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Biomedical subjects

A Etienne

Publications and source records attributed to A Etienne.

At least 19 recordsLinked to original sources
PubMed1994

Effect of hemicholinium-3 on the hypothalamic concentration of a cytochemically detectable glucose-6-phosphate dehydrogenase-stimulating substance.

Hypothalamus and plasma of salt-loaded rats, spontaneously hypertensive rats (SHR), and hypertensive reduced renal mass rats (RRM), and the plasma of patients with essential hypertension and of Milan hypertensive rats contain an increased concentration of a cytochemically detectable glucose-6-phosphate dehydrogenase (G6PD)-stimulating substance that has properties similar to that of a possible choline derivative di-methyl methylene immonium ion. Intracerebroventricular (i.c.v.) administration of hemicholinium-3 (HC-3) selectively blocks high-affinity neuronal choline uptake, inhibits brain acetylcholine (ACh) synthesis, and decreases arterial pressure in SHR through an inhibiting effect on hypothalamic cholinergic function. The experiments were performed to study the effect of centrally administered HC-3 on the content of the cytochemically detectable cholinelike substance in hypothalamus and plasma of SHR. HC-3 or saline was infused into the lateral cerebral ventricle for 6 days with a minipump in 14 SHR. On day 7, the hypothalamic and plasma concentration of the cytochemically detectable substance was significantly reduced in rats that received HC-3. The hypothalamic concentration was 225 +/- 95.6 x 10(8) G6PD U per hypothalamus (range 38.2-775) in SHR that received saline and 1.037 +/- 0.45 x 10(8) G6PD U (range 0.112-3.61) (p < 0.05) in SHR that received HC-3. The respective plasma concentrations were 284.9 +/- 26 U/ml (range 192-374) and 72.7 +/- 14.7 U/ml (range 24-119) (p < 0.05). The findings are consistent with the physicochemical evidence, which suggests that the cytochemically detectable substance is a choline derivative.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

Automatic display of RNA secondary structures.

A set of programs written in C language with the GL library and under UNIX has been developed for generating compact, pleasant and non-overlapping displays of secondary structures of ribonucleic acids. The first program, rnasearch, implements a new search procedure that dynamically rearranges overlapping portions of the two-dimensional drawing while preserving clear and readable displays of the two-dimensional structure. The algorithm is fast (the execution time for the command rnasearch is 38.6 s for the 16S rRNA of Escherichia coli with 1542 bases), accepts outputs from two-dimensional prediction programs and therefore allows for rapid comparison between the various two-dimensional folds generated. A second program, rnadisplay, allows the graphical display of the computed two-dimensional structures on a graphics workstation. Otherwise, it is possible to obtain a paper output of the two-dimensional structure by using the program print2D which builds a Postscript file. Moreover the two-dimensional drawing can be labelled for representing data coming from chemical modifications and/or enzymatic cleavages. Application to a few secondary structures such as RNaseP, 5S rRNA and 16S rRNA are given.

Algorithms↗
PubMed1993

A possible connection between an increased concentration of a cytochemically detectable substance in the hypothalamus of the spontaneously hypertensive rat and certain cerebral cholinergic disturbances.

The hypothalamus of the spontaneously hypertensive rat (SHR) contains an increased concentration of a cytochemically detectable choline-like substance, the physicochemical properties of which are similar to the choline analogue dimethyl methylene immonium. In the hypothalamus of the adult SHR there is an increased turnover of acetylcholine in the cholinergic pressor posterior hypothalamic nucleus and the neurons of the dorsomedial cholinergic depressor nucleus are atrophic, possibly due to diminished cholinergic activity. Both of these changes are pressor. It is suggested that an increased hypothalamic content of a choline-like analogue might either be responsible for, or an indicator of, these abnormalities.

Acetylcholine↗
PubMed1990

Isolation, purification and characterization of beta-hCGRP from human spinal cord.

Human beta-calcitonin gene-related peptide (beta-hCGRP) was isolated and purified from spinal cord. The complete characterization of this material was based on definitive mass analysis by fast atom bombardment mass spectrometry together with gas phase sequencing. Combining these data we have characterized the structure of beta-hCGRP including the C-terminal sequence, the presence of the S-S bridge and of phenylalanineamide as the C-terminal amino acid, and fully confirmed the amino acid sequence predicted from the nucleotide analysis.

