Low Ascorbic Acid Research Articles

QUALITY CURVES FOR GREEN BELL PEPPER (CAPSICUM ANNUUM L.) STORED AT LOW AND RECOMMENDED RELATIVE HUMIDITY LEVELS

'Revolution' green bell peppers were harvested, held for 14 to 22 days at 15°C and five relative humidity (RH) levels and evaluated for quality attributes. The objectives of this work were to obtain quality curves at low and recommended RH levels and identify for each RH which quality attributes limit green bell pepper marketability. Results from this study showed that RH had a significant effect on the shelf life and overall quality of green bell peppers. Peppers stored at RHs lower than 90% were less green, softer, more shriveled, and had higher weight loss, lower acidity, lower soluble solids and lower ascorbic acid contents than those stored at higher RH. Overall, changes in the color of the fruit, softening, shriveling, and loss of aroma were the first quality attributes to reach the limit of acceptability and therefore limiting the shelf life of 'Revolution' green bell peppers. At 90 and 95% RH, pepper acceptability was limited primarily by color changes followed by loss of aroma; at 80% acceptability was reduced due to changes in color, shriveling and loss of aroma. Shelf life of peppers stored at 40 and 60% RH was reduced to approximately 6 and 7 days, respectively, due to changes in coloration, softening, severe shriveling and loss of aroma. Maximum shelf life and best quality was obtained when green bell pepper were stored at 90 or 95% RH. The quality curves obtained from quality evaluations for each RH level showed that a single quality attribute cannot be used to express quality loss of green bell pepper stored over a range of humidity levels.

Quercetin Bioavailability And Biotransformation Are Inversely Related To Vitamin C Status In College‐Aged Adults

Dietary quercetin (Q) may reduce the risk of cardiovascular disease (CVD), but little is known about its bioavailability. We conducted a pharmacokinetics study to define whether antioxidant status affects Q bioavailability in young adults. Participants (n = 8M/5F) ingested 1095 mg Q aglycone with a standardized meal. Then, plasma antioxidants [ascorbic acid (AA), tocopherols, uric acid, carotenoids], Q and its methylated metabolites isorhamnetin (I) and tamarixetin (T) were measured at timed intervals for 24 h. Q bioavailability (AUC0‐24 h 308–1738 μM x min) and maximum concentrations (Cmax 0.4–2.8 μM) exhibited high inter‐subject variability. AUC0‐24 h and Cmax of I and T were also highly variable (120–750 and 33–787 μM x min; 0.1–0.9 and 0.1–1.2 μM, respectively). AA, but no other antioxidants, was inversely related to Q AUC0‐24 h and Q Cmax (P<0.05; r = −0.63 to −0.49). AA was also negatively related to AUC0‐24 h of I + T (P<0.05, r = −0.58) and tended to inversely relate to Cmax of I + T (P=0.06; r = −0.46), suggesting that low AA status increases Q bioavailability and biotransformation. AA was also inversely related to myeloperoxidase (P<0.05, r = −0.56), a proinflammatory enzyme that increases CVD risk. These data suggest that low AA status increases Q bioavailability, possibly through a proinflammatory mechanism that increases its intestinal absorption.Grant Funding Source : Donaghue Nutrition Research Program

Conservação de pimentão verde minimamente processado acondicionado em diferentes embalagens plásticas

