Participation of Serotonergic System in Function of Mammalian Circadian Clock

Summary: Serotonin plays an important role in function of the organism as a regulator of physiological and behavioral processes. Serotonin participates in the control of the biological clock located in suprachiasmatic nuclei (SCN) of the hypothalamus. Serotonergic innervation arises from the midbrain median raphe nuclei and interacts with other two main projections to the SCN. The basic role of serotonin is to modulate function of the biological clock by attenuation of the photic information transmitted to the SCN. This modulation through the activation of 5HT1A, 5HT1B and 5HT7 receptors is important for the entrainment of the clock to the environmental illumination. Serotonin and 5HT agonists are capable to phase-shift the SCN neuronal activity rhythm. Serotonin is also implicated in altering the function of the clock by non-photic stimuli.

Key words: serotonin, circadian rhythms, SCN, photic stimuli, non-photic stimuli.

Triterpenoids Occurrance and their Biosynthesis in
 Cultures in Vitro
 

Summary: Triterpenoids belong to the large group of plant substances, which occur commonly in plants. Considering their valuable properties (insecticidal, fungicidal, antiviral and other), active biosynthesis of triterpenoids in plant cells in vitro enjoys now growing interest. In this review the cases of production of phytoekdysteroids, steroidal and pentacyclic sapogenins by plant cells, in different type of in vitro cultures are described. In general, the amounts of phytoekdysteroids were fewer in undifferentiated cells (callus cultures) in comparison to original plants, despite several exceptions (i. e. callus tissue from Pteridium aquilinum prothalium). To digitoxin biosynthetic pathway being active in cells, the organogenesis was required. Otherwise, other steroidal sapogenis – diosgenin derivatives – are synthesised more intensively in callus tissues. Similarly, very different results were obtained in pentacyclic sapogenins biosynthesis in vitro according to plant species, culture type, medium, hormone and nutrients concentration.

Key words: triterpenoids, phytoekdysteroids, sapogenins, in vitro culture.

The Influence of the 3’ end Processing
of Plant Mitochondrial Transcript on their Stability
 

Summary: Plant primary mitochondrial transcripts undergo several post-transcriptional processes like splicing, editing and 3’/5’ ends processing before become mature RNAs. In other words, the post-transcriptional processes leading to mature RNA molecules are regulated by factors which exert stabilizing or degradating effect on RNA. The steady state level of mitochondrial RNAs is determined primarily by the transcription rate, which is influenced by the promoter structure and the gene copy number. It is suggested that the factor stabilizing mitochondrial transcripts is an RNA stem loop structure, encoded by inverted repeats present in the 3’ untranslated region of many genes. In turn, the attachment of poly(A) tails to the 3’end of mitochondrial transcripts enhances their degradation by accelerating nuclease action. Mitochondrial RNAs do not display conservative sequence elementsclosely connected with polyadenylation. This article focuses on the influence of the 3’end processing of plant mitochondrial RNA on their stability and degradation

Key words:plant mitochondrial transcripts, polyadenylation, inverted repeats.

Genetic Instability in Cancer. I. Chromosomal Instability in Cancer.

Summary: Chromosomal and/or microsatellite genetic instability is one of characteristic features of malignant cells. In solid tumours, as well as in haematological tumours, chromosomal instability is expressed by accumulation of structural and numerical aberrations. Chromosomal aberrations can play a key role in cancer initiation and progression, or can be a feature of genetic instability that cells acquire during tumour development. In this review a role of chromosomal instability in overall genetic instability of cancer cells is presented.

Key words: genetic instability, chromosomal aberrations, aneuploidy, cancer.

