Showing papers by "Laval University published in 1987"

Antigenic map of the rat cerebellar cortex: The distribution of parasagittal bands as revealed by monoclonal anti-purkinje cell antibody mabQ113

Abstract: Both anatomical and physiological mapping methods have revealed that the mammalian cerebellar cortex consists of a family of parasagittal bands of cells, each band with its own pattern of afferent and efferent axons. Monoclonal antibody mabQ113 recognizes an unknown polypeptide antigen that is confined to a subset of rat cerebellar Purkinje cells. Immunoreactive cells are arranged into parasagittal bands extending throughout the vermis and hemispheres. Expression of the Q113 epitope by individual Purkinje cells may not be all-or-nothing, since the bands tend to be more strongly stained in the vermis than the hemispheres. The band display is symmetrical about the midline and reproducible from individual to individual. Wholemount immunocytochemistry and serial reconstruction reveal a median band of mabQ113+ Purkinje cells adjacent to the midline (P1 + ) and six other positive bands disposed symmetrically at either side (P2+ to P7 + ). Bands are distinct throughout most of the cortex but tend to fuse ventrally and caudally. There are two sources of interindividual differences. Firstly, most animals express supernumerary “satellite” bands in the vermis. Satellite bands are usually only one cell wide, are not bilaterally symmetrical, and differ in position and number from individual to individual. Secondly, the precise position of an individual band can differ, perhaps according to the variable cortical lobulation, for example, the position of P4+ in lobules VIII/IX and P6+ in lobule VII. While a scheme of parasagittal bands is a good description of the vermian organization, the distribution of mabQ113+ and mabQ113- Purkinje cells in the hemispheres may be better described as a checkerboard of antigenic patches.

Precise insertion of antibiotic resistance determinants into Tn21-like transposons: nucleotide sequence of the OXA-1 beta-lactamase gene.

Abstract: Several plasmid-encoded beta-lactamases are on multiresistance transposable elements. The OXA-1 beta-lactamase gene is part of Tn2603, which is borne on the R plasmid RGN238. We report here the complete nucleotide sequence of the OXA-1 beta-lactamase gene and flanking sequences. The OXA-1 gene shows a greater than 50% sequence divergence from the OXA-2 gene, yet there is significant functional similarity at the peptide level. Analysis of 5' and 3' flanking sequences shows that Tn2603 differs from its probable precursor, Tn21, by a precise 1004-base-pair insertion, containing the OXA-1 structural gene, at the target sequence AAAGTT, which is located between the Tn21 streptomycin/spectinomycin (aadA) promoter and its structural gene. A 5- for 6-base repeat of the target sequence is found at the end of the insertion. The same precise insertion and repeat of the target sequence are found for the OXA-2 gene from R46. The 5' flanking regions of two other genes, the trimethoprim-resistance gene from R388 and the gentamicin resistance (aadB) gene from pDGO100, are greater than 98% homologous to the 5' flanking sequences of the OXA-1, OXA-2, and aadA genes until they diverge at the target sequence. From the available sequence data a recombinational hot spot is defined at the nucleotide level 5' of the aadA gene of Tn21, and a second potential hot spot is proposed 3' of this gene.

Parasagittal organization of the rat cerebellar cortex: direct correlation between antigenic Purkinje cell bands revealed by mabQ113 and the organization of the olivocerebellar projection

Abstract: The Purkinje cells of the cerebellar cortex and the cortical afferent and efferent projections are organized into parallel parasagittal zones. The parasagittal organization is clearly revealed by immunocytochemistry with a monoclonal antibody, mabQ113. The mabQ113 antigen is confined to a subset of Purkinje cells that are clustered together to form an elaborate, highly reproducible pattern of bands and patches, interspersed with similar mabQ113- regions. The mabQ113+ territories have been classified into seven parasagittal bands (P1+-P7+) in each hemicerebellum. The degree of correspondence between the compartments revealed by the anterograde labeling of the olivocerebellar projection and by mabQ113 immunocytochemistry has been explored in the adult rat. Horseradish peroxide-wheat germ agglutinin conjugate was injected as an anterograde tracer into the inferior olivary complex. When the injection site did not encompass all the olive, an incomplete, patchy labeling of the molecular layer was seen in the cerebellar cortex. Labeled zones of the molecular layer were interrupted by unlabeled regions to give a pattern of parasagittal cortical bands. The positions of these bands were compared with the distribution of the mabQ113+ antigenic bands as seen on the two adjacent sections. Labeled climbing fibers were found to terminate on both mabQ113+ and mabQ113- Purkinje cell zones. The mabQ113+/mabQ113- boundaries and the bands of climbing fibers seen by using the anterograde tracer typically coincide. The one consistent exception is the midline band of mabQ113+ Purkinje cells, P1+. The normal olivocerebellar projection is exclusively contralateral and the climbing fiber projection to the paramedian vermis splits P1+ down the middle, implying that it consists of two adjacent mabQ113+ bands not separated by mabQ113-territory. It is likely that the climbing fiber projection to the cerebellar cortex and the distribution of the two Purkinje cell phenotypes share a common compartmental organization.

