Expression analysis suggests that DNMT3L is required for oocyte de novo DNA methylation only in Muridae and Cricetidae rodents.

BACKGROUND: During early mammalian development, DNA methylation undergoes two waves of reprogramming, enabling transitions between somatic cells, oocyte and embryo. The first wave of de novo DNA methylation establishment occurs in oocytes. Its molecular mechanisms have been studied in mouse, a classical mammalian model. Current model describes DNA methyltransferase 3A (DNMT3A) and its cofactor DNMT3L as two essential factors for oocyte DNA methylation-the ablation of either leads to nearly complete abrogation of DNA methylation. However, DNMT3L is not expressed in human oocytes, suggesting that the mechanism uncovered in mouse is not universal across mammals. RESULTS: We analysed available RNA-seq data sets from oocytes of multiple mammals, including our novel data sets of several rodent species, and revealed that Dnmt3l is expressed only in the oocytes of mouse, rat and golden hamster, and at a low level in guinea pigs. We identified a specific promoter sequence recognised by an oocyte transcription factor complex associated with strong Dnmt3l activity and demonstrated that it emerged in the rodent clade Eumuroida, comprising the families Muridae (mice, rats, gerbils) and Cricetidae (hamsters). In addition, an evolutionarily novel promoter emerged in the guinea pig, driving weak Dnmt3l expression, likely without functional relevance. Therefore, Dnmt3l is expressed and consequently plays a role in oocyte de novo DNA methylation only in a small number of rodent species, instead of being an essential pan-mammalian factor. In contrast to somatic cells, where catalytically inactive DNMT3B interacts with DNMT3A, forming a heterotetramer, we did not find evidence for the expression of such inactive Dnmt3b isoforms in the oocytes of the tested species. CONCLUSIONS: The analysis of RNA-seq data and genomic sequences revealed that DNMT3L is likely to play a role in oocytes de novo DNA methylation only in mice, rats, gerbils and hamsters. The mechanism governing de novo DNA methylation in the oocytes of most mammalian species, including humans, occurs through a yet unknown mechanism that differs from the current model discovered in mouse.

Conservation and divergence of canonical and non-canonical imprinting in murids.

BACKGROUND: Genomic imprinting affects gene expression in a parent-of-origin manner and has a profound impact on complex traits including growth and behavior. While the rat is widely used to model human pathophysiology, few imprinted genes have been identified in this murid. To systematically identify imprinted genes and genomic imprints in the rat, we use low input methods for genome-wide analyses of gene expression and DNA methylation to profile embryonic and extraembryonic tissues at allele-specific resolution. RESULTS: We identify 14 and 26 imprinted genes in these tissues, respectively, with 10 of these genes imprinted in both tissues. Comparative analyses with mouse reveal that orthologous imprinted gene expression and associated canonical DNA methylation imprints are conserved in the embryo proper of the Muridae family. However, only 3 paternally expressed imprinted genes are conserved in the extraembryonic tissue of murids, all of which are associated with non-canonical H3K27me3 imprints. The discovery of 8 novel non-canonical imprinted genes unique to the rat is consistent with more rapid evolution of extraembryonic imprinting. Meta-analysis of novel imprinted genes reveals multiple mechanisms by which species-specific imprinted expression may be established, including H3K27me3 deposition in the oocyte, the appearance of ZFP57 binding motifs, and the insertion of endogenous retroviral promoters. CONCLUSIONS: In summary, we provide an expanded list of imprinted loci in the rat, reveal the extent of conservation of imprinted gene expression, and identify potential mechanisms responsible for the evolution of species-specific imprinting.

Distributions of GABAergic and glutamatergic neurons in the brains of a diurnal and nocturnal rodent.

