Call number: LD2668 .T4 1952 L48 / Master of Science

Includes 25 papers previously published in Journals / 114, 16 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Sc.)--University of Adelaide, Dept. of Biochemistry, 1975

Background: There has been a concern regarding the masking of vitamin B-12 deficiency in the post-fortification period (after January 1, 1998). Objective: The objective of this study was to investigate the potential masking of vitamin B-12 deficiency by comparing the proportion of individuals with low serum B-12 without macrocytosis between pre- and post-fortification periods using data from the National Health and Nutrition Examination Survey (NHANES). Methods: The study included 7242 individuals from NHANES III (pre-fortification group) and combined NHANES 1999-2000, 2001-2002, 2003-2004, 2005-2006 (post-fortification group). Vitamin B-12 deficiency and macrocytosis were defined as having <148 pmol/L of serum vitamin B-12 and mean corpuscular volume (MCV) of>98 fL, respectively. A multivariate logistic regression was performed to estimate the likelihood of being low serum B-12 without macrocytosis in the post-fortification period in relation to the pre-fortification period. Results: Between pre- and post-fortification periods, there was no significant difference in the proportion of individuals with low serum vitamin B-12 without macrocytosis. However, odds of having low serum vitamin B-12 without macrocytosis in the post fortification era increased in men (OR=2.65, 1.24-5.65), non-Hispanic blacks (OR=3.12, 1.04-9.35), Non-smokers (OR=4.63, 1.90-11.27), and those aged 55 and older (OR=2.183, 1.01-4.74) compared their respective counterparts in the pre-fortification period. Conclusions: No significant difference in the proportion of individuals with vitamin B-12 deficiency without macrocytosiss was seen between the pre and post-fortification periods suggesting no making of vitamin B-12 deficiency. In the post-fortification period, serum folate was found to be a predictor of the masking effect. The impact of increased folic acid intake in the post-fortification period needs to be evaluated on a periodic basis especially, in non-target population.

Three experiments were conducted to characterize the fate of B-vitamins in the gastrointestinal tract of dairy cows. Experiment 1 was undertaken to verify if differences among published studies could be explained by methods of collection and preparation of ruminal fluid, using four ruminally cannulated non-lactating Holstein cows. Acidification of fresh ruminal fluid, causing the lysis of bacterial cells, yielded higher B-vitamin concentrations than differential centrifugation, while the method of collection used did not have an important impact. Results suggested that most of the vitamins are present in the bacterial fractions, and that only limited amounts are present in the surrounding fluid. Experiment 2 looked at the vitamin concentrations in ruminal bacterial fractions and particle-free fluid as influenced by diet composition. Six lactating ruminally cannulated Holstein cows were used in a cross-over design, and the diets were formulated to have forage to concentrate ratios of 60:40 (high-forage) and 40:60 (low-forage). B-vitamins were present mainly in the bacterial fractions of the rumen, with greater effects of the forage to concentrate ratio on vitamin concentrations in the bacteria associated to the solid fraction than on those present in the liquid portion of the rumen. These results strongly suggested that ruminal B-vitamin synthesis is influenced by the forage to concentrate ratio. Experiment 3 investigated the fate of supplementary B-vitamins, using four cows equipped with cannulae in the rumen, the proximal duodenum and the distal ileum. Extensive losses of dietary supplements appeared prior to the duodenum for all vitamins, but intestinal disappearance rates of most vitamins were increased by supplementation.

Graduation date: 1936

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Thesis (D.Sc.) -- University of Adelaide, Dept. of Biochemistry, 1975. / Includes 25 papers previously published in Journals.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2006. / Härtill 4 uppsatser.

Zugl.: Göttingen, Univ., Diss., 2009

Thesis (Ph. D.)--University of Wisconsin--Madison, 1932. / Typescript. With this is bound: Lathyrism in the rat / by Beatrice J. Geiger, Harry Steenbock, and Helen T. Parsons. Reprinted from Journal of nutrition, vol. VI, no. 5 (Sep. 1933), p. 427-442. Includes bibliographical references.