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Biomedical subjects

S Fortin

Publications and source records attributed to S Fortin.

At least 19 recordsLinked to original sources
PubMed2004

[Disease prevention and health promotion for children and youth: current status and contemporary issues in CLSC-based nursing practice].

This article aims to provide an overview of the disease prevention and health promotion work carried out by CLSC nurses working with infants, children and youth. A second objective is to present our synthesis of four recent studies on the state of prevention-promotion in these organizations. This is followed by our analysis of several contemporary issues related to nursing practice in this intervention sector. While disease prevention and health promotion is a major component of the practice of CLSC nurses who work with infants, children and youth, it is an intervention sector that has been weakened by numerous changes affecting these organizations in the wake of the reform. The discussion thus proposes several courses of research and action in the hopes of strengthening this major component of the CLSC mission.

Adolescent↗
PubMed2001

Theoretical and experimental determination of the effects governing the transannular Diels-Alder reaction of trans-trans-cis systems with or without activation of the dienophile.

A thorough study of the transannular Diels-Alder (TADA) reaction of trans-trans-cis macrocyclic trienes was carried out. It led to a better understanding of various parameters that govern the TADA reaction in particular and the Diels-Alder reaction in general. Thus, carbonyl activation of the dienophile and substitution of the diene are discussed, as well as the presence of substituents on the macrocycle and their respective effects at the transition-state level.

Journal Article↗
PubMed2001

Preparations, characterizations, and structures of (biimidazole)dihalobis(triphenylphosphine)rhenium(III) salts: strong ion-pairing and acid-base properties.

Two-electron reduction occurs when the Re(V) precursors ReOX3(PPh3)2 and ReO(OEt)X2(PPh3)2 are reacted with biimidazole (biimH2) in boiling chloroform, affording rhenium(III) cationic complexes of the type cis,trans-[ReX2(PPh3)2(biimH2)]X with X = Cl, Br, and I. Crystal structures are determined for the compounds with the three halogens, as well as for the [ReCl2(PPh3)2(biimH2)](benzoate) salt. In all cases, the counterion is attached to the complex cation via hydrogen bonding with the N-H groups of coordinated biimidazole. Variable-temperature 1H NMR spectroscopy shows that a mixture of [ReCl2(PPh3)2(biimH2)](benzoate) and [ReCl2(PPh3)2(biimH2)]Cl is in slow exchange below -50 degrees C in CD2Cl2, indicating that ion pairing is retained in solution. Both N-H groups can be deprotonated with sodium methoxide, and their acidities are evaluated from UV-visible spectra. Competition between monodeprotonated [ReCl2(PPh3)2(biimH)] and various carboxylic acids reveals that the acidity of the first N-H proton corresponds to that of acetic acid (pKa(aq) approximately 4.8). By a similar competitive reaction between bis-deprotonated [ReCl2(PPh3)2(biim)]- and phenols, the second acidity is estimated to be close to that of phenol (pKa(aq) approximately 9.8).

Journal Article↗
PubMed2001

The BioTools Suite. A comprehensive suite of platform-independent bioinformatics tools.

The BioTools Suite is a set of three comprehensive, platform-independent software packages (PepTool, GeneTool, and ChromaTool) developed for sequence assembly and analysis. In addition to supporting a large number of standard bioinformatics functions, these programs also incorporate a number of useful innovations including uniform graphical-user interface (GUI) design, direct internet connectivity, a novel approach to feature annotation, and a variety of enhanced algorithms for large scale proteome and genome analysis. This article describes the key features, recent changes, and general operation of all three programs.

Computational Biology↗
PubMed2000

Preparation and characterization of oxorhenium(V) complexes with 2,2'-biimidazole: the strong affinity of coordinated biimidazole for chloride ions via N-H...Cl- hydrogen bonding.

N,N'-Dimethylbiimidazole and bipyridine (N-N) react with ReOCl3(OPPh3)(Me2S) to give mer-ReOCl3(N-N) compounds. Nonmethylated biimidazole forms a trans-O,O [ReOCl2(OPPh3)(biimH2)]+ cation, which is tightly associated with the Cl- counterion via N-H...Cl- hydrogen bonding. Hydrolysis of ReOCl3(biimMe2) in wet acetone (5% water) leads to the linear oxo-bridged dinuclear species [(OReCl2(biimMe2)2(mu-O)] containing chelated biimMe2. Acetone solutions containing only 1% water yield the bent oxo-bridged dinuclear species [(OReCl2)2(mu-O)(mu-biimMe2)2], where each Re center retains the ReO2Cl2N2 coordination but the biimMe2 ligands are bridging. The linear oxo-bridged [(OReCl2(biimH2)2(mu-O)] complex obtained with nonmethylated biimidazole includes two Cl- ions held via N-H...Cl- hydrogen bonds, leading to a dianionic [(OReCl2(biimH2...Cl)2(mu-O)]2- unit in the crystals of the PPh4+ salt. The compounds are characterized by IR and NMR spectroscopies, and the structures of [ReOCl2(OPPh3)(biimH2)]Cl, [(OReCl2(biimH2)2(mu-O)](PPh4Cl)(2).2H2O, and [(OReCl2)2(mu-O)(mu-biimMe2)2].acetone are determined by X-ray diffraction.