Resuspension in the shallow sublittoral zone of a macrotidal estuarine environment: Wind influence1

Abstract: Several biological and physical variables were measured four times daily for 148 consecutive days at a fixed station to examine fluctuations of phytoplankton abundance in the littoral zone of the lower St. Lawrence estuary. On the seasonal scale, the pattern of variation of phytoplankton was characterized by a midsummer diatom bloom similar to that observed offshore in the pelagic zone. On the shorter time scale, chlorophyll a concentration in the littoral zone was highly variable and closely associated with variations in the wind field. No relationship, however, could be found between phytoplankton cell numbers and wind velocity. The possible influence of wind, tidalinduced upwelling, overturning eddies, and wave-induced mixing processes on resuspension was examined. The higher Chl a values observed irregularly at the sampling stations resulted from the mechanical resuspension of benthic diatoms due to wind, or wind-induced wave, mixing in the littoral zone. Wind velocities >4 m s-l were shown to cause significant resuspension of particulate organic matter (POC) in the water column. For winds >6 m s-l, there was no further increase in POC. These results suggest that the frequency of wind velocities > 4 m s- * plays a significant role on secondary production in the littoral zone by providing an increased food supply to benthic and planktonic filter feeders, especially at times when phytoplankton biomass is normally low in the water column.

Studies on the induction of pharmacological responses to des-Arg9-bradykinin in vitro and in vivo.

Abstract: 1 The mechanisms by which agents modulate the induction of kinin B1-receptors were investigated by studying the effects of kinins in vitro, by use of the rabbit isolated aorta, and in vivo by measuring the blood pressure of anaesthetized rabbits. 2 The contractile response of the rabbit isolated aorta to kinins increased in a time-dependent manner in vitro. This effect was abolished by continuous exposure to the protein synthesis inhibitor cycloheximide (71 microM). 3 Several substances were found to increase specifically the rate of sensitization to des-Arg9-bradykinin (des-Arg9-Bk), when applied continuously in vitro to tissues isolated from normal animals: bacterial lipopolysaccharide (LPS; 1 micrograms ml-1), muramyl-dipeptide (MDP; 2 micrograms ml-1), phorbol myristate acetate (PMA; 320 nM), epidermal growth factor (EGF; 100 ng ml-1) and endothelial cell growth factor (150 micrograms ml-1). 4 The protease inhibitors phenylmethylsulphonyl fluoride and aprotinin, a non-adjuvant isomer of MDP, rabbit purified leukocyte interferon, fibroblast growth factor and the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) did not have this effect. 5. It has been demonstrated that LPS induces B1-receptors in rabbits enabling des-Arg9-Bk to act as a hypotensive agent. In these experiments neutropenia induced by nitrogen mustard, did not prevent the in vivo effect of LPS. MDP (300 micrograms) and PMA (100 micrograms) were also found to induce a state of responsiveness to des-Arg9-Bk in vivo. FMLP (1 mg i.v.) induced a temporary decrease in blood neutrophil counts but had no effect on the induction of responses to des-Arg9-Bk. 6. The development of responses mediated by the B,-receptor in the two experimental systems seems to be unrelated to the activation of neutrophil leukocytes, but may be related to the activation of tissue macrophages. Approximately 3% of cultured adherent cells derived from rabbit aorta strips following protease digestion were stained for non-specific esterase, supporting such a possibility.

