Presupozycje w perspektywie logicznej

Celem artykułu jest przedstawienie problemu presupozycji z perspektywy logicznej analizy języka. Źródła rozważań dotyczących omawianej kwastii sięgają końca XIX wieku i związane są z postacią Gottloba Fregego. W swej pracy pt. Sens i nominat zadaje on pytanie o to, jak mające funkcje referencji wyrażenia z języka naturalnego powinno się tłumaczyć na ścisłe języki logiczne. Przy okazji tych rozważań zauważa istnienie „założeń koniecznych dla samego istnienia nominatu (desygnatu)”, które charakteryzują się tym, że ich prawdziwość jest warunkiem koniecznym, by móc przypisać zdaniu wartość logiczną. Zwrócił zatem uwagę na zasadniczą własność presupozycji, a więc niezmienność względem negacji. Brak jednak w koncepcji Fregego jednoznaczności co do poziomu języka, na którym należałoby lokować założenia, o których mowa. W opozycji do tej wizji presupozycji sytuuje się idea deskrypcji określonych Russella, której zastosowanie pozwala rozwiązać problem tzw. zdań z pustym podmiotem, nie dość precyzyjnie wyjaśniony na gruncie filozofii języka Fregego. Russell uznał, że zwroty denotujące można wyrazić na poziomie logicznym za pomocą koniunkcji pewnych sądów i w ten sposób zdania orzekające o czymś, co nie istnieje, stały się po prostu fałszywe. Rozwiązanie Russella było jednak sprzeczne z językową intuicją innego słynnego XX-wiecznego filozofa – Petera Strawsona. Uznał on, że wszelkie powyższe problemy biorą się z tego, że badacze nie dostrzegają różnic między zdaniami a zdaniami użytymi do tego, żeby coś stwierdzić i zauważył, że zadania nie są prawdziwe ani fałszywe, taką własność mają jedynie stwierdzenia. Dostrzegł przy tym istnienie szczególnego związku między nimi, polegającego na tym, że jedno stwierdzenie stanowi wstępny warunek tego, by innemu stwierdzeniu można było w ogóle przypisać wartość logiczną. Zjawisko to nazwał on presupozycją i twierdził, że można je uznać za szczególny rodzaj wnioskowania pragmatycznego. Artykuł przybliża trzy podstawowe koncepcje dotyczące presupozycji na tle filozofii języka wyżej wspomnianych autorów.The main aim of this article is to show the problem of presupposition from the side of the logical analysis of language. Deliberations on the topic derive from the nineteenth century and are connected to Gottlob Frege. In his work titled “On sense and reference”, he asks how the expressions with a referring function should be translated into logical language. He also emphasizes “assumptions for the existence of referent (designation)”, whose characteristic feature is that their authenticity is a crucial condition to provide a sentence with a logical meaning. Therefore, Frege highlighted the crucial feature of presupposition that is constancy under negation. However, Frege’s concept lacks unity when it comes to the level of the language on which the assumptions should be made. An opposing view on presupposition is presented by Russell and his idea of definite descriptions, which solves the problem of sentences with non-existent subject terms, of which Frege’s language philosophy does not provide a precise explanation. Russell claims that denoting phrases can be expressed in the form of conjunction of the value of the sentence and thus sentences predicating on something that does not exist happen to be false. However, Russel’s view differs from the one presented by a twentieth-century philosopher, Peter Strawson. The latter maintains that the problems mentioned derive from the fact that scholars do not notice the difference between sentences and sentences used to have an assertive meaning and, consequently, that the sentences cannot be true or false since this is a characteristic feature of statements. He also emphasizes a connection between them, in which one statement is a primary condition to give a logical value to another statement. Strawson called the phenomenon a presupposition and claimed that it can be recognized as a specific kind of pragmatic deduction/presupposition. The article focuses on showing the three views on presupposition on the grounds of the philosophies of language presented by scholars mentioned above

MicroRNAs are intensively regulated during induction of somatic embryogenesis in Arabidopsis

Several genes encoding transcription factors (TFs) were indicated to have a key role in the induction of somatic embryogenesis (SE), which is triggered in the somatic cells of plants. In order to further explore the genetic regulatory network that is involved in the embryogenic transition induced in plant somatic cells, micro-RNA (miRNAs) molecules, the products of MIRNA (MIR) genes and the common regulators of TF transcripts, were analyzed in an embryogenic culture of Arabidopsis thaliana. In total, the expression of 190 genes of the 114 MIRNA families was monitored during SE induction and the levels of the primary (pri-miRNAs) transcripts vs. the mature miRNAs were investigated. The results revealed that the majority (98%) of the MIR genes were active and that most of them (64%) were differentially expressed during SE. A distinct attribute of the MIR expression in SE was the strong repression of MIR transcripts at the early stage of SE followed by their significant up-regulation in the advanced stage of SE. Comparison of the mature miRNAs vs. pri-miRNAs suggested that the extensive post-transcriptional regulation of miRNA is associated with SE induction. Candidate miRNA molecules of the assumed function in the embryogenic response were identified among the mature miRNAs that had a differential expression in SE, including miR156, miR157, miR159, miR160, miR164, miR166, miR169, miR319, miR390, miR393, miR396, and miR398. Consistent with the central role of phytohormones and stress factors in SE induction, the functions of the candidate miRNAs were annotated to phytohormone and stress responses. To confirm the functions of the candidate miRNAs in SE, the expression patterns of the mature miRNAs and their presumed targets were compared and regulatory relation during SE was indicated for most of the analyzed miRNA-target pairs. The results of the study contribute to the refinement of the miRNA-controlled regulatory pathways that operate during embryogenic induction in plants and provide a valuable platform for the identification of the genes that are targeted by the candidate miRNAs in SE induction

