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Biomedical subjects

C Gagnon

Publications and source records attributed to C Gagnon.

At least 127 records · Page 7Linked to original sources
PubMed1989

Mammalian protein methylesterase. Physical and enzymic properties.

Protein methylesterase (PME) amino acid composition and substrate specificity towards methylated normal and deamidated protein substrates were investigated. The enzyme contained 23% acidic and 5% basic residues. These values are consistent with a pI of 4.45. The product formed from methylated protein by PME was confirmed as methanol by h.p.l.c. The kcat. and Km values for several methylated protein substrates ranged from 20 x 10(-6) to 560 x 10(-6) s-1 and from 0.5 to 64 microM respectively. However, the kcat./Km ratios ranged within one order of magnitude from 11 to 52 M-1.s-1. Results with the irreversible cysteine-proteinase inhibitor E-64 suggested that these low values were in part due to the fact that only one out of 25 molecules in the PME preparations was enzymically active. When PME was incubated with methylated normal and deamidated calmodulin, the enzyme hydrolysed the latter substrate at a higher rate. The Km and kcat. for methylated normal calmodulin were 0.9 microM and 31 x 10(-6) s-1, whereas for methylated deamidated calmodulin values of 1.6 microM and 188 x 10(-6) s-1 were obtained. The kcat./Km ratios for methylated normal and deamidated calmodulin were 34 and 118 M-1.s-1 respectively. By contrast, results with methylated adrenocorticotropic hormone (ACTH) substrates indicated that the main difference between native and deamidated substrates resides in the Km rather than the kcat. The Km for methylated deamidated ACTH was 5-fold lower than that for methylated native ACTH. The kcat./Km ratios for methylated normal and deamidated ACTH were 43 and 185 M-1.s-1 respectively. These results indicate that PME recognizes native and deamidated methylated substrates as two different entities. This suggests that the methyl groups on native calmodulin and ACTH substrates may not be on the same amino acid residues as those on deamidated calmodulin and ACTH substrates.

Adrenocorticotropic Hormone↗
PubMed1989

Effects of transglutaminase substrates and inhibitors on the motility of demembranated reactivated spermatozoa.

The effects of transglutaminase (TGase) substrates putrescine, dansylcadaverine, spermine, etc., and the TGase inhibitor cystamine were tested on the motility of demembranated mammalian spermatozoa. These products blocked within a few seconds the motility of demembranated reactivated spermatozoa at concentrations ranging from 0.25 to 5 mM. These minimal inhibitory concentrations could be decreased 5-150-fold when TGase substrates and inhibitor were incubated with demembranated spermatozoa for 15 min prior to the addition of Mg.ATP. The inhibition was reversed by higher concentrations of Mg.ATP but none of these TGase substrates or inhibitor could inhibit bull sperm dynein ATPase. TGase activities, as measured by the incorporation of 3H-putrescine into TCA-precipitable proteins, were present in both sperm Triton-soluble and -insoluble fractions. On the other hand, amine acceptor protein substrates for the TGase-catalyzed reaction were present only in the insoluble fraction. The Triton-soluble TGase was similar to the known "tissue" TGases; the Triton-insoluble TGase activity was calcium independent. The same TGase substrates and inhibitor that blocked the motility of reactivated spermatozoa also blocked TGase activities. Linear relationships were observed between the concentrations of these substances required to block sperm motility and those to block TGase activities. These data suggest the involvement of a TGase activity in sperm motility.

Animals↗
PubMed1989

[The outcome of deprived infants: a retrospective study].

What happens to deprived children when they grow up? The authors tried to answer this question by initially selecting 34 subjects clearly identified as suffering a deprivation syndrome in their youth. Following theoretical considerations, the authors formulated hypotheses which they attempted to verify by comparing the nine adult subjects available who had suffered deprivation during their youth with whom they were able to establish contact with nine others diagnosed as neurotic (the control group). The authors predicted that the deprived subjects would present more disability as adults than the neurotic ones. They were predicted to be more inclined towards delinquency and depression. It was hypothesized that they would not drift into psychosis, psychosomatic illness or become "young chronics". We did not expect that they would move very much on the social scale. The authors seized the opportunity to learn more about the satisfaction with the psychiatric interventions experienced during their youth. In this study, the authors used a questionnaire and four scales of the MMPI to compare the two groups. The deprived subjects demonstrated more maladaptation with a strong tendency towards delinquency and possibly depression. They were not mobile on the social scale, and did not drift into psychosomatic illnesses or become "young chronics" but some psychosis was observed among them. In the final discussion, the authors discuss the limitations of the study due to the size of the sample and problems of the methodology, along with ways that this could be strengthened in order to more successfully answer some of the questions raised.

