Biomedical subjects

P Sýkora

Publications and source records attributed to P Sýkora.

10 recordsLinked to original sources

PubMed2000

Results of modified Norwood's operation for hypoplastic left heart syndrome.

OBJECTIVE: The aim of the study was to analyze intermediate results of treatment of the hypoplastic left heart syndrome based on selective indication criteria. METHODS: Between February 1997 and May 1999 38 patients with hypoplastic left heart syndrome (n=35), or with functional variant of hypoplastic left heart syndrome (n=3) were admitted to our department. Contraindications for surgery were birth weight <2500 g, diameter of ascending aorta <2 mm, severe tricuspid regurgitation persisting after initial stabilization, pulmonary regurgitation more than mild, dysfunction of the systemic right ventricle and failure to effectively resuscitate circulation before surgery. RESULTS: Based on these criteria surgery was not indicated in 17 patients. Twenty-one infants were operated on by modified Norwood's procedure using only autologous great vessel tissue for reconstruction of systemic outflow. Overall hospital mortality was 14% (three patients). Eighteen survivors (86%) were discharged with well-balanced circulation. There was one late death (5%). Thirteen patients had already undergone the second stage (bi-directional Glenn) with no death. The mean follow-up was 13. 2+/-9.1 months (range 4-32 months). Considering both early and late events the probability of survival for the whole group (n=21) from the time of surgery was 86% at 1 month, 80% at 12 months, and it remained unchanged at 18 and 24 months of follow-up. CONCLUSIONS: Only a limited number of European countries offer surgical treatment of hypoplastic left heart syndrome. Promising intermediate results (80% survival rate after stage I and II) achieved at our department do not only reflect overcoming the learning curve but also a selective approach to indication for surgery as well. In a country with limited resources selective approach to the patients with hypoplastic left heart syndrome is justified.

Cardiopulmonary Bypass↗

PubMed1992

Macroevolution of plasmids: a model for plasmid speciation.

A new evolutionary model for diversification in plasmid incompatibility groups (plasmid speciation) is suggested. The model is based on the formation of plasmid cointegrates from two compatible plasmids. The existence of plasmid cointegrates is well known, however, their potential key role in plasmid macroevolution has not yet been recognized. In a hypothesis presented here, one of the rep genes is supposed to be relaxed from selection in plasmid cointegrates and thus becomes free to accumulate mutations. These mutations can lead to a change in incompatibility specificity. Evidence supporting this hypothesis comes from the common occurrence of multi-replicon plasmids in nature as well as from experimental studies on plasmid cointegrate formation. A more speculative extension of this model hypothesizes an evolutionary scenario for origin of the eubacterial single-replicon genome and the eukaryotic multi-replicon genome, as well as the place of plasmids and viruses in this picture.

Bacteria↗

PubMed1991

Elimination of plasmids pKM 101 and F'lac from Salmonella typhimurium and Escherichia coli by bisammonium salt. The effect of outer membrane pattern.

Plasmid-curing activity of N,N'-bis(decyldimethyl)-1,6-hexanediammonium dibromide, BDHD, was tested on six different plasmids in E. coli and plasmid pKM 101 in S. typhimurium. BDHD eliminated the F'lac plasmid from E. coli cells only with a low efficiency. Plasmid pKM 101 was eliminated from S. typhimurium cells significantly and this effect was dependent on an outer membrane pattern. A deep-rough mutant of S. typhimurium is completely resistant to curing activity of BDHD, while part-rough and smooth cells are susceptible to it. In contrast to pKM 101, a cryptic plasmid being present in S. typhimurium cells was not eliminated by BDHD. The curing activity of sodium dodecyl sulfate, acridine orange, crystal violet, and promethazine was also affected by the outer membrane pattern of S. typhimurium cells.

Cell Membrane↗

PubMed1989

A kinetic model for plasmid curing.

A simple mathematical model of drug-induced plasmid elimination (curing) considering density-dependent growth rates and plasmid transfers is presented. It describes nonlinear population dynamics of conjugative plasmids during in vitro curing experiments in batch culture. The model was tested on kinetics of acridine orange curing of F'lac plasmid. Effects of density dependence, plasmid elimination, selection for plasmidless segregants, conjugation, initial and maximal population density, and postsegregational killing on curing kinetics are simulated and discussed.

Acridine Orange↗

PubMed1984

The discrepancy between in vivo and in vitro experiments with polycyclic aromatic hydrocarbon(PAH) carcinogens: a hypothetical explanation.

The hypothesis suggested in this paper is an attempt to explain a discrepancy between in vivo and in vitro polycyclic aromatic hydrocarbons (PAH)-carcinogenesis experiments, described frequently in the literature. Whereas, in pretreated animals, a higher level of induced PAH-metabolizing enzymes reduces PAH-carcinogenicity, in the tissues or homogenates from pretreated animals the induced PAH-metabolizing enzymes increase the carcinogenic effects of PAH. In our model, both the pretreatment or route of administration should cause a frameshift in the alternation of active and inactive metabolites in the compartments. In pretreated animals the carcinogenicity of PAH administered per os is reduced, because the PAH metabolism is completed to tetrol, the ultimate inactive metabolite, before it reaches the target tissue. The hypothesis explains the discrepancy and makes predictions which can be tested experimentally.

Animals↗

PubMed1983