duals. The ability of HV-1 Nef to modulate CTLA-4 expression may be different between viral strains and may be linked to the course of disease progression. Our study opens the path for this new type of investigation, with a particular focus on differences in HIV Nef 20534345 immunoregulatory functions between transmitted/founder versus chronic viruses and between subjects with slow versus rapid disease progression. The expansion of a tumour mass is directly related to its growth fraction, which can be assessed by measuring DNA synthesis by following incorporation of or labelled thymidine. This is acceptable for in vitro model systems and in animals but as long lived beta emitters, neither radionuclide is suitable for imaging in humans. Thymidine also has the disadvantage that it is rapidly catabolised and produces large amounts of re-circulating labeled catabolites following administration, reducing tumour-to-normal-tissue signaling during detection and imaging of tracer incorporation into DNA by kinetic modeling. Positron emission tomography has emerged as a very sensitive physiological, metabolic and molecular gamma ray detection technology that is used for imaging in many research and clinical applications but principally in oncology. For several decades the most commonly used PET tracer has been the cyclotron 23382385 produced 2-Fluoro-2-deoxy-D-glucose. However, this is neither cell specific nor very appropriate for measurement of cell proliferation, besides which it has a short half-life of less than 2 h. Several non-catabolised thymidine analogues such as, have been enlisted into clinical use for lymphoma, non-small-cell lung cancer and brain tumors. However, incorporation of F-FLT proceeds only to the triphosphate SCH 58261 manufacturer nucleoside step in the DNA synthetic pathway and not into DNA itself. There are also some practical drawbacks of 18F-FLT for identifying sites of proliferative activity or malignancy in the liver and bone marrow due to the presence of high background radioactivity, and interference with pelvic lesions due to its significant excretion 
into the urinary bladder. The short half-life of PET tracers has also limited their use to centers equipped with an on-site cyclotron. The practical need for longer-lived tracers has been resolved by the use of technetium99m. This radiotracer, is produced by a generator that is readily available in most hospital nuclear medicine departments and does not need an on-site cyclotron to produce it. It’s half-life of 6 h is long enough to perform nuclear medicine tests and short enough to minimize radiation exposure to the patient. Thus 99mTc is a very useful isotope that has been incorporated into many tumor imaging agents such as 99mTc-hexakis-2-methoxyisobutylisonitrile, used to detect metastatic breast cancer. Pentavalent 99mTc-dimercaptosuccinic acid -DMSA) formed from labelling of meso-2,3-dimercaptosuccinic acid with 99mTc under alkaline conditions, has been found to be a tumor-seeking agent. It was introduced to evaluate, image and manage medullary carcinoma of the thyroid. Also it has been reported to be useful in detecting many other types of cancers such as head and neck, soft tissue tumors, breast 18 99m Tc-DMSA Assessment and Cell Proliferation , brain, lung, bone, and particularly for metastatic and high-grade tumors and both primary and metastatic carcinoma of the prostate and melanoma. Several reports from Papantoniou and colleagues suggest that in vivo 99mTc-DMSA uptake by breast lesions is relat