Light influences the daily patterning of activity by both synchronizing internal clocks to environmental light-dark cycles and acutely modulating arousal states, a process known as masking. Masking responses are completely reversed in diurnal and nocturnal species. In nocturnal rodents, masking is mediated through a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) whose projections are similar in diurnal and nocturnal rodents. This raises the possibility that differences in responsivity to signals that these cells release might underlie chronotype differences in masking. We explored one aspect of this hypothesis by examining the distribution of excitatory and inhibitory neuronal populations in many ipRGC target areas of a diurnal species (Nile grass rat) and a nocturnal one (Norway rat). We discovered that while many of these regions were very similar in these two species, there were striking differences in the ventral lateral geniculate nucleus (vLGN; higher density of glutamate cells in Norway rats) and in the lateral habenula (LHb; GABAeric cells present in grass rats, but not Norway rats). These patterns raise the possibility that the vLGN and LHb contribute to differences in masking and/or circadian regulation of diurnal and nocturnal species.

A comparison of the orexin receptor distribution in the brain between diurnal Nile grass rats (Arvicanthis niloticus) and nocturnal mice (Mus musculus).

The neuropeptide orexin/hypocretin regulates a wide range of behaviors and physiology through its receptors OX1R and OX2R, or HCRTR-1 and HCRTR-2. Although the distributions of these receptors have been established in nocturnal rodents, their distributions in the brain of diurnal species have not been studied. In the present study, we examined spatial patterns of OX1R and OX2R mRNA expression in diurnal Nile grass rats (Arvicanthis niloticus) by in situ hybridization and compared them with those in nocturnal mice (Mus musculus). Both receptors showed similar spatial patterns between species in most brain regions. However, species-specific expression was found in several regions that are mainly implicated in regulation of sleep/wakefulness, emotion and cognition. OX1R expression was detected in the caudate putamen and ventral tuberomammillary nucleus only in grass rats, while it was detected in the bed nucleus of the stria terminalis, medial division, posteromedial part only in mice. The distribution of OX2R mRNA was mostly consistent between the two species, although it was more widely expressed in the ventral tuberomammillary nucleus in grass rats compared to mice. These results suggest that neuronal pathways of the orexin system differ between chronotypes, and these differences could underlie the distinct profiles in behaviors and physiology between diurnal and nocturnal species.

Plastic oscillators and fixed rhythms: changes in the phase of clock-gene rhythms in the PVN are not reflected in the phase of the melatonin rhythm of grass rats.

The same clock-genes, including Period (PER) 1 and 2, that show rhythmic expression in the suprachiasmatic nucleus (SCN) are also rhythmically expressed in other brain regions that serve as extra-SCN oscillators. Outside the hypothalamus, the phase of these extra-SCN oscillators appears to be reversed when diurnal and nocturnal mammals are compared. Based on mRNA data, PER1 protein is expected to peak in the late night in the paraventricular nucleus of the hypothalamus (PVN) of nocturnal laboratory rats, but comparable data are not available for a diurnal species. Here we use the diurnal grass rat (Arvicanthis niloticus) to describe rhythms of PER1 and 2 proteins in the PVN of animals that either show the species-typical day-active (DA) profile, or that adopt a night-active (NA) profile when given access to running wheels. For DA animals housed with or without wheels, significant rhythms of PER1 or PER2 protein expression featured peaks in the late morning; NA animals showed patterns similar to those expected from nocturnal laboratory rats. Since the PVN is part of the circuit that controls pineal rhythms, we also measured circulating levels of melatonin during the day and night in DA animals with and without wheels and in NA wheel runners. All three groups showed elevated levels of melatonin at night, with higher levels during both the day and night being associated with the levels of activity displayed by each group. The differential phase of rhythms in the clock-gene protein in the PVN of diurnal and nocturnal animals presents a possible mechanism for explaining species differences in the phase of autonomic rhythms controlled, in part, by the PVN. The present study suggests that the phase of the oscillator of the PVN does not determine that of the melatonin rhythm in diurnal and nocturnal species or in diurnal and nocturnal chronotypes within a species.

Paracellular nutrient absorption is higher in bats than rodents: integrating from intact animals to the molecular level.

