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Biomedical subjects

P Bonnet

Publications and source records attributed to P Bonnet.

At least 19 recordsLinked to original sources
PubMed1992

Diethylbenzene inhalation-induced electrophysiological deficits in peripheral nerves and changes in brainstem auditory evoked potentials in rats.

Motor and sensory conduction velocities (MCV and SCV), amplitude of the sensory action potential (ASAP) of the tail nerve and parameters of brainstem auditory evoked potentials (BAEP) were studied in male Sprague-Dawley rats after prolonged inhalation exposure to a commercial isomer mixture of diethylbenzene (DEB mixture) containing 6% 1,2-DEB. The MCV, SCV and ASAP were studied in one control group (10 rats) and three groups of 12 rats exposed to 500, 700 or 900 ppm DEB mixture for 6 h daily, 5 days per week, for 18 weeks. Rats used for recording BAEP (one control group and two other groups of 15 rats) were exposed to 600 and 800 ppm DEB mixture. The exposure time was the same. Rats exposed to DEB mixture exhibited a time- and concentration-dependent decrease in MCV, SCV and ASAP and a time- and concentration-dependent increase of both the peak latencies of all BAEP components and the interpeak (I-V) differences.

Action Potentials↗
PubMed1992

Growth hormone and prolactin stimulate androgen receptor, insulin-like growth factor-I (IGF-I) and IGF-I receptor levels in the prostate of immature rats.

In this study we investigated the involvement of several different pituitary hormones on rat prostate development. 22-day-old Wistar rats, hypophysectomized (hypox) at 19 days of age were supplemented with highly purified human prolactin (hPRL), human luteinizing hormone (hLH), porcine follicle-stimulating hormone (pFSH), and bovine growth hormone (bGH) or with saline. Quantitative analysis of RNAs shows that treatment with either PRL or GH increases significantly steady-state mRNAs levels of the following genes in the prostate: androgen receptor (AR) (respectively 3.5- and 4.8-fold above hypox controls), IGF-I (5- and 2.7-fold), and IGF-I receptor (2.9- and 2.3-fold). LH and FSH, by contrast, have negative effects on these parameters. To test whether the enhancing effect of PRL and GH on AR-mRNA abundance was followed by increased content in the protein itself, binding assays were performed with the androgen agonist [3H]R1881 (131 and 153 fmol/mg protein while hypox controls contained 110 fmol/mg protein). In addition to the well-documented presence of prolactin receptors in prostatic tissues, we have further demonstrated, by means of nuclease S1 protection assays plus dot- and Northern-blot analyses, that a GH receptor mRNA is produced in the immature rat prostate. Moreover, we observed not only strong lactogenic but also purely somatogenic binding to be occurring in the immature prostates. Finally, we have studied IGF-I mRNA content in separated epithelial/stromal cell fractions and have concluded that IGF-I expression is principally located in the prostatic stroma. Taken together, these results suggest that PRL and GH are involved in regulating AR synthesis, at least partially by direct action on the organ. In this context IGF-I appears as a paracrine factor playing a role in epithelium/stroma interactions during prostatic development.

Age Factors↗
PubMed1992

Evaluation of the interaction of benzene and toluene on the urinary excretion of t,t-muconic acid in rats.

The influence of simultaneous exposure to benzene and toluene on the urine excretion of t,t-muconic acid (t,t-MA) was examined in rats. t,t-MA was measured from 24-h urine of rats subjected to a single 4-h exposure to 5 or 20 ppm benzene and/or 50, 100, 200 or 1000 ppm toluene. Coexposure lowered t,t-MA excretion in a concentration-dependent manner, especially in the 20 ppm benzene group where the decrease averaged 28, 44 and 85% after exposure to 100, 200 and 1000 ppm toluene, respectively, as compared to benzene-exposed groups alone. The data confirm the sensitivity of t,t-MA as an indicator of benzene exposure and point out that measurement of t,t-MA may underestimate the exposure to benzene in the presence of toluene.

Administration, Inhalation↗
PubMed1992

Original lithotomy positioning for transperineal extracorporeal shockwave lithotripsy for distal ureteric calculi with Tripter X1.

