977 resultados para stability studies
Resumo:
The objectives of this study were to develop a questionnaire that evaluates the perception of nursing workers to job factors that may contribute to musculoskeletal symptoms, and to evaluate its psychometric properties. Internationally recommended methodology was followed: construction of domains, items and the instrument as a whole, content validity, and pre-test. Psychometric properties were evaluated among 370 nursing workers. Construct validity was analyzed by the factorial analysis, known-groups technique, and convergent validity. Reliability was assessed through internal consistency and stability. Results indicated satisfactory fit indices during confirmatory factor analysis, significant difference (p < 0.01) between the responses of nursing and office workers, and moderate correlations between the new questionnaire and Numeric Pain Scale, SF-36 and WRFQ. Cronbach's alpha was close to 0.90 and ICC values ranged from 0.64 to 0.76. Therefore, results indicated that the new questionnaire had good psychometric properties for use in studies involving nursing workers.
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Prosopis rubriflora and Prosopis ruscifolia are important species in the Chaquenian regions of Brazil. Because of the restriction and frequency of their physiognomy, they are excellent models for conservation genetics studies. The use of microsatellite markers (Simple Sequence Repeats, SSRs) has become increasingly important in recent years and has proven to be a powerful tool for both ecological and molecular studies. In this study, we present the development and characterization of 10 new markers for P. rubriflora and 13 new markers for P. ruscifolia. The genotyping was performed using 40 P. rubriflora samples and 48 P. ruscifolia samples from the Chaquenian remnants in Brazil. The polymorphism information content (PIC) of the P. rubriflora markers ranged from 0.073 to 0.791, and no null alleles or deviation from Hardy-Weinberg equilibrium (HW) were detected. The PIC values for the P. ruscifolia markers ranged from 0.289 to 0.883, but a departure from HW and null alleles were detected for certain loci; however, this departure may have resulted from anthropic activities, such as the presence of livestock, which is very common in the remnant areas. In this study, we describe novel SSR polymorphic markers that may be helpful in future genetic studies of P. rubriflora and P. ruscifolia.
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High pressure homogenization (HPH) is a non-thermal method, which has been employed to change the activity and stability of biotechnologically relevant enzymes. This work investigated how HPH affects the structural and functional characteristics of a glucose oxidase (GO) from Aspergillus niger. The enzyme was homogenized at 75 and 150 MPa and the effects were evaluated with respect to the enzyme activity, stability, kinetic parameters and molecular structure. The enzyme showed a pH-dependent response to the HPH treatment, with reduction or maintenance of activity at pH 4.5-6.0 and a remarkable activity increase (30-300%) at pH 6.5 in all tested temperatures (15, 50 and 75°C). The enzyme thermal tolerance was reduced due to HPH treatment and the storage for 24 h at high temperatures (50 and 75°C) also caused a reduction of activity. Interestingly, at lower temperatures (15°C) the activity levels were slightly higher than that observed for native enzyme or at least maintained. These effects of HPH treatment on function and stability of GO were further investigated by spectroscopic methods. Both fluorescence and circular dichroism revealed conformational changes in the molecular structure of the enzyme that might be associated with the distinct functional and stability behavior of GO.
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A rapid, sensitive and specific method for quantifying propylthiouracil in human plasma using methylthiouracil as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by liquid-liquid extraction using an organic solvent (ethyl acetate). The extracts were analyzed by high performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC-MS/MS) in negative mode (ES-). Chromatography was performed using a Phenomenex Gemini C18 5μm analytical column (4.6mm×150mm i.d.) and a mobile phase consisting of methanol/water/acetonitrile (40/40/20, v/v/v)+0.1% of formic acid. For propylthiouracil and I.S., the optimized parameters of the declustering potential, collision energy and collision exit potential were -60 (V), -26 (eV) and -5 (V), respectively. The method had a chromatographic run time of 2.5min and a linear calibration curve over the range 20-5000ng/mL. The limit of quantification was 20ng/mL. The stability tests indicated no significant degradation. This HPLC-MS/MS procedure was used to assess the bioequivalence of two propylthiouracil 100mg tablet formulations in healthy volunteers of both sexes in fasted and fed state. The geometric mean and 90% confidence interval CI of Test/Reference percent ratios were, without and with food, respectively: 109.28% (103.63-115.25%) and 115.60% (109.03-122.58%) for Cmax, 103.31% (100.74-105.96%) and 103.40% (101.03-105.84) for AUClast. This method offers advantages over those previously reported, in terms of both a simple liquid-liquid extraction without clean-up procedures, as well as a faster run time (2.5min). The LOQ of 20ng/mL is well suited for pharmacokinetic studies. The assay performance results indicate that the method is precise and accurate enough for the routine determination of the propylthiouracil in human plasma. The test formulation with and without food was bioequivalent to reference formulation. Food administration increased the Tmax and decreased the bioavailability (Cmax and AUC).
