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C Beaulieu

Publications and source records attributed to C Beaulieu.

At least 91 records · Page 5Linked to original sources
PubMed1990

Protein kinase C immunoreactivity in kitten visual cortex is developmentally regulated and input-dependent.

Immunocytochemistry with polyclonal antibodies directed against protein kinase C (PKC) was utilized to investigate the development of the kinase in kitten visual cortex neurons. The immunoreaction product was found at postsynaptic sites at all ages studied. However, PKC was localized in presynaptic terminals only during the first few weeks of postnatal life, during the period when the cortex is most susceptible to visual experience. The overall level of PKC immunoreactivity was high at early postnatal ages (up to 6 weeks) and declined afterwards till adulthood. This decline in reactivity was not equal across the cortex and was particularly marked in the middle cortical layers, especially layer IV. The reduction of PKC immunoreactivity in all cortical layers but layer IV was abolished by isolating a portion of cortex from its neuronal inputs early in life. Indirect evidence points to the lateral geniculate nucleus as the source of input that is required for input-dependent maturational changes in the kinase level. The results reported here suggest that the expression of PKC in kitten visual cortex in not only developmentally regulated but is also use-dependent.

Aging↗
PubMed1990

Effect of the richness of the environment on neurons in cat visual cortex. I. Receptive field properties.

In a recent study, it was demonstrated that the number of synaptic contacts associated with flat vesicles (FS synapses) is higher in the visual cortex of cats raised in an enriched environmental condition (EC) compared to those reared in an impoverished condition (IC). Moreover, the size of the FS synaptic contacts is also affected by the richness of the animal's environment during development. Based on evidence that the vast majority of FS synapses are GABAergic (gamma-aminobutyric acid) and that many of the properties of visual cortex neurons are influenced by GABA-dependent mechanisms, it has been suggested that these morphological synaptic changes induced by the richness of the environment correlate with differences in cortical receptive field properties. In the present study, this has been explored by recording visual responses of area 17 cells in cats raised either in isolation (IC) or in a colony with ample environmental stimulation (EC). Enriched visual cortex contains a higher proportion of orientation selective cells and a lower proportion of orientation biased and unoriented cells. In addition, orientation tuning is significantly sharper in EC animals (mean bandwidth of responsive units is equal to 32 degrees) than in IC cats (mean bandwidth is equal to 38 degrees; P less than 0.001). This is mostly due to the greater incidence of orientation biased units in impoverished cortex (23% in EC and 41% in IC animals; P less than 0.01). Unit responsivity is significantly affected by the richness of the environment. We found that all units of the EC cortex were responsive to light stimuli. In contrast, 14% of the impoverished cells studied fail to increase their response to at least twice the standard deviation of the spontaneous activity and were judged as unresponsive. We suggest that the lower responsivity in IC visual units is related to the higher number of GABAergic synapses per IC neuron, while the broader selectivity in IC cortex might be due to a more diffuse distribution of the GABAergic inhibitory connections.

Animals↗
PubMed1990

Effect of the richness of the environment on neurons in cat visual cortex. II. Spatial and temporal frequency characteristics.

The quantitative distribution of synaptic contacts in the cat cerebral cortex is affected by the richness of the environment: the number of round-asymmetrical (RA) synapses per neuron is higher while the number of flat-symmetrical (FS) contacts is lower in the visual cortex of cats raised in an enriched environmental condition (EC) compared to those reared in an impoverished condition (IC). The size of FS synaptic contacts is also affected by the complexity of the animal's environment. It has been suggested that these morphological synaptic changes induced by the richness of the environment correlate with differences in physiological properties of the visual cortex. This question has been explored by assessing the cortical unit contrast sensitivity as a function of spatial and temporal frequency of area 17 cells in cats raised either in isolation (IC) or in a colony with ample environmental stimulation (EC). Contrast sensitivity is affected by the richness of the environment: at the preferred spatial frequency, an average enriched unit can detect lower contrasts (mean = 0.6%) than an average impoverished cell (0.9%; P less than 0.002). In addition, the mean highest spatial frequency that can be resolved (acuity) is greater in EC than in IC cells (1.7 and 1.2 cycles per degree, respectively, P less than 0.0001), whereas the spatial frequency at which units respond best is not statistically affected by the environment. The preferred temporal frequency also show a significant difference in EC (1.0-6.5 Hz) and IC units (0.9-4.0 Hz; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Cellular and subcellular localization of protein kinase C in cat visual cortex.

