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BACKGROUND The elderly population is particularly at risk for developing vitamin B12-deficiency. Serum cobalamin does not necessarily reflect a normal B12 status. The determination of methylmalonic acid is not available in all laboratories. Issues of sensitivity for holotranscobalamin and the low specificity of total homocysteine limit their utility. The aim of the present study is to establish...

Protein-mediated B12 uptake by isolated respiration. Following uptake, cyanorat liver mitochondria has been shown to cobalamin is converted to adenosyl and be enhanced by plasma transcobalamin methylcobalamins and released from the (TC-lI) but not by salivary R binder in mitochondria. TC-ll appears to be required vitro. The process is enhanced by calcium for both cellular and mitochondrial upta...

www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 979 manifestations (Table 1). It is a common cause of macrocytic (megaloblastic) anemia and, in advanced cases, pancytopenia. Neurologic sequelae from vitamin B12 deficiency include paresthesias, peripheral neuropathy, and demyelination of the corticospinal tract and dorsal columns (subacute combined systems V itamin B12 (cobalamin) plays an important ...

We present a case of a diver who suffered decompression sickness (DCS), but who also was a strict vegetarian for more than 10 years. He presented with symptoms of tingling of both feet and left hand, weakness in both legs and sensory deficits for vibration and propriocepsis after two deep dives with decompression. The initial clinical features of this case were most consistent with DCS, possibl...

Accumulation of methylmalonic acid may provide an early clue to deficiency of cobalamin (vitamin B12) in tissue. Metabolic abnormalities involving precursors of methylmalonic acid are frequently observed in patients with hepatic diseases. To establish whether methylmalonic acid accumulates and thereby gives false-positive test results for cobalamin deficiency, we measured the concentration of m...

The reactivity of the cobalt-carbon bond in cobalamins is the key to their chemical versatility, supporting both methyl transfer and isomerization reactions. During evolution of higher eukaryotes that utilize vitamin B12, the high reactivity of the cofactor coupled with its low abundance pressured development of an efficient system for uptake, assimilation, and delivery of the cofactor to clien...

BACKGROUND Measurement of serum cobalamin (Cbl) levels is the standard investigation for assessing vitamin B12 deficiency. Falsely increased values of Cbl can be caused by alcoholic liver disease. Measurement of total vitamin B12 serum levels might be misleading in alcoholics, because a tissue metabolic deficiency is possible even with normal serum Cbl levels. Holotranscobalamin (HoloTC), the C...

Background and Objectives: Micrograft transplantation is accompanied by a transient induction of telogen in transplanted hair follicles (HF), which might be avoided by supporting the metabolic pathways of the micrograft during the ex vivo period. Vitamin B12 (cobalamin) has been suggested to influence HF growth and cycling in humans, but the mechanisms are unclear. Method: HFs were obtained fro...

This review describes current knowledge of the main causes of vitamin B12 and folate deficiency. The most common explanations for poor vitamin B12 status are a low dietary intake of the vitamin (i.e., a low intake of animal-source foods) and malabsorption. Although it has long been known that strict vegetarians (vegans) are at risk for vitamin B12 deficiency, evidence now indicates that low int...