Somatostatin receptor biology in neuroendocrine and pituitary tumours: part 1 – molecular pathways

Neuroendocrine tumours (NETs) may occur at many sites in the body although the majority occur within the gastroenteropancreatic axis. Non-gastroenteropancreatic NETs encompass phaeochromocytomas and paragangliomas, medullary thyroid carcinoma, anterior pituitary tumour, broncho-pulmonary NETs and parathyroid tumours. Like most endocrine tumours, NETs also express somatostatin (SST) receptors (subtypes 1–5) whose ligand SST is known to inhibit endocrine and exocrine secretions and have anti-tumour effects. In the light of this knowledge, the idea of using SST analogues in the treatment of NETs has become increasingly popular and new studies have centred upon the development of new SST analogues. We attempt to review SST receptor (SSTR) biology primarily in neuroendocrine tissues, focusing on pituitary tumours. A full data search was performed through PubMed over the years 2000–2009 with keywords ‘somatostatin, molecular biology, somatostatin receptors, somatostatin signalling, NET, pituitary’ and all relevant publications have been included, together with selected publications prior to that date. SSTR signalling in non-neuroendocrine solid tumours is beyond the scope of this review. SST is a potent anti-proliferative and anti-secretory agent for some NETs. The successful therapeutic use of SST analogues in the treatment of these tumours depends on a thorough understanding of the diverse effects of SSTR subtypes in different tissues and cell types. Further studies will focus on critical points of SSTR biology such as homo- and heterodimerization of SSTRs and the differences between post-receptor signalling pathways of SSTR subtypes.     

2′, 3′-<Emphasis Type="Italic">O</Emphasis>-(4-benzoylbenzoyl)–ATP-mediated calcium signaling in rat glioma C6 cells: role of the P2Y<Subscript>2</Subscript> nucleotide receptor

In this study, we examined the response of glioma C6 cells to 2′,3′-O-(4-benzoylbenzoyl)-ATP (BzATP) and showed that the BzATP-induced calcium signaling does not involve the P2X₇ receptor activity. We show here that in the absence of extracellular Ca²⁺, BzATP-generated increase in [Ca²⁺]_i via Ca²⁺ release from intracellular stores. In the presence of calcium ions, BzATP established a biphasic Ca²⁺ response, in a manner typical for P2Y receptors. Brilliant Blue G, a selective antagonist of the rat P2X₇ receptor, did not reduce any of the two components of the Ca²⁺ response elicited by BzATP. Periodate-oxidized ATP blocked not only BzATP- but also UTP-induced Ca²⁺ elevation. Moreover, BzATP did not open large transmembrane pores. What is more, a cross-desensitization between UTP and BzATP occurred, which clearly shows that in glioma C6 cells BzATP activates most likely the P2Y₂ but not the P2X₇ receptors.     

Effect of Protease Inhibitors on Early Events of Apoptosis

Proteolysis is an early event of apoptosis which appears to be associated with activation of the endonuclease which is responsible for internucleosomal DNA cleavage. The present study was designed to reveal the possible role of proteolysis in other early events, such as chromatin condensation, nuclear breakdown, and destabilization ofin situDNA double-stranded structure. Apoptosis of human leukemic HL-60 cells and rat thymocytes was induced by different agents, including DNA topoisomerase inhibitors, an RNA antimetabolite, and the glucocorticosteroid, prednisolone. DNA degradation was evaluated by pulsed field and conventional gel electrophoresis and by the presence ofin situDNA strand breaks. DNA stability was estimated by the measure of its sensitivityin situto denaturation. Chromatin condensation, nuclear breakdown, and other morphological changes were monitored by interference contrast and UV microscopy following cell staining with the DNA-specific fluorochrome 4′,6-diamidino-2-phenylindole. Several irreversible or reversible serine protease inhibitors prevented internucleosomal DNA degradation, nuclear breakdown, and destabilization of DNA double-stranded structure. The effective inhibitors, however, did not prevent the onset of chromatin condensation, nor the loss of the fine structural framework, nor the initial step of DNA cleavage generating DNA fragments of ≥50 kb in size. The data indicate that in both cell systems the activity of proteases sensitive to the inhibitors tested is needed for internucleosomal DNA cleavage to occur. The data also suggest that these proteases may be involved in dissolution of the nuclear envelope. Because nuclear matrix proteins and histones stabilize DNAin situ,and the decrease in DNA stability which occurs during apoptosis is precluded by the inhibitors, it is likely that serine proteases may degrade DNA stabilizing proteins. The activity of these proteases, however, appears needed neither for DNA cleavage to ≥50-kb fragments nor for the onset of chromatin condensation which is associated with dissolution of the structural framework of the nucleus.     

