Interstrain Differences Research Articles

ВЛИЯНИЕ БЛОКАДЫ СИНТЕЗА ПРОСТАГЛАНДИНОВ НА НАТРИЙУРЕТИЧЕСКУЮ ФУНКЦИЮ ПОЧЕК КРЫС СО СТРЕСС-ИНДУЦИРУЕМОЙ ГИПЕРТЕНЗИЕЙ (ЛИНИЯ НИСАГ)

Renal responses of hypertensive ISIAH and normotensive WAG rats to intragastrically administered isosmotic (0.9 %) and hyperosmotic (2 %) sodium chloride were studied. It was found, that ISIAH rats are characterized by more active water and sodium excretion under these loadings, while different mechanisms underlie the differences in the response of the kidneys of the ISIAH and WAG rats to iso- and hyperosmotic solutions. The greater efficiency of isoosmotic solution excretion in ISIAH rats was related to significant inhibition of sodium reabsorption in the renal tubules during the baroreceptor reflex as a result of reduced basal activity of renal renin-angiotensin system. When hyperosmotic solution was administered, the excretion rate of the load by ISIAH rats was associated with a more rapid development of the reaction, apparently due to the activation of prostaglandin secretion under hyperosmia, because the preliminary infusion of sodium diclofenac blocking their biosynthesis neutralized interstrain differences.

Predicting the bending properties of long bones: Insights from an experimental mouse model.

Analyses of bone cross-sectional geometry are frequently used by anthropologists and paleontologists to infer the loading histories of past populations. To address some underlying assumptions, we investigated the relative roles of genetics and exercise on bone cross-sectional geometry and bending mechanics in three mouse strains: high bone density (C3H/He), low bone density (C57BL/6), and a high-runner strain homozygous for the Myh4Minimsc allele (MM). Weanlings of each strain were divided into exercise (wheel) or control (sedentary) treatment groups for a 7-week experimental period. Morphometrics of the femoral mid-diaphysis and mechanical testing were used to assess both theoretical and ex vivo bending mechanics. Across all measured morphological and bending traits, we found relatively small effects of exercise treatment compared to larger and more frequent interstrain differences. In the exercised group, total distance run over the experimental period was not a predictor of any morphological or bending traits. Cross-sectional geometry did not accurately predict bone response to loading. Results from this experimental model do not support hypothesized associations among extreme exercise, cross-sectional geometry, and bending mechanics. Our results suggest that analysis of cross-sectional geometry alone is insufficient to predict loading response, and questions the common assumption that cross-sectional geometry differences are indicative of differential loading history.

Fast growth phenotype of E. coli K-12 from adaptive laboratory evolution does not require intracellular flux rewiring

Adaptive laboratory evolution (ALE) is a widely-used method for improving the fitness of microorganisms in selected environmental conditions. It has been applied previously to Escherichia coli K-12 MG1655 during aerobic exponential growth on glucose minimal media, a frequently used model organism and growth condition, to probe the limits of E. coli growth rate and gain insights into fast growth phenotypes. Previous studies have described up to 1.6-fold increases in growth rate following ALE, and have identified key causal genetic mutations and changes in transcriptional patterns. Here, we report for the first time intracellular metabolic fluxes for six such adaptively evolved strains, as determined by high-resolution 13C-metabolic flux analysis. Interestingly, we found that intracellular metabolic pathway usage changed very little following adaptive evolution. Instead, at the level of central carbon metabolism the faster growth was facilitated by proportional increases in glucose uptake and all intracellular rates. Of the six evolved strains studied here, only one strain showed a small degree of flux rewiring, and this was also the strain with unique genetic mutations. A comparison of fluxes with two other wild-type (unevolved) E. coli strains, BW25113 and BL21, showed that inter-strain differences are greater than differences between the parental and evolved strains. Principal component analysis highlighted that nearly all flux differences (95%) between the nine strains were captured by only two principal components. The distance between measured and flux balance analysis predicted fluxes was also investigated. It suggested a relatively wide range of similar stoichiometric optima, which opens new questions about the path-dependency of adaptive evolution.

Two Strains of Lymnaea stagnalis and the Progeny from Their Mating Display Differential Memory-Forming Ability on Associative Learning Tasks.

