This thesis deals with growth and mainly harvest attributes of Cydonia oblonga. There was described history, morphological features, growing conditions, use and including substances characteristic for this fruit specie. On testing space of school agricultural entreprise in Žabčice was graded sortiment of these following 28 varieties:´Asenica´, ´Bereckého´, ´Blanar´, ´BO3´, ´Brna´, ´Buchlovice´, ´Doubravnická´, ´Hemus´ 1, 2, ´Hruškovitá´, ´Champion´, ´Ironda´, ´Izobiljana´, ´Jurák´, ´Juransa´, ´Kocúrova´, ´Leskovačka´, ´Mír´, ´Morava´, ´Muškátová´, ´Otličnica´, ´Pinter´, ´Pražská´, ´Selena´, ´Šuranská´, ´Triumph´, ´Ukrajinská´, ´Úspěch´, ´Vranja´. Found out was the volume of the crown, phenologic phase, total yield of fruit, average weight of fruit, average height and width of fruit, capacity of refractometrical dry matter, total capacity of dry matter and capacity of vitamin C.

Considerable interest exists with regard to the putative therapeutic role of ascorbic acid in various conditions. A condition which has received much attention is cancer, as it is reported that ascorbic acid may be a prophylactic against cancer development. However, the actual involvement of ascorbic acid, an oxidizing/reducing agent, in the development and progression of tumours is presently a subject of much speculation. This study initially addressed the effect of ascorbic acid supplementation over a nutritional concentration range (0 - 100 μg/ml) on the in vitro growth of non-malignant LLCMK and malignant B16 cells. Ascorbic acid supplementation of these two cell types resulted in an overall decrease in the growth of both types of cells. The actual inhibitory mechanism of ascorbic acid on cell growth was not clear. Further study attempted to define and explain a mechanism responsible for this effect. Ascorbic acid has a role in the maintenance of tissue integrity and host defences, thus providing a rational basis for examining its relationship to cancer. Ascorbic acid is lcnown to be essential for the structural integrity of the intercellular matrix of the cells, the latter being a complex aqueous gel containing, amongst other compounds, fats and prostaglandins. Fats and prostaglandins have diverse effects on. membrane stability, enzyme activity and secondary messengers within cells. Hence, this study investigated the effect of ascorbic acid supplementation on certain enzymes and secondary metabolites within the cells, which had the potential to be involved in the control of cell growth. Throughout this study, emphasis was placed on the Bl6 melanoma cells as ascorbic acid supplementation did not significantly affect levels of secondary metabolites within the non-malignant LLCMK cells. Ascorbic acid supplementation of the B16 cells resulted in significant increases in adenylate cyclase activity and cyclic adenosine monophosphate levels, witb a significant decrease in Bl6 cell growth in that particular experiment. As cyclic adenosine monophosphate has a regulatory role in the cell cycle, this study suggested that the inhibitory effect of ascorbic acid supplementation on cell growth was mediated tbrough a final effect provided by the second messenger, cyclic adenosine monophosphate. However, clarification of tbe mechanism of tbe effect of ascorbic acid on adenylate cyclase activity was required. Hence, a further study investigated prostaglandin E₂ levels, as tbese affect adenylate cyclase activity. Prostaglandin E₂ levels were also found to be inversely related to Bl6 cell growth with ascorbic acid supplementation. It thus appeared tbat adenylate cyclase activity was dependent on prostaglandin E₂ levels in the B16 cells, and further study showed that tbis was indeed the case. Here, higher levels of prostaglandin E₂ supplementation of the Bl6 cells inhibited cell growth significantly and also significantly increased adenylate cyclase activity. Arachidonic acid is the precursor of prostaglandin E₂. In the presence of ascorbic acid supplementation, the percentage arachidonic acid composition of the Bl6 cells was inversely correlated with cell growth. Hence, prostaglandin E₂ levels in ascorbic acid supplemented B16 cells appeared dependent on tbe amount of precursor present. This was confirmed when Bl6 cells were supplemented with arachidonic acid. The latter had an inhibitory effect on Bl6 cell growth and also stimulated prostaglandin E₂ production. The cause of tbe inverse relationship between B16 cell growth and arachidonic acid composition with ascorbic acid supplementation was furtber investigated and found to be dependent on tbe uptake of arachidonic acid and other essential fatty acids from tbe medium. The enzymes phospholipase A₂ delta-5 and delta-6-desaturase, and elongase which could influence arachidonic acid levels were not affected to any extent by ascorbic acid supplementation and therefore did not influence the inverse relationship between B16 cell growth and arachidonic acid. Hence, it can be concluded that the effect of ascorbic acid supplementation on the BI6 cells is mediated, in part at least, by cyclic adenosine monophosphate. However, this is not the result of a direct effect of ascorbic acid supplementation. The initial effect of ascorbic acid supplementation concerns fatty acid - in particular arachidonic acid - uptake from the medium, with subsequent cascade effects On secondary metabolites, ultimately affecting the cellular levels of cyclic adenosine monophosphate.

