Creatinine concentration measurement in glucose based peritoneal dialysate.

The measurement of creatinine concentrations in peritoneal dialysate is important for evaluating the effectiveness of peritoneal dialysis treatment. However, peritoneal dialysate often contains glucose, which has been reported to interfere with the measurement of creatinine concentrations in some creatinine assays. In this study creatinine concentrations in solutions containing increasing glucose concentrations (0-250 mmol/L) were evaluated using an enzymatic method. No relevant interference from glucose was observed. The creatinine concentration recovery percentages at creatinine concentrations of 250, 500, and 750 micromol/L in dialysate samples containing 250 mmol/L glucose were 101.9%, 101.6%, and 101.0%, respectively, and 101.64%, 102.2%, and 99.8%, in water samples (0 mmol/L glucose). The measured creatinine concentrations in dialysate samples at constant glucose concentrations were linear at 0-1071 micromol/L creatinine, and the linear regression coefficient was 0.99. It is concluded that the enzymatic method described is reliable in measuring creatinine concentrations in dialysate containing glucose, and that the method can be used to evaluate the effectiveness of peritoneal dialysis treatment.

Digitoxigenin, a digitalis steroid, induces meiotic maturation of Xenopus laevis oocytes.

Digitoxigenin, a C23 digitalis steroid induces meiotic maturation of Xenopus oocyte. The dose of digitoxigenin which induces half maximal response is 3.3 +/- 2.10(-5)M. In contrast the conjugated digitalis steroid, digitoxin (digitoxigenine + 3 digitoxoses) never triggered maturation at any of the doses tested. These experiments which show that only free digitoxigenin mimics progesterone action, suggest that both digitoxigenin and progesterone possess a common initial site of action which is not localized at the level of the outer leaflet of the oocyte plasma membrane.

Sodium channels induced by depolarization of the Xenopus laevis oocyte.

An electrically gated Na+ channel can be made to appear in the membrane of the Xenopus laevis oocyte by simple depolarization. This membrane normally responds passively to imposed transmembrane currents with resting potentials around -60 mV, but when it is held depolarized to more than about +30 mV it becomes possible to obtain long-lasting regenerative depolarizations up to +80 mV; these depolarizations can last as long as 20 min. This potential is due to an "induction" of a Na+-dependent channel that is electrically gated open and closed. Its threshold for opening is about -20 mV and it is selective for Na+ over Cs+ and choline+ but is blocked by relatively small quantities of Li+. When a long voltage clamp step to a positive potential under ENa (+70 to +90 mV) is applied, an inward current is observed for many minutes, implying that this channel does not have an inactivation mechanism. The inward Na+ current is blocked by 0.50 mM tetrodotoxin. When the membrane is held at or near resting potential, the excitability will disappear with time, but it can be made to reappear by again depolarizing the membrane.

[Urinary N-acetyl-beta-glucosaminidase as index of renal toxicity (author's transl)]. / N-Acétyl-beta-glucosaminidase urinaire et toxicité rénale.

Urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) has been studied in rats submitted to potentially nephrotoxic drugs (acetylsalicylic acid, gentamicin). Both drugs induced increase in NAG excretion which was reversible and dose-dependent. The date presented in this paper suggest that urinary NAG determination may have value as screening device for the study of nephrotoxic effects in experimental toxicology.

Electrical membrane properties of the Xenopus laevis oocyte during progesterone-induced meiotic maturation.

The membrane input resistance (R(m)), potential (E(m)), and capacitance (C(m)) of fully grown Xenopus oocytes removed from their follicles have been measured. Before hormonal maturation, R(m), E(m), and C(m) were found to be: 1.86 +/- 0.63 Momega, -49 +/- 17 mV, and 11.9 +/- 4.8 microF/cm2 of apparent surface area. Long-term recording from oocytes in the presence of 1 microM progesterone reveal that during early GVBD (germinal vesicle breakdown) the membrane potential depolarized to about -10 mV, the apparent specific capacitance decreased to 1.5 to 3 microF/cm2, and the membrane resistance transiently increased by a factor of about 3. These results indicate that a decrease in surface area, a transient increase in membrane resistance, and a change in the ionic mechanisms for the membrane potential occur during progesterone-induced meiotic maturation. The continuous monitoring of these parameters has further shown that the major changes occur at about 50 to 60% of the time from progesterone application to GVBD, and that at the sensitivities used, generally 1.25 mV/mm, no changes are seen immediately upon application of the hormone.

[Blood-brain barrier. II. Kinetics of distribution of 3H-parahydroxyamphetamine in brain structures after intravenous administration in the rat]. / Barriére hemato-encephalique II: Cinétique de distribution de la parahydroxyamphetamine 3H dans les structures du cerveau de rat aprés administration intraveineuse

Intravenously injected parahydroxyamphetamine hardly penetrates into the Central Nervous System, since, 5 minutes after injection, the tissue to plamsa concentration ratio for brain and cerebrospinal fluid amounts to 0,67 and 0,35 respectively. Its concentration in muscle is 5 times higher than in plasma. In the brain, the molecule is preferentialy taken up by the corpus striatum and the hypothalamus. Thus, parahydroxylation of amphetamine inhibits the penetration of the molecule into the brain and suppresses its cortical fixation. These characteristics could explain why this parahydroxylated amine has no psychotropic action.