ANÁLISE DE IMAGENS DINÂMICA - CARACTERIZAÇÃO DA DISTRIBUIÇÃO DE TAMANHO E FORMA DE PARTÍCULAS

A distribuição granulométrica e a caracterização da morfologia das partículas são parâmetros que exercem grande influência no comportamento de materiais particulados, que envolve setores desde a mineração até indústrias farmacêuticas, alimentícias, dentre outros Entretanto, a caracterização morfológica consiste basicamente em análises estáticas com restrições em relação ao numero de partículas caracterizadas (baixa representatividade estatística). Na mineração, a possibilidade de avaliar a morfologia das partículas pode ser particularmente interessante em diferentes áreas, tais como[`1] : caracterização de partículas geradas por diferentes mecanismos de cominuição (avaliação de britadores e moinhos), o efeito da morfologia das partículas na eficiência da flotação e de processos de separações minerais que dependam do comportamento cinético das partículas (hidrociclones, mesas vibratórias, espirais concentradoras, jigues). Publicações sobre a influência da morfologia das partículas em diferentes processos de beneficiamento mineral são vastas, no entanto pouca atenção vem sendo dada à sua compreensão, e as pesquisas existentes, em sua maioria, tratam a forma das partículas apenas de uma maneira qualitativa principalmente pela falta de uma técnica que determine quantitativamente tais parâmetros. Neste trabalho é apresentada uma revisão dos métodos de caracterização de tamanho e forma de partículas e três casos de aplicação da técnica de análise de imagens dinâmica.

Osteopontin: a new facilitating factor in alopecia areata pathogenesis?

Osteopontin (OPN) is a multifunctional glycophosphoprotein secreted by many cell types, including osteoblasts, lymphocites, macrophages, epithelial cells, and vascular smooth muscle cells. It has been implicated in many physiological and pathological processes, such as cell-mediated immunity, inflammation, cell survival, and tumor invasion and metastasis. Osteopontin has multiple emerging roles in cutaneous biology and pathology and OPN involvement has been emphasized in Th1-mediated diseases such as psoriasis. Alopecia areata (AA) is a form of non-scarring hair loss affecting anagen stage hair follicles with a multifactorial autoimmune pathogenesis characterized by a prevalent Th1 cytokine profile. Given the role of osteopontin in Th1-mediated inflammation, we have postulated that OPN may be involved in AA pathogenesis. The aim of our study was to investigate plasma OPN level in alopecia areata before and after DPCP treatment. Our results showed that OPN plasma levels in patients with alopecia areata were higher than in healthy controls, but patients achieving complete recovery after DPCP treatment did not show a statistically significant reduction of OPN plasma levels.

Clinical pharmacogenetics of methotrexate

It is well known that interindividual variability can affect the response to many drugs in relation to age, gender, diet, and organ function. Pharmacogenomic studies have also documented that genetic polymorphisms can exert clinically significant effects in terms of drug resistance, efficacy and toxicity by modifying the expression of critical gene products (drug-metabolizing enzymes, transporters, and target molecules) as well as pharmacokinetic and pharmacodynamic parameters. A growing body of in vitro and clinical evidence suggests that common polymorphisms in the folate gene pathway are associated with an altered response to methotrexate (MTX) in patients with malignancy and autoimmune disease. Such polymorphisms may also induce significant MTX toxicity requiring expensive monitoring and treatment. Although the available data are not conclusive, they suggest that in the future MTX pharmacogenetics could play a key role in clinical practice by improving and tailoring treatment. This review describes the genetic polymorphisms that significantly influence MTX resistance, efficacy, and toxicity.

Zoledronic acid induces significant and long-lasting modifications of circulating angiogenic factors in cancer patients

PURPOSE

The commercial availability of zoledronic acid, a third generation bisphosphonate, prompted us to evaluate the modifications in angiogenic cytokines levels after a single i.v. infusion of this drug.

EXPERIMENTAL DESIGN

Thirty consecutive cancer patients with scintigraphic and radiographic evidence of bone metastases were treated with a single infusion of 4 mg of zoledronic acid before any chemotherapy. The patients were prospectively evaluated for circulating levels of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) just before and at 1, 2, 7, and 21 days after zoledronic acid infusion.