The endangered thick-shelled river mussel (<Emphasis Type="Italic">Unio crassus</Emphasis>): a new host species for the European bitterling (<Emphasis Type="Italic">Rhodeus amarus</Emphasis>)

Large freshwater mussels (Unionoida) are declining throughout the world. The European bitterling Rhodeus amarus (Bloch, 1782) female spawns its eggs inside the unionids’ shells, where fertilisation and further embryonic development take place; thus its reproduction depends fully on the presence of large freshwater mussels. Unio crassus, previously regarded as one of the most numerous unionids in Europe, is now listed in the IUCN Red Data List as being globally endangered. Despite its previous prevalence, it was never reported as a host for the bitterling. A large population of U. crassus was studied in small river at the ?wi?tokrzyskie Mts (Poland), where also electrofishing was conducted. In each bitterling territory located on the study plots, we found individuals of U. crassus, with the bitterling eggs or larvae developing on mussel’s gills. That proves that this species can be also used by the bitterling for reproduction. We suggest that this relationship has not been reported to date due to the mussels’ rarity and ongoing decline. However, it is also possible that the endangered mussel is a novel host for the bitterling, which is expanding its range throughout Europe.     

Intraspecies variability of Desulfovibrio desulfuricans strains determined by the genetic profiles

Fifteen (soil and intestinal) strains of Desulfovibrio desulfuricans species were typed by PCR method with the use of primers specific for repetitive extragenic palindromic (REP) and enterobacterial repetitive intergenic consensus (ERIC) sequences. As a result, characteristic DNA fingerprints for the strains were obtained. Moreover, the genetic profiles were found to be useful for typing and distinguishing the strains of D. desulfuricans. According to cluster analysis, PCR with primers complementary to the sequences REP appeared to be slightly more discriminatory than PCR with ERIC primers for the investigated strains. Distinct fingerprint patterns of two isolates derived from the same patient pointed to the different origin of both strains.     

Empirical testing of cryoconite granulation: Role of cyanobacteria in the formation of key biogenic structure darkening glaciers in polar regions

Cryoconite, the dark sediment on the surface of glaciers, often aggregates into oval or irregular granules serving as biogeochemical factories. They reduce a glacier's albedo, act as biodiversity hotspots by supporting aerobic and anaerobic microbial communities, constitute one of the organic matter (OM) sources on glaciers, and are a feeder for micrometazoans. Although cryoconite granules have multiple roles on glaciers, their formation is poorly understood. Cyanobacteria are ubiquitous and abundant engineers of cryoconite hole ecosystems. This study tested whether cyanobacteria may be responsible for cryoconite granulation as a sole biotic element. Incubation of Greenlandic, Svalbard, and Scandinavian cyanobacteria in different nutrient availabilities and substrata for growth (distilled water alone and water with quartz powder, furnaced cryoconite without OM, or powdered rocks from glacial catchment) revealed that cyanobacteria bind mineral particles into granules. The structures formed in the experiment resembled those commonly observed in natural cryoconite holes: they contained numerous cyanobacterial filaments protruding from aggregated mineral particles. Moreover, all examined strains were confirmed to produce extracellular polymeric substances (EPS), which suggests that cryoconite granulation is most likely due to EPS secretion by gliding cyanobacteria. In the presence of water as the only substrate for growth, cyanobacteria formed mostly carpet-like mats. Our data empirically prove that EPS-producing oscillatorialean cyanobacteria isolated from the diverse community of cryoconite microorganisms can form granules from mineral substrate and that the presence of the mineral substrate increases the probability of the formation of these important and complex biogeochemical microstructures on glaciers.     

