Except for strategies whereby genetic modification occurs by transient exposure to nucleases [ 15, 16], most gene therapy approaches require long-term stable expression of the transgene in modified cells.
Since SDF-1 is highly expressed for only 48 h after infarction, the current approaches requiring long-term culture of MSCs to induce CXCR4 expression are not clinically useful.
While adaptive beamforming in a series of narrow frequency bands can suppress coherent multipath interference, this approach requires long observation times to estimate the required narrowband covariance matrices.
This approach requires long labelling phases as isotopic steady-state is required.
However, this approach required long image acquisition times because full data sets corrupted by lateral motion were discarded.
This approach requires long-term follow-up by an experienced specialty team as an adjunct to primary care.
Kinetic modeling approaches often require long scan times and are often followed by complex fitting routines to extract the kinetic parameters from the time activity curves (TACs).
In all likelihood, as is the case for other age-related degenerative disorders (e.g., cardiovascular disease), successful disease-modifying therapeutic approaches will require long-term administration, beginning early in the disease process, that are without side effects or engender readily manageable ones.
A bridge high enough to allow large ships to pass would require long approaches, set well back from the waterfronts.
However, these approaches are known to require long execution times in order to produce acceptable quality documents, and usually present poor convergence to optimal solutions when given (often conflicting) multiple aesthetic criteria [12, 21].
Imposing a monthly limit on the cost of each prescription would be a good approach for those who require long courses of costly drug treatment.
