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  • 1
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Keywords: Neuroscience
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-16
    Keywords: Neuroscience
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  • 3
    Publication Date: 2018-02-16
    Description: Temporal lobe epilepsy (TLE) is characterized by debilitating, recurring seizures and an increased risk for cognitive deficits. Mossy cells (MCs) are key neurons in the hippocampal excitatory circuit, and the partial loss of MCs is a major hallmark of TLE. We investigated how MCs contribute to spontaneous ictal activity and to spatial contextual memory in a mouse model of TLE with hippocampal sclerosis, using a combination of optogenetic, electrophysiological, and behavioral approaches. In chronically epileptic mice, real-time optogenetic modulation of MCs during spontaneous hippocampal seizures controlled the progression of activity from an electrographic to convulsive seizure. Decreased MC activity is sufficient to impede encoding of spatial context, recapitulating observed cognitive deficits in chronically epileptic mice.
    Keywords: Neuroscience
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  • 4
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-27
    Keywords: Neuroscience
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  • 5
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-22
    Keywords: Neuroscience
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  • 6
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-29
    Keywords: Neuroscience
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  • 7
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-03
    Keywords: Neuroscience
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  • 8
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-21
    Keywords: Neuroscience
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  • 9
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Neuroscience
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  • 10
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Neuroscience
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  • 11
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Description: Glia constitute roughly half of the cells of the central nervous system (CNS) but were long-considered to be static bystanders to its formation and function. Here we provide an overview of how the diverse and dynamic functions of glial cells orchestrate essentially all aspects of nervous system formation and function. Radial glia, astrocytes, oligodendrocyte progenitor cells, oligodendrocytes, and microglia each influence nervous system development, from neuronal birth, migration, axon specification, and growth through circuit assembly and synaptogenesis. As neural circuits mature, distinct glia fulfill key roles in synaptic communication, plasticity, homeostasis, and network-level activity through dynamic monitoring and alteration of CNS structure and function. Continued elucidation of glial cell biology, and the dynamic interactions of neurons and glia, will enrich our understanding of nervous system formation, health, and function.
    Keywords: Neuroscience
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  • 12
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Description: To understand how neurons assemble to form functional circuits, it is necessary to obtain a detailed knowledge of their diversity and to define the developmental specification programs that give rise to this diversity. Invertebrates and vertebrates appear to share common developmental principles of neuronal specification in which cascades of transcription factors temporally pattern progenitors, while spatial cues modify the outcomes of this temporal patterning. Here, we highlight these conserved mechanisms and describe how they are used in distinct neural structures. We present the questions that remain for a better understanding of neuronal specification. Single-cell RNA profiling approaches will potentially shed light on these questions, allowing not only the characterization of neuronal diversity in adult brains, but also the investigation of the developmental trajectories leading to the generation and maintenance of this diversity.
    Keywords: Neuroscience
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  • 13
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-12-21
    Keywords: Neuroscience
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  • 14
    Publication Date: 2018-10-26
    Description: Clinical observations indicate that the paramedian region of the thalamus is a critical node for controlling wakefulness. However, the specific nucleus and neural circuitry for this function remain unknown. Using in vivo fiber photometry or multichannel electrophysiological recordings in mice, we found that glutamatergic neurons of the paraventricular thalamus (PVT) exhibited high activities during wakefulness. Suppression of PVT neuronal activity caused a reduction in wakefulness, whereas activation of PVT neurons induced a transition from sleep to wakefulness and an acceleration of emergence from general anesthesia. Moreover, our findings indicate that the PVT–nucleus accumbens projections and hypocretin neurons in the lateral hypothalamus to PVT glutamatergic neurons’ projections are the effector pathways for wakefulness control. These results demonstrate that the PVT is a key wakefulness-controlling nucleus in the thalamus.
    Keywords: Neuroscience
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  • 15
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-26
    Keywords: Neuroscience
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  • 16
    Publication Date: 2018-10-26
    Description: The salience of behaviorally relevant stimuli is dynamic and influenced by internal state and external environment. Monitoring such changes is critical for effective learning and flexible behavior, but the neuronal substrate for tracking the dynamics of stimulus salience is obscure. We found that neurons in the paraventricular thalamus (PVT) are robustly activated by a variety of behaviorally relevant events, including novel ("unfamiliar") stimuli, reinforcing stimuli and their predicting cues, as well as omission of the expected reward. PVT responses are scaled with stimulus intensity and modulated by changes in homeostatic state or behavioral context. Inhibition of the PVT responses suppresses appetitive or aversive associative learning and reward extinction. Our findings demonstrate that the PVT gates associative learning by providing a dynamic representation of stimulus salience.
    Keywords: Neuroscience
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  • 17
    Publication Date: 2018-11-02
    Description: Animals constantly update their body posture to meet behavioral demands, but little is known about the neural signals on which this depends. We therefore tracked freely foraging rats in three dimensions while recording from the posterior parietal cortex (PPC) and the frontal motor cortex (M2), areas critical for movement planning and navigation. Both regions showed strong tuning to posture of the head, neck, and back, but signals for movement were much less dominant. Head and back representations were organized topographically across the PPC and M2, and more neurons represented postures that occurred less often. Simultaneous recordings across areas were sufficiently robust to decode ongoing behavior and showed that spiking in the PPC tended to precede that in M2. Both the PPC and M2 strongly represent posture by using a spatially organized, energetically efficient population code.
    Keywords: Neuroscience
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  • 18
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-16
    Keywords: Neuroscience
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  • 19
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-16
    Keywords: Neuroscience
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  • 20
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-30
    Keywords: Neuroscience
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  • 21
    Publication Date: 2018-04-27
    Description: Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells. In contextual fear conditioning, this enhanced connectivity between engram cells encoded memory strength. CA3 engram to CA1 engram projections strongly occluded long-term potentiation. These results indicate that enhanced structural and functional connectivity between engram cells across two directly connected brain regions forms the synaptic correlate for memory formation.
    Keywords: Neuroscience
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  • 22
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-02
    Keywords: Neuroscience
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  • 23
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-09
    Keywords: Neuroscience
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  • 24
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-09
    Keywords: Neuroscience
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  • 25
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-11-09
    Description: Consolidation of spatial and episodic memories is thought to rely on replay of neuronal activity sequences during sleep. However, the network dynamics underlying the initial storage of memories during wakefulness have never been tested. Although slow, behavioral time scale sequences have been claimed to sustain sequential memory formation, fast ("theta") time scale sequences, nested within slow sequences, could be instrumental. We found that in rats traveling passively on a model train, place cells formed behavioral time scale sequences but theta sequences were degraded, resulting in impaired subsequent sleep replay. In contrast, when the rats actively ran on a treadmill while being transported on the train, place cells generated clear theta sequences and accurate trajectory replay during sleep. Our results support the view that nested sequences underlie the initial formation of memory traces subsequently consolidated during sleep.