O processamento mínimo de hortaliças agrega valor ao produto final, pelo fato de aumentar a sua conveniência e reduzir o tempo de preparo das refeições. O objetivo deste trabalho foi avaliar a conservação de pimentões verdes 'Konan R' minimamente processados, no formato de rodelas, e acondicionados em diferentes embalagens plásticas. Os pimentões foram selecionados, lavados e sanificados em solução de hipoclorito de sódio (200 mg L-1), por 15 minutos. As rodelas (1,0 cm de largura) foram sanificadas em solução de hipoclorito de sódio (50 mg L-1), por 5 minutos, e, em seguida, acondicionadas em: 1) bandeja de poliestireno expandido, envolta com filme de policloreto de vinila (PVC) 0,014 mm; 2) embalagem rígida de polipropileno (PP), com tampa do mesmo polímero; 3) saco plástico de polipropileno biorientado (BOPP) 0,060 mm. O produto foi armazenado a 5±0,1ºC e 95±1% UR, por 6 dias. As seguintes análises foram realizadas a cada 2 dias: perda de massa, teores de acidez titulável e de ácido ascórbico, pH, coloração (expressa em valores L* e a*) e firmeza. As embalagens plásticas e o tempo de armazenamento não alteraram o pH, o valor L* e a firmeza das rodelas. Os teores de acidez titulável e o valor a* foram afetados pelo tempo de armazenamento. A bandeja de poliestireno envolta com filme PVC determinou maior perda de massa e menor teor de ácido ascórbico, nas rodelas de pimentão armazenadas a 5ºC, por 6 dias. Assim, a embalagem rígida de PP e o saco plástico de BOPP são preferíveis para acondicionar pimentão verde minimamente processado.

Low antioxidant concentrations impact on multiple signalling pathways in Arabidopsis thaliana partly through NPR1.

Production of reactive oxygen species (ROS) is linked to signalling in both developmental and stress responses. The level of ROS is controlled by both production and removal through various scavengers including ascorbic acid and glutathione. Here, the role of low ascorbic acid or glutathione concentrations was investigated on ozone-induced cell death, defence signalling, and developmental responses. Low ascorbic acid concentrations in vtc1 activated expression of salicylic acid (SA)-regulated genes, a response found to be dependent on the redox-regulated transcriptional co-regulator NPR1. In contrast, low glutathione concentrations in cad2 or pad2 reduced expression of SA-regulated genes. Testing different responses to jasmonic acid (JA) revealed the presence of at least two separate JA signalling pathways. Treatment of the vtc1 mutant with JA led to hyper-induction of MONODEHYDROASCORBATE REDUCTASE3, indicating that low ascorbic acid concentrations prime the response to JA. Furthermore, NPR1 was found to be a positive regulator of JA-induced expression of MDHAR3 and TAT3. The vtc1 and npr1 mutants were sensitive to glucose inhibition of seed germination; an opposite response was found in cad2 and pad2. Overall, low ascorbic acid concentrations mostly led to opposite phenotypes to low glutathione concentrations, and both antioxidants interacted with SA and JA signalling pathways.

Effect of cutting shapes and thicknesses on the quality of minimally processed pineapple (Ananas comosus) cv. 'Queen Victoria'

Cutting shape and size are physical factors that influence the keeping quality of minimally processed fruits and vegetables. Since these factors have not been studied as determinants of the keeping quality of minimally processed pineapples (MPP) cv. ‘Queen Victoria’, this study was conducted. A 2 x 2 factorial treatment structure laid on a randomized block design (RBD) was used. The treatments, which were blocked by days, were combinations of two cutting shapes (slices and chunks) and two thicknesses (5 mm and 10 mm). Pineapples of 25 - 50% ripeness were minimally processed to give rise to the treatments, which were then vacuum-packed at 47.5 kPa in laminated Low Density Polyethylene (LDPE) vacuum bags and stored at 4 ± 10 C for 12 days. Quality changes were evaluated at three-day intervals over a storage period of 12 days. Translucency score was evaluated by comparison method against standard colour charts. Electrical conductivity of leachate (ECL), firmness and pH were measured instrumentally. Ascorbic acid (AA) content was determined by titration with dichlorophenolindophenol (DCPIP) dye. Yeasts and moulds counts (YMC) were also enumerated using the classical standard method. Data were analysed using analysis of variance (ANOVA), and sum of squares due to treatment were split into main effect cutting shape, main effect thickness and interaction effect. All the keeping quality attributes of the MPP were significantly affected by storage time (p<0.001). Cutting shape also significantly affected translucency score (p<0.01), firmness (p<0.01) and YMC (p<0.01). Slices were firmer and had the lowest translucency score and minimized fungal growth as opposed to chunks. No significant interaction effect (p>0.05) was observed between cutting shapes and thicknesses on translucency score, firmness and YMC of the MPP. However, a significant interaction effect was noted between these two variables on ECL (p<0.05) and AA content (p<0.001). A thickness of 10 mm exhibited lower translucency score, higher ECL, reduced firmness and lower AA losses. pH was not significantly affected (p>0.05) by cutting shapes and thicknesses. Ten-mm slices maintained all the above-stated quality parameters, except ECL and pH, when stored at 4 ± 10 C for 12 days.

