[Alternatives to radiography for determining root canal length]. / Quelle alternative a la radiographie dans la determination de la longueur canalaire?

Location of the apical foramen using an electronic apex locator to determine working length is more accurate than using radiographs alone. The Neosono Co-pilote is not adversely affected by the presence of sodium hypochlorite and gives us acceptable results in dry canals. Hence, it is today possible to realize endodontic treatment without X ray determination.

Metabolism of 14C-moxisylyte in hairless rat. Comparison between intravenous and oral route.

The pharmacokinetics of 14C-thymoxamine (4-(2-dimethylaminoethoxy)-5- isopropyl-2-methyl phenyl acetate hydrochloride) (moxisylyte, Carlytène) was studied on female hairless rats. Animals received 5 mg/kg of thymoxamine-HCl (CAS 964-52-3) intravenously or orally. 14C-thymoxamine was both rapidly and entirely absorbed after oral administration, Tmax value was observed at 0.25 h. The decrease of the total radioactivity followed a biexponential mode. After intravenous and oral administration, the apparent half-live of distribution were 0.20 and 0.31 h, respectively, whereas the apparent half-live of elimination were 9.6 (i.v.) and 8 h (p.o.). The nature and proportions of thymoxamine metabolites recovered in the plasma varied according to the route of administration. After intravenous administration, desacetyl-thymoxamine (DAT) + desacetyl-desmethyl-thymoxamine (DMAT), sulphate conjugates and glucuronides of DAT + DMAT represented 12, 21 and 63%, respectively. After oral administration, the values were 0, 21 and 79%, respectively. These results underlined the importance of the hepatic first-past effect which induced the disappearance of DAT and DMAT, and increased the levels of glucuronides when thymoxamine was orally administered. The level of sulphate conjugates for DAT and DMAT seems always constant.

Comparison of thymoxamine permeation between hairless rat and horse penile mucous membrane using an in vitro diffusion model.

Moxisylyte (or thymoxamine) administered intracavernously is known to improve erection in organically impotent patients. Prior to drug administration by percutaneous route, we have to define its in vitro permeation parameters after application of thymoxamine on both rat skin and horse penile mucous membrane. 24 h after drug application, the percentages of thymoxamine which diffused through the penile mucous and the rat skin were 88 and 75%, respectively. Thymoxamine flux varied according to the biological membrane tested. With regard to the penile mucous membrane, a maximal flux (1,774 nmol.h-1.cm-2) was observed 2.5 h after drug application, whereas for the rat skin a maximal flux (657 nmol.h-1.cm-2) was noted at 3.5 h. Thymoxamine flux decreased rapidly in the penile mucous membrane. This decrease was slower when thymoxamine penetrated the rat skin; the difference could be due to a different morphology of the tested biological membranes. In contrast to the rat skin, the external keratinized layer was absent in the penile mucous membrane. In conclusion, the ability of thymoxamine to penetrate easily and rapidly the biological membrane, and particularly the penile mucous membrane, suggests that thymoxamine could reach the pharmacological target represented by the corpus cavernosum of the penis.

Pharmacokinetic study of fentiazac and its main metabolite hydroxyfentiazac in the elderly.

The pharmacokinetics of fentiazac (F, CAS 18046-21-4) and hydroxyfentiazac (OH-F) were estimated in 12 elderly (> 76 years). After an oral single dose of 200 mg F, the plasma and urine profiles were determined using high-performance liquid chromatography with a fluorescence detection. When compared to results obtained in young adults, the maximum plasma concentrations (5.4 +/- 1.9 mg/l) and-the time to reach them were identical. The terminal half-life (7.0 +/- 9.1 h) was longer, due to a slight increase of the apparent volume of distribution and a decrease of the elimination clearance. The findings suggest that the dosage regimen of this drug should be decreased in the elderly. Moreover, the variability of the pharmacokinetics being larger, individual adaptation of the daily dose should be performed.

Viability and primary culture of rat hepatocytes after hypothermic preservation: the superiority of the Leibovitz medium over the University of Wisconsin solution for cold storage.

Hepatocytes isolated from adult rat livers were hypothermically preserved for 24 or 48 hr before being plated under conventional culture conditions. They were stored either in the Leibovitz medium, a cell culture medium with and without polyethylene glycol (PEG), a compound known to suppress ischemia-induced cell swelling, or in the University of Wisconsin solution, the most effective solution for cold organ preservation. After 24 or 48 hr of storage at 4.5 degrees C in Leibovitz medium, cell viability and adherence efficiency to plastic dish, were only slightly reduced, whereas University of Wisconsin hepatocytes had a decreased viability and (especially after 48-hr storage) lost their adhesion ability; they did not survive in vitro. The metabolic competence of hepatocytes maintained in Leibovitz medium was retained over the 3 days of culture, as shown by low extracellular levels of the membrane-bound and cytosolic hepatic enzymes, as well as by intracellular glutathione content, albumin secretion rate and several phase I and phase II drug metabolic reactions very close to those found with fresh hepatocytes maintained under similar culture conditions. Addition of polyethylene glycol to the Leibovitz medium resulted in slightly higher viability and function of hepatocytes after cold storage. These results clearly demonstrate that viability of a transplanted liver does not correlate with long-term in vitro viability of isolated hepatocytes after hypothermic preservation in University of Wisconsin solution. They also suggest that nutritional and energy substrates as found in the Leibovitz medium are probably required to define a suitable solution for cold preservation of isolated parenchymal cells. The findings with Leibovitz medium favor the conclusion that hypothermically preserved hepatocytes could be used for various metabolic studies and for the treatment of liver insufficiency.