Polyclonal antibodies against 3 protein kinase C (PKC) subtypes (I, II and III) were applied to localize the kinase in cat visual cortex. These antibodies exclusively stained neuronal cells. Both pyramidal and non-pyramidal cells exhibiting PKC-like immunoreactivity were concentrated in layers, II, III, V and VI with relatively few cells in layer IV. Electron microscopic examination did not reveal any presynaptic localization of the kinase. PKC immunoreactivity remained normal in a zone of cortex surgically isolated from the rest of the brain by an undercut procedure. These results suggest that PKC is heterogenously distributed in adult cat visual cortex; the kinase recognized by the polyclonal antibodies is localized postsynaptically in intracortical neurons of the superficial and deep cortical layers and the expression of the kinase is not regulated by extracortical input.

Animals↗
PubMed1990

Identification of plant-inducible genes in Erwinia chrysanthemi 3937.

We present a method for identifying plant-inducible genes of Erwinia chrysanthemi 3937. Mutagenesis was done with the Mu dIIPR3 transposon, which carries a promoterless neomycin phosphotransferase gene (nptI), so upon insertion, the truncated gene can fuse to E. chrysanthemi promoters. Mutants containing insertions in plant-inducible genes were selected for their sensitivity to kanamycin on minimal plates and for their acquired resistance to this antibiotic when an S. ionantha plant extract was added to kanamycin minimal plates. The selection allowed the identification of E. chrysanthemi promoters inducible by host factors present in the S. ionantha plant extract. Using this method, we isolated 30 mutants and characterized 10 of them. Two mutants were defective in cation uptake, one was defective in the galacturonate degradation pathway, and another was altered in the production of the acidic pectate lyase. The functions of the other mutated genes are still unknown, but we show that most of them are involved in pathogenicity.

Coliphages↗
PubMed1990

Vitamin D depletion retards the normal regeneration process after partial hepatectomy in the rat.

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the hormone of the vitamin D3 (D3) endocrine system, has been shown to influence malignant and normal cell proliferation/differentiation, while insulin (I) is known to be essential for liver growth. To investigate the influence of D3 on liver regeneration, the effect of the D status was studied in D-depleted rats (D-) pretreated with: G1, placebo (D-, hypocalcemic); G2, oral calcium only (D-, normocalcemic); G3, D3; and G4, 1,25-(OH)2D3. Two thirds hepatectomy (HX) or sham operation was performed, and regeneration was studied for 3 weeks. I response to glucose challenge and the hepatic I receptor were also studied. Cell volume, DNA, and RNA were not affected by pretreatment. After HX, the pattern of [3H]thymidine incorporation into DNA (P less than 0.003) and the cell labeling index (P less than 0.0001) were highly influenced by pretreatment and suggestive of an earlier appearance of the S phase of the cell cycle in the 1,25-(OH)2D3-treated compared to the D- hypocalcemic group. Furthermore, the mitotic index revealed a significant effect of pretreatment (P less than 0.01), with peak mitosis 24 h after HX in D3-treated and 1,25-(OH)2D3-treated rats compared to 30-36 h after HX in the D- groups. Liver weight restitution was impaired in D- rats (P less than 0.009) and is illustrated by the estimated time required to achieve 70% recovery of the resected liver mass, which was found to be 186 and 300 h in G1 and G2, and 154 and 107 h in G3 and G4. G1 rats had significantly higher glucose concentrations (fasting as well as after glucose injection) and reduced I secretion when challenged with glucose (P less than 0.001); they also had an upregulation in hepatic I receptor number (P less than 0.005) compared to calcium or D3-treated rats, while 1,25-(OH)2D3 led to a liver I receptor number similar to that found in hypocalcemic D- rats; the affinity of the I receptor was, however, only slightly changed by pretreatment (P less than 0.08). Our data indicate that in D depletion, hypocalcemia retards DNA synthesis and liver mass recovery, while normocalcemia contributes to DNA synthesis, but fails to sustain mitosis and compensatory liver growth to a level comparable to that found after D3 and/or 1,25-(OH)2D3 repletion. The observation that both D3 and 1,25-(OH)2D3 significantly promoted normal liver recovery after partial HX illustrates the role of the D endocrine system in normal cell physiology in vivo.

Animals↗
PubMed1989

Number and size of neurons and synapses in the motor cortex of cats raised in different environmental complexities.