Flying vertebrates have been hypothesized to rely heavily on paracellular absorption of nutrients to compensate for having smaller intestines than non-flyers. We tested this hypothesis in an insectivorous bat (Myotis lucifugus) and two insect-eating rodents (Onychomys leucogaster and Peromyscus leucopus). In intact animals, the fractional absorption of orally dosed l-arabinose (Mr 150) was 82% in M. lucifugus, which was more than twice that of the rodents. Absorption of creatinine (Mr 113) was greater than 50% for all species and did not differ between M. lucifugus and the rodents. We also conducted intestinal luminal perfusions on anesthetized animals. Absorption of l-arabinose per nominal surface area in M. lucifugus was nearly double that of the rodents, while absorption of creatinine was not different among species. Using an everted sleeve preparation, we demonstrated that high concentrations of l-arabinose and creatinine did not inhibit their own uptake, validating their use as passive, paracellular probes. Histological measurements indicated that M. lucifugus has more cells, and presumably more tight junctions, per nominal surface area than P. leucopus. This seems unlikely to explain entirely the higher absorption of l-arabinose in M. lucifugus during perfusions, because l-arabinose absorption normalized to the number of enterocytes was still double that of P. leucopus. As an alternative, we investigated tight junction gene expression. M. lucifugus had higher expression of claudin-1 and claudin-15, and lower expression of claudin-2 relative to P. leucopus. Expression of claudin-7 and occludin did not differ among species. Taken together, our results support the hypothesis that bats have evolved higher paracellular nutrient absorption than non-flying animals, and that this phenomenon might be driven by both histological characteristics and differences in tight junction gene expression.

Thermal energetics of the New-Guinean moss-forest rat (Rattus niobe) in comparison with other tropical murid rodents.

The thermal energetics of rodents from cool, wet tropical highlands are poorly known. Metabolic rate, body temperature and thermal conductance were measured in the moss-forest rat, Rattus niobe (Rodentia), a small murid endemic to the highlands of New Guinea. These data were evaluated in the context of the variation observed in the genus Rattus and among tropical murids. In 7 adult R. niobe, basal metabolic rate (BMR) averaged 53.6±6.6mLO2h(-1), or 103% of the value predicted for a body mass of 42.3±5.8g. Compared to other species of Rattus, R. niobe combines a low body temperature (35.5±0.6°C) and a moderately low minimal wet thermal conductance cmin (5.88±0.7mLO2h(-1)°C(-1), 95% of predicted) with a small size, all of which lead to reduced energy expenditure in a constantly cool environment. The correlations of mean annual rainfall and temperature, altitude and body mass with BMR, body temperature and cmin were analyzed comparatively among tropical Muridae. Neither BMR, nor cmin or body temperature correlated with ambient temperature or altitude. Some of the factors which promote high BMR in higher latitude habitats, such as seasonal exposure to very low temperature and short reproductive season, are lacking in wet montane tropical forests. BMR increased with rainfall, confirming a pattern observed among other assemblages of mammals. This correlation was due to the low BMR of several desert adapted murids, while R. niobe and other species from wet habitats had a moderate BMR.

Postcopulatory sexual selection increases ATP content in rodent spermatozoa.

Sperm competition often leads to increase in sperm numbers and sperm quality, and its effects on sperm function are now beginning to emerge. Rapid swimming speeds are crucial for mammalian spermatozoa, because they need to overcome physical barriers in the female tract, reach the ovum, and generate force to penetrate its vestments. Faster velocities associate with high sperm competition levels in many taxa and may be due to increases in sperm dimensions, but they may also relate to higher adenosine triphosphate (ATP) content. We examined if variation in sperm ATP levels relates to both sperm competition and sperm swimming speed in rodents. We found that sperm competition associates with variations in sperm ATP content and sperm-size adjusted ATP concentrations, which suggests proportionally higher ATP content in response to sperm competition. Moreover, both measures were associated with sperm swimming velocities. Our findings thus support the idea that sperm competition may select for higher ATP content leading to faster sperm swimming velocity.

