Decreased activity of lecithin:cholesterol acyltransferase and hepatic lipase in chronic hypothyroid rats: Implications for reverse cholesterol transport

Chronic hypothyroidism is frequently associated with atherosclerosis due to increased cholesterol plasma levels; nevertheless, the contribution of impaired reverse cholesterol transport (RCT) in this process has not been completely elucidated. The aim of this study was to evaluate the effect of thyroidectomy (Htx) upon the main stages of RCT in rats. Plasma lipid alterations induced by thyroidectomy showed a slight, but significant, reduction of total plasma triglycerides, a 300% increase of LDL-cholesterol and a 25% decrease in HDL-cholesterol compared to control rats. We evaluated the first stage of RCT determining ₃H-cholesterol efflux in Fu5AH cells. The capacity of HDL obtained from Htx rats to promote cholesterol efflux was similar to that of controls. Lecithin:cholesterol acyltransferase (LCAT) activity, the second stage and the driving force of RCT was 30% lower in Htx animals compared to controls, as determined by reconstituted HDL used as an external substrate. Lipoproteins are remodeled by hepatic lipase; the mean activity of this enzyme in postheparin plasma of Htx animals was reduced by 30% compared to controls, thus suggesting an impaired HDL remodeling by this enzyme in the hypothyroid status. In contrast, lipoprotein lipase activity in the Htx group was unchanged. In summary, this study demonstrates that chronic hypothyroidism in the rat induced an impaired RCT mainly at the cholesterol esterification, and HDL remodeling mediated by hepatic lipase. The latter probably results in an abnormal HDL structure, i.e. phospholipid enrichment, which contributes to decrease HDL-apo AI fractional catabolic rates.     

Synthesis,characterization and immunochemical evaluation of cephalosporin antigenic determinants

Lack of knowledge of the exact chemical structure of cephalosporin antigenic determinants has hindered clinical interpretation of adverse reactions to these drugs and delayed understanding of the mechanisms involved in the specific recognition and binding of IgE molecules to these antigenic determinants. We further resolve the relationship between structure and activity of proposed antigenic chemicals, including the rational design and synthesis of these haptenic structures. Comparative RAST inhibition studies of the synthesized molecules revealed that they were recognized by IgE antibodies induced by cephalosporin antibiotics. Thus, these data indicate that recognition is mainly directed to the acyl side chain and to the beta-lactam fragment that remains linked to the carrier protein in the cephalosporin conjugation course.     

Voltammetric sensor for vanillylmandelic acid based on molecularly imprinted polymer-modified electrodes

Despite the increasing number of applications of molecularly imprinted polymers (MIPs) in analytical chemistry, the construction of a biomimetic voltammetric sensor remains still challenging. This work investigates the development of a voltammetric sensor for vanillylmandelic acid (VMA) based on acrylic MIP-modified electrodes. Thin layers of MIPs for VMA have been prepared by spin coating the surface of a glassy carbon electrode with the monomers mixture (template, methacrylic acid, a cross-linking agent and solvent), followed by in situ photopolymerisation. After extraction of the template molecule, the peak current recorded with the imprinted sensor after rebinding was linear with VMA concentration in the range 19-350 microg ml(-1), whereas the response of the control electrode is independent of incubation concentration, and was about one-tenth of the value recorded with the imprinted sensor at the maximum concentration tested. Under the conditions used, the sensor is able to differentiate between VMA and other closely structural-related compounds, such as 3-methoxy-4-hydroxyphenylethylene glycol (not detected), or 3,4- and 2,5-dihydroxyphenilacetic acids, which are adsorbed on the bare electrode surface but not at the polymer layer. Homovanillic acid was detected with the imprinted sensors after incubation, indicating that the presence of both methoxy and carboxylic groups in the same position as in VMA is necessary for effective binding in the imprinted sites. Nevertheless, both species can be differentiated by the oxidation potential. It can be concluded that MIP-based voltammetric electrodes are very promising analytical tool for the development of highly selective analytical sensors.     

