The pathophysiology of radiocontrast agent-induced acute renal failure is presently unclear. To test for a possible direct deleterious effect of diatrizoate, a commonly used radiocontrast agent, on renal tubule cells, suspensions enriched in rabbit proximal tubule segments were incubated with sodium diatrizoate. After these manipulations, a variety of well-established metabolic parameters to quantitate the extent of cell injury were measured. Diatrizoate sodium (25 mM) produced significant declines in tubule K+, ATP, and total adenine nucleotide (TAN) contents, significant decreases in tubule basal and uncoupled respiratory rates, and a significant increase in tubule Ca2+ content, demonstrating the development of cell injury induced by diatrizoate. These effects were dose related and were progressive with increasing incubation time from 97.5 to 157.5 min. The effects of N-methylglucosamine (meglumine) on renal tubule cell viability was also evaluated. Meglumine is a low molecular weight amino-substituted cationic compound and is commonly added to radiocontrast dye solutions. Meglumine (25 mM) had significant effects to lower tubule K+ content and to decrease both tubule basal and uncoupled respiratory rates. These alterations were slightly additive to diatrizoate in that meglumine diatrizoate produced greater alterations in tubule-metabolic parameters compared to diatrizoate sodium. A period of 22.5 min of hypoxia also caused deleterious changes in each of these quantitative indices of cell viability, and diatrizoate potentiated the degree of hypoxia-induced cell injury. These results demonstrate that the radiocontrast agent, diatrizoate, is directly toxic to renal proximal tubule cells. Meglumine, a cation added to diatrizoate containing radiocontrast solutions, also had a moderate toxic effect on renal epithelial cells and added to the toxicity of diatrizoate. Diatrizoate also aggravated the degree of cell injury induced by a 22.5-min period of hypoxia. These experiments thus provide evidence for a direct toxic effect of diatrizoate on proximal renal tubule cells which was additive to hypoxic cell injury.

After a weight-maintaining diet base-line, obese female inpatients were provided with either a carbohydrate-restricted diet (827 kcal; 35% protein, 64% fat, 1% carbohydrate) or a carbohydrate-containing diet (827 kcal; 35% protein, 36% fat, 29% carbohydrate) for 6 wk. When compared with the psychological adjustment during the base-line diet, there was a temporary increase in appetite and a tendency toward dysphoric moods and attitudes during the 1st wk of both treatment diets. After adaptation to the treatment diets, appetite and other psychological states were similar to those during the pretreatment weight-maintaining diet. There was no support for the idea that a carbohydrate-free protein-supplemented fast decreases appetite and elevates mood in comparison with an isocaloric carbohydrate-containing diet. Thus, suppression of appetite alone does not appear to be sufficient reason in itself for using diets of this type.

The relative sweetness of fructose and sucrose was evaluated at various concentrations in distilled water, in citric acid solutions (pH = 2.35, and 3.0), in lemon flavored beverages (pH = 2.35 and 2.7), and in vanilla cake. In distilled water and in the less acidic beverage and citric acid solutions, magnitude estimates of sweetness revealed fructose to be sweeter than sucrose by a factor of 1.6-1.9 at lower sugar concentrations. However, the greater relative sweetness of fructose declined-with increasing sugar concentration. In the more acidic beverage and citric acid solutions, no difference in perceived gweetness between fructose and sucrose was fbund at any sugar concentration. Similarly, no difference in the perceived sweetness of the two sugars was found when each was used as a sweetener in vanilla cake. These data suggest that the greatest sweetening advantage of fructose over sucrose occurs at the lower concentrations of the two sugars: However, when used in certain beverages or foods, concomitant tastes may mask or mitigate this differential sweetness.

Two concentrations each of sodium chloride and sucrose solutions were used as stimuli in a study examining taste adaptation. Twenty subjects were presented a 3-min continuous flow of each taste stimulus over the anterior dorsal tongue surface, and periodically gave magnitude estimates of its intensity. The degree of adaptation was greater for the less concentrated solutions than for the more concentrated ones, but the majority of subjects did not adapt completely to any of the stimuli. This result, which is consistent with other reports from this laboratory, is discussed in terms of individual differences among subjects and in relation to recent taste research based on completely adapted subjects.

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