A set of monoclonal antibodies (MAbs) has been generated that recognizes distinct classes of neuroglia in the adult nervous system of the cricket Acheta domesticus corresponding to glial types distinguished by morphological criteria. These include antibodies that bind to the neuroglia of the ganglionic cortex, perineurium, neuropil, and glia associated with the glial lacunar system (interface) and fiber tracts. Another MAb specifically labels components of the neural lamella, a complex extracellular matrix secreted by underlying perineurial cells. Selected adult glial-specific MAbs recognize particular glial antigens expressed during embryonic development of Acheta. Immunohistochemical staining of frozen sections of late- (90-95%) and intermediate- (50-55%) stage whole embryos reveals that the spatial distribution, degree of tissue restriction, or level of expression of some glial determinants changes as development proceeds. Labeling of certain neuroblasts in the embryonic CNS at 50-55% development by an antibody (MAb 3G6) that binds to neuropil glia in the adult CNS implies that at least 1 class of insect glia may be generated by these cells.

The hypothesis that pioneer fibers, which develop relatively early in the differentiation of insect appendages, serve to organize the peripheral sensory nerves was tested by ablating apical regions of the cercal rudiments in embryos of Acheta domesticus. Multiple nerve bundles rather than the normal middorsal and midventral pair of nerves were formed within the cercus following ablation of the cercal tip before pioneer fiber differentiation, but the cercal nerve was normal when lesions were made after formation of the pioneer fiber tracts and associated glia. These results indicate a necessary morphogenetic role for the pioneer fibers.

Chronic cercal deafferentation of the terminal ganglion in developing crickets (Acheta domesticus), which is known to suppress normal development of giant interneuron dendritic arborizations is shown here to reduce [3H]leucine uptake and incorporation into ganglion proteins. Short term deafferentation of adult crickets, in contrast, does not depress amino acid uptake and incorporation significantly. Following unilateral long term deafferentation of the terminal ganglion, a comparison was made of the [3H]leucine incorporation into primary dendritic processes and somata of deafferented and normally innervated medial giant interneurons (MGIs) within the same ganglion by means of quantitative autoradiography. Grain densities within dendrites of deafferented MGIs were significantly lower than in paired control MGIs' grain densities within somata of deafferented MGIs also were reduced, although the effects of deafferentation were less pronounced in somata than in target dendrites. These results imply a specific influence of afferent innervation on protein metabolism during growth and development of target postsynaptic elements.

Following the finding that cereal deafferentation of developing giant interneurons in the terminal abdominal ganglion (TG) of the cricket Ache& dome&us reduces TG protein metabolism within target interneuron dendrites and somata (Meyer and Edwards, 1982), it is now shown that deafferentation alters the turnover of three macromolecules associated with cholinergic transmission in the cereal sensory-giant interneuron pathway.The labeled specific ligands 3H-quinuclidinyl benzilate and 1251-cY-bungarotoxin were used to assay populations of putative TG muscarinic and nicotinic cholinergic receptors, respectively, in control and deafferented groups of ganglia. The AChE activity of TG was also determined by assay and histochemical methods.Long-term deafferentation sustained throughout postembryonic development markedly reduces the densities of both muscarinic and nicotinic binding sites in the TG, short-term deafferentation of adult TG also leads to characteristic alterations in the properties of all three choline@ markers within several days. Rapid changes seen in adults thus correlate with ultrastructural data demonstrating loss of afferent terminals within hours of sensory appendage removal.We propose that peripheral innervation-dependent regulatory mechanisms operate in both the developing and adult insect nervous system. Such mechanisms may influence transsynaptitally the synthesis and turnover of specilic macromolecules, some of which may reside on the cell surface of insect central neurons that are part of the cereal sensory-giant intemeuron system.

. 1997. A comparison of changes in whole body and skin amino acid metabolism of sheep in response to 24 h continuous infusions of variants of insulin-like growth factor 1. Can. J. Anim. Sci. 77: 695-706. Because of the economic significance of wool to many sheep production systems, attempts to partition amino acids towards skin and wool protein synthesis have included both nutritional and hormonal methods of manipulation. A variant of insulin-like growth factor 1 (IGF-1) has previously been shown to transiently increase protein synthesis in the skin of sheep and the current study extended that work by comparing the effects of a 24 h, close-arterial, skin infusion of IGF-1, in the form of either recombinant human (rhIGF-1) or an extended variant (LR 3 IGF-1), on both whole body and skin amino acid metabolism adult, castrated Romney sheep, with three animals allocated to each treatment. There were no differences in food intake between the two treatment groups. The plasma concentration of immunoreactive IGF-1 of sheep infused with rhIGF-1 increased (P < 0.01) with time of administration, but decreased (P < 0.05) after 24 h of LR 3 IGF-1 infusion. Administration of both IGF-1 variants caused a substantial and sustained decrease in arterial insulin to less than 50% (P < 0.05) of pre-infusion values, while arterial plasma glucose concentrations were only reduced by 7%. Alterations in whole body and skin protein metabolism were assessed from continuous infusions of mixed [U-13 C] AA, [2,6 ring 3 H]phenylalanine and [ 35 S]cysteine. Within 4 h both AA concentrations and whole body plasma ILR of essential and non-essential AA were decreased (P < 0.05 for seven AA) by IGF-1 infusions. Both IGF-1 variants caused acute increases (P < 0.05) in skin blood flow and, for 13 of the 15 AA measured, isotopic transfers (range 50-220%; P < 0.05 for cysteine and tyrosine), which probably reflect increased protein synthesis. By 24 h skin blood flow, AA uptake and protein synthesis had returned to pre-infusion values. Strategies based on exogenous application, or enhanced endogenous production, of IGF-1 are unlikely, therefore, to produce persistent anabolic responses.Key words: Insulin-like growth factor 1, skin, sheep, protein synthesis Lobley, G. E., Lee, J., Hocking Edwards, J. et Harris, P. M. 1997. Comparaison des changements du métabolisme des acides aminés de l'organisme entier et de la peau des moutons en réponse à une perfusion de 24 h de variants de somatomédine-C. Can. J. Anim. Sci. 77: 695-706. À cause de l'importance économique de la laine pour plusieurs systèmes de production ovine, les tentatives de partition des acides aminés (AA) vers la synthèse protéique de la peau et la laine ont été effectuées par l'utilisation de méthodes hormonales et nutritionnelles. Dans une étude antérieure, une augmentation temporaire de la synthèse protéique de la peau et de la laine a été obtenue chez les moutons perfusés avec un variant de somatomédine (SM-C). Dans la présente étude, une comparaison des effets d'une perfusion artérielle l...