Carbohydrate analysis of floral nectar using medium infrared

An instrumental method based on a chemometric model of the medium region of the infrared (MIR) was developed to analyse total sugar content and the proportions of glucose, fructose and sucrose. In order to construct the model, a set of 127 standard aqueous solutions of different sugars in the concentration range 0-20% (w/v) were prepared and analysed in the interval 4900-700 cm(-1). The MIR was transformed by normalisation, correction of baseline using the second derivative, and suppression of the signals of water and carbon dioxide. The region between 1150 and 950 cm(-1) showed the highest correlation between signal and concentration. The correlation coefficient for total sugar content was 0.956, whilst those for glucose, fructose and sucrose were 0.982, 0.972 and 0.992, respectively. The method was validated using a set of 28 samples of nectar which had been assayed by chromatographic and refractometric methods. The method shows potential utility for the prediction of nectar sugar components.     

Emission of volatile organic compounds by apple trees under spider mite attack and attraction of predatory mites

Emission rates of volatile organic compounds (VOCs) from Pirus malus L. subsp. mitis (Wallr.) var. Golden Delicious and var. Starking attacked by the phytophagous mite Panonychus ulmi Koch, and their attractiveness to the predatory mites Amblyseius andersoni Chant and Amblyseius californicus McGregor, were studied during three years. A large variability was found in the emission of individual VOCs depending on the infestation, the apple tree variety and the date. There were larger total VOC emission rates and larger total VOC leaf concentrations in apple trees attacked by phytophagous mites, especially in the var. Starking. In infested trees of this variety, there were also more predatory mites. An olfactometer assay showed that predatory mites preferentially chose branches infested by Panonychus ulmi (85% went to infested branches vs 15% to uninfested control branches) indicating that volatiles may be used as cues to find their prey.     

Production of the biocontrol agent Pantoea agglomerans strain CPA-2 using commercial products and by-products

The aim of this paper was to find the nitrogen and carbon sources that provide maximum biomass production of strain CPA-2 of the biocontrol agent Pantoea agglomerans and minimum cost of media, whilst maintaining biocontrol efficacy. To reduce the cost of media, commercial products and by-products were tested. P. agglomerans can be produced using a combination of nitrogen sources such as yeast extract (5 g l(-1)) and dry beer yeast (10 g l(-1)) with inexpensive carbohydrates such as sucrose (10 g l(-1)) and molasses (20 g l(-1)), respectively, maintaining the efficacy of the biocontrol agent against Penicillium digitatum and P. italicum on oranges. The results obtained in this study could be used to provide a reliable basis for a scale-up of this fermentation process to an industrial level.     

Recognition of Carbohydrate Epitopes Specific for Electron-Dense Granule Antigens from Entamoeba histolytica by Monoclonal Antibodies in the Cecal Content of Infected Hamsters

Saccharomyces cerevisiae CGR1 encodes a 120-amino acid protein with a predominant nucleolar localization. In this study we report the identification and cloning of the ortholog, cgrA, from Aspergillus nidulans. The cgrA gene is comprised of three exons on A. nidulans Chromosome 7. The cDNA contains a single open reading frame (ORF) that would encode a protein of 114 amino acids with 44% sequence identity to yeast Cgr1p. A plasmid expressing cgrA complemented the impaired growth phenotype of a yeast strain that can be inducibly depleted of CGR1, and a green fluorescent protein (GFP)-tagged CgrA protein had the same nucleolar localization as the corresponding yeast protein. These results identify cgrA as the A. nidulans ortholog of yeast CGR1 and suggest evolutionary conservation of nucleolar localization mechanisms used by these proteins. Received: 14 September 2000 / Accepted: 13 November 2000     

Melatonin treatment enhances the efficiency of mice immunization with Venezuelan equine encephalomyelitis virus TC-83

To determine whether treatment with melatonin (MLT) improves the efficiency of immunization against Venezuelan equine encephalomyelitis (VEE) virus, mice were vaccinated with TC-83 VEE virus and treated daily with MLT (1 or 5 mg/kg) starting 3 days before immunization, until 10 days after. IgM antibody titers were determined at days 7, 14, and 21 post-immunization. IL-10 levels were assayed at day 14 postvaccination. Treatment with MLT increased antibody titers 14 days after the immunization. IL-10 levels also increased with MLT treatment (1 and 5 mg/kg). Mice were challenged with live VEE virus at day 21 postimmunization, and viral titers were plaque assayed in chicken embryo fibroblasts 4 days after the infection. Following this challenge brain virus levels were significantly reduced. The results suggest that MLT treatment enhances the efficiency of mice immunization against VEE virus.