Journal Article↗
PubMed2000

Cross-correlated and oscillatory visual responses of superficial-layer and tecto-reticular neurones in cat superior colliculus.

The present study examined, in the superior colliculus (SC) of anaesthetised cats, the functional connectivity between superficial-layer neurones (SLNs) and tectoreticular neurones (TRNs: collicular output cells). TRNs were antidromically identified by electrical stimulation of the predorsal bundle. The auto- and cross-correlation histograms of visual responses of both types of neurones were recorded and analysed. A delayed, sharp peak in cross-correlograms allowed us to verify whether SLN and TRN cells were coupled; in addition, oscillatory activities were compared to verify if rhythmic responses of SLN sites were transmitted to TRN sites. We found that oscillatory activity was rarely observed in spontaneous activity of superficial (1/74) and TRN sites (1/48). Moving light bars induced oscillation in 31% (23/74) of the superficial-layer and in 23% (11/48) of the TRN sites. The strength of the rhythmic responses was determined by specific ranges of stimulus velocity in 83% (19/23) and 64% (7/11) of oscillating SLN and TRN sites, respectively. Frequencies of oscillations ranged between 5 and 125 Hz and were confined, for 53% of the cells, to the 5-20 Hz band. Thus, the band-width of frequencies of the stimulus-related oscillations in the superior colliculus was broader than the gamma range. Analysis of cross-correlation histograms revealed a significant predominant peak with a mean delay of 2.7+/-0.9 ms in 46% (17/37) of SLN-TRN pairs. Most correlated SLN-TRN pairs (88%: 15/17) had superimposed receptive fields, suggesting they were functionally interconnected. However, individual oscillatory frequencies of correlated and oscillatory SLN and TRN cells were never the same (0/8). Together, these results suggest that the neurones in collicular superficial layer contact TRNs and, consequently, support the idea that the superficial layers contribute to collicular outputs producing eye- and head-orienting movements.

Animals↗
PubMed1999

Maturation of visual receptive field properties in the rat superior colliculus.

Visually responsive neurons were recorded in the superficial layers of rat superior colliculus from postnatal day 12 to 28. Receptive field properties such as size, type (ON, OFF, ON-OFF and motion sensitive) and direction selectivity were analyzed to disclose changes during maturation. Although some aspects of sensory properties are modified during development (latency, receptive field sizes, and proportions of receptive field types), a high level of sophistication is also present in young animals even before eyelid opening. For instance, direction selective and direction biased cells, which require complex synaptic relations, are already observed when the first light evoked responses emerge in the superior colliculus (P13), strongly suggesting that this property develops without visual experience. Furthermore, direction selectivity is present in the colliculus prior to the appearance of visually evoked activity in the cortex. This indicates that direction selectivity can not be attributable to incoming cortical afferents. This study provides the first direct evidence that, unlike the cat, the rat's cortico-tectal pathway is only weakly involved in the establishment of direction selectivity in collicular neurons.

Aging↗
PubMed1999

Response component analysis of simple and complex cells of area 18 during depression of area 17.

Simple and complex cells of visual areas of cats may be reliably classified according to the modulatory index (MI) of their responses. This investigation is aimed at analysing the MI in area 18 when a small region (about 200-400 microm in diameter) of area 17 was inactivated with a microinjection of GABA, in anesthetized cats. Cells were stimulated with sine-wave gratings whose orientation, spatial, and temporal frequencies were optimal for the studied unit. The AC and DC response components, and the MI were computed along with fast Fourier transforms of evoked discharges recorded as peristimulus time histograms. Results showed that these response components were relatively unaffected in simple cells, whereas complex cells exhibited large changes when area 17 was silenced. In particular, a large proportion of complex cells showed a MI greater than 1, thereby adopting a response pattern resembling simple cells. It is suggested that this subpopulation of complex cells receives a direct input from geniculate X cells.

Animals↗
PubMed1997

ON and OFF field potentials in the rat superior colliculus during development.

