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Biomedical subjects

M Fortin

Publications and source records attributed to M Fortin.

52 records · Page 3Linked to original sources

Calretinin labels a specific neuronal subpopulation in primate globus pallidus.

All pallidal neurones are believed to share the same chemical and morphological phenotype in primates. At variance with this idea is the present finding that calretinin (CR), a calcium binding protein, occurs only in a subset of pallidal neurones in squirrel monkeys. This chemospecific subpopulation comprises both large and small bipolar and multipolar neurones distributed according to a rostrocaudal decreasing gradient. The large neurones outnumber small neurones throughout the pallidum; they abound principally in the external pallidal segment, whereas the small neurones prevail in the internal segment. Some pallidal CR-positive neurones display dorsoventrally elongated dendrites, while others show dendrites radiating in all directions. These findings reveal that pallidal neurones form a chemically and morphologically heterogeneous population in primates.

Animals↗

New classes of antimuscarinic agents endowed with selective antispasmodic properties. 1-Arylsulfonyl pyrrolidin-2-ones and 2-thiones, 1-arylsulfonyl piperidin-2-ones and 2-thiones and 1-arylsulfonyl hexahydro-2H-azepin-2-one.

A series of 1-arylsulfonylpyrrolidin-2-ones (and 2-thiones), 1-aryl sulfonylpiperidin-2-ones (and 2-thiones) and 1-arylsulfonyl hexahydro-2H-azepin-2-one were synthesized and submitted to a battery of binding assays. The compounds showed little or no affinity for the receptors tested other than muscarinic receptors labelled either with [3H]pirenzepine or with [3H]quinuclidinyl benzilate. When tested in the isolated guinea pig ileum, they antagonized the contractions induced by acetylcholine and behaved as competitive muscarinic antagonists. After parenteral administration in mice, most compounds inhibited carbachol-induced diarrhoea but were less effective in counteracting salivation and lacrimation and showed little or no mydriatic action, thus displaying selectivity at the intestinal level. The reference drugs tested, atropine, butyl scopolamine and cimetropium bromide were far less selective. maximal in vivo activity was obtained by introducing diethylamino or 1-piperidino or 1-hexahydroazepinyl groups in the 4-position of the phenyl ring while the enlargement of a 5- to a 6-membered lactam ring or its conversion into a thiolactam had a less marked effect. The most interesting compounds were further evaluated for their ability to antagonize carbachol-induced colonic hypermotility in the rat and arecoline-induced analgesia in mice. The effect on gastric acid secretion in the rat was also investigated. The overall in vivo data showed that compounds 14, 15, 26 and 27, i.e. those bearing a 1-hexahydroazepinyl group in the 4-position of the phenyl ring, were the most potent and selective compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[Fertility goals among students at the University of Sherbrooke].

This paper describes intentions in the matters of fertility expressed by 900 first-year students surveyed at the University of Sherbrooke in Canada. The study seeks to ascertain links between certain attitudes, perceptions, or personal situations and the desired number of children. The desired number of children is shown to be strongly influenced by attitudes regarding marriage and by the importance placed on family life. Other variables which also have a significant impact on projected lifetime fertility, albeit to a lesser degree, include: the perception of the role of housewives, the importance granted to the stability of family income, and the number of siblings among members of the surveyed group. However, one surprising result is that the average desired number of children is 2.45. Given the high level of education of the sample, this appears to be quite a high figure.

Americas↗

Comparison between the interaction of steroids with [35S]TBPS binding to cerebral cortical and to pituitary membranes: correlation with inhibition of prolactin release.

It has been shown previously that 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha P) can inhibit prolactin release from anterior pituitary gland cells in culture through an interaction with a specific modulatory site on the GABAA receptor complex in anterior pituitary gland membranes. In the present work, this receptor site has been labelled with [35S]t-butylbicyclophosphorothionate ([35S]TBPS) to enable a study of the relative binding affinities (RBA) of different steroids for the GABAA receptor complex to be made. We have found a high correlation (r = +0.88) between the inhibition of [35S]TBPS binding to anterior pituitary membranes and the inhibition of [35S]TBPS binding to cerebral cortical membranes by nine different steroids. There was also a high correlation between the inhibition of prolactin release from anterior pituitary gland cells in culture by these steroids and the inhibition of [35S]TBPS binding to anterior pituitary membranes (r = +0.99) or to cortical membranes (r = +0.81). These observations suggest that the measurement of prolactin release from anterior pituitary gland cells in culture is a good indicator of the functional activity of drugs that bind to the allosteric modulatory TBPS-binding site on the GABAA-receptor complex.

