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Smit BA Engels WJ Alewijn M Lommerse GT Kippersluijs EA Wouters JT Smit G 《Journal of agricultural and food chemistry》2004,52(5):1263-1268
Formation of flavor compounds from branched-chain alpha-keto acids in fermented foods such as cheese is believed to be mainly an enzymatic process, while the conversion of phenyl pyruvic acid, which is derived from phenylalanine, also proceeds chemically. In this research, the chemical conversion of alpha-keto acids to aldehydes with strong flavor characteristics was studied, with the main focus on the conversion of alpha-ketoisocaproic acid to the aldehyde 2-methylpropanal, and a manganese-catalyzed reaction mechanism is proposed for this conversion. The mechanism involves keto-enol tautomerism, enabling molecular oxygen to react with the beta-carbon atom of the alpha-keto acid, resulting in a peroxide. This peroxide can react in several ways, leading to unstable dioxylactone or noncyclic intermediates. These intermediates will break down into an aldehyde and oxalate or carbon oxides (CO and CO(2)). All the alpha-keto acids tested were converted at pH 5.5 and in the presence of manganese, although their conversion rates were rather diverse. This chemical reaction might provide new ways for controlling cheese flavor formation with the aim of acceleration of the ripening process or diversification of the flavor characteristics. 相似文献
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Saulo Petinatti Pavarini Danilo Carloto Gomes Marcele Bettim Bandinelli Flademir Wouters Luciana Sonne David Driemeier Cláudio Estêv?o Farias da Cruz 《Acta veterinaria Scandinavica》2013,55(1):7
Chronic cardiac insufficiency was associated with a malignant peripheral nerve sheath tumor in a cow. An eight-year-old cow developed a progressive condition (over a period of three months) characterized by an enhanced abdominal volume, reluctance to move, a positive jugular pulse, watery diarrhea and death. At necropsy, moderate subcutaneous edema and an enhanced hepatic lobular pattern were observed. A 23x20x11 cm firm, grayish-white mass adhered to and infiltrated the right atrium. Multiple firm, yellowish-white nodules of 0.5 to 12 cm in diameter were diffusely scattered in the epicardium and parietal pericardium. Histologically, the tumor was poorly circumscribed with foci of infiltration of the myocardium. The neoplastic cells had two major histologic patterns, Antoni types A and B. Within occasional foci, pleomorphic cells with an epithelioid appearance were present in addition to multinucleated cells with periodic acid Schiff (PAS)-positive cytoplasmic globules. Foci of cartilaginous and granular differentiations were interspersed among the neoplastic cells. Multiple vessels presented wall hyalinization and tumoral embolus. Large necrotic foci with mineralization and cholesterol clefts were also observed. Immunohistochemically, the tumor was positive for S100 protein, vimentin and neuron-specific enolase labeling. 相似文献
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Evaluation of frozen Umbrella‐stage Artemia as first animal live food for Litopenaeus vannamei (Boone) larvae 
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下载免费PDF全文 María de Lourdes Cobo Roeland Wouters Mathieu Wille Stanislaus Sonnenholzner Patrick Sorgeloos 《Aquaculture Research》2015,46(9):2166-2173
An alternative larval shrimp feeding regime, in which umbrella‐stage Artemia were constituting the first zooplankton source was evaluated in the culture of Litopenaeus vannamei. In a preliminary experiment, umbrella‐stage Artemia were fed to larvae from zoea 2 (Z2) to mysis 2 (M2) stages to identify the larval stage at which raptorial feeding starts and to determine daily feeding rates. The following experiment evaluated the performance of two feeding regimen that differed during the late zoea/early mysis stages: a control treatment with frozen Artemia nauplii (FAN), and a treatment with frozen umbrella‐stage Artemia (FUA). The ingestion rate of umbrella‐stage Artemia increased from nine umbrella per larvae day?1 at Z2 stage to 21 umbrella per larvae day?1 at M2. A steep increase in ingestion and dry weight from Z3 to M2 suggests a shift to a raptorial feeding mode at the M1 stage. Treatment FUA exhibited a significantly higher larval stage index (P < 0.05) during the period that zoea larvae metamorphosed to the mysis stage, and a higher final biomass, compared with treatment FAN. Based on these results and on practical considerations, a feeding regime starting with umbrella‐stage Artemia from Z2 sub‐stage can be recommended for L. vannamei larvae rearing. 相似文献
