Cancer and cell cycle

Summary: In January 2001, a conference organized by ISREC (Swiss Institute for Experimental Research on Cancer) entitled "Cancer & Cell Cycle" took place in Lausanne in Switzerland. This article renders account of the most interesting, from my point of view, presentations from this conference. They concern not only the cell cycle aspects of the cancerogenesis, but also the most recent advances in the battle against cancer.

Key words: -

Present conception regarding the effect of reactive oxygen species on functions of mammalian spermatozoa

Summary: The source of reactive oxygen species and the pathway generation of the metabolites were discussed in this article. The enzymatic antioxidants systems occurring in semen were characterized. In this article, positive effect of reactive oxygen species on process of fertilization and the toxic effect of oxidative stress on the structure and biological function of mammalian spermatozoa were introduced.

Key words: spermatozoa, mammal, fertilization, reactive oxygen species, oxidative stress, lipid, peroxidation.
 

The symptoms of programmed cell death during plant development

Summary: Selective elimination of cells is require for the normal development of plants. It plays an essential role in embryogenesis and mature organs homeostasis. In some cases degradation of cell content enables correct functioning of dead elements of tissues. Some symptoms of apoptosis described in animal have been observed during plant cell and tissue degradation. In spite of some similarities in the course of these processes it is suggested that apoptosis does not occur during plant cell death and the process is called apoptosis-like. The autolysis and autophagy, processes accompanying programmed cell death, appear to have an essential influence on self-destruction of plant cells. This review describes and characterizes the symptoms accompanying certain types of plant cell degradation during tissue differentiation and plant development. The main emphasis has been focused on the description of events occurring during terminal differentiation of ephemeric tissues and on degradation processes which enable further proper functioning of the organism cells.

Key words: apoptosis, programmed cell death (PCD), cysteine proteases, autolysis, autophagy, mitochondria, endosperm, tapetum, tracheary elements.

Biosynthesis and immunomodulatory properties of lipoxins - metabolites of arachidonic acid

Summary: Lipoxins belong to the group of eicosanoids, i.e. metabolites of arachidonic acid. Out of three biosynthetic pathways leading to the formation of lipoxins (LXA₄ and LXB₄) two of them are catalysed by a sequential action of 5- and 12/15-lipoxygenases, whereas the third one is catalysed by aspirin-acetylated cyclooxygenase 2 (COX-2). The products of the latter reaction are 15-epi-lipoxins (15 epi-LXA₄ and B₄). Lipoxins are mainly the products of intercellular co-operation (e.g. neutrophils and platelets). There have been characterised two receptors for lipoxins: the LXA₄ specific receptor, expressed in monocytes, granulocytes and enterocytes, and receptor shared with peptidoleukotrienes, found in other cells. In vitro lipoxins were shown to have immunomodulatory properties. Thus far it is suggested that they are mediators of inflammatory reactions, they oppose the action of proinflammatory leukotrienes (stop signalling according to Charles Serhan), and they inhibit the function of neutrophils. But it is difficult to explain how they contribute to the role of all eicosanoids in vivo.

Key words: lipoxins, aspirin, eicosanoids.

Influence of tumor necrosis factor (TNF) on tumor vasculature

Summary: Tumor necrosis factor (TNF-alpha, cachectin) is a pleiotropic proinflammatory cytokine, produced mainly by activated macrophages and monocytes. Besides immunomodulatory activity, TNF also exerts anti-tumor effect by inhibiting growth of some tumors or even by causing tumor regression. Therefore TNF, in spite of its toxicity, is used in some clinical protocols, mainly of inoperable limb melanomas and sarcomas. Analysis of the data from different experimental models distinguishes three main mechanisms responsible for TNF action on tumor growth: 1) direct toxic effect on tumor cells, 2) indirect action effected by immunomodulation, 3) indirect action effected by modulation of tumor vasculature. The presented concentrates mainly on TNF influence on vascular bed of tumors. TNF exerts direct cytostatic or cytotoxic effect on endothelial cells as well as an indirect effect obtained by modulation of neutrophil function of TNF affects also process of angiogenesis, which is a process leading to development of tumor vascularization. TNF modulates also blood coagulation and fibrinolysis, eventually affecting blood supply of tumor tissues. TNF increases infiltration of tumor tissues by immune cells and modulates their activity simultaneously. TNF-mediated modulation of expression of adhesion molecules on surface of endothelial and tumor cells can affect the process of metastasis formation. Effects of TNF on tumor vascular bed are most likely independent of tumor cells sensitivity to direct toxic effect of TNF. Therefore detailed understanding of TNF effect on tumor vasculature has great practical meaning, as tumor blood vessels can be universal destination point of anti-tumor therapies.