Purificação e caracterização da VDAC de mitocôndrias corticais aviares: identificação de modificações pós-traducionais nas porinas neuronais murinas e aviares / Purification and characterization of avian cortical mitochondrial VDAC: identification of post-translational modifications of rat and avian neuronal porins

A VDAC é uma porina presente na MME cuja função é crucial no metabolismo energético, sobrevivência e morte celular. A caracterização da VDAC torna-se importante para a compreensão das inter-relações da mitocôndria com os diferentes componentes citosólicos, tais como a HK. A ligação HK-VDAC favorece a utilização do ATP intramitocondrial em células neuronais, a HK cerebral pode interagir de formas diferentes com a VDAC, o que resulta em diferentes sítios de ligação (sítios A e B). Os variados papéis metabólicos das isoformas da VDAC podem ser explicados pela presença de alterações pós-traducionais. No presente trabalho purificamos a VDAC1 mitocondrial neuronal proveniente de cérebro aviar. Paralelamente, comprovamos que a presença de múltiplas formas das VDACs 1 e 2 em cérebros murino e aviar, seja devida à presença de modificações pós-traducionais, nomeadamente a fosforilação. A proteína isolada apresentou peso molecular de 30KDa. Quando submetida à eletroforese e posteriormente à coloração para a identificação de fosfoproteínas, a mesma mostrou-se desfosforilada. O conhecimento da presença, ou ausência de fosforilação das VDACs, reside na importância de estabelecer-se as bases moleculares ligadas à existência de sítios A e B nas mitocôndrias neuronais.

VDAC (voltage-dependent anion channel) is a pore forming protein from outer mitochondrial membrane. It has key functions on energetic metabolism, and cell death and survival. VDAC characterization is important for understanding mitochondrial interactions with cytosolic proteins, such as hexokinase (HK). HK-VDAC interaction supports preferential access to intramitochondrial ATP in neural cells. Brain HK interacts in different ways with VDAC. It results in two HK binding sites (A and B). VDAC isoforms differential metabolic roles may be explained by the presence of post-translational modifications. In this study we purified avian neuronal mitochondrial VDAC1. At same time we showed that VDACs 1 and 2 pI heterogeneity in rat and avian brains is due to phosphorylation. Purified VDAC had a molecular weight of 30 KDa. The purified VDAC submitted to phosphorylated protein staining on gel, was dephosphorylated. The knowledge of presence or absence of VDAC phosphorylation is important for understanding the molecular nature basis of A and B HK binding sites in brain mitochondria.

Reproductive and metabolic responses of desert adapted common spiny male mice (Acomys cahirinus) to vasopressin treatment.

Sufficient amounts of water and food are important cues for reproduction in an unpredictable environment. We previously demonstrated that increased osmolarity levels, or exogenous vasopressin (VP) treatment halt reproduction of desert adapted golden spiny mice Acomys russatus. In this research we studied gonad regulation by VP and food restriction (FR) in desert adapted common spiny mouse (A. cahirinus) males, kept under two different photoperiod regimes-short (SD-8L:16D) and long (LD-16L:8D) days. Mice were treated with VP, FR, and VP+FR for three weeks. Response was assessed from changes in relative testis mass, serum testosterone levels and mRNA receptor gene expression of VP, aldosterone and leptin in treated groups, compared with their controls. SD-acclimation increased testosterone levels, VP treatment decreased expression of aldosterone mRNA receptor in the testes of SD-acclimated males. FR under SD-conditions resulted in testosterone decrease and elevation of VP- receptor gene expression in testes. Aldosterone receptor mRNA expression was also detected in WAT. These results support the idea that water and food availability in the habitat may be used as signals for activating the reproductive system through direct effects of VP, aldosterone and leptin on the testes or through WAT by indirect effects.

[Participation of the lipid peroxidation processes in the adaptation mechanism of Muridae like rodents to the radioactive contamination of the Chernobyl NPP zone].

