Distribution of MT1 Melatonin Receptor Promoter-Driven RFP Expression in the Brains of BAC C3H/HeN Transgenic Mice

The pineal hormone melatonin activates two G-protein coupled receptors (MT₁ and MT₂) to regulate in part biological functions. The MT₁ and MT₂ melatonin receptors are heterogeneously distributed in the mammalian brain including humans. In the mouse, only a few reports have assessed the expression of the MT₁ melatonin receptor expression using 2-iodomelatonin binding, in situ hybridization and/or polymerase chain reaction (PCR). Here, we described a transgenic mouse in which red fluorescence protein (RFP) is expressed under the control of the endogenous MT₁ promoter, by inserting RFP cDNA at the start codon of MTNR1a gene within a bacterial artificial chromosome (BAC) and expressing this construct as a transgene. The expression of RFP in the brain of this mouse was examined either directly under a fluorescent microscope or immunohistochemically using an antibody against RFP (RFP-MT₁). RFP-MT₁ expression was observed in many brain regions including the subcommissural organ, parts of the ependyma lining the lateral and third ventricles, the aqueduct, the hippocampus, the cerebellum, the pars tuberalis, the habenula and the habenula commissure. This RFP-MT₁ transgenic model provides a unique tool for studying the distribution of the MT₁ receptor in the brain of mice, its cell-specific expression and its function in vivo.     

Vomeronasal/accessory olfactory system and pheromonal recognition

Pregnancy block in mice requires exposure of recently mated females to urinary pheromones of a strange male, and when working with inbred strains this invariably requires urine from an outbred line. The pheromones which induce oestrus and early puberty in mice have been identified as the brevicomins and dihydrothiazoles. Since the same vomeronasal, neural and neuroendocrine pathways are also activated in pregnancy block, these compounds are likely candidates for pregnancy blocking pheromones. However, these relatively simple chemicals lack the capacity to code for differing mouse strains. Since large quantities of the polymorphic major urinary proteins from the lipocalin family found in urine serve as transporters for the dihydrothiazoles and brevicomins, and differ across strains, then these proteins must participate in pheromone recognition in the context of pregnancy block.      

Dynamics of sex ratio in populations of cyclomorphic mammals (rodentia,cricetidae, muridae)

Using the result of long-term monitoring (over 30 years) of the main population parameters of cyclomorphic mammals (genera Clethrionomys, Microtus, and Sylvaemus) in the Il’men Reserve (Chelyabinsk oblast, the Southern Urals), the phenomenology of the sex ratio and its dynamics in their natural populations are analyzed. The main factors potentially influencing the sex structure of rodents are considered, including isolation of settlements, relative abundance, population density, species-specific features, alternative types of ontogeny, exposure to extreme factors, sex-dependent asynchronous mortality, and age cross. It is shown that the analysis of sex structure in rodents should be performed taking into account the type of their ontogeny, with the CMR method (capture-marking-recapture) giving the most objective estimate of the sex ratio. An alternative approach is to analyze samples taken in autumn to winter, after the end of breeding and elimination of reproductive individuals from the population. It is concluded that the dynamics of the sex structure in murine rodents are conditioned ecologically and that no selective elimination of individuals depending on sex takes place upon overwintering. The sex ratio in cyclomorphic mammals is a variable parameter that fluctuates about the average value depending on both regular and random factors. Methodological recommendations are given for the assessment of sex structure in cyclomorphic mammals.     

Cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Ural Radioactive Trace zone

Chromosome instability in bone-marrow cells and ⁹⁰Sr accumulation in the bone tissue are studied in rodents (Apodemus (Sylvaemus) uralensis Pall., 1811 and Apodemus agrarius Pall., 1771)* inhabiting the Eastern Ural Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of the Urals. Intensive mutagenic process in both species from impact plots (soil pollution by ⁹⁰Sr, 2322–16690 kBq/m²) is found. Significant positive correlation of the frequency of aberrant cells and the concentration of ⁹⁰Sr is shown. Possible causes of the lack of resistance to long-term mutagenic factors (over 100 generations in the 50 years since the accident), such as migration of animals and the specific configuration of the EURT zone (an extended narrow territory with a sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.     

Migrations of Rodents in the Zone of Local Radioactive Contamination at Different Phases of Population Dynamics and Their Consequences

Migrations of rodents in the zone of local radioactive contamination (East Urals Radioactive Trace, Southern Urals) at different phases of population dynamics are analyzed for the first time. The absence of any isolation of the rodents in the zone of this radioactive trace is convincingly demonstrated and the migration distances are estimated. As is shown, migration decreases the probability for transfer and fixation of adaptations in the chain of generations in vagile rodent species and increases the within-population genetic diversity of animals in adjacent regions. The need to consider the migration factor in a wide range of studies on assessment of biological effects in the zones of local technogenic contamination is confirmed.