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Biomedical subjects

F Bergeron

Publications and source records attributed to F Bergeron.

11 recordsLinked to original sources
PubMed1992

[Multivariate study of auditory perception using multi-electrode cochlear implants].

The goal of this study was to determine the influence of auditory and cognitive factors in hearing or listening mechanisms with the Nucleus multielectrode cochlear implant. Accordingly, hearing sensitivity, psycho-acoustical masking functions and measures of temporal resolution were obtained from 14 adults with acquired deafness. In addition, six measures of open-set speech discrimination were introduced to represent a possible contribution of cognitive factors. Results indicated the contribution of both auditory and cognitive factors to speech understanding. Cognitive factors were most influential. Differences were also found in the relative importance of various cognitive factors, both before and after an intensive aural rehabilitation program. Initially, subjects relied more heavily on their ability to make efficient use of the linguistic redundancy of speech. At the end of the program, they paid more attention to speech acoustics, as a result of enhanced auditory spectral analysis and temporal resolution at about 2 kHz.

Adolescent↗
PubMed1992

[3H]pBC 264, a suitable probe for studying cholecystokinin-B receptors: binding characteristics in rodent brains and comparison with [3H]SNF 8702.

[3H]Propionyl-Tyr-(SO3H)-gNle-mGly-Trp-(NMe)Nle-Asp-Phe-NH2 ([3H]pBC 264) (98-100 Ci/mmol), a new peptidase-resistant cholecystokinin (CCK) agonist that is 1000-fold more potent for CCK-B than for CCK-A receptors, interacts, with a similar subnanomolar affinity, with a single class of binding sites (Kd, 0.15-0.2 nM) in brain membranes of mouse, rat, guinea pig, and cat, in Tris and Krebs buffers. The concentration of CCK-A receptors in rodent brain was estimated to be 8-10 fmol/mg of protein, by measurement of the Bmax values of the nonselective agonist [3H] propionyl-CCK8, with or without 10 nM pBC 264 to saturate CCK-B sites. In guinea pig and mouse brain, specific [3H]pBC 264 binding was not affected by NaCl and/or guanyl-5'-yl-imidodiphosphate. In contrast, in rat brain the affinity of [3H]pBC 264 was decreased and the maximal number of binding sites was increased by NaCl and the guanyl nucleotide or by alkaline treatment, suggesting that a proportion of CCK-B receptors are linked to guanine nucleotide-binding proteins. The Bmax of a CCK8 analog, [3H]SNF 8702, was higher (57 fmol/mg of protein) than that of [3H]pBC 264 (40 fmol/mg of protein) in guinea pig brain cortex but not in mouse brain. The relative potencies of various analogs differed among species. The CCK-B antagonist L365,260 was 18-, 30-, and 64-fold less potent than [3H]pBC 264 in guinea pig, mouse, and rat, respectively. PD 134308, a CCK-B antagonist, was 20-fold less potent in rat brain than in guinea pig brain. Likewise, the cyclic analog BC 254 displayed a 30- and 60-fold lower affinity for mouse and rat than for guinea pig brain preparations. Together, these results suggest the presence of CCK-B receptor subtypes. In all tissues, the specific binding of [3H]pBC 264 at its Kd values was very high (75-90%) and higher than that of the hydrophobic CCK-B probe [3H]SNF 8702 (approximately 50%). Therefore, unlike [3H]SNF 8702, [3H]pBC 264 can be used to study preparations with low receptor concentrations, such as rat brain, making this radiolabeled molecule the most appropriate ligand available to date for CCK-B receptor studies.

Amino Acid Sequence↗
PubMed1991

Solid phase synthesis of a fully active analogue of cholecystokinin using the acid-stable Boc-Phe (p-CH2) SO3H as a substitute for Boc-Tyr(SO3H) in CCK8.

Substitution of the -OSO3H group in the sulfated-tyrosine by the non-hydrolyzable-CH2SO3H group was the first described modification of the sulfate ester that does not affect CCK8 activity. In addition to its capacity to mimic the sulfated tyrosine residue, the amino acid Phe(p-CH2SO3Na) was shown to be stable in acidic media, including HF containing mixtures. The synthesis of Boc-Phe(p-CH2SO3Na)-OH in racemic and resolved forms and its introduction into the sequence of CCK8 by solid phase using standard Boc/benzyl synthesis conditions and BOP as coupling reagent is now reported. The two CCK8 analogues containing the L- or the D-Phe(p-CH2SO3Na) residue, obtained in satisfactory yields, were separated by HPLC and the stereochemistry of Phe(p-CH2SO3Na) residue in each peptide was established by NMR spectroscopy and confirmed by a separate solid phase synthesis in which the pure L isomer was used. Both CCK8 analogues displayed high affinities for peripheral and central receptors (KI approximately 1 nM) and proved to be full agonists in the stimulation of pancreatic amylase secretion. The "stabilized-CCK8 peptide", easily prepared by solid phase, could replace the native peptide in biochemical and pharmacological studies. Moreover the modified amino acid Phe (p-CH2SO3Na) could also be used in solid phase synthesis to prepare a wide variety of CCK analogues and more generally, peptides analogues containing the acid-labile O-sulfated tyrosine.

