Impairment of select forms of spatial memory and neurotrophin-dependent synaptic plasticity by deletion of glial aquaporin-4.

Aquaporin-4 (AQP4) is the major water channel in the CNS and is primarily expressed in astrocytes. Little is known about the potential for AQP4 to influence synaptic plasticity, although many studies have shown that it regulates the response of the CNS to injury. Therefore, we evaluated long-term potentiation (LTP) and long-term depression (LTD) in AQP4 knock-out (KO) and wild-type mice. KO mice exhibited a selective defect in LTP and LTD without a change in basal transmission or short-term plasticity. Interestingly, the impairment in LTP in KO mice was specific for the type of LTP that depends on the neurotrophin BDNF, which is induced by stimulation at theta rhythm [theta-burst stimulation (TBS)-LTP], but there was no impairment in a form of LTP that is BDNF independent, induced by high-frequency stimulation. LTD was also impaired in KO mice, which was rescued by a scavenger of BDNF or blockade of Trk receptors. TrkB receptors, which mediate effects of BDNF on TBS-LTP, were not altered in KO mice, but p75NTR, the receptor that binds all neurotrophins and has been implicated in some types of LTD, was decreased. The KO mice also exhibited a cognitive defect, which suggests a new role for AQP4 and astrocytes in normal cognitive function. This defect was evident using a test for location-specific object memory but not Morris water maze or contextual fear conditioning. The results suggest that AQP4 channels in astrocytes play an unanticipated role in neurotrophin-dependent plasticity and influence behavior.

Geospatial Mapping as a Guide for Resource Allocation Among Burn Centers in India.

Timely treatment is essential for optimal outcomes after burn injury, but the method of resource distribution to ensure access to proper care in developing countries remains unclear. We therefore sought to examine access to burn care and the presence/absence of resources for burn care in India. We surveyed all eligible burn centers (n = 67) in India to evaluate burn care resources at each facility. We then performed a cross-sectional geospatial analysis using geocoding software (ArcGIS 10.3) and publicly available hospital-level data (WorldStreetMap, WorldPop database) to predict the time required to access care at the nearest burn center. Our primary outcome was the time required to reach a burn facility within India. Descriptive statistics were used to present our results. Of the 67 burn centers that completed the survey, 45% were government funded. More than 1 billion (75.1%) Indian citizens live within 2 hours of a burn center, but only 221.9 million (15.9%) live within 2 hours of a burn center with both an intensive care unit (ICU) and a skin bank. Burn units are staffed primarily by plastic surgeons (n = 62, 93%) with an average of 5.8 physicians per unit. Most burn units (n = 53, 79%) have access to hemodialysis. While many Indian citizens live within 2 hours of a burn center, most centers do not offer ICU and skin bank services that are essential for modern burn care. Reallocation of resources to improve transportation and availability of ICU and skin bank services is necessary to improve burn care in India.