Voluntary wheel running reduces tumor growth and increases capillarity in the heart during doxorubicin chemotherapy in a murine model of breast cancer

Introduction: The possible beneficial effects of physical activity during doxorubicin treatment of breast cancer need further investigation as many of the existing studies have been done on non-tumor-bearing models. Therefore, in this study, we aim to assess whether short-term voluntary wheel-running exercise during doxorubicin treatment of breast cancer-bearing mice could induce beneficial cardiac effects and enhance chemotherapy efficacy. Methods: Murine breast cancer I3TC cells were inoculated subcutaneously to the flank of female FVB mice (n = 16) that were divided into exercised and non-exercised groups. Two weeks later, doxorubicin treatment was started via intraperitoneal administration (5 mg/kg weekly for 3 weeks). Organs were harvested a day after the last dose. Results: The tumor volume over time was significantly different between the groups, with the exercising group having lower tumor volumes. The exercised group had increased body weight gain, tumor apoptosis, capillaries per cardiomyocytes, and cardiac lactate dehydrogenase activity compared to the unexercised group, but tumor blood vessel density and maturation and tumor and cardiac HIF1-α and VEGF-A levels did not differ from those of the non-exercised group. Discussion: We conclude that even short-term light exercise such as voluntary wheel running exercise can decrease the subcutaneous mammary tumor growth, possibly via increased tumor apoptosis. The increase in cardiac capillaries per cardiomyocytes may also have positive effects on cancer treatment outcomes.

Tissue-specific metabolic enzyme levels covary with whole-animal metabolic rates and life-history loci via epistatic effects

Metabolic rates, including standard (SMR) and maximum (MMR) metabolic rate have often been linked with life-history strategies. Variation in context- and tissue-level metabolism underlying SMR and MMR may thus provide a physiological basis for life-history variation. This raises a hypothesis that tissue-specific metabolism covaries with whole-animal metabolic rates and is genetically linked to life history. In Atlantic salmon (Salmo salar), variation in two loci, vgll3 and six6, affects life history via age-at-maturity as well as MMR. Here, using individuals with known SMR and MMR with different vgll3 and six6 genotype combinations, we measured proxies of mitochondrial density and anaerobic metabolism, i.e. maximal activities of the mitochondrial citrate synthase (CS) and lactate dehydrogenase (LDH) enzymes, in four tissues (heart, intestine, liver, white muscle) across low- and high-food regimes. We found enzymatic activities were related to metabolic rates, mainly SMR, in the intestine and heart. Individual loci were not associated with the enzymatic activities, but we found epistatic effects and genotype-by-environment interactions in CS activity in the heart and epistasis in LDH activity in the intestine. These effects suggest that mitochondrial density and anaerobic capacity in the heart and intestine may partly mediate variation in metabolic rates and life history via age-at-maturity. This article is part of the theme issue 'The evolutionary significance of variation in metabolic rates'.

Early-life environmental effects on mitochondrial aerobic metabolism: a brood size manipulation in wild great tits

In avian species, the number of chicks in the nest and subsequent sibling competition for food are major components of the offspring's early-life environment. A large brood size is known to affect chick growth, leading in some cases to long-lasting effects for the offspring, such as a decrease in size at fledgling and in survival after fledging. An important pathway underlying different growth patterns could be the variation in offspring mitochondrial metabolism through its central role in converting energy. Here, we performed a brood size manipulation in great tits (Parus major) to unravel its impact on offspring mitochondrial metabolism and reactive oxygen species (ROS) production in red blood cells. We investigated the effects of brood size on chick growth and survival, and tested for long-lasting effects on juvenile mitochondrial metabolism and phenotype. As expected, chicks raised in reduced broods had a higher body mass compared with enlarged and control groups. However, mitochondrial metabolism and ROS production were not significantly affected by the treatment at either chick or juvenile stages. Interestingly, chicks raised in very small broods were smaller in size and had higher mitochondrial metabolic rates. The nest of rearing had a significant effect on nestling mitochondrial metabolism. The contribution of the rearing environment in determining offspring mitochondrial metabolism emphasizes the plasticity of mitochondrial metabolism in relation to the nest environment. This study opens new avenues regarding the effect of postnatal environmental conditions in shaping offspring early-life mitochondrial metabolism.

Cardiovascular oxygen transport and peripheral oxygen extraction capacity contribute to acute heat tolerance in European seabass

This study evaluated whether different parameters describing cardiovascular function, energy metabolism, oxygen transport and oxidative stress were related to the critical thermal maximum (CT_MAX) of European seabass (Dicentrarchus labrax) and if there were differential changes in these parameters during and after heat shock in animals with different CT_MAX in order to characterize which physiological features make seabass vulnerable to heat waves. Seabass (n = 621) were tested for CT_MAX and the physiological parameters were measured in individuals with good or poor temperature tolerance before and after a heat shock (change in temperature from 15 °C to 28 °C in 1.5 h). Fish with good thermal tolerance had larger ventricles with higher maximal heart rate during the heat shock than individuals with poor tolerance. Furthermore, they initially had a high ventricular Ca²⁺-ATPase activity, which was reduced to a similar level as in fish with poor tolerance following heat shock. The activity of heart lactate dehydrogenase increased in fish with high tolerance, when they were exposed to heat shock, while the aerobic enzyme activity did not differ between groups. The tolerant individuals had smaller red muscle fibers with higher myoglobin content than the poorly tolerant ones. The poorly tolerant individuals had higher hematocrit, which increased with heat shock in both groups. The poorly tolerant individuals had also higher activity of enzymes related to oxidative stress especially after heat shock. In general, CT_MAX was not depending on merely one physiological factor but several organ and cellular parameters were related to the CT_MAX of seabass and when working in combination they might protect the highly tolerant seabass from future heat waves.

Warm, but not hypoxic acclimation, prolongs ventricular diastole and decreases the protein level of Na+/Ca2+ exchanger to enhance cardiac thermal tolerance in European sea bass

One of the physiological mechanisms that can limit the fish's ability to face hypoxia or elevated temperature, is maximal cardiac performance. Yet, few studies have measured how cardiac electrical activity and associated calcium cycling proteins change with acclimation to those environmental stressors. To examine this, we acclimated European sea bass for 6 weeks to three experimental conditions: a seasonal average temperature in normoxia (16 °C; 100% air sat.), an elevated temperature in normoxia (25 °C; 100% air sat.) and a seasonal average temperature in hypoxia (16 °C; 50% air sat.). Following each acclimation, the electrocardiogram was measured to assess how acclimation affected the different phases of cardiac cycle, the maximal heart rate (fH_max) and cardiac thermal performance during an acute increase of temperature. Whereas warm acclimation prolonged especially the diastolic phase of the ventricular contraction, reduced the fH_max and increased the cardiac arrhythmia temperature (T_ARR), hypoxic acclimation was without effect on these functional indices. We measured the level of two key proteins involved with cellular relaxation of cardiomyocytes, i.e. sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) and Na⁺/Ca²⁺ exchanger (NCX). Warm acclimation reduced protein level of both NCX and SERCA and hypoxic acclimation reduced SERCA protein levels without affecting NCX. The changes in ventricular NCX level correlated with the observed changes in diastole duration and fH_max as well as T_ARR. Our results shed new light on mechanisms of cardiac plasticity to environmental stressors and suggest that NCX might be involved with the observed functional changes, yet future studies should also measure its electrophysiological activity.

