Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

[EX Q]: Abstract: The short-term effects of incremental doses of procainamide (7.5, 15, 22.5, and 30 mg/kg) on right ventricular effective refractory period, intraventricular conduction, and induction of ventricular tachycardia were determined in 31 patients who had a history of sustained, unimorphic ventricular tachycardia. QRS duration during incremental ventricular pacing was used as an index of rate-dependent changes in intraventricular conduction. The mean plasma procainamide concentrations corresponding to the incremental doses were 5.5 +/- 1.2 (+/- SD), 9.0 +/- 1.6, 12.6 +/- 2.2, and 16.3 +/- 3.2 mg/liter. Each incremental dose of procainamide up to a dose of 30 mg/kg resulted in a significant increment in right ventricular effective refractory period and each dose up to 22.5 mg/kg potentiated a rate-dependent prolongation of QRS duration. After the 7.5 mg/kg dose of procainamide, induction of ventricular tachycardia was suppressed in eight of 31 patients. After higher doses of procainamide, induction of ventricular tachycardia was suppressed in two additional patients. In three of 10 patients in whom the induction of ventricular tachycardia was suppressed by 7.5, 15, or 22.5 mg/kg of procainamide, sustained unimorphic ventricular tachycardia was again inducible after a higher dose of procainamide. In three of 31 patients, only nonsustained ventricular tachycardia was inducible after a 7.5 to 22.5 mg/kg dose of procainamide; however, in two of these three patients, sustained ventricular tachycardia was again inducible after administration of a higher dose of procainamide. In conclusion, during electropharmacologic testing with procainamide, it is worthwhile to test a dose of 7.5 mg/kg, because this dose is often effective in patients who respond to this drug. However, the results of this study indicate that procainamide may be effective in suppressing the induction of sustained ventricular tachycardia at a relatively low plasma concentration, but not at a higher plasma concentration. Therefore, during long-term therapy with procainamide it may be important to avoid plasma procainamide concentrations not only lower, but also higher than the concentration that results in the suppression of induction of tachycardia.
[EX A]: Effects of incremental doses of procainamide on ventricular refractoriness, intraventricular conduction, and induction of ventricular tachycardia.

[EX Q]: Abstract: In the Drosophila embryo the establishment and specification of metameric units depends upon the selective activation of the segmentation and the homoeotic selector genes. The former are necessary for establishing the appropriate number of metameric or parasegmental units, whereas the latter control the pathways of differentiation followed by particular parasegments. Classical embryological manipulations have show n that these processes must be closely coordinated during normal development. However, previous studies of pair-rule genes have led to the suggestion that the specification of segmental identity proceeds independently of the establishment of metameres as physical units. These apparently conflicting perspectives can be reconciled by envisaging a common maternally derived positional information system which is independently interpreted by the components of both processes. In the case of the partitioning process, the gap and pair-rule genes would be instrumental in translating this information, whereas the activation of the homeotic genes would be mediated via other intermediaries (see ref. 9 for review). It is difficult to see, however, how such a system could ensure the precise regulation of the tw o types of genes implicit in the final differentiated pattern. This difficulty has led to the suggestion that the segmentation mechanism must define the precise boundaries of selector gene expression. Here we confirm this suggestion and propose that the gene fushi tarazu plays a key role in this process, integrating the processes of metameric partitioning and regional specification in the Drosophila embryo.
[EX A]: The correct activation of Antennapedia and bithorax complex genes requires the fushi tarazu gene.

[EX Q]: Abstract: In the radial hemolysis test for rubella virus-specific antibodies, sera obtained shortly after primary rubella produce a characteristically altered hemolysis zone, termed soft hemolysis. The occurrence of soft hemolysis was analyzed statistically in 6,723 sera. The specificity of soft hemolysis for infection with rubella virus was 99.0%. Its sensitivity in primary infections was 97.3%, and the predictive value for rubella serodiagnosis (increase in IgG level or detectable IgM) was 91.2%. The temporal association of soft hemolysis with rubella was determined with sera obtained from 129 persons during late convalescence (70-310 days after onset of symptoms). Soft hemolysis disappeared by 190 days after the onset of symptoms and the presence of ordinary hemolysis ruled out primary rubella in the preceding 70-100 days. Soft hemolysis was caused by IgG antibody to rubella virus, and thus represents a new serodiagnostic principle. This technique, together with an Igm assay, allows rapid diagnosis of recent rubella from a single serum sample.
[EX A]:
Single-serum radial hemolysis to detect recent rubella virus infection.