No description available.

No description available.

No description available.

M.S.

Various aspects of the ascorbic acid (vitamin C) nutrition of Oreochromis niloticus and O. mossambicus are considered in this treatise. The activity of L-gulono-Y-lactone oxidase was assessed in liver and kidney of 14 teleosts of 3 genera, histochemically (qualitatively) and biochemically (quantitatively). Activity of this enzyme was only detected in liver and kidney of common carp, Cyprinus carpio, and kidney of O. spilurus and O. aureus. No activity was detected in the species considered herein. The quantitative dietary ascorbic acid requirements of juvenile O. niloticus and O. mossambicus were determined by feeding diets containing graded levels of the vitamin (O~400mg/lOOg) and were based on growth response, food utilization, gross body composition data, tissue and biochemical changes and ability to prevent signs of ascorbic acid deficiency. The recommended level of supplementation of dietary ascorbic acid is l2Smg/lOOg and the net requirement 42mg/lOOg diet. Long-term ascorbic acid deprivation in £. niloticus and O. mossambicus resulted in poor performance in terms of growth, food utilization and survival. Other parameters evaluated included hepatosomatic index, liver and muscle glycogen content, blood parameters, tissue ascorbate concentrations, collagen contents, hydroxyproline and proline contents, and serum transaminase and cholesterol levels. Signs of ascorbic acid deficiency were severe and included haemorrhage~ opercular deformity, tail erosion, exophthalmia, cataract and spinal deformity (lordosis and scoliosis). Histologically scorbutic fish showed evidence of generalized bone changes associated with excessive production of chondrocytes and failur~ of ossification of growing bone areas. Eye lesions were associated with scleral collapse and also observed was hyperplasia of gill secondary lamellae epithelial cells and pronounced steatitis. Tissue ascorbate concentrations were correlated with dietary ascorbic acid levels and both species exhibited highest concentrations in the ovary, brain and testis, followed by heart, liver, gut, gills, eyes and the lowest levels in muscle and gall-bladder. The physiological role for ascorbic acid in each tissue is discussed. Eight week growth studies were conducted to evaluate the utilization of L-ascorbic acid (AA), the sodium salt of L-ascorbic acid (NaAA), glyceride coated L-ascorbic acid (GCAA), the barium salt of L-ascorbic acid 2-sulphate (AA2S) and ascorbyl palmitate CAP) in diets for O. niloticus and O. mossambicus, All five forms were added to the basal diet, containing no ascorbic acid CAAF), on an equimolar basis to supply 12Smg ascorbic acid/IOOg diet. All forms performed well in terms of growth, food utilization, and prevented signs of deficiency, Retention of ascorbic acid in diets after processing was increased by increasing dietary ascorbic acid level. AA2S and GCAA were more stable than AA and NaAA during processing and storage. The stability of AA, NaAA, GCAA and AA2S under different storage conditions was in descending order as follows: Freezer (_20°C), Fridge (S-BoC), room temperature in black bags (22-24°C) and room temperature in clear bags (22-24°C). Leaching of dietary ascorbic acid increased with increasing immersion time and water temperature. Stability and price of each form evaluated suggested that GCAA is to be preferred for use in fish feeds. The antioxidant effects of ascorbic acid were investigated. The results showed that ascorbic acid was not as effective as butylated hydroxy toluene (BHT) in preventing in vitro oxidation. An experiment was conducted to compare the performance of a commercial trout diet with the same diet supplemented to a level of l2Smg ascorbic acid/lOOg diet (Diet 2) when fed to O. niloticus. Fish fed the supplemented diet performed significantly better in terms of growth and food utilization concomittant with significantly increased tissue ascorbate concentrations. Sex differences in relation to dietary ascorbic acid nutrition were investigated. Females of both species exhibited significantly higher gonado~ and hepatosomatic indices than males. Females in both species eXhibited higher total ascorbate concentrations in gonad, gills, spleen, brain and blood than males whereas the reverse was true for the eyes. Dehydroascorbic acid (DHAA) levels were very low in tissues of both species. Ascorbic acid depleted O. niloticus fingerlings were fed on each of three diets providing nil, adequate Cl2Smg ascorbic acid/lOOg diet), and luxus (400mg/lOOg diet) of the vitamin after small surgical incisions had been made in dorsolateral musclature. Fish from each group were sampled regularly over 16 days and histological evaluation of the lesion area carried out as well as measurement of the tissue ascorbate levels. Epithelial elements of the healing process developed irrespective of the vitamin level but although fibroblast activity was marked in all three groups, collagenisation was very much slower in the deficient group, and in these the lesion was not mature, even at the termination of the experiment. The role of ascorbic acid in reproduction of tilapias was investigated in three experiments. The first showed that ascorbic acid supplementation of broodstock feed improved both hatchability and fry condition. In the second experiment fry produced from fish fed an unsupplemented diet and subsequently fed the same diet performed poorly in respect of growth and food utilization. Fry produced from broodstock fed the supplemented diet and subsequently fed the unsupplemented diet performed better than the previous group. This indicates transfer of ascorbic acid from the ovary to the eggs thence to the fry providing some protection against ascorbic acid deficiency during the early stages of life.