Results of the comparative analysis of the complex investigation of rodent population state caught at areas with different levels of contamination in the accident zone of the Chernobyl NPP during 1986-1993 and 2007, at areas with a practically normal radiation background in the neighborhood of the Kiev City in 1993 and at areas with the normal and increased radiation background in Ukhta region of Komi Republic in 1993-2008 are presented. It is shown that the absence of the linear dependence in changes of the lipid peroxidation (LPO) regulatory system parameters in rodent tissues on the dose of the external gamma-radiation at areas of their trap persists for a long time. Different ability to normalization of the studied indices and nonlinearity of their dose dependences allow us to suggest that changes of the scale and direction of interrelations between the reciprocal parameters of the LPO regulatory system in norm in tissues of rodents which were caught in the accident zone and at areas with an increased radiation background should be the information signal determining selection of the strategy of adaptation to the chronic radiation factor action.

Arsenic transformations in terrestrial small mammal food chains from contaminated sites in Canada.

Arsenic in terrestrial contaminated sites has the potential to cause harm to residential wildlife. The aim of this study was to determine the arsenic species in wild rodents living in arsenic contaminated habitats, specifically deer mice from Yellowknife, NT and meadow voles from Seal Harbour, NS, along with co-located plants. Methanol : water (1 : 1) extractions were used to optimize the extraction of methylated arsenic(v) species. Total arsenic concentrations were substantially higher in the Yellowknife deer mice (1.7-3.2 µg kg(-1) wet weight in livers) and Seal Harbour meadow voles (0.67-0.97 µg kg(-1) wet weight in livers) living on the contaminated sites with respect to the surrounding background locations (0.12-0.34 µg kg(-1) wet weight in livers). Around 50% of arsenic could be identified in Yellowknife deer mouse tissues, but only <10% was identified in Seal Harbour vole tissues; inorganic arsenic (iii and v) and dimethylarsinic acid were all found. Monomethylarsonic acid was only detected in both the mice and voles living in the contaminated sites. In the Yellowknife food chain, methyl arsenic (v) proportions increased from plants to mouse inner organs, but the trend was not for clear as the Seal Harbour food chain. Seal Harbour voles may be sequestering arsenic in a less mobile form, rather than transforming it.

Phase preference for the display of activity is associated with the phase of extra-suprachiasmatic nucleus oscillators within and between species.

Many features of the suprachiasmatic nucleus (SCN) are the same in diurnal and nocturnal animals, suggesting that differences in phase preference are determined by mechanisms downstream from the SCN. Here, we examined this hypothesis by characterizing rhythmic expression of Period 1 (PER1) and Period 2 (PER2) in several extra-SCN areas in the brains of a diurnal murid rodent, Arvicanthis niloticus (grass rats). In the shell of the nucleus accumbens, dorsal striatum, piriform cortex, and CA1 of the hippocampus, both PER1 and PER2 were rhythmic, with peak expression occurring at ZT10. PER1 in the dentate gyrus also peaked at ZT10, but PER2 was arrhythmic in this region. In general, these patterns are 180 degrees out of phase with those reported for nocturnal species. In a second study, we examined inter-individual differences in the multioscillator system of grass rats. Here, we housed grass rats in cages with running wheels, under which conditions some individuals spontaneously adopt a day active (DA) and others a night active (NA) phase preference. In the majority of the extra-SCN regions sampled, the patterns of PER1 and PER2 expression of NA grass rats resembled those of nocturnal species, while those of DA grass rats were similar to the ones seen in grass without access to running wheels. In contrast, the rhythmic expression of both PER proteins was identical in the SCN and ventral subparaventricular zone (vSPZ) of DA and NA animals. Differences in the phase of oscillators downstream from the SCN, and perhaps the vSPZ, appear to determine the phase preference of particular species, as well as that of members of a diurnal species that show voluntary phase reversals. The latter observation has important implications for the understanding of health problems associated with human shift work.

Stress coping styles and singing behavior in the short-tailed singing mouse (Scotinomys teguina).

