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Biomedical subjects

C Dehay

Publications and source records attributed to C Dehay.

48 records · Page 3Linked to original sources
PubMed1986

Organization of the callosal connections of visual areas V1 and V2 in the macaque monkey.

The interhemispheric efferent and afferent connections of the V1/V2 border have been examined in the adult macaque monkey with the tracers horseradish peroxidase and horseradish peroxidase conjugated to wheat germ agglutinin. The V1/V2 border was found to have reciprocal connections with the contralateral visual area V1, as well as with three other cortical sites situated in the posterior bank of the lunate sulcus, the anterior bank of the lunate sulcus, and the posterior bank of the superior temporal sulcus. Within V1, callosal projecting cells were found mainly in layer 4B with a few cells in layer 3. Anterograde labeled terminals were restricted to layers 2, 3, 4B, and 5. In extrastriate cortex, retrograde labeled cells were in layers 2 and 3 and only very rarely in infragranular layers. In the posterior bank of the lunate sulcus, labeled terminals were scattered throughout all cortical layers except layers 1 and 4. In the anterior bank of the lunate sulcus and in the superior temporal sulcus, anterograde labeled terminals were largely focused in layer 4. Callosal connections in all contralateral regions were organized in a columnar fashion. Columnar organization of callosal connections was more apparent for anterograde labeled terminals than for retrograde labeled neurons. In the posterior bank of the lunate sulcus, columns of callosal connections were superimposed on regions of high cytochrome activity. The tangential extent of callosal connections in V1 and V2 was found to be influenced by eccentricity in the visual field. Callosal connections were denser in the region of V1 subserving foveal visual field than in cortex representing the periphery. In V1 subserving the fovea, callosal connections extended up to 2 mm from the V1/V2 border and only up to 1 mm in more peripheral located cortex. In area V2 subserving the fovea, cortical connections extended up to 8 mm from the V1/V2 border and only up to 3 mm in peripheral cortex.

Animals↗
PubMed1985

Cytochrome oxidase activity in the striate cortex and lateral geniculate nucleus of the newborn and adult macaque monkey.

The laminar location of cytochrome oxidase staining has been compared in the lateral geniculate nucleus and area 17 in newborn and adult macaque monkeys. In area 17 of the adult, the distribution of cytochrome oxidase activity confirmed published findings. In the newborn animals, the tissue reacted as strongly for cytochrome oxidase as in the adult but the pattern of labelling was different in two respects. Firstly in layer 1 activity was stronger and occupied a wider portion of this layer. Secondly, cytochrome oxidase staining in layer 4C occupied two separate bands, a small narrow band at the bottom of 4C beta and a wider one occupying the full width of 4C alpha and spilling over into 4B. The pattern of cytochrome oxidase activity did not appear to be influenced by eccentricity in the newborn whereas, in the adult, label in 4C was more intense in cortex subserving central vision. In the lateral geniculate nucleus of the adult, the magnocellular layers and the most dorsal parvocellular layer reacted most strongly for cytochrome oxidase. In the newborn, parvocellular layers were more uniformly labelled and the difference between parvo- and magnocellular layers more pronounced. These results are discussed in relationship to the development of thalamo-cortical projections in the monkey.

Animals↗
PubMed1984

Transient projections from the fronto-parietal and temporal cortex to areas 17, 18 and 19 in the kitten.

Using the retrograde tracers, fast blue and horseradish peroxidase we have shown the presence of projections from extensive regions of the frontoparietal and temporal cortex to areas 17, 18 and 19 in the newborn kitten. These projections are transitory as they do not exist in the adult cat. The anterograde transport of horseradish peroxidase conjugated with wheat germ agglutinin after injections in frontoparietal and temporal cortex revealed that these transitory projections terminate in the gray matter and that they could therefore play a functional role in the development of the visual cortex.

Animals↗
PubMed1981

HLA-A,B,C, Bf and glyoxalase I polymorphisms in a sample of the Kabyle population (Algeria).