The fleshy hips of the briar rose, Rosa rugosa were cultured on a modified medium developed by Gamborg (1963) to produce callus and suspension cultures. These cells were very light, almost white. Reduced ascorbic acid, determined by the 2,6-dichlorophenolindophenol titration method, was found in the suspension cultures. This finding prompted an investigation into culture techniques for obtaining an optimum concentration of ascorbic acid. During the growth of the cells, the pH rose and ascorbic acid concentration increased after the sixth day. Age of culture was also an important factor as cultures older than three or four weeks contained virtually no ascorbic acid. Possible precursors of ascorbic acid in plants were added to cultures and their effect on the ascorbic acid level was determined over a period of twenty-four hours. D-glucose, D-(-)-levulose, D-galactose and D-glucurono-ɣ-lactone caused no increase. L-gulono-ɣ-lactone brought about a slight increase and a comparatively large increase was obtained with L-galactono-ɣ-lactone. Confirmation for the latter was obtained using the 2,4-dinitrophenylhydrazine method to rule out the possibility or microbial contamination and to be sure that another metabolite was not responsible for the increased reducing capacity of the system. Omission of myoinositol from the vitamin solution of the medium decreased total cell yield but had no effect on the level of ascorbic acid. Decreasing the sucrose content of the medium by one-half caused a sharp decrease in ascorbic acid concentration, indicating that an adequate supply of sugar is a prerequisite for optimum production of ascorbic acid. Growing liquid suspensions under controlled illumination resulted in increased ascorbic acid values with each successive transfer; however, total cell yields decreased each time. In addition, there was no evidence of chlorophyll production in the cultures. This exploratory work shows that ascorbic acid is present in the tissue culture of Rosa rugosa. Therefore, tissue culture may be useful for elucidating the complete pathway for ascorbic acid production which is as yet still unclear. This information coupled with the effects of altering the physical environment of the cells may direct cultures of Rosa rugosa to produce ascorbic acid in quantities that would make its recovery industrially attractive. / Land and Food Systems, Faculty of / Graduate

Several short-term assays are in use to assess the carcinogenic hazard of chemicals. While the ability to induce initiating events that may lead to carcinogenesis is measured, compounds and conditions that might modify the ability of chemicals to cause those initiating events are not assessed by such tests. In addition, compounds that affect the ability of cells to react in a normal fashion to the damaging action of carcinogens are not detected by these methods. Shifts in alkaline sucrose gradient profiles of centrifuged DNA (as an indication of DNA fragmentation) and formation of aryl and alkyl DNA adducts (as an indication of DNA modification) have been used as short-term assays for carcinogenic and mutagenic potential. Repair of DNA damage has been measured by restoration of near-control sedimentation profiles of DNA and the loss of aryl and alkyl adducts over time after damage or modification of DNA by carcinogens and mutagens. In this study, the ability of sodium ascorbate to modify the DNA fragmenting and adduct-forming action of the carcinogens N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and benzo(a)pyrene (BP) was investigated. In addition, the ability of cells In vivo and In vitro to repair DNA in the presence of sodium ascorbate was assessed by the two methods described above. It was found that sodium ascorbate inhibited repair in vivo and in vitro. In addition, sodium ascorbate was found to fragment DNA in vivo and in vitro in the presence of copper, and to inhibit the action of carcinogens _in vivo and in vitro by nucleophilic scavenging of electrophilic carcinogens. Sodium ascorbate was also found to inhibit the binding of BP to DNA jLn vivo and In vitro. On the other hand, other reducing agents had other effects. Propyl gallate (a sulphydryl reducing compound) inhibited binding of BP to DNA in vitro, but enhanced binding of BP to DNA in vivo. The sulphydryl reducing agent glutathione enhanced binding of BP to DNA in vivo and in vitro. Alkaline sucrose gradient analysis of DNA damage and recovery from that damage, and BP adduct formation in DNA and disappearance over time, appear to be suitable methods for assessment of the modifying properties of compounds and conditions on the initiating events that may lead to mutation or carcinogenesis. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

The general food supply is usually the source of vitamin C for many people, and since squash is a common food in the popular diets of Texans and is so generally grown over the state, this study has a two-fold purpose: (1) to ascertain the amount of vitamin C in the two varieties of squash most commonly used as food in Texas, and (2) to determine the effect of various methods of cooking upon the vitamin C content of these two varieties of squash.

