Osmoregulatory balance in Murray cod, Maccullochella peelii peelii (Mitchell), affected with chronic ulcerative dermatopathy

This study examined the osmoregulatory capability of Murray cod, Maccullochella peelii peelii, affected by chronic ulcerative dermatopathy (CUD) in intensive aquaculture. This condition appears to arise only in facilities utilizing groundwater, with the causative agent suggested to be a water-borne factor. Healthy Murray cod (~ 700 g) were transferred to a CUD-affected farm to monitor the progression of the syndrome and began to show signs of CUD after approximately five months. In order to evaluate possible effects of CUD on osmoregulation; plasma electrolyte concentrations, osmolality, and Na⁺,K⁺-ATPase activities were measured, and gill histology and immunohistochemistry were analyzed. Plasma electrolyte concentrations and osmolality of CUD-affected Murray cod were consistent with reference values determined for non CUD-affected fish. A greater number of gill mucous cells were observed in Murray cod cultured at the CUD-affected farm compared to non CUD-affected fish. We also found an un-identified cell type that was present solely in the gills of CUD-affected Murray cod. Gill Na⁺,K⁺-ATPase activity was significantly higher in severely CUD-affected Murray cod compared to individuals transferred to the CUD-affected farm. While there appeared to be some minor changes in the gills of CUD-affected fish, this study demonstrated that Murray cod were able to effectively osmoregulate, although, perhaps at an energetic cost.     

Physiological stress responses of Vitis vinifera L. to the fungicides fludioxonil and pyrimethanil

The effects of the fungicides fludioxonil and pyrimethanil were evaluated on grapevine leaves using in vitro-grown plantlets, fruiting cuttings, and plants grown in vineyards. In vitro, both water content and osmotic potential decreased in treated leaves. Moreover, carbohydrate accumulated, suggesting that plantlets could react to the stress through an active osmoregulation process by uptaking sugars from the medium. Besides, pyrimethanil stimulated the accumulation of proteins, whereas no significant effect was observed using fludioxonil. The cuttings exhibited similar responses than in vitro though they appeared to be more tolerant since half of the studied parameters recovered 10 days after treatment. In vineyard, both fungicides modified leaf water content and carbohydrate levels, whereas nitrogenous compounds accumulated transiently. These results suggest that in vineyard-grown plants, a strong sugar translocation from mature leaves to sink organs occurs transiently, as well as a protein synthesis and a stimulation of soil nitrogen uptake.     

Preventing discoloration and lipid oxidation in dark muscle of yellowtail by feeding an extract prepared from mushroom (Flammulina velutipes) cultured medium

Groups of 0+ Atlantic salmon (Salmo salar) smolts were transferred to duplicate seawater tanks, and subjected to five different ration levels, 0% (starved), 25%, 50%, 75% or 100% (full fed). Waste feed was collected after each meal. After six weeks all groups were re-fed in excess. During the trial period body weight and length increased significantly in the 50, 75 and 100% groups, while no significant changes in body weight were observed in the 0% and 25% groups. A significant decrease in SGR was observed in the 0 and 25% groups during the first month in sea water. After re-feeding, SGR increased in all groups. All groups, except the previously starved group, showed peak SGR between weeks 6–8 and 8–12. Food restriction at 0% and 25% of full ration for a period of six weeks resulted in significant osmotic disturbances. After six weeks in sea water, plasma Cl⁻ levels were higher in the 0% group than in the other groups. Branchial Na⁺,K⁺-ATPase activity increased in all groups following exposure to seawater. Re-feeding caused a transient increase in branchial Na⁺,K⁺-ATPase activity after two weeks in the previously starved group, with a concurrent reduction in plasma Cl⁻ levels. Previous exposure to different ration levels significantly influenced growth rate and mean body size. Compensatory growth and partial size compensation was seen in the 0, 25 and 50% feed deprivation groups, whereas full size compensation was found in the 75% group.     

