Changes In Cellular Markers Research Articles

Mutant Tau protein-induced abnormalities in the Na+-dependent glutamine translocation and recycling and their impact on astrocyte-neuron integrity in vitro

Tau-dependent neurodegeneration is accompanied by astrocytosis in a mouse trans-genic model, which replicates the neuropathological characteristic of tauopathy and other human neurodegenerative disorders where astrocyte activation precedes neuronal loss and is associated with disease progression. This indicates an important role of astrocytes in the development of the disease. Astrocytes derived from a transgenic mouse model expressing human Tau, exhibit changes in cellular markers of astrocyte neuroprotective function related to the glutamate-glutamine cycle (GGC), representing a key part of astrocyte-neuron integrity. Here, we focused on investigating the functional properties of key GGC components involved in the astrocyte-neuron network associated with Tau pathology in vitro. Mutant recombinant Tau (rTau) carrying the P301L mutation was added to the neuronal cultures, with or without control astrocyte-conditioned medium (ACM), to study glutamine translocation through the GGC. We demonstrated that mutant Tau in vitro induces neuronal degeneration, while control astrocytes response in neuroprotective way by preventing neurodegeneration. In parallel with this observation, we noticed the Tau-dependent decline of neuronal microtubule associated protein 2 (MAP2), followed by changes in glutamine (Gln) transport. Exposure to rTau decreases sodium-dependent Gln uptake in neurons and that effect was reversed when cells were co-incubated with control ACM after induction of rTau dependent pathology. Further, we found that neuronal Na+-dependent system A is the most specific system that is affected under rTau exposure. In addition, in rTau-treated astrocytes total Na+-dependent uptake of Gln, which is mediated by the N system, increases. Altogether, our study suggest mechanisms operating in Tau pathology may be related to the alterations in glutamine transport and recycling that affect neuronal-astrocytic integrity.

Protective Effects of Acetyl L-Carnitine on Inhalation Anesthetic-Induced Neuronal Damage in the Nonhuman Primate

The inhalation anesthetics nitrous oxide (N2O) and isoflurane (ISO) are commonly used for general anesthesia in human infants. Combined exposures to N2O and ISO are known to cause abnormal apoptotic cell death (neurotoxicity) in pediatric animal models. Acetyl-L-carnitine (ALC), an anti-oxidant dietary supplement, has been reported to minimize neuronal damage in some models of neurotoxicity. MicroPET/CT imaging is capable of detecting and localizing changes in cellular markers of brain damage associated with developmental exposures to general anesthetics. By monitoring changes in glial activation, thought to be a marker of neuroinflammation, it should be possible to determine the intensity, duration and location of neuronal damage associated with exposure to general anesthetics. Here we assessed the uptake of 18F-labeled fluoroethoxybenzyl-N-(4-phenoxypyridin-3-yl) acetamide (FEPPA), a ligand for peripheral benzodiazepine receptors on activated glial cells. On postnatal day (PND) 5, rhesus monkeys (4/group) were exposed to a mixture of 70% N2O, 29% oxygen plus 1% ISO, or ALC (100 mg/kg given i.p.) plus this mixture for 8 hours; control monkeys with and without ALC were exposed to room air only. [18F]-FEPPA was injected intravenously and microPET/CT images were obtained one day and one and three weeks after anesthetic exposure. One day after anesthetic exposure the uptake of FEPPA was significantly increased only in the temporal lobe and one week after exposure uptake was significantly increased in only the frontal lobe. No significant differences in uptake were seen in any area after 3 weeks. Co-administration of ALC effectively blocked the increase in FEPPA uptake in both the temporal and frontal lobes. These findings suggest that microPET/CT imaging of FEPPA uptake may be useful for monitoring the time-course and location of adverse neural events that are associated with developmental exposures to general anesthetics. In addition, ALC appears to be capable of protecting against at least some of the adverse effects associated with such exposures.

Changes in nucleus accumbens and neostriatal c‐Fos and DARPP‐32 immunoreactivity during different stages of food‐reinforced instrumental training

Nucleus accumbens is involved in several aspects of instrumental behavior, motivation and learning. Recent studies showed that dopamine (DA) release in the accumbens shell was significantly increased on the first day of training on a fixed ratio (FR) 5 schedule (i.e. the transition from FR1 to FR5) compared with those rats that continued FR1 training, even though the rats on their first day of FR5 training received less food reinforcement than rats continuing on the FR1 schedule. Additionally, the second day of FR5 responding was marked by a significant increase in DA release in accumbens core. The present studies employed immunohistochemical methods to characterize the changes in cellular markers of accumbens and neostriatal neural activity that occur during various stages of food-reinforced FR5 training. c-Fos and DARPP-32 immunoreactivity in accumbens shell was significantly increased on the first day of FR5 training, while core c-Fos and DARPP-32 expression showed large increases on the second day of FR5 training. Additional studies showed that c-Fos and DARPP-32 expression in neostriatum increased after more extensive training. Double-labeling studies with immunofluorescence methods indicated that increases in accumbens c-Fos and DARPP-32 expression were primarily seen in substance-P-positive neurons. These increases in accumbens c-Fos and DARPP-32 immunoreactivity seen during the initial phases of FR training may reflect several factors, including novelty, learning, stress or the presentation of a work-related challenge to the organism. Moreover, it appears that the separate subregions of the striatal complex are differentially activated at distinct phases of instrumental training.

Cell surface antigens on human marrow cells: dissection of hematopoietic development using monoclonal antibodies and multiparameter flow cytometry.

A single sample of bone marrow includes the entire range of the developmental process, since cells of all stages and lineages are present. By selecting appropriate monoclonal antibodies, marrow cells of different lineages can be identified, even in their immature forms. Maturationally different bone marrow cells can be distinguished on the basis of their cell surface antigen expression and physical characteristics on a flow cytometer. Antigenic markers can be used within a lineage to trace the development from colony-forming cells to functional blood cells. Changes in cellular markers are observed as smooth, quantitative increases or decreases in cellular antigen expression. After defining the composition of normal marrow, it is possible to identify perturbations from the steady state and to monitor the return to homeostasis. Cells at various stages can be enumerated, then isolated for further study. In particular, these studies provide for the identification, purification and manipulation of the earliest hematopoietic progenitor cells.