    Keywords: Neuroscience
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  • 26
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-13
    Keywords: Neuroscience
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  • 27
    Publication Date: 2018-06-15
    Description: Whether fear attenuation is mediated by inhibition of the original memory trace of fear with a new memory trace of safety or by updating of the original fear trace toward safety has been a long-standing question in neuroscience and psychology alike. In particular, which of the two scenarios underlies the attenuation of remote (month-old) fear memories is completely unknown, despite the impetus to better understand this process against the backdrop of enduring traumata. We found—chemogenetically and in an engram-specific manner—that effective remote fear attenuation is accompanied by the reactivation of memory recall–induced neurons in the dentate gyrus and that the continued activity of these neurons is critical for fear reduction. This suggests that the original memory trace of fear actively contributes to remote fear attenuation.
    Keywords: Neuroscience
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  • 28
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-29
    Keywords: Neuroscience
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  • 29
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-03
    Keywords: Neuroscience
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  • 30
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-03
    Keywords: Neuroscience
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  • 31
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-20
    Keywords: Neuroscience
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  • 32
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-11
    Keywords: Neuroscience
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  • 33
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-30
    Keywords: Neuroscience
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  • 34
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-30
    Keywords: Neuroscience
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  • 35
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-27
    Keywords: Neuroscience
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  • 36
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-04
    Keywords: Neuroscience
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  • 37
    Publication Date: 2018-05-04
    Description: Why are some visual stimuli consciously detected, whereas others remain subliminal? We investigated the fate of weak visual stimuli in the visual and frontal cortex of awake monkeys trained to report stimulus presence. Reported stimuli were associated with strong sustained activity in the frontal cortex, and frontal activity was weaker and quickly decayed for unreported stimuli. Information about weak stimuli could be lost at successive stages en route from the visual to the frontal cortex, and these propagation failures were confirmed through microstimulation of area V1. Fluctuations in response bias and sensitivity during perception of identical stimuli were traced back to prestimulus brain-state markers. A model in which stimuli become consciously reportable when they elicit a nonlinear ignition process in higher cortical areas explained our results.
    Keywords: Neuroscience
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  • 38
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-05-04
    Keywords: Neuroscience
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  • 39
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-04-06
    Keywords: Neuroscience
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  • 40
    Publication Date: 2018-03-30
    Description: The specific effects of sleep on synaptic plasticity remain unclear. We report that mouse hippocampal sharp-wave ripple oscillations serve as intrinsic events that trigger long-lasting synaptic depression. Silencing of sharp-wave ripples during slow-wave states prevented the spontaneous down-regulation of net synaptic weights and impaired the learning of new memories. The synaptic down-regulation was dependent on the N -methyl- d -aspartate receptor and selective for a specific input pathway. Thus, our findings are consistent with the role of slow-wave states in refining memory engrams by reducing recent memory-irrelevant neuronal activity and suggest a previously unrecognized function for sharp-wave ripples.
    Keywords: Neuroscience
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  • 41
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-15
    Keywords: Neuroscience
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  • 42
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-15
    Keywords: Neuroscience
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  • 43
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-15
    Keywords: Neuroscience
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  • 44
    Publication Date: 2018-06-15
    Description: Memories are integrated into interconnected networks; nevertheless, each memory has its own identity. How the brain defines specific memory identity out of intermingled memories stored in a shared cell ensemble has remained elusive. We found that after complete retrograde amnesia of auditory fear conditioning in mice, optogenetic stimulation of the auditory inputs to the lateral amygdala failed to induce memory recall, implying that the memory engram no longer existed in that circuit. Complete amnesia of a given fear memory did not affect another linked fear memory encoded in the shared ensemble. Optogenetic potentiation or depotentiation of the plasticity at synapses specific to one memory affected the recall of only that memory. Thus, the sharing of engram cells underlies the linkage between memories, whereas synapse-specific plasticity guarantees the identity and storage of individual memories.
    Keywords: Neuroscience
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  • 45
    Publication Date: 2018-07-06
    Description: The tuberal nucleus (TN) is a surprisingly understudied brain region. We found that somatostatin (SST) neurons in the TN, which is known to exhibit pathological or cytological changes in human neurodegenerative diseases, play a crucial role in regulating feeding in mice. GABAergic tuberal SST ( TN SST) neurons were activated by hunger and by the hunger hormone, ghrelin. Activation of TN SST neurons promoted feeding, whereas inhibition reduced it via projections to the paraventricular nucleus and bed nucleus of the stria terminalis. Ablation of TN SST neurons reduced body weight gain and food intake. These findings reveal a previously unknown mechanism of feeding regulation that operates through orexigenic TN SST neurons, providing a new perspective for understanding appetite changes.
    Keywords: Neuroscience
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  • 46
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-27
    Keywords: Neuroscience
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  • 47
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-07-27
    Description: Episodic memories are encoded by a sparse population of hippocampal neurons. In mice, optogenetic manipulation of this memory engram established that these neurons are indispensable and inducing for memory recall. However, little is known about their in vivo activity or precise role in memory. We found that during memory encoding, only a fraction of CA1 place cells function as engram neurons, distinguished by firing repetitive bursts paced at the theta frequency. During memory recall, these neurons remained highly context specific, yet demonstrated preferential remapping of their place fields. These data demonstrate a dissociation of precise spatial coding and contextual indexing by distinct hippocampal ensembles and suggest that the hippocampal engram serves as an index of memory content.
    Keywords: Neuroscience
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  • 48
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-03
    Keywords: Neuroscience
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  • 49
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-15
    Keywords: Neuroscience
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  • 50
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-15
    Keywords: Neuroscience
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  • 51
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-15
    Keywords: Neuroscience
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  • 52
    Publication Date: 2018-06-15
    Description: Brain size variation over primate evolution and human development is associated with shifts in the proportions of different brain regions. Individual brain size can vary almost twofold among typically developing humans, but the consequences of this for brain organization remain poorly understood. Using in vivo neuroimaging data from more than 3000 individuals, we find that larger human brains show greater areal expansion in distributed frontoparietal cortical networks and related subcortical regions than in limbic, sensory, and motor systems. This areal redistribution recapitulates cortical remodeling across evolution, manifests by early childhood in humans, and is linked to multiple markers of heightened metabolic cost and neuronal connectivity. Thus, human brain shape is systematically coupled to naturally occurring variations in brain size through a scaling map that integrates spatiotemporally diverse aspects of neurobiology.
