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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/General Subjects 93 (1964), S. 625-634 
    ISSN: 0304-4165
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Stimulation of photosynthate excretion from zooxanthellae and free-living algae by tissue homogenate of several bivalves was studied. Mantle tissue homogenate of Tridacna derasa enhanced 10-to 15-fold excretion of photosynthetically fixed carbon from freshly isolated zooxanthellae within 2 h incubation. Maximum carbon excretion was 35 to 45% of the total carbon fixed. This excretion stimulating activity was detected in the homogenates of the mantle, adductor muscle, gill, and kidney. However, no excretion stimulating activity was detected in the haemolymph. The excretion stimulation activity of mantle homogenate, directed against freshly isolated zooxanthellae from T. derasa, was higher in bivalves belonging to the Tridacnidae (T. derasa, T. crocea, T. maxima, T. squamosa, Hippopus hippopus) than in the Cardiidae (Fragum fragum, F. mundum, F. unedo), non-symbiotic bivalves (Mytilus edulis, Meretrix lusoria, Ruditapes philippinarum) or gastropods (Umbonium giganteum, Turbo argyrostoma). The mantle homogenate of T. derasa enhanced photosynthate excretion by free-living algae belonging to the Dinophyceae (Prorocentrum micans, Amphidinium carterae, and Heterocapsa triquetra) but did not enhance its excretion by free-living algae belonging to the Chlorophyceae, Cyanophyceae, Rhodophyceae, Prasinophyceae, and Haptophyceae. T. derase used in this study originated from Belau (Palau). T. crocea, T. squamosa, T. maxima, H. hippopus and F. unedo were collected at Ishigaki Island in Okinawa in 1992. F. mundum and F. fragm were collected at Okinawa Island in 1992.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 117 (1993), S. 685-691 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adaptation of solitary corals, Fungia repanda and F. echinata, and their zooxanthellae to low light and ultraviolet light B (UV-B) was studied with respect to changes in their protein contents, photosynthetic pigment contents and the photosynthesis-irradiance (P-I) curves. The corals were collected from 1 to 50 m depths in the Republic of Belau (Paulau) in 1990 and 1991. The chlorophyll a content in a unit surface area of the coral did not change significantly with the depth of the habitat, whereas cellular chlorophyll a in the algae increased with the depth. Zooxanthellae density and protein content in a unit surface area of Fungia spp. decreased with the depth. Photosynthetic parameters normalized by a unit surface area of the Fungia spp., maximum gross photosynthetic rate (P gmax area-1) and dark respiration rate (R area-1), were negatively correlated with the depth, while initial slope of the P-I curve (α) did not show significant correlation with the depth. Compensation light intensity (Ic) decreased with the depth. In isolated zooxanthellae, P max chl a -1, and R chl a -1 decreased with the depth, while αchl a was constant. P gmax cell-1 and R cell-1 did not change significantly but αcell increased with the depth. Ic decreased with the depth as in the intact corals. Reduction of protein content in a unit area of the coral from deeper habitat implies decrease of host animal tissues. Reduction of Ic can be explained by decrease of R area-1, which may be due to the diminution of animal tissues. The photoadaptational response to low light intensity of intact Fungia spp. was found to be a combination of the photoadaptation of symbiotic algae and the decrease of host animal tissue. In order to study their adaptation to ultraviolet (UV) radiation, P-I curves of Fungia spp. and isolated zooxanthellae were analyzed before and after UV-B irradiation. 1 h UV-B irradiation showed no effect on the photosynthetic rate of the shallow water (1 m) corals, while it inhibited the photosynthesis of the deep water (30 m) corals and zooxanthellae isolated from both shallow and deep water corals. These results indicate that the host, Fungia spp., in shallow water have protective mechanism for intense UV-B in their habitat. These photoadaptational mechanisms seem to allow the Fungia spp. to have wide vertical distribution where light intensity spans more than two orders of magnitude.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanism whereby inorganic carbon (Ci) is acquired by the symbiotic association between the giant clam (Tridacna derasa) and zooxanthellae (Symbiodinium sp.) has been investigated. Ci in the haemolymph of the clam is in equilibrium with the surrounding sea water. The photosynthesis rate exhibited by the intact clam varies as a function of the Ci concentration in the clam haemolymph. The gill tissue contains high carbonic anhydrase activity which may be important in adjusting the Ci equilibrium between haemolymph and sea water. Zooxanthellae (Symbiodinium sp.) isolated from the clam mantle prefer CO2 to HCO 3 - as a source of inorganic carbon. The zooxanthellae have low levels of carbonic anhydrase on the external surface of the cell; however, mantle extracts display high carbonic anhydrase activity. Carbonic anhydrase is absent from the mantle of aposymbiotic clams (T. gigas), indicating that this enzyme may be essential to the symbiosis. The enzyme is probably associated with the zooxanthellae tubes in the mantle. The results indicate that carbonic anhydrase plays an important role in the supply of carbon dioxide within the clam symbiosis.
    Type of Medium: Electronic Resource
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  • 6
    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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  • 7
    ISSN: 1432-072X
    Keywords: Acidic compartments ; Chlorella vulgaris ; Chloroquine ; Compartmentation ; Inorganic phosphate ; Intracellular pH ; in vivo nuclear magnetic resonance ; Neutral red ; Unicellular algae ; Vacuoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acidic inorganic phosphate (Pi) pool (pH around 6) was detected besides the cytoplasmic pool in intact cells of Chlorella vulgaris 11h by 31P-in vivo nuclear magnetic resonance (NMR) spectroscopy. It was characterized as acidic compartments (vacuoles) in combination with the cytochemical technique; staining the cells with neutral red and chloroquine which are known as basic reagents specifically accumulated in acidic compartments. Under various conditions, the results obtained with the cytochemical methods were well correlated with those obtained from in vivo NMR spectra; the vacuoles were well developed in the cells at the stationary growth phase where the acidic Pi signal was detected. In contrast, cells at the logarithmic phase in which no acidic Pi signal was detected contained only smaller vesicles that accumulated these basic reagents. No acidic compartment was detected by both cytochemical technique and 31P-NMR spectroscopy when the cells were treated with NH4OH. The vacuolar pH was lowered by the anaerobic treatment of the cells in the presence of glucose, while it was not affected by the external pH during the preincubation ranging from 3 to 10. Possible vacuolar functions in unicellular algae especially with respect to intracellular pH regulation are discussed.
    Type of Medium: Electronic Resource
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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Archives of Biochemistry and Biophysics 237 (1985), S. 72-79 
    ISSN: 0003-9861
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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