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The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.
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Despite the ecological and economic importance of passion fruit (Passiflora spp.), molecular markers have only recently been utilized in genetic studies of this genus. In addition, both basic genetic researches related to population studies and pre-breeding programs of passion fruit remain scarce for most Passiflora species. Considering the number of Passiflora species and the increasing use of these species as a resource for ornamental, medicinal, and food purposes, the aims of this review are the following: (i) to present the current condition of the passion fruit crop; (ii) to quantify the applications and effects of using molecular markers in studies of Passiflora; (iii) to present the contributions of genetic engineering for passion fruit culture; and (iv) to discuss the progress and perspectives of this research. Thus, the present review aims to summarize and discuss the relationship between historical and current progress on the culture, breeding, and molecular genetics of passion fruit.
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Membrane microdomains enriched in cholesterol, sphingolipids (rafts), and specific proteins are involved in important physiological functions. However their structure, size and stability are still controversial. Given that detergent-resistant membranes (DRMs) are in the liquid-ordered state and are rich in raft-like components, they might correspond to rafts at least to some extent. Here we monitor the lateral order of biological membranes by characterizing DRMs from erythrocytes obtained with Brij-98, Brij-58, and TX-100 at 4 °C and 37 °C. All DRMs were enriched in cholesterol and contained the raft markers flotillin-2 and stomatin. However, sphingomyelin (SM) was only found to be enriched in TX-100-DRMs - a detergent that preferentially solubilizes the membrane inner leaflet - while Band 3 was present solely in Brij-DRMs. Electron paramagnetic resonance spectra showed that the acyl chain packing of Brij-DRMs was lower than TX-100-DRMs, providing evidence of their diverse lipid composition. Fatty acid analysis revealed that the SM fraction of the DRMs was enriched in lignoceric acid, which should specifically contribute to the resistance of SM to detergents. These results indicate that lipids from the outer leaflet, particularly SM, are essential for the formation of the liquid-ordered phase of DRMs. At last, the differential solubilization process induced by Brij-98 and TX-100 was monitored using giant unilamellar vesicles. This study suggests that Brij and TX-100-DRMs reflect different degrees of lateral order of the membrane microdomains. Additionally, Brij DRMs are composed by both inner and outer leaflet components, making them more physiologically relevant than TX-100-DRMs to the studies of membrane rafts.
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Background: Ruthenium (Ru) tetraamines are being increasingly used as nitric oxide (NO) carriers. In this context, pharmacological studies have become highly relevant to better understand the mechanism of action involved. Objective: To evaluate the vascular response of the tetraamines trans-[RuII(NH3)4(Py)(NO)]3+, trans-[RuII(Cl)(NO) (cyclan)](PF6)2, and trans-[RuII(NH3)4(4-acPy)(NO)]3+. Methods: Aortic rings were contracted with noradrenaline (10-6 M). After voltage stabilization, a single concentration (10-6 M) of the compounds was added to the assay medium. The responses were recorded during 120 min. Vascular integrity was assessed functionally using acetylcholine at 10-6 M and sodium nitroprusside at 10-6 M as well as by histological examination. Results: Histological analysis confirmed the presence or absence of endothelial cells in those tissues. All tetraamine complexes altered the contractile response induced by norepinephrine, resulting in increased tone followed by relaxation. In rings with endothelium, the inhibition of endothelial NO caused a reduction of the contractile effect caused by pyridine NO. No significant responses were observed in rings with endothelium after treatment with cyclan NO. In contrast, in rings without endothelium, the inhibition of guanylate cyclase significantly reduced the contractile response caused by the pyridine NO and cyclan NO complexes, and both complexes caused a relaxing effect. Conclusion: The results indicate that the vascular effect of the evaluated complexes involved a decrease in the vascular tone induced by norepinephrine (10-6 M) at the end of the incubation period in aortic rings with and without endothelium, indicating the slow release of NO from these complexes and suggesting that the ligands promoted chemical stability to the molecule. Moreover, we demonstrated that the association of Ru with NO is more stable when the ligands pyridine and cyclan are used in the formulation of the compound.Fundamento: As tetra-aminas de rutênio cada vez mais se destacam como carreadoras da molécula de óxido nítrico. Desse modo, estudos farmacológicos tornam-se altamente relevantes, afim de melhor compreender o mecanismo de ação envolvido. Objetivo: Avaliar a resposta vascular das tetra-aminas trans-[RuII(NH3)4(Py)(NO)]3+, trans-[RuII(Cl)(NO)(Cyclan)](PF6)2 e