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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis by cells of Prochloron sp. freshly isolated from the ascidian host, Lissoclinum patella, collected from shallow waters in Palau, was severely inhibited by ultraviolet (UV) irradiation. No photoinhibition, however, was observed in Prochloron cells isolated from intact colonies after UV irradiation, suggesting some protection by the ascidian host. It was shown that UV protection was brought about by the thick gelatinous tunic covering the whole ascidian colony. Analysis revealed that the surface tunic of L. patella, although transparent to visible light, contains several UV-absorbing substances, identified by high-performance liquid chromatography as mycosporine-like amino acids (MAAs). The predominant MAA identified was shinorine (λmax = 334 nm), followed by mycosporine-glycine (λmax = 310 nm) and a small amount of palythine (λmax = 320 nm). Although isolated Prochloron cells also contained shinorine, on a protein-weight basis it was less than half of that observed in the host tunic. These results suggest that the surface tunic of a L. patella colony, which is transparent to visible light for photosynthesis, also contains UV-absorbing compounds that protect its photoautotrophic symbiont, Prochloron sp., from damage by the intense UV-irradiation that they receive daily in shallow, tropical marine waters.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two picophytoplankters,Prochlorococcus marinus andSynechococcus sp., were isolated from the bottom of the euphotic zone (150 m depth) in the western Pacifie Ocean. The concentration ofP. marinus at this depth was more than 104 cells ml−1 while that ofSynechococcus sp. was less than 102 cells ml−1. TheP. marinus isolate has a high divinyl-chlorophylla:b ratio similar to that of the Mediterranean strain, while theSynechococcus sp. isolate is of the phycourobilinrich type. The growth rate ofP. marinus was higher thanSynechococcus sp. when both were cultured under weak blue-green to blue-violet light (ca. 2 μE m−2 s−1). While the chlorophyll-specific absorption spectra showed higher values inSynechococcus sp., the photosynthetic action spectre revealed thatP. marinus was able to use blue-violet light, whereasSynechococcus sp. was able to use blue-green light, more efficiently for photosynthesis. The photosynthetic quantum yield ofP. marinus was higher than that ofSynechococcus sp. at any wavelength between 400 and 700 nm. The calculated in situ photosynthesis rates per Gell volume forP. marinus were estimated to be higher than forSynechococcus sp. at 50 and 150 m depth. These results indicate thatP. marinus photosynthetically surpassesSynechococcus sp. in the blue-light-rieh environment of the oceanic euphotic zone. This may be why the former predominates at depths in temperate to tropical open ocean waters.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 115 (1997), S. 1-5 
    ISSN: 1432-1106
    Keywords: Key words Procedural learning ; Basal ganglia ; Caudate ; Putamen ; Muscimol ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To study the role of the basal ganglia in learning of sequential movements, we trained two monkeys to perform a sequential button-press task (2×5 task). This task enabled us to examine the process of learning new sequences as well as the execution of well-learned sequences repeatedly. We injected muscimol (a GABA agonist) into different parts of the striatum to inactivate the local neural activity reversibly. The learning of new sequences became deficient after injections in the anterior caudate and putamen, but not the middle-posterior putamen. The execution of well-learned sequences was disrupted after injections in the middle-posterior putamen and, less severely, after injections in the anterior caudate/putamen. These results suggest that the anterior and posterior portions of the striatum participate in different aspects of learning of sequential movements.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 118 (1998), S. 293-297 
    ISSN: 1432-1106
    Keywords: Key words Procedural memory ; Sequential movements ; Memory transfer ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The purpose of this study was to characterize the nature and structure of procedural memory. We have previously studied the process of learning sequential behavioral procedures using monkeys. The monkey’s task was to press five consecutive pairs of buttons (indicated by illumination) in the correct order for every pair, which he had to find by trial-and-error in a block of trials. The whole sequence was called a “hyperset”; each pair was called a “set”. We first examined whether monkeys learned to perform a hyperset as a single sequence or learned the order of button-presses individually for each set. To answer this question, we generated hypersets that were the same as the hypersets that had been