The action of α-amanitin in vivo on the synthesis and maturation of mouse liver ribonucleic acids

α-Amanitin acts in vitro and in vivo as a selective inhibitor of nucleoplasmic RNA polymerases. Treatment of mice with low doses of α-amanitin causes the following changes in the synthesis, maturation and nucleocytoplasmic transfer of liver RNA species. 1. The synthesis of the nuclear precursor of mRNA is strongly inhibited and all electrophoretic components are randomly affected. The labelling of cytoplasmic mRNA is blocked. These effects may be correlated with the rapid and lasting inhibition of nucleoplasmic RNA polymerase. 2. The synthesis and maturation of the nuclear precursor of rRNA is inhibited within 30min. (a) The initial effect is a strong (about 80%) inhibition of the early steps of 45S precursor rRNA maturation. (b) The synthesis of 45S precursor rRNA is also inhibited and the effect increases from about 30% at 30min to more than 70% at 150min. (c) The labelling of nuclear and cytoplasmic 28S and 18S rRNA is almost completely blocked. The labelling of nuclear 5S rRNA is inhibited by about 50%, but that of cytoplasmic 5S rRNA is blocked. (d) The action of α-amanitin on the synthesis of precursor rRNA cannot be correlated with the slight gradual decrease of nucleolar RNA polymerase activity (only 10–20% inhibition at 150min). (e) The inhibition of precursor rRNA maturation and synthesis precedes the ultrastructural lesions of the nucleolus detected by standard electron microscopy. 3. The synthesis of nuclear 4.6S precursor of tRNA is not affected by α-amanitin. However, the labelling of nuclear and cytoplasmic tRNA is decreased by about 50%, which indicates an inhibition of precursor tRNA maturation. The results of this study suggest that the synthesis and maturation of the precursor of rRNA and the maturation of the precursor of tRNA are under the control of nucleoplasmic gene products. The regulator molecules may be either RNA or proteins with exceedingly fast turnover.     

Aspergilosis En Colombia

Resumen Se presentan 15 casos de aspergilosis recolectados en diferentes ciudades del país. Doce fueron casos autopsiados. Los tres restantes se refieren a pacientes en quienes se efectuó una lobectomía pulmonar superior derecha por aspergiloma gigante intracavitario. En los doce primeros existía una enfermedad básica que había alterado seriamente el estado general del paciente; once de ellos habían recibido antibióticos, cinco habían recibido esteroides, y dos, agentes citotóxicos. Se cree que, tanto el estado general del paciente, como la administración de dichas drogas, favorecieron la infección micótica. De los tres casos con aspergiloma intracavitario gigante, se cree que, en uno, la micosis se implantó en una caverna tuberculosa cicatrizada. En los otros dos, la cavidad era un bronquio localmente dilatado y se consideró que no existía una infección tuberculosa.ElAspergillus posee un amplio espectro de patogenicidad. Se le puede observar en lesiones que van desde una localización intrabronquial, acompañada de mínima o nula reacción inflamatoria, hasta casos en los cuales existen lesiones pulmonares necrotizantes con diseminación hematógena a otros órganos (sistema nervioso central, hígado, riñón).     

Informationstheoretisches lernmodell

Summary The formation of the interconnection stimulus-response in a learning system is analysed. The system, a technical or a biological one establishes this correspondence by processing the information fed back from the medium during the learning process. This information has two aspects: a quantitative one related to the probability of the events, and a qualitative one related to the utility of the events in view of a goal. Both aspects are taken into consideration; by successive experiences the system eliminates the double uncertainty concerning the probabilistic dependence: stimulu — sresponse — outcome and its utility. Learning implies then a system for evaluating the utilities of different outcomes in view of a goal, a memory to record them and a decision system for selecting the corresponding responses upon a given criterion.

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Der Beitrag stellt einen Teil der Untersuchungen dar, die zur Ausarbeitung der Doktor-Dissertation am Polytechnischen Institut Gheorghe Gheorghiu-Dej in Bukarest unternommen wurden.     

Morphological comparison ofSqualus blainvillei andS. megalops in the Eastern Atlantic,with notes on the genus

Morphological comparisons are made from the study of 64 specimens belonging to the following species:Squalus acanihias, S. blainvillei, S. megalops andS. acutirostris. The results suggest conspecificity betweenS. acutipinnis andS. megalops. The differences betweenS. blainvillei andS. megalops in the E-Atlantic are stressed. The Indo-Pacific species calledS. blainvillei by Chen et al. (1979) is regarded in this paper as probably an undescribed species. Some consideration on the status of several nominal species and the species grouping withinSqualus are also made.     

Impaired local natural killer cell activity in human colorectal carcinomas

Summary The present study was undertaken to study natural killer (NK) cell activity in patients with colorectal cancer at peripheral and local levels. Mononuclear cells were isolated from uninvolved colorectal mucosa, tumor tissue and peripheral blood, and tested against the colon carcinoma cell line CaCo-2 and the erythroleukemia cell line K-562. Peripheral blood NK cell activity from the patients showed similar levels compared with healthy controls, whereas, mononuclear cells of tumor tissue were found to have a significantly decreased NK cell activity compared to the normal intestinal mucosa (P<0.01). No relation was found between the NK cell activity and the advancement of the disease according to the Duke's stage. Interferon- (IFN-) stimulated the NK cell activity of the mononuclear cells from blood, mucosa and tumor. However, the increase of NK cell activity after IFN- stimulation was lower in the tumor compared to the mucosa (P<0.02). The lectin, phytohaemagglutinin, increased the cytotoxicity of mononuclear cells from blood, mucosa and tumor to a similar level. These results suggest that patients with colorectal tumors exhibit a normal NK cell activity in peripheral blood and intestinal mucosa; however, a diminished NK cell activity exists at the tumor level. Although mononuclear cells isolated from the tumor have a normal response to lectin stimulation they show hyporesponsiveness to IFN- stimulation with regard to their NK cell activity.     

Assembly and disassembly of brain tubulin is affected by high ammonia levels

Rats were fed a diet containing ammonium for up to 6 months. High ammonia levels were attained in brain. The amount of polymerized tubulin in microtubules increased, while the amount of free tubulin remained unchanged. Polymerization of tubulin from brain of ammonium fed rats (30 min, 37°C) was approximately 60% of control. Depolymerization of the microtubules was also affected and took approximately 3 times longer than in controls. These results indicate that both assembly and disassembly of tubulin in brain are impaired by high ammonia levels. Interestingly, the amount of microtubule-associated proteins was not affected.