Net ion fluxes in the facultative air-breather <Emphasis Type="Italic">Hoplosternum littorale</Emphasis> (tamoata) and the obligate air-breather <Emphasis Type="Italic">Arapaima gigas</Emphasis> (pirarucu) exposed to different Amazonian waters

Fishes that live in the Amazon environment may be exposed to several kinds of water: black water (BW), acidic black water (pH 3.5) (ABW) and white water (WW), among others. The aim of the present study was to analyze net ion fluxes in the facultative air-breather Hoplosternum littorale (tamoata) and the obligate air-breather Arapaima gigas (pirarucu) exposed to different types of water. Fishes were acclimated in well water and later placed in individual chambers containing one type of water for ion flux measurements. After 4 h, the water in the chambers was replaced by a different type of water. The transfer of both species to ABW (independent of previous water exposure) increased net ion loss. Tamoatas transferred from ABW to BW or WW presented a net ion influx, but pirarucus showed only small changes on net ion efflux. These results allow us to conclude that tamoatas and pirarucus present differences in terms of ion regulation but that the general aspects of the ion flux are similar: (1) exposure to ABW led to net ion loss; (2) transfer from BW to WW or vice-versa induced only minor changes on net ion fluxes. These observations demonstrate that any osmoregulatory difficulties encountered by either species during changes between these latter two waters can be easily overcome.     

植物渗透调节的研究进展

介绍了渗透调节的过程,并从植物信号转导、渗透调节物质、水通道蛋白等方面对植物渗透调节研究进展进行了探讨。     

木麻黄幼苗渗透调节物对酸雨胁迫的响应研究

对模拟pH2 .5～4 .5酸雨胁迫3个月后木麻黄幼苗渗透调节物含量测定结果表明,pH4 .0～4 .5酸雨胁迫后木麻黄幼苗小枝可溶性糖含量显著低于对照,但(pH2 .5～3.5 )酸雨胁迫后其含量显著高于对照;与对照相比酸雨胁迫使木麻黄幼苗小枝可溶性蛋白质含量增加,游离脯氨酸和谷胱甘肽含量则极显著增加。酸雨胁迫下木麻黄幼苗具有积累较高浓度的有机渗透调节物及改善渗透调节的生理应答能力     

两种苹果砧木对中度干旱胁迫的生理响应

测定比较了以二年生苹果砧木山定子与陇东海棠盆栽幼苗正常供水和中度干旱胁迫下的叶片丙二醛、可溶性糖、可溶性蛋白、游离脯氨酸含量及抗氧化酶活性。结果表明,随着干旱胁迫时间延长,2种植物的丙二醛、可溶性糖、游离脯氨酸和过氧化物酶活性持续上升,且在整个胁迫过程中2种植物间差异显著;可溶性蛋白含量则不断降低,且于第7 d后差异显著。中度干旱胁迫下,超氧化物歧化酶和过氧化氢酶活性于胁迫第7 d达到最大值,随后不断下降,表明2种植物前期对活性氧的清除能力较强,随胁迫时间加长其抗氧化能力减弱。综合分析,山定子的抗旱能力强于陇东海棠。     

Growth performance of gilthead sea bream Sparus aurata in different osmotic conditions: Implications for osmoregulation and energy metabolism

The influence of three different environmental salinities (seawater, SW: 38 ppt salinity; brackish water, BW: 12 ppt; and low salinity water, LSW: 6 ppt salinity) on the growth, osmoregulation and metabolism of young gilthead sea bream (Sparus aurata L.) was studied over a period of 100 days. 480 inmature fish (20 g mean body weight) were randomly divided into six tanks of 2500 l (80 fish per tank) and maintained under three different salinities (38 ppt, 12 ppt and 6 ppt) in an open system. Every three weeks, 10 fish from each tank were anesthetized, weighed and lenghed. At the end of experiment, 10 fish from each tank were anesthetized, weighed and sampled for plasma, brain, gill and liver. Gill Na⁺, K⁺-ATPase activity, plasma osmolality, ions (sodium and chloride), glucose, lactate, protein and triglyceride, and hepatosomatic index were examined. In addition, levels of glycogen, lactate, ATP and activities of potential regulatory enzymes (hexokinase, pyruvate kinase, glycogen phosphorylase, and glucose 6-phosphate dehydrogenase) were assesed in liver, brain, and gill. BW-acclimated fish showed a better growth with respect to SW- or LSW-acclimated fish (12 > 38 > 6 ppt). The same relationship was observed for weight gain and specific growth rate. Osmoregulatory parameters in plasma (osmolality, Na⁺ and Cl⁻ levels) were similar in SW- and BW-acclimated fish but significantly higher than those of LSW-acclimated fish. Gill Na⁺, K⁺-ATPase activity showed lower values in intermediate salinity (6 > 38 > 12 ppt). No changes were observed in metabolic parameters analyzed in plasma, whereas only minor changes were observed in metabolic parameters of liver, gills and brain that could be correlated with the higher growth rates observed in fish acclimated to BW, which do not allow us to attribute the best growth rate observed at 12 ppt to lower metabolic rates in that salinity.