Supression of Apoptosis in Chordopoxvirus Infections

Summary: General characteristics of  proteins encoded  by  some of  the members of Chordopoxvirinae (orthopoxviruses, leporipoxviruses and molluscipoxviruses) involved in apoptosis supression has been described in this paper. Proteins involved in poxvirus modulation of apoptosis include: caspase inhibitors – serpins, soluble cytokine (IL-1a, IL-1b, IL-18, IFN-b, IFN-g, TNF-a, TNF-b)  and chemokine (CC) receptors, PKR inhibitors, v-FLIPs and anti-apoptotic proteins of different functions: M11L, MT4 i p28. Due to apoptosis modyfying genes poxviruses are very well adapted to their hosts and can successfully replicate their genom.

Key words: chordopoxviruses, apoptosis, caspases, death receptors, cytokines, chemokines.

Smith, Lemli, Opitz Syndrome in Clinical, Biochemical And Molecular Studies
 

Summary:  Smith-Lemli-Opitz syndrome (SLOS, MIM 270400) is an autosomal recessive disorder, characterized by facial dysmorphisms, mental retardation and multiple congenital anomalies. Biochemically, the disorder is caused by deficient activity of 7-dehydrocholesterol reductase (DHCR7). Cholesterol plays an important role in early embryonic development probably via the function of specific gene products, such as sonic hedgehog (SHH) signaling proteins. The frequency of SLOS is calculatedto be 1:60000 to 1:10000. The 7-dehydrocholesterol reductase gene (D7 sterol reductase gene, DHCR7) was identified on chromosome 11 in region q13. Up to now 93 different mutations. and have been described in the translated exons 3–9. The mutations are mostly nucleotide substitutions (90%). Insertions and deletions are not so frequent (10%) and were identified in the nine families. The clinical severity scores were correlated with mutation classes. The mildest clinical SLOS phenotypes (SLOS type I) were associated with missense mutations and the severe  phenotypes (SLOS type II) were associated  with splice site and nonsense mutations as well as missense mutations located in the C-terminal domain (CT).

Key words: Smith-Lemli-Opitz syndrome, 7-dehydrocholesterol reductase, DHCR7 gene, sonic hedgehog proteins.

Human Papillomavirus And Apoptosis

Summary: The importance of human papillomavirus infection on apoptosis and cancerogenesis was a subject of many investigations and it is still evaluated. The aim of the reviev is to present recent knowledge concerning the influence of human papillomavirus on chosen aspects of cell  live and death processes. Apoptosis is a quite complex process leading to cell’s death, in which a main role play the proteins of BCL-2 family and cell cycle regulating proteins such as P53 and pRB. The meaning of HPVinfection is associated with surviving process promotion during inactivation of many proteins: P53, pRB, p107, and interaction of viral oncoproteins with cell cycle cyclines, degradation of proapoptotic proteins (BAX, BAK) what in consequence leads to overexpression of antiapoptotic proteins such Bcl-2 proteins. Basing on recent data we described the influence of viral oncoproteins on many cell cycle regulating proteins, proliferation and apoptosis regulating factors (P53, Bcl-2, BAK, BAX, pRB). A particular attention is put on the role, which play viral genes E6 and E7 products in braking apoptosis processes. The course of viral infection seem to play a significant role in cascade of apoptosis processes damage, what may leads to uncontrolled cells proliferation and neoplastic changes development.

Key words: apoptosis, HPV, BAK, BAX, Bcl-2, P53, pRb

Role of Reactive Oxygen Species in Blood Platelets

Summary:Reactive oxygen species (ROS), which include the superoxide anion (O2-),  the hydroxyl radical (ˇOH), hydrogen peroxide (H2O2),  singlet oxygen (1O2) and nitric oxide (NOˇ) are highly reactive substances. They can react with lipids, proteins and DNA, inducing irreversible changes of their biomolecular structure. Several studies have shown that blood platelets, in analogy to other circulating blood cells, can produce ROS, which are involved in the mechanisms of platelet activation. In blood platelets ROS may derive from different sources. Potential sources of reactive oxygen species in blood platelets stimulated by different physiological agonists (thrombin, collagen) are associated with arachidonic acid metabolism (via cyclooxygenase or 12-lipoxygenase), phosphoinositides and glutathione cycle. ROS are also generated in platelets by activation of NADPH oxidase, xanthine oxidase and NOˇ synthase. Reactive oxygen species may behave as second messengers in thrombin- or collagen-activated platelets. This review presents the role of ROS in blood platelets.

