RESUMO
Fat-free chocolate milk formulations containing skim milk, cocoa powder, and sugar were thermally treated and then processed using high-pressure jet (HPJ) technology from 125 to 500 MPa. The rheological properties and stability of HPJ-treated chocolate milks were compared with controls (no HPJ processing) prepared both with and without added κ-carrageenan. As expected, carrageenan-free chocolate milk exhibited immediate phase separation of the cocoa powder, whereas formulations containing κ-carrageenan were stable for 14 d. An increased stability was observed with increasing HPJ processing pressure, with a maximum observed when chocolate milk was processed at 500 MPa. The apparent viscosity at 50 s-1 of HPJ-processed samples increased from ~3 mPa·s to ~9 mPa·s with increasing pressure, and shear-thinning behavior (n < 0.9) was observed for samples processed at HPJ pressures ≥250 MPa. We suggest that HPJ-induced structural changes in casein micelles and new casein-cocoa interactions increased cocoa stability in the chocolate milk. Because casein seemed to be the major component enhancing cocoa stability in HPJ-treated samples, a second study was conducted to determine the effect of additional micellar casein (1, 2, or 4%) and HPJ processing (0-500 MPa) on the stability of fat-free chocolate milk. Formulations with 4% micellar casein processed at 375 and 500 MPa showed no phase separation over a 14-d storage period at 4°C. The addition of micellar casein together with HPJ processing at 500 MPa resulted in a higher apparent viscosity (~17 mPa·s at 50s-1) and more pronounced shear-thinning behavior (n ≤ 0.81) compared with that without added micellar casein. The use of HPJ technology to improve the dispersion stability of cocoa provides the industry with a processing alternative to produce clean-label, yet stable, chocolate milk.
Assuntos
Cacau , Chocolate , Animais , Caseínas , Leite , ViscosidadeRESUMO
We introduce a mass-univariate framework for the analysis of whole-brain structural trajectories using longitudinal Voxel-Based Morphometry data and Bayesian inference. Our approach to developmental and aging longitudinal studies characterizes heterogeneous structural growth/decline between and within groups. In particular, we propose a probabilistic generative model that parameterizes individual and ensemble average changes in brain structure using linear mixed-effects models of age and subject-specific covariates. Model inversion uses Expectation Maximization (EM), while voxelwise (empirical) priors on the size of individual differences are estimated from the data. Bayesian inference on individual and group trajectories is realized using Posterior Probability Maps (PPM). In addition to parameter inference, the framework affords comparisons of models with varying combinations of model order for fixed and random effects using model evidence. We validate the model in simulations and real MRI data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) project. We further demonstrate how subject specific characteristics contribute to individual differences in longitudinal volume changes in healthy subjects, Mild Cognitive Impairment (MCI), and Alzheimer's Disease (AD).
Assuntos
Envelhecimento , Doença de Alzheimer/patologia , Teorema de Bayes , Encéfalo/anatomia & histologia , Disfunção Cognitiva/patologia , Desenvolvimento Humano/fisiologia , Imageamento por Ressonância Magnética/métodos , Modelos Estatísticos , Idoso , Idoso de 80 Anos ou mais , Encéfalo/patologia , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-IdadeRESUMO
Structural imaging based on MRI is an integral component of the clinical assessment of patients with potential dementia. We here propose an individualized Gaussian process-based inference scheme for clinical decision support in healthy and pathological aging elderly subjects using MRI. The approach aims at quantitative and transparent support for clinicians who aim to detect structural abnormalities in patients at risk of Alzheimer's disease or other types of dementia. Firstly, we introduce a generative model incorporating our knowledge about normative decline of local and global gray matter volume across the brain in elderly. By supposing smooth structural trajectories the models account for the general course of age-related structural decline as well as late-life accelerated loss. Considering healthy subjects' demography and global brain parameters as informative about normal brain aging variability affords individualized predictions in single cases. Using Gaussian process models as a normative reference, we predict new subjects' brain scans and quantify the local gray matter abnormalities in terms of Normative Probability Maps (NPM) and global z-scores. By integrating the observed expectation error and the predictive uncertainty, the local maps and global scores exploit the advantages of Bayesian inference for clinical decisions and provide a valuable extension of diagnostic information about pathological aging. We validate the approach in simulated data and real MRI data. We train the GP framework using 1238 healthy subjects with ages 18-94 years, and predict in 415 independent test subjects diagnosed as healthy controls, Mild Cognitive Impairment and Alzheimer's disease.
