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91.
BackgroundPreterm birth rate is increasing and is currently a worldwide concern. The purpose of this study was to estimate the prevalence of preterm birth in a sample of health facilities in Brazil and to identify the main risk factors associated with spontaneous preterm births.ConclusionsThe preterm birth rate in these health facilities in Brazil is high and spontaneous preterm births account for two thirds of them. A better understanding of the factors associated with spontaneous preterm birth is of utmost importance for planning effective measures to reduce the burden of its increasing rates.  相似文献   
92.

Background

Decay Accelerating Factor (DAF) and Coxsackievirus-Adenovirus Receptor (CAR) have been identified as cellular receptors for Coxsackie B viruses (CV-B). The aim of this study is to elucidate the different binding properties of CV-B serotypes and to find out if there are any amino acid changes that could be associated to the different phenotypes.Twenty clinical CV-B isolates were tested on CaCo-2 cell line using anti-DAF (BRIC216) and anti-CAR (RmcB) antibodies. CV-B3 Nancy prototype strain and a recombinant strain (Rec, CV-B3/B4) were tested in parallel. The P1 genomic region of 12 CV-B isolates from different serotypes was sequenced and the Trans-Epithelial Electrical Resistance (TEER) along with the virus growth cycle was measured.

Results

Infectivity assays revealed clear differences between CV-B isolates with regard to their interactions with DAF and CAR. All tested CV-B isolates showed an absolute requirement for CAR but varied in their binding to DAF. We also reported that for some isolates of CV-B, DAF attachment was not adapted. Genetic analysis of the P1 region detected multiple differences in the deduced amino acid sequences.

