RESUMEN

The anatomical specificity of axon growth from fetal pig septal xenografts was studied by transplanting septal cells from E30-35 pig fetuses into cholinergic deafferented (192-IgG-saporin-infused) rats or into aged rats (> 18 months). Cell suspensions (100,000 cells/microl) were injected bilaterally into the dorsal and ventral hippocampus of immunosuppressed rats (10 mg/kg/day cyclosporine A). To assess axonal growth and synapse formation, acetylcholinesterase histochemistry, an antibody to choline acetyltransferase (ChAT), and three pig-positive/rat-negative antibodies: bovine 70kD neurofilament (NF70), human low-affinity NGF receptor (hNGFr), and human synaptobrevin (hSB) were used. In rats with surviving grafts at 6 months, NF70 axonal labeling was more extensive than either ChAT or hNGFr labeling. All three markers demonstrated graft axons extending selectively through the hippocampal CA fields and the molecular layer of the dentate gyrus. Graft axons did not extend into adjacent entorhinal cortex or neocortex. The distribution of pig hSB-positive synapses correlated with AChE-positive fiber outgrowth in to the host. Electron microscopic analysis of hSB-immunostained hippocampal sections revealed pig presynaptic terminals in contact with normal rat postsynaptic structures in the CA fields and the dentate gyrus. These data demonstrate target-appropriate growth of pig cholinergic axons and the formation of cross-species synapses in the deafferented or aged rat hippocampus.

Asunto(s)

RESUMEN

Adults rats were lesioned with 192-IgG-saporin, an immunotoxin that targets cholinergic neurons in the basal forebrain expressing the low-affinity nerve growth factor receptor (p75). One month later, rats received E30-35 porcine cholinergic neurons bilaterally into the hippocampus, and were tested in the Morris water maze and the passive avoidance task 4.5-6 months after transplantation (in two experiments, rats were retested in the water maze) followed by histological and cellular analyses. The 192-IgG-saporin-lesioned animals displayed clear cognitive deficits in the Morris water maze. In all experiments the lesioned animals had spatial probe deficits on day 5 testing. A large variance was found among the transplanted animals, with individual animals exhibiting improved performance, but little overall improvement when compared to lesion-alone animals as a group. The relationships between behavioral performance and graft cholinergic factors were established by histological analyses. Grafted animals exhibited an increase in cholinergic innervation of the dentate gyrus (DG) region of the dorsal hippocampus when compared to lesion-alone animals. There was a significant correlation between the level of cholinergic innervation in the dentate gyrus and spatial navigation performance (latency and spatial probe) in the Morris water maze task. These data provide evidence of memory and spatial deficits following cholinergic denervation, and of target-specific growth of xenogeneic cholinergic neurons into the hippocampus. The lack of a clear treatment (transplant) effect in the behavioral measures leads us to believe that functional restoration of cognitive function would require cholinergic reinnervation of both the hippocampus and the neocortex in this 192-IgG-saporin animal model.

Asunto(s)

RESUMEN

Sixteen female rabbits were fed one of four diets during lactation: 1) a commercial stock diet; 2) the stock diet with 5% added lard; 3) the stock diet with 5% lard and 0.25% cholesterol; or 4) the stock diet with 15% lard and 1% cholesterol. By days 30-35 of lactation, maternal plasma cholesterol concentrations were increased approximately 10-fold in group 3 and 100-fold in group 4 does compared to does in group 1. Milk cholesterol concentration was similar over lactation for does in groups 1, 2 and 3, but was approximately 2 times higher in group 4 does. Milk triglyceride and protein concentrations and milk intake by the pups were not significantly influenced by maternal diet. Average cholesterol intake of pups nursed by group 4 does was significantly higher than that of other pups. Although plasma cholesterol concentration was significantly increased in group 2, 3 and 4 pups at weaning (age 5 weeks), there was no significant effect of maternal diet on plasma cholesterol at 6, 7 or 11 weeks of age after pups had been weaned to the stock diet. Similarly, liver cholesterol concentration was increased in pups from group 4 does at weaning, but these differences were no longer apparent at 11 weeks of age. These data suggest that severe maternal hypercholesterolemia induced by dietary fat and cholesterol in the rabbit can result in increased milk cholesterol concentration and consequent cholesterol intake by the pups. However, the associated elevations in pup plasma and liver cholesterol levels at weaning did not persist when pups were weaned to a low fat/low cholesterol diet.

Asunto(s)

Asunto(s)