Adolescent↗
PubMed1989

Nursing interventions: the infant treated with pancuronium bromide.

Nursing care of the newborn in respiratory distress has become highly sophisticated and technical, requiring skill in principles of neonatal assessment and therapeutic interventions. It is important to be knowledgeable about the technical aspects of the equipment and monitors. However, focus should always remain on the infant as an individual within a family unit.

Humans↗
PubMed1988

Stoichiometric carboxyl methylation of chromogranins from bovine adrenal medullary cells.

The secretory proteins from adrenal chromaffin granules, chromogranins A, A1 and A2, were found to be excellent in vitro methyl acceptor proteins. The purified protein-carboxyl methylase (PCM) from bovine erythrocytes incorporated 660, 2540 and 7890 pmol of methyl group/10 min/mg protein in chromogranins A, A1 and A2, respectively. However, dopamine beta-hydroxylase, another secretory protein within chromaffin granules was poorly methylated. The stoichiometry of methylation for chromogranins A, A1 and A2 was 0.26, 0.89 and 1.3 mol of methyl group/mol of protein, respectively. Kinetic analysis showed that chromogranins A1 had the highest turnover rate followed by chromogranins A2 and A. These chromogranins are the first secretory proteins to be stoichiometrically methylated in vitro without prior deamidation.

Adrenal Medulla↗
PubMed1988

Protein-carboxyl methylation in adrenal medullary cells.

1. The protein-carboxyl methylating system has been studied in adrenal medullary cells either using disrupted cell components or with intact cells. Whereas the enzyme protein-carboxyl methylase (PCM) is cytosolic, the majority of its substrates is on or within chromaffin granules. With intact granules, methylation of surface proteins results in solubilization of membrane proteins. 2. Membrane PCM substrates have been identified as two proteins with apparent molecular weights of 55,000 and 32,000. Among the substrates located inside the granules, the chromogranins are excellent substrates, while dopamine beta-hydroxylase is poorly methylated. 3. Under physiological conditions, stimulation of the splanchnic nerve results in an increase in adrenal medullary protein-methyl ester formation as well as in an augmented methanol production. With adrenal medullary cells in culture, carboxyl-methylated chromogranin A is detected in mature chromaffin granules between 3 and 6 hr after labeling. Methylated chromogranins are secreted concomitantly with catecholamines following cholinergic stimulation. 4. These data coupled with those of Chelsky et al. (J. Biol. Chem. 262:4303-4309, 1987) on lamin B suggest that PCM methylates residues other than D-aspartyl and L-isoaspartyl in proteins. They further suggest that methylation may occur on nascent peptide chains before they are injected into the rough endoplasmic reticulum.

Adrenal Medulla↗
PubMed1988

Inherited rod-cone dysplasia: abnormal distribution of cyclic GMP in visual cells of affected Irish setters.

Light-adapted retinas from Irish setters affected with inherited rod-cone dysplasia accumulate high concentrations of cyclic GMP in the outer plexiform layer (OPL). A 29-fold difference in OPL cGMP levels between affected and normal occurs at 19-20 days. However, the highest concentration, 550 mumol kg-1 (dry) wt, is reached at about 4 weeks of age, at which time OPL cyclic GMP is 20-fold higher than cGMP in the OPL of normal control retinas. Levels remain high in affected OPL until about 7 weeks of age; after this, the cyclic GMP level falls and the peak shifts to the outer nuclear layer (ONL). In the normal retina on the other hand, the highest cyclic GMP levels are in the outer segments (OS). The result is that cyclic GMP is highest at opposite ends of the photoreceptor neuron in normal and affected retinas during the first 7 weeks of development. These differing distributions are established as early as postnatal day 10, before signs of degeneration become evident, as determined by either ERG or morphological examination. Moreover, a 38-fold rise in cyclic GMP occurs in the ONL of affected retinas between 1 and 3 weeks of age significantly before the degeneration of nuclei begins at 4 to 5 weeks. The early differences in cyclic GMP distribution are probably not due to differences in guanylate cyclase activity since enzyme levels in normal and affected photoreceptor cells are virtually identical until about 4 weeks of age. Since cGMP has been observed to reach high levels in normal dark-adapted rabbit and frog OPL, the extraordinary OPL levels seen in affected setters may indicate the importance of cGMP in both normal synaptic function and in the disease process.

Aging↗
PubMed1988

A human seminal plasma protein blocks the motility of human spermatozoa.

