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Growth potential in insects: Effects of temperature on cellular proliferation at hormonal and molecular levels
Abstracts / Comparative Biochemistry and Physiology, Part A 151 (2008) S44–S47
CD-antibodies. In particular, increases in the number of granular (phagocytic) haemocytes were observed; the effects of SCF involved the activation of c-kit tyrosine kinase-like receptors. The results support the hypothesis that common pathways involved in modulating activity, differentiation and proliferation of immune cells are conserved from molluscs to mammals. doi:10.1016/j.cbpa.2008.05.129
3. Growth potential in insects: Effects of temperature on cellular proliferation at hormonal and molecular levels L. Lalouette, D. Renault (Université de Rennes 1, Rennes, France); D. Siaussat, J. Ravaux (Université Pierre et Marie Curie, Paris, France) The relationships among temperature and organismal growth are frequently discussed, but the most subtle sublethal consequences of the temperature are less addressed. Moults in insects are initiated by a peak of 20-hydroxyecdysone inducing a decrease of cyclin expressions responsible of the proliferation of G2/M phase cells and differentiation. In this study, we focused on the impact of cold exposure (4 °C) and subsequent recovery (26 °C) in IAL-PID2 cells derived from the imaginal wing discs of Plodia interpunctella, with or without 20hydroxyecdysone (20E). Cellular cyclic activity, B-type cyclin (PcycB), B1-isoform ecdysone receptor (PIEcR-B1) and hsp70 mRNA expressions were determined. The reduced cell cycle activity at 4 °C was reversible when the cells were returned to 26 °C, but apoptosis increased strongly. PcycB expression decreased at 4 °C, whatever the experimental conditions, and returned towards control values without 20E at 26 °C, whereas it remained at low levels in 20E treated cells. The reduction of PiHsp70 expression was higher with 20E than without this hormone during thermal stress. Our data also demonstrated the incapacity of the cells to respond to the hormonal signal even if 20E integrity is conserved during the cold exposure. Together, our results bring new insights on the impact of thermal stress on hormonal, cellular and molecular mechanisms, that can affect on organisms development during ecdysis. doi:10.1016/j.cbpa.2008.05.130
4. Heterogeneous expression of vitellogenin genes in marine teleosts: How maturational proteolysis of derivative yolk proteins determines the size and nature of the egg R.N. Finn, J. Kolarevic, B.A. Kristoffersen (Department of Biology, University of Bergen, Norway) Marine teleosts spawn eggs that are strongly hypo-osmotic to the marine environment. Current studies are revealing that pre-ovulatory oocyte hydration is an important adaptation in this group. In species that spawn benthic eggs (benthophils), water influx during oocyte maturation results in a 2 to 3-fold increase in egg size, and is mainly driven by the differential movement of inorganic ions. In marine teleosts that spawn pelagic eggs (pelagophils), the appearance of a large pool of FAA represents the main driving force for oocyte hydration, and causes the oocyte to swell up to 8-fold. Comparative analyses of pelagophils show that the water content of the ovulated egg scales in proportion to the FAA content. To determine the origin and adaptive significance of this
S45
organic osmolyte system in marine teleosts, we have analysed the primary structure of several teleost vitellogenins (Vtg) and determined the precursor–product relationships between parent Vtg and derivative yolk proteins. The results show that up to four vtg genes are expressed in acanthomorph teleosts, but only two in a clupeiform teleost. Interestingly, the heterogeneous expression of the different vtg genes correlates well with the Vtg form that is the precursor of the FAA pool in pelagophils. The conserved depolymerisation of sub-domains causes an osmotic influx of water that pre-adapts the embryos to the hyperosmotic condition of seawater and provides the egg with its pelagic character. These adaptive mechanisms are argued to have arisen through neo-functionalisation of vtg genes, and are suggested to be a key event in the most explosive evolutionary history of the vertebrates. Acknowledgements: The present contribution was supported by the Research Council of Norway (Project #178837/40). doi:10.1016/j.cbpa.2008.05.131
