[CROSS-TALK BETWEEN 5-HT1A AND 5-HT7 RECEPTORS: ROLE IN THE AUTOREGULATION OF THE BRAIN SEROTONIN SYSTEM AND IN MECHANISM OF ANTIDEPRESSANTS ACTION].

Recent studies considerably extended our knowledge of the mechanisms and physiological role of the interaction between different receptors in the brain. Current review summarizes data on the formation of receptor complexes and the role of such complexes in the autoregulation of the brain serotonin system, behavioral abnormalities and mechanism of antidepressants action. Particular attention is paid to 5-HT1A and 5-HT7 receptor heterodimers. The results described in the present review indicate that: i) dimerization and formation of mobile receptor complexes is a common feature for the members of G-protein coupled receptor superfamily; ii) 5-HT7 receptor appears to be a modulator for 5-HT1A receptor - the key autoregulator of the brain serotonin system; iii) 5-HT1A/5-HT7 receptor complexes formation is one of the mechanisms for inactivation and desensitization of the 5-HTIA receptors in the brain; iv) differences in the 5-HT7 receptor and 5-HTIA/5-HT7 heterodimers density define different sensitivity of pre- and postsynaptic 5-HTlA receptors to chronic treatment with selective serotonin reuptake inhibitors.

[A retroposition assay for the NLR1Cth from midge Chironomus thummi genome in the Chinese hamster ovary cells].

Non-Long Terminal Repeats (non-LTR or LINE) retrotransposons belong to the class of mobile genetic elements that are transposed into the host genome by reverse transcription of the RNA intermediate. Most of non-LTR retrotransposons contain two open reading frames (ORFs). The ORF1 codes for a gag-like protein, while the ORF2 codes for a reverse transcriptase (RT). We cloned two constructs based on Jockey-like non-LTR retrotransposon from genome Chironomus thummi (NLR1Cth). The retroposition assay performed in Chinese hamster ovary (CHO) cells demonstrated genome integrations of both constructs. The finding that the insect mobile element NLR1Cth is functional in mammalian cells demonstrates that this element possess universal enzymatic machinery allowing for active propagation in the genome of distant taxa. This suggests that the NLR1Cth transposon system may represent a useful tool for genetic analysis and manipulation in vertebrate cells.

Adult-to-embryo chemical signaling in the regulation of larval development in trochophore animals: cellular and molecular mechanisms.

The regulation of larval development by starved adults occurs in both freshwater snails, Helisoma trivolvis and marine polychaetes, Platynereis dumerilii. Serotonin (5-HT) links this environmental signal which is detected by larval apical sensory neurons to changes in larval development. A profile of the stage-dependent expression of 5-HT receptors and coupled G proteins is essential in this regulatory mechanism. The final effect on development depends on the modulation of the activity of the larval digestive system.

5-Hydroxytryptamine 4(a) receptor expressed in Sf9 cells is palmitoylated in an agonist-dependent manner.

The mouse 5-hydroxytryptamine 4(a) receptor [5-HT(4(a))] was expressed with a baculovirus system in insect cells and analysed for acylation. [(3)H]Palmitic acid was effectively incorporated into 5-HT(4(a)) and label was sensitive to the treatment with reducing agents indicating a thioester-type bond. Analysis of protein-bound fatty acids revealed that 5-HT(4(a)) contains predominantly palmitic acid. Treatment of infected Sf9 (Spodoptera frugiperda) cells with BIMU8 [(endo-N-8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dehydro-2-oxo-3-(prop-2-yl)-1H-benzimid-azole-1-carboxamide], a 5-HT(4) receptor-selective agonist, generated a dose-dependent increase in [(3)H]palmitate incorporation into 5-HT(4(a)) with an EC(50) of approx. 10 nM. The change in receptor labelling after stimulation with agonist was receptor-specific and did not result from general metabolic effects. We also used both pulse labelling and pulse-chase labelling to address the dynamics of 5-HT(4(a)) palmitoylation. Incorporation studies revealed that the rate of palmitate incorporation was increased approx. 3-fold after stimulation with agonist. Results of pulse-chase experiments show that activation with BIMU8 promoted the release of radiolabel from 5-HT(4(a)), thereby reducing the levels of receptor-bound palmitate to approximately one-half. Taken together, our results demonstrate that palmitoylation of 5-HT(4(a)) is a reversible process and that stimulation of 5-HT(4(a)) with agonist increases the turnover rate for receptor-bound palmitate. This provides evidence for a regulated cycling of receptor-bound palmitate and suggests a functional role for palmitoylation/depalmitoylation in 5-hydroxytryptamine-mediated signalling.

