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Biomedical subjects

F Bélanger

Publications and source records attributed to F Bélanger.

17 recordsLinked to original sources
PubMed2006

Phenotypic flexibility of digestive system in Atlantic cod (Gadus morhua).

This study examined the restoration of the digestive capacity of Atlantic cod (Gadus morhua Linnaeus) following a long period of food deprivation. Fifty cod (48 cm, 1 kg) were food-deprived for 68 days and then fed in excess with capelin (Mallotus villosus Müller) on alternate days. Ten fish were sampled after 0, 2, 6, 14 and 28 days and the mass of the pyloric caeca, intestine and carcass determined. Two metabolic enzymes (cytochrome c oxidase and citrate synthase) were assayed in white muscle, pyloric caeca and intestine, and trypsin activity was measured in the pyloric caeca. A delay of 14 days was required before body mass started to increase markedly, whereas most of the increase in mass of both the pyloric caeca and intestine relative to fish length occurred earlier in the experiment. By day 14, the activities of trypsin and citrate synthase in the pyloric caeca as well as citrate synthase in the intestine had reached maxima. The growth of the digestive tissues and restoration of their metabolic capacities thus occur early upon refeeding and are likely required for recovery growth to take place. The phenotypic flexibility of the cod digestive system is therefore remarkable: increases in trypsin activity and size of pyloric caeca resulted in a combined 29-fold increase in digestive capacity of the fish during the refeeding period. Our study suggests that Atlantic cod are able to cope with marked fluctuations in food availability in their environment by making a rapid adjustment of their digestive capacity as soon as food availability increases.

Animals↗
PubMed1998

Inducible overexpression of a toxic protein by an adenovirus vector with a tetracycline-regulatable expression cassette.

We have constructed two new adenovirus expression cassettes that expand both the range of genes which can be expressed with adenovirus vectors (AdV) and the range of cells in which high-level expression can be attained. By inclusion of a tetracycline-regulated promoter in the transfer vector pAdTR5, it is now possible to generate recombinant adenoviruses expressing proteins that are either cytotoxic or that interfere with adenovirus replication. We have used this strategy to generate a recombinant adenovirus encoding a deletion in the R1 subunit [R1(delta2-357)] of the herpes simplex virus type 2 ribonucleotide reductase. Cell lines expressing the tetracycline-regulated transactivator (tTA) from an integrated vector or following infection with an AdV expressing tTA are able to produce deltaR1 protein at a level approaching 10% total cell protein (TCP) when infected with Ad5TR5 deltaR1 before they subsequently die. To our knowledge, this is the first report of the overexpression of a toxic gene product with AdV. We have also constructed a new constitutive adenovirus expression cassette based on an optimized cytomegalovirus immediate-early promoter-enhancer that allows the expression of recombinant proteins at a level greater than 20% TCP in nonpermissive cell lines. Together, these new expression cassettes significantly improve the utility of the adenovirus system for high-level expression of recombinant proteins in animal cells and will undoubtedly find useful applications in gene therapy.

Adenoviridae↗
PubMed1993

Cultured epithelium allografts: Langerhans cell and Thy-1+ dendritic epidermal cell depletion effects on allograft rejection.

The effects of in vitro dendritic cell (DC) depletion on the survival of epidermal sheet allografts were studied in a murine model. Newborn (1-3 days old) mouse skin was used. Langerhans cell (LC) and Thy-1+ dendritic epidermal cell (Thy-1+ DEC) depletion was achieved using: (1) a prolonged culture period (7 days), or (2) the anti-IA and anti-Thy-1.2 mAbs followed by complement treatment. DC (LC and Thy-1+ DEC) depletion was assessed on sheets and cultured cell suspensions by an indirect immunofluorescence procedure. They showed that, after 7 days of culture or after the antibody-complement treatment, epidermal cultures were depleted of LC and Thy-1+ DEC. Cultured sheets were grafted onto the muscle of H-2-incompatible recipients. The control experiments were: (1) full epidermis and DC undepleted sheet allografts, and (2) DC depleted and undepleted sheet isografts. The full epidermis was totally rejected after 9 days. However, no rejection sign was ever seen in any of the isografts. The in vitro produced and allografted epithelia did not show any necrotic sign until the 11th day postgrafting. However, on days 12-13, the DC depleted allograft's color changed from pink to brown. On days 14-16, degradation of the allografts resulted in a complete denudation of the underlying muscle. Immunohistological analysis of the allografts revealed the presence of a monocyte and lymphocyte infiltration starting from the 11th day postgrafting, with the presence of polymorphonuclear leukocytes on day 14. These results suggest that LC and Thy-1+ DEC depletions were not sufficient to prevent allograft rejection.

