Postepy Biologii Komorki, vol. 32, 2005, issue 1

Summary: Chicken egg-yolk antibodies are great, alternative to mammalian IgG, tool in research, diagnostics and therapy. Several advantages of IgY over conventional IgG are due to distinct structural and phylogenetic difference. They are successfully used in immunoassays such as Western Blotting, ELISA, immunoprecipitation, immunohistochemistry and others. Advanced IgY technology enables to treat some bacterial and viral diseases where conventional therapy fails. Production of egg-yolk antibodies, as a minimally invasive method, brings great benefit concerning animal welfare. Egg collection and further isolation of desired antibodies is fast, simple and cost-effective. Lack of information, insufficient experience or simply reluctance to new techniques is the main reason for moderate popularity of IgY. The objective of this paper is to provide information on applications and advantages of chicken IgY.

Regulation of Symplastic Continuity in Processes of Growth and Development in Plants

Summary: Symplastic isolation and symplastic continuity are related to a process of cell-to-cell communication via plasmodesmata. Functional states of plasmodesmata are dynamically changing. Opened plasmodesmata facilitate symplastic transport between cells. Closed plasmodesmata isolate a cell or a group of cells and assure their functional integrity. Cell-to-cell communication may also be regulated due to formation of new plasmodesmata and elimination of existing ones. Symplastic continuity is present between mature cells, which perform the same functions, as well as between cells of undifferentiated structures and organs. The cells performing different functions or beginning a differentiation are symplastically isolated. The phenomenon of symplastic isolation is universal in plant organisms. It has been detected in meristematic tissues and in fully differentiated structures. Symplastic continuity, which makes intercellular communication possible and symplastic isolation, which separates particular groups of cells, both regulate processes of growth and development and guarantee proper functioning of cells in mature plant structures.

Key words: plasmodesmata, symplastic isolation, symplastic continuity, cell-to-cell communication, symplastic domains, symplastic fields

Summary: Alternative splicing is defined as a process that increases the diversity of transcripts and protein variety. It is estimated that 5–30% of human genes express alternative variants. Alternative splicing is regulated by different, tissue-specific splicing enhancers and silencers. Numerous proteins are the products of this process, as for example 15-lipoxygenase-b and cyclooxygenase. Alternative variants of proteins may have different functions like for example IL-4. Understanding the mechanism of alternative splicing and its regulation will allow to use this process for diagnosis, genetic predisposition detection or as a target for therapy.

Summary: Nitric oxide (NO), synthesized from L-arginine by NO synthases, is a small, diffusible, highly reactive molecule with dichotomous regulatory roles under physiological and pathological conditions. Apoptosis plays an important role in the development of the organism but also under various pathological conditions. NO can exert both pro- and anti-apoptotic effects, depending on the conditions and cell type. Long-lasting production of NO acts as a proapoptotic modulator by activating caspase family proteases through the release of mitochondrial cytochrome c into the cytosol, upregulation of p53 expression, activation of JNK/SAPK, and altering the expression of apoptosis-associated proteins including Bcl-2 family proteins. However, low or physiological concentrations of NO prevent cells from apoptosis via expression of protective genes such as heat shock proteins, Bcl-2 as well as direct inhibition of the apoptotic caspase family proteases by S-nitrosylation of the cysteine thiol. Our current understanding of the mechanisms by which NO influences both pro- and antiapoptotic actions is discussed in this review.

Key words:: apoptosis, nitric oxide (NO), peroxynitrite, cGMP, S-nitrosylation, caspase, bcl-2

Summary: Developing vertebrate limb is a model system frequently used to study tissue differentiation and patterning. Research methods based on sophisticated genetic and molecular embryology techni-ques allowed revising some of the longstanding hypotheses in this field of research. One of them proposed the mechanism of limb development along proximal-distal axis based on the existence of Progress Zone. Recent results propose an alternative model of limb differentiation along this axis, so called Predetermination Model. Additionally, an unexpected function of sonic hedgehog in the determination of digit number and identity was recently proposed. Some of those findings will be discussed in this article.

The Aspects of the Formation tf Extracellular Matrix in Mineralized Tissues Including the Disturbances Caused by Fluoride. Part I. Enamel

Summary: Dental enamel is the most mineralized tissue all over the body. The enamel development begins with the organic matrix secretion. The enamel extracellular matrix mainly consists of amelogenins and enamelins. As the enamel maturation progress the organic matrix undergoes proteolitic degradation. The remnants, which remain after the degradation are subsequently withdrawn and replaced with hydroxyapatites crystals which form the enamel prisms. The enamel secretion and maturation can be modified by fluoride ions supplemented per os. It is extremely difficult to establish the daily optimal dose of fluoride which if exceeded leads to disturbances in the enamel mineralization and the fluorosis origin. The mechanism of the dental fluorosis origin has not been completely explained yet. Nevertheless the available data confirm that dental fluorosis is a side effect of disturbances in the proteolitic degradation of the proteins that form the enamel extracellular matrix. In the paper we depicted the proteins which are the main components of the enamel extracellular matrix as well as the influence that fluoride exerts on their metabolism, which can result in the fluorosis.

