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Biomedical subjects

F Boucher

Publications and source records attributed to F Boucher.

At least 73 records · Page 4Linked to original sources
PubMed1988

The limited photochemical activity of solid aggregated forms of bovine rhodopsin.

The visual pigment rhodopsin has been purified and depleted of detergent. Under these conditions, the pigment strongly aggregates. When dried, a significant fraction of these aggregates appear insensitive to light. We have characterized them by means of absorption and photoacoustic spectroscopies and we find that their photochemical behavior is best explained by a limited activity that does not reach photointermediates beyond the lumirhodopsin step in the bleaching sequence of rhodopsin. We interpret this result as an indication of a significant conformational change of the protein during the transition from lumi- to meta-rhodopsin.

Animals↗
PubMed1988

[Toxicity of oxygen free radicals in reperfusion. Myth or reality?].

It would appear from numerous experimental data that an overproduction of oxygen free radicals may occur during reperfusion of an ischaemic myocardium. However, this has not yet been confirmed experimentally owing to the lack of a method for direct measurement of these radicals. In this paper, the topic is reviewed, with emphasis on the problems associated with the study of oxygen free radicals in biological tissues. In a second part, spin-trapping studies conducted on the isolated rat heart are reported. They tend to confirm the presence of disturbances in oxygen-derived free radicals occurring as early as the first minute of reperfusion.

Free Radicals↗
PubMed1986

Wavelength modulation by molecular environment in visual pigments.

The absorption and regenerability characteristics are compared for rhodopsin contained in rod outer segment membranes and purified in a series of alkyl sucrose esters. It is found that membrane-bound rhodopsin has maximum absorbance from 504 to 500 nm between 1.5 and 40 degrees C. After purification, rhodopsin absorbance can be blue-shifted by up to 6 nm, depending on the detergent species used. Only the longest chain sucrose esters give purified rhodopsin with maximum absorbance comparable to that of the native pigment. In the same manner, detergent-purified rhodopsin will be easily regenerated as long as its native spectral characteristics are maintained. Sucrose esters thus prove to be mild enough to maintain rhodopsin functionality with respect to these two properties and could probably be used successfully to maintain other membrane proteins' integrity.

Animals↗
PubMed1985

Molar absorptivities of bovine retina rod outer segment phospholipids in n-hexane.

The molar absorptivities of the major bovine rod outer segment (ROS) phospholipids and phophatidylcholine 18:1 have been determined at four wavelengths, i.e., 193.5, 196, 200, and 205 nm. The mean standard error is 1.7% at 95% confidence level. The results obtained can therefore be used for the quantitative analysis of bovine ROS phospholipids. Compared with the existing methods, the spectrophotometric determination of these lipids presents the advantages of being rapid, direct, and very sensitive. The importance of stray light in this type of measurement is also discussed.

Animals↗
PubMed1985

Effect of phospholipids and detergents on transitions and equilibrium between the bleaching intermediates of rhodopsin.

The thermal stability of bleaching intermediates and the metarhodopsins I in equilibrium II equilibrium have been examined for purified rhodopsin in cholic acid and a series of alkyl sucrose esters. The results are compared with rhodopsin contained in its natural phospholipid environment. It is found that detergents modify the transition temperatures of the photointermediates in a complex manner. The equilibrium between metarhodopsins I and II is also strongly dependent on the detergent species. It is shifted according to the micellar rigidity. This effect is reversible and allows direct observation of a back reaction from metarhodopsin II to I.

Animals↗
PubMed1984

An evaluation of purity criteria for bovine rod outer segment membranes.

The purity criteria of bovine rod outer segments (ROS) purified by different procedures were evaluated. Bovine ROS were purified by flotation and/or sedimentation in a continuous concentration gradient of sucrose. The purity of the different fractions was then evaluated according to four purity criteria: (i) the A280/delta A500 ratio, (ii) the moles of phospholipid per mole of rhodopsin, (iii) the fatty acid composition, and (iv) the interfacial properties of ROS membranes. All the purity criteria, except the A280/delta A500 ratio, were found to be adequate. From our results, the A280/delta A500 ratio cannot be used alone to characterize ROS purity. Furthermore, the phospholipid-to-rhodopsin ratio appears as the best purity criterion because of its reliability, its higher sensitivity, and its ease of achievement. It is noteworthy that mechanical treatment of the retinas dramatically affects the purification of ROS.

Animals↗
PubMed1984

Localization of a neutralization epitope of foot-and-mouth disease virus using neutralizing monoclonal antibodies.

Neutralizing monoclonal antibodies raised against intact foot-and-mouth disease virus reacted with intact particles and with isolated VP1 from different strains from the same subtype. Prior treatment of the virus with either trypsin or with arginine-specific protease abolished recognition of both the virus and of VP1, suggesting the presence of a neutralization epitope in the central region of VP1 cleaved by these two enzymes. A synthetic peptide analogue of part of this region showed poor reactivity, however, with neutralizing antibody.

Animals↗
PubMed1984

[A portrait of the student at the Université de Montréal.].

In this article, the author attempts to brush a portrait of students between the ages of 20 and 30. Each year, 5 000 of them come to the Guidance service at the Université de Montreal. Of this number, about 80 % seek advice on how to plan their studies or wish to obtain information on the job market. These statistics are hardly surprising, as students today like those of ten years ago, strive to attain, first and foremost, objectives related to their career plans. However, the present economic situation, the scarcity of openings on the market, the choice of profession made too early in life and the quotas adopted by many faculties make their selection a much more complex process. Those who consult for psychological reasons come in greater number in September and January, at the start of the semester. One of the tables illustrates their concerns which are more serious and critical than they were ten years ago. New attitudes and new behaviour patterns are to be noted. While some young people are more competitive in their studies, others have a casual approach and take more time to complete their training. Generally, students are neither activists nor revolutionaries but, rather, have a peaceful and solitary nature. They are attracted by stable and long-lasting relationships, even think of marriage, but the confusion in their roles, resulting largely from the feminist movement and their difficulty in communicating, puts many obstacles in their path. Notwithstanding their worry about the future, they have decided to survive, come what may, and have adopted a new moral code - the respect of their inner being.

English Abstract↗
PubMed1983

[Surface properties of phospholipids of the retinal rod membrane].

In rod outer segments, most lipids are phospholipids. Among the fatty acid chains of these phospholipids, half are polyunsaturated. Despite their tendency to get oxidized, we have succeeded to purify those phospholipids by a preparative method and to measure their individual area-pressure isotherms at argon-water interface. The analysis of those isotherms reveals that membranes formed from these phospholipids must be highly fluid and should molecular movements in the membrane.

Animals↗
PubMed1982

[Congenital toxoplasmosis with hydranencephaly. A case report (author's transl)].

Hydranencephaly is an uncommon finding in congenital toxoplasmosis. The authors report a new case and emphasize the toxoplasmic etiology of this malformation, the possibility of normal neurologic examination at birth, and the usefulness of cranial transillumination whenever congenital toxoplasmosis is suspected in a neonate.

Anencephaly↗
PubMed1976

[Difficult intubations and proposed solutions. Intubation by fiberscopy].

After a review of the various techniques used in difficult intubations, the authors emphasize recent progress in the field of fiber endoscopy. The advantages of this technique, e.g. absence of trauma, increased field of exploration and reduction in dose of anaesthetic drugs, exceed the present disadvantages, e.g. high price of this material, relatively fragile apparatus, too long and diameter too great for use in children.

Fiber Optic Technology↗