Influence of some environmental variables on the ascorbic acid status of mullet, Mugil cephalus L., tissues. I. Effect of salinity, capture-stress, and temperature

The effects of capture stress, exposure to a hypo-osmotic environment and elevated water temperatures on the ascorbic acid (AsA) content of several mullet, Mugil cephalus , tissues were examined. All the treatments significantly altered tissue AsA levels, but the pattern of AsA fluctuations varied. Gill AsA concentrations increased two fold after exposure to a hypo-osmotic medium (salinity changed from 30‰ to 5‰), whereas AsA content in this tissue declined after capture. Both treatments depleted AsA reserves in the kidney. AsA concentrations in the brain increased after exposure to low salinity and elevated water temperatures, but were unaffected by capture stress. None of the treatments caused long term alteration of hepatic AsA reserves. Ascorbic acid inhibited oubain-sensitive Na⁺, K⁺-ATPase activity of gill tissue in vitro . The results suggest an involvement of AsA in osmo- or ion-regulatory functions of teleosts gills, salinity and thermal adaptation mechanisms in neural tissue, and the response of renal tissue to adverse environmental stimuli.     

Ascorbic acid status of mullet, Mugil cephalus Linn., exposed to cadmium

The effects of acute and chronic cadmium exposures on ascorbic acid concentrations and cadmium accumulation in the tissues of juvenile mullet, Mugil cephalus , are described. Hepatic ascorbic acid reserves were maintained in untreated mullet fed a diet containing ascorbate, but decreased 60% in individuals exposed to 10 mg Cd 1^-1 for six weeks. Ascorbic acid depletion was accompanied by a massive accumulation of cadmium in the liver. Similar changes were found in gill tissue. In contrast, ascorbic acid concentrations were largely unaffected in kidney tissue which had a limited capacity to accumulate the metal. There were marked fluctuations of ascorbic acid levels in the brain. Only small amounts of cadmium were accumulated by this tissue. These results indicate that in mullet liver, gill and brain ascorbic acid stores may be depleted during chronic cadmium poisoning.     

Influence of some environmental variables on the ascorbic acid status of striped mullet, Mugil cephalus Linn., tissues. III. Effects of exposure to oil

Exposure to water-soluble fractions (WSF) of a crude and two fuel oils altered the ascorbic acid (AsA) content of several striped mullet, Mugil cephalus , tissues. Exposure to sublethal concentrations of all three WSFs caused a depletion of AsA reserves in brain, gill, kidney and liver tissues, but not in muscle. There was a marked decline in AsA stores in kidney and gill tissues after only one day of exposure to WSFs of both crude and fuel oils. Liver AsA concentrations were significantly depleted after one week of oil exposure. Brain AsA content was only significantly depleted during chronic exposure to the highest oil concentration (20% WSF). A dose-dependent depletion of AsA reserves in the liver but not in the other tissues was observed one week after a single exposure to 2–20% WSFs of a No. 2 fuel oil. Exposure to 20% WSF of the No. 2 fuel oil caused a 47% decrease in liver AsA content one week later. Hepatic concentrations were still significantly depleted after 15 days, but had returned to control levels 20 days after the initial exposure. The data suggest that the depletion of tissue AsA reserves in fish inhabiting oil-contaminated environments could be sufficient on occasions to lead to AsA deficiency.     

Distribution and metabolism of ascorbic acid in apple fruits (Malus domestica Borkh cv. Gala)