Extracorporeal shockwave lithotripsy (ESWL) has been initially designed for stones located in the kidney and the upper ureter. Our lithotripter is no exception. Its components (the table and the orientation of the semi-ellipsoid reflector) are adapted for the treatment of kidney or lumbar ureter stones. However, the elements forming the unit of treatment (the table, the C-arm and the Tripter) can be modified in such a way that focalization of stones of the lower ureter becomes possible through a perineal exposure. The aim is to avoid the pelvic bone shield while a good focalization of the stone is realized. From June 1989 to March 1991, 35 patients were treated for distal ureteric stones by ESWL in this original positioning.

Adolescent↗
PubMed1992

Phospholipase-A2 action and arachidonic acid metabolism in calcium-mediated parathyroid hormone secretion.

The involvement of arachidonic acid (AA) and its metabolites in the control of PTH secretion by porcine parathyroid cells was investigated. Increasing the extracellular calcium concentration from 0.5 to 2 mM increased free [3H]AA release and decreased PTH secretion from labeled parathyroid cells as a function of time (1-30 min). Free [3H]AA in the medium was significantly increased (+153 +/- 6%) after 5 min, while PTH secretion was significantly decreased (-75 +/- 7%) only after 15 min, suggesting a link between the two. [3H]AA release was associated with a decrease in [3H]AA incorporated into phosphatidylinositol, phosphatidic acid, and phosphatidylcholine, suggesting that these phospholipids are the major source of AA. Exogenous phospholipase-A2 (PL-A2; 1-500 mU/ml) and AA (5-40 microM) inhibited PTH secretion in a dose-dependent manner. PTH secretion inhibited by 2 mM Ca2+ was restored by two PL-A2 inhibitors, indomethacin (30 microM) and mepacrine (50 microM). The cyclooxygenase pathway inhibitor ibuprofen (20 microM) did not restore PTH secretion of affect high Ca(2+)-, AA-, or PL-A2-inhibited PTH secretion. Two inhibitors of the lipoxygenase pathway (LO), phenidone (1 microM) and baicalein (0.1 microM), a relatively selective 12-LO inhibitor, blunted high Ca(2+)-induced inhibition of PTH secretion (+101 +/- 10% and +105 +/- 6%, respectively), but nordihydroguaiaretic acid, which inhibits the 5-LO pathway, did not restore PTH secretion inhibited by high Ca2+, AA, or PL-A2. These results suggested that AA and agents that cause its liberation inhibit PTH secretion. AA may act via the 12-LO, but not via the 5-LO or cyclooxygenase, pathway. Thus, 12-LO products may be second messengers in parathyroid cells.

Acetophenones↗
PubMed1991

Differences in the hypoxic contraction of small isolated pulmonary arteries of cat and rabbit.

In small (less than 300 microns diameter) pulmonary arterial (PA) rings isolated from the cat, hypoxia induced a transient contraction (250 +/- 120 mg, n = 7), whereas in rings of rabbit PA of the same size, hypoxia had no significant effect (n = 19). Precontraction by 40 mmol KCl.1(-1), noradrenaline (NA) 10(-6) mol.1(-1), or histamine (His 10(-5) mol.1(-1)) did not modify this difference between the two species and did not potentiate the hypoxic contraction of small rings of the cat PA. Large rabbit pulmonary arterial segments (300-2000 microns) exhibited no response to hypoxia before precontraction (n = 15). In the presence of procaine (2%) rabbit PA rings (n = 6, small) exhibited no hypoxic contraction. These results in vitro reflect previous in vivo observations.

Animals↗
PubMed1991

Characterization of an outward K+ current in freshly dispersed cerebral arterial muscle cells.