Copper exposure improves the upper thermal tolerance in a sex-specific manner, irrespective of fish thermal history

Ectotherms can respond to climate change via evolutionary adaptation, usually resulting in an increase of their upper thermal tolerance. But whether such adaptation influences the phenotypic plasticity of thermal tolerance when encountering further environmental stressors is not clear yet. This is crucial to understand because organisms experience multiple stressors, besides warming climate, in their natural environment and pollution is one of those. Here, we studied the phenotypic plasticity of thermal tolerance in three-spined stickleback populations inhabiting spatially replicated thermally polluted and pristine areas before and after exposing them to a sublethal concentration of copper for one week. We found that the upper thermal tolerance and its phenotypic plasticity after copper exposure did not depend on the thermal history of fish, suggesting that five decades of thermal pollution did not result in evolutionary adaptation to thermal tolerance. The upper thermal tolerance of fish was, on the other hand, increased by ∼ 1.5 °C after 1-week copper exposure in a sex-specific manner, with males having higher plasticity. To our knowledge this is the first study that shows an improvement of the upper thermal tolerance as a result of metal exposure. The results suggest that three-spined sticklebacks are having high plasticity and they are capable of surviving in a multiple-stressor scenario in the wild and that male sticklebacks seem more resilient to fluctuating environmental conditions than female.

Subcutaneous B16 melanoma impairs intrinsic pressure generation and relaxation of the heart, which are not restored by short-term voluntary exercise in mice

The aim of this study was to investigate whether subcutaneous melanoma impairs intrinsic cardiac function and hypoxia tolerance in mice. Additionally it was investigated whether these changes could be prevented by voluntary running-wheel exercise. The role of different molecular pathways were also analysed. Male mice (C57Bl/6NCrl) were divided into unexercised tumor-free group, unexercised melanoma group and exercised melanoma group. Experiment lasted 2.7±0.1 weeks (determined by the tumor size) after which the heart function was measured in different oxygen levels ex vivo using Langendorff method. All the melanoma mice had lower pressure amplitude (50.3%), rate of pressure production (54.1%) and decline (52.5%) in hearts ex vivo as compared to tumor-free group. There were no functional differences between the two melanoma groups. All the groups had similar weight change, heart weights, cardiomyocyte sizes, levels of Ca²⁺-channels, energy metabolism enzyme activities, lipid peroxidation and reactive oxygen species in their cardiac tissue homogenates. However, all the melanoma mice had 7.4% lower superoxidase dismutase activity compared to the control animals, which might reduce the ability of the heart to react to changes in oxidative stress. The exercising melanoma group had 28.6% higher average heart capillary density compared to the unexercised melanoma group. Short-term wheel running did not affect the tumor growth. In conclusion, subcutaneous melanoma seems to impair intrinsic heart function even prior to cachexia and these functional alterations were not caused by any of the measured molecular markers. Short-term voluntary running-wheel exercise was insufficient to alleviate the intrinsic cardiac impairments caused by melanoma.

The interactive effects of exercise training and functional feeds on the cardiovascular performance of rainbow trout (Oncorhynchus mykiss) at high temperatures

The cardiovascular performance of salmonids in aquaculture can be impaired by acute climate warming, posing risks for fish survival. Exercise training and functional feeds have been shown to be cardioprotective in mammals but their action on the fish heart and its upper thermal performance has not been studied. To investigate this, rainbow trout were trained at a moderate water velocity of 1 body length per second (bl s⁻¹) for 6 h per day, either alone or in combination with one of two functional feed-supplements, allicin and fucoidan. After 6 weeks of exercise training and feeding, maximum heart rate and the temperature coefficient of heart rate were significantly higher in the trained fish as compared to untrained ones. There was a slight increase in hematocrit in trained control fish reared on a normal diet (TC group) compared to untrained fish fed with the same diet (CC). This implies that exercise training enhanced oxygen delivery to trout tissues via an increase of cardiac blood flow in warm water. However, cardiac thermal tolerance was not affected by exercise training or feeding, except from the temperature of peak heart rate which was higher in the trained group fed with fucoidan supplement (TF) as compared to the untrained group fed with same diet (CF). Allicin supplement caused a significant reduction in the maximum heart rate and the temperature coefficient of heart rate, especially in trained fish, while fucoidan supplement did not cause any effect on heart rate. No differences were observed in growth performance among groups. However, fish fed with fucoidan-supplemented diet had a slight reduction in feed conversion efficiency. We suggest further investigations to understand the antagonistic effect of allicin supplemental feeding and exercise training on cardiovascular performance. More studies are also required to investigate if other exercise training intensities could increase cardiac thermal tolerance.

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Exercise training at 1 bl s⁻¹ increased the hematocrit values of rainbow trout.

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Exercise training at 1 bl s⁻¹ increased the maximum heart rate and temperature coefficient of rainbow trout.

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Exercise training at 1bl s⁻¹ did not enhance the cardiac thermal tolerance of rainbow trout.

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Functional feeds, allicin and fucoidan, did not improve the cardiovascular system of rainbow trout at high temperatures.

Compromised thermal tolerance of cardiovascular capacity in upstream migrating Arctic char and brown trout-are hot summers threatening migrating salmonids?

Heat waves are threatening fish around the world, leading sometimes to mass mortality events. One crucial function of fish failing in high temperatures is oxygen delivery capacity, i.e. cardiovascular function. For anadromous salmonids, increased temperature could be especially detrimental during upstream migration since they need efficiently working oxygen delivery system in order to cross the river rapids to reach upstream areas. The migration also occurs during summer and early autumn exposing salmonids to peak water temperatures, and in shallow rivers there is little availability for thermal refuges as compared to thermally stratified coastal and lake habitats. In order to shed light on the mechanisms underpinning the capacity of migrating fish to face high environmental temperatures, we applied a physiological and molecular approach measuring cardiovascular capacities of migrating and resident Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in Northern Norway. The maximum cardiovascular capacity of migrating fish was significantly lower compared to the resident conspecifics. The onset of cardiac impairment started only 2°C higher than river temperature, meaning that even a small increase in water temperature may already compromise cardiac function. The migrating fish were also under significant cellular stress, expressing increased level of cardiac heat shock proteins. We consider these findings highly valuable when addressing climate change effect on migrating fish and encourage taking action in riverine habitat conservation policies. The significant differences in upper thermal tolerance of resident and migrating fish could also lead changes in population dynamics, which should be taken into account in future conservation plans.

