Glucose activity loss

It is well known, even from old literature data (ref. 1) that the presence of metal promotors like molybdenum and chromium in Raney-nickel catalysts increases their activity in hydrogenation reactions. Recently Court et al (ref. 2) reported that Mo, Or and Fe-promoted Raney-nickel catalysts are more active for glucose hydrogenation than unpromoted catalysts. However the effects of metal promotors on the catalytic activity after repeated recycling of the catalyst have not been studied so far. Indeed, catalysts used in industrial operation are recycled many times, stability is then an essential criterion for their selection. From a more fundamental standpoint, the various causes of Raney-nickel deactivation have not been established. This work was intended to address two essential questions pertinent to the stability of Raney-nickel in glucose hydrogenation namely what are the respective activity losses experienced by unpromoted or by molybdenum, chromium and iron-promoted catalysts after recycling and what are the causes for their deactivation ... 

Zhao and Wittstock [19] conducted a comparative investigation of the kinetics of PQQ-dependent glucose dehydrogenase in the feedback and the generation-collection mode. The experiment was performed under conditions such that zero-order kinetics with respect to glucose and first-order kinetics with respect to the different mediators were maintained. This enzyme showed much faster kinetics than GOx despite some activity loss during immobilization. 

Freeze-drying of aequorin. The process of freeze-drying always results in some loss in the luminescence activity of aequorin. Therefore, aequorin should not be dried if a fully active aequorin is required. The loss is usually 10% or more. The loss can be somewhat lessened by adjusting the buffer composition the use of 100 mM KCl and some sugar (50-100 mM) seems to be beneficial. The buffer composition used at the author s laboratory is as follows 100 mM KCl, 50 mM glucose, 3 mM HEPES, 3 mM Bis-Tris, and at least 0.05 mM EDTA, pH 7.0. 

Those with type 1 diabetes mellitus produce insulin in insufficient amounts and tiierefore must have insulin supplementation to survive Type 1 diabetes usually has a rapid onset, occurs before die age of 20 years, produces more severe symptoms tiian type 2 diabetes, and is more difficult to control. Major symptoms of type 1 diabetes include hyperglycemia, polydipsia (increased thirst), polyphagia (increased appetite), polyuria (increased urination), and weight loss. Treatment of type 1 diabetes is particularly difficult to control because of the lack of insulin production by die pancreas. Treatment requires a strict regimen tiiat typically includes a carefully calculated diet, planned physical activity, home glucose testing several times a day, and multiple daily insulin injections. 

Some clinical trials can be completed with only a few visits. Others require more frequent contact with the study staff. As an example of the former, our clinic has conducted many studies intended to assess blood insulin and glucose responses to test products such as snack bars and beverages. These are usually conducted using a cross-over design and may require only three visits one for screening, one for consumption of the control product, and one for consumption of the active product. In contrast, we have also completed several trials to assess dietary and pharmaceutical interventions intended to promote weight loss. These usually require frequent clinic visits over a period of at least 12 weeks and sometimes as long as two years. 

Hypoglycaemia remains the most frequent complication of insulin administration to diabetics. It usually occurs due to (a) administration of an excessive amount of insulin (b) administration of insulin prior to a mealtime, but with subsequent omission of the meal or (c) due to increased physical activity. In severe cases this can lead to loss of consciousness, and even death. Although it may be treated by oral or i.v. administration of glucose, insulin-induced hypoglycaemia is sometimes treated by administration of glucagon. 

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