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Thesis (Ph. D.)--Columbia University, 1926. / Vita. eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--Columbia University, 1926. / Vita.

Vitamin A and its chemical analogues (retinoids) are known to play a role in the maintenance and differentiation of epithelial tissue. Retinoids have been shown to inhibit carcinogenesis in a number of tissues in experimental animals and to inhibit the growth of various untransformed and cancer cell lines in vitro. This study investigated the effect of retinyl acetate supplemented at concentrations of 1 μM, 5 μM, 10 μM and 100 μM to in vitro cultured untransformed LLCMK cells, and transformed BL-6 melanoma and human hepatoma cell lines. A small but non-significant effect of vitamin A addition on the growth of the untransformed cells was observed, while substantial inhibition of proliferation of the two tumour cell lines was found. At the cytotoxic level of 100 μM supplemented vitamin A, all three cell lines showed marked inhibition of growth. This led to an electron microscopy study to examine the ultrastructural effect of the vitamin A addition. At the low non-toxic levels of vitamin A addition (1 - 10 μM), no ultrastructural changes were observed in the untransformed cells. However, at a level of 5 μM and 10 μM vitamin A addition in the tumour cells, an increase in the size of suspected lipid droplets was observed. At the cytotoxic level of 100 μM supplemented vitamin A, large lipid droplets were very apparent, as was much cellular degeneration. This effect was more marked in the tumour cells than in the untransformed cells. The lipid nature of the droplets was confirmed by using the lipid stain, Sudan IV. In order to investigate the effect of added vitamin A at the cell surface level, an ELISA system was used to quantify the level of the cell surface glycoprotein, fibronectin, in the culture media. Vitamin A plays an important role in the production of mature fibronectin by participating in the glycosylation of the molecule. This study showed no major effect of added vitamin A on the release of fibronectin into the culture media. This did not, however, exclude the possibility that the vitamin A was involved in the production and enhanced binding of fibronectin to the cell surface, and was possibly also exerting an effect on the availability of fibronectin receptors. Further studies would, however, be required to substantiate such effects of vitamin A supplementation. No single mechanism of action of vitamin A on tumour cell growth inhibition was identified, but the possibility that at least two mechanisms exist, was suggested

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Background: Folate and cobalamin are essential cofactors for homocysteine (HCY) metabolism. Hyperhomocysteinemia, a multifactorial condition, may reflect B vitamin deficiency and is associated with increased risk of cardiovascular disease, thrombosis, and neurodegenerative and chronic gastrointestinal diseases in humans. Hyperhomocysteinemia has been reported in Greyhounds with suspected chronic enteropathy. Objectives: To evaluate the frequencies of and the association between hypofolatemia and hyperhomocysteinemia in Greyhounds. Animals: Data and serum samples from 559 Greyhounds. Methods: Nested case-control study. The frequency of hypofolatemia in Greyhounds was determined by a laboratory database search. The relationship between hyperhomocysteinemia (measured by gas chromatography-mass spectrometry) and hypocobalaminemia and hypofolatemia was evaluated, and its frequency compared between healthy Greyhounds and Greyhounds with thrombosis or chronic diarrhea. Results: Hypofolatemia was identified in 172 of 423 (41%) Greyhounds and was more common in hypo- than in normocobalaminemic dogs (49% vs. 35%; P = .0064). Hyperhomocysteinemia was detected in 53 of 78 (68%) of Greyhounds, being more common in hypo- than in normofolatemic dogs (88% vs. 59%; P = .0175). All healthy Greyhounds, 21 of 30 (70%) of dogs with chronic diarrhea and 6 of 8 (75%) of those with thrombosis, were hyperhomocysteinemic. Serum HCY concentrations were inversely correlated with serum folate concentration (q = -0.28; P = .0386) and were positively associated with serum albumin concentration (q = 0.66; P = .0022). Conclusions and Clinical Relevance: Hyperhomocysteinemia occurs frequently in the Greyhound population. Its association with hypofolatemia suggests decreased intracellular availability of B vitamins, but the functional implications warrant further investigation. Hyperhomocysteinemia in Greyhounds potentially may serve as a spontaneous canine model to further investigate hyperhomocysteinemia in humans.

Inaugural address delivered on 2 November 2011 / Marietjie Herselman was born in the Langkloof, where she matriculated at the McLachlan High School. She obtained a BSc (Physiology and Dietetics) degree at Stellenbosch University and for the next 18 years worked as a dietitian at Tygerberg Hospital, where she specialised in renal nutrition. She obtained a master’s degree in nutrition in 1985 and in 1991 was appointed as a lecturer in the Department of Human Nutrition, Faculty of Health Sciences, at Stellenbosch University. In the same year she obtained her PhD in nutritional sciences at this university, where she was later promoted to senior lecturer (1995), associate professor (2001) and full professor (2010). From 2008 to 2010 she was appointed first as acting head and later as head of the Division of Human Nutrition. She served on the Professional Board of Dietetics from 1998 to 2003 and also on various sub-committees of the Board. She regularly reviews papers and research applications for scientific councils/associations as well as five national and four international scientific journals. Currently, she serves on the editorial boards of four international scientific journals and in 2008 she was elected as the co-editor (Africa region) of the international journal Nutrition. She successfully delivered 17 master’s students and published 29 scientific papers in national and international journals and three chapters in textbooks. Marietjie also presented papers at 19 international and 37 national conferences. Three international and four national awards were bestowed on her for her research in renal nutrition. She played a leading role in the initiation of the Community Nutrition Security Project (CNSP) in the Breede Valley, as part of Stellenbosch University’s HOPE Project, as well as the NOMA master’s programme in Nutrition, Human Rights and Governance in collaboration with the universities of Oslo and Akershus (Norway) as well as Makerere and Kyambogo (Uganda).

Call number: LD2668 .T4 1965 R214 / Master of Science

The effect of dietary glycosylated vitamin B-6 on the bioavailability of vitamin B-6 was determined in 4 women. A 44-d metabolic-balance diet study was divided into a preliminary 8-d adjustment period followed by two 18-d experimental periods. The subjects were divided into two groups in a crossover design to compare the effect of low- and high-glycosylated vitamin B-6 diets on the bioavailability of vitamin B-6. The total vitamin B-6 content in the low- and high-glycosylated vitamin B-6 diets was 1.506 mg (8.91 nmol) and 1.897 mg (11.22 μmol), respectively, in which 11 and 22% was the glycosylated form, respectively. Daily 24-h urine specimens were collected by each subject throughout the study; 7- or 8-d fecal collections were made at the end of each experimental period. The four subjects' mean urinary total vitamin B-6 excretion during the low- and high-glycosylated vitamin B-6 periods was 0.76 ± 0.20 and 0.67 ± 0.06 μmol/24 h, respectively; fecal total vitamin B-6 excretion was 2.98 ± 0.43 and 4.56 ± 0.87 μmol/24 h, respectively. Expressed as % of total vitamin B-6 intake, the mean urinary total vitamin B-6 excretion was lower during the high-glycosylated vitamin B-6 period (6.0 ± 0.8%) than during the low-glycosylated vitamin B-6 period (8.5 ± 2.4%); in contrast, their mean fecal vitamin B-6 excretion during the high-glycosylated vitamin B-6 period (40.7 ± 8.2%) was greater than the low-glycosylated vitamin B-6 period (33.6 ± 5.4%). In addition, approximately 11% of ingested glycosylated vitamin B-6 was excreted in urine. These results suggest that dietary glycosylated vitamin B-6 is not completely bioavailable to humans, and the extent of its utilization is not affected by dietary glycosylated vitamin B-6 intake. / Graduation date: 1993