Henrik Wallgren, In memoriam

Den 14 augusti 2014 avled filosofie doktor, professor emeritus Henrik Wallgren i sin födelsestad Helsingfors. Han var född den 25 juni 1928

Happi solujen toimintojen säätelijänä

Elämä maapallolla nykymuotoisena olisi mahdotonta ilman happea. Happi osallistuu mitokondrioiden energiantuotantoon vastaanottamalla elektroninsiirtoketjun elektronit. Niin hengityselimistö kuin verenkiertokin ovat kehittyneet, jotta hapen saanti energian tuotantoa varten olisi riittävää. Koska happi on välttämätön energiantuotannossa, on sen merkitystä solujen muiden toimintojen säätelyssä pidetty viime vuosiin asti vähäisenä - on ajateltu, että hapella ei olisi merkitystä solutoimintojen säätelyssä, koska energiantuotannon taso pitkälti määrää sen pitoisuuden eri puolilla elimistöä. Viime vuosina on kuitenkin osoittautunut, että happi toimii monipuolisesti niin kalvotoimintojen, geenien ilmenemisen kuin solun sisäisen viestinnän säätelijänä. Happipitoisuuden muutokset näyttävät vaikuttavan niin yksilönkehitykseen kuin sairauksien syntyyn ainakin näennäisesti energiantuotannosta riippumattomasti

Miksi toiminnan tutkimus (fysiologia) on oleellinen osa ympäristöbiologiaa?

Ilmastonmuutos ja ympäristön pilaantuminen ovat nostaneet ympäristöbiologian yhdeksi keskeisistä luonnontieteiden tutkimusaloista. Perinteisesti ympäristöbiologia on mielletty ekologiseksi tutkimukseksi, joka on sujuvasti ottanut mukaan evoluution ja perinnöllisyyden näkökulmat. Kuitenkin ympäristö voi vaikuttaa eliöihin vain niiden toimintojen (fysiologian) kautta, joten myös elintoimintojen tutkimuksen pitäisi olla oleellinen osa ympäristöbiologiaa. Tässä kirjoituksessa perustelen, miksi näin on

Individual variation in aquatic toxicology: Not only unwanted noise

The mean value of any parameter and its changes are usually discussed, when ecotoxicological studies arecarried 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.</p

In vitro study on the regulation of cellular mRNA levels by changes in transcription rate and transcript stability in fish red blood cells

The interplay of transcriptional and post-transcriptional processes in the regulation of gene expression has been extensively studied in mammals but little is known in other vertebrates so far. Most non-mammalian vertebrates are faced with environmental cues and stressors distinct from those experienced by mammals and thus it is likely that the gene expression strategies differ from those of mammals. Here we performed experiments to study in vitro the various levels of gene expression regulation in nucleated fish red blood cells. Three critical environmental cues frequently experienced by fish were chosen: exposure to hypoxia (2.5%), ambient water temperature increase by 10 °C (from 10 °C to 20 °C), and exposure to stress hormones (represented by the β-adrenergic agonist isoproterenol). We found that β-adrenergic stimulation increases the stability of the β3b-adrenergic receptor (β3b-ar) mRNA, suggesting that mRNA stability can play a role in the regulation of hormonal stress responses in fish. The β3b-ar gene encodes a unique β-adrenergic receptor subtype in fish red blood cells which controls the β-Na+/H+ exchanger activity – an important component of responses to oxygen limitations. Our results furthermore show a yet undescribed link between the Hif1a signaling pathway and the β-adrenergic receptor response. After β-adrenergic stimulation, the transcription of hif1a was activated significantly after 4 hours of exposure. So far, such a response has only been described from mammalian species. This indicates that the β-AR is fundamental to the molecular and physiological responses to hypoxia and that Hif1a might have additional functions than those already known.</p

More than hemoglobin – the unexpected diversity of globins in vertebrate red blood cells

