Transcription of brain chromatin by ribonucleic acid polymerases from brain nuclei and from Escherichia coli

1. Transcription of ox brain chromatin by brain nuclear RNA polymerase II and Escherichia coli RNA polymerase was studied. 2. The soluble chromatin prepared from brain nuclei contained DNA, RNA, histone and non-histone proteins. Such chromatin preparations did not display any endogenous RNA polymerase activity, when assayed in the presence of concentrations of KCl as high as 0.4m. 3. The chromatin-templated activity of brain nuclear polymerase II was stimulated by KCl, with an optimum around 0.25m. 4. The template activity of brain chromatin for brain nuclear polymerase II and E. coli enzyme was about 20-25% of that of pure DNA. This greatly repressed templatecapacity of chromatin was probably due to the acid-soluble chromosomal proteins. 5. Brain nuclear polymerase II was 3-4 times more active with dehistonized chromatin than with pure DNA as template, whereas bacterial enzyme was almost equally active with either of these two templates, reflecting the specificity of the transcriptional control mechanisms in mammalian cells.

Studies on isolated brain nuclear DNA-dependent RNA polymerase

DNA-dependent RNA polymerase, which was isolated from beef brain nuclei, was stimulated by Mn2+ and Mg2+. The polymerase was about four times as active with Mn2+ as with Mg2+ but both of these divalent cations were required for maximum activity. KCl stimulated the enzyme activity with an optimum concentration around 0.2 M. The stimulation by KCl was much more pronounced in the presence of Mn2+ or Mn2+ plus Mg24 than in the presence of Mg2+ alone. Spermidine and spermine also stimulated the RNA polymerase activity and this stimulation was much greater in the presence of Mn2+ than in the presence of Mg2+ or both together. With Mn2+ plus Mg2+, spermidine had little or no stimulatory effect when heat-denatured DNA served as template, whereas with Mn2+ alone, spermidine markedly stimulated the enzyme in the presence of either native or heat-denatured DNA. The effect of spermidine was different with Mg2+ alone. The enzyme was inhibited as much as 75% by actinomycin D and almost completely by α-amanitin but not by rifampicin. Yeast RNA inhibited the enzyme activity considerably while spermidine appeared to overcome and prevent this inhibition of RNA polymerase.

Clinico-hematological study of pancytopenia

Background: Pancytopenia refers to a reduction in all the three cellular elements of blood. The aim of this study was to identify the various causes of pancytopenia in patients attending to Manipal teaching hospital in Pokhara. Materials and Methods: This was a cross-sectional study, carried out in Manipal teaching hospital from August 2008 to August 2010. Fifty-four patients with pancytopenia were included in the study. Complete blood count, bone marrow aspirations and trephine biopsies were performed. Data were analyzed using SPSS 11.0 version. Results: Out of 54 cases, there were 16 cases (29.60%) of hypoplastic bone marrow, 15 cases (27.78%) of hematological malignancies, 13 cases (24.10%) of megaloblastic anemia, 4 cases (11.11%) of erythroid hyperplasia and 6 cases (7.41%) of normcellular bone marrow. Acute myeloid leukemia was the commonest hematological malignancy. Conclusion: The commonest cause of pancytopenia in our study was hypoplastic bone marrow followed by hematological malignancies and megaloblastic anemia. DOI: http://dx.doi.org/10.3126/jpn.v2i3.6023 JPN 2012; 2(3): 207-210