The pond snail Lymnaea stagnalis learns and forms long-term memory (LTM) following both operant conditioning of aerial respiratory behavior and classical conditioning of taste aversive behavior. In the present study, we examined whether there are interstrain differences in the ability to form LTM following these two types of conditioning. A strain of Lymnaea (TC1) collected in Alberta, Canada exhibits superior memory-forming ability following aerial respiratory operant conditioning compared to a laboratory-reared strain of Lymnaea from Netherlands known as the Dutch strain. We asked whether the offspring of the Canadian TC1 and Dutch snails (i.e., filial 1 (F1) cross snails) would have the superior memory ability and found, rather, that their memory ability was average like the Dutch snails. That is, the Canadian TC1 snails have superior ability for LTM formation following aerial respiratory operant conditioning, but the Dutch and the generated F1 cross have average ability for memory forming. We next examined the Canadian TC1, Dutch and F1 cross snails for their ability to learn and form memory following conditioned taste aversion (CTA). All three populations showed similar associative CTA responses. However, both LTM formation and the ratio of good-to-poor performers in the memory retention test were much better in the Dutch snails than the Canadian TC1 and F1 cross snails. The memory abilities of the Canadian TC1 and F1 cross snails were average. Our present findings, therefore, suggest that snails of different strains have different memory abilities, and the F1 cross snails do not inherit the memory ability from the smart strain. To our knowledge, there have been a limited number of studies examining differences in memory ability among invertebrate strains, with the exception of studies using mutant flies.

Inter-Strain Differences in LINE-1 DNA Methylation in the Mouse Hematopoietic System in Response to Exposure to Ionizing Radiation

Long Interspersed Nuclear Element 1 (LINE-1) retrotransposons are the major repetitive elements in mammalian genomes. LINE-1s are well-accepted as driving forces of evolution and critical regulators of the expression of genetic information. Alterations in LINE-1 DNA methylation may lead to its aberrant activity and are reported in virtually all human cancers and in experimental carcinogenesis. In this study, we investigated the endogenous DNA methylation status of the 5′ untranslated region (UTR) of LINE-1 elements in the bone marrow hematopoietic stem cells (HSCs), hematopoietic progenitor cells (HPCs), and mononuclear cells (MNCs) in radioresistant C57BL/6J and radiosensitive CBA/J mice and in response to ionizing radiation (IR). We demonstrated that basal levels of DNA methylation within the 5′-UTRs of LINE-1 elements did not differ significantly between the two mouse strains and were negatively correlated with the evolutionary age of LINE-1 elements. Meanwhile, the expression of LINE-1 elements was higher in CBA/J mice. At two months after irradiation to 0.1 or 1 Gy of 137Cs (dose rate 1.21 Gy/min), significant decreases in LINE-1 DNA methylation in HSCs were observed in prone to radiation-induced carcinogenesis CBA/J, but not C57BL/6J mice. At the same time, no residual DNA damage, increased ROS, or changes in the cell cycle were detected in HSCs of CBA/J mice. These results suggest that epigenetic alterations may potentially serve as driving forces of radiation-induced carcinogenesis; however, future studies are needed to demonstrate the direct link between the LINE-1 DNA hypomethylation and radiation carcinogenesis.

Pup-Associated Conditioned Place Preference Reaction and Maternal Care in Depressive WAG/Rij Rats

The acquisition of a conditioned place preference reaction (CPPR) associated with own pups and foster pups was compared in female WAG/Rij and Wistar rats, along with maternal behavior in a “place preference” chamber from day 2 to day 8 after birth. In addition, females’ behavior was assessed in the open field, elevated plus maze, and forced swimming tests before pregnancy and after birth of pups. Female WAG/Rij rats acquired the CPPR associated with their own pups (WAG/Rij) and foster pups (Wistar) less well. Thus, the number of females with increases in the time spent in the initial non-preferred sector after it was combined with pups and the number of females achieving the CPPR acquisition criterion were smaller in WAG/Rij rats than Wistar rats. Female WAG/Rij rats, as compared with female Wistar rats, showed lower levels of maternal care in the place preference chamber in relation to both their own pups and foster pups: the numbers of approaches to the pups were smaller, as were the numbers of retrievals, and the non-feeding-related times spent in contact with pups were shorter. The durations of immobility in the forced swimming test were greater in WAG/Rij females than Wistar females both before pregnancy and after delivery of pups, which is evidence for a stable depression-like state. Before pregnancy, there were no statistically significant interstrain differences in anxiety levels. After birth of pups, anxiety levels in WAG/Rij females decreased, while those in Wistar females showed no significant change. These results provide evidence that the worse acquisition of the CPPR and the decreased maternal care in depressed WAG/Rij females were not associated with the features of their own pups but were related to their depressive state. In other words, pups provided weaker reinforcement for depressed mothers than for “normal” (nondepressed) mothers.