trans-[RuII(NH3)4(4-acPy)(NO)]3+. Métodos: Anéis de aorta foram pré-contraídos com noradrenalina (10-6M). Após estabilização da tensão, concentração única (10-6M) dos compostos foi adicionada ao banho de incubação. As respostas foram registradas ao longo de 120 minutos. A integridade vascular foi avaliada funcionalmente (acetilcolina 10-6M; nitroprussiato de sódio 10-6M) e histologicamente Resultados: A análise histológica confirmou a presença ou não de células endoteliais nos tecidos analisados. Todos os complexos alteraram a resposta contrátil induzida pela noradrenalina, resultando em aumento de tônus seguido de efeito relaxante. Em anéis com endotélio, a inibição do óxido nítrico endotelial causou redução do efeito contrátil da piridina óxido nítrico. Não foram observadas respostas significativas em anéis com endotélio referente ao composto cyclan óxido nítrico. Por outro lado, em anéis sem endotélio, a inibição da guanilato ciclase reduziu significativamente a resposta contrátil dos complexos piridina óxido nítrico e cyclan óxido nítrico, levando ambos os compostos a um efeito relaxante. Conclusão: Os resultados obtidos demonstram que o efeito vascular dos complexos avaliados apresentaram diminuição no tônus vascular induzido pela noradrenalina (10-6M) ao final do tempo de incubação, em anéis com e sem endotélio, indicando liberação lenta da molécula de óxido nítrico do composto estudado e sugerindo que os ligantes causaram estabilidade química à molécula. Demonstramos que a ligação rutênio óxido nítrico é mais estável quando utilizamos os ligantes piridina e cyclan para a formulação do composto.
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A new platinum(II) complex with the amino acid L-tryptophan (trp), named Pt-trp, was synthesized and characterized. Elemental, thermogravimetric and ESI-QTOF mass spectrometric analyses led to the composition [Pt(C11H11N2O2)2]⋅6H2O. Infrared spectroscopic data indicate the coordination of trp to Pt(II) through the oxygen of the carboxylate group and also through the nitrogen atom of the amino group. The (13)C CP/MAS NMR spectroscopic data confirm coordination through the oxygen atom of the carboxylate group, while the (15)N CP/MAS NMR data confirm coordination of the nitrogen of the NH2 group to the metal. Density functional theory (DFT) studies were applied to evaluate the cis and trans coordination modes of trp to platinum(II). The trans isomer was shown to be energetically more stable than the cis one. The Pt-trp complex was evaluated as a cytotoxic agent against SK-Mel 103 (human melanoma) and Panc-1 (human pancreatic carcinoma) cell lines. The complex was shown to be cytotoxic over the considered cells.
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Growth in the development and production of engineered nanoparticles (ENPs) in recent years has increased the potential for interactions of these nanomaterials with aquatic and terrestrial environments. Carefully designed studies are therefore required in order to understand the fate, transport, stability, and toxicity of nanoparticles. Natural organic matter (NOM), such as the humic substances found in water, sediment, and soil, is one of the substances capable of interacting with ENPs. This review presents the findings of studies of the interaction of ENPs and NOM, and the possible effects on nanoparticle stability and the toxicity of these materials in the environment. In addition, ENPs and NOM are utilized for many different purposes, including the removal of metals and organic compounds from effluents, and the development of new electronic sensors and other devices for the detection of active substances. Discussion is therefore provided of some of the ways in which NOM can be used in the production of nanoparticles. Although there has been an increase in the number of studies in this area, further progress is needed to improve understanding of the dynamic interactions between ENPs and NOM.
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Sunlight exposure causes several types of injury to humans, especially on the skin; among the most common harmful effects due to ultraviolet (UV) exposure are erythema, pigmentation and lesions in DNA, which may lead to cancer. These long-term effects are minimized with the use of sunscreens, a class of cosmetic products that contains UV filters as the main component in the formulation; such molecules can absorb, reflect or diffuse UV rays, and can be used alone or as a combination to broaden the protection on different wavelengths. Currently, worldwide regulatory agencies define which ingredients and what quantities must be used in each country, and enforce companies to conduct tests that confirm the Sun Protection Factor (SPF) and the UVA (Ultraviolet A) factor. Standard SPF determination tests are currently conducted in vivo, using human subjects. In an industrial mindset, apart from economic and ethical reasons, the introduction of an in vitro method emerges as an interesting alternative by reducing risks associated to UV exposure on tests, as well as providing assertive analytical results. The present work aims to describe a novel methodology for SPF determination directly from sunscreen formulations using the previously described cosmetomics platform and mass spectrometry as the analytical methods of choice.
