Direct determination of free bilirubin in serum at sub-nanomolar levels

Direct analysis of free bilirubin in human and animal blood serum samples is reported for the first time. A state-of-the-art system comprised of newly developed high-performance liquid chromatography (HPLC) on reverse-phase (RP) C18 support coupled with thermal lens spectrometric detection (TLS), based on excitation at \u3bb = 457.9 nm by an argon laser was used for this purpose. This HPLC-TLS method enabled a baseline separation of all three structural isomers of bilirubin (XIII-\u3b1, IX-\u3b1 and III-\u3b1) and the respective degradation products in isocratic mode in fewer than 7 min. The method excels in ultra-high sensitivity with limit of detection (LOD) and limit of quantitation (LOQ) of 90 pM and 250 pM, respectively. Moreover, this method also affords high precision and accuracy, with correlation coefficients R2 > 0.997 over a broad linear range (0.250\u2013150 nM) and R2 = 0.9998 in a concentration range of clinical interest (0.500\u201325 nM). The method's boosted sensitivity enabled to streamline sample preparation to just one serum ultrafiltration step, which made qualitative evaluation of sample preparation possible for the first time. The performance of the HPLC-TLS method was assessed to have 20-fold enhanced sensitivity when compared to a comparable method incorporating HPLC coupled with diode array detector (DAD), which is also a novel method by itself, and could be applied for free bilirubin determination in patients with elevated bilirubin levels

Which plant compounds influence the natural resistance of cabbage against onion thrips ( Thrips tabaci Lindeman)?

In a field experiment on the natural resistance of cabbage ( Brassica oleracea var. capitata ) against onion thrips (Thrips tabaci) , 20 cabbage genotypes were included: 9 early, 5 mid-early, 6 mid-late (regarding the longevity of the growing period), 3 red, 17 white (regarding colour), 14 hybrids and 6 varieties (regarding genetic origin). For comparisons between genotypes, we determined significant differences in the mean index of damage on the exterior leaves of cabbage heads (1.12–2.83), the net weight of heads (281.40,151169.6 g), and yield loss (5.8–47.4%). The concentration of several compounds from cabbage leaves (epicuticular wax, α-amyrin, β-amyrin, lupeol, sucrose, glucose, fructose, vitamin C, palmitic acid, stearic acid, and arachidic acid) are measured. For all groups of cabbage genotypes the only confirmed negative correlation was between the extent of damage caused by the sucking of onion thrips and epicuticular wax content on the cabbage leaves (in groups where we artificially placed genotypes with similar characteristics). After this preliminary experiment, the research must be extended in order to determine the effect of the remaining analysed compounds in cabbage leaves for resistance (sensitivity) of cabbage to onion thrips attack

BILITRANSLOCASE MEMBRANE TRANSPORTER: A DRUG TARGET STUDIED IN BOTH ANIMAL AND PLANT SPECIES

Bilitranslocase (TC 2.A.65.1.1) is a membrane protein localised in absorptive epithelia (intestine), excretory epithelia (liver and kidney), and vascular endothelium and probably ubiquitous. It transports water-soluble organic anions. These are bilirubin, dietary flavonoids (anthocyanins) and natural nucleotides. A QSAR model with strong predictive capacity has been built. A battery of functional assays in membrane vesicles, isolated cells and organ fragments, is available. One anti-sequence monoclonal antibody has been produced. Two additional monoclonal antibodies are in production, with the property of inhibiting transport function and allowing for immune-detection of fixed samples. The QSAR model, coupled with established biological assays, allows screening new bilitranslocase ligands and assessing them for transport and bioactivity. Thus, new drugs can be developed, based on their ability to be transported by bilitranslocase. Particularly promising is the perspective to develop nucleotide-like drugs to be used in anti-cancer, anti-viral therapy or flavonoid-based drugs, able to interact with enzymes involved in intracellular signalling pathways and interfering with bilirubin transport. In plants, bilitranslocase-like homologues are found in various species. In grape berries, it has been shown to transport flavonoids and to be up-regulated under water stress

Fatores determinantes da estrutura de capital das maiores empresas que atuam no Brasil Determinant factors of capital structure for the largest companies active in Brazil

Estrutura de capital é um tema ainda controverso em teoria de finanças. Desde a discussão entre a teoria tradicional, que defende a existência de uma estrutura de capital ótima que leva à maximização do valor da empresa, e a proposta por Modigliani e Miller (1958), que considera que o valor da empresa não é afetado pela forma como ela é financiada, diversos estudos empíricos têm sido realizados com o objetivo de identificar os fatores que explicam a forma como as empresas se financiam. Esta pesquisa analisa a estrutura de capital das maiores empresas que atuam no Brasil, investigando a relação entre o nível de endividamento e os fatores apontados pela teoria como seu determinante. O estudo é baseado em dados contábeis extraídos das demonstrações financeiras de empresas de capital aberto e de empresas de capital fechado. A técnica estatística utilizada no estudo é a regressão linear múltipla. Os resultados indicam que os fatores risco, tamanho, composição dos ativos e crescimento são determinantes da estrutura de capital das empresas, enquanto que o fator rentabilidade não é determinante. Os resultados, também, mostram que o nível de endividamento da empresa não é afetado pelo fato de ela ser de capital aberto ou de capital fechado.<br>Capital structure is still a still controversial issue in finance theory. Since the discussion between traditional theory, which asserts the existence of an optimal capital structure that maximizes the firm’s value, and Modigliani and Miller’s theory (1958), which considers that the value of a firm is unaffected by how it is financed, many empirical studies have been carried out to identify the factors that explain how a firm finances itself. This research analyses the capital structure of the largest firms in Brazil and investigates the relationship between the leverage ratio and the factors indicated by theory as determinant. The study is based on accounting data extracted from the financial statements of publicly traded and private companies. Multiple linear regression was applied as a statistical technique. The results indicate that risk, firm size, fixed assets and growth are determinants of the firms’ capital structure, while profitability is not a determinant factor. The results also show that the firms’ leverage is unaffected by whether a firm is publicly-traded or private