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Biomedical subjects

C Gagnon

Publications and source records attributed to C Gagnon.

At least 37 records · Page 2Linked to original sources
PubMed2001

The biologic implications of a rare hemoglobin mutant that decreases oxygen affinity.

Blood from seven newborns, a 13-y-old, and seven adult family members with a suspected hemoglobinopathy because of unexplained cyanosis was obtained for analysis to determine Hb oxygen affinity and to characterize and quantify the Hb variants. Their oxygen saturation was 76 to 84%. The P(50) was 30.3 +/- 2.9 for the newborns and 32.5 +/- 2.6 mm Hg for their related adults. In the same order, the plasma erythropoietin was 7.4 +/- 2.9 and 15.9 +/- 3.7 mU/mL, whereas 2,3-diphosphoglycerate was 16.1. +/- 2.9 and 15.9 +/- 3.7 micromol/g Hb. In four of the newborns with increased P(50), the mother had a normal P(50) (27 mm Hg), which indicated a greater maternal oxygen affinity than the fetus with no adverse effects on the fetus. Genetic analysis of alpha-globin genes demonstrated a heterozygous mutation on the alpha2 gene [alpha94(G1)Asp-->His] for each of the newborns and their related adults. The same mutation was found on the alpha1 gene in an adolescent and her father. The mRNA measurements showed that the alpha2- to alpha1-globin mRNA mean ratio was 2.5, alpha2 mutant globin mRNA/total alpha2-globin mRNA was 45.0%, whereas the alpha1 mutant globin mRNA/total alpha1-globin mRNA was 37.8%. The level of alpha2 mutant globin/total alpha-globin was 27.3 +/- 1%, and alpha1 mutant globin/total alpha-globin was 23.8 +/- 1%. The percentage of synthesized alpha2 and alpha1 mutant globins was 27.5 +/- 2 and 26.1 +/- 1, respectively. The ratio of the alpha2/alpha1 mutant globins was 1.1, which corresponded to a ratio at the mRNA level of alpha2/alpha1 of 2.5 +/- 0.5, which suggested that there is a less efficient translation of the alpha2 mRNA than alpha1 mRNA. The reversal of the physiologic fetomaternal oxygen affinity had no effects on fetal development.

Adolescent↗
PubMed2000

Nitric oxide interacts with the cAMP pathway to modulate capacitation of human spermatozoa.

This study aimed to demonstrate nitric oxide production by human spermatozoa and to characterize the interaction between nitric oxide and cAMP-related pathway in the control of human sperm capacitation and protein tyrosine phosphorylation. Spermatozoa were incubated in Tyrode's medium with or without bovine serum albumin (BSA), and nitric oxide was measured with the spin trap sodium N-methyl-D-glucamine dithiocarbamate. Under noncapacitating conditions, spermatozoa produced low levels of nitric oxide. However, under capacitating conditions, prominent nitric oxide adduct signals were obtained and a time-dependent increase of nitric oxide production was observed. When spermatozoa were incubated in Tyrode+BSA medium with nitric oxide-releasing compounds, intracellular cAMP concentrations increased to levels higher than those of spermatozoa incubated in Tyrode+BSA alone. In contrast, incubation with nitric oxide synthase inhibitors (N(G)-nitro-L-arginine methyl ester or N(G)-monomethyl L-arginine) decreased intracellular sperm cAMP concentrations. The inhibitory effect observed with N(G)-nitro-L-arginine methyl ester on capacitation and tyrosine phosphorylation of two sperm proteins (105, 81 kDa) was overcome by the presence of cAMP analogs or of a phosphodiesterase inhibitor. These results indicate that nitric oxide is produced by capacitating human spermatozoa and that it may act as a cellular messenger by modulating the cAMP pathway involved in capacitation and protein tyrosine phosphorylation.

1-Methyl-3-isobutylxanthine↗
PubMed2000

A vortex-bowl disk atomizer system for the production of alginate beads in a 1500-liter fermentor.