Lipid composition of virosomes modulates their fusion efficiency with cryopreserved bull sperm cells.

Virosomes derived from different fusogenic enveloped viruses have been generated for potential application in gene targeting to sperm cells. Comparative characterization of reconstitution products revealed that virosomes derived from influenza viruses are superior to those generated from Sendai viruses, with respect to the fusion rates with cryopreserved bull sperm cells and to sperm cell vitality after fusion. Modulation of the lipid composition during virosome reconstitution affects fusion sites on target sperms and allows optimization of the fusion rate and sperm cell vitality. A fluorescence-based microscopic fusion assay combined with a vital cell stain revealed that about 90% of sperm cells fused with influenza virosomes containing exogenous cholesterol, sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine. About 85% of the fused sperm cells remained vital. Such optimized influenza-derived virosomes provide the basis for ongoing experiments, which aim at eventually generating biologically active transgenic sperms.

[Mechanism of chromosome loss after irradiation of mature Drosophila sperm]. / Mekhanizm poter' khromosom pri obluchenii zrelykh spermiev Drozofily

The frequency of radiation-induced chromosome losses is not connected with heterochromatic content but depends on the total chromosomal DNA content. This dependence is of the selective nature and appears as a result of the effect of dominant lethality of non-repaired euchromatic breaks. Simultaneous losses of the two chromosomes in one nucleus are not independent, because of the interaction of the heterochromatic breaks underlying these losses. The conclusion is made that the chromosome losses are involved in the exchange events accompanied by the centromere deletion.

[Number of chromosome breaks and the probability of break reunion during irradiation of mature Drosophila sperm]. / Chislo razryvov khromosom i veroiatnost' ikh vossoedineniia pri obluchenii zrelykh spermiev drozofily.

The dose-effect curves for half and full translocations induced in mature sperm with the break points within the same chromosomal region were obtained. Probability of reunion q and the number of breaks N that could be calculated from these curves varies within the range 0.83-0.69 and 0.011-0.078, respectively. The half and full translocations were induced under maternal effect of mus 104D1. In this case, q = 0.86 (for normal genotype 0.79) and N = 0.114 (for normal genotype 0.048). These figures show that the dose increase and the introduction of the mus 104 cause increase in the breaks number and only weak change in break reunion occurs. The method developed can be used for the search for mutations that interfere with break reunion.

[Exchange mechanism of chromosome loss]. / Obmennyi mekhanizm poter' khromosom.

Frequencies of induced losses of autosome 2, free arm of autosome 2 and simultaneous losses of two free arms of autosome 2 were determined as 3.25 x 10(-3), 2.78 x 10(-3), 0.84 x 10(-3), respectively. High frequency of simultaneous losses of two chromosomes may have pointed to the exchange nature of the chromosome losses. The similarity of frequencies of half-translocations in heterochromatin of autosome 2 and frequencies of the losses observed show that the chromosome losses are the consequence of exchanges in chromosomal heterochromatin.

[Incomplete translocations induced in mature sperm of Drosophila]. / Nepolnye translokatsii, indutsirovannye v zrelykh spermiiakh Drozofily.

Frequencies of incomplete translocations in subcentromeric heterochromatin induced by gamma-rays in mature sperm were estimated in the "two right acrocentrics and left compound" system of Drosophila chromosome 2. The value obtained at 3000R was (2.5-2.9) X 10(-3). Apart from incomplete translocations leading to formation of new metacentrics, acrocentrics were also formed. It is suggested that they appear via reunion of fragments after replication of paternal chromosomes. Incomplete translocation were shown to be formed as a result of loss of centric heterochromatin fragment of acrocentric and acentric arm of the compound, as opposed to formation, due to loss of acentric heterochromatin fragment of acrocentric and centric fragment of the compound. Analysis of the dose-effect curve for half-translocations show that the latter are two hit events.

[Comparison of frequencies of complete and incomplete translocations induced in mature sperm of Drosophila]. / Sootnoshenie chastot polnykh i nepolnykh translokatsii indutsirovannykh v zrelykh spermiiakh Drozofily.

A frequency of induction of translocations taking place in mature sperm of Drosophila between heterochromatic portions of the 2L compound and 2R acrocentric was estimated to be 9.62 X 10(-3). This value is being compared with the previously estimated frequency of incomplete translocations in this system which is (2.5-2.9) X 10(-3). The ratio of frequencies of complete and incomplete translocations obtained was intermediate between the Panshin data, on the one hand, and those of Muller and Hershkowitz, on the other. The reasons for these discrepancies are under discussion. Based on the value obtained for this ratio, the probability of reunion of chromosome break (q) is calculated to be 0.79.