Conclusion

Within a given serotype, variations exist in the capacity of virus isolates to bind to specific receptors, and variants with different additional ligands may arise during infection in humans as well as in tissue culture.  相似文献   
93.
A recent analysis of group A Streptococcus (GAS) invasive infections in Australia has shown a predominance of M4 GAS, a serotype recently reported to lack the antiphagocytic hyaluronic acid (HA) capsule. Here, we use molecular genetics and bioinformatics techniques to characterize 17 clinical M4 isolates associated with invasive disease in children during this recent epidemiology. All M4 isolates lacked HA capsule, and whole genome sequence analysis of two isolates revealed the complete absence of the hasABC capsule biosynthesis operon. Conversely, M4 isolates possess a functional HA-degrading hyaluronate lyase (HylA) enzyme that is rendered nonfunctional in other GAS through a point mutation. Transformation with a plasmid expressing hasABC restored partial encapsulation in wild-type (WT) M4 GAS, and full encapsulation in an isogenic M4 mutant lacking HylA. However, partial encapsulation reduced binding to human complement regulatory protein C4BP, did not enhance survival in whole human blood, and did not increase virulence of WT M4 GAS in a mouse model of systemic infection. Bioinformatics analysis found no hasABC homologs in closely related species, suggesting that this operon was a recent acquisition. These data showcase a mutually exclusive interaction of HA capsule and active HylA among strains of this leading human pathogen.  相似文献   
94.
95.
Daniel S  Noda M  Cerione RA  Sharp GW 《Biochemistry》2002,41(30):9663-9671
Mastoparan, a hormone receptor-mimetic peptide isolated from wasp venom, stimulates insulin release from pancreatic beta-cells in a Ca(2+)-independent but GTP-dependent manner. In this report, the role of the Rho family GTP-binding protein Cdc42, in the mastoparan stimulus-secretion pathway, was examined. Overexpression of wild-type Cdc42 in beta HC-9 cells, an insulin-secreting mouse-derived cell line, resulted in a 2-fold increase in mastoparan-stimulated insulin release over vector-transfected beta HC-9 cells. This effect was not seen with secretagogues such as glucose that stimulate secretion via Ca(2+)-dependent pathways. GDP/GTP exchange assay data and studies with pertussis (PTX) toxin suggest that mastoparan may work directly to activate Cdc42 and not via PTX-sensitive heterotrimeric GTP-binding proteins. Using bacterial glutathione S-transferase-Cdc42 fusion proteins and co-immunoprecipitation and transient transfection studies, Cdc42 was shown to be an upstream regulator of the exocytotic protein, syntaxin. These results suggest that the GTP-dependent signal underlying the mastoparan effect acts at a "distal site" in stimulus-secretion coupling on one of the SNARE proteins essential for exocytosis. In vitro binding assays, using purified Cdc42 and syntaxin proteins, show that Cdc42 mediates the GTP signal through an indirect association with syntaxin. The H3 domain at the C-terminus of syntaxin, which participates in the formation of the ternary SNARE complex with the core proteins, SNAP-25 and synaptobrevin, is also required for the association with Cdc42. Thus, these studies indicate that Cdc42 could be a putative GTP-binding protein thought to be involved in the mastoparan-stimulated GTP-dependent pathway of insulin release.  相似文献   
96.
Due to their major medical importance in Latin America, lancehead pitvipers are frequently kept and bred in captivity for venom extraction to the production of antivenom serums. Nevertheless, despite the great contribution given to captive breeding, much of the knowledge of Bothrops' reproductive biology derived from sporadic and insufficient data provided by zoological collections. Thus, we aimed to investigate seasonal changes in gonadosomatic index (GSI) and seminal parameters (e.g., volume, concentration, motility, viability, and acrosome integrity) of five species of lancehead pitvipers from different biomes and phylogenetic groups, maintained in the indoors serpentarium at Butantan Institute (Brazil). Patterns of variation in GSI and semen parameters differed from one species to another, suggesting that captive populations should perhaps be managed distinctly to maximize reproductive success. Furthermore, in none of the studied species did changes in GSI occur concomitantly with seminal variations. GSI remained unaltered year-round for Jararaca (Bothrops jararaca) and Brazilian lancehead (Bothrops moojeni), whereas it peaked in the autumn for Common lancehead (Bothrops atrox), Jararacussu (Bothrops jararacussu), and Whitetail lancehead (Bothrops leucurus). But surprisingly, the scenario was inverted when we estimated the total number of motile spermatozoa per season, as Jararaca and Brazilian lancehead displayed seasonal differences and the other species did not vary throughout the year. Potential ecological and evolutionary factors underlying these differences were also discussed in the present article. Together, these findings can help to better define breeding management strategies for each species in captivity, in addition to optimizing the future use of artificial insemination and semen cryopreservation.  相似文献   
97.
Much of our daily communication occurs in the presence of background noise, compromising our ability to hear. While understanding speech in noise is a challenge for everyone, it becomes increasingly difficult as we age. Although aging is generally accompanied by hearing loss, this perceptual decline cannot fully account for the difficulties experienced by older adults for hearing in noise. Decreased cognitive skills concurrent with reduced perceptual acuity are thought to contribute to the difficulty older adults experience understanding speech in noise. Given that musical experience positively impacts speech perception in noise in young adults (ages 18-30), we asked whether musical experience benefits an older cohort of musicians (ages 45-65), potentially offsetting the age-related decline in speech-in-noise perceptual abilities and associated cognitive function (i.e., working memory). Consistent with performance in young adults, older musicians demonstrated enhanced speech-in-noise perception relative to nonmusicians along with greater auditory, but not visual, working memory capacity. By demonstrating that speech-in-noise perception and related cognitive function are enhanced in older musicians, our results imply that musical training may reduce the impact of age-related auditory decline.  相似文献   
98.
Copper sulfide and zinc sulfide nanostructures were synthesized using a solvo/hydrothermal method and a thio Schiff base ligand, N‐benzylidene ethanethioamide, as a source of sulfide ions. The effects of different synthesis parameters including the type of solvent, temperature, and duration of reactions on the morphology of the CuS and ZnS products were investigated using field emission scanning microscopy and transmission electron microscopy, respectively. The structural aspects of the samples were characterized using powder X‐ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X‐ray analysis. The optical properties of the samples were studied through their optical absorption and photoluminescence spectra. The photocatalytic ability of the as‐synthesized sulfides was explored by studying the colour removal of methylene blue under ultraviolet light irradiation.  相似文献   
99.
The chronic use of opioids leads to tolerance, psychological, and physical dependence that limits their use as an effective long-term pain control. Several studies have shown that mammalian target of rapamycin (mTOR) plays a crucial role in the development of opioid tolerance. Metformin activates 5′ adenosine monophosphate-activated protein kinase (AMPK) which directly suppresses the mTOR complex 1 signaling pathway. On the other hand, metformin can also inhibit mTOR directly and in an AMPK-independent manner. Thus, in the current study, we aimed to investigate the effects of metformin on the development of morphine and/or methadone-induced tolerance in human glioblastoma (T98G) cell line. We examined the effects of chronic treatment of morphine and/or methadone in the presence or absence of metformin with or without AMPK inhibitor (dorsomorphin hydrochloride) on levels of nitric oxide and cyclic adenosine monophosphate (cAMP), phosphorylated and dephosphorylated ribosomal protein S6 kinase β-1 (S6K1) and 4E-binding protein 1 (4E-BP1) in T98G cells. Pretreatment of cells with metformin (40 µM) with or without AMPK inhibitor (dorsomorphin hydrochloride; 1 µM) before adding of morphine (2.5 µM) or methadone (1 µM) revealed a protective effects on the development of opioid tolerance. Prior administration of metformin reversed the elevation of nitric oxide levels induced by morphine (p < 0.001) and methadone (p < 0.001) and also prevented the raise of cAMP levels induced by morphine in T98G cells (p < 0.05). Contribution of mTOR signaling pathway in metformin-induced effect was shown by the inhibition of phosphorylation of S6K1 and 4E-BP1, the downstream targets of mTOR. mTOR activation suppresses opioid-induced antinociception, and its activity has also been increased during opioid tolerance.  相似文献   
100.
In this paper the variation of normal and shear stresses along a path defined on the bone–dental implant interface is investigated. In particular, the effects of implant diameter, collar length and slope, body length, and the effects of four different types of external threads on the interfacial stress distribution are studied. The geometry of the bone is digitized from a CT scan of a mandibular incisor and the surrounding bone. The bone and the implant are assumed to be perfectly bonded. The finite element method with 2D plane strain assumption is used to compute interfacial stresses. Highest continuous interfacial stresses are encountered in the region where the implant collar engages the cortical region, and near the apex of the implant in the subcortical region. Stress concentrations in the interfacial stresses occur near the geometric discontinuities on the implant contour, and jumps in stress values occur where the elastic modulus of the bone transitions between the cortical and trabecular bone values. Among the six contour parameters, the slope and the length of the implant collar, and the implant diameter influence the interfacial stress levels the most, and the effects of changing these parameters are significantly noticed only in the cortical bone (alveolar ridge) area. External threads cause significant stress concentrations in interfacial stresses in otherwise smoothly varying regions. This work shows that the presence of external threads could cause significant variations in both normal and shear stresses along the bone–implant interface, but not reduction in shear stress as previously thought.  相似文献   
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