Distribution of GABA‐immunoreactive neurons in the basal ganglia of the squirrel monkey (Saimiri sciureus)

Abstract: The distribution of GABA-immunoreactive neurons was visualized in the basal ganglia of the squirrel monkey (Saimiri sciureus), by using a highly specific antiserum raised against GABA-glutaraldehyde-lysyl-protein conjugate and revealed by the indirect peroxidase-antiperoxidase immuno-histochemical method. In the dorsal striatum, GABA-immunoreactive nerve cell bodies were small to medium in size (sectional area ranging from 90 to 125 μm2), but some larger ones (500-600 μm2) were also found. These cells displayed no obvious clustering but were significantly more numerous in the caudate nucleus than in the putamen; their number was also markedly greater at caudal than at rostra1 striatal levels. A moderate number of evenly distributed positive axon terminals were visible in both the caudate nucleus and the putamen. In the ventral striatum, GABA-immunoreactive nerve cell bodies and axon terminals were seen in fair number within the nucleus accumbens and in the deep layers of the olfactory tubercle. Many positive terminals but no somata were found in the islands of Calleja. In the globus pallidus, virtually all nerve cell bodies were GABA-immunoreactive and the neuropil exhibited a multitude of positive terminals. In the Substantia innominata, clusters of small, globular GABA-immunoreactive somata were scattered among aggregates of larger, nonimmunoreactive neurons belonging to the nucleus basalis, and the whole region showed a low to moderate number of evenly spread GABA-positive terminals. In the subtha-lamic nucleus, nerve cell bodies were generally surrounded by several GABA-positive terminals but were not themselves immunoreactive. The substantianigra showed many GABA-immunoreactive somata, which predominated in the pars lateralis and diminished progressively in number along the latero-medial axis of the pars reticulata. These cells formed a rather pleomorphic group comprising round, fusiform, or polygonal elements of relatively large size (sectional area ranging from 200 to 800 μm2). In the pars compacta and ventral tegmental area, a few GABA-immunoreactive neurons of small size were dispersed among larger, unreactive neurons. In both pars lateralis and pars reticulata of the substantia nigra, the number of GABA-positive termi-nals was high and their distribution was rather uniform; a smaller number were visible in the pars compacta of the substantia nigra and in the ventral tegmental area. The present results demonstrate that GABA-containing neurons are widely and heterogeneously distributed in the various components of the squirrel monkey's basal ganglia. Such normative data should be useful as a basis for further investigations of the functional role of GABA in the brain of primates.

Puddling in butterflies : sodium affects reproductive success in Thymelicus lineola

Abstract: . Adults of many species of Lepidoptera, principally the males, frequent mud puddles, edges of streams, carrion and animal excreta where they imbibe moisture, an activity referred to as ‘puddling’ Sodium ions are the only known stimulus present which cause males of at least two lepidopteran species to drink for extended periods. In the European skipper Thymelicus lineola (Ochsenheimer) (Lepidoptera: Hesperiidae), only males puddle, even though they have concentrations of abdominal sodium 2–3 times that of females at emergence. During their first mating, males transfer 32% of their abdominal sodium to females. This could be of considerable importance given that an average egg complement contains >50% of the total body sodium of females at emergence. Virgin females, as well as having reduced fecundity, have reduced longevity. This is attributed to virgins not obtaining important nutrients which males transfer to females during mating. Access to sodium ions increases the total number of matings by c. 50% for males living >15 days. Access to sodium ions by once-mated males increases the percentage of males which re-mate on the day following first mating; the percentage of females, mated to the twice-mated males, which lay >50% fertile eggs; and the drought resistance of eggs laid by those females.

Prediction of leisure-time exercise behavior: a path analysis (LISREL V) model.

Abstract: In an attempt to understand the inherent process underlying the regular practice of physical activity, the relationships among subjective norm, attitude, habit, intention, and future behaviors have been investigated in a random sample of 136 University of Toronto employees. For this purpose, leisure-time exercise behavior was measured on two occasions after a statement of intentions had been obtained: 3 weeks later (proximal behavior) and 2 months later (distal behavior). The results of a path analysis (LISREL) suggest that intention is directly influenced by habit and attitude, proximal behavior is the result of habit only, and distal behavior can be explained by a combination of intention and proximal behavior. Subjective norm was not a significant predictor of intention, proximal behavior, or distal behavior. This modeling approach offers a clearer understanding of the dynamics of exercise intention and behavior, strongly supporting the role of habit as a determinant of exercise behavior.

Physiological characteristics of anterior thalamic nuclei, a group devoid of inputs from reticular thalamic nucleus

Abstract: This study tested the hypothesis that neurons of thalamic nuclei, which are normally devoid of inputs from the reticular thalamic nucleus, do not display spindle oscillations and related rhythmic s...