Assuntos
Substância Cinzenta/anormalidades , Substância Cinzenta/patologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Distribuição Normal , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Anatomia Transversal , Inteligência Artificial , Simulação por Computador , Humanos , Pessoa de Meia-Idade , Adulto JovemRESUMO
Intelligent behavior is not a one-dimensional phenomenon. Individual differences in human cognitive abilities might be therefore described by a 'cognitive manifold' of intercorrelated tests from partially independent domains of general intelligence and executive functions. However, the relationship between these individual differences and brain morphology is not yet fully understood. Here we take a multivariate approach to analyzing covariations across individuals in two feature spaces: the low-dimensional space of cognitive ability subtests and the high-dimensional space of local gray matter volume obtained from voxel-based morphometry. By exploiting a partial least squares correlation framework in a large sample of 286 healthy children and adolescents, we identify directions of maximum covariance between both spaces in terms of latent variable modeling. We obtain an orthogonal set of latent variables representing commonalities in the brain-behavior system, which emphasize specific neuronal networks involved in cognitive ability differences. We further explore the early lifespan maturation of the covariance between cognitive abilities and local gray matter volume. The dominant latent variable revealed positive weights across widespread gray matter regions (in the brain domain) and the strongest weights for parents' ratings of children's executive function (in the cognitive domain). The obtained latent variables for brain and cognitive abilities exhibited moderate correlations of 0.46-0.6. Moreover, the multivariate modeling revealed indications for a heterochronic formation of the association as a process of brain maturation across different age groups.
Assuntos
Encéfalo/anatomia & histologia , Encéfalo/fisiologia , Cognição/fisiologia , Inteligência/fisiologia , Adolescente , Criança , Feminino , Humanos , Individualidade , Análise dos Mínimos Quadrados , Masculino , Análise MultivariadaRESUMO
While various materials have been developed for bone substitute and bone tissue engineering applications over the last decades, processing techniques meeting the high demands of scaffold shaping are still under development. Individually adapted and mechanically optimised scaffolds can be derived from calcium phosphate (CaP-) ceramics via rapid prototyping (RP). In this study, porous ceramic scaffolds with a periodic pattern of interconnecting pores were prepared from hydroxyapatite, ß-tricalcium phosphate and biphasic calcium phosphates using a negative-mould RP technique. Moulds predetermining various pore patterns (round and square cross section, perpendicular and 60° inclined orientation) were manufactured via a wax printer and subsequently impregnated with CaP-ceramic slurries. Different pore patterns resulted in macroporosity values ranging from about 26.0-71.9 vol% with pore diameters of approximately 340 µm. Compressive strength of the specimens (1.3-27.6 MPa) was found to be mainly influenced by the phase composition as well as the macroporosity, both exceeding the influence of the pore geometry. A maximum was found for scaffolds with 60 wt% hydroxyapatite and 26.0 vol% open porosity. It has been shown that wax ink-jet printing allows to process CaP-ceramic into scaffolds with highly defined geometry, exhibiting strength values that can be adjusted by phase composition and pore geometry. This strength level is within and above the range of human cancellous bone. Therefore, this technique is well suited to manufacture scaffolds for bone tissue engineering.
