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G Le Breton

Publications and source records attributed to G Le Breton.

15 recordsLinked to original sources
PubMed1995

Endothelin-3 reduces Ca(2+)-uptake and Ca2+ content of platelet internal stores.

In stimulated platelets, endothelin-3 (ET-3) has been previously shown to attenuate Ca2+ mobilization. Using the calcium indicator chlortetracycline, the present study demonstrates that 0.5 microM ET-3 produced a 24% reduction in the Ca2+ pool mobilized by A23187. ET-3 up to 1 microM dose-dependently decreased the initial velocity and steady state value of 45Ca(2+)-uptake into platelet membrane vesicules (p < 0.001). In addition, ET-3 partially reversed the inhibitory effects of half maximally effective concentrations of thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydroquinone, two specific inhibitors of the sarco/endoplasmic reticulum Ca(2+)-ATPases. These results suggest that ET-3 is functionally coupled to Ca(2+)-pumps of the dense tubular system. Based on these findings, we propose that ET-3 decreases the activity of Ca(2+)-pumps in the dense tubular system which accumulates less Ca2+, leading to lowered Ca2+ release in response to agonists.

Analysis of Variance↗
PubMed1995

Endothelin-3 decreases Ca2+ uptake in platelet membrane vesicles.

To analyze the mechanisms by which endothelin-3 (ET-3) attenuates agonist-mediated Ca2+ mobilization from an internal pool, we investigated ET-3 effects on 45Ca2+ uptake in platelet membrane vesicles. They were compared to those of thapsigargin (Tg), a specific inhibitor of the dense tubule Ca2+ pumps. In the absence of ATP, ET-3 up to 1 microM did not affect the amount of Ca2+ bound to membrane sites. In the presence of ATP, ET-3 dose-dependently reduced the initial rate and the extent of Ca2+ uptake (p < 0.001). In comparison, Tg dose-dependently inhibited both the ATP-independent Ca2+ binding (p < 0.001) and the ATP-dependent Ca2+ accumulation (p < 0.001), with half-maximal effects at 7 nM. Pretreatment with 1 microM ET-3 decreased the inhibitory effect of 10 nM Tg, but only on the initial rate of ATP-dependent Ca2+ uptake (p = 0.04; n = 6). These results indicate that ET-3 is functionally coupled to Ca(2+)-ATPases of the dense tubules. Its inhibitory effects are probably due to inhibition of the catalytic cycle of the Ca2+ pumps. Such inhibition could lead to a depletion of Ca2+ stores and therefore to reduced Ca2+ release in response to agonists.

Adenosine Triphosphate↗
PubMed1993

Lingual paresthesia following surgical placement of implants: report of a case.

Lingual paresthesia following the surgical placement of implants does not occur frequently. When it does occur, a serious problem may result for the practitioner, especially if the patient has not been informed of the risk before surgery. This report emphasizes the importance of practitioner experience and competence. It also addresses the need for knowledge of the course of the lingual nerve and preoperative planning of implant placement in the mandible.

Adult↗
PubMed1989

Increased membrane-bound calcium in platelets of hypertensive patients.

The fluorescent indicator chlortetracycline was used to estimate membrane-bound calcium in mild, untreated hypertensive patients (n = 39) and normotensive controls (n = 42). All participants were black. After incubation with chlortetracycline, platelet-rich plasma was centrifuged into a pellet and fluorescence was measured with a microspectrofluorometer. At an interval of 45 minutes mean fluorescence values were 11% higher in the hypertensive than in the normotensive group (567 +/- 95 vs. 512 +/- 100 counts/sec, p less than 0.02). With both groups of participants combined, a correlation of borderline statistical significance was noted between diastolic blood pressure and chlortetracycline fluorescence (r = 0.213, p = 0.056). In parallel experiments, sodium and potassium concentrations were measured in red blood cells. Intracellular sodium was also significantly higher in the hypertensive group (p less than 0.01). These data indicate that the total cell burden of calcium is increased in the platelets of hypertensive individuals, possibly a result of abnormal cell metabolism of calcium, and further suggest that circulating platelets in hypertensive individuals may be in a hyperaggregable state.

Adult↗
PubMedDate not supplied

[Hemostatic pastes].

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Dental Care for Persons with Disabilities↗