , Reacción en Cadena de la Polimerasa , Valores de Referencia , Especificidad de la Especie , Ballenas/genéticaRESUMEN
Currently existing chemotherapeutic compounds are limited and few are effective for treating microsporidiosis. It is possible that resistance of Encephalitozoon to some drugs occurs by efflux mechanisms similar to those previously described for mammalian tumour cells, bacteria or protozoal parasites such as Plasmodium, Leishmania and Entamoeba histolytica. The data in the present study suggest that Encephalitozoon intestinalis contains at least one multidrug resistance gene. We report here two complete sequences EiABC1 and EiABC2, encoding different ATP-binding cassette genes from E. intestinalis, including a P-gp.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/genética , ADN Protozoario/genética , Encephalitozoon/genética , Proteínas Protozoarias/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Resistencia a Múltiples Medicamentos , Encephalitozoon/efectos de los fármacos , Datos de Secuencia Molecular , Filogenia , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de AminoácidoRESUMEN
Experimental infection of BALB/c- or C57BL/6-gamma-interferon-knockout (GKO) mice with Cryptosporidium parvum results in infection in both strains with different outcomes of disease. The BALB/c-GKO mice recover from infection, whereas the C57BL/6-GKO mice succumb to infection in less than 2 weeks. Differences in cytokine mRNA expression suggested that recovery may involve other cytokines. To determine whether the addition of either a Th1 or Th2 cytokine could alter the outcome of infection, we treated GKO mice with either recombinant (r)IL-4 or rIL-12 1 day before infection (DBI) or daily. No effect on the oocyst shedding patterns in either strain nor an increase in survival of the C57BL/6-GKO mice was observed in the rIL-4-treated mice. Whereas one dose of 0.5 microg rIL-12 given 1 DBI had no effect on oocyst shedding, we found that daily doses of rIL-12 administered intraperitoneally exacerbated C. parvum infection in both animal models. Administration of rIL-12 shortened the survival time in the C57BL/6-GKO mice and prevented BALB/c-GKO mice from recovering from infection. Specific proliferation of T cells to cryptosporidial antigen and Th1 and Th2 mRNA cytokine expression was markedly decreased in rIL-12-treated mice. Nitric oxide (NO) may have played a minor role in the decreased proliferation observed since levels of NO present in the splenocyte cultures from rIL-12-treated mice in response to parasite antigen stimulation were higher than those observed in controls. Thus, we propose that resistance to and recovery from C. parvum infections involves a fine balance in the amount and timing of Th1 and Th2 cytokines.
Asunto(s)
Criptosporidiosis/tratamiento farmacológico , Cryptosporidium parvum/efectos de los fármacos , Interferón gamma/genética , Interleucina-12/farmacología , Animales , Criptosporidiosis/inmunología , Cryptosporidium parvum/inmunología , Citocinas/biosíntesis , Citocinas/genética , Interleucina-12/uso terapéutico , Interleucina-4/farmacología , Interleucina-4/uso terapéutico , Intestinos/parasitología , Intestinos/patología , Hígado/parasitología , Hígado/patología , Activación de Linfocitos , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Noqueados , ARN Mensajero/análisis , Proteínas Recombinantes/farmacología , Proteínas Recombinantes/uso terapéutico , Bazo/citología , Bazo/inmunología , Células TH1/inmunología , Células Th2/inmunologíaRESUMEN
The role of target interactions in the development and functional maturation of peripheral neurons was investigated using an immortalized sympathetic precursor cell line. bMAH cells underwent neuronal differentiation in response to neurotrophic factors, but maintained an immature neuronal phenotype characterized by small cell bodies and continued cell division. Co-culture with cardiac myocytes, a target of sympathetic innervation, promoted the appearance of large-diameter postmitotic bMAH neurons. Analysis of bMAH maturation in the presence and absence of co-cultured myocytes indicated that myocyte-derived factors promoted the survival of maturing bMAH neurons prior to their acquisition of nerve growth factor dependence. Myocyte interactions also promoted the functional maturation of bMAH neurons, leading to an increase in the localization of synaptic vesicle proteins into neuritic varicosities and the acquisition of sympathetic-like intrinsic electrical properties. Like primary sympathetic neurons, mature bMAH neurons formed functional connections to cardiac myocytes as measured by evoked postsynaptic responses in connected myocytes. The effects of myocyte co-culture on developing bMAH neurons could be mimicked by myocyte conditioned medium, indicating that cardiac myocytes produce soluble factors that promote the appearance of mature neurons. These experiments indicate that targets of innervation play a role in directing the development and final maturation of peripheral neurons.