Animals↗
PubMed1992

Optimization of murine keratinocyte culture for the production of graftable epidermal sheets.

The aim of the present study was to optimize murine epidermal cell cultures in order to obtain graftable sheets. Newborn (1-3 days old) Balb/c mice skin were used to optimize culture media and plating cell concentration, then epidermal sheet production, and grafting. Epidermal cells were plated at various concentrations in different culture media containing low (0.1 mM) or high (greater than 1 mM) Ca2+ levels. After a 3 day culture at the 10(4) cells/cm2 plating cell concentration, the percentage of differentiated cells was more than 80% in the high Ca2+ culture medium and less than 50% with bulky cells in the low Ca2+ culture medium. Under these conditions confluence was not obtained. At the 10(5) cells/cm2 seeding inoculum, the percentage of confluence increased to 95-100% during the first 72 h of culture in both high and low Ca2+ culture media. Three-day-old culture showed stratified multilayer epidermal sheets in the high calcium medium, and monolayer epidermal sheets were present in the low calcium medium after seeding keratinocytes in fibronectin precoated flasks. Seven days after plating, post confluent cultures were composed of a high percentage of differentiated cells (90%) with an increase in shedding cells in the medium. Considering the above morphological observations, sheets obtained with 10(5) cells/cm2 in MCDB-153 (A), DME-HAM (B) or GMEM (C) media after 3 days in culture were grafted. Twenty days after grafting, histological analysis of biopsies showed an epidermal structure and organization comparable to normal murine epidermis without hair follicles. Epidermal transplants showed a complete basement membrane, hemidesmosomes, and tonofilament bundles. Sheets obtained after seven day culture in all media showed lower coverage of the wound bed. These studies point out the importance of the plating cell and Ca2+ concentrations, and the culture time for murine keratinocyte confluence and differentiation to obtain graftable epidermal sheets.

Animals↗
PubMed1989

Comparison of caprine, human and bovine strains of respiratory syncytial virus.

A new continuous ovine kidney cell line allowing the growth of caprine, human and bovine respiratory syncytial virus was used to minimize host cell related variations for the direct comparison of the viral ultrastructures, serological relationships and structural protein profiles. Results show that all three strains are closely related although a closer relationship was found between bovine and caprine RS.

Animals↗
PubMed1988

Methods to study changing free amino acid pools during embryonic chick development.

During early embryogenesis of the chick, the yolk represents the only source of free amino acids. Leucine and glutamic acid, together with valine, predominate in this nonrenewable nutrient supply; taurine and phosphoethanolamine are present in the lowest concentration. The tyrosine level is already twice as high as phenylalanine. At embryo day 2 (E2), the not-yet fully functioning vitelline blood plexus demonstrates an amino acid profile that rather closely resembles that of the yolk, except for three amino acids. During the transfer process from yolk to plexus, a certain amount of glutamic acid appears to be metabolized to glutamine and aspartic acid. Taurine and phosphoethanolamine are highly concentrated in the circulation, with a ten-fold increase of taurine and a 50-fold rise in phosphoethanolamine. The tyrosine-to-phenylalanine ratio remains 2:1, but their levels relative to valine and other essential amino acids fall by roughly 50%. In the already contracting heart tube and the developing neural tissue on E2, taurine and phosphoethanolamine also accumulate preferentially; the levels in neural tissue are ten- and fivefold higher than in the circulation for the respective amino acids, whereas the heart has three time the plexus content of taurine and two times the amount of phosphoethanolamine. Tyrosine and phenylalanine, still in the same proportion, have risen to approximately twice the circulation values. The heart tube, unlike the primitive brain, concentrates leucine, whereas isoleucine accumulates in both organs. Injections of valine (50 mumol) and taurine (200 mumol) into the yolk on E1 demonstrate that a higher yolk content of an amino acid can result in a two- to threefold tissue increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1988

Development of the amino acid pools in chick embryo brain, heart, and eye: taurine, valine, glutamine, and phosphoethanolamine.

