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Spatiotemporal Differences (spatiotemporal + difference)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Influence of lateral gradients of hydrologic connectivity on trophic positions of fishes in the Upper Mississippi River

FRESHWATER BIOLOGY, Issue 3 2009
KATHERINE A. ROACH
Summary 1. Riverscapes consist of the main channel and lateral slackwater habitats along a gradient of hydrological connectivity from maximum connection in main channel habitats to minimum connection in backwaters. Spatiotemporal differences in water currents along this gradient produce dynamic habitat conditions that influence species diversity, population densities and trophic interactions of fishes. 2. We examined the importance of lateral connectivity gradients for food web dynamics in the Upper Mississippi River during spring (high flow, moderately low temperatures) and summer (low flow, higher temperatures). We used literature information and gut contents analyses to determine feeding guilds and stable isotope analysis to estimate mean trophic position of local fish assemblages. During June and August 2006, we collected over 1000 tissue samples from four habitats (main channel, secondary channels, tertiary channels and backwaters) distributed within four hydrologic connectivity gradients. 3. Mean trophic position differed among feeding guilds and seasons, with highest values in spring. Mean trophic position of fish assemblages, variability in trophic position and food chain length (maximum trophic position) of the two dominant piscivore species (Micropterus salmoides and M. dolomieu) in both seasons were significantly associated with habitat along the lateral connectivity gradient. Food chain length peaked in tertiary channels in both seasons, probably due to higher species diversity of prey at these habitats. We infer that food chain length and trophic position of fish assemblages were lower in backwater habitats in the summer mainly because of the use of alternative food sources in these habitats. 4. A greater number of conspecifics exhibited significant among-habitat variation in trophic position during the summer, indicating that low river stages can constrain fish movements in the Upper Mississippi River. 5. Results of this study should provide a better understanding of the fundamental structure of large river ecosystems and an improved basis for river rehabilitation and management through knowledge of the importance of lateral complexity in rivers. [source]

Upper limb movement interruptions are correlated to freezing of gait in Parkinson's disease

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2009
Alice Nieuwboer
Abstract Freezing of gait (FOG) in patients with Parkinson's disease (PD) is a common problem of unknown origin, which possibly reflects a general motor control deficit. We investigated the relationship between the frequency of freezing episodes during gait and during a bimanual task in control and subjects with PD with and without FOG. Group differences in spatiotemporal characteristics were also examined as well as the effects of visual cueing. Twenty patients with PD in the off-phase of the medication cycle and five age-matched controls performed a repetitive drawing task in an anti-phase pattern on a digitizer tablet. The task was offered at two different speeds (comfortable and maximal) and two different amplitudes (small and large) with and without visual cueing. The results showed that freezing episodes in the upper limbs occurred in only 10.4% of patient trials and that their occurrence was correlated with FOG scores (Spearman's rho = 0.64). Overall, few spatiotemporal differences were found between freezers, non-freezers and controls, except for an overshooting of the target amplitude in controls. Effects of visual cueing were largely similar in all groups, except for the variability of relative phase, which decreased in non-freezers and controls, and was unaffected in freezers. Despite the fact that general motor differences between subgroups were small, freezing episodes were manifest during a bimanual repetitive upper limb task and were correlated to FOG. Further study into upper limb movement breakdown is warranted to understand the parallel deficits that lead up to FOG. [source]

Opioids intrinsically inhibit the genesis of mouse cerebellar granule neuron precursors in vitro: differential impact of , and , receptor activation on proliferation and neurite elongation

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2000
Kurt F. Hauser
Abstract Although opioids are known to affect neurogenesis in vivo, it is uncertain the extent to which opioids directly or indirectly affect the proliferation, differentiation or death of neuronal precursors. To address these questions, the intrinsic role of the opioid system in neurogenesis was systematically explored in cerebellar external granular layer (EGL) neuronal precursors isolated from postnatal mice and maintained in vitro. Isolated neuronal precursors expressed proenkephalin-derived peptides, as well as specific , and ,, but negligible ,, opioid receptors. The developmental effects of opioids were highly selective. Morphine-induced , receptor activation inhibited DNA synthesis, while a preferential ,2 -receptor agonist ([d -Ala2]-deltorphin II) or Met-enkephalin, but not the ,1 agonist [d -Pen2, d -Pen5]-enkephalin, inhibited differentiation within the same neuronal population. If similar patterns occur in the developing cerebellum, spatiotemporal differences in endogenous , and , opioid ligand,receptor interactions may coordinate distinct aspects of granule neuron maturation. The data additionally suggest that perinatal exposure to opiate drugs of abuse directly interfere with cerebellar maturation by disrupting normal opioid signalling and inhibiting the proliferation of granule neuron precursors. [source]

Spatiotemporal changes of apolipoprotein E immunoreactivity and apolipoprotein E mRNA expression after transient middle cerebral artery occlusion in rat brain

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2003
Hiroshi Kamada
Abstract Apolipoprotein E (ApoE) is a constituent of lipoprotein and plays an important role in the maintenance of neural networks. However, spatiotemporal differences in ApoE expression and its long-term role in neural process after brain ischemia have not been studied. We investigated changes of ApoE immunoreactivity and ApoE mRNA expression both in the core and in the periischemic area at 1, 7, 21, or 56 days after 90 min of transient middle cerebral artery occlusion. Double stainings for ApoE plus NeuN or plus ED1 were performed in order to identify cell type of ApoE-positive stainings. The maximal increase of ApoE expression was observed at 7 days in the core and at 7 and 21 days in the periischemic area. In the core, ApoE plus NeuN double-positive cells increased at 1 and 7 days, without ApoE mRNA expression, whereas they increased in the periischemic area, with a peak at 21 days, with ApoE mRNA expression in glial cells but not in neurons. On the other hand, ApoE plus ED1 double-positive cells increased only in the core, with a peak in number at 7 and 21 days and marked ApoE mRNA expression in macrophages. The present study suggests that ApoE plays various important roles in different type of cells, reflecting spatiotemporal dissociation between degenerative and regenerative processes after brain ischemia, and that ApoE is profoundly involved in pathological conditions, such as brain ischemia. © 2003 Wiley-Liss, Inc. [source]