The present investigation is aimed at characterizing the development of ON and OFF visually evoked responses in the rat superior colliculus from postnatal day 13 (P13) to postnatal day 25. Depth profiles of field potentials reveal that ON and OFF long latency biphasic field potentials are already present when collicular cells are first responsive to light (P13). There is an inversion in the polarity of these responses as the electrode penetrates the collicular layers, suggesting a synaptic organization similar to the one found in adult animals. At P15, OFF field potentials begin to exhibit oscillatory activity. Local cobalt injections within the superior colliculus abolishes these OFF oscillations, suggesting a postsynaptic origin. Fast Fourier transform (FFT) analysis of the OFF field potentials demonstrates that oscillatory activity increases in frequency during development. This increase is thought to reflect the myelination and stabilization of synaptic connections that occur during this period. To our knowledge, this is the first report of OFF oscillatory responses in the superior colliculus.

Animals↗
PubMed1995

Evolution of spontaneous activity in the developing rat superior colliculus.

During the first 10 days after birth in the rat there are a succession of major developmental stages in the retinotectal pathway. During most of this time, the only recordable event in the superior colliculus is spontaneous activity. We studied and characterized this spontaneous activity, hypothesizing that it could play an important role in pathway development. The spontaneous discharges are detectable on postnatal day 5 (P5). After P5, the number of spontaneously active cells per penetration increases up to P10, after which they decrease to adult-like levels by P14-P15. Between P5 and P10, the spontaneous discharges exhibit several patterns of activity, from constant firing to intermittent bursts with periods of quiescence, without any bearing to age. We isolated the retina and superior colliculus by injecting xylocaine onto the optic nerve and found no change in collicular activity. While this suggests that the spontaneous activity in the colliculus is independent of the retina at the ages studied, the opposite experiment, i.e., electrically stimulating the optic nerve, resulted in increased firing by collicular neurons, perhaps via nonclassical synaptic transmission. Finally, we compared interval histograms for spontaneously active cells between P5 and P15. The histograms suggest that at certain ages, spontaneous firing is more regular; moreover, these ages precede major functional advances, e.g., onset of numerous spontaneously firing cells at P6, the first response to optic nerve stimulation at P10, and the first light-evoked response at P12-P13. Our results support the hypothesis that spontaneous activity in the neonatal superior colliculus has a role in development of the retinotectal pathway, but the data also indicate that classical synaptic transmission is not involved.

Animals↗
PubMed1994

Spontaneous uterine infections are associated with elevated prostaglandin F(2)alpha metabolite concentrations in postpartum dairy cows.

Postpartum Holstein (n=21) and Jersey (n=4) cows were used to determine if uterine infections are associated with elevated plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F(2)alpha (PGFM). Based upon clinical examinations and bacterial content of intrauterine fluid samples, cows detected with uterine infections between 21 and 28 d post partum were used (infected; n=14). These cows were matched with herdmates that were free of infection (control; n=11). Beginning on the day the cows were assigned to the experiment (Day 1), blood samples were collected on alternate days for the next 14 to 15 d. Plasma samples were stored at -20 degrees C until assayed. From Day 1 until the end of the experiment, uterine fluid samples were collected transcervically twice weekly for aerobic bacterial culture. Endometrial biopsies were collected between Days 6 and 8 and Days 13 and 15. Control cows did not show signs of uterine infection throughout the trial, and bacterial cultures indicated that there were no significant bacterial populations in the uteri of the control cows. The uteri of infected cows harbored numerous microbes. Actinomyces pyogenes was most prominent. Various species of Streptococcus and Pasteurella were also prevalent in the infected cows. Escherichia coli was present in the uterus of both infected and control cows. Biopsies showed that infected cows had more (P<0.05) neutrophils, plasma cells and lymphocytes in the endometrium than did the control cows. As determined by plasma progesterone concentrations, 83% of the control and 50% of the infected cows had functional luteal tissue during the 2-wk sampling period. Plasma PGFM profiles were linear (P<0.03) and did not differ between treatment groups (P>0.01). However, average plasma PGFM concentrations were greater (P<0.0001) in infected than in control cows. These data indicate that plasma PGFM concentrations are greater in postpartum cows with spontaneous uterine infections then in herdmates free of infection.

Journal Article↗
PubMed1988

Monoclonal antibodies as probes for the transmembrane structure of neutral endopeptidase 24.11 ('enkephalinase').

The neutral endopeptidase (EC 3.4.24.11) ('enkephalinase') is a membrane-bound metalloendopeptidase that is present in large amounts in the microvilli of the kidney proximal tubules. By immunizing mice with purified rabbit kidney brush-border membranes, we have obtained four different monoclonal antibodies that recognize this enzyme in dot-blot and Western-blot assays and can be used for immunoprecipitation of neutral endopeptidase from crude kidney solubilizates. One of these monoclonal antibodies (2B12) allows the labeling of proximal tubule cells with colloidal gold particles. This monoclonal antibody also binds to native brush-border membrane vesicles (which are mostly in the right-side-out configuration) and recognizes an epitope which is destroyed after reduction and alkylation of the protein. By contrast, all three other monoclonal antibodies (21G10, 23B11 and 22E2) compete for another epitope of neutral endopeptidase that is not exposed at the extracytoplasmic surface either in intact cells or in sealed brush-border vesicles. Permeabilization of the vesicles with digitonin, however, restores the full binding activity. Binding of these antibodies is not altered by prior reduction and alkylation of the protein. Taken together, these results strongly suggest that the 2B12 monoclonal antibody binds a conformational epitope located on the ectodomain of the enzyme, whereas the three others (21G10, 23B11 and 22E2) bind to a common or to overlapping epitopes located on the cytosolic domain. These results also demonstrate unambiguously the transmembrane nature of neutral endopeptidase.