In a previous study we have shown that the richness of the environment affects the number of neurons, the size of their nuclei, the number of round-asymmetrical synapses per neuron, the numerical density (number per unit volume; NV) of flat-symmetrical synaptic contacts, their number per neuron and their size in the visual cortex of cats. Of these, the number of flat-symmetrical synapses per unit volume is particularly affected (there are nearly twice as many per mm3 in the impoverished cortex). Several studies in the rat have shown that environmentally induced changes in cortical thickness occur in the occipital regions but are much smaller or absent in the frontal regions. In order to determine if the cat motor cortex is also resistant to environmental changes, we have estimated the number and size of neurons and of synapses in individual laminae of motor cortex, area 4 gamma, in six pairs of cats raised either in a colony (EC: enriched condition) or in isolation (IC: impoverished condition). For the neurons, we have found that the numerical density (28,900 neurons per mm3 of EC and 29,500 neurons/mm3 of IC motor cortex), the number under 1 mm2 of cortical surface (49,400 and 49,200 in EC and IC cats), and the size of the neuronal nuclei (82 vs 80 microns2 in EC and IC animals) were not significantly affected. The number of flat-symmetrical synapses per neuron (1,470 in EC vs 1,400 in IC cortex), their size (0.33 micron in both groups) and even their number per unit volume, which was so greatly affected in the visual cortex, remains unchanged (43 million/mm3 and 41 million/mm3 in EC and IC motor cortex). We did find however, a significant difference (p less than 0.05) in the numerical density of round-asymmetrical synapses which is 13% greater in the impoverished motor cortex (216 million/mm3 in EC vs 247 million/mm3 in IC cortex). Our results confirm that the motor cortex is much less affected by the richness of the environment than the visual cortex: In fact, the cat motor cortex is hardly affected at all. Furthermore our results represent the most complete data presently available on the number and size of neurons and synapses in individual laminae of the cat motor cortex.

Animals↗
PubMed1989

Effects of the richness of the environment on six different cortical areas of the cat cerebral cortex.

The number and size of neurons and the cortical thickness were determined in areas 17, 18, 3B, 4 gamma, the posteromedial lateral suprasylvian area, and the primary auditive area of cats raised in an enriched and in an impoverished environment. A significant effect on the numerical density of neurons and on the size of the neuronal nuclei can be demonstrated in areas 17 and 18. We suggest that this preferential effect on occipital cortical regions is due to a different gradient of maturation among cortical regions.

Animals↗
PubMed1989

Number of neurons in individual laminae of areas 3B, 4 gamma, and 6a alpha of the cat cerebral cortex: a comparison with major visual areas.

The number of neurons per mm3 of tissue (number per volume) and the number under 1 mm2 of cortical surface (number per column) have been estimated for each lamina of seven cytoarchitectural areas of the cat cortex by using a method of size frequency distribution. The areas studied consisted of four visual areas (the binocular and monocular portions of area 17: 17B and 17M; area 18; and the posteromedial lateral suprasylvian area: PMLS), a somatosensory area (3B), and two motor areas (4 gamma and 6a alpha). For both series of measurements, significant differences could be demonstrated among the seven areas studied (one-way ANOVA; P less than .001). The number of neurons per volume in the binocular and monocular regions of area 17 (approximately 49,000/mm3) is 85% greater than that of each of the other regions (approximately 27,000) with a P less than .01 on an a posteriori Tukey test, but there are no significant differences between the latter areas. The number of neurons per column is greater in the binocular portion of area 17 (78,000 under 1 mm2 of cortical surface) than in any other area (P less than .01). Other sensory areas (17M, 18, PMLS, and 3B) have fewer neurons per column (P less than .01) and the numbers do not vary significantly between these regions (range from 56,100 to 61,900). Areas 4 gamma and 6a alpha have still fewer neurons (approximately 44,000; P less than .01, except P less than .05 when compared to PMLS). Thus, the seven areas studied fall under three different categories. Motor areas have the smallest number of neurons per column, sensory areas have more, and the greatest number is found in the binocular region of area 17. It appears that these differences are principally (but not exclusively) due to variations in the number of neurons in layer IV: These variations are largely responsible for the differences that we have found between the binocular portion of area 17 and other sensory areas as well as between the latter and motor areas. We thus cannot confirm the view of Rockel et al. (Brain 103:221-244, '80) that there is a basic uniformity of the number of neurons per unit of cortical surface in different cortical areas of the cat.

Animals↗
PubMed1988

Richness of environment affects the number of contacts formed by boutons containing flat vesicles but does not alter the number of these boutons per neuron.