Differential regulation of the ascorbic acid transporter SVCT2 during development and in response to ascorbic acid depletion

The sodium-dependent vitamin C transporter-2 (SVCT2) is the only ascorbic acid (ASC) transporter significantly expressed in brain. It is required for life and is critical during brain development to supply adequate levels of ASC. To assess SVCT2 function in the developing brain, we studied time-dependent SVCT2 mRNA and protein expression in mouse brain, using liver as a comparison tissue because it is the site of ASC synthesis. We found that SVCT2 expression followed an inverse relationship with ASC levels in the developing brain. In cortex and cerebellum, ASC levels were high throughout late embryonic stages and early post-natal stages and decreased with age, whereas SVCT2 mRNA and protein levels were low in embryos and increased with age. A different response was observed for liver, in which ASC levels and SVCT2 expression were both low throughout embryogenesis and increased post-natally. To determine whether low intracellular ASC might be capable of driving SVCT2 expression, we depleted ASC by diet in adult mice unable to synthesize ASC. We observed that SVCT2 mRNA and protein were not affected by ASC depletion in brain cortex, but SVCT2 protein expression was increased by ASC depletion in the cerebellum and liver. The results suggest that expression of the SVCT2 is differentially regulated during embryonic development and in adulthood.

REACTIVE OXYGEN SPECIES SCAVENGING ACTIVITY AND DNA PROTECTING EFFECT OF FRESH AND NATURALLY FERMENTED COCONUT SAP

ABSTRACT Coconut sap is consumed as a juice or used as raw material for fermentation to produce beverages with various health benefits. To understand the underlying mechanisms of the health benefits of coconut sap, we investigated the in vitro reactive oxygen species scavenging activities and DNA protecting effects of fresh and naturally fermented coconut sap using a flow-injection chemiluminescence method. The results show that the fresh sap scavenges superoxide anion, hydroxyl radical and hydrogen peroxide better than the naturally fermented sap; in contrast, the fermented sap shows a more powerful ability to prevent damage to DNA than the fresh sap. The naturally fermented sap had a higher polyphenol level but a lower ascorbic acid content than fresh sap, suggesting that fermentation is beneficial for improving the polyphenol content of coconut sap. PRACTICAL APPLICATION Reactive oxygen species (ROS) are reported to be related to many diseases, such as cancer and Alzheimer's disease. Antioxidants are vital substances that possess the ability to protect the body from damage caused by ROS. There is an increasing interest in natural antioxidants, e.g., polyphenols, present in medicinal and dietary plants, which might help prevent oxidative damage. Coconut sap is obtained by tapping the unopened spadix of the coconut palm, and also used as the resource of sugar and alcoholic beverages by local people. Our experimental results testify that the coconut sap has powerful ROS scavenging activity and can be potentially used as the ingredients of functional food.

Some effects of experimentally-produced cigarette smoke on the growth, vitamin C metabolism and organ weights of guinea-pigs.

