Oxidation of exogenous carbohydrate during prolonged exercise: the effects of the carbohydrate type and its concentration.

We studied rates of exogenous carbohydrate (CHO) oxidation during 90 min of cycling exercise in trained cyclists exercising at 70% of maximal oxygen consumption (VO2max) when they ingested glucose, sucrose, or glucose polymer solutions at concentrations of 7.5%, 10% or 15%. Drinks were labelled with [U-14C]glucose or sucrose and were ingested at a rate of 100 ml.10 min-1. Rates of oxidation of the ingested CHO were calculated from the specific radio-activity of the labelled CHO, expired 14CO2 and carbon dioxide output (VCO2). Total CHO oxidation, determined from oxygen consumption and VCO2 was not influenced by CHO type or concentration. Gastric emptying (P = 0.01) and the rate of exogenous CHO oxidation (P = 0.028) was greatest for the glucose polymer solutions, and least for glucose. Although gastric emptying (P = 0.006) decreased with increasing CHO concentration, CHO delivery to the intestine and exogenous CHO oxidation increased linearly with increasing CHO concentration. The percentage of the CHO delivered to the intestine that was oxidized ranged from 30.0% for 7.5% CHO to 38.1% for 15% CHO. Our results indicated that the rate of gastric emptying for CHO was not controlled to provide a constant rate of energy delivery as is commonly believed and that factors subsequent to gastric emptying limit the rate of exogenous CHO oxidation from the ingested solution.     

Estimating the carbohydrate reserves in fish

The post-mortem pH value of the muscle of cod, Gadus morhua L., is shown to be a valid indicator of the muscle glycogen level after rapid capture, stunning and rapid sampling (a level thought to be little different from that current before capture). Good correlations between initial glycogen values and post-mortem pH were obtained in fish of a wide range of nutritional states comprising fed, starved for different periods, and refed on different diets after starvation. Inconsistencies in results published in the literature are attributed to variations in the initial glycogen values as measured , which in turn stem from the fish struggling on capture, differing degrees of which reduce muscle glycogen by different amounts but probably do not affect the post-mortem pH. Variations in the time taken to sample the glycogen would also affect the results.     

Web resources for the carbohydrate chemist

Bioinformatics has played a pivotal role in advancing genetics and protein sciences. The large amount of information generated by genomics, and now proteomics, has been a driving force. By comparison, glycobiology still generates small amounts of data. The need to organize our knowledge about carbohydrates is however growing constantly and has given rise to an increasing number of public databases and freely available tools. This review gives an overview of the carbohydrate-oriented resources currently available on the Internet. Many of the resources are seldom referred to in the literature and difficult to find, in part because of the constant flux of the net itself, but also because many efforts have been lead by a single individual. As the World Wide Web has matured the number of 'permanent' resources, maintained by organizations rather than individuals, has increased. In this paper, we present some of the more useful and accessible public tools and databases. There are also a few commercial initiatives but these have not been reviewed.