Motoaki Shichiri

WEARABLE ARTIFICIAL ENDOCRINE PANCREAS WITH NEEDLE-TYPE GLUCOSE SENSOR

Miniaturisation of the bedside artificial endocrine pancreas in necessary to provide a means of restoring physiological glycaemic excursions in diabetic patients in the long term. One of the remaining problems in producing such a sophisticated device is the difficulty in developing a sufficiently small glucose-monitoring system. A needle-type glucose sensor has been developed which is suitable for use in a closed-loop glycaemic control system. The wearable artificial endocrine pancreas, incorporating the needle-type glucose sensor, a computer calculating infusion rates of insulin, glucagon, or both, and infusion pumps, was tested in pancreatectomised dogs: the device produced perfect control of blood glucose for up to 7 days.

Glycaemic Control in Pancreatectomized Dogs with a Wearable Artificial Endocrine Pancreas

SummaryA needle-type glucose sensor has been developed using a platinum electrode covered with immobilized glucose oxidase. Experiments with albumin-saline solution in vitro showed that at 5.5 mmol/l glucose concentration the output current generated was 1.2±0.4 nA (mean ± SD). The current increased as a linear function of glucose concentration over the range (0–27.7 mmol/l). The response time to reach 90% of the final plateau value was 16.2±6.2 s. The signal-to-noise ratio of the sensor was 15.8±2.6 decibels. The temperature coefficient in output was 2.3±1.0%/°C. The current output was not affected significantly by changes in oxygen tension of the solution in the range 25–150 mmHg.In vivo, the output current of sensors inserted into the subcutaneous tissues of dogs was directly related to blood glucose concentrations after oral glucose or meals. Daily checking of the sensors maintained in subcutaneous tissues in five dogs showed that the sensitivity decreased gradually to 87.2±7.6% at 72 h, and dropped significantly to 57.4±7.0% of the initial output by 96 h.A wearable artificial endocrine pancreas (18.0 × 17.7 × 7.9 cm, 700 g) was developed, consisting of a needle-type glucose sensor, a microcomputer system and a pump driving mechanism. Three pancreatectomized dogs were fitted with the system by inserting the sensor into subcutaneous tissue. By renewing the sensor every fourth day, the device could maintain the daily glucose variations in diabetic dogs within the range 5–9.5 mmol/l for 7 days.

Enteral absorption of water-in-oil-in-water insulin emulsions in rabbits

SummaryWater-in-oil-in-water (W/O/W) insulin emulsions with a concentration of 100 U/ml of insulin were prepared, and the possible absorption of insulin in emulsion form was examined. The following results were obtained: W/O/W insulin emulsions were quite resistant to proteolytic enzymes in vitro. In the presence of pancreatic lipase, however, W/O/W insulin emulsion gradually lost its activity by the action of proteolytic enzymes. When administered to the jejunum at doses over 10 U/kg, a significant and consistent increase in plasma insulin was observed, followed by a fall in blood glucose. The infusion of W/O/W insulin emulsions into the jejunum was three to four times more effective than the administration of aqueous insulin. Insulin, when administered to the stomach, did not cause hypoglycemia at doses up to 150 U/kg. When W/O/W insulin emulsions were administered orally, on the other hand, definite responses were observed in 3 out of 7 rabbits with 100 U/kg and in 4 out of 7 rabbits with 150 U/kg. For developing an effective method for oral administration of insulin, the present results indicate a possible means of protecting insulin molecule from proteolytic destruction, and of facilitating intestinal absorption of insulin.

Hemoperfusion, rate of oxygen consumption and redox levels of mitochondrial cytochrome c (+c1) in liver in situ of anesthetized rat measured by reflectance spectrophotometry

Utilizing reflectance spectrophotometry, hemoperfusion, rate of oxygen consumption and redox level of mitochondrial cytochrome c (+c1) in livers in situ of anesthetized rats were measured. The transition to the anoxic state was induced by raising the pressure on the liver surface to more than the hepatic blood pressure by pressing with the tip of the optical guide of the reflectance spectrophotometer. During this transition, the average oxygen saturation of hemoglobin in the liver in situ decreased linearly with time until it became 10--20% of the total. This was followed by reduction of mitochondrial cytochrome c (+c1), which reached completion in 10--20 s. The measured O2 consumption rate remained constant until the percentage of oxyhemoglobin in situ decreased to a critical level. There was then a decrease in the rate of O2 consumption which was accompanied by a progressive reduction of cytochrome c (+c1). It was shown that amounts of hemoglobin and mitochondrial respiratory chain cytochromes in the liver in situ could be measured non-invasively and could provide important signals for vital cellular functions. The changes in hemoperfusion and rate of O2 consumption of the liver in situ following ethanol ingestion were also shown in rats, and are briefly discussed with respect to possible application of this method to study the pathophysiology of tissues.

Short-Term Treatment of Alloxan-Diabetic Rats with Intrajejunal Administration of Water-in-Oil-in-Water Insulin Emulsions

Alloxan-diabetic rats with fasting blood glucose levels above 300 mg./100 ml. were treated with intrajejunal administration of water-in-oil-in-water (W/O/W) insulin emulsions via an indwelling catheter at a dose of either 25 or 50 U./100 gm. body weight, three times daily for five to fourteen days. The course of diabetes was followed by determinations of glucose levels in blood and urine. During treatment a significant reduction in urinary glucose levels was observed in all rats studied. In two rats treated with 25 U./100 gm., fasting blood glucose levels did not change significantly. In four of five rats treated with 50 U./100 gm., W/O/W insulin emulsions significantly lessened hyperglycemia during treatment. Quantitative estimates suggested that the effectiveness of 50 U./100 gm. of intrajejunal W/O/W insulin emulsions was comparable to that after intramuscular regular insulin at doses between 1 and 2 U./100 gm. These results would indicate that diabetes can be controlled by enteral administration of insulin preparations.

