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R Marchand

Publications and source records attributed to R Marchand.

68 records · Page 4Linked to original sources
PubMed1977

Morphological characteristics of the acetylcholinesterase-containing neurons in the CNS of DFP-treated monkeys.

The distribution of acetylcholinesterase (AChE, EC3.1.1.7) within extrapyramidal and related structures was studied in 4 monkeys following the i.m. administration of bis-(1-methylethyl) phosphorofluoridate (di-isopropylfluorophosphate: DFP). In 1 animal, sacrificed 4 hr after the injection of 0.43 mg/kg C, AChE is virtually absent in all structures. In the other 3 animals, which received 0.20 mg/kg DFP 10, 12 and 18 hr prior to sacrifice, AChE activity is greatly reduced in the neuropil of those structures which normally show intense AChE activity in pharmacologically unmanipulated monkeys. As a consequence of the lower background AChE activity in the latter 3 DFP-treated monkeys, the perikarya and processes of several groups of neurons can be readily identified. The perikarya and processes of two types of neurons of the neostriatum, representing a small percentage of all neurons in this structure, are intensely stained. They apparently correspond to the chromatic giant aspiny neurons and the achromatic medium-size "spidery aspiny" neurons. Most perikarya and processes of the neurons of the medial and lateral divisions of the pallidum, as well as the morphologically similar neurons of the pars reticulata of the substantia nigra, display light to moderate AChE activity. The pars compacta of the substantia nigra contains a small number of intensely stained elongated and triangular neurons and numerous moderately stained ovoid neurons whose processes are very lightly reactive. The cell bodies of the neurons of the subthalamic nucleus and associated groups of neurons (nucleus ansae peduncularis) are moderately stained whereas the perikarya and processes of the subnucleus compactus of the pedunculopontine tegmental nucleus are intensely and moderately stained, respectively. Numerous large and multipolar neurons associated with the lenticular nucleus (intralamellar groups) or the pallidum (peripallidal groups) including the nucleus ansae lenticularis have somata and processes which show an intense AChE activity. Certain of the latter groups of neurons, partially interspersed with the neurons of the substantia innominata, correspond in part to the nucleus basalis of Meynert. The present data are compatible with the idea that the large AChE neurons of the neostriatum may be the source of the acetylcholinesterasic striatopallidal and strionigral fibers. The similarity between the neurons of the pallidum and those of the pars reticulata of the substantia nigra suggests that the latter structure may represent a caudal extension of pallidal tissue. Therefore, the nigrothalamic projection, which has been claimed to originate in the pars reticulata of the substantia nigra, would correspond to pallidothalamic projections.

Acetylcholinesterase↗
PubMedDate not supplied

Intracerebral implantation of ionic synthetic hydrogels: effect of polar substrata on astrocytosis and axons.

In previous studies, hyperporous synthetic hydrogels of poly(glyceryl methacrylate) or p(GMA), containing bioadhesive substrates of collagen, were implanted into rat cerebral tissue in order to provide systems of oriented guidance channels for directing the growth of the scar and axons /28/. In the present study, ionic p(GMA)-collagen hydrogels containing polar chemical groups, either basic amino groups or acidic carboxyl groups, were evaluated for their tolerance and their effects on the brain scarring response and axonal reactivity after long-term implantation in the cerebral cortex. In all animals, the implants were well tolerated. Although both types of gels influenced the astroglial reaction near the bioimplant, hydrogels carrying carboxyl groups had the strongest influence on the elongation, the direction and the organization of astrocytic processes so that a glial matrix could form in regions of the gel. Extracellular material (e.g. reticulin) was also deposited into the gels carrying carboxyl groups. Although cortical nerve fibers in the surrounding tissue showed a regenerative response, extending onto or into the matrices, this behavior seemed to depend more on the organization of the astrocytic scar imposed by the gel than on the type of gel. We conclude that matrices carrying negatively charged groups influence favorably the astrocytosis and the deposition of connective tissue, and that this approach represents a new avenue in attempting to modulate the brain scar formation.

Animals↗