Animals↗

The use of osmicated tissues for Lowicryl K4M embedding.

Tissue chopper slices of rat incisor, rat parotid gland, and chicken tibiae, fixed with 1% glutaraldehyde, were post-fixed with potassium ferrocyanide-reduced osmium tetroxide, dehydrated with methanol, and conventionally embedded in Lowicryl K4M at -20 degrees C. The tissues showed an ultrastructural appearance comparable with that of their Epon-embedded counterparts and, in particular, the Golgi apparatus was well defined. Furthermore, Lowicryl K4M-embedded osmicated tissues permitted both post-embedding lectin-gold cytochemistry and immunogold labeling.

Acrylic Resins↗

The dopamine D2 agonists RU 24213 and RU 24926 are also kappa-opioid receptor antagonists.

The di-(phenethyl)-amine derivatives, RU 24213 and RU 24926 are widely used as selective dopamine D2-receptor agonists. Binding studies now show that they also have affinity for the kappa-opioid receptor. Their affinity is not greatly reduced in the presence of NaCl/GTP, suggesting an antagonist action. This is confirmed for RU 24926, the more active of the two, using the field-stimulated rabbit vas-deferens. With respect to the mu-receptor, RU 24926 shows low binding affinity and also an antagonist effect. These results demonstrate kappa- as well as mu-antagonist activity in a novel chemical series. Moreover, since the kappa-receptor may regulate dopamine release, the results of experiments using these compounds as dopamine D2 agonists should be interpreted with caution.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

Headshake versus whole-body rotation testing of the vestibulo-ocular reflex.

The vestibulo-ocular reflex (VOR) is usually evaluated by whole-body rotary chair oscillation in darkness, but is limited to ambulatory patients. In order to develop a portable method of VOR assessment, eye movements from 10 normal subjects were studied under three conditions: 1. whole-body rotary chair oscillation in the dark and in the light with a head mounted blank field, 2. passive head-on-body rotation in the light with a blank field, and 3. active head-on-body rotation in the light with a blank field. The influence of visual fixation, neck rotation, and volition on VOR gain was to be assessed. Head oscillations were maintained at 0.5 and 1.0 Hz, 50 degrees/s peak velocity. Mean VOR gains with blank field testing were indistinguishable from those obtained in darkness during whole-body rotation. In addition, there were no significant differences in the mean gain between whole-body, passive head rotation or active head rotation. Two vestibulopathic patients (absent calorics bilaterally and oscillopsia) were also studied to illustrate potential clinical utility of the methods. Rotations under all conditions revealed low but variable gains. The evaluation of the VOR in the light with a blank visual surround and passive or active head rotation is a potentially useful clinical method of bedside assessment of the VOR.

Adult↗

Single appointment insemination for heifers after prostaglandin or progestin synchronization of estrus.

Pregnancy rates to a single appointment insemination were compared in seven groups of beef or dairy heifers following estrus synchronization with the prostaglandin F(2a) product, cloprostenol, versus the progestín product, Syncro-Mate-B. For cloprostenol synchronization, two injections of cloprostenol were given 11 d apart, with insemination occurring at 61+/-1 h after the second injection. The Syncro-Mate-B treatment consisted of a norgestomet/estradiol injection and a norgestomet implant on Day 0, followed by insemination at 49+/-1 h after implant removal on Day 9. Treatments were coordinated so all heifers in each group were housed together at the time of and for 48 h before a common insemination time so that the treatment received by individual heifers was not known. Overall pregnancy rates did not differ between treatment groups: 42% for 111 heifers treated with cloprostenol and 38% for 108 heifers treated with Syncro-Mate-B. Four blood samples per heifer taken during each replicate showed that two groups (n = 67) had many noncyclic heifers, while five groups (n = 152) had very few. Differences in pregnancy rates between these categories existed for both estrus synchronization methods, 18 versus 53% for cloprostenol and 21 versus 45% for Syncro-Mate-B. Thus the two methods were equally effective for cyclic heifers and equally ineffective for noncyclic heifers.

