Contribution of individual features to repetition suppression in macaque inferotemporal cortex.

When an image is presented twice in succession, neurons in area TE of macaque inferotemporal cortex exhibit repetition suppression, responding less strongly to the second presentation than to the first. Suppression is known to occur if the adapter and the test image are subtly different from each other. However, it is not known whether cross suppression occurs between images that are radically different from each other but that share a subset of features. To explore this issue, we measured repetition suppression using colored shapes. On interleaved trials, the test image might be identical to the adapter, might share its shape or color alone, or might differ from it totally. At the level of the neuronal population as a whole, suppression was especially deep when adapter and test were identical, intermediate when they shared only one attribute, and minimal when they shared neither attribute. At the level of the individual neuron, the degree of suppression depended not only on the properties of the two images but also on the preferences of the neuron. Suppression was deeper when the repeated color or shape was preferred by the neuron than when it was not. This effect might arise from feature-specific adaptation or alternatively from adapter-induced fatigue. Both mechanisms conform to the principle that the degree of suppression is determined by the preferences of the neuron.NEW & NOTEWORTHY When an image is presented twice in rapid succession, neurons of inferotemporal cortex exhibit repetition suppression, responding less strongly to the second than to the first presentation. It has been unclear whether this phenomenon depends on the selectivity of the neuron under study. Here, we show that, for a given neuron, suppression is deepest when features preferred by that neuron are repeated. The results argue for a mechanism based either on feature-specific suppression or fatigue.

Positive selection of mC46-expressing CD4+ T cells and maintenance of virus specific immunity in a primate AIDS model.

Despite continued progress in the development of novel antiretroviral therapies, it has become increasingly evident that drug-based treatments will not lead to a functional or sterilizing cure for HIV(+) patients. In 2009, an HIV(+) patient was effectively cured of HIV following allogeneic transplantation of hematopoietic stem cells (HSCs) from a CCR5(-/-) donor. The utility of this approach, however, is severely limited because of the difficulty in finding matched donors. Hence, we studied the potential of HIV-resistant stem cells in the autologous setting in a nonhuman primate AIDS model and incorporated a fusion inhibitor (mC46) as the means for developing infection-resistant cells. Pigtail macaques underwent identical transplants and Simian-Human Immunodeficiency Virus (SHIV) challenge procedures with the only variation between control and mC46 macaques being the inclusion of a fusion-inhibitor expression cassette. Following SHIV challenge, mC46 macaques, but not control macaques, showed a positive selection of gene-modified CD4(+) T cells in peripheral blood, gastrointestinal tract, and lymph nodes, accounting for >90% of the total CD4(+) T-cell population. mC46 macaques also maintained high frequencies of SHIV-specific, gene-modified CD4(+) T cells, an increase in nonmodified CD4(+) T cells, enhanced cytotoxic T lymphocyte function, and antibody responses. These data suggest that HSC protection may be a potential alternative to conventional antiretroviral therapy in patients with HIV/AIDS.

Integrated Microprism and Microelectrode Array for Simultaneous Electrophysiology and Two-Photon Imaging across All Cortical Layers.

Cerebral neural electronics play a crucial role in neuroscience research with increasing translational applications such as brain-computer interfaces for sensory input and motor output restoration. While widely utilized for decades, the understanding of the cellular mechanisms underlying this technology remains limited. Although two-photon microscopy (TPM) has shown great promise in imaging superficial neural electrodes, its application to deep-penetrating electrodes is technically difficult. Here, a novel device integrating transparent microelectrode arrays with glass microprisms, enabling electrophysiology recording and stimulation alongside TPM imaging across all cortical layers in a vertical plane, is introduced. Tested in Thy1-GCaMP6 mice for over 4 months, the integrated device demonstrates the capability for multisite electrophysiological recording/stimulation and simultaneous TPM calcium imaging. As a proof of concept, the impact of microstimulation amplitude, frequency, and depth on neural activation patterns is investigated using the setup. With future improvements in material stability and single unit yield, this multimodal tool greatly expands integrated electrophysiology and optical imaging from the superficial brain to the entire cortical column, opening new avenues for neuroscience research and neurotechnology development.

In vivo protection of activated Tyr22-dihydrofolate reductase gene-modified canine T lymphocytes from methotrexate.

BACKGROUND: Nonmyeloablative allogeneic hematopoietic stem cell (HSC) transplantation can cure malignant and nonmalignant diseases affecting the hematopoietic system, such as severe combined immunodeficiencies, aplastic anemia and hemoglobinopathies. Although nonmyeloablative is favored over myeloablative transplantation for many patients, graft rejection remains problematic. One strategy for decreasing rejection is to protect donor activated T cells in the graft from methotrexate (MTX) by genetically modifying the cells to express MTX-resistant dihydrofolate reductase (Tyr22-DHFR), leaving the immunosuppressive effects of MTX to act solely on activated host T lymphocytes, shifting the balance to favor allogeneic engraftment. METHODS: To evaluate MTX resistance of Tyr22-DHFR(+) T lymphocytes in vivo, we transplanted dogs with autologous CD34(+) cells modified with yellow fluorescent protein (YFP) and DHFR-green fluorescent protein (GFP) lentivirus vectors. Dogs were then treated with a standard MTX regimen days 1, 3, 6 and 11) following immune activation with a foreign antigen as a surrogate assay to mimic early transplantation. RESULTS: DHFR-GFP(+) gene marking was maintained in CD3(+) CD25(+) and CD4(+) T lymphocytes after MTX treatment, whereas the level of T lymphocytes that expressed only a fluorescent reporter (YFP(+) ) decreased. These data show that Tyr22-DHFR expression protects T lymphocytes from MTX toxicity in dogs, highlighting a clinically relevant application for preserving donor T lymphocytes during post-transplantation immunosuppression. CONCLUSIONS: The findings of the present study have implications for the clinical translation of MTX-resistant T cells to facilitate engraftment of allogeneic cells following nonmyeloablative conditioning and to minimize the risk of rejection. In summary, Tyr22-DHFR expression in T lymphocytes provides chemoprotection from MTX-mediated elimination in the context of immune activation in vivo.

Effects of central nervous system electrical stimulation on non-neuronal cells.

Over the past few decades, much progress has been made in the clinical use of electrical stimulation of the central nervous system (CNS) to treat an ever-growing number of conditions from Parkinson's disease (PD) to epilepsy as well as for sensory restoration and many other applications. However, little is known about the effects of microstimulation at the cellular level. Most of the existing research focuses on the effects of electrical stimulation on neurons. Other cells of the CNS such as microglia, astrocytes, oligodendrocytes, and vascular endothelial cells have been understudied in terms of their response to stimulation. The varied and critical functions of these cell types are now beginning to be better understood, and their vital roles in brain function in both health and disease are becoming better appreciated. To shed light on the importance of the way electrical stimulation as distinct from device implantation impacts non-neuronal cell types, this review will first summarize common stimulation modalities from the perspective of device design and stimulation parameters and how these different parameters have an impact on the physiological response. Following this, what is known about the responses of different cell types to different stimulation modalities will be summarized, drawing on findings from both clinical studies as well as clinically relevant animal models and in vitro systems.