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Biomedical subjects

A Etienne

Publications and source records attributed to A Etienne.

At least 19 recordsLinked to original sources
PubMed2000

Photosystem II fluorescence quenching in the cyanobacterium Synechocystis PCC 6803: involvement of two different mechanisms.

The structural changes associated to non-photochemical quenching in cyanobacteria is still a matter of discussion. The role of phycobilisome and/or photosystem mobility in this mechanism is a point of interest to be elucidated. Changes in photosystem II fluorescence induced by different quality of illumination (state transitions) or by strong light were characterized at different temperatures in wild-type and mutant cells, that lacked polyunsaturated fatty acids, of the cyanobacterium Synechocystis PCC 6803. The amplitude and the rate of state transitions decreased by lowering temperature in both strains. Our results support the hypothesis that a movement of membrane complexes and/or changes in the oligomerization state of these complexes are involved in the mechanism of state transitions. The quenching induced by strong blue light which was not associated to D1 damage and photoinhibition, did not depend on temperature or on the membrane state. Thus, the mechanism involved in the formation of this type of quenching seems to be unrelated to the movement of membrane complexes. Our results strongly support the idea that the mechanism involved in the fluorescence quenching induced by light 2 is different from that involved in strong blue light induced quenching.

Cyanobacteria↗
PubMed2000

Biovector nanoparticles improve antinociceptive efficacy of nasal morphine.

PURPOSE: We have studied the antinociceptive activity and blood and brain delivery of nasal morphine with or without Biovector nanoparticles in mice. METHODS: A tail flick assay was used to evaluate the antinociceptive activity. The kinetics of morphine were evaluated in blood and brain, using tritiated morphine as tracer. RESULTS: These nanoparticles were shown to increase the duration of the antinociceptive activity of morphine after nasal administration. This effect was not due to an increase of morphine in the blood; and the analgesic activity of morphine in association with nanoparticles was reversed by naloxone. The ED50 value was 33.6+/-15.6 mg/kg for morphine alone and 14.4+/-7.6 mg/kg in presence of nanoparticles. They were only effective at low doses (1.5 to 2.5 microg), a higher or a lower dose had no effect. No interaction was found between nanoparticles and morphine. NaDOC, a permeation enhancer, was unable to improve nasal morphine activity. CONCLUSIONS: These results show the presence of nanoparticles only at a very specific dose increases the antinociceptive activity of nasal morphine in mice. The occurrence of a direct transport of morphine from the nasal mucosa to the brain is discussed.

Administration, Intranasal↗
PubMed2000

Topical colchicine therapy for actinic keratoses.

BACKGROUND: The beneficial effect of topical colchicine therapy for actinic keratoses has already been described in 1968. OBJECTIVE: To confirm that the application of a 1% colchicine gel is a safe and effective treatment for actinic keratoses. METHODS: Twenty patients were included in a double-blinded protocol. They all had actinic keratoses on the scalp, most of which had been previously treated with 5-fluorouracil or cryotherapy. Ten patients applied twice daily on the forehead a hydrophilic gel (placebo group), while the other 10 where treated with the same gel containing 1% of colchicine (colchicine group). Erythema and efficacy were evaluated at each control on days 7, 30 and 60, with repetitive blood tests to exclude a possible systemic absorption. RESULTS: A complete healing of the solar keratoses was observed in 7 out of the 10 patients treated with 1% colchicine gel; these showed no recurrence after 2 months of follow-up. Burning and itching occurred only in the colchicine group after 2 or 3 days of application, with an inflammatory reaction on the areas where the gel was applied, while pustules and crusts were located specifically on the actinic keratoses. Repeated blood controls showed that there was no systemic absorption. CONCLUSIONS: This double-blind placebo-controlled study confirms the activity of colchicine for the treatment of actinic keratosis. A comparison with other topical treatments in terms of efficacy and practicability is needed.

Administration, Topical↗
PubMed1999

DNA packing in stable lipid complexes designed for gene transfer imitates DNA compaction in bacteriophage.

The structure of complexes made from DNA and suitable lipids (lipoplex, Lx) was examined by cryo-electron microscopy (cryoEM). We observed a distinct concentric ring-like pattern with striated shells when using plasmid DNA. These spherical multilamellar particles have a mean diameter of 254 nm with repetitive spacing of 7.5 nm with striation of 5.3 nm width. Small angle x-ray scattering revealed repetitive ordering of 6.9 nm, suggesting a lamellar structure containing at least 12 layers. This concentric and lamellar structure with different packing regimes also was observed by cryoEM when using linear double-stranded DNA, single-stranded DNA, and oligodeoxynucleotides. DNA chains could be visualized in DNA/lipid complexes. Such specific supramolecular organization is the result of thermodynamic forces, which cause compaction to occur through concentric winding of DNA in a liquid crystalline phase. CryoEM examination of T4 phage DNA packed either in T4 capsides or in lipidic particles showed similar patterns. Small angle x-ray scattering suggested an hexagonal phase in Lx-T4 DNA. Our results indicate that both lamellar and hexagonal phases may coexist in the same Lx preparation or particle and that transition between both phases may depend on equilibrium influenced by type and length of the DNA used.

