Pesticide detection with a liposome-based nano-biosensor

Monitoring of the organophosphorus pesticides dichlorvos and paraoxon at very low levels has been achieved with liposome-based nano-biosensors. The enzyme acetylcholinesterase was effectively stabilized within the internal nano-environment of the liposomes. Within the liposomes, the pH sensitive fluorescent indicator pyranine was also immobilized for the optical transduction of the enzymatic activity. Increasing amounts of pesticides lead to the decrease of the enzymatic activity for the hydrolysis of the acetylcholine and thus to a decrease in the fluorescent signal of the pH indicator. The decrease of the liposome biosensors signal is relative to the concentration of dichlorvos and paraoxon down to 10⁻¹⁰ M levels. This biosensor system has been applied successfully to the detection of total toxicity in drinking water samples. Also a colorimetric screening device for pesticide analysis has been evaluated.     

Dispersion patterns of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in citrus orchards in southeast Brazil

We studied the dispersion patterns of the exotic endoparasitoid, Diachasmimorpha longicaudata (Ahsmed) (Hymenoptera: Braconidae), in 1999 (summer) and in 2000 (winter) in a citrus orchard in southeast Brazil. Different population densities of D. longicaudata were released in the centre of the orchard, and their dispersion was determined by using yellow, sticky, rectangular traps, placed in various distances and heights around the release point. Our results suggest that during summer, climatic conditions did not affect dispersion. However, in winter, dispersion rates were positively affected by temperature, and negatively by rainfall. Both estimated dispersal distance and surface were higher in summer than in winter for all release densities. Dispersion peaked at 2000 parasitoids ha^?1 in summer and 8000 parasitoids ha^?1 in winter. The importance of our results for the biological control of fruit flies by augmented or innoculative releases of D. longicaudata in southeast Brazil is discussed.     

Development of potent, orally active 1-substituted-3,4-dihydro-2-quinolone glycogen phosphorylase inhibitors

A series of substituted 3,4-dihydro-2-quinolone glycogen phosphorylase inhibitors, which have potential as antidiabetic agents, is described. Initial members of the series showed good enzyme inhibitory potency but poor physical properties. Optimisation of the 1-substituent led to 2,3-dihydroxypropyl compounds which showed good in vitro potency and improved physical properties, together with good DMPK profiles and acute in vivo efficacy in a rat model. X-ray crystallographic data are presented, showing an unexpected variety of binding orientations at the dimer interface site.     

In vivo measurement of cortical impedance spectrum in monkeys: implications for signal propagation

To combine insights obtained from electric field potentials (LFPs) and neuronal spiking activity (MUA) we need a better understanding of the relative spatial summation of these indices of neuronal activity. Compared to MUA, the LFP has greater spatial coherence, resulting in lower spatial specificity and lower stimulus selectivity. A differential propagation of low- and high-frequency electric signals supposedly underlies this phenomenon, which could result from cortical tissue specifically attenuating higher frequencies, i.e., from a frequency-dependent impedance spectrum. Here we directly measure the cortical impedance spectrum in vivo in monkey primary visual cortex. Our results show that impedance is independent of frequency, is homogeneous and tangentially isotropic within gray matter, and can be theoretically predicted assuming a pure-resistive conductor. We propose that the spatial summation of LFP and MUA is determined by the size of these signals' generators and the nature of neural events underlying them, rather than by biophysical properties of gray matter.     

(2-Benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indol-8-yl)-acetic acid: an aldose reductase inhibitor and antioxidant of zwitterionic nature

Novel carboxymethylated pyridoindoles, characterized by antioxidant activity combined with the ability to inhibit aldose reductase, represent an example of a multitarget approach to the treatment of diabetic complications - severe diabetes-related health disorders of multifunctional nature. One of the novel carboxymethylated pyridoindoles, (2-benzyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indol-8-yl)-acetic acid (compound 1), was found to inhibit aldose reductase with the IC(50) value 18.2 ± 1.2 μM. Owing to aldose reductase pharmacophore requirements for an acidic proton, most aldose reductase inhibitors contain an acetic acid moiety, ionized at physiological pH, resulting in poor bioavailability of the drugs. The presence of a basicity center at the tertiary nitrogen of the carboxymethylated pyridoindoles, in addition to the acidic carboxylic function, predisposes these compounds to form double-charged zwitterionic species. The zwitterionic nature of compound 1 may remarkably affect its pH-lipophilicity profile allowing for increased membrane penetration in the pH region around its isoelectric point, which lies close to the physiological pH 7.4. In the first part of this study, the presence of zwitterionic species was experimentally proved by the concentration-dependent effect of sodium 1-hexanesulphonate on the distribution profile of compound 1. Then a series of experiments was performed in the cellular system of isolated erythrocytes in vitro. Isolated rat erythrocytes exposed to peroxyl radicals, generated in the solution by decomposition of the hydrophilic azoinitiator AAPH or intracellularly by decay of lipophilic t-BuOOH, underwent progressive hemolysis. The onset of the hemolysis was shifted from the starting zero point by the time interval assigned as a lag period. In the presence of compound 1 the lag period was significantly prolonged. Finally, under conditions of a short-term experiment in STZ-diabetic rats in vivo, increase in sorbitol levels in erythrocytes was recorded. Compound 1 administered in the dose 50mg/kg/day (i.g.) significantly decreased the sorbitol level in the erythrocytes. To conclude, the physico-chemical proof of the zwitterionic nature of compound 1 was established and the results obtained in isolated red blood cells indicated good cellular availability of the compound. In addition, in diabetic rats, sorbitol accumulation in red blood cells was significantly inhibited by compound 1 administered intra-gastrically, suggesting its ready uptake into the central compartment. The zwitterionic principle thus may have significant consequences for increased bioavailability of drugs bearing an acidic function.     

