In intact rats 16 h of fasting reduced the plasma insulin response to i.v. stimulation with either glucose, tolbutamide or glibenelamide by 50--80 %, without affecting the extractable insulin content of the pantreas. In subsequent studies with the isolated perfused rat panereas two distinct patterns of insulin release could be discerned during the secondary phase. In the fed state, glucose 1.5 mg/ml induced a more or less constant elevation of the insulin secretion rate over 30 rain (type I). At glucose concentrations of 2 and 3 mg/ml the release pattern was characterized by progressively increasing secretion rates (type II pattern). Infusion of tolbutamide (0.2 mg/ml) lowered the threshold for glueose stimulation and induced both patterns of secretion at lower glucose concentrations. Fasting for 24~ h caused a 70--80 % in-hibition of insulin secretion per 30 rain a~ glucose levels of 1.5 and. 2 mg/ml. Decreased glucose sensitivity was indicated by a shift to the right of the entire dose-response curve for glucose and by reduced inhibition (30 %) at a glucose level of 3 mg/ml. The effect of tolbutamide was also strongly diminished. The percent inhibition of the response to tolbutamide at different levels of glucose showed a pattern of inhibition similar to that observed with glucose alone. These findings suggest that the glucose-dependent release mechanism is highly sensitive to relatively short periods of fasting.

ABSTRACT. Using a sucrose and deuterium oxide dilution technique body water compartments and solids were serially determined in small for dates newborn infants at birth, at the moment of maximum postnatal weight loss and on recovery of birth weight. Compositions of weight loss and subsequent weight gain were calculated from the differences in body water compartments and solids between the first and the second and the second and the third study, respectively. Birth weight of the infants was 1.55 ± 0.46 kg (mean ± SD) (n=7). gestational age was 35.7 ± 3.1 weeks. Results show that despite changes in extra‐ and intracellular water volumes during weight loss, total body water volume and solids per unit of body weight remained remarkably constant throughout the study. Compositions of weight loss and subsequent weight gain were simlar to body composition. This suggests that in small for dates newborn infants postnatal weight loss is the result of catabolism rather than dehydration and subsequent weight gain is the result of growth rather than rehydration.

A new method for the spectrophotometric determination of Evans Blue in plasma is presented. The method is based on the precipitation of the non-albumin fraction of the plasma proteins with polyethylene glycol, in order to eliminate the variable background absorption of plasma at the wavelength of maximum absorbance of Evans Blue. The accuracy and precision of the method is excellent: at an Evans Blue concentration in plasma of 5 mg · 1 the coefficient of variation of the method is < 1 %. Five different procedures currently in use for the calculation of the plasma volume from the amount of indicator injected and the concentration at zero time (c 0 ) were compared. Extrapolation to zero time of the early part (10 to 60 min) of the log concentration vs time curve turned out to be the best method for the calculation of c 0 , and hence yields the best estimate of the plasma volume. Eine verbesserte Methode fur die Bestimmung des Plasmavolumens mit Evans BlueZusammenfassung: Eine neue Methode für die spektrophotometrische Bestimmung von Evans Blue wird beschrieben. Sie beruht auf der Fällung der Nicht-Albumin-Fraktion der Plasmaproteine mit Polyethylenglycol, um die variierende Untergrundabsorption von Plasma bei der Wellenlänge des Absorptionsmaximums von Evans Blue zu eliminieren. Richtigkeit und Genauigkeit der Methode sind hervorragend: bei einer Evans Blue-Konzentration von 5 mg/1 Plasma ist der Variationskoeffizient der Methode < 1%. Fünf verschiedene Verfahren, die gegenwärtig zur Ermittlung des Plasmavolumens aus der Menge an injiziertem Indikator und der Konzentration zum Zeitpunkt t = 0 (c 0 ) Verwendung finden, wurden verglichen. Extrapolation des frühen Teils (10-60 min) der log Konzentration gegen Zeit-Kurve auf die Zeit t = 0 erwies sich als die beste Methode für die Ermittlung von c 0 und ergibt deshalb den besten Wert für das Plasmavolumen.

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