Détermination de constantes d'acidité d'amidines N-N′-substituées. Relations entre les pKA et les vibrations IR — I. Acétamidines et métacrylamidines

Changes in the ultraviolet absorption spectra with pH in aqueous solution were used to determine the pK_A values of amidines. A new mathematical procedure was used to study sparingly soluble compounds. In this technique, all the experimental data are used to solve for the absorbance of the insoluble basic species and for the pK_A value by a ‘complex method’ of optimization, which is more general than the classical least-squares method. A relationship between a double bond vibration frequency and the acidity constants of these compounds has been demonstrated.     

Binding, internalization, and degradation of insulin in vascular endothelial cells

The interaction of insulin with the vascular endothelium was studied using bovine aortic endothelial cells in monolayer cultures. Confluent cell cultures exhibited specific binding of 125I-insulin to high- and low-affinity cell surface receptor sites. Binding was reversible, saturable, and accompanied by internalization and degradation of the bound hormone in a temperature- and time-dependent manner. Pre-exposure of the cultures to insulin resulted in a time-dependent reduction in the availability of cell surface receptors (downregulation). It is concluded that the occurrence of reversible insulin binding and of insulin degradation in endothelial cells supports the concept that the vascular endothelium compartment may regulate the level of insulin in the circulation.     

In Loco Parentis: Minimal Risk as an Ethical Threshold for Research upon Children

To what risks may children participating in research be subjected? Institutional review boards can stand surrogate for parents by filtering out studies whose risk is unacceptably high.     

Randomized study of cyclophosphamide, doxorubicin, and etoposide (VP16-213) with or without cisplatinum in non-small cell lung cancer

Sixty-eight patients with non-small cell lung cancer were treated in a prospectively randomized study with cyclophosphamide, doxorubicin (Adriamycin), and etoposide (VP16-213) with cisplatinum (CAE +/- P). Response rate, time to progression, and survival of CAE-P treated patients were each superior compared to those of patients who received CAE therapy. Of 36 patients, 10 (4 complete remissions, 6 partial remissions) responded to CAE-P and of 29 patients 3 (1 complete remission, 2 partial remissions) responded to CAE (p = 0.073). The median time to treatment failure was 22.9 wk for the CAE-P regimen and 15.0 wk for CAE (p = 0.032). The median survival for patients treated on the regimen with and without cisplatinum was 34.5 and 22.5 wk, respectively (p = 0.04). There were two CAE-P and one CAE drug-related deaths. Toxic effects were more severe in the CAE-P regimen. The addition of cisplatinum to the CAE combination produced an increase in response rate with significant prolongation in both time to progression and survival, but did add morbidity. These results suggest that the combined use of cisplatinum with at least one of the chemotherapeutic agents in the CAE regimen is synergistic.     

The effects of ionizing irradiation on production of thromboxane and prostacyclin by the isolated perfused rat kidney

Exposure to whole body radiation is associated with prompt changes in urinary excretion of prostaglandins. We investigated the separate effects of radiation on rat kidney capillary and tubular system prostaglandin synthesis. Animals were irradiated to the left kidney area with a single dose of 15 Gy. One week later the rats were anesthesized, the renal artery, vein and ureter of the left kidney cannulated, and the kidney removed and perfused with Krebs-Henseleit physiological buffer at a rate of 10-12 ml/min. Effluent fluids were collected separately from the renal vein and from the ureter of irradiated and control (operated sham-irradiated animals) and were assayed by radioimmunoassays for thromboxane A2 (TXB2) and prostacyclin (6 keto PGF1 alpha). Histological examination of the irradiated kidneys showed no significant changes, and electron microscopy revealed minimal interstitial edema. In contrast to these minimal changes, TXB2 assays showed a significant increase both in the venous and ureter effluents. Following stimulation with angiotensin II in the perfusate, a further significant increase in TXB2 production was observed both by the capillary and the tubular systems. With 6 Keto PGF1 a slightly different response was seen. The basal production was increased only in the ureter effluent of the irradiated animals, while there were no changes in the release in the venous effluents. In parallel, radiation significantly increased the angiotensin II stimulated production capacity of prostacyclin by the tubular system. The response of the capillary system following irradiation may create imbalance between these two important substances and lead to the radiation effects in the renal tissue.