    Keywords: Neuroscience
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  • 53
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-22
    Keywords: Neuroscience
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  • 54
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-06-22
    Keywords: Neuroscience
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  • 55
    Publication Date: 2018-06-22
    Description: Plasticity of cortical responses in vivo involves activity-dependent changes at synapses, but the manner in which different forms of synaptic plasticity act together to create functional changes in neurons remains unknown. We found that spike timing–induced receptive field plasticity of visual cortex neurons in mice is anchored by increases in the synaptic strength of identified spines. This is accompanied by a decrease in the strength of adjacent spines on a slower time scale. The locally coordinated potentiation and depression of spines involves prominent AMPA receptor redistribution via targeted expression of the immediate early gene product Arc. Hebbian strengthening of activated synapses and heterosynaptic weakening of adjacent synapses thus cooperatively orchestrate cell-wide plasticity of functional neuronal responses.
    Keywords: Neuroscience
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  • 56
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-10
    Keywords: Neuroscience
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  • 57
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-10
    Keywords: Neuroscience
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  • 58
    Publication Date: 2018-02-10
    Description: Neural stem and progenitor cells (NSPCs) generate neurons throughout life in the mammalian hippocampus. We used chronic in vivo imaging and followed genetically labeled individual NSPCs and their progeny in the mouse hippocampus for up to 2 months. We show that NSPCs targeted by the endogenous Achaete-scute homolog 1 (Ascl1) promoter undergo limited rounds of symmetric and asymmetric divisions, eliciting a burst of neurogenic activity, after which they are lost. Further, our data reveal unexpected asymmetric divisions of nonradial glia-like NSPCs. Cell fates of Ascl1-labeled lineages suggest a developmental-like program involving a sequential transition from a proliferative to a neurogenic phase. By providing a comprehensive description of lineage relationships, from dividing NSPCs to newborn neurons integrating into the hippocampal circuitry, our data offer insight into how NSPCs support life-long hippocampal neurogenesis.
    Keywords: Neuroscience
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  • 59
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-01-12
    Description: An animal’s awareness of its location in space depends on the activity of place cells in the hippocampus. How the brain encodes the spatial position of others has not yet been identified. We investigated neuronal representations of other animals’ locations in the dorsal CA1 region of the hippocampus with an observational T-maze task in which one rat was required to observe another rat’s trajectory to successfully retrieve a reward. Information reflecting the spatial location of both the self and the other was jointly and discretely encoded by CA1 pyramidal cells in the observer rat. A subset of CA1 pyramidal cells exhibited spatial receptive fields that were identical for the self and the other. These findings demonstrate that hippocampal spatial representations include dimensions for both self and nonself.
    Keywords: Neuroscience
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  • 60
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-01-26
    Keywords: Neuroscience
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  • 61
    Publication Date: 2018-01-26
    Description: Prior studies have demonstrated that correlated variability changes with cognitive processes that improve perceptual performance. We tested whether correlated variability covaries with subjects’ performance—whether performance improves quickly with attention or slowly with perceptual learning. We found a single, consistent relationship between correlated variability and behavioral performance, regardless of the time frame of correlated variability change. This correlated variability was oriented along the dimensions in population space used by the animal on a trial-by-trial basis to make decisions. That subjects’ choices were predicted by specific dimensions that were aligned with the correlated variability axis clarifies long-standing paradoxes about the relationship between shared variability and behavior.
    Keywords: Neuroscience
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  • 62
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-02-03
    Keywords: Neuroscience
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 63
    Publication Date: 2018-02-03
    Description: It has long been hypothesized that aging and neurodegeneration are associated with somatic mutation in neurons; however, methodological hurdles have prevented testing this hypothesis directly. We used single-cell whole-genome sequencing to perform genome-wide somatic single-nucleotide variant (sSNV) identification on DNA from 161 single neurons from the prefrontal cortex and hippocampus of 15 normal individuals (aged 4 months to 82 years), as well as 9 individuals affected by early-onset neurodegeneration due to genetic disorders of DNA repair (Cockayne syndrome and xeroderma pigmentosum). sSNVs increased approximately linearly with age in both areas (with a higher rate in hippocampus) and were more abundant in neurodegenerative disease. The accumulation of somatic mutations with age—which we term genosenium—shows age-related, region-related, and disease-related molecular signatures and may be important in other human age-associated conditions.
    Keywords: Neuroscience
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  • 64
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-14
    Keywords: Neuroscience
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  • 65
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-09-21
    Keywords: Neuroscience
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  • 66
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Keywords: Neuroscience
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  • 67
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-10-12
    Description: Cross-talk between the nervous and immune systems has been well described in the context of adult physiology and disease. Recent advances in our understanding of immune cell ontogeny have revealed a notable interplay between neurons and microglia during the prenatal and postnatal emergence of functional circuits. This Review focuses on the brain, where the early symbiotic relationship between microglia and neuronal cells critically regulates wiring, contributes to sex-specific differences in neural circuits, and relays crucial information from the periphery, including signals derived from the microbiota. These observations underscore the importance of studying neurodevelopment as part of a broader framework that considers nervous system interactions with microglia in a whole-body context.
    Keywords: Neuroscience
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  • 68
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-06
    Keywords: Neuroscience
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  • 69
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-09
    Keywords: Neuroscience
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  • 70
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-09
    Description: Grid cells are neurons active in multiple fields arranged in a hexagonal lattice and are thought to represent the "universal metric for space." However, they become nonhomogeneously distorted in polarized enclosures, which challenges this view. We found that local changes to the configuration of the enclosure induce individual grid fields to shift in a manner inversely related to their distance from the reconfigured boundary. The grid remained primarily anchored to the unchanged stable walls and showed a nonuniform rescaling. Shifts in simultaneously recorded colocalized grid fields were strongly correlated, which suggests that the readout of the animal’s position might still be intact. Similar field shifts were also observed in place and boundary cells—albeit of greater magnitude and more pronounced closer to the reconfigured boundary—which suggests that there is no simple one-to-one relationship between these three different cell types.
    Keywords: Neuroscience
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  • 71
    Publication Date: 2018-03-16
    Description: Neuronal synapse formation and remodeling are essential to central nervous system (CNS) development and are dysfunctional in neurodevelopmental diseases. Innate immune signals regulate tissue remodeling in the periphery, but how this affects CNS synapses is largely unknown. Here, we show that the interleukin-1 family cytokine interleukin-33 (IL-33) is produced by developing astrocytes and is developmentally required for normal synapse numbers and neural circuit function in the spinal cord and thalamus. We find that IL-33 signals primarily to microglia under physiologic conditions, that it promotes microglial synapse engulfment, and that it can drive microglial-dependent synapse depletion in vivo. These data reveal a cytokine-mediated mechanism required to maintain synapse homeostasis during CNS development.