Using a model system, a concept for the immobilization of microbial cultures within alginate beads directly in a 1500-L fermentor with a height to diameter ratio of 1.85 is described. The system is comprised of a 60-cm diameter bowl fixed to the top of an agitation shaft, where calcium-ion-rich media is continuously recirculated from the bulk solution to the bowl. The rotation of the shaft and bowl creates a climbing film (vortex) of solution. An atomizing disk centrally recessed within the bowl sprays an alginate solution into the climbing film where the droplets harden into beads. The effect of heat treatment on the alginate solution on resulting bead properties was examined. The sterilization operation did not appear to have a major effect on the alginate bead mechanical properties of firmness and elasticity which was much more a function of alginate concentration. Beads of various sizes were produced by the unit. The system was characterized by the dimensionless numbers Reomega = (omega x rho x D(2))/mu and ReQ = (Q x rho)/(mu x D). At Reomega and ReQ values less than 500 and 0.15, respectively, the mechanism was direct drop. Parent droplets followed by satellite droplets were observed. When either the flow rate or speed was increased, filaments formed predominantly, which was unwanted in this system because filament breakdown into smaller droplets does not occur due to the proximity of the disk to the climbing film in the bowl. This system could be applied to the immobilization of microorganisms, as well as plant or animal cell cultures, and for other sizes or fermentors. The overflow from the bowl carries the gellified beads into the bulk solution where immobilized cells could act upon the fermentation media.

Alginates↗
PubMed2000

Levels of antioxidant defenses are decreased in bovine spermatozoa after a cycle of freezing and thawing.

Growing evidence suggests that the generation of reactive oxygen species (ROS) and their detoxification by antioxidants plays a very important role in fertility. However, the relationship between the level of antioxidants in spermatozoa and the decreased fecundity following a freeze/thaw cycle remains poorly understood. We assessed the activities of antioxidant enzymes such as catalase, glutathione peroxidase (GPx), superoxide dismutase (SOD), and levels of reduced/oxidized glutathione (GSH/GSSG) in bovine semen. Sperm cells were isolated using a Percoll gradient to avoid contamination from seminal plasma, cellular debris, and other cell types. We found that bovine spermatozoa are poorly adapted to metabolize the toxic hydrogen peroxide (H(2)O(2)). Indeed, very low levels of GPx and an absence of catalase were observed. We also studied the effect of freezing and thawing bovine spermatozoa in a egg yolk-Tris-glycerol extender (EYTG). Cryopreservation significantly reduced sperm GSH levels by 78% and SOD activity by 50%. We also investigated whether the decrease in GSH level could be linked to oxidative metabolism and found that a greater reduction in intracellular GSH level occurred when fresh sperm cells were incubated in EYTG for 6 hr at 38.5 degrees C under aerobic conditions than when incubated under restricted oxygen availability. Our results strongly suggest the involvement of an oxidative stress during a freeze/thaw cycle and are consistent with the hypothesis that ROS generated during such a cycle are detrimental to sperm function.

Animals↗
PubMed1999

Semenogelin I: a coagulum forming, multifunctional seminal vesicle protein.

Human seminal plasma spontaneously coagulates after ejaculation. The major component of this coagulum is semenogelin 1, a 52-kDa protein expressed exclusively in the seminal vesicles. Recently, a sperm motility inhibitor has been found to be identical to semenogelin I, suggesting that it may also be a physiological sperm motility inhibitor. The protein is rapidly cleaved after ejaculation by the chymotrypsin-like prostatic protease prostate-specific antigen, resulting in liquefaction of the semen coagulum and the progressive release of motile spermatozoa. Some of the cleavage products of Sg I may also have various biological functions. While the semenogelin I protein is unique to human and higher primates, it has recently been shown to belong to a gene family having a similar gene structure but encoding widely differing proteins. The recently elucidated characteristics of the semenogelin I gene as well as the biochemical and functional properties of the encoded protein are reviewed, and an attempt is made to integrate the various findings into a model for semen coagulation, sperm immobilization and potential other functions.

Amino Acid Sequence↗
PubMed1999

The carboxy-terminal sequence Asp427-Glu432 of beta-tubulin plays an important function in axonemal motility.

Flagellar motility is the result of specific interactions between axonemal microtubular proteins and the dynein motors. Tubulin, the main component of microtubule, is a very polymorphic protein resulting from the expression of several isogenes and from the existence of various post-translational modifications. In order to characterize tubulin isoforms and tubulin domains that are important for flagellar movement, we prepared monoclonal antibodies against axonemal proteins from whole sea-urchin sperm tails. The monoclonal antibodies obtained were screened for their potency to inhibit demembranated-reactivated sperm models and for their monospecific immunoreactivity on immunoblot. Among the different antibodies we obtained, D66 reacted specifically with a subset of beta-tubulin isoforms. Limited proteolysis, HPLC, peptide sequencing, mass spectroscopy and immunoblotting experiments indicated that D66 recognized an epitope localized in the primary sequence Gln423-Glu435 of the C-terminal domain of Lytechinus pictus beta2-tubulin, and that this sequence belongs to class IVb. The use of synthetic peptides and immunoblotting analysis further narrowed the amino acids important for antibody recognition to Asp427-Glu432. Because the primary effect of this antibody on sperm motility is to decrease the flagellar beat frequency, we suggest that this sequence is involved in the tubulin-dynein head interaction.

