PubMed · 7311582
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V Sitaramam, M K Sarma. 1981-06-07. Does sucrose space exist?. https://doi.org/10.1016/0022-5193(81)90315-5
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The control of gene transcription by antigene oligonucleotides rests upon the specific recognition of double-helical DNA by triplex-forming oligonucleotides. The development of the antigene strategy requires access to the targeted DNA sequence within the chromatin structure of the cell nucleus. In this sudy we have used HIV-1 chronically infected cells containing the HIV provirus as endogenous genes to demonstrate that the integrated HIV-1 proviral genome is accessible to triplex-forming oligonucleotides within cell nuclei. An oligonucleotide-psoralen conjugate targeted to the polypurine tract (PPT) of the HIV-1 proviral sequence was used as a tool to convert the noncovalent triple-helical complex into a covalent lesion on genomic DNA after UV irradiation of cells. Triplex-derived adducts were analyzed using two different methods. The photo-induced psoralen cross-link prevented cleavage of the target sequence by DraI restriction endonuclease, and the sequence-specific inhibition of cleavage was revealed and quantitated by Southern blot analysis. A quantitative analysis of cross-linking efficiency was also carried out by a competitive PCR-based assay. These two approaches allowed us to demonstrate that a triplex-forming oligonucleotide can recognize and bind specifically to a 15-bp sequence within the chromatin structure of cell nuclei.
BACKGROUND & AIMS: Diarrhea associated with shellfish poisoning is poorly understood. The responsible toxin, dinophysistoxin 1, has been identified as okadaic acid, a potent phosphatase inhibitor, but its effects on intestinal epithelia have not been examined. The aim of this study was to investigate the effect of okadaic acid on intestinal epithelial function, both Cl- secretion and barrier function. METHODS: Cultured human intestinal epithelial T84 cell monolayers were used. The effect of okadaic acid on these monolayers was assessed by measuring electrophysiological parameters, lactate dehydrogenase release, and 22Na+ and [3H]mannitol flux rates. Protein phosphorylation studies were performed to identify potentially involved proteins. RESULTS: Okadaic acid does not directly stimulate Cl- secretion from intestinal epithelial cells. On the contrary, the response to well-characterized secretagogues is attenuated by okadaic acid. However, it does decrease transepithelial electrical resistance in a polarized fashion without inducing cytotoxicity. Sodium-mannitol flux studies suggest that the observed decrease in resistance is attributable to an increase in paracellular permeability. CONCLUSIONS: Okadaic acid, the toxin responsible for diarrheic shellfish poisoning, does not stimulate Cl- secretion but increases the paracellular permeability of intestinal epithelia. This alteration in intestinal epithelial physiology may contribute to the diarrhea of shellfish poisoning.
The uptake kinetics of cisplatin analogs of 1,2-cyclohexanediamine(dach) isomers with various leaving groups, by human erythrocytes in plasma isotonic buffer, were studied. The experimental results showed that the uptake rate constants (k values) decrease with the change of leaving group in the sequence: chloride (Cl) > squaric acid (SA) > oxalate (OX) > demethylcantharic acid (DA), with the same dach isomer as carrier group. It is noteworthy that for the platinum (II) complexes with the same leaving group, the k values always reduce as: 1R, 2R-dach > 1R, 2S-dach > 1S, 2S-dach. This result reflects the chirality selectivity. No differences in reactivity to protein thiols and effects on membrane permeability were found for the R,R-, R,S-, S,S-isomeric complexes. It is proposed that the chirality selectivity in uptake is due to the recognition of the chirality of the platinum complexes by the erythrocyte membrane. The interactions between the chiral platinum complexes and the head groups of the membrane phospholipid molecules are probably involved.