    Keywords: Neuroscience
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  • 72
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-03-06
    Description: Thorndike’s law of effect states that actions that lead to reinforcements tend to be repeated more often. Accordingly, neural activity patterns leading to reinforcement are also reentered more frequently. Reinforcement relies on dopaminergic activity in the ventral tegmental area (VTA), and animals shape their behavior to receive dopaminergic stimulation. Seeking evidence for a neural law of effect, we found that mice learn to reenter more frequently motor cortical activity patterns that trigger optogenetic VTA self-stimulation. Learning was accompanied by gradual shaping of these patterns, with participating neurons progressively increasing and aligning their covariance to that of the target pattern. Motor cortex patterns that lead to phasic dopaminergic VTA activity are progressively reinforced and shaped, suggesting a mechanism by which animals select and shape actions to reliably achieve reinforcement.
    Keywords: Neuroscience
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  • 73
    ISSN: 1432-0789
    Keywords: Key words Phosphorus dynamics ; Olsen ; phosphorus ; Soil phosphorus fractions ; Manure ; Soybean-wheat rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (Pi) and organic P (P0) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha–1 applied to both soybean and wheat) in the absence and presence of 16 t ha–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg–1 was 17.9 kg ha–1 of fertilizer P in unmanured plots and 5.6 kg ha–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO3-extractable Pi (NaHCO3-Pi) and NaHCO3-extractable P0 (NaHCO3-P0)], moderately labile [NaOH-extractable Pi (NaOH-Pi) and NaOH-extractable P0 (NaOH-P0)] and stable [HCl-extractable P (HCl-P) and H2SO4/H2O2-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO3-Pi and -P0 and NaOH-Pi, and -P0 fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO3-Pi, NaOH-Pi and NaOH-P0 fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P.
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  • 74
    ISSN: 1573-0417
    Keywords: carbon isotopes ; diatoms ; lake management ; nitrogen isotopes ; phosphorus ; radium-226 ; sediments ; trophic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.
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  • 75
    ISSN: 1573-0417
    Keywords: diatoms ; Everglades ; phosphorus ; wetland ; calibration ; multivariate ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781 μg g-1, and was not found to be correlated with the other geochemical variables. Canonical correspondence analysis (CCA) was used to examine which environmental variables correlated most closely with the distributions in diatom taxa. Canonical correspondence analysis with forward selection, constrained and partial CCA, and Monte Carlo permutation tests of significance show the most significant changes in diatom assemblages along the P gradient (p 〈 0.01), with additional species differences correlated with soil C, N, Ca, and BSi. Weighted-averaging (WA) regression and calibration models of diatom assemblages to P and BSi were developed. The diatom-based inference model for soil [P] had a high apparent r2 (0.86) with RMSEboot = 218 μg g-1. Indicator diatom species identified by assessing species WA optima and WA tolerance to [P], such as Nitzschia amphibia and N. palea for high [P] (~1300-1400 μ g-1) and Achnanthes minutissima var. scotica and Mastogloia smithii for low [P] (~400-600 μg g-1), may be useful as monitoring tools for eutrophication in WCA-2A as well as other areas of the Everglades. Diatom assemblages analyzed by cluster analysis were related to location within WCA-2A, and dominant taxa within clusters are discussed in relation to the geochemical variables measured as well as hydrology and pH. Diversity of diatom assemblages and a ‘Disturbance Index’ based on diatom data are discussed in relation to the historically P-limited Everglades ecosystem. Diatom assemblages should be very useful for reconstructions of [P] through time in the Florida Everglades, provided diatoms are well preserved in soil cores.
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  • 76
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 7-14 
    ISSN: 1573-0867
    Keywords: fertiliser formulation ; nutrients ; phosphorus ; relative humidity ; soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 °C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 °C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
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  • 77
    ISSN: 1573-0867
    Keywords: dairy systems ; feeds ; fertilizers ; phosphorus ; P surplus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inputs of phosphorus (P) above requirements for production on dairy farms lead to surplus P with increased risk of P transfer in land run-off to surface waters causing eutrophication. The impact of reducing surplus P inputs in purchased feeds and fertilizers on milk and forage production was investigated in a comparison of three dairy farm systems on chalkland soils in southern England over a 3-year period. In accordance with current commercial practice, no attempt was made to regulate P inputs in system 1, which accumulated an average annual surplus of 23 kg P ha-1. Progressive reductions in purchased feed and/or fertilizer inputs into systems 2 and 3 decreased surplus P to 17 and 3 kg ha-1, respectively, without apparently limiting either milk or herbage dry matter production. The estimated reduction in faecal P output from system 3 cows fed a low P diet compared to system 1 cows fed a high P diet was 26%. Milk P concentrations significantly (P 〈0.001) increased in systems 2 and 3 which included maize in the diet. Output of P in milk and meat products, as a proportion of the total dietary P inputs, increased from 28% in system 1 to 36% in system 3. Surplus P was greatest in continuous maize fields receiving both dairy manure and starter P fertilizer. Withholding P fertilizer in system 3 did not reduce P offtake in cut herbage on soils of moderate P fertility. Total annual losses of P in storm run-off and leaching were no greater than annual inputs of P from the atmosphere (0.5 kg ha-1). The results indicate there is scope to reduce surplus P on commercial dairy farms without sacrificing production targets at least in the short term. Purchased feeds are the largest of the P inputs on intensive dairy farms, yet these are rarely quantified on commercial holdings.
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  • 78
    ISSN: 1573-0867
    Keywords: leaching ; phosphorus ; poultry litter ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine P loadings, added through poultry litter, sufficient to cause downward movement of P from the cultivated layer of a sandy soil, six rates of poultry litter were applied annually for four years to a site in central England. (total loading 0 – 1119 kg P ha-1). A single extra plot also received an extra 1000 kg ha-1 as triple superphosphate (TSP; total loading 2119 kg P ha-1) and three other treatments received 200 – 800 kg ha-1 P as TSP only. Annual soil sampling in 30-cm increments to 1.5-m depth provided information on P build-up in the topsoil and P movement to depth. There were strong linear trends between P balance (P applied – P removed in crops) and total P, Olsen bicarbonate extractable P and water-soluble P in the topsoil. Phosphorus from TSP and poultry litter fell on the same regression lines, suggesting that both would be equally effective as fertilizer sources. We calculated that 100 kg ha-1 surplus total P would increase the Olsen extractable P content by c. 6 mg kg-1 and the water-soluble P by c. 5 mg kg-1. Thus, relatively large amounts of P would need to be applied to raise soil P status. We found some evidence of P movement into the soil layers immediately below cultivation depth. However, neither soil sampling nor soil solution extracted through Teflon water samplers showed evidence of movement into the deep subsoil (1 m) despite large P loadings.