The Development of Intestinal Preservation Injury

The efficient translation of various experimental findings is hampered by interspecies (or even inter-strain) differences that may often invalidate findings, mechanisms or therapeutic approaches. Intestinal preservation/reperfusion injury is a field where rodents were extensively used yet any eventual clinical application would require validation in large animal models. We compared the development of tissue injury in rat and porcine intestines undergoing static cold storage (SCS) in histidine-tryptophane-ketoglutarate (HTK) solution. Methods: Standard procurement and perfusion of the small intestine was performed in Sprague Dawley rats and Landrace pigs (N=7 in each group). At 8h, 14h and 24 hours’ tissue samples were obtained and assessed for tissue damage (Chiu/Park score), apoptosis (active caspase-3) and tissue expression of ZO-1, claudin-3 and villin (immunofluorescence). Results: Rats showed a moderate mucosal injury (median Chiu/Park grade 3) already after 8h while pigs showed normal or near-normal histology (median grade 1). Histology remained significantly superior in pigs after 14h and 24h (see figure). Rats had advanced mucosal injury while only mild/moderate mucosal injury (median grade 2) was noted in pigs after 24h of SCS. Apoptotic enterocytes were abundant in rat but not pig intestines after 14 hours of SCS. After 14 hours of SCS, immunofluorescence revealed the virtual absence of ZO-1 staining in the rat but not in porcine intestines where a strong signal was detected even after 24 hours of SCS. Claudin-3 expression gradually changed from reticular staining on the basolateral membrane to a combined (membrane & cytoplasmic) signal in both species (albeit faster in rats). Conclusions: Pig intestines are significantly more resilient to preservation injury than rat intestines and longer SCS should be considered to attain a visible histological injury. The sequential alterations of certain molecular targets could serve as surrogate injury markers.Figure

Interstrain differences in the expression and activity of Cyp2a5 in the mouse liver

BackgroundCytochrome P450 2A5 (Cyp2a5), a mouse enzyme orthologous of human CYP2A6, catalyzes a number of toxicologically important reactions, including the metabolism of nicotine, aflatoxin B1, and several other xeno- and endobiotics. Cyp2a5 expression is complex and not yet fully understood. We investigated inter-strain differences in the activity and mRNA expression of hepatic Cyp2a5. Cyp1a1/2 and Cyp2b9/10 activities were evaluated for comparative purposes. Data on the interstrain differences in the expression and activity of Cyp2a5 are important to select a suitable mouse model for studying CYP2A6-mediated metabolism.ResultsActivity of Cyp2a5 (coumarin 7-hydroxylase) was highest in DBA-2 and DBA-1, intermediate in B6D2F1 (hybrid) and low in the remaining strains (C57BL/6, C57BL/10, CBA, BALB/cAn, SW). Contrasting with the activity, background levels of Cyp2a4/5 mRNA did not differ between high- and low-activity murine strains. Phenobarbital (PB, 80 mg/kg body weight/day × 3 days, i.p.) increased Cyp2a5, Cyp1a1/2 (ethoxyresorufin-O-deethylase) and Cyp2b9/10 (bezyloxyresorufin-O-debenzylase) activities while only Cyp2a5 was enhanced by pyrazole (PYR, 100 mg/kg body weight/day × 3 days, i.p.). Inductions of Cyp2a5 activity by PYR and PB were accompanied by increases of Cyp2a4/5 mRNA. PYR and PB did not upregulate heme oxygenase-1 (hmox-1) mRNA expression in any strain, a finding that is apparently at odds with the notion that Cyp2a5 and hmox-1 inductions are coordinated events.ConclusionsSince background levels of Cyp2a4/5 gene transcripts of high-activity strains did not differ from those of low-activity mice, distinct constitutive activities did not result from different transcription rates and/or mRNA half-lives. Results therefore suggested that interstrain differences in constitutive activity of Cyp2a5 possibly arise from distinct translation efficiencies, protein half-lives and/or enzyme kinetics toward the substrate. Data from this study indicated that all tested strains are suitable models for studying toxicants that are substrates for human CYP2A6; DBA-2, DBA-1 and the hybrid B62DF1, however, have the advantage of presenting high constitutive activities of Cyp2a5.

