Biomedical subjects

A Goette

Publications and source records attributed to A Goette.

22 records · Page 2Linked to original sources

PubMed1996

Transcatheter subendocardial infusion. A novel technique for mapping and ablation of ventricular myocardium.

BACKGROUND: Catheter ablation with radiofrequency energy is feasible in a limited subset of patients with ventricular tachycardia. The purpose of this study was to evaluate a technique for mapping and ablation of ventricular myocardium with the use of transcatheter subendocardial infusion. METHODS AND RESULTS: A needle-tipped deflectable electrode catheter was used to deliver reagents to endocardial target sites. This was equipped with two central lumens to allow sequential administration of mapping and ablation injectants with minimal admixture. The mapping injectant consisted of a mixture of lidocaine, iohexal, and glycerin; the ablation injectant contained ethanol, iohexal, and glycerin. Infusion of the mapping injectant (1 cm3 over 3 or 5 seconds, n = 14) produced a stain on fluoroscopy and increased local capture threshold by 61%. No lesions resulted from mapping infusions. Infusion of the ethanol-containing injectant (n = 48) produced discrete lesions, with a mean volume ranging from 0.6 to 1.5 cm3. There was a direct relationship between infusion volume, infusion duration, and resultant lesion volume. Fibrosis in a region of healed myocardial infarction did not impair diffusion of the injectant or affect lesion dimensions. Microscopic analysis of chronic lesions showed a sharply demarcated border zone between fibrotic and normal myocardium. CONCLUSIONS: Transcatheter subendocardial infusion can be used to reversibly impair local excitability and mark an injection site fluoroscopically. Subendocardial injection of ethanol can predictably ablate a large volume of ventricular myocardium. Additional study of this system in an arrhythmia model will help to define its potential for mapping and ablation of hypotensive ventricular tachycardia.

Animals↗

PubMed1985

The cytotoxic action of diethyldithiocarbamate in vitro. Different inhibition of scheduled and unscheduled DNA synthesis of rat thymic and splenic cells.

Within a concentration range of 1-10 micrograms/ml, an addition of diethyldithiocarbamate (DDC) to splenic and thymic rat lymphocytes (2 X 10(6)-4 X 10(6) cells/ml) resulted in a complete inhibition of scheduled (semiconservative) DNA synthesis. Lower and higher concentrations were less effective. Under the same conditions, a strictly dose-dependent inhibition of unscheduled (excision repair) DNA synthesis, a decrease of the sedimentation rate of nucleoids, as well as changes of the thymidine pool were observed. The results suggest that the cytotoxic action of DDC in vitro may be mediated a) by the chelating properties of the drug with inhibitory effects on a variety of cellular functions, including nucleic acid precursor metabolism, b) by an immediate radiomimetic attack of the SH-group of DDC on the DNA.

Animals↗

PubMed1984

[Comparative studies on the DNA synthesis of rat thymus and spleen cells in vitro under the influence of x rays, UV light and radiomimetic compounds].

In order to further characterize the different repairing behavior of thymus and spleen cells of rats in vitro under the influence of X-rays, UV radiation and methylmethanesulfonate (MMS), the effect of bleomycin (BM), L-cysteine (CY-E), N-ethylmaleimide (NEM), 1-beta-D-arabinofuranosylcytosine (araC), dideoxythymidine (ddT), and novobiocin (NB) on the semiconservative and restorative DNA synthesis as well as on the behavior of DNA under the alkaline elution was studied. The semiconservative DNA synthesis was inhibited by all examined agents except ddT, the restorative DNA synthesis only by NEM, araC, and NB. The stimulation of the restorative DNA synthesis was increased by UV radiation and MMS in spleen cells and by X-rays, BM and CY-E in thymus cells. Under the conditions of alkaline elution, there was a more sensitive reaction of spleen cells than of thymus cells to X-rays, BM and CY-E. The results show that thymus cells are especially qualified for the repair of short chains and spleen cells for the repair of long chains.

Animals↗

PubMed1984

[Differences between spleen and thymus cells of rats with respect to the effects of ethidium bromide on unscheduled DNA synthesis (DNA repair synthesis) and nucleoid sedimentation].

To get further insight into the causes of differences between rat splenic and thymic cells with regard to DNA repair synthesis, scheduled (SDS) and unscheduled (UDS) DNA synthesis as well as nucleoid sedimentation of the cells were investigated under the influence of ethidium bromide (EB, 1-1000 micrograms/ml). - At concentrations of greater than or equal to 25 micrograms/ml, EB inhibited SDS of both cell species and UDS of thymic cells; much higher additions of the drug (greater than 200 micrograms/ml) were needed to diminish UDS of splenic cells, lower EB-concentrations (25-175 micrograms/ml) stimulating the UDS of the splenic cell preparation. - The sedimentation rate of splenic and thymic cell nucleoids within neutral sucrose gradients had a biphasic dependence on the EB-concentrations. As compared to thymic cells however, preincubation of splenic cells with 50-250 micrograms EB/ml resulted in a significant greater (15-30 percent) sedimentation distance. - The results suggest that a relationship exists between the stimulation of UDS and the ability of cells to establish a greater DNA compactness in the presence of EB.

Animals↗