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Hypobromous acid (HOBr) is an inorganic acid produced by the oxidation of the bromide anion (Br(-)). The blood plasma level of Br(-) is more than 1,000-fold lower than that of chloride anion (Cl(-)). Consequently, the endogenous production of HOBr is also lower compared to hypochlorous acid (HOCl). Nevertheless, there is much evidence of the deleterious effects of HOBr. From these data, we hypothesized that the reactivity of HOBr could be better associated with its electrophilic strength. Our hypothesis was confirmed, since HOBr was significantly more reactive than HOCl when the oxidability of the studied compounds was not relevant. For instance: anisole (HOBr, k2=2.3×10(2)M(-1)s(-1), HOCl non-reactive); dansylglycine (HOBr, k2=7.3×10(6)M(-1)s(-1), HOCl, 5.2×10(2)M(-1)s(-1)); salicylic acid (HOBr, k2=4.0×10(4)M(-1)s(-1), non-reactive); 3-hydroxybenzoic acid (HOBr, k2=5.9×10(4)M(-1)s(-1), HOCl, k2=1.1×10(1)M(-1)s(-1)); uridine (HOBr, k2=1.3×10(3)M(-1)s(-1), HOCl non-reactive). The compounds 4-bromoanisole and 5-bromouridine were identified as the products of the reactions between HOBr and anisole or uridine, respectively, i.e. typical products of electrophilic substitutions. Together, these results show that, rather than an oxidant, HOBr is a powerful electrophilic reactant. This chemical property was theoretically confirmed by measuring the positive Mulliken and ChelpG charges upon bromine and chlorine. In conclusion, the high electrophilicity of HOBr could be behind its well-established deleterious effects. We propose that HOBr is the most powerful endogenous electrophile.
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We report a combined study of external pressure and Cu-substitution on BaFe2As2 single crystals grown by the in-flux technique. At ambient pressure, the Cu-substitution is known to suppress the spin density wave (SDW) phase in pure BaFe2As2(TSDW ≈ 140 K) and to induce a superconducting (SC) dome with a maximum transition temperature [Formula: see text]. This [Formula: see text] is much lower than the Tc ∼ 15-28 K achieved in the case of Ru, Ni and Co substitutions. Such a lower Tc is attributed to a Cu(2+) magnetic pair-breaking effect. The latter is strongly suppressed by applied pressure, as shown herein, Tc can be significantly enhanced by applying high pressures. In this work, we investigated the pressure effects on Cu(2+) magnetic pair-breaking in the BaFe2-xCuxAs2 series. Around the optimal concentration (xopd = 0.11), all samples showed a substantial increase of Tc as a function of pressure. Yet for those samples with a slightly higher doping level (over-doped regime), Tc presented a dome-like shape with maximum Tc ≃ 8 K. Remarkably interesting, the under-doped samples, e.g. x = 0.02 display a maximum pressure induced Tc ≃ 30 K which is comparable to the maximum Tc's found for the pure compound under external pressures. Furthermore, the magnetoresistance effect as a function of pressure in the normal state of the x = 0.02 sample also presented an evolution consistent with the screening of the Cu(2+) local moments. These findings demonstrate that the Cu(2+) magnetic pair-breaking effect is completely suppressed by applying pressure in the low concentration regime of Cu(2+) substituted BaFe2As2.
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Brain death results in the breakdown of effective central regulatory mechanisms of cardiocirculatory stability, even in patients with artificial mechanical ventilation, correction of electrolytic and acid-basic disorders and maximal conventional pharmacological support of the circulation. Recent evidences have shown that the fall of vasopressin levels in the blood circulation significantly influences the cardiocirculatory stability of patients with brain death, and its exogenous administration is defended by many authors for the management of multiorgan donor patients. In this brief review we analyse and discuss some experimental and clinical relevant studies about the role of vasopressin in the control of cardiocirculatory stability in brain death, and its potential usefulness in the management of multiorgan donor. We conclude that the role of vasopressin in the pathophysiology of brain death and its usefulness as a pharmacological agent in the management of multiorgan donor are not well elucidated, deserving further investigations.
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The XX male syndrome - Testicular Disorder of Sexual Differentiation (DSD) is a rare condition characterized by a spectrum of clinical presentations, ranging from ambiguous to normal male genitalia. We report hormonal, molecular and cytogenetic evaluations of a boy presenting with this syndrome. Examination of the genitalia at age of 16 months, showed: penis of 3.5 cm, proximal hypospadia and scrotal testes. Pelvic ultrasound did not demonstrate Mullerian duct structures. Karyotype was 46,XX. Gonadotrophin stimulation test yielded insufficient testosterone production. Gonadal biopsy showed seminiferous tubules without evidence of Leydig cells. Molecular studies revealed that SRY and TSPY genes and also DYZ3 sequences were absent. In addition, the lack of deletions or duplications of SOX9, NR5A1, WNT4 and NROB1 regions was verified. The infant was heterozygous for all microsatellites at the 9p region, including DMRT1 gene, investigated. Only 10% of the patients are SRY-negative and usually they have ambiguous genitalia, as the aforementioned patient. The incomplete masculinization suggests gain of function mutation in one or more genes downstream to SRY gene.