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  • 1
    Electronic Resource
    Electronic Resource
    Passage of debris flows and turbidity currents through a topographic constriction: seafloor erosion and deflection of flow pathways (2001)
    Oxford UK : Blackwell Science Ltd.
    Sedimentology 48 (2001), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Some of the Earth's largest submarine debris flows are found on the NW African margin. These debris flows are highly efficient, spreading hundreds of cubic kilometres of sediment over a wide area of the continental rise where slopes angles are often 〈1°. However, the processes by which these debris flows achieve such long run-outs, affecting tens of thousands of square kilometres of seafloor, are poorly understood. The Saharan debris flow has a run-out of ≈700 km, making it one of the longest debris flows on Earth. For its distal 450 km, it is underlain by a relatively thin and highly sheared basal volcaniclastic layer, which may have provided the low-friction conditions that enabled its extraordinarily long run-out. Between El Hierro Island and the Hijas Seamount on the continental rise, an ≈25- to 40-km-wide topographic gap is present, through which the Saharan debris flow and turbidites from the continental margin and flanks of the Canary Islands passed. Recently, the first deep-towed sonar images have been obtained, showing dramatic erosional and depositional processes operating within this topographic `gap' or `constriction'. These images show evidence for the passage of the Saharan debris flow and highly erosive turbidity currents, including the largest comet marks reported from the deep ocean. Sonar data and a seismic reflection profile obtained 70 km to the east, upslope of the topographic `gap', indicate that seafloor sediments to a depth of ≈30 m have been eroded by the Saharan debris flow to form the basal volcaniclastic layer. Within the topographic `gap', the Saharan debris flow appears to have been deflected by a low (≈20 m) topographic ridge, whereas turbidity currents predating the debris flow appear to have overtopped the ridge. This evidence suggests that, as turbidity currents passed into the topographic constriction, they experienced flow acceleration and, as a result, became highly erosive. Such observations have implications for the mechanics of long run-out debris flows and turbidity currents elsewhere in the deep sea, in particular how such large-scale flows erode the substrate and interact with seafloor topography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2001.00427.x
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  • 2
    Electronic Resource
    Electronic Resource
    β-APP Cognitive Function versus β-Amyloid–induced Cell Death (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 777 (1996), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: The β-amyloid precursor protein (β-APP) has been hypothesized to play an important role in the establishment of synaptic connections. Icv injections of anti-βAPP antibodies into rat brains produced no appreciable effect on subsequent learning of a passive avoidance task whereas memory assessed 1 day later in a retention test was impaired in anti-β-APP– but not control-IgG–injected animals. This suggests a possible involvement of β-APPs in cognitive functions. In order to evaluate the properties of the proteolytic Aβ-fragment accumulating in Alzheimer's disease brains, four different neuronal cell types were exposed to Aβ1–42 for 24 hours. All cells degenerated in response to Aβ, yet chromosomal condensation and internucleosomal DNA fragmentation, typical for apoptosis, occurred in only three of the cell types tested. These findings suggest that β-APPs may play an important role in cognitive processes and additionally, that their alternative proteolytic product Aβ may be differentially toxic to neuronal cell types, inducing cell death either by necrosis or by apoptosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1996.tb34435.x
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  • 3
    Electronic Resource
    Electronic Resource
    Central complex substructures are required for the maintenance of locomotor activity in Drosophila melanogaster (1999)
    Springer
    Journal of comparative physiology 185 (1999), S. 277-288 
    Details
    ISSN: 1432-1351
    Keywords: Key words Motivational control ; Protocerebral bridge ; Fan-shape body ; Noduli ; Spontaneous walking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In Drosophila melanogaster, former studies based on structural brain mutants have suggested that the central complex is a higher control center of locomotor behavior. Continuing this investigation we studied the effect of the central complex on the temporal structure of spontaneous locomotor activity in the time domain of a few hours. In an attempt to dissect the internal circuitry of the central complex we perturbed a putative local neuronal network connecting the four neuropil regions of the central complex, the protocerebral bridge, the fan-shape body, the noduli and the ellipsoid body. Two independent and non-invasive methods were applied: mutations affecting the neuroarchitecture of the protocerebral bridge, and the targeted expression of tetanus toxin in small subsets of central complex neurons using the binary enhancer trap P[GAL4] system. All groups of flies with a disturbed component of this network exhibited a common phenotype: a drastic decrease in locomotor activity. While locomotor activity was still clustered in bouts and these were initiated at the normal rate, their duration was reduced. This finding suggests that the bridge and some of its neural connections to the other neuropil regions of the central complex are required for the maintenance but not the initiation of walking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050387
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  • 4
    Electronic Resource
    Electronic Resource
    Temporal pattern of locomotor activity in Drosophila melanogaster (1999)
    Springer
    Journal of comparative physiology 184 (1999), S. 73-84 
    Details
    ISSN: 1432-1351