Hsp70s transcription-translation relationship depends on the heat shock temperature in zebrafish

Virtually all organisms respond to heat shock by transcription of genes encoding for heat shock proteins (HSPs), but the mechanisms behind post-transcriptional regulation are not known in detail. When we exposed zebrafish to 5 and 7 °C above normal rearing temperature for 30 min, hsp70 mRNA expression was 28 and 150 -fold higher than in control, respectively. Protein expression, on the other hand, showed no significant change at the +5 °C and a 2-fold increase at the +7 °C exposure. This suggests that the transcription of hsp70 gene does not immediately correspond to translation to related proteins under certain stress temperatures, but, when the temperature is higher, and potentially detrimental, transcription and translation are intimately coupled. Those results confirm that temperature is an important abiotic factor involved in heat shock post-transcriptional regulation mechanisms in fish. However, further studies are needed to determine the relationship between this environmental factor and post-transcriptional regulation mechanisms. Earlier, the coupling/uncoupling of hsp transcription and translation has only been studied using cold-water fish, or zebrafish embryos. With current findings, we suggest this mechanism might be present even in adult warm water fish like the zebrafish.

Water-soluble fraction of crude oil affects variability and has transgenerational effects in Daphnia magna

The importance of interindividual variability in environmental responses has been little studied, although the available information suggests that, e.g., changes in environmental temperature may be associated with changes in variability. We studied, if exposure to water-soluble fraction (WSF) of crude oil can be associated with changes in interindividual variability in phenotype in Daphnia magna, which reproduces parthenogenetically. By using these clonal organisms, we could exclude the possibility that the observed changes were caused by genetic variability. The results show that the variability of oxygen consumption rate decreased in 48 h 30% WSF-exposed animals as compared to 10% WSF-exposed or control animals without a change in the mean of oxygen consumption rate. The clonal Daphnia magna could also be used to study transgenerational effects without genetic contribution, as the different generations are genetically identical. We observed that the oxygen consumption rates in F₁ and F₂ generations of unexposed and 10% WSF-exposed Daphnia had decreased from parental F₀ generation and were also lower than in offspring of 30% WSF-exposed specimens. The studies did not aim at environmental realism but were designed to show the possibility of variability changes without changes in the mean value of a parameter, and transgenerational effects as a result of environmental contamination.

Individual variation in aquatic toxicology: Not only unwanted noise

The mean value of any parameter and its changes are usually discussed, when ecotoxicological studies are carried out. However, also the variation of any parameter and its changes can be important components of the responses to environmental contamination. Although the homogeneity of variances is commonly tested, testing is done for the use of correct statistical methods, not because of exploring the possibility that variability and its changes could be important components of environmental responses. We evaluated recent aquatic toxicological literature and found that in the majority of articles indicating that homogeneity of variances was tested and giving the result of testing, the assumption of homogeneity was not fulfilled. Further, it was observed that in some studies experimental treatment clearly affected the variability. In this commentary we discuss the reasons for variability: measurement errors, experimental design, genetic heterogeneity and phenotypic plasticity, and conclude that even after accounting for experimental design and genetic makeup significant variability remains. This plasticity may change in environmental responses as suggested by a hypothetical example, and as confirmed by experimental data. As a consequence, the changes of variability can be significant, even when the means do not differ. Because of this, variability and its changes should always be analysed and reported. This will be easy, since the datasets are exactly the same for comparing the variances and means, and as normally variances are tested for homogeneity. It is likely that much new information about the responses of organisms to environmental contamination will be obtained. However, the present journal practises tend to discourage one from concentrating on anything but the mean. In contrast, we think it is imperative that variability is always included as an endpoint in data analysis in the future.

Cold temperature represses daily rhythms in the liver transcriptome of a stenothermal teleost under decreasing day length

The climate-change-driven increase in temperature is occurring rapidly and decreasing the predictability of seasonal rhythms at high latitudes. It is therefore urgent to understand how a change in the relationship between photoperiod and temperature can affect ectotherms in these environments. We tested whether temperature affects daily rhythms of transcription in a cold-adapted salmonid using high-throughput RNA sequencing. Arctic char (Salvelinus alpinus) from a subarctic population were reared at a high and a low temperature (15 and 8°C) for 1 month under natural, decreasing day length during late summer. Liver transcriptomes were compared between samples collected in the middle and towards the end of the light period and in the middle of the dark period. Daily variation in transcription was lower in fish from the low temperature compared with strong daily variation in warm-acclimated fish, suggesting that cold temperatures dampen the cycling of transcriptional rhythms under a simultaneously decreasing day length. Different circadian clock genes had divergent expression patterns, responding either by decreased expression or by increased rhythmicity at 15°C compared with 8°C. The results point out mechanisms that can affect the ability of fish to adapt to increasing temperatures caused by climate change.

Influence of crude oil exposure on cardiac function and thermal tolerance of juvenile rainbow trout and European sea bass

Oil spills pose a threat to aquatic organisms. However, the physiological effects of crude oil on cardiac function and on thermal tolerance of juvenile fish are still poorly understood. Consequently, in this paper, we will present results of two separate experiments where we exposed juvenile rainbow trout and European sea bass to crude oil and made cardiac thermal tolerances and maximum heart rate (f _Hmax) measurements after 1 week (rainbow trout) and 6-month recovery (sea bass). In both species, the f _Hmax was lower in crude oil-exposed fish than in the control ones at temperatures below the optimum but this difference disappeared at higher temperatures. More importantly, the oil-exposed fish had significantly higher Arrhenius break point temperature for f _Hmax, which gave an estimate for optimum temperature, than the control fish in both species even though the exposure conditions and recovery times differed between species. The results indicated that exposure of juvenile fish to crude oil did not have a significant negative impact upon their cardiac performance in high temperatures and upper thermal tolerance increased when the fish were tested 1 week or 6 months after the exposure. Our findings suggest that the cardiac function and thermal tolerance of juvenile fish are relatively resistant to a crude oil exposure.

Hypoxia exposure and B-type natriuretic peptide release from Langendorff heart of rats

Aim

We studied whether available oxygen without induced mechanical stretch regulates the release of the biologically active B‐type natriuretic peptide (BNP) from Langendorff heart.

Methods

Rat hearts were isolated and perfused with a physiological Krebs–Henseleit solution at a constant hydrostatic pressure in Langendorff set‐up. The basal O₂ level of perfusate (24.4 ± 0.04 mg L⁻¹) was gradually lowered to 3.0 ± 0.01 mg L⁻¹ over 20 min using N₂ gas (n = 7). BNP and O₂ level were measured from coronary flow. During control perfusions (n = 5), the O₂ concentration was kept at 26.6 ± 0.3 mg L⁻¹.