An inhibitor of the motility of demembranated spermatozoa has been shown to be present in human seminal plasma. This seminal plasma motility inhibitor (SPMI) was purified to apparent homogeneity and tested on intact human spermatozoa. Motility parameters of spermatozoa incubated with the sperm motility inhibitor were evaluated with the video automated Cell Soft system. SPMI decreased the percentage of motile spermatozoa in a dose-dependent manner and motility was completely blocked in the presence of 1600 units/ml. Sperm velocity and beat/cross frequency showed a similar progressive decrease as the inhibitor was augmented. However, linearity was essentially not affected. The effects of SPMI on the percentage of motile spermatozoa increased with the time of contact between the inhibitor and spermatozoa. After 120 min., the IC50 was 35% lower than that observed at five min. The presence of seminal plasma did not prevent the inhibitory effects of the seminal plasma factor on sperm motility parameters. On the contrary, a potentiating effects was observed. The data suggest that the SPMI could play a significant role in cases of infertility caused by asthenospermia.

Humans↗
PubMed1988

A highly specific radioreceptor assay for the active circulating form of atrial natriuretic factor in human plasma.

This highly sensitive radioreceptor assay (RRA) for the active circulating form of atrial natriuretic factor (ANF), fragment 99-126, in human plasma requires 125I-labeled ANF, bovine zona-glomerulosa membrane receptors, and amiloride HCl. The amiloride elicits an increase in the binding affinity of ANF to its receptors. ANF is extracted from human plasma with "Sep-Pak" cyano cartridges. After a 90-min incubation at 25 degrees C, bound and free fractions are separated by filtration. The ANF concentration that inhibits receptor binding of the radioligand by 50% is 12.4 fmol of unlabeled ANF per tube. The minimum detectable concentration is 0.2 fmol per tube. Using ANF-supplemented plasma samples, there was a good correlation (r = 0.99) between ANF concentrations found and those expected. Only the active circulating form of ANF fully cross-reacts in this assay, which confirms its high selectivity. Results correlated strongly (r = 0.93) for clinical samples tested by RRA and RIA.

Adrenal Cortex↗
PubMed1987

Bull sperm 19S dynein polymerizes brain tubulin into microtubules.

Crude dynein extracted from bull sperm flagella polymerized pure phosphocellulose tubulin isolated from brain tissues into microtubules. This effect was predominantly due to the 19S dynein particle in the extract. ATP stimulated up to five fold the polymerization of brain tubulin by bull sperm dynein. Hydrolysis of ATP was not required since vanadate at a concentration sufficient to block dynein ATPase activity did not interfere with ATP stimulation and because the non hydrolyzable ATP analogue adenylyl (beta-gamma-methylene) diphosphate (AMPPCP) had effects similar to those of ATP. These results suggest that, in addition to hydrolyzing ATP to generate the driving force necessary for microtubule sliding within the axoneme, dynein may also interact with ATP to polymerize tubulin into microtubules.

Adenosine Triphosphatases↗
PubMed1987

Leupeptin and chymostatin inhibit mammalian protein methylesterase activity.

Purified protein methylesterase (PME) from rat kidneys was incubated with ovalbumin-methyl esters and a series of protease inhibitors. All four inhibitors with C-terminal aldehyde, leupeptin, chymostatin, Boc-Gln-Leu-Lys-H and D-Phe-Pro-Arg-H completely blocked PME activity. Other inhibitors including, alpha-1 antitrypsin, soybean trypsin inhibitor, antithrombin III, phenylmethylsulfonylfluoride, aprotinin and lima bean trypsin inhibitor had no significant effect whereas pepstatin, at high concentration reduced the enzymatic activity by 25%. The most potent inhibitors, leupeptin and chymostatin, had a Ki of 3.5 X 10(-8) and 5.4 X 10(-7) M, respectively. These inhibitors provide two new tools to study PME function.

Animals↗
PubMed1987

Structure and mass analysis of 12S and 19S dynein obtained from bull sperm flagella.

The Brookhaven scanning transmission electron microscope (STEM) was used to elucidate the structures and masses of 12S and 19S dynein extracted from bull sperm flagella. The 12S particle was a single globular particle with an average mass of 311 +/- 10 kdaltons. The 19S dynein particles consisted of two globular heads joined to a common base. The average mass of the 19S particle was 1.6 +/- 0.04 X 10(6) daltons. Thus, with the exception of the larger mass, the bull sperm 19S dynein molecule resembles the two-headed 21S dynein obtained from sea urchin sperm flagella and the 18S dynein obtained from Chlamydomonas with the possibility of a third head giving rise to the 12S particle. The structure, mass and polypeptide composition of bull sperm flagella dynein is compared with outer arm dyneins previously obtained from Chlamydomonas, Tetrahymena, and sea urchin sperm flagella.