Bifidobacterium adolescentis Exerts Strain-Specific Effects on Constipation Induced by Loperamide in BALB/c Mice.

Constipation is one of the most common gastrointestinal complaints worldwide. This study was performed to determine whether Bifidobacterium adolescentis exerts inter-strain differences in alleviating constipation induced by loperamide in BALB/c mice and to analyze the main reasons for these differences. BALB/c mice underwent gavage with B. adolescentis (CCFM 626, 667, and 669) once per day for 17 days. The primary outcome measures included related constipation indicators, and the secondary outcome measures were the basic biological characteristics of the strains, the concentration changes of short-chain fatty acids in feces, and the changes in the fecal flora. B. adolescentis CCFM 669 and 667 relieved constipation symptoms by adhering to intestinal epithelial cells, growing quickly in vitro and increasing the concentrations of propionic and butyric acids. The effect of B. adolescentis on the gut microbiota in mice with constipation was investigated via 16S rRNA metagenomic analysis. The results revealed that the relative abundance of Lactobacillus increased and the amount of Clostridium decreased in the B. adolescentis CCFM 669 and 667 treatment groups. In conclusion, B. adolescentis exhibits strain-specific effects in the alleviation of constipation, mostly due to the strains’ growth rates, adhesive capacity and effects on the gut microbiome and microenvironment.

выявление мембраносвязанных протеаз FRANCISEllA TUlARENSIS

Sterile preparations of membrane fractions were prepared by processing of live Francisella tularensis cells of different subspecies with 4.5M urea solution and differential centrifugation. For the first time, proteolytic activity was detected and studied by tests of radial enzyme diffusion and substrate polyacrylamide gel electrophoresis using gelatin as a substrate. Spectrum of gelatinases in the resulted preparation were detected. Quantitative inter-strain differences in the protease activities and their qualitative composition in membrane preparations of various virulent F.tularensis strains was analyzed. Avirulent F.tularensis 21/400 subsp. holarctica (I-214) strain demonstrated the greatest gelatinase activity in enzyme diffusion method and the lowest hydrolytic activity was seen in F.tularensis B-399 A-Cole subsp. tularensis (I-386) and F.tularensis Utah 112 subsp. novicida (I-384), other preparations showed intermediate activity. Enzyme electrophoresis in the protease spectra determined the presence of proteins with proteases activity 50–100kDa, and in the spectrum preparations of F. tularensis I-386 and I-384 were detected additional bands of proteases.

Molecular determinants of the adrenal gland functioning related to stress-sensitive hypertension in ISIAH rats.

BackgroundThe adrenals are known as an important link in pathogenesis of arterial hypertensive disease. The study was directed to the adrenal transcriptome analysis in ISIAH rats with stress-sensitive arterial hypertension and predominant involvement in pathogenesis of the hypothalamic-pituitary-adrenal and sympathoadrenal systems.ResultsThe RNA-Seq approach was used to perform the comparative adrenal transcriptome profiling in hypertensive ISIAH and normotensive WAG rats. Multiple differentially expressed genes (DEGs) related to different biological processes and metabolic pathways were detected.The discussion of the results helped to prioritize the several DEGs as the promising candidates for further studies of the genetic background underlying the stress-sensitive hypertension development in the ISIAH rats. Two of these were transcription factor genes (Nr4a3 and Ppard), which may be related to the predominant activation of the sympathetic-adrenal medullary axis in ISIAH rats. The other genes are known as associated with hypertension and were defined in the current study as DEGs making the most significant contribution to the inter-strain differences. Four of them (Avpr1a, Hsd11b2, Agt, Ephx2) may provoke the hypertension development, and Mpo may contribute to insulin resistance and inflammation in the ISIAH rats.ConclusionsThe study strongly highlighted the complex nature of the pathogenesis of stress-sensitive hypertension. The data obtained may be useful for identifying the common molecular determinants in different animal models of arterial hypertension, which may be potentially used as therapeutic targets for pharmacological intervention.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3354-2) contains supplementary material, which is available to authorized users.

Cross-Mating Compatibility and Competitiveness among Aedes albopictus Strains from Distinct Geographic Origins - Implications for Future Application of SIT Programs in the South West Indian Ocean Islands.