Results

A low oxygen concentration in the perfusate was associated with a significant increase in BNP release (F = 40.4, P < 0.001). Heart rate decreased when the oxygen concentration in the perfusate reached 9.1 ± 0.02 mg L⁻¹ and continued to fall in lower oxygen concentrations (F = 14.8, P < 0.001). There was also a significant but inverse correlation between BNP and oxygen in the coronary flow (R² = 0.27, P < 0.001).

Conclusion

In the spontaneously beating Langendorff rat heart, a decreasing concentration of oxygen in the ingoing perfusion increased the secretion of BNP. The effect of oxygen was independent of mechanical stretch of the heart as it occurred even when the heart rate decreased but the pressure conditions remained constant. The difference in the oxygen capacitance of blood and Krebs–Henseleit solution appears to be a major factor affecting secretion of BNP, which is correlated with the oxygen tension of myocardial cells and affected both by the oxygen concentration and capacitance of solution perfusing the heart and by the coronary flow.

Different Relationship between hsp70 mRNA and hsp70 Levels in the Heat Shock Response of Two Salmonids with Dissimilar Temperature Preference

The heat shock response (HSR) refers to the rapid production of heat shock proteins (hsps) in response to a sudden increase in temperature. Its regulation by heat shock factors is a good example of how gene expression is transcriptionally regulated by environmental stresses. In contrast, little is known about post-transcriptional regulation of the response. The heat shock response is often used to characterize the temperature tolerance of species with the rationale that whenever the response sets on, a species is approaching its lethal temperature. It has commonly been considered that an increase in hsp mRNA gives an accurate indication that the same happens to the protein level, but this need not be the case. With climate change, understanding the effects of temperature on gene expression of especially polar organisms has become imperative to evaluate how both biodiversity and commercially important species respond, since temperature increases are expected to be largest in polar areas. Here we studied the HSR of two phylogenetically related Arctic species, which differ in their temperature tolerance with Arctic charr having lower maximally tolerated temperature than Atlantic salmon. Arctic charr acclimated to 15°C and exposed to 7°C temperature increase for 30 min showed both an increase in hsp70 mRNA and hsp70 whereas in salmon only hsp70 mRNA increased. Our results indicate that the temperature for transcriptional induction of hsp can be different from the one required for a measurable change in inducible hsp level. The species with lower temperature tolerance, Arctic charr, are experiencing temperature stress already at the higher acclimation temperature, 15°C, as their hsp70 mRNA and hsp70 levels were higher, and they grow less than fish at 8°C (whereas for salmon the opposite is true). Consequently, charr experience more drastic heat shock than salmon. Although further studies are needed to establish the temperature range and length of exposure where hsp mRNA and hsp level are disconnected, the observation suggests that by measuring both hsp mRNA and hsp level, one can evaluate if a species is approaching the higher end of its temperature tolerance, and thus evaluate the vulnerability of an organism to the challenges imposed by elevated water temperature.

Warm acclimation and oxygen depletion induce species-specific responses in salmonids

Anthropogenic activities are greatly altering the habitats of animals, whereby fish are already encountering several stressors simultaneously. The purpose of the current study was to investigate the capacity of fish to respond to two different environmental stressors (high temperature and overnight hypoxia) separately and together. We found that acclimation to increased temperature (from 7.7±0.02°C to 14.9±0.05°C) and overnight hypoxia (daily changes from normoxia to 63-67% oxygen saturation), simulating climate change and eutrophication, had both antagonistic and synergistic effects on the capacity of fish to tolerate these stressors. The thermal tolerance of Arctic char (Salvelinus alpinus) and landlocked salmon (Salmo salar m. sebago) increased with warm acclimation by 1.3 and 2.2°C, respectively, but decreased when warm temperature was combined with overnight hypoxia (by 0.2 and 0.4°C, respectively). In contrast, the combination of the stressors more than doubled hypoxia tolerance in salmon and also increased hypoxia tolerance in char by 22%. Salmon had 1.2°C higher thermal tolerance than char, but char tolerated much lower oxygen levels than salmon at a given temperature. The changes in hypoxia tolerance were connected to the responses of the oxygen supply and delivery system. The relative ventricle mass was higher in cold- than in warm-acclimated salmon but the thickness of the compact layer of the ventricle increased with the combination of warm and hypoxia acclimation in both species. Char had also significantly larger hearts and thicker compact layers than salmon. The results illustrate that while fish can have protective responses when encountering a single environmental stressor, the combination of stressors can have unexpected species-specific effects that will influence their survival capacity.

Indirect genetic effects underlie oxygen-limited thermal tolerance within a coastal population of chinook salmon

With global temperatures projected to surpass the limits of thermal tolerance for many species, evaluating the heritable variation underlying thermal tolerance is critical for understanding the potential for adaptation to climate change. We examined the evolutionary potential of thermal tolerance within a population of chinook salmon (Oncorhynchus tshawytscha) by conducting a full-factorial breeding design and measuring the thermal performance of cardiac function and the critical thermal maximum (CTmax) of offspring from each family. Additive genetic variation in offspring phenotype was mostly negligible, although these direct genetic effects explained 53% of the variation in resting heart rate (fH). Conversely, maternal effects had a significant influence on resting fH, scope for fH, cardiac arrhythmia temperature and CTmax. These maternal effects were associated with egg size, as indicated by strong relationships between the mean egg diameter of mothers and offspring thermal tolerance. Because egg size can be highly heritable in chinook salmon, our finding indicates that the maternal effects of egg size constitute an indirect genetic effect contributing to thermal tolerance. Such indirect genetic effects could accelerate evolutionary responses to the selection imposed by rising temperatures and could contribute to the population-specific thermal tolerance that has recently been uncovered among Pacific salmon populations.