Assuntos
Substitutos Ósseos/síntese química , Fosfatos de Cálcio/química , Modelos Anatômicos , Alicerces Teciduais/química , Algoritmos , Fenômenos Biomecânicos/fisiologia , Substitutos Ósseos/química , Força Compressiva , Humanos , Tamanho da Partícula , Transição de Fase , Porosidade , Estresse Mecânico , Propriedades de Superfície , Fatores de Tempo , Engenharia Tecidual/métodosRESUMO
The adequate regeneration of large bone defects is still a major problem in orthopaedic surgery. Synthetic bone substitute materials have to be biocompatible, biodegradable, osteoconductive and processable into macroporous scaffolds tailored to the patient specific defect. Hydroxyapatite (HA) and tricalcium phosphate (TCP) as well as mixtures of both phases, biphasic calcium phosphate ceramics (BCP), meet all these requirements and are considered to be optimal synthetic bone substitute materials. Rapid prototyping (RP) can be applied to manufacture scaffolds, meeting the criteria required to ensure bone ingrowth such as high porosity and defined pore characteristics. Such scaffolds can be used for bone tissue engineering (BTE), a concept based on the cultivation of osteogenic cells on osteoconductive scaffolds. In this study, scaffolds with interconnecting macroporosity were manufactured from HA, TCP and BCP (60 wt% HA) using an indirect rapid prototyping technique involving wax ink-jet printing. ST-2 bone marrow stromal cells (BMSCs) were seeded onto the scaffolds and cultivated for 17 days under either static or dynamic culture conditions and osteogenic stimulation. While cell number within the scaffold pore system decreased in case of static conditions, dynamic cultivation allowed homogeneous cell growth even within deep pores of large (1,440 mm(3)) scaffolds. Osteogenic cell differentiation was most advanced on BCP scaffolds in both culture systems, while cells cultured under perfusion conditions were generally more differentiated after 17 days. Therefore, scaffolds manufactured from BCP ceramic and seeded with BMSCs using a dynamic culture system are the method of choice for bone tissue engineering.
Assuntos
Células da Medula Óssea/citologia , Fosfatos de Cálcio/química , Fosfatos de Cálcio/farmacologia , Engenharia Tecidual/métodos , Alicerces Teciduais/química , Animais , Células da Medula Óssea/efeitos dos fármacos , Células da Medula Óssea/fisiologia , Substitutos Ósseos/síntese química , Substitutos Ósseos/química , Substitutos Ósseos/farmacologia , Fosfatos de Cálcio/síntese química , Técnicas de Cultura de Células/métodos , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Humanos , Camundongos , Microscopia Eletrônica de Varredura , Modelos Anatômicos , Modelos BiológicosRESUMO
Chitosan crosslinked with glutaraldehyde or oxidised dextran was studied as a potential scaffold material in tissue engineering for cartilage regeneration. By mixing two solutions of both components it became a gel, which was frozen. After lyophilization a scaffold was generated with interconnected pores with diameters ranging between 120-350 microm. The mechanical properties (yielding point, elastic and viscous moduli), absolute porosity, pore morphology were determined depending on the ratio of chitosan to crosslinker. ATDC5 (murine cell line) and bovine articular chondrocytes (primary cells) were cultured for 14 days on the scaffolds. Cultivation with ATDC5 cells and bovine chondrocytes showed no negative influence of glutaraldehyde on cell vitality and growth.
Assuntos
Cartilagem Articular/crescimento & desenvolvimento , Quitosana/química , Condrócitos/fisiologia , Dextranos/química , Glutaral/química , Glutaral/farmacologia , Engenharia Tecidual/métodos , Animais , Materiais Biocompatíveis/química , Cartilagem Articular/citologia , Bovinos , Técnicas de Cultura de Células/métodos , Células Cultivadas , Condrócitos/citologia , Reagentes de Ligações Cruzadas/química , Teste de Materiais , Camundongos , OxirreduçãoRESUMO
As human exposure to heavy metals increases, the impact these metals are having on morbidity is a growing concern. Methods of evaluating potential toxicity in medical device materials are discussed.
Assuntos
Análise de Falha de Equipamento/métodos , Segurança de Equipamentos/métodos , Equipamentos e Provisões , Metais/toxicidade , Testes de Toxicidade/métodos , Estados UnidosRESUMO
An essential property of bone substitute materials is that they are integrated into the natural bone remodelling process, which involves the resorption by osteoclast cells and the formation by osteoblast cells. If monocyte cells adhere to a calcium phosphate surface (bone or bone substitute material), they can fuse together and form multinucleated osteoclast cells. In this study we show that osteoclast-like cells derived from a human leukoma monocytic lineage responded in a different way to tricalciumphosphate (TCP) than to hydroxyapatite (HA) ceramics. Both ceramics were degraded by resorbing cells; however, HA enhanced the formation of giant cells. The osteoclast-like cells on HA formed a more pronounced actin ring, and larger lacunas could be observed. TCP ceramics are medically used as bone substitute materials because of their high dissolution rate. On the other hand, highly soluble calcium phosphate ceramics like TCP seem to be inappropriate for osteoclast resorption because they produce a high calcium concentration in the osteoclast interface and in the environment.