The redistribution of valine, from the nonrenewable yolk supply into excitable tissues, was studied during the first 15 days of chick embryogenesis. Valine levels in the extraembryonic circulation (the vitelline plexus) peak between days 7-9 (E7-9) and then decline steeply. In their first phase of differentiation (E2-E4), all embryonic tissues contain more valine than the blood plexus. From E4 to E7, the heart and brain exhibit initially a rapid fall in valine, but from day 7 on the decrease becomes more gradual. The eye during the same period reaches an equilibrium with circulating valine; as these levels fall from E9 to E15, the eye retains the valine that accumulated. Against this pattern of change, characteristic for an essential amino acid during embryogenesis, glutamine levels are at any time from two- to threefold higher than valine in all tissues. In the circulation, this ratio remains constant throughout the 15 days of embryonic development. Eye glutamine, higher on day 4, by E7 has entered into an equilibrium with glutamine in the plexus. A steady but two times higher glutamine level is maintained in the heart, although during the later stages of development it gradually tends to approach the plexus content. In sharp contrast, starting on E7 and accelerating on E9, a large increase of glutamine relative to valine or other essential amino acids is seen in developing brain tissue. This appears typical for most metabolic amino acids, suggesting that by days 9-10 the essential amino acid supply in the brain is being exhausted.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1988

Embryonic exposure to high taurine: a possible nutritional contribution to Friedreich's ataxia.

When fertilized eggs (50 g) are injected on day 1 with 100 mumol taurine (0.2 ml), 15-day-old embryos exhibit increased taurine content in heart and brain. Lethal toxicity was no higher than with equimolar injections of NaCl (50 mumol) or valine (100 mumol) of the same volume. That same dose of taurine injected either on embryonic day 1 or 7 produced in hatchlings a typical syndrome of ataxia, reduced muscle strength and motor incoordination. When injected on embryo day 15 (E15) most chicks appeared incapable of pecking out of the egg, and the resulting delay in hatching, if if did occur, precluded presuming that the poor condition of such chicks was exclusively due to the late taurine injections. In view of the tendency of Friedreich's ataxia patients to exhibit increased alimentary absorption of taurine, and to demonstrate an excessive accumulation of taurine in the cerebellum and heart tissue on autopsy, fetal exposure to high taurine levels or neonatal high taurine milk ingestion may, by analogy, contribute to the slowly progressing disease process.

Animals↗
PubMed1988

The establishment of essential and metabolically derived amino acid profiles in developing chick embryo organs.

The accumulation of certain essential and metabolically derived amino acids in the free amino acid pools of three excitable tissues has been studied in the chick embryo. Valine together with leucine are at the onset present in the yolk at higher concentrations than any of the other essential amino acids. By 15 days all the amino acids studied have accumulated in the embryonic pools at a higher rate than valine, although certain amino acids, such as phenylalanine or methionine, always remain at lower relative concentrations than valine. This reflects their low supply in the yolk, rather than a more rapid rate of disappearance (utilization). During early embryogenesis (E2-E4), tissues preferentially concentrate glutamic acid, besides taurine and phosphoethanolamine (6). The next distinct stage of development (E4-E7) is marked in the brain by a gradual rise in glutamic acid, glutamine and aspartic acid; the same three amino acids do not demonstrate a further increase in the pool of the heart, while in the whole eye the amino acid profile begins to resemble the blood. Leucine in all three tissues declines rapidly, to reach isoleucine levels by day 7 of development; tyrosine increases slowly in apparent reciprocity to an equally gradual phenylalanine decrease. Into the second week of embryo growth (E7-E15), GABA appears in the mesencephalon (E7) and the eye (E9-E10). In the mesencephalon, the free amino acid pool composition exhibits a rather sudden increase of most metabolically derived amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1988

Rapid titration of bovine, caprine and human RS virus by a micro-immunoperoxidase assay using a monoclonal antibody and a permissive ovine kidney cell line.