Enhanced bioavailability of insulin after rectal administration with enamine as adjuvant in depancreatized dogs

Rectal absorption of insulin by depancreatized dogs was significantly enhanced by the coadministration of enamine as a suppository adjuvant and if this was followed by a further suppository containing enamine alone, the insulin absorption was even further enhanced. The additional enamine suppository resulted in high serum insulin concentrations for a longer time and effected a significant decrease in serum glucose concentrations. To decrease serum glucose concentrations effectively in depancreatized dogs, serum insulin levels had to remain high for a long period of time, rather than be transient.

Insulin suppository: enhanced rectal absorption of insulin using an enamine derivative as a new promoter

basic solution. One of the major degradation products of triamcinolone in basic media is the D-homosteroid I11 (Timmins & Gray, unpublished observations) and this reaction is therefore not dependent on an enolization step. D-homosteroids were not observed as major degradation products of triamcinolone acetonide. In summary, it may be seen that in neutral and basic media the presence of the acetonide function stabilizes the steroid ketal in comparison with the parent 1601hydroxysteroid, preventing hydroxide ion-catalysed decomposition to the D-homosteroid. Below pH 7 the shape of the pH-rate profile for the steroid ketal is almost identical to that for the parent 1601-hydroxy steroid. The shape of the pH-rate profile for the steroid ketal can be explained in terms of enol formation ionization of the enol whereas this has little influence on the decomposition of the parent 16a-hydroxysteroid. The decomposition of the steroid ketal thus parallels that of steroids possessing no C16 hydroxyl such as hydrocortisone.

High frequency of class 3 allele in the human insulin gene in Japanese Type 2 (non-insulin-dependent) diabetic patients with a family history of diabetes

SummaryThe restriction fragment length polymorphism in the 5′ flanking region of the human insulin gene was studied in 155 nonobese Japanese subjects. The subjects consisted of 36 Type 2 (non-insulin-dependent) diabetic patients with a family history of diabetes mellitus, 42 Type 2 diabetic patients without a family history of diabetes, 42 Type 1 (insulin-dependent) diabetic patients, and 35 healthy volunteers who served as control subjects. It was demonstrated that, in Japanese healthy subjects and diabetic patients, the incidence of the insertion into 5′ flanking region of the insulin gene was found to be significantly lower (p<0.05) than those in Caucasians and other races already investigated. Even though the class 3 gene allelic frequency in Type 2 diabetic patients without a family history of diabetes (0.060) was not higher than that in healthy subjects (0.014), in nonobese Type 2 diabetic patients with a family history of diabetes the allelic frequency of the inserted class 3 gene (0.111) was found to be significantly higher (p<0.02) than that in control subjects. These data suggest that the insulin gene polymorphism relates to the aetiology of diabetes mellitus.

Increased intestinal absorption of insulin in a micellar solution: Water-in-oil-in-water insulin micelles

SummaryWater-in-oil-in-water (W/O/W) insulin micelles were prepared, and the possibility of insulin absorption in a micellar form was examined. In this preparation, insulin was trapped in oil droplets of oleic acid in glyceryl-α-monooleate. (1) W/O/W insulin micelles were absorbed from the ligated jejunal loop of rabbits to the order of 12.3 to 58.5% of the dose given (10 U/kg body weight) during the 3-h experimental period. (2) Alloxan diabetic rats were treated with intrajejunal administration of W/O/W insulin micelles at a dosage of either 25 or 50 U/100 g body weight, three times daily for as longs as 14 days. During treatment, a significant reduction in the daily excretion of urinary glucose was observed, concomitant with a decrease in fasting blood glucose. Quantitative estimates suggested that the effectiveness of 25 U/100 g of intrajejunal W/O/W insulin micelles was comparable to that of regular insulin at a dosage of 1 U/100 g i.m. These results would indicate that W/O/W insulin micelles, when given enterally, are more effective in lowering blood and urinary glucose levels than W/O/W insulin emulsions in which insulin was trapped in oil droplets of triglyceride.

Radioselenium pancreozymin-secretin test as a clinical test for pancreatic exocrine function

The appearance of radioselenium in the protein fraction of duodenal aspirates has been studied after an intravenous injection of75Se-selenomethionine. The continuous flow of pancreatic juice was stimulated by pancreozymin at 120 minutes and by secretin at 140 minutes. A good distinction between normal subjects and patients with pancreatic disease was obtained by measuring75Se-radioactivity in the protein fraction of duodenal aspirates; either cumulative radioactivity during the combined 80-minute post-pancreozymin-secretin period, or maximum75Se-specific activity during the postsecretin period was used as an index. The test presented here might be a useful and sufficiently reliable method for detecting abnormal pancreatic exocrine function. This test can be performed along with the conventional pancreozymin-secretin test, serum enzyme response to pancreozymin and secretin, and pancreatic scintiscanning.