Assuntos
Substitutos Ósseos/química , Fosfatos de Cálcio/química , Cerâmica/química , Durapatita/química , Osteoclastos/citologia , Substitutos Ósseos/metabolismo , Fosfatos de Cálcio/metabolismo , Cerâmica/metabolismo , Durapatita/metabolismo , Humanos , Microscopia Eletrônica de Varredura , Osteoclastos/metabolismo , Propriedades de Superfície , Células U937RESUMO
A new centric scan imaging methodology for density profiling of materials with short transverse relaxation times is presented. This method is shown to be more robust than our previously reported centric scan pure phase encode methodologies. The method is particularly well suited to density imaging of low gyro-magnetic ratio non-proton nuclei through the use of a novel dedicated one-dimensional magnetic field gradient coil. The design and construction of this multi-layer, water cooled, gradient coil is presented. Although of large diameter (7.62 cm) to maximize sample cross section, the gradient coil has an efficiency of several times that offered by conventional designs (6 mT/m/A). The application of these ideas is illustrated with high resolution density-weighted proton (1H) images of hazelnut oil penetration into chocolate, and lithium ion (7Li) penetration into cement paste. The methods described in this paper provide a straightforward and reliable means for imaging a class of samples that, until now, have been very difficult to image.
Assuntos
Aumento da Imagem/instrumentação , Imageamento por Ressonância Magnética/instrumentação , Cacau/química , Materiais de Construção , Desenho de Equipamento , Lítio/química , Imagens de Fantasmas , Óleos de Plantas/química , PorosidadeRESUMO
Redistribution of lysosomes to the cell surface and secretion of lysosomal proteases appear to be general phenomena in cells that participate in local proteolysis. In the present study, we have determined whether malignant progression affects the intracellular distribution and secretion of the lysosomal protease cathepsin B in three model systems, each of which consists of cell pairs that differ in their degree of malignancy. The intracellular distribution of vesicles staining for cathepsin B was evaluated by immunofluorescent microscopy and the secretion of cathepsin B was evaluated by two complementary techniques: stopped assays of activity secreted into culture media; and continuous assays of activity secreted from viable (> or = 95%) cells growing on coverslips. We observed that the intracellular distribution of cathepsin B+ vesicles was more peripheral in the cells of higher malignancy in all three model systems and that active cathepsin B was secreted constitutively from these cells. Because an acidic pericellular pH has been shown to induce translocation of lysosomes in macrophages and fibroblasts, we evaluated the intracellular distribution of cathepsin B+ vesicles and secretion of cathepsin B in cell pairs incubated at slightly acidic pH. Acidic pericellular pH induced a redistribution of cathepsin B+ vesicles toward the cell periphery. In the more malignant cells, this resulted with time in reduced intracellular staining for cathepsin B and enhanced secretion of active cathepsin B. Translocation and secretion of cathepsin B were dependent on a functional microtubular system. Both the redistribution of cathepsin B+ vesicles toward the cell surface induced by acidic pH and the constitutive and acidic pH-induced secretion of active cathepsin B could be inhibited by microtubule poisons and stabilizers. We suggest that the redistribution of active cathepsin B to the surface of malignant cells and its secretion may facilitate invasion of these cells.
