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M Dabrowski

Publications and source records attributed to M Dabrowski.

141 records · Page 8Linked to original sources
PubMedDate not supplied

The elongating ribosome: structural and functional aspects.

We determined the positions and arrangements of RNA ligands within the ribosome with a new neutron-scattering technique, the proton-spin contrast-variation. Two tRNAs were bound to the ribosome in the pre-translocational and the post-translocational state. The mass centre of gravity of both tRNAs resides at the subunit interface of the body of the 30S subunit. Both tRNAs are separated by an angle of 50-55 degrees, and their mutual arrangement does not change during translocation. The mass centre of gravity moves by 13 +/- 3 A (1A = 0.1 nm) during translocation, corresponding well with the length of one codon. Using an RNase-digestion technique, the length of the mRNA sequence covered by the ribosome was determined to be 39 +/- 3 nucleotides before and after translocation. The ribosome moves like a rigid frame along the mRNA during translocation. In contrast, both tRNAs seem to be located on a movable ribosomal domain, which carries the tRNAs before, during, and after translocation, leaving the microtopography of the tRNAs with the ribosome unaltered. This conclusion was derived from an analysis of the contract patterns of thioated tRNAs on the ribosome. The results have led to a new model of the elongation cycle, which reinterprets the features of the previous "allosteric three-sites model" in a surprisingly simple fashion. Finally, a mutational analysis has identified a single nucleotide of the 23S rRNA essential for the peptidyltransferase activity.

Amino Acid Sequence↗
PubMedDate not supplied

Different mechanisms of positive chronotropic actions of isoprenaline and noradrenaline on isolated guinea pig right atria revealed by pretreatment with rilmakalim.

In this study we tested the influence of activation of ATP-sensitive K+ channels (KATP) on the changes in automatism induced by isoprenaline, noradrenaline and phenylephrine. Experiments were performed on the spontaneously beating right atria isolated from guinea pig. The rate of spontaneously beating preparations was measured under different experimental conditions. Rilmakalim (formerly HOE 234) was used as an activator of KATP channels. Isoprenaline induced significant, concentration-dependent positive inotropic action. This effect was strongly attenuated only in the presence of selective blockers of beta1- (metoprolol), but not beta2-adrenoceptor subtype (ICI 11855). Pretreatment with 4 microM rilmakalim resulted in a significant increase in the described effects of isoprenaline on automatism of isolated right atria. Phenylephrine (1 to 100 microM) in the presence of 1 microM propranolol, did not cause any changes in automatism of guinea pig right atria. Slight but significant positive chronotropic action induced by noradrenaline at lower concentrations (0.1 to 10 microM) in the presence of 1 microM propranolol was significantly decreased by pretreatment with rilmakalim. However, the effects obtained at higher concentrations (30 and 100 microM) of noradrenaline were enhanced. Interactions mentioned above were prevented by addition of 3 microM glibenclamide. The results imply that positive chronotropic effect of noradrenaline in the presence of propranolol is mediated by adrenoceptor subtype different from alpha1-, beta1- and beta2-adrenoceptors.

ATP-Binding Cassette Transporters↗
PubMedDate not supplied

[Evaluation of the treatment of chronic active hepatitis (HBsAg+) with isoprinosine. II. Immunological studies].

A two-month treatment of the chronic active hepatitis (HBsAg+) with isoprinosine produced quantitative and functional T-cells populations in patients with cellular response disorders. Immunological studies have shown that such an effect of isoprinosine lasted for about 4-5 months. Repeated administration of isoprinosine for one month normalized recurrent abnormalities in the monitored immunological parameters.

Adjuvants, Immunologic↗
PubMedDate not supplied

[Results of the treatment of children with brain neoplasms. I. Survival of children and cause of death].

In a group of 146 children aged from 8 months to 16 years treated for brain neoplasms the authors analysed the therapeutic results. Excluding the so called operative losses the survival over 4 years was obtained in one-fourth of patients with medulloblastoma, in over one-third of those with ependymoma, one-half of astrocytoma cases, and over one-third of children with other neoplasms. The authors estimate positively the therapeutic methods used (operation, radiotherapy and chemotherapy by Bloom's schedule) and see the possibility of increasing the survival rate by improvement in the diagnosis of brain tumours in children and by optimalization of treatment, especially in its early period, for reducing the number of operative losses.

Adolescent↗