The objective of this study was to determine ascorbic acid (AsA) distribution, biosynthesis and recycling in different tissues of young and mature fruit of cv. Gala apple (Malus domestica Borkh). Our results showed that the peel of ‘Gala’ apple had the highest AsA levels among all the tissue types, which resulted from a combination of, lower ascorbate peroxidase (APX, EC 1.11.1.11) activity consuming AsA, and higher dehydroascorbate reductase (DHAR, EC 1.8.5.1) and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activities used to recycle AsA. Exogenous feeding of AsA synthesis precursors demonstrated that the peel was capable of de nono AsA biosynthesis via l-galactose and d-galacturonic acid pathways whereas the flesh and seed were only able to synthesize AsA via l-galactose pathway. The young fruit had higher AsA concentration and stronger capability of AsA biosynthesis and recycling. The sun-exposed peel had higher AsA concentration and stronger capability of recycling AsA than the shaded peel, while there was no difference in the flesh between the sun-exposed side and the shaded side. Abundant AsA was found in fruit vascular tissue, which suggests that AsA can be transported to vascular tissues of fruit or vascular tissues could synthesize AsA itself in ‘Gala’ apple.     

Role of exogenous ascorbic acid in tissue status of ascorbic acid-2-sulphate in guinea pigs.

Guinea pigs were given ascorbic acid orally in two doses; a low and a high dose. The tissue levels of ascorbic acid-2-sulphate was estimated in these animals after 15 days of feeding and a subsequent deprivation period of 15 days. The specific activity of the enzymes ascorbic acid sulphotransferase and ascorbic acid-2-sulphate sulphohydrolase was studied. During higher ascorbic acid intake, the activity of ascorbic acid sulphotransferase was increased, whereas ascorbic acid-2-sulphate sulphohydrolase showed a decreased activity. But when ascorbic acid intake was lowered or ceased, the activity of the above enzymes showed a reverse pattern. Possible reasons for the lack of antiscorbutic activity of ascorbic acid-2-sulphate in guinea pigs is discussed.     

Comparative tissue ascorbic acid studies in fishes

Comparative tissue ascorbic acid levels in four species of major carp viz., Labeo rohila, L. calbasu, Cirrhina tnrigala and Catla catla , were investigated. The ascorbic acid level was found to be the highest in the spleen in the four species studied (range 430–380 μg/g) followed by the anterior (adrenal) kidney, gonads, liver, renal kidney, brain and/or eye. Heart and blood had the lowest levels (range 26–18 μg/ml) amongst the tissues studied. Overall tissue ascorbic acid levels were the highest in L. rohita and the lowest in C. mrigala . Investigation on seasonal variations in blood and kidney ascorbic acid levels of Notopterus notopterus revealed peak levels in spring (February-April) and the lowest levels in the postspawning period (August-September).     

Ascorbic acid deficiency induces hepatic and intestinal expression of inflammation-related genes irrespective of the presence or absence of gut microbiota in ODS rats

We have previously demonstrated that ascorbic acid (AsA) deficiency causes inflammatory changes in the liver and intestine in Osteogenic Disorder Shionogi (ODS) rats, which are unable to synthesize AsA. We have suggested that AsA deficiency increased intestinal interleukine (IL)-6 production, stimulating hepatic acute phase proteins (APPs) expression via the portal vein. In this study, we determined whether these hepatic and intestinal inflammatory changes by AsA deficiency are induced in germ-free (GF) ODS rats. For 18 days, male specific pathogen-free (SPF) ODS rats were fed the basal diet containing 600 mg AsA/kg (control group) or the AsA-free diet (AsA-deficient group) in SPF conditions, while male GF ODS rats were fed the basal diet (control group) or the AsA-free diet (AsA-deficient group) in GF conditions. Firstly, AsA deficiency significantly elevated the hepatic expression of APPs in both SPF and GF rats. In hepatic mRNA levels of some APPs, significant interaction between GF and AsA-deficiency effects was observed. Secondly, AsA deficiency elevated intestinal IL-6 and IL-1β mRNA levels in both SPF and GF rats, and significant interaction between GF and AsA-deficiency effects was observed in these mRNA levels of jejunum and cecum. In SPF and GF rats, AsA deficiency elevated portal IL-6 concentration. These results show that AsA deficiency caused hepatic and intestinal inflammatory changes in both the GF and SPF ODS rats and indicate that AsA deficiency could directly induce intestinal inflammatory changes without the involvement of gut microbiota.     