Variations and trends of birch pollen seasons during 15 years (1996–2010) in relation to weather conditions in Poznań (western Poland)

Birch (Betula) pollen seasons were examined in relation to meteorological conditions in Poznań (1996–2010). Birch pollen grains were collected using a volumetric spore trap. An alternate biennial cycle of birch pollen season intensity was noticed in Poznań. The main factors influencing birch pollen season intensity were average daily minimum temperatures during the second fortnight of May and the month of June one year before pollination as well as the intensity of the pollen season of the previous year. Most of the pollen grains are recorded during the first week of the season; the number of pollen grains recorded at this time is positively correlated with mean maximum temperature and negatively correlated with daily rainfall. The significant effect of rainfall in reducing the season pollen index was noticed only during weak pollen seasons (season pollen index <?mean). In addition, mean daily maximum temperature during the first two weeks of the birch pollen season markedly influences its duration. No significant trends in duration and intensity of the pollen season were recorded, however, a slight tendency towards early pollination was observed (?0.4 days/year, p?=?0.310).     

Design,synthesis and evaluation of activity and pharmacokinetic profile of new derivatives of xanthone and piperazine in the central nervous system

Searching for CNS active cyclic amines derivatives containing heterocyclic xanthone core we designed and synthesized a set of fourteen novel 2- or 4-methylxanthone substituted by alkyl- or aryl-piperazine moieties. The compounds were evaluated in vivo for their potential antidepressant-like activity (in the forced swim test) and anxiolytic-like activity (four-plate test) and their inhibitory effect against rat 5-HT₂ receptor was checked. The pharmacokinetic analysis of active compounds done by a non-compartmental approach have shown a rapid absorption of all studied molecules from intraperitoneal cavity and good penetration the blood-brain barrier after i.p. administration with brain to plasma ratios varied from 2.8 to 31.6. Genotoxicity and biotransformation of active compounds were studied. Compound 19 interactions with major classes of GPCRs, uptake systems and ion channels were tested and results indicated that it binds to 5-HT_2A, 5-HT_2B receptors and sodium channels.     

Autism‐related behaviors in the cyclooxygenase‐2‐deficient mouse model

Prostaglandin E2 (PGE2) is an endogenous lipid molecule involved in normal brain development. Cyclooxygenase‐2 (COX2) is the main regulator of PGE2 synthesis. Emerging clinical and molecular research provides compelling evidence that abnormal COX2/PGE2 signaling is associated with autism spectrum disorder (ASD). We previously found that COX2 knockout mice had dysregulated expression of many ASD genes belonging to important biological pathways for neurodevelopment. The present study is the first to show the connection between irregular COX2/PGE2 signaling and autism‐related behaviors in male and female COX2‐deficient knockin, (COX)‐2^?, mice at young (4‐6 weeks) or adult (8‐11 weeks) ages. Autism‐related behaviors were prominent in male (COX)‐2^? mice for most behavioral tests. In the open field test, (COX)‐2^? mice traveled more than controls and adult male (COX)‐2^? mice spent less time in the center indicating elevated hyperactive and anxiety‐linked behaviors. (COX)‐2^? mice also buried more marbles, with males burying more than females, suggesting increased anxiety and repetitive behaviors. Young male (COX)‐2^? mice fell more frequently in the inverted screen test revealing motor deficits. The three‐chamber sociability test found that adult female (COX)‐2^? mice spent less time in the novel mouse chamber indicative of social abnormalities. In addition, male (COX)‐2^? mice showed altered expression of several autism‐linked genes: Wnt2, Glo1, Grm5 and Mmp9. Overall, our findings offer new insight into the involvement of disrupted COX2/PGE2 signaling in ASD pathology with age‐related differences and greater impact on males. We propose that (COX)‐2^? mice might serve as a novel model system to study specific types of autism.