Stress coping styles have been characterized as a proactive/reactive dichotomy in laboratory and domesticated animals. In this study, we examined the prevalence of proactive/reactive stress coping styles in wild-caught short-tailed singing mice (Scotinomys teguina). We compared stress responses to spontaneous singing, a social and reproductive behavior that characterizes this species. To establish proactive/reactive profiles for singing mice, we measured exploratory and anxiety behavior using an open-field behavioral test. We examined correlations between open-field behaviors and fecal corticosterone (CORT) metabolites, baseline plasma CORT, and stress-induced CORT. Mice with proactive behavioral responses in the open-field had higher fecal CORT titers than reactive males, but did not differ in baseline or stress-induced plasma CORT. We suggest that individual differences in CORT metabolism may contribute to this surprising pattern. Males that sang in the open-field were behaviorally proactive and had lower stress-induced CORT, indicating a link between stress responses and singing in this species. Overall, the data demonstrate that singing mice offer an interesting model for exploring how stress reactivity can shape social behaviors.

[The metabolic homeostasis of the small mammals in the conditions of the East Ural radioactive trace].

The difference in the mechanism of radioresistance, the strategy and the level of the adaptation are determined at Apodemus (Sylvaemus) Uralensis and Clethrionomys Rutilus living on the territory of the East Urals Radioactive Trace with the 90Sr contamination density of 180-450 Ci/km2. The mechanism of radioresistance Apodemus (Sylvaemus) Uralensis is based on the use of lipid reserves in energy provision of the physiological functions, what provided of the growth oxidation metabolism in the mitochondria. Found changes testify in favor of stress-realization mechanism of increase of the level energy homeostasis and, inquest, heightened regime of the functioning cells. As a result there is the cellular disadaptation, marked of decrease nuclear, mitochondrial proteins and process of the cellular regeneration, that put obstacles in tissue adaptation. The opposite focus of the metabolic homeostasis at Clethrionomys Rutilus points to limitation use of the lipid reserves in energy provision of the physiological functions, what provided the suppression oxidation metabolism in the mitochondria. The minimization of the functional activity cellular and subcellular structures compensate the growth of theirs numbers as a result of the level tissue and longtime adaptation. This fact characterizes more safety of the level adaptability at Clethrionomys Rutilus to radiation surroundings.

Heavy metal transfers between trophic compartments in different ecosystems in galicia (northwest Spain): essential elements.

In the present study, we determined the concentrations of Cu, Fe, Mn, and Zn in soil and several trophic compartments at a total of 16 sampling stations. The trophic compartments studied were primary producers, represented by two species of terrestrial mosses (Pseudoescleropodium purum and Hypnum cupressiforme) and oak trees (Quercus robur or Q. pyrenaica); primary consumers, represented by the wood mouse (Apodemus sylvaticus) and the yellow necked mouse (A. flavicollis); secondary consumers, represented by the shrew (Sorex granarius); and finally, detritivores, represented by slugs (Arion ater). Thirteen of the sampling stations were located in mature oak woodlands (Quercus sp.); two of the sampling stations were located in the area surrounding a restored lignite mine dump, and the other in an ultrabasic area. The analytical determinations revealed a lack of significant correlations among trophic compartments, possibly caused by effective regulation of metals by organisms and/or spatial variation in availability of metals from soil or food. Furthermore, the only element that showed a clear pattern of biomagnification was Cu; as for the other elements, there was always some divergence from such a pattern. Finally, the patterns of bioaccumulation in contaminated and woodland sampling stations were very similar, although there was enrichment of the concentrations of Cu, Mn, and Zn in the mice viscera, which, except for Mn, were related to higher edaphic concentrations.

Risk assessment methodologies for exposure of great horned owls (Bubo virginianus) to PCBs on the Kalamazoo River, Michigan.