Thermal optima and tolerance in the eurythermic goldfish (Carassius auratus): relationships between whole-animal aerobic capacity and maximum heart rate

The wide thermal tolerance range of a eurythermic fish (goldfish, Carassius auratus) was used to evaluate how temperature performance curves derived from maximum heart rate (fH) related to those for aerobic scope. For acclimation temperatures of 12°, 20°, and 28°C, optimum temperatures derived from aerobic scope curves (Topt) were 19.9° ± 0.4°, 19.3° ± 0.8°, and 28.7° ± 0.8°C, respectively. The Arrhenius breakpoint temperatures (TAB) for maximum fH were 21.5° ± 0.6°, 23.8° ± 0.9°, and 24.6° ± 0.5°C, respectively. The TQB (temperature where the incremental Q10 of maximum fH decreased abruptly below 1.9) was 24.0° ± 0.7° and 29.8° ± 0.6°C for the 12° and 28°C acclimation temperatures, respectively, and was within the Topt window (11.5°-30.3° and 26.9°-30.5°C, respectively), but TQB for the 20°C acclimation temperature (27.3° ± 0.6°C) was higher than the Topt window (15.4°-23.2°C). Warm acclimation increased the upper critical temperature (Tcrit; from 37.2° ± 0.7° to 44.7° ± 11.8°C) as well as the temperature that triggered a cardiac arrhythmia (Tarr; from 31.1° ± 0.7° to 39.3° ± 0.4°C). In conclusion, we propose that maximum fH and its associated rate transition temperatures (TAB, TQB, and Tarr) can be used to estimate the upper thermal tolerance of eurythermic as well as stenothermic fish independent of acclimation temperature. All the same, great care is needed with such evaluations. For the goldfish, while TAB and TQB were always within the Topt window for 90% of maximum aerobic scope and Topt was closely associated with TAB for 12°C-acclimated fish, TQB had the closest association after 28°C acclimation, and both TAB and TQB were above the Topt window after 20°C acclimation.

Facing warm temperatures during migration: cardiac mRNA responses of two adult Oncorhynchus nerka populations to warming and swimming challenges

The main findings of the current study were that exposing adult sockeye salmon Onchorhynchus nerka to a warm temperature that they regularly encounter during their river migration induced a heat shock response at an mRNA level, and this response was exacerbated with forced swimming. Similar to the heat shock response, increased immune defence-related responses were also observed after warm temperature treatment and with a swimming challenge in two different populations (Chilko and Nechako), but with some important differences. Microarray analyses revealed that 347 genes were differentially expressed between the cold (12-13° C) and warm (18-19° C) treated fish, with stress response (GO:0006950) and response to fungus (GO:0009620) elevated with warm treatment, while expression for genes involved in oxidative phosphorylation (GO:0006119) and electron transport chain (GO:0022900) elevated for cold-treated fish. Analysis of single genes with real-time quantitative PCR revealed that temperature had the most significant effect on mRNA expression levels, with swimming and population having secondary influences. Warm temperature treatment for the Chilko population induced expression of heat shock protein (hsp) 90α, hsp90β and hsp30 as well as interferon-inducible protein. The Nechako population, which is known to have a narrower thermal tolerance window than the Chilko population, showed even more pronounced stress responses to the warm treatment and there was significant interaction between population and temperature treatment for hsp90β expression. Moreover, significant interactions were noted between temperature treatment and swimming challenge for hsp90α and hsp30, and while swimming challenge alone increased expression of these hsps, the expression levels were significantly elevated in warm-treated fish swum to exhaustion. In conclusion, it seems that adult O. nerka currently encounter conditions that induce several cellular defence mechanisms during their once-in-the-lifetime migration. As river temperatures continue to increase, it remains to be seen whether or not these cellular defences provide sufficient protection for all O. nerka populations.

Upper thermal tolerance of closely related Danio species

The main finding of this study was that measuring maximum heart rate during incremental warming was an effective tool to estimate upper thermal limits in three small cyprinid Danio species, which differed significantly. Arrhenius breakpoint temperature for maximum heart rate, purportedly an index of optimum temperature, was 21·2 ± 0·4, 20·1 ± 0·4 and 18·9 ± 0·8° C (mean ± s.e.) for zebrafish Danio rerio, pearl danio Danio albolineatus and glowlight danio Danio choprae, respectively. The temperature where cardiac arrhythmias were first induced during warming (T(arr)) was 36·6 ± 0·7, 36·9 ± 0·8 and 33·2 ± 0·8° C (mean ± s.e.) and critical thermal maximum (T(Cm)) was 39·9 ± 0·1, 38·9 ± 0·1 and 37·2 ± 0·1° C (mean ± s.e.) for D. rerio, D. albolineatus and D. choprae, respectively. The finding that T(arr) was consistently 3-4° C lower than T(Cm) suggests that collapse of the cardiac life support system may be a critical trigger for upper temperature tolerance. The upper thermal limits established here, which correlate well with a broad natural environmental temperature range for D. rerio and a narrow one for D. choprae, suggest that upper thermal tolerance may be a genetic trait even among closely related species acclimated to common temperatures.

Responses to temperature and hypoxia as interacting stressors in fish: implications for adaptation to environmental change

Anthropogenic environmental change is exposing animals to changes in a complex array of interacting stressors and is already having important effects on the distribution and abundance of species. However, despite extensive examination of the effects of stressors in isolation, knowledge of the effects of stressors in combination is limited. This lack of information makes predicting the responses of organisms to anthropogenic environmental change challenging. Here, we focus on the effects of temperature and hypoxia as interacting stressors in fishes. A review of the available evidence suggests that temperature and hypoxia act synergistically such that small shifts in one stressor could result in large effects on organismal performance when a fish is exposed to the 2 stressors in combination. Although these stressors pose substantial challenges for fish, there also is substantial intraspecific variation in tolerance to these stressors that could act as the raw material for the evolution of improved tolerance. However, the potential for adaptive change is, in part, dependent on the nature of the correlations among traits associated with tolerance. For example, negative genetic correlations (or trade-offs) between tolerances to temperature and hypoxia could limit the potential for adaptation to the combined stressors, while positive genetic correlations might be of benefit. The limited data currently available suggest that tolerances to hypoxia and to high-temperature may be positively correlated in some species of fish, suggesting the possibility for adaptive evolution in these traits in response to anthropogenic environmental change.

Optimum and maximum temperatures of sockeye salmon (Oncorhynchus nerka) populations hatched at different temperatures

Temperature tolerance and heart rates were compared among nine sockeye salmon (Oncorhynchus nerka (Walbaum in Artedi, 1792)) populations, whose eggs were incubated at 10, 14, and 16 °C before rearing all hatchlings at a common temperature. Critical thermal maximum (CTmax) significantly differed among populations and temperature treatments. Populations with shorter migration distance and a lower migration and spawning temperature tended to have higher CTmax at 90 days posthatch. However, the relationship was reversed when fish of similar size were compared at 135–214 days posthatch. CTmax at 90 days posthatch was also positively related to body mass, which differed appreciably among populations at this development stage. With growth, the population differences in CTmax diminished from 3.1 to 1 °C. Elevated incubation temperature also decreased CTmax. Arrhenius breakpoint temperature (ABT) for maximum heart rate differed among populations incubated at 14 °C. The Chilko Lake population, which rear at 1.2 km above sea level, had the highest heart rate across all temperatures when incubated at 14 °C, but the lowest ABT among populations. This study provides clear evidence for the local adaptation among sockeye salmon populations with respect to temperature tolerance and cardiac capacity, information that adds to the debate on whether intraspecific variance is adaptive, or a constraint, or both.

