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During the first postnatal week in rodents, cholinergic retinal waves initiate in starburst amacrine cells (SACs), propagating to retinal ganglion cells (RGCs) and visual centers, essential for visual circuit refinement. By modulating exocytosis in SACs, dynamic changes in the protein kinase A (PKA) activity can regulate the spatiotemporal patterns of cholinergic waves. Previously, cysteine string protein-α (CSPα) is found to interact with the core exocytotic machinery by PKA-mediated phosphorylation at serine 10 (S10). However, whether PKA-mediated CSPα phosphorylation may regulate cholinergic waves via SACs remains unknown. Here, we examined how CSPα phosphorylation in SACs regulates cholinergic waves. First, we identified that CSPα1 is the major isoform in developing rat SACs and the inner plexiform layer during the first postnatal week. Using SAC-specific expression, we found that the CSPα1-PKA-phosphodeficient mutant (CSP-S10A) decreased wave frequency, but did not alter the wave spatial correlation compared to control, wild-type CSPα1 (CSP-WT), or two PKA-phosphomimetic mutants (CSP-S10D and CSP-S10E). These suggest that CSPα-S10 phosphodeficiency in SACs dampens the frequency of cholinergic waves. Moreover, the level of phospho-PKA substrates was significantly reduced in SACs overexpressing CSP-S10A compared to control or CSP-WT, suggesting that the dampened wave frequency is correlated with the decreased PKA activity. Further, compared to control or CSP-WT, CSP-S10A in SACs reduced the periodicity of wave-associated postsynaptic currents (PSCs) in neighboring RGCs, suggesting that these RGCs received the weakened synaptic inputs from SACs overexpressing CSP-S10A. Finally, CSP-S10A in SACs decreased the PSC amplitude and the slope to peak PSC compared to control or CSP-WT, suggesting that CSPα-S10 phosphodeficiency may dampen the speed of the SAC-RGC transmission. Thus, via PKA-mediated phosphorylation, CSPα in SACs may facilitate the SAC-RGC transmission, contributing to the robust frequency of cholinergic waves.
We use two-dimensional numerical simulation to study the interaction between a pair of ferrofluid drops suspended in a rotating uniform magnetic field. Numerical results show four distinct regimes over the range of parameters tested: independent spin, planetary motion, drop locking and direct coalescence. These are in qualitative agreement with experiments, and the transition between them can be understood from the competition between magnetophoretic forces and viscous drag. We further analyse in detail the planetary motion, i.e. the revolution of the drops around each other while each spins in phase with the external magnetic field. For drops, as opposed to solid microspheres, the interaction is dominated by viscous sweeping, a form of hydrodynamic interaction. Magnetic dipole–dipole interaction via mutual induction only plays a secondary role. This insight helps us explain novel features of the planetary revolution of the ferrofluid drops that cannot be explained by a dipole model, including the increase of the angular velocity of planetary motion with the rotational rate of the external field, and the attainment of a limit separation between the drops that is independent of the initial separation.
During 1997–2012 we conducted a nationwide camera-trapping survey and assessed the availability of prey and habitat for the clouded leopard Neofelis nebulosa in Taiwan. We surveyed 1,249 camera-trap sites over 113,636 camera-trap days, from the seashore to an altitude of 3,796 m and covering various types of vegetation. No clouded leopards were photographed during 128,394 camera-trap days, including at 209 sites in other studies, confirming the presumed extinction of clouded leopards in Taiwan. Assessment of the prey base revealed altitudinal distribution patterns of prey species and prey biomass. Areas at lower altitudes and with less human encroachment and hunting supported a higher prey biomass and more of the typical prey species of clouded leopards. Habitat analysis revealed 8,523 km2 of suitable habitat but this was reduced to 6,734 km2 when adjacent areas of human encroachment were subtracted. In the absence of hunting and large mammalian carnivores the major prey of clouded leopards in Taiwan, such as Formosan macaques Macaca cyclopis, Reeves's muntjacs Muntiacus reevesi, Formosan serow Capricornis swinhoei and sambar Rusa unicolor, could become over-abundant. Thus, it is important to address the cascading effect of the disappearance of top-down predator control. Our assessment indicated that, with proper regulation of hunting, habitat restoration and corridor improvement, it may be possible to reintroduce the clouded leopard.
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