Acetylcholinesterase from the charru mussel Mytella charruana: kinetic characterization, physicochemical properties and potential as in vitro biomarker in environmental monitoring of mollusk extraction areas.

Acetylcholinesterase (AChE; EC 3.1.1.7) from aquatic organisms have been used to evaluate the exposure of specimens to pesticides and heavy metals at sublethal levels in environmental samples. AChE of Mytella charruana was extracted to characterize its physicochemical and kinetic properties as well as the effect of organophosphate (dichlorvos, diazinon, chlorpyrifos, methyl-parathion and temephos), carbamates (carbaryl, carbofuran and aldicarb), benzoylureas (diflubenzuron and novaluron), pyrethroid (cypermethrin) and juvenile hormone analog - JHA (pyriproxyfen) and the effect of metal ions: Hg2+, Cd2+, Pb2+, As3+, Cu2+ and Zn2+, in order to evaluate the potential of the enzyme as biomarker. The optimum pH of M. charruana AChE was 8.5 and the maximum activity peak occurred at 48 °C, being highly thermostable maintaining 97.8% of its activity after incubation at 60 °C. The Michaelis-Menten constants (km) for the substrates acetylthiocholine and propionylthiocholine were 2.8 ± 1.26 and 4.94 ± 6.9 mmol·L-1, respectively. The Vmax values for the same substrates were 22.6 ± 0.90 and 10.2 ± 4.94 mU·mg-1, respectively. Specific inhibition results suggest an AChE presenting active site with dimensions between those of AChE and butyrylcholinesterase (BChE). The IC20 values related to the effect of the pesticides on the enzyme showed higher inhibitory power of temephos (0.17 µmol·L-1), followed by aldicarb (0.19 µmol·L-1) and diflubenzuron (0.23 µmol·L-1). Metal ions inhibited M. charruana enzyme in the following order: Hg2+ > Pb2+ > Cd2+ > As3+ > Cu2+ > Zn2+. These data suggest that the enzyme showed potential as in vitro biomarker of the exposure to temephos, mercury, zinc and copper.

Aluminium sulfate exposure: A set of effects on hydrolases from brain, muscle and digestive tract of juvenile Nile tilapia (Oreochromis niloticus).

Aluminium is a major pollutant due to its constant disposal in aquatic environments through anthropogenic activities. The physiological effects of this metal in fish are still scarce in the literature. This study investigated the in vivo and in vitro effects of aluminium sulfate on the activity of enzymes from Nile tilapia (Oreochromis niloticus): brain acetylcholinesterase (AChE), muscle cholinesterases (AChE-like and BChE-like activities), pepsin, trypsin, chymotrypsin and amylase. Fish were in vivo exposed during 14days when the following experimental groups were assayed: control group (CG), exposure to Al2(SO4)3 at 1µg·mL-1 (G1) and 3µg·mL-1 (G3) (concentrations compatible with the use of aluminium sulfate as coagulant in water treatment). In vitro exposure was performed using animals of CG treatment. Both in vivo and in vitro exposure increased cholinesterase activity in relation to controls. The highest cholinesterase activity was observed for muscle BChE-like enzyme in G3. In contrast, the digestive enzymes showed decreased activity in both in vivo and in vitro exposures. The highest inhibitory effect was observed for pepsin activity. The inhibition of serine proteases was also quantitatively analyzed in zymograms using pixel optical densitometry as area under the peaks (AUP) and integrated density (ID). These results suggest that the inhibition of digestive enzymes in combination with activation of cholinesterases in O. niloticus is a set of biochemical effects that evidence the presence of aluminium in the aquatic environment. Moreover, these enzymatic alterations may support further studies on physiological changes in this species with implications for its neurological and digestive metabolisms.

Bovine pancreatic trypsin inhibitor immobilized onto sepharose as a new strategy to purify a thermostable alkaline peptidase from cobia (Rachycentron canadum) processing waste.

