The influence of serum folate on urinary excretion of vitamin B12

It was found that in patients with decreased serum folate concentration, urinary excretion of vitamin B₁₂ was increased in a statistically highly significant way with both oral administration of ⁵⁸Co-labeled vitamin B₁₂ and with a ⁵⁷Co-labeled vitamin B₁₂ intrinsic factor complex. This increased vitamin B₁₂ excretion may account for some false normal Schilling test results.Furthermore, in folate deficiency, the intrinsic factor no longer seems required for vitamin B₁₂ to pass the intestinal wall. It is also questionable whether vitamin B₁₂ absorbed through the intestine under these circumstances could be properly metabolized.Besides statistical evidence, some clinical support for this theory is presented. These findings offer a possible clue for some literature reports that have lacked a satisfactory explanation.     

Effect of physical activity on levels of homocysteine,folate, and vitamin B12 in the elderly

Objectives: Homocysteine (Hcy) has emerged as a risk factor for cardiovascular diseases (CVD). However the relationship of physical activity (PA) with Hcy levels in the elderly is controversial. Accordingly, the current study examined the effect of low and high participation in PA on serum Hcy in young (n = 77; 18–50 years) and old (n = 207; > 65 years) males (n = 141) and females (n = 142). Methods: Level of PA was obtained in a 1-to-1 interview and participants divided into low and high groups. Serum Hcy, folate, and vitamin B₁₂ were obtained after 12 hour fast drawn by venipuncture. Results: Levels of Hcy correlated with folate (r = ?0. 5; p = 0.000) and vitamin B₁₂ (r = ?0.3; p = 0.000). The ANOVA revealed a main effect of PA for Hcy (p = 0.04) but not for folate (p = 0.2) and vitamin B₁₂ (p = 0.2). Main effects were found also of age for Hcy (p = 0.000) and folate (p = 0.005) as well as of gender for Hcy (p = 0.000) and vitamin B₁₂ (p = 0.000). Subsequent ANCOVA showed lower levels of Hcy in the participants with greater versus lower PA even after controlling for B₁₂ vitamin. Conclusion: These results confirm the importance of the vitamins for regulating Hcy levels. Additionally, the data suggests that PA affects Hcy levels without affecting and independent of B vitamins in the elderly.     

Intrathoracic extramedullary hematopoiesis secondary to B12 and folate deficiency: CT appearance

Intrathoracic extramedullary hematopoiesis is an unusual condition, usually associated with congenital hemolytic anemias. We present a rare case due to vitamin B12 and folate deficiency diagnosed by CT-guided biopsy.     

A racial difference in serum vitamin B12 levels

Measurements of the serum Vitamin B12 concentrations of 49 black and 49 white healthy adults demonstrate a significantly higher mean serum Vitamin B12 level in blacks when compared to whites (p less than 0.001). The reason for this difference appears to be genetic, although environmental factors may also be involved. It is suggested that clinical laboratories should establish their own separate reference values of serum Vitamin B12 for blacks and whites in order to prevent misinterpretation of test results.     

Comparison of toadfish-serum competitive binding and microbiologic assays of vitamin B12

Toadfish serum (TFS) offers several advantages over other proteins as the binder in a competitive-binding assay for vitamin B12. It is unaffected by pH changes in the range 5.6-9.4 or by the addition of human serum albumin. Prolonged incubation with charcoal does not disrupt the TFS-cyanocobalamin bond, and the addition of albumin as a protein source in the standard tubes was proven unnecessary. The binding capacity of TFS does not increase significantly with increasing concentrations of cyanocobalamin as does the binding capacity of intrinsic factor, normal serum, or transcobalamin I. A single extract was prepared from each of 44 sera and measured for vitamin B12 content simultaneously by the TFS assay and the conventional microbiologic method using Lactobacillus leichmannii. The values obtained with TFS were in each instance higher than those obtained by the microbiologic assay (p less than 0.001).     

