Effect of various factors on the activity of sucrase from the larvae of Sesamia inferens

Salivary gland sucrase activity fromSesamia inferens Wlk. was optimal at pH 5.8 and temperature 35°. It increased up to 1.5% final sucrose concentration, but higher concentrations had no effect. A dialysed preparation showed a 37.5% reduction in the activity. It was accelerated by tryptophan and inhibited by all other amino acids used. Gut sucrase activity ofS. inferens was optimal at pH 6.2 and temperature 30°. It increased sharply up to 0.66% final sucrose concentration, and then gradually up to 1.5% while further increase in the concentration had no effect. A dialysed preparation showed an 8% increase in activity. Activity was not affected by serine; was accelerated by arginine, cystine, methionine, tryptophan and valine; and inhibited by alanine, glutamine, glycine, hydroxyproline, leucine, phenylalanine, proline and tyrosine. End-products increased with the incubation period and showed inhibitory effects. With the increase of enzyme concentration the rate of sucrose hydrolysis also increased. K⁺ ions accelerated the activity of the dialysed preparation. It was also accelerated by Li⁺⁺ ions up to their final concentration of 0.001 M, but inhibited when their final concentration increased (0.01 M and 0.025 M). TRIS also inhibited the activity.

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Résumé Deux types d'extraits ont été étudiés séparément: la sucrase extraite des glandes salivaires et celle extraite de l'intestin moyen. L'activité optimale de la sucrase salivaire s'observe pour un pH 5,8 et une température de 35°; celle de la sucrase de l'intestin moyen pour un pH 6,2 et une température de 30°. Cependant les extraits dialysés, d' origine salivaire ou d'origine intestinale, ont une activité optimum pour un même pH (5,8). L'activité des deux sucrases s'accro?t proportionnellement à la durée de la période d'incubation. L'activité de la sucrase salivaire s'accro?t nettement, jusqu'à une concentration finale en sucrose de 1.5%, alors que pour la sucrase intestinale, 90% de l'activité maximale est réalisée pour une concentration finale en sucrose de 0.66%. Quand la concentration en sucrose atteint ou dépasse 1,5% il se forme alors un oligosaccharide dont la synthèse équilibre l'hydrolyse du sucrose, ce qui rend l'activité de la sucrase constante au-dessus d'une concentration finale en sucrose≥1,5%. Cette synthèse d'un oligosaccharide intervient quand on utilise une forte concentration de sucrase, ce qui entraine la production de glucose et fructose en grande quantité; avec une faible concentration de l'extrait on n'observe pas la synthèse d'oligosaccharide. Les ions K⁺ accélèrent l'activité des extraits dialysés, d'origine salivarie ou intestinale; les ions Li⁺⁺ sont également favorables jusqu'à une concentration de 0,001 M, cette action devenant inhibitrice à partir de 0,005 ou 0.025 M; les ions TRIS, à 0,025 M ont également un effet inhibiteur. Certains acides aminés accélèrent l'activité de la sucrase salivaire ou intestinale, d'autres au contraire ont une action inhibitrice.

     

Chromium‐Based Regulations Applicable to Metal Finishing Industries in the United States: A Policy Assessment

This article seeks to briefly evaluate the context behind the development of regulations related to chromium pollution control in metal finishing industries. The available evidence suggests the possibility of elevation of the issue to the agenda for agency rule‐making, and subsequent implementation can occur even in the absence of focusing events. Based on historical evidence, this article illustrates that gradual accumulation of knowledge of harmful effects of chromium over the period of decades has been instrumental in the formulation and implementation of standards and guidelines to regulate chromium in the environment under major statutes such as the Clean Air Act, the Clean Water Act, the Safe Drinking Water Act, and so on. The implementation of command and control regulations has resulted in appreciable reduction of chromium released into the environment, thereby minimizing the impact on human health and the environment. However, achieving full compliance from metal finishing industries is still an illusion. There are examples of violations committed by industries. In response to this realization, policy evolution in the chromium pollution control domain has occurred in two directions: (1) gradual replacement of existing standards with more stringent standards and guidelines and (2) emphasis on multimedia, voluntary, and participatory approaches to improve compliance. But the results from the latter are not as dramatic as previously envisioned. Borrowing from the experience of the Common Sense Initiative (CSI), this article argues that consensus‐based, multistakeholder collaboration can be a policy development tool.     

Classification of Porcine Cranial Fracture Patterns Using a Fracture Printing Interface,,

Distinguishing between accidental and abusive head trauma in children can be difficult, as there is a lack of baseline data for pediatric cranial fracture patterns. A porcine head model has recently been developed and utilized in a series of studies to investigate the effects of impact energy level, surface type, and constraint condition on cranial fracture patterns. In the current study, an automated pattern recognition method, or a fracture printing interface (FPI), was developed to classify cranial fracture patterns that were associated with different impact scenarios documented in previous experiments. The FPI accurately predicted the energy level when the impact surface type was rigid. Additionally, the FPI was exceedingly successful in determining fractures caused by skulls being dropped with a high‐level energy (97% accuracy). The FPI, currently developed on the porcine data, may in the future be transformed to the task of cranial fracture pattern classification for human infant skulls.