Identification of human tRNA:m(5)C methyltransferase catalysing intron-dependent m(5)C formation in the first position of the anticodon of the [Formula: see text]

We identified a human orthologue of tRNA:m(5)C methyltransferase from Saccharomyces cerevisiae, which has been previously shown to catalyse the specific modification of C(34) in the intron-containing yeast [Formula: see text]. Using transcripts of intron-less and intron-containing human [Formula: see text] genes as substrates, we have shown that m(5)C(34) is introduced only in the intron-containing tRNA precursors when the substrates were incubated in the HeLa extract. m(5)C(34) formation depends on the nucleotide sequence surrounding the wobble cytidine and on the structure of the prolongated anticodon stem. Expression of the human Trm4 (hTrm4) cDNA in yeast partially complements the lack of the endogenous Trm4p enzyme. The yeast extract prepared from the strain deprived of the endogenous TRM4 gene and transformed with hTrm4 cDNA exhibits the same activity and substrate specificity toward human pre-tRNA(Leu) transcripts as the HeLa extract. The hTrm4 MTase has a much narrower specificity against the yeast substrates than its yeast orthologue: human enzyme is not able to form m(5)C at positions 48 and 49 of human and yeast tRNA precursors. To our knowledge, this is the first report showing intron-dependent methylation of human [Formula: see text] and identification of human gene encoding tRNA methylase responsible for this reaction

Presupposition from a logical perspective

The main aim of this article is to show the problem of presupposition from the side of the logical analysis of language. Deliberations on the topic derive from the nineteenth century and are connected to Gottlob Frege. In his work titled "On sense and reference", he asks how the expressions with a referring function should be translated into logical language. He also emphasizes "assumptions for the existence of referent (designation)", whose characteristic feature is that their authenticity is a crucial condition to provide a sentence with a logical meaning. Therefore, Frege highlighted the crucial feature of presupposition that is constancy under negation. However, Frege's concept lacks unity when it comes to the level of the language on which the assumptions should be made. An opposing view on presupposition is presented by Russell and his idea of definite descriptions, which solves the problem of sentences with non-existent subject terms, of which Frege's language philosophy does not provide a precise explanation. Russel claims that denoting phrases can be expressed in the form on conjunction of the value of the sentence and thus sentences predicating on something that does not exist happen to be false. However, Russel's view differs from the one presented by a twentieth-century philosopher, Peter Strawson. The latter maintains that the problems mentioned derive from the fact that scholars do not notice the difference between sentences and sentences used to have an assertive meaning and, consequently, that the sentences cannot be true or false since this is a characteristic feature of statements. He also emphasizes a connection between them, in which one statement is a primary condition to give a logical value to another statement. Strawson called the phenomenon a presupposition and claimed that it can be recognized as a specific kind of pragmatic deduction/presupposition. The article focuses on showing the three views on presupposition on the grounds of the philosophies of language presented by scholars mentioned above

The Old and New RNA World

Among the numerous hypotheses offering a scenario for the origin of life on Earth, the one called “The RNA World” has gained the most attention. According to this hypothesis RNA acted as a genetic information storage material, as a catalyst of all metabolic reactions, and as a regulator of all processes in the primordial world. Various experiments show that RNA molecules could have been synthesized abiotically, with the potential to mediate a whole repertoire of metabolic reactions. Ribozymes carrying out aminoacyl-tRNA reactions have been found in SELEX (systematic evolution of ligands by exponential enrichment) approaches and the development of a ribosome from a RNA-built protoribosome is easy to imagine. Transfer RNA aminoacylation, protoribosome origin, and the availability of amino acids on early Earth allowed the genetic code to evolve. Encoded proteins most likely stabilized RNA molecules and were able to create channels across membranes. In the modern cell, DNA replaced RNA as the main depositor of genetic information and proteins carry out almost all metabolic reactions. However, RNA is still playing versatile, crucial roles in the cell. Apart from its classical functions in the cell, a huge small RNA world is controlling gene expression, chromatin condensation, response to environmental cues, and protecting the cell against the invasion of various nucleic acids forms. Long non-coding RNAs act as crucial gene expression regulators. Riboswitches act at the level of transcription, splicing or translation and mediate feedback regulation on biosynthesis and transport of the ligand they sense. Alternative splicing generates genetic variability and increases the protein repertoire in response to developmental or environmental changes. All these regulatory functions are essential in shaping cell plasticity in the changing milieu. Recent discoveries of new, unexpected and important functions of RNA molecules support the hypothesis that we live in a New RNA World