Abstract Guinea-pigs receiving a controlled dietary intake of L-xyloascorbic acid (ascorbic acid, vitamin C) inhaled experimentally produced cigarette smoke for periods of up to 20 min each day. Growth rate was significantly depressed by the smoke treatment, an effect at least in part attributable to a reduction in food intake. Growth of individual organs was not depressed to the same extent as that of the body as a whole. The lungs of the animals receiving smoke were significantly heavier than those of control animals (P < 0·05). The concentration of ascorbic acid in the adrenal glands was significantly lower in the animals receiving smoke than in the controls (P < 0·01). The smoke-induced depression of the adrenal gland ascorbic acid was apparent after 4 days; after 18 days marked adrenal hypertrophy accompanied the lowered ascorbic acid levels.

The importance of reductive mechanisms for intestinal uptake of iron from ferric maltol and ferric nitrilotriacetic acid (NTA)

Intestinal iron absorption is thought to proceed with iron mainly in the ferrous form, yet the novel iron complex, ferric maltol is an effective oral preparation. Although possessing a high oil: water partition coefficient, ferric maltol does not diffuse across the intestine but donates its iron to the endogenous uptake system. Reduction of the ferric iron in the gut lumen appears to precede iron uptake both from ferric maltol and from ferric nitrilotriacetic acid (NTA) which is a non-penetrating iron ligand. Uptake of radiolabelled iron (59Fe) into isolated fragments of rat small intestine was inhibited by the ferrous chelator, bathophenanthroline sulphonate (BPS) and enhanced at low concentrations by the reducing agent ascorbic acid. Spectrophotometric evidence was obtained that ferrous ions are generated from these ferric complexes in the presence of ascorbic acid and other reducing agents. The rate of ferrous ion formation was independent of ferric maltol concentration at low ascorbic acid levels and decreased with increasing ferric maltol concentration at higher levels of ascorbate. Maltol has a high affinity for ferric ions and may delay reduction at higher concentrations. By contrast, a higher rate of ferrous ion generation was seen with ferric NTA and this increased with iron ligand concentration. Washings from the intestinal lumen also brought about ferrous ion formation from these ferric ligands. Gel filtration revealed these reducing factors to be of low molecular weight. The washings, however, interfered with 59Fe uptake into the isolated fragments, but when reducing fractions only from the filtered washings were used, enhanced iron uptake was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in enzymes, phenolic compounds, tannins, and vitamin C in various stages of jambolan (Syzygium cumini Lamark) development

The physiological state of a fruit is closely related to ripening and climatic conditions during the growing period when the fruit undergo changes in color, texture, and flavor. The ripening of the fruit can involve a complex series of biochemical reactions with alteration in enzymes activities, phenols, tannins, and ascorbic acid. The activity of enzymes (carboximethylcellulase, polygalacturonase, and pectinlyase), the total concentration of phenolic compounds, condensed tannins, and vitamin C in five stages of maturation were studied. Significant changes were observed between the maturity stages. The phenolic compounds were higher at green stage (705.01 ± 7.41); tannins were higher at green/purple stage (699.45 ± 0.22). The results showed that the ascorbic acid levels of the pulp varied significantly from 50.81 ± 1.43 to 6.61 ± 1.04 mg.100 g-1 during maturation. The specific activity of pectin lyase was higher at green stage (1531.90 ± 5.83). The specific activity of polygalacturonase was higher at mature stage (1.83 ± 0.0018). The specific activity of carboximetilcelulose was higher at ripe mature stage (4.61 ± 0.0024). The low ascorbic acid content found in jambolan fruit indicates that this fruit is not a rich source of this nutrient; however, other characteristics can make jambolan products fit for human consumption.