5. Role of pontine neurons in central O2 chemoreflex during development in bullfrogs (Lithobates catesbeiana) R. Kinkead, S. Fournier (Université Laval, Québec, Canada) The present study used an in vitro brainstem preparation from premetamorphic tadpoles and adult bullfrogs (Lithobates catesbeiana) to understand the neural mechanisms associated with central O2 chemosensitivity and its maturation. In this species, brainstem hypoxia increases fictive lung ventilation in tadpoles but decreases in adults. Previous studies have shown that α1-adrenoceptor inactivation prevents these responses, suggesting that noradrenergic neurons are involved. We first tested the hypothesis that locus coeruleus (LC) neurons are necessary to the lung burst frequency response to central hypoxia by comparing the effects of brainstem transection at the LC level between pre-metamorphic tadpoles and adults. Data show that brainstem transection prevents the lung burst frequency response in both stage groups. During development, the progressive decrease in the Na+/K+/Cl− co-transporter NKCC1 contributes to the maturation of neural networks. Because NKCC1 becomes activated during hypoxia, we then tested the hypothesis that NKCC1 contributes to maturation of the central O2 chemoreflex. Double labelling experiments showed that the proportion of tyrosine hydroxylase positive neurons expressing NKCC1 in the LC decreases during development. Inactivation of NKCC1 with bumetanide bath application reversed the lung burst response to hypoxia in tadpoles. Bumetanide inhibited the response in adults. These data indicate that a structure within the pons (including the LC) are necessary to the central hypoxic chemoreflex and demonstrate that NKCC1 plays an important role in central O2 chemosensitivity and its maturation in this species. doi:10.1016/j.cbpa.2008.05.132
6. Ion transport by the amphibian primary ureter N. Møbjerg (University of Copenhagen, Denmark)
Three kidney systems appear during vertebrate development — the pronephros, mesonephros and metanephros. A characteristic of vertebrate organogenesis is the development of a primary ureter in association with the pronephros. This duct forms the collecting duct system of the
CD-antibodies. In particular, increases in the number of granular (phagocytic) haemocytes were observed; the effects of SCF involved the activation of c-kit tyrosine kinase-like receptors. The results support the hypothesis that common pathways involved in modulating activity, differentiation and proliferation of immune cells are conserved from molluscs to mammals. doi:10.1016/j.cbpa.2008.05.129
3. Growth potential in insects: Effects of temperature on cellular proliferation at hormonal and molecular levels L. Lalouette, D. Renault (Université de Rennes 1, Rennes, France); D. Siaussat, J. Ravaux (Université Pierre et Marie Curie, Paris, France) The relationships among temperature and organismal growth are frequently discussed, but the most subtle sublethal consequences of the temperature are less addressed. Moults in insects are initiated by a peak of 20-hydroxyecdysone inducing a decrease of cyclin expressions responsible of the proliferation of G2/M phase cells and differentiation. In this study, we focused on the impact of cold exposure (4 °C) and subsequent recovery (26 °C) in IAL-PID2 cells derived from the imaginal wing discs of Plodia interpunctella, with or without 20hydroxyecdysone (20E). Cellular cyclic activity, B-type cyclin (PcycB), B1-isoform ecdysone receptor (PIEcR-B1) and hsp70 mRNA expressions were determined. The reduced cell cycle activity at 4 °C was reversible when the cells were returned to 26 °C, but apoptosis increased strongly. PcycB expression decreased at 4 °C, whatever the experimental conditions, and returned towards control values without 20E at 26 °C, whereas it remained at low levels in 20E treated cells. The reduction of PiHsp70 expression was higher with 20E than without this hormone during thermal stress. Our data also demonstrated the incapacity of the cells to respond to the hormonal signal even if 20E integrity is conserved during the cold exposure. Together, our results bring new insights on the impact of thermal stress on hormonal, cellular and molecular mechanisms, that can affect on organisms development during ecdysis. doi:10.1016/j.cbpa.2008.05.130