Keywords: reactive oxygen species, blood platelets, glutathione.

Gene Silencing as a Strategy for Analysis of Gene Function in Plants

Summary: One of the strategies for identification of gene function is the comparative morphological, cytological and molecular analysis of phenotypes obtained after introduction of the gene construct causing gene silencing or its overexpression. This paper describes some aspects of the gene silencing (transcriptional gene silencing, posttranscriptional gene silencing, co-suppression, homology dependent gene silencing, RNA interference, quelling), its application as a strategy for analysis of gene function and also the examples of plant silencing vectors.

Key words: gene silencing, posttranscriptional gene silencing (PTGS), RNA silencing, silencing vectors.

Genome Surveillance System

Summary: Genome surveillance system and progression through the cell cycle. Upon examination of cell cycle regulation relations were discovered of the cell cycle control mechanisms with a complicated web of signaling pathways, eventually called the genome surveillance system. 2 Cellular response toDNA damage. Protein components in the surveillance system that respond to DNA damage can be divided as follows: PIKL kinases (phosphatidyl inositol 3-kinase like); trimer-forming proteins similar to PCNA (proliferating cell nuclear antigen); sensor proteins (9-1-1 complex); serine-treonine (effector) kinases (Chk 1 and Chk 2); adaptor proteins. DNA damage generates an alarm signal through PIKL kinases and sensor proteins. The signal is amplified and transduced to recruit DNA repair systems and to activate transcription of genes necessary for blocking priogression through the cell cycle, for DNA repair or apoptosis. 3. Cell cycle checkpoints . Signalling essential for blocking progression through G1, S and G2 phases starts at the Atm kinase; its downstream substrates are effector kinases, acting in all 3 checkpoints, Tp53, acting as transcription factor essential for G1/S block, nibrine (S phase checkpoint) and Brca1(checkpoints S and G2). The two latter proteins also participate in DNA repair. 4.Concluding remarks. Upon examination, the picture of the genome surveillance system becomes more and more complex. The functions best characterised in mammalian cells – control of cell cycle progression and its coordination with DNA repair - have been recently completed by new functions, mostly due to analysis of the same functions in yeast.

Key words:.genome surveillance system; Atm kinase; Tp53; Brca1; nibrine; cell cycle

Embryo Implantation

Summary: The paper presents comprehensively process of implantation with its stages of apposition, adhesion and invasion. Both endocrine and paracrine regulatory networks are also presented. The described phenomena are complicated and strictly controlled, thus any disorders in reproductive homeostasis in woman are connected with restriction in fertility. Pathology of apposition may lead to ectopic pregnancy or placenta praevia, early abortions are linked to disorders of adhesion, and finally pathology of invasion may cause improper placentation like placenta acreta or may predispose to pregnancy induced hypertension with its complications.

Key words: embryo, implantation

Function of Calcium Binding Proteins of the S100 Family

Summary: Calcium ions and calcium binding proteins are involved in many cellular processes. Among the calcium binding proteins containing “EF-hand” motifs one can distinguish a group of proteins called S100 family. The majority of S100 proteins were discovered during the last ten years and, at present, this family contains 20 proteins. S100 proteins have similar primary structure since they possess 30-60% identity in amino acid sequences. Individual S100 proteins exhibit cell and tissue specific expression and their function has not been fully explained. However, the involvement of S100 proteins in many processes such as phosphorylation, enzyme activity, adhesion, survival and regeneration of neurons or apoptosis of neuronal cells, indicates, that S100 proteins might play an important intracellular and extracellular role.

Key words: calcium binding proteins, S100 proteins, function