The present study investigated the neuroanatomical and behavioral effects of human stem cell transplants into the striatum of quinolinic acid (QA)-lesioned rats. Twenty-four rats received unilateral QA (200 nM/microl) injections into the striatum. One week later, rats were transplanted with stem cells derived from human fetal cortex (12 weeks postconception) that were either 1) pretreated in culture media with the differentiating cytokine ciliary neurotrophic factor (CNTF; n = 9) or 2) allowed to grow in culture media alone (n=7). Each rat was injected with a total of 200,000 cells. A third group of rats (n=8) was given a sham injection of vehicle. Rats transplanted with human stem cells performed significantly better over the 8 weeks of testing on the cylinder test compared with those treated with vehicle (P < or = 0.001). Stereological striatal volume analyses performed on Nissl-stained sections revealed that rats transplanted with CNTF-treated neurospheres had a 22% greater striatal volume on the lesioned side compared with those receiving transplants of untreated neurospheres (P = 0.0003) and a 26% greater striatal volume compared with rats injected with vehicle (P < or = 0.0001). Numerous human nuclei-positive cells were visualized in the striatum in both transplantation groups. Grafted cells were also observed in the globus pallidus, entopeduncular nucleus, and substantia nigra pars reticulata, areas of the basal ganglia receiving striatal projections. Some of the human nuclei-positive cells coexpressed glial fibrillary acidic protein and NeuN, suggesting that they had differentiated into neurons and astrocytes. Taken together, these data demonstrate that striatal transplants of human fetal stem cells elicit behavioral and anatomical recovery in a rodent model of Huntington's disease.

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Electrical potentials were recorded from different levels within the skate retina. Comparing the adaptive properties of the various responses revealed that the isolated receptor potential and the S-potential always exhibited similar changes in sensitivity, and that the b-wave and ganglion-cell thresholds acted in concert. However, the two sets of responses behaved differently under certain conditions. For example, a dimly illuminated background that had no measurable effect on the sensitivities of either of the distal responses, raised significantly the thresholds of both the b-wave and the ganglion cell responses. In addition, the rate of recovery during the early, "neural" phase of dark adaptation was significantly faster for the receptor and S-potentials than for the b-wave or ganglion cell discharge. These results indicate that there is an adaptive ("network") mechanism in the retina which can influence significantly b-wave and ganglion cell activity and which behaves independently of the receptors and horizontal cells. We conclude that visual adaptation in the skate retina is regulated by a combination of receptoral and network mechanisms.

OBJECTIVE To measure “on” freezing during unassisted walking (UW) and test if two devices, a modified inverted stick (MIS) and a visual laser beam stick (LBS) improved walking speed and number of “on” freezing episodes in patients with Parkinson's disease (PD). BACKGROUND Multiple visual cues can overcome “off” freezing episodes and can be useful in improving gait function in parkinsonian patients. These devices have not been specifically tested in “on” freezing, which is unresponsive to pharmacologic manipulations. METHODS Patients with PD, motor fluctuations and freezing while “on,” attempted walking on a 60‐ft track with each of three walking conditions in a randomized order: UW, MIS, and LBS. Total time to complete a trial, number of freezes, and the ratio of walking time to the number of freezes were compared using Friedman's test. RESULTS Twenty‐eight patients with PD, mean age 67.81 years (standard deviation [SD] 7.54), mean disease duration 13.04 years (SD 7.49), and mean motor Unified Parkinson's Disease Rating Scale score “on” 32.59 (SD 10.93), participated in the study. There was a statistically significant correlation of time needed to complete a trial and number of freezes for all three conditions (Spearman correlations: UW 0.973, LBS 0.0.930, and MIS 0.842). The median number of freezes, median time to walk in each condition, and median walking time per freeze were not significantly different in pairwise comparisons of the three conditions (Friedman's test). Of the 28 subjects, six showed improvement with the MIS and six with the LBS in at least one outcome measure. CONCLUSION Assisting devices, specifically based on visual cues, are not consistently beneficial in overcoming “on” freezing in most patients with PD. Because this is an otherwise untreatable clinical problem and because occasional subjects do respond, cautious trials of such devices under the supervision of a health professional should be conducted to identify those patients who might benefit from their long‐term use.

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Ocular lesions have been experimentally produced in rabbit by a pulsed optical maser (laser). The high-energy density delivered in a single 0.5 msec pulse was sufficient to cause instantaneous thermal injury to the pigmented retina and iris of the brown rabbit. Ophthalmoscopically, the retinal lesions resembled flash burns from an atomic fireball.

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