HLA (A,B and C) gene and haplotype frequencies were determined in 44 Berber families from the Kabyle tribe. The Bf and Glo polymorphisms were also defined and the haplotypes were deduced from these family data. The main association (A1, B8, BfS; A29, B12, Glo2, Aw33, B14, BfS, Glo1; Cw5, B18, BfF1; A1, Bw17) showed the relationship between the populations from the southwest of Europe, and this population. Another association, A11 and Bw21, was found also in Twareg, which are probably of the same origin.

Adult↗
PubMed1980

HLA-A and B typing in the Sarakole population of West Africa.

The distribution of HLA genes and haplotype frequencies was studied in a population of 119 Sarakole West Africans. The absence of HLA-B15, the rarity of HLA-A10, B12 and B17 and the relatively high frequency of HLA-A2 and B5 were noted. The presence of a Da 6 gene in the African populations is confirmed. The main gametic associations were Aw19-Bw35 and Aw23-B5.

Africa, Western↗
PubMed1979

Seventh allele of the HLA-C series (Cve).

Serum VE reacting with 29.8% of French individuals seemed to define the seventh allele of the HLA-C series as shown by serologic and genetic investigations. The gene frequency of Cve is 0.163.

Alleles↗
PubMedDate not supplied

Cortical specification of mice and men.

The developmental basis for the localization of function in the mammalian cortex remains a controversial issue. The newly formed rodent cortex displays a considerable uniformity in terms of its connectivity. This contrasts with the primate, where even the first formed connections can show a high degree of areal specificity. An important clue to understanding these species differences can be obtained by examining how and when the sensory periphery exerts its organizing influence on the developing cortex. In rodents the developmental timetable ensures that the organizational control of the periphery persists late in development, when neurons are forming their first connections. By contrast, in primates the late onset and prolonged duration of corticogenesis result in the periphery being able to exert its influence much earlier, during the phase of precursor proliferation. Differences and similarities between primate and rodent corticogenesis are highly informative. In rodents, recent results with molecular markers show that regional differences in developmental potential exist in the cerebral cortex before innervation from the periphery. Similar findings are predicted in primates. It is to be expected that a more complete understanding of the rules governing the emergence of distinct cortical areas will come from resolving how afferent specification acts within the confines of such regional specializations.

Animals↗
PubMedDate not supplied

Developmental remodeling of primate visual cortical pathways.

The pre- and postnatal developmental changes of the cortical afferents to area 17 were studied in the macaque monkey. Paired injections of the retrograde tracers fast blue and diamidino yellow were made in area 17. Quantitative techniques were used to examine the spatial patterns of labeling in three distinct locations of the extrastriate cortex that correspond to known visual areas. In the adult, each cortical region has a characteristic laminar distribution. In the fetus the proportion of supragranular layer neurons in all cortical regions was much higher than in the adult. The present study shows that despite the very high levels of labeled supragranular layer neurons, there is some early areal specialization so that the adult configuration does not emerge from a uniform distribution. The developmental decline in the proportion of labeled supragranular neurons is complete by 1 month after birth. Each injection of tracer gave rise in each cortical area to dense labeling in a restricted region (projection zone). Areal measurements of projection zones in the supra- and infragranular layers showed that the developmental decrease in the proportion of labeled supragranular layer neurons is accompanied by a relative change of the dimensions of supra- and infragranular projection zones: the supragranular projection zone in the fetus is larger than the infragranular projection zone and vice versa in the adult. In the fetus, the two projection zones corresponding to each of the two tracers overlap in the supragranular layers whereas they are largely separated in the infragranular layers. During development there is a progressive decrease in the overlap of the supragranular projection zones and an increase in the overlap in the infragranular layers. Again, the adult configuration is achieved 1 month after birth. This developmental inversion of the areal dimensions of the projection zones in supra- and infragranular layers is accompanied by a drastic decrease in the proportion of double-labeled neurons located in supragranular layers. These results clearly show that early in development, axonal projections to area V1 are modified in very different ways according to whether they originate from supra- or infragranular layers. This developmental process lasts for about 80 d. These findings show that in the primate there is a prolonged remodeling of axonal projections that is a highly characteristic feature of this species.

Amidines↗