A recent quantitative analysis of cat visual cortex has demonstrated that the numerical density (Nv) of symmetrical synaptic contacts formed by boutons containing flat vesicles (FS synapses) is nearly twice as large in animals raised in isolation (impoverished condition: IC) as in animals raised in a colony (enriched condition: EC). Although some FS synapses have been shown to be cholinergic there is evidence that many, indeed the vast majority, are GABAergic. In order to estimate whether the change in the Nv of FS contacts was accompanied by a change in the number of boutons containing GABA, we have incubated sections of tissue from both groups of animals in an antiserum for GAD. In spite of the large increase in the number of FS contacts in impoverished cortex, we saw no obvious change in the apparent amount of labelled GAD terminals. In retrospect we realized that though the amount of labelled GAD terminals might reasonably be expected to reflect the number of F-boutons, it might not correspond so closely to the number of contacts formed by these boutons (which is what we had measured in the previous study): The richness of the environment could conceivably affect the number of contacts formed by the F-boutons without affecting the number of boutons! We thus extended our study by estimating the number of F-boutons in the two conditions. For the total cortical thickness, the Nv of F-boutons is only 17% lower (P less than .05) in enriched than in impoverished cats. The diameter of the boutons is 6% larger (P less than .001) in the enriched cortex. Because the F-boutons become fewer in number as they become larger in size, the total percentage volume occupied by these boutons does not change between the two experimental conditions. We conclude that this is the reason why there appears to be no change in the general amount of GAD label between the two groups of cats. More importantly, since the Nv of neurons is also 17% lower in enriched cortex, the number of F-boutons per neuron (and presumably the total number of F-boutons in the visual area) actually remains unchanged. In contrast, the previous study showed that the number of FS contacts per neuron is significantly decreased in enriched cortex. It follows that the number of contacts formed by each bouton must be altered.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

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

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 due 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.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

A comparison of the number of neurons in individual laminae of cortical areas 17, 18 and posteromedial suprasylvian (PMLS) area in the cat.

The binocular region of area 17 (17B) has a greater number of neurons under a given unit of cortical surface (NC, number per column) than either the monocular region of area 17 (17M), area 18 or the posteromedial suprasylvian area (PMLS). The latter three areas follow the general principle of basic uniformity in the number of neurons under given units of cortical surface formulated by Rockel et al. This basic uniformity is maintained in layers I and II. The NC of other layers varies. The greatest differences are found in layer IV where the NC of each area is significantly different from that of each other area. Though the difference between layer IV of 17M and of either 18 and PMLS is largely offset by changes in the third layer, layers V (PMLS) and VI (18 and PMLS) also contribute to the compensation. The compensation between 18 and PMLS is due entirely to changes in layer VI. It is important to note that there are statistically demonstrable interindividual differences in the neuronal NC of the cats used in the present study. We suggest that these may be due to age, breeding, or rearing conditions, probably the latter.

Animals↗
PubMed1985

An empirical assessment of stereological formulae applied to the counting of synaptic disks in the cerebral cortex.

Known quantities of test objects approximating the parameters of cortical synapses were embedded in known volumes of a transparent embedding medium. The material was cut in slabs of appropriate thickness. The mean trace length (d) of the profiles of the test objects was measured and the number of profiles per unit area (NA) was calculated. Various stereological formulae were applied to these data to determine the number of test objects per unit volume (NV). For large numbers of those test objects most closely approximating the parameters of cortical synapses, the formula NV = NA/d and the DeHoff and Rhines formula ('61) for polydispersed circular disks NV = 8NAZ/ pi 2 (where Z is the mean of the reciprocals of the trace lengths) gave accurate results (error less than or equal to 5%). Other popular formulae and procedures were not as accurate and underestimated their number by as much as 32%.

Animals↗
PubMed1985

A laminar analysis of the number of round-asymmetrical and flat-symmetrical synapses on spines, dendritic trunks, and cell bodies in area 17 of the cat.

The number of synapses per unit volume of tissue (NV) has been estimated in individual laminae of the binocular and monocular regions of area 17 in six adult cats by using a method of size-frequency distribution. Separate estimates were obtained for RA synapses (containing round vesicles associated with asymmetric membrane differentiations) and for FS synapses (containing flat vesicles associated with symmetric membrane differentiations). For the total cortical thickness, the NV of all synapses is not statistically different between binocular (286 million per mm1(3] and monocular (281 million) regions, nor is it different between the two regions for any of the laminae. Eighty-four percent of synapses are of the RA type. Of those, 79% are found on dendritic spines, 21% on dendritic trunks, 0.1% on somata. FS synapses represent 16% of the total, with 31% of them on spines, 62% on dendritic trunks, and 7% on somata. The ratio of RA to FS synapses is kept relatively constant throughout the layers. A two-way analysis of variance shows no difference in the NV of either RA or FS synapses in the two regions nor in the NV or RA synapses between cats. It does, however, clearly demonstrate (p less than 0.001) interindividual differences for FS synapses. These variations between individual cats may be due to differences in age, breed, or environmental factors. In contrast to the relative uniformity of the NV of synapses between regions, the number of each type under 1 mm2 of cortical surface is 33% higher in the binocular region. This is due mainly to the greater thickness of the binocular region.

Animals↗