Joint explorative analysis of neuroreceptor subsystems in the human brain: application to receptor-transporter correlation using PET data

Positron emission tomography (PET) has proved to be a highly successful technique in the qualitative and quantitative exploration of the human brain's neurotransmitter-receptor systems. In recent years, the number of PET radioligands, targeted to different neuroreceptor systems of the human brain, has increased considerably. This development paves the way for a simultaneous analysis of different receptor systems and subsystems in the same individual. The detailed exploration of the versatility of neuroreceptor systems requires novel technical approaches, capable of operating on huge parametric image datasets. An initial step of such explorative data processing and analysis should be the development of novel exploratory data-mining tools to gain insight into the "structure" of complex multi-individual, multi-receptor data sets. For practical reasons, a possible and feasible starting point of multi-receptor research can be the analysis of the pre- and post-synaptic binding sites of the same neurotransmitter. In the present study, we propose an unsupervised, unbiased data-mining tool for this task and demonstrate its usefulness by using quantitative receptor maps, obtained with positron emission tomography, from five healthy subjects on (pre-synaptic) serotonin transporters (5-HTT or SERT) and (post-synaptic) 5-HT(1A) receptors. Major components of the proposed technique include the projection of the input receptor maps to a feature space, the quasi-clustering and classification of projected data (neighbourhood formation), trans-individual analysis of neighbourhood properties (trajectory analysis), and the back-projection of the results of trajectory analysis to normal space (creation of multi-receptor maps). The resulting multi-receptor maps suggest that complex relationships and tendencies in the relationship between pre- and post-synaptic transporter-receptor systems can be revealed and classified by using this method. As an example, we demonstrate the regional correlation of the serotonin transporter-receptor systems. These parameter-specific multi-receptor maps can usefully guide the researchers in their endeavour to formulate models of multi-receptor interactions and changes in the human brain.     

Solid-phase synthesis of an N-(phenylalkyl)cinnamide library via Horner-Wadsworth-Emmons reaction

A readily automated solid-phase approach to the synthesis of diverse N-(phenylalkyl)cinnamides, analogues of the NR2B antagonist 2, is described. The procedure utilizes polymer supported N-(phenylalkyl)amines, (diethylphosphono)acetic acid and a wide range of commercially available hydroxybenzaldehydes. The key step, a Horner-Wadsworth-Emmons reaction is achieved under mild conditions and was found to be general for a large number of benzaldehydes. A 225-member focused library was synthesized using a Tecan Combitec synthesizer.     

A simple fold with variations: the pacifastin inhibitor family

Members of the pacifastin family are small, approximately 35-residue serine protease inhibitors isolated from arthropod species. Several locust inhibitors exhibit intriguing taxon specificity while others do not. The structural basis of this phenomenon may lie in the different dynamical properties of the proteins originating from different stabilizing interactions. In this study, we identify new members of the family to confirm the universal role of these interactions in the family. Structural investigations show that both the disulfide pattern and the stabilizing interactions are unique among small all-beta proteins.     

Selective increase of dATP pools upon activation of deoxycytidine kinase in lymphocytes: implications in apoptosis

Stimulation of the activity of deoxycytidine kinase (dCK), the principal deoxynucleoside salvage enzyme, has been recently considered as a protective cellular response to a wide range of agents interfering with DNA repair and apoptosis. In light of this, the potential contribution of dCK activation to apoptosis induction--presumably by supplying dATP or its analogues for the apoptosome formation--deserves consideration. Two-hour exposure of human tonsillar lymphocytes to 2-chloro-deoxyadenosine (CdA) led to a two-fold activation of dCK. This activation process was inhibited by pifithrin-alpha, a potent inhibitor of p53. When the dNTP pools were determined, both deoxypyrimidine triphosphate and dGTP pools were reduced after the treatments, while dATP levels elevated by 62%, 77% and 50% in the CdA, aphidicolin and etoposide-treated cells, respectively. We assume that dCK activation elicited by cellular damage might be a proapoptotic factor in terms of generating dATP well before the release of cytochrome c and deoxyguanosine kinase from mitochondria.     

Synthesis and neuropharmacological evaluation of R(-)-N-alkyl-11-hydroxynoraporphines and their esters

We synthesized several N-substituted-11-hydroxynoraporphines and their esters of varying chain length, evaluated their binding affinity at dopamine (DA) receptor sites in rat caudate-putamen membranes, and quantified their effects on motor activity in normal adult male rats. The 11-hydroxyaporphines showed similar neuropharmacological properties to the corresponding 10,11-catecholaporphines. At moderate doses, their esters proved to have more prolonged behavioral actions and superior oral bioavailability.     