Asunto(s)
Miocardio/citología , Neuronas/citología , Células Madre/citología , Sistema Nervioso Simpático/citología , Potenciales de Acción , Animales , Antimetabolitos Antineoplásicos/farmacología , Comunicación Celular/fisiología , Diferenciación Celular , División Celular/efectos de los fármacos , Línea Celular , Citarabina/farmacología , Electrofisiología , Neuronas/fisiología , RatasRESUMEN
Cryptosporidial infection in humans results in parasite-specific IgG, IgM, and IgA antibody responses, but little is known of the cell-mediated immune responses to cryptosporidial antigens. In a convenience sample of 35 Haitian residents, there was a high level of cryptosporidial exposure (>90%) as determined by immunoblot reactivity of serum against cryptosporidial antigens. An attempt was made to determine if there was a relationship between antibody and T cell-mediated responses to recombinant Cp23 antigen and how this correlated with reactivity to crude sporozoite antigen preparations (SAg). T cell reactivity was greater against SAg (57%) than to Cp23 (34.3%) as measured by [3H]thymidine incorporation. Proliferative responses to Cp23 were significantly correlated with SAg responses. By enzyme-linked immunosorbent assay, most persons had IgG responses to both SAg (91.4%) and to recombinant Cp23 (88.5%). Antibody responses were greater among persons who exhibited T cell responses to SAg and Cp23. This study demonstrates that recombinant Cp23 antigen could be a useful antigen for detection of both antibody and cell-mediated responses in epidemiologic studies.
Asunto(s)
Antígenos de Protozoos/inmunología , Linfocitos B/inmunología , Criptosporidiosis/inmunología , Cryptosporidium parvum/inmunología , Linfocitos T/inmunología , Adolescente , Adulto , Anciano , Animales , Anticuerpos Antiprotozoarios/sangre , Western Blotting , Bovinos , Criopreservación , Criptosporidiosis/epidemiología , Ensayo de Inmunoadsorción Enzimática , Femenino , Haití/epidemiología , Humanos , Inmunidad Celular , Activación de Linfocitos , Masculino , Persona de Mediana Edad , Proteínas Recombinantes/inmunología , Estudios SeroepidemiológicosAsunto(s)
Criptosporidiosis , Cryptosporidium parvum , Adulto , Animales , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/parasitología , Niño , Criptosporidiosis/tratamiento farmacológico , Criptosporidiosis/epidemiología , Criptosporidiosis/inmunología , Criptosporidiosis/parasitología , Cryptosporidium parvum/clasificación , Cryptosporidium parvum/genética , Cryptosporidium parvum/fisiología , Genotipo , Interacciones Huésped-Parásitos , Humanos , RatonesRESUMEN
In the present study, we focused on a 23-kDa antigen, Cp23, which has been shown to be a major target of humoral immune responses in Cryptosporidium parvum infections and is present in both the sporozoite and merozoite stages. Recombinant Cp23 antigen was shown to stimulate a specific proliferative response by splenocytes and mesenteric lymph node cells from infected interferon gamma knockout BALB/c mice. Cp23 stimulation also induced TNF-alpha, IL-2, and IL-5 mRNA production by spleen cells from infected animals. In contrast, IL-12 mRNA was decreased by Cp23 stimulation compared with unstimulated splenocytes. These data suggest that, as with humoral responses, Cp23 is an important target of cellular immune responses in experimental C. parvum infections. The potential role of this antigen in conferring protective immunity is also discussed.