extensively learned except that the order of the sets was reversed. The performance of these “reversed hypersets” was much worse than the performance of the original learned hypersets and was similar to the performance of new hypersets, as regards both the number of errors and the performance time. The result suggests that monkeys learned a hyperset as a sequence. To examine whether the learned performance was specific to the hand used for practice, we had monkeys use the same hand throughout the long-term practice of each hyperset, and then tested the opposite hand. The performance using the opposite hand was worse than the performance using the trained hand, but was better than the performance for new hypersets. This indicates that the memory for the sequential procedure is only partially accessible to the hand that was not used for the practice.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1920
    Keywords: Key words Aneurysm ; intracranial ; Embolisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We treated 38 patients with 39 aneurysms of the posterior circulation by an endovascular technique using balloons, free coils or Guglielmi detachable coils (GDC) from 1986 to May 1993. The patients ranged in age from 10 to 71 years. Subarachnoid haemorrhage was the most frequent presentation (29 patients), followed by mass effect (5 patients) and epilepsy (2 patients). Treatment consisted of embolisation of the aneurysm with preservation of the parent vessel (in 29) or occlusion of the parent vessel (in 5). Multiple procedures were performed in 12 patients (32 %, maximum 3 embolisations, total 17 treatments), because of incomplete initial aneurysm occlusion (in 8 cases) or re-opening of the aneurysm (in 9). Treatment could not be achieved in 5 patients. Good to excellent aneurysm occlusion was obtained in 28 patients (72 %). Little or no neurological impairment occurred in 31 patients (82 %). Complications related to treatment (11 patients, 29 %) included 4 cases of transient cerebral ischaemia, 7 of stroke resulting in minimal neurological impairment (in 5), severe impairment (in 1) and one death. There were 6 patients who died, of rebleeding from the same aneurysm (2), basilar stroke (1) and unrelated causes (3). Comparison of the different occlusion techniques showed that the best angiographic results were obtained with balloons (good to excellent aneurysm occlusion was obtained in 17 of 22 patients treated) and the GDC (12 of 13 patients), and that less good results were given by free coils (4 of 9 patients). Complications related to treatment were fewest in patients treated with GDC (1 of 16 treatments, including multiple procedures) or free coils (2 of 12 treatments) and were more frequent with balloons (6 of 27 treatments). All five treatment failures occurred with balloon embolisation, whereas treatment was possible in all cases treated with free coils or GDC.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1920
    Keywords: Aneurysm, intracranial ; Embolisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We treated 38 patients with 39 aneurysms of the posterior circulation by an endovascular technique using balloons, free coils or Guglielmi detachable coils (GDC) from 1986 to May 1993. The patients ranged in age from 10 to 71 years. Subarachnoid haemorrhage was the most frequent presentation (29 patients), followed by mass effect (5 patients) and epilepsy (2 patients). Treatment consisted of embolisation of the aneurysm with preservation of the parent vessel (in 29) or occlusion of the parent vessel (in 5). Multiple procedures were performed in 12 patients (32 %, maximum 3 embolisations, total 17 treatments), because of incomplete initial aneurysm occlusion (in 8 cases) or re-opening of the aneurysm (in 9). Treatment could not be achieved in 5 patients. Good to excellent aneurysm occlusion was obtained in 28 patients (72 %). Little or no neurological impairment occurred in 31 patients (82 %). Complications related to treatment (11 patients, 29 %) included 4 cases of transient cerebral ischaemia, 7 of stroke resulting in minimal neurological impairment (in 5), severe impairment (in 1) and one death. There were 6 patients who died, of rebleeding from the same aneurysm (2), basilar stroke (1) and unrelated causes (3). Comparison of the different occlusion techniques showed that the best angiographic results were obtained with balloons (good to excellent aneurysm occlusion was obtained in 17 of 22 patients treated) and the GDC (12 of 13 patients), and that less good results were given by free coils (4 of 9 patients). Complications related to treatment were fewest in patients treated with GDC (1 of 16 treatments, including multiple procedures) or free coils (2 of 12 treatments) and were more frequent with balloons (6 of 27 treatments). All five treatment failures occurred with balloon embolisation, whereas treatment was possible in all cases treated with free coils or GDC.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1920
