A syringe and a reconstitution syringe are provided for the delivery of controlled doses of any of numerous different sterile substances, such as vaccines, medicaments, pharmaceutical preparations, cosmetics, and food products. A plunger of the syringe defines a resealable stopper frictionally and slidably received within a hollow syringe body for dispensing the medicament or other substance through a dispensing tip of the syringe upon movement of the plunger. The resealable stopper defines a heat-sealable portion to allow the stopper to be penetrated by a needle or other filling device to fill the syringe with a medicament or other substance, and in turn allow the hole remaining upon withdrawal of the needle to be heat sealed by transmission of laser energy thereon. The plunger assembly further defines a plurality of cam-like members that each engage and cooperate with a respective helical path of steps formed on the inner wall of the syringe body to provide stepwise movement of the plunger and, in turn, precise metering of the substance dispensed therefrom. A reconstitution syringe defines within a syringe body plural compartments, wherein each compartment stores a respective component of a multi-component medicament or other preparation. An elastomeric plug is coupled to the plunger and connected between the two compartments to prevent intermixing of the components. Upon moving the plunger, the plug is released to thereby place the compartments in fluid communication with each other, and to facilitate intermixing of the components upon shaking the syringe.