放射性标记的维生素B12及其衍生物在肿瘤诊治中的应用进展

综述了基于维生素B12及其衍生物的放射性标记化合物的研究与临床试验情况,并着重介绍维生素B12的生物活性和放射性核素111In,10B,99Tcm(Re)标记的衍生物及其在肿瘤诊治方面的应用。     

Gastric emptying in patients with vitamin B(12) deficiency

The clinical presentation of patients with vitamin B(12) deficiency varies in a spectrum ranging from haematological disorders to neuropsychiatric diseases. In rare cases, orthostatic hypotension, impotence, constipation and urinary retention have been attributed to autonomic nervous system dysfunction due to vitamin B(12) deficiency. The aim of this study was to evaluate the effect of vitamin B(12) deficiency on autonomic nervous system function by studying gastric emptying times ( T(1/2)). Twenty patients with newly diagnosed vitamin B(12) deficiency and 12 control patients with gastritis and normal vitamin B(12) levels were enrolled in this study. Gastroduodenoscopy, endoscopic biopsy, histopathological evaluation of the biopsy specimens and radionuclide gastric emptying studies were performed. After vitamin B(12) replacement therapy for 3 months, radionuclide gastric emptying studies were repeated. Mean gastric emptying T(1/2) in patients before and after treatment and in controls were 103.83+/-48.80 min, 90.00+/-17.29 min and 74.55+/-8.52 min, respectively. The difference in mean gastric emptying T(1/2) between patients before treatment and controls was statistically significant ( P<0.01). The statistically significant difference persisted after vitamin B(12) treatment ( P<0.05), though mean gastric emptying T(1/2) was somewhat shorter. There were no positive or negative correlations between gastric emptying T(1/2) and the following parameters: haemoglobin, vitamin B(12) level and Helicobacter pylori positivity. In conclusion, gastric emptying T(1/2) was prolonged in patients with vitamin B(12) deficiency and this prolongation was not corrected after vitamin B(12) replacement therapy. Although autonomic nervous system dysfunction due to vitamin B(12) deficiency rarely gives rise to clinical manifestations, latent dysfunction demonstrated by laboratory tests seems to be a frequent phenomenon. The level of vitamin B(12) does not correlate with the degree of autonomic nervous system dysfunction measured by radionuclide gastric emptying studies.     

Diffusion tensor tractography and neuropsychological assessment in patients with vitamin B12 deficiency

Introduction

Structural imaging of the brain does not demonstrate any changes in a vast majority of patients with vitamin B12 deficiency, even in advanced stages. In this study, we aimed to assess and correlate the functional integrity of the brain fiber tracts using diffusion tensor tractography with neuropsychological examination in patients with vitamin B12 deficiency.

Methods

The study was conducted at two tertiary care centers. Thirty-two patients with vitamin B12 deficiency were enrolled and subjected to diffusion tensor tractography, as an extension of diffusion tensor imaging, and neuropsychological assessment. Tests of significance were done to detect changes, pre- and post-vitamin B12 supplementation in the diffusivity parameters (fractional anisotropy and mean diffusivity) and the neuropsychological test scores.

Results

Statistically significant changes were observed in the diffusivity parameters and the neuropsychological test scores between the controls and the patients with vitamin B12deficiency in the pre- and post-treatment phases.

Conclusions

This is the first study to evaluate the diffusion tensor tractography (DTT) parameters in the light of clinical neuropsychological assessment in patients with vitamin B12 deficiency. Utilization of DTT parameters may antedate structural changes and may quantify the neurocognitive deficits.     

Measurement of total-body cobalt-57 vitamin B12 absorption with a gamma camera

Previously described techniques for the measurement of the absorption of [57Co]vitamin B12 by total-body counting have required an iron room equipped with scanning or multiple detectors. The present study uses simplifying modifications which make the technique more available and include the use of static geometry, the measurement of body thickness to correct for attenuation, a simple formula to convert the capsule-in-air count to a 100% absorption count, and finally the use of an adequately shielded gamma camera obviating the need of an iron room.