Amino Acid Sequence↗
PubMed1999

Nitric oxide regulates human sperm capacitation and protein-tyrosine phosphorylation in vitro.

The aim of the present study was to investigate whether the generation of nitric oxide by human spermatozoa is associated with human sperm capacitation and with the tyrosine phosphorylation of sperm proteins. Human spermatozoa were capacitated in the presence or absence of nitric oxide-releasing compounds or nitric oxide synthase inhibitors, and then the percentage of acrosome loss induced by human follicular fluid or by calcium ionophore was determined. The presence of the nitric oxide-releasing compounds primed spermatozoa to respond earlier to human follicular fluid whereas nitric oxide synthase inhibitors decreased the percentage of acrosome reaction. Moreover, nitric oxide modulated tyrosine phosphorylation of sperm proteins. A tight correlation between capacitation and tyrosine phosphorylation regulated by nitric oxide was observed. Results indicate that nitric oxide is involved in human sperm capacitation and emphasize the importance of oxidoreduction reactions in the fine control of sperm physiology.

Acrosome↗
PubMed1999

HbF synthesis during stress erythropoiesis as determined by gamma-mRNA/non-alpha-mRNA quantification.

To determine whether a quantitative relationship exists between globin mRNAs and their translation product during stress erythropoiesis in infants with increased production of fetal hemoglobin (HbF), we measured and compared the relative amounts of the mRNAs of alpha-, beta-, and gamma-globins and their protein synthesis. The synthesis of globin in immature red cells was determined by the incorporation of [3H]leucine, followed by separation and quantification of the polypeptides by C4-reverse phase HPLC. The relative proportions of the mRNAs of the globins were determined by RNase protection assay. A comparison of blood samples from 17 infants expected to have increased production of HbF in relation to their developmental age (five infants of diabetic mothers, two infants with intrauterine growth retardation, one infant with bronchopulmonary dysplasia, and seven infants with cyanotic heart disease) revealed a very significant correlation (r2 = 0.994; p < 0.001) between the ratio of globin mRNAs encoding HbF ([gamma/(gamma + beta)] mRNAs) and the ratios of the de novo synthesis of HbF [gamma/(gamma + beta)]. When only the 10 infants who had increased HbF synthesis are included, the correlation remains unchanged (r2 = 0.997, p < 0.001). The data demonstrated that under conditions of erythropoietic stress, when HbF production is increased, there is a close relationship between the quantification of gamma-globin mRNA and gamma-globin synthesis. The usual methods of determining HbF synthesis can be replaced by globin mRNA determination, which can be performed rapidly with a minimal amount of blood.

Aging↗
PubMed1999

Pulmonary hemorrhage in neonates of early and late gestation.

Our objectives in this study of pulmonary hemorrhage (PH) were to define common characteristics of infants who develop PH, identify factors associated with PH and report the outcome. Neonates (42/2980 admissions) with PH and matched controls were identified. Early gestation (< or = 35 weeks) infants with PH [EGPH] (n = 34; 12 survived) had occurrence of PH at 3.6 +/- 1.1 (mean +/- sem) days and were significantly associated with multiple births (p = 0.03), RDS (p < 0.01) and use of Survanta (p < 0.02). Among EGPH, small for gestational age (SGA) infants (n = 7) had a 100% mortality rate. Late gestation (> or = 36 weeks) infants with PH [LGPH] (n = 8; 6 survived) had occurrence of PH at 0.7 +/- 0.3 days and were significantly associated with low 1 minute (p = 0.04) and 5 minutes (p = 0.01) Apgar scores. All infants were managed with increases in mean airway pressure (MAP) and/or use of cocaine/epinephrine through the endotracheal tube. We have identified 2 groups of neonates with distinct factors associated with PH; use of 1:10,000 epinephrine (0.1 ml/kg) and/or 4% cocaine (4 mg/kg) may be useful adjuncts to increases in MAP for management of PH.

Biological Products↗
PubMed1998

Paradoxical effect of reagents for sulfhydryl and disulfide groups on human sperm capacitation and superoxide production.