The role of ascorbic acid transporter in the lens of streptozotocin-induced diabetic rat

Ascorbic acid (AA) is found in high concentrations in the lens and protects the lens from photochemical events such as photo-oxidation. Diabetes reduces the concentration of AA in the lens, and it has been suggested that AA supplementation may rescue lens AA in diabetic patients. In the present study, the effects of dietary supplementation with AA were studied to assess changes in AA concentration and AA transporter expression in the lenses of streptozotocin (STZ)-induced diabetic rats. AA was lower in the aqueous humors and lenses of diabetic rats than in control rats, and low AA levels could be normalized with dietary AA supplementation. The sodium-dependent ascorbic acid transporter2, SVCT2, is transporter of AA, and glucose transporter 1 and 3 (GLUT1 and GLUT3) are transporters of dehydroascobic acid. Transcription of GLUT1 and GLUT3 was not changed as a result of diabetes or AA treatment, and the SVCT2 was increased in diabetic rats and normalized by AA supplementation in diabetic rats. Aquaporin 0 (AQP0) expression was increased in diabetic rats and by AA treatment. The rate of AA transport of vesicle originally from diabetic lens and that with AA treatment were greater than that from control rats with or without AA treatment. These results suggest that ascorbates are transported by AQP0 as well as by SVCT2, GLUT1 and GLUT3, and that supplementation with AA may help prevent diabetic cataracts.

260 IN VITRO DEVELOPMENTAL COMPETENCE OF PREPUBERTAL GOAT OOCYTES CULTURED IN GROWTH MEDIUM

The prepubertal goat ovary presents a large number of small oocytes with a compromised competence to develop up to blastocyst stage. In pigs (Wu et al. 2006), using growth medium (GM) composed by low hormone concentrations, ascorbic acid, and insulin transferrin selenium (ITS) during the first 24 h of in vitro maturation (IVM) improved embryo development of small oocytes. The aim of this study was to test the GM in small prepubertal goat oocytes in order to increase blastocyst yield. The cumulus–oocyte complexes (COC) were recovered from prepubertal (1–2 months old) goat ovaries by slicing. The COC with a compact cumulus and homogeneous cytoplasm were selected and classified into 2 categories based on oocyte diameter: <125 μm and ≥125 μm. The ≥125 μm oocytes were matured in groups of 25 to 30 COC/100 μL drops of conventional IVM medium covered with mineral oil for 24 h (Treatment A). This medium was TCM-199 supplemented with 10% donor bovine serum, 10 μg mL–1 FSH, 10 μg mL–1 LH, 1 μg mL–1 17β-oestradiol, and 100 μM cysteamine. The <125 μm oocytes were distributed into 3 experimental groups: Treatment B, COC matured in the conventional IVM medium; Treatment C, COC cultured in GM (TCM-199, 10% donor bovine serum, 0.04 μg mL–1 FSH, 0.04 μg mL–1 LH, 0.004 μg mL–1 17β-oestradiol, 100 μM cysteamine, 100 μg mL–1 ascorbic acid, and 5 μL mL–1 ITS) for 12 h before placement for other 12 h in the conventional IVM medium, all drops of growth or maturation medium were covered with mineral oil; Treatment D, COC cultured during the first 12 h in GM and other 12 h into the conventional medium supplemented with 100 μg mL–1 ascorbic acid and 5 μL mL–1 ITS. After IVM, oocytes were fertilized for 24 h with a sperm concentration of 4 × 106 spz mL–1. Presumptive zygotes were cultured in SOF for 9 days. The cleavage rate was evaluated at 48 h post-insemination and blastocyst percentages at the final in vitro embryo culture (treatments A, B, C: 5 replicates; treatment D: 4 replicates). The results are shown in the Table 1. Cleavage and embryo development did not show different results when we compared small oocytes matured in GM to those matured in conventional IVM medium. However, the biggest oocytes (≥125 μm) showed the highest percentage of blastocyst development. The current study shows that the culture of small prepubertal goat oocytes in GM does not improve blastocyst yield. Table 1.Effect of growth medium on embryo development of small oocytes (<125 μm) from prepubertal goats