Bacteriophage T4↗
PubMed1999

Evaluation of peroral silicone dosage forms in humans by gamma-scintigraphy.

Gastric emptying of oral silicone dosage forms was studied in humans by gamma-scintigraphy. To achieve a constant and predictable residence time in the stomach, three different formulations based on known concepts such as controlled swelling were investigated. The importance of physical parameters such as size or shape were also examined to assess the feasibility of designing a dosage form for gastric retention. Three shapes: minimatrices, extruded rods and moulded slabs were screened. To label the silicone polymer, two isotopes, used routinely in nuclear medicine departments, were selected: iodine-123 and indium-111. To select the most suitable isotope, the yield and the stability of the labelling were determined in vitro on the pharmaceutical dosage forms. The residence time of these silicone formulations, labelled with iodine and administered in hard gelatine capsules, was monitored in 12 subjects with a gamma camera. The study was performed under fed conditions after ingestion of a standardised meal labelled with indium. The minimatrices provided at least 3 h retention, slabs exhibited 4 h 40 min retention. For the rods the mean residence time in the stomach was around 4 h 20 min. In addition, a correlation was established between the gastric emptying of rods and the half-gastric residence time of meal. On the contrary, such a correlation was not observed for the slabs.

Administration, Oral↗
PubMed1999

Incidence of transient acantholytic dermatosis (Grover's disease) in a hospital setting.

BACKGROUND: Grovers's disease may be triggered by bed rest. METHODS: We have prospectively analyzed, over a 30-month period, all cases of transient acantholytic dermatosis (TAD) diagnosed in the context of a dermatological consultation for inpatients of a community hospital. RESULTS: A total of 28 cases of TAD were diagnosed within a total of 3,750 patients examined (0.8%). The mean age of patients with TAD was 66.7 years, and the male-to-female ratio was 1.8. In 83% of cases the length of hospitalization preceding TAD was 66.7 years, and the male-to-female ratio was 1.8. In 83% of cases the length of hospitalization preceding TAD exceeded 2 weeks, and in all cases there was an association with strict bed rest. No association with malignant disease or other specific pathologies was observed. CONCLUSION: Our results suggest that TAD, which is frequent in elderly patients within a hospital setting, is not paraneoplastic and favor the hypothesis of a sweat-related pathogenesis.

Acantholysis↗
PubMed1998

[Epidermolysis bullosa acquisita and metastatic cancer of the uterine cervix].

INTRODUCTION: Epidermolysis bullosa acquisita may be associated to a systemic or malignant disease. Here, we report a case of epidermolysis bullosa acquisita associated with a carcinoma of the cervix. CASE REPORT: A 44-year-old woman presented inflammatory, bullous and erosive mucocutaneous lesions. Investigations lead to the diagnosis of epidermolysis bullosa acquisita and revealed pelvic metastases originating from a poorly differentiated carcinoma. The cutaneous lesions completely regressed after the treatment of the tumor but reappeared with tumoral relapse. DISCUSSION: This is the first report of an association of epidermolysis bullosa acquisita and carcinoma of the cervix. The clinical course of these two entities suggests that the EBA in this case may be paraneoplastic.

Adult↗
PubMed1996

[Cutaneous manifestations of parvovirus B19 infection].

Parvovirus B19 can cause a wide range of cutaneous or extracutaneous diseases. There are three types of exanthemas, erythematous maculopapulous or vesicopapulous exanthema including erythema infectiosum, the less common maculoerythematous exanthemas and purpural exanthemas including vascular, thrombocytopenic or non-vascular or non-thrombopenic forms such as le socks and gloves syndrome. Reports of other manifestations have been more sporadic: generalized livedo, polymorphous rash, lupus-like rash and Kawasaki syndromes. The presence of unusual presentations and the risk of fetomaternal transmission are two reasons for better understanding this virus.

Erythema Infectiosum↗
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↗
PubMed1993

Involvement of platelet-activating factor (PAF) in endotoxin- or ischaemia-induced intestinal hyperpermeability in the rat.

We have investigated the influence of BN 50727, a PAF antagonist, and allopurinol, a free radical scavenger, on the damaging effects of ischaemia-reperfusion and endotoxin in the small intestinal mucosa. Using a rat experimental model, we determined the alterations in intestinal permeability and mucosal levels of PAF and lysoPAF following ischaemia or intravenous administration of endotoxin. Both of these treatments increased intestinal permeability and enhanced PAF levels in the mucosa. Preventive oral or intraduodenal administration of BN 50727 reduced both of these effects, by decreasing mucosal PAF formation, probably as a result of neutrophil infiltration and activation reduction. Pretreatment of the rats with allopurinol also resulted in similar protection except that the free radical scavenger was unable to inhibit the increase in PAF levels after ischaemia, suggesting that oxidative reagents are implicated in this pathology to a much greater extent than PAF.

Allopurinol↗
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↗