Effect of the richness of the environment on the cat visual cortex

Abstract: In a recent study of the cat visual cortex, it was shown that there are interindividual differences in the numerical density (Nv) of symmetrical synapses associated with flat vesicles (FS synapses) but not of asymmetrical synapses associated with round vesicles (RA synapses). Since many of the environment-sensitive properties of visual cortex neurons are GABA-dependent, it was suggested that the interindividual differences in FS synapses might be duo to environmental factors. To verify this possibility we estimated the Nv of both types of synapses in two groups of six cats, paired by litter and by sex, and raised either in isolation or in a colony from the time of weaning to the age of 8 months. We also measured the Nv of neurons and the thickness of the cortex and made some gross anatomical measurements. The brains of animals raised in the enriched environment are 7% heavier, and their total body weight is 10% greater: The brain-to-body-weight ratio remains unchanged. The total length of the brain is not affected, but the length and width of the cerebral hemispheres are each 5% greater in the enriched cats. As in comparable rat studies, the thickness of the cortex is 4% greater, but in the present study this difference is not significant. The numerical density of neurons is diminished by 17% in enriched animals. This is probably due to a wider separation of neuronal cell bodies in a larger cortical volume, rather than to a loss of neurons. There are no significant changes in the numerical density of RA synapses between the two milieux, but there are nearly twice as many FS synapses per mm3 of tissue in the impoverished cortex. The coefficient of variation of FS synapses, which in the previous study was on the order of 30%, has been reduced to 10% and 7% in enriched and impoverished cats, respectively. We conclude that environmental conditions can lead to selective interindividual differences in the Nv of FS synapses, as seen in our previous study of animals whose rearing conditions were not controlled. The average diameter of RA synaptic profiles is not affected by the environment but FS synapses are 25% wider in the enriched animals. Because of the smaller neuronal Nv in enriched animals, there are, in fact, 18% more RA synapses and 34% fewer FS synapses per neuron in the enriched condition. As a consequence the total area of RA contacts per neuron is 16% greater in enriched animals, hut changes in size of FS contacts compensate perfectly for the change in number so fiat the total area of contact per neuron is not affected. Changes in the number of neurons and synapses are similar in all individual laminae. Modifications in the number of FS synapses occur on both dendritic spines and on dendritic trunks. It is not clear whether axosomatic synapses are also affected. Changes in the number of neurons and synapses are similar in all individual laminae. Modifications in the number of FS synapses occur on both dendritic spines and on dendritic trunks. It is not clear whether axosomatic synapses are also affected. We conclude that the richness of the environment modifies the excitatory-inhibitory equilibrium on the neurons of the visual cortex through a restructuring of inhibitory circuits. We predict that this will have a profound effect on the receptive field properties of the cortical neurons. The dramatic differences in the reaction of the two types of synapses to the environment suggest that different mechanisms subserve the adaptation of excitatory and inhibitory circuits to environmental stimuli.

Genetic and environmental sources of variation in physical fitness.

Abstract: The technique of path analysis was used to assess inherited and environmental variance components in physical fitness indicators measured in 1630 subjects from 375 families of French descent living in the greater Quebec city area. For that purpose, submaximal power output (PWC150/kg), muscular endurance, muscular strength, reaction time and movement time were evaluated during a visit of the family to the laboratory. Inter-class correlations in various types of relatives were computed from scores adjusted for linear and non-linear effects of age and sex by a regression procedure (Y = age + sex + (age X sex) + age2). Correlations were then used in the path analytic BETA model which allows the partition of transmissible variance (t2) into genetic (h2) and cultural (b2) components. Results indicated that t2 accounted for 18% (movement time) to 63% (muscular strength) of the phenotypic variance. The contribution of genetic factors was found to be negligible for PWC150/kg and movement time, and accounted for about 20% of the phenotypic variance for reaction time and muscular endurance and 30% for muscular strength, while non-transmissible variance (1 - t2) accounted for 37% (muscular strength) to 82% (movement time) of the phenotypic variance. These results suggest that biological variation observed in the physical fitness level of a healthy population is mainly associated with non-transmissible environment factors and that the contribution of heredity is moderate and clearly lower than previously reported.

The ecological implications of growth forms in epibenthic diatoms

Abstract: This paper evaluates the utilisation of space by epibenthic diatom cells, as a response to environmental variations. The aggregation pattern of five species of epibenthic diatoms was quantified and compared to provide evidence for the significance of cell motility as an adaptive mechanism for space occupation and monopoly. The epibenthic diatoms included (1) non-mobile colonial species forming either fan-shaped (Synedra tabulata (Ag)Kz.) or arborescent (Gomphonema kamtschaticum var. californicum Grun.) colonies; (2) slow-moving (Cocconeis costata Greg, and Amphora pusio Cl.), and (3) fast-moving (Navicula direct a (W. Sm.) Ra.) non-colonial species. The aggregation pattern of S. tabulata did not vary significantly among six different light intensities manipulated in nature. The major patterns of aggregation were identified using analysis of covariance and dummy-variable regression. Highly mobile N. directa are significantly less aggregated than the four other diatom species. Non-mobile and slow-moving species show a similar, highly aggregated pattern. The occurrence of two patterns of spatial dispersion indicates that growth forms bear far-ranging ecological implications with respect to colonization strategies, immigration, and possibly impact by grazers. An integrated model of growth form characteristics, biological properties, and ecological implications is presented for epibenthic diatoms.