Dietary exposures of great horned owls (GHO; Bubo virginianus) to polychlorinated biphenyls (PCBs) in the terrestrial food web at the Kalamazoo River, Michigan, USA, were examined. Average potential daily doses (APDD) in GHO diets were 7- to 10-fold and 3-fold greater at the more contaminated location versus a reference location for site-specific exposures quantified as total PCBs and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ(WHO-Avian)), respectively. Wetland/aquatic prey contributed significantly to PCB exposure and APDD. Estimates of risk based on comparison of modeled dietary intake (e.g., APDD) to toxicity reference values (TRVs), using a hazard quotient (HQ) methodology, varied between diet composition methods (mass basis vs numeric basis). Mass-basis compositions yielded greater HQs at all sites. Potential risks associated with dietary exposures ("bottom-up" risk assessment methodology) were less than (HQ < 1) benchmarks for effects. This result is consistent with risk estimates based on concentrations in tissues ("top-down" risk assessment methodology), and indicated PCBs posed no significant risk to terrestrial raptor species. Colocated and concurrent studies that evaluated GHO reproductive performance (nestling productivity) and relative abundance were consistent with results of the risk assessment. Measures of risk based on HQs were consistent with direct measures of ecologically relevant endpoints (reproductive fitness). Uncertainty in risk estimates is contributed during the selection of TRVs for effects in GHO based on TEQ(WHO-Avian) because of the absence of species-specific, dose-response thresholds. This evaluation indicated that a multiple-lines-of-evidence approach provided the best estimate of risk.

Photoreceptor organisation and phenotypic characterization in retinas of two diurnal rodent species: potential use as experimental animal models for human vision research.

To characterize rod and cone distribution and composition in two diurnal mouse-like rodents, retinas from adult Arvicanthis ansorgei and Lemniscomys barbarus were processed for immunohistochemistry using multiple rod- and cone-specific antibodies. Antibodies tested included rhodopsin, cone opsins, pan-arrestin and cone arrestin, recoverin, and cGMP dependent ion channel. In both species, retinas were composed of approximately 33% cones, and most antibodies gave similar staining patterns. Data show these two diurnal rodents possess large numbers of cones, organised in a strict anatomical array. This suggests that diurnal rodents in general possess elevated cone numbers and could constitute valuable models for investigating cone pathophysiology.

[The regulation of the oxidative processes in the tissues of Muridae like rodents caught in the Chernobyl accident zone].

The results of the investigations of the radioactive contamination consequences on the lipid peroxidation (LPO) processes in organs and tissues of wild rodents which were caught in the Chernobyl NPP accident 30-km zone during 1986-1993 are generalized. The behaviors of the technogenic contamination effect on dynamic of changes of the LPO physico-chemical regulatory system parameters and the generalized parameters of the phospholipid composition in organs of the different radioresistance wild rodents are revealed in dependence on the radioactive contamination level and the duration of the radiation factor exposure. Different sensitivity of the LPO regulatory system parameters in wild rodent tissues to the radioactive contamination of their environment and the unequal ability to normalization of the antioxidant status and the energy exchange in tissues result in the change of the scale and character of interrelations between the reciprocal parameters in norm and have an influence on the development of qualitatively new subpopulations of wild rodents due to the transition of the cell regulatory system to the another level of the function.

Of mice and women: light as a circadian stimulus in breast cancer research.

OBJECTIVE: Nocturnal rodents are frequently used as models in human breast cancer research, but these species have very different visual and circadian systems and, therefore, very different responses to optical radiation or, informally, light. Because of the impact of light on the circadian system and because recent evidence suggests that cancer risk might be related to circadian disruption, it is becoming increasingly clear that optical radiation must be properly characterized for both nocturnal rodents and diurnal humans to make significant progress in unraveling links between circadian disruption and breast cancer. In this paper, we propose a quantitative framework for comparing radiometric and photometric quantities in human and rodent studies. METHODS: We reviewed published research on light as a circadian stimulus for humans and rodents. Both suppression of nocturnal melatonin and phase shifting were examined as outcome measures for the circadian system. RESULTS: The data were used to develop quantitative comparisons regarding the absolute and spectral sensitivity for the circadian systems of humans and nocturnal rodents. CONCLUSIONS: Two models of circadian phototransduction, for mouse and humans, have been published providing spectral sensitivities for these two species. Despite some methodological variations among the studies reviewed, the circadian systems of nocturnal rodents are approximately 10,000 times more sensitive to optical radiation than that of humans. Circadian effectiveness of different sources for both humans and nocturnal rodents are offered together with a scale relating their absolute sensitivities. Instruments calibrated in terms of conventional photometric units (e.g., lux) will not accurately characterize the circadian stimulus for either humans or rodents.