4. Heterogeneous expression of vitellogenin genes in marine teleosts: How maturational proteolysis of derivative yolk proteins determines the size and nature of the egg R.N. Finn, J. Kolarevic, B.A. Kristoffersen (Department of Biology, University of Bergen, Norway) Marine teleosts spawn eggs that are strongly hypo-osmotic to the marine environment. Current studies are revealing that pre-ovulatory oocyte hydration is an important adaptation in this group. In species that spawn benthic eggs (benthophils), water influx during oocyte maturation results in a 2 to 3-fold increase in egg size, and is mainly driven by the differential movement of inorganic ions. In marine teleosts that spawn pelagic eggs (pelagophils), the appearance of a large pool of FAA represents the main driving force for oocyte hydration, and causes the oocyte to swell up to 8-fold. Comparative analyses of pelagophils show that the water content of the ovulated egg scales in proportion to the FAA content. To determine the origin and adaptive significance of this
S45
organic osmolyte system in marine teleosts, we have analysed the primary structure of several teleost vitellogenins (Vtg) and determined the precursor–product relationships between parent Vtg and derivative yolk proteins. The results show that up to four vtg genes are expressed in acanthomorph teleosts, but only two in a clupeiform teleost. Interestingly, the heterogeneous expression of the different vtg genes correlates well with the Vtg form that is the precursor of the FAA pool in pelagophils. The conserved depolymerisation of sub-domains causes an osmotic influx of water that pre-adapts the embryos to the hyperosmotic condition of seawater and provides the egg with its pelagic character. These adaptive mechanisms are argued to have arisen through neo-functionalisation of vtg genes, and are suggested to be a key event in the most explosive evolutionary history of the vertebrates. Acknowledgements: The present contribution was supported by the Research Council of Norway (Project #178837/40). doi:10.1016/j.cbpa.2008.05.131
5. Role of pontine neurons in central O2 chemoreflex during development in bullfrogs (Lithobates catesbeiana) R. Kinkead, S. Fournier (Université Laval, Québec, Canada) The present study used an in vitro brainstem preparation from premetamorphic tadpoles and adult bullfrogs (Lithobates catesbeiana) to understand the neural mechanisms associated with central O2 chemosensitivity and its maturation. In this species, brainstem hypoxia increases fictive lung ventilation in tadpoles but decreases in adults. Previous studies have shown that α1-adrenoceptor inactivation prevents these responses, suggesting that noradrenergic neurons are involved. We first tested the hypothesis that locus coeruleus (LC) neurons are necessary to the lung burst frequency response to central hypoxia by comparing the effects of brainstem transection at the LC level between pre-metamorphic tadpoles and adults. Data show that brainstem transection prevents the lung burst frequency response in both stage groups. During development, the progressive decrease in the Na+/K+/Cl− co-transporter NKCC1 contributes to the maturation of neural networks. Because NKCC1 becomes activated during hypoxia, we then tested the hypothesis that NKCC1 contributes to maturation of the central O2 chemoreflex. Double labelling experiments showed that the proportion of tyrosine hydroxylase positive neurons expressing NKCC1 in the LC decreases during development. Inactivation of NKCC1 with bumetanide bath application reversed the lung burst response to hypoxia in tadpoles. Bumetanide inhibited the response in adults. These data indicate that a structure within the pons (including the LC) are necessary to the central hypoxic chemoreflex and demonstrate that NKCC1 plays an important role in central O2 chemosensitivity and its maturation in this species. doi:10.1016/j.cbpa.2008.05.132
6. Ion transport by the amphibian primary ureter N. Møbjerg (University of Copenhagen, Denmark)
Three kidney systems appear during vertebrate development — the pronephros, mesonephros and metanephros. A characteristic of vertebrate organogenesis is the development of a primary ureter in association with the pronephros. This duct forms the collecting duct system of the