Dietary ascorbic acid requirement of cobia, Rachycentron canadum Linneaus

A 10-week feeding trial was conducted to determine the optimal requirement of cobia (Rachycentron canadum Linneaus) for dietary ascorbic acid (AA). Graded levels of L-ascorbyl-2-polyphosphate (LAPP) were supplemented in basal diet to formulate six semi-purified diets containing 2.70 (the control diet), 8.47, 28.3, 80.6, 241 and 733 mg AA equivalent kg−1 diet, respectively. Each diet was randomly fed to triplicate groups of fish in flow-through plastic tanks (300 L), and each tank was stocked with 25 fish with average initial weight of 4.59 ± 0.36 g. Observed deficiency signs included poor growth, higher mortality and lower feeding rate (FR) in the fish of the control group. Fish fed the control diet had significantly lower weight gain (WG), lower feed efficiency ratio (FER) and lower tissue AA concentrations in fish liver and muscle. With the increase of dietary AA, the survival, WG, FER, hepatic and muscular AA concentrations of cobia significantly increased and then levelled off. The dietary AA requirement of cobia was estimated to be 44.7 mg kg−1 based on WG, 53.9 mg kg−1 or 104 mg kg−1 based on either hepatic or muscular AA concentration, respectively.

Ascorbic acid status of female camels during different phases of reproduction

There is suggestive evidence that a low status of ascorbic acid in camels enhances their risk for infectious diseases. This study was carried out to disclose the role of reproduction, if any, in affecting ascorbic acid status. The associations between the reproductive cycle and ascorbic acid contents in plasma and leukocytes were studied in Sudanese camels browsing on local vegetation. Ascorbic acid status was found to be lowest during pregnancy and highest during lactation. Estrus versus non-estrus was associated with high vitamin C status. Brucellosis-positive camels showed decreased levels of ascorbic acid in plasma and leukocytes. Possibly, the phases of non-estrus and pregnancy in camels invoke an increased susceptibility to infectious diseases due to a lower ascorbic acid status.

Impact of edible coatings and mild heat shocks on quality of minimally processed broccoli ( Brassica oleracea L.) during refrigerated storage

The effects of edible coatings and mild heat shocks on quality aspects of refrigerated broccoli were studied. Minimally processed broccoli was coated with either chitosan or carboxymethyl-cellulose with or without a previous application of a mild heat shock of 1.5 min at 50 °C. Product was packaged in multilayered polyolefin bags and stored at 5 °C for 18 d. Quality parameters such as weight loss, texture, colour, ascorbic acid content, total chlorophyll content, oxygen concentration inside the bags, browning potential, mesophilic aerobic counts, and sensory quality, were evaluated during storage. Edible coatings exhibited a beneficial impact on broccoli quality. The weight loss in uncoated broccoli was found to be between 2 and 5 times higher compared to coated samples. During storage, coated florets from both thermally and non-thermally treated samples, presented higher retention of the (− a*/ b*) ratio indicating better green colour retention and a reduced rate of floret yellowing. Chitosan coating always presented the lower ascorbic acid degradation rates (twofold lower compared with control samples). Broccoli texture for uncoated samples increased significantly during storage. However, for carboxymethyl-cellulose coated broccoli a slight increase in texture was observed while for chitosan coated broccoli no significant changes in texture were observed throughout the storage period. After the edible coating application the microbial broccoli load dropped by around 1.5 and 0.9 logarithmic units in chitosan and carboxymethyl-cellulose films, respectively. During storage, the application of chitosan coating significantly reduced total microbial counts in the thermally and non-thermally treated uncoated samples. Among the assayed edible coatings, chitosan effectively maintained quality attributes and extended shelf life of minimally processed broccoli. The single application of a mild heat shock had a measurable influence in reducing weight loss, enzymatic browning in broccoli stems, and in delaying yellowing of broccoli florets. Moreover, chitosan coating combined with a mild heat shock showed the best performance for long-term refrigerated storage of minimally processed broccoli.

