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.     

肠功能障碍进展

随着对肠功能研究的不断深入,肠衰竭和肠功能障碍的内涵不断丰富。肠黏膜屏障功能的改变是肠功能障碍发生的关键因素之一。在临床上肠功能是判断危急重患者预后的重要指标,正确地预防和诊治肠功能障碍则对改善危急重患者的预后具有重要价值。     

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.     

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.     

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).     

Estimated radiation dose to breast feeding infant following maternal administration of 57Co labelled to vitamin B12

Administration of a radiopharmaceutical may result in a radiation dose to an infant due to ingestion of the radiopharmaceutical secreted in the breast milk. Following a maternal administration of Co labelled to vitamin B12 (cyanocobalamin) as part of a Schilling test an estimate of the absorbed dose to a breast feeding infant was calculated. Milk samples were collected from every feed in the first 24 h, and at approximately 48 and 72 h post-administration. The absorbed dose to the infant's liver (the organ receiving the highest dose) was calculated to be 0.23 mGy. The effective dose to the infant was calculated to be 0.025 mSv, which is considerably lower than the current regulatory limit of 1 mSv. The Administration of Radioactive Substances Advisory Committee advise that the first feed, at approximately 4 h after administration, be discarded. The data show that this was unwarranted, and that the peak concentration of Co in the breast milk occurred at around 24 h.     

MDCT findings of intestinal ischemia due to midgut torsion without small bowel obstruction in a 12-year-old boy

Intestinal ischemia in the pediatric age group is a rare occurrence. We describe a case of MDCT findings of ischemia due to midgut torsion without intestinal obstruction in a 12-year-old boy, successfully submitted to surgery without any intestinal resection required.     

高原汽车兵血清Hcy、叶酸和维生素B12的测定及相关性研究

目的 了解高原汽车兵血清同型半胱氨酸(Hcy)水平和营养状况,为合理补充营养提供依据.方法 采用S-腺苷酶法和酶促间接化学发光法,对36名在海拔3700 m以上高原生活9个月的汽车兵和40名在海拔1500 m平原生活的汽车兵进行了血清Hcy、叶酸和维生素B12含量的测定.结果 高原组血清Hcy含量明显高于平原组(P＜0.05),而血清叶酸和维生素B12的含量明显低于平原组(P＜0.05).结论 高原汽车兵血清Hcy明显偏高,营养不够合理,有必要进行营养干预.     

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.     

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。