This study was carried out to define some of the cellular ionic mechanisms controlling cerebral arterial muscle. Muscle cells were enzymatically dispersed from cat cerebral arteries. Cells were dialyzed and voltage-clamped using patch pipettes and whole-cell currents measured. Using pipette solutions allowing us to record K+ currents we identified an outward current elicited by depolarizing voltage steps beyond -20 mV. This outward current exhibited properties of delayed outward rectification having a peak macroscopic current at +90 mV of 504 +/- 236 pA. The current was sensitive to 4-aminopyridine, but was sensitive to tetraethylammonium only at very high doses. When CsCl was in the recording pipette, macroscopic outward currents could not be recorded. Variations in the extracellular Ca2+ concentration from 0.5 to 5.0 mM had no effect on current amplitude or voltage dependence; similarly the Ca2+ channel blockers nifedipine and Mn2+ were without effect on this outward current. The current inactivated slowly with no decay seen even with 3-s command pulses. Repetitive voltage pulses from -60 to +90 mV at a frequency of 1 Hz resulted in "cumulative reduction", depressing peak current by 60% after ten pulses. Upon reduction of pH from 7.43 to 7.20 we observed a 350% increase in peak outward current in 7 of 12 cells studied in this regard. Thus, the cellular mechanism responsible for cerebral vascular dilation to acidosis and/or hypercapnia may involve an increase in outward K+ current.

4-Aminopyridine↗
PubMed1991

Interdependence of polymorphonuclear neutrophils and macrophages stained for N-acetyl-beta-glucosaminidase in lavage effluents from toluene diisocyanate-exposed rat lungs.

Male Sprague-Dawley rats were exposed to toluene diisocyanate (TDI) concentrations between 0.082 and 1.087 ppm for 4 h, and pulmonary lavage was carried out 24 h after initiation of the exposure. Cells recovered from the lavage effluents of TDI-exposed rat lungs were identified and counted, then pulmonary macrophages (PMs) resulting from cytocentrifuged preparations were examined for N-acetyl-beta-glucosaminidase (NAG) cytochemical staining. Exposure to TDI led to a parallel and concentration-dependent increase in the number of polymorphonuclear neutrophils (PMNs) and the proportion of PMs stained for NAG, suggesting that the same primary event initiates the two cell responses.

Acetylglucosaminidase↗
PubMed1991

[Ureteroscopic resection of a fibrous polyp of the ureter].

From a new case of fibroepithelial polyp in a 41 year old woman, we reviewed literature on this rare and benign pathology, for which differential diagnosis with malignant tumor is most often obtained surgically. We emphasize both diagnostic and therapeutic advantages of endoscopic approach of this lesion.

Adult↗
PubMed1991

[Comparative study of 2 types of bifocal implants by measurement of visual acuity and contrast sensitivity].

Evaluation of multifocal IOLs suggests the possibility of two retinal images, one for near and one for distant vision. But the optic principles of multifocal IOLs created overlying images and incident light division. We performed this study to evaluate visual acuity and contrast sensitivity for two types of bifocal IOLs (3M bifocal and IOLAB bifocal IOL) and for a control group of monofocal IOL testing in different levels of luminance simulating the normal environmental conditions of the patient's experience. The results showed a visual functional loss especially at the low luminance level for the 3M bifocal group and at bright luminance for the IOLAB bifocal group, which was previously unknown with and consequences for the indications and exclusions of this kind of IOL.

Aged↗
PubMed1991

Effects of hypoxia on a potassium channel in cat cerebral arterial muscle cells.

We have shown that exposure of isolated cat cerebral arterial muscle cells to hypoxic environments increases K+ channel activity when recorded in the cell-attached mode. Inhibition by glibenclamide of the "hypoxia-induced" increase in K+ channel activity may suggest that increased activity is mediated by an ATP sensitive K+ channel. Thus, the level of O2 may modulate cerebral vascular tone by an action on membrane K+ channels, possibly mediated by the concentration of intracellular ATP.

Animals↗
PubMed1990

Adrenal-dependent leucopenia after short-term exposure to various airborne irritants in rats.

Leucopenia without any change in differential or red blood cell counts was observed in rats exposed for 4 h to increasing concentrations of the following airborne irritants: acetic acid, benzyl chloride, 1,2-dichlorobenzene, ethyl acetate, ethyl acrylate, formaldehyde, isophorone, mesityl oxide, phenol, styrene, toluene diisocyanate and vinyl toluene. This effect was abolished by adrenalectomy. Vinyl toluene and 1,2-dichlorobenzene induced leucopenia at levels as low as their current occupational standards of 50 ppm. With the exception of 1,2-dichlorobenzene, the tested compounds caused leucopenia only when exposure reached the irritant level. It is discussed that stress associated with the irritative effect of chemicals can confound specific haematological effects.

Adrenal Glands↗