Variation in temperature tolerance among families of Atlantic salmon (Salmo salar) is associated with hypoxia tolerance, ventricle size and myoglobin level

In fishes, performance failure at high temperature is thought to be due to a limitation on oxygen delivery (the theory of oxygen and capacity limited thermal tolerance, OCLTT), which suggests that thermal tolerance and hypoxia tolerance might be functionally associated. Here we examined variation in temperature and hypoxia tolerance among 41 families of Atlantic salmon (Salmo salar), which allowed us to evaluate the association between these two traits. Both temperature and hypoxia tolerance varied significantly among families and there was a significant positive correlation between critical maximum temperature (CTmax) and hypoxia tolerance, supporting the OCLTT concept. At the organ and cellular levels, we also discovered support for the OCLTT concept as relative ventricle mass (RVM) and cardiac myoglobin (Mb) levels both correlated positively with CTmax (R2=0.21, P&lt;0.001 and R2=0.17, P=0.003, respectively). A large RVM has previously been shown to be associated with high cardiac output, which might facilitate tissue oxygen supply during elevated oxygen demand at high temperatures, while Mb facilitates the oxygen transfer from the blood to tissues, especially during hypoxia. The data presented here demonstrate for the first time that RVM and Mb are correlated with increased upper temperature tolerance in fish. High phenotypic variation between families and greater similarity among full- and half-siblings suggests that there is substantial standing genetic variation in thermal and hypoxia tolerance, which could respond to selection either in aquaculture or in response to anthropogenic stressors such as global climate change.

Optimum temperature in juvenile salmonids: connecting subcellular indicators to tissue function and whole-organism thermal optimum

Temperature affects processes at all levels of biological organization, but it is unclear whether processes at different levels have similar thermal optima (T(opt)). Here, we compare the T(opt) for aerobic scope, a whole-organism measure of performance, with both the Arrhenius breakpoint temperature for maximum heart rate (HR-ABT), a measure of tissue level performance, and the temperature at which AMP-activated protein kinase (AMPK) is phosphorylated in the heart, an indicator of an increase in dependence on anaerobic energy metabolism at the cellular level in juvenile rainbow trout Oncorhynchus mykiss. The T(opt) for aerobic scope was 19°C, with aerobic scope being maintained at ≥90% of maximum (termed a "T(opt) window") from 16.5° to 20.5°C. HR-ABT occurred at [Formula: see text], while the profile of AMPK phosphorylation started to change from baseline at 19°C, suggesting that these processes have similar thermal sensitivities as a fish is warmed to T(opt). The effects of temperature on AMPK phosphorylation were also measured in coho salmon Oncorhynchus kisutch hearts and compared with previously published values for HR-ABT and aerobic scope T(opt). AMPK phosphorylation in coho hearts began to change at temperatures above 17°C, which again is comparable with the published T(opt) for aerobic scope (17°C) and HR-ABT ([Formula: see text]) in these individuals. Thus, the thermal sensitivity of these subcellular, tissue, and whole-organism functions are highly correlated in both rainbow trout and coho salmon and may depend on each other.

Using maximum heart rate as a rapid screening tool to determine optimum temperature for aerobic scope in Pacific salmon Oncorhynchus spp

The mean ±s.e. optimum temperature (T(opt)) for aerobic scope in juvenile coho salmon Oncorhynchus kisutch was determined to be 17·0 ± 0·7° C. The repeated measures protocol took 3 weeks to complete the T(opt) determination using 12 fish tested at five temperatures separated by 2° C increments. This experiment also demonstrated that the T(opt) was associated with maximum heart rate (f(H)) failing to maintain a Q(10) -related increase with temperature. When maximum f(H) was produced in anaesthetized fish with pharmacological stimulation and f(H) measured from electrocardiogram recordings during acute warming, the Arrhenius break temperature (ABT) for Q(10) discontinuities in maximum f(H) (mean ±s.e. = 17·1 ± 0·5° C for 15 ppm clove oil and 16·5 ± 0·2° C for 50 ppm MS-222) was statistically indistinguishable from the T(opt) measured using aerobic scope. Such a determination took only 3 days rather than 3 weeks. Therefore, it is proposed that determining ABT for discontinuities in maximum f(H) in anaesthetized fish presents itself as a valuable, high-throughput screening tool to assess T(opt) in fishes, a metric that has become recognized as being extremely valuable in fish biology and fisheries management.

Effects of training on functional variables of muscles in reared Atlantic salmon Salmo salar smolts: connection to downstream migration pattern

The relative amount of muscle contraction regulating dihydropyridine and ryanodine receptors in the swimming muscles of trained reared Atlantic salmon Salmo salar smolts was compared with those of untrained and wild smolts. After an optimized 2 week training period, i.e. swimming with a velocity of 1·5 body lengths per second for 6 h per day, the level of both receptors was significantly higher in the muscles of trained S. salar than in the untrained ones before they were released into the natural environment. This difference persisted after downstream migration in the river. The highest level of receptors was observed in wild S. salar. Swimming performance was also higher in trained fish compared to untrained ones. Furthermore, swimming performance was positively associated with the level of receptors in both red and white muscle types. Downstream migration after release into the wild was significantly slower in trained smolts than in untrained fish. This indicates that trained smolts were most probably swimming harder against the current in the river than untrained smolts. The possible advantages for a slower migration in the river are discussed. This study shows that the prerequisites for effective contraction of the swimming muscles are better met in trained S. salar compared to untrained fish, and the muscles of trained smolts more closely resemble those of wild smolts. The results also imply that the capacity of untrained, reared smolts to swim against the current is not equal to that of their trained or wild counterparts which affects the downstream migration pattern of S. salar smolts.

Ultrastructural differences and histochemical characteristics in swimming muscles between wild and reared Atlantic salmon

AIM

The swimming capacity of wild and reared fish differs. Whether the differences are associated with metabolic, contractile or structural variation in swimming musculature is unknown. In the present study, some aspects of contractile machinery in swimming muscles of wild and reared salmon are compared.

METHODS

Several morphological parameters and key enzyme activities were measured using electron microscopy and histochemical methods.

RESULTS

The density and size of the mitochondria was significantly higher in the muscle samples from wild fish when compared with the reared ones. Similar variability was also seen in the density of triads. Conversely, the size and density of lipid droplets was significantly lower in the red muscle of wild vs. reared salmon. The densities of two excitation contraction coupling components, dihydropyridine and ryanodine receptor, were considerably higher in swimming muscles of wild salmon than in reared fish. A similar difference was observed in the activities of aerobic enzymes. Moreover, oxygen consumption followed the same pattern, being significantly higher in the samples of wild salmon. Phosphorylase activity was, on the other hand, significantly lower in the muscles of wild fish.

