Biomedical subjects
Publications and source records attributed to A Dasgupta.
Gross changes of myelinated fibres and Schwann cells at different degenerative stages were present in all five ENL nerve lesions. Besides these changes, infiltrating cells mainly macrophages, deposition of excessive collagen and perineurial vessel damage were also observed.
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The peptide chain initiation factor, Co-EIF-1 has been purified to homogeneity. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the homogeneous preparation gives a single protein band corresponding to a molecular weight of approximately 20,000. In the crude preparation, Co-EIF-1 exists in two molecular forms: Co-EIF-1H (Mr = 200,000) and Co-EIF-1L (Mr = 20,000). Both forms are equally active in all the reactions studied. Upon heating, the heavy form (Co-EIF-1H) is completely converted into the light form (Co-EIF-1L). Radioactively labeled [14C]Co-EIF-1 was prepared by reductive alkylation using [14C]formaldehyde and borohydride. [14C]Methyl-Co-EIF-1 binds specifically to EIF-1; EIF-1.[14C]Co-EIF-1 complex was analyzed by gel (Sephadex G-100) filtration. EIF-1.Co-EIF-1 complex is distinctly more stable towards heat than EIF-1 alone and the quarternary complex, Met-tRNAf.EIF-1.Co-EIF-1.GTP is more resistant to aurintricarboxylic acid than the ternary complex, Met-tRNAf.EIF-1.GTP. Both the quarternary complex, Met-tRNAf.EIF-1.Co-EIF-1.GTP, and the ternary complex, Met-tRNAf.EIF-1.GTP, are equally sensitive to Mg2+ in the presence of EIF-2 (TDF). In the presence of Co-EIF-1, the initial rate of Met-tRNAf binding to 40 S ribosomes was significantly increased.
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A ribosomal salt (0.5 M KCl) wash factor (RF) that reverses inhibition of protein synthesis in heme-deficient reticulocyte lysates has been resolved from the bulk of Met-tRNAfMet-binding factor (EIF-1), Co-EIF-1, and EIF-2 (ternary complex dissociation factor, TDF). The purified RF restores protein synthesis activity of heme-deficient lysates to the level observed in the presence of hemin. No direct correlation exists between amount of EIF-1 activity and ability to reverse inhibition of protein synthesis in heme-deficient lysates. Homogeneous preparations of EIF-1 are completely inactive in reversal of protein synthesis inhibition in heme-deficient lysates. These findings suggest that RF activity is not due to EIF-1 alone but may or may not require EIF-1 as a component of a complex factor.
Protein synthesis in reticulocytes and their lysates is regulated by heme. In heme deficiency a heme-regulated translational inhibitor (HRI) that blocks initiation of polypeptide chains is activated. HRI is a protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) that specifically phosphorylates the 38,000-dalton subunit of the Met-tRNA(f) (Met) binding factor (IF), which forms a ternary complex with Met-tRNA(f) (Met) and GTP, a finding that suggests that the inhibition by HRI involves the phosphorylation of IF. We have investigated the effect of HRI in the partial reactions of protein chain initiation in which the IF-promoted binding of Met-tRNA(f) (Met) to 40S ribosomal subunits is enhanced by another initiation factor [ternary complex dissociation factor (TDF)] and AUG. The results show that HRI at very low concentrations markedly inhibits the binding of Met-tRNA(f) (Met) to 40S subunits. The inhibitory effect of HRI requires ATP. Under these conditions HRI phosphorylates only the 38,000-dalton subunit of IF. The TDF preparations not only promote the binding of the ternary complex to 40S subunits but also promote the dissociation of the ternary complex in the presence of 5 mM Mg(2+) at 0 degrees . The preincubation of purified IF alone with low concentrations of HRI and ATP does not significantly affect its capacity to form the ternary complex; however, the TDF-promoted dissociation of the ternary complex is inhibited. The nonhydrolyzable analog adenosine 5'-[beta,gamma-imido]triphosphate does not substitute for ATP. These findings suggest that phosphorylation causes a conformational modification in IF, which results in inhibition of the interaction between the ternary complex and TDF that is required for the binding of the ternary complex to 40S subunits.
Pyrolysis of underivatized homogeneous oligoribonucleotides in the source of a mass spectrometer leads to production of simple mass spectra which resemble the spectra of the bases themselves. It is proposed that pyrolysis occurs by hydrogen transfer to the base moiety followed by elimination of the neutral base. Ionization by electron impact gives rise to the observed spectra. Mixed oligoribonucleotides pyrolyze readily to give spectra of adenine and uracil, but evidence for the presence of guanine and cytosine in mixed polymers and native RNA's is difficult to obtain presumably because of their low vapor pressure. The method may be useful for detection of modified bases in tRNA and for studies of temperature effects on RNA pyrolysis.
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In the mouse foot pad model five different parameters were employed to simulate the condition of ENL as observed in the human. The experimental groups with five to six months leprosy infection were injected intravenously with various anti-mycobacterial antibodies, M. leprae sonicate and 'B' cells obtained from syngenic donors. The control group of animals, infected similarly, were treated either with M. leprae sonicate or gamma globulins precipitated from normal human serum. All recipients were killed at one day interval excepting those with 'B' cell transfer, which were sacrificed at seven days. The sites of predilection for immune complex deposition viz. foot pad and kidney as well as the spleen were examined by light and fluorescence microscopy. These findings are described and discussed.
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47 normal healthy controls and 45 atopic individuals together with five families with allergic diathesis and sensitive to mite antigen were typed for 13 HLA antigens. In general population, HLA-A1 and HLA-A8 were found to be higher than in normal controls. But the difference was significant at a level of p 0.05 after correction was made for the number of HLA antigens used. In one family, an HLA-A1 -B8 haplotype seems to be linked to the manifestation of atopic disease. The pattern of association of an HLA-A9 -B7 haplotype with the disease process in another family indicates that multiple genes may be involved in the manifestation of a variety of allergic disorders. Although more than one HLA haplotype of HLA-associated Ir gene for one antigen have been postulated, we still do not have enough evidence to suggest linkage between HLA haplotypes and atopic allergy. Further studies utilizing mixed lymphocyte culture and carefully matched control with a large number of subjects and more families are in progress to study the genetic basis of allergic diseases.
Medullary bundles of Piperaceae resemble those of Ranunculaceae. The nature of tracheary elements of primary xylem suggests that Houttuynia cordata (Saururaceae), Piper cubeba (Piperaceae) and Chloranthus officinalis (Chloranthaceae) are of lower evolutionary status than others. Among these three, P. cubeba shows stratification of secondary xylem, a specialized character. Lateral wall of metaxylem tracheary elements and distribution of bundles of Peperomia, suggest their primitive status and distinctness, supporting separation of "Peperomiacea:" (of NOVAK). Piper cubeba, Houttuynia and Chloranthus bear one important Ranunculaceous character: scalariform perforation in primary vessels. Primitive species of Peperomia carry probably another Ranunculaceous character, i.e., many circles of medullary bundles. Shape and pattern of vascular bundles of Piper cubeba, Houttuynia and Chloranthus are similar. Other species of Piper show modifications. Peperomia represents another distinct pattern.