Blood-glucose experiment

Commercially available kits for monitoring blood-glucose use an amperometric biosensor incorporating the enzyme glucose oxidase. This experiment describes how such monitors can be adapted to the quantitative analysis of glucose in beverages. 

The classic experiments of Von Meting and Minkowski in 1889 first impHcated the pancreas in regulating blood glucose levels removal of a dog s pancreas led directly to the development of hyperglycemia. Then in the early 1920s it was shown that an internal secretion of the pancreas could be isolated... 

As blood glucose falls, there is a window of experience between sanity and coma in which self-control is lost and that precious feeling of conscious choice disappears. 

One question that is often asked of statisticians is in what sense can we be 95% confident that the population mean lies within the limits 3.84 and 4.13 To answer the question we can again conduct a sampling experiment as follows. Suppose that the 40 blood glucose measurements in Figure 8.3 comprised the total population of values. For random sample of size 10 from the populations of blood glucose values determine the sample mean, standard error and the corresponding 95% confidence interval. Repeat the process 100 times. The results of such an experiment are shown in Figure 8.6. 

Phloridzin, a toxic glycoside from the bark of the pear tree, blocks the normal reabsorption of glucose from the kidney tubule, thus causing blood glucose to be almost completely excreted in the urine. In an experiment, rats fed phloridzin... 

Minkowski tried unsuccessfully to prepare an extract of dog pancreas that would reverse the effect of removing the pancreas—that is, would lower the urinary or blood glucose levels. We now know that insulin is a protein, and that the pancreas is very rich in proteases (trypsin and chymotrypsin), normally released directly into the small intestine to aid in digestion. These proteases doubtless degraded the insulin in the pancreatic extracts in Minkowski s experiments. 

Is it possible to eat a food low on the glycemic index and still experience a significant increase in blood glucose ... 

A rapid fall in blood glucose in a diabetic patient can cause symptoms of hypoglycemia, even when blood glucose concentrations are still normal or above normal. Experience with pumps has shown that many patients continue to feel hypoglycemic for a long time after nor-moglycemia has been restored. After an attack of... 

Before dealing with the central topic, I would like to raise some further issues pertinent to it, and indeed to the development of thick-film sensors in general. Thick-film sensors are an important part of biosensor research because some blood glucose sensors for use in the home are made this way—if these are successful surely others can be Further, thick-film technology is not expensive and allows research laboratories to produce quickly, reasonably uniform devices in sufficient numbers for well replicated experiments. At the same time, some insight can be gained into the nature and demands of an industrial production process. 

Ex vivo blood monitoring experiments with human volunteers were performed by placing a device comprising two glucose and two lactate sensors into the sampling line of a double lumen catheter. Venous blood was continuously withdrawn and in line heparinized with a dilution of less then 5 %. 

Chronoamperometry is often used for measuring the diffusion coefficient of electroactive species or the surface area of the working electrode. Some analytical applications of chronoamperometry (e.g., in vivo bioanalysis) rely on pulsing of the potential of the working electrode repetitively at fixed time intervals. Some popular test strips for blood glucose (discussed in Chapter 6) involve potential-step measurements of an enzymatically liberated product (in connection with a preceding incubation reaction). Chronoamperometry can also be applied to the study of mechanisms of electrode processes. Particularly attractive for this task are reversal double-step chronoamperometric experiments (where the second step is used to probe the fate of a species generated in the first one). 

---