Intestinal absorption of protein-bound vitamin B12 in the malabsorption syndrome

Summary The absorption of free and I.F.-bound B₁₂ has been studied in 14 cases with intestinal malabsorption (Table 6). Eight had a normal absorption of free B₁₂, but in all of these the absorption of intrinsic factor-bound B₁₂ was subnormal. This finding may be diagnostically useful. The absorption of liver-bound vitamin B₁₂ in cases with the malabsorption syndrome was also lower than that of free B₁₂. This is contrary to earlier findings in controls and in cases of pernicious anemia.The fact that B₁₂-protein complexes are split into dialyzable molecules, either in the intestinal lumen or in the intestinal wall, before absorption, could explain why defective intralumenal digestion or defective intestinal-wall function could prevent absorption of bound B₁₂.The work reported here was supported by Ekhaga Foundation. Stockholm, Sweden, and Merck & Co., Inc., Rahway, N. J.     

Carcinogenicity of radiation doses caused by the Chernobyl fall-out in Sweden, and prevention of possible tumors

The fallout from the Chernobyl reactor resulted in radioactive fall-out in eastern Sweden leading to a ground radiation intensity of between 2 and 500 microR h-1 above the 10-15 microR h-1 background, an average external cumulative dose of about 3-4 mSv (0.3-0.4 rem) to about 1 million people, or about 3500 man-Sv (350,000 man-rem) over 50 years, or 70 man-Sv per year with a maximum dose to a few individuals of 40 mSv. The corresponding figures reported for civilians around Chernobyl is 8.6 million man-rem in 1986 and 29 million man-rem over 50 years, or 600,000 man-rem (equivalent to about 6000 man-Sv) per year. If Swedish doses are averaged over the whole population, the average is about 1 mSv or 10,000 man-Sv, or 200 man-Sv per year. The thyroid uptake of 131I is approximately 0.1-0.2 kBq (0.005 microCi) and the total body uptake of 137Cs, 1 kBq (0.03 microCi), resulting in an approximate internal dose of 0.02 mSv. If a linear dose-response curve is assumed, an increase of the normal cancer mortality incidence in the million Swedes affected by 3500 man-Sv per 50 years from 200,000 to about 200,070 can be assumed. Corresponding figures for all of Sweden are 8,000,000 inhabitants, 7000 man-Sv, 1,720,000 normal cancer deaths, and 1,720,140 expected cancer deaths. Corresponding figures reported for the population outside the 30 km evacuation zone around Chernobyl are 300,000 man-Sv, and an increase from 6,800,000 cancer deaths per 50 years to 6,806,000 cancer deaths.     

Adriamycin, vincristine, cyclophosphamide and 5-fluorouracil (AVCF) compared with cyclophosphamide, methotrexate and 5-fluorouracil (CMF) in premenopausal breast carcinoma. Personal results

Adjuvant treatment of breast cancer with AVCF gave significantly longer disease-free survival than CMF in the group of patients taken as a whole, in the subgroup with lymph node involvement and in the premenopausal subgroup. No significant difference was found regarding overall survival.     

Iron,free radicals and cancer

Free radicals, intermediates in the tissue damage caused by radiation, are formed,inter alia, in interactions catalyzed by iron, which synergizes with radiation and some cytostatics (anthracyclins) in causing cell damage. Conversely, iron chelators can counteract cell damage. Similarly, antioxidants can slow atherogenesis, caused in part by oxidative stress and free radicals. Cell damage is also prevented by physiological defense systems like Superoxide dismutase, against endogenous free radicals formed by granulocytes, monocytes, etc. Iron can thus induce free radicals which cause DNA double strand breaks and oncogene activation. This is suggested by four epidemiological studies suggesting a higher cancer risk in patients with larger iron stores than in those with small iron stores. In addition to its effect on carcinogenesis, iron can also maintain the growth of malignant cells as well as growth of pathogens. Breast cancer cells, for instance, display 5-15 times more transferrin receptors than normal breast tissue. Iron-carrying transferrin is in fact a growth factor. Hyposideremia in patients with cancer or infection is not a paraphenomenon but a functioning defense mechanism (’nutritional immunity’). If this immunity is broken by iron administration, relapses of diseases like tuberculosis, brucellosis, and malaria have been described. While iron-deficiency anemia should of course be diagnosed, treated and if possible prevented, there are good reasons to avoid over-utilization of medicamental iron.