Amino Acid Sequence↗
PubMed1990

Boc-Trp-Orn(Z)-Asp-NH2 and derivatives: a new family of CCK antagonists.

The respective roles of the benzyloxycarbonyl group (Z) and of the N-terminal tripeptide moiety in the antagonist properties of the cholecystokinin CCK8 analogue Boc-[Nle28,Orn(Z)31]CCK27-33 (Marseigne et al. J. Med. Chem. 1988, 31, 966.) were studied with the following derivatives: Boc-[Nle28,Orn(X)31]CCK27-33, Boc[Nle28,Orn(X)31]CCK27-32, Boc-[Orn(X)31]CCK30-33, and Boc-[Orn(X)31]CCK30-32 (X = Z, Boc, H). These derivatives, the synthesis of eight of which is reported here, were tested for their abilities to inhibit the binding of [3H]pCCK8 to guinea pig pancreatic and brain membranes and for their potencies in stimulating amylase release from guinea pig pancreatic acini. None of the Z derivatives produced amylase secretion, but they competitively antagonized the stimulation induced by CCK8. The deletion of the N-terminal tripeptide and/or Phe-NH2(33) residue did not play a key role in the recognition of peripheral receptors and in the activity of these peptides, whereas replacement of the Z group by a Boc group slightly decreased the affinities of the compounds for both pancreatic and brain binding sites and their potencies as peripheral antagonists. Moreover, the tetrapeptide Boc-Trp-Orn(Boc)-Asp-Phe-NH2 behaved as a partial agonist and analogues in which the Z or Boc groups on the ornithine residue were removed were full agonists. Interestingly, the short peptide derivative Boc-Trp-Orn(Z)-Asp-NH2 displayed the same affinity (KI = 2.0 +/- 0.2 x 10(-7] and the same antagonist activity (pA2 = 6.63) as its parent compound Boc-[Nle28,Orn(Z)31]CCK27-33. This tripeptide could be an interesting tool for studying the structural relationships between peptide and non-peptide CCK antagonists.

Amino Acid Sequence↗
PubMed1990

Multielectrode cochlear implantation in children: the Quebec experience.

The Quebec Cochlear Implant Research Program has implanted three children since August 1987. This paper reports the results obtained with these children. All of them improved their auditory abilities with cochlear implantation and training. However, the abilities which spontaneously recovered following implantation, the speed of improvement, and the overall level of performance are different from one child to the other. Our data suggest that the age at onset of hearing loss, and possibly the number of years of deafness, may be related to the differences in performance.

Age Factors↗
PubMed1989

Cochlear implantation in Quebec city: auditory performance in a recently trained patient.

The Quebec Cochlear Implant Research Program has implanted nine patients since 1984. At the same time, we have been developing some original rehabilitative material for these French speaking patients. This paper reports the results obtained with our last adult patient. With his implant, J-P.F. has clearly improved his auditory response to sounds. After the training period, he demonstrated good abilities in detection, discrimination, identification and comprehension of sounds, phonemes, words and sentences. His lipreading has improved. The performance observed with this patient is comparable with the data reported in other studies using the same implant device.

Adult↗
PubMed1985

Ultrastructural localization of DNA and RNA in Allium porrum interphase cells by means of nuclease-gold complexes.

Nucleic acids have been localized in Allium porrum interphase meristematic cells by means of labelling with nuclease-gold complexes, a technique which provides high resolution and improved specificity. DNase-gold labelling was observed over dense chromatin and to a lesser extent over dispersed chromatin. Nucleolar labelling was restricted to the dense fibrillar component, very few particles being located over the fibrillar centres. Labelling by the RNase-gold complex was present over both the cytoplasm and the nucleoplasm. Cytoplasm labelling was intense over the rough endoplasmic reticulum but absent over vacuoles. In the nucleoplasm many gold particles were located at the border between the condensed and the dispersed chromatin. Nucleolar labelling was intense over the granular zones but many gold particles were also seen over the dense fibrillar component. Fibrillar centres showed, however, no labelling with the RNase-gold complex. These results are consistent with previous autoradiographic and cytochemical observations carried out on the same plant material.

Cell Nucleolus↗
PubMedDate not supplied

[Development of auditory handicap after a multi-electrode cochlear implantation].

The efficacy of cochlear implantation as an aid to communication for profoundly hearing impaired persons is now established. International data show that some comprehension without visual cues is possible in many cases. Up to now, the bulk of research has been focused on psychoacoustical and speech perception measures. Hearing handicap changes following an implantation were rarely explored. On a longitudinal study on the benefits of cochlear implantation for twelve adults with profound acquired deafness, we explored the evolution of the hearing loss handicap. Two questionnaires were completed by the participants before and after implantation. A descriptive analysis of the data shows a rather moderate diminution of the handicap. The importance of the diminution appears inversely correlated to the length of deafness.

Adolescent↗