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141.
142.
The endemic Antarctic brown macroalga Desmarestia anceps colonizes the subtidal between 5 and 30 m in Potter Cove on King George Island (South Shetland Islands, Antarctica). Experiments were conducted to study photosynthetic activities, antioxidative enzymes and UV tolerance of field-grown individuals with respect to the light histories along different subtidal positions. Individuals collected from the upper (5.5 m) and mid-subtidal (9.0 m) are characterized by high maximum electron transport rates (ETRmax) measured by PAM-fluorometry and high activities of superoxide dismutase (SOD) supported by considerable activities of glutathione reductase. Individuals of this species from the upper subtidal are able to tolerate high irradiances of UV-B radiation because its photosynthetic apparatus is putatively well protected by phlorotannins. In contrast, individuals from lower subtidal positions (13.5 and 15.5 m) showed an opposite trend: lower ETRmax and SOD activities as well as a lower UV tolerance of photosynthesis. Moreover, a non-denaturing polyacrylamide gel electrophoresis (native PAGE) of a partially purified crude extract reveals that D. anceps has probably six isoforms of SOD. These intra-specific patterns imply a high phenotypical plasticity of D. anceps with respect to its photosynthesis and photoprotective mechanisms. Overall, photosynthesis, UV tolerance and antioxidative potential are highly regulated in D. anceps corresponding to the respective light regimes along its natural growth sites. 相似文献
143.
J. K. Wiencke 《Experimental cell research》1987,171(2):518-523
Human lymphocytes treated with [3H]thymidine ([3H]dThd) become refractory to the induction of chromosomal aberrations by subsequent doses of X rays. This adaptive response to [3H]dThd does not occur in the presence of 3-aminobenzamide (3AB). 3AB inhibits the synthesis of poly(ADP-ribose) by the enzyme adenosine diphosphate ribosyl transferase (ADPRT), which requires NAD as a substrate. 3AB also prevents chromosomal repair, as measured in X-ray dose-fractionation studies. Because 3AB might interfere with metabolic reactions other than those mediated by ADPRT, experiments were carried out to see if the adaptive response was also inhibited in nicotinamide-free medium, which prevents poly(ADP-ribosyl)ation by depleting cellular NAD. The experiments show that the incorporation of [3H]dThd has no effect on the induction of chromosomal aberrations by subsequent doses of X rays if the cells are cultured in nicotinamide-free medium. Nicotinamide deficiency mimics the effects of 3AB on both the adaptive response and chromosome repair. The results indicate that ADPRT activity itself, and not other metabolic processes affected by inhibitors of this enzyme, plays an essential role in the adaptive response. 相似文献
144.
145.
On the competitive balance of macroalgae at Potter Cove (King George Island,South Shetlands) 总被引:3,自引:2,他引:1
The sublittoral zonation of macroalgae and abundant animals in Potter Cove, King George Island, is described in relation to substrate, exposure to turbulence and impact of grounding icebergs. Implications on the ecological niches of the most prominent phaeophytes are discussed. It is concluded that Desmarestia anceps and D. menziesii exclude Himantothallus grandifolius under favourable conditions. However, Himantothallus, by its potential to inhabit unstable substrates, may be better adapted to withstand the ice impact. The replacement of Desmarestia by Himantothallus at greater depth can be explained only partially at present. 相似文献
146.
The ion composition of cell compartments in the intertidal red alga Porphyra umbilicalis adapted for two weeks in 3.5 x artificial seawater was determined by X-ray microanalysis of unfixed, frozen, bulk specimens. A procedure is described for the calculation of ion concentrations in the main cell compartment, cytoplasm, vacuoles and plastid. The results indicate high K+ and low Na+ concentrations in cytoplasm and plastid. Sodium ions are preferentially localized in vacuoles. Both, vacuoles and plastid contain high Cl- concentrations. 相似文献
147.
148.
C. Wiencke 《Polar Biology》1996,16(4):231-240
The paper summarizes our present knowledge of Antarctic macroalgae with regard to the following topics: explorative history
of Antarctic macroalgae, the environment of macroalgae in the Antarctic, life histories and physiological anatomy, seasonal
development, light demands and depth zonation, temperature demands and geographical distribution and the effect of desiccation,
salinity and temperature on supra- and eulittoral algae. A baseline is visible, but much more work is necessary, especially
to assess the susceptibility of macroalgae and coastal ecosystems in Antarctica to global climatic changes.
Received: 29 June 1995/Accepted: 3 October 1995 相似文献
149.
The temperature requirements for growth and upper temperature tolerance were determined in 16 macroalgal species collected
on Disko Island (Greenland). The upper survival temperatures were examined in 1°C steps, and growth measured at 5°C intervals
between 0 and 20°C using a refined method, where the fresh weight was determined weekly or fortnightly over a period of 5
or 6 weeks. To express temperature-growth responses, growth rates of temperature-acclimated plants were taken. Two groups
with different temperature requirements were identified: (1) A stenothermal group includingAcrosiphonia arcta, Acrosiphonia sonderi, Urospora penicilliformis, Devaleraea ramentacea, Desmarestia aculeata, Pilayella
littoralis, growing between 0 and (10 to) 15 (or 20)°C with optima between 0 and 10°C. The upper survival temperatures in these species
and inChromastrum secundatum, Chromastrum virgatulum, Chordaria flagelliformis were between 17 and 23°C (duration of experiment: 2 weeks). (2) A eurythermal group includingEnteromorpha clathrata, Enteromorpha intestinalis andPolysiphonia urceolata growing between 0 and 20°C with growth optima at 10 or 15°C. The upper survival temperatures in these species and inChaetomorpha tortuosa, Bangia atropurpurea andEudesme virescens were between 24 and 31°C. These algal species showed little adaptation to the Arctic temperatures. In contrast, algae from
the first group exhibited a relatively high adaptation to low temperatures — approaching the low temperature requirements
of Antarctic algae. The results are discussed in relation to the geographic distribution of individual species. 相似文献
150.
Because tool and die workers are exposed to a number of potentially genotoxic agents, including mutagenic metals, polyaromatic hydrocarbons, and nitrosamines, and may be at increased cancer risk, the present study was undertaken to test whether chromosomal damage in peripheral blood cells is associated with work in the tool and die industry. Lymphocyte cultures were established from 27 tool and die fabrication workers from one manufacturing plant who had worked in the trade for more than 15 years. 15 of these workers also had some form of malignancy at the time of the study, but had not been treated with radiation or chemotherapies that could themselves induce chromosomal damage. The frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) were measured in workers and the data compared with those of a control group consisting of 7 non-fabrication workers from the same plant and 8 age-matched community controls. In addition, the relative rates of lymphocyte proliferation were estimated for each group by analyzing the percentages of first-, second- and third-division mitotic cells after 72 h of culture. The results of the chromosomal studies show that tool and die workers have significantly increased frequencies of aberrations whether engaged in fabrication work or not, compared to control subjects. The frequency of SCEs and the frequencies of 1st, 2nd and 3rd division figures are not different among the study groups. Among workers who are engaged in fabrication, including those who are cancer patients, the frequency of more complex aberrations (i.e., interstitial deletions and small acentric fragments) is increased. In a five-year follow-up of these workers, 2 of the 13 workers with these aberrations developed some form of colon cancer. Whether the presence of interstitial deletions and small acentric fragments is related to the occupation of these workers, or is tangentially related to the development of cancer, is presently under consideration. 相似文献