Journal Article↗

Hemagglutination by Pasteurella multocida of porcine origin.

A total of 25 fresh isolates of Pasteurella multocida from pigs were tested for the ability to agglutinate erythrocytes of different origins. Of the 18 isolates from pigs with atrophic rhinitis (AR), 8 (44%) agglutinated human type O erythrocytes, whereas none of the 7 isolates from pigs without AR did so. Hemagglutination was mannose sensitive, and the activity was destroyed by heating and by trypsinization but was not affected by formaldehyde treatment or by homogenization of bacterial cells. The other 14 erythrocyte species tested, including human types A and B, were not agglutinated by P. multocida. The present study provides evidence that certain P. multocida isolates from pigs with AR possess a mannose-sensitive hemagglutinin.

Animals↗

Substituted derivatives of A-nor-5 alpha-androstane and A-nor-5 alpha-estrane--structure and affinity for hormonal receptors.

The interactions of A-nor-5 alpha-androstane and A-nor-5 alpha-estrane derivatives with the estrogen and androgen receptors, have been evaluated by measuring their relative binding affinities (RBAs), under two sets of incubation conditions in order to discriminate between potent agonists from weak agonists with potential antagonist activities. Surprisingly some of these compounds which do not possess a phenolic hydroxyl group interact somewhat markedly with the estrogen receptor. This interaction is characteristic of weak estrogens, with potential anti-estrogenic activity (RBA values decreasing when increasing time and temperature of incubation). Results are in good agreement with data obtained in vivo. Moreover, some of these compounds interact also to some extent with the androgen receptor. Results will be discussed in order to outline some structure-activity relationships in these series.

Animals↗

17 alpha-alkynyl-11 beta, 17-dihydroxyandrostane derivatives : a new class of potent glucocorticoids.

Replacement of the characteristic dihydroxyacetone side chain of corticoids by a 17 alpha-alkynyl-17 beta-hydroxy moiety was investigated. It was found that, in particular, the 17 alpha-propynyl substitution is favorable for high local anti-inflammatory activity with reduced systemic effects. Moreover, these compounds were found to be devoid of any affinity for the aldosterone receptor, and may thus be considered as pure glucocorticoids.

Androstanols↗

An approach to the development of hearing standards for hearing-critical jobs.

Many jobs at the Department of Fisheries and Oceans Canada (DFO) have several features in common: they are often performed in noisy environments and involve a number of auditory skills and abilities, such as speech communication, sound localization, and sound detection. If an individual lacks these skills and abilities, it may constitute a safety risk for this individual, as well as for fellow workers and the general public. A number of scientific models have been developed to predict performance on these auditory skills based on diagnostic measures of hearing such as pure-tone audiograms. While these models have significant scientific and research value, they are unable to provide accurate predictions of real life performance on auditory skills necessary to perform hearing-critical jobs. An alternative and more accurate approach has been developed in this research project. A direct measure of functional speech perception in noise (Hearing in Noise Test: HINT) has been identified and validated for use in screening applicants for hearing-critical jobs in DFO. This screening tool has adequate and well-defined psychometric properties (e.g. reliability, sensitivity, and validity) so that screening test results can be used to predict an individual's ability to perform critical auditory skills in noisy environments, with a known degree of prediction error. Important issues must be considered when setting screening criteria. First, the concept of hearing-critical tasks must be reviewed, since these tasks are often performed in high noise levels where normally-hearing people cannot hear adequately. Second, noise-induced hearing loss is frequent in these noisy environments, and workers who acquire a hearing loss might not continue to meet the minimal auditory screening criteria throughout their career. Other senses (e.g., vision, touch) also play an important role in these environments. Third, adaptation strategies have to be considered when recruits or incumbents fail the screening test.

Adult↗