Asunto(s)
Antígenos de Protozoos/inmunología , Cryptosporidium parvum/inmunología , Ganglios Linfáticos/inmunología , Bazo/inmunología , Animales , Western Blotting , Citocinas/biosíntesis , Citocinas/genética , Regulación de la Expresión Génica/inmunología , Inmunidad Celular , Interferón gamma/biosíntesis , Mesenterio , Ratones , Ratones Endogámicos BALB C , ARN Mensajero/biosíntesis , Proteínas Recombinantes/inmunologíaRESUMEN
Differences in the immune response between 2 strains of interferon-gamma knockout mice (BALB/c-GKO and C57BL/6-GKO) infected with Cryptosporidium parvum were examined because the course of infection among these 2 strains is markedly different. Infection of the BALB/c-GKO with C. parvum (2 X 10(6) oocysts/mouse) resulted in slight weight loss, oocyst shedding, and recovery from infection by 2 wk postinfection (PI). Infection with 100 oocysts in the C57BL/6-GKO mice resulted in significant weight loss, oocyst shedding, and death by day 10 PI. Splenocytes from infected mice were able to proliferate in a dose-dependent manner to soluble C. parvum-sporozoite antigen (SAg). In vitro stimulation with SAg resulted in an increase in interleukin (IL)-2, IL-4, IL-5, and tumor necrosis factor-alpha mRNA cytokine expression from splenocytes of infected BALB/cGKO mice. In contrast, only IL-5 mRNA expression was increased in the splenocytes from C. parvum-infected C57BL/6-GKO mice. Phenotypic analysis indicated no significant differences in the splenic cell populations. Previous studies indicated that susceptibility to C. parvum is dependent on CD4+ T cells and interferon-gamma production. The present study indicates that although both of these strains of knockout mice become infected with C. parvum, resolution of infection may be in part dependent on the expression of Th2 cytokines.
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Criptosporidiosis/inmunología , Cryptosporidium parvum/inmunología , Citocinas/biosíntesis , Interferón gamma/fisiología , Activación de Linfocitos , Animales , Citocinas/genética , Heces/parasitología , Inmunofenotipificación , Interferón gamma/genética , Activación de Linfocitos/genética , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Noqueados , Reacción en Cadena de la Polimerasa , ARN Mensajero/biosíntesis , Bazo/citología , Bazo/inmunologíaRESUMEN
Nerve growth factor (NGF) acutely modulates synaptic transmission between sympathetic neurons and their cardiac myocyte targets. NGF also has developmental effects in establishing the level of synaptic transmission between sympathetic neurons and myocytes in culture, although little is known about the mechanisms by which NGF influences this synaptic connectivity. Here we report that NGF acts in conjunction with factors produced by cardiac myocytes to promote neuronal contact with the target and the extension of synaptic vesicle-containing growth cones. In conjunction with previously published results showing that NGF has long-term effects on synaptic transmission between sympathetic neurons and myocytes, this work suggests that NGF acts to promote sympathetic neurotransmission by increasing the number of sympathetic fibers establishing target contact. Further, we found that developmental changes in cardiac myocytes led to an increase in the density of synaptic vesicle-containing variocosities along sympathetic fibers, a process regulated by NGF. Thus, as myocytes mature they produce factors that promote the formation of sympathetic presynaptic structures. These results argue that multiple target interactions regulate the extent of synapse formation between sympathetic neurons and cardiac cells and suggest that NGF promotes presynaptic development by increasing neuronal contact with myocyte-derived cell surface or matrix-associated factors.
Asunto(s)
Miocardio/metabolismo , Factor de Crecimiento Nervioso/metabolismo , Neuronas/metabolismo , Terminales Presinápticos/metabolismo , Sistema Nervioso Simpático/metabolismo , Actinina/metabolismo , Animales , Células Cultivadas , Técnicas de Cocultivo , Medios de Cultivo Condicionados/farmacología , Relación Dosis-Respuesta a Droga , Conos de Crecimiento/efectos de los fármacos , Conos de Crecimiento/metabolismo , Inmunohistoquímica , Uniones Intercelulares/metabolismo , Proteínas de Filamentos Intermediarios/metabolismo , Glicoproteínas de Membrana/biosíntesis , Miocardio/citología , Factor de Crecimiento Nervioso/genética , Factor de Crecimiento Nervioso/farmacología , Proteínas del Tejido Nervioso/biosíntesis , Proteínas del Tejido Nervioso/metabolismo , Proteínas de Neurofilamentos/genética , Proteínas de Neurofilamentos/metabolismo , Neuronas/citología , Neuronas/efectos de los fármacos , Periferinas , Terminales Presinápticos/efectos de los fármacos , ARN Mensajero/biosíntesis , Ratas , Receptor de Factor de Crecimiento Nervioso/genética , Receptor de Factor de Crecimiento Nervioso/metabolismo , Receptor trkA/genética , Receptor trkA/metabolismo , Sistema Nervioso Simpático/citología , Sistema Nervioso Simpático/efectos de los fármacosRESUMEN
A new species of Cryptosporidium is described from the feces of domestic cattle, Bos taurus. Oocysts are structurally similar to those of Cryptosporidium muris described from mice but are larger than those of Cryptosporidium parvum. Oocysts of the new species are ellipsoidal, lack sporocysts, and measure 7.4 x 5.5 microm (range, 6.0-8.1 by 5.0-6.5 microm). The length to width ratio is 1.35 (range, 1.07-1.50). The colorless oocyst wall is < 1 microm thick, lacks a micropyle, and possesses a longitudinal suture at one pole. A polar granule is absent, whereas an oocyst residuum is present. Oocysts were passed fully sporulated and are not infectious to outbred, inbred immunocompetent or immunodeficient mice, chickens or goats. Recent molecular analyses of the rDNA 18S and ITS1 regions and heat-shock protein 70 (HSP-70) genes demonstrate this species to be distinct from C. muris infecting rodents. Based on transmission studies and molecular data, we consider the large form of Cryptosporidium infecting the abomasum of cattle to be a new species and have proposed the name Cryptosporidium andersoni n. sp. for this parasite.