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Karen Vancampenhout Katinka Wouters Peter Buurman Jozef Deckers 《Soil biology & biochemistry》2009,41(3):568-579
Soil organic matter (SOM) is a key factor in ecosystem dynamics. A better understanding of the global relationship between environmental characteristics, ecosystems and SOM chemistry is vital in order to assess its specific influence on carbon cycles. This study compared the composition of extracted SOM in 18 topsoil samples taken under tundra, taiga, steppe, temperate forest and tropical forest using pyrolysis-GC/MS. Results indicate that SOM from cold climates (tundra, taiga) still resembles the composition of litter, evidenced by high quantities of levosugars and long alkanes relative to N-compounds and a clear odd-over-even dominance of the longer alkanes. Under temperate conditions, increased microbial degradation generally results in a more altered SOM chemistry. SOM formed under temperate coniferous forests shows an accumulation of aromatic and aliphatic moieties, probably induced by substrate limitations. Tropical SOM was characterized by an SOM composition rich in N-compounds and low in lignins, without any accumulation of recalcitrant fractions (i.e. aliphatic and aromatic compounds). Lignin composition moreover varies according to vegetation type. Results were validated against 13 new samples. The humic signature of topsoil organic matter formed under different biomes indicates a dominating effect of (i) SOM input composition related to vegetation, and (ii) SOM breakdown reflecting both climate and input quality. No evidence was found for a chemically stabilized SOM fraction under favorable decomposition conditions (temperate or warm climate with broadleaved vegetation). 相似文献
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Serge R. Boileau Jean J. Simard Jean R. Wouters Jean G. Alary D.Jit S. Arora 《Pesticide biochemistry and physiology》1985,24(3):336-342
The interactions between trans,trans-muconate and p,p′-DDT were examined. Male Wistar rats were injected intraperitoneally with 6.67 mg kg?1 [14C]p,p′-DDT. Two hours later the experimental animals received orally a solution of sodium muconate (75 mg kg?1, 0.3 ml) in physiological saline, pH 7.2; control animals received an equal volume of physiological saline. Treatment was repeated every 12 hr for 10 days. Sodium muconate does not modify urinary excretion of labeled compounds, yet it reduces body burden by accelerating the excretion rate of these compounds in rat feces. This action was observed only during the first 24 hr after the animals were exposed to p,p′-DDT. 相似文献
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Rat bite fever is a bacterial zoonosis transmitted through the bite of rats. One of the two etiological agents that cause rat bite fever is Streptobacillus moniliformis. Rat bite fever is rare and very likely under diagnosed but occurs worldwide. Other animals, like dogs and cats that have mouthed a rat are often mentioned in the literature as potential risks for the attraction of rat bite fever. However, rat bite fever caused by the bite of a dog or cat has very seldom been documented. Therefore, to identify the possible risk for humans to become infected with S. moniliformis after having been bitten by a dog that has been in contact with rats, the presence of S. moniliformis in the mouth of these dogs was tested with molecular methods. Swabs taken from the mouth of 18 dogs with proven contacts with rats were tested for the presence of S. moniliformis DNA by PCR. An amplicon of the right size was obtained in 10 of the 18 dogs. Nucleotide sequencing of five amplicons of PCR positive samples demonstrated the presence of S. moniliformis DNA in the mouth of three dogs. A bite by these dogs therefore might infect humans with S. moniliformis and cause rat bite disease. 相似文献