Amino Acid Sequence↗
PubMed1990

Effects of endothelin on the lethality induced by platelet-activating factor or endotoxin in the mouse.

Platelet-activating factor (PAF) is a mediator that decreases cardiac output and total peripheral resistances leading to profound hypotension. It seems to be involved in shock states and in the deleterious effects of endotoxin. As the natural peptide endothelin (ET) shows potent vasoconstrictor properties, we evaluate its activity towards PAF and endotoxin-induced lethality in mice. ET, at doses which per se did not exert any effects on mice vitality, produced a dose-dependent decrease in the PAF-induced lethality with a total protection at 5 micrograms/kg. But conversely to these results, ET potentiated the mortality induced by endotoxin. These results suggest that ET or endothelin analogs could be worthy for therapeutic use in some types of shock, at least when endotoxin is not involved. Complementary studies are necessary to strengthen these preliminary results.

Animals↗
PubMed1989

Modulation of eosinophil recruitment in the rat by the platelet-activating factor (PAF) antagonist, BN 52021, the somatostatin analog, BIM 23014, and by cyclosporin A.

The factors responsible for in vivo eosinophil recruitment are poorly defined, although T-lymphocytes appear to be involved in the etiology of eosinophilia. In order to clarify this relationship, we studied the modulation of eosinophil mobilization in the rat after immune challenge, by chronic treatment with the PAF-antagonist, BN 52021, the somatostatin analog, BIM 23014 and with Cyclosporin A (CsA). In rats made hypereosinophilic by pretreatment with cyclophosphamide or sephadex, a significant increase of the eosinophil count in blood and peritoneal fluid was induced by anaphylactic reaction. CsA totally abolished both hypereosinophilia and peritoneal eosinophil infiltration. BIM 23014 also, significantly reduced the circulating eosinophils (-68%, p less than 0.001) and cell infiltration (-86%, p less than 0.05). In contrast, BN 52021 decreased peritoneal eosinophil recruitment, while having relatively little effect on circulating cells. CsA and somatostatin are known to affect T-cell proliferation, and as T-cells are involved in the differentiation of hematopoietic cells into eosinophils, these drugs could decrease eosinophil availability for recruitment. In contrast, the PAF antagonist may act by inhibiting PAF-induced eosinophil chemotaxis, providing a more specific inhibition of this process than that exerted by CsA, BIM 23014 and other immunosuppressive agents.

Animals↗
PubMed1989

Modulation by drugs of eosinophil recruitment induced by immune challenge in the rat. Possible roles of interleukin 5 and platelet-activating factor.

The factors responsible for eosinophil recruitment are poorly defined, although both platelet-activating factor (PAF) and cytokines appear to be involved in regulating this process. We compared eosinophil mobilization induced by PAF or antigen injection in the peritoneal cavity of hypereosinophilic rats and the effects of the PAF antagonist BN 52021, the somatostatin analog BIM 23014, and cyclosporin A on this process. PAF induced a significant increase of both peritoneal and circulating eosinophil count. Cyclosporin A almost totally abrogated these variations, whereas BN 52021 reduced the peritoneal increase. Similarly to PAF, peritoneal antigen challenge in actively sensitized animals increased peritoneal and circulating eosinophil counts. Cyclosporin A abolished both hypereosinophilia and peritoneal eosinophil infiltration. BIM 23014 reduced the circulating eosinophils and cell infiltration. In contrast, BN 52021 primarily decreased peritoneal eosinophil recruitment, while having little effect on circulating cells. The different mechanisms of action of these drugs and the involvement of interleukin 5 in eosinophil recruitment are discussed.

Animals↗
PubMed1989

Chemotactic effect of PAF-acether on peritoneal eosinophils from normal rats.

The chemotactic activity of PAF-acether was compared with that of tetrapeptide eosinophil chemotactic factors of anaphylaxis (ECF-A, Ala-Gly-Ser-Glu and Val-Gly-Ser-Glu) using eosinophils obtained from the peritoneal cavity of normal rats. Cells were isolated by separation over discontinuous metrizamide gradients which resulted in eosinophil suspensions of 80 to 90% purity. PAF-acether produced a dose-dependent effect which, at its maximum, was more than 30-fold greater than control and about 5- to 7-fold greater than the maximal activity obtained with the ECF-A-tetrapeptides. BN 52021 and WEB 2086 inhibited PAF-acether-induced eosinophil chemotaxis in a dose-dependent manner, suggesting that this phenomenon is mediated by specific PAF-acether receptors.