Regulation in vitro of metallothionein gene binding factors

Abstract: Mouse nuclear factors that bind to an upstream metal regulatory element of the mouse metallothionein-I gene have been identified by DNA footprinting and oligonucleotide band shift assays. The formation of complexes at this site can be activated 20- to 40-fold by the vitro addition of ionic cadmium. The activation reaction is rapid, reversible by a metal chelator, and may involve multiple proteins. These results suggest that the initial step in cadmium detoxification is an interaction between the metal and nuclear DNA-binding factors leading to an increase in metallothionein gene transcription. The ability to observe metal activation in vitro makes this a powerful system to study the biochemistry of eukaryotic gene regulation.

Fractionation of Anhydrous Milk Fat by Superficial Carbon Dioxide

Abstract: Milk fat was fractionated with supercritical CO2 (SC-CO2) into 8 fractions at temperatures of 50° and 7O°C, over a pressure range of 100–350 bar. Two fractions (L1 and 2) were liquid, 3 fractions (11–3) were semi-solid and 3 fractions (Sl-3) were solid at 20°C. The peak melting temperature progressively increased (9.7° to 38.3°C) from fraction L1 to S3. The concentration of short chain (C24-C34) triglycerides decreased from fraction L1 to S3 while that of long chain (C42-C54) triglycerides increased gradually. The medium chain triglycerides were more concentrated in fractions L2 and 11–3. The proportion of short (C4-C8) and medium (ClO-C12) chain fatty acids decreased and that of long (C14-C18) chain fatty acids increased gradually from fraction Ll-S3. The weight average molecular weights and geometric mean-carbon number of milk fat fractions were in the range from 625.6 to 805.0 and 34.2 to 47.6, respectively, in comparison to 729.3 and 41.O, respectively, for native milk fat, suggesting SC-CO2 effected a fair degree of molecular weight separation.

Characterization and autoradiographic localization of LHRH receptors in the rat brain.

Abstract: Luteinizing-hormone-releasing hormone (LHRH) is distributed in several extrahypothalamic areas, suggesting that it might act as a neurotransmitter or neuromodulator in the central nervous system. This study was undertaken to characterize and localize LHRH receptors in the rat brain by using slide-mounted frozen sections. The radioligand used was an iodinated stable LHRH agonist, [D-Ser(TBU)6, des-Gly-NH2(10)]LHRH ethylamide. It was clearly established that LHRH receptors with characteristics similar to those of pituitary LHRH receptors were present in the brain. They were found in high concentrations in the dorsal hippocampus, amygdala, septum, and subiculum and in very low amounts in the hypothalamus. Generally, a good correlation could be observed between receptor distribution and immunohistologically localized LHRH. These results strongly suggest that LHRH has multiple sites of action in the rat brain and reinforce the hypothesis that the peptide could act as a neurotransmitter/neuromodulator in the central nervous system.

Effects of two high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performance.

Abstract: The purpose of this study was to investigate the effects of repeated high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performances. First, nineteen subjects were submitted to a 15-week cycle ergometer training program which involved both continuous and high-intensity interval work patterns. Among these 19 subjects, six participated in a second 15-week training program after 7 weeks of detraining. Subjects were tested before and after each training program for maximal aerobic power and maximal short-term ergocycle performances of 10 and 90s. Muscle biopsy from the vastus lateralis before and after both training programs served for the determination of creatine kinase (CK), hexokinase, phosphofructokinase (PFK), lactate dehydrogenase (LDH), malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH) activities. The first training program induced significant increases in all performances and enzyme activities but not in CK. Seven weeks of detraining provoked significant decreases in maximal aerobic power and maximal 90s ergocycle performance. While the interruption of training had no effect on glycolytic enzyme markers (PFK and LDH), oxidative enzyme activities (HADH and OGDH) declined. These results suggest that a fairly long interruption in training has negligeable effects on glycolytic enzymes while a persistent training stimulus is required to maintain high oxidative enzyme levels in human skeletal muscle. The degree of adaptation observed after the second training program confirms that the magnitude of the adaptive response to exercise-training is limited.