Assuntos
Catepsina B/metabolismo , Neoplasias Colorretais/metabolismo , Doença da Mama Fibrocística/metabolismo , Concentração de Íons de Hidrogênio , Melanoma Experimental/metabolismo , Animais , Catepsina B/análise , Membrana Celular/metabolismo , Neoplasias Colorretais/química , Neoplasias Colorretais/patologia , Doença da Mama Fibrocística/química , Doença da Mama Fibrocística/patologia , Humanos , Masculino , Melanoma Experimental/química , Melanoma Experimental/patologia , Camundongos , Camundongos Endogâmicos C57BL , Microtúbulos/efeitos dos fármacos , Nocodazol/farmacologia , Paclitaxel/farmacologia , Células Tumorais CultivadasRESUMO
Our laboratories have previously demonstrated that the malignancy of human and animal tumors is associated with increases in cathepsin B activity, due in part to increases in cathepsin B-specific RNA transcripts and in part to decreased regulation by the endogenous low molecular weight cysteine proteinase inhibitors (CPIs). In this study we have extended these observations to tumor cell subpopulations of B16 amelanotic melanoma (B16a) and Lewis lung carcinoma (3LL) isolated by centrifugal elutriation. B16a subpopulations exhibited a 10-fold differential in lung colonization potential, whereas 3LL subpopulations exhibited no differential. In the B16a subpopulations, cathepsin B activities, total cellular and plasma membrane-associated, corresponded positively (4- and 10-fold increase, respectively) with their lung colonization potentials. CPI activities, total cellular and plasma membrane-associated, corresponded inversely (2- and 5-fold decrease, respectively) with the lung colonization potential of the B16a subpopulations. In the 3LL subpopulations, neither cathepsin B nor CPI activities changed. In the plasma membrane fractions of all 3LL subpopulations the ratio of cathepsin B activity to CPI activity was less than 1, whereas in the plasma membrane fractions of all B16a subpopulations the ratio was 1 or greater. In the plasma membrane fractions of the B16a subpopulations of higher lung colonization potential the ratios were 2.5 and 7, indicating that the levels of endogenous CPIs in these fractions may not be sufficient to regulate cathepsin B activity. Cathepsin B mRNA levels were not increased in the B16a subpopulations expressing increased cathepsin B activity. Thus increased cathepsin B activity in these subpopulations was apparently due not to increased synthesis but to decreased regulation by the endogenous CPIs. These results suggest that membrane-associated cathepsin B and CPIs may both play a role in the expression of the experimental metastatic phenotype.
Assuntos
Catepsina B/análise , Inibidores de Cisteína Proteinase/análise , Melanoma Experimental/análise , RNA Mensageiro/análise , RNA Neoplásico/análise , Animais , Carcinoma/patologia , Carcinoma/secundário , Catepsina B/antagonistas & inibidores , Catepsina B/genética , Ciclo Celular , Neoplasias Pulmonares/secundário , Melanoma Experimental/patologia , Melanoma Experimental/secundário , Proteínas de Membrana/análise , Camundongos , Células Tumorais CultivadasRESUMO
The poor prognosis of human malignant gliomas is due to their invasion and recurrence, the molecular mechanisms of which remain poorly characterized. We have accumulated substantial evidence implicating the cysteine protease cathepsin B in human glioma malignancy. Increases in cathepsin B expression were observed throughout progression. In primary brain tumor tissue, transcript abundance (Northern blot analysis) increased in low-grade astrocytoma to high-grade glioblastoma from 3- to 6-fold, respectively, above normal brain levels. This increase correlated with increases in protein abundance (from + to ) as measured by immunohistochemistry. Furthermore, in glioblastoma cell lines increases in transcript abundance (ranging from 3- to 12-fold) were accompanied by increases in enzyme activity (44-133 nmol/min x mg protein). Altered subcellular localization was observed both immunohistochemically and by indirect immunofluorescence confocal microscopy and was found to correlate with increased grade. In addition, this increase in cathepsin B expression and altered subcellular localization correlated with histomorphological invasion and clinical evidence of invasion as detected by magnetic resonance imaging. These data support the hypothesis that cathepsin B plays a role in human glioma progression and invasion.
Assuntos
Catepsina B/análise , Glioma/enzimologia , Animais , Northern Blotting , Catepsina B/genética , Glioma/diagnóstico , Glioma/patologia , Humanos , Imuno-Histoquímica , Imageamento por Ressonância Magnética , Invasividade Neoplásica , CoelhosRESUMO
Adrenodoxin reductase is a monomeric 51 kDa flavoenzyme that is involved in the biosynthesis of all steroid hormones. The structure of the native bovine enzyme was determined at 2.8 A resolution, and the structure of the respective recombinant enzyme at 1.7 A resolution. Adrenodoxin reductase receives a two-electron package from NADPH and converts it to two single electrons that are transferred via adrenodoxin to all mitochondrial cytochromes P 450. The structure suggests how the observed flavin semiquinone is stabilized. A striking feature is the asymmetric charge distribution, which most likely controls the approach of the electron carrier adrenodoxin. A model for the interaction is proposed. Adrenodoxin reductase shows clear sequence homology to half a dozen proteins identified in genome analysis projects, but neither sequence nor structural homology to established, functionally related electron transferases. Yet, the structure revealed a relationship to the disulfide oxidoreductases, permitting the assignment of the NADP-binding site.