Key words: TNF, tumor, vasculature, angiogenesis, cell adhesion.
 

Nucleocytoplasmic transport of proteins and ribonucleic acids

Summary: In eukaryotic cells nuclear envelope separate nucleus � the place of DNA replication and transcription from cytoplasm where occurs biosynthesis of proteins. Regular function of cell is dependent on efficient exchange of proteins and RNAs between the two cellular compartments. Nucleocytoplasmic transport occurs through large multiprotein structures termed nuclear pore complex. Transport of proteins and RNAs is selective, signal-mediated and dependent on energy and specific nuclear and cytoplasmic receptors.

Key words: protein import, RNA export, signals of nuclear import and export, importins, exportins, GTPase Ran.
 

Small tissue - large strength. Brown adipose tissue: structure, existence and significance

Summary: Brown adipose tissue is a kind of connective tissue, existing in adults in small amounts. This tissue has much more signifance for small mammals and animals sinking  into  winter sleep. This part in animals coming into the hibernation state is an exciting subject to consider this scantly occurring tissue and a possibility to utilize its thermogenic properties for people.The present paper is intented to systematize data concerning existence and tissue distribution in people. It presents microscopic structure of brown adipose tissue cells and calls attention to its significance in heat generation process. Mechanisms affecting fatty acid oxidation by this tissue with CO₂ and H₂O generation and release of large heat amount are reasons of interest in brown adipose tissue by modern medicine and its utilization in struggle against adiposity and its consequences, such as: arterial hypertension, coronary disease and diabetes. Detailed knowledge in structure and mechanisms managing brown adipose tissue at animals may open new possibilities to treat human adiposity.

Keywords: brown adipose tissue, uncoupling protein, adiposity.

DNA damage in mammalian cells

Summary: DNA damages are divided into endogenous, connected with activity of endogenous cellular processes, and exogenous. Electron transport in respiratory chain, enzymatic reactions of oxidases and cytochromes, redox cycling, inflammatory processes are the cellular processes responsible for changes in genetic material. Interest in the exogenous factors is continuously growing because of hazard related to their occurrence in environment, food, and their application in treatment of cancer and other diseases. DNA damage effects on mutations and can modulate living processes. Transcription factor TFIID binds to DNA modified by activated cis-diamminodichloroplatin and consequently mRNA synthesis is stopped. Knowledge of mechanisms of influence of different factors on DNA and cell should enable us to prevent from undesirable consequences of presence of genotoxic compounds in environment and to improve methods of treatment of not only cancer diseases.

Key words: DNA damage, mutations, mammals, human

Application of DNA sequence analysis to phylogenetic and taxonomic studies of Bryophytes

Summary: DNA sequence analysis has enabled to put forward several new hypotheses concerning phylogeny and systematics of  living organisms. The application of new methodology has contributed to a significant  progress in  research on taxonomy and phylogeny of bryophytes. In this paper, the state of the art as well as new hypotheses concerning phylogeny, based on Bryophyta DNA sequence analysis, were presented. Moreover, hypotheses on the subject of the origin of land plants were discussed in the aspect of the studies of molecular evolution of bryophytes. Results of the described studies give a new insight into systematics of bryophytes and origin of  land plants.

Key words: Bryophyta, molecular evolution, phylogeny

[Postepy Biologii Komorki 2002; 28: 431–442]

Katarzyna ROSZEK, Jadwiga GNIOT-SZULŻYCKA

Transport of macromolecules between endoplasmic reticulum and Golgi apparatus.                                The role of COPI- and COPII- coated vesicles and the intermediate compartment

Summary: Transport of the macromolecules synthesized in the endoplasmic reticulum (ER) is mediated by COP I- and COP II-coated vesicles. The polymorphic vesicular-tubular structure, ER-Golgi intermediate compartment (IC, VTCs or ERGIC), regulates transport and sorting of macromolecules via recognition of signal motifs. For example, the diphenylalanine (FF) signal is important for the export from ER while the dilysine (KKXX) signal is necessary for retrograde transport of proteins back to the reticulum. The role of constitutively cycling proteins, especially those from the p24 family, which participate in the concentration and sorting in compartment ER <-> IC <-> Golgi, has been described.

Key words: coated vesicles, COP I, COP II, ER-Golgi intermediate compartment (IC, VTCs or ERGIC).