Service oriented application development has gained wide acceptance in the Grid computing community. A number of projects and community efforts have been developing standards (OGSA and WSRF), tools, and middleware systems to support development, deployment, and execution of Grid Services. In this paper, we present the use of Grid Services in two application scenarios; servicing of large scale data from simulation-based oil reservoir management studies and computer-aided analysis of large microscopy images for neuroblastoma prognosis. We describe how the high-performance backend systems have been developed for these applications and how these backend systems have been exposed through Grid Service interfaces. Our work illustrates that with the help of appropriate middleware systems, it is possible to develop and deploy high-performance Grid Services that support storage, retrieval and processing of large scale scientific and biomedical datasets, while enabling remote access to the data via well-defined interfaces and protocols.