晚熟脐橙果实发育过程中抗坏血酸含量及相关酶活性的变化

以‘鲍威尔’脐橙为试材, 研究了果实发育期间果皮和果肉中抗坏血酸（AsA）含量及相关酶活性的变化。结果表明, 果皮中总抗坏血酸（T-AsA）和AsA含量显著高于果肉, 且在发育期间T-AsA和AsA的变化趋势一致; 果皮中L-半乳糖内酯脱氢酶（g·LLDH）活性与T-AsA和AsA积累速率的变化趋势基本一致, 呈显著正相关关系, 而在果肉中的变化趋势却不明显; 在发育过程各阶段中果皮的抗坏血酸氧化酶（AAO）、抗坏血酸过氧化物酶（APX）、脱氢抗坏血酸还原酶（DHAR）和单脱氢抗坏血酸还原酶（MDHAR）活性均高于果肉; 相关性分析显示, 果皮中AsA含量积累主要取决于g·LLDH活性, 而果肉中AsA含量水平可能取决于AsA的再生循环系统。     

Gulonolactone oxidase is missing in teleost fish. The direct spectrophotometric assay

Data in the literature imply that some fish species evolved with the capacity to synthesize ascorbic acid. Gulonolactone oxidase activity has been reported in kidney and/or liver tissues. However, it is shown here that this microsomal enzyme activity is missing in common carp hepatopancreas and kidney, whereas high activity was confirmed in pigeon kidney, rat liver, bovine liver and amphibian (Xenopus) kidney tissues. A new assay using either the whole tissue homogenate or microsomes solubilized by sodium deoxycholate was developed to directly measure the formation of ascorbic acid spectrophotometrically. Identical values were found using this assay as well as the assay in which formed ascorbate was determined by the dinitrophenyl hydrazine (DNPH) method. In some experiments, these results were confirmed by polarographically measured oxygen consumption.     

Effect of abandonment and plant classification on carbohydrate reserves of meadow plants

We studied the effect of cessation of management on carbohydrate reserves of plants in meadows with different environmental characteristics and plant composition. We recorded storage carbohydrates and seasonal changes for 40 plant species. We asked whether there are differences in responses of carbohydrate reserves in forbs versus graminoids and in plants storing starch versus plants storing osmotically active carbohydrates. We analysed belowground organs before the meadows were mown and at the end of the vegetation season in mown versus recently abandoned plots. Whereas starch and fructans were widely distributed, raffinose family oligosaccharides were the main carbohydrate reserves of the Lamiaceae and Plantago lanceolata. Properties of carbohydrate reserves differed between forbs and graminoids but no difference was found between plants storing starch versus osmotically active carbohydrates. Graminoids had lower carbohydrate concentrations than forbs. We observed a positive effect of mowing on carbohydrate concentrations of graminoids in the dry, calcium-rich meadow and higher seasonal fluctuations of these values in the acid, wet meadow, suggesting that local factors and/or the species pool affect carbohydrate reserves. Despite local conditions, graminoids represent a distinct functional group in meadows from the point of view of their storage economy. We suggest that as well as growth, storage processes should also be considered for understanding the functioning of meadow plant communities.     

缺乏抗坏血酸对豚鼠胆固醇代谢的影响

边缘性缺乏抗坏血酸之豚鼠,于三周内其肝脏及小肠粘膜3-羟-3-甲基戊二酰辅酶A还原酶(HMGR)活力均下降到原有水平的50％,但肝脏胆固醇7α-羟化酶活力尚无显著性改变。坏血病豚鼠(三周内)上述几种酶活力都下降至原有水平的50％左右。豚鼠摄取抗坏血酸不足,其血清总胆固醇浓度显著增加,而血清高密度脂蛋自胆固醇浓度显著减少,其改变程度与抗坏血酸缺乏状况一致。     