Animals↗
PubMed1989

Protective effect of the PAF-antagonist BN 52021 on several models of gastro-intestinal mucosal damage in rats.

Platelet-activating factor (PAF) has been shown to induce gastro-intestinal damage similar to that evoked by endotoxin, suggesting that this mediator may be involved in the formation of gastrointestinal lesions observed in various pathologies. Thus, the effects of BN 52021, a specific PAF antagonist, were investigated in several experimental models of gastro-intestinal damage in rats. BN 52021 markedly reduced the gastric alterations and almost totally abolished the intestinal lesions induced by PAF. Similarly, BN 52021 reduced gastro-intestinal damage induced by endotoxin, but it afforded less protection against endotoxin-induced changes than those caused by PAF. This difference is probably due to the multicomponent activating effect of endotoxin. In the cold restraint stress model, BN 52021 decreased both gastro-intestinal lesions and the change in plasma transaminase level. The results presented in this paper confirm the role of PAF in gastro-intestinal damage induced by endotoxin but also suggest the involvement of this mediator in stress-induced lesions. PAF-antagonists could thus be of therapeutic use in such pathologies.

Animals↗
PubMed1989

[A study by infrared spectroscopy of interactions between the time of disintegration of tablets and liberation of the active principal].

It was shown that the study of the infrared spectra of a drug and of the mixture drug + additives facilitates the preliminary studies for a tablet formulation. Thus, any interaction that may occur or affect the product stability can be detected and located. Furthermore, it was noticed that an interaction between an active ingredient and the various additives may modify the tablet desintegration time, but not necessarily the dissolution rate of this substance.

Solubility↗
PubMed1988

Effects of the specific platelet-activating factor antagonists, BN 52021 and BN 52063, on various experimental gastrointestinal ulcerations.

Platelet-activating factor (PAF) has been shown recently to induce gastrointestinal damage similar to that evoked by endotoxin, suggesting that the autacoid could be implicated in other types of gastrointestinal damage. Thus, the effects of BN 52021 and BN 52063, two specific PAF antagonists, were investigated in various experimental models of gastrointestinal damage in rats. BN 52021 and BN 52063, markedly reduced both the PAF- and endotoxin-induced alterations of the mucosa, suggesting a role for the autacoid in the latter process. BN 52021 and another unrelated PAF antagonist, triazolam, partially reduced the restraint-stress-induced gastric damage in young female, but not male, rats. Similar partial protection was obtained in rats with ethanol-induced gastric damage. In contrast with atropine and ranitidine, BN 52021 did not affect the gastric hypersecretion in pylorus-ligated rats nor the aspirin-induced gastric ulcerations. The present results indicate that PAF plays a major role in the gastric damage induced by endotoxin and may also partially contribute to the gastric lesions induced by ethanol and stress. The results suggest that there is a potential therapeutic use for PAF antagonists in certain types of gastrointestinal lesions in man.

Animals↗
PubMed1988

Role of neutrophils in gastric damage induced by platelet activating factor.

Platelet-activating factor (PAF) has recently been shown to be a potent ulcerogenic agent in the stomach and intestinal mucosa. Its extract mechanism of action is not yet known although histological studies suggest that vasocongestion is an important feature of PAF-induced damage. We have therefore studied the activity of various agents with different modes of action toward PAF-induced gastrointestinal lesions in the rat (PAF 2 micrograms/kg i.v.; macroscopic lesions of tissue scored 20 min later; arbitrary scale from 0 to 4). Drugs were administered either i.m., s.c. (5 min) or orally (30 min) before PAF injection. PAF-induced gastric lesions were strongly inhibited by the natural PAF-antagonist BN 52021 as well as by atropine sulphate and cimetidine which implicates cholinergic stimulation in the ulcerogenic activity of PAF. The somatostatin analog BIM 23014 was also very potent against PAF, perhaps by reducing the parasympathetic stimulation in the gastric wall as described for somatostatin. Allopurinol, which is a free radical scavenger also almost totally inhibited PAF-induced gastric damage, suggesting that neutrophils are involved in the mucosal lesions. The considerable inhibition of the gastric effects of PAF found in neutrophil-depleted animal supports this hypothesis. Theophylline and disodium cromoglycate, mast cell stabilizing drugs which were also active in our model, could act by protecting mast cell degranulation induced by free radicals released from activated neutrophils. A multifunctional process seems to determine the mucosal gastric damage induced by PAF, but parasympathetic stimulation and neutrophil activation play a major role in this pathology.