An indirect immunoperoxidase micro-assay, using a continuous cell line derived from ovine kidney cells (OK) and a previously characterized monoclonal antibody (7C2), specific for an exposed and highly conserved epitope of the fusion protein of different strains of RS virus, was used advantageously to rapidly titrate bovine, caprine and human strains of RSV by either quantal (TCID50) or plaque forming assays. Virus titers, obtained in less than 36 h, were in agreement with those obtained by the conventional plaque assays which required an incubation period of 4 days or more. This assay is also applicable to micro-neutralization of fusion inhibition assays for testing serum or screening monoclonal antibodies.

Animals↗
PubMed1988

Electron microscopic evidence for bridges between bovine respiratory syncytial virus particles.

Electron microscopic examination of ultrathin sections of a continuous cell line of ovine kidney (OK) origin, infected by bovine respiratory syncytial virus (BRSV), revealed the presence of well defined bridges between virus particles. This is the first report of this novel structure. Observation of ultrathin sections of human RSV Long strain also grown on OK cells did not show inter-particle bridges and therefore suggested that this structure could be specific to BRSV. The biological significance of these bridges is not clear at this time; a possibility is that the bridges are formed by the fusion protein of BRSV which is known to cause cell fusion. Besides the structural implications, the importance is in relation to purification strategies for this virus, which must now take into account that most of the viral particles occur in large aggregates.

Animals↗
PubMed1984

Platelet taurine content in Friedreich's disease.

We have studied the concentrations of taurine and of 6 other amino acids in platelets from 12 patients with Friedreich's disease and 12 age sex-matched normal control subjects. No significant differences could be demonstrated between the two groups. The glycine/serine ratio was lower in all the patients but this change did not reach statistical significance. From these and other data, we conclude that the taurine retention deficit observed previously in Friedreich's disease cannot be the primary causal defect.

Adult↗
PubMed1981

The hypotensive effect of centrally administered neurotensin in rats.

We have evaluated the cardiovascular effects of intracerebroventricular (i.c.v.) injections of neurotensin (NT) in pentobarbital-anesthetized rats. In most animals, the i.c.v. injection of NT (5.4, 10.8 and 16.2 nmol/rat) induced a dose-dependent fall of the arterial blood pressure. This effect was usually rapid in onset (30-60 sec) and of short duration (approximately 1-4 min). It was not preceded nor accompanied by any significant alteration of the heart rate. In about 25% of the animals, the vasodepressor effect of i.c.v. injections of NT was long lasting (30-45 min). Conscious rats were much less sensitive than anesthetized animals. The hypotensive effects of intravenously (i.v.) administered NT was fully maintained in animals made tolerant to the hypotensive effect of centrally administered NT. Similarly, the animals made unresponsive to i.v. injections of NT either by repeated i.v. injections of NT (e.g. tachyphylaxis) or by a chronic treatment with compound 48/80, still responded normally to centrally administered NT. The results suggest the existence of at least two anatomically distinct sites of action through which NT can induce hypotension in rats. One appears to be located in the periphery and the other, in the central nervous system.

Animals↗
PubMed1978

Hypokinesia produced by anterolateral hypothalamic 6-hydroxydopamine lesions and its reversal by some antiparkinson drugs.

Hypokinesia produced by stereotaxic microinjection of solutions of 6-hydroxydopamine into the anterolateral hypothalamus of male rats is accompanied by a generalized reduction in brain noradrenaline levels and a reduction of dopamine in the striatum and cerebral cortex. The hypokinesia is reversed by the putative dopamine-receptor agonists apomorphine, ET-495 and CB-154 as well as by the amino acids L-Dopa and m-tyrosine when administered in combination with the peripheral decarboxylase inhibitor Ro 4-4602. The relative importance of noradrenergic and dopaminergic systems in the mediation of the action of anti-akinesia drugs is discussed.

Animals↗
PubMed1978

Ouabain induced stereotyped behavior in rats.

Stereotyped behavior was induced in rats with ouabain administered intraventricularly in doses of 2, 3 and 4 microgram in 50 microliter saline. Haloperiodol reduced the stereotyped behaviour. Monoamine turnover studies showed a reduction in concentration of norepinephrine in hippocampus and midbrain, an increase in norepinephrine turnover in the medulla oblongata and a reduction in dopamine turnover in the striatum. The interpretation of these finds is discussed. It is suggested that this model could be significant clinically as it demonstrates that impairment of Na+-K+-ATP'ase may result in behavioral abnormalities characterised by stereotypy.

Animals↗