The Aspects of the Formation of Extracellular Matrix in Mineralized Tissues Including the Disturbances Caused by Fluoride. Part II. Dentin

Summary: The dentin formation and mineralization proceeds in the defined, matrix-mediated manner. It begins from the secretion of the organic matrix and ends with the complete mineral deposition. The dentin apposition takes place when odontoblasts begin the secretion of type I collagen into the extracellular compartment. Type I collagen is the main component of the dentin extracellular organic matrix and forms the specific scaffold for the deposition of dentin hydroxyapatite crystals. The dentin mineralization begins from the secretion of noncollagenous proteins directly at the mineralization front. These noncollagenous, strongly acidic proteins are able to bind covalently to type I collagen fibrils. Concurrently they have the strong affinity to calcium ions. The available data confirm that the right interaction between collagen and noncollagenous proteins secretion as well as mineral deposition is the prerequisite for the complete dentin mineralization. The fluoride hypersupplementation when provided internally can alter this coordination. The mechanism of the formation of dentin extracellular matrix has been described. We focused our attention on the metabolism of the most important dentin matrix protein and emphasized the stages in the proteins metabolism which can be adversely affected by fluoride leading to the subsequent disturbances in the proper mineralization of dentin.

Summary: Genetic, biochemical and cytological studies on cytosine methylation in eukaryotic orga-nisms indicate intriguing links between DNA methylation, histone methylation, RNA interference and chromatin remodeling. It is clear that no single pathway accounts for all DNA methylations found in Eukaryota. In this article several general mechanisms which control methylation are briefly described.

Summary: Intracellular protein destroying and impairment of their synthesis result in disturbance of cell homeostasis and can lead to cell death. Counteracting these changes the cell induces synthesis of stress proteins among others. Physical exercise has stress attributes, especially if it is a long-lasting and intensive one. It can be assumed that this will bring about an intensification of stress protein expression what was experimentally confirmed. However the significance of this reaction is not fully clear taking into account the variety of functions the stress protein act in the organism. Stress proteins, called also heat shock proteins (HSP) display mainly the enzymatic function used in a direct protection against negative effects of stress. Taking into account their molecular weight one can distinguish two main groups of HSP, the low-molecular and high-molecular ones. HSPs belonging to the low-molecular group act mainly as chaperons and facilitate the degradation of destroyed proteins. Some of them, as HSP27 and HSP40, enhance the protective potential of other stress proteins. In high-molecular group one can distinguish HSP60, HSP70 and HSP90. As the mostly known and important for humans is HSP70. Stress proteins of this group act against protein aggregation and refolding of denaturized and non-native proteins, and in removing them out of the cell. They act as chaperons of polypeptides synthesized along ribosomes and participate in protecting mechanisms against negative influences of stressors on intracellular processes. Main role of HSP90 is a cooperation in the regulation of cytoskeleton function, and HSP110 is functionally related to HSP70. The activity of muscle fibers is performed against a background enclosing influences of numerous mechanical and physiological stressors. During this activity there appear various intracellular changes having adaptative value. It has been shown that muscular activity particularly in changes of HSP27, HSP72 and HSP73 amounts. During the muscular activity there appear preliminary signs of reactive stress where the reactive oxygen species act as second messengers. They influence upon the gene expression, especially upon the transcription factor NF?B being an apoptosis induction factor. In higher concentrations the reactive oxygen species destroy cell structure giving the appearance of TNF? and apoptosis, or an enhancing of Ca2+ concentration in sarcoplasm with the activation of endonuclease, resulting finally in necrosis. The HSP induction is in this situation a part of anti-oxidant defense strategy, acting as mitochondrial protection, and inducing leukocytosis and activating anti-inflammatory cytokines. The course of the above reactions is determined by the character of exercise, its intensity and performing time, and they are probably a part of mechanisms resulting in work adaptation.

Summary: One of the major components of the cellular response to oxygen deprivation is a heterodimeric transcription factor - hypoxia inducible factor-1 (HIF-1). HIF-1 is constitutively produced and degraded by the ubiquitin-proteasome system under normoxic conditions but becomes stabilized and transcriptionally active under hypoxic conditions. Hypoxia is one of the typical features of growing tumor and enhanced activity of HIF-1 observed in several different malignancies, is one of the most important factors responsible for activating pathways leading to tumor angiogenesis. Therefore better understanding of HIF-1 function may provide new targets for tumor therapy.

Molecular Factor in Reproduction; the Role and Characteristics of Antisperm Antibodies

Summary: Rapid progress of biological and medical research depends largely on steadily growing information in online databases and its accessibility for researchers. All centers involved in the collection of nucleotide and aminoacid sequences exchange and update available data. Full benefit from this information may be obtained only by proper analysis provided by several bioinformatic services. In their formation people from broad scientific community are engaged and their effects of work are accessible free of charge in internet. This software permits to analyze collected data in various aspects. For example, properties of neural cell adhesion molecule (NCAM) depend a lot on multiple posttranscriptional and posttranslational modifications. Bioinformatic approach allows to assess their significance. Due to bioinformatic tools it was shown that NCAM may theoretically possess 40 up to 46 exons, while genetic screening indicated 20 only. Application of Spidey software revealed novel data about VASE exon, showing links with decreased brain plasticity. Other tools permitted to obtain details about NCAM protein formation in the cell, its transmembrane and soluble forms as well as tertiary structure and its possible modifications. I was also shown that NCAM is able to intracytoplasmic signal transduction and emphasized the role of protein phosphorylation in this process. This will make possible to determine precisely the role of NCAM molecule both in health and disease.:

Key words: bioinformatics, databases and tools, neural cell adhession molecule – NCAM, posttranscriptional and posttranslational modifications.