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  • 79
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 259-266 
    ISSN: 1573-0867
    Keywords: bahiagrass ; manure ; pasture fertilization ; phosphorus ; phosphorus cycling ; Spodosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations have traditionally been based upon clipping studies. Inclusion of P from manure, not originally considered when P recommendations were developed for pastures, may minimize the need for P fertilization without reducing bahiagrass production or P uptake. The objective of this research was to determine if manure contributes greatly to the P crop nutrient requirement. A 2-year field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried manure ha-1 with 0, 17, 34, 51, and 68 kg inorganic P ha-1 from triple superphosphate to evaluate bahiagrass yield, root distribution, and P uptake response on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). Because air-dried manure was used in the field study, a greenhouse study was employed to confirm that there were no differences in bahiagrass yield or P uptake from either air-dried or fresh cattle (Bos spp.) manure sources. There were no manure or manure by P interaction effects on yield or P uptake of bahiagrass indicating that manure source did not effect grass production in the greenhouse. In the field study, bahiagrass roots were distributed into the Bh horizon, and the Bh horizon had at least four times more Mehlich-1 extractable P than that of the Ap horizon. This horizon was most likely acting as a main source for P-uptake by the grass. This observation was further confirmed by no yield response to levels of inorganic P application in 1989. A linear-response-and-plateau (R2=0.196) relationship with a critical point of 15.4 kg P ha-1 was found in 1990. Bahiagrass yield and P uptake were not dependent on P fertilization, either from manure or inorganic P, due to the availability of P from the Bh horizon.
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  • 80
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    Integrated pest management reviews 4 (1999), S. 127-143 
    ISSN: 1572-9745
    Keywords: wheat ; stored-grain ; integrated pest management ; aeration ; biological control ; grain sampling ; insect monitoring ; modeling ; area-wide IPM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Management of stored-grain insect pests by farmers or elevator managers should be based upon a knowledge of the grain storage environment and the ecology of insect pests. Grain storage facilities and practices, geographical location, government policies, and marketing demands for grain quality are discussed as factors influencing stored-grain insect pest management decisions in the United States. Typical practices include a small number of grain samples designed to provide grain quality information for segregation, blending and marketing. This low sampling rate results in subjective evaluation and inconsistent penalties for insect-related quality factors. Information on the efficacy of insect pest management practices in the United States, mainly for farm-stored wheat, is discussed, and stored-grain integrated pest management (IPM) is compared to field-crop IPM. The transition from traditional stored-grain insect pest control to IPM will require greater emphasis on sampling to estimate insect densities, the development of sound economic thresholds and decision-making strategies, more selective use of pesticides, and greater use of nonchemical methods such as aeration. New developments in insect monitoring, predictive computer models, grain cooling by aeration, biological control, and fumigation are reviewed, their potential for improving insect pest management is discussed, and future research needs are examined.
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  • 81
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    Integrated pest management reviews 4 (1999), S. 21-37 
    ISSN: 1572-9745
    Keywords: carrot weevil ; IPM ; Anaphes spp. ; biological control ; ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The carrot weevil, Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae) is a major pest of carrots in northeastern North America. The females oviposit in the leaf petiole and the developing larvae make tunnels in the carrot roots. Exclusive reliance on chemical control and the poor control obtained, prompted, in the early 1980s, research on the ecology and physiology of the pest and its natural enemies. Carrot weevil females start their oviposition by 147±9 DD7°C but they oviposit only in carrots past the 4 true-leaf-stage. As a result, oviposition is delayed, and damage reduced, in late-sown carrots. Monitoring carrot weevil adults in the spring with either carrot root sections or wooden plate traps enables growers to apply control treatments only if the population density justifies it. Egg parasitoids of the genus Anaphes (Hymenoptera: Mymaridae) are the most important natural enemies and they account, in untreated plots, for up to 80% mortality. Their effectiveness could be improved by managing field borders to establish secondary host species. An IPM programme was developed in the 1980s based on the research results obtained and, through regular monitoring, has achieved a substantial decrease in pesticide use.
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  • 82
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    Integrated pest management reviews 4 (1999), S. 39-52 
    ISSN: 1572-9745
    Keywords: Scapteriscus ; Neocurtilla ; Gryllotalpa ; biological control ; turf ; pastures ; vegetables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There are at least 70 species of mole crickets (Orthoptera: Gryllotalpidae). Some are rare, others are innocuous, and a few are important pests. These soil-dwelling pests damage underground parts of a long list of cultivated plants. Although tillage and flooding are used successfully in some situations to bring these pests to the soil surface and expose them to vertebrate and other predators, chemical pesticides are widely used against them. Knowledge of their life history is used to time application of chemical treatments to save money, but is not used as widely as it might be. Classical biological control has been used against immigrant mole crickets in Hawaii, Puerto Rico, and the southern USA. In Florida, three Scapteriscus species from South America cause major damage to pastures and turf and are targets of a classical biological control program. Population levels of two of the pest species have been reduced substantially in Florida by establishment of a tachinid fly (Ormia depleta) and a steinernematid nematode (Steinernema scapterisci) from South America. The nematode also functions as a biopesticide. Managers of pastures and turf in Florida have thus far derived benefit from these classical biological control agents without understanding their function: use of chemicals is reduced when mole cricket populations are lower due to action of these organisms. Future enhancement of the action of O. depleta and of a sphecid wasp (Larra bicolor, which also was introduced from South America) probably will demand deliberate planting of nectar sources for adults of these biological control agents, and the advantage will be to managers who adopt such a strategy. Chemical pesticide use is strongly promoted by a large chemical industry, whereas biopesticidal use has thus far been little promoted and sales have been few. Even managers who do not change their simple strategy of pesticide use in response to damage by mole crickets, and have no knowledge of the differing life cycles of the three Scapteriscus species or of the presence and action of the classical biological control agents, will derive benefit as these biological control agents (and a predatory beetle which has not yet been released) increase their distribution.