Well-defined homopolypeptides, copolypeptides, and hybrids of poly(l-proline)

l-Proline is the only, out of 20 essential, amino acid that contains a cyclized substituted α-amino group (is formally an imino acid), which restricts its conformational shape. The synthesis of well-defined homo- and copolymers of l-proline has been plagued either by the low purity of the monomer or the inability of most initiating species to polymerize the corresponding N-carboxy anhydride (NCA) because they require a hydrogen on the 3-N position of the five-member ring of the NCA, which is missing. Herein, highly pure l-proline NCA was synthesized by using the Boc-protected, rather than the free amino acid. The protection of the amine group as well as the efficient purification method utilized resulted in the synthesis of highly pure l-proline NCA. The high purity of the monomer and the use of an amino initiator, which does not require the presence of the 3-N hydrogen, led for the first time to well-defined poly(l-proline) (PLP) homopolymers, poly(ethylene oxide)-b-poly(l-proline), and poly(l-proline)-b-poly(ethylene oxide)-b-poly(l-proline) hybrids, along with poly(γ-benzyl-l-glutamate)-b-poly(l-proline) and poly(Boc-l-lysine)-b-poly(l-proline) copolypeptides. The combined characterization (NMR, FTIR, and MS) that results for the l-proline NCA revealed its high purity. In addition, all synthesized polymers exhibit high molecular and compositional homogeneity.     

Lumican regulates osteosarcoma cell adhesion by modulating TGFβ2 activity

Human osteosarcoma cell lines were recently shown to express and secrete the small leucine rich proteoglycan (SLRP) lumican, with the ability to regulate the growth and motility of these cells. In this study, lumican-deficient Saos 2 cells were demonstrated to have increased adhesive capability onto fibronectin (FN) (p≤0.01). Upon neutralization of endogenous transforming growth factor β2 (TGF-β2) activity, no difference in the ability of lumican siRNA-transfected and scramble siRNA-transfected Saos 2 cells to adhere onto FN was detected (p=NS). Exogenous TGF-β2 was shown to stimulate Saos 2 cell adhesion to FN (p≤0.01). These results therefore, suggest that the inverse correlation existing between lumican expression and Saos 2 cell adhesion is dependent on active TGF-β2 signaling. Furthermore, the significant increase in Smad 2 activation present in lumican-deficient cells (p≤0.01) was annulled in the presence of the anti-TGF-β2 peptide, demonstrating that lumican is an upstream regulator of the TGF-β2/Smad 2 signaling cascade. Crucial to FN-dependent adhesion, β1 integrin expression and pFAK activation were likewise identified as downstream TGF-β2 effectors regulated by lumican expression. In conclusion, this study demonstrates a novel out-in signaling circuit in human osteosarcoma cells: secreted to extracellular matrix lumican is an endogenous inhibitor of TGF-β2 activity, resulting in downstream effector modulation including pSmad 2, integrin β1 and pFAK to regulate osteosarcoma adhesion.     

Complete genome sequence of Ferroglobus placidus AEDII12DO

Ferroglobus placidus belongs to the order Archaeoglobales within the archaeal phylum Euryarchaeota. Strain AEDII12DO is the type strain of the species and was isolated from a shallow marine hydrothermal system at Vulcano, Italy. It is a hyperthermophilic, anaerobic chemolithoautotroph, but it can also use a variety of aromatic compounds as electron donors. Here we describe the features of this organism together with the complete genome sequence and annotation. The 2,196,266 bp genome with its 2,567 protein-coding and 55 RNA genes was sequenced as part of a DOE Joint Genome Institute Laboratory Sequencing Program (LSP) project.