Adenosine Triphosphatases↗
PubMed1987

Secretory proteins from adrenal medullary cells are carboxyl-methylated in vivo and released under their methylated form by acetylcholine.

The carboxyl methylation of secretory proteins in vivo was investigated in bovine adrenal medullary cells in culture. Chromogranin A, the major intragranular secretory protein in adrenal medullary cells, and other secretory proteins were found to be carboxyl-methylated within secretory vesicles. The in vivo labeling pattern using [methyl-3H]methionine and the in vitro labeling pattern using S-adenosyl-[methyl-14C]methionine of intravesicular secretory proteins were similar. The detection of methylated chromogranin A in mature secretory vesicles required 3-6 h, a time consistent with the synthesis and storage of secretory proteins in this tissue. Carboxyl-methylated chromogranin A was secreted from medullary cells by exocytosis via activation of nicotinic cholinergic receptor and recovered still under the methylated form in the incubation medium. Since protein-carboxyl-methylase is cytosolic, these results suggest that methylation of secretory proteins is a cotranslational phenomenon.

Acetylcholine↗
PubMed1987

Mother and child characteristics and involvement in dyads in which very young children have eczema.

The purpose of this study was to verify statements made in the literature concerning the personality characteristics of mothers of children who have eczema, those of the children, and their dyadic interaction. Three observers made five 2-hour home visits to 14 mother-child dyads when the children were 29, 33, 37, 41, and 45 weeks old. Seven dyads included a child who had eczema. The results showed these dyads to be significantly different from the control dyads, in that they were less aware and less involved with each other, and less mutually positively reinforcing. However, neither the mothers nor the children, nor the interaction between them fit the descriptions made of them in the literature. The authors therefore caution against making generalizations about the psychological contributions to or psychomaintenance of childhood eczema.

Eczema↗
PubMed1986

Isolation and characterization of dynein ATPase from bull spermatozoa.

Dialysis of demembranated bull spermatozoa against a low-salt buffer resulted in the solubilization of the outer dynein arms and 15-25% of the total ATPase activity. Low-salt extracts contained three high-Mr peptides with Mr values above 300,000. The ATPase activity was associated with two particles sedimenting at 19 S and 12 S. The heavier particle contained two major high-Mr peptides with Mr values above 300,000, one major and one minor intermediate peptides with Mr values of 91,000 and 140,000 respectively and lower-Mr peptides. The 12 S particle contained one high-Mr peptide positioned between the two heavy peptides of the 19 S particle. Even though the peptide compositions of these two particles were different, the enzymic properties of their ATPases were similar. Both particles hydrolysed in the following preference order: ATP greater than CTP greater than UTP greater than ITP greater than GTP. ATPase activities were not affected by ouabain and oligomycin but were inhibited by vanadate, erythro-9-[3-(2-hydroxynonyl)]adenine and EDTA. Enzyme activities were dependent on the presence of a bivalent cation with the following preference order: Mn2+ greater than Mg2+ greater than Ca2+ greater than Ni2+. Optimal activity was observed between pH 6.5 and 9.5. The Km for ATP ranged from 40 to 50 microM for both 19 S and 12 S ATPases. These results suggest that the 12 S and 19 S particles are dyneins from outer dynein arms.

Adenosine Triphosphatases↗
PubMed1986

Positive correlation between the level of protein-carboxyl methylase in spermatozoa and sperm motility.

Levels of protein-carboxyl methylase (PCM) activity were measured in spermatozoa from infertile patients with less than 50% sperm motility and compared with those of normal fertile controls. When spermatozoa were washed by a standard centrifugation procedure, the level of PCM activity in a subgroup of patients with sperm motility ranging from 0% and 20% (24.0 +/- 5.2 pmol/mg protein, mean +/- standard error of the mean) was significantly different from that of controls (35.9 +/- 2.3 pmol/mg). However, when the entire population of patients with sperm motility ranging from 0% to 50% (32.6 +/- 6.2 pmol/mg) was compared with controls, no significant difference was observed in sperm PCM levels. With this standard washing procedure no significant relationship (r = 0.28; P greater than 0.05) between sperm PCM activity and motility was observed. By contrast, when spermatozoa were washed on a Percoll gradient, to eliminate other cellular elements, both groups of patients with 0% to 20% (14.6 +/- 2.5 pmol/mg) and with 0% to 50% (21.5 +/- 2.4 pmol/mg) sperm motility had sperm PCM levels significantly lower than that of controls (34.7 +/- 3.6). A highly significant relationship (r = 0.78; P less than 0.001) was observed between the levels of sperm PCM activity and motility.

Adult↗