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  • 83
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    Integrated pest management reviews 4 (1999), S. 97-126 
    ISSN: 1572-9745
    Keywords: agriculture ; biological control ; campaign ; chemosterilent ; commensal ; control methods ; economics ; environmental and cultural methods ; horticulture ; India ; pest management ; pre- and post-harvest crop losses ; poultry farms ; rodent ; rodenticide ; South Asia ; trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Eighteen species of rodents are pests in agriculture, horticulture, forestry, animal and human dwellings and rural and urban storage facilities in India. Their habitat, distribution, abundance and economic significance varies in different crops, seasons and geographical regions of the country. Of these, Bandicota bengalensis is the most predominant and widespread pest of agriculture in wet and irrigated soils and has also established in houses and godowns in metropolitan cities like Bombay, Delhi and Calcutta. In dryland agriculture Tatera indica and Meriones hurrianae are the predominant rodent pests. Some species like Rattus meltada, Mus musculus and M. booduga occur in both wet and dry lands. Species like R. nitidus in north-eastern hill region and Gerbillus gleadowi in the Indian desert are important locally. The common commensal pests are Rattus rattus and M. musculus throughout the country including the islands. R. rattus along with squirrels Funambulus palmarum and F. tristriatus are serious pests of plantation crops such as coconut and oil palm in the southern peninsula. F. pennanti is abundant in orchards and gardens in the north and central plains and sub-mountain regions. Analysis of the information available on the damage and economic losses caused by rodents in rice, wheat, sugarcane, maize, pearl millet, sorghum, oil seed, legume and vegetable crop fields, horticulture and forestry, poultry farms, and rural and urban dwellings and storage facilities clearly shows that chronic damage ranging from 2% to 15% persists throughout the country and severe damage, sometimes even up to 100% loss of the field crop, is not rare. Several traditional and modern approaches and methods of rodent control are being used. The existing knowledge of the environmental, cultural, biological, mechanical and chemical methods of rodent control in India is reviewed. Considerable variations exist in the susceptibility of the pest species to different methods, particularly to rodenticides and trapping, their field applicability, efficacy and economics in different crops, seasons and geographical regions, behavioural responses of the pest species to these methods in different ecological conditions and their adoption by farmers in different regions of India. Environmental and cultural techniques, such as clean cultivation, proper soil tillage and crop scheduling, barriers, repellents and proofing which may reduce rodent harbourage, food sources and immigration have long lasting effects but are seldom adopted. However, their significance in relation to normal agricultural practices, intensification and diversification are discussed. Rodenticides, which provide an immediate solution to the rodent problem, form the major component of rodent control strategies in India. Poison baiting of rodents with zinc phosphide and burrow fumigation with aluminium phosphide are common in agricultural fields and recently Racumin (coumatetralyl) and bromadiolone have been introduced for the control of both agricultural and commensal rodent pests in India. Methods and timings of campaigns and successes and problems in implementation of rodent control are also reviewed.
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  • 84
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    Integrated pest management reviews 4 (1999), S. 307-312 
    ISSN: 1572-9745
    Keywords: microbial control ; biological control ; biopesticide ; mycopesticide ; Metarhizium ; Beauveria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microbial control agents generally kill insects more slowly than chemical pesticides, and fast-moving migratory pests may not at first sight appear to offer the most promising targets for microbial control. Operators responsible for control may need to have recourse to chemical control agents. Nevertheless, there are many occasions when pests breed and feed outside the crop and a microbial control agent can be used. Similarly, immature stages may cause little damage and early treatment in the crop can avoid damage. Microbial control agents are particularly likely to be favoured if the pest breeds in a conservation area, and if a publicly-accountable agency is responsible for control. Other key points of importance are the IPM context, in particular detection, planning and forecasting of outbreaks and the role of natural enemies. With these points in mind, we identify several locust and grasshopper systems where microbial control is becoming established; additionally, Sunn pest of wheat and Armyworm are identified as promising situations forbreak microbials.
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  • 85
    ISSN: 1871-4528
    Keywords: Solanin ; Chaconin ; Magnesium ; Kalium ; Stickstoff ; Solanum tuberosum L. ; Phytophthora infestans ; Feldversuch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary Field experiments were carried out for three years to study the effect of various magnesium, potassium and nitrogen fertilization rates on two medium-early edible potato cultivars. Additionally, one of the experimental areas was sprayed againstPhytophthora infestans to ascertain the effect of fungicides on the content of total glycoalkaloids (TGA) in potato tubers after harvest and after six months of storage. The applied fungicide treatments increased total glycoalkaloids (TGA) of potato tubers (Fig. 4). Fertilization with mineral nitrogen caused different reactions in both cultivars. There was a tendency for cv. Beryl to accumulate more glycoalkaloids with increasing nitrogen fertilization rates, while the opposite was observed for cv. Mila (Fig. 7). Fertilization with potassium and magnesium did not affect the results. On the basis of these results there was no conclusive evidence that the TGA content in the tubers was dependent on cultivar or on the weather during the growing season (Figs 1,2 and 3). The TGA content increased during storage, independently of previous treatments, (Figs 4–7).
    Notes: Zusammenfassung Es wurden Feldversuche in drei Jahren mit zwei Speisekartoffelsorten, verschiedenen Mengen an Mineraldüngern und der Anwendungen eines Pflanzenschutzmittelns gegenPhytophthora infestans angelegt. Die Knollen wurden direkt nach der Ernte sowie nach einer sechsmonatigen Lagerung auf Glykoalkaloidgehalt untersucht. Zwischen den Sorten treten statistisch gesicherte Unterschiede im Gehalt an Glykoalkaloiden auf. Die Anwendung von Pflanzenschutzmitteln während der Vegetation erhöht den Gesamtgehalt an Glykoalkaloiden (TGA) in den Kartoffelknollen kurz nach der Ernte. Eine variierte Mineraldüngung hat keinen statistisch signifikanten Einfluss auf den TGA-Gehalt in den Proben kurz nach der Ernte, N- und K-Düngung verändern diesen jedoch im Laufe der Lagerung. Unabhängig von den übrigen Bedingungen erhöht sich der TGA-Gehalt in diesem Versuch während der Lagerung im Mittel von 5,8 auf 7,7 mg/100g Frischsubstanz.
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  • 86
    ISSN: 1871-4528
    Keywords: growth regulator ; sucrose ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ancymidol-induced in vitro tuberisation under different photoperiodic regimes (dark, SD=8 h, LD=16 h) and sucrose concentrations (2, 4, 6 and 8%) in cv. Jaerla (early) and cv. Baraka (late) was studied. Tuberisation was scored after 4 (dark) or 8 (light) weeks. Ancymidol significantly increased tuberisation under LD-SD for any sucrose concentration in both cultivars. Ancymidol also significantly increased tuberisation under LD-dark for 6% sucrose in both cultivars. Tuberisation in cv. Jaerla was significantly higher than in cv. Baraka for any photoperiodic treatment in the presence or absence of ancymidol with 4, 6 or 8% sucrose. The photoperiod SD-SD resulted in the higher level of tuberisation for any combination of sucrose, cultivar and ancymidol. The possible role of ancymidol is discussed.