Effect of aging on aqueous-phase antioxidants in tissues of male Fischer rats

The purpose of this study was to determine the influence of aging on concentrations of the important aqueous-phase antioxidants in rat tissues. Ascorbic acid, glutathione and uric acid were measured in tissues and organs of male Fischer 344 rats at 6, 15 and 26 months of age. Blood, liver, lungs, heart, kidneys, brain, testes and lenses were excised rapidly and were extracted with cold metaphosphoric acid. Aging diminished the concentration of ascorbic acid in liver, lung and lens; levels in 26-month-old rats were 40-60% of those in 6-month-old rats. Glutathione content was diminished only in lens, where it decreased almost 50% between 15 and 26 months. Some age-associated increases in antioxidant levels also were seen; testis ascorbic acid and kidney glutathione levels were elevated in the old compared with the younger rats. Uric acid concentrations were much lower than glutathione or ascorbic acid concentrations in every tissue except plasma. Old rats had lower levels of uric acid in liver but higher levels in heart, kidney and testis. These results demonstrate that aqueous-phase antioxidant levels are not uniformly diminished in tissues of old rats.     

Extrahepatic tissue copper concentrations in white perch with hepatic copper storage

Hepatic copper storage in man (Wilson's disease), Bedtington and West Highland white terriers, and white perch ( Morone americana ) is characterized by the progressive accumulation of copper in hepatic lysosomes bound to cytoprotective metallothionein. In man, saturation of the liver storage capacity results in the distribution of copper to extrahepatic tissues with multiple organ system dysfunction. To determine if extrahepatic tissue copper concentrations also increase in white perch, copper and zinc levels in liver, brain, heart, gills, serum, and bile were determined by atomic absorption spectrophotometry and compared to striped bass ( Morone saxatilis ). Results showed that brain copper concentrations in. white perch were elevated and significantly correlated with liver copper. Bile and serum copper also increased significantly with liver copper. Copper levels in heart and gill tissues were low. Liver zinc was increased in white perch but not to the same magnitude as copper, and was correlated significantly with liver copper; possibly a non-specific secondary increase related to an overall increase in hepatic metallothionein. Histochemical staining of liver with rubeimc acid for copper was proportional to copper concentrations, and clusters of positive mononuclear cells were also seen in brain and spleen. Foci of macrophages in spleen were also intensely positive with Perl's iron stain which may have been indicative of haemolysis. The patterns of copper distribution seen in white perch present a useful comparative model to study alterations in copper metabolism.     

Analysis of physiological variations of piperidine levels in tissues by mass fragmentography

By use of a mass fragmentographic technique the distribution of piperidine in tissues and changes in levels under physiological conditions were examined. Only trace amounts of piperidine existed in the brain of several animal species, although higher concentrations were detected in other species. In the brain of rats and rabbits, some regional differences were seen and high concentrations were found in the striatum. Piperidine levels in the brain and adrenal gland similarly showed the daily and seasonal rhythmic fluctuations.     

Over-expression of strawberry d-galacturonic acid reductase in potato leads to accumulation of vitamin C with enhanced abiotic stress tolerance

Vitamin C (ascorbic acid) is an essential component for collagen biosynthesis and also for the proper functioning of the cardiovascular system in humans. Unlike most of the animals, humans lack the ability to synthesize ascorbic acid on their own due to a mutation in the gene encoding the last enzyme of ascorbate biosynthesis. As a result, vitamin C must be obtained from dietary sources like plants. In this study, we have developed transgenic potato plants (Solanum tuberosum L. cv. Taedong Valley) over-expressing strawberry GalUR gene under the control of CaMV 35S promoter with increased ascorbic acid levels. Integration of the GalUR gene in the plant genome was confirmed by PCR and Southern blotting. Ascorbic acid (AsA) levels in transgenic tubers were determined by high-performance liquid chromatography (HPLC). The over-expression of GalUR resulted in 1.6–2-fold increase in AsA in transgenic potato and the levels of AsA were positively correlated with increased GalUR activity. The transgenic lines with enhanced vitamin C content showed enhanced tolerance to abiotic stresses induced by methyl viologen (MV), NaCl or mannitol as compared to untransformed control plants. The leaf disc senescence assay showed better tolerance in transgenic lines by retaining higher chlorophyll as compared to the untransformed control plants. Present study demonstrated that the over-expression of GalUR gene enhanced the level of AsA in potato tubers and these transgenics performed better under different abiotic stresses as compared to untransformed control.     