Spermatozoa must undergo capacitation prior to fertilization. In humans, this process appears regulated by oxidoreduction reactions. We investigated the possibility that these reactions involved the sulfhydryl-disulfide pair, which offers a reversible regulation of cellular processes. The effects of reagents targeted for sulfhydryl and disulfide groups on human sperm capacitation, superoxide (O2-.) generation and protein tyrosine phosphorylation were evaluated. The sulfhydryl targeted agents, phenylarsine oxide (PAO), diamide, dithiopyridine (DTP), N-ethylmaleimide (NEM), maleimidylpropionyl biocytin (MPB), p-chloromercuribenzoic acid (PCMB), and bromobimane analogs (mBBr and qBBr) triggered sperm capacitation to levels comparable to those observed with a biological inducer, fetal cord serum ultrafiltrate (FCSu). Capacitation induced by NEM, MPB, PCMB, and PAO was prevented by superoxide dismutase (SOD) and associated with an increased sperm production of O2-.. However, SOD did not affect the increase in protein tyrosine phosphorylation of spermatozoa treated with NEM, PAO, or MPB. Disulfide reductants, dithiothreitol (DTT), thioredoxin (TRX), glutathione (GSH), tris-(2-carboxyethyl) phosphine (TCEP), and tris-(2-cyanoethyl) phosphine (TCP) partially to totally inhibited FCSu-induced sperm capacitation and O2-. production. TCEP, DTT, and TRX decreased the capacitation-associated tyrosine phosphorylation of sperm proteins. The strong time-dependent increase of sperm membrane sulfhydryl groups exposed to the extracellular space occurring during the first hour of capacitation could indicate an important rearrangement of sulfhydryl carrying proteins during the initiation of capacitation. Therefore, protein sulfhydryl-disulfide status may be important for the regulation of human sperm capacitation and the mechanisms involved may be complex and multifactorial.

Disulfides↗
PubMed1998

Peroxynitrite production by human neutrophils, monocytes and lymphocytes challenged with lipopolysaccharide.

To assess peroxynitrite formation in lipopolysaccharide (LPS)-stimulated human blood, we have measured nitric oxide (NO)-dependent intracellular oxidation of dihydrorhodamine 123 (DHR 123) to rhodamine. LPS increased DHR 123 oxidation in neutrophil granulocytes, monocytes and lymphocytes in a time-dependent fashion. Greater extent of DHR 123 oxidation was detected in neutrophils and monocytes than in lymphocytes. These changes were accompanied by accumulation of rhodamine in the plasma. While intracellular DHR 123 oxidation and rhodamine accumulation in the plasma were not affected by inhibition of constitutive NO synthase at 30 and 60 min after addition of LPS, they were markedly attenuated by inhibition of inducible NO synthase at 4, 8, 16 and 24 h after addition of LPS. These results demonstrate that human leukocytes can produce high amounts of peroxynitrite in response to LPS, and may contribute to the elevated plasma peroxynitrite levels observed during endotoxic shock.

Adult↗
PubMed1998

Influence of water hardness on accumulation and elimination of cadmium in two aquatic mosses under laboratory conditions.

This study investigated the effect of water hardness on the accumulation and elimination of cadmium (Cd) by two aquatic mosses, Fontinalis dalecarlica and Platyhypnidium riparioides, under laboratory conditions. The two mosses were exposed to nominal Cd concentrations of 0, 0.8, 2, and 10 microg . L-1, which includes the concentration range generally found in nature. The influence of three levels of water hardness (very soft: 11.7 mg . L-1; soft: 44.2 mg . L-1; and hard water: 92.3 mg . L-1 as CaCO3) was measured while maintaining the alkalinity and pH constant during the 28-day exposure. The Cd accumulation by the aquatic mosses was rapid, showing the potential of accumulation and the sensitivity of this biomonitor. Even if the actual Cd concentration in the water was low (concentration <0.15 microg . L-1 to 6.82 microg . L-1 of Cd), the uptake of Cd was very fast and mostly linear. This study was conducted in water hardness comparable to that found in the Canadian shield (hardness was <100 mg . L-1 as CaCO3). When the actual Cd concentration in the water was as high as 6.82 microg . L-1, the uptake of Cd was mostly linear and the steady state condition was not reach. Accumulation rates of Cd were significantly different when the mosses were in very soft (11.7 mg . L-1) as compared to hard water (92.3 mg . L-1 as CaCO3). The elimination of Cd followed a very slow process for the two species studied. The elimination rates of Cd from the mosses were not influenced by water hardness.

Bryopsida↗
PubMed1998

Molecular cloning and characterization of a radial spoke head protein of sea urchin sperm axonemes: involvement of the protein in the regulation of sperm motility.