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    Potato research 42 (1999), S. 611-617 
    ISSN: 1871-4528
    Keywords: dormancy ; potato ; losses ; Solanum tuberosum L. ; seed potato production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microtubers can be stored longer, transported and handled easier than plantlets, but they have some disadvantages related to long dormancy. Dormancy, number of sprouts per tuber and loss of microtubers under different storage temperatures were studied. Microtubers of four genotypes originated from different tuberization treatments (photoperiod combinations) were observed. We found that dormancy depended on cultivar and — in some cases — on the photoperiod treatment applied during tuberization. Generally, the dormacy was long and was greatly elongated by low storage temperature. One of the photoperiod treatments shortened while the other treatment prolonged the rest-period compared to the control, maybe due to a change in temperature accompanying the change in daily light (photoperiod combination). Besides, these treatments affected the number of sprouts per tuber. There was no significant difference in duration of dormancy between different tuber-size groups, but the loss increased significanctly with a decrease in tuber size. Based on this information we can use microtubers more effectively in the seed potato production programme.
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    Potato research 42 (1999), S. 101-105 
    ISSN: 1871-4528
    Keywords: late blight ; testing methods ; electrolyte leakage ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The resistance of ten potato cultivars (Agria, Ajax, Désirée, Liseta, Kennebec, Majestic. Monalisa, Prima, Spunta and Tonda di Berlino) toPhytophthora infestans was analyzed in vitro using 8 fungal strains. An assay based on electrolyte leakage was used for screening leaves and tuber tissues with fungal culture filtrates. With almost all cultivars the resistance of leaves did not correlate with the resistance of tubers. Cv. Ajax appeared the least susceptible in both leaf and tuber tests, while the cv. Prima was the most susceptible in tuber tests.
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  • 89
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    Potato research 42 (1999), S. 229-240 
    ISSN: 1871-4528
    Keywords: earliness ; planting season ; Mediterranean area ; off-season production ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In Italy, the early potato cultivars of greatest economic significance are those grown off-season, in a cycle which is generally much earlier than the typical spring-summer cycle. Of the area given over to early potatoes in Italy, more than 90% is in the southern regions. The economic value of this production is due to its extraseasonality, which allows much of the early potato harvest to be sold on foreign markets. In Sicily, more than 5000 ha of potato are grown, with a high frequency of potato crops on small plots. Early potatoes are often rotated with various fruits and vegetables, and the length of the cycle is variable, from 100 to 140 days. Choosing the most suitable cultivar is the most complex aspect of early potato growing. Of the criteria used, tuber growth rate has shown most validity. In Sicily two cultivars are mainly grown: Sieglinde and the more recent but well-established Spunta. Agricultural techniques used for early potato cultivation vary depending on the area. An overview of the agronomic practices used in different areas is given in this paper.
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  • 90
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    Potato research 42 (1999), S. 381-395 
    ISSN: 1871-4528
    Keywords: agronomy ; breeding ; pathology ; physiology ; Solanum tuberosum L. ; storage ; utilisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This contribution presents highlights of the oral and poster presentations in the various sessions of the 14th Triennial Conference of the European Association for Potato Research, held in Sorrento, Italy, May 1999. It is based on the reports of the session chairpersons and the book of abstracts. The paper reports the progress made in many aspects of potato research, but also stresses the need for further collaborative work, especially in the fields of molecular physiology, marker assisted breeding, control of late blight, potato tuber moth and other pests and diseases, stress physiology and stress resistance, and sustainable cropping systems with both short and long cycle potato crops.
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  • 91
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; tuberisation ; extensin ; acyl carrier protein thioesterase ; high mobility group protein ; gene expression ; plant development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In screening to isolate a full-length copy of a previously isolated cDNA clone, a further three cDNAs were also isolated from a library prepared from sub-apical swelling-stolon tissue of potato (Solanum tuberosum L.). Sequence analysis showed these clones to be similar to extensin-like protein genes, acyl carrier protein thioesterase genes and high mobility group protein genes, respectively. A further cDNA, isolated by subtractive hybridisation, was similar to a tomato cDNA previously isolated on the basis of its down-regulation following nematode infection. While all the newly isolated genes were expressed in swelling stolons, for most, maximal expression was seen to be in stem tissue. Possible roles for these genes in the development of potato plants are discussed, as is the significance of gene expression in stems and stolons to the process of tuberisation.
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  • 92
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    Potato research 42 (1999), S. 89-93 
    ISSN: 1871-4528
    Keywords: analysis ; HPLC ; β-glucoside ; 1,2-dihydro-3,6-pyridazinedione ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The method of Vadukul (1991) for determining maleic hydrazide (MH) was modified and gave recoveries of free MH of 89%±4%. The values recorded on individual tubers ranged from 2–14 mg kg−1. Maleic hydrazide was evenly distributed throughout the tuber (peel, outer and inner flesh) but concentration increased slightly as tuber size increased. The concentration of free MH decreased from 7 to 3 mg kg−1 over the storage period of 5 1/2 months. Acid hydrolysis released substantial amounts of MH particularly from older potatoes (13 mg kg−1) compared with 6 mg kg−1 from new potatoes, implying that free MH is gradually converted to a bound form with time after treatment. No evidence was found for the presence of a β-glucoside of MH.
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  • 93
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    Potato research 42 (1999), S. 241-264 
    ISSN: 1871-4528
    Keywords: global distribution ; prospects ; diversification ; specialization ; price risk ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We examine the changing character of supply and demand for potatoes over time and space with an eye towards implications for agricultural research. Diversification in consumption and specialization in production are our organizing themes. The foundation for comparative analysis is a map of the global distribution of potato growing area. We highlight the adverse impact of price risk on specialization and discuss several sources of uncertainty that condition the size but not the direction of major trends.
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    Potato research 42 (1999), S. 499-504 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; microtuber ; liquid medium ; temporary immersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary CIRAD developed a new apparatus for plant tissue culture, using temporary immersion in a liquid medium. This apparatus was adapted to the microtuber production in potato. The procedure is as follows: single node cultivation on MS medium containing 30 g/l sucrose in the light for 2 weeks, induction of microtuberisation with 80 g/l sucrose over a 2 week period in the light, followed by a further 6 weeks in the dark. All experiments were performed at 20 °C. The basic vessel had a capacity of approximately 11;30 nodes were cultivated per vessel. Depending on the cultivars tested (Bintje, Ostara and Désirée) 47 to 115 microtubers were harvested per vessel. Between 30 and 60% of the microtubers weighted over 0.5 g and between 10 and 40% over 0.8 g. Sprouting is still under investigation. Preliminary results indicate that the dormancy period was relatively short and several stems were obtained per microtuber. These results seem to be better than those usually reported. Only one simple protocol has been tested and further improvements are probably easy to obtain.