CONCLUSIONS

There are significant differences in morphology, Ca(2+)-regulating capacity and enzyme activities in swimming muscles between wild and reared salmon. These results provide evidence that the prerequisites for efficient contraction of the swimming muscles are better met in wild than in reared salmon. Importantly, the results also suggest that the observed variation is a major contributing factor to the difference in the swimming capacity between wild and hatchery-reared salmon.

Testosterone stimulates myoglobin expression in different muscles of the mouse

The regulation of energy metabolism is one of the major functions of steroid hormones. This study was performed to explore whether testosterone can regulate the aerobic capacity of skeletal muscles via myoglobin expression. To study this, changes in testosterone level were quantified, and the level of myoglobin protein was analyzed using Western blot in mice subjected to 6 weeks of training (T) or testosterone administration (A). Both treatments significantly increased the plasma testosterone level when compared to the untrained (U) or control (C) group. Training induced a significant increase in the myoglobin content in gastrocnemius and plantaris muscles (287 and 83%, respectively). Testosterone administration increased myoglobin concentration in plantaris (183%) but not in gastrocnemius. In extensor digitorum longus muscle the protein content decreased slightly after exercise, but increased 78% after testosterone administration. In soleus and rectus femoris muscles the myoglobin content was unchanged after both treatments. The data show that testosterone and training have differential effects on the concentration of myoglobin in some, but not all muscles. This may have an influence on the aerobic capacity in mouse skeletal muscles. The data demonstrated that both testosterone administration and training induced an increase in plasma testosterone level. However, the effects of the treatments on the myoglobin concentration differ.

Effects of low-intensity training on dihydropyridine and ryanodine receptor content in skeletal muscle of mouse

To evaluate low-intensity exercise training induced changes in the expression of dihydropyridine (DHP) and ryanodine (Ry) receptors both mRNA and protein levels were determined by quantitative RT-PCR and immunoblot analysis from gastrocnemius (GAS) and rectus femoris (RF) muscles of mice subjected to a 15-week aerobic exercise program. The level of muscular work was assayed by changes in myosin heavy chain (MHC) content, myoglobin (Mb) expression and muscle size. The mRNA expression and optical density of DHP receptor increased significantly in GAS by 66.8 and 39.5%, respectively. The expression of Ry receptor, on the other hand, was not up-regulated. In RF, there was a significant increase of 38.4% in the mRNA expression of DHP receptor, although the protein level remained the same. No changes in Ry receptor expression was observed. The training resulted in a 1.58% increase in the amount of MHC IIa and a 2.34% decrease in that of IIb and IId in GAS. A significant 8.3% increase in the Mb content was observed. In RF, no significant changes in MHC or in Mb content were noted. Our results show that an evident increase in the mRNA and protein expression of DHP receptor was induced in GAS even by a relatively low-intensity exercise. Surprisingly, contrast to DHP receptor expression, no changes in Ry receptor mRNA, or protein levels were found, indicating more abundant demand for DHP receptor after increased muscle activity.

Expression of dihydropyridine and ryanodine receptors in type IIA fibers of rat skeletal muscle

In this study, the fiber type specificity of dihydropyridine receptors (DHPRs) and ryanodine receptors (RyRs) in different rat limb muscles was investigated. Western blot and histochemical analyses provided for the first time evidence that the expression of both receptors correlates to a specific myosin heavy chain (MHC) composition. We observed a significant (p=0.01) correlation between DHP as well as Ry receptor density and the expression of MHC IIa (correlation factor r=0.674 and r=0.645, respectively) in one slow-twitch, postural muscle (m. soleus), one mixed, fast-twitch muscle (m. gastrocnemius) and two fast-twitch muscles (m. rectus femoris, m. extensor digitorum longus). The highest DHP and Ry receptor density was found in the white part of m. rectus femoris (0.058+/-0.0060 and 0.057+/-0.0158 ODu, respectively). As expected, the highest relative percentage of MHC IIa was also found in the white part of m. rectus femoris (70.0+/-7.77%). Furthermore, histochemical experiments revealed that the IIA fibers stained most strongly for the fluorophore-conjugated receptor blockers. Our data clearly suggest that the expression of DHPRs and RyRs follows a fiber type-specific pattern, indicating an important role for these proteins in the maintenance of an effective Ca2+ cycle in the fast contracting fiber type IIA.

Effects of different training protocols on Ca2+ handling and oxidative capacity in skeletal muscle of Atlantic salmon (Salmo salarL.)

The modulation of calcium channel density and oxidative capacity in skeletal muscle after different training protocols were studied in 3-year-old Atlantic salmon smolts. The effect of endurance exercise on dihydropyridine(DHP) and ryanodine (Ry) receptor densities as well as on muscle metabolism were determined by immunoblot and histochemical analysis from swimming muscles of fish subjected to nine different training protocols varying in duration and water current velocity.

In general, exercise training caused a significant increase in the density of both DHP and Ry receptors in both muscle types studied. In red muscle, the most notable increase in DHP and Ry receptor expression was observed in muscle sections from fish swimming against intermediate current velocity for a 2-week period (182.3±16.3%, 234.6±30.3%, respectively). In white muscle, the expression of DHP and Ry receptors was most upregulated after a 6-week swimming period also at intermediate water current velocity(270.4±23.9%, 114.4±15.3%, respectively). As with the activity of enzymes involved in muscle energy supply, endurance exercise resulted in a significant increase in succinate dehydrogenase (SDH) activity, but a significant decrease in phosphorylase activity.

We conclude that the expression of both DHP and Ry receptors was upregulated in the swimming muscles of salmon as a consequence of exercise training. This, along with the increased oxidative enzyme activity, provides benefits to the contraction efficiency of fish muscles while swimming. However, it was also observed that optimal oxidative swimming capacity is achieved only with a proper exercise program, since the most relevant changes in DHP and Ry receptor expression, as well as in oxidative capacity, were seen in the group training with the intermediate swimming velocity.

Effect of selenate supplementation on glycoalkaloid content of potato (Solanum tuberosum L.)

