Restorative Neurology and Neuroscience

In rats, sectioning the fimbria-fornix leads to a decrease in cells reactive for acetylcholinesterase and choline acetyltransferase, as well as other types of cells, in the medial septal area that project to the hippocampus. In this study cells in the medial septal area were stained for acetylcholinesterase reaction product or by a Nissl method two weeks after unilateral section of the fimbria-fornix. Counts were made of cells on each side of the midline by independent observers. The counts of the cells on the two sides of the brain were compared in rats that had been given nimodipine (70 μg/kg) just after the lesion and for 7 additional days and in rats that had been given only the vehicle for an equivalent amount of time. The number of cells reactive for acetylcholinesterase was reduced in the medial septal area on the side of the brain in which the forebrain fornix was sectioned, but this occurred to a significantly less extent in the nimodipine-treated rats. No differences were noted in the number of cells on the two sides of the medial septal area when counted in Nissl-stained sections.

Human embryonic retinas (postconceptional age 3–10 weeks) with or without retinal pigment epithelium were grafted to the retina of immuno-suppressed adult rat hosts. The development of the xenografts was followed up to 37 weeks of total age by histology and by immunohistochemistry for S-antigen. The donor tissue became rearranged in folded sheets with rosettes. The grafts developed approximately according to their intrinsic timetable, but with a developmental delay in the later stages. Occasionally, the grafts were well fused with the host retina. At 13 weeks of total age, the grafts contained areas of inner plexiform layer with presumptive ganglion cells, one neuroblastic layer, and cone precursor cells around rosettes. At 19 weeks, an outer plexiform layer and inner segments of the cones started to form. At 20 weeks, the first immunoreactivity for S-antigen was observed in photoreceptor precursors. Cone inner segments were clearly distinguishable at 28 weeks, and more S-antigen-positive rods were seen. At 31 weeks, rods were more differentiated, showing S-antigen-positive inner and outer segments. An inner limiting membrane with an apparent ganglion cell layer was only seen in one cograft of retina and retinal pigment epithelium at 37 weeks, indicating an important role of retinal pigment epithelium for graft differentiation. This study shows that human embryonic retina can be grafted to immuno-suppressed adult rat retina with long-term survival. A high degree of maturation can be obtained in the grafted tissue comparable to the layering of newborn human retina. It appears that most cell types develop. This model opens up possibilities for studying human retinal development with the goal of reaching a treatment for human degenerative retinal disorders.

The present study describes reinnervation and restoration of rat skeletal muscle denervated for the duration of 3, 6 or 12 months. Denervation of extensor digitorum longus (EDL) muscle was achieved by cutting and ligating the donor rat sciatic nerve in situ. At 3, 6 and 12 months, the denervated EDL muscles were removed and transplanted into an innervated normal leg of another rat. In addition, normal (i.e., no prior denervation) muscles were transplanted as controls for comparison. The muscles were analyzed at 4 and 12 weeks after transplantation. The EDL muscle weight and myofiber size decreased with extended denervation times. After transplantation, the muscles underwent regeneration and reinnervation, and recovered as determined by an increase in muscle mass and myofiber size. The 3-month denervated muscle regenerates recovered completely, and were similar to the non-denervated normal muscle regenerates. Reinnervation, and partial recovery of muscle weight and myofiber size was observed in 6- and 12-month denervated muscle transplants. These results document that while regeneration and reinnervation does occur in denervated muscles after transplantation, the extent of recovery is related to the duration of denervation.

In the present study, we have developed an animal model for central nervous system (CNS) damage using the graded crush injury of the adult rat optic nerve. This injury model has the following characteristics: (a) the injuries are reproducible; (b) the injuries can be created with controlled severity; and (c) variations in the severity of the injuries correlate with definable electrophysiological and behavioral outcomes. Self-closing forceps, modified by attaching a screw to the handle, were used as a lesion-causing device. Rat optic nerves were crushed in vitro. The severity of the injury, calibrated by a measured applied force, was determined, electrophysiologically, in vitro. Compound action potential was assessed and recorded by suction electrodes connected to both sides of the nerve. In vivo studies correlated the calibrated crush injuries with behavioral outcome. After severe crush (applied force: 205 g or higher), the rats were unable to orient towards visual stimuli presented in the visual field of the damaged nerve and only minor transient recovery was observed. After moderate crush (applied force: 120 g), however, there was a significant recovery of orienting performance up to the 6th postoperative day, followed by a gradual, secondary loss of function. In the mildly injured group (applied force lower than 30 g), functional improvement continued for up to 10 days and remained stable thereafter, with only minor secondary loss. This CNS graded injury model may be valuable to study the molecular and anatomical mechanisms underlying secondary degeneration and the potency of various posttraumatic treatments in leading to recovery of function.

Patients with unilateral (left-sided) spatial neglect following right-hemisphere stroke were tested for the effects of visual stimulation on performance of a line-bisection task. As predicted from research on brain mechanisms of spatial orientation and attention, dynamic visual stimuli presented on the left side substantially reduced neglect in the task. In contrast, left sided static stimuli reduced neglect significantly less and dynamic stimuli presented in the center had no effect on neglect. Neglect patients with hemianopia did not show significantly less benefit of left-sided dynamic stimuli compared to neglect patients without hemianopia, suggesting that the effect of these stimuli was unconscious and automatic. The potential advantages of lateralized dynamic stimuli in the rehabilitation of neglect are discussed.