Animals↗
PubMed1988

In vivo immunomodulation by monoclonal anti-CD4 antibody. II. Effect on T cell response to myelin basic protein and experimental allergic encephalomyelitis.

In vivo administration of anti-CD4 mAb (GK1.5) has been shown to be effective in preventing acute and relapsing experimental allergic encephalomyelitis (EAE). In the present report we have studied the depletion of CD4+ cells by a single dose of GK1.5 on the immune response to myelin basic protein and in the development of EAE. Our studies show that depletion of CD4 cells in mice that had received encephalitogenic CD4+ T cells altered the kinetics of acute and relapsing EAE, but did not prevent disease altogether. The in vitro T cell proliferative response to myelin basic protein in lymph node cells was maintained in the presence of significant depletion of CD4+ cells. These studies indicate that the population of Ag-reactive cells to be large and relatively refractory to antibody therapy. The implication of these results to therapy of human autoimmune disease is discussed.

Adjuvants, Immunologic↗
PubMed1988

In vivo modulation of murine collagen induced arthritis.

The effects of in vivo modulation of murine collagen induced arthritis with monoclonal anti-CD4 antibodies, monoclonal anti-Ia antibodies, and gamma interferon are reviewed. We detail the mechanism of action of monoclonal anti-CD4 antibody on humoral and cell mediated immune responses and discuss the implications for designing therapeutic strategies. To further explore the induction of collagen induced arthritis, a syngeneic cell transfer system using collagen primed T lymphocytes is described. This cell transfer system provides an opportunity to study the role of CD4 positive T lymphocytes in arthritis induction during a short, defined time period.

Animals↗
PubMed1987

Anticytoskeletal autoantibody to microfilament anchorage sites recognizes novel focal contact proteins.

Actin microfilaments are anchored to the plasma membrane at focal contacts. Using an indirect immunofluorescence method, we detected an autoantibody reactive with focal contacts in PtK2, HEp-2, and BHK-21 cells in serum from two patients with early systemic sclerosis. With double immunofluorescence, using the actin-binding drug phalloidin, we localized the plaques decorated by these sera specifically at the termini of microfilament bundles. The reactive antigens were identified by immunoblotting as proteins of 80,000- and 75,300-mol wt in PtK2, and of 53,500-mol wt in HEp-2 and BHK-21 cells. The 53,500-mol wt protein was also identified in rat skeletal, myocardial, and smooth muscle tissues. The detergent solubility of these proteins suggested that they may be linked to the plasma membrane. The autoantigens were immunologically distinct from vinculin and alpha-actinin, two major proteins also known to be concentrated at the ends of microfilament bundles. Our observations suggest that this novel anticytoskeletal autoantibody may identify a novel family of vertebrate cell proteins involved in the linkage of microfilaments to the plasma membrane at focal contacts.

Actin Cytoskeleton↗
PubMed1986

Elimination of human enteric viruses during conventional waste water treatment by activated sludge.

The present study was undertaken to determine if viruses were selectively eliminated during waste water treatment. Human enteric viruses were detected at all steps of treatment in a conventional activated sludge waste water treatment plant. Liquid overlays and large volume sampling with multiple passages on BGM cells permitted the detection of poliovirus (serotypes 1, 2, and 3), coxsackievirus B (serotypes 1, 2, 3, 4, and 5), and echovirus (serotypes 3, 14, and 22), as well as reoviruses. The mean virus concentration was 95.1 most probable number of infectious units per litre (mpniu/L) in raw sewage, 23.3 in settled water, 1.4 in effluent after activated sludge treatment, and 40.3 mpniu/L in sludge samples. All samples of raw sewage and settled water, 79% of effluent water, and 94% of sludge samples contained viruses. The mean reduction was 75% after settling and 98% after activated sludge treatment. Poliovirus type 3 was rarely isolated after the activated sludge treatment, but was still detected in about one-third of the sludge samples. Reoviruses and coxsackieviruses were detected at similar rates from all samples and appear to be more resistant to the activated sludge treatment than poliovirus type 3. Poliovirus types 1 and 2 were present in almost every sample of raw sewage and settled water and still found in about half of the effluent and sludge samples, indicating a level of resistance similar to that of reoviruses and coxsackieviruses.

Cell Line↗