Monoclonal antibodies raised against axonemal proteins of sea urchin spermatozoa have been used to study regulatory mechanisms involved in flagellar motility. Here, we report that one of these antibodies, monoclonal antibody D-316, has an unusual perturbating effect on the motility of sea urchin sperm models; it does not affect the beat frequency, the amplitude of beating or the percentage of motile sperm models, but instead promotes a marked transformation of the flagellar beating pattern which changes from a two-dimensional to a three-dimensional type of movement. On immunoblots of axonemal proteins separated by SDS-PAGE, D-316 recognized a single polypeptide of 90 kDa. This protein was purified following its extraction by exposure of axonemes to a brief heat treatment at 40 degrees C. The protein copurified and coimmunoprecipitated with proteins of 43 and 34 kDa, suggesting that it exists as a complex in its native form. Using D-316 as a probe, a full-length cDNA clone encoding the 90-kDa protein was obtained from a sea urchin cDNA library. The sequence predicts a highly acidic (pI = 4.0) protein of 552 amino acids with a mass of 62,720 Da (p63). Comparison with protein sequences in databases indicated that the protein is related to radial spoke proteins 4 and 6 (RSP4 and RSP6) of Chlamydomonas reinhardtii, which share 37% and 25% similarity, respectively, with p63. However, the sea urchin protein possesses structural features distinct from RSP4 and RSP6, such as the presence of three major acidic stretches which contains 25, 17, and 12 aspartate and glutamate residues of 34-, 22-, and 14-amino acid long stretches, respectively, that are predicted to form alpha-helical coiled-coil secondary structures. These results suggest a major role for p63 in the maintenance of a planar form of sperm flagellar beating and provide new tools to study the function of radial spoke heads in more evolved species.

Amino Acid Sequence↗
PubMed1998

Quantitative correlation between globin mRNAs and synthesis of fetal and adult hemoglobins during hemoglobin switchover in the perinatal period.

To determine whether a quantitative relationship existed between globin mRNAs and their translation products during the period of switchover, the relative amounts of the mRNAs of alpha-, beta-, and gamma-globins and their protein synthesis in cord blood samples were measured and compared. The synthesis of globins in immature red cells was measured by the incorporation of [3H]leucine followed by separation and quantitation of the polypeptides on a C4-reverse phase HPLC. The relative proportions of the mRNAs of globins were determined by RNase protection assay. A comparison of cord blood samples from 45 newborn infants of different gestational ages (25-41 wk; birth weight, 850-4695 g) revealed a very significant correlation (r2 = 0.924) between the ratio of globin mRNAs encoding HbF ([gamma/(gamma + beta)] mRNAs) and HbA ([beta/(gamma + beta)] mRNAs) and the ratio of de novo synthesis of HbF [gamma/(gamma + beta)] and HbA [beta/(gamma + beta)]. There was a linear relationship between the proportions of globin mRNAs encoding HbF with the proportional synthesis of HbF throughout the developmental stage studied. The ratio of alpha2/alpha1-globin mRNAs increased from 2.0 +/- 0.2 between 24 and 36 wk of gestation to 2.3+/-0.4 (p = 0.02) during 37-41 wk of gestation. These results of the complementary changes at alpha- and beta-loci during fetal development may further the understanding of the coordinated regulation of globin gene expression.

Adult↗
PubMed1998

[Reflection on the project PSI-La Boussole].

The "Psi-La Boussole" project constitutes a model of coordination of services characterized by two currents: case management and coordination of Individualized Service Plan (ISP). Its objectives consists in improving autonomy, social integration and quality of life of persons with severe mental disorders, as well as reducing the burden of families and favor a partnership between different resources. From Spring 1992 to January 1996, in Quebec City, 28 people with mental disorder participated in the project. After presenting their profiles, a synthesis of the analysis of 8 history cases allows to put in light the particularities of the model and its functioning.

Adult↗
PubMed1997

Impaired fertility in mice deficient for the testicular germ-cell protease PC4.

PC4 is a member of the proprotein convertase family of serine proteases implicated in the processing of a variety of polypeptides including prohormones, proneuropeptides, and cell surface proteins. In rodents, PC4 transcripts have been detected in spermatocytes and round spermatids exclusively, suggesting a reproductive function for this enzyme. In an effort to elucidate this function, we have disrupted its locus (Pcsk4) by homologous recombination in embryonic stem cells and have produced mice carrying the mutation. In intercrosses of heterozygous mutant mice, there was low transmission of the mutant Pcsk4 allele to the progeny, resulting in lower than expected incidence of heterozygosity and null homozygosity. The in vivo fertility of homozygous mutant males was severely impaired in the absence of any evident spermatogenic abnormality. In vitro, the fertilizing ability of Pcsk4 null spermatozoa was also found to be significantly reduced. Moreover, eggs fertilized by these spermatozoa failed to grow to the blastocyst stage. These results suggest that PC4 in the male may be important for achieving fertilization and for supporting early embryonic development in mice.

Animals↗