Potatoes (Solanum tuberosum L.) supplemented with increasing amounts of sodium selenate were analyzed for glycoalkaloid (GA) content. GAs were extracted with 5% acetic acid from freeze-dried tubers of two potato cultivars, Satu and Sini, harvested 10 weeks after planting as immature. The GAs alpha-solanine and alpha-chaconine were quantified by reverse-phase high-performance liquid chromatography (RP-HPLC) with diode array detection. Two independent experiments were performed. In the first experiment, the total GA concentration +/- standard error of the tubers ranged between 105 +/- 9 and 124 +/- 10 mg kg(-1) fresh weight in Satu and between 194 +/- 26 and 228 +/- 10 mg kg(-1) fresh weight in Sini. The ratio of alpha-solanine to alpha-chaconine was 0.2 in Satu and 0.5-0.6 in Sini. In the second experiment, the total GA concentration +/- standard error was 75 +/- 4 to 96 +/- 11 mg kg(-1) fresh weight, and the ratio of alpha-solanine to alpha-chaconine was 0.3-0.4 in Satu. A high sodium selenate supplementation (0.9 mg of Se kg(-1) quartz sand) slightly decreased the GA content in Satu, but this decrease was not statistically significant. Furthermore, at this addition level the Se concentration increased to a very high level of 20 microg g(-1) dry weight, which cannot be recommended for human consumption. In both experiments, the Se concentration in tubers increased with increasing sodium selenate application levels. Our results show that acceptable application levels of selenate did not have an effect on the GA concentration in immature potato tubers.

Measurement of free beam neutron spectra at eight BNCT facilities worldwide

Eight epithermal neutron beams, constructed for clinical or preclinical studies of NCT, have been dosimetrically characterized by in-air measurements with a set of activation foils for the determination of the neutron energy spectra in free beam. Measurements have been made on the already closed epithermal BNCT facility at the BMRR of the Brookhaven National Laboratory, on the HFR at JRC in Petten, The Netherlands, on the epithermal mode beam at KURRI, Japan, on the fission converter beam at MIT, USA, on the epithermal beam of the RA-6 facility in Bariloche, Argentina, on the epithermal beam at WSU, USA, on the mixed mode beam at JRR-4 at JAERI, Japan, as well as on the epithermal beam at FiR 1 at VTT, Espoo, Finland.

Immediate effects of docetaxel alone or in combination with epirubicin on cardiac function in advanced breast cancer

The immediate effects on cardiac function of 3-weekly docetaxel and combined docetaxel-epirubicin were evaluated during treatment of metastatic breast cancer using assessment of heart rate variability (HVR) and left ventricular ejection fraction (LVEF) measured by echocardiography. Twenty-four breast cancer patients were treated with docetaxel alone (starting dose 100 mg/m2) and 34 with a combination of docetaxel and epirubicin (starting dose for both drugs 75 mg/m2) administered 3-weekly. Single docetaxel caused no significant changes in HVR or cardiac function, whereas during combined treatment statistically significant changes were observed in mean RR intervals and in the number of supraventricular extrasystoles. Clinically the observed changes were insignificant. In conclusion, in 3-weekly administration the combined use of docetaxel and epirubicin was more likely than single docetaxel to cause changes in cardiac function.

Mycotoxins, fungus and 'electrohypersensitivity'

'Electrohypersensitivity' is often explained as a psychological syndrome. Our modern environment contains a lot of different substances and some of them are toxic. Mycotoxins are types of toxins that are biologically very active and that affect living organisms. Mycotoxins and fungi capable of producing toxins have been detected in ventilation systems, water damage and in foodstuff. Many of those displaying symptoms caused by electromagnetic fields have fungus infections or have been living in fungus-contaminated environments for long periods. In animal studies mycotoxins have shown the same effects as those seen in the 'electrohypersensitivity' syndrome. Phototoxic reactions are well known in veterinary medicine and in medical science, so the question is whether the 'electrohypersensitivity' syndrome is caused by 'phototoxic' reactions?

The A1 allele of the human D2 dopamine receptor gene predicts low D2 receptor availability in healthy volunteers

Positron emission tomography (PET) studies have revealed significant interindividual variation in dopamine D2 receptor density in vivo in human striatum. Low D2 receptor binding in vivo has been found to associate with alcohol/substance dependence. It has been suggested that the A1 allele of human D2 receptor gene might be associated to a specific type of alcoholism and possibly to a reduced D2 receptor density in vitro. We have determined D2 dopamine receptor-binding density (Bmax), affinity (Kd) and availability (Bmax/Kd) in 54 healthy Finnish volunteers using PET and [11C]raclopride in order to determine whether the A1 allele is associated with a 'baseline' difference in D2 receptor characteristics in vivo. A statistically significant reduction in D2 receptor availability reflecting an alteration in receptor density was observed in the A1/A2 genotype group compared to the A2/A2 group. There was no difference in apparent Kd between the two groups. In conclusion, the association between the A1 allele and low D2 receptor availability in healthy subjects indicates that the A1 allele of the TaqIA polymorphism might be in linkage disequilibrium with a mutation in the promoter/regulatory gene element that affects dopamine D2 receptor expression. This study provides an in vivo neurobiological correlate to the A1 allele in healthy volunteers.

Increase of HLA-DRB1*0408 and -DQB1*0301 in HLA-B27 positive reactive arthritis

OBJECTIVE

To study HLA class II association in reactive arthritis.

METHODS

63 patients with reactive arthritis and 46 with rheumatoid arthritis were included in the study. HLA-DR alleles were determined by using a sequence specific PCR method. Oligonucleotide hybridisation was used for definition of DRB1*04 subtypes and DQB1 alleles. HLA-B27 was determined by standard microcytotoxity test or by PCR. HLA-B27 subtyping was made by sequencing.

RESULTS

46 (73%) of 63 patients with reactive arthritis were HLA-B27 positive and 24 (38%) were HLA-DRB1*04 positive. When haplotypes were inferred according to the known associations between DRB1 and DQB1 alleles, the frequency of DRB1*04-DQB1*0301 haplotype was found to be 13% (12/92) in HLA-B27 positive reactive arthritis patients, in contrast to 0% in HLA-B27 negative reactive arthritis (P = 0.04) and 1% in random controls (P = 0.0009). However, this combination was also found in 5% of 84 HLA-B27 positive control haplotypes, showing a linkage disequilibrium between B27 and this particular class II haplotype. HLA-DRB1*0408 subtype was found in 8/24 (33%) of the HLA-DRB1*04 alleles in patients with reactive arthritis, accounting for most DQB1*0301 haplotypes, but only in 5/55 (9%) of the DRB1*04 alleles in random controls (P = 0.017). All reactive arthritis patients with this subtype were positive for HLA-B27. DRB1*04-DQB1*0302 haplotype was increased in patients with rheumatoid arthritis (28/92, 30%) compared with reactive arthritis (12/126, 10%) or with the controls (12/100, 12%; P = 0.003). HLA-B*2705 was by far the dominant B27 subtype both in reactive arthritis patients with the particular DRB1*0408-DQB1*0301 haplotype and in controls. It was found in 11 out of 12 DR analysed patients, as well as in 10 out of 11 randomly selected B27 positive controls.

CONCLUSIONS

Although no single class II allele was found to be increased among patients with reactive arthritis, HLA-B27, DRB1*0408, and DQB1*0301 might exert a haplotypic effect in the pathogenesis of reactive arthritis, or they may be markers of a subset of B27 haplotypes conferring susceptibility.