The effect of a single bolus will also be examined in a third cohort. The single bolus infusion will consist of the following cell doses: approximately 10 billion, 20 billion, and 30 billion, respectively. Subjects will be allotted to the respective cell dose groups according to the order in which they are enrolled. Three to 5 subjects will be allotted to the lower cell dose group and followed for safety for 4 weeks. After safety is evaluated, the next group (3 to 5 subjects) will be allotted to the next higher cell dose group and followed for safety for 4 weeks. If the intermediate cell dose group is determined to be safe, an additional 3 to 5 subjects will be allotted to the highest cell dose group. All subjects will be followed for safety at biweekly intervals for the first 4 weeks and thereafter at monthly intervals up to 6 months and then at 9 months.