A thermostable alkaline peptidase was purified from the processing waste of cobia (Rachycentron canadum) using bovine pancreatic trypsin inhibitor (BPTI) immobilized onto Sepharose. The purified enzyme had an apparent molecular mass of 24kDa by both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry. Its optimal temperature and pH were 50°C and 8.5, respectively. The enzyme was thermostable until 55°C and its activity was strongly inhibited by the classic trypsin inhibitors N-ρ-tosyl-l-lysine chloromethyl ketone (TLCK) and benzamidine. BPTI column allowed at least 15 assays without loss of efficacy. The purified enzyme was identified as a trypsin and the N-terminal amino acid sequence of this trypsin was IVGGYECTPHSQAHQVSLNSGYHFC, which was highly homologous to trypsin from cold water fish species. Using Nα-benzoyl-dl-arginine ρ-nitroanilide hydrochloride (BApNA) as substrate, the apparent km value of the purified trypsin was 0.38mM, kcat value was 3.14s(-1), and kcat/km was 8.26s(-1)mM(-1). The catalytic proficiency of the purified enzyme was 2.75×10(12)M(-1) showing higher affinity for the substrate at the transition state than other fish trypsin. The activation energy (AE) of the BApNA hydrolysis catalyzed by this enzyme was estimated to be 11.93kcalmol(-1) while the resulting rate enhancement of this reaction was found to be approximately in a range from 10(9) to 10(10)-fold evidencing its efficiency in comparison to other trypsin. This new purification strategy showed to be appropriate to obtain an alkaline peptidase from cobia processing waste with high purification degree. According with N-terminal homology and kinetic parameters, R. canadum trypsin may gathers desirable properties of psychrophilic and thermostable enzymes.

Phase 2 Trial of Metformin Combined With 5-Fluorouracil in Patients With Refractory Metastatic Colorectal Cancer.

BACKGROUND: Observational and preclinical studies have suggested that metformin has antitumor effects in solid tumors, including colorectal cancer (CRC). However, the effects of metformin in CRC have not been tested in clinical trials. PATIENTS AND METHODS: This was a single-center, single-arm phase 2 clinical trial where histologically confirmed CRC patients with measurable and progressing metastatic disease previously treated with 5-fluorouracil (5-FU), irinotecan, oxaliplatin, and an anti-epidermal growth factor receptor (if the tumor was RAS wild type) were enrolled to receive metformin 850 mg orally continuously 2 times a day plus 5-FU 425 mg/m2 and leucovorin 50 mg intravenously weekly until disease progression, unacceptable toxicity, or withdrawal of consent. The primary end point was disease control rate at 8 weeks. RESULTS: Among 50 patients included, 11 (22%) met the primary end point. The median progression-free survival was 1.8 months and the median overall survival 7.9 months. Analyzing only the 11 patients who experienced disease control at 8 weeks, their median progression-free survival was 5.6 months and their median overall survival was 16.2 months. There was a trend for prolonged median survival for obese patients (12.4 vs. 5.8 months) and those longer off 5-FU. The treatment was well tolerated; the main adverse effects were diarrhea, nausea, vomiting, and myelotoxicity. CONCLUSION: Metformin and 5-FU showed an overall modest but intriguing activity in patients with refractory CRC in this phase 2 study. Some patients experienced long-term disease control. Further trials are needed to confirm these results, particularly in obese patients with CRC.

Digestive enzyme activity in the intestine of Nile tilapia (Oreochromis niloticus L.) under pond and cage farming systems.

The effect of different farming systems (cage, pond) upon digestive enzyme activities of Nile tilapia was evaluated. Juvenile Nile tilapia (87.61 ± 1.52 g) were simultaneously cultured in pond and cage systems during 90 days. Cages used nutritional biphasic plan (35 and 32 % crude protein-CP feeds) and ponds used nutritional triphasic plan (35, 32 and 28 % CP feeds). Biometric measurements were monthly performed for adjustments in feeding regimes and removal of intestine tissues to evaluate the performance of enzyme activities. Total proteolytic, amylase and lipase activities were not statistically different between the treatments throughout the periods analyzed (31, 63 and 94 days of culture). However, trypsin and chymotrypsin activities were higher with 31 and 63 days of culture in fish from pond system, suggesting that natural food may have influenced these activities. A positive correlation was observed between the recommended concentration of essential amino acids for Nile tilapia and specific aminopeptidases activity in fish cage system. Substrate-SDS-PAGE revealed 12 active proteolytic bands in both systems. However, integrated density (ID) values were higher in the bands of ponds. Specimens of either cage or pond exhibited five bands of amylolytic activity. Fish from cage and pond systems showed the highest values of ID within 31 days of cultivation. In this study, the complexity of digestive functions could be verified for animals maintained under commercial conditions. Some of the assessed enzymes may show adaptations of their activities and/or expression that allow the fish to achieve a more efficient nutrient assimilation.