The production of large numbers of males needed for a sustainable sterile insect technique (SIT) control program requires significant developmental and operational costs. This may constitute a significant economic barrier to the installation of large scale rearing facilities in countries that are undergoing a transition from being largely dependent on insecticide use to be in a position to integrate the SIT against Aedes albopictus. Alternative options available for those countries could be to rely on outsourcing of sterile males from a foreign supplier, or for one centralised facility to produce mosquitoes for several countries, thus increasing the efficiency of the mass-rearing effort. However, demonstration of strain compatibility is a prerequisite for the export of mosquitoes for transborder SIT applications. Here, we compared mating compatibility among Ae. albopictus populations originating from three islands of the South Western Indian Ocean, and assessed both insemination rates and egg fertility in all possible cross-mating combinations. Furthermore, competitiveness between irradiated and non-irradiated males from the three studied strains, and the subsequent effect on female fertility were also examined. Although morphometric analysis of wing shapes suggested phenoptypic differences between Ae. albopictus strains, perfect reproductive compatibility between them was observed. Furthermore, irradiated males from the different islands demonstrated similar levels of competitiveness and induced sterility when confronted with fertile males from any of the other island populations tested. In conclusion, despite the evidence of inter-strain differences based on male wing morphology, collectively, our results provide a new set of expectations for the use of a single candidate strain of mass-reared sterile males for area-wide scale application of SIT against Ae. albopictus populations in different islands across the South Western Indian Ocean. Cross-mating competitiveness tests such as those applied here are necessary to assess the quality of mass reared strains for the trans-border application of sterile male release programs.

Spermatogenesis parameters and testosterone production at puberty as predictors of testicular functional activity in mice (Mus musculus)

The aim of this study was to investigate fertility-associated parameters of spermatogenesis and androgenic status in male laboratory mice at puberty and to assess their prognostic significance in the realization of the definitive testicular function. In three inbred murine strains, BALB/cLac, CBA/Lac and PT, the serum testosterone level, its testicular concentration, epididymal sperm count (sperm reserve) and portion of sperm with abnormal head morphology were evaluated on days 45 (puberty) and 90 (adulthood) of postnatal development. CBA/Lac males were characterized by a lower epididymal sperm count vs. other strains at both ages indicative of poorer spermatogenesis. At the same time, CBA/Lac males had a lower portion of sperm with abnormal head morphology, and this could be considered as a compensatory reaction aimed at improving sperm fertility. Distinct inter-strain differences in the portion of sperm with morphologically abnormal heads were established at both ages, while the inter-strain ratio remained invariable (BALB/cLac > PT > CBA/Lac). Thus, the level of abnormal spermatogenesis in the pubertal period may have a predictive significance for the definitive testicular activity in adult mice. No inter-strain and age-dependent changes were found in serum and testicular testosterone levels except for the PT strain, in which both testosterone levels rose from puberty to adulthood, suggesting a shift of the pubertal testosterone peak towards later times. Our data show that in male laboratory mice the genetic peculiarities of the testicular function manifest themselves during puberty and persist until adulthood.

The development of inter-strain variation in cortical and trabecular traits during growth of the mouse lumbar vertebral body.

Age-related changes in cortical and trabecular traits have been well studied; however, very little is known about how these bone tissues co-develop from day 1 of postnatal growth to establish functional structures by adulthood. In this study, we aimed to establish how cortical and trabecular tissues within the lumbar vertebral body change during growth for three inbred mouse strains that express wide variation in adult bone structure and function. Bone traits were quantified for lumbar vertebral bodies of female A/J, C57BL/6J (B6), and C3H/HeJ (C3H) inbred mouse strains from 1 to 105days of age (n = 6-10 mice/age/strain). Inter-strain differences in external bone size were observed as early as 1day of age. Reciprocal and rapid changes in the trabecular bone volume fraction and alignment in the direction of axial compression were observed by 7days of age. Importantly, the inter-strain difference in adult trabecular bone volume fraction was established by 7days of age. Early variation in external bone size and trabecular architecture was followed by progressive increases in cortical area between 28 and 105days of age, with the greatest increases in cortical area seen in the mouse strain with the lowest trabecular mass. Establishing the temporal changes in bone morphology for three inbred mouse strains revealed that genetic variation in adult trabecular traits were established early in postnatal development. Early variation in trabecular architecture preceded strain-specific increases in cortical area and changes in cortical thickness. This study established the sequence of how cortical and trabecular traits co-develop during growth, which is important for identifying critical early ages to further focus on intervention studies that optimize adult bone strength.