Asunto(s)
Enfermedades de los Bovinos/parasitología , Criptosporidiosis/veterinaria , Cryptosporidium/clasificación , Cryptosporidium/aislamiento & purificación , Animales , Bovinos , Enfermedades de los Bovinos/transmisión , Pollos , Criptosporidiosis/parasitología , Criptosporidiosis/transmisión , Cryptosporidium/citología , Cryptosporidium/fisiología , Heces/parasitología , Cabras , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos ICR , Ratones DesnudosRESUMEN
MCM1 is an essential gene in the yeast Saccharomyces cerevisiae and is a member of the MADS-box family of transcriptional regulatory factors. To understand the nature of the protein-DNA interactions of this class of proteins, we have made a series of alanine substitutions in the DNA-binding domain of Mcm1 and examined the effects of these mutations in vivo and in vitro. Our results indicate which residues of Mcm1 are important for viability, transcriptional activation, and DNA binding and bending. Substitution of residues in Mcm1 which are highly conserved among the MADS-box proteins are lethal to the cell and abolish DNA binding in vitro. These positions have almost identical interactions with DNA in both the serum response factor-DNA and alpha2-Mcm1-DNA crystal structures, suggesting that these residues make up a conserved core of protein-DNA interactions responsible for docking MADS-box proteins to DNA. Substitution of residues which are not as well conserved among members of the MADS-box family play important roles in contributing to the specificity of DNA binding. These results suggest a general model of how MADS-box proteins recognize and bind DNA. We also provide evidence that the N-terminal extension of Mcm1 may have considerable conformational freedom, possibly to allow binding to different DNA sites. Finally, we have identified two mutants at positions which are critical for Mcm1-mediated DNA bending that have a slow-growth phenotype. This finding is consistent with our earlier results, indicating that DNA bending may have a role in Mcm1 function in the cell.
Asunto(s)
Proteínas de Unión al ADN/genética , ADN/genética , Proteínas de Homeodominio/genética , Factores de Transcripción/genética , Activación Transcripcional , Animales , Sitios de Unión/genética , Línea Celular Transformada , ADN/química , Proteínas Fúngicas/genética , Genes Fúngicos , Proteína 1 de Mantenimiento de Minicromosoma , Conformación de Ácido Nucleico , Unión Proteica , Saccharomyces cerevisiaeRESUMEN
Lipoprotein lipase (LPL) plays a central role in lipid metabolism and transport by catalysing the hydrolysis of triacylglycerol-rich lipoproteins. The importance of LPL expressed by the adipose tissue and muscles in the provision of non-esterified fatty acids and 2-monoacylglycerol for tissue utilisation is well established. However, recent studies on LPL expressed by cells of the vascular wall, particularly macrophages, have identified additional actions of the enzyme that contribute to the promotion of foam cell formation and atherosclerosis. This review deals with the role of LPL in atherosclerosis, and its regulation by mediators that are known to be present in the lesion.
Asunto(s)
Arteriosclerosis/enzimología , Lipoproteína Lipasa/fisiología , Arteriosclerosis/metabolismo , Arteriosclerosis/patología , Transporte Biológico , Citocinas/metabolismo , Células Espumosas/patología , Humanos , Macrófagos/enzimología , Macrófagos/metabolismoRESUMEN
A gene encoding an alpha-tubulin of Cryptosporidium parvum was isolated and characterized. It had no introns, and encoded a 441-amino acid protein whose predicted ORF represented a typical alpha-tubulin protein with a MW of 50.5 kDa. This tubulin had an amino acid sequence similarity with Apicomplexa Plasmodium falciparum and Toxoplasma gondii higher than 88% and shared a number of conserved motifs.