Led by positive growth for shares of UnitedHealth and Caterpillar, the Dow Jones Industrial Average is rallying Thursday morning. The Dow was most recently trading 459 points, or 1.3%, higher, as shares of UnitedHealth and Caterpillar have contributed about 50% of the blue-chip gauge’s intraday rally. UnitedHealth’s shares have gained $22.62, or 5.6%, while those of Caterpillar have risen $4.76 (2.5%), combining for a roughly 180-point boost for the Dow. Intel Dow Inc. and American Express are also contributing significantly to the gain. A $1 move in any of the benchmark’s 30 components equates to a 6.58-point swing.