Assuntos
Sistema Enzimático do Citocromo P-450/metabolismo , Ferredoxina-NADP Redutase/química , Mitocôndrias/metabolismo , Esteroides/biossíntese , Adrenodoxina/metabolismo , Animais , Sítios de Ligação , Bovinos , Transporte de Elétrons , Ferredoxina-NADP Redutase/metabolismo , Flavina-Adenina Dinucleotídeo/metabolismo , Glicosilação , Modelos Moleculares , NADP/metabolismo , Conformação Proteica , Dobramento de Proteína , Tiorredoxina Dissulfeto Redutase/químicaRESUMO
The mitochondrial import receptor of 70 kDa, Tom70, preferentially recognizes precursors of membrane proteins with internal targeting signals. We report the identification of a stably folded 25 kDa core domain located in the middle portion of Tom70 that contains two of the seven tetratricopeptide repeat motifs of the receptor. The core domain binds non-cleavable and cleavable preproteins carrying internal targeting signals with a specificity indistinguishable from the full-length receptor. Competition studies indicate that both types of preproteins interact with overlapping binding sites of the core domain and that at least one additional interaction site is present in the full-length receptor. We suggest a model of Tom70 function in import of membrane proteins whereby a hydrophobic preprotein concomitantly interacts with several binding sites of the receptor.
Assuntos
Proteínas Fúngicas/metabolismo , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Precursores de Proteínas/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/metabolismo , Ligação Competitiva/efeitos dos fármacos , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Proteínas de Membrana/química , Proteínas de Membrana/genética , Mitocôndrias/efeitos dos fármacos , Proteínas de Transporte da Membrana Mitocondrial , Proteínas do Complexo de Importação de Proteína Precursora Mitocondrial , Peso Molecular , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/farmacologia , Ligação Proteica/efeitos dos fármacos , Dobramento de Proteína , Precursores de Proteínas/química , Sinais Direcionadores de Proteínas/genética , Sinais Direcionadores de Proteínas/fisiologia , Estrutura Terciária de Proteína , Transporte Proteico/efeitos dos fármacos , Proteínas Recombinantes , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Deleção de Sequência/genética , Especificidade por Substrato , Termodinâmica , Tripsina/metabolismoRESUMO
Alloys based on titanium or cobalt have been used as implant materials for decades with good success. Because of their natural oxide layer these alloys reveal good corrosion behaviour. In contact with physiological solution metal release takes place, which can cause inflammation. Coatings can improve the corrosion behaviour. In this study Ti6Al4V and Co28Cr6Mo alloys, which are frequently used as implant materials, were tested. Polished discs of these alloys and polished discs, which were coated with TiO2-layers by sol-gel chemistry, were compared regarding their corrosion behaviour and metal ion releasing. The releasing of Al, V, Ti, Co, Cr and Mo was quantified by ICP-MS analysis. The TiO2-coating reduced the release of all ions except of the Al-ion. Both alloys showed a deviating kinetic of ion releasing. In addition, cell response (cell vitality, cell proliferation, endothelial marker CD31 and actin allocation) of osteoblasts and endothelial cells were investigated.
