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Biomedical subjects

A Summerfield

Publications and source records attributed to A Summerfield.

52 records · Page 3Linked to original sources
PubMed1988

Graft-derived recovery from 6-OHDA lesions: specificity of ventral mesencephalic graft tissues.

A series of experiments have been conducted to assess the specificity of recovery from motor asymmetries that is provided by dopamine-rich grafts in the neostriatum of rats with unilateral dopamine-depleting lesions produced by injection of 6-hydroxydopamine into the ascending nigrostriatal pathway. Grafts of embryonic tissue taken from the substantia nigra (rich in dopamine neurons could provide a complete recovery of methamphetamine-induced rotation and a partial recovery of apomorphine-induced rotation, whereas no recovery was seen in rats with grafts of tissue rich in another monoamine (serotonin, dissected from the mesencephalic raphe) or of tissue appropriate to the target (dissected from the striatal eminence). 6-Hydroxydopamine lesions of dopamine cells in the grafts of recovered animals reinstated the initial lesion-induced asymmetry. Dopamine-rich grafts implanted into the intact neostriatum did not induce any "supernormal" asymmetry in the rats, but did provide a "prophylactic" protection against subsequent lesions of the intrinsic ipsilateral dopamine nigrostriatal system. Post-mortem biochemical assays indicated that the extent of dopamine depletion in the neostriatum of lesioned rats correlated highly with both methamphetamine and apomorphine turning rates. Similarly, both drug rotation tests correlated significantly with the extent of dopamine restoration in the dorsal striatum of rats with dopamine-rich grafts, the correlation being significantly higher for the methamphetamine than for the apomorphine test.

Acetylcholinesterase↗
PubMed1977

Central and peripheral cholinergic involvement in the habituation of investigatory head poking in rats.

The effects of some centrally and peripherally acting cholinergic agonists and antagonists on locomotor exploration and investigatory head poking were studied in rats. An apparent disruption of within-trials habituation of locomotion and head-poke frequency was demonstrated for arecoline, nicotine, carbachol, scopolamine, and methylscopolamine. It is suggested that the effect may be a consequence of a drug-induced depression of initial activity. When this factor was eliminated, both scopolamine and methylscopolamine showed some slight attenuation of habituation. The increase in head-poke duration over time in controls was blocked by scopolamine; although peripheral factors were involved, the scopolamine effect had a singinficant central component. The results are discussed in relation to hypothetical links between the cholinergic system and habituation.

Acetylcholine↗
PubMedDate not supplied

Interleukin-2 dependent selective activation of porcine gamma delta T lymphocytes by an extract from the leaves of Acanthospermum hispidum.

The immunostimulatory capacity of Acanthospermum hispidum, a tropical plant which is used in the traditional medicine of Benin for the treatment of infectious diseases, was studied in the porcine immune system. These in vitro studies revealed the capacity of A. hispidum to enhance the proliferation of T lymphocytes after stimulation with ConA or allogeneic stimulator cells in the mixed leucocyte culture (MLC). The virus-specific MHC class II-restricted in vitro immune response against pseudorabies virus (PRV) was also enhanced in a co-stimulating manner. Phenotyping of T lymphocytes that had been activated in vitro in the presence of A. hispidum revealed an increase of activated gamma delta T lymphocytes with the phenotype CD2-CD5low+CD8-. In vitro analysis of the influence on the lymphocyte function demonstrated neither an increase of the immunoglobulin synthesis, nor of the interleukin-2 production, nor of the cytolytic activities. Experiments using separated T-lymphocyte subpopulations showed that the co-stimulatory activity was based on a synergism between T helper and gamma delta T lymphocytes, and that gamma delta T lymphocytes were the targets of the plant-derived extract. The gamma delta T cells which could not activated in mixed leukocyte cultures or with pseudorabies virus antigen in a secondary immune response, were reactive to the interleukin-2 released from antigen-stimulated T helper lymphocytes.

Animals↗