À propos d’un nouveau cas d’oesophage noir

IntroductionAcute necrotising oesophagitis is an uncommon emergency condition.Case reportA 46-year-old insulin dependent, diabetic woman presented with haematemesis, melaena and macroscopic haematuria, in association with necrotic cutaneous lesions of the limbs. On examination, she was haemodynamically stable, appeared to have giantism without acromegalic features and exhibited bullous skin necrosis. Endoscopy showed the appearances of “black oesophagus” with biopsy revealing mucosal and submucosal necrosis. Blood tests yielded a glucose level of 3 g/l, polymorph leucocytosis, a low ascorbic acid level, hypogonadotrophic hypogonadism and low TSH. Biopsy of the cutaneous lesions demonstrated leucocytoclastic angiopathy. Cerebral MRI showed a completely cystic macroadenoma. Treatment comprised control of her diabetes, vitamin therapy, thyroid hormone replacement and antibiotics. On repeat endoscopy, the oesophageal necrosis had completely disappeared. During her hospital stay, she had a massive fatal pulmonary embolus.DiscussionThe incidence of acute necrotising oesophagitis is thought to be between 0.008% and 0.2%. The diagnosis depends on endoscopy (black oesophagus).ConclusionAs far as we know, this is the first report of its association with vitamin C deficiency and a pituitary macroadenoma.

The role of ascorbic acid transporter in the lens of streptozotocin-induced diabetic rat

Ascorbic acid (AA) is found in high concentrations in the lens and protects the lens from photochemical events such as photo-oxidation. Diabetes reduces the concentration of AA in the lens, and it has been suggested that AA supplementation may rescue lens AA in diabetic patients. In the present study, the effects of dietary supplementation with AA were studied to assess changes in AA concentration and AA transporter expression in the lenses of streptozotocin (STZ)-induced diabetic rats. AA was lower in the aqueous humors and lenses of diabetic rats than in control rats, and low AA levels could be normalized with dietary AA supplementation. The sodium-dependent ascorbic acid transporter2, SVCT2, is transporter of AA, and glucose transporter 1 and 3 (GLUT1 and GLUT3) are transporters of dehydroascobic acid. Transcription of GLUT1 and GLUT3 was not changed as a result of diabetes or AA treatment, and the SVCT2 was increased in diabetic rats and normalized by AA supplementation in diabetic rats. Aquaporin 0 (AQP0) expression was increased in diabetic rats and by AA treatment. The rate of AA transport of vesicle originally from diabetic lens and that with AA treatment were greater than that from control rats with or without AA treatment. These results suggest that ascorbates are transported by AQP0 as well as by SVCT2, GLUT1 and GLUT3, and that supplementation with AA may help prevent diabetic cataracts.

Amperometric microsensor for direct probing of ascorbic acid in human gastric juice

This article reports on a novel microsensor for amperometric measurement of ascorbic acid (AA) under acidic conditions (pH 2) based on a carbon fiber microelectrode (CFME) modified with nickel oxide and ruthenium hexacyanoferrate (NiO–RuHCF). This sensing layer was deposited electrochemically in a two-step procedure involving an initial galvanostatic NiO deposition followed by a potentiodynamic RuHCF deposition from solutions containing the precursor salts. Several important parameters were examined to characterize and optimize the NiO–RuHCF sensing layer with respect to its current response to AA by using cyclic voltammetry, and scanning electron microscopy–energy dispersive X-ray spectroscopy methods. With the NiO–RuHCF coated CFME, the AA oxidation potential under acidic conditions was shifted to a less positive value for about 0.2 V ( E p of ca. 0.23 V vs. Ag/AgCl) as compared to a bare CFME, which greatly improves the electrochemical selectivity. Using the hydrodynamic amperometry mode, the current vs. AA concentration in 0.01 M HCl, at a selected operating potential of 0.30 V, was found to be linear over a wide range of 10–1610 μM ( n = 22, r = 0.999) with a calculated limit of detection of 1.0 μM. The measurement repeatability was satisfactory with a relative standard deviation (r.s.d.) ranging from 4% to 5% ( n = 6), depending on the AA concentration, and with a sensor-to-sensor reproducibility (r.s.d.) of 6.9% at 100 μM AA. The long-term reproducibility, using the same microsensor for 112 consecutive measurements of 20 μM AA over 11 h of periodic probing sets over 4 days, was 16.1% r.s.d., thus showing very good stability at low AA levels and suitability for use over a prolonged period of time. Moreover, using the proposed microsensor, additionally coated with a protective cellulose acetate membrane, the calibration plot obtained in the extremely complex matrix of real undiluted gastric juice was linear from 10 to 520 μM ( n = 14, r = 0.998). These results demonstrated the unique featuring of the proposed NiO–RuHCF microsensor under acidic conditions with enhanced sensitivity and stability and proved its promising potentiality for direct amperometric probing of AA at physiological levels in real gastric juice environments.