Animals↗
PubMed1988

Role of platelet-activating factor (PAF) in the ovoimplantation in the rat: effect of the specific PAF-acether antagonist, BN 52021.

The role of PAF (platelet-activating factor) in early pregnancy has been recently postulated. Indeed, platelet count is markedly reduced immediately prior to and returns to normal following ovoimplantation. Using a pharmacological approach, we therefore further investigated the possible involvement of PAF in ovoimplantation. BN 52021 (10 nmol), a PAF antagonist, was administered after fecondation in the lumen of the left uterine horn. A group of animals was injected with the vehicle alone. The animals were sacrificed 1 week latter and the number of implanted embryos in the treated horn and in the untreated contralateral one was assessed. When injected on day 4 of pregnancy, the PAF antagonist, BN 52021, inhibited in a dose-dependent fashion ovoimplantation suggesting a role for this lipid mediator in this process. Total inhibition of ovoimplantation was observed in the horns treated with indomethacin, NDGA or BW 755 C. In addition, a significant inhibition of ovoimplantation was also produced by the lipoxygenase inhibitor, EP 10045 (10nmol). Since both PAF and leukotrienes trigger the generation of prostaglandins in various tissues, our results indicate that these two lipid mediators may be implicated in early stages of the inflammatory reaction accompanying ovoimplantation and may contribute to the local generation of cyclooxygenase metabolites.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1988

General pharmacology of cicletanine.

Cicletanine is a new antihypertensive molecule which acts directly on vascular smooth muscle by increasing prostacyclin synthesis and interacting with various agents which mobilize intracellular Ca2+ ions. General pharmacological studies have shown that in the anaesthetized normotensive dog, cicletanine does not induce tachycardia (even at high doses) and does not modify aortic, femoral or coronary blood flow. Moreover, cicletanine shows a protective effect on vascular permeability and capillary hyperpermeability. This protective action on the vascular wall is of importance, since one of the direct vascular consequences of arterial hypertension is a fragilisation of vessel walls, tissue oedema and even vascular rupture. Cicletanine slows down the thrombogenic process initiated by electric arterial stimulation. Retardation of the thrombogenic process by the drug may be explained by the stimulation that cicletanine exerts on the synthesis and production of prostacyclin. Behavioural studies in mice, rats and primates have shown that cicletanine has no sedative effects, even at very high doses. General pharmacological studies have demonstrated that both cardiovascular function and the central nervous system are equally tolerant to cicletanine. Cicletanine is an antihypertensive agent which has no effect on cardiovascular haemodynamics and is able to prevent some rheological and vascular-linked cardiac risks of hypertension.

Animals↗
PubMed1987

[Evaluation of the control quality of arterial hypertension over a 10-year period at a hemodialysis center].

Using the "Diaphane" computed medical record system enables multicentric statistical studies to be conducted. With this system, the quality of arterial hypertension control (supine systolic and diastolic arterial pressure before and after dialysis) was evaluated over a 10-year period in chronic haemodialysis patients in comparison with a multicentric population. A continuous statistical study of the results showed a regular voluntary decrease in arterial pressure. The evaluation of the quality of medical care represented by this comparison contributes to a therapeutic improvement.

Adult↗
PubMed1987

Inhibition of rat endotoxin-induced lethality by BN 52021 and BN 52063, compounds with PAF-acether antagonistic effect and protease-inhibitory activity.

Since proteolytic enzymes play a key role in endotoxaemia and anaphylaxis, diseases in which PAF-acether may be involved, we have investigated the activity of BN 52021 and BN 52063, two potent and specific PAF-acether antagonists, on plasma protease activity in the rat. After oral administration, both drugs dose-dependently decreased plasma trypsin-like activity (PTLA) although they did not show any inhibitory effect in vitro. PAF-acether and endotoxin injected into rats increased PTLA, the increase with endotoxin appearing more slowly but to a higher extent than with PAF-acether. Inhibition of the endotoxin-induced increase in PTLA was obtained with BN 52021, BN 52063 and dexamethasone, whereas aprotinin was ineffective. Since BN 52021 and BN 52063 reduced also the endotoxin-induced lethality in the rat, their antiprotease activity may be a consequence of their PAF-antagonistic effect. Further studies will be required with other PAF antagonists to assess fully this assumption.

Animals↗