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Biomedical subjects

L Petit

Publications and source records attributed to L Petit.

At least 73 records · Page 4Linked to original sources
PubMed1992

[Measurement of mitral flow at the extremity of the valves. Validation of a simplified method based on 101 cases].

The measurement of cardiac output at the extremity of the mitral cusps, by Doppler-echocardiography, is of fundamental value, in particular for the evaluation of valve regurgitation. However, it comes up against a theoretical difficulty resulting from constant variation in the surface area of this orifice during diastole. After reviewing the main measurement methods available in the literature, a simplified method based upon the diameter of the ring and calculation of a mean diastolic intercusp distance by TM is suggested. Evaluation of this technique in 101 patients free of valve of leak showed its feasibility to be close to 100% and the correlation with aortic (r = 0.90), pulmonary (r = 0.91) and mitral ring (r = 0.88) outputs was entirely satisfactory. Our method would thus seem to be a good compromise between digitalised integration methods for the measurement of mitral surface area--optimal but complex--and the aim of simplification compatible with routine clinical use.

Adult↗
PubMed1982

[Toxic effects of nitrosamines with respect to marine organisms].

Nitrosamins present in the aquatic medium are considered as carcinogenic substances to the laboratory animals. This experimentation has for object to precise toxicity effects of the nitroso-compounds: nitrosodimethyllamine (NDMA) on two phytoplankton cultures, and on the common mussels. The addition of NDMA to the seawater of aquarium, in particular experimental conditions induces toxicity effects on the growth and behavior of phytoplanktonic cultures and of the common mussels: Mytilus edulis (tissus modification, and attack of some organs).

Animals↗
PubMed1976

[A new synthesis of delta 9-tetrahydrocannabinol].

The authors effected the synthesis of delta9-tetrahydrocannabinol (delta9-THC) by first preparing the raw materials: olivetol and p-menthadiene-2.8 ol-1. Then these two reactants were put into contact in the presence of p-toluene sulphonic acid to give the isomer delta8-THC which was converted into the isomer delta9-THC.

Dealkylation↗
PubMedDate not supplied

Polymorphism and signalling of melatonin receptors.

Melatonin receptors belong to the superfamily of G protein-coupled receptors. Cloning of Mel1c receptors expressed in Xenopus skin revealed the existence of a polymorphism for these receptors. Heterologous expression of the two allelic isoforms, called Mel1c(alpha) and Mel1c(beta), indicated functional differences in their signalling properties. Both isoforms are coupled to the cAMP and cGMP pathways. However, the alpha isoform is preferentially coupled to the cAMP pathway, whereas the beta isoform couples preferentially to the cGMP pathway. Coupling differences may be explained by the fact that five of the six amino acid substitutions between the two isoforms are localized within intracellular receptor regions potentially involved in G protein coupling. Allelic isoforms were also observed for Mel1a receptors expressed in ovine pars tuberalis, suggesting that polymorphism is a general feature of the melatonin receptor family. We also evaluated the potential of the two human melatonin receptor subtypes, Mel1a and Mel1b, to modulate the cGMP pathway. Melatonin inhibited intracellular cGMP levels in a dose-dependent manner in HEK293 cells transfected with the human Mel1b receptor. This was not the case for HEK293 cells transfected with the human Mel1a receptor. In conclusion, our results indicate that the expression of receptor subtypes and isoforms may permit differential signalling between melatonin receptors.

1-Methyl-3-isobutylxanthine↗