Bromodeoxyuridine labelling as an alternative method to identify 6-thioguanine-resistant mutant lymphocytes in humans

Microglia release activators of neuronal proliferation mediated by activation of mitogen-activated protein kinase, phosphatidylinositol-3-kinase/Akt and delta-Notch signalling cascades

Microglia, the resident macrophage of the brain, can release substances that aid neuronal development, differentiation and survival. We have investigated the effects of non-activated microglia on the survival of cultured rat cerebellar granule neurones. Microglial-conditioned medium, collected from primary rat microglial cultures, was used to treat 7-day-in-vitro neurones, and neuronal viability and proliferation was assessed following a further 1 or 7 days in culture. Microglial-conditioned medium enhanced neuronal survival by up to 50% compared with untreated neurones and this effect was completely abated by pretreatment of the microglia with l-leucine methyl ester. The expression of the proliferation marker Ki-67 increased in neuronal cultures treated with microglial-conditioned medium suggesting enhanced proliferation of precursor neurones. Microglial-induced neuronal proliferation could be attenuated by specific inhibition of mitogen-activated protein kinase or phosphatidylinositol-3-kinase/Akt signalling pathways, and by selective fractionation and immunodepletion of the microglial-conditioned medium. Activation of the Notch pathway was enhanced as antibody against the Notch ligand, delta-1, prevented the microglial-induced neuronal proliferation. These results show that microglia release stable neurotrophic factors that can promote neuronal precursor cell proliferation.

Intrathecal administration of epidermal growth factor and fibroblast growth factor 2 promotes ependymal proliferation and functional recovery after spinal cord injury in adult rats

We have shown previously that epidermal growth factor (EGF) plus fibroblast growth factor (FGF2) expands the neural precursor cells in the ependyma of the normal adult rat spinal cord in vivo. To investigate the therapeutic effect of these factors on spinal cord injury (SCI), we administered EGF, FGF2, EGF plus FGF2, or artificial cerebrospinal fluid (aCSF) intrathecally (15 ng/h of EGF or FGF2) for 3 or 14 days after mild (2.4-g) or moderate (20-g) clip compression injury at T1 in adult rats. Histological and functional assessments were used to evaluate the therapeutic effects. The EGF plus FGF2 group, which received these agents for 14 days, showed better functional recovery than the aCSF group 42 days after moderate SCI (p < 0.05). At 14 days, the EGF plus FGF2 group showed a much greater expansion of ependymal cells and astrocytes compared to the other groups, and there was evidence for extensive migration of ependymal cells into the surrounding injured cord. These mitogens did not significantly enhance nestin expression in the ependymal layer or alter the expansion of oligodendrocyte precursor cells or microglia/macrophages, and dividing cells did not show the neuron-specific marker NeuN except immediately adjacent to the ependyma. The exact mechanism for improved functional recovery after EGF plus FGF2 is not known.

Flow cytometric determination of HPRT-variants in human peripheral blood lymphocytes

Hypoxanthine guanine phosphoribosyl transferase (HPRT) deficient human peripheral blood lymphocytes are usually enumerated either by the cloning assay or by the autoradiographic short-term assay. The short-term approach presented here is based on flow cytometric (FCM) scoring of 6-thioguanine (6-TG) resistant lymphocytes. HPRT-variants are enumerated on the basis of both DNA synthesis (by use of immunofluorescent detection of incorporated 5-bromo-2-deoxyuridine, BrdU) and total DNA content (by propidium iodide (PI) incorporation) of proliferating cells, i.e. the cells must both be labelled with BrdU and reside in late-S or G2 phase in order to be scored as a HPRT-variant. This approach is combined with a stringent discrimination of false-positive events, minimising occurrence of phenocopies or other non-specifically labelled cells that might falsely be scored as true HPRT-variants. The HPRT-variant frequency (V(f)) found by the presented method varied between 0.8 x 10(-5) and 5.8 x 10(-5) for healthy male and female donors aged between 20 and 74 years. There was no significant gender difference in V(f). A strong linear correlation was found between HPRT-variant frequency and age, showing an increase of 0.56 x 10(-6) per year of age (r(2)=0.62, P<0.001). The frequencies of false-positive events found showed a mean of 0.22 x 10(-5) in comparison with a pooled mean V(f) of 2.87 x 10(-5). There was no significant age effect on the frequency of false events (r(2)=0.15, P<0.095). The method presented here may provide a rapid and sensitive alternative to the autoradiographic technique for the short-term enumeration of HPRT-variants.