Vitamin C är en populär ingrediens i hudvårdsprodukter, bland annat på grund av dess positiva effekter på kollagen-produktionen i huden och dess antioxidativa egenskaper. Dessvärre är vitamin C en känslig ingrediens som lätt bryts ned av ljus, syre, hög temperatur eller fel pH-värde. I dagsläget finns inga regleringar för kontroll av nedbrytning av aktiva ingredienser i kosmetiska produkter.  I den här studien har en metod utvecklats med omvänd-fas högupplösande vätskekromatografi (RP-HPLC) och detektor med ultraviolett (UV) ljus för att analysera halten C-vitamin i en kosmetisk testprodukt, hädanefter kallad OTP och en modifierad variant av denna, kallad MTP. En stabilitetstudie gjordes vid olika temperaturer och ljusförhållanden på dessa produkter. En jämförelse gjordes även mellan en högre och lägre syretillgång. I metoden som valdes för stabilitetsanalys använde UV-detektor (254 nm). Den kromatografiska kolonnen innehöll C-18-stationärfasoch hade en längd om - 250x4.6 mm, med 5 µm partikelstorlek, från Chrompack. Mobilfasen bestod av 20 mM lösning av ättiksyra i Milli Q-vatten och metanol i förhållandet 95:5 (v/v) och mobilfashastigheten 2 ml/min, vilket gav en retentionstid på ca 2.4 min för vitamin C. I MTP bröts vitamin C ned snabbare än i OTP. Den lägsta nedbrytningshastigheten kunde ses vid den lägsta temperaturen (4℃) och den lägre syretillgången av dem som studerades. Ett linjärt samband kunde ses mellan förvaringstiden och koncentrationen av vitamin C som fanns kvar i produkten vid detta förvaringsförhållande. / Vitamin C is a popular ingredient in skin care products, due to its positive effect on the collagen production and its antioxidative characteristics. Unfortunately, vitamin C is a sensitive ingredient that is easily degraded by light, oxygen, elevated temperatures, or the wrong pH-value. To today’s date, there are no regulations controlling the degradation of active ingredients in cosmetic products.  In this study, a method has been developed for Reversed Phase-Liquid Chromatography (RP-HPLC) and Ultra Violet (UV)-light detector to analyze the vitamin C content in a cosmetic test product, in this study called OTP and a modified variant of the same product, called MTP. A stability study was made at different temperatures and light conditions. A comparison was also made between higher or lower levels of oxygen present. The method chosen was performed at a wavelength of 254 nm. The column used contained a C-18 stationary phase (250x4.6 mm, 5 µm particle size) from Crompack. The mobile phase consisted of 20mM solution of acetic acid in Milli Q water and methanol 95:5 (v/v) and the flow rate was set to 2 ml/min, which gave a retention time of approximately 2.4 min for vitamin C. Vitamin C was degraded faster in MTP than in OTP. The lowest degradation rate was found at the lowest temperature (4℃) and the lower oxygen content among the ones studied. A linear relationship was found between storage time and the vitamin C concentration left in the product at this storage condition.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

LD2668 .T4 1946 W3 / Master of Science

Call number: LD2668 .T4 1953 R62 / Master of Science

published_or_final_version / Biochemistry / Master / Master of Philosophy