Hen egg riboflavin binding protein (RfBP) acts as a source of riboflavin to the developing embryo. It is the most abundant vitamin binding protein in the egg white. Mutations giving rise to a lack of RfBP lead to embryo death at approximately 13 days. RfBP binds riboflavin tightly in a 1:1 ratio. On formation of this complex, the fluorescence of riboflavin is completely quenched; this quenching is thought to be due to the stacking of aromatic groups within the hydrophobic binding pocket. This quenching provides a convenient assay for the integrity of the riboflavin-binding site of the protein. RfBP consists of a single polypeptide chain of 219 amino acids of molecular mass 29.2 kDa. RfBP undergoes a number of post-translational modifications, namely: the formation of nine disulphide bonds, extensive glycosylation on Asn 36 and Asn 147, and the phosphorylation of eight serine side chains from between Ser 186 and Ser 197. The unfolding and refolding of RfBP was studied by denaturing in 6M guanidium chloride, followed by dilution in buffer, to start refolding. The processes were followed by both steady-state and stopped-flow circular dichroism and fluorescence spectroscopy. RfBP was found to readily unfold and refold, provided the disulphide bonds were intact. The regain of secondary structure was found to be too rapid to measure by the methods available (<12msec). The regain of tertiary structure was found to consist of 4 main phases, and a large proportion (80%) of the tertiary structure formed within 2 msec. The regain of riboflavin binding ability was complete at the end of the second phase, a reaction with a half-life of around 30 msec. In the presence and absence of riboflavin, the kinetics for the first 3 stages of tertiary structure changes seemed to be identical. In the presence of riboflavin, however, seemed to impede the completion of the final, very slow stage, with the refolding reaction only going to 95% completion. The dephosphorylation of the protein seemed to have no affect on this process. When the 9 disulphide bonds are reduced however, RfBP is unable to spontaneously reoxidise to a native-like state in the presence of an oxidised/reduced glutathione redox system. However, the addition of protein disulphide isomerase to the system increases significantly the yield of successfully reoxidised RfBP to about 50%. Attempts to prepare deglycosylated RfBP by chemical methods were unsuccessful since the treatment led to fragmentation of the polypeptide chain.

B vitamins are of interest in preventative and protective strategies in cardiovascular disease. However, the safety and efficacy of B vitamins has been questioned. Previous research from this group has demonstrated that B6 supplementation alone or in combination with folic acid and B12 reduces angiogenic response. This study determined the effect of vitamin B6 deficiency on the angiogenic response after ischemia in vivo and in vitro using a rodent model. Results indicated that vitamin B6 deficiency enhanced the early angiogenic response by increasing blood flow in vivo after an ischemic event. In vitro measurements demonstrated that vitamin B6 deficiency influenced endothelial progenitor cell (EPC) function and angiogenic growth factor release early after ischemia. In conclusion, B6 deficiency appears to have a modest effect on increasing blood flow and angiogenic markers after ischemia. Additional research is needed to further characterize the impact of lowered vitamin B6 on angiogenesis and its mechanisms.

B vitamins are of interest in preventative and protective strategies in cardiovascular disease. However, the safety and efficacy of B vitamins has been questioned. Previous research from this group has demonstrated that B6 supplementation alone or in combination with folic acid and B12 reduces angiogenic response. This study determined the effect of vitamin B6 deficiency on the angiogenic response after ischemia in vivo and in vitro using a rodent model. Results indicated that vitamin B6 deficiency enhanced the early angiogenic response by increasing blood flow in vivo after an ischemic event. In vitro measurements demonstrated that vitamin B6 deficiency influenced endothelial progenitor cell (EPC) function and angiogenic growth factor release early after ischemia. In conclusion, B6 deficiency appears to have a modest effect on increasing blood flow and angiogenic markers after ischemia. Additional research is needed to further characterize the impact of lowered vitamin B6 on angiogenesis and its mechanisms.

No description available.

No description available.

The concentration of ascorbic acid in the plasma was determined on four levels of ascorbic acid intake for seven day periods in 1946-47 and on three levels of ascorbic acid intake for ten day periods in 1947-48. The subjects, eight girls and eight boys, were 16 to 19 year old freshman students at Oregon State College. All of the food eaten by the subjects during the experimental periods was weighed and the quantities were recorded. The reduced ascorbic acid in the foods was determined after each meal by the method of Loeffler and Ponting (1942) and daily fasting plasma ascorbic acid values were determined by the micro-method of Farmer and Abt (1936). The data in this study were analyzed statistically by testing the significance of the differences between the means and by analysis of variance. The recommended allowance of the National Research Council (1945) for these subjects (80 mg for the girls and 100 mg for the boys) did not maintain mean plasma values as high as their respective means during the saturation period when they were receiving 200 mg of crystalline ascorbic acid in addition to the ascorbic acid from their food. On the recommended allowance all the mean plasma values for the girls were above 0.80 mg per cent, ranging from 0.83 to 1.07. The boys values ranged from 0.67 to 0.91 mg per cent; two out of seven values were below 0.80 mg per cent (data for one boy were excluded due to illness). A decrease in ascorbic acid intake to 10 mg less than the recommended allowance of the National Research Council made a statistically significant decrease in the plasma ascorbic acid concentration for only two of the eight girls and for one of the seven boys. The plasma ascorbic acid concentrations of these subjects showed individual variation even when the ascorbic acid intake was considered on the basis of mg of ascorbic acid per kg of body weight. The ten day experimental periods were more desirable than the periods of one week. This was particularly true for the saturation period when some of the subjects had been on diets low in ascorbic acid prior to the study. / Graduation date: 1949

Graduation date: 1943

Graduation date: 1944

Graduation date: 1945

Graduation date: 1980