Behavior, Memory, and Immunological Status in Mice in a Model of Desynchronosis

Interstrain differences in behavior and parameters of the immune system of CBA and C57BL/6 mice with round the clock coverage (KO) were investigated. Open field, light/dark, acoustic startle response, forced swimming, elevated plus-maze, passive avoidance were used for measuring emotional behavior and memory. The number of lymphocyte subpopulations CD3+, CD4+8-, CD4-8+, CD4+8+, CD19+, CD3+hi spleen and thymus, the ratio of cells in different phases of the cell cycle was determined by flow cytometry. C57BL/6J mice strictly increased anxiety in response to the KO compared to CBA mice. Moreover, KO-treated C57BL/6J mice impaired the passive avoidance learning. We found that KO evoked significant changes in the cellular composition of the thymus and decrease of thymocytes proliferation in C57BL/6J mice. In opposite KO-treated CBA mice showed change of splenic cellular structure with increased % CD19+ cells and the proliferation of splenocytes. Our study demonstrated genotype-dependent reactions of the nervous and immune systems in response chronic constant light.

Interplay between RNA interference and heat shock response systems in Drosophila melanogaster.

The genome expression pattern is strongly modified during the heat shock response (HSR) to form an adaptive state. This may be partly achieved by modulating microRNA levels that control the expression of a great number of genes that are embedded within the gene circuitry. Here, we investigated the cross-talk between two highly conserved and universal house-keeping systems, the HSR and microRNA machinery, in Drosophila melanogaster. We demonstrated that pronounced interstrain differences in the microRNA levels are alleviated after heat shock (HS) to form a uniform microRNA pattern. However, individual strains exhibit different patterns of microRNA expression during the course of recovery. Importantly, HS-regulated microRNAs may target functionally similar HS-responsive genes involved in the HSR. Despite the observed general downregulation of primary microRNA precursor expression as well as core microRNA pathway genes after HS, the levels of many mature microRNAs are upregulated. This indicates that the regulation of miRNA expression after HS occurs at transcriptional and post-transcriptional levels. It was also shown that deletion of all hsp70 genes had no significant effect on microRNA biogenesis but might influence the dynamics of microRNA expression during the HSR.

Cohesion of Clonal Life History, Senescence and Rejuvenation Induced by Autogamy of the Histophagous Ciliate Tetrahymena rostrata

The histophagous ciliate Tetrahymena rostrata was found as a parasite in the renal organs of the land snails Zonitoides nitidus and Cochlicopa lubrica. A starvation medium induced encystment, meiosis, autogamy, and development of new macronuclei. The cell division rate declined linearly with number of divisions from the last autogamy until senescence. The senescing strains were rejuvenated by further encystment-induced autogamy. It is expected, that these processes contribute to genetic variability among the local, small, and isolated T. rostrata populations. Consistent with this expectation, small divergences in the cox-1 sequences appeared even among these strains, which had been isolated from different specimens of the same host species at the same site. The divergences in this gene between our T. rostrata strains from Z. nitidus and other strains from C. lubrica, Helix aspersa, and Deroceras reticulatum in Spain (Segade et al. 2009, Parasitology 136:771-782), were beyond the limits of intra-species variability within the genus Tetrahymena. However there is the lack of inter-strain differences in the life history and cytology among our, the Spanish, and those T.rostrata strains, that are not available for "barcoding" anymore. Therefore, variability in the life history and morphology within T .rostrata is constrained by natural selection.

The influence of changes in expression of redox-sensitive genes on the development of retinopathy in rats

