Biomedical subjects

P Perreault

Publications and source records attributed to P Perreault.

23 records · Page 2Linked to original sources

PubMed1988

A depolarizing inhibitory postsynaptic potential activated by synaptically released gamma-aminobutyric acid under physiological conditions in rat hippocampal pyramidal cells.

We report that CA1 pyramidal neurons of the rat hippocampus respond to high intensity afferent stimulation by generating a late depolarizing potential that typically occurs between the early (fast) inhibitory postsynaptic potential (IPSP) and the late (slow) IPSP. This potential is reminiscent of the response seen after the application of 4-aminopyridine and can be blocked by bicuculline, indicating that GABAA receptors are involved in its generation.

4-Aminopyridine↗

PubMed1987

A GABAergic depolarizing potential in the hippocampus disclosed by the convulsant 4-aminopyridine.

Intracellular recordings from hippocampal pyramidal cells in the CA1 subfield of the 'in vitro' slice in the presence of 4-aminopyridine (4-AP, 5-50 microM) revealed a long-lasting (up to 1.5 s) depolarizing potential which occurred either spontaneously or following orthodromic stimulation. This potential was: capable of blocking both direct and synaptic activation of the cell; sensitive to bath application of low concentrations of bicuculline methiodide; and associated to an extracellular current sink in the dendrites as suggested by the extracellular field potentials recorded at different levels along an axis perpendicular to the stratum pyramidale. It is concluded that the long-lasting depolarizing potential evoked by 4-AP is caused by the activation of GABA receptors localized in the dendritic region of the CA1 subfield.

4-Aminopyridine↗

PubMedDate not supplied

Usefulness of transjugular intrahepatic portosystemic shunt in the management of bleeding ectopic varices in cirrhotic patients.

PURPOSE: To evaluate the safety and efficacy of transjugular intrahepatic portosystemic shunt (TIPS) in the control of bleeding from ectopic varices. METHODS: From 1995 to 2004, 24 cirrhotic patients, bleeding from ectopic varices, mean age 54.5 years (range 15-76 years), were treated by TIPS. The etiology of cirrhosis was alcoholic in 13 patients and nonalcoholic in 11 patients. The location of the varices was duodenal (n = 5), stomal (n = 8), ileocolic (n = 6), anorectal (n = 3), umbilical (n = 1), and peritoneal (n = 1). RESULTS: TIPS controlled the bleeding in all patients and induced a decrease in the portacaval gradient from 19.7 +/- 5.4 to 6.4 +/- 3.1 mmHg. Postoperative complications included self-limited intra-abdominal bleeding (n = 2), self-limited hemobilia (n = 1), acute thrombosis of the shunt (n = 1), and bile leak treated by a covered stent (n = 1). Median follow-up was 592 days (range 28-2482 days). Rebleeding occurred in 6 patients. In 2 cases rebleeding was observed despite a post-TIPS portacaval gradient lower than 12 mmHg and was controlled by variceal embolization; 1 patient underwent surgical portacaval shunt and never rebled; in 3 patients rebleeding was related to TIPS stenosis and treated with shunt dilatation with addition of a new stent. The cumulative rate of rebleeding was 23% and 31% at 1 and 2 years, respectively. One- and 2-year survival rates were 80% and 76%, respectively. CONCLUSION: The present series demonstrates that bleeding from ectopic varices, a challenging clinical problem, can be managed safely by TIPS placement with low rebleeding and good survival rates.

Adolescent↗

PubMedDate not supplied

Failure of the antiepileptic drug valproic acid to modify synaptic and non-synaptic responses of CA1 hippocampal pyramidal cells maintained 'in vitro'.

The mechanisms of action of the antiepileptic drug valproic acid (VPA) were analyzed in 24 CA1 pyramidal neurons of the 'in vitro' hippocampal slice by using standard intracellular recording techniques. VPA (0.5-2 mM) failed to induce any significant change in the amplitude of the orthodromic EPSPs and the amplitude and duration of the IPSPs evoked by orthodromic or antidromic stimuli. The repetitive firing induced by depolarizing current pulses and the subsequent long lasting afterhyperpolarization were also not affected by VPA. We conclude that VPA, at doses within the therapeutic range, does not potentiate GABA-mediated inhibition in this preparation and probably acts on mechanisms which are not operating or fully expressed in normal (i.e., non-epileptic) situations.

Action Potentials↗

PubMedDate not supplied

Value of CT fluoroscopy for percutaneous biopsy procedures.

PURPOSE: To assess the clinical impact of computed tomographic (CT) fluoroscopy (CTF) with regard to procedure time and success rate for CT image-guided biopsy procedures. MATERIALS AND METHODS: One hundred ninety consecutive patients referred to the same radiologist underwent biopsy procedures performed with use of a CT scanner equipped with fluoroscopic capabilities during a 15-month period. CTF procedures were performed predominantly by means of a continuous fluoroscopic technique, with typical exposure factors of 50 mA at 120 kV and a slice thickness of 10 mm. The total procedure time, fluoroscopy time, and complication and procedure success rates were documented prospectively in this group. A control group consisted of retrospective analysis of 93 consecutive patients who had undergone a classic CT-guided procedure performed by the same radiologist. RESULTS: Procedure success rate was increased in the CTF group (93.7 versus 88.2%), although the difference was not statistically significant (P > .05: Fisher exact test). A statistically significant difference was noted when comparing mean procedure times (CTF, 27.56 minutes; range, 20-60 minutes versus control, 43.17 minutes; range, 35-80 minutes; P < .0001; Welch unpaired t test). CONCLUSION: CT fluoroscopy facilitates CT-guided biopsy procedures by allowing visualization of the needle trajectory from skin entry to the target point, allowing procedures to be performed more rapidly and efficiently.

Adolescent↗