Weaning Strategies for Striped Trumpeter, Latris lineata, Postlarvae Culture

The striped trumpeter, Latris lineata, is a native fish being developed for aquaculture in Tasmania, Australia. Striped trumpeter have a long postlarval stage and rearing has been reliant on the long-term use of Artemia. Two experiments were conducted to investigate weaning strategies. The first experiment used 52 d posthatch (dph) postlarvae previously reared on Artemia from 16 to 52 dph enriched with either low or high ascorbic acid. The treatments were Artemia, a microdiet, or cofeeding. The postlarvae were reared until 67 dph. The Artemia treatment yielded significantly higher mean survival, followed by cofeeding, and the microdiet. Feeding Artemia yielded significantly heavier postlarvae and the microdiet produced significantly smaller postlarvae. A second experiment used 41 dph postlarvae and investigated the effect of cofeeding duration prior to feeding with Artemia and microdiet as controls. Cofeeding periods of 5, 10, and 15 d were tested. Cofeeding for 5 d and microdiet feeding yielded significantly poorer survival compared with Artemia. Artemia feeding yielded significantly heavier postlarvae. In both experiments, the diets did not have a significant effect on jaw morphology. These experiments are the first to examine weaning strategies for striped trumpeter postlarvae and suggest cofeeding postlarvae from 40 dph and feeding microdiet exclusively at 50 dph.

Low ascorbic acid and increased oxidative stress in gulo (−/−) mice during development

Vitamin C (ascorbic acid, AA) depletion during prenatal and postnatal development can lead to oxidative stress in the developing brain and other organs. Such damage may lead to irreversible effects on later brain function. We studied the relationship between AA deficiency and oxidative stress during development in gulonolactone oxidase ( gulo) knockout mice that are unable to synthesize their own ascorbic acid. Heterozygous gulo (+/ − ) mice can synthesize AA and typically have similar tissue levels to wild-type mice. Gulo ( +/− ) dams were mated with gulo ( +/− ) males to provide offspring of each possible genotype. Overall, embryonic day 20 (E20) and postnatal day 1 (P1) pups were protected against oxidative stress by sufficient AA transfer during pregnancy. On postnatal day 10 (P10) AA levels were dramatically lower in liver and cerebellum in gulo ( − / − ) mice and malondialdehyde (MDA) levels were significantly increased. In postnatal day 18 pups (P18) AA levels decreased further in gulo ( −/− ) mice and oxidative stress was observed in the accompanying elevations in MDA in liver, and F 2-isoprostanes in cortex. Further, total glutathione levels were higher in gulo ( −/− ) mice in cortex, cerebellum and liver, indicating that a compensatory antioxidant system was activated. These data show a direct relationship between AA level and oxidative stress in the gulo ( −/− ) mice. They reinforce the critical role of ascorbic acid in preventing oxidative stress in the developing brain in animals that, like humans, cannot synthesize their own AA.