The purpose of this study is to determine the reduced and dehydroascorbic acid of certain frozen fruits prepared with and without ascorbic acid as an antioxidant.

The aim of this thesis was in cooperation with commercial grower to evaluate the experiment with available varieties of chilli peppers from the perspektive of yield and growth. Furthermore, to analyze selected substances and the results obtained statistically process, evaluate and determine the differences between the different varieties of chilli peppers. Chilli peppers have quickly become a popular crop, especially due to their pungency and high vitamin C content. Pungency is due to the presence of capsaicin, whose content can reach up to 2 200 000 SHU. From chilli peppers you can prepare a wide range of products from jams to sweets to drinks. Chilli peppers are very perspective species, especially in the pharmaceutical industry.

This diploma thesis deals with monitoring changes in vitamin C content in food supplements due to storage conditions. Changes were observed for two types of effervescent tablets with different vitamin C content (40 mg and 500 mg). Each type was packed into a tablet tub with different caps - molecular sieve, silica gel, and only the cap itself. The analysis was carried out immediately after the production and subsequently after 3 months. The vitamin C content was determined by titration and high-performance liquid chromatography. Based on the measurements, it was found that the storage time after 3 months and the type of cap did not have a significant effect on the vitamin C content of the effervescent tablets. Differences may occur due to imperfect homogenization and degradation of vitamin C in daylight. During the supplementary evaluation the solubility time, flavour and colour were determined by dissolving effervescent tablets. As a result of supplementary evaluation all the effervescent tablets, both in the first and second assessments, exhibited the properties declared by the producer.

The role of ascorbic acid with regard to lipid peroxidation and aging has been examined. A thorough literature analysis indicates that free radical-induced lipid peroxidation is a plausible biochemical explanation for aging. Lipid peroxidation causes cellular damage due to altered enzyme activities, error-prone nucleic acid metabolism, and membrane dysfunction, as well as the accumulation of aging pigments in the lysomes. Ascorbic acid, a water soluble free radical quencher, was examined with regard to carbon tetra-chloride-induced lipid peroxidation and in vivo aging. Carbon tetrachloride, a well-known free radical inducer, caused marked increases in the ration of oxidized/reduced vitamin C only in the organs which metabolize carbon tetrachloride to the free radical form. Vitamin C treatment, 250 mg% in the drinking water, reduced the extent of carbon tetrachloride=induced lipid peroxidation. Aging is associated with marked increases in the ration of oxidized/reduced vitamin C in all organs examined with the exception of thymus. In organs exposed to high oxygen tensions, or in those exposed to high levels of free radicals, the ration of oxidized/reduced vitamin C exceeded the in vitro ration, indicating extensive lipid peroxidation. Vitamin C treatment reduced the extent of lipid peroxidation in vivo as determined by the ratio of oxidized/reduced vitamin C.

Hemorrhagic Enteritis (HE) vaccine is perhaps the most commonly used vaccine in the turkey industry. Although it provides protection against clinical disease, the vaccine is still thought to produce transient immunosuppression. In the field, HE still remains a significant concern for turkey producers. Research conducted over the years has shown that management stressors such as movement of turkeys from brooding to finishing environments and the timing of these stressors may influence the short-term response to vaccination. Strategic stress application may be of benefit in the optimization of protective responses and the development of vaccination protocols without detrimental effects on performance. Ascorbic acid may also have important implications on social stress and may play a role in immunity and response to HE vaccination in turkeys. Trials were conducted to examine the interrelationship among social stress, nutrition (vitamin C), immunity and their influence on response to hemorrhagic enteritis virus (HEV) vaccination. Stress is unavoidable, however if it is managed properly, it can be beneficial. In this dissertation, it was first demonstrated that stress in the form of social disruption can have negative physiological and immunological effects on turkey poults and that these effects can be alleviated with the addition of 300mg/kg vitamin C to the diet. Secondly, it was also demonstrated that when stress is applied on the day of vaccination, response to HEV vaccination can be improved. Thirdly, vitamin C supplementation at 300mg/kg can improve responses to HEV vaccination. However, it was concluded that vitamin C supplementation during periods of simultaneous stress application and vaccination does not provide benefit to response to vaccination. / Ph. D.