Assuntos
Materiais Revestidos Biocompatíveis/química , Materiais Revestidos Biocompatíveis/farmacologia , Cristalização/métodos , Células Endoteliais/fisiologia , Osteoblastos/fisiologia , Próteses e Implantes , Titânio/química , Titânio/farmacologia , Células Cultivadas , Corrosão , Células Endoteliais/citologia , Células Endoteliais/efeitos dos fármacos , Humanos , Teste de Materiais , Metais/química , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Transição de Fase , Propriedades de SuperfícieRESUMO
Midazolam kinetics were evaluated in six healthy male subjects after single oral (15 mg)and intravenous (0.075 mg/kg) doses. The three-part randomized crossover study consisted of a morning dose in supine position (part A) and morning (part B) and evening (part C) doses under ambulant (sitting/walking) conditions. While no significant changes could be observed in the absorption and distribution process or the elimination half lives, total plasma clearance was higher during part A (616+/-157 ml/min, P=0.01) and C(463+/-82 ml/min, P=0.02), than in part B (317+/-110 ml/min, +/-SD). Since the intrinsic (oral) clearance was also higher during part A (1656+/-657 ml/min, P=0.003) and C(1310+/-579 ml/min, P=0.024) than during part B(710+/-241 ml/min), bioavailability did not change (range 37 to 44%). These data indicate that posture and circadian rhythm are important variables affecting blood flow-dependent hepatic elimination of midazolam.
Assuntos
Benzodiazepinas/metabolismo , Fígado/metabolismo , Adulto , Benzodiazepinas/administração & dosagem , Disponibilidade Biológica , Ritmo Circadiano , Humanos , Cinética , Masculino , Taxa de Depuração Metabólica , Midazolam , Postura , Fatores de TempoRESUMO
The effect-kinetics of the new benzodiazepine midazolam was evaluated in six subjects after single oral (7.5 and 15 mg) and intravenous (0.075 mg/kg) doses and infusion programs. The drug is bound to plasma proteins by 94%, and less than 0.5% is excreted unchanged in urine. Hepatic elimination is rapid: t1/2 beta is 2.4 +/- 0.8 hr (mean +/- S.D) and total body clearance is 283 +/- 43 ml/min (plasma) or 502 +/- 105 ml/min (blood). This substantial first-pass effect leads to bioavailability of only 44%, despite very rapid absorption (t1/2abs = 0.23 +/- 0.37 hr) after oral dosing. There is good intraindividual linear correlations (r between 0.68 and 0.97) between plasma levels and dynamic effects, as assessed by the d2 letter cancellation test and a sedation index formed from visual analogue scales.
Assuntos
Ansiolíticos/metabolismo , Benzodiazepinas/metabolismo , Administração Oral , Adulto , Ansiolíticos/farmacologia , Benzodiazepinas/farmacologia , Disponibilidade Biológica , Humanos , Infusões Parenterais , Cinética , Masculino , MidazolamRESUMO
Adrenodoxin reductase is an essential component of the mitochondrial monooxygenase systems that are involved in the synthesis of steroid hormones and related compounds. After removing by mutagenesis a secondary ribosome binding site and an mRNA loop formed between the gene and the vector, large amounts of the enzyme could be produced in Escherichia coli by coexpression with the HSP60-chaperone system. The purified protein was homogeneous enough for reproducible crystallization. The crystals diffracted X-rays isotropically beyond 1.7 A resolution permitting a structure analysis.
Assuntos
Ferredoxina-NADP Redutase/genética , Chaperonas Moleculares/metabolismo , Animais , Sequência de Bases , Bovinos , Clonagem Molecular , Cristalografia por Raios X , Primers do DNA , Eletroforese em Gel de Poliacrilamida , Escherichia coli/genética , Ferredoxina-NADP Redutase/química , MutagêneseRESUMO
A sandwich enzyme-immunoassay (EIA) has been applied to the determination of the rheumatoid factor (RF). This non-competeitive assay comprises 3 steps: 1) the RF to be assayed is extracted for the biological medium by an immunosorbent of aggregated IgG linked to cellulose; 2) the solid phase is then incubated with the enzyme-labeled aggregated IgG; 3) the enzymatic activity of the immunosorbent is then measured with a suitable chromogenic reagent. This activity is a direct function of the amount of RF to be assayed. This assay gave reproducible results in the range 0.5-50.0 IU/ml. A good agreement was obtained between the EIA and the Waaler-Rose test but no correlation was obtained with the latex slide-test. This assay permits a quantitation of RF with a good reproducibility (coefficient of variation in the range of 10% for moderately elevated values) and thus allows a closer follow-up of patients. The results do not depend on the interpretation of the technician performing the test, which can be easily automated. Finally, it may detect some RF devoid of agglutinating activity.