    Keywords: Key words Locomotor activity ; Time series analysis ; Bout structure ; Fractal structure ; Aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The temporal pattern of locomotor activity of single Drosophila melanogaster flies freely walking in small tubes is described. Locomotor activity monitored by a light gate has a characteristic time-course that depends upon age and the environmental conditions. Several methods are applied to assess the complexity of the temporal pattern. The pattern varies according to sex, genotype, age and environmental conditions (food; light). Activity occurs clustered in bouts. The intrinsic bout structure is quantified by four parameters: number of light gate passages (counts) per bout, duration of a bout, pause between two successive bouts and mean bout period. In addition, the distribution of the periods between light-gate crossings (inter-count intervals) as function of inter-count interval duration reveals a power law, suggesting that the overall distribution of episodes of activity and inactivity has a fractal structure. In the dark without food, the fractal dimension which represents a measure of the complexity of the pattern is sex, genotype and age specific. Fractality is abolished by additional sensory stimulation (food; light). We propose that time-course, bout structure and fractal dimension of the temporal pattern of locomotor activity describe different aspects of the fly's central pattern generator for locomotion and its motivational control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050307
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  • 5
    Electronic Resource
    Electronic Resource
    Precipitated withdrawal in squirrel monkeys after repeated daily oral administration of alprazolam, diazepam, flunitrazepam or oxazepam (1995)
    Springer
    Psychopharmacology 118 (1995), S. 273-279 
    Details
    ISSN: 1432-2072
    Keywords: Physical dependence ; Precipitated withdrawal ; Tolerance ; Squirrel monkeys ; Alprazolam ; Diazepam ; Flunitrazepam ; Oxazepam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The lowest dose of alprazolam, diazepam, flunitrazepam and oxazepam consistently to induce loss of righting reflex in squirrel monkeys or vehicle was orally administered to monkeys on 18 consecutive days: 2 mg/kg alprazolam (n=4), 30 mg/kg diazepam (n=4), 1 mg/kg flunitrazepam (n=4), 280 mg/kg oxazepam (n=5), or vehicle (n=4). Tolerance developed rapidly for loss of righting reflex, more slowly for sleep and only minimally for muscle relaxation observed during the period immediately following daily oral administration. Injection of the specific benzodiazepine receptor antagonist flumazenil (10 mg/kg IV) 5 h after the ninth daily oral treatment produced signs of precipitated withdrawal (tremor, vomiting and/or convulsions) in one alprazolam-, four diazepam-, one flunitrazepam- and four oxazepam-treated monkeys, but not in the vehicle-treated monkeys. Physiological saline injected intravenously several days later under these same experimental conditions failed to provoke a precipitated withdrawal reaction. When flumazenil-induced precipitated withdrawal was again evaluated after the 18th daily oral treatment, withdrawal signs were observed in all alprazolam- and all diazepam-treated monkeys, as well as in three flunitrazepam- and three oxazepam-treated monkeys, but not in the vehicle-treated monkeys (convulsions were observed in one alprazolam-, two diazepam-, one flunitrazepam- and two oxazepam-treated monkeys). No signs of spontaneous withdrawal were observed in any of the monkeys during a subsequent 3-week drug-free period. Thus, repeated administration of approximately equieffective doses of these four benzodiazepines resulted in a similar development of tolerance and physical dependence (indicated by the occurrence of a precipitated withdrawal reaction).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245955
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of diclofenac (Voltarol) and pethidine on ureteric peristalsis and the isotope renogram (1998)
    Springer
    European journal of nuclear medicine 25 (1998), S. 1520-1523 
    Details
    ISSN: 1619-7089
    Keywords: Key words: Diclofenac ; Pethidine ; Renography ; Peristalsis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Diclofenac (a non-steroidal anti-inflammatory drug) and pethidine (a synthetic opiate) are the two analgesics most commonly used to relieve the pain of ureteric colic. Fast frame renography is a non-invasive means of imaging ureteric peristalsis and renal drainage. The aim of this study was to determine the effects of each of these drugs on the drainage pattern of the upper tracts. Twelve normal male volunteers were studied. All underwent a standard fast frame renogram using 75 MBq of technetium-99m-mercaptoacetyltriglycine, and were then administered either 100 mg pethidine or 75 mg diclofenac by intramuscular injection. Fast frame renography was then repeated. Peristalsis was determined from the condensed image of each ureter and the renogram curves were analysed to obtain standard parameters and deconvolution analysis. Diclofenac caused a profound disruption to both ureteric peristalsis and the renogram curve. This effect was not seen after the administration of pethidine. Deconvolution analysis suggests the effects of diclofenac are mediated via a direct effect on drainage rather than by any alteration of blood flow to the kidney. This study suggests that pethidine is the analgesic of choice prior to renography and that inferences about alterations of drainage in the presence of diclofenac should be interpreted with care.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002590050330
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  • 7
    Electronic Resource
    Electronic Resource
    Efficacy of ivermectin and moxidectin injection against larvae of Wohlfahrtia magnifica (Diptera: Sarcophagidae) in sheep (1995)
    Springer
    Parasitology research 82 (1995), S. 82-86 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The therapeutic efficacies of ivermectin (Ivomec injection, Merck Sharp & Dohme B.V.) and moxidectin (Cydectin 1% injection, American Cyanamid Company) were evaluated in sheep naturally infested with larvae of Wohlfahrtia magnifica. Sheep were randomly allocated to one of the 2 groups, each consisting of 19 animals. Sheep in one group received ivermectin and those in the other, moxidectin by subcutaneous injection at a dose of 0.2 mg/kg body weight. Evaluation was performed at 19, 24, 28, 39, 43, 48, 52, 63, 67, 72, 87, 96, 120, 144 and 168 h after treatment. At 144 and 168 h post-treatment, late third-instar larvae were collected from wounds of four sheep in both groups and from untreated, infested sheep. These larvae were reared in the laboratory to assess adult emergence. Neither ivermectin nor moxidectin was effective as a rapid acting treatment or as a long-term, or even short-term, prophylactic. Despite the treatment, 30–40% of sheep had live larvae at every evaluation. Although larvae disappeared from the wounds of some sheep in both groups after the treatment, the wounds in these animals failed to recover and were reinfested by larvae of W. magnifica. On day 7 post-treatment the trial had to be finished because the majority of treated sheep were severely infested by Wohlfahrtia maggots. The average number of infested sheep in the two groups and the number of adults that were produced from larvae collected from treated sheep indicate that ivermectin and moxidectin did not differ significantly in efficacy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004360050073
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