Age-related macular degeneration (AMD) is a complex multifactorial disease of the elderly, with unclear pathogenesis; AMD is the leading cause of blindness. One of the destructive processes in AMD is oxidative stress, which leads to an imbalance in the processes responsible for production and detoxification of reactive oxygen species. The aryl hydrocarbon receptor (AhR) signaling pathway can participate in the development of oxidative stress, but the main regulator of antioxidant defense is nuclear factor, erythroid derived 2 (Nrf2). AhR-dependent oxidative stress can be attenuated by activation of Nrf2, and defects in the Nrf2 signaling pathway can increase sensitivity of the cell to oxidative stress. Our aim was to determine the role of the pro-oxidant (AhR-dependent) and antioxidant (Nrf2-dependent) systems in the pathogenesis of AMD using rats of OXYS strain and of OXYSb substrain with signs of AMD-like retinopathy of varying severity. We compared the retinal levels of mRNA expression of Nrf2- and AhR-dependent redox-sensitive systems between 1-, 3-, and 12- month-old senescence-accelerated OXYS rats (have been shown to be a valid experimental model of AMD) and the rat substrain OXYSb, which shows low morbidity of AMD. We uncovered interstrain differences in the expression of Nrf2 and Nrf2-dependent genes (glutathione S-reductase [Gsr] and heme oxygenase 1 [Hmox1]), in the expression of AhR-dependent genes (cytochrome P450 1A2 [Cyp1a2] and cytochrome P450 1B1 [Cyp1b1]), and in the NADPH-quinone oxidoreductase (Nqo1) expression, which is controlled by both AhR and Nrf2. Binding of AhR and Nrf2 proteins to the regulatory regions of AhR and Nrf2 genes, respectively, was detected by chromatin immunoprecipitation in the retina of 1-, 3-, and 12-month-old OXYS, OXYSb, and Wistar (control) rats. We compared the strength of DNA-protein interactions of AhR and Nrf2 with regulatory sequences and found that the level of autoupregulation of the AhR gene was higher in the retina of 1-month-old OXYSb rats in comparison with OXYS rats. An imbalance between pro-oxidant (AhR-dependent) and antioxidant (Nrf2-dependent) systems may play a crucial role in the onset and/or progression of AMD.

Robust effects of genetic background on responses to subarachnoid hemorrhage in mice

Outcome varies among patients with subarachnoid hemorrhage but known prognostic factors explain only a small portion of the variation in outcome. We hypothesized that individual genetic variations influence brain and vascular responses to subarachnoid hemorrhage and investigated this using inbred strains of mice. Subarachnoid hemorrhage was induced in seven inbred and a chromosome 7 substitution strain of mouse. Cerebral blood flow, vasospasm of the middle cerebral artery, and brain injury were assessed. After 48 h of subarachnoid hemorrhage, mice showed significant middle cerebral artery vasospasm that correlated positively with reduction in cerebral blood flow at 45 min. Mice also had increased neuronal injury compared to sham controls; A/J and C57BL/6 J strains represented the most and least severe, respectively. However, brain injury did not correlate with cerebral blood flow reduction at 45 min or with vasospasm at 48 h. Chromosome 7 substitution did not influence the degree of vasospasm or brain injury. Our data suggested that mouse genetic background influences outcome of subarachnoid hemorrhage. Investigations into the genetic factors causing these inter-strain differences may provide insight into the etiology of the brain damage following subarachnoid hemorrhage. These findings also have implications for animal modeling of disease and suggest that genetic differences may also modulate outcome in other cardiovascular diseases.

Effect of Light Colour, Timing, and Duration of Light Exposure on the Hatchability of Artemia Spp. (Branchiopoda: Anostraca) Eggs

We investigated the effect of illumination on the hatching of eggs of one strain of Artemia franciscana Kellogg, 1906 and two strains of parthenogenetic Artemia (Branchiopoda, Anostraca). The following light parameters were used: colour (red, blue, and white light, having different intensities in the range 22-27 mu mol E/m(2) per s, corresponding with different wavelengths in the range 400-700 nm), and additionally (Experiment I) duration of light exposure (varying between 15 min and continuous light) or (Experiment 2) timing of light exposure (from the 1st to the 13th hour of incubation of eggs for hatching). Continuous darkness was included as negative control. Hatching percentage was determined after 24 and 48 h, and additionally after 72 h in Experiment 2. For all samples a relatively short exposure to light (6 h or less) during the initial hours of incubation maximally triggered the hatching process; I h of light had highest efficiency when given during the 4th hour of incubation of eggs for hatching, and less so when supplied earlier or later. Lower sensitivity was observed for the red light spectral region (600-700 nm), with mostly limited differences between blue (400-500 nm) and white (400-700 nm) light. Differences between samples could be linked to factors such as chorion thickness, pigmentation, storage conditions, diapause status and genotypic differences in general, but to what extent each of these factors contributes to the variability among the strains needs to be studied by analysing a more comprehensive set of samples. The fact that the inter-strain differences observed in our study were only of quantitative nature nevertheless suggests that light triggers hatching in Anemia eggs through a process that is consistent throughout the genus. Our work could contribute to a better understanding of the hatching biology of dormant life stages in Crustacea in general.