The Activity Requirements for Spike Timing-Dependent Plasticity in the Hippocampus

Synaptic plasticity has historically been investigated most intensely in the hippocampus and therefore it is somewhat surprising that the majority of studies on spike timing-dependent plasticity (STDP) have focused not in the hippocampus but on synapses in the cortex. One of the major reasons for this bias is the relative ease in obtaining paired electrophysiological recordings from synaptically coupled neurons in cortical slices, in comparison to hippocampal slices. Another less obvious reason has been the difficulty in achieving reliable STDP in the hippocampal slice preparation and confusion surrounding the conditions required. The original descriptions of STDP in the hippocampus was performed on paired recordings from neurons in dissociated or slice cultures utilizing single pairs of presynaptic and postsynaptic spikes and were subsequently replicated in acute hippocampal slices. Further work in several laboratories using conditions that more closely replicate the situation in vivo revealed a requirement for multiple postsynaptic spikes that necessarily complicate the absolute timing rules for STDP. Here we review the hippocampal STDP literature focusing on data from acute hippocampal slice preparations and highlighting apparently contradictory results and the variations in experimental conditions that might account for the discrepancies. We conclude by relating the majority of the available experimental data to a model for STDP induction in the hippocampus based on a critical role for postsynaptic Ca2+ dynamics

Estimation of Juvenile Striped Bass Relative Abundance in the Virginia Portion of Chesapeake Bay Annual Progress Report: 2021 - 2022

The 2021 juvenile Striped Bass abundance index was 6.30 and was not significantly different than the reference mean of 7.77 for the period 1980 to 2009. Abundance indices were average in the York and Rappahannock rivers and below average in the James River in 2021 compared with the river‐specific reference means (1980‐2009). Relatively low catches of young‐of‐the‐year Striped Bass from sites upriver and downriver of core nursery areas suggest juvenile Striped Bass largely remained within core nursery areas in 2021. Juvenile abundance indices for Alewife, American Shad, Atlantic Croaker, Atlantic Silverside, and Spot were generally below their historic averages in 2021. In contrast, abundance indices for Banded Killifish, and Spottail Shiner in 2021 were generally greater than their historic averages in Virginia waters. Inland Silverside abundance in 2021 was similar to the historic average observed in Virginia waters. Juvenile White Perch abundance indices in 2021 were above historic averages in the York and Rappahannock river systems, but below historic averages in the James River. The juvenile abundance index for Blueback Herring was average in all rivers, except the Pamunkey River, where below‐average recruitment was observed. Together, these results suggest modest production of forage fish prey for piscivores in Virginia

Estimation of Juvenile Striped Bass Relative Abundance in the Virginia Portion of Chesapeake Bay Annual Progress Report: 2022 - 2023

The 2022 juvenile Striped Bass abundance index was 7.95 and was not significantly different than the reference mean of 7.77 for the period 1980 to 2009. Abundance indices were average in the York and Rappahannock rivers and below average in the James River in 2022 compared with the river-specific reference means (1980-2009). Relatively low catches of young‐of‐the‐year Striped Bass from sites upriver and downriver of core nursery areas suggest juvenile Striped Bass largely remained within core nursery areas in 2022. Indices of abundance were also calculated for three additional economically and recreationally important fishes in Virginia waters. Juvenile White Perch abundance indices in 2022 were above historic averages in the York and Rappahannock river systems, but similar to the historic average in the James River. Atlantic Croaker abundance in 2022 was similar to the historic average observed in Virginia waters. In contrast, the abundance index for Spot in 2022 was generally below the historic average in Virginia waters

Predation Impacts of Invasive Blue Catfish on Blue Crabs in Estuarine Environments

Blue crab (Callinectes sapidus) is an important resource in Chesapeake Bay serving as predator and prey in the estuarine food web and supporting one of the most valuable fisheries in the region with landings in 2019 exceeding 55,501,000 lbs. and valued at more than $81,465,000 (NOAA Fisheries 2021). Fluctuations in the abundance of blue crabs in the Chesapeake Bay reflect annual changes in recruitment, fishing mortality, and natural mortality (Lipcius and Van Engel 1990). During the 1990s, blue crab abundance in Chesapeake Bay declined markedly (Lipcius and Stockhausen 2002) and management plans were subsequently enacted to rebuild blue crab stocks to former levels of abundance. Such rebuilding plans aim to protect the spawning stock to ensure recruitment and required significant reductions in fishing mortality rates. Recruitment in this stock is closely monitored, and fishing mortality is regulated through area closures, minimum size, and seasonal harvest limits, but natural mortality due to predation is not well known or estimated. Indeed, a comprehensive list of blue crab predators is lacking for Chesapeake Bay (Bromilow and Lipcius 2017). Nonetheless, predation mortality on blue crabs may contribute to notable annual fluctuations in the abundance of juvenile and harvestable blue crabs