RESULTS

Basal serum VEGF median levels were significantly decreased at days 2 (-23%), 7 (-28%), and 21 (-34%) after zoledronic acid infusion (P = 0.0498, 0.0090, and 0.0011, respectively). Serum PDGF levels were significantly decreased by 25% 1 day after zoledronic acid infusion (P = 0.0032). This effect on circulating PDGF levels persisted for 2 days after bisphosphonate infusion (P = 0.0050). PDGF levels had returned to values similar to the median basal value at 7 and 21 days. Moreover, a linear regression model with variance analysis showed a significant positive correlation between basal VEGF and PDGF values but not at the following time points. No significant differences were recorded in platelet levels, WBC count, or hemoglobin concentration before and after zoledronic acid single infusion.

CONCLUSIONS

This study confirms that zoledronic acid could have an in vivo antiangiogenic property through a significant and long-lasting reduction in serum VEGF levels.

Requirements for reproducibility, trueness and error of measurement in internal quality control schemes

Among the various models proposed to meet requirements for metrological performance in clinical laboratory measurements, that most widely used is intra- and inter-biological variation. However, this model has weaknesses: a) in some cases, intra-individual biological variation is so small that requirements based on such data may not be met by routine methods; b) there is great variation among the intra- and inter-individual biological variations themselves. We therefore propose integration between "state-of-the-art" methods to minimize imprecision, and also suggest that requirements calculated on the basis of biological variations should be used in setting requirements for minimizing imprecision. Furthermore, we describe a new scale for setting requirements from biological variation data and suggest that systematic error should be corrected whenever it is statistically significant.

Fast, simple and cost-effective determination of thiopental in human plasma by a new HPLC technique

BACKGROUND

Thiopental is an anaesthetic drug that is largely used in both short-term and long-term infusion. After long-term infusion of thiopental, non-linear and inter-individual-dependent pharmacokinetics occur because of the saturation and/or induction of the metabolism. Clinical monitoring is important so that therapeutic adjustments can be made in many of the different pharmacological treatments, especially when long-term infusion is required. We describe a new, rapid HPLC method for the determination of plasma thiopental.

METHODS

Sample preparation involved precipitation of plasma proteins using a mixture of methanol, zinc sulfate and ethylene glycol, and containing the internal standard 5-ethyl-5-p-tolyl-barbituric acid. After adding trichloroacetic acid, the sample was centrifuged and the supernatant was injected into a C(18) reversed-phase column. The mobile phase used was water-methanol-acetonitrile (50:40:10, v/v). The eluent was monitored at 290 nm.

RESULTS

The calibration curve was linear from 0.2 to 100 microg/mL. Precision, calculated as the coefficient of variation (%), was in the range of 3.62-0.70% for the within-day assay and 5.77-1.51% for the between-day assay. The absolute recoveries obtained from supplemented samples were never less than 100%.

CONCLUSIONS

This technique shows good reliability and seems to be suitable for a very fast and simple therapeutic monitoring of plasma thiopental.

Effect of hydroxymethylglutaryl-CoA reductase inhibitors on the functional properties of erythrocyte membranes

We studied 56 patients affected by primary hypercholesterolemia treated with placebo for 1 month and with simvastatin (20 mg/day) or pravastatin (20 mg/day) for 6 months during a double-blind clinical trial. At 1-month intervals we determined the following parameters in the serum: total and HDL cholesterol, triglycerides, and apolipoprotein A-1 and B. At the same time intervals we also determined the cholesterol and phospholipid concentration, the Na+/K+ ATPase activity, and the fluidity of erythrocyte membranes. Our results demonstrated the following modifications in the erythrocyte membranes during simvastatin and pravastatin treatments: (1) an initial increase in cholesterol concentration and in cholesterol/phospholipid molar ratio, with a significant decrease only after 4 months; (2) a similar behavior of membrane fluidity, with an initial decrease and an elevation after 4 months; (3) an increase in the Na+/K+ ATPase activity only after 4 months. We hypothesize that simvastatin and pravastatin not only inhibit the hepatic synthesis of cholesterol, but also modify the cholesterol exchange between plasma and the erythrocyte membrane.