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    Potato research 42 (1999), S. 585-591 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; microtubers ; acetic acid ; propionic acid ; asscorbic acid ; salicylic acid ; acetylsalicylic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato microtubers are usually induced in media containing growth regulatory, typically cytokinins and growth retardants. However, since these substances may imbalance the physiology of the cultured explants and cause adverse carry-over effects on the subsequent performance of the microtubers, the potential acid-induction of in vitro-mass tuberization was investigated as an alternative. For this purpose, a range of explant types (stolons, single-node or apex-containing multinodal sections), organic acids (acetic, propionic, ascorbic, acetylsalicylic or salicylic acid), and photoperiods (continuous dark, 8 or 16 h photoperiod) were established. Gellified medium or raft membranes on liquid medium were also tested. Although variations due to explant type, photoperiod, organic acid supplemented, and medium type were found, all organic acids tested under the different experiments caused tuberization. Multiple tuber formation or bigger tubers did not develop on multinodal explants. In terms of tuberization rate and mean tuber weight, gellified medium performed better than liquid medium with rafts. The recently established role of the salicylic and acetylsalicylic acids on tuberization is corroborated by our system. The results with the acetic, propionic and ascorbic acids show that in vitro hormone-free tuberization can be easily and rapidly achieved.
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    Potato research 42 (1999), S. 73-78 
    ISSN: 1871-4528
    Keywords: growth parameters ; K+/Na+ ratio ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Increased potassium (K) fertilization of saline soils has been implicated in alleviating salt stress in plants. We examined whether varying K concentrations in Murashige & Skoog (MS: 1962) basal medium could affect salt (NaCl) stress in micropropagated potatoes. Plantlets of cvs Sierra and Russet Burbank were evaluated after 1 month of growth in a medium containing 0. 40, or 80 mM NaCl and 6,20, or 30 mMK. The medium K was adjusted using KNO3 while total nitrogen was kept constant using NH4NO3. Growth parameters were less affected in Sierra than Russet Burbank, and roots were less affected than shoots, as the medium salinity increased. Tissue Na levels were greater when the medium K was 6 mM compared with 20 mM MS control. The medium K concentration 50% greater than MS control did not promote growth and did not limit tissue Na levels. While this should be confirmed by field assessment, our results suggest that while K deficiency promotes salt damage, its addition beyond the usual fertilizer recommendations is not beneficial in alleviating salinity stress.
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  • 97
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    Potato research 42 (1999), S. 607-610 
    ISSN: 1871-4528
    Keywords: seed production ; Greece ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Large scale, commercial production of potato minitubers, cvs Spunta, Jaerla and Kennebec, has been carried out in VITRO HELLAS S.A. since 1995, according to protocols based on in vitro methods. Apical meristems were cultured on MS medium supplemented with 1 μM IBA, 20 g/l sucrose and 6 g/l agar (pH 5.8). Subculture was carried out every 15 days. Multiplication rate was 4–5 per cycle. Self-rooted microplants were transferred into screen houses (200 plants/m2) in a mixture of peat and perlite 1∶1 (v/v). Cultivation period was 15 August to 15 November each year. During the period 1995–1997, the number of minitubers produced/plant was 2.07 for cv. Spunta, 1.85 for cv. Jaerla and 2.52 for cv. Kennebec and their average weights were 10.8 g, 10.9 g and 9.8 g, respectively. The percentage of minitubers〈10 mm in diameter was 2%, 50.1% were 10–20 mm and 47.9% were〉20 mm.
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  • 98
    ISSN: 1871-4528
    Keywords: cultivar ; virus diseases ; nematodes ; ground cover ; physiological age ; seed production ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In Argentina, different areas are suitable for seed potato production: however, each has particular problems, mainly related to different pest and diseases. Tierra del Fuego Island is well isolated from traditional potato growing areas. Therefore, it was tested for its potential for seed production. The cultivars Achatt. Mailén INTA. Pampeana INTA and Spunta were grown in Río Grande, San Pablo and Ushuaia from 1991–1994. Nematode presence and aphid population dynamics were recorded. Average tuber yield ranged from 20.1–37.6 t ha−1. After three years PVY and PLRV remained low (0–1% for different cultivars and locations). Moreover, seed tubers obtained were physiologically young. Long days, early frosts and strong winds may limit tuber yield in some years. The island can be considered as an ecological “safe haven” and is very suitable to obtain healthy and physiologically adequate seed potatoes.
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  • 99
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    Potato research 42 (1999), S. 25-29 
    ISSN: 1871-4528
    Keywords: chlorpropham ; particulates ; dusts ; solvents ; ignition source ; explosive limits ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An appraisal was undertaken of the key factors involved in explosion and combustion processes mainly associated with the fogging of chlorpropham formulations into potato stores. The key factors considered are source of ignition, solvents, explosive limits of solvents, the presence and atmospheric concentrations of particulate clouds and the role of particulate material in dust explosions. Also the sequence of events that takes place in a dust explosion, including critical concentrations of dust required to initiate the reactions involved and the particular relevance of the above events to the behaviour of chlorpropham fogs both at the time of application and when distributed throughout a store. The relevance of fine dust already present in the store to the initiation of explosions, particularly secondary explosions, which are considered to be a major cause of concern due to their severity, is also emphasised.
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    Potato research 42 (1999), S. 95-99 
    ISSN: 1871-4528
    Keywords: analysis ; HPLC ; filter paper model ; Diels-Alder reaction ; 1,2-dihydro-3,6-pyridazinedione ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method used for estimating extractable maleic hydrazide (MH) concentrations in fresh potato material, concentration range 5–17 mg kg−1, was found not to be suitable for processed potato products (10–33% recoveries) although, boiling potato pieces enhanced recovery by 20%. Each step of the determination was examined and a modified procedure developed with particular emphasis on the extraction of MH from the dried potato matrix, and the quality of the HPLC column used. Potato slices and model systems based on filter papers plus additives were used. Recoveries from fried potato slices were 74±6%. Based on the effect of glucose in reducing extractable MH recoveries, it is suggested that the remainder of the MH (20–25%) is converted into a conjugated structure on reaction with dehydrated sugar (Diels-Alder reaction).
    Type of Medium: Electronic Resource
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