    Keywords: Key words Aneurysm ; experimental ; Stent ; vein-loaded ; Vein graft ; autologous
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We treated 13 experimental wide-necked aneurysms of lateral type produced in dog carotid arteries with a vein-loaded stent system consisting of an autologous vein graft, a vein-carrier stent, and two other self-expanding Z-shaped stents. The vein-loaded stent, made by connecting the autologous vein graft to the vein-carrier stent, was implanted in the common carotid artery to seal the aneurysm's orifice, after which two booster stents were deployed. The distal stent was placed to fix the distal end of the vein graft, and the proximal stent was placed at the proximal venous portion of the vein-loaded stent to reinforce its proximal end. In this manner an intra-arterial bypass was established across the aneurysm. Of 13 aneurysms seven were completely occluded, preserving the parent artery. The remaining six procedures resulted in parent artery occlusion because of failures in stent deployment. Angiograms performed in within 1 week six successfully treated dogs revealed the parent artery to be patent in four but thrombosed in two. Histological study of successful cases showed as smooth intima with slight endothelial hypertrophy and partially organised thrombus. The intraluminal features were also observed with a vascular endoscope at the time of treatment in four dogs and at the time of follow-up angiography in two. The appearances corresponded well to the macroscopic findings in the specimens. Our vein-loaded stent system offers complete closure of the orifice, which does not occur with conventional stent placement. The method is believed to show clinical promise for treating wide-necked aneurysms not curable by embolisation of the sac.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The ability of a photobioreactor to fix CO2 was evaluated with the thermophilic cyanobacterium, Synechocystis aquatilis SI-2. The reactor consisted of three to five flat plates of transparent acrylic plastic standing upright and in parallel and giving a 0.015-m light path. The reactor was 0.8 m high and 1 m long with 9 l working volume. The effects of the orientation of the vertical bioreactor, distance between the plates, and culture temperature on the productivity of biomass were investigated during the summer of 1998 in Kamaishi (39°N, 142°E), Japan. When the illuminated surface reactor was placed in an east–west-facing orientation, the biomass productivity was roughly 1.4-fold higher than that obtained in a north–south-facing orientation, because the former received more solar energy than the latter. The productivity based on the overall land area was the same for plates set either 0.25 m or 0.5 m apart. However, the volumetric productivity of the reactor in which the plates were set 0.25 m apart was lower than that when the plates were set 0.5 m apart, since the former plates received relatively lower solar irradiation because of severe mutual shading. When the culture temperature was maintained in its optimal range (37–43 °C), the productivity was 50% greater than that obtained in a culture at ambient temperature (20–44 °C). The biomass productivity and CO2 fixation rate were investigated under various experimental conditions. The maximum rate of 53 g CO2 m−2 day−1 was achieved in the temperature-regulated culture with the reactor set in an east–west-facing orientation, the distance between plates being 0.25 m.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 655-662 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To test the feasibility of CO2 remediation by microalgal photosynthesis, a modified type of flat-plate photobioreactor [Hu et al. (1996) Biotechnol Bioeng 51:51–60] has been designed for cultivation of a high-CO2-tolerant unicellular green alga Chlorococcum littorale. The modified reactor has a narrow light path in which intensive turbulent flow is provided by streaming compressed air through perforated tubing into the culture suspension. The length of the reactor light path was optimized for the productivity of biomass. The interrelationship between cell density and productivity, as affected by incident light intensity, was quantitatively assessed. Cellular ultrastructural and biochemical changes in response to ultrahigh cell density were investigated. The potential of biomass production under extremely high CO2 concentrations was also evaluated. By growing C. littorale cells in this reactor, a CO2 fixation rate of 16.7 g CO2 l−1 24 h−1 (or 200.4 g CO2 m−2 24 h−1) could readily be sustained at a light intensity of 2000 μmol m−2 s−1 at 25 °C, and an ultrahigh cell density of well over 80 g l−1 could be maintained by daily replacing the culture medium.
    Type of Medium: Electronic Resource
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