Deoxyribonucleotide synthesis and the role of vitamin B12 in erythropoiesis

Antimicrobial, insect sterilizing and ovicidal activity of some cobalt(II) and cobalt(III) complexes

Twenty-one mixed-ligand complexes of cobalt(II) and cobalt(III) have been screened for their antimicrobial, insect sterilizing and ovicidal activities. Three of these cobalt(III) complexes exhibit broad antimicrobial spectra, including against human bacterial pathogens, dermatophytes and plant pathogenic fungi, while one exhibits feeble activity against a human pathogenic bacterium. These results have been compared with the activity of the corresponding cobalt(II) complexes, which have been found to be inactive, while the free ligands show reduced activity compared with the cobalt(III) complexes. Change in biological activity induced by a particular complex appears to be dependent on the composition of the first co-ordination sphere. Two of these complexes showed 50% inhibition of the conidial germination of Helminthosporium oryzae and Alternaria triticina. These results indicate their potential for use against human and plant pathogenic microbes. Minimum inhibitory concentrations of the cobalt(III) complexes were determined. Three of these cobalt(III) complexes have been tested for insect sterilizing and ovicidal activities on Dysdercus koenigi F. Positive sterilizing and ovicidal actions of [Co(BSOP)(NH3)2]NO3 (where BSOP-H2 is the Schiff base derived from salicylaldehyde and orthophenylene-diamine) were obtained. Possible mechanism(s) of all these activities are discussed qualitatively.

Possible interrelationship between vitamins E and b12 in the disturbance in methylmalonate metabolism in vitamin E deficiency

1. The disturbance in 2-methylmalonate metabolism resulting in its increased urinary excretion observed in vitamin E deficiency is not caused by increased formation of methylmalonate from propionate as is evident from the activity of the enzyme propionyl-CoA carboxylase (EC 6.4.1.3), but can be traced to an impairment in the conversion of methylmalonate into succinate by the vitamin B12-requiring enzyme, methylmalonyl-CoA mutase (EC 5.4.99.2) in rat liver. 2. It is shown that the decrease in the activity of methylmalonyl-CoA mutase in vitamin E deficiency is not a consequence of a secondary vitamin B12 deficiency. Peroxidative destruction of the coenzyme in vitamin E deficiency was also ruled out. The results suggest a defect in the conversion of cyanocobalamin into its coenzyme form.

Serum "uracil+uridine" levels before and after vitamin B12 therapy in pernicious anaemia

The serum "uracil+uridine" levels, expressed as uracil, have been measured in 10 cases of pernicious anaemia both before and after treatment, and compared with the levels in 97 normal subjects. The mean pre-treamtent value (8.82 mumol/1., range 6.0-12.0 mumol/1.) differed significantly from that of the normal controls (15.7 mumol/1., range 5.7-40.5 mumol/1., t = 8.8, P less than 0.001). This confirms the low serum uracil level previously reported in pernicious anaemia relapse. The level rose progressively after treatment, reaching a maximum on the fourth day (mean 17.85 mumol/1., range 9.3-23.4 mumol/1.). This was not significantly different from the mean of the normal control group. The difference between the pre- and post-treatment levels was significant on days 3,4 and 5 (P less than 0.005, P less than 0.001 and P less than 0.005 respectively) and the rise preceded the reticulocyte response by 24 h. A further case was treated with pysiological doses of vitamin B12 (2 mug daily for 6 d) and a similar rise in the serum uracil level noted. These results are not explained by any of the known functions of vitamin B12. They are, however, similar to the changes in the serum methionine levels previously reported in pernicious anaemia. The latter were readily explained by the known action of vitamin B12 on "de novo" methionine synthesis and it is suggested that the synthesis of uracil, like that of methionine, might be influenced by vitamin B12 in man.

The bone marrow colony forming cell in megaloblastic anaemia and iron deficiency anaemia

Bone marrow samples from patients with megaloblastosis and iron deficiency have been assayed for their content of in vitro colony forming cells (CFC), and compared with a group of normal patients. The concentration of these cells was found to be significantly increased in the megaloblastic group, while their content in the iron deficient patients was slightly higher than the controls. An in vitro thymidine suicide procedures was utilised to assay the proportion of CFC in the S phase of the cycle. This was found to be increased in the megaloblastic group and only slightly increased in the iron deficient group. The findings in megaloblastosis seem to be consistent with the concept of impaired DNA synthesis. As the CFC monitors an early granulocytic progenitor these data suggest some impairment in DNA synthesis or an abnormal increase in amplification in this myeloid stem cell compartment. Such alterations in granulopoietic proliferation may contribute to the ineffective granulopoiesis of megaloblastosis and accordingly may be an important factor in the development of neutropenia sometimes associated with this condition. The slightly increased CFC concentration and altered cell cycle status found in iron deficiency suggest that iron is not a major requirement for granulopoiesis.