抗坏血酸对高温胁迫下猕猴桃苗抗热性相关生理指标的影响

以美味猕猴桃组培苗品种秦美为试材,研究抗坏血酸（AsA）对高温胁迫下猕猴桃苗抗热性相关生理指标影响的结果表明,抗坏血酸可抑制高温胁迫下猕猴叶细胞膜透性和丙二醛（MDA）含量的增大,但增强超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）和抗坏血酸过氧化物酶（APX）的活性。     

Population biology of parasites of striped mullet, Mugil cephalus L. Crustacea

Class 0 and class 1 striped mullet, Mugil cephalus , were collected from May 1970 to June 1971 to study development, seasonal abundance of parasite populations, and distribution of gill parasites. Crustacean parasites observed were Ergasilus lizae, E. versicolor, E.funduli, Bomolochus concinnus, Brachiella oblonga, Caligus mfimaculatus, Clavella inversa, Lernaeeni–cus longiventris, Argulus funduli and A. chesapeakensis sp.n. Cressey. Cyclipoid copepods initially infected class 0 mullet in late spring and populations were characterized by surges in intensity at 6 to 8 week intervals. Caligoid copepods initially infected class 0 mullet in late summer and fall or appeared only on class 1 mullet. Intensity remained low, but they were observed consistently. Branchiurans were rarely observed on class 0 mullet and occurred consistently at low intensity on class 1 mullet. Study of distribution of five gill parasites indicated a high degree of gill habitat subdivision, but competitive exclusion was not observed.     

Inhibitory Effect of Ascorbic Acid on the Proliferation and Invasion of Hepatoma Cells in Culture

Effect of ascorbic acid (AsA) on the proliferation and invasion of rat ascites hepatoma AH109A cells was investigated by measuring [³H]thymidine incorporation into acid-insoluble fraction of the cells and by co-culturing the hepatoma cells with rat mesentery-derived mesothelial cells, respectively. AsA suppressed the invasion of AH109A cells in a dose-dependent manner at concentrations of 62.5–500 μM, while it inhibited the proliferation of the cells at higher concentrations of 250 and 500 μM. Hepatoma cells previously cultured with hypoxanthine (HX) and xanthine oxidase (XO) or with hydrogen peroxide showed increased invasive activities. AsA suppressed the reactive oxygen species-potentiated invasive capacity by simultaneously treating AH109A cells with AsA, HX and XO or with AsA and hydrogen peroxide. Furthermore, AsA reduced the intracellular peroxide levels in AH109A cells. These results suggest that the antioxidative property of AsA may be involved in its anti-invasive action on hepatoma cells.     

外源抗坏血酸对镉胁迫下黑藻抗氧化系统的保护作用

研究了不同浓度抗坏血酸(ascorbic acid,AsA)对5 mg·L^-1Cd²⁺胁迫下黑藻（Hydrilla verticillata）体内超氧阴离子(O₂^-)产生速率、过氧化氢(H₂O₂)含量、抗坏血酸和谷胱甘肽(GSH)含量,以及超氧化物歧化酶(SOD)、超氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的影响.结果表明,与单一Cd²⁺胁迫相比,随着外源AsA浓度的升高,黑藻体内活性氧生成速率逐步降低;抗氧化物质AsA先升后降,GSH缓慢升高;抗氧化酶APX和CAT活性先升后降,POD活性逐步下降,并接近正常状态,对SOD活性影响不大.可见AsA能够有效缓解Cd²⁺对黑藻的毒害,且60 mg·L^-1浓度下的缓解效果最好.