Use of cryopreserved animal and human hepatocytes for cytotoxicity studies.

To evaluate the potential use of cryopreserved hepatocytes for toxicological studies, rat, dog and human hepatocytes were frozen in Leibovitz medium containing 20% foetal calf serum and various concentrations of dimethylsulphoxide and stored in liquid nitrogen. 50% or more of the hepatocytes that attached and survived immediately after isolation still possessed these properties after freezing/thawing. Thawed hepatocytes from the three species showed only a slight reduction in their ability to metabolize phenacetin or to conjugate paracetamol with glucuronic acid. Sensitivity to the toxic effects of erythromycin was not affected by the MTT and neutral red assays. Similar observations were made with rat hepatocytes for five other toxic agents-chloramphenicol, chlorpromazine, acrylamide, chloroquine sulphate and p-chloromercuribenzoic acid. These results suggest that, after cryopreservation, isolated hepatocytes represent a suitable model for drug metabolism and toxicity screening studies.

Metabolism of amineptine in rat, dog and man.

After oral administration of amineptine (7-[(10-11)-dihydro-5H-dibenzo(a,d)cycloheptane-5yl] amino heptanoic acid), an original tricyclic antidepressant, seven metabolites were isolated from urine and plasma of rat, dog and man. The metabolic pathways were similar for the three species studied. The two major pathways consisted of the beta-oxidation of the heptanoic side chain leading to pentanoic (first step) and propanoic (second step) side chain metabolites and the hydroxylation of the dibenzocycloheptyl ring on carbon atom 10 (C10) causing the formation of two diastereoisomers. Lactamization by internal dehydration of beta-oxidized metabolites appeared to be a minor route of biotransformation. Conjugation reactions were of minor importance in the rat, in contrast to findings for dog and man. Urinary elimination was the major route of excretion in man while in dog and in rat faecal excretion was predominant.

The metabolic pathways of tianeptine, a new antidepressant, in healthy volunteers.

The metabolism of tianeptine, a novel antidepressant that presents original neurochemical properties, was studied after a single oral administration of radioisotopically (14C) labeled compound to six healthy male volunteers. After 7 days, approximately 66% of the dose was eliminated by renal excretion (55% during the first 24 hr). Tianeptine is extensively metabolized, and 24 hr after the administration, the unchanged molecule contributed in urine for less than 3% of the administered dose. Chromatographic and mass spectral studies showed that beta-oxidation of the amino acid side chain is the major route of biotransformation for tianeptine. Three major metabolites, accounting for 29% of the dose, were products of beta-oxidation. The metabolite profiles of tianeptine in feces and plasma were qualitatively similar to that in urine.

Interspecies comparison of the metabolic pathways of perindopril, a new angiotensin-converting enzyme (ACE) inhibitor.

1. The metabolism of perindopril (non-thiol angiotensin-converting enzyme inhibitor) was studied in rat, dog and monkey after single oral and i.v. administration of 14C-perindopril, and in man after a single oral dose. 2. Six biotransformation products of perindopril from urine, faecal and plasma samples (bile only for rats) were identified. 3. The main route of biotransformation in all species is the hydrolysis of the carboxylic ethyl ester side-chain, with the formation of perindoprilate, the active metabolite. 4. A minor route of biotransformation led to the acyl glucuronides of perindopril and perindoprilate. 5. Internal dehydration of perindopril and perindoprilate into cyclic lactam structures occurs. This route of metabolism is of minor importance except in humans.

Use of hepatocyte cultures for preliminary metabolism and cytotoxicity studies of a new anti-hypertensive agent, oxaminozoline.

1. Adult rat hepatocytes co-cultured with rat liver epithelial cells were used to evaluate chronic cytotoxicity of a new alpha 2 agonist, oxaminozoline (S-3341-3) compared to that of clonidine. The same maximum non-toxic concentration (25 micrograms per ml of medium) was found for both drugs after a daily treatment for 12 days. 2. Oxaminozoline metabolism was analysed in short-term hepatocyte cultures. Four metabolites resulting from oxidation or hydrolysis of the parent drug were identified. Three of the metabolites were identical to those reported in vivo. The presence of an additional minor metabolite in culture may be due to the higher metabolic rate of the drug in this model system.

In vivo uptake of polyisobutyl cyanoacrylate nanoparticles by rat liver Kupffer, endothelial, and parenchymal cells.

Polyalkyl cyanoacrylate nanoparticles were previously developed as a biodegradable, ultrafine, solid drug carrier. Distribution studies in the rat showed an intense and rapid hepatic uptake. This liver accumulation appears to represent, to a certain extent, extracellularly bound nanoparticles. During liver perfusion, 15-20% of the liver-associated nanoparticles were washed out. The cellular distribution of strongly cell-associated nanoparticles was determined. At different intervals after injection of radioactive nanoparticles to rats, the cells were isolated according to a recently developed, low-temperature procedure during which processing of the carrier was inhibited. At all tested times, a relatively intense capture by Kupffer cells in comparison with endothelial and especially parenchymal cells was observed. This distribution pattern was not influenced by the size of the nanoparticles (0.08-0.215-micron diameter). This specific interaction of nanoparticles with Kupffer cells opens possibilities for the treatment of some parasitic diseases involving this cell type.