Enzyme replacement therapy in the mouse model of Pompe disease

Deficiency of acid alpha-glucosidase (GAA) results in widespread cellular deposition of lysosomal glycogen manifesting as myopathy and cardiomyopathy. When GAA-/- mice were treated with rhGAA (20 mg/kg/week for up to 5 months), skeletal muscle cells took up little enzyme compared to liver and heart. Glycogen reduction was less than 50%, and some fibers showed little or no glycogen clearance. A dose of 100 mg/kg/week resulted in approximately 75% glycogen clearance in skeletal muscle. The enzyme reduced cardiac glycogen to undetectable levels at either dose. Skeletal muscle fibers with residual glycogen showed immunoreactivity for LAMP-1/LAMP-2, indicating that undigested glycogen remained in proliferating lysosomes. Glycogen clearance was more pronounced in type 1 fibers, and histochemical analysis suggested an increased mannose-6-phosphate receptor immunoreactivity in these fibers. Differential transport of enzyme into lysosomes may explain the strikingly uneven pattern of glycogen removal. Autophagic vacuoles, a feature of both the mouse model and the human disease, persisted despite glycogen clearance. In some groups a modest glycogen reduction was accompanied by improved muscle strength. These studies suggest that enzyme replacement therapy, although at much higher doses than in other lysosomal diseases, has the potential to reverse cardiac pathology and to reduce the glycogen level in skeletal muscle.     

A proposed autacoid mechanism controlling mastocyte behaviour

Evidence is provided here supporting the existence of a novel autacoid mechanism negatively modulating mast cell behaviour in response to noxious stimuliin vivo; hence, the denomination “autacoid local inflammation antagonism” (ALIA). In particular, as lipid amides of theN-acylethanolamine type have been reported to accumulate in tissues in degenerative inflammatory conditions, we examined whether theseN-acylated lipids could exert regulatory effects on mast cell activationin vivo. The results reported show that both long- and short-chainN-acylethanolamines, when systemically administered, are effective in reducing mast cell degranulation induced by local injection of substance P in the earpinna of developing rats. These and other data suggest that the endogenous production ofN-acylethanolamines may constitute a local autocrine/paracrine response for the negative feedback control of mast cell responses to various activating signals. Such a process may be of physio-pathological relevance in the regulation of functional neuroimmune-mast cell interactions.

     

Electron microscopy of the red pulp of human spleen

Terminating arterial vessels, the structure of sinuses and cords, and the passage of cells through the sinus wall in the red pulp of human spleen were studied. All terminating arterial capillaries arterial capillaries observed opened into cords. The distance between terminating arterial capillaries and sinuses varied. Macrophages were commonly present at arterial terminations. Arterial capillary endothelium contained filaments about 80 Å in diameter. Blood cells were frequently present in the capillary lumen or in passage through the capillary wall into cords. Endothelial cells of sinuses contained three distinctive structures: loosely organized cytoplasmic filaments, tightly organized finer filaments, and micropinocytotic vesicles. Many micropinocytotic vesicles about 0.1 μ in diameter were present just beneath the plasma membrane of the lateral and luminal sides of sinus endothelial cells and a few at the basal aspect. Loosely organized filaments about 80 Å in diameter ran parallel to the longitudinal axis of the sinus endothelium. The finer filaments about 30–50 Å in diameter were tightly organized as filamentous bands and present basally. The filaments of the bands appeared inserted upon the plasma membrane. They were also present in the cordal reticular cells and terminating arterial capillaries. Free cells were frequently present in passage through the slits of the sinus wall. There were no preformed or fixed apertures in the sinus wall. The basement membrane and reticular fibers were completely covered by the endothelial cells and/or cordal reticular cells. It is likely that those slits between endothelial cells in the sinus wall not covered by the basement membrane are potential passageways for cells moving from the cords into the sinus. The larger cytoplasmic filaments are likely contractile. The filamentous bands appear to maintain cell shape, stabilize the wall in relation to the basement membrane, and are probably operative in the control of cellular passage through the slits of sinus wall.     

Cellular localization of nerve growth factor-like immunoreactivity in hippocampus and septum of adult rat brain.

The cellular localization of the nerve growth factor-like immunoreactivity (NGF-LIR) has been studied in the intact adult rat brain at the level of the hippocampus and the septum. Immunolabelling for NGF combined with counterstaining with cresyl violet and double immunostaining technique, which allowed simultaneous localization of NGF-LIR and that of astroglial marker -GFAP, were used. The data indicate neuronal localization of NGF-like immunoreactivity and a lack of colocalization of NGF-LIR with the immunoreactivity of GFAP in the hippocampus. These data are consistent with in situ hybridization results for NGF and immunocytochemical results for pro-NGF localization obtained by others. At the septal level, apart from neuronal localization of NGF-LIR, single NGF-like immunoreactive astrocytes have been observed. This suggests that, although to a very small extent, in vivo intact brain astrocytes may, just as astrocytes growing in vitro, synthesize NGF-like molecules. This finding may be of importance in better understanding the trophic support for NGF responsive cholinergic neurones in the brain.