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  • 1990-1994  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Sensitivity of zooxanthellae and non-symbiotic microalgae to stimulation of photosynthate excretion by giant clam tissue homogenate (1994)
    Springer
    Marine biology 118 (1994), S. 687-693 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00347517
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Adaptation of solitary corals and their zooxanthellae to low light and UV radiation (1993)
    Springer
    Marine biology 117 (1993), S. 685-691 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00349781
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Role of carbonic anhydrase in the supply of inorganic carbon to the giant clam—zooxanthellate symbiosis (1993)
    Springer
    Marine biology 115 (1993), S. 605-611 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00349368
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Contribution of meningeal arteries to cerebral arteriovenous malformations (1993)
    Springer
    Neuroradiology 35 (1993), S. 205-209 
    Details
    ISSN: 1432-1920
    Keywords: Cerebral arteriovenous malformation ; Meningeal arterial feeders ; Angiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied 52 patients with cerebral arteriovenous malformations (AVMs) by selective angiography and found that half received supply from meningeal branches of the external carotid artery. The frequency of meningeal arteral contribution was significantly higher in superficial AVMs, especially in the temporal, parietal and occipital regions. Larger lesions and higher shunt with steal phenomena on angiography were other factors favouring a meningeal arterial contribution. Diffuse AVMs with pial arterial networks around the nidus commonly received meningeal blood supply. In the past, meningeal feeders have been though to be congenital, but this study suggests that they may develop during growth of the AVM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588495
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    Paper (German National Licenses)
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