RESUMEN
Metal-ion assisted, gamma-radiation-induced B-Z conformation changes have been observed with UV and circular dichroism spectroscopy for poly (dGdC), calf thymus and herring testis DNA. These conformational changes are similar to those induced by increasing multivalent metal ion concentrations in DNA containing alternating purine and pyrimidine base sequences. In both the metal-ion-induced and the metal-ion-assisted, radiation-induced conformation changes, the conversions were from the right-handed B-DNA to the left-handed Z-DNA conformation. It is proposed that radiation-induced DNA strand breaks markedly reduce the high activation energy barrier in the metal ion-driven B-Z conformation conversion and allow much smaller metal ion concentrations to induce this conversion than in the absence of strand breaks. The biological importance of such radiation-induced conformational changes is discussed in terms of the potential significance of the Z-DNA conformation in the control of the DNA transcription process.
Asunto(s)
ADN/efectos de la radiación , Metales/farmacología , Conformación de Ácido Nucleico/efectos de la radiación , Polidesoxirribonucleótidos/efectos de la radiación , ADN/química , Rayos gamma , Polidesoxirribonucleótidos/químicaRESUMEN
Lambs naturally infected with mixed species of Eimeria were fed monensin (30 mg/kg of feed) and aureomycin (10 mg/kg of feed) separately and in combination. An evaluation was made of the efficacy of the treatments in the suppression of oocyst production. Comparisons were made of the parasitic damage to the intestinal surface. Performance of the lambs was measured by weight gains and feed efficiency. Monensin given separately or in combination with aureomycin produced decreases in oocyst counts that were not significantly different from those in the lambs given only aureomycin. Body weight gains and feed efficiency were best in the aureomycin-treated group, and less so in the monensin-treated and the control groups. Animals fed the monensin-aureomycin combination had the poorest weight gains and feed efficiency. Scanning electron microscopy indicated that the groups fed monensin or aureomycin separately had morphologically normal intestinal surfaces. This was in contrast to the control group and the group fed the monensin-aureomycin combination, wherein there was disrupted intestinal surface morphology.