Structure-activity relationships for the inhibition of DNA polymerase alpha by aphidicolin derivatives.

Aphidicolin and 17 derivatives that have been structurally modified in the A- and D-rings were assessed for their ability to inhibit DNA polymerase alpha. No derivative surpassed the activity of aphidicolin; derivatives with structural alterations in the A-ring exhibited significantly greater loss of activity relative to derivatives with structural alterations in the D-ring. The conclusions of these studies indicate a critical role for the C-18 function in the interaction of aphidicolin with polymerase alpha. Molecular modelling studies could not identify structural features of the aphidicolin-dCTP "overlap" that is unique to dCTP, relative to the remaining dNTPs, and that is consistent with the extant structure-activity data.     

Sequence divergence and open regions of RNA secondary structures in the envelope regions of the 17 human immunodeficiency virus isolates.

Genetic variation during the course of infection of an individual is a remarkable feature of the acquired immune deficiency syndrome (AIDS) disease. This variation has been studied for the envelope protein encoding regions of seventeen different sequences from various isolates of human immunodeficiency virus (HIV) using multiple sequence comparison and calculation of variability. The open regions with little intramolecular base pairing in these envelope sequences are predicted by a recently developed statistical method. The minimum length L for a run of hypervariable sites, conserved sites, or open regions that gives significance at the 1% (or 0.1%) level is then determined by a scan statistical method. The results show that significant clusters of open regions predicted at the RNA levels correlate with significant clusters of hypervariable sites in the HIV envelope gene. Those significant genomic variations in HIVs seem to be manifested mainly in the extracellular portion of the envelope protein. Twelve potential antigenic determinants are predicted using an antigenic index method. Interestingly, the majority of the significant hypervariable regions in the exterior envelope protein (gp120) were predicted potential epitopes.     

Development of the neo-morphic air breathing organs in three genera of estuarine gobies

The rudiment of the neo-morphic organ for O2 uptake arises in the form of a gill mass formed by the gill material of the embryonic 5th gill arch. Ectodermal induction to the gill mass takes place in the post-embryonic stage of development to produce a respiratory epithelium of the neo-morphic air breathing organ. The respiratory epithelium of the opercular chamber and the buccal cavity is formed by the cells of the gill mass alone. The respiratory epithelium of the suprabranchial chamber is formed by the cells of the gill mass as well as the gill lamellae derived from the dorsal aspects of the functional gill arches (1 to 4). Extension of the suprabranchial chamber into the buccal region anteriorly is a device to increase the respiratory surface area available for O2 uptake by air. The epithelial position of the blood capillaries in the suprabranchial chamber of Periophthalmodon schlosseri signifies terrestrial nature of the fish.     

Immunomodulatory role of thyroid hormones: effect on humoral immune response to Salmonella typhi O antigen

Effect of long term administration of thyroid hormones and the removal of thyroid on humoral antibody response to S. typhi O antigen was studied in male albino rats of HM strain. Humoral antibody response to S. typhi O antigen was enhanced in animals pretreated with T3 or T4 at a dose of 10 micrograms daily for 15 days. Administration of thyroid hormones simultaneously along with antigen, resulted in suppression of antibody response. In thyroidectomized animals, the antibody titer to S. typhi O antigen was decreased; this decrease in antibody titer was restored to normal level following hormone supplementation. Thyroidectomy significantly depressed TLC as well. Total leucocyte count and absolute lymphocyte count were increased following hormone treatment. Present findings, thus show the lymphoproliferative response of thyroid hormones and their effect on antibody response suggesting the immunomodulatory role of thyroid hormones.     

Effect of thyroid hormones on delayed type hypersensitivity reaction

The effect of long term administration of thyroid hormones and its deprivation on delayed type hypersensitivity (DTH) reaction to 2-4 dinitrochlorobenzene (DNCB) was studied. Animals were either pre-treated with thyroid hormones (T3 or T4) for 15 days and then subjected to DNCB skin test or the animals received thyroid hormones and simultaneously subjected to DNCB skin test. In both the cases DTH reaction was found to be increased significantly. When DNCB skin test was performed in the thyroidectomized animals, DNCB skin reaction was significantly decreased and the reaction was restored to normal following supplementation of thyroid hormones to the thyroidectomized animals. TLC and ALC were increased significantly following hormone treatment and thyroidectomized animals. TLC hand, induced significant depression in the count which was restored by hormone administration to the thyroidectomized animals.     

Storage deterioration of maize having pre-harvest infection with Aspergillus flavus

Deteriorative changes during storage of two different lots of field-contaminated (by Aspergillus flavus ), equally matured and freshly harvested (from two different fields) maize grains of the same cultivar (Ganga) and genotype, and stored under the same natural atmospheric conditions prevailing in the store-house, were studied and compared. It was found that the rate and extent or grain deterioration were much less in lot-2 than in lot-1 which had relatively high pre-harvest internal fungal ( A. flavus ) load. However, the deteriorative changes of both the lots could be reduced when the initial A. flavus infection was completely eliminated. Furthermore, of these already contaminated lots, the kernels selected as free of such infection at harvest also suffered less deterioration during storage.     