Characterization of catalytic efficiency parameters of brain cholinesterases in tropical fish.

Brain cholinesterases from four fish (Arapaima gigas, Colossoma macropomum, Rachycentron canadum and Oreochromis niloticus) were characterized using specific substrates and selective inhibitors. Parameters of catalytic efficiency such as activation energy (AE), k(cat) and k(cat)/k(m) as well as rate enhancements produced by these enzymes were estimated by a method using crude extracts described here. Despite the BChE-like activity, specific substrate kinetic analysis pointed to the existence of only acetylcholinesterase (AChE) in brain of the species studied. Selective inhibition suggests that C. macropomum brain AChE presents atypical activity regarding its behavior in the presence of selective inhibitors. AE data showed that the enzymes increased the rate of reactions up to 10(12) in relation to the uncatalyzed reactions. Zymograms showed the presence of AChE isoforms with molecular weights ranging from 202 to 299 kDa. Values of k(cat) and k(cat)/k(m) were similar to those found in the literature.

Correlação entre o achado ultra-sonográfico isolado de cisto de cordão umbilical e anomalias fetais / Correlation between isolated sonographic finding of umbilical cord cyst and fetal anomalies

OBJETIVO: Correlacionar o achado ultra-sonográfico isolado de cisto de cordão umbilical com anomalias fetais, como cromossomopatias e alterações estruturais. Segundo a literatura médica, as implicações clínicas do achado ultra-sonográfico de cisto de cordão nos segundo e terceiro trimestres de gestação estão bem estabelecidas, entretanto, quando no primeiro trimestre, o significado ainda permanece controverso. MATERIAIS E MÉTODOS: Foi realizado estudo retrospectivo de gestantes da população geral, consecutivas, com fetos únicos e vivos, que apresentavam apenas o achado de cisto de cordão umbilical, num período de dez anos (1996-2006). Em todos os casos foram realizados exames ultra-sonográficos para o rastreamento de anomalias fetais após o diagnóstico de cisto de cordão. Os recém-nascidos e o cordão umbilical foram examinados após o parto para se verificar a presença de anomalias. RESULTADOS: Foram estudados nove casos que apresentavam cisto de cordão umbilical como único achado, sem outros marcadores ultra-sonográficos de anomalias fetais. Detectaram-se dois casos no primeiro trimestre de gestação e sete nos segundo e terceiro trimestres. Dois casos foram submetidos a estudo citogenético fetal, por meio de amniocentese. Nenhum recém-nascido apresentou anomalias estruturais ou aneuploidia. CONCLUSÃO: O achado ultra-sonográfico isolado de cisto de cordão umbilical não significou aumento de risco para anomalias estruturais ou aneuploidias.

OBJECTIVE: To correlate the isolated sonographic finding of umbilical cord cyst with fetal anomalies such as chromosomopathies and structural changes. According to the medical literature, the clinical implications of the sonographic finding of umbilical cord cyst in the second and third trimesters of pregnancy are well established; however, the meaning of this finding in the first trimester still remains controversial. MATERIALS AND METHODS: A retrospective study was developed with consecutive, pregnant women with single living fetuses presenting with umbilical cord cyst as an isolated finding, over a 10-year period (1996-2006). Ultrasound studies were performed in all cases for screening of fetal anomalies after the diagnosis of umbilical cord cyst. Neonates and umbilical cords were evaluated after delivery for the presence of abnormalities. RESULTS: Nine cases presenting umbilical cord cyst as a sole finding with no other sonographic marker for fetal abnormality were evaluated. Two cases were detected in the first pregnancy trimester and seven cases in the second and third trimesters. Fetal cytogenetic study was done by means of amniocentesis in two cases. No newborn presented with structural anomalies or aneuploidy. CONCLUSION: Isolated sonographic finding of umbilical cord cyst did not imply increased risk for fetal structural anomalies or aneuploidies.