In many multicellular organisms, oxygen is transported by respiratory proteins, which are globins in vertebrates, between respiratory organs and tissues. In jawed vertebrates, eight globins are known which are expressed in a highly tissue-specific manner. Until now, hemoglobin (Hb) had been agreed to be the only globin expressed in vertebrate erythrocytes. Here, we investigate for the first time the mRNA expression of globin genes in nucleated and anucleated erythrocytes of model vertebrate species by quantitative real-time reverse transcription PCR (qRT-PCR). Surprisingly, we found transcripts of the whole gnathostome globin superfamily in RBCs. The mRNA expression levels varied among species, with Hb being by far the dominant globin. Only in stickleback, a globin previously thought to be neuron-specific, neuroglobin, had higher mRNA expression. We furthermore show that in birds transcripts of globin E, which was earlier reported to be transcribed only in the eye, are also present in RBCs. Even in anucleated RBCs of mammals, we found transcripts of myoglobin, neuroglobin, and cytoglobin. Our findings add new aspects to the current knowledge on the expression of globins in vertebrate tissues. However, whether or not the mRNA expression of these globin genes has any functional significance in RBCs has to be investigated in future studies.</p

Circadian rhythms and environmental disturbances–underexplored interactions

Biological rhythms control the life of virtually all organisms, impacting numerous aspects ranging from subcellular processes to behaviour. Many studies have shown that changes in abiotic environmental conditions can disturb or entrain circadian (∼24 h) rhythms. These expected changes are so large that they could impose risks to the long-term viability of populations. Climate change is a major global stressor affecting the fitness of animals, partially because it challenges the adaptive associations between endogenous clocks and temperature – consequently, one can posit that a large-scale natural experiment on the plasticity of rhythm–temperature interactions is underway. Further risks are posed by chemical pollution and the depletion of oxygen levels in aquatic environments. Here, we focused our attention on fish, which are at heightened risk of being affected by human influence and are adapted to diverse environments showing predictable changes in light conditions, oxygen saturation and temperature. The examined literature to date suggests an abundance of mechanisms that can lead to interactions between responses to hypoxia, pollutants or pathogens and regulation of endogenous rhythms, but also reveals gaps in our understanding of the plasticity of endogenous rhythms in fish and in how these interactions may be disturbed by human influence and affect natural populations. Here, we summarize research on the molecular mechanisms behind environment–clock interactions as they relate to oxygen variability, temperature and responses to pollutants, and propose ways to address these interactions more conclusively in future studies.</p

Molecular Markers of Yolk Sac Fry Development in Nine Families of Lake Trout

Salmonids in certain areas of North America and northern Europe suffer from reproductive disturbances manifested through the death of yolk sac fry. These disturbances are referred to as early mortality syndrome (EMS) in the Great Lakes region and M74 in the Baltic Sea. Both of these syndromes have been associated with reduced concentrations of thiamine in affected females and their eggs. However, large variations in signs and mortality, both within and between the individual syndromes, have been reported. Yolk sac fry mortality (M74) in Atlantic salmon Salmo salar has been shown to be associated with reduced DNA binding of the hypoxia-inducible transcription factor 1 (HIF-1), reduced production of vascular endothelial growth factor (VEGF) protein, decreased capillary density, and down-regulation of adult-type globin gene transcription (which is responsible for the protein part of adult hemoglobin). One of the main effects of all of these changes is reduced oxygen transport to the tissues of affected fry. In this study, the developmental patterns of HIF-1 DNA binding, VEGF protein expression, and adult-type globin gene transcription were analyzed in nine family groups of Lake Michigan lake trout Salvelinus namaycush. The results indicate that HIF-1 DNA binding and globin gene transcription increase from hatch to the end of yolk sac stage. Interindividual and between-family biological variations were detected, especially in VEGF protein expression and globin gene transcription. Our results demonstrate the possibility of using these molecular markers in investigating the etiology of EMS and making comparisons between the mechanisms of different salmonid yolk sac fry mortalities