The Secret to Successful User Communities: An Analysis of Computer Associates’ User Groups

This paper provides the first large scale study that examines the impact of both individual- and group-specific factors on the benefits users obtain from their user communities. By empirically analysing 924 survey responses from individuals in 161 Computer Associates' user groups, this paper aims to identify the determinants of successful user communities. To measure success, the amount of time individual members save through having access to their user networks is used. As firms can significantly profit from successful user communities, this study proposes four key implications of the empirical results for the management of user communities

Control of Ca2+ Influx and Calmodulin Activation by SK-Channels in Dendritic Spines

© 2016 Griffith et al. The key trigger for Hebbian synaptic plasticity is influx of Ca2+ into postsynaptic dendritic spines. The magnitude of [Ca2+] increase caused by NMDA-receptor (NMDAR) and voltage-gated Ca2+ -channel (VGCC) activation is thought to determine both the amplitude and direction of synaptic plasticity by differential activation of Ca2+ -sensitive enzymes such as calmodulin. Ca2+ influx is negatively regulated by Ca2+ -activated K+ channels (SK-channels) which are in turn inhibited by neuromodulators such as acetylcholine. However, the precise mechanisms by which SK-channels control the induction of synaptic plasticity remain unclear. Using a 3-dimensional model of Ca2+ and calmodulin dynamics within an idealised, but biophysically-plausible, dendritic spine, we show that SK-channels regulate calmodulin activation specifically during neuron-firing patterns associated with induction of spike timing-dependent plasticity. SK-channel activation and the subsequent reduction in Ca2+ influx through NMDARs and L-type VGCCs results in an order of magnitude decrease in calmodulin (CaM) activation, providing a mechanism for the effective gating of synaptic plasticity induction. This provides a common mechanism for the regulation of synaptic plasticity by neuromodulators

Addressing fluorogenic real-time qPCR inhibition using the novel custom Excel file system 'FocusField2-6GallupqPCRSet-upTool-001' to attain consistently high fidelity qPCR reactions

The purpose of this manuscript is to discuss fluorogenic real-time quantitative polymerase chain reaction (qPCR) inhibition and to introduce/define a novel Microsoft Excel-based file system which provides a way to detect and avoid inhibition, and enables investigators to consistently design dynamically-sound, truly LOG-linear qPCR reactions very quickly. The qPCR problems this invention solves are universal to all qPCR reactions, and it performs all necessary qPCR set-up calculations in about 52 seconds (using a pentium 4 processor) for up to seven qPCR targets and seventy-two samples at a time – calculations that commonly take capable investigators days to finish. We have named this custom Excel-based file system "FocusField2-6GallupqPCRSet-upTool-001" (FF2-6-001 qPCR set-up tool), and are in the process of transforming it into professional qPCR set-up software to be made available in 2007. The current prototype is already fully functional

1974

History of Golf (1) The Nine Toughest Holes in the World (2) Stockie Madness (3) Bartender, One More Round for Pythium (3) Panel: 1973 Turf Problems in Review - 1974 Possible Remedies (A1-A12) Movement of Water to a Holding Pond (A13) Maintenance of Low Budget, Short Season Golf Courses (A16) Turfgrass Fertilization (A18) Determining Turfgrass Fertilizer Needs (A25) Shortage of Plant Food and How to Adjust to Supply and Cost (A29) Panel: Tricalcium Arsenate - Use and Abuse (A33-A46) Operating and Maintaining Municipal Golf Courses (A48) Maintenance of a High Budget Golf Course (A51) Trends in Agricultural Education and Where Are the Emphases (A58) Maintenance of Municipal Parks and Recreation Areas (A60) Maintenance of Grass Tennis Courts (A63) Transition from Natural to Artificial Turf (A67) Plant materials for Outlying Areas (A71) Care of University Grounds (A76) Maintenance of Industrial Sites (A79) Turfgrass Diseases and Systemic Fungicides (A81) A Look at the Future (A 84) Watering of Golf Course Turf (A92