Clinical and experimental mycotic keratitis caused by Aspergillus terreus and the effect of subconjunctival oxiconazole treatment in the animal model

Aspergillus terreus was isolated from a case of Keratomycosis. The patient, a 50 year old, female presented with a large corneal ulcer with hypopyon. The direct microscopic examination of the scrapings revealed hyaline, thin, septate and branched hyphae. In vitro some antimycotics (amphotericin B,5-fluorocytosine, oxiconazole, amorolfine and ketoconazole) were tested against A. terreus by agar dilution method. Ketoconazole with MIC of 3 gmg/ml after 7 days of incubation was most effective followed by oxiconazole (10g/ml). Experimental corneal ulcer was produced by injecting intralamellary 0.1 ml of the spore suspension containing 10×10₆ cfu/ml into the eyes of previously immunocompressed albino rabbits. Histopathologic examination showed infiltration and large destruction of the corneal stroma. Subconjunctival oxiconazole therapy exhibited complete cure. Based on our findings, a clinical evaluation of oxiconazole in human keratomycosis seems to be justified.     

DNA-binding properties of an adenovirus 289R E1A protein.

An adenovirus 2 289 amino acid (289R) E1A protein purified from Escherichia coli has been shown to interact with DNA by two independent methods. UV-crosslinking of complexes containing unmodified, uniformly 32P-labelled DNA and purified E1A protein induced efficient labelling of the protein with covalently attached oligonucleotides, indicating that the E1A protein itself contacts DNA. Discrete nucleoprotein species were also observed when E1A protein--DNA complexes were analysed by gel electrophoresis. Although the 289R E1A protein exhibited no significant binding to single-stranded DNA or to RNA, no evidence for its sequence-specific binding to double-stranded DNA was obtained with either assay. Identification of the sites of covalent attachment of 32P-labelled oligonucleotides by partial proteolysis of the crosslinked E1A protein indicated that the interaction of this protein with DNA is mediated via domain(s) in the C-terminal half of the protein. Such previously unrecognized DNA-binding activity is likely to contribute to the regulatory activities of this important adenoviral protein.     

Oxygen free radicals induced release of lysosomal enzymes in vitro

Summary The effect of oxygen free radicals, generated by xanthine and xanthine oxidase, was studied on the release of lysosomal hydrolase from rat liver lysosomes in vitro. A lysosomal enriched subcellular fraction was prepared, using differential centrifugation technique, from the homogenate of rat liver. The biochemical purity of the lysosomal fraction was established by using the markers of different cellular organelles. Oxygen free radicals were generated in vitro by the addition of xanthine and xanthine oxidase. The release of lysosomal hydrolase (-glucuronidase) from the lysosomal fraction was measured. There was a 3 to 4 fold increase in the release of -glucuronidase activity in the presence of xanthine and xanthine oxidase when compared to that in the absence of xanthine and xanthine oxidase. In the presence of superoxide dismutase (SOD), a scavenger of oxygen free radicals, the xanthine and xanthine oxidase system was unable to induce the release of -glucuronidase activity from the lysosomes. Sonication (2 bursts for 15 sec each) and Lubrol (2 mg/10 mg lysosomal protein) treatment, which are known to cause membrane disruption, also induced the release of -glucuronidase from lysosomal fraction. This release of -glucuronidase by sonication and lubrol treatment was not prevented by SOD. These data indicate that lysosomal disruption is a consequence of oxygen free radicals, generated by xanthine and xanthine oxidase.Abbreviations HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - EGTA Ethylene Glycol Bis-(-aminoethyl ether)N,N,-N,N-tetracetic acid - Tris Tris (hydroxymethyl) aminomethane - SOD Superoxide Dismutase     

In vitro acetylation of the liver HMG non-histone proteins and its modulation by spermine and dexamethasone during aging of rats

The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and old (138-week) male rats. Acetylation of total HMG proteins is lower in old age. The incorporation of (¹⁴C) acetate into individual HMG proteins varies remarkably with advancing age. Whereas acetylation of high mol. wt. proteins (HMG 1 and 2) is higher, that of low mol. wt. proteins (HMG 14 and 17) is lower in the liver of young rats as compared to the old ones. Spermine stimulates the acetylation of HMG 1 and 14 in young and HMG 1, 2 and 14 in old age. It inhibits the acetylation of HMG 17 in both ages. Dexamethasone decreases the level of incorporation of (¹⁴C) into HMG 1 and 17 in young and HMG 14 and 17 in old rats. On the other hand, it stimulates the acetylation of HMG 14 by two-fold in young and that of HMG 1 and 2 by more than three-fold in old rats. Such alteration in the acetylation of HMG proteins may account for age-related changes in the structure and function of chromatin.