Servers for sequence-structure relationship analysis and prediction

We describe several algorithms and public servers that were developed to analyze and predict various features of protein structures. These servers provide information about the covalent state of cysteine (CYSREDOX), as well as about residues involved in non-covalent cross links that play an important role in the structural stability of proteins (SCIDE and SCPRED). We also discuss methods and servers developed to identify helical transmembrane proteins from large databases and rough genomic data, including two of the most popular transmembrane prediction methods, DAS and HMMTOP. Several biologically interesting applications of these servers are also presented. The servers are available through http://www.enzim.hu/servers.html.     

Heparan sulfate 6-o-sulfotransferase is essential for muscle development in zebrafish

Heparan sulfate proteoglycans function in development and disease. They consist of a core protein with attached heparan sulfate chains that are altered by a series of carbohydrate-modifying enzymes and sulfotransferases. Here, we report on the identification and characterization of a gene encoding zebrafish heparan sulfate 6-O-sulfotransferase (hs6st) that shows high homology to other heparan sulfate 6-O-sulfotransferases. When expressed as a fusion protein in cultured cells, the protein shows specific 6-O-sulfotransferase activity and preferentially acts on the iduronosyl N-sulfoglycosamine. In the developing embryo, hs6st is expressed in the brain, the somites, and the fins; the same structures that were affected upon morpholino-mediated functional knockdown. Morpholino injections significantly inhibited 6-O- but not 2-O-sulfation as assessed by HPLC. Morphants display disturbed somite specification independent of the somite oscillator mechanism and have impaired muscle differentiation. In conclusion, our results show that transfer of sulfate to specific positions on glycosaminoglycans is essential for muscle development.     

Sporadic chromosome aberrations in healthy individuals studied between 1986-2001

In the second half of 2002, IARC for Central and Eastern European countries targeted studies on the relationship between chromosomal aberrations (CAs) and cancer risk. For these purposes we preliminarily investigated, under identical methodological circumstances, the base-line level of CAs in peripheral blood lymphocytes of 1414 healthy Hungarian persons between 1986 and 2001. The age and sex as biological, and smoking habit and residency (Budapest, industrial- and agricultural settlements) as environmental confounding factors were evaluated. Previously, people were not exposed to any known potential mutagens. The overall frequencies of aberrant cells (1.60+/-0.05%) were not influenced by sex, age and residency, but the smoking habits (1.84+/-0.09%) had significant impact on the elevation of aberrant cells. Aneuploidy, exchange-type dicentric chromosomes and the total of aberrations increased significantly with the age of the donors. The individual frequency of aberrant cells ranged between 0-12%. No aberrant cells were detected in 35% of individuals, and 1 aberrant cell was found in 23% of the total population, while 42% of the examined persons were characterized with aberrant cell rates between 2-12%. The initial value of 0.85% of aberrant cells doubled by the end of the examined 16-year period, following 2-4-fold fluctuations. None of the investigated biological or environmental factors was responsible for the elevation of the CAs. The causes of the elevation of CA-level can be explained more precisely when these data will be compared to cancer registry database of these persons.     

Causes of local recurrence after curative surgery for rectal cancer

The rate of local recurrence (LR) has been 20-40% after resective surgery for rectal cancer by the traditional - Miles or Dixon - operative technics. The authors performed curative resection in 358 patients with rectal cancer in a 10 year period (01.01.1990 - 31.12.2000) in the Surgical Department of Szeged University. Since 01.01.1996 the authors changed this type of surgery for the Heald technics (total mesorectal excision - TME - with sharp dissection, using the UltraCision device) for the surgical treatment of middle or lower third rectal cancer. To compare the results of the two procedures, the authors analysed their material in two periods: Period I: 01.01.1991 - 31.12.1992: 62 patients operated on with the traditional operative technics; LR 15% within 2 years after surgery. Period II: 01.01.1997 - 31.12.1998: 78 patients operated on with the Heald technics (TME with sharp dissection); LR 6.4% within 2 years after surgery. Based on their results, the authors found that the modern operative technics by Heald, used in the second period of the study, was a relevant factor decreasing LR from 15% to 6.4%, while the gender, age of the patients, ratio of the abdominoperineal extirpation versus anterior resection (APRE/AR) and the free margin of more than 3 cm proved to be irrelevant.